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Full text of "Michigan Electrical Code"





^ Labor & Economic Growth 



Michigan.gov Home SOAIHR l-lome | Site Map | Contact SOAHR 

DEPARTMENT OF LABOR AND ECONOMIC GROWTH 
DIRECTOR'S OFFICE 
CONSTRUCTION CODE 



(By authority conferred on the director of the department of labor and 
economic growth by section 4 of 1972 PA 230, MCL 125.1504, and Executive 
Reorganization Order Nos . 1996-2 and 2003-1, MCL 445.2001 and 445.2011) 



PART 8 . ELECTRICAL CODE 



R 408.30801 National electrical code; adoption by reference; inspection; 
purchase. 

Rule 801. The standards contained in the national electrical code, 2 005 
edition, except sections 501. 30B, 502. 30B, 503. 30B, 505. 25B, 506. 25B, 547.1 
to 547.10, and Annex G, as published by the national fire protection 
association, shall govern the installation, replacement, alteration, 
relocation, and use of electrical systems or material. With the exceptions 
noted, the national electrical code is adopted in these rules by reference. 
Fine print notes contained within the body of the code are not adopted as a 
part of the code. All references to the ANSI/ASME A17.1 2004, Safety Code 
for Elevators and Escalators means the Michigan Elevator Code and all 
references to the National Electrical Code means the Michigan Electrical 
Code. The code is available for inspection at the Okemos office of the 
Michigan department of labor and economic growth, bureau of construction 
codes. The National Electrical Code may be purchased from the National Fire 
Protection Association, Batterymarch Park, Quincy, Massachusetts 02269, or 
from the Michigan Department of Labor and Economic Growth, Bureau of 
Construction Codes, 2501 Woodlake Circle, Okemos, Michigan 48864, at a cost 
as of the time of adoption of these rules of $72.50 each. 

History: 1979 AC; 1980 AACS; 1981 AACS; 1985 AACS; 1986 AACS; 1988 AACS; 
1991 AACS; 1995 AACS; 1998-2000 AACS; 2004 AACS; 2007 AACS. 



R 408.30805 Rescission. 

Rule 805. Rules 41 through 77 of the rules of the electrical 
administrative board, being R 338.1041 to R 338.1077 of the Michigan 
Administrative Code, are rescinded. 

History: 1979 AC. 



R 408.30806 Application. 

Rule 8 06. Section 8 0.9 is added to the code to read as follows: 
80.9. Application. 

(a) New installations. The code applies to new installations. Buildings 
with construction permits dated after adoption of the code shall comply with 
its requirements . 

(b) Existing installations. Existing electrical installations that do not 
comply with the provisions of the code shall be permitted to be continued in 
use unless the authority having jurisdiction determines that the lack of 
conformity with the code presents an imminent danger to occupants. Where 
changes are required for correction of hazards, a reasonable amount of time 
shall be given for compliance, depending on the degree of the hazard. 

(c) Additions, alterations, or repairs. Additions, alterations, or 



repairs to any building, structure, or premises shall conform to that 
required of a new building without requiring the existing building to comply 
with all the requirements of the code. Additions, alterations, 
installations, or repairs shall not cause an existing building to become 
unsafe or to adversely affect the performance of the building as determined 
by the authority having jurisdiction. Electrical wiring added to an existing 
service, feeder, or branch circuit shall not result in an installation that 
violates the provisions of the code in force at the time the additions are 
made. 

History: 1979 AC; 1981 AACS; 2007 AACS. 

R 408.30807 Title. 

Rule 807. Title. These rules shall be known as the Michigan electrical 
code, hereinafter referred to as "the code." 

History: 1979 AC; 2004 AACS. 

R 408.30808 Scope. 

Rule 808. Sections 80.1, 80.1.1, 80.1.2, and 80.1.3 are added to the code 
to read as follows: 

80.1. Scope. The code regulates the design, installation, maintenance, 
alteration, and inspection of electrical systems including all wiring, 
fixtures, appliances, and appurtenances in connection with the utilization of 
electrical energy, within or on a building, structure, or properties, and 
including service entrance wiring as defined by the code. 

Exception: Electrical wiring and equipment within 1- and 2-family 
dwellings shall be constructed, installed, and maintained in accordance with 
the Michigan residential code. 

80.1.1. Intent. The purpose of the code is to provide minimum standards 
to safeguard life or limb, health, property, and public welfare by regulating 
and controlling the design, construction, installation, quality of materials, 
location, operation, and maintenance or use of electrical wiring and 
equipment. 

80.1.2. Severability. If a section, subsection, sentence, clause, or 
phrase of the code is, for any reason, held to be unconstitutional, such 
decision shall not affect the validity of the remaining portions of the code. 

80.1.3. Code conformity required. A person shall not install, alter, 
maintain, service, or repair, or cause or permit the installation, altering, 
maintaining, servicing, or repairing of electrical equipment in or on any 
building, structure, or part thereof, or on any premises, if by the person's 
action the work does not conform to the provisions of the code. 

History: 2004 AACS; 2007 AACS. 

R 408.30809 Purpose. 

Rule 8 09. Section 8 0.3 is added to the code to read as follows: 

80.3. Purpose. The purpose of this article shall be to provide 

requirements for administration and enforcement of the Michigan electrical 

code. 

History: 2004 AACS; 2007 AACS. 

R 408.30810 Authority. 

Rule 810. Section 8 0.13 is added to the code to read as follows: 

80.13. Authority. Where used in the code, "authority having jurisdiction" 

means the enforcing agency in accordance with the act, as defined in R 

408.30828. The code shall be administered and enforced by the enforcing 

agency in accordance with the act. 

History: 1979 AC; 1980 AACS; 1981 AACS; 2004 AACS; 2007 AACS. 



R 408.30811 Duties and powers of the code official. 

Rule 811. Section 8 0.14 is added to the code to read as follows: 

80.14. Duties and powers of the code official. The code official shall 
enforce the provisions of the code and shall act on any question relative to 
the installation, alteration, repair, maintenance, or operation of electrical 
wiring and equipment, except as otherwise specifically provided for by 
statute. 

History: 2004 AACS. 

R 408.30812 Means of Appeal. 

Rule 812. Sections 80.15 and 80.15.1 are added to the code to read as 
follows: 

80.15. Means of appeal. A person may appeal a decision of the enforcing 
agency to the board of appeals. An application for appeal shall be based on 
a claim that the true intent of the code or the rules governing construction 
have been incorrectly interpreted, the provisions of the code do not apply, 
or an equal or better form of construction is proposed. The application 
shall be filed under the act. 

80.15.1. Limitation of authority. The board of appeals shall have no 
authority relative to interpretation of the administration of the code nor 
shall such board be empowered to waive requirements of the code. 

History: 1979 AC; 1981 AACS; 2004 AACS; 2007 AACS. 

R 408.30813 Code arrangement. 

Rule 813. Section 9 0.3 of the code is amended to read as follows: 

90.3. Code arrangement. The code includes an administration section. 
Additionally, the code is divided into the introduction and 9 chapters. 
Chapters 1, 2, 3, and 4 apply generally; chapters 5, 6, and 7 apply to 
special occupancies, special equipment, or other special conditions. 
Chapters 5, 6, and 7 supplement or modify the general rules. Chapters 1 to 4 
apply except as amended by chapters 5, 6, and 7 for the particular conditions, 

Chapter 8 covers communications systems and is not subject to the 
requirements of chapters 1 to 7 except where the requirements are 
specifically referenced in chapter 8. 

Chapter 9 consists of tables. 

Annexes are not part of the requirements of the code but are included for 
informational purposes only. 

History: 2004 AACS. 

R 408.30814 Enforcement. 

Rule 814. Sections 90.4 and 90.6 of the code are amended to read as 
follows: 

90.4. Enforcement. The code is intended to be suitable for mandatory 
application by governmental bodies that exercise legal jurisdiction over 
electrical installations, including signaling and communications systems. 
The enforcing agency shall interpret the rules, decide on the approval of 
equipment and materials, and grant special permission set forth in the rules. 

By special permission, the enforcing agency may permit alternative methods 
where equivalent objectives may be achieved by establishing and maintaining 
effective safety. 

90.6. Formal interpretations. Formal interpretations shall be issued in 
accordance with 1972 PA 230, MCL 125.1501 et seq. 

History: 2004 AACS. 

R 408.30815 Maintenance of existing wiring. 

Rule 815. Section 8 0.18 of the code is added to read as follows: 

80.18. Maintenance of existing wiring. Every building, structure, or part 

thereof shall be kept in good electrical repair by the owner. 



History: 1979 AC; 1981 AACS; 2004 AACS. 

R 408.30816 Rescinded. 

History: 1979 AC; 1981 AACS; 2004 AACS. 

R 408.30817 Disconnection of dangerous electrical equipment. 

Rule 817. Section 8 0.18.1 is added to the code to read as follows: 
80.18.1. Disconnection of dangerous electrical equipment. If the use of 
any electrical equipment is found imminently dangerous to human life or 
property, the enforcing agency may condemn the equipment or disconnect it 
from its source of electric supply, except that the enforcing agency shall 
not disconnect the service entrance equipment or utility service drop wires 
unless the entrance equipment or utility wires in themselves constitute a 
hazard to life or property. If the enforcing agency condemns or disconnects 
dangerous equipment, then the agency shall place a red tag on the equipment 
listing the causes for the condemnation or disconnection and the penalty 
under the act for the unlawful use of the equipment. The agency shall give 
written notice of the condemnation or disconnection and the causes for 
condemning or disconnecting the equipment to the owner or the occupant of the 
building, structure, or premises. A person shall not remove the tag or 
reconnect the electrical equipment to its source of electric supply, or use 
or permit the use of electrical current in the electrical equipment, until 
the causes for the condemnation or disconnection are remedied and a permit 
for the electrical repairs of the equipment is obtained from the enforcing 
agency. 

History: 1979 AC; 1981 AACS; 1998-2000 AACS; 2004 AACS. 

R 408.30818 Permits and certificates. 

Rule 818. Sections 80.19, 80.19.1, 80.19.2, 80.19.3, 80.19.4, 80.19.5, 
80.19.6, 80.19.7, and 80.19.8 are added to the code to read as follows: 

80.19. Permits and certificates. A person shall not equip a building with 
electrical conductors or equipment or make an alteration of, change in, or 
addition to, electrical conductors or equipment without receiving a written 
permit to do the work described. If the electrical installation or 
alterations of, changes in, or addition to, electrical conductors or 
equipment are found to be in compliance with the provisions of the code and 
if the work has passed the inspection of the enforcing agency, then the 
enforcing agency shall, upon the request of the permit holder to whom the 
permit was issued, issue a certificate of final electrical inspection. The 
certificate certifies that the provisions of the code have been complied 
with. This section does not apply to installations that are referred to in 
section 7(3)(a), (b), (c), (d), (e), (f), (h), (k), (1), or (o) of 1956 PA 
217, MCL 338.887 

80.19.1. To whom permits are issued. (1) To obtain an electrical permit, 
an applicant shall be 1 of the following: 

(a) A holder of an electrical contractor license or the qualifying master 
for the electrical contractor when authorized by the electrical contractor to 
secure a permit. 

(b) A person, firm, or corporation holding an affidavit as provided by R 
338.1039a. 

(c) A homeowner who occupies or will occupy a single-family dwelling and 
other accessory structures located on the same lot intended for use by the 
homeowner for which the permit is obtained and who will install the 
electrical equipment as certified by the homeowner on the permit application 
in accordance with the act. 

(2) To obtain a permit for a fire alarm system, as defined in section 
la(l) of 1956 PA 217, MCL 338.881a (1), an applicant shall be 1 of the 
following: 

(a) A holder of an electrical contractor license. 

(b) A holder of a fire alarm specialty contractor license or the 



qualifying fire alarm specialty technician qualifying the fire alarm 
specialty contractor when authorized by the fire alarm specialty contractor 
to secure a permit. 

(c) A homeowner qualifying under section 80.19.1(l)(c) of the code. 

(3) To obtain a permit for an electrical sign or outline lighting, as 
defined in section lb(l) and (2) of 1956 PA 217, MCL 338.881b(l) and (2), an 
applicant shall be 1 of the following: 

(a) A holder of an electrical contractor license. 

(b) A holder of a sign specialty contractor license or the sign specialty 
technician qualifying the sign specialty contractor when authorized by the 
sign specialty contractor to secure a permit. 

(c) A homeowner qualifying under section 80.19.1(l)(c) of the code. 

(4) To obtain a permit for electrical wiring associated with the 
installation, removal, alteration, or repair of a water well pump on a 
single-family dwelling to the first point of attachment in the house from the 
well, an applicant shall be 1 of the following: 

(a) A holder of an electrical contractor license. 

(b) A registered pump installer under part 127 of 1978 PA 368, MCL 
333.12701 to 333.12771. 

(c) A homeowner qualifying under section 80.19.1(l)(c) of the code. 

(5) To obtain a permit for wiring associated with existing mechanical and 
plumbing systems referenced in section 7(3) (i) of 1956 PA 217, MCL 
338 . 887 ( 3 ) (i) , a person shall be 1 of the following: 

(a) A holder of an electrical contractor license or the qualifying master 
for the electrical contractor when authorized by the electrical contractor to 
secure a permit. 

(b) A holder of a mechanical contractor license issued in accordance with 
section 6(3)(a), (b), (d), (e), and (f) of 1984 PA 192, MCL 338 . 976 ( 3 ) ( a) , 
(b), (d), (e), and (f). 

(c) A holder of a plumbing contractor license issued in accordance with 
2002 PA 733, MCL 338.3511to 338.3569. 

80.19.2. Application for permit. Each application for a permit, with the 
required fee, shall be filed with the code official on a form furnished for 
that purpose and shall contain a general description of the proposed work and 
its location. The permit application shall contain all applicable 
information in accordance with the act and shall include the signature of the 
applicant in compliance with section 8 0.19.1 of the code. 

80.19.3. Permit expiration. If work for which a permit is issued is not 
started within 6 months of the date of permit issuance or if work is 
abandoned for a period of 6 months, then the permit shall lapse and cease to 
be in effect. 

80.19.4. Uncompleted installation notification. If a person to whom a 
permit is issued for the installation and inspection of electrical conductors 
and electrical equipment quits the installation for any reason, then the 
person shall notify the enforcing agency. 

80.19.5. Inspection and refunds for partial installation. If an 
installation is partially completed, then a permit holder, upon quitting the 
installation, shall notify the enforcing agency and shall request an 
inspection. The inspector shall record the acceptance of, or violations 
against, the work installed on the permit record according to the findings of 
the inspector. The enforcing agency shall not grant a refund to the permit 
holder of the permit fee covering electrical equipment installed and 
inspected. 

80.19.6. Owner notification to enforcing agency. If a permit holder quits 
an installation after the electrical equipment is installed and fails to 
notify the enforcing agency, then the building owner or his or her agent may 
notify the enforcing agency and request inspection. Upon inspection, the 
enforcing agency shall send the permit holder a notice of a violation. The 
owner may then secure another licensed contractor to proceed with the work if 
the new contractor is properly covered by a permit. 

80.19.7. Transfer of permit. An electrical permit is not transferable. 

80.19.8. Fraudulent application for permit. A permit that is issued in 
violation of the laws of this state or as a result of false or fraudulent 
information or misinterpretation of conditions is subject to revocation at 
the direction of the enforcing agency. The enforcing agency shall notify the 
person holding the permit to appear and show cause why the permit should not 



be revoked. Failure to appear is sufficient grounds for revocation of the 
permit . 

History: 1979 AC; 1981 AACS; 1991 AACS; 1995 AACS; 1998-2000 AACS; 
2004 AACS; 2007 AACS. 



R 408.30819 Plans and specifications. 

Rule 819. Sections 80.21, 80.21.1 and 80.21.2 are added to the code to 
read as follows: 

80.21. Plans and specifications. An applicant shall submit a detailed set 
of plans and specifications with the application for an electrical permit for 
any wiring or alteration to an electrical system if the system requires 
installation of electrical equipment that has an ampacity of more than 400 
amperes for the service or feeder and if the calculated floor area in a 
building is more than 3,500 square feet. The enforcing agency may request 
plans for projects that include an unusual design. The electrical drawings 
shall include all of the following details: 

(a) Lighting layout. 

(b) Circuiting. 

(c) Switching. 

(d) Conductor and raceway sizes. 

(e) Wattage schedule. 

(f) Service location and riser diagram. 

(g) Load calculations. 

(h) A proposed method of construction that is drawn with symbols of a 
standard form. 

All conductors are assumed to be copper unless otherwise stated in the 
plan. Specifications, when provided, shall also include the information 
listed in this rule. The selection of suitable disconnect and overcurrent 
devices to provide proper coordination and interrupting capacity for a wiring 
system is the responsibility of the designer. The enforcing agency, when 
approving electrical plans, does not assume responsibility for the design or 
for any deviations from any electrical drawings. The permit holder shall 
ensure that the plans and specifications approved by the enforcing agency, or 
a certified copy of the plans and specifications, where required, are 
available on the jobsite for the use of the enforcing agency. 

80.21.1. Preparation of plans. An architect or engineer shall prepare, or 
supervise the preparation of, all plans and specifications for new 
construction work or repair, expansion, addition, or modification work. The 
architect or engineer shall be licensed under 1980 PA 299, MCL 339.101 to 
339.2919. The plans and specifications shall bear the architect's or 
engineer's signature and seal. 

Note: For exceptions, see 1980 PA 299, MCL 339.101 to 339.2919. 

80.21.2. Review of construction documents. The enforcing agency shall 
review the application, construction documents, and other data filed by an 
applicant for a permit. If the enforcing agency finds that the proposed work 
conforms to the requirements of the code and related laws and ordinances and 
that the fees are paid, then the agency shall issue a permit to the applicant. 

History: 1979 AC; 1981 AACS; 1988 AACS; 1991 AACS; 1995 AACS; 
1998-2000 AACS; 2004 AACS; 2007 AACS. 



R 408.30820 Representative on jobsite. 

Rule 820. Sections 80.20 and 80.20.1 are added to the code to read as 
follows: 

80.20. Representative on jobsite. The enforcing agency reserves the right 
to require a representative of the permit holder to be on the job when an 
inspection is made. 

80.20.1. Licensed supervision required. A person who is licensed under 
1956 PA 217, MCL 338.881 et seq. , and who is employed by and represents the 
permit holder who is responsible for the electrical installation shall be 
present at all times when electrical construction is in progress. 

History: 1979 AC; 1981 AACS; 1988 AACS; 1991 AACS; 1995 AACS; 



1998-2000 AACS; 2004 AACS, 



R 408.30821 Occupancy of building or structure. 

Rule 821. Section 8 0.11 is added to the code to read as follows: 
80.11. Occupancy of building or structure. 

(a) New construction. No newly constructed building may be occupied in 
whole or in part in violation of the provisions of the code. 

(b) Existing buildings. Existing buildings that are occupied at the time 
of adoption of the code shall be permitted to remain in use provided the 
following conditions apply: 

(1) The occupancy classification remains unchanged. 

(2) There exists no condition deemed hazardous to life or property that 
would constitute an imminent danger. 

History: 1979 AC; 1981 AACS; 1995 AACS; 2007 AACS. 

R 408.30822 Inspections. 

Rule 822. Sections 80.22, 80.22.1 and 80.22.2 are added to the code to 
read as follows: 

80.22. Scheduling inspection. An enforcing agency shall be given not less 
than 24 hours' notice to inspect electrical equipment. An enforcing agency 
shall perform the inspection within a reasonable period of time after the 
request for inspection is made. 

80.22.1. Inspection notice. Only the enforcing agency shall post a notice 
of inspection at, or remove a notice from, the jobsite. The enforcing agency 
shall maintain a record of all inspections. 

80.22.2. Concealing electrical installation. A person shall not conceal, 
or cause to be concealed, any conductors and equipment before the equipment 
is approved by the enforcing agency. 

History: 1979 AC; 1981 AACS; 1995 AACS; 1998-2000 AACS; 2004 AACS. 

R 408.30823 Connection to electricity supply. 

Rule 823. Section 80.25 added to the code to read as follows: 
80.25. Connection to electricity supply. Except where work is performed 
under an annual permit or except as otherwise provided in the code, a person, 
firm, or corporation shall not make connection to a supply of electricity or 
to supply electricity to any electric equipment installation for which a 
permit is required or that has been disconnected or ordered to be 
disconnected . 

History: 1979 AC; 1981 AACS; 1991 AACS; 2004 AACS; 2007 AACS. 

R 408.30824 Fees. 

Rule 824. Section 80.24 of the code is added to read as follows: 
80.24. Fees. The fees prescribed by section 22 of 1972 PA 230, MCL 
125.1522, shall be paid to the enforcing agency of the jurisdiction before a 
permit to begin work for new construction, alteration, removal, demolition, 
or other building operation may be issued. In addition, an amendment to a 
permit necessitating an additional fee shall not be approved until the 
additional fee is paid. 

History: 1979 AC; 1981 AACS; 2004 AACS. 

R 408.30825 Rescinded. 

History: 1979 AC; 1981 AACS; 1991 AACS; 1995 AACS; 1998-2000 AACS. 



R 408.30826 Violations. 

Rule 826. Section 80.23 is added to the code to read as follows 



80.23. Violations. If it is found that any electrical equipment does not 
conform to the provisions of the code, then the enforcing agency shall 
notify, in writing, the person who installs, or who is responsible for 
installing, the electrical equipment, in accordance with the act, of the 
defect, misuse, or violation. Violations and penalties shall be as specified 
in the act. 

History: 1979 AC; 1981 AACS; 1991 AACS; 1998-2000 AACS; 2004 AACS; 
2007 AACS. 



R 408.30827 Service equipment. 

Rule 827. Section 80.26 is added to the code to read as follows: 

80.26. Service equipment. The enforcing agency shall approve service 

equipment installed, altered, or repaired before the load side of the meter 

is energized. 

History: 1991 AACS; 1995 AACS; 1998-2000 AACS; 2004 AACS. 

R 408.30828 Definitions. 

Rule 828. The definitions of authority having jurisdiction, dwelling unit, 
dwelling, 1-family, dwelling, 2-family, and dwelling, multifamily in article 
100 of the code are amended and the definitions of act, chief electrical 
inspector, code official, electrical inspector, and enforcing agency are 
added to article 100 of the code to read as follows: 

"Act" means 1972 PA 230, MCL 125.1501 to 125.1531 and known as the 
Stille-DeRossett-Hale single state construction code act. 

"Authority having jurisdiction" where used in the code means the enforcing 
agency. 

"Dwelling unit" means a single unit providing complete independent living 
facilities for 1 or more persons, including permanent provisions for living, 
sleeping, eating, cooking, and sanitation. 

"Dwelling, 1-family" means a building that consists solely of 1 dwelling 
unit complying with the provisions of the Michigan residential code. 

"Dwelling, 2-family" means a building that consists solely of 2 dwelling 
units complying with the provisions of the Michigan residential code. 

"Dwelling, multifamily" means a building that contains 3 or more dwelling 
units. Residential occupancies containing more than 2 dwelling units where 
the occupants are primarily permanent in nature, including all of the 
following: 

1 . Apartment houses . 

2. Boarding housing, not transient. 

3 . Convents . 

4. Dormitories. 

5. Fraternities and sororities. 

6. Monasteries. 

"Chief electrical inspector" where used in the code means the code official, 

"Code official" means a person who is appointed and employed by a 
governmental subdivision who is charged with the administration and 
enforcement of the state code or codes, and who is registered in accordance 
with 1986 PA 54, MCL 338.2301 to 338.2313. 

"Electrical inspector" where used in the code means the code official. 

"Enforcing agency" means the enforcing agency, in accordance with the act, 
which is responsible for administration and enforcement of the code within a 
governmental subdivision, except for the purposes of the act. 

History: 2004 AACS; 2007 AACS. 

R 408.30829 Approval 

Rule 829. Section 110.2 of the code is amended to read as follows: 

110.2. Approval. Materials, equipment, and devices shall be constructed 

and installed in accordance with approvals granted under section 21 of 1972 

PA 230, MCL 125.1521, or by the code official. 



History: 2004 AACS. 

R 408.30830 Rescinded. 

History: 1979 AC; 1998-2000 AACS. 

R 408.30831 Rescinded. 

History: 1981 AACS; 1988 AACS; 1997 AACS; 1998-2000 AACS; 2004 AACS. 

R 408.30832 Rescinded. 

History: 1981 AACS; 1985 AACS; 1995 AACS; 1997 AACS. 

R 408.30834 Maximum number of disconnects. 

Rule 834. Section 230.71(A) of the code is amended to read as follows: 
230.71(A). General. The service disconnecting means for each service 
permitted by section 2 30.2 of the code, or for each set of service-entrance 
conductors permitted by section 230.40, exception nos. 1, 2, 3, or 4, of the 
code, shall consist of not more than 6 switches or sets of circuit 
breakers, or a combination of not more than 6 switches and sets of circuit 
breakers, mounted in a single enclosure, in a group of separate 
enclosures, in a switchboard or on a switchboard. There shall be not 
more than 6 sets of disconnects per service grouped in any 1 location. For 
the purpose of this section, disconnecting means used solely for power 
monitoring equipment, transient voltage surge suppressors, or the control 
circuit of the ground-fault protection system or power-operable service 
disconnecting means, installed as part of the listed equipment, shall not 
be considered a service disconnecting means. 

History: 2007 MR 14, Eff. Nov. 23, 2007. 

R 408.30835 Number of service-entrance conductor sets. 

Rule 835 Section 230.40 of the code is amended to read as follows: 
230.40. Number of Service-Entrance Conductor Sets. Each service drop or 
lateral shall supply 1 set of service-entrance conductors. 

Exception 1: A building may have 1 set of service-entrance conductors for 
each service, as defined in section 230.2 of the code, run to each occupancy 
or group of occupancies. 

Exception 2: Where 2 to 6 service disconnecting means in separate enclosures 
are grouped at 1 location and supply separate loads from 1 service drop or 
lateral, 1 set of service-entrance conductors may supply each or several such 
service equipment enclosures. 

Exception 3: A 2-family dwelling or a multifamily dwelling may have 1 set of 
service-entrance conductors installed to supply the circuits covered in 
section 210.25 of the code. 

Exception 4: One set of service-entrance conductors connected to the supply 
side of the normal service disconnecting means may supply each or several 
systems covered by section 230.82(4) or section 230.82(5) of the code. 

History: 1985 AACS; 1988 AACS; 1997 AACS; 1998-2000 AACS; 2004 AACS; 
2007 AACS. 

R 408.30837 Rescinded. 

History: 1985 AACS; 1988 AACS; 1997 AACS; 1998-2000 AACS; 2004 AACS. 

R 408.30838 Rescinded. 



History: 1986 AACS; 1988 AACS; 1997 AACS. 

R 408.30839 Rescinded. 

History: 1985 AACS; 1988 AACS; 1997 AACS; 1998-2000 AACS. 

R 408.30843 Rescinded. 

History: 1985 AACS; 1988 AACS; 1991 AACS; 1998-2000 AACS; 2004 AACS. 

R 408.30865 Rescinded. 

History: 1979 AC; 1980 AACS; 1988 AACS; 1997 AACS. 

R 408.30866 Rescinded. 

History: 1988 AACS; 1991 AACS; 1998-2000 AACS; 2004 AACS. 

R 408.30867 Grounding and bonding of flexible metal conduit. 

Rule 867. Section 348.60 of the code is amended to read as follows: 
348.60. An equipment grounding conductor or equipment bonding jumpers 
shall be installed. Equipment grounding conductors shall be installed in 
accordance with section 250.134(B) of the code. Equipment bonding jumpers 
shall be installed in accordance with section 250.102 of the code. 

History: 1988 AACS; 1998-2000 AACS; 2007 AACS. 

R 408.30868 Grounding and bonding of liquidtight flexible metal conduit. 
Rule 868. Section 350.60 of the code is amended to read as follows: 
350.60. An equipment grounding conductor or equipment bonding jumpers 
shall be installed. Equipment grounding conductors shall be installed in 
accordance with section 250.134(B) of the code. Equipment bonding jumpers 
shall be installed in accordance with section 250.102 of the code. 

History: 1988 AACS; 1998-2000 AACS; 2004 AACS; 2007 AACS. 

R 408.30869 Grounding conductors. 

Rule 869. Section 250.118 of the code is amended to read as follows: 
250.118. Types of equipment grounding conductors. The equipment grounding 

conductor run with or enclosing the circuit conductors shall be 1 or more or 

a combination of the following: 

(1) A copper, aluminum, or copper-clad aluminum conductor. This conductor 
shall be solid or stranded; insulated, covered, or bare; and, in the form of 
a wire or a busbar of any shape. 

(2) Rigid metal conduit. 

(3) Intermediate metal conduit. 

(4) Electrical metallic tubing. 

(5) Flexible metallic tubing where the tubing is terminated in fittings 
listed for grounding and meeting both of the following conditions: 

(a) The circuit conductors contained in the tubing are protected by 
overcurrent devices rated at 2 amperes or less. 

(b) The length of flexible metallic tubing in the ground return path does 
not exceed 1.8m (6 feet). 

(6) Armor of type AC cable as provided in section 320.108 of the code. 

(7) The copper sheath of mineral-insulated, metal-sheathed cable. 

(8) Type MC cable where listed and identified for grounding in accordance 
with both of the following: 

(a) The combined metallic sheath and grounding conductor of interlocked 



metal tape-type MC cable. 

(b) The metallic sheath or the combined metallic sheath and grounding 
conductors of the smooth or corrugated tube type MC cable. 

(9) Cable trays as permitted by sections 392.3(c) and 392.7 of the code. 

(10) Cablebus framework as permitted by section 370.3 of the code. 

(11) Other listed electrically continuous metal raceways and listed 
auxiliary gutters. 

(12) Surface metal raceways listed for grounding. 

History: 1988 AACS; 1991 AACS; 1998-2000 AACS; 2004 AACS; 2007 AACS . 

R 408.30870 Rescinded. 

History: 1988 AACS; 1991 AACS; 1997 AACS. 

R 408.30871 Rescinded. 

History: 1991 MR 8, Eff. Aug. 17, 1991; 1995 MR 8, Eff. Sept. 6, 1995; 
rescinded 1998 MR 11, Eff. Nov 30, 1998. 

R 408.30872 Rescinded. 

History: 1991 AACS; 1995 AACS; 1997 AACS. 

R 408.30873 Uses permitted. 

Rule 873 Section 334.10 of the code is amended to read as follows: 

334.10. Uses Permitted. Type NM, type NMC, and type NMS cables may be 

used in the following: 

(1) One- and 2-family dwellings. 

(2) Multifamily dwellings except as prohibited in section 334.12 of the 
code. 

(3) Other structures except as prohibited in section 334.12 of the code. 
In structures exceeding 1 floor above grade, cables shall be concealed within 
walls, floors, or ceilings that provide a thermal barrier of material that 
has at least a 15-minute finish rating as identified in listings of fire 
rated assemblies in accordance with the Michigan building code. 

(4) Cable trays in structures permitted to be types III, IV, or V where 
the cables are identified for the use. 

History: 1991 AACS; 1995 AACS; 1998-2000 AACS; 2007 AACS. 

R 408.30880 Rescinded. 

History: 1979 AC; 1980 AACS; 1997 AACS. 



Michigan.gov Home | SOAHR Home | State Web Sites 

Privacy Policy | Linl< Policy | Accessibility Policy | Security Policy 

Copyright © 2005 State of Michigan 






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NFPA 70: Natiooal Electrics 
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Copyright © 2004 

National Fire Protection Association, Inc. 

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veloped through a consensus standards development process approved by the American National Standards Institute. 
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Important Notices and Disclaimers continue on inside back cover. 



09 08 07 06 05 04 10 9 8 7 6 5 4 3 2 1 



• 



Copyright © 2004, National Fire Protection Association, All Rights Reserved 

NFPA 70 
National Electrical Code® 

2005 Edition 

This edition of NFPA 70, National Electrical Code, was prepared by the National Electrical Code 
Committee and acted on by NFPA at its May Association Technical Meeting held May 23-26, 
2004, in Salt Lake City, UT. It was issued by the Standards Council on July 16, 2004, with an 
effective date of August 5, 2004, and supersedes all previous editions. 

A tentative interim amendment (TIA) to Section 604.6(A)(1) was issued on July 15, 2004. 
For further information on tentative interim amendments see Section 5 of the NFPA Regulations 
Governing Committee Projects available at: 

http://www.nfpa.org/Codes/NFPADirectory.asp#Regs&Procedures 

This edition of NFPA 70 was approved as an American National Standard on August 5, 2004. 

History and Development of the National Electrical Code® 

The National Fire Protection Association has acted as sponsor of the National Electrical 
Code since 1911. The original Code document was developed in 1897 as a result of the united 
efforts of various insurance, electrical, architectural, and allied interests. 

In accordance with the provisions of the NFPA Regulations Governing Committee Projects, 
a National Electrical Code Committee Report on Proposals containing proposed amendments to 
the 2002 National Electrical Code was pubUshed by NFPA in July 2003. This report recorded the 
actions of the various Code-Making Panels and the Correlating Committee of the National 
Electrical Code Committee on each proposal that had been made to revise the 2002 Code. The 
report was circulated to all members of the National Electrical Code Committee and was made 
available to other interested NFPA members and to the public for review and comment. Follow- 
ing the close of the public comment period, the Code-Making Panels met, acted on each com- 
ment, and reported their action to the Correlating Committee. NFPA published the National 
Electrical Code Committee Report on Comments in April 2004, which recorded the actions of the 
Code-Making Panels and the Correlating Committee on each public comment to the National 
Electrical Code Committee Report on Proposals. The National Electrical Code Committee Report 
on Proposals and the National Electrical Code Committee Report on Comments were presented 
to the 2004 May Association Technical Meeting for adoption. 

NFPA has an Electrical Section that provides particular opportunity for NFPA members 
interested in electrical safety to become better informed and to contribute to the development of 
the National Electrical Code and other NFPA electrical standards. Each of the Code-Making 
Panels and the Chairman of the Correlating Committee reported their recommendations to meet- 
ings of the Electrical Section at the 2004 NFPA World Safety Conference and Exposition. The 
Electrical Section thus had opportunity to discuss and review the report of the National Electrical 
Code Committee prior to the adoption of this edition of the Code by the Association at its 2004 
May Technical Session. 

This 2005 edition supersedes all other previous editions, supplements, and printings dated 
1897, 1899, 1901, 1903, 1904, 1905, 1907, 1909, 1911, 1913, 1915, 1918, 1920, 1923, 1925, 
1926, 1928, 1930, 1931, 1933, 1935, 1937, 1940, 1942, 1943, 1947, 1949, 1951, 1953, 1954, 1955, 1956, 
1957, 1958, 1959, 1962, 1965, 1968, 1971, 1975, 1978, 1981, 1984, 1987, 1990, 1993, 1996, 1999, and 
2002. The 2005 edition marks the 50th edition of the National Electrical Code. 

Changes other than editorial are indicated by a vertical rule beside the paragraph, table, or 
figure in which the change occurred. These rules are included as an aid to the user in identifying 
changes from the previous edition. Where one or more complete paragraphs have been deleted, 
the deletion is indicated by a bullet (•) between the paragraphs that remain. 

This Code is purely advisory as far as NFPA is concerned. It is made available for a wide 
variety of both public and private uses in the interest of life and property protection. These 
include both use in law and for regulatory purposes, and use in private self-regulation and 
standardization activities as insurance underwriting, building and facilities construction and man- 
agement, and product testing and certification. 



2005 Edition NATIONAL ELECTRICAL CODE 70- 



CONTENTS 



Contents 



ARTICLE 

90 Introduction 70- 23 

Chapter 1 General 

100 Definitions 70- 26 

I. General 70- 26 

II. Over 600 Volts, Nominal 70- 32 

110 Requirements for Electrical Installations 70- 33 

I. General 70- 33 

II. 600 Volts, Nominal, or Less 70- 36 

III. Over 600 Volts, Nominal 70- 38 

IV. Tunnel Installations over 600 Volts, 

Nominal 70- 40 

V. Manholes and Other Electric 
Enclosures Intended for Personnel 
Entry, All Voltages 70- 41 

Chapter 2 Wiring and Protection 

200 Use and Identification of Grounded 

Conductors 70- 43 

210 Branch Circuits 70-45 

I. General Provisions 70- 45 

II. Branch-Circuit Ratings 70-49 

III. Required Outlets 70- 51 

215 Feeders 70- 55 

220 Branch-Circuit, Feeder, and Service 

Calculations 70- 56 

I. General 70- 56 

II. Branch Circuit Load Calculations 70- 57 

III. Feeder and Service Load Calculations 70- 59 

IV. Optional Feeder and Service Load 

Calculations 70- 61 

V. Farm Load Calculation 70- 65 

225 Outside Branch Circuits and Feeders 70- 66 

L General 70- 66 

II. More Than One Building or Other 

Structure 70- 69 

III. Over 600 Volts 70- 71 

230 Services 70- 72 

L General 70- 72 

II. Overhead Service-Drop Conductors 70- 73 

III. Underground Service-Lateral 

Conductors 70- 74 

IV. Service-Entrance Conductors 70- 74 

V. Service Equipment — General 70- 77 

VI. Service Equipment — Disconnecting 

Means 70- 77 

VII. Service Equipment — Overcurrent 

Protection 70- 79 

Vm. Services Exceeding 600 Volts, Nominal ... 70- 80 



ARTICLE 

240 Overcurrent Protection 70- 81 

L General 70- 81 

II. Location 70- 84 

III. Enclosures 70- 87 

IV. Disconnecting and Guarding 70- 88 

V. Plug Fuses, Fuseholders, and Adapters .... 70- 88 

VI. Cartridge Fuses and Fuseholders 70- 89 

VIL Circuit Breakers 70- 89 

VIII. Supervised Industrial Installations 70- 90 

IX. Overcurrent Protection Over 600 Volts, 

Nominal 70- 91 

250 Grounding and Bonding 70-92 

I. General 70- 92 

II. System Grounding 70- 95 

III. Grounding Electrode System and 

Grounding Electrode Conductor 70-101 

IV. Enclosure, Raceway, and Service Cable 
Grounding 70-105 

V. Bonding 70-105 

VI. Equipment Grounding and Equipment 

Grounding Conductors 70-108 

VII. Methods of Equipment Grounding 70-113 

VIII. Direct-Current Systems 70-115 

IX. Instruments, Meters, and Relays 70-116 

X. Grounding of Systems and Circuits of 

1 kV and Over (High Voltage) 70-117 

280 Surge Arresters 70-119 

I. General 70-119 

II. Installation 70-119 

III. Connecting Surge Arresters 70-1 19 

285 Transient Voltage Surge Suppressors: 

TVSSs 70-120 

I. General 70-120 

II. Installation 70-120 

III. Connecting Transient Voltage Surge 

Suppressors 70-1 2 1 

Chapter 3 Wiring Methods and Materials 

300 Wiring Methods 70-122 

I. General Requirements 70-122 

II. Requirements for Over 600 Volts, 

Nominal 70-131 

3 10 Conductors for General Wiring 70-133 

312 Cabinets, Cutout Boxes, and Meter Socket 

Enclosures 70-158 

L Installation 70-158 

II. Construction Specifications 70-160 

314 Outlet, Device, Pull, and Junction Boxes; 
Conduit Bodies; Fittings; and Handhole 
Enclosures 70-161 

I. Scope and General 70-161 

II. Installation 70-162 



• 



70-2 



NATIONAL ELECTRICAL CODE 2005 Edition 



CONTENTS 






ARTICLE 

III. Construction Specifications 70-167 

IV. Pull and Junction Boxes for Use on 

Systems Over 600 Volts, Nominal 70-168 

320 Armored Cable: Type AC 70-169 

I. General 70-169 

II. Installation 70-169 

III. Construction Specifications 70-170 

322 Flat Cable Assemblies: Type FC 70-170 

I. General 70-170 

II. Installation 70-170 

III. Construction 70-171 

324 Flat Conductor Cable: Type FCC 70-171 

I. General 70-171 

II. Installation 70-172 

III. Construction 70-173 

326 Integrated Gas Spacer Cable: Type IGS 70-174 

I. General 70-174 

II. Installation 70-174 

III. Construction Specifications 70-174 

328 Medium Voltage Cable: Type MV 70-175 

I. General 70-175 

II. Installation 70-175 

III. Construction Specifications 70-175 

330 Metal-Clad Cable: Type MC 70-175 

I. General 70-175 

II. Installation 70-175 

III. Construction Specifications 70-177 

332 Mineral-Insulated, Metal-Sheathed Cable: 

Type MI 70-177 

I. General 70-177 

11. Installation 70-177 

III. Construction Specifications 70-178 

334 Nonmetallic-Sheathed Cable: Types NM, 

NMC, andNMS 70-178 

I. General 70-178 

II. Installation 70-179 

III. Construction Specifications 70—180 

336 Power and Control Tray Cable: Type TC ....70-181 

I. General 70-181 

II. Installation 70-181 

III. Construction Specifications 70-182 

338 Service-Entrance Cable: Types SE and 

USE 70-182 

I. General 70-182 

II. Installation 70-182 

III. Construction 70-183 

340 Underground Feeder and Branch-Circuit 

Cable: Type UF 70-183 

I. General 70-183 

II. Installation 70-183 



ARTICLE 

III. Construction Specifications 70-184 

342 Intermediate Metal Conduit: Type IMC 70-184 

I. General 70-184 

II. Installation 70-184 

III. Construction Specifications 70-185 

344 Rigid Metal Conduit: Type RMC 70-185 

I. General 70-185 

II. Installation 70-185 

III. Construction Specifications 70-187 

348 Flexible Metal Conduit: Type FMC 70-1 87 

I. General 70-187 

II. Installation 70-187 

350 Liquidtight Flexible Metal Conduit: Type 

LFMC 70-189 

I. General 70-189 

II. Installation 70-189 

III. Construction Specifications 70-190 

352 Rigid Nonmetallic Conduit: Type RNC 70-190 

I. General 70-190 

II. Installation 70-190 

III. Construction Specifications 70-193 

353 High Density Polyethylene Conduit: Type 

HDPE Conduit 70-193 

I. General 70-193 

II. Installation 70-193 

III. Construction Specifications 70-194 

354 Nonmetallic Underground Conduit with 
Conductors: Type NUCC 70-194 

I. General 70-194 

11. Installation 70-194 

III. Construction Specifications 70-195 

356 Liquidtight Flexible Nonmetallic Conduit: 

TypeLFNC 70-195 

I. General 70-195 

II. Installation 70-196 

III. Construction Specifications 70-197 

358 Electrical Metallic Tubing: Type EMT 70-197 

I. General 70-197 

II. Installation 70-197 

III. Construction Specifications 70-198 

360 Flexible Metallic Tubing: Type FMT 70-198 

I. General 70-198 

II. Installation 70-199 

III. Construction Specifications 70-199 

362 Electrical Nonmetallic Tubing: Type ENT ...70-200 

I. General 70-200 

II. Installation 70-200 

III. Construction Specifications 70-201 



2005 Edition 



NATIONAL ELECTRICAL CODE 



70-3 



CONTENTS 



ARTICLE 

366 Auxiliary Gutters 70-202 

I. General 70-202 

II. Installation 70-202 

III. Construction Specifications 70-203 

368 Busways 70-204 

I. General Requirements 70-204 

II. Installation 70-204 

III. Construction 70-205 

IV. Requirements for Over 600 Volts, 

Nominal 70-205 

370 Cablebus 70-206 

372 Cellular Concrete Floor Raceways 70-207 

374 Cellular Metal Floor Raceways 70-208 

I. Installation 70-209 

II. Construction Specifications 70-209 

376 Metal Wireways 70-209 

I. General 70-209 

II. Installation 70-209 

III. Construction Specifications 70-210 

378 Nonmetallic Wireways 70-210 

I. General 70-210 

II. Installation 70-211 

III. Construction Specifications 70-212 

380 Multioutlet Assembly 70-212 

382 Nonmetallic Extensions 70-212 

I. General 70-212 

II. Installation 70-212 

384 Strut-Type Channel Raceway 70-2 1 3 

I. Genera] 70-213 

n. Installation 70-213 

III. Construction Specifications 70-214 

386 Surface Metal Raceways 70-214 

I. General 70-214 

II. Installation 70-214 

III. Construction Specifications 70-215 

388 Surface Nonmetallic Raceways 70-215 

I. General 70-215 

II. Installation 70-215 

III. Construction Specifications 70-216 

390 Underfloor Raceways 70-2 16 

392 Cable Trays 70-217 

394 Concealed Knob-and-Tube Wiring 70-224 

I. General 70-224 

II. Installation 70-224 

III. Construction Specifications 70-225 

396 Messenger Supported Wiring 70-225 

I. General 70-225 

II. Installation 70-225 



ARTICLE 

398 Open Wiring on Insulators 70-226 

I. General 70-226 

II. Installation 70-226 

III. Construction Specifications 70-227 

Chapter 4 Equipment for General Use 

400 Flexible Cords and Cables 70-228 

I. General 70-228 

II. Construction Specifications 70-238 

III. Portable Cables Over 600 Volts, 

Nominal 70-238 

402 Fixture Wires 70-239 

404 Switches 70-242 

I. Installation 70-242 

II. Construction Specifications 70-245 

406 Receptacles, Cord Connectors, and 

Attachment Plugs (Caps) 70-245 

408 Switchboards and Panelboards 70-248 

I. General 70-248 

II. Switchboards 70-249 

III. Panelboards 70-250 

IV. Construction Specifications 70-251 

409 Industrial Control Panels 70-252 

I. General 70-252 

II. Installation 70-252 

III. Construction Specifications 70-253 

410 Luminaires (Lighting Fixtures), 

Lampholders, and Lamps 70-254 

I. General 70-254 

II. Luminaire (Fixture) Locations 70—254 

III. Provisions at Luminaire (Fixture) 

Outlet Boxes, Canopies, and Pans 70-255 

IV. Luminaire (Fixture) Supports 70-256 

V. Grounding 70-257 

VI. Wiring of Luminaires (Fixtures) 70-257 

VII. Construction of Luminaires (Fixtures) 70-259 

VIII. Installation of Lampholders 70-260 

IX. Construction of Lampholders 70-260 

X. Lamps and Auxiliary Equipment 70—260 

XI. Special Provisions for Flush and 

Recessed Luminaires (Fixtures) 70-260 

XII. Construction of Flush and Recessed 

Luminaires (Fixtures) 70-261 

XIII. Special Provisions for 
Electric-Discharge Lighting Systems of 

1000 Volts or Less 70-261 

XIV. Special Provisions for 
Electric-Discharge Lighting Systems of 

More Than 1000 Volts 70-263 

XV. Lighting Track 70-263 

XVI. Decorative Lighting and Similar 

Accessories 70-264 

411 Lighting Systems Operating at 30 Volts or 

Less 70-264 






• 



70^ 



NATIONAL ELECTRICAL CODE 2005 Edition 



CONTENTS 



• 



• 



ARTICLE 

422 Appliances 70-265 

I. General 70-265 

II. Installation 70-265 

III. Disconnecting Means 70-267 

IV. Construction 70-268 

V. Marking 70-269 

424 Fixed Electric Space-Heating Equipment 70-270 

I. General 70-270 

II. Installation 70-270 

III. Control and Protection of Fixed 

Electric Space-Heating Equipment 70-270 

IV. Marking of Heating Equipment 70-272 

V. Electric Space-Heating Cables 70-272 

VI. Duct Heaters 70-274 

VII. Resistance-Type Boilers 70-274 

VIII. Electrode-Type Boilers 70-275 

IX. Electric Radiant Heating Panels and 

Heating Panel Sets 70-276 

426 Fixed Outdoor Electric Deicing and 
Snow-Melting Equipment 70-278 

I. General 70-278 

II. Installation 70-279 

III. Resistance Heating Elements 70-279 

IV. Impedance Heating 70-280 

V. Skin-Effect Heating 70-280 

VI. Control and Protection 70-280 

427 Fixed Electric Heating Equipment for 

Pipelines and Vessels 70-28 1 

I. General 70-281 

II. Installation 70-282 

III. Resistance Heating Elements 70-282 

IV. Impedance Heating 70-283 

V. Induction Heating 70-283 

VI. Skin-Effect Heating 70-283 

VII. Control and Protection 70-283 

430 Motors, Motor Circuits, and Controllers 70-284 

I. General 70-284 

II. Motor Circuit Conductors 70-290 

III. Motor and Branch-Circuit Overload 

Protection 70-292 

IV. Motor Branch-Circuit Short-Circuit and ' 
Ground-Fault Protection 70-295 

V. Motor Feeder Short-Circuit and 

Ground-Fault Protection 70-298 

VI. Motor Control Circuits 70-299 

VII. Motor Controllers 70-300 

VIII. Motor Control Centers 70-302 

IX. Disconnecting Means 70-304 

X. Adjustable-Speed Drive Systems 70-307 

XI. Over 600 Volts, Nominal 70-308 

XII. Protection of Live Parts — All 

Voltages 70-308 

XIII. Grounding — All Voltages 70-309 

XIV. Tables 70-310 

440 Air-Conditioning and Refrigerating 

Equipment 70-313 

I. General 70-313 



ARTICLE 

II. Disconnecting Means 70-3 1 5 

III. Branch-Circuit Short-Circuit and 

Ground-Fault Protection 70-3 16 

IV. Branch-Circuit Conductors 70-3 17 

V. Controllers for Motor-Compressors 70-3 1 7 

VI. Motor-Compressor and Branch-Circuit 

Overload Protection 70-318 

VII. Provisions for Room Air Conditioners 70-319 

445 Generators 70-319 

450 Transformers and Transformer Vaults 

(Including Secondary Ties) 70-321 

I. General Provisions 70-321 

II. Specific Provisions Applicable to 

Different Types of Transformers 70-325 

III. Transformer Vaults 70-327 

455 Phase Converters 70-328 

I. General 70-328 

II. Specific Provisions Apphcable to 

Different Types of Phase Converters 70-329 

460 Capacitors 70-329 

I. 600 Volts, Nominal, and Under 70-330 

II. Over 600 Volts, Nominal 70-330 

470 Resistors and Reactors 70-33 1 

I. 600 Volts, Nominal, and Under 70-33 1 

II. Over 600 Volts, Nominal 70-332 

480 Storage Batteries 70-332 

490 Equipment, Over 600 Volts, Nominal 70-333 

I. General 70-333 

II. Equipment — Specific Provisions 70-333 

III. Equipment — Metal-Enclosed Power 
Switchgear and Industrial Control 

Assemblies 70-336 

IV. Mobile and Portable Equipment 70-338 

V. Electrode-Type Boilers 70-338 

Chapter 5 Special Occupancies 

500 Hazardous (Classified) Locations, Classes 

L II, and III, Divisions 1 and 2 70-340 

501 Class I Locations 70-348 

L General 70-348 

IL Wiring 70-348 

m. Equipment 70-354 

502 Class II Locations 70-358 

L Genera] 70-358 

II. Wiring 70-358 

III. Equipment 70-360 

503 Class in Locations 70-364 

I. General 70-364 

II. Wiring 70-364 

III. Equipment 70-365 

504 Intrinsically Safe Systems 70-367 



2005 Edition NATIONAL ELECTRICAL CODE 



70-5 



CONTENTS 



ARTICLE 

505 Class I, Zone 0, 1 , and 2 Locations 70-369 

506 Zone 20, 21, and 22 Locations for 

Combustible Dusts, Fibers, and Flyings 70-383 

510 Hazardous (Classified) Locations — 

Specific 70-388 

511 Commercial Garages, Repair and Storage .... 70-388 

513 Aircraft Hangars 70-391 

514 Motor Fuel Dispensing Facilities 70-393 

515 Bulk Storage Plants 70-397 

516 Spray Application, Dipping, and Coating 

Processes 70-402 

517 Health Care Facilities 70-408 

L General 70^08 

II. Wiring and Protection 70-410 

III. Essential Electrical System 70-413 

IV. Inhalation Anesthetizing Locations 70^20 

V. X-Ray Installations 70-422 

VI. Communications, Signaling Systems, 
Data Systems, Fire Alarm Systems, and 

Systems Less Than 120 Volts, Nominal .... 70-424 

VII. Isolated Power Systems 70-424 

518 Assembly Occupancies 70-425 

520 Theaters, Audience Areas of Motion 
Picture and Television Studios, 

Performance Areas, and Similar Locations . . . 70^27 

I. General 70-427 

II. Fixed Stage Switchboards 7Q-428 

III. Fixed Stage Equipment Other Than 
Switchboards 70-429 

IV. Portable Switchboards on Stage 70-430 

V. Portable Stage Equipment Other Than 

Switchboards 70-433 

VI. Dressing Rooms 70^34 

VIL Grounding 70-435 

525 Carnivals, Circuses, Fairs, and Similar 

Events 70-435 

I. General Requirements 70—435 

II. Power Sources 70^35 

m. Wiring Methods 70-435 

IV Grounding and Bonding 70^36 

530 Motion Picture and Television Studios 

and Similar Locations 70^37 

L General 70-437 

IL Stage or Set 70-437 

IIL Dressing Rooms 70^40 

IV. Viewing, Cutting, and Patching Tables .... 70-440 

V. Cellulose Nitrate Film Storage Vaults 70-440 

VI. Substations 70-440 

540 Motion Picture Projection Rooms 70-440 

L General 70-440 

II. Equipment and Projectors of the 

Professional Type 70^41 



ARTICLE 

III. Nonprofessional Projectors 10-^42 

IV. Audio Signal Processing, Amplification, 

and Reproduction Equipment 10—442 

545 Manufactured Buildings 70-442 

547 Agricultural Buildings 70-443 

550 Mobile Homes, Manufactured Homes, and 

Mobile Home Parks 70^46 

I. General 70^46 

II. Mobile and Manufactured Homes 70^47 

III. Services and Feeders 70-454 

551 Recreational Vehicles and Recreational 

Vehicle Parks 70-455 

L General 70^55 

II. Combination Electrical Systems 70-456 

m. Other Power Sources 70-457 

IV. Nominal 120- Volt or 120/240- Volt 

Systems 70^58 

V. Factory Tests 70^64 

VI. Recreational Vehicle Parks 70-465 

552 Park Trailers 70-467 

L General 70-467 

II. Low-Voltage Systems 70^67 

III. Combination Electrical Systems 70^69 

IV. Nominal 120- Volt or 120/240- Volt 

Systems 70^69 

V. Factory Tests 10-416 

553 Floating Buildings 70^76 

L General 70^76 

II. Services and Feeders 70-476 

III. Grounding 70-477 

555 Marinas and Boatyards 70^77 

590 Temporary Installations 70^80 

Chapter 6 Special Equipment 

600 Electric Signs and Outline Lighting 70-483 

L General 70-483 

II. Field-Installed Skeleton Tubing 70-486 

604 Manufactured Wiring Systems 70-487 

605 Office Furnishings (Consisting of Lighting 
Accessories and Wired Partitions) 70-488 

610 Cranes and Hoists 70-489 

L General 70^89 

n. Wiring 70^89 

m. Contact Conductors 70^92 

IV. Disconnecting Means 10—492 

V. Overcurrent Protection 70^93 

VL Control 70^94 

VII. Grounding 70-494 



• 



70-6 



NATIONAL ELECTRICAL CODE 2005 Edition 



CONTENTS 



• 



• 



• 



ARTICLE 

620 Elevators, Dumbwaiters, Escalators, 
Moving Walks, Wheelchair Lifts, and 

Stairway Chair Lifts 70-494 

I. General 70-494 

n. Conductors 70-496 

m. Wiring 70^97 

IV. Installation of Conductors 70-500 

V. Traveling Cables 70-500 

VI. Disconnecting Means and Control 70-501 

VII. Overcurrent Protection 70-502 

VIII. Machine Rooms, Control Rooms, 

Machinery Spaces, and Control Spaces .... 70-503 

IX. Grounding 70-503 

X. Emergency and Standby Power 

Systems 70-503 

625 Electric Vehicle Charging System 70-504 

I. General 70-504 

II. Wiring Methods 70-504 

III. Equipment Construction 70-505 

IV. Control and Protection 70-505 

V. Electric Vehicle Supply Equipment 

Locations 70-506 

630 Electric Welders 70-507 

L General 70-507 

n. Arc Welders 70-508 

IIL Resistance Welders 70-509 

IV. Welding Cable 70-509 

640 Audio Signal Processing, Amplification, 

and Reproduction Equipment 70-5 10 

L General 70-510 

II. Permanent Audio System Installations 70-513 

III. Portable and Temporary Audio System 

Installations 70-514 

645 Information Technology Equipment 70-5 1 5 

647 Sensitive Electronic Equipment 70-5 1 6 

650 Pipe Organs 70-518 

660 X-Ray Equipment 70-518 

I. General 70-518 

IL Control 70-519 

III. Transformers and Capacitors 70-520 

IV. Guarding and Grounding 70-520 

665 Induction and Dielectric Heating 

Equipment 70-520 

L General 70-520 

II. Guarding, Grounding, and Labeling 70-521 

668 Electrolytic Cells 70-522 

669 Electroplating 70-524 

670 Industrial Machinery 70-525 

675 Electrically Driven or Controlled 

Irrigation Machines 70-526 

I. General 70-526 

II. Center Pivot Irrigation Machines 70-528 



ARTICLE 

680 Swimming Pools, Fountains, and Similar 

Installations 70-528 

L General 70-528 

II. Permanently Installed Pools 70-531 

in. Storable Pools 70-538 

IV Spas and Hot Tubs 70-538 

V. Fountains 70-540 

VI. Pools and Tubs for Therapeutic Use 70-542 

VII. Hydromassage Bathtubs 70-542 

682 Natural and Artificially Made Bodies of 

Water 70-543 

I. General 70-543 

n. Installation 70-543 

in. Grounding and Bonding 70-544 

685 Integrated Electrical Systems 70-544 

I. General 70-544 

II. Orderly Shutdown 70-545 

690 Solar Photovoltaic Systems 70-545 

I. Genera] 70-545 

II. Circuit Requirements 70-547 

III. Disconnecting Means 70-549 

IV Wiring Methods 70-551 

V. Grounding 70-552 

VL Marking 70-553 

VII. Connection to Other Sources 70-554 

Vm. Storage Batteries 70-554 

IX. Systems Over 600 Volts 70-556 

692 Fuel Cell Systems 70-556 

L General 70-556 

II. Circuit Requirements 70-556 

III. Disconnecting Means 70-557 

IV. Wiring Methods 70-557 

V. Grounding 70-557 

VI. Marking 70-558 

VII. Connection to Other Circuits 70-558 

VIII. Outputs Over 600 Volts 70-559 

695 Fire Pumps 70-559 

Chapter 7 Special Conditions 

700 Emergency Systems 70-563 

I. General 70-563 

II. Circuit Wiring 70-564 

III. Sources of Power 70-565 

IV. Emergency System Circuits for 

Lighting and Power 70-566 

V. Control — Emergency Lighting 

Circuits 70-567 

VI. Overcurrent Protection 70-567 

701 Legally Required Standby Systems 70-567 

I. General 70-567 

II. Circuit Wiring 70-568 

m. Sources of Power 70-569 

IV. Overcurrent Protection 70-570 



2005 Edition 



NATIONAL ELECTRICAL CODE 



70-7 



CONTENTS 



ARTICLE 

702 Optional Standby Systems 70-570 

I. General 70-570 

II. Circuit Wiring 70-571 

III. Grounding 70-571 

IV. Sources of Power 70-571 

705 Interconnected Electric Power Production 

Sources 70-57 1 

720 Circuits and Equipment Operating at Less 

Than 50 Volts 70-573 

725 Class 1, Class 2, and Class 3 

Remote-Control, Signaling, and 

Power-Limited Circuits 70-573 

L General 70-573 

IL Class 1 Circuits 70-575 

III. Class 2 and Class 3 Circuits 70-577 

IV. Listing Requirements 70-581 

727 Instrumentation Tray Cable: Type ITC 70-583 

760 Fire Alarm Systems 70-584 

L General 70-584 

II. Non-Power-Limited Fire Alarm 

(NPLFA) Circuits 70-585 

III. Power-Limited Fire Alarm (PLFA) 

Circuits 70-587 

IV. Listing Requirements 70-590 

770 Optical Fiber Cables and Raceways 70-592 

L General 70-592 

II. Protection 70-593 

III. Cables Within Buildings 70-593 

IV. Listing Requirements 70-595 

780 Closed-Loop and Programmed Power 

Distribution 70-596 

Chapter 8 Communications Systems 

800 Communications Circuits 70-597 

I. General 70-597 

II. Wires and Cables Outside and Entering 

Buildings 70-598 

m. Protection 70-599 

IV. Grounding Methods 70-600 

V. Communications Wires and Cables 

Within Buildings 70-601 

VI. Listing Requirements 70-603 

810 Radio, and Television Equipment 70-606 

I. General 70-606 

II. Receiving Equipment — Antenna 

Systems 70-606 

III. Amateur Transmitting and Receiving 

Stations — Antenna Systems 70-608 

IV. Interior Installation — Transmitting 

Stations 70-609 

820 Community Antenna Television and Radio 

Distribution Systems 70-609 

I. General 70-609 



ARTICLE 

II. Cables Outside and Entering Buildings .... 70-610 

III. Protection 70-611 

IV. Grounding Methods 70-611 

V. Cables Within Buildings 70-612 

VI. Listing Requirements 70-614 

830 Network-Powered Broadband 

Communications Systems 70-615 

I. General 70-615 

II. Cables Outside and Entering Buildings .... 70-617 

III. Protection 70-619 

IV. Grounding Methods 70-620 

V. Wiring Methods Within Buildings 70-621 

VI. Listing Requirements 70-623 

TABLES 

Chapter 9 Tables 

1 Percent of Cross Section of Conduit and 

Tubing for Conductors 70-625 

2 Radius of Conduit and Tubing Bends 70-625 

4 Dimensions and Percent Area of Conduit 
and Tubing (Areas of Conduit or Tubing 
for the Combinations of Wires Permitted 

in Table 1, Chapter 9) 70-626 

5 Dimensions of Insulated Conductors and 

Fixture Wires 70-630 

5A Compact Aluminum Building Wire 

Nominal Dimensions and Areas 70-634 

8 Conductor Properties 70-634 

9 Alternating-Current Resistance and 
Reactance for 600- Volt Cables, 3-Phase, 
60 Hz, 75°C (167°F) — Three Single 

Conductors in Conduit 70—636 

11(A) Class 2 and Class 3 Alternating-Current 

Power Source Limitations 70-638 

11(B) Class 2 and Class 3 Direct-Current Power 

Source Limitations 70-638 

12(A) PLFA Alternating-Current Power Source 

Limitations 70-639 

12(B) PLFA Direct-Current Power Source 

Limitations 70-639 

AnnexA 70-640 

Annex B 70-643 

Annexe 70-657 

AnnexD 70-717 

Annex E 70-726 

AnnexF 70-728 

Annex G 70-731 

Index 70-738 



• 



70-8 



NATIONAL ELECTRICAL CODE 2005 Edition 



NATIONAL ELECTRICAL CODE COMMITTEE 



NATIONAL ELECTRICAL CODE COMMITTEE 

These lists represent the membership at the time the Committee was balloted on the final text of this edition. Since 
that time, changes in the membership may have occurred. A key to classifications is found at the back of this 
document. 



Technical Correlating Committee 

James W. Carpenter, Chair 

International Association of Electrical Inspectors, TX [E] 

Rep. International Association of Electrical Inspectors 



• 



Mark W. Earley, Secretary 
NFPA, MA 
(nonvoting) 

Jean A. O'Connor, Recording Secretary 
NFPA, MA 
(nonvoting) 



James E. Brunssen, Telcordia, NJ [UT] 

Rep. Alliance for Telecommunications Industry Solutions 
Michael L Callanan, National Joint Apprentice & Training 
Committee, MD [L] 

Rep. International Brotherhood of Electrical Workers 
William R. Drake, Marinco, CA [M] 
John R. Kovacik, Underwriters Laboratories Incorporated, 
IL [RT] 
James T. Pauley, Square D Company, KY [M] 

Rep. National Electrical Manufacturers Association 
Michael D. Toman, MEGA Power Electrical Services, 
Incorporated, MD [IM] 

Rep. National Electrical Contractors Association 
John W. Troglia, Edison Electric Institute, WI [UT] 

Rep. Electric Light & Power Group/EEI 
Craig M. Wellman, DuPont Engineering, DE [U] 

Rep. American Chemistry Council 

Alternates 
Jeffrey Boksiner, Telcordia Technologies, Incorporated, 
NJ [UT] 

Rep. Alliance for Telecommunications Industry Solutions 

(Alt. to J. E. Brunssen) 
Philip H. Cox, Bigelow, AR [E] 

Rep. International Association of Electrical Inspectors 

(Alt. to J. W. Carpenter) 



James M. Daly, General Cable, NJ [M] 

Rep. National Electrical Manufacturers Association 

(Alt. to J. T. Pauley) 
Stanley J. Folz, Folz Electric, Incorporated, IL [IM] 

Rep. National Electrical Contractors Association 

(Alt. to M. D. Toman) 
Palmer L. Hickman, National Joint Apprentice & Training 
Committee, MD [L] 

Rep. International Brotherhood of Electrical Workers 

(Alt. to M. I. Callanan) 
Neil F. LaBrake, Jr., Niagara Mohawk, a National Grid 
Company, NY [UT] 

Rep. Electric Light & Power Group/EEI 

(Alt. to J. W. Troglia) 
William M. Lewis, Eli Lilly & Company, IN [U] 

Rep. American Chemistry Council 

(Alt. to C. M. Wellman) 
Mark C. Ode, Underwriters Laboratories Incorporated, 
NC [RT] 

(Alt. to J. R. Kovacik) 

Nonvoting 

Richard G. Biermann, Biermann Electric Company, 

Incorporated, lA [IM] 

D. Harold Ware, Libra Electric Company, OK [IM] 



CODE-MAKING PANEL NO. 1 
Articles 90, 100, 110, Annex A, Annex G 



John D. Minick, Chair 

National Electrical Manufacturers Association, TX [M] 

Rep. National Electrical Manufacturers Association 



Michael A. Anthony, University of Michigan, MI [U] 
Rep. The Association of Higher Education Facilities 
Officers 

Louis A. Barrios, Jr., Shell Global Solutions, TX [U] 
Rep. American Chemistry Council 

David A. Dini, Underwriters Laboratories Incorporated, 

IL [RT] 

William T. Fiske, Intertek Testing Services NA, 

Incorporated, NY [RT] 



H. Landis Floyd H, The DuPont Company, DE [U] 

Rep. Institute of Electrical & Electronics Engineers, 

Incorporated 
Palmer L. Hickman, National Joint Apprentice & Training 
Committee, MD [L] 

Rep. International Brotherhood of Electrical Workers 
David L. Hittinger, lEC of Greater Cincinnati, OH [IM] 

Rep. Independent Electrical Contractors, Incorporated 



2005 Edition 



NATIONAL ELECTRICAL CODE 



70-9 



NATIONAL ELECTRICAL CODE COMMITTEE 



Randall R. McCarver, Telcordia Technologies, Incorporated, 
NJ [U] 

Rep. Alliance for Telecommunications Industry Solutions 
Lanny G. McMahill, City of Phoenix, AZ [E] 

Rep. International Association of Electrical Inspectors 
H. Brooke Stauffer, National Electrical Contractors 
Association, MD [IM] 

Rep. National Electrical Contractors Association 
John W. Troglia, Edison Electric Institute, WI [UT] 

Rep. Electric Light & Power Group/EEI 

Alternates 

Lawrence S. Ayer, Biz Com Electric, Incorporated, OH [IM] 

Rep. Independent Electrical Contractors, Incorporated 

(Alt. to D. L. Hittinger) 
Kenneth P. Boyce, Underwriters Laboratories Incorporated, 
IL [RT] 

(Ah. to D. A. Dini) 
Ernest J. Gallo, Telcordia Technologies, Incorporated, NJ [U] 

Rep. Alliance for Telecommunications Industry Solutions 

(Alt. to R. R. McCarver) 
Russell J. Helmick, Jr., City of Irvine, CA [E] 

Rep. International Association of Electrical Inspectors 

(Ah. to L. G. McMahill) 



Neil F. LaBrake, Jr., Niagara Mohawk, a National Grid 
Company, NY [UT] 

Rep. Electric Light & Power Group/EEI 

(Alt. to J. W. Troglia) 
Donald H. McCullough, II, Westinghouse Savannah River 
Company, SC [U] 

Rep. Institute of Electrical & Electronics Engineers, 

Incorporated 

(Alt. to H. L. Floyd II) 
Gil Moniz, National Electrical Manufacturers Association, 
MA[M] 

Rep. National Electrical Manufacturers 

Association 

(Alt. to J. D. Minick) 
Rick Munch, Frischhertz Electric Company, LA [L] 

Rep. International Brotherhood of Electrical 

Workers 

(Alt. to P. L. Hickman) 

Nonvoting 

Ark Tsisserev, City of Vancouver, BC, Canada 

Rep. Canadian Standards Association International 



CODE-MAKING PANEL NO. 2 
Articles 210, 215, 220, Annex D, Examples 1 through 6 



Raymond W. Weber, Chair 

State of Wisconsin, WI [E] 

Rep. International Association of Electrical Inspectors 



Richard W. Becker, Engineered Electrical Systems, 
Incorporated, WA [U] 

Rep. Institute of Electrical & Electronics Engineers, 

Incorporated 
Frank Coluccio, New York City Department of Buildings, 
NY[E] 

Matthew D. Dobson, National Association of Home 
Builders, DC [U] 

Rep. National Association of Home Builders 
Thomas L. Harman, University of Houston/Clear Lake, TX 
[SE] 
Donald M. King, IBEW Local Union 313, DE [L] 

Rep. International Brotherhood of Electrical Workers 
Christopher P. O'Neil, National Grid USA Service 
Company, MA 

Rep. Electric Light & Power Group/EEI, MA 
James T. Pauley, Square D Company, KY [M] 

Rep. National Electrical Manufacturers Association 
Susan W. Porter, Underwriters Laboratories Incorporated, 
NY [RT] 
Joseph Patterson Roche, Celanese Acetate, SC [U] 

Rep. American Chemistry Council 
Albert F. Sidhom, U.S. Army Corps of Engineers, CA [U] 
Michael D. Toman, MEGA Power Electrical Services, 
Incorporated, MD [IM] 

Rep. National Electrical Contractors Association 
Robert G. Wilkinson, Independent Electrical Contractors of 
Texas Gulf Coast, TX [IM] 

Rep. Independent Electrical Contractors, Incorporated 

Alternates 
Kevin J. Brooks, IBEW Local Union 16, IN [L] 

Rep. International Brotherhood of Electrical Workers 
(Alt. to D. M King) 



Ernest S. Broome, City of Knoxville, TN [E] 

Rep. International Association of Electrical Inspectors 

(Alt. to R. W. Weber) 
James R. Jones, University of Alabama at Birmingham, AL 
[U] 

Rep. Institute of Electrical & Electronics Engineers, 

Incorporated 

(Alt. to R. W. Becker) 
Daniel J. Kissane, Pass & Seymour/Legrand, NY [M] 

Rep. National Electrical Manufacturers Association 

(Alt. to J. T. Pauley) 
Brian J. Nenninger, The Dow Chemical Company, TX [U] 

Rep. American Chemistry Council 

(Alt. to J. P Roche) 
Clifford L. Rediger, Independent Electrical Contractors 
Training Fund, CO [IM] 

Rep. Independent Electrical Contractors, Incorporated 

(Alt. to R. G. Wilkinson) 
Richard V. Wagner, Underwriters Laboratories Incorporated, 
NY [RT] 

(Alt. to S. W. Porter) 
Joseph E. Wiehagen, National Association of Home 
Builders, MD [U] 

Rep. National Association of Home Builders 

(Alt. to M. D. Dobson) 

Nonvoting 

Douglas A. Lee, U.S. Consumer Product Safety 
Commission, MD [C] 

Andrew M. Trotta, U.S. Consumer Product Safety 
Commission, MD [C] 
(Alt. to D. A. Lee) 



70-10 



NATIONAL ELECTRICAL CODE 2005 Edition 



NATIONAL ELECTRICAL CODE COMMITTEE 



CODE-MAKING PANEL NO. 3 
Articles 300, 590, 720, 725, 727, 760, Chapter 9, Tables 11(a) and (b), and Tables 12(a) and (b) 



Richard P. Owen, Chair 

City of St. Paul, MN [E] 

Rep. International Association of Electrical Inspectors 



Lawrence S. Ayer, Biz Com Electric, Incorporated, OH [IM] 

Rep. Independent Electrical Contractors, Incorporated 
Paul J, Casparro, Scranton Electricians lATC, PA [L] 

Rep. International Brotherhood of Electrical Workers 
Les Easter, Allied Tube and Conduit, IL [M] 

Rep. National Electrical Manufacturers Association 
Sanford E. Egesdal, Egesdal Associates PLC, MN [M] 

Rep. Automatic Fire Alarm Association, Incorporated 
Thomas J, Guida, Underwriters Laboratories, Inc., NY [RT] 
Dennis B. Horman, PacifiCorp, UT [UT] 

Rep. Electric Light & Power Group/EEI 
Ray R, Keden, ERICO, Incorporated, CA [M] 

Rep. Building Industry Consulting Services International 
Ronald E. Maassen, Lemberg Electric Company, 
Incorporated, WI [IM] 

Rep. National Electrical Contractors Association 
Steven J. Owen, Steven J. Owen, Incorporated, AL [IM] 

Rep. Associated Builders and Contractors, Incorporated 
David A. Pace, Olin Corporation, AL [U] 

Rep. American Chemistry Council 
Melvin K. Sanders, Things Electrical Company, 
Incorporated (TECo., Incorporated), lA [U] 

Rep. Institute of Electrical & Electronics Engineers, 

Incorporated 
John E. Sleights, Travelers Insurance, CT [I] 

Alternates 

Mark E Christian, Chattanooga Electrical JATC, TN [L] 

Rep. International Brotherhood of Electrical Workers 

(Alt. to P I. Casparro) 
Dr. Shane M. Clary, Bay Alarm Company, Incorporated, 
CA[M] 

Rep. Automatic Fire Alarm Association, Incorporated 

(Alt. to S. E. Egesdal) 



Adam D. Corbin, Corbin Electrical Services, Incorporated, 
NJ [IM] 

Rep. Independent Electrical Contractors, Inc. 

(Alt. to L. S. Ayer) 
John C. Hudak, Old Forge, PA [E] 

Rep. International Association of Electrical Inspectors 

(Alt. to R. P Owen) 
Danny Liggett, DuPont Engineering, DE [U] 

Rep. American Chemistry Council 

(Alt. to D. A. Pace) 
Juan C. Menendez, Southern California Edison Company, 
CA [UT] 

Rep. Electric Light & Power Group/EEI 

(Alt. to D. B. Horman) 
T. David Mills, Bechtel Savannah River, Incorporated, 
SC [U] 

Rep. Institute of Electrical & Electronics Engineers, 

Incorporated 

(Alt. to M. K. Sanders) 
Mark C. Ode, Underwriters Laboratories Incorporated, 
NC [RT] 

(Alt. to T. J. Guida) 
Lorena Orbanic, Carlon, Lamson & Sessions, OH [M] 

Rep. Building Industry Consulting Services International 

(Alt. to R. R. Keden) 
Roger S. Passmore, Davis Electrical Constructors, 
Incorporated, SC [IM] 

Rep. Associated Builders and Contractors, Incorporated 

(Alt. to S. J. Owen) 
George A. Straniero, AFC Cable Systems, Incorporated, 
NJ [M] 

Rep. National Electrical Manufacturers Association 

(Alt. to L. Easter) 



CODE-MAKING PANEL NO. 4 
Articles 225, 230 



James M. Naughton, Chair 

IBEW Local Union 103, MA [L] 

Rep. International Brotherhood of Electrical Workers 



Malcolm Allison, Ferraz Shawmut, MA [M] 

C. John Beck, Pacific Gas and Electric Company, 

CA [UT] 

Rep. Electric Light & Power Group/EEI 
Robert J. Deaton, The Dow Chemical Company, TX [U] 

Rep. Institute of Electrical & Electronics Engineers, 

Incorporated 
Howard D. Hughes, Hughes Electric Company 
Incorporated, AR [IM] 

Rep. National Electrical Contractors Association 
William M. Lewis, Eli Lilly & Company, IN [U] 

Rep. American Chemistry Council 
Mark C. Ode, Underwriters Laboratories Incorporated, 
NC [RT] 

James J. Rogers, Towns of Oak Bluffs, Tisbury, West 
Tisbury, MA [E] 

Rep. International Association of Electrical Inspectors 



John W. Young, Siemens Energy & Automation, 
Incorporated, GA [M] 

Rep. National Electrical Manufacturers Association 
Vincent Zinnante, Advantage Electric, Incorporated, 
TX [IM] 

Rep. Independent Electrical Contractors, Incorporated 

Alternates 
Thomas L. Adams, Exelon Corporation, IL [UT] 

Rep. Electric Light & Power Group/EEI 

(Alt. to C. J. Beck) 
Ronald Breschini, Underwriters Laboratories Incorporated, 
CA [RT] 

(Alt. to M. C. Ode) 
Terry D. Cole, Hamer Electric, WA [IM] 

Rep. Independent Electrical Contractors, Incorporated 

(Alt. to V. Zinnante) 



2005 Edition NATIONAL ELECTRICAL CODE 



70-11 



NATIONAL ELECTRICAL CODE COMMITTEE 



Mark R. Hilbert, State of New Hampshire, NH [E] 

Rep. International Association of Electrical Inspectors 

(Alt. to J. J. Rogers) 
Philip M. Piqueira, General Electric Company, CT [M] 

Rep. National Electrical Manufacturers Association 

(Alt. to J. W. Young) 
Francis E. Rose, Jr., W. S. Nelson and Company, 
Incorporated, LA [U] 

Rep. Institute of Electrical & Electronics Engineers, 

Incorporated 

(Alt. to R. J. Deaton) 



John Sigmund, PPG Industries, Incorporated, 
LA[U] 

Rep. American Chemistry Council 

(Alt. to W. M. Lewis) 
Mark H. Sumrall, IBEW Local Union 527, TX [L] 

Rep. International Brotherhood of Electrical 

Workers 

(Alt. to J. M. Naughton) 
Kent Walker, Ferraz Shawmut, MA [M] 

.(Alt. to M. Allison) 



CODE-MAKING PANEL NO. 5 
Articles 200, 250, 280, 285 



Ronald J. Toomer, Chair 

Toomer Electrical Company Incorporated, LA [IM] 

Rep. National Electrical Contractors Association 



Jeffrey Boksiner, Telcordia Technologies, Incorporated, 
NJ [UT] 

Rep. AUiance for Telecommunications Industry 

Solutions 
David T. Brender, Copper Development Association, 
Incorporated, NY [M] 

Rep. Copper Development Association, Incorporated 
Martin J. Brett, Jr., Wheatland Tube Company, 
NJ [M] 

Rep. American Iron and Steel Institute 
Elio L. Checca, U.S. Department of Labor, VA [E] 
Paul Dobrowsky, Eastman Kodak Company, NY [U] 

Rep. American Chemistry Council 
Gerald L. Hadeen, Tehachapi, CA [M] 

Rep. The Aluminum Association 
Dan Hammel, IBEW Local Union 704, lA [L] 

Rep. International Brotherhood of Electrical Workers 
Michael J. Johnston, International Association of Electrical 
Inspectors, TX [E] 

Rep. International Association of Electrical Inspectors 
Charles Mello, Electro-Test, Incorporated, OR [IM] 

Rep. InterNational Electrical Testing Association 

Incorporated 
Elliot Rappaport, Electro Technology Consultants, 
Incorporated, PL [U] 

Rep. Institute of Electrical & Electronics Engineers, 

Incorporated 
Ted G. Robertson, Robertson Electric, Incorporated, 
TX [IM] 

Rep. Independent Electrical Contractors, Incorporated 
Walter Skuggevig, Underwriters Laboratories Incorporated, 
NY [RT] 

Gregory J. Steinman, Thomas & Betts Corporation, 
TN [M] 

Rep. National Electrical Manufacturers Association 
Robert G. Stoll, Thomas Associates, Incorporated, 
OH [M] 

Rep. Power Tool Institute, Incorporated 
C. Douglas White, CenterPoint Energy, Incorporated, 
TX [UT] 

Rep. Electric Light & Power Group/EEI 



Alternates 
Martin D. Adams, Adams Electric, Incorporated, CO [IM] 

Rep. National Electrical Contractors Association 

(Alt. to R. J. Toomer) 
David A. Dini, Underwriters Laboratories Incorporated, IL 
[RT] 

(Alt. to W. Skuggevig) 
Timothy Edwards, Alcan Cable Company, GA [M] 

Rep. The Aluminum Association 

(Alt. to G. L. Hadeen) 
Robert Figlia, New York Board of Fire Underwriters, NY 
[E] 

Rep. International Association of Electrical Inspectors 

(Alt. to M. J. Johnston) 
G. Scott Harding, F. B. Harding, Incorporated, MD [IM] 

Rep. Independent Electrical Contractors, Incorporated 

(Alt. to T. G. Robertson) 
William J. Helfrich, U.S. Department of Labor, PA [E] 

(Alt. to E. L. Checca) 
Ronald Lai, FCI Electrical, NH [M] 

Rep. National Electrical Manufacturers Association 

(Alt. to G. J. Steinman) 
Paul J. LeVasseur, Bay City JEATC, MI [L] 

Rep. International Brotherhood of Electrical Workers 

(Alt. to D. Hammel) 
Richard E. Loyd, R & N Associates, AZ [M] 

Rep. American Iron and Steel Institute 

(Alt. to M. J. Brett, Jr.) 
Daleep C. Mohia, DCM Electrical Consulting Services, 
Incorporated, TX [U] 

Rep. Institute of Electrical & Electronics Engineers, 

Incorporated 

(Alt. to E. Rappaport) 
David Peot, Ryobi, SC [M] 

Rep. Power Tool Institute, Incorporated 

(Alt. to R. G. Stoll) 
J. PhiUp Simmons, Simmons Electrical Services, WA [M] 

Rep. Copper Development Association, Incorporated 

(Alt. to D. T. Brender) 
James S. Simpson, Southern Company Services, AL [UT] 

Rep. Electric Light & Power Group/EEI 

(Alt. to C. D.White) 



70-12 



NATIONAL ELECTRICAL CODE 2005 Edition 



NATIONAL ELECTRICAL CODE COMMITTEE 



CODE-MAKING PANEL NO. 6 
Articles 310, 400, 402, Chapter 9 Tables 5 through 9, Annex B 



Stephen J. Thorwegen, Jr., Chair 

Fisk Electric Company, TX [IM] 

Rep. National Electrical Contractors Association 



Robert Edwards, Alcan Aluminum Corporation, ON, 
Canada [M] 

Rep. The Aluminum Association 
Samuel B. Friedman, BICC General Cable Corporation, 
RI [M] 

Rep. National Electrical Manufacturers Association 
G. W. "Jerry" Kent, Kent Electric & Plumbing Systems, 
TX [IM] 

Rep. Independent Electrical Contractors, Incorporated 
David G. Komassa, WE Energies, WI [UT] 

Rep. Electric Light & Power Group/EEI 
William F. Laidler, South Shore VoTech/IBEW 223, MA [L] 

Rep. International Brotherhood of Electrical Workers 
Danny P. Liggett, DuPont Engineering, TX [U] 

Rep. American Chemistry Council 
L. Bruce McClung, Electrical Safety Consulting Services, 
Incorporated, WV [U] 

Rep. Institute of Electrical & Electronics Engineers, 

Incorporated 
Gran P. Post, City of Cuyahoga Falls, OH [E] 

Rep. International Association of Electrical Inspectors 
Austin D. Wetherell, Underwriters Laboratories 
Incorporated, NY [RT] 
Joseph S. Zimnoch, The Okonite Company, NJ [M] 

Rep. Copper Development Association, Incorporated 

Alternates 
Peter E. Bowers, SateUite Electric Company, Incorporated, 
MD [IM] 

Rep. Independent Electrical Contractors, Incorporated 

(Alt. to G. W. Kent) 



James M. Daly, General Cable, NJ [M] 

Rep. Copper Development Association, Incorporated 

(Alt. to J. S. Zimnoch) 
Robert L. Huddleston, Jr., Eastman Chemical Company, 
TN [U] 

Rep. American Chemistry Council 

(Alt. to D. P. Liggett) 
Philip T. Laudicini, Underwriters Laboratories Incorporated, 
NY [RT] 

(Alt. to A. D. Wetherell) 
Lowell S. Lisker, American Insulated Wire Corporation, 
RI [M] 

Rep. National Electrical Manufacturers Association 

(Alt. to S. B. Friedman) 
Paul R. Picard, AFC Cable Systems, Incorporated, MA [M] 

Rep. The Aluminum Association 

(Alt. to R. Edwards) 
Harry J. Sassaman, Forest Electric Corporation, NJ [IM] 

Rep. National Electrical Contractors Association 

(Alt. to S. J. Thorwegen, Jr.) 
John Stacey, City of St. Louis, MO [E] 

Rep. International Association of Electrical Inspectors 

(Alt. to O. R Post) 
Donald A. Voltz, Mustang Engineering, Incorporated, 
TX[U] 

Rep. Institute of Electrical & Electronics Engineers, 

Incorporated 

(Alt. to L. B. McClung) 
David R. Wellington, Toledo Electrical JATC, OH [L] 

Rep. International Brotherhood of Electrical Workers 

(Alt. to W. F. Laidler) 



CODE-MAKING PANEL NO. 7 
Articles 320, 322, 324, 326, 328, 330, 332, 334, 336, 338, 340, 382, 394, 396, 398 



Gaylen D. Rogers, Chair 

State of Utah, UT [E] 

Rep. International Association of Electrical Inspectors 



# 



James J. Anastasi, Intertek/ETL Semko, NY [RT] 
Harry C. Brown, IBEW Local Union 606, FL [L] 

Rep. International Brotherhood of Electrical 

Workers 
John J. Cangemi, Underwriters Laboratories Incorporated, 
NY [RT] 
James M. Daly, General Cable, NJ [M] 

Rep. National Electrical Manufacturers Association 
Chris J. Fahrenthold, Encompass Electrical Technologies, 
TX [IM] 

Rep. Independent Electrical Contractors, Incorporated 
Robert L, Gotham, Rose City Electric Company, 
Incorporated, OR [IM] 

Rep. National Electrical Contractors Association 
Herman J. Hall, Austin, TX [M] 

Rep. Society of the Plastics Industry Incorporated 
Ronald G. Nickson, National Multi Housing Council, 
DC [U] 

Rep. National Multi Housing Council 
Bruce W. Nutt, Oncor, TX [UT] 

Rep. Electric Light & Power Group/EEI 



Gregory L. Runyon, Eli Lilly and Company, IN [U] 

Rep. American Chemistry Council 
David E. Schumacher, All County Electric Company, 
IA[IM] 

Rep. Associated Builders and Contractors, Incorporated 
H. R. Stewart, HRS Consulting, TX [U] 

Rep. Institute of Electrical & Electronics Engineers, 

Incorporated 
George A. Straniero, AFC Cable Systems, Incorporated, 
NJ [M] 

Rep. Copper Development Association, Incorporated 
Richard Temblador, Alflex Corporation, CA [M] 

Rep. The Aluminum Association 

Alternates 
William B. Crist, Houston Stafford Electric Company, 
TX [IM] 

Rep. Independent Electrical Contractors, Incorporated 

(Alt. to C. J. Fahrenthold) 
James D. Erwin, Celanese, Limited, TX [U] 

Rep. American Chemistry Council 

(Alt. to G. L. Runyon) 



2005 Edition 



NATIONAL ELECTRICAL CODE 



70-13 



NATIONAL ELECTRICAL CODE COMMITTEE 



James K. Hinrichs, State of Washington, WA [E] 

Rep. International Association of Electrical Inspectors 

(Alt. to G. D. Rogers) 
Samuel R. LaDart, City of Memphis, TN [L] 

Rep. International Brotherhood of Electrical Workers 

(Alt. to H. C. Brown) 
C. David Mercier, Southwire Company, GA [M] 

Rep. National Electrical Manufacturers Association 

(Alt. to J. M. Daly) 
Dennis A. Nielsen, Lawrence Berkeley National Laboratory, 
CA [U] 

Rep. Institute of Electrical & Electronics Engineers, 

Incorporated 

(Alt. to H. R. Stewart) 
Paul A. Orr, Underwriters Laboratories Incorporated, 
NY [RT] 

(Alt. to J. J. Cangemi) 



John W. "Wes" Ray, Duke Energy Corporation, NC [UT] 

Rep. Electric Light & Power Group/EEI 

(Alt. to B. W. Nutt) 
David K. Smith, Encore Wire Limited, TX [M] 

Rep. Copper Development Association, Incorporated 

(Alt. to G. A. Straniero) 
John Thomas Thompson, ABC Marathon Electrical 
Company, Incorporated, AL [IM] 

Rep. Associated Builders and Contractors, Incorporated 

(Alt. to D. E. Schumacher) 
Larry G. Watkins, Alcan Aluminum Corporation, GA [M] 

Rep. The Aluminum Association 

(Alt. to R. Temblador) 
Thomas H. Wood, Cecil B. Wood Incorporated, IL [IM] 

Rep. National Electrical Contractors Association 

(Alt. to R. L. Gotham) 



CODE-MAKING PANEL NO. 8 

Articles 342, 344, 348, 350, 352, 353, 354, 356, 358, 360, 362, 366, 368, 370, 372, 374, 376, 378, 380, 384, 
386, 388, 390, 392, Chapter 9 Tables 1 through 4, Annex C 



Julian R. Burns, Chair 

Burns Electrical/Quality Power Solutions, Incorporated, NC [IM] 

Rep. Independent Electrical Contractors, Incorporated 



John S. Corry, Corry Electric Incorporated, CA [IM] 

Rep. Associated Builders and Contractors, Incorporated 
Joseph G. Dabe, City of St. Paul, MN [L] 

Rep. International Brotherhood of Electrical Workers 
George R. Dauberger, Thomas & Betts Corporation, TN [M] 

Rep. National Electrical Manufacturers Association 
James C. Dollins, AFC Cable Systems, MA [M] 

Rep. The Aluminum Association 
Ronald E. Duren, PacifiCorp, WA [UT] 

Rep. Electric Light & Power Group/EEI 
M. Shan Griffith, Kelloff, Brown & Root, Incorporated, 
TX [U] 

Rep. Institute of Electrical & Electronics Engineers, 

Incorporated 
David H. Kendall, Carlon, Lamson & Sessions, OH [M] 

Rep. Society of the Plastics Industry Incorporated 
Wayne A. Lilly, City of Harrisonburg, VA [E] 

Rep. International Association of Electrical Inspectors 
Richard E. Loyd, R & N Associates, AZ [M] 

Rep. American Iron and Steel Institute 
Stephen P. Poholski, Newkirk Electric Associates, 
Incorporated, MI [IM] 

Rep. National Electrical Contractors Association 
Dennis L. Rowe, New York Board of Fire Underwriters, 
NY [E] 

Rep. New York Board of Fire Underwriters 
George F. Walbrecht, Underwriters Laboratories 
Incorporated, IL [RT] 

Alternates 

Richard Herman, Underwriters Laboratories Incorporated, 
IL [RT] 

(Alt. to G. E Walbrecht) 
Duane A. Carlson, PRS Consulting Engineers, WA [U] 

Rep. Institute of Electrical & Electronics Engineers, 

Incorporated 

(Alt. to M. S. Griffith) 



Charles W. Forsberg, Shaker Heights, OH [M] 

Rep. Society of the Plastics Industry Incorporated 

(Alt. to D. H. Kendall) 
Dr. Jack A. Gruber, Wheatland Tube Company, PA [M] 

Rep. American Iron and Steel Institute 

(Alt. to R. E. Loyd) 
James M. Imlah, City of Hillsboro, OR [E] 

Rep. International Association of Electrical Inspectors 

(Alt. to W. A. Lilly) 
Alan Manche, Schneider Electric/Square D Company, 
KY[M] 

Rep. National Electrical Manufacturers Association 

(Alt. to G. R. Dauberger) 
Jamie McNamara, City of St. Paul, MN [L] 

Rep. International Brotherhood of Electrical Workers 

(Alt. to J. G. Dabe) 
C. Ernest Reynolds, Hatfield-Reynolds Electric Company, 
AZ [IM] 

Rep. Independent Electrical Contractors, Incorporated 

(Alt. to J. R. Burns) 
Richard Temblador, Alfiex Corporation, CA [M] 

Rep. The Aluminum Association 

(Alt. to J. C. DoUins) 
Ronald J. Toomer, Toomer Electrical Company 
Incorporated, LA [IM] 

Rep. National Electrical Contractors Association 

(Alt. to S. R Poholski) 
James Van Den Heuvel, West Electric Incorporated, 
WI [IM] 

Rep. Associated Builders and Contractors, Incorporated 

(Alt. to J. S. Corry) 
Leslie R. Zielke, South Carolina Electric & Gas Company, 
SC [UT] 

Rep. Electric Light & Power Group/EEI 

(Alt. to R. E. Duren) 



m 



70-14 



NATIONAL ELECTRICAL CODE 2005 Edition 



NATIONAL ELECTRICAL CODE COMMITTEE 



CODE-MAKING PANEL NO. 9 
Articles 312, 314, 404, 408, 450, 490 



Timothy M. Croushore, Chair 

Allegheny Power, PA [UT] 

Rep. Electric Light & Power Group/EEI 



Jeflfery Bernson, IBEW Local Union 701, IL [L] 

Rep. International Brotherhood of Electrical Workers 
Hector R. de Vega, Fluor Daniel, TX [U] 

Rep. Associated Builders and Contractors, Incorporated 
Frederic P. Hartwell, Hartwell Electrical Services, MA [SE] 
Robert J. Kaemmerlen, Kaemmerlen Electric Company, 
MO [IM] 

Rep. National Electrical Contractors Association 
Jacob Killinger, Underwriters Laboratories Incorporated, 
IL[RT] 
Thomas J. LeMay, LeMay Electric, Incorporated, GA [IM] 

Rep. Independent Electrical Contractors, Incorporated 
Donald R. Olferdahl, North Dakota State Electrical Board, 
ND [E] 

Rep. International Association of Electrical Inspectors 
Bradford D. Rupp, Allied Moulded Products, Incorporated, 
OH [M] 

Rep. National Electrical Manufacturers Association 
Sukanta Sengupta, EMC Corporation, NJ [U] 

Rep. Institute of Electrical & Electronics Engineers, 

Incorporated 
Ralph H. Young, Eastman Chemical Company, TN [U] 

Rep. American Chemistry Council 

Alternates 

Rodney D. Belisle, NECA-IBEW Training Center, WA [L] 
Rep. International Brotherhood of Electrical Workers 
(Alt. to L. Bernson) 



Joseph M. Bolesina, Pinellas County Building Inspections, 
FL[E] 

Rep. International Association of Electrical Inspectors 

(Alt. to D. R. Offerdahl) 
Julian R. Burns, Burns Electrical/Quahty Power Solutions, 
Incorporated, NC [LM] 

Rep. Independent Electrical Contractors, Incorporated 

(Alt. to T J. LeMay) 
James C. Carroll, Square D Company, TN [M] 

Rep. National Electrical Manufacturers Association 

(Alt. to B. D. Rupp) 
Richard P. Fogarty, Consolidated Edison Company of NY, 
Incorporated, NY [UT] 

Rep. Electric Light & Power Group/EEI 

(Alt. to T. M. Croushore) 
Robert D. Osborne, Underwriters Laboratories Incorporated, 
NC [RT] 

(Alt. to J. Killinger) 
Jerome W. Seigel, West Hartford, CT [U] 

Rep. Institute of Electrical & Electronics Engineers, 

Incorporated 

(Alt. to S. Sengupta) 
Monte Szendre, Wilson Construction Company, OR [IM] 

Rep. National Electrical Contractors Association 

(Alt. to R. J. Kaemmerlen) 



CODE-MAKING PANEL NO. 10 
Articles 240, 780 



James T. Dollard, Jr., Chair 

IBEW Local Union 98, PA [L] 

Rep. International Brotherhood of Electrical Workers 



Charles K. Blizard, American Electrical Testing Company, 
Incorporated, MA [IM] 

Rep. InterNational Electrical Testing Association 

Incorporated 
Madeline Borthick, lEC of Houston, Incorporated, TX [IM] 

Rep. Independent Electrical Contractors, Incorporated 
Scott Cline, McMurtrey Electric, Incorporated, CA [IM] 

Rep. National Electrical Contractors Association 
Dennis M. Darling, Ayres, Lewis, Norris & May, 
Incorporated, MI [U] 

Rep. Institute of Electrical & Electronics Engineers, 

Incorporated 
Charles K. Eldridge, Indianapolis Power & Light Company, 
IN [UT] 

Rep. Electric Light & Power Group/EEI 
Carl J. Fredericks, The Dow Chemical Company, TX [U] 

Rep. American Chemistry Council 
C. W. Kimblin, Cutler-Hammer, Incorporated, PA [M] 

Rep. National Electrical Manufacturers Association 
Arden L. Munson, Hussmann Corporation, MO [M] 

Rep. Air-Conditioning and Refrigeration Institute 
George J. Ockuly, Chesterfield, MO [M] 
Gerald W. Williams, County of Ventura, California, CA [E] 

Rep. International Association of Electrical Inspectors 



John A. Zaplatosch, Underwriters Laboratories 
Incorporated, IL [RT] 

Alternates 

Robert R. Gage, Niagara Mohawk, A National Grid 
Company, NY [UT] 

Rep. Electric Light & Power Group/EEI 

(Alt. to C. K. Eldridge) 
George D. Gregory, Square D Company, lA [M] 

Rep. National Electrical Manufacturers Association 

(Alt. to C. W. Kimblin) 
Roderic L. Hageman, PRIT Service, Incorporated, IL [IM] 

Rep. InterNational Electrical Testing Association 

Incorporated 

(Alt. to C. K. Blizard) 
Charles D. Hughes, Westinghouse Savannah River 
Company, SC [U] 

Rep. Institute of Electrical & Electronics Engineers, 

Incorporated 

(Alt. to D. M. Darling) 
Robert J. Kauer, Middle Department Inspection Agency, 
Incorporated, PA [E] 

Rep. International Association of Electrical Inspectors 

(Alt. to G. W. Williams) 



2005 Edition NATIONAL ELECTRICAL CODE 



70-15 



NATIONAL ELECTRICAL CODE COMMITTEE 



Richard E. Lofton, II, IBEW Local Union 280, OR [L] 

Rep. International Brotherhood of Electrical Workers 

(Alt. to J. T. DoUard, Jr.) 
Robert W. Mount, Jr., Hussmann Corporation, MO [M] 

Rep. Air-Conditioning and Refrigeration Institute 

(Alt. to A. L. Munson) 
Paul J. Notarian, Underwriters Laboratories Incorporated, 
NY [RT] 

(Alt. to J. A. Zaplatosch) 
Vincent J. Saporita, Cooper Bussmann, MO [M] 

(Alt. to G. J. Ockuly) 



James R. Sicard, Shell Oil Company, TX [U] 

Rep. American Chemistry Council 

(Alt. to C. J. Fredericks) 
Steve A. Struble, Freeman's Electric Service, Incorporated, 
SD [IM] 

Rep. Independent Electrical Contractors, Incorporated 

(Alt. to M. Borthick) 

Nonvoting 

Ricli C. Gilmour, Canadian Standards Association (CSA), 
ON, Canada 



CODE-MAKING PANEL NO. 11 
Articles 409, 430, 440, 460, 470, Annex D, Example D8 



Wayne Brinkmeyer, Chair 

Biddle Electric Corporation, TX [IM] 

Rep. National Electrical Contractors Association 



Frederick Bried, Spring, TX [U] 

Rep. American Petroleum Institute 
Rick L. Bunch, Tecumseh Products Company, MI [M] 

Rep. Air-Conditioning and Refrigeration Institute 
Joe David Cox, Eastman Chemical Company, TN [U] 

Rep. American Chemistry Council 
Michael A. D'Amico, IBEW Local Union 488, CT [L] 

Rep. International Brotherhood of Electrical Workers 
Thomas J. Garvey, State of Wisconsin, WI [E] 

Rep. International Association of Electrical Inspectors 
Charles A. Goetz, Underwriters Laboratories Incorporated, 
IL [RT] 

Rep. Associated Builders and Contractors, Incorporated 
Paul E. Guidry, Fluor Enterprises, Incorporated, TX [U] 

Rep. Associated Builders & Contractors, Incorporated 
Leo H. Haas, Jr., CenterPoint Energy, Incorporated, 
TX, [UT] 

Rep. Electric Light & Power Group/EEI 
Vincent J. Saporita, Cooper Bussmann, MO [M] 
Lynn F. Saunders, General Motors WFG-Utilities Services, 
MI [U] 

Rep. Institute of Electrical & Electronics Engineers, 

Incorporated 
Lawrence E. Todd, Intertek Testing Services NA, 
Incorporated, OR [RT] 
Ron Widup, Shermco Industries, Incorporated, TX [IM] 

Rep. InterNational Electrical Testing Association 

Incorporated 
James R. Wright, Siemens Energy & Automation, 
Incorporated, IL [M] 

Rep. National Electrical Manufacturers Association 

Alternates 
Elwood J. Dodge, Addison Products Company, FL [M] 
Rep. Air-Conditioning and Refrigeration Institute 
(Alt. to R. L. Bunch) 



Ralph M. Esemplare, Consolidated Edison Company of 
New York, NY [UT] 

Rep. Electric Light & Power Group/EEI 

(Alt. to L. H. Haas, Jr.) 
James M. Fahey, IBEW Local Union 103, MA [L] 

Rep. International Brotherhood of Electrical Workers 

(Alt. to M. A. D'Amico) 
Stanley J. Folz, Folz Electric, Incorporated, IL [IM] 

Rep. National Electrical Contractors Association 

(Alt. to W. Brinkmeyer) 
William D. Glover, PPG Industries, Incorporated, WV [U] 

Rep. American Chemistry Council 

(Alt. to J. D. Cox) 
Paul S. Hamer, ChevronTexaco Corporation, CA [U] 

Rep. American Petroleum Institute 

(Alt. to R Bried) 
Robert J. Keough, Emerson Motor Company, MO [M] 

Rep. National Electrical Manufacturers Association 

(Alt. to J. R. Wright) 
Thomas E. Moore, Stark County Building Department, 
OH [E] 

Rep. International Association of Electrical Inspectors 

(Alt. to T J. Garvey) 
George J. Ockuly, Chesterfield, MO [M] 

(Alt. to V. J. Saporita) 
Frederic A. Salzman, Underwriters Laboratories 
Incorporated, IL [RT] 

(Alt. to C. A. Goetz) 
Arthur J. Smith, III, Waldemar S. Nelson & Company, 
Incorporated, LA [U] 

Rep. Institute of Electrical & Electronics Engineers, 

Incorporated 

(Alt. to L. F. Saunders) 

Nonvoting 

Nino Mancini, CSA International, ON, Canada 



70-16 



NATIONAL ELECTRICAL CODE 2005 Edition 



NATIONAL ELECTRICAL CODE COMMITTEE 



CODE-MAKING PANEL NO. 12 

Articles 610, 620, 625, 630, 640, 645, 647, 650, 660, 665, 668, 669, 670, 685, 
Annex D, Examples D9 and DIO 



Charles M. Trout, Chair 

Maron Electric Company, PL [IM] 

Rep. National Electrical Contractors Association 



Thomas M. Burke, Underwriters Laboratories Incorporated, 

CA [RT] 

Kent B. Givens, Aluminum Company of America, TX [M] 

Rep. The Aluminum Association 

(VL to 610, 625, 630, 645, 660, 665, 668, 669, 685) 
Ron L. Janikowski, City of Wausau, Wisconsin, WI [E] 

Rep. International Association of Electrical Inspectors 
Robert E. Johnson, ITE Safety, MA [U] 

Rep. Information Technology Industry Council 

(VL to 640, 645, 647, 685) 
Robert A. Jones, Independent Electrical Contractors, 
Incorporated, TX [IM] 

Rep. Independent Electrical Contractors, Incorporated 
Andy Juhasz, Kone Incorporated, IL [M] 

Rep. National Elevator Industry Incorporated 

(VLto610, 620, 630) 
Sam Marcovici, New York City Department of Buildings, 
NY[E] 
John H. Mortimer, Inductotherm Corporation, NJ [M] 

(VL to 665) 
Ralph C. Prichard, Hercules Incorporated, DE [U] 

Rep. Institute of Electrical & Electronics Engineers, 

Incorporated 
Ronald L. Purvis, Georgia Power Company, GA [UT] 

Rep. Electric Light & Power Group/EEI 
David R. Quave, IBEW Local Union 903, MS [L] 

Rep. International Brotherhood of Electrical Workers 
Robert H. Reuss, Morris Material Handling, LLC, WI [M] 

Rep. Crane Manufacturers Association of America 

Incorporated 

(VL to 610) 
Arthur E. Schlueter, Jr., A. E. Schlueter Pipe Organ 
Company, GA [M] 

Rep. American Institute of Organ Builders 

(VL to 640, 650) 
Kenneth P. White, Olin Corporation, TN [U] 

Rep. American Chemistry Council 



James E. Winfrey, Square D Company, NC [M] 
Rep. National Electrical Manufacturers Association 

Alternates 
William E. Anderson, The Procter & Gamble Company, OH 
[U] 

Rep. Institute of Electrical & Electronics Engineers, 

Incorporated 

(Alt. to R. C. Prichard) 
Jeffrey W. Blain, Schindler Elevator Corporation, NJ [M] 

Rep. National Elevator Industry Incorporated 

(Alt. to A. Juhasz ) 

(VL to 610, 620, 630) 
William A. Brunner, IBEW Local Union 714, ND [L] 

Rep. International Brotherhood of Electrical Workers 

(Alt. to D. R. Quave) 
Scott Cline, McMurtrey Electric, Incorporated, CA [IM] 

Rep. National Electrical Contractors Association 

(Alt. to C. M. Trout) 
Robert Michael Forister, City of Sheridan, Wyoming, 
WY[E] 

Rep. International Association of Electrical Inspectors 

(Alt. to R. L. Janikowski) 
Barry G. Karnes, Underwriters Laboratories Incorporated, 
CA [RT] 

(Alt. to T. M. Burke) 
Todd F. Lottmann, Cooper Bussmann, MO [M] 

Rep. National Electrical Manufacturers Association 

(Alt. to J. E. Winfrey) 
Roger D. McDaniel, Georgia Power Company, GA [UT] 

Rep. Electric Light & Power Group/EEI 

(Alt. to R. L. Purvis) 
George S. Tidden, George's Electrical Service Incorporated, 
TX [IM] 

Rep. Independent Electrical Contractors, Incorporated 

(Alt. to R. A. Jones) 
Robert C. Turner, Inductotherm Corporation, NJ [M] 

(Alt. to J. H. Mortimer) 

(VL to 665) 



CODE-IVIAKING PANEL NO. 13 
Articles 445, 455, 480, 690, 692, 695, 700, 701, 702, 705 



Thomas H. Wood, Chair 

Cecil B. Wood Incorporated, IL [IM] 

Rep. National Electrical Contractors Association 



Tarry L. Baker, Broward County Board of Rules & 
Appeals, FL [E] 

Rep. International Association of Electrical Inspectors 
Ward L Bower, Sandia National Laboratories, NM [U] 

Rep. Solar Energy Industries Association 

(VL to 690, 692, 705) 
Douglas L. Elkins, ExxonMobil Chemical Company, 
TX [U] 

Rep. American Chemistry Council 
George W. Flach, George W. Flach Consultant, 
Incorporated, LA [SE] 



Ernest J. Gallo, Telcordia Technologies, Incorporated, 
NJ [U] 

Rep. Alliance for Telecommunications Industry Solutions 

(VL to 445, 480, 690, 692) 
Michael V. Glenn, Longview Fibre Company, WA [U] 

Rep. Institute of Electrical & Electronics Engineers, 

Incorporated 
Banks Hattaway, Hattaway Brothers, Incorporated, AL [IM] 

Rep. Associated Builders and Contractors, Incorporated 
Timothy D. Holleman, AC Corporation, NC [IM] 

Rep. Independent Electrical Contractors, Incorporated 



2005 Edition 



NATIONAL ELECTRICAL CODE 



70-17 



NATIONAL ELECTRICAL CODE COMMITTEE 



Barry N. Hornberger, PECO Energy Company, PA [UT] 

Rep. Electric Light & Power Group/EEI 
John R. Kovacik, Underwriters Laboratories Incorporated, 
IL [RT] 
Kenneth Krastins, Plug Power, Incorporated, NY [M] 

Rep. U.S. Fuel Cell Council 

(VL to 690, 692, 705) 
James S. Nasby, Master Control Systems, Inc., IL [M] 

Rep. National Electrical Manufacturers Association 
Steven H. Pasternack, Intertek Testing Services NA, 
Incorporated, NY [RT] 

Todd W. Stafford, National Joint Apprentice & Training 
Committee, IBEW-NJATC, TN [L] 

Rep. International Brotherhood of Electrical Workers 
La Verne E. Stetson, Lincoln, NE [U] 

Rep. American Society of Agricultural Engineers 
Herbert V. Whittall, Electrical Generating Systems 
Association, FL [M] 

Rep. Electrical Generating Systems Association 

Alternates 

Daniel Batta, Jr., Constellation Generation Group, LLC, 
MD [UT] 

Rep. Electric Light & Power Group/EEI 

(Alt. to B. N. Hornberger) 
Sonya M. Bird, Underwriters Laboratories Incorporated, 
NC [RT] 

(Alt. to J. R. Kovacik) 



Ron B. Chilton, North Carolina Department of Insurance, 
NC [E] 

Rep. International Association of Electrical Inspectors 

(Alt. to T. L. Baker) 
Brian L. Crise, NIETC, OR [L] 

Rep. International Brotherhood of Electrical Workers 

(Alt. to T. W. Stafford) 
Steven J. Fredette, UTC Cells, LLC, CT [M] 

Rep. U.S. Fuel Cell Council 

(Alt. to K. Krastins) 

(VL to 690, 692, 705) 
Ronald H. Minter, Thomas & Betts, TN [M] 

Rep. National Electrical Manufacturers Association 

(Alt. to J. S. Nasby) 
Duke W, Schamel, Copperhead Electric Inc, CA [IM] 

Rep. Independent Electrical Contractors, Incorporated 

(Alt. to T. D. Holleman) 
Robert L. Simpson, Simpson Electrical Engineering 
Company, GA [U] 

Rep. Institute of Electrical & Electronics Engineers, 

Incorporated 

(Alt. to M. V. Glenn) 
Richard Sobel, Quantum Electric Corporation, NY [IM] 

Rep. National Electrical Contractors Association 

(Alt. to T. H. Wood) 
Dale A. Triffo, Shell Oil Products US, TX [U] 

Rep. American Chemistry Council 

(Alt. to D. L. Elkins) 



CODE-MAKING PANEL NO. 14 
Articles 500, 501, 502, 503, 504, 505, 506, 510, 511, 513, 514, 515, 516 



Donald R. Cook, Chair 

Shelby County Building Inspections, AL [E] 

Rep. International Association of Electrical Inspectors 



Troy Beall, B & D Electric Company, Incorporated, NM [IM] 

Rep. National Electrical Contractors Association 
Edward M. Briesch, Underwriters Laboratories 
Incorporated, IL [RT] 
A! Engler, EGS Electrical Group, IL [M] 

Rep. International Society for Measurement and Control 
Mark Goodman, Jacobs Engineering Group, CA [U] 

Rep. American Petroleum Institute 
Gregory D. Hall, Better- Way Electric, Incorporated, CO [IM] 

Rep. Independent Electrical Contractors, Incorporated 
John Katunar, HI, GE Global Asset Protection Services, 
MO [I] 

Rep. GE Global Asset Protection Services 
Joseph H. Kuczka, Killark Electric Manufacturing 
Company, MO [M] 

Rep. National Electrical Manufacturers Association 
William G. Lawrence, Jr., FM Global, MA [I] 

Rep. FM Global/FM Research 
Jeremy Neagle, Intertek Testing Services NA, Incorporated, 
NY [RT] 
Mike O'Meara, Arizona Public Service Company, AZ [UT] 

Rep. Electric Light & Power Group/EEI 
David B. Wechsler, The Dow Chemical Company, TX [U] 

Rep. American Chemistry Council 
James A. Weldon, IBEW Local Union 728, FL [L] 

Rep. International Brotherhood of Electrical Workers 
Mark C. Wirfs, R & W Engineering Incorporated, OR [U] 

Rep. Grain Elevator and Processing Society 
Donald W. Zipse, Zipse Electrical Engineering Incorporated, 
PA [U] 

Rep. Institute of Electrical & Electronics Engineers, 

Incorporated 



Alternates 



A. W. Ballard, Grouse-Hinds, NY [M] 

Rep. National Electrical Manufacturers Association 

(Alt. to J. H. Kuczka) 
Marc J. Bernsen, Southwestern Idaho Electrical JATC, 
ID[L] 

Rep. International Brotherhood of Electrical Workers 

(Alt. to J. A. Weldon) 
Mark W. Bonk, Cargill Incorporated, MN [U] 

Rep. Grain Elevator and Processing Society 

(Alt. to M. C. Wirfs) 
Giovanni Hummel Borges, Underwriters Laboratories 
Incorporated, Brasil [RT] 

(Alt. to E. M. Briesch) 
James D. Cospolich, Waldemar S. Nelson & Company 
Incorporated, LA [U] 

Rep. Institute of Electrical & Electronics Engineers, 

Incorporated 

(Alt. to D. W. Zipse) 
Larry E. Fuhrman, City of Titusville, FL [E] 

Rep. International Association of Electrical Inspectors 

(Alt. to D. R. Cook) 
Nicholas P. Ludlam, FM Global, MA [I] 

Rep. FM Global/FM Research 

(Alt. to W. G. Lawrence, Jr.) 
Michael E. McNeil, FMC Corporation/Bio Polymer, ME [U] 

Rep. American Chemistry Council 

(Ah. to D. B. Wechsler) 
Ted H. Schnaare, Rosemount Incorporated, MN [M] 

Rep. International Society for Measurement and Control 

(Alt. to A. Engler) 



70-18 



NATIONAL ELECTRICAL CODE 2005 Edition 



NATIONAL ELECTRICAL CODE COMMITTEE 



Francis M. Stone, Jr., Shell Exploration and Production 
Company, TX [U] 

Rep. American Petroleum Institute 

(Alt. to M. Goodman) 



Nonvoting 

Eduardo N. Solano, Estudio Ingeniero Solano S.A., 
Argentina [SE] 

Fred K, Walker, U.S. Air Force, PL [U] 
Rep. TC on Airport Facilities 



CODE-MAKING PANEL NO. 15 
Articles 517, 518, 520, 525, 530, 540 



Donald J. Talka, Chair 
Underwriters Laboratories Incorporated, NY [RT] 



• 



James R. Duncan, Sparling Electrical Engineering, WA [U] 

Rep. Institute of Electrical & Electronics Engineers, 

Incorporated 
Tom Dunn, Butler Amusements, CA [U] 

Rep. Outdoor Amusement Business Association, 

Incorporated 

(VL to 525) 
Douglas S. Erickson, American Society for Healthcare 
Engineering, Virgin Islands [U] 

Rep. American Society for Healthcare Engineering 
Michael B. Klein, Metropolitan Engineering, Incorporated, 
DC [IM] 

Rep. Illuminating Engineering Society of North America 

(VL to 518, 520, 525, 530, 540) 
Edwin S. Kramer, Radio City Music Hall, NY [L] 

Rep. International Alliance of Theatrical Stage Employees 

(VL to 518, 520, 525, 530, 540) 
Larry Lau, U.S. Department of Veterans Affairs, DC [U] 

(VLto517, 518) 
Dennis W. Marshall, TAG Electric Companies, TX [IM] 

Rep. Independent Electrical Contractors, Incorporated 
Eugene E. Morgan, County of Clackamas, Oregon, OR [E] 

Rep. International Association of Electrical Inspectors 
Hugh O. Nash, Jr., Nash Lipsey Burch, LLC, TN [SE] 

Rep. TC on Electrical Systems 
Bruce D. Shelly, Shelly Electric Company, Inc., PA [IM] 

Rep. National Electrical Contractors Association 
Donald J. Sherratt, Intertek Testing Services NA, 
Incorporated, MA [RT] 
Michael D. Skinner, CBS Studio Center, CA [U] 

Rep. Alliance of Motion Picture and Television Producers 

(VL to 518, 520, 525, 530, 540) 
Richard H. Smith, OG&E Electric Services, OK [UT] 

Rep. Electric Light & Power Group/EEI 
Kenneth E. Vannice, Leviton Manufacturing Company 
Incorporated, OR [M] 

Rep. U.S. Institute for Theatre Technology 

(VL to 518, 520, 525, 530, 540) 
Michael Velvikis, High Voltage Maintenance Corporation, 
WI [IM] 

Rep. InterNational Electrical Testing Association 

Incorporated 



Andrew White, IBEW Local Union 3, NY [L] 

Rep. International Brotherhood of Electrical Workers 

James L, Wiseman, Square D Company, TN [M] 
Rep. National Electrical Manufacturers Association 

Alternates 
James R. Cook, IBEW Local Union 364, IL [L] 

Rep. International Brotherhood of Electrical Workers 

(Alt. to A. White) 
Matthew B. Dozier, IDesign Services, TN [U] 

Rep. Institute of Electrical & Electronics Engineers, 

Incorporated 

(Alt. to J. R. Duncan) 
Samuel B. Friedman, BICC General Cable Corporation, 
RI [M] 

Rep. National Electrical Manufacturers Association 

(Alt. to J. L. Wiseman) 
Dale A. Hallerberg, Underwriters Laboratories Incorporated, 
IL[RT] 

(Alt. to D. J. Talka) 
Mitchell K. Hefter, Entertainment Technology, TX [IM] 

Rep. Illuminating Engineering Society of North America 

(Alt. to M. B. Klein) 

(VL to 518, 520, 525, 530, 540)) 
Stanley D. Kahn, Tri-City Electric Company, Incorporated, 
CA[IM] 

Rep. National Electrical Contractors Association 

(Alt. to B. D. Shelly) 
Malinda Joyce Sampson, Minnesota Electricity Board, 
MN [E] 

Rep. International Association of Electrical Inspectors 

(Alt. to E. E. Morgan) 
James C. Seabury, III, Enterprise Electric, LLC, TN [IM] 

Rep. Independent Electrical Contractors, Incorporated 

(Alt. to D. W. Marshall) 
Steven R. Terry, Electronic Theatre Controls Incorporated, 
NY[M] 

Rep. U.S. Institute for Theatre Technology 

(Alt. to K. E. Vannice) 

(VL to 518, 520, 525, 530, 540) 
Rodney M. Young, Detroit Edison Company, MI [UT] 

Rep. Electric Light & Power Group/EEI 

(Alt. to R. H. Smith) 



2005 Edition 



NATIONAL ELECTRICAL CODE 



70-19 



NATIONAL ELECTRICAL CODE COMMITTEE 



CODE-MAKING PANEL NO. 16 
Articles 770, 800, 810, 820, 830 



Stanley D. Kahn, Chair 

Tri-City Electric Company, Incorporated, CA [IM] 

Rep. National Electrical Contractors Association 



J. Robert Boyer, Edwards Systems Technology, 
Incorporated, NJ [M] 

Rep. National Electrical Manufacturers Association 
James E. Brunssen, Telcordia, NJ [U] 

Rep. Alliance for Telecommunications Industry Solutions 
Larry Chan, City of New Orleans, LA [E] 

Rep. International Association of Electrical Inspectors 
Gerald Lee Dorna, Belden Wire & Cable, IN [M] 

Rep. Insulated Cable Engineers Association Incorporated 
Roland W. Gubisch, Intertek Testing Services NA, 
Incorporated, MA [RT] 
Robert L. Hughes, The DuPont Company, TN [U] 

Rep. American Chemistry Council 
Robert W. Jensen, dbi-Telecommunication Infrastructure 
Design, TX [M] 

Rep. Building Industry Consulting Services International 
Steven C. Johnson, Time Warner Cable, NC [UT] 

Rep. National Cable & Telecommunications Association 
Ronald G. Jones, Ronald G. Jones, RE., TX [U] 

Rep. Institute of Electrical & Electronics Engineers, 

Incorporated 
Barrett (Barry) Kalian, Underwriters Laboratories of 
Canada, ON, Canada [RT] 
Harold C. Ohde, IBEW/NECA Technical Institute, IL [L] 

Rep. International Brotherhood of Electrical Workers 
Joseph W. Rao, R.A.O. Electric Company, FL [IM] 

Rep. Independent Electrical Contractors, Incorporated 
James W. Romlein, MV Labs LLC, WI [M] 

Rep. Telecommunications Industry Association 
Kyle E. Todd, Entergy Corporation, TX [UT] 

Rep. Electric Light & Power Group/EEI 

Alternates 

Alan Amato, Times Fiber Communications, Incorporated, 
CT [UT] 

Rep. National Cable & Telecommunications Association 

(Alt. to S. C. Johnson) 
Donna Ballast, University of Texas at Austin, TX [M] 

Rep. Building Industry Consulting Services International 

(Alt. to R. W. Jensen) 



Chrysanthos Chrysanthou, Telcordia Technologies/SAIC, 
NJ [U] 

Rep. Alliance for Telecommunications Industry Solutions 

(Alt. to J. E. Brunssen) 
Terry C. Coleman, National Joint Apprentice & Training 
Committee, TN [L] 

Rep. International Brotherhood of Electrical Workers 

(Alt. to H. C. Ohde) 
William K. Hopple, Tyco/SimplexGrinnell, CA [M] 

Rep. National Electrical Manufacturers Association 

(Alt. to J. R. Boyer) 
Dr. Stanley Kaufman, CableSafe/OFS, GA [M] 

Rep. Insulated Cable Engineers Association Incorporated 

(Alt. to G. L. Dorna) 
Robert W. McCourt, Public Service Electric and Gas 
Company, NJ [UT] 

Rep. Electric Light & Power Group/EEI 

(Alt. to K. E. Todd) 
William J. McCoy, Verizon Wireless, TX [U] 

Rep. Institute of Electrical & Electronics Engineers, 

Incorporated 

(Alt. to R. G. Jones) 
Robert P. McGann, City of Cambridge, MA [E] 

Rep. International Association of Electrical Inspectors 

(Alt. to L. Chan) 
W. Douglas Pirkle, Pirkle Electric Company, Incorporated, 
GA [IM] 

Rep. National Electrical Contractors Association 

(Alt. to S. D. Kahn) 
Luigi G. Prezioso, M. C. Dean, Incorporated, VA [IM] 

Rep. Independent Electrical Contractors, Incorporated 

(Alt. to J. W. Rao) 
Bradley C. Rowe, Underwriters Laboratories Incorporated, 
IL[RT] 

(Alt. to B. Kalian) 

Nonvoting 
Irving Mande, Westport, CT [M] 



• 



CODE-IVIAKING PANEL NO. 17 
Articles 422, 424, 426, 427, 680, 682 



Don W. Jhonson, Chair 

Interior Electric, Incorporated, FL [IM] 

Rep. National Electrical Contractors Association 



Richard J. Cripps, Association of Home Appliance 
Manufacturers, DC [M] 

Rep. Association of Home Appliance Manufacturers 

(VL to 422, 424) 
Bill Hanthorn, Tyco Thermal Controls, ON, Canada [M] 

Rep. Copper Development Association, Incorporated 
Bruce R. Hirsch, Baltimore Gas & Electric Company, MD 
[UT] 

Rep. Electric Light & Power Group/EEI 
Christopher T. Hutchings, Underwriters Laboratories 
Incorporated, CA [RT] 



Walter Koessel, Intertek Testing Services NA, Incorporated, 
MO [RT] 

Robert M. Milatovich, Clark County Building Department, 
NV [E] 

Rep. International Association of Electrical Inspectors 
Marcos Ramirez, Hatfield-Reynolds Electric Company, AZ 
[IM] 

Rep. Independent Electrical Contractors, Incorporated 
Brian E. Rock, Hubbell Incorporated, CT [M] 

Rep. National Electrical Manufacturers Association 



70-20 



NATIONAL ELECTRICAL CODE 2005 Edition 



NATIONAL ELECTRICAL CODE COMMITTEE 



• 



Anthony P. Sardina, UTC Carrier Corporation, NY [M] 

Rep. Air-Conditioning and Refrigeration Institute 

(VL to 422, 424) 
Lee L. West, Balboa Instruments, Incorporated, CA [M] 

Rep. National Spa and Pool Institute 

(VL to 680) 
Randy J. Yasenchak, IBEW Local Union 607, PA [L] 

Rep. International Brotherhood of Electrical Workers 
Robert M. Yurkanin, Electran Process International 
Incorporated, NJ [U] 

Rep. Institute of Electrical & Electronics Engineers, 

Incorporated 

Alternates 

Dennis L. Baker, Springs & Sons Electrical Contractors 
Incorporated, AZ [IM] 

Rep. Independent Electrical Contractors, Incorporated 

(Alt. to M. Ramirez) 
Mark R. Berner, PPL Electric Utilities Corporation, 
PA [UT] 

Rep. Electric Light & Power Group/EEI 

(Alt. to B. R. Hirsch) 
J. Ron Caccamese, Nathan Electric Company, LTD., TX [L] 

Rep. International Brotherhood of Electrical Workers 

(Alt. to R. J. Yasenchak) 
Aaron B. Chase, Leviton Manufacturing Company, 
Incorporated, NY [M] 

Rep. National Electrical Manufacturers Association 

(Alt. to B. E. Rock) 



Paul Crivell, Kennedy Jenks Consultants, WA [U] 

Rep. Institute of Electrical & Electronics Engineers, 

Incorporated 

(Alt. to R. M. Yurkanin) 
James E. Maldonado, City of Tempe, AZ [E] 

Rep. International Association of Electrical Inspectors 

(Alt. to R. M. Milatovich) 
Cannon Sun, Underwriters Laboratories Incorporated, 
Taiwan [RT] 

(Alt. to C. T. Hatchings) 
D. Harold Ware, Libra Electric Company, OK [IM] 

Rep. National Electrical Contractors Association 

(Alt. to D. W. Jhonson) 
Robert E. Wisenburg, Coates Heater Company, 
Incorporated, WA [M] 

Rep. National Spa and Pool Institute 

(Alt. to L. L. West) 

(VL to 680) 

Nonvoting 

William H. King, Jr., U.S. Consumer Product Safety 
Commission, MD [C] 

(Alt. to A. M. Trotta) 
Andrew M. Trotta, U.S. Consumer Product Safety 
Commission, MD [C] 



CODE-MAKING PANEL NO. 18 
Articles 406, 410, 411, 600, 605 



Michael N. Ber, Chair 

lEC, Houston, TX [IM] 

Rep. Independent Electrical Contractors, Incorporated 



Paul Costello, NECA and IBEW Local 90 JATC, CT [L] 

Rep. International Brotherhood of Electrical Workers 
Kenneth A. Fetzer, Underwriters Laboratories Incorporated, 
NC [RT] 

Stephen G. Kiefifer, Kiefifer & Company, Incorporated, 
WI [M] 

Rep. International Sign Association 

(VL to 600) 
Steven A. Larson, BWXT Y-12, LLC, TN [U] 

Rep. Institute of Electrical & Electronics Engineers, 

Incorporated 
Michael S. O'Boyle, Genlyte Thomas Group, MA [M] 

Rep. American Lighting Association 

(VL to 410, 411) 
Timothy S. Owens, City of San Diego, CA [E] 

Rep. International Association of Electrical Inspectors 
Jim F. Pierce, Intertek Testing Services NA, Incorporated, 
OR [RT] 

Saul Rosenbaum, Leviton Manufacturing Company 
Incorporated, NY [M] 

Rep. National Electrical Manufacturers Association 
Michael W. Smith, Guarantee Electrical Company, 
MO [IM] 

Rep. National Electrical Contractors Association 
Carl Tim Wall, Alabama Power Company, AL [UT] 

Rep. Electric Light & Power Group/EEI 
Jack Wells, Pass & Seymour/Legrand, NY [M] 



Alternates 

Robert T. Carlock, R. T Carlock Company, TN [IM] 

Rep. Independent Electrical Contractors, Incorporated 

(Alt. to M. N. Ber) 
Frederick L. Carpenter, Lithonia Lighting, GA [M] 

Rep. National Electrical Manufacturers Association 

(Alt. to S. Rosenbaum) 
Amos D. Lowrance, Jr., City of Chattanooga, Tennessee, 
TN [E] 

Rep. International Association of Electrical Inspectors 

(Alt. to T. S. Owens) 
Ronald Michaelis, South Bend Vicinity Electrical JATC, 
IN[L] 

Rep. International Brotherhood of Electrical Workers 

(Alt. to R Costello) 
Christopher P. O'Neil, National Grid USA Service 
Company, MA [UT] 

Rep. Electric Light & Power Group/EEI 

(Alt. to C. T Wall) 
Alan M. Smith, France/Scott Fetzer Company, TN [M] 

Rep. International Sign Association 

(Alt. to S. G. Kieffer) 

(VL to 600) 
Rachna Stegall, Underwriters Laboratories Incorporated, 
IL[RT] 

(Alt. to K. A. Fetzer) 
Charles M. Trout, Maron Electric Company, FL [IM] 

Rep. National Electrical Contractors Association 

(Alt. to M. W. Smith) 



2005 Edition NATIONAL ELECTRICAL CODE 



70-21 



NATIONAL ELECTRICAL CODE COMMITTEE 



CODE-MAKING PANEL NO. 19 
Articles 545, 547, 550, 551, 552, 553, 555, 604, 675, Annex D, Examples Dll and D12 



Robert A. McCullough, Chair 

Ocean County Construction Inspection Department, NJ [E] 

Rep. International Association of Electrical Inspectors 



Barry Bauman, Alliant Energy, WI [U] 

Rep. American Society of Agricultural Engineers 
James W. Finch, Kampgrounds of America, Incorporated, 
MT[U1 

(VLto550, 551, 552, 555) 
Bruce A. Hopkins, Recreation Vehicle Industry Association, 
VA[M] 

Rep. Recreation Vehicle Industry Association 

(VLto550, 551,552) 
Robert L. La Rocca, Underwriters Laboratories 
Incorporated, NY [RT] 
Timothy P. McNeive, Thomas & Betts Corporation, TN [M] 

Rep. National Electrical Manufacturers Association 
John Mikel, Skyline Corporation, IN [M] 

Rep. Manufactured Housing Institute 

(VLto550, 551, 552) 
T\ig L, Miller, National Association of RV Parks & 
Campgrounds, CA [U] 

Rep. National Association of RV Parks & Campgrounds 

(VLto550, 551, 552) 
Leslie Sabin-Mercado, San Diego Gas & Electric Company, 
CA [UT] 

Rep. Electric Light & Power Group/EEI 
William J. Tipton, IBEW Local Union 575, OH [L] 

Rep. International Brotherhood of Electrical Workers 
Kenneth Weakley, Mountain Electric, Incorporated, 
CA [IM] 

Rep. National Electrical Contractors Association 
William A. Zanicchi, AAA Certified Electric Incorporated, 
PL [IM] 

Rep. Independent Electrical Contractors, Incorporated 
Michael L. Zieman, RADCO, CA [RT] 

(VLto545, 550, 551,552) 

Alternates 

Glenn H. Ankenbrand, Conectiv Power, MD [UT] 
Rep. Electric Light & Power Group/EEI 
(Alt. to L. Sabin-Mercado) 



Steven J, Blais, EGS Electrical Group, IL [M] 

Rep. National Electrical Manufacturers Association 

(Alt. to T. R McNeive) 
Monte R. Ewing, Wisconsin Department of Commerce, 
WI [E] 

Rep. International Association of Electrical Inspectors 

(Alt. to R. A. McCullough) 
Thomas R. Lichtenstein, Underwriters Laboratories 
Incorporated, IL [RT] 

(Ah. to R. L. La Rocca) 
Linda J. Little, IBEW Local Union 1, MO [L] 

Rep. International Brotherhood of Electrical Workers 

(Alt. to W. J. Tipton) 
Suzanne Mark, National Association of RV Parks & 
Campgrounds, VA [U] 

Rep. National Association of RV Parks & Campgrounds 

(Alt. to T L. Miller) 

(VLto550, 551, 552) 
N. Kent Morgan, AC Corporation, NC [IM] 

Rep. Independent Electrical Contractors, Incorporated 

(Alt. to W. A. Zanicchi) 
Kent Perkins, Recreation Vehicle Industry Association, 
VA[M] 

Rep. Recreation Vehicle Industry Association 

(Alt. to B. A. Hopkins) 

(VLto550, 551, 552) 
John G. Sims, NTA Incorporated, IN [M] 

Rep. Manufactured Housing Institute 

(Alt. to J. Mikel) 

(VL to 550, 551, 552) 
Keith G. Tinsey, Michigan State University, MI [U] 

Rep. American Society of Agricultural Engineers 

(AU. to B. Bauman) 
Raymond F. l\icker. Consulting Professional Engineer, 
CA [RT] 

(Alt. to M. L. Zieman) 

(VLto 545, 550, 551, 552) 



NFPA Electrical Engineering Division Technical Staff 



Mark W. Earley, Assistant Vice President/Chief Electrical 

Engineer 

Kenneth G. Mastrullo, Senior Electrical Speciahst 

Jean A. O'Connor, Electrical Project Speciahst/Support 

Supervisor 



Lee F. Richardson, Senior Electrical Engineer 
Richard J. Roux, Senior Electrical Specialist 
Jeffrey S. Sargent, Senior Electrical Specialist 
Joseph V. Sheehan, Principal Electrical Engineer 
Donald W. Shields, Senior Electrical Specialist 



NFPA Staff Editor 
Joyce G. Grandy, Senior Project Editor 

Note: IVIembership on a committee shall not in and of itself constitute an endorsement of the Association 
or any document developed by the Committee on which the member serves. 

Committee Scope: This Committee shall have primary responsibility for documents on minimizing 
the risk of electricity as a source of electric shock and as a potential ignition source of fires and 
explosions. It shall also be responsible for text to minimize the propagation of fire and explosions due 
to electrical installations. 



• 



70-22 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 90 — INTRODUCTION 



90.2 



NFPA 70 
National Electrical Code® 

2005 Edition 

IMPORTANT NOTE: This NFPA document is made 
available for use subject to important notices and legal dis- 
claimers. These notices and disclaimers appear in all publi- 
cations containing this document and may be found under 
the heading "Important Notices and Disclaimers Concern- 
ing NFPA Documents." They can also be obtained on re- 
quest from NFPA or viewed at www.njpa.org/disclaimers. 



ARTICLE90 
Introduetion 



90.1 Purpose. 

(A) Practical Safeguarding. The purpose of this Code is 
the practical safeguarding of persons and property from 
hazards arising from the use of electricity. 

(B) Adequacy. This Code contains provisions that are con- 
sidered necessary for safety. Compliance therewith and 
proper maintenance results in an installation that is essen- 
tially free from hazard but not necessarily efficient, conve- 
nient, or adequate for good service or future expansion of 
electrical use. 

FPN: Hazards often occur because of overloading of wiring 
systems by methods or usage not in conformity with this 
Code. This occurs because initial wiring did not provide for 
increases in the use of electricity. An initial adequate installa- 
tion and reasonable provisions for system changes provide for 
future increases in the use of electricity. 

(C) Intention. This Code is not intended as a design speci- 
fication or an instruction manual for untrained persons. 

(D) Relation to Other International Standards. The re- 
quirements in this Code address the fundamental principles 
of protection for safety contained in Section 131 of Inter- 
national Electrotechnical Commission Standard 60364-1, 
Electrical Installations of Buildings. 

FPN: lEC 60364-1, Section 131, contains fundamental 
principles of protection for safety that encompass protec- 
tion against electric shock, protection against thermal ef- 
fects, protection against overcurrent, . protection against 
fault currents, and protection against overvoltage. All of 
these potential hazards are addressed by the requirements in 
this Code. 



90.2 Scope. 

(A) Covered. This Code covers the installation of electri- 
cal conductors, equipment, and raceways; signaling and 
communications conductors, equipment, and raceways; and 
optical fiber cables and raceways for the following: 

(1) Public and private premises, including buildings, struc- 
tures, mobile homes, recreational vehicles, and floating 
buildings 

(2) Yards, lots, parking lots, carnivals, and industrial sub- 
stations 

FPN to (2): For additional information concerning such instal- 
lations in an industrial or multibuilding complex, see ANSI 
C2-2002, National Electrical Safety Code. 

(3) Installations of conductors and equipment that connect 
to the supply of electricity 

(4) Installations used by the electric utility, such as office 
buildings, warehouses, garages, machine shops, and 
recreational buildings, that are not an integral part of a 
generating plant, substation, or control center. 

(B) Not Covered. This Code does not cover the following: 

(1) Installations in ships, watercraft other than floating build- 
ings, railway roUing stock, aircraft, or automotive vehicles 
other than mobile homes and recreational vehicles 

FPN: Although the scope of this Code indicates that the 
Code does not cover installations in ships, portions of this 
Code are incorporated by reference into Title 46, Code of 
Federal Regulations, Parts 110-113. 

(2) Installations underground in mines and self-propelled 
mobile surface mining machinery and its attendant 
electrical trailing cable 

(3) Installations of railways for generation, transformation, 
transmission, or distribution of power used exclusively 
for operation of rolling stock or installations used ex- 
clusively for signaling and communications purposes 

(4) Installations of communications equipment under the 
exclusive control of communications utilities located 
outdoors or in building spaces used exclusively for 
such installations 

(5) Installations under the exclusive control of an electric 
utility where such installations 

a. Consist of service drops or service laterals, and as- 
sociated metering, or 

b. Are located in legally established easements, rights- 
of-way, or by other agreements either designated by 
or recognized by public service commissions, utility 
commissions, or other regulatory agencies having 
jurisdiction for such installations, or 

c. Are on property owned or leased by the electric 
utility for the purpose of communications, metering, 
generation, control, transformation, transmission, or 
distribution of electric energy. 



2005 Edition NATIONAL ELECTRICAL CODE 



70-23 



90.3 



ARTICLE 90 — INTRODUCTION 



FPN to (4) and (5): Examples of utilities may include those 
entities that are typically designated or recognized by govern- 
mental law or regulation by public service/utility commissions 
and that install, operate, and maintain electric supply (such as 
generation, transmission, or distribution systems) or communica- 
tion systems (such as telephone, CATV, Internet, satellite, or data 
services). Utilities may be subject to compHance with codes and 
standards covering their regulated activities as adopted under gov- 
ernmental law or regulation. Additional information can be found 
through consultation with the appropriate governmental bodies, 
such as state regulatory commissions. Federal Energy Regulatory 
Commission, and Federal Communications Commission. 

(C) Special Permission. The authority having jurisdiction 
for enforcing this Code may grant exception for the instal- 
lation of conductors and equipment that are not under the 
exclusive control of the electric utilities and are used to 
connect the electric utility supply system to the service- 
entrance conductors of the premises served, provided such 
installations are outside a building or terminate immedi- 
ately inside a building wall. 

90.3 Code Arrangement. This Code is divided into the in- 
troduction and nine chapters, as shown in Figure 90.3. Chap- 
ters 1, 2, 3, and 4 apply generally; Chapters 5, 6, and 7 apply 
to special occupancies, special equipment, or other special 
conditions. These latter chapters supplement or modify the 
general rules. Chapters 1 through 4 apply except as amended 
by Chapters 5, 6, and 7 for the particular conditions. 

Chapter 8 covers communications systems and is not sub- 
ject to the requirements of Chapters 1 through 7 except where 
the requirements are specifically referenced in Chapter 8. 

Chapter 9 consists of tables. 

Annexes are not part of the requirements of this Code 
but are included for informational purposes only. 

90.4 Enforcement. This Code is intended to be suitable 
for mandatory application by governmental bodies that ex- 
ercise legal jurisdiction over electrical installations, includ- 
ing signaling and communications systems, and for use by 
insurance inspectors. The authority having jurisdiction for 
enforcement of the Code has the responsibility for making 
interpretations of the rules, for deciding on the approval of 
equipment and materials, and for granting the special per- 
mission contemplated in a number of the rules. 

By special permission, the authority having jurisdiction 
may waive specific requirements in this Code or permit 
alternative methods where it is assured that equivalent ob- 
jectives can be achieved by establishing and maintaining 
effective safety. 

This Code may require new products, constructions, or 
materials that may not yet be available at the time the Code 
is adopted. In such event, the authority having jurisdiction 
may permit the use of the products, constructions, or mate- 
rials that comply with the most recent previous edition of 
this Code adopted by the jurisdiction. 



Chapter 1 — General 



Chapter 2 — Wiring and Protection 



Chapter 3 — Wiring IVIethods and IVIaterials 



Chapter 4 — Equipment for General Use 



Applies generally 
y to all electrical 
installations 



Supplements or modifies ^ 
Chapters 1 through 4 



Chapter 5 — Special Occupancies 



Chapter 6 — Special Equipment 



Chapter 7 — Special Conditions 



Chapter 8 — Communications Systems 



Chapter 9 — Tables 



Chapter 8 is not subject 

to the requirements of 
"\ Chapters 1 through 7 except 
J where the requirements are 

specifically referenced in 

Chapter 8. 



Annex A through Annex G 



Applicable as referenced 

Informational only; 
not mandatory 



Figure 90.3 Code Arrangement. 



90.5 Mandatory Rules, Permissive Rules, and 
Explanatory Material. 

(A) Mandatory Rules. Mandatory rules of this Code are 
those that identify actions that are specifically required or 
prohibited and are characterized by the use of the terms 
shall or shall not. 

(B) Permissive Rules. Permissive rules of this Code are 
those that identify actions that are allowed but not required, 
are normally used to describe options or alternative meth- 
ods, and are characterized by the use of the terms shall be 
permitted or shall not be required. 

(C) Explanatory Material. Explanatory material, such as 
references to other standards, references to related sections 
of this Code, or information related to a Code rule, is in- 
cluded in this Code in the form of fine print notes (FPNs). 
Fine print notes are informational only and are not enforce- 
able as requirements of this Code. 

Brackets containing section references to another NFPA 
document are for informational purposes only and are pro- 
vided as a guide to indicate the source of the extracted text. 
These bracketed references immediately follow the extracted 
text. 

FPN: The format and language used in this Code follows 
guidelines established by NFPA and published in the NEC 
Style Manual. Copies of this manual can be obtained from 
NFPA. 



70-24 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 90 — INTRODUCTION 



90.9 



• 



90.6 Formal Interpretations. To promote uniformity of 
interpretation and application of the provisions of this 
Code, formal interpretation procedures have been estab- 
lished and are found in the NFPA Regulations Governing 
Committee Projects. 

90.7 Examination of Equipment for Safety. For specific 
items of equipment and materials referred to in this Code, 
examinations for safety made under standard conditions 
provide a basis for approval where the record is made gen- 
erally available through promulgation by organizations 
properly equipped and qualified for experimental testing, 
inspections of the run of goods at factories, and service- 
value determination through field inspections. This avoids 
the necessity for repetition of examinations by different 
examiners, frequently with inadequate facilities for such 
work, and the confusion that would result from conflicting 
reports on the suitability of devices and materials examined 
for a given purpose. 

It is the intent of this Code that factory-installed inter- 
nal wiring or the construction of equipment need not be 
inspected at the time of installation of the equipment, ex- 
cept to detect alterations or damage, if the equipment has 
been listed by a qualified electrical testing laboratory that is 
recognized as having the facilities described in the preced- 
ing paragraph and that requires suitability for installation in 
accordance with this Code. 

FPN No. 1: See requirements in 110.3. 

FPN No. 2: Listed is defined in Article 100. 

FPN No. 3: Annex A contains an informative list of prod- 
uct safety standards for electrical equipment. 

90.8 Wiring Planning. 

(A) Future Expansion and Convenience. Plans and 
specifications that provide ample space in raceways, spare 
raceways, and additional spaces allow for future increases 
in electric power and communication circuits. Distribution 
centers located in readily accessible locations provide con- 
venience and safety of operation. 

(B) Number of Circuits in Enclosures. It is elsewhere pro- 
vided in this Code that the number of wires and circuits con- 
fined in a single enclosure be varyingly restricted. Limiting the 
number of circuits in a single enclosure minimizes the effects 
from a short circuit or ground fault in one circuit. 



90.9 Units of Measurement. 

(A) Measurement System of Preference. For the purpose 
of this Code, metric units of measurement are in accor- 
dance with the modernized metric system known as the 
International System of Units (SI). 

(B) Dual System of Units. SI units shall appear first, and 
inch-pound units shall immediately follow in parentheses. 
Conversion from inch-pound units to SI units shall be 
based on hard conversion except as provided in 90.9(C). 

(C) Permitted Uses of Soft Conversion. The cases given 
in 90.9(C)(1) through (C)(4) shall not be required to use hard 
conversion and shall be permitted to use soft conversion. 

(1) Trade Sizes. Where the actual measured size of a prod- 
uct is not the same as the nominal size, trade size designa- 
tors shall be used rather than dimensions. Trade practices 
shall be followed in all cases. 

(2) Extracted Material. Where material is extracted from 
another standard, the context of the original material shall 
not be compromised or violated. Any editing of the ex- 
tracted text shall be confined to making the style consistent 
with that of the NEC. 

(3) Industry Practice. Where industry practice is to ex- 
press units in inch-pound units, the inclusion of SI units 
shall not be required. 

(4) Safety. Where a negative impact on safety would re- 
sult, soft conversion shall be used. 

(D) Compliance. Conversion from inch-pound units to SI 
units shall be permitted to be an approximate conversion. 
Compliance with the numbers shown in either the SI sys- 
tem or the inch-pound system shall constitute compliance 
with this Code. 

FPN No. 1: Hard conversion is considered a change in 
dimensions or properties of an item into new sizes that 
might or might not be interchangeable with the sizes used 
in the original measurement. Soft conversion is considered 
a direct mathematical conversion and involves a change in 
the description of an existing measurement but not in the 
actual dimension. 

FPN No. 2: SI conversions are based on lEEE/ASTM SI 
10-1997, Standard for the Use of the International System 
of Units (SI): The Modern Metric System. 



2005 Edition 



NATIONAL ELECTRICAL CODE 



70-25 



100 



ARTICLE 100 — DEFINITIONS 



Chapter 1 General 



Scope. This article contains only those definitions essential 
to the proper apphcation of this Code. It is not intended to 
include commonly defined general terms or commonly de- 
fined technical terms from related codes and standards. In 
general, only those terms that are used in two or more 
articles are defined in Article 100. Other definitions are 
included in the article in which they are used but may be 
referenced in Article 100. 

Part I of this article contains definitions intended to 
apply wherever the terms are used throughout this Code. 
Part II contains definitions applicable only to the parts of 
articles specifically covering installations and equipment 
operating at over 600 volts, nominal. 

I. General 

Accessible (as applied to equipment). Admitting close 
approach; not guarded by locked doors, elevation, or other 
effective means. 

Accessible (as applied to wiring methods). Capable of 
being removed or exposed without damaging the building 
structure or finish or not permanently closed in by the struc- 
ture or finish of the building. 

Accessible, Readily (Readily Accessible). Capable of be- 
ing reached quickly for operation, renewal, or inspections 
without requiring those to whom ready access is requisite 
to climb over or remove obstacles or to resort to portable 
ladders, and so forth. 

Ampacity. The current, in amperes, that a conductor can 
carry continuously under the conditions of use without ex- 
ceeding its temperature rating. 

Appliance. Utilization equipment, generally other than in- 
dustrial, that is normally built in standardized sizes or types 
and is installed or connected as a unit to perform one or 
more functions such as clothes washing, air conditioning, 
food mixing, deep frying, and so forth. 

Approved. Acceptable to the authority having jurisdiction. 

Askarel. A generic term for a group of nonflammable syn- 
thetic chlorinated hydrocarbons used as electrical insulating 
media. Askarels of various compositional types are used. 
Under arcing conditions, the gases produced, while consist- 
ing predominantly of noncombustible hydrogen chloride, 



can include varying amounts of combustible gases, depend- 
ing on the askarel type. 

Attachment Plug (Plug Cap) (Plug). A device that, by 
insertion in a receptacle, establishes a connection between 
the conductors of the attached flexible cord and the conduc- 
tors connected permanently to the receptacle. 

Authority Having Jurisdiction (AHJ). The organization, 
office, or individual responsible for approving equipment, 
materials, an installation, or a procedure. 

FPN: The phrase "authority having jurisdiction" is used in 
NFPA documents in a broad manner, since jurisdictions and 
approval agencies vary, as do their responsibilities. Where 
public safety is primary, the AHJ may be a federal, state, 
local, or other regional department or individual such as a 
fire chief; fire marshal; chief of a fire prevention bureau, 
labor department, or health department; building official; 
electrical inspector; or others having statutory authority. 
For insurance purposes, an insurance inspection depart- 
ment, rating bureau, or other insurance company represen- 
tative may be the AHJ. In many circumstances, the property 
owner or his or her designated agent assumes the role of the 
AHJ; at government installations, the commanding officer 
or departmental official may be the AHJ. 

Automatic. Self-acting, operating by its own mechanism 
when actuated by some impersonal influence, as, for ex- 
ample, a change in current, pressure, temperature, or me- 
chanical configuration. 

Bathroom. An area including a basin with one or more of 
the following: a toilet, a tub, or a shower. 

Bonding (Bonded). The permanent joining of metaUic parts 
to form an electricaUy conductive path that ensures electrical 
continuity and the capacity to conduct safely any current likely 
to be imposed. 

Bonding Jumper. A reUable conductor to ensure the required 
electrical conductivity between metal parts required to be elec- 
trically connected. 

Bonding Jumper, Equipment. The connection between two 
or more portions of the equipment grounding conductor. 

Bonding Jumper, Main. The connection between the 
grounded circuit conductor and the equipment grounding 
conductor at the service. 

Bonding Jumper, System. The connection between the 
grounded circuit conductor and the equipment grounding 
conductor at a separately derived system. 

Branch Circuit. The circuit conductors between the final 
overcurrent device protecting the circuit and the outlet(s). 



70-26 



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ARTICLE 100 — DEFINITIONS 



100 



Branch Circuit, Appliance. A branch circuit that supplies 
energy to one or more outlets to which appliances are to be 
connected and that has no permanently connected lumi- 
naires (lighting fixtures) that are not a part of an appHance. 

Branch Circuit, General-Purpose. A branch circuit that 
supplies two or more receptacles or outlets for lighting and 
appliances. 

Branch Circuit, Individual. A branch circuit that supplies 
only one utilization equipment. 

Branch Circuit, Multiwire. A branch circuit that consists 
of two or more ungrounded conductors that have a voltage 
between them, and a grounded conductor that has equal 
voltage between it and each ungrounded conductor of the 
circuit and that is connected to the neutral or grounded 
conductor of the system. 

Building. A structure that stands alone or that is cut off 
from adjoining structures by fire walls with all openings 
therein protected by approved fire doors. 

Cabinet. An enclosure that is designed for either surface 
mounting or flush mounting and is provided with a frame, 
mat, or trim in which a swinging door or doors are or can 
be hung. 

Circuit Breaker. A device designed to open and close a 
circuit by nonautomatic means and to open the circuit au- 
tomatically on a predetermined overcurrent without damage 
to itself when properly applied within its rating. 

FPN: The automatic opening means can be integral, direct 
acting with the circuit breaker, or remote from the circuit 
breaker. 

Adjustable (as applied to circuit breakers). A qualifying 
term indicating that the circuit breaker can be set to trip at 
various values of current, time, or both, within a predeter- 
mined range. 

Instantaneous Trip (as applied to circuit breakers). A quali- 
fying term indicating that no delay is purposely introduced 
in the tripping action of the circuit breaker. 

Inverse Time (as applied to circuit breakers). A qualifying 
term indicating that there is purposely introduced a delay in 
the tripping action of the circuit breaker, which delay de- 
creases as the magnitude of the current increases. 

Nonadjustable (as applied to circuit breakers). A quali- 
fying term indicating that the circuit breaker does not have 
any adjustment to alter the value of current at which it will 
trip or the time required for its operation. 

Setting (of circuit breakers). The value of current, time, or 
both, at which an adjustable circuit breaker is set to trip. 

Concealed. Rendered inaccessible by the structure or 
finish of the building. Wires in concealed raceways are 



considered concealed, even though they may become ac- 
cessible by withdrawing them. 

Conductor, Bare. A conductor having no covering or elec- 
trical insulation whatsoever. 

Conductor, Covered. A conductor encased within material 
of composition or thickness that is not recognized by this 
Code as electrical insulation. 

Conductor, Insulated. A conductor encased within mate- 
rial of composition and thickness that is recognized by this 
Code as electrical insulation. 

Conduit Body. A separate portion of a conduit or tubing 
system that provides access through a removable cover(s) 
to the interior of the system at a junction of two or more 
sections of the system or at a terminal point of the system. 
Boxes such as FS and FD or larger cast or sheet metal 
boxes are not classified as conduit bodies. 

Connector, Pressure (Solderless). A device that estabUshes 
a connection between two or more conductors or between one 
or more conductors and a terminal by means of mechanical 
pressure and without the use of solder. 

Continuous Load. A load where the maximum current is 
expected to continue for 3 hours or more. 

Controller. A device or group of devices that serves to 
govern, in some predetermined manner, the electric power 
delivered to the apparatus to which it is connected. 

Cooking Unit, Counter-Mounted. A cooking appliance 
designed for mounting in or on a counter and consisting of 
one or more heating elements, internal wiring, and built-in 
or mountable controls. 

Coordination (Selective). Localization of an overcurrent 
condition to restrict outages to the circuit or equipment 
affected, accompUshed by the choice of overcurrent protec- 
tive devices and their ratings or settings. 

Copper-Clad Aluminum Conductors. Conductors drawn 
from a copper-clad aluminum rod with the copper metallur- 
gically bonded to an aluminum core. The copper forms a 
minimum of 10 percent of the cross-sectional area of a 
solid conductor or each strand of a stranded conductor. 

Cutout Box. An enclosure designed for surface mounting 
that has swinging doors or covers secured directly to and 
telescoping with the walls of the box proper. 

Dead Front. Without live parts exposed to a person on the 
operating side of the equipment. 

Demand Factor. The ratio of the maximum demand of a 
system, or part of a system, to the total connected load of a 
system or the part of the system under consideration. 



2005 Edition NATIONAL ELECTRICAL CODE 



70-27 



100 



ARTICLE 100 — DEFINITIONS 



Device. A unit of an electrical system that is intended to 
carry or control but not utilize electric energy. 

Disconnecting Means. A device, or group of devices, or 
other means by which the conductors of a circuit can be 
disconnected from their source of supply. 

Dusttight. Constructed so that dust will not enter the en- 
closing case under specified test conditions. 

Duty, Continuous. Operation at a substantially constant 
load for an indefinitely long time. 

Duty, Intermittent. Operation for alternate intervals of 
(1) load and no load; or (2) load and rest; or (3) load, no 
load, and rest. 

Duty, Periodic. Intermittent operation in which the load 
conditions are regularly recurrent. 

Duty, Short-Time. Operation at a substantially constant 
load for a short and definite, specified time. 

Duty, Varying. Operation at loads, and for intervals of 
time, both of which may be subject to wide variation. 

Dwelling Unit. A single unit, providing complete and in- 
dependent living facilities for one or more persons, includ- 
ing permanent provisions for living, sleeping, cooking, and 
sanitation. 

Dwelling, One-Family. A building that consists solely of 
one dwelling unit. 

Dwelling, Two-Family. A building that consists solely of 
two dwelling units. 

Dwelling, Multifamily. A building that contains three or 
more dwelling units. 

Electric Sign. A fixed, stationary, or portable self-contained, 
electrically illuminated utilization equipment with words or 
symbols designed to convey information or attract attention. 

Enclosed. Surrounded by a case, housing, fence, or wall(s) 
that prevents persons from accidentally contacting ener- 
gized parts. 

Enclosure. The case or housing of apparatus, or the fence 
or walls surrounding an installation to prevent personnel 
from accidentally contacting energized parts or to protect 
the equipment from physical damage. 

FPN: See Table 430.91 for examples of enclosure types. 

Energized. Electrically connected to, or is, a source of 
voltage. 

Equipment. A general term including material, fittings, de- 
vices, appliances, luminaires (fixtures), apparatus, and the 
like used as a part of, or in connection with, an electrical 
installation. 



Explosionproof Apparatus. Apparatus enclosed in a case 
that is capable of withstanding an explosion of a specified 
gas or vapor that may occur within it and of preventing the 
ignition of a specified gas or vapor surrounding the enclo- 
sure by sparks, flashes, or explosion of the gas or vapor 
within, and that operates at such an external temperature 
that a surrounding flammable atmosphere will not be ig- 
nited thereby. 

FPN: For further information, see ANSI/UL 1203-1999, 
Explosion-Proof and Dust-Ignition-Proof Electrical Equip- 
ment for Use in Hazardous (Classified) Locations. 

Exposed (as applied to live parts). Capable of being in- 
advertently touched or approached nearer than a safe dis- 
tance by a person. It is applied to parts that are not suitably 
guarded, isolated, or insulated. 

Exposed (as applied to wiring methods). On or attached 
to the surface or behind panels designed to allow access. 

Externally Operable. Capable of being operated without 
exposing the operator to contact with live parts. 

Feeder. All circuit conductors between the service equip- 
ment, the source of a separately derived system, or other 
power supply source and the final branch-circuit overcur- 
rent device. 

Festoon Lighting. A string of outdoor lights that is sus- 
pended between two points. 

Fitting. An accessory such as a locknut, bushing, or other 
part of a wiring system that is intended primarily to per- 
form a mechanical rather than an electrical function. 

Garage. A building or portion of a building in which one or 
more self-propelled vehicles can be kept for use, sale, stor- 
age, rental, repair, exhibition, or demonstration purposes. 

FPN: For commercial garages, repair and storage, see Ar- 
ticle 511. 

Ground. A conducting connection, whether intentional or 
accidental, between an electrical circuit or equipment and 
the earth or to some conducting body that serves in place of 
the earth. 

Grounded. Connected to earth or to some conducting body 
that serves in place of the earth. 

Grounded, Effectively. Intentionally connected to earth 
through a ground connection or connections of sufiBciently 
low impedance and having suflBcient current-carrying ca- 
pacity to prevent the buildup of voltages that may result in 
undue hazards to connected equipment or to persons. 

Grounded, Solidly. Connected to ground without inserting 
any resistor or impedance device. 

Grounded Conductor. A system or circuit conductor that 
is intentionally grounded. 



70-28 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 100 — DEFINITIONS 



100 



• 



Ground-Fault Circuit Interrupter (GFCI). A device in- 
tended for the protection of personnel that functions to de- 
energize a circuit or portion thereof within an estabhshed 
period of time when a current to ground exceeds the values 
established for a Class A device. 

FPN: Class A ground-fault circuit interrupters trip when the 
current to ground has a value in the range of 4 mA to 6 mA. 
For further information, see UL 943, Standard for Ground- 
Fault Circuit Interrupters. 

Ground-Fault Protection of Equipment. A system in- 
tended to provide protection of equipment from damaging 
line-to-ground fault currents by operating to cause a discon- 
necting means to open all ungrounded conductors of the 
faulted circuit. This protection is provided at current levels less 
than those required to protect conductors from damage 
through the operation of a supply circuit overcurrent device. 

Grounding Conductor. A conductor used to connect 
equipment or the grounded ckcuit of a wiring system to a 
grounding electrode or electrodes. 

Grounding Conductor, Equipment. The conductor used 
to connect the non-current-carrying metal parts of equip- 
ment, raceways, and other enclosures to the system 
grounded conductor, the grounding electrode conductor, or 
both, at the service equipment or at the source of a sepa- 
rately derived system. 

Grounding Electrode. A device that establishes an electri- 
cal connection to the earth. 

Grounding Electrode Conductor. The conductor used to 
connect the grounding electrode(s) to the equipment 
grounding conductor, to the grounded conductor, or to both, 
at the service, at each building or structure where supplied 
by a feeder(s) or branch circuit(s), or at the source of a 
separately derived system. 

Guarded. Covered, shielded, fenced, enclosed, or otherwise 
protected by means of suitable covers, casings, barriers, rails, 
screens, mats, or platforms to remove the likelihood of ap- 
proach or contact by persons or objects to a point of danger. 

Guest Room. An accommodation combining living, sleep- 
ing, sanitary, and storage facilities within a compartment. 

Guest Suite. An accommodation with two or more con- 
tiguous rooms comprising a compartment, with or without 
doors between such rooms, that provides living, sleeping, 
sanitary, and storage faciUties. 

Handhole Enclosure. An enclosure identified for use in 
underground systems, provided with an open or closed bot- 
tom, and sized to allow personnel to reach into, but not 
enter, for the purpose of installing, operating, or maintain- 
ing equipment or wiring or both. 

Hoistway. Any shaftway, hatchway, well hole, or other ver- 
tical opening or space in which an elevator or dumbwaiter 
is designed to operate. 



Identified (as applied to equipment). Recognizable as 
suitable for the specific purpose, function, use, environ- 
ment, application, and so forth, where described in a par- 
ticular Code requirement. 

FPN: Some examples of ways to determine suitability of 
equipment for a specific purpose, environment, or applica- 
tion include investigations by a qualified testing laboratory 
(lisdng and labeling), an inspecfion agency, or other orga- 
nizations concerned with product evaluation. 

In Sight From (Within Sight From, Within Sight). Where 
this Code specifies that one equipment shall be "in sight 
from," "within sight from," or "within sight," and so forth, 
of another equipment, the specified equipment is to be vis- 
ible and not more than 15 m (50 ft) distant from the other. 

Interrupting Rating. The highest current at rated voltage 
that a device is intended to interrupt under standard test 
conditions. 

FPN: Equipment intended to interrupt current at other than 
fault levels may have its interrupting rating implied in other 
ratings, such as horsepower or locked rotor current. 

Isolated (as applied to location). Not readily accessible 
to persons unless special means for access are used. 

Labeled. Equipment or materials to which has been attached 
a label, symbol, or other identifying mark of an organization 
that is acceptable to the authority having jurisdiction and con- 
cerned with product evaluation, that maintains periodic in- 
spection of production of labeled equipment or materials, and 
by whose labeling the manufacturer indicates compUance with 
appropriate standards or performance in a specified manner. 

Lighting Outlet. An outlet intended for the direct connec- 
tion of a lampholder, a luminaire (lighting fixture), or a 
pendant cord terminating in a lampholder. 

Listed. Equipment, materials, or services included in a list 
published by an organization that is acceptable to the au- 
thority having jurisdiction and concerned with evaluation 
of products or services, that maintains periodic inspection 
of production of listed equipment or materials or periodic 
evaluation of services, and whose fisting states that the 
equipment, material, or services either meets appropriate 
designated standards or has been tested and found suitable 
for a specified purpose. 

FPN: The means for identifying listed equipment may 
vary for each organization concerned with product evalua- 
tion, some of which do not recognize equipment as listed 
unless it is also labeled. Use of the system employed by the 
listing organization allows the authority having jurisdiction 
to identify a listed product. 

Live Parts. Energized conductive components. 



2005 Edition NATIONAL ELECTRICAL CODE 



70-29 



100 



ARTICLE 100 — DEFINITIONS 



Location, Damp. Locations protected from weather and 
not subject to saturation with water or other liquids but 
subject to moderate degrees of moisture. Examples of such 
locations include partially protected locations under cano- 
pies, marquees, roofed open porches, and like locations, 
and interior locations subject to moderate degrees of mois- 
ture, such as some basements, some barns, and some cold- 
storage warehouses. 

Location, Dry. A location not normally subject to damp- 
ness or wetness. A location classified as dry may be tem- 
porarily subject to dampness or wetness, as in the case of a 
building under construction. 

Location, Wet. Installations under ground or in concrete 
slabs or masonry in direct contact with the earth; in loca- 
tions subject to saturation with water or other liquids, such 
as vehicle washing areas; and in unprotected locations ex- 
posed to weather. 

Luminaire. A complete lighting unit consisting of a lamp 
or lamps together with the parts designed to distribute the 
light, to position and protect the lamps and ballast (where 
applicable), and to connect the lamps to the power supply. 

Metal-Enclosed Power Switchgear. A switchgear assem- 
bly completely enclosed on all sides and top with sheet 
metal (except for ventilating openings and inspection win- 
dows) containing primary power circuit switching, inter- 
rupting devices, or both, with buses and connections. The 
assembly may include control and auxiliary devices. Access 
to the interior of the enclosure is provided by doors, remov- 
able covers, or both. 

Motor Control Center. An assembly of one or more en- 
closed sections having a common power bus and princi- 
pally containing motor control units. 

Multioutlet Assembly. A type of surface, flush, or free- 
standing raceway designed to hold conductors and recep- 
tacles, assembled in the field or at the factory. 

Nonautomatic. Action requiring personal intervention for 
its control. As applied to an electric controller, nonauto- 
matic control does not necessarily imply a manual control- 
ler, but only that personal intervention is necessary. 

Nonlinear Load. A load where the wave shape of the 
steady-state current does not follow the wave shape of the 
applied voltage. 

FPN: Electronic equipment, electronic/electric-discharge 
lighting, adjustable-speed drive systems, and similar equip- 
ment may be nonlinear loads. 

Outlet. A point on the wiring system at which current is 
taken to supply utilization equipment. 

Outline Lighting. An arrangement of incandescent lamps, 
electric discharge lighting, or other electrically powered light 



sources to outline or call attention to certain features such as 
the shape of a building or the decoration of a window. 

Overcurrent. Any current in excess of the rated current of 
equipment or the ampacity of a conductor. It may result 
from overload, short circuit, or ground fault. 

FPN: A current in excess of rating may be accommodated 
by certain equipment and conductors for a given set of 
conditions. Therefore, the rules for overcurrent protection 
are specific for particular situations. 

Overload. Operation of equipment in excess of normal, 
full-load rating, or of a conductor in excess of rated ampac- 
ity that, when it persists for a sufficient length of time, 
would cause damage or dangerous overheating. A fault, 
such as a short circuit or ground fault, is not an overload. 

Panelboard. A single panel or group of panel units de- 
signed for assembly in the form of a single panel, including 
buses and automatic overcurrent devices, and equipped 
with or without switches for the control of light, heat, or 
power circuits; designed to be placed in a cabinet or cutout 
box placed in or against a wall, partition, or other support; 
and accessible only from the front. 

Plenum. A compartment or chamber to which one or more 
air ducts are connected and that forms part of the air distri- 
bution system. 

Power Outlet. An enclosed assembly that may include re- 
ceptacles, circuit breakers, fuseholders, fused switches, 
buses, and watt-hour meter mounting means; intended to 
supply and control power to mobile homes, recreational 
vehicles, park trailers, or boats or to serve as a means for 
distributing power required to operate mobile or tempo- 
rarily installed equipment. 

Premises Wiring (System). That interior and exterior wir- 
ing, including power, lighting, control, and signal circuit 
wiring together with all their associated hardware, fittings, 
and wiring devices, both permanently and temporarily in- 
stalled, that extends from the service point or source of 
power, such as a battery, a solar photovoltaic system, or a 
generator, transformer, or converter windings, to the out- 
let(s). Such wiring does not include wiring internal to ap- 
phances, luminaires (fixtures), motors, controllers, motor 
control centers, and similar equipment. 

Qualified Person. One who has skills and knowledge re- 
lated to the construction and operation of the electrical 
equipment and installations and has received safety training 
on the hazards involved. 

FPN: Refer to NFPA 70E-2004, Standard for Electrical 
Safety in the Workplace, for electrical safety training 
requirements. 

Raceway. An enclosed channel of metal or nonmetallic 
materials designed expressly for holding wires, cables, or 



# 



70-30 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 100 — DEFINITIONS 



100 



• 



busbars, with additional functions as permitted in this Code. 
Raceways include, but are not limited to, rigid metal conduit, 
rigid nonmetaUic conduit, intermediate metal conduit, liq- 
uidtight flexible conduit, flexible metallic tubing, flexible 
metal conduit, electrical normietalhc tubing, electrical metallic 
tubing, underfloor raceways, cellular concrete floor raceways, 
cellular metal floor raceways, surface raceways, wireways, 
and busways. 

Rainproof. Constructed, protected, or treated so as to pre- 
vent rain from interfering with the successful operation of 
the apparatus under specified test conditions. 

Raintight. Constructed or protected so that exposure to a 
beating rain will not result in the entrance of water under 
specified test conditions. 

Receptacle. A receptacle is a contact device installed at the 
outlet for the connection of an attachment plug. A single 
receptacle is a single contact device with no other contact 
device on the same yoke. A multiple receptacle is two or 
more contact devices on the same yoke. 

Receptacle Outlet. An outlet where one or more recep- 
tacles are installed. 

Remote-Control Circuit. Any electric circuit that controls 
any other circuit through a relay or an equivalent device. 

Scalable Equipment. Equipment enclosed in a case or 
cabinet that is provided with a means of seahng or locking 
so that live parts cannot be made accessible without open- 
ing the enclosure. The equipment may or may not be oper- 
able without opening the enclosure. 

Separately Derived System. A premises wiring system 
whose power is derived from a source of electric energy or 
equipment other than a service. Such systems have no di- 
rect electrical connection, including a solidly connected 
grounded circuit conductor, to supply conductors originat- 
ing in another system. 

Service. The conductors and equipment for delivering elec- 
tric energy from the serving utility to the wiring system of 
the premises served. 

Service Cable. Service conductors made up in the form of 
a cable. 

Service Conductors. The conductors from the service point 
to the service disconnecting means. 

Service Drop. The overhead service conductors from the 
last pole or other aerial support to and including the splices, 
if any, connecting to the service-entrance conductors at the 
building or other structure. 

Service-Entrance Conductors, Overhead System. The ser- 
vice conductors between the terminals of the service equip- 



ment and a point usually outside the building, clear of building 
walls, where joined by tap or splice to the service drop. 

Service-Entrance Conductors, Underground System. The 

service conductors between the terminals of the service 
equipment and the point of connection to the service lateral. 

FPN: Where service equipment is located outside the 
building walls, there may be no service-entrance conduc- 
tors or they may be entirely outside the building. 

Service Equipment. The necessary equipment, usually con- 
sisting of a circuit breaker(s) or switch(es) and fuse(s) and 
their accessories, connected to the load end of service conduc- 
tors to a building or other structure, or an otherwise designated 
area, and intended to constitute the main control and cutoff of 
the supply. 

Service Lateral. The underground service conductors be- 
tween the street main, including any risers at a pole or other 
structure or from transformers, and the first point of con- 
nection to the service-entrance conductors in a terminal box 
or meter or other enclosure, inside or outside the building 
wall. Where there is no terminal box, meter, or other enclo- 
sure, the point of connection is considered to be the point of 
entrance of the service conductors into the building. 

Service Point. The point of connection between the facili- 
ties of the serving utihty and the premises wiring. 

Show Window. Any window used or designed to be used 
for the display of goods or advertising material, whether it 
is fully or partly enclosed or entirely open at the rear and 
whether or not it has a platform raised higher than the street 
floor level. 

Signaling Circuit. Any electric circuit that energizes sig- 
naling equipment. 

Solar Photovoltaic System. The total components and sub- 
systems that, in combination, convert solar energy into elec- 
trical energy suitable for connection to a utilization load. 

Special Permission. The written consent of the authority 
having jurisdiction. 

Structure. That which is built or constructed. 

Supplementary Overcurrent Protective Device. A device 
intended to provide limited overcurrent protection for specific 
applications and utiUzation equipment such as luminaires 
(Ughting fixtures) and appliances. This limited protection is in 
addition to the protection provided in the required branch cir- 
cuit by the branch circuit overcurrent protective device. 

Switch, Bypass Isolation. A manually operated device 
used in conjunction with a transfer switch to provide a 
means of directly connecting load conductors to a power 
source and of disconnecting the transfer switch. 



2005 Edition NATIONAL ELECTRICAL CODE 



70-31 



100 



ARTICLE 100 — DEFINITIONS 



Switch, General-Use. A switch intended for use in general 
distribution and branch circuits. It is rated in amperes, and it is 
capable of interrupting its rated current at its rated voltage. 

Switch, General-Use Snap. A form of general-use switch 
constructed so that it can be installed in device boxes or on 
box covers, or otherwise used in conjunction with wiring 
systems recognized by this Code. 

Switch, Isolating. A switch intended for isolating an elec- 
tric circuit from the source of power. It has no interrupting 
rating, and it is intended to be operated only after the circuit 
has been opened by some other means. 

Switch, Motor-Circuit. A switch rated in horsepower that 
is capable of interrupting the maximum operating overload 
current of a motor of the same horsepower rating as the 
switch at the rated voltage. 

Switch, Transfer. An automatic or nonautomatic device for 
transferring one or more load conductor connections from 
one power source to another. 

Switchboard. A large single panel, frame, or assembly of 
panels on which are mounted on the face, back, or both, 
switches, overcurrent and other protective devices, buses, 
and usually instruments. Switchboards are generally acces- 
sible from the rear as well as from the front and are not 
intended to be installed in cabinets. 

Thermally Protected (as applied to motors). The words 
Thermally Protected appearing on the nameplate of a motor 
or motor-compressor indicate that the motor is provided 
with a thermal protector. 

Thermal Protector (as applied to motors). A protective 
device for assembly as an integral part of a motor or motor- 
compressor that, when properly applied, protects the motor 
against dangerous overheating due to overload and failure 
to start. 

FPN: The thermal protector may consist of one or more 
sensing elements integral with the motor or motor-compressor 
and an external control device. 

Utilization Equipment. Equipment that utilizes electric 
energy for electronic, electromechanical, chemical, heating, 
lighting, or similar purposes. 

Ventilated. Provided with a means to permit circulation of 
air sufficient to remove an excess of heat, fumes, or vapors. 

Volatile Flammable Liquid. A flammable liquid having a 
flash point below 38°C (100°F), or a flammable liquid 
whose temperature is above its flash point, or a Class II 
combustible liquid that has a vapor pressure not exceeding 
276 kPa (40 psia) at 38°C (100°F) and whose temperature 
is above its flash point. 



Voltage (of a circuit). The greatest root-mean- square (rms) 
(effective) difference of potential between any two conduc- 
tors of the circuit concerned. 

FPN: Some systems, such as 3-phase 4-wire, single-phase 
3-wire, and 3-wire direct current, may have various circuits 
of various voltages. 

Voltage, Nominal. A nominal value assigned to a circuit or 
system for the purpose of conveniently designating its volt- 
age class (e.g., 120/240 volts, 480Y/277 volts, 600 volts). 
The actual voltage at which a circuit operates can vary from 
the nominal within a range that permits satisfactory opera- 
tion of equipment. 

FPN: See ANSI C84. 1-1995, Voltage Ratings for Electric 
Power Systems and Equipment (60 Hz). 

Voltage to Ground. For grounded circuits, the voltage be- 
tween the given conductor and that point or conductor of 
the circuit that is grounded; for ungrounded circuits, the 
greatest voltage between the given conductor and any other 
conductor of the circuit. 

Watertight. Constructed so that moisture will not enter the 
enclosure under specified test conditions. 

Weatherproof. Constructed or protected so that exposure 
to the weather will not interfere with successful operation. 

FPN: Rainproof, raintight, or watertight equipment can 
fulfill the requirements for weatherproof where varying 
weather conditions other than wetness, such as snow, ice, 
dust, or temperature extremes, are not a factor. 



II. Over 600 Volts, Nominal 

Whereas the preceding definitions are intended to apply 
wherever the terms are used throughout this Code, the fol- 
lowing definitions are applicable only to parts of the article 
specifically covering installations and equipment operating 
at over 600 volts, nominal. 

Electronically Actuated Fuse. An overcurrent protective 
device that generally consists of a control module that pro- 
vides current sensing, electronically derived time-current 
characteristics, energy to initiate tripping, and an interrupt- 
ing module that interrupts current when an overcurrent oc- 
curs. Electronically actuated fuses may or may not operate 
in a current-limiting fashion, depending on the type of con- 
trol selected. 

Fuse. An overcurrent protective device with a circuit- 
opening fusible part that is heated and severed by the pas- 
sage of overcurrent through it. 

FPN: A fuse comprises all the parts that form a unit ca- 
pable of performing the prescribed functions. It may or may 
not be the complete device necessary to connect it into an 
electrical circuit. 



• 



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ARTICLE 110 — REQUIREMENTS FOR ELECTRICAL INSTALLATIONS 



110.3 



• 



# 



Controlled Vented Power Fuse. A fuse with provision for 
controlling discharge circuit interruption such that no soUd 
material may be exhausted into the surrounding atmosphere. 

FPN: The fuse is designed so that discharged gases will not 
ignite or damage insulation in the path of the discharge or 
propagate a flashover to or between grounded members or 
conduction members in the path of the discharge where the 
distance between the vent and such insulation or conduction 
members conforms to manufacturer's recommendations. 

Expulsion Fuse Unit (Expulsion Fuse). A vented fuse unit 
in which the expulsion effect of gases produced by the arc 
and lining of the fuseholder, either alone or aided by a 
spring, extinguishes the arc. 

Nonvented Power Fuse. A fuse without intentional provi- 
sion for the escape of arc gases, liquids, or solid particles to 
the atmosphere during circuit interruption. 

Power Fuse Unit. A vented, nonvented, or controlled vented 
fuse unit in which the arc is extinguished by being drawn 
through solid material, granular material, or liquid, either 
alone or aided by a spring. 

Vented Power Fuse. A fuse with provision for the escape 
of arc gases, liquids, or solid particles to the surrounding 
atmosphere during circuit interruption. 

Multiple Fuse. An assembly of two or more single-pole 
fuses. 

Switching Device. A device designed to close, open, or 
both, one or more electric circuits. 

Circuit Breaker A switching device capable of making, car- 
rying, and interrupting currents under normal circuit condi- 
tions, and also of making, carrying for a specified time, and 
interrupting currents under specified abnormal circuit condi- 
tions, such as those of short circuit. 

Cutout. An assembly of a fuse support with either a fuse- 
holder, fuse carrier, or disconnecting blade. The fuseholder 
or fuse carrier may include a conducting element (fuse link) 
or may act as the disconnecting blade by the inclusion of a 
nonfusible member. 

Disconnecting (or Isolating) Switch (Disconnector, Isolator). 
A mechanical switching device used for isolating a circuit 
or equipment from a source of power. 

Disconnecting Means. A device, group of devices, or other 
means whereby the conductors of a circuit can be discon- 
nected from their source of supply. 

Interrupter Switch. A switch capable of making, carrying, 
and interrupting specified currents. 

Oil Cutout (Oil-Filled Cutout). A cutout in which all or 
part of the fuse support and its fuse link or disconnecting 
blade is mounted in oil with complete immersion of the 
contacts and the fusible portion of the conducting element 



(fuse link) so that arc interruption by severing of the fuse 
link or by opening of the contacts will occur under oil. 

Oil Switch. A switch having contacts that operate under oil 
(or askarel or other suitable liquid). 

Regulator Bypass Switch. A specific device or combina- 
tion of devices designed to bypass a regulator. 



ARTICLE 110 
Requirements for Electrical Installations 

I. General 

110.1 Scope. This article covers general requirements for the 
examination and approval, installation and use, access to and 
spaces about electrical conductors and equipment; enclosures 
intended for personnel entry; and tunnel instaDations. 

110.2 Approval. The conductors and equipment required or 
permitted by this Code shall be acceptable only if approved. 

FPN: See 90.7, Examination of Equipment for Safety, and 
110.3, Examinadon, Identificadon, Installadon, and Use of 
Equipment. See definitions of Approved, Identified, La- 
beled, and Listed. 

110.3 Examination, Identification, Installation, and Use 
of Equipment. 

(A) Examination. In judging equipment, considerations 
such as the following shall be evaluated: 

(1) Suitability for installation and use in conformity with 
the provisions of this Code 

FPN: Suitability of equipment use may be identified by a 
descripUon marked on or provided with a product to iden- 
dfy the suitability of the product for a specific purpose, 
environment, or application. Suitability of equipment may 
be evidenced by listing or labeling. 

(2) Mechanical strength and durability, including, for parts 
designed to enclose and protect other equipment, the 
adequacy of the protection thus provided 

(3) Wire-bending and connection space 

(4) Electrical insulation 

(5) Heating effects under normal conditions of use and also 
under abnormal conditions likely to arise in service 

(6) Arcing effects 

(7) Classification by type, size, voltage, current capacity, 
and specific use 

(8) Other factors that contribute to the practical safeguard- 
ing of persons using or likely to come in contact with 
the equipment 



2005 Edition 



NATIONAL ELECTRICAL CODE 



70-33 



110.4 



ARTICLE 110 — REQUIREMENTS FOR ELECTRICAL INSTALLATIONS 



(B) Installation and Use. Listed or labeled equipment 
shall be installed and used in accordance with any instruc- 
tions included in the listing or labeling. 

110.4 Voltages. Throughout this Code, the voltage consid- 
ered shall be that at which the circuit operates. The voltage 
rating of electrical equipment shall not be less than the 
noriiinal voltage of a circuit to which it is connected. 

110.5 Conductors. Conductors normally used to carry cur- 
rent shall be of copper unless otherwise provided in this 
Code. Where the conductor material is not specified, the 
material and the sizes given in this Code shall apply to 
copper conductors. Where other materials are used, the size 
shall be changed accordingly. 

FPN: For aluminum and copper-clad aluminum conduc- 
tors, see 310.15. 

110.6 Conductor Sizes. Conductor sizes are expressed in 
American Wire Gage (AWG) or in circular mils. 

110.7 Insulation Integrity. Completed wiring installations 
shall be free from short circuits and from grounds other 
than as required or permitted in Article 250. 

110.8 Wiring Methods. Only wiring methods recognized 
as suitable are included in this Code. The recognized meth- 
ods of wiring shall be permitted to be installed in any type 
of building or occupancy, except as otherwise provided in 
this Code. 

110.9 Interrupting Rating. Equipment intended to inter- 
rupt current at fault levels shall have an interrupting rating 
sufficient for the nominal circuit voltage and the current 
that is available at the line terminals of the equipment. 

Equipment intended to interrupt current at other than fault 
levels shall have an interrupting rating at nominal circuit volt- 
age sufficient for the current that must be interrupted. 

110.10 Circuit Impedance and Other Characteristics. 

The overcurrent protective devices, the total impedance, the 
component short-circuit current ratings, and other charac- 
teristics of the circuit to be protected shall be selected and 
coordinated to permit the circuit-protective devices used to 
clear a fault to do so without extensive damage to the elec- 
trical components of the circuit. This fault shall be assumed 
to be either between two or more of the circuit conductors 
or between any circuit conductor and the grounding con- 
ductor or enclosing metal raceway. Listed products applied 
in accordance with their listing shall be considered to meet 
the requirements of this section. 

110.11 Deteriorating Agents. Unless identified for use in 
the operating environment, no conductors or equipment 



shall be located in damp or wet locations; where exposed to 
gases, fumes, vapors, hquids, or other agents that have a 
deteriorating effect on the conductors or equipment; or 
where exposed to excessive temperatures. 

FPN No. I : See 300.6 for protection against corrosion. 

FPN No. 2: Some cleaning and lubricating compounds 
can cause severe deterioration of many plastic rnaterials 
used for insulating and structural applications in equipment. 

Equipment identified only as "dry locations," "Type 1 ," 
or "indoor use only" shall be protected against permanent 
damage from the weather during building construction. 

110.12 Mechanical Execution of Work. Electrical equip- 
ment shall be installed in a neat and workmanlike manner. 

FPN: Accepted industry practices are described in 
ANSI/NEC A 1-2000, Standard Practices for Good 
Workmanship in Electrical Contracting, and other ANSI- 
approved installation standards. 

(A) Unused Openings. Unused cable or raceway openings 
in boxes, raceways, auxiUary gutters, cabinets, cutout boxes, 
meter socket enclosures, equipment cases, or housings shall be 
effectively closed to afford protection substantially equivalent 
to the wall of the equipment. Where metallic plugs or plates 
are used with nonmetalUc enclosures, they shall be recessed at 
least 6 mm {Va in.) from the outer surface of the enclosure. 

(B) Subsurface Enclosures. Conductors shall be racked to 
provide ready and safe access in underground and subsur- 
face enclosures into which persons enter for installation and 
maintenance. 

(C) Integrity of Electrical Equipment and Connections. 

Internal parts of electrical equipment, including busbars, 
wiring terminals, insulators, and other surfaces, shall not be 
damaged or contaminated by foreign materials such as 
paint, plaster, cleaners, abrasives, or corrosive residues. 
There shall be no damaged parts that may adversely affect 
safe operation or mechanical strength of the equipment 
such as parts that are broken; bent; cut; or deteriorated by 
corrosion, chemical action, or overheating. 

110.13 Mounting and Cooling of Equipment. 

(A) Mounting. Electrical equipment shall be firmly se- 
cured to the surface on which it is mounted. Wooden plugs 
driven into holes in masonry, concrete, plaster, or similar 
materials shall not be used. 

(B) Cooling. Electrical equipment that depends on the 
natural circulation of air and convection principles for cool- 
ing of exposed surfaces shall be installed so that room 
airflow over such surfaces is not prevented by walls or by 
adjacent installed equipment. For equipment designed for 



• 



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ARTICLE 110 — REQUIREMENTS FOR ELECTRICAL INSTALLATIONS 



110.16 



• 



• 



• 



floor mounting, clearance between top surfaces and adja- 
cent surfaces shall be provided to dissipate rising warm air. 
Electrical equipment provided with ventilating openings 
shall be installed so that walls or other obstructions do not 
prevent the free circulation of air through the equipment. 

110.14 Electrical Connections. Because of different char- 
acteristics of dissimilar metals, devices such as pressure 
terminal or pressure splicing connectors and soldering lugs 
shall be identified for the material of the conductor and 
shall be properly installed and used. Conductors of dissimi- 
lar metals shall not be intermixed in a terminal or splicing 
connector where physical contact occurs between dissimilar 
conductors (such as copper and aluminum, copper and 
copper-clad aluminum, or aluminum and copper-clad alu- 
minum), unless the device is identified for the purpose and 
conditions of use. Materials such as solder, fluxes, inhibi- 
tors, and compounds, where employed, shall be suitable for 
the use and shall be of a type that will not adversely affect 
the conductors, installation, or equipment. 

FPN: Many terminations and equipment are marked with 
a tightening torque. 

(A) Terminals. Connection of conductors to terminal parts 
shall ensure a thoroughly good connection without damaging 
the conductors and shall be made by means of pressure con- 
nectors (including set-screw type), solder lugs, or splices to 
flexible leads. Connection by means of wire-binding screws or 
studs and nuts that have upturned lugs or the equivalent shall 
be permitted for 10 AWG or smaller conductors. 

Terminals for more than one conductor and terminals 
used to connect aluminum shall be so identified. 

(B) Splices. Conductors shall be spliced or joined with splic- 
ing devices identified for the use or by brazing, welding, or 
soldering with a fusible metal or alloy. Soldered splices shall 
first be spliced or joined so as to be mechanically and electri- 
caUy secure without solder and then be soldered. All splices 
and joints and the free ends of conductors shall be covered 
with an insulation equivalent to that of the conductors or with 
an insulating device identified for the purpose. 

Wire connectors or splicing means installed on conduc- 
tors for direct burial shall be listed for such use. 

(C) Temperature Limitations. The temperature rating as- 
sociated with the ampacity of a conductor shall be selected 
and coordinated so as not to exceed the lowest temperature 
rating of any connected termination, conductor, or device. 
Conductors with temperature ratings higher than specified 
for terminations shall be permitted to be used for ampacity 
adjustment, correction, or both. 

(1) Equipment Provisions. The determination of termination 
provisions of equipment shall be based on 110.14(C)(1)(a) 
or (C)(1)(b). Unless the equipment is listed and marked 



otherwise, conductor ampacities used in determining 
equipment termination provisions shall be based on 
Table 310.16 as appropriately modified by 310.15(B)(6). 

(a) Termination provisions of equipment for circuits 
rated 100 amperes or less, or marked for 14 AWG through 
1 AWG conductors, shaU be used only for one of the fol- 
lowing: 

(1) Conductors rated 60°C (140°F). 

(2) Conductors with higher temperature ratings, provided the 
ampacity of such conductors is determined based on the 
60°C (140°F) ampacity of the conductor size used. 

(3) Conductors with higher temperature ratings if the equip- 
ment is Usted and identified for use with such conductors. 

(4) For motors marked with design letters B, C, or D, con- 
ductors having an insulation rating of 75°C (167°F) or 
higher shall be permitted to be used, provided the am- 
pacity of such conductors does not exceed the 75°C 
(167°F) ampacity. 

(b) Termination provisions of equipment for circuits 
rated over 100 amperes, or marked for conductors larger 
than 1 AWG, shall be used only for one of the following: 

(1) Conductors rated 75°C (167°F) 

(2) Conductors with higher temperature ratings, provided 
the ampacity of such conductors does not exceed the 
75°C (167°F) ampacity of the conductor size used, or 
up to their ampacity if the equipment is listed and iden- 
tified for use with such conductors 

(2) Separate Connector Provisions. Separately installed 
pressure connectors shall be used with conductors at the 
ampacities not exceeding the ampacity at the listed and 
identified temperature rating of the connector. 

FPN: With respect to 110.14(C)(1) and (C)(2), equipment 
markings or listing information may additionally restrict 
the sizing and temperature ratings of connected conductors. 

110.15 High-Leg Marliing. On a 4-wire, delta-connected 
system where the midpoint of one phase winding is 
grounded, only the conductor or busbar having the higher 
phase voltage to ground shall be durably and permanently 
marked by an outer finish that is orange in color or by other 
effective means. Such identification shall be placed at each 
point on the system where a connection is made if the 
grounded conductor is also present. 

110.16 Flash Protection. Switchboards, panelboards, in- 
dustrial control panels, meter socket enclosures, and motor 
control centers that are in other than dwelling occupancies 
and are likely to require examination, adjustment, servic- 
ing, or maintenance while energized shall be field marked 
to warn qualified persons of potential electric arc flash haz- 
ards. The marking shall be located so as to be clearly vis- 
ible to qualified persons before examination, adjustment, 
servicing, or maintenance of the equipment. 



2005 Edition NATIONAL ELECTRICAL CODE 



70-35 



110.18 



ARTICLE 110 — REQUIREMENTS FOR ELECTRICAL INSTALLATIONS 



FPN No. 1: NFPA 70E-2004, Standard for Electrical 
Safety in the Workplace, provides assistance in determining 
severity of potential exposure, planning safe work prac- 
tices, and selecting personal protective equipment. 

FPN No. 2: ANSI Z535.4-1998, Product Safety Signs and 
Labels, provides guidelines for the design of safety signs 
and labels for application to products. 

110.18 Arcing Parts. Parts of electric equipment that in or- 
dinary operation produce arcs, sparks, fiames, or molten metal 
shall be enclosed or separated and isolated from aU combus- 
tible material. 

FPN: For hazardous (classified) locations, see Articles 500 
through 517. For motors, see 430.14. 

110.19 Light and Power from Railway Conductors. Cir- 
cuits for lighting and power shall not be connected to any 
system that contains trolley wires with a ground return. 

Exception: Such circuit connections shall be permitted in 
car houses, power houses, or passenger and freight stations 
operated in connection with electric railways. 

110.21 Marking. The manufacturer's name, trademark, or 
other descriptive marking by which the organization re- 
sponsible for the product can be identified shall be placed 
on all electric equipment. Other markings that indicate volt- 
age, current, wattage, or other ratings shall be provided as 
specified elsewhere in this Code. The marking shall be of 
sufficient durability to withstand the environment involved. 

110.22 Identification of Disconnecting Means. Each dis- 
connecting means shall be legibly marked to indicate its 
purpose unless located and arranged so the purpose is evi- 
dent. The marking shall be of sufficient durability to with- 
stand the environment involved. 

Where circuit breakers or fuses are applied in compliance 
with the series combination ratings marked on the equipment 
by the manufacturer, the equipment enclosure(s) shall be leg- 
ibly marked in the field to indicate the equipment has been 
appUed with a series combination rating. The marking shall be 
readily visible and state the following: 

CAUTION — SERIES COMBINATION SYSTEM 

RATED AMPERES. IDENTIFIED 

REPLACEMENT COMPONENTS REQUIRED. 

FPN: See 240.86(B) for interrupting rating marking for 
end-use equipment. 

110.23 Current Transformers. Unused current transform- 
ers associated with potentially energized circuits shall be 
short-circuited. 



IL 600 Volts, Nominal, or Less 

110.26 Spaces About Electrical Equipment. Sufficient 
access and working space shall be provided and maintained 
about all electric equipment to permit ready and safe opera- 
tion and maintenance of such equipment. Enclosures hous- 
ing electrical apparatus that are controlled by a lock(s) shall 
be considered accessible to qualified persons. 

(A) Working Space. Working space for equipment operat- 
ing at 600 volts, nominal, or less to ground and likely to 
require examination, adjustment, servicing, or maintenance 
while energized shall comply with the dimensions of 
110.26(A)(1), (A)(2), and (A)(3) or as required or permitted 
elsewhere in this Code. 

(1) Depth of Working Space. The depth of the working 
space in the direction of live parts shall not be less than that 
specified in Table 110.26(A)(1)(1) unless the requirements 
of 110.26(A)(1)(a), (A)(1)(b), or (A)(1)(c) are met. Dis- 
tances shall be measured from the exposed live parts or 
from the enclosure or opening if the live parts are enclosed. 

Table 110.26(A)(1) Working Spaces 



• 



Nominal 

Voltage to 

Ground 


Minimum Clear Distance 


Condition 1 Condition 2 Condition 3 


0-150 
151-600 


900 mm (3 ft) 900 mm (3 ft) 900 mm (3 ft) 
900 mm (3 ft) 1.1m (3 '/a ft) 1.2 m (4 ft) 



Note: Where the conditions are as follows: 

Condition 1 — Exposed live parts on one side of the working space 

and no Uve or grounded parts on the other side of the working space, 

or exposed live parts on both sides of the working space that are 

effectively guarded by insulating materials. 

Condition 2 — Exposed live parts on one side of the working space 

and grounded parts on the other side of the working space. Concrete, 

brick, or tile walls shall be considered as grounded. 

Condition 3 — Exposed live parts on both sides of the working 

space. 



(a) Dead-Front Assemblies. Working space shall not 
be required in the back or sides of assemblies, such as 
dead-front switchboards or motor control centers, where all 
connections and all renewable or adjustable parts, such as 
fuses or switches, are accessible from locations other than 
the back or sides. Where rear access is required to work on 
nonelectrical parts on the back of enclosed equipment, a 
minimum horizontal working space of 762 mm (30 in.) 
shall be provided. 

(b) Low Voltage. By special permission, smaller working 
spaces shall be permitted where all exposed live parts operate 
at not greater than 30 volts rms, 42 volts peak, or 60 volts dc. 

(c) Existing Buildings. In existing buildings where 
electrical equipment is being replaced. Condition 2 working 
clearance shall be permitted between dead-front switch- 



• 



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NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 110 — REQUIREMENTS FOR ELECTRICAL INSTALLATIONS 



110.26 



• 



• 



boards, panelboards, or motor control centers located 
across the aisle from each other where conditions of main- 
tenance and supervision ensure that written procedures 
have been adopted to prohibit equipment on both sides of 
the aisle from being open at the same time and quaUfied 
persons who are authorized will service the installation. 

(2) Width of Working Space. The width of the working 
space in front of the electric equipment shall be the width 
of the equipment or 750 mm (30 in.), whichever is greater. 
In all cases, the work space shall permit at least a 90 degree 
opening of equipment doors or hinged panels. 

(3) Height of Working Space. The work space shall be 
clear and extend from the grade, floor, or platform to the 
height required by 110.26(E). Within the height require- 
ments of this section, other equipment that is associated 
with the electrical installation and is located above or be- 
low the electrical equipment shall be permitted to extend 
not more than 150 mm (6 in.) beyond the front of the 
electrical equipment. 

(B) Clear Spaces. Working space required by this section 
shall not be used for storage. When normally enclosed live 
parts are exposed for inspection or servicing, the working 
space, if in a passageway or general open space, shall be 
suitably guarded. 

(C) Entrance to Working Space. 

(1) Minimum Required. At least one entrance of suffi- 
cient area shall be provided to give access to working space 
about electrical equipment. 

(2) Large Equipment. For equipment rated 1200 amperes 
or more that contains overcurrent devices, switching de- 
vices, or control devices, there shall be one entrance to the 
required working space not less than 610 mm (24 in.) wide 
and 2.0 m (6^/2 ft) high at each end of the working space. 
Where the entrance has a personnel door(s), the door(s) 
shall open in the direction of egress and be equipped with 
panic bars, pressure plates, or other devices that are nor- 
mally latched but open under simple pressure. 

A single entrance to the required working space shall be 
permitted where either of the conditions in 110.26(C)(2)(a) 
or (C)(2)(b) is met. 

(a) Unobstructed Exit. Where the location permits a 
continuous and unobstructed way of exit travel, a single 
entrance to the working space shall be permitted. 

(b) Extra Working Space. Where the depth of the 
working space is twice that required by 110.26(A)(1), a 
single entrance shall be permitted. It shall be located so that 
the distance from the equipment to the nearest edge of the 
entrance is not less than the minimum clear distance speci- 
fied in Table 110.26(A)(1) for equipment operating at that 
voltage and in that condition. 



(D) Illumination. Illumination shall be provided for all 
working spaces about service equipment, switchboards, 
panelboards, or motor control centers installed indoors. Ad- 
ditional lighting outlets shall not be required where the 
work space is illuminated by an adjacent light source or as 
permitted by 210.70(A)(1), Exception No. 1, for switched 
receptacles. In electrical equipment rooms, the illumination 
shall not be controlled by automatic means only. 

(E) Headroom. The minimum headroom of working 
spaces about service equipment, switchboards, panelboards, 
or motor control centers shall be 2.0 m (6"/2 ft). Where the 
electrical equipment exceeds 2.0 m (6 '/a ft) in height, the 
minimum headroom shall not be less than the height of the 
equipment. 

Exception: In existing dwelling units, service equipment 
or panelboards that do not exceed 200 amperes shall be 
permitted in spaces where the headroom is less than 2.0 m 
(6V2ft). 

(F) Dedicated Equipment Space. All switchboards, panel- 
boards, distribution boards, and motor control centers shall be 
located in dedicated spaces and protected from damage. 

Exception: Control equipment that by its very nature or 
because of other rules of the Code must be adjacent to or 
within sight of its operating machinery shall be permitted 
in those locations. 

(1) Indoor. Indoor installations shall comply with 
110.26(F)(1)(a) through (F)(1)(d). 

(a) Dedicated Electrical Space. The space equal to the 
width and depth of the equipment and extending from the 
floor to a height of 1.8 m (6 ft) above the equipment or to 
the structural ceiling, whichever is lower, shall be dedicated 
to the electrical installation. No piping, ducts, leak protec- 
tion apparatus, or other equipment foreign to the electrical 
installation shall be located in this zone. 

Exception: Suspended ceilings with removable panels shall 
be permitted within the 1.8-m (6-ft) zone. 

(b) Foreign Systems. The area above the dedicated 
space required by 110.26(F)(1)(a) shall be permitted to con- 
tain foreign systems, provided protection is installed to 
avoid damage to the electrical equipment from condensa- 
tion, leaks, or breaks in such foreign systems. 

(c) Sprinkler Protection. Sprinkler protection shall be 
permitted for the dedicated space where the piping com- 
plies with this section. 

(d) Suspended Ceilings. A dropped, suspended, or simi- 
lar ceiling that does not add strength to the building structure 
shall not be considered a structural ceihng. 



2005 Edition 



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70-37 



110.27 



ARTICLE 110 — REQUIREMENTS FOR ELECTRICAL INSTALLATIONS 



(2) Outdoor. Outdoor electrical equipment shall be in- 
stalled in suitable enclosures and shall be protected from 
accidental contact by unauthorized personnel, or by vehicu- 
lar traffic, or by accidental spillage or leakage from piping 
systems. The working clearance space shall include the 
zone described in 110.26(A). No architectural appurtenance 
or other equipment shall be located in this zone. 

110.27 Guarding of Live Parts. 

(A) Live Parts Guarded Against Accidental Contact. 

Except as elsewhere required or permitted by this Code, 
live parts of electrical equipment operating at 50 volts or 
more shall be guarded against accidental contact by ap- 
proved enclosures or by any of the following means: 

(1) By location in a room, vault, or similar enclosure that is 
accessible only to qualified persons. 

(2) By suitable permanent, substantial partitions or screens 
arranged so that only qualified persons have access to 
the space within reach of the live parts. Any openings 
in such partitions or screens shall be sized and located 
so that persons are not likely to come into accidental 
contact with the live parts or to bring conducting ob- 
jects into contact with them. 

(3) By location on a suitable balcony, gallery, or platform 
elevated and arranged so as to exclude unqualified per- 
sons. 

(4) By elevation of 2.5 m (8 ft) or more above the floor or 
other working surface. 

(B) Prevent Physical Damage. In locations where electric 
equipment is likely to be exposed to physical damage, en- 
closures or guards shall be so arranged and of such strength 
as to prevent such damage. 

(C) Warning Signs. Entrances to rooms and other guarded 
locations that contain exposed live parts shall be marked 
with conspicuous warning signs forbidding unqualified per- 
sons to enter. 

FPN: For motors, see 430.232 and 430.233. For over 
600 volts, see 110.34. 

III. Over 600 Volts, Nominal 

110.30 General. Conductors and equipment used on cir- 
cuits over 600 volts, nominal, shall comply with Part I of 
this article and with the following sections, which supple- 
ment or modify Part I. In no case shall the provisions of 
this part apply to equipment on the supply side of the ser- 
vice point. 

110.31 Enclosure for Electrical Installations. Electrical in- 
stallations in a vault, room, or closet or in an area surrounded 
by a wall, screen, or fence, access to which is controlled by a 



lock(s) or other approved means, shall be considered to be 
accessible to quahfied persons only. The type of enclosure 
used in a given case shall be designed and constructed accord- 
ing to the nature and degree of the hazard(s) associated with 
the installation. 

For installations other than equipment as described in 
110.31(D), a wall, screen, or fence shall be used to enclose 
an outdoor electrical installation to deter access by persons 
who are not qualified. A fence shall not be less than 2.1 m 
(7 ft) in height or a combination of 1.8 m (6 ft) or more of 
fence fabric and a 300-mm (1-ft) or more extension utiliz- 
ing three or more strands of barbed wire or equivalent. The 
distance from the fence to live parts shall be not less than 
given in Table 110.31. 

Table 110.31 Minimum Distance from Fence to Live Parts 



Minimum Distance to Live Parts 


Nominal Voltage 


m ft 


601 - 13,799 
13,800 - 230,000 
Over 230,000 


3.05 10 
4.57 15 
5.49 18 



Note: For clearances of conductors for specific system voltages and typi- 
cal BIL ratings, see ANSI C2-2002, National Electrical Safety Code. 



FPN: See Article 450 for construction requirements for 
transformer vaults. 

(A) Fire Resistivity of Electrical Vaults. The walls, roof, 
floors, and doorways of vaults containing conductors and 
equipment over 600 volts, nominal, shall be constructed of 
materials that have adequate structural strength for the con- 
ditions, with a minimum fire rating of 3 hours. The floors of 
vaults in contact with the earth shall be of concrete that is 
not less than 4 in. (102 mm) thick, but where the vault is 
constructed with a vacant space or other stories below it, 
the floor shall have adequate structural strength for the load 
imposed on it and a minimum fire resistance of 3 hours. For 
the purpose of this section, studs and wallboards shall not 
be considered acceptable. 

(6) Indoor Installations. 

(1) In Places Accessible to Unqualified Persons. Indoor 
electrical installations that are accessible to unqualified per- 
sons shall be made with metal-enclosed equipment. Metal- 
enclosed switchgear, unit substations, transformers, pull 
boxes, connection boxes, and other similar associated 
equipment shall be marked with appropriate caution signs. 
Openings in ventilated dry-type transformers or similar 
openings in other equipment shall be designed so that for- 
eign objects inserted through these openings are deflected 
from energized parts. 



• 



• 



70-38 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 110 — REQUIREMENTS FOR ELECTRICAL INSTALLATIONS 



110.34 



(2) In Places Accessible to Qualified Persons Only. In- 
door electrical installations considered accessible only to 
qualified persons in accordance with this section shall com- 
ply with 110.34, 110.36, and 490.24. 

(C) Outdoor Installations. 

(1) In Places Accessible to Unqualified Persons. Outdoor 
electrical installations that are open to unqualified persons 
shall comply with Parts I, II, and III of Article 225. 

FPN: For clearances of conductors for system voltages 
over 600 volts, nominal, see ANSI C2-2002, National Elec- 
trical Safety Code. 

(2) In Places Accessible to Qualified Persons Only. Out- 
door electrical installations that have exposed live parts 
shall be accessible to qualified persons only in accordance 
with the first paragraph of this section and shall comply 
with 110.34, 110.36, and 490.24. 

(D) Enclosed Equipment Accessible to Unqualified Per- 
sons. Ventilating or similar openings in equipment shall be 
designed such that foreign objects inserted through these 
openings are deflected from energized parts. Where exposed 
to physical damage from vehicular traffic, suitable guards shall 
be provided. Nonmetallic or metal-enclosed equipment lo- 
cated outdoors and accessible to the general public shall be 
designed such that exposed nuts or bolts cannot be readily 
removed, permitting access to live parts. Where nonmetalhc or 
metal-enclosed equipment is accessible to the general public 
and the bottom of the enclosure is less than 2.5 m (8 ft) above 
the floor or grade level, the enclosure door or hinged cover 
shall be kept locked. Doors and covers of enclosures used 
solely as pull boxes, splice boxes, or junction boxes shall be 
locked, bolted, or screwed on. Underground box covers that 
weigh over 45.4 kg (100 lb) shall be considered as meeting 
this requirement. 

110.32 Work Space About Equipment. Sufficient space 
shall be provided and maintained about electric equipment 
to permit ready and safe operation and maintenance of such 
equipment. Where energized parts are exposed, the mini- 
mum clear work space shall not be less than 2.0 m (6V2 ft) 
high (measured vertically from the floor or platform) or less 
than 900 mm (3 ft) wide (measured parallel to the equip- 
ment). The depth shall be as required in 110.34(A). In all 
cases, the work space shall permit at least a 90 degree 
opening of doors or hinged panels. 

110.33 Entrance and Access to Work Space. 

(A) Entrance. At least one entrance not less than 610 mm 
(24 in.) wide and 2.0 m (6!/2 ft) high shall be provided to 
give access to the working space about electric equipment. 
Where the entrance has a personnel door(s), the door(s) 
shall open in the direction of egress and be equipped with 



panic bars, pressure plates, or other devices that are nor- 
mally latched but open under simple pressure. 

(1) Large Equipment. On switchboard and control panels 
exceeding 1.8 m (6 ft) in width, there shall be one entrance 
at each end of the equipment. A single entrance to the 
required working space shall be permitted where either of 
the conditions in 110.33(A)(1)(a) or (A)(1)(b) is met. 

(a) Unobstructed Exit. Where the location permits a 
continuous and unobstructed way of exit travel, a single 
entrance to the working space shall be permitted. 

(b) Extra Working Space. Where the depth of the 
working space is twice that required by 110.34(A), a single 
entrance shall be permitted. It shall be located so that the 
distance from the equipment to the nearest edge of the 
entrance is not less than the minimum clear distance speci- 
fied in Table 110.34(A) for equipment operating at that 
voltage and in that condition. 

(2) Guarding. Where bare energized parts at any voltage 
or insulated energized parts above 600 volts, nominal, to 
ground are located adjacent to such entrance, they shall be 
suitably guarded. 

(B) Access. Permanent ladders or stairways shall be provided 
to give safe access to the working space around electric equip- 
ment installed on platforms, balconies, or mezzanine floors or 
in attic or roof rooms or spaces. 

110.34 Work Space and Guarding. 

(A) Working Space. Except as elsewhere required or per- 
mitted in this Code, the minimum clear working space in 
the direction of access to live parts of electrical equipment 
shall not be less than specified in Table 110.34(A). Dis- 
tances shall be measured from the live parts, if such are 
exposed, or from the enclosure front or opening if such are 
enclosed. 

Exception: Working space shall not be required in back of 
equipment such as dead-front switchboards or control as- 
semblies where there are no renewable or adjustable parts 
(such as fuses or switches) on the back and where all con- 
nections are accessible from locations other than the back. 
Where rear access is required to work on de-energized 
parts on the back of enclosed equipment, a minimum work- 
ing space of 750 mm (30 in.) horizontally shall be provided. 

(B) Separation from Low-Voltage Equipment. Where 
switches, cutouts, or otiier equipment operating at 600 volts, 
nominal, or less are installed in a vault, room, or enclosure 
where there are exposed Live parts or exposed wiring operating 
at over 600 volts, nominal, the high-voltage equipment shall 
be effectively separated from the space occupied by the low- 
voltage equipment by a suitable partition, fence, or screen. 



2005 Edition 



NATIONAL ELECTRICAL CODE 



70-39 



110.36 



ARTICLE 110 — REQUIREMENTS FOR ELECTRICAL INSTALLATIONS 



Table 110.34(A) Minimum Depth of Clear Working Space at 
Electrical Equipment 



Table 110.34(E) Elevation of Unguarded Live Parts Above 
Working Space 



Nominal 


Minimum Clear Distance 


Nominal Voltage 
Between Phases 


Elevation 


Voltage to 
Ground 


Condition 1 


Condition 2 


Condition 3 


m ft 


601-2500 V 

2501-9000 V 

9001-25,000 V 

25,00 lV-75 kV 


900 mm (3 ft) 
1.2 m (4 ft) 
1.5 m (5 ft) 
1.8 m(6ft) 
2.5 m (8 ft) 


1.2 m (4 ft) 
1.5 m (5 ft) 
1.8 m (6 ft) 
2.5 m (8 ft) 
3.0 m (10 ft) 


1.5 m (5 ft) 
1.8 m (6 ft) 
2.8 m (9 ft) 
3.0 m (10 ft) 
3.7 m (12 ft) 


601-7500 V 

7501-35,000 V 

Over 35 kV 


2.8 9 

2.9 9'/2 

2.9 m + 9.5 mm/kV Wi ft + 0.37 in./kV 
above 35 above 35 


Above 75 kV 







Note: Where the conditions are as follows: 

Condition 1 — Exposed live parts on one side of the working space 

and no hve or grounded parts on the other side of the working space, 

or exposed live parts on both sides of the working space that are 

effectively guarded by insulating materials. 

Condition 2 — Exposed live parts on one side of the working space 

and grounded parts on the other side of the working space. Concrete, 

brick, or tile walls shall be considered as grounded. 

Condition 3 — Exposed live parts on both sides of the working space. 



Exception: Switches or other equipment operating at 
600 volts, nominal, or less and serving only equipment 
within the high-voltage vault, room, or enclosure shall 
be permitted to be installed in the high-voltage vault, 
room or enclosure without a partition, fence, or screen if 
accessible to qualified persons only. 

(C) Locked Rooms or Enclosures. The entrance to all build- 
ings, vaults, rooms, or enclosures containing exposed live 
parts or exposed conductors operating at over 600 volts, nomi- 
nal, shall be kept locked unless such entrances are under the 
observation of a qualified person at all times. 

Where the voltage exceeds 600 volts, nominal, perma- 
nent and conspicuous warning signs shall be provided, 
reading as follows: 

DANGER — HIGH VOLTAGE — KEEP OUT 

(D) Illumination. Illumination shall be provided for all 
working spaces about electrical equipment. The lighting 
outlets shall be arranged so that persons changing lamps or 
making repairs on the lighting system are not endangered 
by hve parts or other equipment. 

The points of control shall be located so that persons 
are not likely to come in contact with any hve part or 
moving part of the equipment while turning on the lights. 

(E) Elevation of Unguarded Live Parts. Unguarded live 
parts above working space shall be maintained at elevations 
not less than required by Table 110.34(E). 

(F) Protection of Service Equipment, Metal-Enclosed 
Power Switchgear, and Industrial Control Assemblies. 

Pipes or ducts foreign to the electrical installation and 
requiring periodic maintenance or whose malfunction 
would endanger the operation of the electrical system 



shall not be located in the vicinity of the service equip- 
ment, metal-enclosed power switchgear, or industrial control 
assemblies. Protection shall be provided where necessary to 
avoid damage from condensation leaks and breaks in such 
foreign systems. Piping and other facihties shall not be con- 
sidered foreign if provided for fire protection of the electrical 
installation. 

110.36 Circuit Conductors. Circuit conductors shall be 
permitted to be installed in raceways; in cable trays; as 
metal-clad cable, as bare wire, cable, and busbars; or as 
Type MV cables or conductors as provided in 300.37, 
300.39, 300.40, and 300.50. Bare live conductors shall con- 
form with 490.24. 

Insulators, together with their mounting and conductor at- 
tachments, where used as supports for wires, single-conductor 
cables, or busbars, shall be capable of safely withstanding the 
maximum magnetic forces that would prevail when two or 
more conductors of a circuit were subjected to short-circuit 
current. 

Exposed runs of insulated wires and cables that have a 
bare lead sheath or a braided outer covering shall be sup- 
ported in a manner designed to prevent physical damage to 
the braid or sheath. Supports for lead-covered cables shall 
be designed to prevent electrolysis of the sheath. 

110.40 Temperature Limitations at Terminations. Con- 
ductors shall be permitted to be terminated based on the 
90°C (194°F) temperature rating and ampacity as given 
in Table 310.67 through Table 310.86, unless otherwise 
identified. 

IV. T\innel Installations over 600 Volts, Nominal 

110.51 General. 

(A) Covered. The provisions of this part shall apply to the 
installation and use of high-voltage power distribution and 
utilization equipment that is portable, mobile, or both, such 
as substations, trailers, cars, mobile shovels, draglines, 
hoists, drills, dredges, compressors, pumps, conveyors, un- 
derground excavators, and the like. 



70^0 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 110 — REQUIREMENTS FOR ELECTRICAL INSTALLATIONS 



110.72 



(B) Other Articles. The requirements of this part shall be 
additional to, or amendatory of, those prescribed in Articles 
100 through 490 of this Code. Special attention shall be 
paid to Article 250. 

(C) Protection Against Physical Damage. Conductors and 
cables in tunnels shall be located above the tunnel floor and so 
placed or guarded to protect them from physical damage. 

110.52 Overcurrent Protection. Motor-operated equip- 
ment shall be protected from overcurrent in accordance 
with Parts III, IV, and V of Article 430. Transformers shall 
be protected from overcurrent in accordance with 450.3. 

110.53 Conductors. High-voltage conductors in tunnels 
shall be installed in metal conduit or other metal raceway. 
Type MC cable, or other approved multiconductor cable. 
Multiconductor portable cable shall be permitted to supply 
mobile equipment. 

110.54 Bonding and Equipment Grounding Conductors. 

(A) Grounded and Bonded. All non-current-carrying 
metal parts of electric equipment and all metal raceways 
and cable sheaths shall be effectively grounded and bonded 
to all metal pipes and rails at the portal and at intervals not 
exceeding 300 m (1000 ft) throughout the tunnel. 

(B) Equipment Grounding Conductors. An equipment 
grounding conductor shall be run with circuit conductors 
inside the metal raceway or inside the multiconductor cable 
jacket. The equipment grounding conductor shall be per- 
mitted to be insulated or bare. 

110.55 Transformers, Switches, and Electrical Equip- 
ment. All transformers, switches, motor controllers, motors, 
rectifiers, and other equipment installed below ground shall be 
protected from physical damage by location or guarding. 

110.56 Energized Parts. Bare terminals of transformers, 
switches, motor controllers, and other equipment shall be 
enclosed to prevent accidental contact with energized parts. 

110.57 Ventilation System Controls. Electrical controls 
for the ventilation system shall be arranged so that the 
airflow can be reversed. 

110.58 Disconnecting Means. A switch or circuit breaker 
that simultaneously opens all ungrounded conductors of the 
circuit shall be installed within sight of each transformer or 
motor location for disconnecting the transformer or motor. 
The switch or circuit breaker for a transformer shall have an 
ampere rating not less than the ampacity of the transformer 
supply conductors. The switch or circuit breaker for a motor 
shall comply with the appUcable requirements of Article 430. 



110.59 Enclosures. Enclosures for use in tunnels shall be 
dripproof, weatherproof, or submersible as required by the 
environmental conditions. Switch or contactor enclosures 
shall not be used as junction boxes or as raceways for 
conductors feeding through or tapping off to other switches, 
unless the enclosures comply with 312.8. 

V. Manholes and Other Electric Enclosures Intended 
for Personnel Entry, All Voltages 

110.70 General. Electric enclosures intended for personnel 
entry and specifically fabricated for this purpose shall be of 
sufficient size to provide safe work space about electric 
equipment with live parts that is likely to require examina- 
tion, adjustment, servicing, or maintenance while ener- 
gized. Such enclosures shall have sufficient size to permit 
ready installation or withdrawal of the conductors em- 
ployed without damage to the conductors or to their insu- 
lation. They shall comply with the provisions of this part. 

Exception: Where electric enclosures covered by Part V of 
this article are part of an industrial wiring system operat- 
ing under conditions of maintenance and supervision that 
ensure that only qualified persons monitor and supervise 
the system, they shall be permitted to be designed and in- 
stalled in accordance with appropriate engineering prac- 
tice. If required by the authority having jurisdiction, design 
documentation shall be provided. 

110.71 Strength. Manholes, vaults, and their means of ac- 
cess shall be designed under qualified engineering supervi- 
sion and shall withstand all loads likely to be imposed on 
the structures. 

FPN: See ANSI C2-2002, National Electrical Safety 
Code, for additional information on the loading that can be 
expected to bear on underground enclosures. 

110.72 Cabling Work Space. A clear work space not less 
than 900 mm (3 ft) wide shall be provided where cables are 
located on both sides, and not less than 750 mm (ZVi ft) 
where cables are only on one side. The vertical headroom 
shall not be less than 1.8 m (6 ft) unless the opening is 
within 300 nmi (1 ft), measured horizontally, of the adja- 
cent interior side wall of the enclosure. 

Exception: A manhole containing only one or more of the 
following shall be permitted to have one of the horizontal 
work space dimensions reduced to 600 mm (2 ft) where the 
other horizontal clear work space is increased so the sum 
of the two dimensions is not less than 1.8 m (6 ft): 

(1) Optical fiber cables as covered in Article 770 

(2) Power-limited fire alarm circuits supplied in accor- 
dance with 760.41(A) 

(3) Class 2 or Class 3 remote-control and signaling cir- 
cuits, or both, supplied in accordance with 725.41 



2005 Edition NATIONAL ELECTRICAL CODE 



70-41 



110.73 



ARTICLE 110 — REQUIREMENTS FOR ELECTRICAL INSTALLATIONS 



110.73 Equipment Work Space. Where electric equipment 
with live parts that is likely to require examination, adjust- 
ment, servicing, or maintenance while energized is installed in 
a manhole, vault, or other enclosure designed for personnel 
access, the work space and associated requirements in 110.26 
shall be met for installations operating at 600 volts or less. 
Where the installation is over 600 volts, the work space and 
associated requirements in 110.34 shall be met. A manhole 
access cover that weighs over 45 kg (100 lb) shall be consid- 
ered as meeting the requirements of 110.34(C). 

110.74 Bending Space for Conductors. Bending space for 
conductors operating at 600 volts or below shall be provided 
in accordance with the requirements of 314.28. Conductors 
operating over 600 volts shall be provided with bending space 
in accordance with 314.71(A) and 314.71(B), as applicable. 
All conductors shall be cabled, racked up, or arranged in an 
approved manner that provides ready and safe access for per- 
sons to enter for installation and maintenance. 

Exception: Where 314.71(B) applies, each row or column 
of ducts on one wall of the enclosure shall be calculated 
individually, and the single row or column that provides the 
maximum distance shall be used. 

110.75 Access to Manholes. 

(A) Dimensions. Rectangular access openings shall not be 
less than 650 mm x 550 mm (26 in. x 22 in.). Round access 
openings in a manhole shall not be less than 650 mm 
(26 in.) in diameter. 

Exception: A manhole that has a fixed ladder that does not 
obstruct the opening or that contains only one or more of 
the following shall be permitted to reduce the minimum 
cover diameter to 600 mm (2 ft): 

(1) Optical fiber cables as covered in Article 770 

(2) Power-limited fire alarm circuits supplied in accor- 
dance with 760.41 

(3) Class 2 or Class 3 remote-control and signaling cir- 
cuits, or both, supplied in accordance with 725.41 

(B) Obstructions. Manhole openings shall be free of pro- 
trusions that could injure personnel or prevent ready egress. 



(C) Location. Manhole openings for personnel shall be lo- 
cated where they are not directly above electric equipment or 
conductors in the enclosure. Where this is not practicable, 
either a protective barrier or a fixed ladder shall be provided. 

(D) Covers. Covers shall be over 45 kg (100 lb) or other- 
wise designed to require the use of tools to open. They shall 
be designed or restrained so they cannot fall into the man- 
hole or protrude sufficiently to contact electrical conductors 
or equipment within the manhole. 

(E) Marking. Manhole covers shall have an identifying 
mark or logo that prominently indicates their function, such 
as "electric." 

110.76 Access to Vaults and Tunnels. 

(A) Location. Access openings for personnel shall be lo- 
cated where they are not directly above electric equipment 
or conductors in the enclosure. Other openings shall be 
permitted over equipment to facilitate installation, mainte- 
nance, or replacement of equipment. 

(B) Locks. In addition to compliance with the requirements 
of 110.34, if applicable, access openings for personnel shall 
be arranged such that a person on the inside can exit when 
the access door is locked from the outside, or in the case of 
normally locking by padlock, the locking arrangement shall 
be such that the padlock can be closed on the locking sys- 
tem to prevent locking from the outside. 

110.77 Ventilation. Where manholes, tunnels, and vaults 
have communicating openings into enclosed areas used by 
the public, ventilation to open air shall be provided wher- 
ever practicable. 

110.78 Guarding. Where conductors or equipment, or both, 
could be contacted by objects falling or being pushed through 
a ventilating grating, both conductors and live paits shall be 
protected in accordance with the requirements of 110.27(A)(2) 
or 110.31(B)(1), depending on the voltage. 

110.79 Fixed Ladders. Fixed ladders shall be corrosion 
resistant. 



70^2 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 200 — USE AND IDENTIFICATION OF GROUNDED CONDUCTORS 



200.6 



Chapter 2 Wiring and Protection 



ARTICLE 200 

Use and Identification br Grounded 

Conductors 



• 



# 



200.1 Scope. This article provides requirements for the 
following: 

(1) Identification of terminals 

(2) Grounded conductors in premises wiring systems 

(3) Identification of grounded conductors 

FPN: See Article 100 for definitions of Grounded Conduc- 
tor and Grounding Conductor. 

200.2 General. All premises wiring systems, other than 
circuits and systems exempted or prohibited by 210.10, 
215.7, 250.21, 250.22, 250.162, 503.155, 517.63, 668.11, 
668.21, and 690.41 Exception, shall have a grounded con- 
ductor that is identified in accordance with 200.6. 

The grounded conductor, where insulated, shall have 
insulation that is (1) suitable, other than color, for any un- 
grounded conductor of the same circuit on circuits of less 
than 1000 volts or impedance grounded neutral systems of 
1 kV and over, or (2) rated not less than 600 volts for 
solidly grounded neutral systems of 1 kV and over as de- 
scribed in 250.184(A). 

200.3 Connection to Grounded System. Premises wiring 
shall not be electrically connected to a supply system unless 
the latter contains, for any grounded conductor of the interior 
system, a corresponding conductor that is grounded. For the 
purpose of this section, electrically connected shall mean con- 
nected so as to be capable of carrying current, as distinguished 
from connection through electromagnetic induction. 

200.6 Means of Identifying Grounded Conductors. 

(A) Sizes 6 AWG or Smaller. An insulated grounded con- 
ductor of 6 AWG or smaller shall be identified by a con- 
tinuous white or gray outer finish or by three continuous 
white stripes on other than green insulation along its entire 
length. Wires that have their outer covering finished to 
show a white or gray color but have colored tracer threads 
in the braid identifying the source of manufacture shall be 
considered as meeting the provisions of this section. Insu- 
lated grounded conductors shall also be permitted to be 
identified as follows: 

(1) The grounded conductor of a mineral-insulated, metal- 
sheathed cable shall be identified at the time of instal- 
lation by distinctive marking at its terminations. 



(2) A single-conductor, sunlight-resistant, outdoor-rated 
cable used as a grounded conductor in photovoltaic 
power systems as permitted by 690.31 shall be identi- 
fied at the time of installation by distinctive white 
marking at all terminations. 

(3) Fixture wire shall comply with the requirements for 
grounded conductor identification as specified in 402.8. 

(4) For aerial cable, the identification shall be as above, or 
by means of a ridge located on the exterior of the cable 
so as to identify it. 

(B) Sizes Larger Than 6 AWG. An insulated grounded 
conductor larger than 6 AWG shall be identified by one of 
the following means: 

(1) By a continuous white or gray outer finish. 

(2) By three continuous white stripes along its entire length 
on other than green insulation. 

(3) At the time of installation, by a distinctive white or 
gray marking at its terminations. This marking shall 
encircle the conductor or insulation. 

(C) Flexible Cords. An insulated conductor that is in- 
tended for use as a grounded conductor, where contained 
within a flexible cord, shall be identified by a white or gray 
outer finish or by methods permitted by 400.22. 

(D) Grounded Conductors of Different Systems. Where 
grounded conductors of different systems are installed in 
the same raceway, cable, box, auxiliary gutter, or other type 
of enclosure, each grounded conductor shall be identified 
by system. Identification that distinguishes each system 
grounded conductor shall be permitted by one of the fol- 
lowing means: 

(1) One system grounded conductor shall have an outer 
covering conforming to 200.6(A) or 200.6(B). 

(2) The grounded conductor(s) of other systems shall have 
a different outer covering conforming to 200.6(A) or 
200.6(B) or by an outer covering of white or gray with 
a readily distinguishable colored stripe other than green 
running along the insulation. 

(3) Other and different means of identification as allowed 
by 200.6(A) or 200.6(B) that will distinguish each sys- 
tem grounded conductor. 

This means of identification shall be permanently posted at 
each branch-circuit panelboard. 

(E) Grounded Conductors of Multiconductor Cables. 

The insulated grounded conductors in a multiconductor 
cable shall be identified by a continuous white or gray outer 
finish or by three continuous white stripes on other than 



2005 Edition NATIONAL ELECTRICAL CODE 



70-43 



200.7 



ARTICLE 200 — USE AND IDENTIFICATION OF GROUNDED CONDUCTORS 



green insulation along its entire length. Multiconductor flat 
cable 4 AWG or larger shall be permitted to employ an 
external ridge on the grounded conductor. 

Exception No. J: Where the conditions of maintenance 
and supervision ensure that only qualified persons service 
the installation, grounded conductors in multiconductor 
cables shall be permitted to be permanently identified at 
their terminations at the time of installation by a distinctive 
white marking or other equally effective means. 

Exception No. 2: The grounded conductor of a multiconduc- 
tor vamished-cloth-insulated cable shall be permitted to be 
identified at its terminations at the time of installation by a 
distinctive white marking or other equally effective means. 

FPN: The color gray may have been used in the past as an 
ungrounded conductor. Care should be taken when working 
on existing systems. 

200.7 Use of Insulation of a White or Gray Color or 
with Three Continuous White Stripes. 

(A) General. The following shall be used only for the 
grounded circuit conductor, unless otherwise permitted in 
200.7(B) and 200.7(C): 

(1) A conductor with continuous white or gray covering 

(2) A conductor with three continuous white stripes on 
other than green insulation 

(3) A marking of white or gray color at the termination 

(B) Circuits of Less Than 50 Volts. A conductor with 
white or gray color insulation or three continuous white 
stripes or having a marking of white or gray at the termi- 
nation for circuits of less than 50 volts shall be required to 
be grounded only as required by 250.20(A). 

(C) Circuits of 50 Volts or More. The use of insulation that 
is white or gray or that has three continuous white stripes for 
other than a grounded conductor for circuits of 50 volts or 
more shall be permitted only as in (1) through (3). 

(1) If part of a cable assembly and where the insulation is 
permanently reidentified to indicate its use as an un- 
grounded conductor, by painting or other effective 
means at its termination, and at each location where the 
conductor is visible and accessible. Identification shall 
encircle the insulation and shall be a color other than 
white, gray, or green. 

(2) Where a cable assembly contains an insulated conduc- 
tor for single-pole, 3-way or 4-way switch loops and 
the conductor with white or gray insulation or a mark- 
ing of three continuous white stripes is used for the 
supply to the switch but not as a return conductor from 
the switch to the switched outlet. In these applications, 
the conductor with white or gray insulation or with 
three continuous white stripes shall be permanently re- 
identified to indicate its use by painting or other effec- 



tive means at its terminations and at each location 
where the conductor is visible and accessible. 
(3) Where a flexible cord, having one conductor identified 
by a white or gray outer finish or three continuous 
white stripes or by any other means permitted by 
400.22, is used for connecting an appliance or equip- 
ment permitted by 400.7. This shall apply to flexible 
cords connected to outlets whether or not the outlet is 
supplied by a circuit that has a grounded conductor. 

FPN: The color gray may have been used in the past as an 
ungrounded conductor Care should be taken when working 
on existing systems. 

200.9 Means of Identification of Terminals. The identifi- 
cation of terminals to which a grounded conductor is to be 
connected shall be substantially white in color. The identi- 
fication of other terminals shall be of a readily distinguish- 
able different color. 

Exception: Where the conditions of maintenance and super- 
vision ensure that only qualified persons service the installa- 
tions, terminals for grounded conductors shall be permitted to 
be permanently identified at the time of installation by a dis- 
tinctive white marking or other equally effective means. 

200.10 Identification of Terminals. 

(A) Device Terminals. All devices, excluding panelboards, 
provided with terminals for the attachment of conductors and 
intended for connection to more than one side of the circuit 
shall have terminals properly marked for identification, unless 
the electrical connection of the terminal intended to be con- 
nected to the grounded conductor is clearly evident. 

Exception: Terminal identification shall not be required for 
devices that have a normal current rating of over 30 amperes, 
other than polarized attachment plugs and polarized recep- 
tacles for attachment plugs as required in 200.10(B). 

(B) Receptacles, Plugs, and Connectors. Receptacles, 
polarized attachment plugs, and cord connectors for plugs 
and polarized plugs shall have the terminal intended for 
connection to the grounded conductor identified as follows: 

(1) Identification shall be by a metal or metal coating that 
is substantially white in color or by the word white or 
the letter W located adjacent to the identified terminal. 

(2) If the terminal is not visible, the conductor entrance 
hole for the connection shall be colored white or 
marked with the word white or the letter W. 

FPN: See 250.126 for identification of wiring device 
equipment grounding conductor terminals. 

(C) Screw Shells. For devices with screw shells, the ter- 
minal for the grounded conductor shall be the one con- 
nected to the screw shell. 



• 



70^4 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 210 — BRANCH CIRCUITS 



210.3 



# 



• 



• 



(D) Screw Shell Devices with Leads. For screw shell de- 
vices with attached leads, the conductor attached to the 
screw shell shall have a white or gray finish. The outer 
finish of the other conductor shall be of a solid color that 
will not be confused with the white or gray finish used to 
identify the grounded conductor. 

FPN: The color gray may have been used in the past as an 
ungrounded conductor. Care should be taken when working 
on existing systems. 

(E) Appliances. Appliances that have a single-pole 
switch or a single-pole overcurrent device in the line or 
any line-connected screw shell lampholders, and that are 
to be connected by (1) a permanent wiring method or (2) 
field-installed attachment plugs and cords with three or 
more wires (including the equipment grounding conduc- 
tor), shall have means to identify the terminal for the 
grounded circuit conductor (if any). 

200.11 Polarity of Connections. No grounded conductor 
shall be attached to any terminal or lead so as to reverse the 
designated polarity. 



ARTICLE t210 
Eranch Circuits 



I. General Provisions 

210.1 Scope. This article covers branch circuits except for 
branch circuits that supply only motor loads, which are 
covered in Article 430. Provisions of this article and Article 
430 apply to branch circuits with combination loads. 

210.2 Other Articles for Specific-Purpose Branch Cir- 
cuits. Branch circuits shall comply with this article and also 
with the appHcable provisions of other articles of this Code. 
The provisions for branch circuits supplying equipment listed 
in Table 210.2 amend or supplement the provisions in this 
article and shall apply to branch circuits referred to therein. 

210.3 Rating. Branch circuits recognized by this article shall 
be rated in accordance with the maximum permitted ampere 
rating or setting of the overcurrent device. The rating for other 
than individual branch circuits shall be 15, 20, 30, 40, and 50 
amperes. Where conductors of higher ampacity are used for 
any reason, the ampere rating or setting of the specified over- 
current device shall determine the circuit rating. 

Exception: Multioutlet branch circuits greater than 50 
amperes shall be permitted to supply nonlighting outlet 
loads on industrial premises where conditions of mainte- 
nance and supervision ensure that only qualified persons 
service the equipment. 



Table 210.2 Specific-Purpose Branch Circuits 



Equipment 



Article 



Section 



Air-conditioning and 

refrigerating equipment 
Audio signal processing, 

amplification, and 

reproduction equipment 
Busways 
Circuits and equipment 720 

operating at less than 50 

volts 
Central heating equipment 

other than fixed electric 

space-heating equipment 
Class 1, Class 2, and Class 3 725 

remote-control, signaling, 

and power-limited circuits 
Closed-loop and programmed 780 

power distribution 
Cranes and hoists 
Electric signs and outline 

lighting 
Electric welders 630 

Elevators, dumbwaiters, 

escalators, moving walks, 

wheelchair lifts, and 

stairway chair lifts 
Fire alarm systems 760 

Fixed electric heating 

equipment for pipelines 

and vessels 
Fixed electric space-heating 

equipment 
Fixed outdoor electric 

deicing and snow-melting 

equipment 
Information technology 

equipment 
Infrared lamp industrial 

heating equipment 
Induction and dielectric 665 

heating equipment 
Marinas and boatyards 
Mobile homes, manufactured 550 

homes, and mobile home 

parks 
Motion picture and television 530 

studios and similar 

locations 
Motors, motor circuits, and 430 

controllers 
Pipe organs 
Recreational vehicles and 551 

recreational vehicle parks 
Switchboards and 

panelboards 
Theaters, audience areas of 

motion picture and 

television studios, and 

similar locations 
X-ray equipment 



440.6, 440.31, 
440.32 
640.8 



368.17 



422.12 



610.42 
600.6 



620.61 

427.4 

424.3 
426.4 

645.5 
422.48, 424.3 

555.19 



650.7 



408.52 

520.41, 
520.52, 520.62 



660.2, 517.73 



2005 Edition NATIONAL ELECTRICAL CODE 



70^5 



210.4 



ARTICLE 210 — BRANCH CIRCUITS 



210.4 Multiwire Branch Circuits. 

(A) General. Branch circuits recognized by this article 
shall be permitted as multiwire circuits. A multiwire circuit 
shall be permitted to be considered as multiple circuits. All 
conductors shall originate from the same panelboard or 
similar distribution equipment. 

FPN: A 3-phase, 4-wire, wye-connected power system 
used to supply power to nonlinear loads may necessitate 
that the power system design allow for the possibility of 
high harmonic neutral currents. 

(B) Devices or Equipment. Where a multiwire branch ck- 
cuit supphes more than one device or equipment on the same 
yoke, a means shall be provided to disconnect simultaneously 
all ungrounded conductors supplying those devices or equip- 
ment at the point where the branch circuit originates. 

(C) Line-to-Neutral Loads. Multiwire branch circuits 
shall supply only line-to-neutral loads. 

Exception No. 1: A multiwire branch circuit that supplies 
only one utilization equipment. 

Exception No. 2: Where all ungrounded conductors of the 
multiwire branch circuit are opened simultaneously by the 
branch-circuit overcurrent device. 

FPN: See 300.13(B) for continuity of grounded conductor 
on multiwire circuits. 

210.5 Identification for Branch Circuits. 

(A) Grounded Conductor. The grounded conductor of a 
branch circuit shall be identified in accordance with 200.6. 

(B) Equipment Grounding Conductor. The equipment 
grounding conductor shall be identified in accordance with 
250.119. 

(C) Ungrounded Conductors. Where the premises wiring 
system has branch circuits supphed from more than one nomi- 
nal voltage system, each ungrounded conductor of a branch 
circuit, where accessible, shall be identified by system. The 
means of identification shall be permitted to be by separate 
color coding, marking tape, tagging, or other approved means 
and shall be permanently posted at each branch-circuit panel- 
board or similar branch-circuit distribution equipment. 

210.6 Branch-Circuit Voltage Limitations. The nominal 
voltage of branch circuits shall not exceed the values per- 
mitted by 210.6(A) through 210.6(E). 

(A) Occupancy Limitation. In dwelling units and guest 
rooms or guest suites of hotels, motels, and similar occupan- 
cies, the voltage shall not exceed 120 volts, nominal, between 
conductors that supply the terminals of the following: 
(1) Luminaires (lighting fixtures) 



(2) Cord-and-plug-connected loads 1440 volt-amperes, 
nominal, or less or less than Va hp 

(B) 120 Volts Between Conductors. Circuits not exceed- 
ing 120 volts, nominal, between conductors shall be permit- 
ted to supply the following: 

(1) The terminals of lampholders applied within their volt- 
age ratings 

(2) Auxiliary equipment of electric-discharge lamps 

(3) Cord-and-plug-connected or permanently connected 
utilization equipment 

(C) 277 Volts to Ground. Circuits exceeding 120 volts, 
nominal, between conductors and not exceeding 277 volts, 
nominal, to ground shall be permitted to supply the following: 

(1) Listed electric-discharge luminaires (lighting fixtures) 

(2) Listed incandescent luminaires (lighting fixtures), where 
suppUed at 120 volts or less from the output of a step- 
down autotransformer that is an integral component of 
the luminaire (fixture) and the outer shell terminal is 
electrically connected to a grounded conductor of the 
branch circuit 

(3) Luminaires (lighting fixtures) equipped with mogul- 
base screw shell lampholders 

(4) Lampholders, other than the screw shell type, applied 
within their voltage ratings 

(5) Auxiliary equipment of electric-discharge lamps 

(6) Cord-and-plug-connected or permanently connected 
utilization equipment 

(D) 600 Volts Between Conductors. Circuits exceeding 
277 volts, nominal, to ground and not exceeding 600 volts, 
nominal, between conductors shall be permitted to supply 
the following: 

(1) The auxiliary equipment of electric-discharge lamps 
mounted in permanently installed luminaires (fixtures) 
where the luminaires (fixtures) are mounted in accor- 
dance with one of the following: 

a. Not less than a height of 6.7 m (22 ft) on poles or 
similar structures for the illumination of outdoor ar- 
eas such as highways, roads, bridges, athletic fields, 
or parking lots 

b. Not less than a height of 5.5 m (18 ft) on other 
structures such as tunnels 

(2) Cord-and-plug-connected or permanently connected 
utilization equipment other than luminaires (fixtures) 

FPN: See 410.78 for auxiliary equipment limitations. 

Exception No. 1 to (B), (C), and (D): For lampholders of 
infrared industrial heating appliances as provided in 422. 14. 

Exception No. 2 to (B), (C), and (D): For railway proper- 
ties as described in 110.19. 



• 



• 



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NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 210 — BRANCH CIRCUITS 



210.9 



• 



(E) Over 600 Volts Between Conductors. Circuits ex- 
ceeding 600 volts, nominal, between conductors shall be 
permitted to supply utilization equipment in installations 
where conditions of maintenance and supervision ensure 
that only qualified persons service the installation. 

210.7 Branch Circuit Receptacle Requirements. 

(A) Receptacle Outlet Location. Receptacle outlets shall 
be located in branch circuits in accordance with Part III of 
Article 210. 

(B) Multiple Branch Circuits. Where two or more branch 
circuits supply devices or equipment on the same yoke, a 
means to simultaneously disconnect the ungrounded con- 
ductors supplying those devices shall be provided at the 
point at which the branch circuits originate. 

210.8 Ground-Fault Circuit-Interrupter Protection for 
Personnel. 

FPN: See 215.9 for ground-fault circuit-interrupter protec- 
tion for personnel on feeders. 

(A) Dwelling Units. All 125- volt, single-phase, 15- and 
20-ampere receptacles installed in the locations specified in 
(1) through (8) shall have ground-fault circuit-interrupter 
protection for personnel. 

(1) Bathrooms 

(2) Garages, and also accessory buildings that have a floor 
located at or below grade level not intended as habit- 
able rooms and limited to storage areas, work areas, 
and areas of similar use 



Exception No. 
accessible. 



1 to (2): Receptacles that are not readily 



Exception No. 2 to (2): A single receptacle or a duplex re- 
ceptacle for two appliances located within dedicated space for 
each appliance that, in normal use, is not easily moved from 
one place to another and that is cord-and-plug connected in 
accordance with 400.7(A)(6), (A)(7), or (A)(8). 

Receptacles installed under the exceptions to 210.8(A)(2) 
shall not be considered as meeting the requirements of 
210.52(G) 

(3) Outdoors 

Exception to (3): Receptacles that are not readily acces- 
sible and are supplied by a dedicated branch circuit for 
electric snow-melting or deicing equipment shall be permit- 
ted to be installed in accordance with 426.28. 

Receptacles installed under the exceptions to 210.8(A)(5) 
shall not be considered as meeting the requirements of 
210.52(G). 



(4) Crawl spaces — at or below grade level 

(5) Unfinished basements — for purposes of this section, 
unfinished basements are defined as portions or areas of 
the basement not intended as habitable rooms and lim- 
ited to storage areas, work areas, and the like 

Exception No. 1 to (5): Receptacles that are not readily 
accessible. 

Exception No. 2 to (5): A single receptacle or a duplex re- 
ceptacle for two appliances located within dedicated space for 
each appliance that, in normal use, is not easily moved from 
one place to another and that is cord-and-plug connected in 
accordance with 400.7(A)(6), (A)(7), or (A)(8). 

Exception No. 3 to (5): A receptacle supplying only a perma- 
nently installed fire alarm or burglar alarm system shall not 
be required to have ground-fault circuit-interrupter protection. 

(6) Kitchens — where the receptacles are installed to serve 
the countertop surfaces 

(7) Laundry, utility, and wet bar sinks — where the recep- 
tacles are installed within 1.8 m (6 ft) of the outside 
edge of the sink 

(8) Boathouses 

(B) Other Than Dwelling Units. All 125-volt, single- 
phase, 15- and 20-ampere receptacles installed in the loca- 
tions specified in (1) through (5) shall have ground-fault 
circuit-interrupter protection for personnel: 

(1) Bathrooms 

(2) Commercial and institutional kitchens — for the purposes 
of this section, a kitchen is an area with a sink and per- 
manent faciUties for food preparation and cooking 

(3) Rooftops 

(4) Outdoors in public spaces — for the purpose of this sec- 
tion a public space is defined as any space that is for 
use by, or is accessible to, the public 

Exception to (3) and (4): Receptacles that are not readily 
accessible and are supplied from a dedicated branch circuit 
for electric snow-melting or deicing equipment shall be 
permitted to be installed in accordance with the applicable 
provisions of Article 426. 

(5) Outdoors, where installed to comply with 210.63 

(C) Boat Hoists. Ground-fault circuit-interrupter protec- 
tion for personnel shall be provided for oudets that supply 
boat hoists installed in dwelling unit locations and supplied 
by 125-volt, 15- and 20-ampere branch circuits. 

210.9 Circuits Derived from Autotransformers. Branch 
circuits shall not be derived from autotransformers unless 
the circuit supplied has a grounded conductor that is elec- 
trically connected to a grounded conductor of the system 
supplying the autotransformer. 



2005 Edition NATIONAL ELECTRICAL CODE 



70-47 



210.10 



ARTICLE 210 — BRANCH CIRCUITS 



Exception No. 1: An autotransformer shall be permitted 
without the connection to a grounded conductor where 
transforming from a nominal 208 volts to a nominal 
240-volt supply or similarly from 240 volts to 208 volts. 

Exception No. 2: In industrial occupancies, where condi- 
tions of maintenance and supervision ensure that only quali- 
fied persons service the installation, autotransformers shall be 
permitted to supply nominal 600-volt loads from nominal 480- 
volt systems, and 480-volt loads from nominal 600-volt sys- 
tems, without the connection to a similar grounded conductor. 

210.10 Ungrounded Conductors Tapped from Grounded 
Systems. Two-wire dc circuits and ac circuits of two or more 
ungrounded conductors shall be permitted to be tapped from 
the ungrounded conductors of circuits that have a grounded 
neutral conductor. Switching devices in each tapped circuit 
shall have a pole in each ungrounded conductor. All poles of 
multipole switching devices shall manually switch together 
where such switching devices also serve as a disconnecting 
means as required by the following: 

(1) 410.48 for double-pole switched lampholders 

(2) 410.54(B) for electric-discharge lamp auxiliary equip- 
ment switching devices 

(3) 422.31(B) for an appHance 

(4) 424.20 for a fixed electric space-heating unit 

(5) 426.51 for electric deicing and snow-melting equipment 

(6) 430.85 for a motor controller 

(7) 430.103 for a motor 

210.11 Branch Circuits Required. Branch circuits for 
lighting and for appliances, including motor- operated appU- 
ances, shall be provided to supply the loads calculated in 
accordance with 220.10. In addition, branch circuits shall 
be provided for specific loads not covered by 220.10 where 
required elsewhere in this Code and for dwelling unit loads 
as specified in 210.11(C). 

(A) Number of Branch Circuits. The minimum number 
of branch circuits shall be determined from the total calcu- 
lated load and the size or rating of the circuits used. In all 
installations, the number of circuits shall be sufficient to 
supply the load served. In no case shall the load on any 
circuit exceed the maximum specified by 220.18. 

(B) Load Evenly Proportioned Among Branch Circuits. 

Where the load is calculated on the basis of volt-amperes 
per square meter or per square foot, the wiring system up to 
and including the branch-circuit panelboard(s) shall be pro- 
vided to serve not less than the calculated load. This load 
shall be evenly proportioned among multioutlet branch cir- 
cuits within the panelboard(s). Branch-circuit overcurrent 
devices and circuits shall only be required to be installed to 
serve the connected load. 



(C) Dwelling Units. 

(1) Small-Appliance Branch Circuits. In addition to the 
number of branch circuits required by other parts of this 
section, two or more 20-ampere small-appliance branch cir- 
cuits shall be provided for all receptacle outlets specified by 
210.52(B). 

(2) Laundry Branch Circuits. In addition to the number 
of branch circuits required by other parts of this section, at 
least one additional 20-ampere branch circuit shall be pro- 
vided to supply the laundry receptacle outlet(s) required by 
210.52(F). This circuit shall have no other outlets. 

(3) Bathroom Branch Circuits. In addition to the number 
of branch circuits required by other parts of this section, at 
least one 20-ampere branch circuit shall be provided to 
supply bathroom receptacle outlet(s). Such circuits shall 
have no other outlets. 

Exception: Where the 20-ampere circuit supplies a single 
bathroom, outlets for other equipment within the same 
bathroom shall be permitted to be supplied in accordance 
with 210.23(A)(1) and (A)(2). 

FPN: See Examples D1(A), D1(B), D2(B), and D4(A) in 
Annex D. 

210.12 Arc-Fault Circuit-Interrupter Protection. 

(A) Definition: Arc-Fault Circuit Interrupter. An arc-fault 
circuit interrupter is a device intended to provide protection 
from the effects of arc faults by recognizing characteristics 
unique to arcing and by functioning to de-energize the circuit 
when an arc fault is detected. 

(B) Dwelling Unit Bedrooms. All 120-volt, single phase, 
15- and 20-ampere branch circuits supplying outlets in- 
stalled in dwelling unit bedrooms shall be protected by a 
listed arc-fault circuit interrupter, combination type in- 
stalled to provide protection of the branch circuit. 

Branch/feeder AFCIs shall be permitted to be used to 
meet the requirements of 210.12(B) until January 1, 2008. 

FPN: For information on types of arc-fault circuit inter- 
rupters, see UL 1699-1999, Standard for Arc-Fault Circuit 
Interrupters. 

Exception: The location of the arc-fault circuit interrupter 
shall be permitted to be at other than the origination of the 
branch circuit in compliance with (a) and (b): 

(a) The arc-fault circuit interrupter installed within 
1.8 m (6 ft) of the branch circuit overcurrent device as 
measured along the branch circuit conductors. 

(b) The circuit conductors between the branch circuit 
overcurrent device and the arc-fault circuit interrupter 
shall be installed in a metal raceway or a cable with a 
metallic sheath. 



70^8 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 210 — BRANCH CIRCUITS 



210.19 



• 



210.18 Guest Rooms and Guest Suites. Guest rooms and 
guest suites that are provided with permanent provisions for 
cooking shall have branch circuits and outlets installed to 
meet the rules for dwelling units. 

II. Branch-Circuit Ratings 

210.19 Conductors — Minimum Ampacity and Size. 
(A) Branch Circuits Not More Than 600 Volts. 

(1) General. Branch-circuit conductors shall have an am- 
pacity not less than the maximum load to be served. Where 
a branch circuit supplies continuous loads or any combina- 
tion of continuous and noncontinuous loads, the minimum 
branch-circuit conductor size, before the application of any 
adjustment or correction factors, shall have an allowable 
ampacity not less than the noncontinuous load plus 
125 percent of the continuous load. 

Exception: Where the assembly, including the overcurrent 
devices protecting the branch circuit(s), is listed for opera- 
tion at 100 percent of its rating, the allowable ampacity of 
the branch circuit conductors shall be permitted to be not 
less than the sum of the continuous load plus the noncon- 
tinuous load. 

FPN No. 1: See 310.15 for ampacity ratings of 
conductors. 

FPN No. 2: See Part II of Article 430 for minimum rating 
of motor branch-circuit conductors. 

FPN No. 3: See 310.10 for temperature limitation of 
conductors. 

FPN No. 4: Conductors for brancli circuits as defined in 
Article 100, sized to prevent a voltage drop exceeding 
3 percent at the feuthest outlet of power] heating, and light- 
ing loads, or combinations of such loads, and where the 
maximum total voltage drop on both feeders and branch 
circuits to the farthest outlet does not exceed 5 percent, 
provide reasonable efficiency of operation. See FPN No. 2 
of 215.2(A)(3) for voltage drop on feeder conductors. 

(2) Multioutlet Branch Circuits. Conductors of branch 
circuits supplying more than one receptacle for cord-and- 
plug-connected portable loads shall have an ampacity of 
not less than the rating of the branch circuit. 

(3) Household Ranges and Cooking Appliances. Branch- 
circuit conductors supplying household ranges, wall-mounted 
ovens, counter-mounted cooking units, and other household 
cooking appliances shall have an ampacity not less than the 
rating of the branch circuit and not less than the maximum 
load to be served. For ranges of 82/4 kW or more rating, the 
minimum branch-circuit rating shall be 40 amperes. 

Exception No. 1: Tap conductors supplying electric 
ranges, wall-mounted electric ovens, and counter-mounted 
electric cooking units from a 50-ampere branch circuit 
shall have an ampacity of not less than 20 and shall be 



sufficient for the load to be served. These tap conductors 
include any conductors that are a part of the leads supplied 
with the appliance that are smaller than the branch circuit 
conductors. The taps shall not be longer than necessary for 
sei-vicing the appliance. 

Exception No. 2: The neutral conductor of a 3-wire 
branch circuit supplying a household electric range, a 
wall-mounted oven, or a counter-mounted cooking unit 
shall be permitted to be smaller than the ungrounded con- 
ductors where the maximum demand of a range of 8V4 kW 
or more rating has been calculated according to Column C 
of Table 220.55, but such conductor shall have an ampacity 
of not less than 70 percent of the branch-circuit rating and 
shall not be smaller than 10 AWG. 

(4) Other Loads. Branch-circuit conductors that supply 
loads other than those specified in 210.2 and other than 
cooking appliances as covered in 210.19(A)(3) shall have 
an ampacity sufficient for the loads served and shall not be 
smaller than 14 AWG. 

Exception No. 1: Tap conductors shall have an ampacity 
sufficient for the load served. In addition, they shall have an 
ampacity of not less than 15 for circuits rated less than 
40 amperes and not less than 20 for circuits rated at 40 or 
50 amperes and only where these tap conductors supply 
any of the following loads: 

(a) Individual lampholders or luminaires (fixtures) 
with taps extending not longer than 450 mm (18 in.) beyond 
any portion of the lampholder or luminaire (fixture). 

(b) A fixture having tap conductors as provided in 
410.67. 

(c) Individual outlets, other than receptacle outlets, 
with taps not over 450 mm (18 in.) long., 

(d) Infrared lamp industrial heating appliances. 

(e) Nonheating leads of deicing and snow-melting 
cables and mats. 

Exception No. 2: Fixture wires and flexible cords shall be 
permitted to be smaller than 14 AWG as permitted by 240.5. 

(B) Branch Circuits Over 600 Volts. The ampacity of 
conductors shall be in accordance with 310.15 and 310.60, 
as applicable. Branch-circuit conductors over 600 volts 
shall be sized in accordance with 210.19(B)(1) or (B)(2). 

(1) General. The ampacity of branch-circuit conductors shall 
not be less than 125 percent of the designed potential load of 
utilization equipment that will be operated simultaneously. 

(2) Supervised Installations. For supervised installations, 
branch-circuit conductor sizing shall be permitted to be de- 
termined by qualified persons under engineering supervi- 
sion. Supervised installations are defined as those portions 
of a facility where both of the following conditions are met: 
(1) Conditions of design and installation are provided un- 
der engineering supervision. 



2005 Edition 



NATIONAL ELECTRICAL CODE 



70-49 



210.20 



ARTICLE 210 — BRANCH CIRCUITS 



(2) Qualified persons with documented training and expe- 
rience in over 600-volt systems provide maintenance, 
monitoring, and servicing of the system. 

210.20 Overcurrent Protection. Branch-circuit conduc- 
tors and equipment shall be protected by overcurrent pro- 
tective devices that have a rating or setting that complies 
with 210.20(A) through (D). 

(A) Continuous and Noncontinuous Loads. Where a 
branch circuit supplies continuous loads or any combina- 
tion of continuous and noncontinuous loads, the rating of 
the overcurrent device shall not be less than the noncon- 
tinuous load plus 125 percent of the continuous load. 

Exception: Where the assembly, including the overcurrent 
devices protecting the branch circuit(s), is listed for opera- 
tion at 100 percent of its rating, the ampere rating of the 
overcurrent device shall be permitted to be not less than the 
sum of the continuous load plus the noncontinuous load. 

(B) Conductor Protection. Conductors shall be protected 
in accordance with 240.4. Flexible cords and fixture wires 
shall be protected in accordance with 240.5. 

(C) Equipment. The rating or setting of the overcurrent 
protective device shall not exceed that specified in the ap- 
plicable articles referenced in Table 240.3 for equipment. 

(D) Outlet Devices. The rating or setting shall not exceed 
that specified in 210.21 for outlet devices. 

210.21 Outlet Devices. Outlet devices shall have an am- 
pere rating that is not less than the load to be served and 
shall comply with 210.21(A) and (B). 

(A) Lampholders. Where connected to a branch circuit 
having a rating in excess of 20 amperes, lampholders shall 
be of the heavy-duty type. A heavy-duty lampholder shall 
have a rating of not less than 660 watts if of the admedium 
type, or not less than 750 watts if of any other type. 

(B) Receptacles. 

(1) Single Receptacle on an Individual Branch Circuit. 

A single receptacle installed on an individual branch circuit 
shall have an ampere rating not less than that of the branch 
circuit. 

Exception No. 1: A receptacle installed in accordance 
with 430.81(B). 

Exception No. 2: A receptacle installed exclusively for 
the use of a cord-and-plug-connected arc welder shall be 
permitted to have an ampere rating not less than the 
minimum branch-circuit conductor ampacity determined 
by 630.11(A) for arc welders. 

FPN: See the definition of receptacle in Article 100. 



(2) Total Cord-and-Plug-Connected Load. Where con- 
nected to a branch circuit supplying two or more recep- 
tacles or outlets, a receptacle shall not supply a total 
cord-and-plug-connected load in excess of the maximum 
specified in Table 210.21(B)(2). 



Table 210.21(B)(2) Maximum Cord-and-Plug-Connected 
Load to Receptacle 



Circuit Rating 
(Amperes) 



Receptacle Rating 
(Amperes) 



Maximum Load 
(Amperes) 



15 or 20 
20 
30 



15 
20 
30 



12 
16 

24 



(3) Receptacle Ratings. Where connected to a branch cir- 
cuit supplying two or more receptacles or outlets, recep- 
tacle ratings shall conform to the values listed in Table 
210.21(B)(3), or where larger than 50 amperes, the recep- 
tacle rating shall not be less than the branch-circuit rating. 

Exception No. 1: Receptacles for one or more cord-and- 
plug-connected arc welders shall be permitted to have am- 
pere ratings not less than the minimum branch- circuit con- 
ductor ampacity permitted by 630.11(A) or (B) as 
applicable for arc welders. 

Exception No. 2: The ampere rating of a receptacle in- 
stalled for electric discharge lighting shall be permitted to 
be based on 410.30(C). 



Table 210.21(B)(3) Receptacle Ratings for Various 
Size Circuits 



Circuit Rating 


Receptacle Rating 


(Amperes) 


(Amperes) 


15 


Not over 15 


20 


15 or 20 


30 


30 


40 


40 or 50 


50 


50 



(4) Range Receptacle Rating. The ampere rating of a 
range receptacle shall be permitted to be based on a single 
range demand load as specified in Table 220.55. 

210.23 Permissible Loads. In no case shall the load ex- 
ceed the branch-circuit ampere rating. An individual branch 
circuit shall be permitted to supply any load for which it is 
rated. A branch circuit supplying two or more outlets or 
receptacles shall supply only the loads specified according 
to its size as specified in 210.23(A) through (D) and as 
summarized in 210.24 and Table 210.24. 



# 



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NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 210 — BRANCH CIRCUITS 



210.50 



(A) 15- and 20-Ampere Branch Circuits. A 15- or 20- 

ampere branch circuit shall be permitted to supply lighting 
units or other utilization equipment, or a combination of 
both, and shall comply with 210.23(A)(1) and (A)(2). 

Exception: The small appliance branch circuits, laundry 
branch circuits, and bathroom branch circuits required in a 
dwelling unit(s) by 210.11(C)(1), (C)(2), and (C)(3) shall 
supply only the receptacle outlets specified in that section. 

(1) Cord-and-Plug-Connected Equipment Not Fastened 
in Place. The rating of any one cord-and-plug-connected 
utilization equipment not fastened in place shall not exceed 
80 percent of the branch-circuit ampere rating. 

(2) Utilization Equipment Fastened in Place. The total 
rating of utilization equipment fastened in place, other than 
luminaires (lighting fixtures), shall not exceed 50 percent of 
the branch-circuit ampere rating where fighting units, cord- 
and-plug-connected utilization equipment not fastened in 
place, or both, are also supplied. 

(B) 30-Ampere Branch Circuits. A 30-ampere branch cir- 
cuit shall be permitted to supply fixed lighting units with 
heavy-duty lampholders in other than a dwelling unit(s) or 
utilization equipment in any occupancy. A rating of any one 
cord-and-plug-connected utilization equipment shall not 
exceed 80 percent of the branch-circuit ampere rating. 

(C) 40- and 50-Ampere Branch Circuits. A 40- or 50- 

ampere branch circuit shall be permitted to supply cooking 
appliances that are fastened in place in any occupancy. In 
other than dwelling units, such circuits shall be permitted to 
supply fixed lighting units with heavy-duty lampholders, 
infrared heating units, or other utilization equipment. 



(D) Branch Circuits Larger Than 50 Amperes. Branch 
circuits larger than 50 amperes shall supply only nonlight- 
ing outlet loads. 

210.24 Branch-Circuit Requirements — Summary. The 

requirements for circuits that have two or more outlets or 
receptacles, other than the receptacle circuits of 210.11(C)(1) 
and (C)(2), are summarized in Table 210.24. This table pro- 
vides only a summary of minimum requirements. See 210.19, 
210.20, and 210.21 for the specific requirements applying to 
branch circuits. 

210.25 Common Area Branch Circuits. Branch circuits 
in dweUing units shall supply only loads within that dwell- 
ing unit or loads associated only with that dwelling unit. 
Branch circuits required for the purpose of lighting, central 
alarm, signal, communications, or other needs for public or 
common areas of a two-family or multifamily dwelling 
shall not be supplied from equipment that supplies an indi- 
vidual dwelling unit. 

III. Required Outlets 

210.50 General. Receptacle outlets shall be installed as 
specified in 210.52 through 210.63. 

(A) Cord Pendants. A cord connector that is supplied by a 
permanently connected cord pendant shall be considered a 
receptacle outlet. 

(B) Cord Connections. A receptacle outlet shall be in- 
stalled wherever flexible cords with attachment plugs are 
used. Where flexible cords are permitted to be permanently 
connected, receptacles shall be permitted to be omitted for 
such cords. 



Table 210.24 Summary of Branch-Circuit Requirements 



Circuit Rating 


15 A 


20 A 


30 A 


40 A 


50 A 


Conductors (min. size): 
Circuit wires' 
Taps 
Fixture wires and cords - 


14 
14 
— see 240.5 


12 
14 


10 

14 


8 
12 


6 

12 


Overcurrent 
Protection 


15 A 


20 A 


30 A 


40 A 


50 A 


Outlet devices: 
Lampiiolders 
permitted 
Receptacle rating^ 


Any type 
15 max. A 


Any type 
15 or 20 A 


Heavy duty 
30 A 


Heavy duty 
40 or 50 A 


Heavy duty 
50 A 


Maximum Load 


15 A 


20 A 


30 A 


40 A 


50 A 


Permissible load 


See 210.23(A) 


See 210.23(A) 


See 210.23(B) 


See 210.23(C) 


See 210.23(C) 



'These gauges are for copper conductors. 

^For receptacle rating of cord-connected electric-discharge luminaires (lighting fixtures), see 410.30(C). 



2005 Edition NATIONAL ELECTRICAL CODE 



70-51 



210.52 



ARTICLE 210 — BRANCH CIRCUITS 



(C) Appliance Outlets. Appliance receptacle outlets in- 
stalled in a dwelling unit for specific appliances, such as 
laundry equipment, shall be installed within 1.8 m (6 ft) of 
the intended location of the appliance. 

210.52 Dwelling Unit Receptacle Outlets. This section 
provides requirements for 125- volt, 15- and 20-ampere recep- 
tacle outlets. Receptacle outlets required by this section shall 
be in addition to any receptacle that is part of a luminaire 
(lighting fixture) or appliance, located within cabinets or cup- 
boards, or located more than 1.7 m (SVi ft) above the floor. 

Permanently installed electric baseboard heaters equipped 
with factory-installed receptacle oudets or outlets provided as 
a separate assembly by the manufacturer shall be permitted as 
the required outlet or outiets for the wall space utilized by 
such permanendy installed heaters. Such receptacle outlets 
shall not be connected to the heater circuits. 

FPN: Listed baseboard heaters include instructions that 
may not permit their installation below receptacle outlets. 

(A) General Provisions. In every kitchen, family room, 
dining room, living room, parlor, library, den, sunroom, 
bedroom, recreation room, or similar room or area of 
dwelling units, receptacle outlets shaU be installed in accor- 
dance with the general provisions specified in 210.52(A)(1) 
through (A)(3). 

(1) Spacing. Receptacles shall be installed so that no point 
measured horizontally along the floor line in any wall space 
is more than 1.8 m (6 ft) from a receptacle outlet. 

(2) Wall Space. As used in this section, a wall space shall 
include the following: 

(1) Any space 600 mm (2 ft) or more in width (including 
space measured around comers) and unbroken along the 
floor line by doorways, fireplaces, and similar openings 

(2) The space occupied by fixed panels in exterior walls, 
excluding sliding panels 

(3) The space afforded by fixed room dividers such as free- 
standing bar-type counters or railings 

(3) Floor Receptacles. Receptacle outlets in floors shall 
not be counted as part of the required number of receptacle 
outlets unless located within 450 mm (18 in.) of the wall. 

(B) Small Appliances. 

(1) Receptacle Outlets Served. In the kitchen, pantry, 
breakfast room, dining room, or similar area of a dwelling 
unit, the two or more 20-ampere smafl-appliance branch 
circuits required by 210.11(C)(1) shall serve all wall and 
floor receptacle outlets covered by 210.52(A), all counter- 
top outlets covered by 210.52(C), and receptacle outlets for 
refrigeration equipment. 



Exception No. 1: In addition to the required receptacles 
specified by 210.52, switched receptacles supplied from a 
general-purpose branch circuit as defined in 210.70(A)(1), 
Exception No. 1, shall be permitted. 

Exception No. 2: The receptacle outlet for refrigeration 
equipment shall be permitted to be supplied from an indi- 
vidual branch circuit rated 15 amperes or greater 

(2) No Other Outlets. The two or more small-appliance 
branch circuits specified in 210.52(B)(1) shall have no 
other outlets. 

Exception No. 1: A receptacle installed solely for the elec- 
trical supply to and support of an electric clock in any of 
the rooms specified in 210.52(B)(1). 

Exception No. 2: Receptacles installed to provide power 
for supplemental equipment and lighting on gas-fired 
ranges, ovens, or counter-mounted cooking units. 

(3) Kitchen Receptacle Requirements. Receptacles in- 
stalled in a kitchen to serve countertop surfaces shall be 
supplied by not fewer than two small-appliance branch cir- 
cuits, either or both of which shall also be permitted to supply 
receptacle outlets in the same kitchen and in other rooms 
specified in 210.52(B)(1). Additional small-appliance branch 
circuits shall be permitted to supply receptacle outlets in the 
kitchen and other rooms specified in 210.52(B)(1). No smaU- 
appliance branch circuit shall serve more than one kitchen. 

(C) Countertops. In kitchens and dining rooms of dwell- 
ing units, receptacle outlets for counter spaces shall be in- 
stalled in accordance with 210.52(C)(1) through (C)(5). 

(1) Wall Counter Spaces. A receptacle outlet shall be in- 
stalled at each wall counter space that is 300 mm (12 in.) or 
wider. Receptacle outlets shall be installed so that no point 
along the wall line is more than 600 mm (24 in.) measured 
horizontally from a receptacle outlet in that space. 

Exception: Receptacle outlets shall not be required on a 
wall directly behind a range or sink in the installation de- 
scribed in Figure 210.52. 

(2) Island Counter Spaces. At least one receptacle shall 
be installed at each island counter space with a long dimen- 
sion of 600 mm (24 in.) or greater and a short dimension of 
300 ntmi (12 in.) or greater. Where a rangetop or sink is 
installed in an island counter and the width of the counter 
behind the rangetop or sink is less than 300 mm (12 in.), 
the rangetop or sink is considered to divide the island into 
two separate countertop spaces as defined in 210.52(C)(4). 

(3) Peninsular Counter Spaces. At least one receptacle 
outlet shall be installed at each peninsular counter space 
with a long dimension of 600 mm (24 in.) or greater and a 
short dimension of 300 mm (12 in.) or greater. A peninsular 
countertop is measured from the connecting edge. 



70-52 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 210 — BRANCH CIRCUITS 



210.52 



Outlet within 
600 mm (24 in.) 


Outlet not required 
ifX<300mm(12in.) 


<- 


Outlet within 
600 mm (24 in.) 




h 
X 

1 ' 




V J 





















Sink or range extending from face of counter 



Outlets not required 
ifX<450mm(18in.) 


- 


Outlet within 600 mm (24 in.) — ► 




\ 

X 


\ 


> 


within 

mm 

n.) 




/ 


Outlet 
600 
(24 

> 


/ 


\ 



Sink or range mounted in corner 
Figure 210.52 Determination of Area Behind Sinlc or Range. 

(4) Separate Spaces. Countertop spaces separated by 
rangetops, refrigerators, or sinks shall be considered as 
separate countertop spaces in applying the requirements of 
210.52(C)(1), (C)(2), and (C)(3). 

(5) Receptacle Outlet Location. Receptacle outlets shall 
be located above, but not more than 500 mm (20 in.) above, 
the countertop. Receptacle outlets rendered not readily ac- 
cessible by appliances fastened in place, appliance garages, 
sinks, or rangetops as covered in 210.52(C)(1), Exception, 
or appliances occupying dedicated space shall not be con- 
sidered as these required outlets. 

Exception to (5): To comply with the conditions specified in 
(1) or (2), receptacle outlets shall be permitted to be 
mounted not more than 300 mm (12 in.) below the counter- 
top. Receptacles mounted below a countertop in accor- 
dance with this exception shall not be located where the 
countertop extends more than 150 mm (6 in.) beyond its 
support base. 



(1) Construction for the physically impaired 

(2) On island and peninsular countertops where the coun- 
tertop is flat across its entire surface (no backsplashes, 
dividers, etc.) and there are no means to mount a re- 
ceptacle within 500 mm (20 in.) above the countertop, 
such as an overhead cabinet 

(D) Bathrooms. In dwelling units, at least one receptacle 
outlet shall be installed in bathrooms within 900 mm (3 ft) 
of the outside edge of each basin. The receptacle outlet 
shall be located on a wall or partition that is adjacent to the 
basin or basin countertop. 

Exception: The receptacle shall not be required to be 
mounted in the wall or partition where it is installed on the 
side or face of the basin cabinet not more than 300 mm 
(12 in.) below the countertop. 

(E) Outdoor Outlets. For a one-family dweUing and each 
unit of a two-family dwelling that is at grade level, at least 
one receptacle outlet accessible at grade level and not more 
than 2.0 m (6^2 ft) above grade shall be installed at the 
front and back of the dwelling. 

For each dwelhng unit of a multifamily dwelling where 
the dwelling unit is located at grade level and provided with 
individual exterior entrance/egress, at least one receptacle 
outlet accessible from grade level and not more than 2.0 m 
(6^2 ft) above grade shall be installed. See 210.8(A)(3). 

(F) Laundry Areas. In dwelhng units, at least one recep- 
tacle outlet shall be installed for the laundry. 

Exception No. 1: In a dwelling unit that is an apartment 
or living area in a multifamily building where laundry fa- 
cilities are provided on the premises and are available to 
all building occupants, a laundry receptacle shall not be 
required. 

Exception No. 2: In other than one-family dwellings where 
laundry facilities are not to be installed or permitted, a 
laundry receptacle shall not be required. 

(G) Basements and Garages. For a one-family dwelling, 
at least one receptacle outlet, in addition to any provided 
for laundry equipment, shall be installed in each basement 
and in each attached garage, and in each detached garage 
with electric power. See 210.8(A)(2) and (A)(5). Where a 
portion of the basement is finished into one or more habit- 
able rooms, eacji separate unfinished portion shall have a 
receptacle outlet installed in accordance with this section. 

(H) Hallways. In dwelhng units, hallways of 3.0 m (10 ft) 
or more in length shall have at least one receptacle outlet. 
As used in this subsection, the hall length shall be con- 
sidered the length along the centerline of the hall without 
passing through a doorway. 



2005 Edition NATIONAL ELECTRICAL CODE 



70-53 



210.60 



ARTICLE 210 — BRANCH CIRCUITS 



210.60 Guest Rooms or Guest Suites. 

(A) General. Guest rooms or guest suites in hotels, motels, 
and similar occupancies shall have receptacle outlets in- 
stalled in accordance with 210.52(A) and 210.52(D). Guest 
rooms or guest suites provided with permanent provisions 
for cooking shall have receptacle outlets installed in accor- 
dance with all of the applicable rules in 210.52. 

(B) Receptacle Placement. In applying the provisions of 
210.52(A), the total number of receptacle outlets shall not 
be less than the minimum number that would comply with 
the provisions of that section. These receptacle outlets shall 
be permitted to be located conveniently for permanent fur- 
niture layout. At least two receptacle outlets shall be readily 
accessible. Where receptacles are installed behind the bed, 
the receptacle shall be located to prevent the bed from 
contacting any attachment plug that may be installed or the 
receptacle shall be provided with a suitable guard. 

210.62 Show Windows. At least one receptacle outlet 
shall be installed directly above a show window for each 
3.7 linear m (12 linear ft) or major fraction thereof of show 
window area measured horizontally at its maximum width. 

210.63 Heating, Air-Conditioning, and Refrigeration 
Equipment Outlet. A 125-volt, single-phase, 15- or 20- 
ampere-rated receptacle outlet shall be installed at an ac- 
cessible location for the servicing of heating, air- 
conditioning, and refrigeration equipment. The receptacle 
shall be located on the same level and within 7.5 m (25 ft) 
of the heating, air-conditioning, and refrigeration equip- 
ment. The receptacle outlet shall not be connected to the 
load side of the equipment disconnecting means. 

Exception: A receptacle outlet shall not be required at 
one- and two-family dwellings for the service of evapora- 
tive coolers. 

FPN: See 210.8 for ground-fault circuit-interrupter 
requirements. 

210.70 Lighting Outlets Required. Lighting outlets shall 
be installed where specified in 210.70(A), (B), and (C). 

(A) Dwelling Units. In dwelling units, lighting outlets 
shall be installed in accordance with 210.70(A)(1), (A)(2), 
and (A)(3). 

(1) Habitable Rooms. At least one wall switch-controlled 
lighting outlet shall be installed in every habitable room 
and bathroom. 

Exception No. 1: In other than kitchens and bathrooms, 
one or more receptacles controlled by a wall switch shall 
be permitted in lieu of lighting outlets. 

Exception No. 2: Lighting outlets shall be permitted to be 
controlled by occupancy sensors that are (1) in addition to 



wall switches or (2) located at a customary wall switch 
location and equipped with a manual override that will 
allow the sensor to function as a wall switch. 

(2) Additional Locations. Additional lighting outlets shall 
be installed in accordance with (A)(2)(a), (A)(2)(b), and 
(A)(2)(c). 

(a) At least one wall switch-controlled lighting outlet 
shall be installed in hallways, stairways, attached garages, 
and detached garages with electric power. 

(b) For dwelling units, attached garages, and detached 
garages with electric power, at least one wall switch- 
controlled lighting outlet shall be installed to provide illu- 
mination on the exterior side of outdoor entrances or exits 
with grade level access. A vehicle door in a garage shall not 
be considered as an outdoor entrance or exit. 

(c) Where one or more lighting outlet(s) are installed 
for interior stairways, there shall be a wall switch at each 
floor level, and landing level that includes an entryway, to 
control the hghting outlet(s) where the stairway between 
floor levels has six risers or more. 

Exception to (A)(2)(a), (A)(2)(b), and (A)(2)(c): In hall- 
ways, stairways, and at outdoor entrances, remote, central, 
or automatic control of lighting shall be permitted. 

(3) Storage or Equipment Spaces. For attics, underfloor 
spaces, utility rooms, and basements, at least one lighting 
outlet containing a switch or controlled by a wall switch 
shall be. installed where these spaces are used for storage or 
contain equipment requiring servicing. At least one point of 
control shall be at the usual point of entry to these spaces. 
The lighting outlet shall be provided at or near the equip- 
ment requiring servicing. 

(B) Guest Rooms or Guest Suites. In hotels, motels, or 
similar occupancies, guest rooms or guest suites shall have 
at least one w^ll switch-controlled lighting outlet installed 
in every habitable room and bathroom. 

Exception No. 1: In other than bathrooms and kitchens 
where provided, one or more receptacles controlled by a 
wall switch shall be permitted in lieu of lighting outlets. 

Exception No. 2: Lighting outlets shall be permitted to be 
controlled by occupancy sensors that are (1) in addition to 
wall switches or (2) located at a customary wall switch 
location and equipped with a manual override that will 
allow the sensor to function as a wall switch. 

(C) Other Than Dwelling Units. For attics and underfloor 
spaces containing equipment requiring servicing, such as 
heating, air-conditioning, and refrigeration equipment, at 
least one lighting outlet containing a switch or controlled 
by a wall switch shall be installed in such spaces. At least 
one point of control shall be at the usual point of entry to 
these spaces. The lighting outlet shall be provided at or 
near the equipment requiring servicing. 



• 



70-54 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 215 — FEEDERS 



215.4 



• 



ARTICLE 215 
Feeders 

215.1 Scope. This article covers the installation require- 
ments, overcurrent protection requirements, minimum size, 
and ampacity of conductors for feeders supplying branch- 
circuit loads. 

Exception: Feeders for electrolytic cells as covered in 
668.3(C)(1) and (C)(4). 

215.2 Minimum Rating and Size. 

(A) Feeders Not More Than 600 Volts. 

(1) General. Feeder conductors shall have an ampacity not 
less than required to supply the load as calculated in Parts 
III, IV, and V of Article 220. The minimum feeder-circuit 
conductor size, before the application of any adjustment or 
correction factors, shall have an allowable ampacity not 
less than the noncontinuous load plus 125 percent of the 
continuous load. 

Exception: Where the assembly, including the overcurrent 
devices protecting the feeder(s), is listed for operation at 
100 percent of its rating, the allowable ampacity of the 
feeder conductors shall be permitted to be not less than the 
sum of the continuous load plus the noncontinuous load. 

The size of the feeder circuit grounded conductor shall not 
be smaller than that required by 250.122, except that 
250.122(F) shaU not apply where grounded conductors are run 
in parallel. 

Additional minimum sizes shall be as specified in 
215.2(A)(2) and (A)(3) under the conditions stipulated. 

(2) Ampacity Relative to Service Conductors. The 

feeder conductor ampacity shall not be less than that of the 
service conductors where the feeder conductors carry the 
total load supplied by service conductors with an ampacity 
of 55 amperes or less. 

(3) Individual Dwelling Unit or Mobile Home Conduc- 
tors. Feeder conductors for individual dwelling units or 
mobile homes need not be larger than service conductors. 
Paragraph 310.15(B)(6) shall be permitted to be used for 
conductor size. 

FPN No. 1: See Examples Dl through Dll in Annex D. 

FPN No. 2: Conductors for feeders as defined in Article 
100, sized to prevent a voltage drop exceeding 3 percent at 
the farthest oudet of power, heating, and lighting loads, or 
combinations of such loads, and where the maximurn total 
voltage drop on both feeders and branch circuits to the 
farthest outlet does not exceed 5 percent, will provide rea- 
sonable efiSciency of operation. 

FPN No. 3: See 210.19(A), FPN No. 4, for voltage drop 
for branch circuits. 



(B) Feeders Over 600 Volts. The ampacity of conductors 
shaU be in accordance with 310.15 and 310.60 as applicable. 
Where installed, the size of the feeder circuit grounded con- 
ductor shall not be smaller than that required by 250.122, 
except diat 250.122(F) shall not apply where grounded con- 
ductors are run in parallel. Feeder conductors over 600 volts 
shall be sized in accordance with 215.2(B)(1), (B)(2), or 
(B)(3). 

(1) Feeders Supplying Transformers. The ampacity of 
feeder conductors shall not be less than the sum of the 
nameplate ratings of the transformers supplied when only 
transformers are supplied. 

(2) Feeders Supplying Transformers and Utilization 
Fquipment. The ampacity of feeders supplying a combina- 
tion of transformers and utilization equipment shall not be 
less than the sum of the nameplate ratings of the transform- 
ers and 125 percent of the designed potential load of the 
utilization equipment that will be operated simultaneously. 

(3) Supervised Installations. For supervised installations, 
feeder conductor sizing shall be permitted to be determined 
by qualified persons under engineering supervision. Super- 
vised installations are defined as those portions of a facility 
where all of the following conditions are met: 

(1) Conditions of design and installation are provided un- 
der engineering supervision. 

(2) Qualified persons with documented training and expe- 
rience in over 600-volt systems provide maintenance, 
monitoring, and servicing of the system. 

215.3 Overcurrent Protection. Feeders shall be protected 
against overcurrent in accordance with the provisions of 
Part I of Article 240. Where a feeder supplies continuous 
loads or any combination of continuous and noncontinuous 
loads, the rating of the overcurrent device shall not be less 
than the noncontinuous load plus 125 percent of the con- 
tinuous load. 

Exception No. 1: Where the assembly, including the over- 
current devices protecting the feeder(s), is listed for opera- 
tion at 100 percent of its rating, the ampere rating of the 
overcurrent device shall be permitted to be not less than the 
sum of the continuous load plus the noncontinuous load. 

Exception No. 2: Overcurrent protection for feeders 
over 600 volts, nominal, shall comply with Part XI of 
Article 240. 

215.4 Feeders with Common Neutral. 

(A) Feeders with Common Neutral. Two or three sets of 
3-wire feeders or two sets of 4-wire or 5-wire feeders shall 
be permitted to utilize a common neutral. 



2005 Edition NATIONAL ELECTRICAL CODE 



70-55 



215.5 



ARTICLE 220 — BRANCH-CIRCUIT, FEEDER, AND SERVICE CALCULATIONS 



(B) In Metal Raceway or Enclosure. Where installed in a 
metal raceway or other metal enclosure, all conductors of 
all feeders using a common neutral shall be enclosed within 
the same raceway or other enclosure as required in 300.20. 

215.5 Diagrams of Feeders. If required by the authority 
having jurisdiction, a diagram showing feeder details shall 
be provided prior to the installation of the feeders. Such a 
diagram shall show the area in square feet of the building 
or other structure supplied by each feeder, the total calcu- 
lated load before applying demand factors, the demand fac- 
tors used, the calculated load after applying demand fac- 
tors, and the size and type of conductors to be used. 

215.6 Feeder Conductor Grounding Means. Where a 
feeder supplies branch circuits in which equipment ground- 
ing conductors are required, the feeder shall include or pro- 
vide a grounding means, in accordance with the provisions 
of 250.134, to which the equipment grounding conductors 
of the branch circuits shall be connected. 

215.7 Ungrounded Conductors Tapped from Grounded 
Systems. Two-wire dc circuits and ac circuits of two or more 
ungrounded conductors shall be permitted to be tapped from 
the ungrounded conductors of circuits having a grounded neu- 
tral conductor. Switching devices in each tapped circuit shall 
have a pole in each ungrounded conductor. 

215.9 Ground-Fault Circuit-Interrupter Protection for 
Personnel. Feeders supplying 15- and 20-ampere recep- 
tacle branch circuits shall be permitted to be protected by a 
ground-fault circuit interrupter in lieu of the provisions for 
such interrupters as specified in 210.8 and 590.6(A). 

215.10 Ground-Fault Protection of Equipment. Each 
feeder disconnect rated 1000 amperes or more and installed 
on solidly grounded wye electrical systems of more than 
150 volts to ground, but not exceeding 600 volts phase-to- 
phase, shall be provided with ground-fault protection of 
equipment in accordance with the provisions of 230.95. 

FPN: For buildings that contain healthcare occupancies, 
see the requirements of 517.17. 

Exception No. 1: The provisions of this section shall not 
apply to a disconnecting means for a continuous industrial 
process where a nonorderly shutdown will introduce addi- 
tional or increased hazards. 

Exception No. 2: The provisions of this section shall not 
apply to fire pumps. 

Exception No. 3: The provisions of this section shall not 
apply if ground-fault protection of equipment is provided on 
the supply side of the feeder 

215.11 Circuits Derived from Autotransformers. Feed- 
ers shall not be derived from autotransformers unless the 



system supplied has a grounded conductor that is electri- 
cally connected to a grounded conductor of the system sup- 
plying the autotransformer. 

Exception No. 1: An autotransformer shall he permitted 
without the connection to a grounded conductor where 
transforming from a nominal 208 volts to a nominal 240- 
volt supply or similarly from 240 volts to 208 volts. 

Exception No. 2: In industrial occupancies, where condi- 
tions of maintenance and supervision ensure that only quali- 
fied persons service the installation, autotransformers shall be 
permitted to supply nominal 600- volt loads from nominal 480- 
volt systems, and 480-volt loads from nominal 600-volt sys- 
tems, without the connection to a similar grounded conductor. 

215.12 Identification for Feeders. 

(A) Grounded Conductor. The grounded conductor of a 
feeder shall be identified in accordance with 200.6. 

(B) Equipment Grounding Conductor. The equipment 
grounding conductor shall be identified in accordance with 
250.119. 

(C) Ungrounded Conductors. Where the premises wiring 
system has feeders supplied from more than one nominal 
voltage system, each ungrounded conductor of a feeder, 
where accessible, shall be identified by system. The means 
of identification shall be permitted to be by separate color 
coding, marking tape, tagging, or other approved means 
and shall be permanently posted at each feeder panelboard 
or similar feeder distribution equipment. 



ARTICLE 220 

Branch-Circuit, Feeder, and Service 

Calculations 

I. General 

220.1 Scope. This article provides requirements for calculat- 
ing branch-circuit, feeder, and service loads. Part I provides 
for general requirements for calculation methods. Part 11 pro- 
vides calculation methods for branch circuit loads. Parts HI 
and rv provide calculation methods for feeders and services. 
Part V provides calculation methods for farms. 

FPN: See Figure 220. 1 for information on the organization 
of Article 220. 

220.3 Application of Other Articles. In other articles ap- 
plying to the calculation of loads in specialized applications, 
there are requirements provided in Table 220.3 that are in 
addition to, or modifications of, those within this article. 



• 



70-56 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 220 — BRANCH-CIRCUIT, FEEDER, AND SERVICE CALCULATIONS 



220.12 



Part 1 General 






Part II Branch circuit load calculations 






















Part III 
Feeder and 
service load 
calculations 








Part IV 

Optional 

feeder and 

service load 

calculations 








220.61 
Neutral 
Loads 




























1 




1 








Farm dwellings 
only 




Farm dwellings 
only 












1 
1 
1 




Part V Farm load calculations 



Figure 220.1 Branch-Circuit, Feeder, and Service Calculation 
Methods. 



220.5 Calculations. 

(A) Voltages. Unless other voltages are specified, for pur- 
poses of calculating branch-circuit and feeder loads, nomi- 
nal system voltages of 120, 120/240, 208Y/120, 240, 347, 
480Y/277, 480, 600Y/347, and 600 volts shall be used. 

(B) Fractions of an Ampere. Where calculations result in 
a fraction of an ampere that is less than 0.5, such fractions 
shall be permitted to be dropped. 

11. Branch Circuit Load Calculations 

220.10 General. Branch-circuit loads shall be calculated 
as shown in 220.12, 220.14, and 220.16. 

220.12 Lighting Load for Specified Occupancies. A unit 
load of not less than that specified in Table 220.12 for 
occupancies specified therein shall constitute the minimum 



Table 220.3 Additional Load Calculation References 



Calculation 



Article 



Section (or Part) 



Air-Conditioning and Refrigerating Equipment, Branch-Circuit 

Conductor Sizing 
Cranes and Hoists, Rating and Size of Conductors 
Electric Welders, ampacity calculations 
Electrically Driven or Controlled Irrigation Machines 

Electrolytic Cell Lines 

Electroplating, Branch-Circuit Conductor Sizing 

Elevator Feeder Demand Factors 

Fire Pumps, Voltage Drop (mandatory calculation) 

Fixed Electric Heating Equipment for Pipelines and Vessels, 

Branch-Circuit Sizing 
Fixed Electric Space Heating Equipment, Branch-Circuit Sizing 
Fixed Outdoor Electric Deicing and Snow-Melting Equipment, 

Branch-Circuit Sizing 

Industrial Machinery, Supply Conductor Sizing 
Marinas and Boatyards, Feeder and Service Load Calculations 
Mobile Homes, Manufactured Homes, and Mobile Home Parks, 
Total Load for Determining Power Supply 

Mobile Homes, Manufactured Homes, and Mobile Home Parks, 
Allowable Demand Factors for Park Electrical Wiring Systems 

Motion Picture and Television Studios and Similar Locations - 
Sizing of Feeder Conductors for Television Studio Sets 

Motors, Feeder Demand Factor 

Motors, Multimotor and Combination-Load Equipment 

Motors, Several Motors or a Motor(s) and Other Load(s) 

Over 600 Volt Branch Circuit Calculations 

Over 600 Volt Feeder Calculations 

Phase Converters, Conductors 

Recreational Vehicle Parks, Basis of Calculations 

Sensitive Electrical Equipment, Voltage Drop (mandatory calculation) 

Solar Photovoltaic Systems, Circuit Sizing and Current 

Storage-Type Water Heaters 

Theaters, Stage Switchboard Feeders 



440 

610 
630 

675 



660 
620 
695 

427 

424 
426 



670 

555 
550 



550 
530 



430 
430 
430 
210 
215 

455 
551 
647 
690 
422 
520 



Part IV 

610.14 

630.11, 630.31 

675.7(A), 675.22(A) 

668.3(C) 

669.5 
620.14 
695.7 

427.4 

424.3 
426.4 



670.4(A) 

555.12 

550.18(B) 

550.31 
530.19 



430.26 

430.25 

430.24 

210.19(B) 

215.2(B) 

455.6 
551.73(A) 
647.4(D) 

690.8 
422.11(E) 

520.27 



2005 Edition 



NATIONAL ELECTRICAL CODE 



70-57 



220.14 



ARTICLE 220 — BRANCH-CIRCUIT, FEEDER, AND SERVICE CALCULATIONS 



lighting load. The floor area for each floor shall be calcu- 
lated from the outside dimensions of the building, dwelling 
unit, or other area involved. For dwelling units, the calcu- 
lated floor area shall not include open porches, garages, or 
unused or unfinished spaces not adaptable for future use. 

FPN: The unit values herein are based on minimum load 
conditions and 100 percent power factor and may not pro- 
vide sufficient capacity for the installation contemplated. 

Table 220.12 General Lighting Loads by Occupancy 



Unit Load 




Volt- Amperes 


Volt-Amperes 




per Square 


per Square 


Type of Occupancy 


Meter 


Foot 


Armories and auditoriums 


11 


1 


Banks 


39" 


31/2" 


Barber shops and beauty 


33 


3 


parlors 






Churches 


11 


1 


Clubs 


22 


2 


Court rooms 


22 


2 


Dwelling umts'' 


33 


3 


Garages — commercial 


6 


1/2 


(storage) 






Hospitals 


22 


2 


Hotels and motels, including 


22 


2 


apartment houses without 






provision for cooking by 






tenants" 






Industrial commercial (loft) 


22 


2 


buildings 






Lodge rooms 


17 


11/2 


Office buildings 


39^^ 


31/2" 


Restaurants 


22 


2 


Schools 


33 


3 


Stores 


33 


3 


Warehouses (storage) 


3 


'/4 


In any of the preceding 






occupancies except 






one-family dwellings and 






individual dwelling units of 






two-family and multifamily 






dwellings: 






Assembly halls and 


11 


1 


auditoriums 






Halls, corridors, closets, 


6 


1/2 


stairways 






Storage spaces 


3 


1/4 



"See 220.14(J). 
''See 220.14(K). 

220.14 Other Loads — All Occupancies. In all occupan- 
cies, the minimum load for each outlet for general-use re- 
ceptacles and outlets not used for general illumination shall 
not be less than that calculated in 220.14(A) through (L), 
the loads shown being based on nominal branch-circuit 
voltages. 



Exception: The loads of outlets serving switchboards and 
switching frames in telephone exchanges shall be waived 
from the calculations. 

(A) Specific Appliances or Loads. An outlet for a specific 
appliance or other load not covered in 220.14(B) through 
(L) shall be calculated based on the ampere rating of the 
appliance or load served. 

(B) Electric Dryers and Household Electric Cooking 
Appliances. Load calculations shall be permitted as speci- 
fied in 220.54 for electric dryers and in 220.55 for electric 
ranges and other cooking apphances. 

(C) Motor Loads. Outlets for motor loads shaU be calcu- 
lated in accordance with the requirements in 430.22, 
430.24, and 440.6. 

(D) Luminaires (Lighting Fixtures). An outlet supplying 
luminaire(s) [lighting fixture(s)] shall be calculated based 
on the maximum volt-ampere rating of the equipment and 
lamps for which the luminaire(s) [fixture(s)] is rated. 

(E) Heavy-Duty Lampholders. Outlets for heavy-duty 
lampholders shall be calculated at a minimum of 600 volt- 
amperes. 

(F) Sign and Outline Lighting. Sign and outline lighting 
outlets shall be calculated at a minimum of 1200 volt- 
amperes for each required branch circuit specified in 
600.5(A). 

(G) Show Windows. Show windows shall be calculated in 
accordance with either of the following; 

(1) The unit load per outlet as required in other provisions 
of this section 

(2) At 200 volt-amperes per 300 mm (1 ft) of show 
window 

(H) Fixed Multioutlet Assemblies. Fixed multioutlet as- 
semblies used in other than dwelling units or the guest 
rooms or guest suites of hotels or motels shall be calculated 
in accordance with (H)(1) or (H)(2). For the purposes of 
this section, the calculation shall be permitted to be based 
on the portion that contains receptacle outlets. 

(1) Where apphances are unlikely to be used simulta- 
neously, each 1.5 m (5 ft) or fraction thereof of each 
separate and continuous length shall be considered as 
one outlet of not less than 180 volt-amperes. 

(2) Where appliances are likely to be used simultaneously, 
each 300 mm (1 ft) or fraction thereof shall be consid- 
ered as an outlet of not less than 180 volt-amperes. 

(I) Receptacle Outlets. Except as covered in 220.14(J) 
and (K), receptacle outlets shall be calculated at not less 
than 180 volt-amperes for each single or for each multiple 



• 



70-58 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 220 — BRANCH-CIRCUIT, FEEDER, AND SERVICE CALCULATIONS 



220.50 



receptacle on one yoke. A single piece of equipment consist- 
ing of a multiple receptacle comprised of four or more recep- 
tacles shall be calculated at not less than 90 volt-amperes per 
receptacle. This provision shall not be applicable to the recep- 
tacle outlets specified in 210.11(C)(1) and (C)(2). 

(J) Dwelling Occupancies. In one-family, two-family, and 
multifamily dwellings and in guest rooms or guest suites of 
hotels and motels, the outlets specified in (J)(l), (J)(2), and 
(J)(3) are included in the general lighting load calculations 
of 220.12. No additional load calculations shall be required 
for such outlets. 

(1) All general-use receptacle outlets of 20-ampere rating 
or less, including receptacles connected to the circuits 
in 210.11(C)(3) 

(2) The receptacle outlets specified in 210.52(E) and (G) 

(3) The fighting outlets specified in 210.70(A) and (B) 

(K) Banks and Office Buildings. In banks or office build- 
ings, the receptacle loads shall be calculated to be the larger 
of (1) or (2): 

(1) The computed load from 220.14 

(2) 11 volt-amperes/m^ or 1 volt-ampere/ft^ 

(L) Other Outlets. Other outlets not covered in 220.14(A) 
through (K) shall be calculated based on 180 volt-amperes 
per outlet. 

220.16 Loads for Additions to Existing Installations. 

(A) Dwelling Units. Loads added to an existing dweUing 
unit(s) shall comply with the following as applicable: 

(1) Loads for structural additions to an existing dwelling unit 
or for a previously unwired portion of an existing dwell- 
ing unit, either of which exceeds 46.5 m^ (500 ft^), shall 
be calculated in accordance with 220.12 and 220.14. 

(2) Loads for new circuits or extended circuits in previ- 
ously wired dwelling units shall be calculated in accor- 
dance with either 220.12 or 220.14, as applicable. 

(B) Other Than Dwelling Units. Loads for new circuits 
or extended circuits in other than dwelling units shall be 
calculated in accordance with either 220.12 or 220.14, as 
applicable. 

220.18 Maximum Loads. The total load shall not exceed 
the rating of the branch circuit, and it shall not exceed the 
maximum loads specified in 220.18(A) through (C) under 
the conditions specified therein. 

(A) Motor-Operated and Combination Loads. Where a 
circuit supplies only motor-operated loads, Article 430 shall 
apply. Where a circuit supplies only air-conditioning equip- 
ment, refrigerating equipment, or both. Article 440 shall apply. 
For circuits supplying loads consisting of motor-operated uti- 



lization equipment that is fastened in place and has a motor 
larger than Vs hp in combination with other loads, the total 
calculated load shall be based on 125 percent of the largest 
motor load plus the sum of the other loads. 

(B) Inductive Lighting Loads. For circuits supplying 
lighting units that have ballasts, transformers, or autotrans- 
formers, the calculated load shall be based on the total 
ampere ratings of such units and not on the total watts of 
the lamps. 

(C) Range Loads. It shall be permissible to apply demand 
factors for range loads in accordance with Table 220.55, 
including Note 4. 

III. Feeder and Service Load Calculations 

220.40 General. The calculated load of a feeder or service 
shall not be less than the sum of the loads on the branch 
circuits supplied, as determined by Part II of this article, 
after any applicable demand factors permitted by Parts III 
or IV or required by Part V have been applied. 

FPN: See Examples D1(A) through DIO in Annex D. See 
220.18(B) for the maximum load in amperes permitted for 
lighting units operating at less than 100 percent power factor. 

220.42 General Lighting. The demand factors specified in 
Table 220.42 shall apply to that portion of the total branch- 
circuit load calculated for general illumination. They shall 
not be applied in determining the number of branch circuits 
for general illumination. 

220.43 Show- Window and Track Lighting. 

(A) Show Windows. For show-window lighting, a load of 
not less than 660 volt-amperes/linear meter or 200 volt- 
amperes/linear foot shall be included for a show window, 
measured horizontally along its base. 

FPN: See 220.14(G) for branch circuits supplying show 
windows. 

(B) Track Lighting. For track lighting in other than dwell- 
ing units or guest rooms or guest suites of hotels or motels, 
an additional load of 150 volt-amperes shall be included for 
every 600 mm (2 ft) of lighting track or fraction thereof. 
Where multicircuit track is installed, the load shall be con- 
sidered to be divided equally between the track circuits. 

220.44 Receptacle Loads — Other Than Dwelling 
Units. Receptacle loads calculated in accordance with 
220.14(H) and (I) shall be permitted to be made subject to 
the demand factors given in Table 220.42 or Table 220.44. 

220.50 Motors. Motor loads shall be calculated in accor- 
dance with 430.24, 430.25, and 430.26 and with 440.6 for 
hermetic refrigerant motor compressors. 



2005 Edition 



NATIONAL ELECTRICAL CODE 



70-59 



220.51 



ARTICLE 220 — BRANCH-CIRCUIT, FEEDER, AND SERVICE CALCULATIONS 



Table 220.42 Lighting Load Demand Factors 





Portion of Lighting 






Load to Which 






Demand Factor 




Type of 


Applies 


Demand Factor 


Occupancy 


(Volt-Amperes) 


(Percent) 


Dwelling units 


First 3000 or less at 
From 3001 to 


100 




120,000 at 


35 




Remainder over 






120,000 at 


25 


Hospitals* 


First 50,000 or less at 
Remainder over 


40 




50,000 at 


20 


Hotels and motels, 


First 20,000 or less at 


50 


including 
apartment houses 
without provision 
for cooking by 
tenants* 


From 20,001 to 
100,000 at 

Remainder over 
100,000 at 


40 
30 


Warehouses 


First 12,500 or less at 


100 


(storage) 


Remainder over 






12,500 at 


50 


All others 


Total volt-amperes 


100 



*The demand factors of this table shall not apply to the calculated load 
of feeders or services supplying areas in hospitals, hotels, and motels 
where the entire lighting is likely to be used at one time, as in oper- 
ating rooms, ballrooms, or dining rooms. 



Table 220.44 Demand Factors for Non-dwelling Receptacle 
Loads 

Portion of Receptacle Load to Which 

Demand Factor AppHes Demand Factor 

(Volt-Amperes) (Percent) 



First 10 kVA or less at 
Remainder over 10 kVA at 



100 
50 



220.51 Fixed Electric Space Heating. Fixed electric 
space heating loads shall be calculated at 100 percent of the 
total connected load. However, in no case shall a feeder or 
service load current rating be less than the rating of the 
largest branch circuit supplied. 

Exception: Where reduced loading of the conductors re- 
sults from units operating on duty-cycle, intermittently, or 
from all units not operating at the same time, the authority 
having jurisdiction may grant permission for feeder and 
service conductors to have an ampacity less than 100 per- 
cent, provided the conductors have an ampacity for the 
load so determined. 



220.52 Small Appliance and Laundry Loads — Dwell- 
ing Unit. 

(A) Small Appliance Circuit Load. In each dwelling 
unit, the load shall be calculated at 1500 volt-amperes 
for each 2-wire small-appliance branch circuit required 
by 210.11(C)(1). Where the load is subdivided through 
two or more feeders, the calculated load for each shall 
include not less than 1500 volt-amperes for each 2-wire 
small-appliance branch circuit. These loads shall be per- 
mitted to be included with the general lighting load and 
subjected to the demand factors provided in Table 220.42. 

Exception: The individual branch circuit permitted by 
210.52(B)(1), Exception No. 2, shall be permitted to be 
excluded from the calculation required by 220.52. 

(B) Laundry Circuit Load. A load of not less than 1500 
volt-amperes shall be included for each 2-wire laundry branch 
circuit installed as required by 210.11(C)(2). This load shall be 
permitted to be included with the general lighting load and 
subjected to the demand factors provided in Table 220.42. 

220.53 Appliance Load — Dwelling Unit(s). It shall be 
permissible to apply a demand factor of 75 percent to the 
nameplate rating load of four or more appliances fastened 
in place, other than electric ranges, clothes dryers, space- 
heating equipment, or air-conditioning equipment, that are 
served by the same feeder or service in a one-family, two- 
family, or multifamily dwelling. 

220.54 Electric Clothes Dryers — Dwelling Unit(s). The 

load for household electric clothes dryers in a dwelling 
unit(s) shall be either 5000 watts (volt-amperes) or the 
nameplate rating, whichever is larger, for each dryer 
served. The use of the demand factors in Table 220.54 shall 
be permitted. Where two or more single-phase dryers are 
supphed by a 3-phase, 4-wire feeder or service, the total 
load shall be calculated on the basis of twice the maximum 
number connected between any two phases. , 

220.55 Electric Ranges and Other Cooking Appliances 
— Dwelling Unit(s). The load for household electric 
ranges, wall-mounted ovens, counter-mounted cooking 
units, and other household cooking appliances individually 
rated in excess of VA kW shall be permitted to be calcu- 
lated in accordance with Table 220.55. Kilovolt-amperes 
(kVA) shall be considered equivalent to kilowatts (kW) for 
loads calculated under this section. 

Where two or more single-phase ranges are supplied by 
a 3-phase, 4-wire feeder or service, the total load shall be 
calculated on the basis of twice the maximum number con- 
nected between any two phases. 



70-60 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 220 — BRANCH-CIRCUIT, FEEDER, AND SERVICE CALCULATIONS 



220.80 



Table 220.54 Demand Factors for Household Electric 
Clothes Dryers 



• 



Number of 




Demand Factor 


Dryers 




(Percent) 


1^ 




100% 


5 




85% 


6 




75% 


1 




65% 


8 




60% 


9 




55% 


10 




50% 


11 




47% 


12-22 


% = 


47 - (number of dryers - 11) 


23 




35% 


24^2 


% = 35 


- [0.5 X (number of dryers - 23)] 


43 and over 




25% 



FPN No. 1: See Example D5(A) in Annex D. 

FPN No. 2: See Table 220.56 for commercial cooking 
equipment. 

FPN No. 3: See the examples in Annex D. 



220.56 Kitchen Equipment — Other Than Dwelling 
Unit(s). It shall be permissible to calculate the load for 
commercial electric cooking equipment, dishwasher 
booster heaters, water heaters, and other kitchen equipment 
in accordance with Table 220.56. These demand factors 
shall be applied to all equipment that has either thermo- 
static control or intermittent use as kitchen equipment. 
These demand factors shall not apply to space-heating, ven- 
tilating, or air-conditioning equipment. 

However, in no case shall the feeder or service calcu- 
lated load be less than the sum of the largest two kitchen 
equipment loads. 



Table 220.56 Demand Factors for KJtchen Equipment 
Other Than Dwelling Unit(s) 



• 



Number of Units of 


Demand Factor 


Equipment 


(Percent) 


1 


100 


2 


100 


3 


90 


4 


80 


5 


70 


6 and over 


65 



220.60 Noncoincident Loads. Where it is unlikely that 
two or more noncoincident loads will be in use simulta- 
neously, it shall be permissible to use only the largest 
load(s) that will be used at one time for calculating the total 
load of a feeder or service. 

220.61 Feeder or Service Neutral Load. 

(A) Basic Calculation. The feeder or service neutral load 
shall be the maximum unbalance of the load determined by 
this article. The maximum unbalanced load shall be the 
maximum net calculated load between the neutral and any 
one ungrounded conductor. 

Exception: For 3-wire, 2-phase or 5-wire, 2-phase sys- 
tems, the maximum unbalanced load shall be the maximum 
net calculated load between the neutral and any one un- 
grounded conductor multiplied by 140 percent. 

(B) Permitted Reductions. A service or feeder supplying 
the following loads shall be permitted to have an additional 
demand factor of 70 percent applied to the amount in 
220.61(B)(1) or portion of the amount in 220.61(B)(2) de- 
termined by the basic calculation: 

(1) A feeder or service supplying household electric 
ranges, wall-mounted ovens, counter-mounted cooking 
units, and electric dryers, where the maximum unbal- 
anced load has been determined in accordance with 
Table 220.55 for ranges and Table 220.54 for dryers 

(2) That portion of the unbalanced load in excess of 200 am- 
peres where the feeder or service is supplied from a 
3-wire dc or single-phase ac system, or a 4-wire, 3-phase; 
3-wire, 2-phase system, or a 5-wire, 2-phase system 

(C) Prohibited Reductions. There shall be no reduction of 
the neutral or grounded conductor capacity applied to the 
amount in 220.61(C)(1), or portion of the amount in (C)(2), 
from that determined by the basic calculation: 

(1) Any portion of a 3-wire circuit consisting of 2-phase 
wires and the neutral of a 4-wire, 3-phase, wye- 
connected system 

(2) That portion consisting of nonlinear loads supplied 
from a 4-wire, wye-connected, 3-phase system 

FPN No. 1: See Examples D1(A), D1(B), D2(B), D4(A), 
and D5(A) in Annex D. 

FPN No. 2: A 3-phase, 4-wire, wye-connected power sys- 
tem used to supply power to nonlinear loads may necessi- 
tate that the power system design allow for the possibility 
of high harmonic neutral currents. 

IV. Optional Feeder and Service Load Calculations 

220.80 General. Optional feeder and service load calcula- 
tions shall be permitted in accordance with Part IV. 



2005 Edition NATIONAL ELECTRICAL CODE 



70-61 



220.80 



ARTICLE 220 — BRANCH-CIRCUIT, FEEDER, AND SERVICE CALCULATIONS 



Table 220.55 Demand Factors and Loads for Household Electric Ranges, Wall-Mounted Ovens, Counter-Mounted Cooking 
Units, and Other Household Cooking Appliances over 1% kW Rating (Column C to be used in all cases except as otherwise 
permitted in Note 3.) 



Demand Factor (Percent) (See Notes) 



Number of Appliances 



Column A 
(Less than SVa kW Rating) 



Column B 
(31/2 kW to 8% kW Rating) 



Column C 

Maximum Demand (kW) (See 

Notes) (Not over 12 kW Rating) 



80 
75 
70 
66 
62 



80 
65 

55 
50 
45 



11 

14 
17 
20 



10 



59 
56 

53 
51 
49 



43 
40 
36 
35 
34 



21 

22 
23 
24 
25 



11 
12 
13 
14 
15 



47 
45 
43 
41 
40 



32 
32 
32 
32 
32 



26 
27 
28 
29 
30 



16 
17 
18 
19 
20 



21 

22 
23 
24 
25 



39 

38 
37 
36 
35 



34 
33 
32 
31 
30 



28 
28 
28 
28 
28 



26 
26 
26 
26 
26 



31 

32 
33 
34 
35 



36 
37 
38 
39 
40 



• 



26-30 
31-40 



30 
30 



24 
22 



15 kW + 1 kW for each range 



41-50 

51-60 

61 and over 



30 
30 
30 



20 
18 
16 



25 kW + % kW for each range 



1. Over 12 kW through 27 kW ranges all of same rating. For ranges individually rated more than 12 kW but not more than 27 kW, the maximum 
demand in Column C shall be increased 5 percent for each additional kilowatt of rating or major fraction thereof by which the rating of individual 
ranges exceeds 12 kW. 

2. Over SYa kW through 27 kW ranges of unequal ratings. For ranges individually rated more than ^¥4 kW and of different ratings, but none 
exceeding 27 kW, an average value of rating shall be calculated by adding together the ratings of all ranges to obtain the total connected load (using 
12 kW for any range rated less than 12 kW) and dividing by the total number of ranges. Then the maximum demand in Column C shall be increased 
5 percent for each kilowatt or major fraction thereof by which this average value exceeds 12 kW. 

3. Over PA kW through 8^4 kW. In lieu of the method provided in Column C, it shall be permissible to add the nameplate ratings of all household 
cooking appliances rated more than PA kW but not more than 8V4 kW and multiply the sum by the demand factors specified in Column A or B for 
the given number of appHances. Where the rating of cooking appUances falls under both Column A and Column B, the demand factors for each 
column shall be applied to the appliances for that column, and the results added together. 

4. Branch-Circuit Load. It shall be permissible to calculate the branch-circuit load for one range in accordance with Table 220.55. The branch- 
circuit load for one wall-mounted oven or one counter-mounted cooking unit shall be the nameplate rating of the appliance. The branch-circuit load 
for a counter-mounted cooking unit and not more than two wall-mounted ovens, all supplied from a single branch circuit and located in the same 
room, shall be calculated by adding the nameplate rating of the individual appliances and treating this total as equivalent to one range. 

5. This table also applies to household cooking appliances rated over PA kW and used in instructional programs. 



70-62 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 220 — BRANCH-CIRCUIT, FEEDER, AND SERVICE CALCULATIONS 



220.83 



220.82 Dwelling Unit. 

(A) Feeder and Service Load. This section applies to a 
dwelling unit having the total connected load served by a 
single 120/240- volt or 208 Y/1 20- volt set of 3- wire service 
or feeder conductors with an ampacity of 100 or greater. It 
shall be permissible to calculate the feeder and service 
loads in accordance with this section instead of the method 
specified in Part III of this article. The calculated load shall 
be the result of adding the loads from 220.82(B) and (C). 
Feeder and service-entrance conductors whose calculated 
load is determined by this optional calculation shall be per- 
mitted to have the neutral load determined by 220.61. 

(B) General Loads. The general calculated load shall be 
not less than 100 percent of the first 10 kVA plus 40 percent 
of the remainder of the following loads: 

(1) 33 volt-amperes/m^ or 3 volt-amperes/ft^ for general 
lighting and general-use receptacles. The floor area for 
each floor shall be calculated from the outside dimen- 
sions of the dwelling unit. The calculated floor area 
shall not include open porches, garages, or unused or 
unfinished spaces not adaptable for future use. 

(2) 1500 volt-amperes for each 2- wire, 20-ampere small- 
appliance branch circuit and each laundry branch cir- 
cuit specified in 220.52. 

(3) The nameplate rating of all appliances that are fastened in 
place, permanently connected, or located to be on a spe- 
cific circuit, ranges, wall-mounted ovens, counter- 
mounted cooking units, clothes dryers, and water heaters. 

(4) The nameplate ampere or kVA rating of all motors and 
of all low-power-factor loads. 

(C) Heating and Air-Conditioning Load. The largest of 
the following six selections (load in kVA) shall be included: 

(1) 100 percent of the nameplate rating(s) of the air condi- 
tioning and cooling. 

(2) iOO percent of the nameplate rating(s) of the heating 
when a heat pump is used without any supplemental 
electric heating. 

(3) 100 percent of the nameplate ratings of electric thermal 
storage and other heating systems where the usual load 
is expected to be continuous at the full nameplate 
value. Systems qualifying under this selection shall not 
be. calculated under any other selection in 220.82(C). 

(4) 100 percent of the nameplate rating(s) of the heat pump 
compressor and 65 percent of the supplemental electric 
heating for central electric space heating systems. If the 
heat pump compressor is prevented from operating at 
the same time as the supplementary heat, it does not 
need to be added to the supplementary heat for the total 
central space heating load. 

(5) 65 percent of the nameplate rating(s) of electric space 
heating if less than four separately controlled units. 



(6) 40 percent df the nameplate rating(s) of electric space 
heating if four or more separately controlled units. 

220.83 Existing Dwelling Unit. This section shall be per- 
mitted to be used to determine if the existing service or feeder 
is of sufficient capacity to serve additional loads. Where the 
dweUing unit is served by a 120/240-volt or 208Y/ 120- volt, 
3-wire service, it shall be permissible to calculate the total load 
in accordance with 220.83(A) or (B). 

(A) Where Additional Air-Conditioning Equipment or 
Electric Space-Heating Equipment Is Not to Be In- 
stalled. The following formula shall be used for existing 
and additional new loads. 



Load (kVA) 



Percent of Load 



First 8 kVA of load at 
Remainder of load at 



100 
40 



Load calculations shall include the foUowing: 

(1) General lighting and general-use receptacles at 33 volt- 
amperes/m^ or 3 volt-amperes/ft^ as determined by 220.12 

(2) 1500 volt-amperes for each 2-wire, 20-ampere small- 
appliance branch circuit and each laundry branch cir- 
cuit specified in 220.52 

(3) Household range(s), wall-mounted oven(s), and counter- 
mounted cooking unit(s) 

(4) All other appliances that are permanently connected, 
fastened in place, or connected to a dedicated circuit, at 
nameplate rating 

(B) Where Additional Air-Conditioning Equipment or 
Electric Space-Heating Equipment Is to Be Installed. 

The following formula shall be used for existing and addi- 
tional new loads. The larger connected load of air- 
conditioning or space-heating, but not both, shall be used. 



Load 


Percent of Load 


Air-conditioning equipment 


loo 


Central electric space heating 


100 


Less than four separately 


100 


controlled space-heating units 




First 8 kVA of all other loads 


100 


Remainder of all other loads 


40 



Other loads shall include the following: 

(1) General lighting and general-use receptacles at 33 volt- 
amperes/m^ or 3 volt-amperes/ft^ as determined by 220.12 

(2) 1500 volt-amperes for each 2-wire, 20-ampere small- 
appliance branch circuit and each laundry branch cir- 
cuit specified in 220.52 



2005 Edition NATIONAL ELECTRICAL CODE 



70-63 



220.84 



ARTICLE 220 — BRANCH-CIRCUIT, FEEDER, AND SERVICE CALCULATIONS 



(3) Household range(s), wall-mounted oven(s), and 
counter-mounted cooking unit(s) 

(4) All other appliances that are permanently connected, 
fastened in place, or connected to a dedicated circuit, 
including four or more separately controlled space- 
heating units, at nameplate rating 

220.84 Multifamily Dwelling. 

(A) Feeder or Service Load. It shall be permissible to 
calculate the load of a feeder or service that supplies three 
or more dwelling units of a multifamily dwelling in accor- 
dance with Table 220.84 instead of Part III of this article if 
all the following conditions are met: 

(1) No dwelling unit is supplied by more than one feeder. 

(2) Each dwelling unit is equipped with electric cooking 
equipment. 

Exception: When the calculated load for multifamily dwell- 
ings without electric cooking in Part III of this article ex- 
ceeds that calculated under Part IV for the identical load 
plus electric cooking (based on 8 kW per unit), the lesser of 
the two loads shall be permitted to be used. 

(3) Each dwelling unit is equipped with either electric 
space heating or air conditioning, or both. Feeders and 
service conductors whose calculated load is determined 
by this optional calculation shall be permitted to have 
the neutral load determined by 220.61. 

(B) House Loads. House loads shall be calculated in ac- 
cordance with Part III of this article and shall be in addition 
to the dwelling unit loads calculated in accordance with 
Table 220.84. 

(C) Connected Loads. The calculated load to which the 
demand factors of Table 220.84 apply shall include the 
following: 

(1) 33 volt-amperes/m^ or 3 volt-amperes/ft^ for general 
lighting and general-use receptacles. 

(2) 1500 volt-amperes for each 2-wire, 20-ampere small- 
appliance branch circuit and each laundry branch cir- 
cuit specified in 220.52. 

(3) The nameplate rating of all appliances that are fastened 
in place, permanently connected or located to be on a 
specific circuit, ranges, wall-mounted ovens, counter- 
mounted cooking units, clothes dryers, water heaters, 
and space heaters. If water heater elements are inter- 
locked so that all elements cannot be used at the same 
time, the maximum possible load shall be considered 
the nameplate load. 

(4) The nameplate ampere or kilovolt-ampere rating of all 
motors and of all low-power-factor loads. 

(5) The larger of the air-conditioning load or the space- 
heating load. 



Table 220.84 Optional Calculations — Demand Factors for 
Three or More Multifamily Dwelling Units 



Number of 


Demand Factor 


Dwelling Units 


(Percent) 


3-5 


45 


6-7 


44 


8-10 


43 


11 


42 


12-13 


41 


14-i5 


40 


16-17 


39 


18-20 


38 


21 


37 


22-23 


36 


24-25 


35 


26-27 


34 


28-30 


33 


31 , 


32 


32-33 


31 


34-36 


30 


37-38 


29 


39^2 


28 


43^5 


27 


46-50 


26 


51-55 


25 


56-61 


24 


62 and over 


23 



220.85 Two Dwelling Units. Where two dwelling units 
are supplied by a single feeder and the calculated load 
under Part III of this article exceeds that for three identical 
units calculated under 220.84, the lesser of the two loads 
shall be permitted to be used. 

220.86 Schools. The calculation of a feeder or service 
load for schools shall be permitted in accordance with 
Table 220.86 in lieu of Part III of this article where 
equipped with electric space heating, air conditioning, or 
both. The connected load to which the demand factors of 
Table 220.86 apply shall include all of the interior and 
exterior lighting, power, water heating, cooking, other 
loads, and the larger of the air-conditioning load or space- 
heating load within the building or structure. 

Feeders and service-entrance conductors whose calculated 
load is determined by this optional calculation shall be permit- 
ted to have the neutral load determined by 220.61. Where the 
building or structure load is calculated by this optional 
method, feeders within the building or structure shall have 
ampacity as permitted in Part HI of this article; however, the 
ampacity of an individual feeder shall not be required to be 
larger than the ampacity for the entire building. 

This section shall not apply to portable classroom 
buildings. 



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NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 220 — BRANCH-CIRCUIT, FEEDER, AND SERVICE CALCULATIONS 



220.103 



Table 220.86 Optional Method — Demand Factors for 
Feeders and Service-Entrance Conductors for Schools 



• 







Demand 






Factor 


Connected Load 


(Percent) 


First 33 VA/m^ 


(3 VA/ft^) at 


100 


Plus, 






Over 33 to 220 VA/m^ 


(3 to 20 VA/ft^) at 


75 


Plus, 






Remainder over 220 


(20 VA/ft^) at 


25 


VA/m^ 







220.87 Determining Existing Loads. The calculation of a 
feeder or service load for existing installations shall be 
permitted to use actual maximum demand to determine the 
existing load under all of the following conditions: 

(1) The maximum demand data is available for a 1-year 
period. 

Exception: If the maximum demand data for a 1 -year pe- 
riod is not available, the calculated load shall be permitted 
to be based on the maximum demand (measure of average 
power demand over a 15 -minute period) continuously re- 
corded over a minimum 30-day period using a recording 
ammeter or power meter connected to the highest loaded 
phase of the feeder or service, based on the initial loading 
at the start of the recording. The recording shall reflect the 
maximum demand of the feeder or service by being taken 
when the building or space is occupied and shall include by 
measurement or calculation the larger of the heating or 
cooling equipment load, and other loads that may be peri- 
odic in nature due to seasonal or similar conditions. 

(2) The maximum demand at 125 percent plus the new 
load does not exceed the ampacity of the feeder or 
rating of the service. 

(3) The feeder has overcurrent protection in accordance 
with 240.4, and the service has overload protection in 
accordance with 230.90. 

220.88 New Restaurants. Calculation of a service or 
feeder load, where the feeder serves the total load, for a 



new restaurant shall be permitted in accordance with Table 
220.88 in heu of Part III of this article. 

The overload protection of the service conductors shall 
be in accordance with 230.90 and 240.4. 

Feeder conductors shall not be required to be of greater 
ampacity than the service conductors. 

Service or feeder conductors whose calculated load is 
determined by this optional calculation shall be permitted 
to have the neutral load determined by 220.61. 

V. Farm Load Calculation 

220.100 General. Farm loads shall be calculated in accor- 
dance with Part V. 

220.102 Farm Loads — Buildings and Other Loads. 

(A) Dwelling Unit. The feeder or service load of a farm 
dwelhng unit shall be calculated in accordance with the 
provisions for dwellings in Part III or IV of this article. 
Where the dwelling has electric heat and the farm has elec- 
tric grain-drying systems. Part IV of this article shall not be 
used to calculate the dwelling load where the dwelling and 
farm load are supplied by a common service. 

(B) Other Than Dwelling Unit. Where a feeder or service 
supplies a farm building or other load having two or more 
separate branch circuits, the load for feeders, service con- 
ductors, and service equipment shall be calculated in accor- 
dance with demand factors not less than indicated in Table 
220.102. 

220.103 Farm Loads — Total. Where supplied by a com- 
mon service, the total load of the farm for service conduc- 
tors and service equipment shall be calculated in accor- 
dance with the farm dwelling unit load and demand factors 
specified in Table 220.103. Where there is equipment in 
two or more farm equipment buildings or for loads having 
the same function, such loads shall be calculated in accor- 
dance with Table 220.102 and shall be permitted to be 
combined as a single load in Table 220.103 for calculating 
the total load. 



• 



Table 220.88 Optional Method — Permitted Load Calculations for Service and Feeder Conductors for New Restaurants 



Not All Electric Restaurant 
Calculated Loads (kVA) 



Total Connected 


All Electric Restaurant 


Load (kVA) 


Calculated Loads (kVA) 


0-200 


80% 


201-325 


10% (amount over 200) + 160.0 


326-800 


50% (amount over 325) + 172.5 


Over 800 


50% (amount over 800) + 410.0 



100% 
50% (amount over 200) + 200.0 
45% (amount over 325) + 262.5 
20% (amount over 800) + 476.3 



Note: Add all electrical loads, including both heating and cooling loads, to calculate the total connected load. Select 
the one demand factor that applies from the table, then multiply the total connected load by this single demand factor. 



2005 Edition NATIONAL ELECTRICAL CODE 



70-65 



225.1 



ARTICLE 225 — OUTSIDE BRANCH CIRCUITS AND FEEDERS 



Table 220.102 Method for Calculating Farm Loads for 
Other Than Dwelling Unit 



Table 225.2 Other Articles 



Ampere Load at 240 Volts 
Maximum 



Demand Factor 
(Percent) 



Loads expected to operate 
simultaneously, but not less than 
125 percent full-load current of the 
largest motor and not less than the 
first 60 amperes of load 

Next 60 amperes of all other loads 

Remainder of other load 



100 



50 

25 



Table 220.103 Method for Calculating Total Farm Load 



Individual Loads Calculated in 
Accordance with Table 220.102 



Demand Factor 
(Percent) 



Largest load 
Second largest load 
Third largest load 
Remaining loads 



100 
75 
65 
50 



Note: To this total load, add the load of the farm dwelling unit calcu- 
lated in accordance with Part III or IV of this article. Where the 
dwelling has electric heat and the farm has electric grain-drying sys- 
tems. Part IV of this article shall not be used to calculate the dwelling 
load. 



ARTICLE 225 
Outside Branch Circuits and Feeders 



225.1 Scope. This article covers requirements for outside 
branch circuits and feeders run on or between buildings, 
structures, or poles on the premises; and electric equipment 
and wiring for the supply of utilization equipment that is 
located on or attached to the outside of buildings, struc- 
tures, or poles. 

FPN: For additional information on wiring over 600 volts, 
see ANSI C2-2002, National Electrical Safety Code. 

225.2 Other Articles. Application of other articles, includ- 
ing additional requirements to specific cases of equipment 
and conductors, is shown in Table 225.2. 



I. General 

225.3 Calculation of Loads 600 Volts, Nominal, or Less. 

(A) Branch Circuits. The load on outdoor branch circuits 
shall be as determined by 220.10. 

(B) Feeders. The load on outdoor feeders shall be as de- 
termined by Part III of Article 220. 



Equipment/Conductors 



Branch circuits 

Class 1, Class 2, and Class 3 

remote-control, signahng, and 

power-limited circuits 
Communications circuits 
Community antenna television and radio 

distribution systems 
Conductors for general wiring 
Electrically driven or controlled 

irrigation machines 
Electric signs and outline lighting 
Feeders 

Fire alarm systems 
Fixed outdoor electric deicing and 

snow-melting equipment 
Floating buildings 
Grounding 

Hazardous (classified) locations 
Hazardous (classified) locations — 

specific 
Marinas and boatyards 
Messenger supported wiring 
Mobile homes, manufactured homes, 

and mobile home parks 
Open wiring on insulators 
Over 600 volts, general 
Overcurrent protection 
Radio and television equipment 
Services 

Solar photovoltaic systems 
Swimming pools, fountains, and similar 

installations 
Use and identification of grounded 

conductors 



Article 



210 

725 



800 
820 

310 
675 

600 

215 
760 
426 

553 
250 
500 
510 

555 
396 
550 

398 
490 
240 
810 
230 
690 
680 

200 



225.4 Conductor Covering. Where within 3.0 m (10 ft) of 
any building or structure other than supporting poles or 
towers, open individual (aerial) overhead conductors shall 
be insulated or covered. Conductors in cables or raceways, 
except Type MI cable, shall be of the rubber-covered type 
or thermoplastic type and, in wet locations, shall comply 
with 310.8. Conductors for festoon lighting shall be of the 
rubber-covered or thermoplastic type. 

Exception: Equipment grounding conductors and grounded 
circuit conductors shall be permitted to be bare or covered as 
specifically permitted elsewhere in this Code. 

225.5 Size of Conductors 600 Volts, Nominal, or Less. 

The ampacity of outdoor branch-circuit and feeder conduc- 
tors shall be in accordance with 310.15 based on loads as 
determined under 220.10 and Part III of Article 220. 

225.6 Conductor Size and Support. 

(A) Overhead Spans. Open individual conductors shall 
not be smaller than the following: 



• 



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NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 225 — OUTSIDE BRANCH CIRCUITS AND FEEDERS 



225.17 



(1) For 600 volts, nominal, or less, 10 AWG copper or 8 
AWG aluminum for spans up to 15 m (50 ft) in length, 
and 8 AWG copper or 6 AWG aluminum for a longer 
span unless supported by a messenger wire 

(2) For over 600 volts, nominal, 6 AWG copper or 4 AWG 
aluminum where open individual conductors, and 
8 AWG copper or 6 AWG aluminum where in cable 

(B) Festoon Lighting. Overhead conductors for festoon 
lighting shall not be smaller than 12 AWG unless the con- 
ductors are supported by messenger wires. In all spahs ex- 
ceeding 12 m (40 ft), the conductors shall be supported by 
messenger wire. The messenger wire shall be supported by 
strain insulators. Conductors or messenger wires shall not 
be attached to any fire escape, downspout, or plumbing 
equipment. 

225.7 Lighting Equipment Installed Outdoors. 

(A) General. For the supply of lighting equipment in- 
stalled outdoors, the branch circuits shall comply with 
Article 210 and 225.7(B) through (D). 

(B) Common Neutral. The ampacity of the neutral con- 
ductor shall not be less than the maximum net computed 
load current between the neutral and all ungrounded con- 
ductors connected to any one phase of the circuit. 

(C) 277 Volts to Ground. Circuits exceeding 120 volts, 
nominal, between conductors and not exceeding 277 volts, 
nominal, to ground shall be permitted to supply luminaires 
(lighting fixtures) for illumination of outdoor areas of in- 
dustrial establishments, office buildings, schools, stores, 
and other commercial or public buildings where the lumi- 
naires (fixtures) are not less than 900 mm (3 ft) from win- 
dows, platforms, fire escapes, and the like. 

(D) 600 Volts Between Conductors. Circuits exceeding 
277 volts, nominal, to ground and not exceeding 600 volts, 
nominal, between conductors shall be permitted to supply 
the auxiliary equipment of electric-discharge lamps in ac- 
cordance with 210.6(D)(1). 

225.10 Wiring on Buildings. The installation of outside 
wiring on surfaces of buildings shall be permitted for cir- 
cuits of not over 600 volts, nominal, as open wiring on 
insulators, as multiconductor cable, as Type MC cable, as 
Type MI cable, as messenger supported wiring, in rigid 
metal conduit, in intermediate metal conduit, in rigid non- 
metallic conduit, in cable trays, as cablebus, in wireways, 
in auxiliary gutters, in electrical metallic tubing, in flexible 
metal conduit, in liquidtight flexible metal conduit, in liq- 
uidtight flexible nonmetallic conduit, and in busways. Cir- 
cuits of over 600 volts, nominal, shall be installed as pro- 
vided in 300.37. 



225.11 Circuit Exits and Entrances. Where outside 
branch and feeder circuits leave or enter a building, the 
requirements of 230.52 and 230.54 shall apply. 

225.12 Open-Conductor Supports. Open conductors 
shall be supported on glass or porcelain knobs, racks, 
brackets, or strain insulators. 

225.14 Open-Conductor Spacings. 

(A) 600 Volts, Nominal, or Less. Conductors of 600 volts, 
nominal, or less, shall comply with the spacings provided 
in Table 230.51(C). 

(B) Over 600 Volts, Nominal. Conductors of over 600 volts, 
nominal, shall comply with the spacings provided in 110.36 
and 490.24. 

(C) Separation from Other Circuits. Open conductors 
shall be separated from open conductors of other circuits or 
systems by not less than 100 nmn (4 in.). 

(D) Conductors on Poles. Conductors on poles shall have a 
separation of not less than 300 mm (1 ft) where not placed on 
racks or brackets. Conductors supported on poles shall provide 
a horizontal climbing space not less than the following: 

(1) Power conductors below communications conductors 

— 750 mm (30 in.) 

(2) Power conductors alone or above communications 
conductors: 

a. 300 volts or less — 600 mm (24 in.) 

b. Over 300 volts — 750 mm (30 in.) 

(3) Communications conductors below power conductors 

— same as power conductors 

(4) Communications conductors alone — no requirement 

225.15 Supports over Buildings. Supports over a building 
shall be in accordance with 230.29. 

225.16 Attachment to Buildings. 

(A) Point of Attachment. The point of attachment to a 
building shall be in accordance with 230.26. 

(B) Means of Attachment. The means of attachment to a 
building shall be in accordance with 230.27. 

225.17 Masts as Supports. Where a mast is used for the 
support of final spans of feeders or branch circuits, it shall 
be of adequate strength or be supported by braces or guys 
to withstand safely the strain imposed by the overhead 
drop. Where raceway-type masts are used, all raceway fit- 
tings shall be identified for use with masts. Only the feeder 
or branch circuit conductors specified within this section 
shall be permitted to be attached to the feeder and/or branch 
circuit mast. 



2005 Edition 



NATIONAL ELECTRICAL CODE 



70-67 



225.18 



ARTICLE 225 — OUTSIDE BRANCH CIRCUITS AND FEEDERS 



225.18 Clearance from Ground. Overhead spans of open 
conductors and open multiconductor cables of not over 600 
volts, nominal, shall have a clearance of not less than the 
following: 

(1) 3.0 m (10 ft) — above finished grade, sidewalks, or 
from any platform or projection from which they might 
be reached where the voltage does not exceed 150 volts 
to ground and accessible to pedestrians only 

(2) 3.7 m (12 ft) — over residential property and drive- 
ways, and those commercial areas not subject to truck 
traffic where the voltage does not exceed 300 volts to 
ground 

(3) 4.5 m (15 ft) — for those areas listed in the 3.7-m 
(12-ft) classification where the voltage exceeds 300 
volts to ground 

(4) 5.5 m (18 ft) — over public streets, alleys, roads, park- 
ing areas subject to truck traffic, driveways on other 
than residential property, and other land traversed by 
vehicles, such as cultivated, grazing, forest, and 
orchard 

225.19 Clearances from Buildings for Conductors of 
Not Over 600 Volts, Nominal. 

(A) Above Roofs. Overhead spans of open conductors and 
open multiconductor cables shall have a vertical clearance 
of not less than 2.5 m (8 ft) above the roof surface. The 
vertical clearance above the roof level shall be maintained 
for a distance not less than 900 mm (3 ft) in all directions 
from the edge of the roof. 

Exception No. 1: The area above a roof surface subject to 
pedestrian or vehicular traffic shall have a vertical clear- 
ance from the roof surface in accordance with the clear- 
ance requirements of 225.18. 

Exception No. 2: Where the voltage between conductors 
does not exceed 300, and the roof has a slope of 100 mm in 
300 mm (4 in. in 12 in.) or greater, a reduction in clearance 
to 900 mm (3 ft) shall be permitted. 

Exception No. 3: Where the voltage between conductors 
does not exceed 300, a reduction in clearance above only 
the overhanging portion of the roof to not less than 450 mm 
(18 in.) shall be permitted if (1) not more than 1.8 m (6 ft) 
of the conductors, 1.2 m (4 ft) horizontally, pass above the 
roof overhang and (2) they are terminated at a through-the- 
roof raceway or approved support. 

Exception No. 4: The requirement for maintaining the ver- 
tical clearance 900 mm (3 ft) from the edge of the roof shall 
not apply to the final conductor span where the conductors 
are attached to the side of a building. 

(B) From Nonbuilding or Nonbridge Structures. From 
signs, chimneys, radio and television antennas, tanks, and 
other nonbuilding or nonbridge structures, clearances — 



vertical, diagonal, and horizontal — shall not be less than 
900 mm (3 ft). 

(C) Horizontal Clearances. Clearances shall not be less 
than 900 mm (3 ft). 

(D) Final Spans. Final spans of feeders or branch circuits 
shall comply with 225.19(D)(1), (D)(2), and (D)(3). 

(1) Clearance from Windows. Final spans to the building 
they supply, or from which they are fed, shall be permitted 
to be attached to the building, but they shall be kept not less 
than 900 mm (3 ft) from windows that are designed to be 
opened, and from doors, porches, balconies, ladders, stairs, 
fire escapes, or similar locations. 

Exception: Conductors run above the top level of a win- 
dow shall be permitted to be less than the 900-mm (3-ft) 
requirement. 

(2) Vertical Clearance. The vertical clearance of final 
spans above, or within 900 mm (3 ft) measured horizontally 
of, platforms, projections, or surfaces from which they 
might be reached shall be maintained in accordance with 

225.18. 

(3) Building Openings. The overhead branch-circuit and 
feeder conductors shall not be installed beneath openings 
through which materials may be moved, such as openings 
in farm and commercial buildings, and shall not be installed 
where they obstruct entrance to these buildings' openings. 

(E) Zone for Fire Ladders. Where buildings exceed three 
stories or 15 m (50 ft) in height, overhead lines shall be ar- 
ranged, where practicable, so that a clear space (or zone) at 
least 1.8 m (6 ft) wide will be left either adjacent to the build- 
ings or beginning not over 2.5 m (8 ft) from them to faciUtate 
the raising of ladders when necessary for fire fighting. 

225.20 Mechanical Protection of Conductors. Mechani- 
cal protection of conductors on buildings, structures, or 
poles shall be as provided for services in 230.50. 

225.21 Multiconductor Cables on Exterior Surfaces of 
Buildings. Supports for multiconductor cables on exterior 
surfaces of buildings shall be as provided in 230.51. 

225.22 Raceways on Exterior Surfaces of Buildings or 
Other Structures. Raceways on exteriors of buildings or 
other structures shall be arranged to drain and shall be 
raintight in wet locations. 

Exception: Flexible metal conduit, where permitted in 
348.12(1), shall not be required to be raintight. 

IIS.I'X Outdoor Lampholders. Where outdoor lamphold- 
ers are attached as pendants, the connections to the circuit 
wires shall be staggered. Where such lampholders have 



70-68 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 225 — OUTSIDE BRANCH CIRCUITS AND FEEDERS 



225.33 



• 



• 



terminals of a type that puncture the insulation and make 
contact with the conductors, they shall be attached only to 
conductors of the stranded type. 

225.25 Location of Outdoor Lamps. Locations of lamps 
for outdoor lighting shall be below all energized conduc- 
tors, transformers, or other electric utilization equipment, 
unless either of the following apply: 

(1) Clearances or other safeguards are provided for relamping 
operations. 

(2) Equipment is controlled by a disconnecting means that 
can be locked in the open position. 

225.26 Vegetation as Support. Vegetation such as trees 
shall not be used for support of overhead conductor spans. 

IL More Than One Building or Other Structure 

225.30 Number of Supplies. Where more than one build- 
ing or other structure is on the same property and under 
single management, each additional building or other struc- 
ture that is served by a branch circuit or feeder on the load 
side of the service disconnecting means shall be supplied 
by only one feeder or branch circuit unless permitted in 
225.30(A) through (E). For the purpose of this section, a 
multiwire branch circuit shall be considered a single circuit. 

(A) Special Conditions. Additional feeders or branch cir- 
cuits shall be permitted to supply the following: 

(1) Fire pumps 

(2) Emergency systems 

(3) Legally required standby systems 

(4) Optional standby systems 

(5) Parallel power production systems 

(6) Systems designed for connection to multiple sources of 
supply for the purpose of enhanced reliability 

(B) Special Occupancies. By special permission, addi- 
tional feeders or branch circuits shall be permitted for ei- 
ther of the following: 

(1) Multiple-occupancy buildings where there is no space 
available for supply equipment accessible to all occupants 

(2) A single building or other structure sufficiently large to 
make two or more supplies necessary 

(C) Capacity Requirements. Additional feeders or 
branch circuits shall be permitted where the capacity 
requirements are in excess of 2000 amperes at a supply 
voltage of 600 volts or less. 

(D) Different Characteristics. Additional feeders or branch 
circuits shall be permitted for different voltages, frequencies, 
or phases or for different uses, such as control of outside light- 
ing from multiple locations. 



(E) Documented Switching Procedures. Additional feed- 
ers or branch circuits shall be permitted to supply installa- 
tions under single management where documented safe 
switching procedures are established and maintained for 
disconnection. 

225.31 Disconnecting Means. Means shall be provided 
for disconnecting all ungrounded conductors that supply or 
pass through the building or structure. 

225.32 Location. The disconnecting means shall be in- 
stalled either inside or outside of the building or structure 
served or where the conductors pass through the building or 
structure. The disconnecting means shall be at a readily 
accessible location nearest the point of entrance of the con- 
ductors. For the purposes of this section, the requirements 
in 230.6 shall be utilized. 

Exception No. 1: For installations under single manage- 
ment, where documented safe switching procedures are es- 
tablished and maintained for disconnection, and where the 
installation is monitored by qualified individuals, the dis- 
connecting means shall be permitted to be located else- 
where on the premises. 

Exception No. 2: For buildings or other structures quali- 
fying under the provisions of Article 685, the disconnecting 
means shall be permitted to be located elsewhere on the 
premises. 

Exception No. 3: For towers or poles used as lighting 
standards, the disconnecting means shall be permitted to be 
located elsewhere on the premises. 

Exception No. 4: For poles or similar structures used only 
for support of signs installed in accordance with Article 
600, the disconnecting means shall be permitted to be lo- 
cated elsewhere on the premises. 

225.33 Maximum Number of Disconnects. 

(A) General. The disconnecting means for each supply 
permitted by 225.30 shall consist of not more than six 
switches or six circuit breakers mounted in a single enclo- 
sure, in a group of separate enclosures, or in or on a switch- 
board. There shall be no more than six disconnects per 
supply grouped in any one location. 

Exception: For the purposes of this section, disconnecting 
means used solely for the control circuit of the ground-fault 
protection system, or the control circuit of the power- 
operated supply disconnecting means, installed as part of 
the listed equipment, shall not be considered a supply dis- 
connecting means. 

(B) Single-Pole Units. Two or three single-pole switches 
or breakers capable of individual operation shall be permit- 
ted on multiwire circuits, one pole for each ungrounded 
conductor, as one multipole disconnect, provided they are 



2005 Edition NATIONAL ELECTRICAL CODE 



70-69 



225.34 



ARTICLE 225 — OUTSIDE BRANCH CIRCUITS AND FEEDERS 



equipped with handle ties or a master handle to disconnect 
all ungrounded conductors with no more than six opera- 
tions of the hand. 

225.34 Grouping of Disconnects. 

(A) General. The two to six disconnects as permitted in 
225.33 shall be grouped. Each disconnect shall be marked 
to indicate the load served. 

Exception: One of the two to six disconnecting means 
permitted in 225.33, where used only for a water pump also 
intended to provide fire protection, shall be permitted to be 
located remote from the other disconnecting means. 

(B) Additional Disconnecting Means. The one or more 
additional disconnecting means for fire pumps or for emer- 
gency, legally required standby or optional standby system 
permitted by 225.30 shall be installed sufficiently remote from 
the one to six disconnecting means for normal supply to mini- 
mize the possibility of simultaneous interruption of supply. 

225.35 Access to Occupants. In a multiple-occupancy 
building, each occupant shall have access to the occupant's 
supply disconnecting means. 

Exception: In a multiple-occupancy building where elec- 
tric supply and electrical maintenance are provided by the 
building management and where these are under continu- 
ous building management supervision, the supply discon- 
necting means supplying more than one occupancy shall be 
permitted to be accessible to authorized management per- 
sonnel only. 

225.36 Suitable for Service Equipment. The disconnect- 
ing means specified in 225.31 shall be suitable for use as 
service equipment. 

Exception: For garages and outbuildings on residential 
property, a snap switch or a set of 3-way or 4-way snap 
switches shall be permitted as the disconnecting means. 

225.37 Identification. Where a building or structure has any 
combination of feeders, branch circuits, or services passing 
through it or supplying it, a permanent plaque or directory 
shall be installed at each feeder and branch-circuit disconnect 
location denoting all other services, feeders, or branch circuits 
supplying that building or structure or passing through that 
building or structure and the area served by each. 

Exception No. 1: A plaque or directory shall not be re- 
quired for large-capacity multibuilding industrial installa- 
tions under single management, where it is ensured that 
disconnection can be accomplished by establishing and 
maintaining safe switching procedures. 

Exception No. 2: This identification shall not be required 
for branch circuits installed from a dwelling unit to a sec- 
ond building or structure. 



225.38 Disconnect Construction. Disconnecting means 
shall meet the requirements of 225.38(A) through (D). 

Exception: For garages and outbuildings on residential 
property, snap switches or sets of 3-way or 4-way snap 
switches shall be permitted as the disconnecting means. 

(A) Manually or Power Operable. The disconnecting 
means shall consist of either (1) a manually operable switch 
or a circuit breaker equipped with a handle or other suitable 
operating means or (2) a power-operable switch or circuit 
breaker, provided the switch or circuit breaker can be 
opened by hand in the event of a powfer failure. 

(B) Simultaneous Opening of Poles. Each building or 
structure disconnecting means shall simultaneously discon- 
nect all ungrounded supply conductors that it controls from 
the building or structure wiring system. 

(C) Disconnection of Grounded Conductor. Where the 
building or structure disconnecting means does not discon- 
nect the grounded conductor from the grounded conductors 
in the building or structure wiring, other means shall be 
provided for this purpose at the location of disconnecting 
means. A terminal or bus to which all grounded conductors 
can be attached by means of pressure connectors shall be 
permitted for this purpose. 

In a multisection switchboard, disconnects" for the 
grounded conductor shall be permitted to be in any of the 
switchboard, provided any such switchboard is marked. 

(D) Indicating. The building or structure disconnecting 
means shall plainly indicate whether it is in the open or 
closed position. 

225.39 Rating of Disconnect. The feeder or branch-circuit 
disconnecting means shall have a rating of not less than the 
load to be suppHed, determined in accordance with Parts I 
and II of Article 220 for branch circuits. Parts III or IV of 
Article 220 for feeders, or Part V of Article 220 for farm 
loads. In no case shall the rating be lower than specified in 
225.39(A), (B), (C), or (D). 

(A) One-Circuit Installation. For installations to supply 
only limited loads of a single branch circuit, the branch 
circuit disconnecting means shall have a rating of not less 
than 15 amperes. 

(B) Two-Circuit Installations. For installations consisting 
of not more than two 2-wire branch circuits, the feeder or 
branch-circuit disconnecting means shall have a rating of 
not less than 30 amperes. 

(C) One-Family Dwelling. For a one-family dwelling, the 
feeder disconnecting means shall have a rating of not less 
than 100 amperes, 3-wire. 

(D) All Others. For all other installations, the feeder or 
branch-circuit disconnecting means shall have a rating of 
not less than 60 amperes. 



• 



• 



• 



70-70 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 225 — OUTSIDE BRANCH CIRCUITS AND FEEDERS 



225.61 



225.40 Access to Overcurrent Protective Devices. Where 
a feeder overcurrent device is not readily accessible, branch- 
circuit overcurrent devices shall be installed on the load side, 
shall be mounted in a readily accessible location, and shall be 
of a lower ampere rating than the feeder overcurrent device. 



be engineered considering the special circumstances and 
shall be approved by the authority having jurisdiction. 

FPN: For additional information, see ANSI C2-2002, Na- 
tional Electrical Safety Code. 



• 






III. Over 600 Volts 

225.50 Sizing of Conductors. The sizing of conductors 
over 600 volts shall be in accordance with 210.19(B) for 
branch circuits and 215.2(B) for feeders. 

225.51 Isolating Switches. Where oil switches or air, oil, 
vacuum, or sulfur hexafluoride circuit breakers constitute a 
building disconnecting means, an isolating switch with visible 
break contacts and meeting the requirements of 230.204(B), 
(C), and (D) shall be installed on the supply side of the dis- 
connecting means and all associated equipment. 

Exception: The isolating switch shall not be required where 
the disconnecting means is mounted on removable truck pan- 
els or metal-enclosed switchgear units that cannot be opened 
unless the circuit is disconnected and that, when removed from 
the normal operating position, automatically disconnect the 
circuit breaker or switch from all energized parts. 

225.52 Location. A building or structure disconnecting 
means shall be located in accordance with 225.32, or it 
shall be electrically operated by a similarly located remote- 
control device. 

225.53 Type. Each building or structure disconnect shall 
simultaneously disconnect all ungrounded supply conduc- 
tors it controls and shall have a fault-closing rating not less 
than the maximum available short-circuit current available 
at its supply terminals. 

Where fused switches or separately mounted fuses are in- 
stalled, the fuse characteristics shall be permitted to contribute 
to the fault closing rating of the disconnecting means. 

225.60 Clearances over Roadways, Walkways, Rail, 
Water, and Open Land. 

(A) 22 kV Nominal to Ground or Less. The clearances 
over roadways, walkways, rail, water, and open land for 
conductors and live parts up to 22 kV nominal to ground or 
less shall be not less than the values shown in Table 225.60. 

(B) Over 22 kV Nominal to Ground. Clearances for the 
categories shown in Table 225.60 shall be increased by 
10 mm (0.4 in.) per kV above 22,000 volts. 

(C) Special Cases. For special cases, such as where cross- 
ings will be made over lakes, rivers, or areas using large 
vehicles such as mining operations, specific designs shall 



Table 225.60 Clearances over Roadways, Walkways, Rail, 
Water, and Open Land 



Clearance 


Location 


m 


ft 


Open land subject to vehicles, 


5.6 


18.5 


cultivation, or grazing 






Roadways, driveways, parking lots, 


5.6 


18.5 


and alleys 






Walkways 


4.1 


13.5 


Rails 


8.1 


26.5 


Spaces and ways for pedestrians 


4.4 


14.5 


and restricted traffic 






Water areas not suitable for boating 


5.2 


17 



225.61 Clearances over Buildings and Other Structures. 

(A) 22 kV Nominal to Ground or Less. The clearances 
over buildings and other structures for conductors and live 
parts up to 22 kV, nominal, to ground or less shall be not 
less than the values shown in Table 225.61. 

(B) Over 22 kV Nominal to Ground. Clearances for the 
categories shown in Table 225.61 shall be increased by 
10 mm (0.4 in.) per kV above 22,000 volts. 

FPN: For additional information, see ANSI C2-2002, Na- 
tional Electrical Safety Code. 



Table 225.61 Clearances over Buildings and Other 
Structures 



Clearance from 

Conductors or Live 

Parts from: 



Horizontal 



m ft 



Vertical 



m ft 



Building walls, 

projections, and 

windows 
Balconies, catwalks, and 

similar areas accessible 

to people 
Over or under roofs or 

projections not readily 

accessible to people 
Over roofs accessible to 

vehicles but not trucks 
Over roofs accessible to 

trucks 
Other structures 



2.3 7.5 



2.3 7.5 



4.1 

3.8 

4.1 
5.6 



13.5 

12.5 

13.5 
18.5 



2.3 7.5 



2005 Edition 



NATIONAL ELECTRICAL CODE 



70-71 



230.1 



ARTICLE 230 — SERVICES 



■^: Services \ ;- 



230.1 Scope. This article covers service conductors and 
equipment for control and protection of services and their 
installation requirements. 

FPN: See Figure 230.1. 



General 

Overhead Service-Drop Con 
Underground Service-Latera 
Service-Entrance Conductors 
Service Equipment — Genera 
Service Equipment — Disconr 
Service Equipment — Overcu 
Services Exceeding 600 Volt 

Sou 

t 
Overhead 
Last pole 


ductors 
Condu 

5 

ecting 
■rent Pr 
3, Nomi 

rce 


Parti 
Part II 
ctors Part III 
Part IV 
PartV 
VIeans Part VI 
Dtection Part VII 
nal Part VIII 

Underground 
Street main 

Service lateral 

Depth of burial 
and protection 

Terminal box, 
meter, or other 
enclosure 




Part II Service drop 
230.24 Clearances 

Service head 






Part III 
230.49 


























Service-entrance 
conductors 


Part IV 


Service equipment — general 
Grounding 

Disconnecting means 


\ 








Art 


PartV 
icIe 250 

Part VI 


Overcurrent protection 






Part VII 












Branch circuits 
Feeders 


Articles 210, 225 
Articles 215, 225 



Figure 230.1 Services. 

I. General 

230.2 Number of Services. A building or other structure 
served shall be supplied by only one service unless permitted 
in 230.2(A) through (D). For the purpose of 230.40, Exception 
No. 2 only, underground sets of conductors, 1/0 AWG and 
larger, running to the same location and connected together at 
their supply end but not connected together at their load end 
shall be considered to be supplying one service. 



(A) Special Conditions. Additional services shall be per- 
mitted to supply the following: 

(1) Fire pumps 

(2) Emergency systems 

(3) Legally required standby systems 

(4) Optional standby systems 

(5) Parallel power production systems 

(6) Systems designed for connection to multiple sources of 
supply for the purpose of enhanced reliability 

(B) Special Occupancies. By special permission, additional 
services shall be permitted for either of the following: 

(1) Multiple-occupancy buildings where there is no available 
space for service equipment accessible to all occupants 

(2) A single building or other structure sufficiently large to 
make two or more services necessary 

(C) Capacity Requirements. Additional services shall be 
permitted under any of the following: 

(1) Where the capacity requirements are in excess of 
2000 amperes at a supply voltage of 600 volts or less 

(2) Where the load requirements of a single-phase installa- 
tion are greater than the serving agency normally sup- 
plies through one service 

(3) By special permission 

(D) Different Characteristics. Additional services shall 
be permitted for diflferent voltages, frequencies, or phases, 
or for different uses, such as for different rate schedules. 

(E) Identification. Where a building or structure is supphed 
by more than one service, or any combination of branch cir- 
cuits, feeders, and services, a permanent plaque or directory 
shall be installed at each service disconnect location denoting 
all other services, feeders, and branch circuits supplying that 
building or structure and the area served by each. See 225.37. 

230.3 One Building or Other Structure Not to Be Sup- 
plied Through Another. Service conductors supplying a 
building or other structure shall not pass through the inte- 
rior of another building or other structure. 

230.6 Conductors Considered Outside the Building. 

Conductors shall be considered outside of a building or 
other structure under any of the following conditions: 

(1) Where installed under not less than 50 mm (2 in.) of 
concrete beneath a building or other structure 

(2) Where installed within a building or other structure in a 
raceway that is encased in concrete or brick not less 
than 50 mm (2 in.) thick 

(3) Where installed in any vault that meets the construction 
requirements of Article 450, Part III 



• 



• 






70-72 



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ARTICLE 230 — SERVICES 



230.24 



• 



• 



(4) Where installed in conduit and under not less than 
450 mm (18 in.) of earth beneath a building or other 
structure 

230.7 Other Conductors in Raceway or Cable. Conduc- 
tors other than service conductors shall not be installed in 
the same service raceway or service cable. 

Exception No. 1: Grounding conductors and bonding jumpers. 

Exception No. 2: Load management control conductors 
having overcurrent protection. 

230.8 Raceway Seal. Where a service raceway enters a 
building or structure from an underground distribution sys- 
tem, it shall be sealed in accordance with 300.5(G). Spare 
or unused raceways shall also be sealed. Sealants shall be 
identified for use with the cable insulation, shield, or other 
components. 

230.9 Clearances on Buildings. Service conductors and 
final spans shall comply with 230.9(A), (B), and (C). 

(A) Clearances. Service conductors installed as open con- 
ductors or multiconductor cable without an overall outer 
jacket shall have a clearance of not less than 900 mm (3 ft) 
from windows that are designed to be opened, doors, porches, 
balconies, ladders, stairs, fire escapes, or similar locations. 

Exception: Conductors run above the top level of a win- 
dow shall be permitted to be less than the 900-mm (3-ft) 
requirement. 

(B) Vertical Clearance. The vertical clearance of final 
spans above, or within 900 mm (3 ft) measured horizontally 
of, platforms, projections, or surfaces from which they might 
be reached shall be maintained in accordance with 230.24(B). 

(C) Building Openings. Overhead service conductors 
shall not be installed beneath openings through which ma- 
terials may be moved, such as openings in farm and com- 
mercial buildings, and shall not be installed where they 
obstruct entrance to these building openings. 

230.10 Vegetation as Support. Vegetation such as trees 
shall not be used for support of overhead service conductors. 

II. Overhead Service-Drop Conductors 

230.22 Insulation or Covering. Individual conductors 
shall be insulated or covered. 

Exception: The grounded conductor of a multiconductor 
cable shall be permitted to be bare. 

230.23 Size and Rating. 

(A) General. Conductors shall have suflBcient ampacity to 
carry the current for the load as calculated in accordance with 
Article 220 and shall have adequate mechanical strength. 



(B) Minimum Size. The conductors shall not be smaller 
than 8 AWG copper or 6 AWG aluminum or copper-clad 
aluminum. 

Exception: Conductors supplying only limited loads of a 
single branch circuit — such as small polyphase power, 
controlled water heaters, and similar loads — shall not be 
smaller than 12 AWG hard-drawn copper or equivalent. 

(C) Grounded Conductors. The grounded conductor shall 
not be less than the minimum size as required by 250.24(C). 

230.24 Clearances. Service-drop conductors shall not be 
readily accessible and shall comply with 230.24(A) through 

(D) for services not over 600 volts, nominal. 

(A) Above Roofs. Conductors shall have a vertical clear- 
ance of not less than 2.5 m (8 ft) above the roof surface. 
The vertical clearance above the roof level shall be main- 
tained for a distance of not less than 900 mm (3 ft) in all 
directions from the edge of the roof. 

Exception No. 1: The area above a roof surface subject to 
pedestrian or vehicular traffic shall have a vertical clear- 
ance from the roof surface in accordance with the clear- 
ance requirements of 230.24(B). 

Exception No. 2: Where the voltage between conductors 
does not exceed 300 and the roof has a slope of 100 mm in 
300 mm (4 in. in 12 in.) or greater, a reduction in clearance 
to 900 mm (3 ft) shall be permitted. 

Exception No. 3: Where the voltage between conductors 
does not exceed 300, a reduction in clearance above only 
the overhanging portion of the roof to not less than 450 mm 
(18 in.) shall be permitted if (1) not more than 1.8 m (6 ft) 
of service-drop conductors, 1.2 m (4 ft) horizontally, pass 
above the roof overhang, and (2) they are terminated at a 
through-the-roof raceway or approved support. 

FPN: See 230.28 for mast supports. 

Exception: The requirement for maintaining the vertical 
clearance 900 mm (3 ft) from the edge of the roof shall not 
apply to the final conductor span where the service drop is 
attached to the side of a building. 

(B) Vertical Clearance from Ground. Service-drop con- 
ductors, where not in excess of 600 volts, nominal, shall 
have the following minimum clearance from final grade: 
(1) 3.0 m (10 ft) — at the electric service entrance to 

buildings, also at the lowest point of the drip loop of 
the building electric entrance, and above areas or side- 
walks accessible only to pedestrians, measured from 
final grade or other accessible surface only for service- 
drop cables supported on and cabled together with a 
grounded bare messenger where the voltage does not 
exceed 150 volts to ground 



2005 Edition 



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70-73 



230.26 



ARTICLE 230 — SERVICES 



(2) 3.7 m (12 ft) — over residential property and driveways, 
and those commercial areas not subject to truck traflBc 
where the voltage does not exceed 300 volts to ground 

(3) 4.5 m (15 ft) — for those areas listed in the 3.7-m (12-ft) 
classification where the voltage exceeds 300 volts to 
ground 

(4) 5.5 m (18 ft) — over public streets, alleys, roads, park- 
ing areas subject to truck traffic, driveways on other 
than residential property, and other land such as culti- 
vated, grazing, forest, and orchard 

(C) Clearance from Building Openings. See 230.9. 

(D) Clearance from Swimming Pools. See 680.8. 

230.26 Point of Attachment. The point of attachment of 
the service-drop conductors to a building or other structure 
shall provide the minimum clearances as specified in 230.9 
and 230.24. In no case shall this point of attachment be less 
than 3.0 m (10 ft) above finished grade. 

230.27 Means of Attachment. Multiconductor cables used 
for service drops shall be attached to buildings or other 
structures by fittings identified for use with service conduc- 
tors. Open conductors shall be attached to fittings identified 
for use with service conductors or to noncombustible, non- 
absorbent insulators securely attached to the building or 
other structure. 

230.28 Service Masts as Supports. Where a service mast 
is used for the support of service-drop conductors, it shall 
be of adequate strength or be supported by braces or guys 
to withstand safely the strain imposed by the service drop. 
Where raceway-type service masts are used, all raceway 
fittings shall be identified for use with service masts. Only 
power service-drop conductors shall be permitted to be at- 
tached to a service mast. 

230.29 Supports over Buildings. Service-drop conductors 
passing over a roof shall be securely supported by substan- 
tial structures. Where practicable, such supports shall be 
independent of the building. 

III. Underground Service-Lateral Conductors 

230.30 Insulation. Service-lateral conductors shall be in- 
sulated for the applied voltage. 

Exception: A grounded conductor shall be permitted to be 
uninsulated as follows: 

(1) Bare copper used in a raceway. 

(2) Bare copper for direct burial where bare copper is 
judged to be suitable for the soil conditions. 



(3) Bare copper for direct burial without regard to soil 
conditions where part of a cable assembly identified for 
underground use. 

(4) Aluminum or copper-clad aluminum without individual 
insulation or covering where part of a cable assembly 
identified for underground use in a raceway or for direct 
burial. 

230.31 Size and Rating. 

(A) General. Service-lateral conductors shall have suffi- 
cient ampacity to carry the current for the load as calculated 
in accordance with Article 220 and shall have adequate 
mechanical strength. 

(B) Minimum Size. The conductors shall not be smaller 
than 8 AWG copper or 6 AWG aluminum or copper-clad 
aluminum. 

Exception: Conductors supplying only limited loads of a 
single branch circuit — such as small polyphase power, 
controlled water heaters, and similar loads — shall not be 
smaller than 12 AWG copper or 10 AWG aluminum or 
copper-clad aluminum. 

(C) Grounded Conductors. The grounded conductor shall 
not be less than the minimum size required by 250.24(C). 

230.32 Protection Against Damage. Underground service- 
lateral conductors shall be protected against damage in ac- 
cordance with 300.5. Service-lateral conductors entering a 
building shall be installed in accordance with 230.6 or pro- 
tected by a raceway wiring method identified in 230.43. 

230.33 Spliced Conductors. Service-lateral conductors 
shall be permitted to be spliced or tapped in accordance 
with 110.14, 300.5(E), 300.13, and 300.15. 

IV. Service-Entrance Conductors 

230.40 Number of Service-Entrance Conductor Sets. 

Each service drop or lateral shall supply only one set of 
service-entrance conductors. 

Exception No. 1 : A building shall be permitted to have one 
set of service-entrance conductors for each service, as defined 
in 230.2, run to each occupancy or group of occupancies. 

Exception No. 2: Where two to six service disconnecting 
means in separate enclosures are grouped at one location 
and supply separate loads from one service drop or lateral, 
one set of service-entrance conductors shall be permitted to 
supply each or several such service equipment enclosures. 

Exception No. 3: A single-family dwelling unit and a sepa- 
rate structure shall be permitted to have one set of service - 
entrance conductors run to each from a single service drop 
or lateral. 



• 



• 



70-74 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 230 — SERVICES 



230.50 



• 



Exception No. 4: A two-family dwelling or a multifamily 
dwelling shall be permitted to have one set of service- 
entrance conductors installed to supply the circuits covered 
in 210.25. 

Exception No. 5: One set of service-entrance conductors 
connected to the supply side of the normal service discon- 
necting means shall be permitted to supply each or several 
systems covered by 230.82(4) or 230.82(5). 

230.41 Insulation of Service-Entrance Conductors. 

Service-entrance conductors entering or on the exterior of 
buildings or other structures shall be insulated. 

Exception: A grounded conductor shall be permitted to be 
uninsulated as follows: 

(1) Bare copper used in a raceway or part of a service 
cable assembly. 

(2) Bare copper for direct burial where bare copper is 
judged to be suitable for the soil conditions. 

(3) Bare copper for direct burial without regard to soil 
conditions where part of a cable assembly identified for 
underground use. 

(4) Aluminum or copper-clad aluminum without individual 
insulation or covering where part of a cable assembly 
or identified for underground use in a raceway, or for 
direct burial. 

(5) Bare conductors used in an auxiliary gutter 

230.42 Minimum Size and Rating. 

(A) General. The ampacity of the service-entrance con- 
ductors before the application of any adjustment or correc- 
tion factors shall not be less than either (A)(1) or (A)(2). 
Loads shall be determined in accordance with Article 220. 
Ampacity shall be determined from 310.15. The maximum 
allowable current of busways shall be that value for which 
the busway has been listed or labeled. 

(1) The sum of the noncontinuous loads plus 125 percent 
of continuous loads 

(2) The sum of the noncontinuous load plus the continuous 
load if the service-entrance conductors terminate in an 
overcurrent device where both the overcurrent device 
and its assembly are listed for operation at 100 percent 
of their rating 

(B) Specific Installations. In addition to the requirements 
of 230.42(A), the minimum ampacity for ungrounded con- 
ductors for specific installations shall not be less than the 
rating of the service disconnecting means specified in 
230.79(A) through (D). 

(C) Grounded Conductors. The grounded conductor shall 
not be less than the minimum size as required by 250.24(C). 



230.43 Wiring Methods for 600 Volts, Nominal, or Less. 

Service-entrance conductors shall be installed in accor- 
dance with the applicable requirements of this Code cover- 
ing the type of wiring method used and shall be limited to 
the following methods: 

(1) Open wiring on insulators 

(2) Type IGS cable 

(3) Rigid metal conduit 

(4) Intermediate metal conduit 

(5) Electrical metallic tubing 

(6) Electrical nonmetallic tubing (ENT) 

(7) Service-entrance cables 

(8) Wireways 

(9) Busways 

(10) Auxiliary gutters 

(11) Rigid nonmetallic conduit 

(12) Cablebus 

(13) Type MC cable 

(14) Mineral-insulated, metal-sheathed cable 

(15) Flexible metal conduit not over 1.8 m (6 ft) long or 
liquidtight flexible metal conduit not over 1.8 m (6 ft) 
long between raceways, or between raceway and ser- 
vice equipment, with equipment bonding jumper 
routed with the flexible metal conduit or the liq- 
uidtight flexible metal conduit according to the provi- 
sions of 250.102(A), (B), (C), and (E) 

(16) Liquidtight flexible nonmetallic conduit 

230.44 Cable Trays. Cable tray systems shall be permitted 
to support service-entrance conductors. Cable trays used to 
support service-entrance conductors shall contain only 
service-entrance conductors. 

Exception: Conductors other than service-entrance con- 
ductors shall be permitted to be installed in a cable tray 
with service-entrance conductors, provided a solid fixed 
barrier of a material compatible with the cable tray is 
installed to separate the service-entrance conductors from 
other conductors installed in the cable tray. 

230.46 Spliced Conductors. Service-entrance conductors 
shall be permitted to be spliced or tapped in accordance 
with 110.14, 300.5(E), 300.13, and 300.15. 

230.49 Protection Against Physical Damage — Under- 
ground. Underground service-entrance conductors shall be 
protected against physical damage in accordance with 300.5. 

230.50 Protection of Open Conductors and Cables 
Against Damage — Above Ground. Service-entrance 
conductors installed above ground shall be protected 
against physical damage as specified in 230.50(A) or (B). 



2005 Edition 



NATIONAL ELECTRICAL CODE 



70-75 



230.51 



ARTICLE 230 — SERVICES 



(A) Service Cables. Service cables, where subject to physi- 
cal damage, shall be protected by any of the following: 

(1) Rigid metal conduit 

(2) Intermediate metal conduit 

(3) Schedule 80 rigid nonmetallic conduit 

(4) Electrical metallic tubing 

(5) Other approved means 

(B) Other Than Service Cable. Individual open conduc- 
tors and cables other than service cables shall not be in- 
stalled within 3.0 m (10 ft) of grade level or where exposed 
to physical damage. 

Exception: Type MI and Type MC cable shall be permitted 
within 3.0 m (10 ft) of grade level where not exposed to physi- 
cal damage or where protected in accordance with 300.5(D). 

230.51 Mounting Supports. Cables or individual open ser- 
vice conductors shall be supported as specified in 230.51(A), 
(B), or (C). 

(A) Service Cables. Service cables shall be supported by 
straps or other approved means within 300 mm (12 in.) of 
every service head, gooseneck, or connection to a raceway or 
enclosure and at intervals not exceeding 750 mm (30 in.). 

(B) Other Cables. Cables that are not approved for mount- 
ing in contact with a building or other structure shall be 
mounted on insulating supports installed at intervals not ex- 
ceeding 4.5 m (15 ft) and in a manner that maintains a clear- 
ance of not less than 50 mm (2 in.) from the surface over 
which they pass. 

(C) Individual Open Conductors. Individual open con- 
ductors shall be installed in accordance with Table 230.51(C). 
Where exposed to the weather, the conductors shall be 
mounted on insulators or on insulating supports attached to 
racks, brackets, or other approved means. Where not exposed 
to the weather, the conductors shall be mounted on glass or 
porcelain knobs. 



230.52 Individual Conductors Entering Buildings or 
Other Structures. Where individual open conductors enter a 
building or other structure, they shall enter through roof bush- 
ings or through the wall in an upward slant through individual, 
noncombustible, nonabsorbent insulating tubes. Drip loops 
shall be formed on the conductors before they enter the tubes. 

230.53 Raceways to Drain. Where exposed to the weather, 
raceways enclosing service-entrance conductors shall be rain- 
tight and arranged to drain. Where embedded in masonry, 
raceways shall be arranged to drain. 

Exception: As permitted in 348.12(1). 

230.54 Overhead Service Locations. 

(A) Raintight Service Head. Service raceways shall be 
equipped with a raintight service head at the point of con- 
nection to service-drop conductors. 

(B) Service Cable Equipped with Raintight Service 
Head or Gooseneck. Service cables shall be equipped with 
a raintight service head. 

Exception: Type SE cable shall be permitted to be formed 
in a gooseneck and taped with a self-sealing weather- 
resistant thermoplastic. 

(C) Service Heads and Goosenecks Above Service-Drop 
Attachment. Service heads and goosenecks in service- 
entrance cables shall be located above the point of attach- 
ment of the service-drop conductors to the building or other 
structure. 

Exception: Where it is impracticable to locate the service 
head or gooseneck above the point of attachment, the ser- 
vice head or gooseneck location shall be permitted not 
farther than 600 mm (24 in.) from the point of attachment. 

(D) Secured. Service cables shall be held securely in place. 

(E) Separately Bushed Openings. Service heads shall 
have conductors of different potential brought out through 
separately bushed openings. 



Table 230,51(C) Supports 





Maximum Distance Between 




Minimum Clearance 












Maximum 


Supports 


Between Conductors 


From Surface 










Volts 


m ft 


mm 


m. 


mm m. 


600 


2.7 9 


150 


6 


50 2 


600 


4.5 15 


300 


12 


50 2 


300 


1.4 41/2 


75 


3 


50 2 


600* 


1.4='= 41/2* 


65* 


21/2* 


25* 1* 



*Where not exposed to weather. 



70-76 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 230 — SERVICES 



230.72 



Exception: For jacketed multiconductor service cable 
without splice. 

(F) Drip Loops. Drip loops shall be formed on individual 
conductors. To prevent the entrance of moisture, service- 
entrance conductors shall be connected to the service-drop 
conductors either (1) below the level of the service head or 
(2) below the level of the termination of the service- 
entrance cable sheath. 

(G) Arranged That Water Will Not Enter Service Race- 
way or Equipment. Service-drop conductors and service- 
entrance conductors shall be arranged so that water will not 
enter service raceway or equipment. 

230.56 Service Conductor with the Higher Voltage to 
Groiind. On a 4-wire, delta-connected service where the 
midpoint of one phase winding is grounded, the service 
conductor having the higher phase voltage to ground shall 
be durably and permanently marked by an outer finish that 
is orange in color, or by other effective means, at each 
termination or junction point. 

V. Service Equipment — General 

230.62 Service Equipment — Enclosed or Guarded. Ener- 
gized parts of service equipment shall be enclosed as specified 
in 230.62(A) or guarded as specified in 230.62(B). 

(A) Endosed. Energized parts shall be enclosed so that 
they will not be exposed to accidental contact or shall be 
guarded as in 230.62(B). 

(B) Guarded. Energized parts that are not enclosed shall 
be installed on a switchboard, panelboard, or control board 
and guarded in accordance with 110.18 and 110.27. Where 
energized parts are guarded as provided in 110.27(A)(1) 
and (A)(2), a means for locking or sealing doors providing 
access to energized parts shall be provided. 

230.66 Marking. Service equipment rated at 600 volts or 
less shall be marked to identify it as being suitable for use 
as service equipment. Individual meter socket enclosures 
shall not be considered service equipment. 

VI. Service Equipment — Disconnecting Means 

230.70 General. Means shall be provided to disconnect all 
conductors in a building or other structure from the service- 
entrance conductors. 

(A) Location. The service disconnecting means shall be in- 
staUed in accordance with 230.70(A)(1), (A)(2), and (A)(3). 



(1) Readily Accessible Location. The service disconnect- 
ing means shall be installed at a readily accessible location 
either outside of a building or structure or inside nearest the 
point of entrance of the service conductors. 

(2) Bathrooms. Service disconnecting means shall not be 
installed in bathrooms. 

(3) Remote Control. Where a remote control device(s) is 
used to actuate the service disconnecting means, the service 
disconnecting means shall be located in accordance with 
230.70(A)(1). 

(B) Marking. Each service disconnect shall be perma- 
nently marked to identify it as a service disconnect. 

(C) Suitable for Use. Each service disconnecting means 
shall be suitable for the prevailing conditions. Service 
equipment installed in hazardous (classified) locations shall 
comply with the requirements of Articles 500 through 517. 

230.71 Maximum Number of Disconnects. 

(A) General. The service disconnecting means for each 
service permitted by 230.2, or for each set of service- 
entrance conductors permitted by 230.40, Exception Nos. 
1, 3, 4, or 5, shall consist of not more than six switches or 
sets of circuit breakers, or a combination of not more than 
six switches and sets of circuit breakers, mounted in a 
single enclosure, in a group of separate enclosures, or in or 
on a switchboard. There shall be not more than six sets of 
disconnects per service grouped in any one location. For 
the purpose of this section, disconnecting means used 
solely for power monitoring equipment, transient voltage 
surge suppressors, or the control circuit of the ground-fault 
protection system or power-operable service disconnecting 
means, installed as part of the listed equipment, shall not be 
considered a service disconnecting means. 

(B) Single-Pole Units. Two or three single-pole switches 
or breakers, capable of individual operation, shall be per- 
mitted on multiwire circuits, one pole for each ungrounded 
conductor, as one multipole disconnect, provided they are 
equipped with handle ties or a master handle to disconnect 
all conductors of the service with no more than six opera- 
tions of the hand. 

FPN: See 408.36(A) for service equipment in panelboards, 
and see 430.95 for service equipment in motor control centers. 

230.72 Grouping of Disconnects. 

(A) General. The two to six disconnects as permitted in 
230.71 shall be grouped. Each disconnect shall be marked 
to indicate the load served. 

Exception: One of the two to six service disconnecting 
means permitted in 230.71, where used only for a water pump 
also intended to provide fire protection, shall be permitted to 
be located remote from the other disconnecting means. 



2005 Edition NATIONAL ELECTRICAL CODE 



70-77 



230.74 



ARTICLE 230 — SERVICES 



(B) Additional Service Disconnecting Means. The one or 

ore additional service disconnecting means for fire 
pumps, emergency systems, legally required standby, or 
optional standby services permitted by 230.2 shall be 
installed remote from the one to six service disconnect- 
ing means for normal service to minimize the possibility 
of simultaneous interruption of supply. 

(C) Access to Occupants. In a multiple-occupancy build- 
ing, each occupant shall have access to the occupant's ser- 
vice disconnecting means. 

Exception: In a multiple -occupancy building where electric 
service and electrical maintenance are provided by the build- 
ing management and where these are under continuous build- 
ing management supervision, the service disconnecting means 
supplying more than one occupancy shall be permitted to be 
accessible to authorized management personnel only. 

230.74 Simultaneous Opening of Poles. Each service 
disconnect shall simultaneously disconnect all ungrounded 
service conductors that it controls from the premises wiring 
system. 

230.75 Disconnection of Grounded Conductor. Where 
the service disconnecting means does not disconnect the 
grounded conductor from the premises wiring, other means 
shall be provided for this purpose in the service equipment. 
A terminal or bus to which all grounded conductors can be 
attached by means of pressure connectors shall be permit- 
ted for this purpose. In a multisection switchboard, discon- 
nects for the grounded conductor shall be permitted to be in 
any section of the switchboard, provided any such switch- 
board section is marked. 

230.76 Manually or Power Operable. The service dis- 
connecting means for ungrounded service conductors shall 
consist of one of the following: 

(1) A manually operable switch or circuit breaker equipped 
with a handle or other suitable operating means 

(2) A power-operated switch or circuit breaker, provided 
the switch or circuit breaker can be opened by hand in 
the event of a power supply failure 

230.77 Indicating. The service disconnecting means shall 
plainly indicate whether it is in the open or closed position. 

230.79 Rating of Service Disconnecting Means. The ser- 
vice disconnecting means shall have a rating not less than 
the load to be carried, determined in accordance with Ar- 
ticle 220. In no case shall the rating be lower than specified 
in 230.79(A), (B), (C), or (D). 



(A) One-Circuit Installation. For installations to supply 
only limited loads of a single branch circuit, the service 
disconnecting means shall have a rating of not less than 15 
amperes. 

(B) Two-Circuit Installations. For installations consisting of 
not more than two 2-wire branch circuits, the service discon- 
necting means shall have a rating of not less than 30 amperes. 

(C) One-Family Dwelling. For a one-family dwelling, the 
service disconnecting means shall have a rating of not less 
than 100 amperes, 3-wire. 

(D) All Others. For all other installations, the service discon- 
necting means shall have a rating of not less than 60 amperes. 

230.80 Combined Rating of Disconnects. Where the ser- 
vice disconnecting means consists of more than one switch 
or circuit breaker, as permitted by 230.71, the combined 
ratings of all the switches or circuit breakers used shall not 
be less than the rating required by 230.79. 

230.81 Connection to Terminals. The service conductors 
shall be connected to the service disconnecting means by 
pressure connectors, clamps, or other approved means. 
Connections that depend on solder shall not be used. 

230.82 Equipment Connected to the Supply Side of Ser- 
vice Disconnect. Only the following equipment shall be 
permitted to be connected to the supply side of the service 
disconnecting means: 

(1) Cable limiters or other current-limiting devices 

(2) Meters and meter sockets nominally rated not in excess 
of 600 volts, provided all metal housings and service 
enclosures are grounded 

(3) Meter disconnect switches nominally rated not in ex- 
cess of 600 volts that have a short-circuit current rating 
equal to or greater than the available short circuit cur- 
rent, provided all metal housings and service enclo- 
sures are grounded 

(4) Instrument transformers (current and voltage), imped- 
ance shunts, load management devices, and arresters 

(5) Taps used only to supply load management devices, 
circuits for standby power systems, fire pump equip- 
ment, and fire and sprinkler alarms, if provided with 
service equipment and installed in accordance with re- 
quirements for service-entrance conductors 

(6) Solar photovoltaic systems, fuel cell systems, or inter- 
connected electric power production sources 

(7) Control circuits for power-operable service disconnect- 
ing means, if suitable overcurrent protection and dis- 
connecting means are provided 

(8) Ground-fault protection systems or transient voltage 
surge suppressors, where installed as part of listed 
equipment, if suitable overcurrent protection and dis- 
connecting means are provided 



70-78 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 230 — SERVICES 



230.95 



VII. Service Equipment — Overcurrent Protection 

230.90 Where Required. Each ungrounded service conduc- 
tor shall have overload protection. 

(A) Ungrounded Conductor. Such protection shall be pro- 
vided by an overcurrent device in series with each ungrounded 
service conductor that has a rating or setting not higher than 
the allowable ampacity of the condiictor. A set of fuses shall 
be considered aU the fuses required to protect all the un- 
grounded conductors of a circuit. Single-pole circuit breakers, 
grouped in accordance with 230.71(B), shall be considered as 
one protective device. 

Exception No. 1: For motor-starting currents, ratings that 
conform with 430.52, 430.62, and 430.63 shall be permitted. 

Exception No. 2: Fuses and circuit breakers with a rating 
or setting that conforms with 240.4(B) or (C) and 240.6 
shall be permitted. 

Exception No. 3: Two to six circuit breakers or sets of fuses 
shall be permitted as the overcurrent device to provide the 
overload protection. The sum of the ratings of the circuit 
breakers or fuses shall be permitted to exceed the ampacity of 
the service conductors, provided the calculated load does not 
exceed the ampacity of the service conductors. 

Exception No. 4: Overload protection for fire pump supply 
conductors shall conform with 695.4(B)(1). 

Exception No. 5: Overload protection for 120/240-volt, 
3-wire, single-phase dwelling services shall be permitted in 
accordance with the requirements of 310.15(B)(6). 

(B) Not in Grounded Conductoi*. No overcurrent device 
shall be inserted in a grounded service conductor except a 
circuit breaker that simultaneously opens all conductors of 
the circuit. 

230.91 Location. The service overcurrent device shall be 
an integral part of the service disconnecting means or shall 
be located immediately adjacent thereto. 

230.92 Locked Service Overcurrent Devices. Where the 
service overcurrent devices are locked or sealed or are not 
readily accessible to the occupant, branch-circuit overcur- 
rent devices shall be installed on the load side, shall be 
mounted in a readily accessible location, and shall be of 
lower ampere rating than the service overcurrent device. 

230.93 Protection of Specific Circuits. Where necessary 
to prevent tampering, an automatic overcurrent device that 
protects service conductors supplying only a specific load, 
such as a water heater, shall be permitted to be locked or 
sealed where located so as to be accessible. 

230.94 Relative Location of Overcurrent Device and 
Other Service Equipment. The overcurrent device shall 
protect all circuits and devices. 



Exception No. 1: The service switch shall be permitted on 
the supply side. 

Exception No. 2: High-impedance shunt circuits, surge 
arresters, surge-protective capacitors, and instrument 
transformers (current and voltage) shall be permitted to be 
connected and installed on the supply side of the service 
disconnecting means as permitted in 230.82. 

Exception No. 3: Circuits for load management devices 
shall be permitted to be connected on the supply side of the 
service overcurrent device where separately provided with 
overcurrent protection. 

Exception No. 4: Circuits used only for the operation of 
fire alarm, other protective signaling systems, or the supply 
to fire pump equipment shall be permitted to be connected 
on the supply side of the service overcurrent device where 
separately provided with overcurrent protection. 

Exception No. 5: Meters nominally rated not in excess of 
600 volts shall be permitted, provided all metal housings 
and service enclosures are grounded. 

Exception No. 6: Where service equipment is power oper- 
able, the control circuit shall be permitted to be connected 
ahead of the service equipment if suitable overcurrent pro- 
tection and disconnecting means are provided. 

230.95 Ground-Fault Protection of Equipment. Ground- 
fault protection of equipment shall be provided for soUdly 
grounded wye electrical services of more than 150 volts to 
ground but not exceeding 600 volts phase-to-phase for each 
service disconnect rated 1000 amperes or more. The grounded 
conductor for the sohdly grounded wye system shall be con- 
nected directly to ground without inserting any resistor or im- 
pedance device. 

The rating of the service disconnect shall be considered 
to be the rating of the largest fuse that can be installed or 
the highest continuous current trip setting for which the 
actual overcurrent device installed in a circuit breaker is 
rated or can be adjusted. 

Exception No. 1: The ground-fault protection provisions of 
this section shall not apply to a service disconnect for a 
continuous industrial process where a nonorderly shutdown 
will introduce additional or increased hazards. 

Exception No. 2: The ground-fault protection provisions of 
this section shall not apply to fire pumps. 

(A) Setting. The ground-fault protection system shall operate 
to cause the service disconnect to open all ungrounded con- 
ductors of the faulted circuit. The maximum setting of the 
ground-fault protection shall be 1200 amperes, and the maxi- 
mum time delay shall be one second for ground-fault currents 
equal to or greater than 3000 amperes. 



2005 Edition 



NATIONAL ELECTRICAL CODE 



70-79 



230.200 



ARTICLE 230 — SERVICES 



(B) Fuses. If a switch and fuse combination is used, the 
fuses employed shall be capable of interrupting any current 
higher than the interrupting capacity of the switch during a 
time that the ground-fault protective system will not cause 
the switch to open. 

(C) Performance Testing. The ground-fault protection 
system shall be performance tested when first installed on 
site. The test shall be conducted in accordance with instruc- 
tions that shall be provided with the equipment. A written 
record of this test shall be made and shall be available to 
the authority having jurisdiction. 

FPN No. 1 : Ground-fault protection that functions to open 
the service disconnect affords no protection from faults on 
the line side of the protective element. It serves only to 
limit damage to conductors and equipment on the load side 
in the event of an arcing ground fault on the load side of the 
protective element. 

FPN No. 2: This added protective equipment at the service 
equipment may make it necessary to review the overall wiring 
system for proper selective overcurrent protection coordina- 
tion. Additional installations of ground-fault protective equip- 
ment may be needed on feeders and branch circuits where 
maximum continuity of electrical service is necessary. 

FPN No. 3: Where ground-fault protection is provided for 
the service disconnect and interconnection is made with an- 
other supply system by a transfer device, means or devices 
may be needed to ensure proper ground-fault sensing by the 
ground-fault protection equipment. 

FPN No. 4: See 517.17(A) for information on where an 
additional step of ground fault protection is required for 
hospitals and other buildings with critical areas or life sup- 
port equipment. 



VIII. Services Exceeding 600 Volts, Nominal 

230.200 General. Service conductors and equipment used 
on circuits exceeding 600 volts, nominal, shall comply with 
all the applicable provisions of the preceding sections of 
this article and with the following sections that supplement 
or modify the preceding sections. In no case shall the pro- 
visions of Part VIII apply to equipment on the supply side 
of the service point. 

FPN: For clearances of conductors of over 600 volts, nomi- 
nal, see ANSI C2-2002, National Electrical Safety Code. 

230.202 Service-Entrance Conductors. Service-entrance 
conductors to buildings or enclosures shall be installed to 
conform to 230.202(A) and (B). 

(A) Conductor Size. Service-entrance conductors shall not 
be smaller than 6 AWG unless in multiconductor cable. 
Multiconductor cable shall not be smaller than 8 AWG. 

(B) Wiring Methods. Service-entrance conductors shall be 
installed by one of the wiring methods covered in 300.37 and 
300.50. 



230.204 Isolating Switches. 

(A) Where Required. Where oil switches or air, oil, 
vacuum, or sulfur hexafluoride circuit breakers constitute 
the service disconnecting means, an isolating switch with 
visible break contacts shall be installed on the supply side 
of the disconnecting means and all associated service 
equipment. 

Exception: An isolating switch shall not be required where 
the circuit breaker or switch is mounted on removable truck 
panels or metal-enclosed switchgear units where both of 
the following conditions apply: 

(1) Cannot be opened unless the circuit is disconnected. 

(2) Where all energized parts are automatically discon- 
nected when the circuit breaker or switch is removed 
from the normal operating position. 

(B) Fuses as Isolating Switch. Where fuses are of the type 
that can be operated as a disconnecting switch, a set of such 
fuses shall be permitted as the isolating switch. 

(C) Accessible to Qualified Persons Only. The isolating 
switch shall be accessible to qualified persons only. 

(D) Grounding Connection. Isolating switches shall be 
provided with a means for readily connecting the load side 
conductors to ground when disconnected from the source of 
supply. 

A means for grounding the load side conductors shall 
not be required for any duplicate isolating switch installed 
and maintained by the electric supply company. 

230.205 Disconnecting Means. 

(A) Location. The service disconnecting means shall be 
located in accordance with 230.70. 

(B) Type. Each service disconnect shall simultaneously 
disconnect all ungrounded service conductors that it con- 
trols and shall have a fault-closing rating that is not less 
than the maximum short-circuit current available at its sup- 
ply terminals. 

Where fused switches or separately mounted fuses 
are installed, the fuse characteristics shall be permitted 
to contribute to the fault-closing rating of the discon- 
necting means. 

(C) Remote Control. For multibuilding, industrial instal- 
lations under single management, the service disconnecting 
means shall be permitted to be located at a separate build- 
ing or structure. In such cases, the service disconnecting 
means shall be permitted to be electrically operated by a 
readily accessible, remote-control device. 



70-80 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 240 — OVERCURRENT PROTECTION 



240.3 



• 



230.206 Overcurrent Devices as Disconnecting Means. 

Where the circuit breaker or alternative for it, as specified 
in 230.208 for service overcurrent devices, meets the re- 
quirements specified in 230.205, they shall constitute the 
service disconnecting means. 

230.208 Protection Requirements. A short-circuit protec- 
tive device shall be provided on the load side of, or as an 
integral part of, the service disconnect, and shall protect all 
ungrounded conductors that it supplies. The protective 
device shall be capable of detecting and interrupting all 
values of current, in excess of its trip setting or melting 
point, that can occur at its location. A fuse rated in con- 
tinuous amperes not to exceed three times the ampacity 
of the conductor, or a circuit breaker with a trip setting 
of not more than six times the ampacity of the conduc- 
tors, shall be considered as providing the required short- 
circuit protection. 

FPN: See Table 310.67 through Table 310.86 for ampaci- 
ties of conductors rated 2001 volts and above. 

Overcurrent devices shall conform to 230.208(A) and (B). 

(A) Equipment Type. Equipment used to protect service- 
entrance conductors shall meet the requirements of Ar- 
ticle 490, Part IL 

(B) Enclosed Overcurrent Devices. The restriction to 
80 percent of the rating for an enclosed overcurrent device 
for continuous loads shall not apply to overcurrent devices 
installed in systems operating at over 600 volts. 

230.209 Surge Arresters (Lightning Arresters). Surge 
arresters installed in accordance with the requirements of 
Article 280 shall be permitted on each ungrounded over- 
head service conductor. 

230.210 Service Equipment — General Provisions. Ser- 
vice equipment, including instrument transformers, shall 
conform to Article 490, Part I. 

230.211 Metal-Enclosed Switchgear. Metal-enclosed 
switchgear shall consist of a substantial metal structure and 
a sheet metal enclosure. Where installed over a combustible 
floor, suitable protection thereto shall be provided. 

230.212 Over 35,000 Volts. Where the voltage exceeds 
35,000 volts between conductors that enter a building, they 
shall terminate in a metal-enclosed switchgear compart- 
ment or a vault conforming to the requirements of 450.41 
through 450.48. 



ARTICLE 240 
Overcurrent Protection 



I. General 

240.1 Scope. Parts I through VII of this article provide the 
general requirements for overcurrent protection and over- 
cun-ent protective devices not more than 600 volts, nominal. 
Part Vin covers overcurrent protection for those portions of 
supervised industrial installations operating at voltages of not 
more than 600 volts, nominal. Part EX covers overcurrent pro- 
tection over 600 volts, nominal. 

FPN: Overcurrent protection for conductors and equip- 
ment is provided to open the circuit if the current reaches a 
value that will cause an excessive or dangerous temperature 
in conductors or conductor insulation. See also 110.9 for 
requirements for interrupting ratings and 110.10 for re- 
quirements for protection against fault currents. 

240.2 Definitions. 

Current-Limiting Overcurrent Protective Device. A de- 
vice that, when interrupting currents in its current-limiting 
range, reduces the current flowing in the faulted circuit to a 
magnitude substantially less than that obtainable in the 
same circuit if the device were replaced with a solid con- 
ductor having comparable impedance. 

Supervised Industrial Installation. For the purposes of 
Part VIII, the industrial portions of a facility where all of 
the following conditions are met: 

(1) Conditions of maintenance and engineering supervision 
ensure that only qualified persons monitor and service 
the system. 

(2) The premises wiring system has 2500 kVA or greater of 
load used in industrial process(es), manufacturing activi- 
ties, or both, as calculated in accordance with Article 220. 

(3) The premises has at least one service or feeder that is 
more than 150 volts to ground and more than 300 volts 
phase-to-phase. 

This definition excludes installations in buildings used by 
the industrial facility for offices, warehouses, garages, ma- 
chine shops, and recreational facilities that are not an integral 
part of the industrial plant, substation, or control center. 

Tap Conductors. As used in this article, a tap conductor is 
defined as a conductor, other than a service conductor, that 
has overcurrent protection ahead of its point of supply that 
exceeds the value permitted for similar conductors that are 
protected as described elsewhere in 240.4. 

240.3 Other Articles. Equipment shall be protected against 
overcurrent in accordance with the article in this Code that 
covers the type of equipment specified in Table 240.3. 



2005 Edition 



NATIONAL ELECTRICAL CODE 



70-81 



240.4 



ARTICLE 240 — OVERCURRENT PROTECTION 



Table 240.3 Other Articles 



Equipment 


Article 


Air-conditioning and refrigerating 


440 


equipment 




Appliances 


422 


Assembly occupancies 


518 


Audio signal processing, 


640 


amplification, and reproduction 




equipment 




BrancH circuits 


210 


Busways 


368 


Capacitors 


460 


Class 1, Class 2, and (Zlass 3 


725 


remote-control, signaling, and 




power-limited circuits 




Closedrloop and programmed power 


780 


distribution 




Cranes and hoists 


610 


Electric signs and outline lighting 


600 


Electric welders 


630 


Electrolytic cells 


668 


Elevators, dumbwaiters, escalators. 


620 


moving walks, wheelchair lifts, and 




stairway chair lifts 




Emergency systems 


700 


Fire alarm systems 


760 


Fire purrips 


695 


Fixed electric heating equipment for 


427 


pipelines and vessels 




Fixed electric space-heating 


424 


equipment 




Fixed outdoor electric deicing and 


426 


snow-melting equipment 




Generators 


445 


Health care facilities 


517 


Induction and dielectric heating 


665 


equipment 




Industrial machinery 


670 


Luminaires (lighting fixtures). 


410 


lampholders, and lamps 




Motion picture and television studios 


530 


and similar locations 




Motors, motor circuits, and 


430 


controllers 




Phase converters 


455 


Pipe organs 


650 


Receptacles 


406 


Services 


230 


Solar photovoltaic systems 


690 


Switchboards and panelboards 


408 


Theaters, audience areas of motion 


520 


picture and television studios, and 




similar locations 




Transformers and transformer vaults 


450 


X-ray equipment 


660 



240.4 Protection of Conductors. Conductors, other than 
flexible cords, flexible cables, and fixture wires, shall be 
protected against overcurrent in accordance with their am- 
pacities specified in 310.15, unless otherwise permitted or 
required in 240.4(A) through (G). 



(A) Power Loss Hazard. Conductor overload protection 
shall not be required where the interruption of the circuit 
would create a hazard, such as in a material-handhng mag- 
net circuit or fire pump circuit. Short-circuit protection 
shall be provided. 

FPN: See NFPA 20-2003, Standard for the Installation of 
Stationary Pumps for Fire Protection. 

(B) Devices Rated 800 Amperes or Less. The next higher 
standard overcurrent device rating (above the ampacity of 
the conductors being protected) shall be permitted to be 
used, provided all of the following conditions are met: 

(1) The conductors being protected are not part of a mul- 
tioutlet branch circuit supplying receptacles for cord- 
and-plug-connected portable loads. 

(2) The ampacity of the conductors does not correspond 
with the standard ampere rating of a fuse or a circuit 
breaker without overload trip adjustments above its rat- 
ing (but that shall be permitted to have other trip or 
rating adjustments). 

(3) The next higher standard rating selected does not ex- 
ceed 800 amperes. 

(C) Devices Rated Over 800 Amperes. Where the over- 
current device is rated over 800 amperes, the ampacity of 
the conductors it protects shall be equal to or greater than 
the rating of the overcurrent device defined in 240.6. 

(D) Small Conductors. Unless specifically permitted in 
240.4(E) or 240.4(G), the overcurrent protection shall not 
exceed 15 amperes for 14 AWG, 20 amperes for 12 AWG, 
and 30 amperes for 10 AWG copper; or 15 amperes for 
12 AWG and 25 amperes for 10 AWG aluminum and 
copper-clad aluminum after any correction factors for 
ambient temperature and number of conductors have 
been applied. 

(E) Tap Conductors. Tap conductors shall be permitted to 
be protected against overcurrent in accordance with the fol- 
lowing: 

(1) 210.19(A)(3) and (A)(4) Household Ranges and Cook- 
ing Appliances and Other Loads 

(2) 240.5(B)(2) Fixture Wire 

(3) 240.21 Location in Circuit 

(4) 368.17(B) Reduction in Ampacity Size of Busway 

(5) 368.17(C) Feeder or Branch Circuits (busway taps) 

(6) 430.53(D) Single Motor Taps 

(F) IVansformer Secondary Conductors. Single-phase 
(other than 2-wire) and multiphase (other than delta-delta, 
3-wire) transformer secondary conductors shall not be consid- 
ered to be protected by the primary overcurrent protective 
device. Conductors supplied by the secondary side of a single- 
phase transformer having a 2-wire (single-voltage) secondary, 



• 



70-82 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 240 — OVERCURRENT PROTECTION 



240.6 



• 



or a three-phase, delta-delta connected transformer having a 
3-wire (single-voltage) secondary, shall be permitted to be 
protected by overcurrent protection provided on the primary 
(supply) side of the transformer, provided this protection is in 
accordance with 450.3 and does not exceed the value deter- 
mined by multiplying the secondary conductor ampacity by 
the secondary to primary transformer voltage ratio. 

(G) Overcurrent Protection for Specific Conductor 
Applications. Overcurrent protection for the specific con- 
ductors shall be permitted to be provided as referenced in 
Table 240.4(G). 

Table 240.4(G) Specific Conductor Applications 



Conductor 


Article 


Section 


Air-conditioning and 


440, Parts III, 




refrigeration 


VI 




equipment circuit 






conductors 






Capacitor circuit 


460 


460.8(B) and 


conductors 




460.25(A)-(D) 


Control and 


727 


727.9 


instrumentation 






circuit conductors 






(Type ITC) 






Electric welder 


630 


630.12 and 630.32 


circuit conductors 






Fire alarm system 


760 


760.23, 760.24, 


circuit conductors 




760.41, and Chapter 9, 

Tables 12(A) and 

12(B) 


Motor-operated 


422, Part H 




appliance circuit 






conductors 






Motor and 


430, Parts III, 




motor-control 


IV, V, VI, VII 




circuit conductors 






Phase converter 


455 


455.7 


supply conductors 






Remote-control, 


725 


725.23, 725.24, 


signaling, and 




725.41, and Chapter 9, 


power- limited 




Tables 11(A) and 


circuit conductors 




11(B) 


Secondary tie 


450 


450.6 


conductors 







240.5 Protection of Flexible Cords, Flexible Cables, and 
Fixture Wires. Flexible cord and flexible cable, including 
tinsel cord and extension cords, and fixture wires shall be 
protected against overcurrent by either 240.5(A) or (B). 

(A) Ampacities. Flexible cord and flexible cable shall be 
protected by an overcurrent device in accordance with their 
ampacity as specified in Table 400.5(A) and Table 400.5(B). 
Fixture wire shall be protected against overcurrent in 
accordance with its ampacity as specified in Table 402.5. 



Supplementary overcurrent protection, as in 240.10, shall 
be permitted to be an acceptable means for providing this 
protection. 

(B) Branch Circuit Overcurrent Device. Flexible cord 
shall be protected where supplied by a branch circuit in 
accordance with one of the methods described in 
240.5(B)(1), (B)(2), (B)(3), or (B)(4). 

(1) Supply Cord of Listed Appliance or Portable 
Lamps. Where flexible cord or tinsel cord is approved for 
and used with a specific listed apphance or portable lamp, it 
shall be considered to be protected when applied within the 
apphance or portable lamp listing requirements. 

(2) Fixture Wire. Fixture wire shall be permitted to be 
tapped to the branch circuit conductor of a branch circuit in 
accordance with the following: 

(1) 20-ampere circuits — 18 AWG, up to 15 m (50 ft) of 
run length 

(2) 20-ampere circuits — 16 AWG, up to 30 m (100 ft) of 
run length 

(3) 20-ampere circuits — 14 AWG and larger 

(4) 30-ampere circuits — 14 AWG and larger 

(5) 40-ampere circuits — 12 AWG and larger 

(6) 50-ampere circuits — 12 AWG and larger 

(3) Extension Cord Sets. Flexible cord used in listed ex- 
tension cord sets shall be considered to be protected when 
applied within the extension cord listing requirements. 

(4) Field Assembled Extension Cord Sets. Flexible cord 
used in extension cords made with separately listed and 
installed components shall be permitted to be supplied by a 
branch circuit in accordance with the following: 

20-ampere circuits — 16 AWG and larger 

240.6 Standard Ampere Ratings. 

(A) Fuses and Fixed-Trip Circuit Breakers. The stan- 
dard ampere ratings for fuses and inverse time circuit 
breakers shall be considered 15, 20, 25, 30, 35, 40, 45, 50, 
60, 70, 80, 90, 100, 110, 125, 150, 175, 200, 225, 250, 300, 
350, 400, 450, 500, 600, 700, 800, 1000, 1200, 1600, 2000, 
2500, 3000, 4000, 5000, and 6000 amperes. Additional 
standard ampere ratings for fuses shall be 1, 3, 6, 10, and 
601. The use of fuses and inverse time circuit breakers with 
nonstandard ampere ratings shall be permitted. 

(B) Adjustable-Trip Circuit Breakers. The rating of 
adjustable-trip circuit breakers having external means for 
adjusting the current setting (long-time pickup setting), not 
meeting the requirements of 240.6(C), shall be the maxi- 
mum setting possible. 



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240.8 



ARTICLE 240 — OVERCURRENT PROTECTION 



(C) Restricted Access Adjustable-TVip Circuit Breakers. 

A circuit breaker(s) that has restricted access to the adjusting 
means shall be permitted to have an ampere rating(s) that is 
equal to the adjusted current setting (long-time pickup setting). 
Restricted access shall be defined as located behind one of the 
following: 

(1) Removable and scalable covers over the adjusting means 

(2) Bolted equipment enclosure doors 

(3) Locked doors accessible only to qualified personnel 

240.8 Fuses or Circuit Breakers in Parallel. Fuses and 
circuit breakers shall be permitted to be connected in par- 
allel where they are factory assembled in parallel and listed 
as a unit. Individual fuses, circuit breakers, or combinations 
thereof shall not otherwise be connected in parallel. 

240.9 Thermal Devices. Thermal relays and other devices 
not designed to open short circuits or ground faults shall not 
be used for the protection of conductors against overcurrent 
due to short circuits or ground faults, but the use of such 
devices shall be permitted to protect motor branch-circuit con- 
ductors from overload if protected in accordance with 430.40. 

240.10 Supplementary Overcurrent Protection. Where 
supplementary overcurrent protection is used for luminaires 
(Ughting fixtures), apphances, and other equipment or for in- 
ternal circuits and components of equipment, it shall not be 
used as a substitute for required branch-circuit overcurrent 
devices or in place of the required branch-circuit protection. 
Supplementary overcurrent devices shall not be required to be 
readily accessible. 

240.12 Electrical System Coordination. Where an orderly 
shutdown is required to minimize the hazard(s) to personnel 
and equipment, a system of coordination based on the follow- 
ing two conditions shall be permitted: 

(1) Coordinated short-circuit protection 

(2) Overload indication based on monitoring systems or 
devices 

FPN: The monitoring system may cause the condition to go 
to alarm, allowing corrective action or an orderly shutdown, 
thereby minimizing personnel hazard and equipment damage. 

240.13 Ground-Fault Protection of Equipment. Ground- 
fault protection of equipment shall be provided in accor- 
dance with the provisions of 230.95 for solidly grounded 
wye electrical systems of more than 150 volts to ground but 
not exceeding 600 volts phase-to-phase for each individual 
device used as a building or structure main disconnecting 
means rated 1000 amperes or more. 

The provisions of this section shall not apply to the 

disconnecting means for the following: 

(1) Continuous industrial processes where a nonorderly shut- 
down will introduce additional or increased hazards 



(2) Installations where ground-fault protection is provided 
by other requirements for services or feeders 

(3) Fire pumps 

II. Location 

240.20 Ungrounded Conductors. 

(A) Overcurrent Device Required. A fuse or an overcur- 
rent trip unit of a circuit breaker shall be connected in 
series with each ungrounded conductor. A combination of a 
current transformer and overcurrent relay shall be consid- 
ered equivalent to an overcurrent trip unit. 

FPN: For motor circuits, see Parts III, IV, V, and XI of 
Article 430. 

(B) Circuit Breaker as Overcurrent Device. Circuit 
breakers shall open all ungrounded conductors of the circuit 
both manually and automatically unless otherwise permit- 
ted in 240.20(B)(1), (B)(2), and (B)(3). 

(1) Multiwire Branch Circuit. Except where limited by 
210.4(B), individual single-pole circuit breakers, with or 
without identified handle ties, shall be permitted as the pro- 
tection for each ungrounded conductor of multiwire branch 
circuits that serve only single-phase line-to-neutral loads. 

(2) Grounded Single-Phase and 3-Wire dc Circuits. In 

grounded systems, individual single-pole circuit breakers with 
identified handle ties shall be permitted as the protection for 
each ungrounded conductor for line-to-line connected loads 
for single-phase circuits or 3-wire, direct-current circuits. 

(3) 3-Phase and 2-Phase Systems. For Hne-to-hne loads 
in 4-wire, 3-phase systems or 5-wire, 2-phase systems hav- 
ing a grounded neutral and no conductor operating at a 
voltage greater than permitted iii 210.6, individual single- 
pole circuit breakers with identified handle ties shall be 
permitted as the protection for each ungrounded conductor. 

(C) Closed-Loop Po>yer Distribution Systems. Listed de- 
vices that provide equivalent overcurrent protection in 
closed-loop power distribution systems shall be permitted 
as a substitute for fuses or circuit breakers. 

240.21 Location in Circuit. Overcurrent protection shall 
be provided in each ungrounded circuit conductor and shall 
be located at the point where the conductors receive their 
supply except as specified in 240.21(A) through (G). No 
conductor supplied under the provisions of 240.21(A) 
through (G) shall supply another conductor under those 
provisions, except through an overcurrent protective device 
meeting the requirements of 240.4. 



• 



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ARTICLE 240 — OVERCURRENT PROTECTION 



240.21 



• 



(A) Branch-Circuit Conductors. Branch-circuit tap con- 
ductors meeting the requirements specified in 210.19 shall 
be permitted to have overcurrent protection located as 
specified in that section. 

(B) Feeder Taps. Conductors shall be permitted to be 
tapped, without overcurrent protection at the tap, to a feeder as 
specified in 240.21(B)(1) through (B)(5). The provisions of 
240.4(B) shall not be permitted for tap conductors. 

(1) Taps Not Over 3 m (10 ft) Long. Where the length of 
the tap conductors does not exceed 3 m (10 ft) and the tap 
conductors comply with all of the following: 

(1) The ampacity of the tap conductors is 

a. Not less than the combined calculated loads on the 
circuits supplied by the tap conductors, and 

b. Not less than the rating of the device supplied by 
the tap conductors or not less than the rating of the 
overcurrent-protective device at the termination of 
the tap conductors. 

(2) The tap conductors do not extend beyond the switch- 
board, panelboard, disconnecting means, or control de- 
vices they supply. 

(3) Except at the point of connection to the feeder, the tap 
conductors are enclosed in a raceway, which shall ex- 
tend from the tap to the enclosure of an enclosed 
switchboard, panelboard, or control devices, or to the 
back of an open switchboard. 

(4) For field installations where the tap conductors leave 
the enclosure or vault in which the tap is made, the 
rating of the overcurrent device on the line side of the 
tap conductors shall not exceed 10 times the ampacity 
of the tap conductor. 

FPN: For overcurrent protection requirements for lighting 
and appliance branch-circuit panelboards and certain power 
panelboards, see 408.36(A), (B), and (E). 

(2) Taps Not Over 7.5 m (25 ft) Long. Where the length 
of the tap conductors does not exceed 7.5 m (25 ft) and the 
tap conductors comply with all the following: 

(1) The ampacity of the tap conductors is not less than 
one-third of the rating of the overcurrent device pro- 
tecting the feeder conductors. 

(2) The tap conductors terminate in a single circuit breaker 
or a single set of fuses that will limit the load to the 
ampacity of the tap conductors. This device shall be 
permitted to supply any number of additional overcur- 
rent devices on its load side. 

(3) The tap conductors are protected from physical damage 
by being enclosed in an approved raceway or by other 
approved means. 



(3) Taps Supplying a Transformer [Primary Plus Sec- 
ondary Not Over 7.5 m (25 ft) Long]. Where the tap 
conductors supply a transformer and comply with all the 
following conditions: 

(1) The conductors supplying the primary of a transformer 
have an ampacity at least one-third the rating of the 
overcurrent device protecting the feeder conductors. 

(2) The conductors supplied by the secondary of the trans- 
former shall have an ampacity that is not less than the 
value of the primary-to-secondary voltage ratio multi- 
plied by one-third of the rating of the overcurrent de- 
vice protecting the feeder conductors. 

(3) The total length of one primary plus one secondary con- 
ductor, excluding any portion of the primary conductor 
that is protected at its ampacity, is not over 7.5 m (25 ft). 

(4) The primary and secondary conductors are protected 
from physical damage by being enclosed in an ap- 
proved raceway or by other approved means. 

(5) The secondary conductors terminate in a single circuit 
breaker or set of fuses that limit the load current to not 
more than the conductor ampacity that is permitted by 
310.15. 

(4) Taps Over 7.5 m (25 ft) Long. Where the feeder is in 
a high bay manufacturing building over 11 m (35 ft) high at 
walls and the installation complies with all the following 
conditions: 

(1) Conditions of maintenance and supervision ensure that 
only qualified persons service the systems. 

(2) The tap conductors are not over 7.5 m (25 ft) long 
horizontally and not over 30 m (100 ft) total length. 

(3) The ampacity of the tap conductors is not less than 
one-third the rating of the overcurrent device protecting 
the feeder conductors. 

(4) The tap conductors terminate at a single circuit breaker 
or a single set of fuses that limit the load to the ampac- 
ity of the tap conductors. This single overcurrent de- 
vice shall be permitted to supply any number of addi- 
tional overcurrent devices on its load side. 

(5) The tap conductors are protected from physical damage 
by being enclosed in an approved raceway or by other 
approved means. 

(6) The tap conductors are continuous from end-to-end and 
contain no splices. 

(7) The tap conductors are sized 6 AWG copper or 4 AWG 
aluminum or larger. 

(8) The tap conductors do not penetrate walls, floors, or 
ceihngs. 

(9) The tap is made no less than 9 m (30 ft) from the floor. 

(5) Outside Taps of Unlimited Length. Where the con- 
ductors are located outdoors of a building or structure, ex- 
cept at the point of load termination, and comply with all of 
the following conditions: 



2005 Edition 



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240.21 



ARTICLE 240 — OVERCURRENT PROTECTION 



(1) The conductors are protected from physical damage in 
an approved manner. 

(2) The conductors terminate at a single circuit breaker or 
a single set of fuses that limit the load to the ampacity 
of the conductors. This single overcurrent device shall 
be permitted to supply any number of additional over- 
current devices on its load side. 

(3) The overcurrent device for the conductors is an integral 
part of a disconnecting means or shall be located im- 
mediately adjacent thereto. 

(4) The disconnecting means for the conductors is installed 
at a readily accessible location complying with one of 
the following: 

a. Outside of a building or structure 

b. Inside, nearest the point of entrance of the conductors 

c. Where installed in accordance with 230.6, nearest 
the point of entrance of the conductors 

(C) Transformer Secondary Conductors. Each set of 
conductors feeding separate loads shall be permitted to be 
connected to a transformer secondary, without overcurrent 
protection at the secondary, as specified in 240.21(C)(1) 
through (C)(6). The provisions of 240.4(B) shall not be 
permitted for transformer secondary conductors. 

FPN: For overcurrent protection requirements for trans- 
formers, see 450.3. 

(1) Protection by Primary Overcurrent Device. Conduc- 
tors supplied by the secondary side of a single-phase trans- 
former having a 2-wire (single-voltage) secondary, or a 
three-phase, delta-delta connected transformer having a 
3-wire (single-voltage) secondary, shall be permitted to be 
protected by overcurrent protection provided on the pri- 
mary (supply) side of the transformer, provided this protec- 
tion is in accordance with 450.3 and does not exceed the value 
determined by multiplying the secondary conductor ampacity 
by the secondary to primary transformer voltage ratio. 

Single -phase (other than 2-wire) and multiphase (other 
than delta-delta, 3-wire) transformer secondary conductors 
are not considered to be protected by the primary overcur- 
rent protective device. 

(2) Transformer Secondary Conductors Not Over 3 m 
(10 ft) Long. Where the length of secondary conductor does 
not exceed 3 m (10 ft) and comphes with all of the following: 
(1) The ampacity of the secondary conductors is 

a. Not less than the combined calculated loads on the 
circuits supplied by the secondary conductors, and 

b. Not less than the rating of the device supplied by 
the secondary conductors or not less than the rating 
of the overcurrent-protective device at the termina- 
tion of the secondary conductors, and 



c. Not less than one-tenth of the rating of the overcurrent 
device protecting the primary of the transformer, mul- 
tiplied by the primary to secondary transformer volt- 
age ratio 

(2) The secondary conductors do not extend beyond the 
switchboard, panelboard, disconnecting means, or con- 
trol devices they supply. 

(3) The secondary conductors are enclosed in a raceway, 
which shall extend from the transformer to the enclo- 
sure of an enclosed switchboard, panelboard, or control 
devices or to the back of an open switchboard. 

FPN: For overcurrent protection requirements for lighting 
and appliance branch-circuit panelboards and certain power 
panelboards, see 408.36(A), (B), and (E). 

(3) Industrial Installation Secondary Conductors Not 

Over 7.5 m (25 ft) Long. For industrial installations only, 
where the length of the secondary conductors does not ex- 
ceed 7.5 m (25 ft) and complies with all of the following: 

(1) The ampacity of the secondary conductors is not less than 
the secondary current rating of the transformer, and the 
sum of the ratings of the overcurrent devices does not 
exceed the ampacity of the secondary conductors. 

(2) All overcurrent devices are grouped. 

(3) The secondary conductors are protected from physical 
damage by being enclosed in an approved raceway or 
by other approved means. 

(4) Outside Secondary Conductors. Where the conduc- 
tors are located outdoors of a building or structure, except 
at the point of load termination, and comply with all of the 
following conditions: 

(1) The conductors are protected from physical damage in 
an approved manner. 

(2) The conductors terminate at a single circuit breaker or 
a single set of fuses that limit the load to the ampacity 
of the conductors. This single overcurrent device shall 
be permitted to supply any number of additional over- 
current devices on its load side. 

(3) The overcurrent device for the conductors is an integral 
part of a disconnecting means or shall be located im- 
mediately adjacent thereto. 

(4) The disconnecting means for the conductors is installed 
at a readily accessible location complying with one of 
the following: 

a. Outside of a building or structure 

b. Inside, nearest the point of entrance of the conductors 

c. Where installed in accordance with 230.6, nearest 
the point of entrance of the conductors 

(5) Secondary Conductors from a Feeder Tapped 
Transformer. Transformer secondary conductors installed 
in accordance with 240.21(B)(3) shall be permitted to have 
overcurrent protection as specified in that section. 



• 



70-86 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 240 — OVERCURRENT PROTECTION 



240.30 



(6) Secondary Conductors Not Over 7.5 m (25 ft) Long. 

Where the length of secondary conductor does not exceed 
7.5 m (25 ft) and complies with all of the following: 

(1) The secondary conductors shall have an ampacity that is 
not less than the value of the primary-to-secondary volt- 
age ratio multiplied by one-third of the rating of the over- 
current device protecting the primary of the transformer. 

(2) The secondary conductors terminate in a single circuit 
breaker or set of fuses that limit the load current to not 
more than the conductor ampacity that is permitted by 
310.15. 

(3) The secondary conductors are protected from physical 
damage by being enclosed in an approved raceway or 
by other approved means. 

(D) Service Conductors. Service-entrance conductors shall 
be permitted to be protected by overcurrent devices in accor- 
dance with 230.91. 

(E) Busway Taps. Busways and busway taps shall be per- 
mitted to be protected against overcurrent in accordance 
with 368.17. 

(F) Motor Circuit Taps. Motor-feeder and branch-circuit 
conductors shall be permitted to be protected against over- 
current in accordance with 430.28 and 430.53, respectively. 

(G) Conductors from Generator Terminals. Conductors 
from generator terminals that meet the size requirement in 
445.13 shall be permitted to be protected against overload 
by the generator overload protective device(s) required by 
445.12. 

240.22 Grounded Conductor. No overcurrent device shall 
be connected in series with any conductor that is intentionally 
grounded, unless one of the following two conditions is met: 

(1) The overcurrent device opens all conductors of the cir- 
cuit, including the grounded conductor, and is designed 
so that no pole can operate independently. 

(2) Where required by 430.36 or 430.37 for motor over- 
load protection. 

240.23 Change in Size of Grounded Conductor. Where a 
change occurs in the size of the ungrounded conductor, a 
similar change shall be permitted to be made in the size of 
the grounded conductor. 

240.24 Location in or on Premises. 

(A) Accessibility. Overcurrent devices shall be readily ac- 
cessible and shall be installed so that the center of the grip 
of the operating handle of the switch or circuit breaker, 
when in its highest position, is not more than 2.0 m (6 ft 
7 in.) above the floor or working platform unless one of the 
following applies: 



(1) For busways, as provided in 368.12. 

(2) For supplementary overcurrent protection, as described 
in 240.10. 

(3) For overcurrent devices, as described in 225.40 and 
230.92. 

(4) For overcurrent devices adjacent to utilization equip- 
ment that they supply, access shall be permitted to be 
by portable means. 

(B) Occupancy. Each occupant shall have ready access to 
all overcurrent devices protecting the conductors supplying 
that occupancy. 

Exception No. 1: Where electric service and electrical 
maintenance are provided by the building management and 
where these are under continuous building management 
supervision, the service overcurrent devices and feeder 
overcurrent devices supplying more than one occupancy 
shall be permitted to be accessible to only authorized man- 
agement personnel in the following: 

(1) Multiple-occupancy buildings 

(2) Guest rooms or guest suites of hotels and motels that 
are intended for transient occupancy 

Exception No. 2: Where electric service and electrical main- 
tenance are provided by the building management and where 
these are under continuous building management supervision, 
the branch circuit overcurrent devices supplying any guest 
rooms or guest suites shall be permitted to be accessible to 
only authorized management personnel for guest rooms of 
hotels and motels that are intended for transient occupancy. 

(C) Not Exposed to Physical Damage. Overcurrent de- 
vices shall be located where they will not be exposed to 
physical damage. 

FPN: See 110.11, Deteriorating Agents. 

(D) Not in Vicinity of Easily Ignitible Material. Overcur- 
rent devices shall not be located in the vicinity of easily 
ignitible material, such as in clothes closets. 

(E) Not Located in Bathrooms. In dwelling units and 
guest rooms or guest suites of hotels and motels, overcur- 
rent devices, other than supplementary overcurrent protec- 
tion, shall not be located in bathrooms. 

IIL Enclosures 

240.30 General. 

(A) Protection from Physical Damage. Overcurrent de- 
vices shall be protected from physical damage by one of the 
following: 

(1) Installation in enclosures, cabinets, cutout boxes, or 
equipment assemblies 



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70-87 



240.32 



ARTICLE 240 — OVERCURRENT PROTECTION 



(2) Mounting on open-type switchboards, panelboards, or 
control boards that are in rooms or enclosures free from 
dampness and easily ignitible material and are acces- 
sible only to qualified personnel 

(B) Operating Handle. The operating handle of a circuit 
breaker shall be permitted to be accessible without opening 
a door or cover. 

240.32 Damp or Wet Locations. Enclosures for overcur- 
rent devices in damp or wet locations shall comply with 

312.2(A). 

240.33 Vertical Position. Enclosures for overcurrent de- 
vices shall be mounted in a vertical position unless that is 
shown to be impracticable. Circuit breaker enclosures shall be 
permitted to be installed horizontally where the circuit breaker 
is installed in accordance with 240.81. Listed busway plug-in 
units shall be permitted to be mounted in orientations corre- 
sponding to the busway mounting position. 

IV. Disconnecting and Guarding 

240.40 Disconnecting Means for Fuses. A disconnecting 
means shall be provided on the supply side of all fuses in 
circuits over 150 volts to ground and cartridge fuses in 
circuits of any voltage where accessible to other than quali- 
fied persons, so that each circuit containing fuses can be 
independently disconnected from the source of power. A 
current-limiting device without a disconnecting means shall 
be permitted on the supply side of the service disconnecting 
means as permitted by 230.82. A single disconnecting 
means shall be permitted on the supply side of more than 
one set of fuses as permitted by 430.112, Exception, for 
group operation of motors and 424.22(C) for fixed electric 
space-heating equipment. 

240.41 Arcing or Suddenly Moving Parts. Arcing or sud- 
denly moving parts shall comply with 240.41(A) and (B). 

(A) Location. Fuses and circuit breakers shall be located 
or shielded so that persons will not be burned or otherwise 
injured by their operation. 

(B) Suddenly Moving Parts. Handles or levers of circuit 
breakers, and similar parts that may move suddenly in such 
a way that persons in the vicinity are likely to be injured by 
being struck by them, shall be guarded or isolated. 

V. Plug Fuses, Fuseholders, and Adapters 

240.50 General. 

(A) Maximum Voltage. Plug fuses shall be permitted to 

be used in the following circuits: 

(1) Circuits not exceeding 125 volts between conductors 



(2) Circuits supplied by a system having a grounded neu- 
tral where the line-to-neutral voltage does not exceed 
150 volts 

(B) Marking. Each fuse, fuseholder, and adapter shall be 
marked with its ampere rating. 

(C) Hexagonal Configuration. Plug fuses of 15-ampere 
and lower rating shall be identified by a hexagonal configu- 
ration of the window, cap, or other prominent part to dis- 
tinguish them from fuses of higher ampere ratings. 

(D) No Energized Parts. Plug fuses, fuseholders, and adapt- 
ers shall have no exposed energized parts after fuses or fuses 
and adapters have been installed. 

(E) Screw Shell. The screw shell of a plug-type fuseholder 
shall be connected to the load side of the circuit. 

240.51 Edison-Base Fuses. 

(A) Classification. Plug fuses of the Edison-base type shall 
be classified at not over 125 volts and 30 amperes and below. 

(B) Replacement Only. Plug fuses of the Edison-base type 
shall be used only for replacements in existing installations 
where there is no evidence of overfusing or tampering. 

240.52 Edison-Base Fuseholders. Fuseholders of the 
Edison-base type shall be installed only where they are 
made to accept Type S fuses by the use of adapters. 

240.53 Type S Fuses. Type S fuses shall be of the plug 
type and shall comply with 240.53(A) and (B). 

(A) Classification. Type S fuses shall be classified at not 
over 125 volts and to 15 amperes, 16 to 20 amperes, and 
21 to 30 amperes. 

(B) Noninterchangeable. Type S fuses of an ampere clas- 
sification as specified in 240.53(A) shall not be inter- 
changeable with a lower ampere classification. They shall 
be designed so that they cannot be used in any fuseholder 
other than a Type S fuseholder or a fuseholder with a Type S 
adapter inserted. 

240.54 Type S Fuses, Adapters, and Fuseholders. 

(A) To Fit Edison-Base Fuseholders. Type S adapters 
shall fit Edison-base fuseholders. 

(B) To Fit Type S Fuses Only. Type S fuseholders and 
adapters shall be designed so that either the fuseholder it- 
self or the fuseholder with a Type S adapter inserted cannot 
be used for any fuse other than a Type S fuse. 

(C) Nonremovable. Type S adapters shall be designed so 
that once inserted in a fuseholder, they cannot be removed. 



70-88 



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ARTICLE 240 — OVERCURRENT PROTECTION 



240.85 



• 



(D) Nontamperable. Type S fuses, fuseholders, and adapt- 
ers shall be designed so that tampering or shunting (bridg- 
ing) would be difficult. 

(E) Interchangeability. Dimensions of Type S fuses, fuse- 
holders, and adapters shall be standardized to permit inter- 
changeability regardless of the manufacturer. 

VI. Cartridge Fuses and Fuseholders 

240.60 General. 

(A) Maximum Voltage — 300- Volt Type. Cartridge fuses 
and fuseholders of the 300-volt type shall be permitted to 
be used in the following circuits: 

(1) Circuits not exceeding 300 volts between conductors 

(2) Single-phase line-to-neutral circuits supplied from a 
3-phase, 4-wire, solidly grounded neutral source where 
the line-to-neutral voltage does not exceed 300 volts 

(B) Noninterchangeable — 0-6000-Ampere Cartridge 
Fuseholders. Fuseholders shall be designed so that it will 
be difficult to put a fuse of any given class into a fuseholder 
that is designed for a current lower, or voltage higher, than 
that of the class to which the fuse belongs. Fuseholders for 
current-limiting fuses shall not permit insertion of fuses 
that are not current- limiting. 

(C) Marking. Fuses shall be plainly marked, either by 
printing on the fuse barrel or by a label attached to the 
barrel showing the following: 

(1) Ampere rating 

(2) Voltage rating 

(3) Interrupting rating where other than 10,000 amperes 

(4) Current limiting where applicable 

(5) The name or trademark of the manufacturer 

The interrupting rating shall not be required to be 
marked on fuses used for supplementary protection. 

(D) Renewable Fuses. Class H cartridge fuses of the re- 
newable type shall only be permitted to be used for replace- 
ment in existing installations where there is no evidence of 
overfusing or tampering. 

240.61 Classification. Cartridge fuses and ftaseholders shall 
be classified according to voltage and amperage ranges. Fuses 
rated 600 volts, nominal, or less shall be permitted to be used 
for voltages at or below their ratings. 

VII. Circuit Breakers 

240.80 Method of Operation. Circuit breakers shall be 
trip free and capable of being closed and opened by manual 
operation. Their normal method of operation by other than 



manual means, such as electrical or pneumatic, shall be 
permitted if means for manual operation are also provided. 

240.81 Indicating. Circuit breakers shall clearly indicate 
whether they are in the open "off' or closed "on" position. 

Where circuit breaker handles are operated vertically 
rather than rotationally or horizontally, the "up" position of 
the handle shall be the "on" position. 

240.82 Nontamperable. A circuit breaker shall be of such 
design that any alteration of its trip point (calibration) or 
the time required for its operation requires dismantling of 
the device or breaking of a seal for other than intended 
adjustments. 

240.83 Marking. 

(A) Durable and Visible. Circuit breakers shall be marked 
with their ampere rating in a manner that will be durable 
and visible after installation. Such marking shall be permit- 
ted to be made visible by removal of a trim or cover. 

(B) Location. Circuit breakers rated at 100 amperes or less 
and 600 volts or less shall have the ampere rating molded, 
stamped, etched, or similarly marked into their handles or 
escutcheon areas. 

(C) Interrupting Rating. Every circuit breaker having an 
interrupting rating other than 5000 amperes shall have its 
interrupting rating shown on the circuit breaker. The inter- 
rupting rating shall not be required to be marked on circuit 
breakers used for supplementary protection. 

(D) Used as Switches. Circuit breakers used as switches in 
120- volt and 277- volt fluorescent lighting circuits shall be 
listed and shall be marked SWD or HID. Circuit breakers 
used as switches in high-intensity discharge lighting cir- 
cuits shall be listed and shall be marked as HID. 

(E) Voltage Marking. Circuit breakers shall be marked 
with a voltage rating not less than the nominal system volt- 
age that is indicative of their capability to interrupt fault 
cun'ents between phases or phase to ground. 

240.85 Applications. A circuit breaker with a straight volt- 
age rating, such as 240V or 480V, shall be permitted to be 
applied in a circuit in which the nominal voltage between 
any two conductors does not exceed the circuit breaker's 
voltage rating. A two-pole circuit breaker shall not be used 
for protecting a 3-phase, comer-grounded delta circuit un- 
less the circuit breaker is marked l(t)-3(t) to indicate such 
suitability. 

A circuit breaker with a slash rating, such as 1 20/240 V 
or 480Y/277V, shall be permitted to be applied in a solidly 
grounded circuit where the nominal voltage of any conduc- 
tor to ground does not exceed the lower of the two values 



2005 Edition NATIONAL ELECTRICAL CODE 



70-89 



240.86 



ARTICLE 240 — OVERCURRENT PROTECTION 



of the circuit breaker's voltage rating and the nominal volt- 
age between any two conductors does not exceed the higher 
value of the circuit breaker's voltage rating. 

FPN: Proper application of molded case circuit breakers 
on 3-phase systems, other than solidly grounded wye, par- 
ticularly on corner grounded delta systems, considers the 
circuit breakers' individual pole-interrupting capability. 

240.86 Series Ratings. Where a circuit breaker is used on 
a circuit having an available fault current higher than the 
marked interrupting rating by being connected on the load 
side of an acceptable overcurrent protective device having a 
higher rating, the circuit breaker shall meet the require- 
ments specified in (A) or (B), and (C). 

(A) Selected Under Engineering Supervision in Existing 
Installations. The series rated combination devices shall be 
selected by a licensed professional engineer engaged pri- 
marily in the design or maintenance of electrical installa- 
tions. The selection shall be documented and stamped by 
the professional engineer. This documentation shall be 
available to those authorized to design, install, inspect, 
maintain, and operate the system. This series combination 
rating, including identification of the upstream device, shall 
be field marked on the end use equipment. 

(B) Tested Combinations. The combination of fine-side 
overcurrent device and load-side circuit breaker(s) is tested 
and marked on the end use equipment, such as switch- 
boards and panelboards. 

(C) Motor Contribution. Series ratings shall not be used 
where 

(1) Motors are connected on the load side of the higher- 
rated overcurrent device and on the line side of the 
lower-rated overcurrent device, and 

(2) The sum of the motor full-load currents exceeds 1 per- 
cent of the interrupting rating of the lower-rated circuit 
breaker. 



VIII. Supervised Industrial Installations 

240.90 General. Overcurrent protection in areas of super- 
vised industrial installations shaU comply with all of the 
other applicable provisions of this article, except as pro- 
vided in Part VIII. The provisions of Part VIII shall be 
permitted only to apply to those portions of the electrical 
system in the supervised industrial installation used exclu- 
sively for manufacturing or process control activities. 

240.92 Location in Circuit. An overcurrent device shall 
be connected in each ungrounded circuit conductor as re- 
quired in 240.92(A) through (D). 



(A) Feeder and Branch-Circuit Conductors. Feeder and 
branch-circuit conductors shall be protected at the point the 
conductors receive their supply as permitted in 240.21 or as 
otherwise permitted in 240.92(B), (C), or (D). 

(B) Transformer Secondary Conductors of Separately 
Derived Systems. Conductors shall be permitted to be con- 
nected to a transformer secondary of a separately derived sys- 
tem, without overcurrent protection at the connection, where 
the conditions of 240.92(B)(1), (B)(2), and (B)(3) are met. 

(1) Short-Circuit and Ground-Fault Protection. The con- 
ductors shall be protected from short-circuit and ground-fault 
conditions by complying with one of the following conditions: 

(1) The length of the secondary conductors does not ex- 
ceed 30 m (100 ft) and the transformer primary over- 
current device has a rating or setting that does not 
exceed 150 percent of the value determined by mul- 
tiplying the secondary conductor ampacity by the 
secondary-to-primary transformer voltage ratio. 

(2) The conductors are protected by a differential relay 
with a trip setting equal to or less than the conductor 
ampacity. 

FPN: A difiFerential relay is connected to be sensitive only 
to short-circuit or fault currents within the protected zone 
and is normally set much lower than the conductor ampac- 
ity. The differential relay is connected to trip protective 
devices that will de-energize the protected conductors if a 
short-circuit condition occurs. 

(3) The conductors shall be considered to be protected if 
calculations, made under engineering supervision, de- 
termine that the system overcurrent devices will protect 
the conductors within recognized time vs. current limits 
for all short-circuit and ground-fault conditions. 

(2) Overload Protection. The conductors shall be pro- 
tected against overload conditions by complying with one 
of the following: 

(1) The conductors terminate in a single overcurrent device 
that will limit the load to the conductor ampacity. 

(2) The sum of the overcurrent devices at the conductor 
termination fimits the load to the conductor ampacity. 
The overcurrent devices shall consist of not more than 
six circuit breakers or sets of fuses, mounted in a single 
enclosure, in a group of separate enclosures, or in or on 
a switchboard. There shall be no more than six over- 
current devices grouped in any one location. 

(3) Overcurrent relaying is connected [with a current trans- 
former(s), if needed] to sense all of the secondary con- 
ductor current and limit the load to the conductor am- 
pacity by opening upstream or downstream devices. 

(4) Conductors shall be considered to be protected if cal- 
culations, made under engineering supervision, deter- 
mine that the system overcurrent devices will protect 
the conductors from overload conditions. 



70-90 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 240 — OVERCURRENT PROTECTION 



240.100 



(3) Physical Protection. The secondary conductors are 
protected from physical damage by being enclosed in an 
approved raceway or by other approved means. 

(C) Outside Feeder Taps. Outside conductors shall be per- 
mitted to be tapped to a feeder or to be connected at a trans- 
former secondary, without overcurrent protection at the tap or 
connection, where all the following conditions are met: 

(1) The conductors are protected from physical damage in 
an approved manner. 

(2) The sum of the overcurrent devices at the conductor 
termination limits the load to the conductor ampacity. 
The overcurrent devices shall consist of not more than 
six circuit breakers or sets of fuses mounted in a single 
enclosure, in a group of separate enclosures, or in or on 
a switchboard. There shall be no more than six over- 
current devices grouped in any one location. 

(3) The tap conductors are installed outdoors of a building 
or structure except at the point of load termination. 

(4) The overcurrent device for the conductors is an integral 
part of a disconnecting means or shall be located im- 
mediately adjacent thereto. 

(5) The disconnecting means for the conductors are in- 
stalled at a readily accessible location complying with 
one of the following: 

a. Outside of a building or structure 

b. Inside, nearest the point of entrance of the conductors 

c. Where installed in accordance with 230.6, nearest 
the point of entrance of the conductors 

(D) Protection by Primary Overcurrent Device. Con- 
ductors supplied by the secondary side of a transformer 
shall be permitted to be protected by overcurrent protection 
provided on the primary (supply) side of the transformer, 
provided the primary device time-current protection char- 
acteristic, multipHed by the maximum effective primary-to- 
secondary transformer voltage ratio, effectively protects the 
secondary conductors. 

240.93 Series Ratings. Where a circuit breaker is used on 
a circuit having an available fault current higher than its 
marked interrupting rating by being connected on the load 
side of an acceptable overcurrent protective device having 
the higher rating, the circuit breaker shall meet the require- 
ments specified in 240.93(A) or (B) and (C). 

(A) Tested Combinations. The combination of line-side 
overcurrent device and load-side circuit breaker(s) is tested 
and marked on the end use equipment, such as switch- 
boards and panelboards. 

(B) Selected Under Engineering Supervision. The line- 
side device is selected under engineering supervision. This 
series combination rating, including identification of the up- 
stream device, shall be field marked on the end use equipment. 



(C) Motor Contribution. Series ratings shall not be used 
where 

(1) Motors are connected on the load side of the higher-rated 
overcurrent device and on the line side of the lower-rated 
overcurrent device, and 

(2) The sum of the motor full-load currents exceeds J percent 
of the interrupting rating of the lower-rated circuit breaker. 

IX. Overcurrent Protection Over 600 Volts, Nominal 
240.100 Feeders and Branch Circuits. 

(A) Location and Type of Protection. Feeder and branch- 
circuit conductors shall have overcurrent protection in each 
ungrounded conductor located at the point where the con- 
ductor receives its supply or at an alternative location in the 
circuit when designed under engineering supervision that 
includes but is not limited to considering the appropriate 
fault studies and time-current coordination analysis of the 
protective devices and the conductor damage curves. The 
overcurrent protection shall be permitted to be provided by 
either 240.100(A)(1) or (A)(2). 

(1) Overcurrent Relays and Current Transformers. 

Circuit breakers used for overcurrent protection of 3-phase 
circuits shall have a minimum of three overcurrent relay 
elements operated from three current transformers. The 
separate overcurrent relay elements (or protective func- 
tions) shall be permitted to be part of a single electronic 
protective relay unit. 

On 3-phase, 3-wire circuits, an overcurrent relay ele- 
ment in the residual circuit of the current transformers shall 
be permitted to replace one of the phase relay elements. 

An overcurrent relay element, operated from a current 
transformer that links all phases of a 3-phase, 3-wire circuit, 
shall be permitted to replace the residual relay element and 
one of the phase-conductor current transformers. Where the 
neutral is not regrounded on the load side of the circuit as 
permitted in 250.184(B), the current transformer shall be per- 
mitted to link all 3-phase conductors and the grounded circuit 
conductor (neutral). 

(2) Fuses. A fuse shall be connected in series with each 
ungrounded conductor. 

(B) Protective Devices. The protective device(s) shall be 
capable of detecting and interrupting all values of current 
that can occur at their location in excess of their trip-setting 
or melting point. 

(C) Conductor Protection. The operating time of the pro- 
tective device, the available short-circuit current, and the 
conductor used shall be coordinated to prevent damaging or 
dangerous temperatures in conductors or conductor insula- 
tion under short-circuit conditions. 



2005 Edition 



NATIONAL ELECTRICAL CODE 



70-91 



240,101 



ARTICLE 250 — GROUNDING AND BONDING 



240.101 Additional Requirements for Feeders. 

(A) Rating or Setting of Overcurrent Protective De- 
vices. The continuous ampere rating of a fuse shall not 
exceed three times the ampacity of the conductors. The 
long-time trip element setting of a breaker or the minimum 
trip setting of an electronically actuated fuse shall not ex- 
ceed six times the ampacity of the conductor. For fire 
pumps, conductors shall be permitted to be protected for 
overcurrent in accordance with 695.4(B). 

(B) Feeder Taps. Conductors tapped to a feeder shall be 
permitted to be protected by the feeder overcurrent device 
where that overcurrent device also protects the tap conductor. 



(>rouii4ing and Bpiidiftg 

I. General 

250.1 Scope. This article covers general requirements for 
grounding and bonding of electrical installations, and spe- 
cific requirements in (1) through (6). 

(1) Systems, circuits, and equipment required, permitted, 
or not permitted to be grounded 

(2) Circuit conductor to be grounded on grounded systems 

(3) Location of grounding connections 

(4) Types and sizes of grounding and bonding conductors 
and electrodes 

(5) Methods of grounding and bonding 

(6) Conditions under which guards, isolation, or insulation 
may be substituted for grounding 

250.2 Definitions. 

Effective Ground-Fault Current Path. An intentionally 
constructed, permanent, low-impedance electrically conduc- 
tive path designed and intended to carry current under ground- 
fault conditions from the point of a ground fault on a wiring 
system to the electrical supply source and that faciUtates the 
operation of the overcurrent protective device or ground fault 
detectors on high-impedance grounded systems. 

Ground Fault. An unintentional, electrically conducting 
connection between an ungrounded conductor of an electrical 
circuit and the normally noh-current-carrying conductors, me- 
tallic enclosures, metalhc raceways, metallic equipment, or 
earth. 

Ground-Fault Current Path. An electrically conductive 
path from the point of a ground fault on a wiring system 
through normally non-current-carrying conductors, equip- 
ment, or the earth to the electrical supply source. 



FPN: Examples of ground-fault current paths could con- 
sist of any combination of equipment grounding conduc- 
tors, metallic raceways, metallic cable sheaths, electrical 
equipment, and any other electrically conductive material 
such as metal water and gas piping, steel framing members, 
stucco mesh, metal ducting, reinforcing steel, shields of 
communications cables, and the earth itself 

250.3 Application of Other Articles. In other articles ap- 
plying to particular cases of installation of conductors and 
equipment, requirements are identified in Table 250.3 that 
are in addition to, or modifications of, those of this article. 

250.4 General Requirements for Grounding and Bonding. 

The following general requirements identify what grounding 
and bonding of electrical systems are required to accomplish. 
The prescriptive methods contained in Article 250 shall be 
followed to comply with the performance requirements of this 
section. 

(A) Grounded Systems. 

(1) Electrical System Grounding. Electrical systems that 
are grounded shall be connected to earth in a manner that 
will limit the voltage imposed by lightning, line surges, or 
unintentional contact with higher-voltage lines and that will 
stabilize the voltage to earth during normal operation. 

(2) Grounding of Electrical Equipment. Non-current- 
carrying conductive materials enclosing electrical conduc- 
tors or equipment, or forming part of such equipment, shall 
be connected to earth so as to limit the voltage to ground on 
these materials. 

(3) Bonding of Electrical Equipment. Non-current-carrying 
conductive materials enclosing electrical conductors or equip- 
ment, or forming part of such equipment, shall be connected 
together and to the electrical supply source in a manner that 
estabhshes an effective ground-fault current path. 

(4) Bonding of Electrically Conductive Materials and 
Other Equipment. Electrically conductive materials that 
are likely to become energized shall be connected together 
and to the electrical supply source in a manner that estab- 
lishes an effective ground-fault current path. 

(5) Effective Ground-Fault Current Path. Electrical 
equipment and wiring and other electrically conductive ma- 
terial likely to become energized shall be installed in a 
manner that creates a permanent, low-impedance circuit 
facilitating the operation of the overcurrent device or 
ground detector for high-impedance grounded systems. It 
shall be capable of safely carrying the maximum ground- 
fault current likely to be imposed on it from any point on 
the wiring system where a ground fault may occur to the 
electrical supply source. The earth shall not be considered 
as an effective ground-fault current path. 



70-92 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 250 — GROUNDING AND BONDING 



250.4 



Table 250.3 Additional Grounding Requirements 



Conductor/Equipment 



Article 



Section 



Agricultural buildings 

Audio signal processing, amplification, and reproduction 

equipment 
Branch circuits 
Cablebus 
Cable trays 

Capacitors 

Circuits and equipment operating at less than 50 volts 

Closed-loop and programmed power distribution 

Communications circuits 

Community antenna television and radio distribution systems 

Conductors for general wiring 

Cranes and hoists 

Electrically driven or controlled irrigation machines 

Electric signs and outline lighting 

Electrolytic cells 

Elevators, dumbwaiters, escalators, moving walks, wheelchair 

lifts, and stairway chair lifts 
Fire alarm systems 

Fixed electric heating equipment for pipelines and vessels 
Fixed outdoor electric deicing and snow-melting equipment 
Flexible cords and cables 

Floating buildings 

Grounding-type receptacles, adapters, cord connectors, and 

attachment plugs 
Hazardous (classified) locations 
Health care facilities 
Induction and dielectric heating equipment 

Industrial machinery 

Information technology equipment 

Intrinsically safe systems 

Luminaires (lighting fixtures) and lighting equipment 

Luminaires (fixtures), lampholders, and lamps 

Marinas and boatyards 
Mobile homes and mobile home park 
Motion picture and television studios and similar locations 
Motors, motor circuits, and controllers 
Outlet, device, pull, and junction boxes; conduit bodies; and 
fittings 

Over 600 volts, nominal, underground wiring methods 

Panelboards 

Pipe organs 

Radio and television equipment 

Receptacles and cord connectors 

Recreational vehicles and recreational vehicle parks 

Services 

Solar photovoltaic systems 

Swimming pools, fountains, and similar installations 

Switchboards and panelboards 

Switches 

Theaters, audience areas of motion picture and television 

studios, and similar locations 
Transformers and transformer vaults 
Use and identification of grounded conductors 
X-ray equipment 



392 

720 
800 

310 
610 

600 
668 

620 



500-517 
517 
665 

670 



410 

550 
430 



650 
810 

551 
230 

680 



547.9 and 547.10 
640.7 

210.5, 210.6, 406.3 

370.9 

392.3(C), 392.7 

460.10, 460.27 

780.3 
820.93, 820.100, 820.103 

675.11(C), 675.12, 675.13, 675.14, 675.15 



760.9 

427.29, 427.48 

426.27 
400.22, 400.23 

553.8, 553.10, 553.11 
406.9 



200 
660 



645.15 

504.50 

410.17, 410.18, 410.20, 410.21, 410.105(B) 

555.15 

530.20, 530.64(B) 

314.4, 314.25 

300.50(B) 
408.40 

406.3 



690.41, 690.42, 690.43, 690.45, 690.47 

408.3(D) 

404.12 
520.81 



450.10 
517.78 



2005 Edition NATIONAL ELECTRICAL CODE 



70-93 



250.6 



ARTICLE 250 — GROUNDING AND BONDING 



(B) Ungrounded Systems. 

(1) Grounding Electrical Equipment. Non-current- 
carrying conductive materials enclosing electrical conduc- 
tors or equipment, or forming part of such equipment, shall 
be connected to earth in a manner that will limit the voltage 
imposed by lightning or unintentional contact with higher- 
voltage lines and limit the voltage to ground on these ma- 
terials. 

(2) Bonding of Electrical Equipment. Non-current- 
carrying conductive materials enclosing electrical conductors 
or equipment, or forming part of such equipment, shall be 
connected together and to the supply system grounded equip- 
ment in a manner that creates a permanent, low-impedance 
path for ground-fault current that is capable of carrying the 
maximum fault current likely to be imposed on it. 

(3) Bonding of Electrically Conductive Materials and 
Other Equipment. Electrically conductive materials that 
are likely to become energized shall be connected together 
and to the supply system grounded equipment in a manner 
that creates a permanent, low-impedance path for ground- 
fault current that is capable of carrying the maximum fault 
current likely to be imposed on it. 



(4) Path for Fault Current. Electrical equipment, wiring, 
and other electrically conductive material likely to become 
energized shall be installed in a manner that creates a per- 
manent, low-impedance circuit from any point on the wir- 
ing system to the electrical supply source to facilitate the 
operation of overcurrent devices should a second fault oc- 
cur on the wiring system. The earth shall not be considered 
as an effective fault-current path. 

FPN No. 1: A second fault that occurs through the equip- 
ment enclosures and bonding is considered a ground fault. 

FPN No. 2: See Figure 250.4 for information on the orga- 
nization of Article 250. 

250.6 Objectionable Current over Grounding 
Conductors. 

(A) Arrangement to Prevent Objectionable Current. 

The grounding of electrical systems, circuit conductors, 
surge arresters, and conductive non-current-carrying mate- 
rials and equipment shall be installed and arranged in a 
manner that will prevent objectionable current over the 
grounding conductors or grounding paths. 



Part I General 



Part II System 
grounding 



Part VIM Direct-current 
systems 



Part X Grounding of 

systems and circuits of 

1 kV and over (high voltage) 



Part III Grounding electrode 

system and grounding 

electrode conductor 



Part IV Enclosure, 

raceway, and service 

cable grounding 



Part VI Equiprnent 

grounding and equipment 

grounding conductors 




Part VII Methods of 
equipment grounding 



Part V Bonding 



Part IX Instruments, 
meters, and relays 



Figure 250.4 Grounding. 



(B) Alterations to Stop Objectionable Current. If the 

use of multiple grounding connections results in objection- 
able current, one or more of the following alterations shall 
be permitted to be made, provided that the requirements of 
250.4(A)(5) or (B)(4) are met: 

(1) Discontinue one or more but not all of such grounding 
connections. 

(2) Change the locations of the grounding connections. 

(3) Interrupt the continuity of the conductor or conductive 
path interconnecting the grounding connections. 

(4) Take other suitable remedial and approved action. 

(C) Temporary Currents Not Classified as Objection- 
able Currents. Temporary currents resulting from acciden- 
tal conditions, such as ground-fault currents, that occur 
only while the grounding conductors are performing their 
intended protective functions shall not be classified as ob- 
jectionable current for the purposes specified in 250.6(A) 
and (B). 

(D) Limitations to Permissible Alterations. The provi- 
sions of this section shall not be considered as permitting 
electronic equipment from being operated on ac systems or 
branch circuits that are not grounded as required by this 
article. Currents that introduce noise or data errors in elec- 
tronic equipment shall not be considered the objectionable 
currents addressed in this section. 



70-94 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 250 — GROUNDING AND BONDING 



250.21 



• 



• 



(E) Isolation of Objectionable Direct-Current Ground 
Currents. Where isolation of objectionable dc ground cur- 
rents from cathodic protection systems is required, a listed 
ac coupling/dc isolating device shall be permitted in the 
equipment grounding path to provide an effective return 
path for ac ground-fault current while blocking dc current. 

250.8 Connection of Grounding and Bonding Equipment. 

Grounding conductors and bonding jumpers shall be con- 
nected by exothermic welding, listed pressure connectors, 
listed clamps, or other listed means. Connection devices or 
fittings that depend solely on solder shall not be used. Sheet 
metal screws shall not be used to connect grounding con- 
ductors or connection devices to enclosures. 

250.10 Protection of Ground Clamps and Fittings. 

Ground clamps or other fittings shall be approved for gen- 
eral use without protection or shall be protected from 
physical damage as indicated in (1) or (2) as follows: 

(1) In installations where they are not likely to be damaged 

(2) Where enclosed in metal, wood, or equivalent protec- 
tive covering 

250.12 Clean Surfaces. Nonconductive coafings (such as 
paint, lacquer, and enamel) on equipment to be grounded shall 
be removed from threads and other contact surfaces to ensure 
good electrical continuity or be connected by means of fittings 
designed so as to make such removal unnecessary. 

11. System Grounding 

250.20 Alternating-Current Systems to Be Grounded. 

Alternating-current systems shall be grounded as provided for 
in 250.20(A), (B), (C), or (D). Other systems shall be permit- 
ted to be grounded. If such systems are grounded, they shall 
comply with the applicable provisions of this article. 

FPN: An example of a system permitted to be grounded is a 
comer-grounded delta transformer connection. See 250.26(4) 
for conductor to be grounded. 

(A) Alternating-Current Systems of Less Than 50 Volts. 

Alternating-current systems of less than 50 volts shall be 
grounded under any of the following conditions: 

(1) Where supplied by transformers, if the transformer sup- 
ply system exceeds 150 volts to ground 

(2) Where supplied by transformers, if the transformer sup- 
ply system is ungrounded 

(3) Where installed as overhead conductors outside of 
buildings 

(B) Alternating-Current Systems of 50 Volts to 1000 
Volts. Alternating-current systems of 50 volts to 1000 volts 
that supply premises wiring and premises wiring systems 
shall be grounded under any of the following conditions: 



(1) Where the system can be grounded so that the maxi- 
mum voltage to ground on the ungrounded conductors 
does not exceed 150 volts 

(2) Where the system is 3-phase, 4-wire, wye connected in 
which the neutral is used as a circuit conductor 

(3) Where the system is 3-phase, 4-wire, delta connected in 
which the midpoint of one phase winding is used as a 
circuit conductor 

(C) Alternating-Current Systems of 1 kV and Over. 

Alternating-current systems supplying mobile or portable 
equipment shall be grounded as specified in 250.188. 
Where supplying other than mobile or portable equipment, 
such systems shall be permitted to be grounded. 

(D) Separately Derived Systems. Separately derived sys- 
tems, as covered in 250.20(A) or (B), shall be grounded as 
specified in 250.30. 

FPN No. 1: An alternate ac power source such as an on-site 
generator is not a separately derived system if the neutral is 
solidly interconnected to a service-supplied system neutral. 

FPN No. 2: For systems that are not separately derived 
and are not required to be grounded as specified in 250.30, 
see 445.13 for minimum size of conductors that must carry 
fault current. 

(E) Impedance Grounded Neutral Systems. Impedance 
grounded neutral systems shall be grounded in accordance 
with 250.36 or 250.186. 

250.21 Alternating-Current Systems of 50 Volts to 
1000 Volts Not Required to Be Grounded. The follow- 
ing ac systems of 50 volts to 1000 volts shall be permitted 
to be grounded but shall not be required to be grounded: 

(1) Electric systems used exclusively to supply industrial 
electric furnaces for melting, refining, tempering, and 
the like 

(2) Separately derived systems used exclusively for recti- 
fiers that supply only adjustable- speed industrial drives 

(3) Separately derived systems supplied by transformers 
that have a primary voltage rating less than 1000 volts, 
provided that all the following conditions are met: 

a. The system is used exclusively for control circuits. 

b. The conditions of maintenance and supervision ensure 
that only qualified persons service the installation. 

c. Continuity of control power is required. 

d. Ground detectors are installed on the control 
system. 

(4) Other systems that are not required to be grounded in 
accordance with the requirements of 250.20(B). 

Where an alternating-current system is not grounded as per- 
mitted in 250.21(1) through (4), ground detectors shall be 
installed on the system. 



2005 Edition NATIONAL liLEC TRICAL CODE 



70-95 



250.22 



ARTICLE 250 — GROUNDING AND BONDING 



Exception: Systems of less than 120 volts to ground as 
permitted by this Code shall not be required to have ground 
detectors. 

250.22 Circuits Not to Be Grounded. The following cir- 
cuits shall not be grounded: 

(1) Circuits for electric cranes operating over combustible 
fibers in Class III locations, as provided in 503.155 

(2) Circuits in health care facilities as provided in 517.61 
and 517.160 

(3) Circuits for equipment within electrolytic cell working 
zone as provided in Article 668 

(4) Secondary circuits of lighting systems as provided in 
411.5(A) 

250.24 Grounding Service-Supplied Alternating-Current 
Systems. 

(A) System Grounding Connections. A premises wiring 
system supplied by a grounded ac service shall have a 
grounding electrode conductor connected to the grounded 
service conductor, at each service, in accordance with 
250.24(A)(1) through (A)(5). 

(1) General. The connection shall be made at any acces- 
sible point from the load end of the service drop or service 
lateral to and including the terminal or bus to which the 
grounded service conductor is connected at the service dis- 
connecting means. 

FPN: See definitions of Service Drop and Service Lateral 
in Article 100. 

(2) Outdoor Transformer. Where the transformer supply- 
ing the service is located outside the building, at least one 
additional grounding connection shall be made from the 
grounded service conductor to a grounding electrode, either 
at the transformer or elsewhere outside the building. 

Exception: The additional grounding connection shall not 
be made on high-impedance grounded neutral systems. The 
system shall meet the requirements of 250.36. 

(3) Dual Fed Services. For services that are dual fed (double 
ended) in a common enclosure or grouped together in separate 
enclosures and employing a secondary tie, a single grounding 
electrode connection to the tie point of the grounded conduc- 
tor(s) from each power source shall be permitted. 

(4) Main Bonding Jumper as Wire or Busbar. Where the 
main bonding jumper specified in 250.28 is a wire or bus- 
bar and is installed from the grounded conductor terminal 
bar or bus to the equipment grounding terminal bar or bus 
in the service equipment, the grounding electrode conduc- 
tor shall be permitted to be connected to the equipment 
grounding terminal, bar, or bus to which the main bonding 
jumper is connected. 



(5) Load-Side Grounding Connections. A grounding 
connection shall not be made to any grounded conductor on 
the load side of the service disconnecting means except as 
otherwise permitted in this article. 

FPN: See 250.30(A) for separately derived systems, 
250.32 for connections at separate buildings or structures, 
and 250.142 for use of the grounded circuit conductor for 
grounding equipment. 

(B) Main Bonding Jumper. For a grounded system, an un- 
spliced main bonding jumper shall be used to connect the 
equipment grounding conductor(s) and the service-disconnect 
enclosure to the grounded conductor within the enclosure for 
each service disconnect in accordance with 250.28. 

Exception No. 1: Where more than one service disconnect- 
ing means is located in an assembly listed for use as ser- 
vice equipment, an unspliced main bonding jumper shall 
bond the grounded conductor(s) to the assembly enclosure. 

Exception No. 2: Impedance grounded neutral systems shall 
be permitted to be connected as provided in 250.36 and 
250.186. 

(C) Grounded Conductor Brought to Service Equipment. 

Where an ac system operating at less than 1000 volts is 
grounded at any point, the grounded conductor(s) shall be run 
to each service disconnecting means and shall be bonded to 
each disconnecting means enclosure. The grounded conduc- 
tor(s) shall be installed in accordance with 250.24(C)(1) 
through (C)(3). 

Exception: Where more than one service disconnecting 
means are located in an assembly listed for use as service 
equipment, it shall be permitted to run the grounded con- 
ductor(s) to the assembly, and the conductor(s) shall be 
bonded to the assembly enclosure. 

(1) Routing and Sizing. This conductor shall be routed with 
the phase conductors and shall not be smaller than the required 
grounding electrode conductor specified in Table 250.66 but 
shall not be required to be larger than the largest ungrounded 
service-entrance phase conductor. In addition, for service- 
entrance phase conductors larger than 1100 kcmil copper or 
1750 kcmil aluminum, the grounded conductor shall not be 
smaller than 12'/2 percent of the area of the largest service- 
entrance phase conductor. The grounded conductor of a 
3-phase, 3-wire delta service shall have an ampacity not less 
than that of the ungrounded conductors. 

(2) Parallel Conductors. Where the service-entrance 
phase conductors are installed in parallel, the size of the 
grounded conductor shall be based on the total circular mil 
area of the parallel conductors as indicated in this section. 
Where installed in two or more raceways, the size of the 
grounded conductor in each raceway shall be based on the 



• 



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ARTICLE 250 — GROUNDING AND BONDING 



250.30 



• 



• 



size of the ungrounded service-entrance conductor in the 
raceway but not smaller than 1/0 AWG. 

FPN: See 310.4 for grounded conductors connected in parallel. 

(3) High Impedance. The grounded conductor on a high- 
impedance grounded neutral system shall be grounded in 
accordance with 250.36. 

(D) Grounding Electrode Conductor. A grounding elec- 
trode conductor shall be used to connect the equipment 
grounding conductors, the service-equipment enclosures, 
and, where the system is grounded, the grounded service 
conductor to the grounding electrode(s) required by Part III 
of this article. 

High-impedance grounded neutral system connections 
shall be made as covered in 250.36. 

FPN: See 250.24(A) for ac system grounding connections. 

(E) Ungrounded System Grounding Connections. A pre- 
mises wiring system that is supplied by an ac service that is 
ungrounded shall have, at each service, a grounding elec- 
trode conductor connected to the grounding electrode(s) 
required by Part III of this article. The grounding electrode 
conductor shall be connected to a metal enclosure of the 
service conductors at any accessible point from the load 
end of the service drop or service lateral to the service 
disconnecting means. 

250.26 Conductor to Be Grounded — Alternating- 
Current Systems. For ac premises wiring systems, the con- 
ductor to be grounded shall be as specified in the following: 

(1) Single-phase, 2- wire — one conductor 

(2) Single-phase, 3-wire — the neutral conductor 

(3) Multiphase systems having one wire common to all 
phases — the common conductor 

(4) Multiphase systems where one phase is grounded — 
one phase conductor 

(5) Multiphase systems in which one phase is used as in 
(2) — the neutral conductor 

250.28 Main Bonding Jumper and System Bonding 
Jumper. For a grounded system, main bonding jumpers 
and system bonding jumpers shall be installed as follows: 

(A) Material. Main bonding jumpers and system bonding 
jumpers shall be of copper or odier corrosion-resistant mate- 
rial. A main bonding jumper and a system bonding jumper 
shall be a wire, bus, screw, or similar suitable conductor. 

(B) Construction. Where a main bonding jumper or a sys- 
tem bonding jumper is a screw only, the screw shall be 
identified with a green finish that shall be visible with the 
screw installed. 

(C) Attachment. Main bonding jumpers and system bond- 
ing jumpers shall be attached in the manner specified by the 
applicable provisions of 250.8. 



(D) Size. Main bonding jumpers and system bonding jump- 
ers shall not be smaller than the sizes shown in Table 250.66. 
Where the supply conductors are larger than 1100 kcmil cop- 
per or 1750 kcmil aluminum, the bonding jumper shall have 
an area that is not less than 12'/2 percent of the area of the 
largest phase conductor except that, where the phase conduc- 
tors and the bonding jumper are of different materials (copper 
or aluminum), the minimum size of the bonding jumper shall 
be based on the assumed use of phase conductors of the same 
material as the bonding jumper and with an ampacity equiva- 
lent to that of the installed phase conductors. 

250.30 Grounding Separately Derived Alternating- 
Current Systems. 

(A) Grounded Systems. A separately derived ac system 
that is grounded shall comply with 250.30(A)(1) through 
(A)(8). A grounding connection shall not be made to any 
grounded circuit conductor on the load side of the point of 
grounding of the separately derived system except as oth- 
erwise permitted in this article. 

FPN: See 250.32 for connections at separate buildings or 
structures, and 250.142 for use of the grounded circuit con- 
ductor for grounding equipment. 

Exception: Impedance grounded neutral system grounding 
connections shall be made as specified in 250.36 or 250.186. 

(1) System Bonding Jumper. An unspliced system bond- 
ing jumper in compliance with 250.28(A) through (D) that 
is sized based on the derived phase conductors shall be 
used to connect the equipment grounding conductors of the 
separately derived system to the grounded conductor. This 
connection shall be made at any single point on the sepa- 
rately derived system from the source to the first system 
disconnecting means or overcurrent device, or it shall be 
made at the source of a separately derived system that has 
no disconnecting means or overcurrent devices. 

Exception No. 1: For separately derived systems that are 
dual fed {double ended) in a common enclosure or grouped 
together in separate enclosures and employing a secondary 
tie, a single system bonding jumper connection to the tie 
point of the grounded circuit conductors from each power 
source shall be permitted. 

Exception No. 2: A system bonding jumper at both the 
source and the first disconnecting means shall be permitted 
where doing so does not establish a parallel path for the 
grounded conductor Where a grounded conductor is used 
in this manner, it shall not be smaller than the size specified 
for the system bonding jumper but shall not be required to 
be larger than the ungrounded conductor(s). For the pur- 
poses of this exception, connection through the earth shall 
not be considered as providing a parallel path. 



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250.30 



ARTICLE 250 — GROUNDING AND BONDING 



Exception No. 3: The size of the system bonding jumper 
for a system that supplies a Class 1, Class 2, or Class 3 
circuit, and is derived from a transformer rated not more 
than 1000 volt-amperes, shall not be smaller than the derived 
phase conductors and shall not be smaller than 14 AWG cop- 
per or 12 AWG aluminum. 

(2) Equipment Bonding Jumper Size. Where a bonding 
jumper of the wire type is run with the derived phase con- 
ductors from the source of a separately derived system to 
the first disconnecting means, it shall be sized in accor- 
dance with 250.102(C), based on the size of the derived 
phase conductors. 

(3) Grounding Electrode Conductor, Single Separately 
Derived System. A grounding electrode conductor for a 
single separately derived system shall be sized in accor- 
dance with 250.66 for the derived phase conductors and 
shall be used to connect the grounded conductor of the 
derived system to the grounding electrode as specified in 
250.30(A)(7). This connection shall be made at the same 
point on the separately derived system where the system 
bonding jumper is installed. 

Exception No. 1: Where the system bonding jumper speci- 
fied in 250.30(A)(1) is a wire or busbar, it shall be permit- 
ted to connect the grounding electrode conductor to the 
equipment grounding terminal, bar, or bus, provided the 
equipment grounding terminal, bar, or bus is of sufficient 
size for the separately derived system. 

Exception No. 2: Where a separately derived system origi- 
nates in listed equipment suitable as service equipment, the 
grounding electrode conductor from the service or feeder 
equipment to the grounding electrode shall be permitted as 
the grounding electrode conductor for the separately de- 
rived system, provided the grounding electrode conductor is 
of sufficient size for the separately derived system. Where 
the equipment ground bus internal to the equipment is not 
smaller than the required grounding electrode conductor 
for the separately derived system, the grounding electrode 
connection for the separately derived system shall be per- 
mitted to be made to the bus. 

Exception No. 3: A grounding electrode conductor shall 
not be required for a system that supplies a Class 1, Class 
2, or Class 3 circuit and is derived from a transformer 
rated not more than 1000 volt-amperes, provided the 
grounded conductor is bonded to the transformer frame or 
enclosure by a jumper sized in accordance with 250.30(A)(1), 
Exception No. 3, and the transformer frame or enclosure is 
grounded by one of the means specified in 250.134. 

(4) Grounding Electrode Conductor, Multiple Sepa- 
rately Derived Systems. Where more than one separately 
derived system is installed, it shall be permissible to con- 
nect a tap from each separately derived system to a com- 
mon grounding electrode conductor. Each tap conductor 



shall connect the grounded conductor of the separately de- 
rived system to the common grounding electrode conduc- 
tor. The grounding electrode conductors and taps shall 
comply with 250.30(A)(4)(a) through (A)(4)(c). 

Exception No. 1: Where the system bonding jumper speci- 
fied in 250.30(A)(1) is a wire or busbar, it shall be permit- 
ted to connect the grounding electrode conductor to the 
equipment grounding terminal, bar, or bus, provided the 
equipment grounding terminal, bar, or bus is of sufficient 
size for the separately derived system. 

Exception No. 2: A grounding electrode conductor shall 
not be required for a system that supplies a Class 1, Class 2, 
or Class 3 circuit and is derived from a transformer rated not 
more than 1000 volt-amperes, provided the system grounded 
conductor is bonded to the transformer frame or enclosure by 
a jumper sized in accordance with 250.30(A)(1), Excep- 
tion No. 3 and the transformer frame or enclosure is grounded 
by one of the means specified in 250.134. 

(a) Common Grounding Electrode Conductor Size. 
The common grounding electrode conductor shall not be 
smaller than 3/0 AWG copper or 250 kcmil aluminum. 

(b) Tap Conductor Size. Each tap conductor shall be 
sized in accordance with 250.66 based on the derived phase 
conductors of the separately derived system it serves. 

Exception: Where a separately derived system originates 
in listed equipment suitable as service equipment, the 
grounding electrode conductor from the service or feeder 
equipment to the grounding electrode shall be permitted as 
the grounding electrode conductor for the separately de- 
rived system, provided the grounding electrode conductor is 
of sufficient size for the separately derived system. Where 
the equipment ground bus internal to the equipment is not 
smaller than the required grounding electrode conductor 
for the separately derived system, the grounding electrode 
connection for the separately derived system shall be per- 
mitted to be made to the bus. 

(c) Connections. All tap connections to the common 
grounding electrode conductor shall be made at an acces- 
sible location by one of the following methods: 

(1) A listed connector. 

(2) Listed connections to aluminum or copper busbars not 
less than 6 mm x 50 mm (Vi in. x 2 in.). Where alu- 
minum busbars are used, the installation shall comply 
with 250.64(A). 

(3) By the exothermic welding process. 

Tap conductors shall be connected to the common 
grounding electrode conductor in such a manner that the 
common grounding electrode conductor remains without a 
splice or joint. 

(5) Installation. The installation of all grounding electrode 
conductors shall comply with 250.64(A), (B), (C), and (E). 



• 



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ARTICLE 250 — GROUNDING AND BONDING 



250.32 



(6) Bonding. Structural steel and metal piping shall be 
bonded in accordance with 250.104(D). 

(7) Grounding Electrode. The grounding electrode shall be 
as near as practicable to and preferably in the same area as the 
grounding electrode conductor connection to the system. The 
grounding electrode shall be the nearest one of the following: 

(1) Metal water pipe grounding electrode as specified in 
250.52(A)(1) 

(2) Structural metal grounding electrode as specified in 
250.52(A)(2) 

Exception No. 1: Any of the other electrodes identified in 
250.52(A) shall be used where the electrodes specified by 
250.30(A)(7) are not available. 

Exception No. 2 to (1) and (2): Where a separately derived 
system originates in listed equipment suitable for use as 
service equipment, the grounding electrode used for the 
service or feeder equipment shall be permitted as the 
grounding electrode for the separately derived system. 

FPN: See 250. 104(D) for bonding requirements of interior 
metal water piping in the area served by separately derived 
systems. 

(8) Grounded Conductor. Where a grounded conductor is 
installed and the system bonding jumper is not located at the 
source of the separately derived system, 250.30(A)(8)(a), 
(A)(8)(b), and (A)(8)(c) shaU apply. 

(a) Routing and Sizing. This conductor shall be routed 
with the derived phase conductors and shall not be smaller 
than the required grounding electrode conductor specified 
in Table 250.66 but shall not be required to be larger than 
the largest ungrounded derived phase conductor. In addi- 
tion, for phase conductors larger than 1100 kcmil copper or 
1750 kcmil aluminum, the grounded conductor shall not be 
smaller than 12!/2 percent of the area of the largest derived 
phase conductor. The grounded conductor of a 3 -phase, 
3-wire delta system shall have an ampacity not less than 
that of the ungrounded conductors. 

(b) Parallel Conductors. Where the derived phase con- 
ductors are installed in parallel, the size of the grounded 
conductor shall be based on the total circular mil area of the 
parallel conductors, as indicated in this section. Where in- 
stalled in two or more raceways, the size of the grounded 
conductor in each raceway shall be based on the size of the 
ungrounded conductors in the raceway but not smaller than 
1/0 AWG. 

FPN: See 310.4 for grounded conductors connected in 
parallel. 

(c) Impedance Grounded System. The grounded con- 
ductor of an impedance grounded neutral system shall be 
installed in accordance with 250.36 or 250.186. 



(B) Ungrounded Systems. The equipment of an ungrounded 
separately derived system shall be grounded as specified in 
250.30(B)(1) and (B)(2). 

(1) Grounding Electrode Conductor. A grounding elec- 
trode conductor, sized in accordance with 250.66 for the 
derived phase conductors, shall be used to connect the 
metal enclosures of the derived system to the grounding 
electrode as specified in 250.30(B)(2). This connection 
shall be made at any point on the separately derived system 
from the source to the first system disconnecting means. 

(2) Grounding Electrode. Except as permitted by 250.34 
for portable and vehicle-mounted generators, the grounding 
electrode shall comply with 250.30(A)(7). 

250.32 Buildings or Structures Supplied by Feeder(s) or 
Branch Circuit(s). 

(A) Grounding Electrode. Building(s) or structure(s) sup- 
plied by feeder(s) or branch circuit(s) shall have a ground- 
ing electrode or grounding electrode system installed in 
accordance with 250.50. The grounding electrode conduc- 
tor(s) shall be connected in accordance with 250.32(B) or 
(C). Where there is no existing grounding electrode, the 
grounding electrode(s) required in 250.50 shall be installed. 

Exception: A grounding electrode shall not be required 
where only a single branch circuit supplies the building or 
structure and the branch circuit includes an equipment 
grounding conductor for grounding the conductive non- 
current-carrying parts of equipment. For the purpose of 
this section, a multiwire branch circuit shall be considered 
as a single branch circuit. 

(B) Grounded Systems. For a grounded system at the 
separate building or structure, the connection to the ground- 
ing electrode and grounding or bonding of equipment, 
structures, or frames required to be grounded or bonded 
shall comply with either 250.32(B)(1) or (B)(2). 

(1) Equipment Grounding Conductor. An equipment 
grounding conductor as described in 250.118 shall be run with 
the supply conductors and connected to die building or struc- 
ture disconnecting means and to the grounding electrode(s). 
The equipment grounding conductor shall be used for ground- 
ing or bonding of equipment, structures, or frames required to 
be grounded or bonded. The equipment grounding conductor 
shall be sized in accordance wi± 250.122. Any installed 
grounded conductor shall not be connected to die equipment 
grounding conductor or to die grounding electrode(s). 

(2) Grounded Conductor. Where (1) an equipment 
grounding conductor is not run with the supply to the build- 
ing or structure, (2) there are no continuous metallic paths 
bonded to the grounding system in each building or struc- 
ture involved, and (3) ground-fault protection of equipment 



2005 Edition NATIONAL ELECTRICAL CODE 



70-99 



250.34 



ARTICLE 250 — GROUNDING AND BONDING 



has not been installed on the supply side of the feeder(s), 
the grounded conductor run with the supply to the building 
or structure shall be connected to the building or structure 
disconnecting means and to the grounding electrode(s) and 
shall be used for grounding or bonding of equipment, struc- 
tures, or frames required to be grounded or bonded. The 
size of the grounded conductor shall not be smaller than the 
larger of either of the following: 

(1) That required by 220.61 

(2) That required by 250.122 

(C) Ungrounded Systems. The grounding electrode(s) 
shall be connected to the building or structure disconnect- 
ing means. 

(D) Disconnecting Means Located in Separate Building 
or Structure on the Same Premises. Where one or more 
disconnecting means supply one or more additional build- 
ings or structures under single management, and where 
these disconnecting means are located remote from those 
buildings or structures in accordance with the provisions of 
225.32, Exception Nos. 1 and 2, all of the following con- 
ditions shall be met: 

(1) The connection of the grounded conductor to the ground- 
ing electrode at a separate building or strucmre shall not 
be made. 

(2) An equipment grounding conductor for grounding any 
non-current-carrying equipment, interior metal piping 
systems, and building or structural metal frames is run 
with the circuit conductors to a separate building or 
structure and bonded to existing grounding electrode(s) 
required in Part III of this article, or, where there are no 
existing electrodes, the grounding electrode(s) required 
in Part III of this article shall be installed where a 
separate building or structure is supplied by more than 
one branch circuit. 

(3) Bonding the equipment grounding conductor to the 
grounding electrode at a separate building or structure 
shall be made in a junction box, panelboard, or similar 
enclosure located immediately inside or outside the 
separate building or structure. 

(E) Grounding Electrode Conductor. The size of the 
grounding electrode conductor to the grounding elec- 
trode(s) shall not be smaller than given in 250.66, based on 
the largest ungrounded supply conductor. The installation 
shall comply with Part III of this article. 

250.34 Portable and Vehicle-Mounted Generators. 

(A) Portable Generators. The frame of a portable genera- 
tor shall not be required to be connected to a grounding 
electrode as defined in 250.52 for a system supplied by the 
generator under the following conditions: 



(1) The generator supplies only equipment mounted on the 
generator, cord-and-plug-connected equipment through 
receptacles mounted on the generator, or both, and 

(2) The non-current-carrying metal parts of equipment and 
the equipment grounding conductor terminals of the 
receptacles are bonded to the generator frame. 

(B) Vehicle-Mounted Generators. The frame of a vehicle 
shall not be required to be connected to a grounding electrode 
as defined in 250.52 for a system supplied by a generator 
located on this vehicle under the following conditions: 

(1) The frame of the generator is bonded to the vehicle 
frame, and 

(2) The generator supplies only equipment located on the 
vehicle or cord-and-plug-connected equipment through 
receptacles mounted on the vehicle, or both equipment 
located on the vehicle and cord-and-plug-connected 
equipment through receptacles mounted on the vehicle 
or on the generator, and 

(3) The non-current-carrying metal parts of equipment and 
the equipment grounding conductor terminals of the 
receptacles are bonded to the generator frame. 

(C) Grounded Conductor Bonding. A system conductor 
that is required to be grounded by 250.26 shall be bonded 
to the generator frame where the generator is a component 
of a separately derived system. 

FPN: For grounding portable generators supplying fixed 
wiring systems, see 250.20(D). 

250.36 High-Impedance Grounded Neutral Systems. 

High-impedance grounded neutral systems in which a 
grounding impedance, usually a resistor, limits the ground- 
fault current to a low value shall be permitted for 3 -phase 
ac systems of 480 volts to 1000 volts where all the follow- 
ing conditions are met: 

(1) The conditions of maintenance and supervision ensure 
that only qualified persons service the installation. 

(2) Continuity of power is required. 

(3) Ground detectors are installed on the system. 

(4) Line-to-neutral loads are not served. 

High-impedance grounded neutral systems shall com- 
ply with the provisions of 250.36(A) through (G). 

(A) Grounding Impedance Location. The grounding im- 
pedance shall be installed between the grounding electrode 
conductor and the system neutral. Where a neutral is not 
available, the grounding impedance shall be installed be- 
tween the grounding electrode conductor and the neutral 
derived from a grounding transformer. 

(B) Neutral Conductor. The neutral conductor from the 
neutral point of the transformer or generator to its connection 
point to the grounding impedance shall be fully insulated. 



• 



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NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 250 — GROUNDING AND BONDING 



250.52 



« 



The neutral conductor shall have an ampacity of not 
less than the maximum current rating of the grounding im- 
pedance. In no case shall the neutral conductor be smaller 
than 8 AWG copper or 6 AWG aluminum or copper-clad 
aluminum. 

(C) System Neutral Connection. The system neutral con- 
ductor shall not be connected to ground except through the 
grounding impedance. 

FPN: The impedance is normally selected to limit the 
ground-fault current to a value slightly greater than or equal to 
the capacitive charging current of the system. This value of 
impedance will also limit transient overvoltages to safe values. 
For guidance, refer to criteria for limiting transient overvolt- 
ages in ANSI/IEEE 142-1991, Recommended Practice for 
Grounding of Industrial and Commercial Power Systems. 

(D) Neutral Conductor Routing. The conductor connect- 
ing the neutral point of the transformer or generator to the 
grounding impedance shall be permitted to be installed in a 
separate raceway. It shall not be required to run this con- 
ductor with the phase conductors to the first system discon- 
necting means or overcurrent device. 

(E) Equipment Bonding Jumper. The equipment bond- 
ing jumper (the connection between the equipment ground- 
ing conductors and the grounding impedance) shall be an 
unspliced conductor run from the first system disconnecting 
means or overcurrent device to the grounded side of the 
grounding impedance. 

(F) Grounding Electrode Conductor Location. The 

grounding electrode conductor shall be attached at any 
point from the grounded side of the grounding impedance 
to the equipment grounding connection at the service 
equipment or first system disconnecting means. 

(G) Equipment Bonding Jumper Size. The equipment 
bonding jumper shall be sized in accordance with (1) or (2) 
as follows: 

(1) Where the grounding electrode conductor connection is 
made at the grounding impedance, the equipment bond- 
ing jumper shall be sized in accordance with 250.66, 
based on the size of the service entrance conductors for 
a service or the derived phase conductors for a sepa- 
rately derived system. 

(2) Where the grounding electrode conductor is connected 
at the first system disconnecting means or overcurrent 
device, the equipment bonding jumper shall be sized 
the same as the neutral conductor in 250.36(B). 

III. Grounding Electrode System and Grounding 
Electrode Conductor 

250.50 Grounding Electrode System. All grounding elec- 
trodes as described in 250.52(A)(1) through' (A)(6) that are 
present at each building or structure served shall be bonded 



together to form the grounding electrode system. Where 
none of these grounding electrodes exist, one or more of 
the grounding electrodes specified in 250.52(A)(4) through 
(A)(7) shall be installed and used. 

Exception: Concrete-encased electrodes of existing build- 
ings or structures shall not be required to be part of the 
grounding electrode system where the steel reinforcing bars 
or rods are not accessible for use without disturbing the 
concrete. 

250.52 Grounding Electrodes. 

(A) Electrodes Permitted for Grounding. 

(1) Metal Underground Water Pipe. A metal under- 
ground water pipe in direct contact with the earth for 3.0 m 
(10 ft) or more (including any metal well casing effectively 
bonded to the pipe) and electrically continuous (or made 
electrically continuous by bonding around insulating joints 
or insulating pipe) to the points of connection of the 
grounding electrode conductor and the bonding conductors. 
Interior metal water piping located more than 1.52 m (5 ft) 
from the point of entrance to the building shall not be used 
as a part of the grounding electrode system or as a conduc- 
tor to interconnect electrodes that are part of the grounding 
electrode system. 

Exception: In industrial and commercial buildings or 
structures where conditions of maintenance and supervi- 
sion ensure that only qualified persons service the installa- 
tion, interior metal water piping located more than 1.52 m 
(5 ft) from the point of entrance to the building shall be 
permitted as a part of the grounding electrode system or as 
a conductor to interconnect electrodes that are part of the 
grounding electrode system, provided that the entire length, 
other than short sections passing perpendicular through 
walls, floors, or ceilings, of the interior metal water pipe 
that is being used for the conductor is exposed. 

(2) Metal Frame of the Building or Structure. The metal 
frame of the building or structure, where any of the follow- 
ing methods are used to make an earth connection: 

(1) 3.0 m (10 ft) or more of a single structural metal mem- 
ber in direct contact with the earth or encased in con- 
crete that is in direct contact with the earth 

(2) The structural metal frame is bonded to one or more of 
the grounding electrodes as defined in 250.52(A)(1), 
(A)(3), or (A)(4) 

(3) The structural metal frame is bonded to one or more of 
the grounding electrodes as defined in 250.52(A)(5) or 
(A)(6) that comply with 250.56, or 

(4) Other approved means of establishing a connection to 
earth. 



2005 Edition 



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70-101 



250.53 



ARTICLE 250 — GROUNDING AND BONDING 



(3) Concrete-Encased Electrode. An electrode encased 
by at least 50 mm (2 in.) of concrete, located within and 
near the bottom of a concrete foundation or footing that is 
in direct contact with the earth, consisting of at least 6.0 m 
(20 ft) of one or more bare or zinc galvanized or other 
electrically conductive coated steel reinforcing bars or rods 
of not less than 13 mm (Vi in.) in diameter, or consisting of 
at least 6.0 m (20 ft) of bare copper conductor not smaller 
than 4 AWG. Reinforcing bars shall be permitted to be 
bonded together by the usual steel tie wires or other effec- 
tive means. 

(4) Ground Ring. A ground ring encircling the building or 
structure, in direct contact with the earth, consisting of at 
least 6.0 m (20 ft) of bare copper conductor not smaller 
than 2 AWG. 

(5) Rod and Pipe Electrodes. Rod and pipe electrodes 
shall not be less than 2.5 m (8 ft) in length and shall consist 
of the following materials. 

(a) Electrodes of pipe or conduit shall not be smaller 
than metric designator 21 (trade size Va) and, where of iron 
or steel, shall have the outer surface galvanized or other- 
wise metal-coated for corrosion protection. 

(b) Electrodes of rods of iron or steel shall be at least 
15.87 mm (Vs in.) in diameter. Stainless steel rods less than 
16 mm (Vs in.) in diameter, nonferrous rods, or their equiva- 
lent shall be Usted and shall not be less than 13 mm {V2 in.) in 
diameter. 

(6) Plate Electrodes. Each plate electrode shall expose not 
less than 0.186 m^ (2 ft^) of surface to exterior soil. Elec- 
trodes of iron or steel plates shall be at least 6.4 mm ('^ in.) 
in thickness. Electrodes of nonferrous metal shall be at least 
1.5 mm (0.06 in.) in thickness. 

(7) Other Local Metal Underground Systems or Struc- 
tures. Other local metal underground systems or structures 
such as piping systems, underground tanks, and under- 
ground metal well casings that are not effectively bonded to 
a metal water pipe. 

(B) Electrodes Not Permitted for Grounding. The fol- 
lowing shall not be used as grounding electrodes: 

(1) Metal underground gas piping system 

(2) Aluminum electrodes 

FPN: See 250.104(B) for bonding requirements of gas 
piping. 

250.53 Grounding Electrode System Installation. 

FPN: See 547.9 and 547.10 for special grounding and 
bonding requirements for agricultural buildings. 



(A) Rod, Pipe, and Plate Electrodes. Where practicable, 
rod, pipe, and plate electrodes shall be embedded below per- 
manent moisture level. Rod, pipe, and plate electrodes shall be 
free from nonconductive coatings such as paint or enamel. 

(B) Electrode Spacing. Where more than one of the elec- 
trodes of the type specified in 250.52(A)(5) or (A)(6) are 
used, each electrode of one grounding system (including 
that used for air terminals) shall not be less than 1.83 m 
(6 ft) from any other electrode of another grounding sys- 
tem. Two or more grounding electrodes that are effectively 
bonded together shall be considered a single grounding 
electrode system. 

(C) Bonding Jumper. The bonding jumper(s) used to con- 
nect the grounding electrodes together to form the ground- 
ing electrode system shall be installed in accordance with 
250.64(A), (B), and (E), shall be sized in accordance with 
250.66, and shall be connected in the manner specified in 
250.70. 

(D) Metal Underground Water Pipe. Where used as a 
grounding electrode, metal underground water pipe shall 
meet the requirements of 250.53(D)(1) and (D)(2). 

(1) Continuity. Continuity of the grounding path or the 
bonding connection to interior piping shall not rely on wa- 
ter meters or filtering devices and similar equipment. 

(2) Supplemental Electrode Required. A metal under- 
ground water pipe shall be supplemented by an additional 
electrode of a type specified in 250.52(A)(2) through 
(A)(7). Where the supplemental electrode is a rod, pipe, or 
plate type, it shall comply with 250.56. The supplemental 
electrode shall be permitted to be bonded to the grounding 
electrode conductor, the grounded service-entrance conductor, 
the nonflexible grounded service raceway, or any grounded 
service enclosure. 

Exception: The supplemental electrode shall be permitted 
to be bonded to the interior metal water piping at any 
convenient point as covered in 250.52(A)(1), Exception. 

(E) Supplemental Electrode Bonding Connection Size. 

Where the supplemental electrode is a rod, pipe, or plate elec- 
trode, that portion of the bonding jumper that is the sole con- 
nection to the supplemental grounding electrode shall not be 
required to be larger than 6 AWG copper wire or 4 AWG 
aluminum wire. 

(F) Ground Ring. The ground ring shall be buried at a 
depth below the earth's surface of not less than 750 mm 
(30 in.). 

(G) Rod and Pipe Electrodes. The electrode shall be in- 
stalled such that at least 2.44 m (8 ft) of length is in contact 
with the soil. It shall be driven to a depth of not less than 



* 



70-102 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 250 — GROUNDING AND BONDING 



250.64 



2.44 m (8 ft) except that, where rock bottom is encountered, 
the electrode shall be driven at an oblique angle not to exceed 
45 degrees from the vertical or, where rock bottom is encoun- 
tered at an angle up to 45 degrees, the electrode shall be 
permitted to be buried in a trench that is at least 750 mm 
(30 in.) deep. The upper end of the electrode shall be flush 
with or below ground level unless the aboveground end and 
the grounding electrode conductor attachment are protected 
against physical damage as specified in 250.10. 

(H) Plate Electrode. Plate electrodes shall be installed not 
less than 750 mm (30 in.) below the surface of the earth. 

250.54 Supplementary Grounding Electrodes. Supple- 
mentary grounding electrodes shall be permitted to be con- 
nected to the equipment grounding conductors specified in 
250.118 and shall not be required to comply with the elec- 
trode bonding requirements of 250.50 or 250.53(C) or the 
resistance requirements of 250.56, but the earth shall not be 
used as an effective ground-fault current path as specified 
in 250.4(A)(5) and 250.4(B)(4). 

250.56 Resistance of Rod, Pipe, and Plate Electrodes. A 

single electrode consisting of a rod, pipe, or plate that does 
not have a resistance to ground of 25 ohms or less shall be 
augmented by one additional electrode of any of the types 
specified by 250.52(A)(2) through (A)(7). Where multiple 
rod, pipe, or plate electrodes are installed to meet the re- 
quirements of this section, they shall not be less than 1.8 m 
(6 ft) apart. 

FPN: The paralleling efficiency of rods longer than 2.5 m 
(8 ft) is improved by spacing greater than 1.8 m (6 ft). 

250.58 Common Grounding Electrode. Where an ac sys- 
tem is connected to a grounding electrode in or at a build- 
ing or structure, the same electrode shall be used to ground 
conductor enclosures and equipment in or on that building 
or structure. Where separate services, feeders, or branch 
circuits supply a building and are required to be connected 
to a grounding electrode(s), the same grounding elec- 
trode(s) shall be used. 

Two or more grounding electrodes that are effectively 
bonded together shall be considered as a single grounding 
electrode system in this sense. 

250.60 Use of Air Terminals. Air terminal conductors and 
driven pipes, rods, or plate electrodes used for grounding air 
terminals shall not be used in lieu of the grounding electrodes 
required by 250.50 for grounding wiring systems and equip- 
ment. This provision shall not prohibit the required bonding 
together of grounding electrodes of different systems. 

FPN No. 1: See 250.106 for spacing from air terminals. 
See 800.100(D), 8 10.21 (J), and 820.100(D) for bonding of 
electrodes. 



FPN No. 2: Bonding together of all separate grounding 
electrodes will limit potential differences between them and 
between their associated wiring systems. 

250.62 Grounding Electrode Conductor Material. The 

grounding electrode conductor shall be of copper, aluminum, 
or copper-clad aluminum. The material selected shall be resis- 
tant to any corrosive condition existing at the installation or 
shall be suitably protected against corrosion. The conductor 
shall be solid or stranded, insulated, covered, or bare. 

250.64 Grounding Electrode Conductor Installation. 

Grounding electrode conductors shall be installed as speci- 
fied in 250.64(A) through (F). 

(A) Aluminum or Copper-Clad Aluminum Conductors. 

Bare aluminum or copper-clad aluminum grounding con- 
ductors shall not be used where in direct contact with ma- 
sonry or the earth or where subject to corrosive conditions. 
Where used outside, aluminum or copper-clad aluminum 
grounding conductors shall not be terminated within 450 mm 
(18 in.) of the earth. 

(B) Securing and Protection Against Physical Damage. 

Where exposed, a grounding electrode conductor or its enclo- 
sure shall be securely fastened to the surface on which it is 
carried. A 4 AWG or larger copper or aluminum grounding 
electrode conductor shall be protected where exposed to 
physical damage. A 6 AWG grounding electrode conductor 
that is free from exposure to physical damage shall be permit- 
ted to be run along the surface of the building construction 
without metal covering or protection where it is securely fas- 
tened to the construction; otherwise, it shall be in rigid metal 
conduit, intermediate metal conduit, rigid nonmetalhc conduit, 
electrical metallic tubing, or cable armor. Grounding electrode 
conductors smaller than 6 AWG shall be in rigid metal con- 
duit, intermediate metal conduit, rigid nonmetalhc conduit, 
electrical metaUic tubing, or cable armor. 

(C) Continuous. Grounding electrode conductor(s) shall be 
installed in one continuous length without a sphce or joint 
except as permitted in (1) through (4): 

(1) Splicing shall be permitted only by irreversible 
compression-type connectors listed as grounding and 
bonding equipment or by the exothermic welding 
process. 

(2) Sections of busbars shall be permitted to be connected 
together to form a grounding electrode conductor. 

(3) Bonding jumper(s) from grounding electrode(s) and 
grounding electrode conductor(s) shall be permitted to 
be connected to an aluminum or copper busbar not less 
than 6 mm x 50 mm QA in. x 2 in.). The busbar shall be 
securely fastened and shall be installed in an accessible 
location. Connections shall be made by a listed connec- 
tor or by the exothermic welding process. 

(4) Where aluminum busbars are used, the installation 
shall comply with 250.64(A). 



2005 Edition NATIONAL ELECTRICAL CODE 



70-103 



250.66 



ARTICLE 250 — GROUNDING AND BONDING 



(D) Grounding Electrode Conductor Taps. Where a ser- 
vice consists of more than a single enclosure as permitted in 
230.71(A), it shall be permitted to connect taps to the common 
grounding electrode conductor. Each such tap conductor shall 
extend to the inside of each such enclosure. The common 
grounding electrode conductor shall be sized in accordance 
with 250.66, based on the sum of the circular mil area of the 
largest ungrounded service entrance conductors. Where more 
than one set of service entrance conductors as permitted by 
230.40, Exception No. 2 connect directly to a service drop or 
lateral, the common grounding electrode conductor shall be 
sized in accordance with Table 250.66 Note 1. The tap con- 
ductors shall be permitted to be sized in accordance with the 
grounding electrode conductors specified in 250.66 for the 
largest conductor serving the respective enclosures. The tap 
conductors shall be connected to the common grounding elec- 
trode conductor in such a manner that the common grounding 
electrode conductor remains without a splice or joint. 

(E) Enclosures for Grounding Electrode Conductors. 

Ferrous metal enclosures for grounding electrode conductors 
shall be electrically continuous from the point of attachment to 
cabinets or equipment to the grounding electrode and shall be 
securely fastened to the ground clamp or fitting. Nonferrous 
metal enclosures shall not be required to be electrically con- 
tinuous. Ferrous metal enclosures that are not physically con- 
tinuous from cabinets or equipment to the grounding electrode 
shall be made electrically continuous by bonding each end of 
the raceway or enclosure to the grounding electrode conduc- 
tor. Bonding shall apply at each end and to all intervening 
ferrous raceways, boxes, and enclosures between the service 
equipment and the grounding electrode. The bonding jumper 
for a grounding electrode conductor raceway or cable armor 
shall be the same size as, or larger than, the required enclosed 
grounding electrode conductor. Where a raceway is used as 
protection for a grounding electrode conductor, the installation 
shall comply with the requirements of the appropriate raceway 
article. 

(F) To Electrode(s). A grounding electrode conductor 
shall be permitted to be run to any convenient grounding 
electrode available in the grounding electrode system, or to 
one or more grounding electrode(s) individually, or to the 
aluminum or copper busbar as permitted in 250.64(C). The 
grounding electrode conductor shall be sized for the largest 
grounding electrode conductor required among all the elec- 
trodes connected to it. 

250.66 Size of Alternating-Current Grounding Elec- 
trode Conductor. The size of the grounding electrode con- 
ductor of a grounded or ungrounded ac system shall not be 
less than given in Table 250.66, except as permitted in 
250.66(A) through (C). 

FPN: See 250.24(C) for size of ac system conductor brought 
to service equipment. 



Table 250.66 Grounding Electrode Conductor for 
Alternating-Current Systems 



Size of Largest Ungrounded 

Service-Entrance Conductor or 

Equivalent Area for Parallel 

Conductors^ (AWG/kcmil) 



Copper 



Aluminum or 

Copper-Clad 

Aluminum 



Size of Grounding 

Electrode Conductor 

(AWG/kcmil) 

Aluminum 
or 
Copper-Clad 
Copper Aluminum"* 



2 or smaller 


1/0 or smaller 


8 


6 


1 or 1/0 


2/0 or 3/0 


6 


4 


2/0 or 3/0 


4/0 or 250 


4 


2 


Over 3/0 
through 350 


Over 250 
through 500 


2 


1/0 


Over 350 
through 600 


Over 500 
through 900 


1/0 


3/0 


Over 600 
through 1100 


Over 900 
through 1750 


2/0 


4/0 


Over 1100 


Over 1750 


3/0 


250 



Notes: 

1. Where multiple sets of service-entrance conductors are used as 
permitted in 230.40, Exception No. 2, the equivalent size of the larg- 
est service-entrance conductor shall be determined by the largest sum 
of the areas of the corresponding conductors of each set. 

2. Where diere are no service-entrance conductors, the grounding elec- 
trode conductor size shall be determined by the equivalent size of the 
largest service-entrance conductor required for the load to be served. 
"^This table also applies to the derived conductors of separately de- 
rived ac systems. 

''See installation restrictions in 250.64(A). 



(A) Connections to Rod, Pipe, or Plate Electrodes. Where 
the grounding electrode conductor is connected to rod, pipe, or 
plate electrodes as permitted in 250.52(A)(5) or (A)(6), that 
portion of the conductor that is the sole connection to the 
grounding electrode shall not be required to be larger than 6 
AWG copper wire or 4 AWG aluminum wire. 

(B) Connections to Concrete-Encased Electrodes. 

Where the grounding electrode conductor is connected to a 
concrete-encased electrode as permitted in 250.52(A)(3), 
that portion of the conductor that is the sole connection to 
the grounding electrode shall not be required to be larger 
than 4 AWG copper wire. 

(C) Connections to Ground Rings. Where the grounding 
electrode conductor is connected to a ground ring as permitted 
in 250.52(A)(4), that portion of the conductor that is the sole 
connection to the grounding electrode shall not be required to 
be larger than the conductor used for the ground ring. 



70-104 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 250 — GROUNDING AND BONDING 



250.90 



• 



250.68 Grounding Electrode Conductor and Bonding 
Jumper Connection to Grounding Electrodes. 

(A) Accessibility. The connection of a grounding electrode 
conductor or bonding jumper to a grounding electrode shall 
be accessible. 

Exception No. 1: An encased or buried connection to a 
concrete-encased, driven, or buried grounding electrode 
shall not be required to be accessible. 

Exception No. 2: An exothermic or irreversible compres- 
sion connection to fire-proofed structural metal shall not be 
required to be accessible. 

(B) Effective Grounding Path. The connection of a 
grounding electrode conductor or bonding jumper to a ground- 
ing electrode shall be made in a manner that will ensure a 
permanent and effective grounding path. Where necessary to 
ensure the grounding path for a metal piping system used as a 
grounding electrode, effective bonding shall be provided 
around insulated joints and around any equipment likely to be 
disconnected for repairs or replacement. Bonding conductors 
shall be of suflBcient length to permit removal of such equip- 
ment while retaining the integrity of the bond. 

250.70 Methods of Grounding and Bonding Conductor 
Connection to Electrodes. The grounding or bonding con- 
ductor shall be connected to the grounding electrode by 
exothermic welding, listed lugs, listed pressure connectors, 
listed clamps, or other listed means. Connections depend- 
ing on solder shall not be used. Ground clamps shall be 
listed for the materials of the grounding electrode and the 
grounding electrode conductor and, where used on pipe, 
rod, or other buried electrodes, shall also be listed for direct 
soil burial or concrete encasement. Not more than one con- 
ductor shall be connected to the grounding electrode by a 
single clamp or fitting unless the clamp or fitting is listed 
for multiple conductors. One of the following methods 
shall be used: 

(1) A pipe fitting, pipe plug, or other approved device 
screwed into a pipe or pipe fitting 

(2) A listed bolted clamp of cast bronze or brass, or plain 
or malleable iron 

(3) For indoor telecommunications purposes only, a listed 
sheet metal strap-type ground clamp having a rigid 
metal base that seats on the electrode and having a 
strap of such material and dimensions that it is not 
likely to stretch during or after installation 

(4) An equally substantial approved means 



Exception: A metal elbow that is installed in an under- 
ground installation of rigid nonmetallic conduit and is iso- 
lated from possible contact by a minimum cover of 450 mm 
(18 in.) to any part of the elbow shall not be required to be 
grounded. 

250.84 Underground Service Cable or Raceway. 

(A) Underground Service Cable. The sheath or armor of 
a continuous underground metal- sheathed or armored ser- 
vice cable system that is bonded to the grounded under- 
ground system shall not be required to be grounded at the 
building or structure. The sheath or armor shall be permit- 
ted to be insulated from the interior metal raceway conduit 
or piping. 

(B) Underground Service Raceway Containing Cable. 

An underground metal service raceway that contains a metal- 
sheathed or armored cable bonded to the grounded under- 
ground system shall not be required to be grounded at the 
building or structure. The sheath or armor shall be permitted to 
be insulated from the interior metal raceway or piping. 

250.86 Other Conductor Enclosures and Raceways. Ex- 
cept as permitted by 250.112(1), metal enclosures and race- 
ways for other than service conductors shall be grounded. 

Exception No. 1: Metal enclosures and raceways for con- 
ductors added to existing installations of open wire, knob 
and tube wiring, and nonmetallic-sheathed cable shall not 
be required to be grounded where these enclosures or wir- 
ing methods comply with (1) through (4) as follows : 

(1) Do not provide an equipment ground 

(2) Are in runs of less than 7.5 m (25 ft) 

(3) Are free from probable contact with ground, grounded 
metal, metal lath, or other conductive material 

(4) Are guarded against contact by persons 

Exception No. 2: Short sections of metal enclosures or 
raceways used to provide support or protection of cable 
assemblies from physical damage shall not be required to 
be grounded. 

Exception No. 3: A metal elbow shall not be required to be 
grounded where it is installed in a nonmetallic raceway 
and is isolated from possible contact by a minimum cover 
of 450 mm (18 in.) to any part of the elbow or is encased in 
not less than 50 mm (2 in.) of concrete. 



IV. Enclosure, Raceway, and Service Cable Grounding '• Bonding 



250.80 Service Raceways and Enclosures. Metal enclo- 
sures and raceways for service conductors and equipment 
shall be grounded. 



250.90 General. Bonding shall be provided where neces- 
sary to ensure electrical continuity and the capacity to con- 
duct safely any fault current likely to be imposed. 



2005 Edition NATIONAL ELECTRICAL CODE 



70-105 



250.92 



ARTICLE 250 — GROUNDING AND BONDING 



250.92 Services. 

(A) Bonding of Services. The non-current-carrying metal 
parts of equipment indicated in 250.92(A)(1), (A)(2), and 
(A)(3) shall be effectively bonded together. 

(1) The service raceways, cable trays, cablebus framework, 
auxiliary gutters, or service cable armor or sheath ex- 
cept as permitted in 250.84. 

(2) All service enclosures containing service conductors, 
including meter fittings, boxes, or the like, interposed 
in the service raceway or armor. 

(3) Any metallic raceway or armor enclosing a grounding 
electrode conductor as specified in 250.64(B). Bonding 
shall apply at each end and to all intervening raceways, 
boxes, and enclosures between the service equipment 
and the grounding electrode. 

(B) Method of Bonding at the Service. Electrical conti- 
nuity at service equipment, service raceways, and service 
conductor enclosures shall be ensured by one of the follow- 
ing methods: 

(1) Bonding equipment to the grounded service conductor 
in a manner provided in 250.8 

(2) Connections utilizing threaded couplings or threaded 
bosses on enclosures where made up wrenchtight 

(3) Threadless couplings and connectors where made up 
tight for metal raceways and metal-clad cables 

(4) Other listed devices, such as bonding-type lockouts, 
bushings, or bushings with bonding jumpers 

Bonding jumpers meeting the other requirements of this 
article shall be used around concentric or eccentric knock- 
outs that are punched or otherwise formed so as to impair 
the electrical connection to ground. Standard locknuts or 
bushings shall not be the sole means for the bonding re- 
quired by this section. 

250.94 Bonding for Other Systems. An accessible means 
external to enclosures for connecting intersystem bonding 
and grounding electrode conductors shall be provided at the 
service equipment and at the disconnecting means for any 
additional buildings or structures by at least one of the 
following means: 

(1) Exposed nonflexible metallic raceways 

(2) Exposed grounding electrode conductor 

(3) Approved means for the external connection of a cop- 
per or other corrosion-resistant bonding or grounding 
conductor to the grounded raceway or equipment 

FPN No. 1: A 6 AWG copper conductor with one end 
bonded to the grounded nonflexible metallic raceway or 
equipment and with 150 mm (6 in.) or more of the other 
end made accessible on the outside wall is an example of 
the approved means covered in 250.94(3). 



FPN No. 2: See 800.100, 810.21, and 820.100 for bonding 
and grounding requirements for communications circuits, 
radio and television equipment, and CATV circuits. 

250.96 Bonding Other Enclosures. 

(A) General. Metal raceways, cable trays, cable armor, cable 
sheath, enclosures, frames, fittings, and other metal non- 
current-carrying parts that are to serve as grounding conduc- 
tors, with or without the use of supplementary equipment 
grounding conductors, shall be effectively bonded where nec- 
essary to ensure electrical continuity and the capacity to con- 
duct safely any fault current likely to be imposed on them. 
Any nonconductive paint, enamel, or similar coating shall be 
removed at threads, contact points, and contact surfaces or be 
connected by means of fittings designed so as to make such 
removal unnecessary. 

(B) Isolated Grounding Circuits. Where required for the 
reduction of electrical noise (electromagnetic interference) on 
the grounding circuit, an equipment enclosure suppUed by a 
branch circuit shall be permitted to be isolated from a raceway 
containing circuits supplying only that equipment by one or 
more listed nonmetallic raceway fittings located at the point of 
attachment of the raceway to the equipment enclosure. The 
metal raceway shall comply with provisions of this article and 
shall be supplemented by an internal insulated equipment 
grounding conductor installed in accordance with 250.146(D) 
to ground the equipment enclosure. 



FPN: Use of an isolated equipment grounding conductor 
does not relieve the requirement for grounding the raceway 
system. 



250.97 Bonding for Over 250 Volts. For circuits of over 
250 volts to ground, the electrical continuity of metal race- 
ways and cables with metal sheaths that contain any con- 
ductor other than service conductors shall be ensured by 
one or more of the methods specified for services in 
250.92(B), except for (B)(1). 

Exception: Where oversized, concentric, or eccentric 
knockouts are not encountered, or where a box or enclosure 
with concentric or eccentric knockouts listed to provide a 
permanent, reliable electrical bond, the following methods 
shall be permitted: 

(1) Threadless couplings and connectors for cables with 
metal sheaths 

(2) Two locknuts, on rigid metal conduit or intermediate 
metal conduit, one inside and one outside of boxes and 
cabinets 

(3) Fittings with shoulders that seat firmly against the box or 
cabinet, such as electrical metallic tubing connectors, 
flexible metal conduit connectors, and cable connectors, 
with one locknut on the inside of boxes and cabinets 

(4) Listed fittings 



70-106 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 250 — GROUNDING AND BONDING 



250.104 



• 



250.98 Bonding Loosely Jointed Metal Raceways. Ex- 
pansion fittings and telescoping sections of metal raceways 
shall be made electrically continuous by equipment bond- 
ing jumpers or other means. 

250.100 Bonding in Hazardous (Classified) Locations. 

Regardless of the voltage of the electrical system, the elec- 
trical continuity of non-current-carrying metal parts of 
equipment, raceways, and other enclosures in any hazardous 
(classified) location as defined in Article 500 shall be ensured 
by any of the methods specified in 250.92(B)(2) through 
(B)(4) that are approved for the wiring method used. One or 
more of these bonding methods shall be used whether or not 
supplementary equipment grounding conductors are installed. 

250.102 Equipment Bonding Jumpers. 

(A) Material. Equipment bonding jumpers shall be of cop- 
per or other corrosion-resistant material. A bonding jumper 
shall be a wire, bus, screw, or similar suitable conductor. 

(B) Attachment. Equipment bonding jumpers shall be at- 
tached in the manner specified by the applicable provisions 
of 250.8 for circuits and equipment and by 250.70 for 
grounding electrodes. 

(C) Size — Equipment Bonding Jumper on Supply Side 
of Service. The bonding jumper shall not be smaller than the 
sizes shown in Table 250.66 for grounding electrode conduc- 
tors. Where the service-entrance phase conductors are larger 
than 1100 kcmil copper or 1750 kcmil aluminum, the bonding 
jumper shall have an area not less than 12V2 percent of the 
area of the largest phase conductor except that, where the 
phase conductors and the bonding jumper are of different ma- 
terials (copper or aluminum), the minimum size of the bond- 
ing jumper shall be based on the assumed use of phase con- 
ductors of the same material as the bonding jumper and with 
an ampacity equivalent to that of the installed phase conduc- 
tors. Where the service-entrance conductors are paralleled in 
two or more raceways or cables, the equipment bonding 
jumper, where routed with the raceways or cables, shall be run 
in parallel. The size of the bonding jumper for each raceway 
or cable shall be based on the size of the service-entrance 
conductors in each raceway or cable. 

(D) Size — Equipment Bonding Jumper on Load Side 
of Service. The equipment bonding jumper on the load side 
of the service overcurrent devices shall be sized, as a mini- 
mum, in accordance with the sizes listed in Table 250.122, 
but shall not be required to be larger than the largest un- 
grounded circuit conductors supplying the equipment and 
shall not be smaller than 14 AWG. 

A single common continuous equipment bonding 
jumper shall be permitted to bond two or more raceways or 
cables where the bonding jumper is sized in accordance 



with Table 250.122 for the largest overcurrent device sup- 
plying circuits therein. 

(E) Installation. The equipment bonding jumper shall be 
permitted to be installed inside or outside of a raceway or 
enclosure. Where installed on the outside, the length of the 
equipment bonding jumper shall not exceed 1.8 m (6 ft) and 
shall be routed with the raceway or enclosure. Where installed 
inside of a raceway, the equipment bonding jumper shall com- 
ply with the requirements of 250.119 and 250.148. 

Exception: An equipment bonding jumper longer than 1.8 m 
(6 ft) shall be permitted at outside pole locations for the pur- 
pose of bonding or grounding isolated sections of metal race- 
ways or elbows installed in exposed risers of metal conduit or 
other metal raceway. 

250.104 Bonding of Piping Systems and Exposed 
Structural Steel. 

(A) Metal Water Piping. The metal water piping system 
shall be bonded as required in (A)(1), (A)(2), or (A)(3) of 
this section. The bonding jumper(s) shall be installed in 
accordance with 250.64(A), (B), and (E). The points of 
attachment of the bonding jumper(s) shall be accessible. 

(1) General. Metal water piping system(s) installed in or at- 
tached to a building or structure shall be bonded to the service 
equipment enclosure, the grounded conductor at the service, 
the grounding electrode conductor where of sufficient size, or 
to the one or more grounding electrodes used. The bonding 
jumper(s) shall be sized in accordance with Table 250.66 ex- 
cept as permitted in 250.104(A)(2) and (A)(3). 

(2) Buildings of Multiple Occupancy. In buildings of 
multiple occupancy where the metal water piping system(s) 
installed in or attached to a building or structure for the 
individual occupancies is metallically isolated from all 
other occupancies by use of nonmetallic water piping, the 
metal water piping system(s) for each occupancy shall be 
permitted to be bonded to the equipment grounding termi- 
nal of the panelboard or switchboard enclosure (other than 
service equipment) supplying that occupancy. The bonding 
jumper shall be sized in accordance with Table 250.122. 

(3) Multiple Buildings or Structures Supplied by a 
Feeder(s) or Branch Circuit(s). The metal water piping 
system(s) installed in or attached to a building or structure 
shall be bonded to the building or structure disconnecting 
means enclosure where located at the building or structure, to 
the equipment grounding conductor run with the supply con- 
ductors, or to the one or more grounding electrodes used. The 
bonding jumper(s) shall be sized in accordance with 250.66, 
based on the size of the feeder or branch circuit conductors 
that supply the building. The bonding jumper shall not be 
required to be larger than the largest ungrounded feeder or 
branch circuit conductor supplying the building. 



2005 Edition NATIONAL ELECTRICAL CODE 



70-107 



250.106 



ARTICLE 250 — GROUNDING AND BONDING 



(B) Other Metal Piping. Where installed in or attached to a 
building or structure, metal piping system(s), including gas 
piping, that is likely to become energized shall be bonded to 
the service equipment enclosure, the grounded conductor at 
the service, the grounding electrode conductor where of suffi- 
cient size, or to the one or more grounding electrodes used. 
The bonding jumper(s) shall be sized in accordance with 
250.122, using the rating of the circuit that is likely to energize 
the piping system(s). The equipment grounding conductor for 
the circuit that is likely to energize the piping shall be permit- 
ted to serve as the bonding means. The points of attachment of 
the bonding jumper(s) shall be accessible. 

FPN: Bonding all piping and metal air ducts within the 
premises will provide additional safety. 

(C) Structural Metal. Exposed structural metal that is in- 
terconnected to form a metal building frame and is not 
intentionally grounded and is hkely to become energized 
shall be bonded to the service equipment enclosure, the 
grounded conductor at the service, the grounding electrode 
conductor where of sufficient size, or the one or more 
grounding electrodes used. The bonding jumper(s) shall be 
sized in accordance with Table 250.66 and installed in ac- 
cordance with 250.64(A), (B), and (E). The points of at- 
tachment of the bonding jumper(s) shall be accessible. 

(D) Separately Derived Systems. Metal water piping sys- 
tems and structural metal that is interconnected to form a 
building frame shall be bonded to separately derived sys- 
tems in accordance with (D)(1) through (D)(3). 

(1) Metal Water Piping System(s). The grounded conduc- 
tor of each separately derived system shall be bonded to the 
nearest available point of the metal water piping system(s) 
in the area served by each separately derived system. This 
connection shall be made at the same point on the sepa- 
rately derived system where the grounding electrode con- 
ductor is connected. Each bonding jumper shall be sized in 
accordance with Table 250.66 based on the largest un- 
grounded conductor of the separately derived system. 

Exception No. 1: A separate bonding jumper to the metal 
water piping system shall not be required where the metal 
water piping system is used as the grounding electrode for 
the separately derived system. 

Exception No. 2: A separate water piping bonding jumper 
shall not be required where the metal frame of a building or 
structure is used as the grounding electrode for a sepa- 
rately derived system and is bonded to the metal water 
piping in the area served by the separately derived system. 

(2) Structural Metal. Where exposed structural metal that 
is interconnected to form the building frame exists in the area 
served by the separately derived system, it shall be bonded to 
the grounded conductor of each separately derived system. 



This connection shall be made at the same point on the sepa- 
rately derived system where the grounding electrode conduc- 
tor is connected. Each bonding jumper shall be sized in accor- 
dance with Table 250.66 based on the largest ungrounded 
conductor of the separately derived system. 

Exception No. 1: A separate bonding jumper to the build- 
ing structural metal shall not be required where the metal 
frame of a building or structure is used as the grounding 
electrode for the separately derived system. 
Exception No. 2: A separate bonding jumper to the building 
structural metal shall not be required where the water piping 
of a building or structure is used as the grounding electrode 
for a separately derived system and is bonded to the building 
structural metal in the area served by the separately derived 
system. 

(3) Common Grounding Electrode Conductor. Where a 
common grounding electrode conductor is installed for mul- 
tiple separately derived systems as permitted by 250.30(A)(4), 
and exposed structural metal that is interconnected to form the 
building frame or interior metal piping exists in the area 
served by the separately derived system, the metal piping and 
the structural metal member shall be bonded to the common 
grounding electrode conductor. 

Exception: A separate bonding jumper from each derived 
system to metal water piping and to structural metal mem- 
bers shall not be required where the metal water piping and 
the structural metal members in the area served by the 
separately derived system are bonded to the common 
grounding electrode conductor. 

250.106 Lightning Protection Systems. The lightning 
protection system ground terminals shall be bonded to the 
building or structure grounding electrode system. 

FPN No. 1 : See 250.60 for use of air terminals. For further 
information, see NFPA 780-2004, Standard for the Instal- 
lation of Lightning Protection Systems, which contains de- 
tailed information on grounding, bonding, and spacing from 
lightning protection systems. 

FPN No. 2: Metal raceways, enclosures, frames, and other 
non-current-carrying metal parts of electric equipment in- 
stalled on a building equipped with a lightning protection 
system may require bonding or spacing from the lightning 
protection conductors in accordance with NFPA 780-2004, 
Standard for the Installation of Lightning Protection Sys- 
tems. Separation from lightning protection conductors is 
typically 1.8 m (6 ft) through air or 900 mm (3 ft) through 
dense materials such as concrete, brick, or wood. 

VI. Equipment Grounding and Equipment 
Grounding Conductors 

250.110 Equipment Fastened in Place or Connected by 
Permanent Wiring Methods (Fixed). Exposed non- 
current-carrying metal parts of fixed equipment likely to 
become energized shall be grounded under any of the fol- 
lowing conditions: 



• 



70-108 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 250 — GROUNDING AND BONDING 



250.114 



• 



• 



(1) Where within 2.5 m (8 ft) vertically or 1.5 m (5 ft) 
horizontally of ground or grounded metal objects and 
subject to contact by persons 

(2) Where located in a wet or damp location and not isolated 

(3) Where in electrical contact with metal 

(4) Where in a hazardous (classified) location as covered 
by Articles 500 through 517 

(5) Where supphed by a metal-clad, metal-sheathed, metal- 
raceway, or other wiring method that provides an equip- 
ment ground, except as permitted by 250.86, Exception 
No. 2, for short sections of metal enclosures 

(6) Where equipment operates with any terminal at over 
150 volts to ground 

Exception No. 1: Metal frames of electrically heated ap- 
pliances, exempted by special permission, in which case the 
frames shall be permanently and effectively insulated from 
ground. 

Exception No. 2: Distribution apparatus, such as trans- 
former and capacitor cases, mounted on wooden poles, at a 
height exceeding 2.5 m (8 ft) above ground or grade level. 

Exception No. 3: Listed equipment protected by a system 
of double insulation, or its equivalent, shall not be required 
to be grounded. Where such a system is employed, the 
equipment shall be distinctively marked. 

250.112 Fastened in Place or Connected by Permanent 
Wiring Methods (Fixed) — Specific. Exposed, non-current- 
carrying metal parts of the kinds of equipment described in 
250.112(A) through (K), and non-current-carrying metal parts 
of equipment and enclosures described in 250.112(L) and (M), 
shall be grounded regardless of voltage. 

(A) Switchboard Frames and Structures. Switchboard 
frames and structures supporting switching equipment, ex- 
cept frames of 2-wire dc switchboards where effectively 
insulated from ground. 

(B) Pipe Organs. Generator and motor frames in an elec- 
trically operated pipe organ, unless effectively insulated 
from ground and the motor driving it. 

(C) Motor Frames. Motor frames, as provided by 430.242. 

(D) Enclosures for Motor Controllers. Enclosures for 
motor controllers unless attached to ungrounded portable 
equipment. 

(E) Elevators and Cranes. Electric equipment for eleva- 
tors and cranes. 

(F) Garages, Theaters, and Motion Picture Studios. 

Electric equipment in commercial garages, theaters, and 
motion picture studios, except pendant lampholders sup- 
plied by circuits not over 150 volts to ground. 



(G) Electric Signs. Electric signs, outline lighting, and as- 
sociated equipment as provided in Article 600. 

(H) Motion Picture Projection Equipment. Motion pic- 
ture projection equipment. 

(I) Power-Limited Remote-Control, Signaling, and Fire 
Alarm Circuits. Equipment supplied by Class 1 power- 
limited circuits and Class 1, Class 2, and Class 3 remote- 
control and signaling circuits, and by fire alarm circuits, 
shall be grounded where system grounding is required by 
Part II or Part VIII of this article. 

(J) Luminaires (Lighting Fixtures). Luminaires (lighting 
fixtures) as provided in Part V of Article 410. 

(K) Skid Mounted Equipment. Permanently mounted 
electrical equipment and skids shall be grounded with an 
equipment bonding jumper sized as required by 250.122. 

(L) Motor-Operated Water Pumps. Motor-operated wa- 
ter pumps, including the submersible type. 

(M) Metal Well Casings. Where a submersible pump is 
used in a metal well casing, the well casing shall be bonded 
to the pump circuit equipment grounding conductor. 

250.114 Equipment Connected by Cord and Plug. Un- 
der any of the conditions described in 250.114(1) through 
(4), exposed non-current-carrying metal parts of cord-and- 
plug-connected equipment likely to become energized shall 
be grounded. 

Exception: Listed tools, listed appliances, and listed equip- 
ment covered in 250.114(2) through (4) shall not be required 
to be grounded where protected by a system of double insula- 
tion or its equivalent. Double insulated equipment shall be 
distinctively marked. 

(1) In hazardous (classified) locations (see Articles 500 
through 517) 

(2) Where operated at over 150 volts to ground 

Exception No. 1: Motors, where guarded, shall not be 
required to be grounded. 

Exception No. 2: Metal frames of electrically heated ap- 
pliances, exempted by special permission, shall not be re- 
quired to be grounded, in which case the frames shall be 
permanently and effectively insulated from ground. 

(3) In residential occupancies: 

a. Refrigerators, freezers, and air conditioners 

b. Clothes-washing, clothes-drying, dish-washing ma- 
chines; kitchen waste disposers; information tech- 
nology equipment; sump pumps and electrical 
aquarium equipment 



2005 Edition 



NATIONAL ELECTRICAL CODE 



70-109 



250.116 



ARTICLE 250 — GROUNDING AND BONDING 



c. Hand-held motor-operated tools, stationary and fixed 
motor-operated tools, light industrial motor-operated 
tools 

d. Motor-operated appliances of the following types: 
hedge clippers, lawn mowers, snow blowers, and 
wet scrubbers 

e. Portable handlamps 

(4) In other than residential occupancies: 

a. Refrigerators, freezers, and air conditioners 

b. Clothes-washing, clothes-drying, dish-washing ma- 
chines; information technology equipment; sump 
pumps and electrical aquarium equipment 

c. Hand-held motor-operated tools, stationary and fixed 
motor-operated tools, Ught industrial motor-operated 
tools 

d. Motor-operated appliances of the following types: 
hedge chppers, lawn mowers, snow blowers, and 
wet scrubbers 

e. Portable handlamps 

f. Cord-and-plug-connected appliances used in damp 
or wet locations or by persons standing on the 
ground or on metal floors or working inside of metal 
tanks or boilers 

g. Tools likely to be used in wet or conductive locations 

Exception: Tools and portable handlamps likely to be used 
in wet or conductive locations shall not be required to be 
grounded where supplied through an isolating transformer 
with an ungrounded secondary of not over 50 volts. 

250.116 Nonelectric Equipment. The metal parts of 
nonelectric equipment described in this section shall be 
grounded. 

(1) Frames and tracks of electrically operated cranes and 
hoists 

(2) Frames of nonelectrically driven elevator cars to which 
electric conductors are attached 

(3) Hand-operated metal shifting ropes or cables of electric 
elevators 

FPN: Where extensive metal in or on buildings may be- 
come energized and is subject to personal contact, adequate 
bonding and grounding will provide additional safety. 

250.118 Types of Equipment Grounding Conductors. 

The equipment grounding conductor run with or enclosing 
the circuit conductors shall be one or more or a combina- 
tion of the following: 

(1) A copper, aluminum, or copper-clad aluminum con- 
ductor. This conductor shall be solid or stranded; in- 
sulated, covered, or bare; and in the form of a wire or 
a busbar of any shape. 

(2) Rigid metal conduit. 



(3) Intermediate metal conduit. 

(4) Electrical metallic tubing. 

(5) Listed flexible metal conduit meeting all the following 
conditions: 

a. The conduit is terminated in fittings listed for 
grounding. 

b. The circuit conductors contained in the conduit are 
protected by overcurrent devices rated at 20 am- 
peres or less. 

c. The combined length of flexible metal conduit and 
flexible metallic tubing and liquidtight flexible 
metal conduit in the same ground return path does 
not exceed 1.8 m (6 ft). 

d. Where used to connect equipment where flexibility 
is necessary after installation, an equipment 
grounding conductor shall be installed. 

(6) Listed liquidtight flexible metal conduit meeting all 
the following conditions: 

a. The conduit is terminated in fittings listed for 
grounding. 

b. For metric designators 12 through 16 (trade sizes 
Vs through Vi), the circuit conductors contained in 
the conduit are protected by overcurrent devices 
rated at 20 amperes or less. 

c. For metric designators 21 through 35 (trade sizes 
3/4 through 1 V4), the circuit conductors contained in 
the conduit are protected by overcurrent devices 
rated not more than 60 amperes and there is no 
flexible metal conduit, flexible metallic tubing, or 
liquidtight flexible metal conduit in trade sizes 
metric designators 12 through 16 (trade sizes Vs 
through V2) in the grounding path. 

d. The combined length of flexible metal conduit and 
flexible metallic tubing and liquidtight flexible 
metal conduit in the same ground return path does 
not exceed 1.8 m (6 ft). 

e. Where used to connect equipment where flexibility is 
necessary after installation, an equipment grounding 
conductor shall be installed. 

(7) Flexible metallic tubing where the tubing is termi- 
nated in fittings listed for grounding and meeting the 
following conditions: 

a. The circuit conductors contained in the tubing are 
protected by overcurrent devices rated at 20 am- 
peres or less. 

b. The combined length of flexible metal conduit and 
flexible metallic tubing and liquidtight flexible 
metal conduit in the same ground return path does 
not exceed 1.8 m (6 ft). 

(8) Armor of Type AC cable as provided in 320.108. 

(9) The copper sheath of mineral-insulated, metal-sheathed 
cable. 



• 



70-110 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 250 — GROUNDING AND BONDING 



250.122 



• 



(10) Type MC cable where listed and identified for ground- 
ing in accordance with the following: 

a. The combined metallic sheath and grounding con- 
ductor of interlocked metal tape-type MC cable 

b. The metallic sheath or the combined metallic 
sheath and grounding conductors of the smooth or 
corrugated tube type MC cable 

(11) Cable trays as permitted in 392.3(C) and 392.7. 

(12) Cablebus framework as permitted in 370.3. 

(13) Other fisted electrically continuous metal raceways 
and fisted auxiliary gutters. 

(14) Surface metal raceways listed for grounding. 

250.119 Identification of Equipment Grounding Con- 
ductors. Unless required elsewhere in this Code, equip- 
ment grounding conductors shall be permitted to be bare, 
covered, or insulated. Individually covered or insulated 
equipment grounding conductors shall have a continuous 
outer finish that is either green or green with one or more 
yellow stripes except as permitted in this section. Conduc- 
tors with insulation or individual covering that is green, 
green with one or more yellow stripes, or otherwise identi- 
fied as permitted by this section shall not be used for un- 
grounded or grounded circuit conductors. 

(A) Conductors Larger Than 6 AWG. Equipment ground- 
ing conductors larger than 6 AWG shall comply with 
250.119(A)(1) and (A)(2). 

(1) An insulated or covered conductor larger than 6 AWG 
shall be permitted, at the time of installation, to be 
permanently identified as an equipment grounding con- 
ductor at each end and at every point where the con- 
ductor is accessible. 

Exception: Conductors larger than 6 AWG shall not be 
required to be marked in conduit bodies that contain no 
splices or unused hubs. 

(2) Identification shall encircle the conductor and shall be 
accomplished by one of the following: 

a. Stripping the insulation or covering from the entire 
exposed length 

b. Coloring the exposed insulation or covering green 

c. Marking the exposed insulation or covering with 
green tape or green- adhesive labels 

(B) Multiconductor Cable. Where the conditions of main- 
tenance and supervision ensure that only quafified persons ser- 
vice the installation, one or more insulated conductors in a 
multiconductor cable, at the time of installation, shall be per- 
mitted to be permanentiy identified as equipment grounding 
conductors at each end and at every point where the conduc- 
tors are accessible by one of the following means: 

(1) Stripping the insulation from the entire exposed length 

(2) Coloring the exposed insulation green 



(3) Marking the exposed insulation with green tape or 
green adhesive labels 

(C) Flexible Cord. An uninsulated equipment grounding 
conductor shall be permitted, but, if individually covered, 
the covering shall have a continuous outer finish that is 
either green or green with one or more yellow stripes. 

250.120 Equipment Grounding Conductor Installation. 

An equipment grounding conductor shall be installed in 
accordance with 250.120(A), (B), and (C). 

(A) Raceway, Cable Trays, Cable Armor, Cablebus, or 
Cable Sheaths. Where it consists of a raceway, cable tray, 
cable armor, cablebus framework, or cable sheath or where 
it is a wire within a raceway or cable, it shall be instaUed in 
accordance with the applicable provisions in this Code us- 
ing fittings for joints and terminations approved for use 
with the type raceway or cable used. All connections, 
joints, and fittings shah be made tight using suitable tools. 

(B) Aluminum and Copper-Clad Aluminum Conductors. 

Equipment grounding conductors of bare or insulated alu- 
minum or copper-clad aluminum shall be permitted. Bare 
conductors shall not come in direct contact with masonry or 
the earth or where subject to corrosive conditions. Alumi- 
num or copper-clad aluminum conductors shall not be ter- 
minated within 450 mm (18 in.) of the earth. 

(C) Equipment Grounding Conductors Smaller Than 

6 AWG. Equipment grounding conductors smaller than 
6 AWG shall be protected from physical damage by a 
raceway or cable armor except where run in hollow 
spaces of walls or partitions, where not subject to physi- 
cal damage, or where protected from physical damage. 

250.122 Size of Equipment Grounding Conductors. 

(A) General. Copper, aluminum, or copper-clad aluminum 
equipment grounding conductors of the wire type shall not be 
smaller than shown in Table 250.122 but shall not be required 
to be larger than the circuit conductors supplying the equip- 
ment. Where a raceway or a cable armor or sheath is used as 
the equipment grounding conductor, as provided in 250.118 
and 250.134(A), it shall comply with 250.4(A)(5) or (B)(4). 

(B) Increased in Size. Where ungrounded conductors are 
increased in size, equipment grounding conductors, where 
installed, shall be increased in size proportionately accord- 
ing to circular mil area of the ungrounded conductors. 

(C) Multiple Circuits. Where a single equipment ground- 
ing conductor is run with multiple circuits in the same 
raceway or cable, it shall be sized for the largest overcur- 
rent device protecting conductors in the raceway or cable. 



2005 Edition 



NATIONAL ELECTRICAL CODE 



70-11] 



250.124 



ARTICLE 250 — GROUNDING AND BONDING 



(D) Motor Circuits. Where the overcurrent device consists 
of an instantaneous trip circuit breaker or a motor short-circuit 
protector, as allowed in 430.52, the equipment grounding con- 
ductor size shall be permitted to be based on the rating of the 
motor overload protective device but shall not be less than the 
size shown in Table 250.122. 

(E) Flexible Cord and Fixture Wire. The equipment 
grounding conductor in a flexible cord with the largest cir- 
cuit conductor 10 AWG or smaller, and the equipment 
grounding conductor used with fixture wires of any size in 
accordance with 240.5, shall not be smaller than 18 AWG 
copper and shall not be smaller than the circuit conductors. 
The equipment grounding conductor in a flexible cord with 
a circuit conductor larger than 10 AWG shall be sized in 
accordance with Table 250.122. 

(F) Conductors in Parallel. Where conductors are run in 
parallel in multiple raceways or cables as permitted in 
310.4, the equipment grounding conductors, where used, 
shall be run in parallel in each raceway or cable. One of the 
methods in 250.122(F)(1) or (F)(2) shall be used to ensure 
the equipment grounding conductors are protected. 

(1) Based on Rating of Overcurrent Protective Device. 

Each parallel equipment grounding conductor shall be sized 
on the basis of the ampere rating of the overcurrent device 
protecting the circuit conductors in the raceway or cable in 
accordance with Table 250.122. 

(2) Ground-Fault Protection of Equipment Installed. 

Where ground-fault protection of equipment is installed, 
each parallel equipment grounding conductor in a multi- 
conductor cable shall be permitted to be sized in accor- 
dance with Table 250.122 on the basis of the trip rating of 
the ground-fault protection where the following conditions 
are met: 

(1) Conditions of maintenance and supervision ensure that 
only qualified persons will service the installation. 

(2) The ground-fault protection equipment is set to trip at 
not more than the ampacity of a single ungrounded 
conductor of one of the cables in parallel. 

(3) The ground-fault protection is listed for the purpose of 
protecting the equipment grounding conductor. 

(G) Feeder Taps. Equipment grounding conductors run with 
feeder taps shall not be smaller than shown in Table 250.122 
based on the rating of the overcurrent device ahead of 
the feeder but shall not be required to be larger than the 
tap conductors. 

250.124 Equipment Grounding Conductor Continuity. 

(A) Separable Connections. Separable connections such 
as those provided in drawout equipment or attachment 
plugs and mating connectors and receptacles shall provide 



Table 250.122 Minimum Size Equipment Grounding 
Conductors for Grounding Raceway and Equipment 



Rating or Setting of 
Automatic Overcurrent 
Device in Circuit Ahead 
of Equipment, Conduit, 

etc., Not Exceeding 
(Amperes) 



Size (AWG or Ikcmil) 



Copper 



Aluminum or 
Copper-Clad 
Aluminum''' 



15 


14 


12 


20 


12 


10 


30 


10 


8 


40 


10 


8 


60 


10 


8 


100 


8 


6 


200 


6 


4 


300 


4 


2 


400 


3 


1 


500 


2 


1/0 


600 


1 


2/0 


800 


1/0 


3/0 


1000 


2/0 


4/0 


1200 


3/0 


250 


1600 


4/0 


350 


2000 


250 


400 


2500 


350 


600 


3000 


400 


600 


4000 


500 


800 


5000 


700 


1200 


6000 


800 


1200 



Note: Where necessary to comply with 250.4(A)(5) oi' (B)(4), the 

equipment grounding conductor shall be sized larger than given in this 

table. 

*See installation restrictions in 250.120. 



for first-make, last-break of the equipment grounding con- 
ductor. First-make, last-break shall not be required where 
interlocked equipment, plugs, receptacles, and connectors 
preclude energization without grounding continuity. 

(B) Switches. No automatic cutout or switch shall be 
placed in the equipment grounding conductor of a premises 
wiring system unless the opening of the cutout or switch 
disconnects all sources of energy. 

250.126 Identification of Wiring Device Terminals. 

The terminal for the connection of the equipment ground- 
ing conductor shall be identified by one of the following: 

(1) A green, not readily removable terminal screw with a 
hexagonal head. 

(2) A green, hexagonal, not readily removable teiininal nut. 



• 



70-112 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 250 — GROUNDING AND BONDING 



250.138 



# 



(3) A green pressure wire connector. If the terminal for the 
grounding conductor is not visible, the conductor entrance 
hole shall be marked with the word green or ground, the 
letters G or GR, a grounding symbol, or otherwise identi- 
fied by a distinctive green color. If the terminal for the 
equipment grounding conductor is readily removable, the 
area adjacent to the terminal shall be similarly marked. 

FPN: See FPN Figure 250.126. 



FPN Figure 250.126 One Example of a Symbol Used to Iden- 
tify the Grounding Termination Point for an Equipment 
Grounding Conductor. 

VII. Methods of Equipment Grounding 

250.130 Equipment Grounding Conductor Connections. 

Equipment grounding conductor connections at the source of 
separately derived systems shall be made in accordance with 
250.30(A)(1). Equipment grounding conductor connections at 
service equipment shall be made as indicated in 250.130(A) or 
(B). For replacement of non-grounding-type receptacles with 
grounding-type receptacles and for branch-circuit extensions 
only in existing installations that do not have an equipment 
grounding conductor in the branch circuit, connections shall 
be permitted as indicated in 250.130(C). 

(A) For Grounded Systems. The connection shall be 
made by bonding the equipment grounding conductor to the 
grounded service conductor and the grounding electrode 
conductor. 

(B) For Ungrounded Systems. The connection shall be 
made by bonding the equipment grounding conductor to the 
grounding electrode conductor. 

(C) Nongrounding Receptacle Replacement or Branch 
Circuit Extensions. The equipment grounding conductor 
of a grounding-type receptacle or a branch-circuit extension 
shall be permitted to be connected to any of the following: 

(1) Any accessible point on the grounding electrode sys- 
tem as described in 250.50 

(2) Any accessible point on the grounding electrode con- 
ductor 

(3) The equipment grounding terminal bar within the en- 
closure where the branch circuit for the receptacle or 
branch circuit originates 

(4) For grounded systems, the grounded service conductor 
within the service equipment enclosure 

(5) For ungrounded systems, the grounding terminal bar 
within the service equipment enclosure 

FPN: See 406.3(D) for the use of a ground-fault circuit- 
interrupting type of receptacle. 



250.132 Short Sections of Raceway. Isolated sections of 
metal raceway or cable armor, where required to be grounded, 
shall be grounded in accordance with 250.134. 

250.134 Equipment Fastened in Place or Connected by 
Permanent Wiring Methods (Fixed) — Grounding. Unless 
grounded by connection to the grounded circuit conductor 
as permitted by 250.32, 250.140, and 250.142, non- 
current-carrying metal parts of equipment, raceways, and 
other enclosures, if grounded, shall be grounded by one of 
the following methods. 

(A) Equipment Grounding Conductor Types. By any of 

the equipment grounding conductors permitted by 250.118. 

(B) With Circuit Conductors. By an equipment ground- 
ing conductor contained within the same raceway, cable, or 
otherwise run with the circuit conductors. 

Exception No. 1: As provided in 250.130(C), the equipment 
grounding conductor shall be permitted to be run separately 
from the circuit conductors. 

Exception No. 2: For dc circuits, the equipment grounding 
conductor shall be permitted to be run separately from the 
circuit conductors. 

FPN No. 1 : See 250. 1 02 and 250. 1 68 for equipment bond- 
ing jumper requirements. 

FPN No. 2: See 400.7 for use of cords for fixed equipment. 

250.136 Equipment Considered Effectively Grounded. 

Under the conditions specified in 250.136(A) and (B), the 
non-current-carrying metal parts of the equipment shall be 
considered effectively grounded. 

(A) Equipment Secured to Grounded Metal Supports. 

Electrical equipment secured to and in electrical contact 
with a metal rack or structure provided for its support and 
grounded by one of the means indicated in 250.134. The 
structural metal frame of a building shall not be used as the 
required equipment grounding conductor for ac equipment. 

(B) Metal Car Frames. Metal car frames supported by 
metal hoisting cables attached to or running over metal 
sheaves or drums of elevator machines that are grounded 
by one of the methods indicated in 250.134. 

250.138 Cord-and-Plug-Connected Equipment. Non- 
current-carrying metal parts of cord-and-plug-connected 
equipment, if grounded, shall be grounded by one of the 
methods in 250.138(A) or (B). 

(A) By Means of an Equipment Grounding Conductor. 

By means of an equipment grounding conductor run with 
the power supply conductors in a cable assembly or flexible 
cord properly terminated in a grounding-type attachment 
plug with one fixed grounding contact. 



2005 Edition NATIONAL ELECTRICAL CODE 



70-113 



250.140 



ARTICLE 250 — GROUNDING AND BONDING 



Exception: The grounding contacting pole of grounding - 
type plug-in ground-fault circuit interrupters shall be 
permitted to be of the movable, self-restoring type on 
circuits operating at not over 150 volts between any two 
conductors or over 150 volts between any conductor and 
ground. 

(B) By Means of a Separate Flexible Wire or Strap. By 

means of a separate flexible wire or strap, insulated or bare, 
protected as well as practicable against physical damage, 
where part of equipment. 

250.140 Frames of Ranges and Clothes Dryers. Frames 
of electric ranges, wall-mounted ovens, counter-mounted 
cooking units, clothes dryers, and outlet or junction 
boxes that are part of the circuit for these appliances 
shall be grounded in the manner specified by 250.134 or 
250.138. 

Exception: For existing branch circuit installations only 
where an equipment grounding conductor is not present in 
the outlet or junction box, the frames of electric ranges, 
wall-mounted ovens, counter-mounted cooking units, clothes 
dryers, and outlet or junction boxes that are part of the 
circuit for these appliances shall be permitted to be 
grounded to the grounded circuit conductor if all the 
following conditions are met. 

(1) The supply circuit is 120/240-volt, single-phase, 3-wire; 
or 208Y/120-volt derived from a 3-phase, 4-wire, wye- 
connected system. 

(2) The grounded conductor is not smaller than 10 AWG 
copper or 8 AWG aluminum. 

(3) The grounded conductor is insulated, or the grounded 
conductor is uninsulated and part of a Type SE service- 
entrance cable and the branch circuit originates at the 
service equipment. 

(4) Grounding contacts of receptacles furnished as part of 
the equipment are bonded to the equipment. 

250.142 Use of Grounded Circuit Conductor for 
Grounding Equipment. 

(A) Supply-Side Equipment. A grounded circuit conduc- 
tor shall be permitted to ground non-current-carrying metal 
parts of equipment, raceways, and other enclosures at any 
of the following locations: 

(1) On the supply side or within the enclosure of the ac 
service-disconnecting means 

(2) On the supply side or within the enclosure of the main 
disconnecting means for separate buildings as provided 
in 250.32(B) 



(3) On the supply side or within the enclosure of the 
main disconnecting means or overcurrent devices of 
a separately derived system where permitted by 
250.30(A)(1) 

(B) Load-Side Equipment. Except as permitted in 
250.30(A)(1) and 250.32(B), a grounded circuit conductor 
shall not be used for grounding non-current-carrying metal 
parts of equipment on the load side of the service discon- 
necting means or on the load side of a separately derived 
system disconnecting means or the overcurrent devices for 
a separately derived system not having a main disconnect- 
ing means. 

Exception No. 1: The frames of ranges, wall-mounted 
ovens, counter-mounted cooking units, and clothes dry- 
ers under the conditions permitted for existing installa- 
tions by 250.140 shall be permitted to be grounded by a 
grounded circuit conductor 

Exception No. 2: It shall be permissible to ground meter 
enclosures by connection to the grounded circuit conductor 
on the load side of the service disconnect where all of the 
following conditions apply: 

(1) No service ground-fault protection is installed. 

(2) All meter socket enclosures are located immediately 
adjacent to the service disconnecting means. 

(3) The size of the grounded circuit conductor is not smaller 
than the size specified in Table 250.122 for equipment 
grounding conductors. 

Exception No. 3: Direct-current systems shall be permitted 
to be grounded on the load side of the disconnecting means 
or overcurrent device in accordance with 250.164. 

Exception No. 4: Electrode-type boilers operating at over 
600 volts shall be grounded as required in 490.72(E)(1) and 
490.74. 



250.144 Multiple Circuit Connections. Where (equipment 
is required to be grounded and is supplied by separate con- 
nection to more than one circuit or grounded premises wir- 
ing system, a means for grounding shall be provided for 
each such connection as specified in 250.134 and 250.138. 

250.146 Connecting Receptacle Grounding Terminal to 
Box. An equipment bonding jumper shall be used to con- 
nect the grounding terminal of a grounding-type receptacle 
to a grounded box unless grounded as in 250.146(A) 
through (D). 



• 



70-114 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 250 — GROUNDING AND BONDING 



250.162 



• 



(A) Surface Mounted Box. Where the box is mounted on 
the surface, direct metal-to-metal contact between the de- 
vice yoke and the box or a contact yoke or device that 
complies with 250.146(B) shall be permitted to ground the 
receptacle to the box. At least one of the insulating washers 
shall be removed from receptacles that do not have a con- 
tact yoke or device that complies with 250.146(B) to ensure 
direct metal-to-metal contact. This provision shall not apply 
to cover-mounted receptacles unless the box and cover 
combination are listed as providing satisfactory ground 
continuity between the box and the receptacle. 

(B) Contact Devices or Yokes. Contact devices or yokes 
designed and listed as self-grounding shall be permitted 
in conjunction with the supporting screws to establish 
the grounding circuit between the device yoke and flush- 
type boxes. 

(C) Floor Boxes. Floor boxes designed for and listed as 
providing satisfactory ground continuity between the box 
and the device shall be permitted. 

(D) Isolated Receptacles. Where required for the reduc- 
tion of electrical noise (electromagnetic interference) on the 
grounding circuit, a receptacle in which the grounding ter- 
minal is purposely insulated from the receptacle mounting 
means shall be permitted. The receptacle grounding termi- 
nal shall be grounded by an insulated equipment grounding 
conductor run with the circuit conductors. This grounding 
conductor shall be permitted to pass through one or more 
panelboards without connection to the panelboard ground- 
ing terminal as permitted in 408.40, Exception, so as to 
terminate within the same building or structure directly at 
an equipment grounding conductor terminal of the appli- 
cable derived system or service. 

FPN: Use of an isolated equipment grounding conductor 
does not relieve the requirement for grounding the raceway 
system and outlet box. 

250.148 Continuity and Attachment of Equipment 
Grounding Conductors to Boxes. Where circuit conduc- 
tors are spliced within a box, or terminated on equipment 
within or supported by a box, any equipment grounding 
conductor(s) associated with those circuit conductors 
shall be spliced or joined within the box or to the box 
with devices suitable for the use in accordance with 
250.148(A) through (E). 

Exception: The equipment grounding conductor permit- 
ted in 250.146(D) shall not be required to be connected 
to the other equipment grounding conductors or to the 
box. 



(A) Connections. Connections and splices shall be made 
in accordance with 110.14(B) except that insulation shall 
not be required. 

(B) Grounding Continuity. The arrangement of ground- 
ing connections shall be such that the disconnection or the 
removal of a receptacle, luminaire (fixture), or other device 
fed from the box does not interfere with or interrupt the 
grounding continuity. 

(C) Metal Boxes. A connection shall be made between the 
one or more equipment grounding conductors and a metal 
box by means of a grounding screw that shall be used for 
no other purpose or a listed grounding device. 

(D) Nonmetallic Boxes. One or more equipment ground- 
ing conductors brought into a nonmetallic outlet box shall 
be arranged such that a connection can be made to any 
fitting or device in that box requiring grounding. 

(E) Solder. Connections depending solely on solder shall 
not be used. 



VIII. Direct-Current Systems 

250.160 General. Direct-current systems shall comply 
with Part VIII and other sections of Article 250 not specifi- 
cally intended for ac systems. 

250.162 Direct-Current Circuits and Systems to Be 
Grounded. Direct-current circuits and systems shall be 
grounded as provided for in 250.162(A) and (B). 

(A) Two-Wire, Direct-Current Systems. A 2-wire, dc sys- 
tem supplying premises wiring and operating at greater than 
50 volts but not greater than 300 volts shall be grounded. 

Exception No. 1: A system equipped with a ground detec- 
tor and supplying only industrial equipment in limited ar- 
eas shall not be required to be grounded. 

Exception No. 2: A rectifier-derived dc system supplied 
from an ac system complying with 250.20 shall not be re- 
quired to be grounded. 

Exception No. 3: Direct-current fire alarm circuits having 
a maximum current of 0.030 amperes as specified in Article 
760, Part III, shall not be required to be grounded. 

(B) Three-Wire, Direct-Current Systems. The neutral 
conductor of all 3-wire, dc systems supplying premises wir- 
ing shall be grounded. 



2005 Edition NATIONAL ELECTRICAL CODE 



70-115 



250.164 



ARTICLE 250 — GROUNDING AND BONDING 



250.164 Point of Connection for Direct-Current Systems. 

(A) Off-Premises Source. Direct-current systems to be 
grounded and supplied from an off-premises source shall 
have the grounding connection made at one or more supply 
stations. A grounding connection shall not be made at indi- 
vidual services or at any point on the premises wiring. 

(B) On-Premises Source. Where the dc system source is 
located on the premises, a grounding connection shall be 
made at one of the following: 

(1) The source 

(2) The first system disconnection means or overcurrent 
device 

(3) By other means that accomplish equivalent system pro- 
tection and that utilize equipment listed and identified 
for the use 

250.166 Size of Direct-Current Grounding Electrode 
Conductor. The size of the grounding electrode conductor for 
a dc system shall be as specified in 250.166(A) through (E). 

(A) Not Smaller Than the Neutral Conductor. Where 
the dc system consists of a 3-wire balancer set or a balancer 
winding with overcurrent protection as provided in 445.12(D), 
the grounding electrode conductor shall not be smaller than 
the neutral conductor and not smaller than 8 AWG copper or 
6 AWG aluminum. 

(B) Not Smaller Than the Largest Conductor. Where the 
dc system is other than as in 250.166(A), the grounding 
electrode conductor shall not be smaller than the largest 
conductor supplied by the system, and not smaller than 
8 AWG copper or 6 AWG aluminum. 

(C) Connected to Rod, Pipe, or Plate Electrodes. Where 
connected to rod, pipe, or plate electrodes as in 250.52(A)(5) 
or 250.52(A)(6), that portion of the grounding electrode con- 
ductor that is the sole connection to the grounding electrode 
shall not be required to be larger than 6 AWG copper wire or 
4 AWG aluminum wire. 

(D) Connected to a Concrete-Encased Electrode. Where 
connected to a concrete-encased electrode as in 250.52(A)(3), 
that portion of the grounding electrode conductor that is the 
sole connection to the grounding electrode shall not be re- 
quired to be larger than 4 AWG copper wire. 

(E) Connected to a Ground Ring. Where connected to a 
ground ring as in 250.52(A)(4), that portion of the ground- 
ing electrode conductor that is the sole connection to the 
grounding electrode shall not be required to be larger than 
the conductor used for the ground ring. 



250.168 Direct-Current Bonding Jumper. For dc sys- 
tems, the size of the bonding jumper shall not be smaller 
than the system grounding electrode conductor specified in 
250.166. 

250.169 Ungrounded Direct-Current Separately Derived 
Systems. Except as otherwise permitted in 250.34 for 
portable and vehicle-mounted generators, an ungrounded 
dc separately derived system supplied from a stand-alone 
power source (such as an engine-generator set) shall 
have a grounding electrode conductor connected to an 
electrode that complies with Part III to provide for 
grounding of metal enclosures, raceways, cables, and ex- 
posed non-current-carrying metal parts of equipment. 
The grounding electrode conductor connection shall be 
to the metal enclosure at any point on the separately 
derived system from the source to the first system dis- 
connecting means or overcurrent device, or it shall be 
made at the source of a separately derived system that 
has no disconnecting means or overcurrent devices. 

The size of the grounding electrode conductor shall be 
in accordance with 250.166. 

IX. Instruments, Meters, and Relays 

250.170 Instrument Transformer Circuits. Secondary 
circuits of current and potential instrument transformers shall 
be grounded where the primary windings are connected to 
circuits of 300 volts or more to ground and, where on switch- 
boards, shall be grounded irrespective of voltage. 

Exception: Circuits where the primary windings are con- 
nected to circuits of less than 1000 volts with no live parts or 
wiring exposed or accessible to other than qualified persons. 

250.172 Instrument Transformer Cases. Cases or frames 
of instrument transformers shall be grounded where acces- 
sible to other than qualified persons. 

Exception: Cases or frames of current transformers, the 
primaries of which are not over 150 volts to ground and 
that are used exclusively to supply current to meters. 

250.174 Cases of Instruments, Meters, and Relays Op- 
erating at Less Than 1000 Volts. Instruments, meters, and 
relays operating with windings or working parts at less than 
1000 volts shall be grounded as specified in 250.174(A), 
(B), or (C). 

(A) Not on Switchboards. Instruments, meters, and re- 
lays not located on switchboards, operating with wind- 
ings or working parts at 300 volts or more to ground, and 
accessible to other than qualified persons, shall have the 
cases and other exposed metal parts grounded. 



70-116 



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ARTICLE 250 — GROUNDING AND BONDING 



250.184 



(B) On Dead-Front Switchboards. Instruments, meters, 
and relays (whether operated from current and potential 
transformers or connected directly in the circuit) on switch- 
boards having no live parts on the front of the panels shall 
have the cases grounded. 

(C) On Live-Front Switchboards. Instruments, meters, 
and relays (whether operated from current and potential 
transformers or connected directly in the circuit) on 
switchboards having exposed live parts on the front of 
panels shall not have their cases grounded. Mats of in- 
sulating rubber or other suitable floor insulation shall be 
provided for the operator where the voltage to ground 
exceeds 150. 

250.176 Cases of Instruments, Meters, and Relays — 
Operating Voltage 1 kV and Over. Where instruments, 
meters, and relays have current-carrying parts of 1 kV and 
over to ground, they shall be isolated by elevation or pro- 
tected by suitable barriers, grounded metal, or insulating 
covers or guards. Their cases shall not be grounded. 

Exception: Cases of electrostatic ground detectors where 
the internal ground segments of the instrument are con- 
nected to the instrument case and grounded and the ground 
detector is isolated by elevation. 

250.178 Instrument Grounding Conductor. The ground- 
ing conductor for secondary circuits of instrument trans- 
formers and for instrument cases shall not be smaller than 
12 AWG copper or 10 AWG aluminum. Cases of instru- 
ment transformers, instruments, meters, and relays that are 
mounted directly on grounded metal surfaces of enclosures 
or grounded metal switchboard panels shall be considered 
to be grounded, and no additional grounding conductor 
shall be required. 

X. Grounding of Systems and Circuits of 1 kV and 
Over (High Voltage) 

250.180 General. Where high-voltage systems are 
grounded, they shall comply with all applicable provi- 
sions of the preceding sections of this article and with 
250.182 through 250.190, which supplement and modify 
the preceding sections. 

250.182 Derived Neutral Systems. A system neutral de- 
rived from a grounding transformer shall be permitted to be 
used for grounding high-voltage systems. 

250.184 Solidly Grounded Neutral Systems. Solidly 
grounded neutral systems shall be permitted to be either 
single point grounded or multigrounded neutral. 



(A) Neutral Conductor. 

(1) Insulation Level. The minimum insulation level for 
neutral conductors of solidly grounded systems shall be 
600 volts. 

Exception No. 1: Bare copper conductors shall be permit- 
ted to be used for the neutral of service entrances and the 
neutral of direct-buried portions of feeders. 

Exception No. 2: Bare conductors shall be permitted for 
the neutral of overhead portions installed outdoors. 

Exception No. 3: The neutral grounded conductor shall be 
permitted to be a bare conductor if isolated from phase 
conductors and protected from physical damage. 

FPN: See 225.4 for conductor covering where within 3.0 m 
(10 ft) of any building or other structure. 

(2) Ampacity. The neutral conductor shall be of suffi- 
cient ampacity for the load imposed on the conductor but 
not less than 33 Vs percent of the ampacity of the phase 
conductors. 

Exception: In industrial and commercial premises under 
engineering supervision, it shall be permissible to size the 
ampacity of the neutral conductor to not less than 20 per- 
cent of the ampacity of the phase conductor 

(B) Single Point Grounded System. Where a single point 
grounded neutral system is used, the following shall apply: 

(1) A single point grounded system shall be permitted to be 
supplied from (a) or (b): 

a. A separately derived system 

b. A multigrounded neutral system with an equipment 
grounding conductor connected to the multigrounded 
neutral at the source of the single point grounded 
system 

(2) A grounding electrode shall be provided for the system. 

(3) A grounding electrode conductor shall connect the 
grounding electrode to the system neutral. 

(4) A bonding jumper shall connect the equipment ground- 
ing conductor to the grounding electrode conductor. 

(5) An equipment bonding conductor shall be provided to 
each building, structure, and equipment enclosure. 

(6) A neutral shall only be required where phase to neutral 
loads are supplied. 

(7) The neutral, where provided, shall be insulated and iso- 
lated from earth except at one location. 

(8) An equipment grounding conductor shall be run with the 
phase conductors and shaU comply with (a), (b), and (c): 

a. Shall not carry continuous load 
• b. May be bare or insulated 

c. Shall have sufficient ampacity for fault current duty 



2005 Edition 



NATIONAL ELECTRICAL CODE 



70-117 



250.186 



ARTICLE 250 — GROUNDING AND BONDING 



(C) Multigrounded Neutral Systems. Where a multi- 
grounded neutral system is used, the following shall apply: 

(1) The neutral of a solidly grounded neutral system shall 
be permitted to be grounded at more than one point. 
Grounding shall be permitted at one or more of the fol- 
lowing locations: 

a. Transformers supplying conductors to a building or 
other structure 

b. Underground circuits where the neutral is exposed 

c. Overhead circuits installed outdoors 

(2) The multigrounded neutral conductor shall be grounded 
at each transformer and at other additional locations by 
connection to a made or existing electrode. 

(3) At least one grounding electrode shall be installed and 
connected to the multigrounded neutral circuit conduc- 
tor every 400 m (1300 ft). 

(4) The maximum distance between any two adjacent elec- 
trodes shall not be more than 400 m (1300 ft). 

(5) In a multigrounded shielded cable system, the shielding 
shall be grounded at each cable joint that is exposed to 
personnel contact. 

250.186 Impedance Grounded Neutral Systems. Imped- 
ance grounded neutral systems in which a grounding imped- 
ance, usually a resistor, limits the ground-fault current, shall be 
permitted where all of the following conditions are met: 

(1) The conditions of maintenance and supervision ensure 
that only qualified persons will service the installation. 

(2) Ground detectors are installed on the system. 

(3) Line-to-neutral loads are not served. 

Impedance grounded neutral systems shall comply with 
the provisions of 250.186(A) through (D). 

(A) Location. The grounding impedance shall be inserted 
in the grounding conductor between the grounding elec- 
trode of the supply system and the neutral point of the 
supply transformer or generator. 

(B) Identified and Insulated. The neutral conductor of an 
impedance grounded neutral system shall be identified, as 
well as fully insulated with the same insulation as the phase 
conductors. 

(C) System Neutral Connection. The system neutral 
shall not be connected to ground, except through the 
neutral grounding impedance. 

(D) Equipment Grounding Conductors. Equipment 
grounding conductors shall be permitted to be bare and 
shall be electrically connected to the ground bus and 
grounding electrode conductor. 

250.188 Grounding of Systems Supplying Portable or 
Mobile Equipment. Systems supplying portable or mobile 
high-voltage equipment, other than substations installed on a 
temporary basis, shall comply with 250.188(A) through (F). 



(A) Portable or Mobile Equipment. Portable or mobile 
high-voltage equipment shall be supplied from a system 
having its neutral grounded through an impedance. Where 
a delta-connected high-voltage system is used to supply 
portable or mobile equipment, a system neutral shall be 
derived. 

(B) Exposed Non-Current-Carrying Metal Parts. Ex- 
posed non-current-carrying metal parts of portable or mo- 
bile equipment shall be connected by an equipment ground- 
ing conductor to the point at which the system neutral 
impedance is grounded. 

(C) Ground-Fault Current. The voltage developed be- 
tween the portable or mobile equipment frame and ground 
by the flow of maximum ground-fault current shall not 
exceed 100 volts. 

(D) Ground-Fault Detection and Relaying. Ground-fault 
detection and relaying shall be provided to automatically 
de-energize any high-voltage system component that has 
developed a ground fault. The continuity of the equipment 
grounding conductor shall be continuously monitored so as 
to de-energize automatically the high-voltage circuit to the 
portable or mobile equipment upon loss of continuity of the 
equipment grounding conductor. 

(E) Isolation. The grounding electrode to which the por- 
table or mobile equipment system neutral impedance is 
connected shall be isolated from and separated in the 
ground by at least 6.0 m (20 ft) from any other system or 
equipment grounding electrode, and there shall be no direct 
connection between the grounding electrodes, such as bur- 
ied pipe and fence, and so forth. 

(F) Trailing Cable and Couplers. High-voltage trailing 
cable and couplers for interconnection of portable or mo- 
bile equipment shall meet the requirements of Part III of 
Article 400 for cables and 490.55 for couplers. 

250.190 Grounding of Equipment. All non-current- 
carrying metal parts of fixed, portable, and mobile equip- 
ment and associated fences, housings, enclosures, and sup- 
porting structures shall be grounded. 

Exception: Where isolated from ground and located so as to 
prevent any person who can make contact with ground from 
contacting such metal parts when the equipment is energized. 

Grounding conductors not an integral part of a cable 
assembly shall not be smaller than 6 AWG copper or 4 
AWG aluminum. 

FPN: See 250.110, Exception No. 2, for pole-mounted 
distribution apparatus. 



70-118 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 280 — SURGE ARRESTERS 



280.24 



'■-. n : y ■:.,:> ^^Sftrgc AiTesters ;. ;..,\ 

I. General 

280.1 Scope. This article covers general requirements, in- 
stallation requirements, and connection requirements for 
surge arresters installed on premises wiring systems. 

280.2 Definition. 

Surge Arrester. A protective device for limiting surge volt- 
ages by discharging or bypassing surge current, and it also 
prevents continued flow of foUow current while remaining 
capable of repeating these functions. 

280.3 Number Required. Where used at a point on a cir- 
cuit, a surge arrester shall be connected to each ungrounded 
conductor. A single installation of such surge arresters shall 
be permitted to protect a number of interconnected circuits, 
provided that no circuit is exposed to surges while discon- 
nected from the surge arresters. 

280.4 Surge Arrester Selection. 

(A) Circuits of Less Than 1000 Volts. Surge arresters in- 
stalled on a circuit of less than 1000 volts shall comply 
with all of the following: 

(1) The rating of the surge arrester shall be equal to or greater 
than the maximum continuous phase-to-ground power 
frequency voltage available at the point of application. 

(2) Surge arresters installed on circuits of less than 1000 volts 
shall be listed. 

(3) Surge arresters shall be marked with a short circuit 
current rating and shall not be installed at a point on the 
system where the available fault current is in excess of 
that rating. 

(4) Surge arresters shall not be installed on ungrounded 
systems, impedance grounded systems, or corner 
grounded delta systems unless listed specifically for 
use on these systems. 

(B) Circuits of 1 kV and Over — Silicon Carbide Types. 

The rating of a silicon carbide-type surge arrester shall be not 
less than 125 percent of the maximum continuous phase- to- 
ground voltage available at the point of application. 

FPN No. 1: For further information on surge arresters, see 
ANSI/IEEE C62. 1-1989, Standard for Gapped Silicon- 
Carbide Surge Arresters for AC Power Circuits; 
ANSI/IEEE C62.2-1987, Guide for the Application of 
Gapped Silicon-Carbide Surge Arresters for Alternating- 
Current Systems; ANSI/IEEE C62.11-1993, Standard for 
Metal-Oxide Surge Arresters for Alternating-Current Power 
Circuits; and ANSI/ffiEE C62.22-1991, Guide for the Appli- 
cation of Metal-Oxide Surge Arresters for Alternating-Current 
Systems. 



FPN No. 2: The selection of a properly rated metal oxide 
arrester is based on considerations of maximum continuous 
operating voltage and the magnitude and duration of over- 
voltages at the arrester location as affected by phase-to- 
ground faults, system grounding techniques, switching 
surges, and other causes. See the manufacturer's applica- 
tion rules for selection of the specific arrester to be used at 
a particular locadon. 



II. Installation 

280.11 Location. Surge arresters shall be permitted to be 
located indoors or outdoors. Surge arresters shall be made 
inaccessible to unqualified persons, unless listed for instal- 
lation in accessible locations. 

280.12 Routing of Surge Arrester Connections. The con- 
ductor used to connect the surge arrester to fine or bus and 
to ground shall not be any longer than necessary and shall 
avoid unnecessary bends. 

III. Connecting Surge Arresters 

280.21 Installed at Services of Less Than 1000 Volts. 

Line and ground connecting conductors shall not be smaller 
than 14 AWG copper or 12 AWG aluminum. The arrester 
grounding conductor shall be connected to one of the fol- 
lowing: 

(1) Grounded service conductor 

(2) Grounding electrode conductor 

(3) Grounding electrode for the service 

(4) Equipment grounding terminal in the service equipment 

280.22 Installed on the Load Side Services of Less 
Than 1000 Volts. Line and ground connecting conductors 
shall not be smaller than 14 AWG copper or 12 AWG alu- 
minum. A surge arrester shall be permitted to be connected 
between any two conductors — ungrounded conductor(s), 
grounded conductor, grounding conductor. The grounded 
conductor and the grounding conductor shall be intercon- 
nected only by the normal operation of the surge arrester 
during a surge. 

280.23 Circuits of 1 kV and Over — Surge-Arrester 
Conductors. The conductor between the surge arrester 
and the line and the surge arrester and the grounding 
connection shall not be smaller than 6 AWG copper or 
aluminum. 

280.24 Circuits of 1 kV and Over — Interconnections. 

The grounding conductor of a surge arrester protecting a trans- 
former that supphes a secondary distribution system shall be 
interconnected as specified in 280.24(A), (B), or (C). 



2005 Edition 



NATIONAL ELECTRICAL CODE 



70-119 



280.25 



ARTICLE 285 — TRANSIENT VOLTAGE SURGE SUPPRESSORS: TVSSs 



(A) Metallic Interconnections. A metallic interconnection 
shall be made to the secondary grounded circuit conductor 
or the secondary circuit grounding conductor provided that, 
in addition to the direct grounding connection at the surge 
arrester, the following occurs: 

(1) The grounded conductor of the secondary has else- 
where a grounding connection to a continuous metal 
underground water piping system. However, in urban 
water-pipe areas where there are at least four water- 
pipe connections on the neutral and not fewer than four 
such connections in each mile of neutral, the metaUic 
interconnection shall be permitted to be made to the 
secondary neutral with omission of the direct ground- 
ing connection at the surge arrester. 

(2) The grounded conductor of the secondary system is a 
part of a multiground neutral system or static wire of 
which the primary neutral or static wire has at least 
four ground connections in each mile of line in addition 
to a ground at each service. 

(B) Through Spark Gap or Device. Where the surge 
arrester grounding conductor is not connected as in 
280.24(A) or where the secondary is not grounded as in 
280.24(A) but is otherwise grounded as in 250.52, an 
interconnection shall be made through a spark gap or 
listed device as follows: 

(1) For ungrounded or unigrounded primary systems, the 
spark gap or listed device shall have a 60-Hz break- 
down voltage of at least twice the primary circuit 
voltage but not necessarily more than 10 kV, and 
there shall be at least one other ground on the 
grounded conductor of the secondary that is not less 
than 6.0 m (20 ft) distant from the surge arrester 
grounding electrode. 

(2) For multigrounded neutral primary systems, the spark 
gap or listed device shall have a 60-Hz breakdown of 
not more than 3 kV, and there shall be at least one other 
ground on the grounded conductor of the secondary 
that is not less than 6.0 m (20 ft) distant from the surge 
arrester grounding electrode. 

(C) By Special Permission. An interconnection of the 
surge arrester ground and the secondary neutral, other than 
as provided in 280.24(A) or (B), shall be permitted to be 
made only by special permission. 

280.25 Grounding. Except as indicated in this article, 
surge arrester grounding connections shall be made as 
specified in Article 250. Grounding conductors shall not be 
run in metal enclosures unless bonded to both ends of such 
enclosure. 



ARTICLE 285 
Transient Voltage Surge Suppressors: 

■i^:-:^--:- -■- ■'■ TVSSs- ■^^■'■■-' ^;.--V-^^ ^ 



I. General 

285.1 Scope. This article covers general requirements, in- 
stallation requirements, and connection requirements for 
transient voltage surge suppressors (TVSSs) permanently 
installed on premises wiring systems. 

285.2 Definition. 

Transient Voltage Surge Suppressor (TVSS). A protec- 
tive device for limiting transient voltages by diverting or 
limiting surge current; it also prevents continued flow of 
follow current while remaining capable of repeating these 
functions. 

285.3 Uses Not Permitted. A TVSS device shall not be 
installed in the following: 

(1) Circuits exceeding 600 volts 

(2) On ungrounded systems, impedance grounded systems, 
or comer grounded delta systems unless listed specifi- 
cally for use on these systems. 

(3) Where the rating of the TVSS is less than the maxi- 
mum continuous phase-to-ground power frequency 
voltage available at the point of application 

FPN: For further information on TVSSs, see NEMA LS 
1-1992, Standard for Low Voltage Surge Suppression De- 
vices. The selection of a properly rated TVSS is based on 
criteria such as maximum continuous operating voltage, the 
magnitude and duration of overvoltages at the suppressor 
location as affected by phase-to-ground faults, system 
grounding techniques, and switching surges. 

285.4 Number Required. Where used at a point on a 
circuit, the TVSS shall be connected to each ungrounded 
conductor. 

285.5 Listing. A TVSS shall be a listed device. 

285.6 Short Circuit Current Rating. The TVSS shall be 
marked with a short circuit current rating and shall not be 
installed at a point on the system where the available fault 
current is in excess of that rating. This marking requirement 
shall not apply to receptacles. 

II. Installation 

285.11 Location. TVSSs shall be permitted to be located 
indoors or outdoors and shall be made inaccessible to un- 
qualified persons, unless listed for installation in accessible 
locations. 



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NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 285 — TRANSIENT VOLTAGE SURGE SUPPRESSORS: TVSSs 



285.25 



285.12 Routing of Connections. The conductors used to 
connect the TVSS to the line or bus and to ground shall not be 
any longer than necessary and shall avoid unnecessary bends. 

III. Connecting Transient Voltage Surge Suppressors 

285.21 Connection. Where a TVSS is installed, it shall 
comply with 285.21(A) through (C). 

(A) Location. 

(1) Service Supplied Building or Structure. The transient 
voltage surge suppressor shall be connected on the load 
side of a service disconnect overcurrent device required in 
230.91, unless installed in accordance with 230.82(8). 

(2) Feeder Supplied Building or Structure. The tran- 
sient voltage surge suppressor shall be connected on the 
load side of the first overcurrent device at the building or 
structure. 



Exception to (1) and (2): Where the TVSS is also listed as a 
surge arrester, the connection shall be as permitted by Ar- 
ticle 280. 

(3) Separately Derived System. The TVSS shall be con- 
nected on the load side of the first overcurrent device in a 
separately derived system. 

(B) Conductor Size. Line and ground connecting conduc- 
tors shall not be smaller than 14 AWG copper or 12 AWG 
aluminum. 

(C) Connection Between Conductors. A TVSS shall be 
permitted to be connected between any two conductors — 
ungrounded conductor(s), grounded conductor, grounding 
conductor. The grounded conductor and the grounding con- 
ductor shall be interconnected only by the normal operation 
of the TVSS during a surge. 

285.25 Grounding. Grounding conductors shall not be run 
in metal enclosures unless bonded to both ends of such 
enclosure. 



2005 Edition 



NATIONAL ELECTRICAL CODE 



70-121 



300.1 



ARTICLE 300 — WIRING METHODS 



Chapter 3 Wiring Methods and Materials 



./ARTICLE 300; . 
Wiring Methods - 

I. General Requirements 
300.1 Scope. 

(A) All Wiring Installations. This article covers wiring 
methods for all wiring installations unless modified by 
other articles. 

(B) Integral Parts of Equipment. The provisions of this 
article are not intended to apply' to the conductors that form 
an integral part of equipment, such as motors, controllers, 
motor control centers, or factory assembled control equip- 
ment or listed utilization equipment. 

(C) Metric Designators and Trade Sizes. Metric designa- 
tors and trade sizes for conduit, tubing, and associated fittings 
and accessories shall be as designated in Table 300.1(C). 

Table 300.1(C) Metric Designator and Trade Sizes 



Metric 


Trade 




Designator 


Size 




12 


3/8 




16 


Vl 




21 


3/4 




27 


1 




35 


l'/4 




41 


l'/2 




53 


2 




63 


21/2 




78 


3 




91 


31/2 




103 


4 




129 


5 




155 


6 





Note: The metric designators and trade sizes are for identification 
purposes only and are not actual dimensions. 



300.2 Limitations. 

(A) Voltage. Wiring methods specified in Chapter 3 shall 
be used for 600 volts, nominal, or less where not specifi- 
cally limited in some section of Chapter 3. They shall be 
permitted for over 600 volts, nominal, where specifically 
permitted elsewhere in this Code. 

(B) Temperature. Temperature limitation of conductors 
shall be in accordance with 310.10. 



300.3 Conductors. 

(A) Single Conductors. Single conductors specified in 
Table 310.13 shall only be installed where part of a recog- 
nized wiring method of Chapter 3. 

Exception: Individual conductors shall be permitted 
where installed as separate overhead conductors in accor- 
dance with 225.6. 

(B) Conductors of the Same Circuit. All conductors of 
the same circuit and, where used, the grounded conductor 
and all equipment grounding conductors and bonding con- 
ductors shall be contained within the same raceway, auxil- 
iary gutter, cable tray, cablebus assembly, trench, cable, or 
cord, unless otherwise permitted in accordance with 
300.3(B)(1) through (B)(4). 

(1) Paralleled Installations. Conductors shall be permit- 
ted to be run in parallel in accordance with the provisions 
of 310.4. The requirement to run all circuit conductors 
within the same raceway, auxiliary gutter, cable tray, 
trench, cable, or cord shall apply separately to each portion 
of the paralleled installation, and the equipment grounding 
conductors shall comply with the provisions of 250.122. 
Parallel runs in cable tray shall comply with the provisions 
of 392.8(D). 

Exception: Conductors installed in nonmetallic raceways 
run underground shall be permitted to be arranged as iso- 
lated phase installations. The raceways shall be installed in 
close proximity, and the conductors shall comply with the 
provisions of 300.20(B). 

(2) Grounding and Bonding Conductors. Equipment 
grounding conductors shall be permitted to be installed out- 
side a raceway or cable assembly where in accordance with 
the provisions of 250.130(C) for certain existing installa- 
tions or in accordance with 250.134(B), Exception No. 2, 
for dc circuits. Equipment bonding conductors shall be per- 
mitted to be installed on the outside of raceways in accor- 
dance with 250.102(E). 

(3) Nonferrous Wiring Methods. Conductors in wiring 
methods with a nonmetallic or other nonmagnetic sheath, 
where run in different raceways, auxiliary gutters, cable 
trays, trenches, cables, or cords, shall comply with the pro- 
visions of 300.20(B). Conductors in single-conductor Type 
MI cable with a nonmagnetic sheath shall comply with the 
provisions of 332.31. Conductors of single-conductor Type 
MC cable with a nonmagnetic sheath shall comply with the 
provisions of 330.31, 330.116, and 300.20(B). 



• 



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ARTICLE 300 — WIRING METHODS 



300.4 



• 



• 



(4) Enclosures. Where an auxiliary gutter runs between a 
column-width panelboard and a pull box, and the pull box 
includes neutral terminations, the neutral conductors of cir- 
cuits supplied from the panelboard shall be permitted to 
originate in the pull box. 

(C) Conductors of Different Systems. 

(1) 600 Volts, Nominal, or Less. Conductors of circuits rated 
600 volts, nominal, or less, ac circuits, and dc circuits shall be 
permitted to occupy the same equipment wiring enclosure, 
cable, or raceway. All conductors shall have an insulation rat- 
ing equal to at least the maximum circuit voltage applied to 
any conductor within the enclosure, cable, or raceway. 

Exception: For solar photovoltaic systems in accordance 
with 690.4(B). 

FPN: See 725.55(A) for Class 2 and Class 3 circuit 
conductors. 

(2) Over 600 Volts, Nominal. Conductors of circuits rated 
over 600 volts, nominal, shall not occupy the same equip- 
ment wiring enclosure, cable, or raceway with conductors 
of circuits rated 600 volts, nominal, or less unless otherwise 
permitted in (C)(2)(a) through (C)(2)(e). 

(a) Secondary wiring to electric-discharge lamps of 
1000 volts or less, if insulated for the secondary voltage 
involved, shall be permitted to occupy the same luminaire 
(fixture), sign, or outline lighting enclosure as the branch- 
circuit conductors. 

(b) Primary leads of electric-discharge lamp ballasts 
insulated for the primary voltage of the ballast, where con- 
tained within the individual wiring enclosure, shall be per- 
mitted to occupy the same luminaire (fixture), sign, or out- 
line lighting enclosure as the branch-circuit conductors. 

(c) Excitation, control, relay, and ammeter conductors 
used in connection with any individual motor or starter 
shall be permitted to occupy the same enclosure as the 
motor-circuit conductors. 

(d) In motors, switchgear and control assemblies, and 
similar equipment, conductors of different voltage ratings 
shall be permitted. 

(e) In manholes, if the conductors of each system are 
permanently and effectively separated from the conductors 
of the other systems and securely fastened to racks, insula- 
tors, or other approved supports, conductors of different 
voltage ratings shall be permitted. 

Conductors having nonshielded insulation and operat- 
ing at different voltage levels shall not occupy the same 
enclosure, cable, or raceway. 

300.4 Protection Against Physical Damage. Where sub- 
ject to physical damage, conductors shall be protected. 



(A) Cables and Raceways Through Wood Members. 

(1) Bored Holes. In both exposed and concealed locations, 
where a cable- or raceway-type wiring method is installed 
through bored holes in joists, rafters, or wood members, 
holes shall be bored so that the edge of the hole is not less 
than 32 mm (l'/4 in.) from the nearest edge of the wood 
member. Where this distance cannot be maintained, the 
cable or raceway shall be protected from penetration by 
screws or nails by a steel plate or bushing, at least 1.6 mm 
(Vi6 in.) thick, and of appropriate length and width installed 
to cover the area of the wiring. 

Exception No. 1: Steel plates shall not be required to 
protect rigid metal conduit, intermediate metal conduit, 
rigid nonmetallic conduit, or electrical metallic tubing. 

Exception No. 2: A listed and marked steel plate less than 
1.6 mm (Vj6 in.) thick that provides equal or better protec- 
tion against nail or screw penetration shall be permitted. 

(2) Notches in Wood. Where there is no objection because 
of weakening the building structure, in both exposed and 
concealed locations, cables or raceways shall be permitted 
to be laid in notches in wood studs, joists, rafters, or other 
wood members where the cable or raceway at those points 
is protected against nails or screws by a steel plate at least 
1.6 mm (V\6 in.) thick, and of appropriate length and width, 
installed to cover the area of the wiring. The steel plate 
shall be installed before the building finish is applied. 

Exception No. 1: Steel plates shall not be required to 
protect rigid metal conduit, intermediate metal conduit, 
rigid nonmetallic conduit, or electrical metallic tubing. 

Exception No. 2: A listed and marked steel plate less than 
1.6 mm {'/i6 in.) thick that provides equal or better protec- 
tion against nail or screw penetration shall be permitted. 

(B) Nonmetallic-Sheathed Cables and Electrical Non- 
metallic Tubing Through Metal Framing Members. 

(1) Nonmetallic-Sheathed Cable. In both exposed and 
concealed locations where nonmetallic-sheathed cables 
pass through either factory or field punched, cut, or 
drilled slots or holes in metal members, the cable shall 
be protected by listed bushings or listed grommets cov- 
ering all metal edges that are securely fastened in the 
opening prior to installation of the cable. 

(2) Nonmetallic-Sheathed Cable and Electrical Nonme- 
tallic 1\ibing. Where nails or screws are likely to pen- 
etrate nonmetallic-sheathed cable or electrical nonmetal- 
lic tubing, a steel sleeve, steel plate, or steel clip not less 
than 1.6 mm (Vie in.) in thickness shall be used to pro- 
tect the cable or tubing. 

Exception: A listed and marked steel plate less than 
1.6 mm (Vj6 in.) thick that provides equal or better protec- 
tion against nail or screw penetration shall be permitted. 



2005 Edition NATIONAL ELECTRICAL CODE 



70-123 



300.5 



ARTICLE 300 — WIRING METHODS 



(C) Cables Through Spaces Behind Panels Designed to 
Allow Access. Cables or raceway-type wiring methods, in- 
stalled behind panels designed to allow access, shall be 
supported according to their applicable articles. 

(D) Cables and Raceways Parallel to Framing Mem- 
bers and Furring Strips. In both exposed and concealed 
locations, where a cable- or raceway-type wiring method is 
installed parallel to framing members, such as joists, 
rafters, or studs, or is installed parallel to furring strips, the 
cable or raceway shall be installed and supported so that the 
nearest outside surface of the cable or raceway is not less 
than 32 mm (VA in.) from the nearest edge of the framing 
member or furring strips where nails or screws are likely to 
penetrate. Where this distance cannot be maintained, the 
cable or raceway shall be protected from penetration by 
nails or screws by a steel plate, sleeve, or equivalent at least 
1.6 mm (Vie in.) thick. 

Exception No. 1: Steel plates, sleeves, or the equivalent 
shall not be required to protect rigid metal conduit, inter- 
mediate metal conduit, rigid nonmetallic conduit, or elec- 
trical metallic tubing. 

Exception No. 2: For concealed work in finished build- 
ings, or finished panels for prefabricated buildings where 
such supporting is impracticable, it shall be permissible to 
fish the cables between access points. 

Exception No. 3: A listed and marked steel plate less than 
1.6 mm (Vj6 in.) thick that provides equal or better protec- 
tion against nail or screw penetration shall be permitted. 

(E) Cables and Raceways Installed in Shallow Grooves. 

Cable- or raceway-type wiring methods installed in a groove, 
to be covered by wallboard, siding, paneling, carpeting, or 
similar finish, shall be protected by 1.6 mm {Vie in.) thick steel 
plate, sleeve, or equivalent or by not less than 32-mm (1 Vi-in.) 
free space for the full length of the groove in which the cable 
or raceway is installed. 

Exception No. 1: Steel plates, sleeves, or the equivalent 
shall not be required to protect rigid metal conduit, inter- 
mediate metal conduit, rigid nonmetallic conduit, or elec- 
trical metallic tubing. 

Exception No. 2: A listed and marked steel plate less than 
1.6 mm (Vi6 in.) thick that provides equal or better protec- 
tion against nail or screw penetration shall be permitted. 

(F) Insulated Fittings. Where raceways containing un- 
grounded conductors 4 AWG or larger enter a cabinet, box 
enclosure, or raceway, the conductors shall be protected by 
a substantial fitting providing a smoothly rounded insulat- 
ing surface, unless the conductors are separated from the 
fitting or raceway by substantial insulating material that is 
securely fastened in place. 



Exception: Where threaded hubs or bosses that are an 
integral part of a cabinet, box enclosure, or raceway pro- 
vide a smoothly rounded or fiared entry for conductors. 

Conduit bushings constructed wholly of insulating ma- 
terial shall not be used to secure a fitting or raceway. The 
insulating fitting or insulating material shall have a tem- 
perature rating not less than the insulation temperature rat- 
ing of the installed conductors. 

300.5 Underground Installations. 

(A) Minimum Cover Requirements. Direct-buried cable 
or conduit or other raceways shall be installed to meet the 
minimum cover requirements of Table 300.5. 

(B) Listing. Cables and insulated conductors installed in 
enclosures or raceways in underground installations shall 
be listed for use in wet locations. 

(C) Underground Cables Under Buildings. Underground 
cable installed under a building shall be in a raceway that is 
extended beyond the outside walls of the building. 

(D) Protection from Damage. Direct-buried conductors 
and cables shall be protected from damage in accordance 
with 300.5(D)(1) through (D)(4). 

(1) Emerging from Grade. Direct-buried conductors and 
enclosures emerging from grade shall be protected by en- 
closures or raceways extending from the minimum cover 
distance below grade required by 300.5(A) to a point at 
least 2.5 m (8 ft) above finished grade. In no case shall the 
protection be required to exceed 450 mm (18 in.) below 
finished grade. 

(2) Conductors Entering Buildings. Conductors entering 
a building shall be protected to the point of entrance. 

(3) Service Conductors. Underground service conductors 
that are not encased in concrete and that are buried 450 mm 
(18 in.) or more below grade shall have their location iden- 
tified by a warning ribbon that is placed in the trench at 
least 300 mm (12 in.) above the underground installation. 

(4) Enclosure or Raceway Damage. Where the enclosure 
or raceway is subject to physical damage, the conductors shall 
be installed in rigid metal conduit, intermediate metal conduit, 
Schedule 80 rigid nonmetallic conduit, or equivalent. 

(E) Splices and Taps. Direct-buried conductors or cables 
shall be permitted to be spliced or tapped without the use of 
sphce boxes. The splices or taps shall be made in accor- 
dance with 110.14(B). 

(F) Backfill. Backfill that contains large rocks, paving ma- 
terials, cinders, large or sharply angular substances, or cor- 
rosive material shall not be placed in an excavation where 
materials may damage raceways, cables, or other substruc- 
tures or prevent adequate compaction of fill or contribute to 
corrosion of raceways, cables, or other substructures. 



• 



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ARTICLE 300 — WIRING METHODS 



300.5 



Table 300.5 Minimum Cover Requirements, to 600 Volts, Nominal, Burial in Millimeters (Inches) 

Type of Wiring Method or Circuit 



• 













Column 5 












Circuits for 












Control of 










Column 4 


Irrigation and 










Residential 


Landscape 








Column 3 


Branch Circuits 


Lighting Limited 








Nonmetallic 


Rated 120 Volts 


to Not More 








Raceways Listed 


or Less with 


Than 30 Volts 






Column 2 


for Direct Burial 


GFCI Protection 


and Installed 




Column 1 


Rigid Metal 


Without Concrete 


and Maximum 


with Type UF or 




Direct Burial 


Conduit or 


Encasement or 


Overcurrent 


in Other 




Cables or 


Intermediate 


Other Approved 


Protection of 20 


Identified Cable 




Conductors 


Metal Conduit 


Raceways 


Amperes 


or Raceway 


Location of Wiring Method or 






















Circuit 


mm m. 


mm m. 


mm m. 


mm in. 


mm m. 


All locations not specified 


600 24 


150 6 


450 18 


300 12 


150 6 


below 












In trench below 50-mm (2-in.) 


450 18 


150 6 


300 12 


150 6 


150 6 


thick concrete or equivalent 












Under a building 



















(in raceway only) 






(in raceway only) 


(in raceway only) 


Under minimum of 102-mm 


450 18 


100 4 


100 4 


150 6 


150 6 


(4-in.) thick concrete exterior 












slab with no vehicular traffic 








(direct burial) 




and the slab extending not 








100 4 




less than 152 mm (6 in.) 










beyond the underground 








(in raceway) 




installation 












Under streets, highways, roads. 


600 24 


600 24 


600 24 


600 24 


600 24 


alleys, driveways, and parking 












lots 












One- and two-family dwelling 


450 18 


450 18 


450 18 


300 12 


450 18 


driveways and outdoor 












parking areas, and used only 












for dwelling-related purposes 












In or under airport runways. 


450 18 


450 18 


450 18 


450 18 


450 18 


including adjacent areas 












where trespassing prohibited 













Notes: 

1. Cover is defined as the shortest distance in millimeters (inches) measured between a point on the top surface of any direct-buried conductor, 
cable, conduit, or other raceway and the top surface of finished grade, concrete, or similar cover. 

2. Raceways approved for burial only where concrete encased shall require concrete envelope not less than 50 mm (2 in.) thick. 

3. Lesser depths shall be permitted where cables and conductors rise for terminations or splices or where access is otherwise required. 

4. Where one of the wiring method types listed in Columns 1-3 is used for one of the circuit types in Columns 4 and 5, the shallowest depth of 
burial shall be permitted. 

5. Where solid rock prevents compliance with the cover depths specified in this table, the wiring shall be installed in metal or nonmetallic raceway 
permitted for direct burial. The raceways shall be covered by a minimum of 50 mm (2 in.) of concrete extending down to rock. 



2005 Edition NATIONAL ELECTRICAL CODE 



70-125 



300.6 



ARTICLE 300 — WIRING METHODS 



Where necessary to prevent physical damage to the race- 
way or cable, protection shall be provided in the form of 
granular or selected material, suitable running boards, suit- 
able sleeves, or other approved means. 

(G) Raceway Seals. Conduits or raceways through which 
moisture may contact live parts shall be sealed or plugged 
at either or both ends. 

FPN: Presence of hazardous gases or vapors may also 
necessitate sealing of underground conduits or raceways 
entering buildings. 

(H) Bushing. A bushing, or terminal fitting, with an integral 
bushed opening shall be used at the end of a conduit or other 
raceway that terminates underground where the conductors or 
cables emerge as a direct burial wiring method. A seal incor- 
porating the physical protection characteristics of a bushing 
shall be permitted to be used in lieu of a bushing. 

(I) Conductors of the Same Circuit. All conductors of 
the same circuit and, where used, the grounded conductor 
and all equipment grounding conductors shall be installed 
in the same raceway or cable or shall be installed in close 
proximity in the same trench. 

Exception No. 1: Conductors in parallel in raceways or 
cables shall be permitted, but each raceway or cable shall 
contain all conductors of the same circuit including 
grounding conductors. 

Exception No. 2: Isolated phase, polarity, grounded conduc- 
tor, and equipment grounding and bonding conductor instal- 
lations shall be permitted in nonmetallic raceways or cables 
with a nonmetallic covering or nonmagnetic sheath in close 
proximity where conductors are paralleled as permitted in 
310.4, and where the conditions of 300.20(B) are met. 

(J) Ground Movement. Where direct-buried conductors, 
raceways, or cables are subject to movement by settlement 
or frost, direct-buried conductors, raceways, or cables shall 
be arranged so as to prevent damage to the enclosed con- 
ductors or to equipment connected to the raceways. 

FPN: This section recognizes "S" loops in underground 
direct burial to raceway transitions, expansion fittings in 
raceway risers to fixed equipment, and, generally, the pro- 
vision of flexible connections to equipment subject to 
settlement or frost heaves. 

(K) Directional Boring. Cables or raceways installed us- 
ing directional boring equipment shall be approved for the 
purpose. 

300.6 Protection Against Corrosion and Deterioration. 

Raceways, cable trays, cablebus, auxiliary gutters, cable ar- 
mor, boxes, cable sheathing, cabinets, elbows, couplings, fit- 
tings, supports, and support hardware shall be of materials 
suitable for the environment in which they are to be installed. 



(A) Ferrous Metal Equipment. Ferrous metal raceways, 
cable trays, cablebus, auxiliary gutters, cable armor, boxes, 
cable sheathing, cabinets, metal elbows, couplings, nipples, 
fittings, supports, and support hardware shall be suitably pro- 
tected against corrosion inside and outside (except threads at 
joints) by a coating of hsted corrosion-resistant material. 
Where corrosion protection is necessary and the conduit is 
threaded in the field, the threads shall be coated with an ap- 
proved electrically conductive, corrosion-resistant compound. 

Exception: Stainless steel shall not be required to have 
protective coatings. 

(1) Protected from Corrosion Solely by Enamel. Where 
protected from corrosion solely by enamel, ferrous metal 
raceways, cable trays, cablebus, auxiliary gutters, cable ar- 
mor, boxes, cable sheathing, cabinets, metal elbows, cou- 
plings, nipples, fittings, supports, and support hardware 
shall not be used outdoors or in wet locations as described 
in 300.6(D). 

(2) Organic Coatings on Boxes or Cabinets. Where 
boxes or cabinets have an approved system of organic coat- 
ings and are marked "Raintight," "Rainproof," or "Outdoor 
Type," they shall be permitted outdoors. 

(3) In Concrete or in Direct Contact with the Earth. 

Ferrous metal raceways, cable armor, boxes, cable sheath- 
ing, cabinets, elbows, couplings, nipples, fittings, supports, 
and support hardware shall be permitted to be installed in 
concrete or in direct contact with the earth, or in areas 
subject to severe corrosive influences where made of mate- 
rial approved for the condition, or where provided with 
corrosion protection approved for the condition. 

(B) Non-Ferrous Metal Equipment. Non-ferrous race- 
ways, cable trays, cablebus, auxiliary gutters, cable armor, 
boxes, cable sheathing, cabinets, elbows, couplings, 
nipples, fittings, supports, and support hardware embedded 
or encased in concrete or in direct contact with the earth 
shall be provided with supplementary corrosion protection. 

(C) Nonmetallic Equipment. Nonmetallic raceways, cable 
trays, cablebus, auxiliary gutters, boxes, cables with a nonme- 
tallic outer jacket and internal metal armor or jacket, cable 
sheathing, cabinets, elbows, coupHngs, nipples, fittings, sup- 
ports, and support hardware shall be made of material ap- 
proved for the condition and shall comply with (C)(1) and 
(C)(2) as applicable to the specific installation. 

(1) Exposed to Sunlight. Where exposed to sunlight, the 
materials shall be listed as sunlight resistant or shall be 
identified as sunlight resistant. 

(2) Chemical Exposure. Where subject to exposure to 
chemical solvents, vapors, splashing, or immersion, mate- 
rials or coatings shall either be inherently resistant to 



• 



70-126 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 300 — WIRING METHODS 



300.11 



chemicals based on its listing or be identified for the spe- 
cific chemical reagent. 

(D) Indoor Wet Locations. In portions of dairy processing 
facilities, laundries, canneries, and other indoor wet loca- 
tions, and in locations where walls are frequendy washed or 
where there are surfaces of absorbent materials, such as 
damp paper or wood, the entire wiring system, where in- 
stalled exposed, including all boxes, fittings, raceways, and 
cable used therewith, shall be mounted so that there is at 
least a 6-mm ('/4-in.) airspace between it and the wall or 
supporting surface. 

Exception: Nonmetallic raceways, boxes, and fittings shall 
be permitted to be installed without the airspace on a con- 
crete, masonry, tile, or similar surface. 

FPN: In general, areas where acids and alkali chemicals 
are handled and stored may present such corrosive condi- 
tions, particularly when wet or damp. Severe corrosive con- 
ditions may also be present in portions of meatpacking 
plants, tanneries, glue houses, and some stables; in instal- 
lations immediately adjacent to a seashore and swimming 
pool areas; in areas where chemical deicers are used; and in 
storage cellars or rooms for hides, casings, fertilizer, salt, 
and bulk chemicals. 

300.7 Raceways Exposed to Different Temperatures. 

(A) Sealing. Where portions of a cable raceway or sleeve 
are known to be subjected to different temperatures and 
where condensation is known to be a problem, as in cold 
storage areas of buildings or where passing from the inte- 
rior to the exterior of a building, the raceway or sleeve shall 
be filled with an approved material to prevent the circula- 
tion of warm air to a colder section of the raceway or 
sleeve. An explosionproof seal shall not be required for this 
purpose. 

(B) Expansion Fittings. Raceways shall be provided with 
expansion fittings where necessary to compensate for ther- 
mal expansion and contraction. 

FPN: Table 352.44(A) provides the expansion information 
for polyvinyl chloride (PVC). A nominal number for steel 
conduit can be determined by multiplying the expansion 
length in this table by 0.20. The coefficient of expansion for 
steel electrical metallic tubing, intermediate metal conduit, 
and rigid conduit is 11.70 x 10"^ (0.0000117 mm per mm 
of conduit for each °C in temperature change) [6.50 x 10"^ 
(0.0000065 in. per inch of conduit for each °F in tempera- 
ture change)]. 

300.8 Installation of Conductors with Other Systems. 

Raceways or cable trays containing electric conductors 
shall not contain any pipe, tube, or equal for steam, water, 
air, gas, drainage, or any service other than electrical. 

300.10 Electrical Continuity of Metal Raceways and 
Enclosures. Metal raceways, cable armor, and other metal 



enclosures for conductors shall be metallically joined together 
into a continuous electric conductor and shall be connected to 
all boxes, fittings, and cabinets so as to provide effective elec- 
trical continuity. Unless specifically permitted elsewhere in 
this Code, raceways and cable assembUes shall be mechani- 
cally secured to boxes, fittings, cabinets, and other enclosures. 

Exception No. 1: Short sections of raceways used to pro- 
vide support or protection of cable assemblies from physi- 
cal damage shall not be required to be made electrically 
continuous. 

Exception No. 2: Equipment enclosures to be isolated, as 
permitted by 250.96(B), shall not be required to be metal- 
lically joined to the metal raceway. 

300.11 Securing and Supporting. 

(A) Secured in Place. Raceways, cable assemblies, boxes, 
cabinets, and fittings shall be securely fastened in place. 
Support wires that do not provide secure support shall not 
be permitted as the sole support. Support wires and associ- 
ated fittings that provide secure support and that are in- 
stalled in addition to the ceiling grid support wires shall be 
permitted as the sole support. Where independent support 
wires are used, they shall be secured at both ends. Cables 
and raceways shall not be supported by ceiling grids. 

(1) Fire-Rated Assemblies. Wiring located within the cav- 
ity of a fire-rated floor-ceiling or roof-ceiling assembly 
shall not be secured to, or supported by, the ceiling assem- 
bly, including the ceiling support wires. An independent 
means of secure support shall be provided and shall be 
permitted to be attached to the assembly. Where indepen- 
dent support wires are used, they shall be distinguishable 
by color, tagging, or other effective means from those that 
are part of the fire-rated design. 

Exception: The ceiling support system shall be permitted 
to support wiring and equipment that have been tested as 
part of the fire-rated assembly. 

FPN: One method of determining fire rating is testing in 
accordance with NFPA 251-1999, Standard Methods of 
Tests of Fire Endurance of Building Construction and 
Materials. 

(2) Non-Fire-Rated Assemblies. Wiring located within 
the cavity of a non-fire-rated floor-ceiling or roof-ceihng 
assembly shall not be secured to, or supported by, the ceil- 
ing assembly, including the ceiling support wires. An inde- 
pendent means of secure support shall be provided. 

Exception: The ceiling support system shall be permitted 
to support branch- circuit wiring and associated equipment 
where installed in accordance with the ceiling system 
manufacturer 's instructions. 



2005 Edition NATIONAL ELECTRICAL CODE 



70-127 



300.12 



ARTICLE 300 — WIRING METHODS 



(B) Raceways Used as Means of Support. Raceways 
shall be used only as a means of support for other race- 
ways, cables, or nonelectric equipment under any of the 
following conditions: 

(1) Where the raceway or means of support is identified for 
the purpose 

(2) Where the raceway contains power supply conductors 
for electrically controlled equipment and is used to sup- 
port Class 2 circuit conductors or cables that are solely 
for the purpose of connection to the equipment control 
circuits 

(3) Where the raceway is used to support boxes or conduit 
bodies in accordance with 314.23 or to support lumi- 
naires (fixtures) in accordance with 410.16(F) 

(C) Cables Not Used as Means of Support. Cable wiring 
methods shall not be used as a means of support for other 
cables, raceways, or nonelectrical equipment. 

300.12 Mechanical Continuity — Raceways and Cables. 

Metal or nonmetallic raceways, cable armors, and cable 
sheaths shall be continuous between cabinets, boxes, fit- 
tings, or other enclosures or outlets. 

Exception: Short sections of raceways used to provide sup- 
port or protection of cable assemblies from physical damage 
shall not be required to be mechanically continuous. 

300.13 Mechanical and Electrical Continuity — 
Conductors. 

(A) General. Conductors in raceways shall be continuous 
between outlets, boxes, devices, and so forth. There shall be 
no splice or tap within a raceway unless permitted by 300.15; 
368.56(A); 376.56; 378.56; 384.56; 386.56; 388.56; or 390.6. 

(B) Device Removal. In multiwire branch circuits, the 
continuity of a grounded conductor shall not depend on 
device connections such as lampholders, receptacles, and 
so forth, where the removal of such devices would interrupt 
the continuity. 

300.14 Length of Free Conductors at Outlets, Junc- 
tions, and Switch Points. At least 150 mm (6 in.) of free 
conductor, measured from the point in the box where it 
emerges from its raceway or cable sheath, shall be left at each 
outlet, junction, and switch point for sphces or the connection 
of luminaires (fixtures) or devices. Where the opening to an 
outlet, junction, or switch point is less than 200 mm (8 in.) in 
any dimension, each conductor shall be long enough to extend 
at least 75 mm (3 in.) outside the opening. 

Exception: Conductors that are not spliced or terminated 
at the outlet, junction, or switch point shall not be required 
to comply with 300.14. 



300.15 Boxes, Conduit Bodies, or Fittings — Where Re- 
quired. A box shall be installed at each outlet and switch 
point for concealed knob-and-tube wiring. 

Fittings and connectors shall be used only with the spe- 
cific wiring methods for which they are designed and listed. 

Where the wiring method is conduit, tubing. Type AC 
cable. Type MC cable. Type MI cable, nonmetallic-sheathed 
cable, or other cables, a box or conduit body shall be installed 
at each conductor splice point, oudet point, switch point, junc- 
tion point, termination point, or pull point, unless otherwise 
permitted in 300.15(A) through (M). 

(A) Wiring Methods with Interior Access. A box or con- 
duit body shall not be required for each splice, junction, 
switch, pull, termination, or outlet points in wiring methods 
with removable covers, such as wireways, multioutlet as- 
semblies, auxiliary gutters, and surface raceways. The cov- 
ers shall be accessible after installation. 

(B) Equipment. An integral junction box or wiring com- 
partment as part of approved equipment shall be permitted 
in lieu of a box. 

(C) Protection. A box or conduit body shall not be re- 
quired where cables enter or exit from conduit or tubing 
that is used to provide cable support or protection against 
physical damage. A fitting shall be provided on the end(s) 
of the conduit or tubing to protect the cable from abrasion. 

(D) Type MI Cable. A box or conduit body shall not be 
required where accessible fittings are used for straight- 
through splices in mineral-insulated metal-sheathed cable. 

(E) Integral Enclosure. A wiring device with integral en- 
closure identified for the use, having brackets that securely 
fasten the device to walls or ceilings of conventional on- 
site frame construction, for use with nonmetallic-sheathed 
cable, shall be permitted in lieu of a box or conduit body. 

FPN: See 334.30(C); 545.10; 550.15(1); 551.47(E), Ex- 
ception No. 1; and 552.48(E), Exception No. 1. 

(F) Fitting. A fitting identified for the use shall be permit- 
ted in lieu of a box or conduit body where conductors are 
not spliced or terminated within the fitting. The fitting shall 
be accessible after installation. 

(G) Direct-Buried Conductors. As permitted in 300.5(E), 
a box or conduit body shall not be required for splices and 
taps in direct- buried conductors and cables. 

(H) Insulated Devices. As permitted in 334.40(B), a box 
or conduit body shall not be required for insulated devices 
supplied by nonmetallic-sheathed cable. 

(I) Enclosures. A box or conduit body shall not be re- 
quired where a splice, switch, terminal, or pull point is in a 
cabinet or cutout box, in an enclosure for a switch or over- 



• 



70-128 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 300 — WIRING METHODS 



300.19 



• 



I 



• 



current device as permitted in 312.8, in a motor controller 
as permitted in 430.10(A), or in a motor control center. 

(J) Luminaires (Fixtures). A box or conduit body shall 
not be required where a luminaire (fixture) is used as a 
raceway as permitted in 410.31 and 410.32. 

(K) Embedded. A box or conduit body shall not be required 
for splices where conductors are embedded as permitted in 
424.40, 424.41(D), 426.22(B), 426.24(A), and 427.19(A). 

(L) Manholes and Handhole Enclosures. Where acces- 
sible only to qualified persons, a box or conduit body shall 
not be required for conductors in manholes or handhole 
enclosures, except where connecting to electrical equip- 
ment. The installation shall comply with the provisions of 
Part V of Article 110 for manholes, and 314.30 for hand- 
hole enclosures. 

(M) Closed Loop. A box shaU not be required with a closed- 
loop power distribution system where a device identified and 
listed as suitable for installation without a box is used. 

300.16 Raceway or Cable to Open or Concealed Wiring. 

(A) Box or Fitting. A box or terminal fitting having a 
separately bushed hole for each conductor shall be used 
wherever a change is made from conduit, electrical metalhc 
tubing, electrical nonmetallic tubing, nonmetallic-sheathed 
cable. Type AC cable. Type MC cable, or mineral-insulated, 
metal-sheathed cable and surface raceway wiring to open 
wiring or to concealed knob-and-tube wiring. A fitting used 
for this purpose shall contain no taps or spHces and shall 
not be used at luminaire (fixture) outlets. 

(B) Bushing. A bushing shall be permitted in lieu of a box 
or terminal where the conductors emerge from a raceway 
and enter or terminate at equipment, such as open switch- 
boards, unenclosed control equipment, or similar equip- 
ment. The bushing shall be of the insulating type for other 
than lead-sheathed conductors. 

300.17 Number and Size of Conductors in Raceway. 

The number and size of conductors in any raceway shall 
not be more than will permit dissipation of the heat and 
ready installation or withdrawal of the conductors without 
damage to the conductors or to their insulation. 

FPN: See the following sections of this Code: intermedi- 
ate metal conduit, 342.22; rigid metal conduit, 344.22; flex- 
ible metal conduit, 348.22; liquidtight flexible metal con- 
duit, 350.22; rigid nonmetallic conduit, 352.22; liquiddght 
nonmetallic flexible conduit, 356.22; electrical metallic tub- 
ing, 358.22; flexible metallic tubing, 360.22; electrical non- 
metallic tubing, 362.22; cellular concrete floor raceways, 
372.11; cellular metal floor raceways, 374.5; metal wire- 
ways, 376.22; nonmetallic wireways, 378.22; surface metal 
raceways, 386.22; surface nonmetallic raceways, 388.22; 
underfloor raceways, 390.5; fixture wire, 402.7; theaters, 



520.6; signs, 600.31(C); elevators, 620.33; audio signal 
processing, amplification, and reproduction equipment, 
640.23(A) and 640.24; Class 1 , Class 2, and Class 3 cir- 
cuits. Article 725; fire alarm circuits, Article 760; and opti- 
cal fiber cables and raceways, Article 770. 

300.18 Raceway Installations. 

(A) Complete Runs. Raceways, other dian busways or ex- 
posed raceways having hinged or removable covers, shall be 
installed complete between outlet, junction, or splicing points 
prior to the installation of conductors. Where required to fa- 
cihtate the installation of utiUzation equipment, the raceway 
shall be permitted to be initially installed without a terminat- 
ing cormection at the equipment. Prewired raceway assemblies 
shall be permitted only where specifically permitted in this 
Code for the applicable wiring mediod. 

Exception: Short sections of raceways used to contain 
conductors or cable assemblies for protection from physi- 
cal damage shall not be required to be installed complete 
between outlet, junction, or splicing points. 

(B) Welding. Metal raceways shall not be supported, ter- 
minated, or connected by welding to the raceway unless 
specifically designed to be or otherwise specifically permit- 
ted to be in this Code. 

300.19 Supporting Conductors in Vertical Raceways. 

(A) Spacing Intervals — Maximum. Conductors in ver- 
tical raceways shall be supported if the vertical rise exceeds 
the values in Table 300.19(A). One cable support shall be 
provided at the top of the vertical raceway or as close to the 
top as practical. Intermediate supports shall be provided as 
necessary to limit supported conductor lengths to not 
greater than those values specified in Table 300.19(A). 

Exception: Steel wire armor cable shall be supported at 
the top of the riser with a cable support that clamps the 
steel wire armor A safety device shall be permitted at the 
lower end of the riser to hold the cable in the event there is 
slippage of the cable in the wire-armored cable support. 
Additional wedge-type supports shall be permitted to re- 
lieve the strain on the equipment terminals caused by ex- 
pansion of the cable under load. 

(B) Support Methods. One of the following methods of 
support shall be used. 

(1) By clamping devices constructed of or employing insu- 
lating wedges inserted in the ends of the raceways. 
Where clamping of insulation does not adequately sup- 
port the cable, the conductor also shall be clamped. 

(2) By inserting boxes at the required intervals in which in- 
sulating supports are installed and secured in a satisfac- 
tory manner to withstand the weight of the conductors 
attached thereto, the boxes being provided with covers. 



2005 Edition 



NATIONAL ELECTRICAL CODE 



70-129 



300.20 



ARTICLE 300 — WIRING METHODS 



Table 300.19(A) Spacings for Conductor Supports 





Support of 

Conductors in 

Vertical 

Raceways 












Conductors 










Aluminum or Copp 
Aluminum 


er-Clad 




Copper 




Size of Wire 


m 








ft 




m 




ft 


18 AWG through 8 AWG 
6 AWG through 1/0 AWG 
2/0 AWG through 4/0 AWG 
Over 4/0 AWG through 350 kcmil 
Over 350 kcmil through 500 kcmil 
Over 500 kcmil through 750 kcmil 
Over 750 kcmil 


Not greater than 
Not greater than 
Not greater than 
Not greater than 
Not greater than 
Not greater than 
Not greater than 


30 
60 
55 
41 
36 
28 
26 








100 
200 
180 
135 
120 
95 
85 




30 
30 
25 
18 
15 
12 
11 




100 
100 
80 
60 
50 
40 
35 



• 



(3) In junction boxes, by deflecting the cables not less than 
90 degrees and cairying them horizontally to a distance 
not less than twice the diameter of the cable, the cables 
being carried on two or more insulating supports and 
additionally secured thereto by tie wires if desired. 
Where this method is used, cables shall be supported at 
intervals not greater than 20 percent of those mentioned 
in the preceding tabulation. 

(4) By a method of equal effectiveness. 

300.20 Induced Currents in Metal Enclosures 
or Metal Raceways. 

(A) Conductors Grouped Together. Where conductors 
carrying alternating current are installed in metal enclo- 
sures or metal raceways, they shall be arranged so as to 
avoid heating the surrounding metal by induction. To ac- 
complish this, all phase conductors and, where used, the 
grounded conductor and all equipment grounding conduc- 
tors shall be grouped together. 

Exception No. 1: Equipment grounding conductors for 
certain existing installations shall be permitted to be in- 
stalled separate from their associated circuit conductors 
where run in accordance with the provisions of 250.130(C). 

Exception No. 2: A single conductor shall be permitted to 
be installed in a ferromagnetic enclosure and used for skin- 
effect heating in accordance with the provisions of 426.42 
and 427.47. 

(B) Individual Conductors. Where a single conductor 
carrying alternating current passes through metal with mag- 
netic properties, the inductive effect shall be minimized by 
(1) cutting slots in the metal between the individual holes 
through which the individual conductors pass or (2) passing 
all the conductors in the circuit through an insulating wall 
sufficiently large for all of the conductors of the circuit. 

Exception: In the case of circuits supplying vacuum or 
electric-discharge lighting systems or signs or X-ray appara- 



tus, the currents carried by the conductors are so small that 
the inductive heating effect can be ignored where these con- 
ductors are placed in metal enclosures or pass through metal. 

FPN: Because aluminum is not a magnetic metal, there 
will be no heating due to hysteresis; however, induced cur- 
rents will be present. They will not be of sufficient magni- 
tude to require grouping of conductors or special treatment 
in passing conductors through aluminum wall sections. 

300.21 Spread of Fire or Products of Combustion. Elec- 
trical installations in hollow spaces, vertical shafts, and 
ventilation or air-handling ducts shall be made so that the 
possible spread of fire or products of combustion will not 
be substantially increased. Openings around electrical pen- 
etrations through fire-resistant-rated walls, partitions, 
floors, or ceilings shall be firestopped using approved meth- 
ods to maintain the fire resistance rating. 

FPN: Directories of electrical construction materials pub- 
lished by qualified testing laboratories contain many listing 
installation restrictions necessary to maintain the fire- 
resisdve rating of assemblies where penetrations or open- 
ings are made. Building codes also contain restrictions on 
membrane penetrations on opposite sides of a fire- 
resistance-rated wall assembly. An example is the 600-mm 
(24-in.) minimum horizontal separadon that usually applies 
between boxes installed on opposite sides of the wall. As- 
sistance in complying with 300.21 can be found in building 
codes, fire resistance directories, and product listings. 

300.22 Wiring in Ducts, Plenums, and Other Air- 
Handling Spaces. The provisions of this section apply to 
the installation and uses of electric wiring and equipment in 
ducts, plenums, and other air-handling spaces. 

FPN: See Article 424, Part VI, for duct heaters. 

(A) Ducts for Dust, Loose Stock, or Vapor Removal. No 

wiring systems of any type shall be installed in ducts used 
to transport dust, loose stock, or flammable vapors. No 
wiring system of any type shall be installed in any duct, or 



• 



70-130 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 300 — WIRING METHODS 



300.39 



shaft containing only such ducts, used for vapor removal or 
for ventilation of commercial-type cooking equipment. 

(B) Ducts or Plenums Used for Environmental Air. Only 
wiring methods consisting of Type MI cable, Type MC 
cable employing a smooth or corrugated impervious metal 
sheath without an overall nonmetallic covering, electrical 
metallic tubing, flexible metallic tubing, intermediate metal 
conduit, or rigid metal conduit without an overall nonme- 
tallic covering shall be installed in ducts or plenums spe- 
cifically fabricated to transport environmental air. Flexible 
metal conduit shall be permitted, in lengths not to exceed 
1.2 m (4 ft), to connect physically adjustable equipment 
and devices permitted to be in these ducts and plenum 
chambers. The connectors used with flexible metal conduit 
shall effectively close any openings in the connection. 
Equipment and devices shall be permitted within such ducts 
or plenum chambers only if necessary for their direct action 
upon, or sensing of, the contained air. Where equipment or 
devices are installed and illumination is necessary to facili- 
tate maintenance and repair, enclosed gasketed-type lumi- 
naires (fixtures) shall be permitted. 

(C) Other Space Used for Environmental Air. This sec- 
tion applies to space used for environmental air-handhng pur- 
poses other than ducts and plenums as specified in 300.22(A) 
and (B). It does not include habitable rooms or areas of build- 
ings, the prime purpose of which is not air handling. 

FPN: The space over a hung ceiling used for environmen- 
tal air-handling purposes is an example of the type of other 
space to which this section applies. 

Exception: This section shall not apply to the joist or stud 
spaces of dwelling units where the wiring passes through 
such spaces perpendicular to the long dimension of such 
spaces. 

(1) Wiring Methods. The wiring methods for such other 
space shall be limited to totally enclosed, nonventilated, 
insulated busway having no provisions for plug-in connec- 
tions. Type MI cable. Type MC cable without an overall 
nonmetallic covering. Type AC cable, or other factory- 
assembled multiconductor control or power cable that is 
specifically listed for the use, or listed prefabricated cable 
assemblies of metallic manufactured wiring systems with- 
out nonmetallic sheath. Other types of cables and conduc- 
tors shall be installed in electrical metallic tubing, flexible 
metallic tubing, intermediate metal conduit, rigid metal 
conduit without an overall nonmetallic covering, flexible 
metal conduit, or, where accessible, surface metal raceway 
or metal wireway with metal covers or solid bottom metal 
cable tray with solid metal covers. 

(2) Equipment. Electrical equipment with a metal enclosure, 
or with a nonmetallic enclosure listed for the use and having 
adequate fire-resistant and low-smoke-producing characteris- 



tics, and associated wiring material suitable for the ambient 
temperature shall be permitted to be installed in such other 
space unless prohibited elsewhere in this Code. 

Exception: Integral fan systems shall be permitted where 
specifically identified for such use. 

(D) Information Technology Equipment. Electric wiring 
in air-handhng areas beneath raised floors for information 
technology equipment shall be permitted in accordance 
with Article 645. 

300.23 Panels Designed to Allow Access. Cables, race- 
ways, and equipment installed behind panels designed to 
allow access, including suspended ceiling panels, shall be 
arranged and secured so as to allow the removal of panels 
and access to the equipment. 

II. Requirements for Over 600 Volts, Nominal 

300.31 Covers Required. Suitable covers shall be in- 
stalled on all boxes, fittings, and similar enclosures to pre- 
vent accidental contact with energized parts or physical 
damage to parts or insulation. 

300.32 Conductors of Different Systems. See 300.3(C)(2). 

300.34 Conductor Bending Radius. The conductor shall 
not be bent to a radius less than 8 times the overall diameter 
for nonshielded conductors or 12 times the overall diameter 
for shielded or lead-covered conductors during or after in- 
stallation. For multiconductor or multiplexed single con- 
ductor cables having individually shielded conductors, the 
minimum bending radius is 12 times the diameter of the 
individually shielded conductors or 7 times the overall di- 
ameter, whichever is greater. 

300.35 Protection Against Induction Heating. Metallic 
raceways and associated conductors shall be arranged so as 
to avoid heating of the raceway in accordance with the 
applicable provisions of 300.20. 

300.37 Aboveground Wiring Methods. Aboveground 
conductors shall be installed in rigid metal conduit, in in- 
termediate metal conduit, in electrical metallic tubing, in 
rigid nonmetallic conduit, in cable trays, as busways, as 
cablebus, in other identified raceways, or as exposed runs 
of metal-clad cable suitable for the use and purpose. In 
locations accessible to qualified persons only, exposed runs 
of Type MV cables, bare conductors, and bare busbars shah 
also be permitted. Busbars shall be permitted to be either 
copper or aluminum. 

300.39 Braid-Covered Insulated Conductors — Exposed 
Installation. Exposed runs of braid-covered insulated con- 
ductors shall have a flame-retardant braid. If the conductors 



2005 Edition NATIONAL ELECTRICAL CODE 



70-131 



300.40 



ARTICLE 300 — WIRING METHODS 



used do not have this protection, a flame-retardant saturant 
shall be applied to the braid covering after installation. This 
treated braid covering shall be stripped back a safe distance 
at conductor terminals, according to the operating voltage. 
Where practicable, this distance shall not be less than 
25 mm (1 in.) for each kilovolt of the conductor-to-ground 
voltage of the circuit. 

300.40 Insulation Shielding. Metalhc and semiconducting 
insulation shielding components of shielded cables shall be 
removed for a distance dependent on the circuit voltage and 
insulation. Stress reduction means shall be provided at all 
terminations of factory-applied shielding. 

Metallic shielding components such as tapes, wires, or 
braids, or combinations thereof, and their associated con- 
ducting or semiconducting components shall be grounded. 

300.42 Moisture or Mechanical Protection for Metal- 
Sheathed Cables. Where cable conductors emerge from a 
metal sheath and where protection against moisture or 
physical damage is necessary, the insulation of the conduc- 
tors shall be protected by a cable sheath terminating device. 



300.50 Underground Installations. 

(A) General. Underground conductors shall be identified 
for the voltage and conditions under which they are in- 
stalled. Direct burial cables shall comply with the provi- 
sions of 310.7. Underground cables shall be installed in 
accordance with 300.50(A)(1) or (A)(2), and the installa- 
tion shall meet the depth requirements of Table 300.50. 

(1) Shielded Cables and Nonshielded Cables in Metal- 
Sheathed Cable Assemblies. Underground cables, includ- 
ing nonshielded. Type MC and moisture-impervious metal 
sheath cables, shall have those sheaths grounded through an 
effective grounding path meeting the requirements of 
250.4(A)(5) or (B)(4). They shall be direct buried or in- 
stalled in raceways identified for the use. 

(2) Other Nonshielded Cables. Other nonshielded cables 
not covered in 300.50(A)(1) shall be installed in rigid metal 
conduit, intermediate metal conduit, or rigid nonmetallic 
conduit encased in not less than 75 mm (3 in.) of concrete. 

(B) Protection from Damage. Conductors emerging from 
the ground shall be enclosed in Usted raceways. Raceways 
installed on poles shall be of rigid metal conduit, intermediate 



Table 300.50 Minimum Cover^ Requirements 





General Conditions (not otherwise specified) 


Special Conditions (use if applicable) 












(4) 
















Raceways 
















under 
















buildings or 


(5) 


(6) 












exterior 


Cables in 


Areas subject to 










(3) 


concrete slabs, 


airport 


vehicular trafiBc, 








(2) 


Rigid Metal 


100 mm 


runways or 


such as 








Rigid 


Conduit and 


(4 in.) 


adjacent areas 


thoroughfares and 




(1) 




Nonmetallic 


Intermediate 


mmimum 


where trespass 


commercial 




Direct-Buried Cables 


Conduit^ 


Metal Conduit 


thickness^ 


is prohibited 


parking areas 


Circuit Voltage 


mm 


in. 


mm 


in. 


mm 


in. 


mm 


in. 


mm 


in. 


mm 


in. 


Over 600 V 


























through 22 kV 


750 


30 


450 


18 


150 


6 


100 


4 


450 


18 


600 


24 


Over 22 kV 


























through 40 kV 


900 


36 


600 


24 


150 


6 


100 


4 


450 


18 


600 


24 


Over 40 kV 


1000 


42 


750 


30 


150 


6 


100 


4 


450 


18 


600 


24 



Notes: 

1. Lesser depths shall be permitted where cables and conductors rise for terminations or splices or where access is otherwise required. 

2. Where solid rock prevents compliance with the cover depths specified in this table, the wiring shall be installed in a metal or nonmetallic raceway 
permitted for direct burial. The raceways shall be covered by a minimum of 50 mm (2 in.) of concrete extending down to rock. 

' Cover is defined as the shortest distance in millimeters (inches) measured between a point on the top surface of any direct-buried conductor, cable, 

conduit, or other raceway and the top surface of finished grade, concrete, or similar coven 

^ Listed by a qualified testing agency as suitable for direct burial without encasement. All other nonmetallic systems shall require 50 mm (2 in.) 

of concrete or equivalent above conduit in addition to the table depth. 

^ The slab shall extend a minimum of 150 mm (6 in.) beyond the underground installation, and a warning ribbon or other effective means suitable 

for the conditions shall be placed above the underground installation. 



70-132 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



310.4 



• 



metal conduit, PVC Schedule 80, or equivalent, extending 
from the minimum cover depth specified in Table 300.50 to a 
point 2.5 m (8 ft) above finished grade. Conductors entering a 
building shall be protected by an approved enclosure or race- 
way from the minimum cover depth to the point of en- 
trance. Where direct-buried conductors, raceways, or cables 
are subject to movement by settlement or frost, they shall 
be installed to prevent damage to the enclosed conductors 
or to the equipment connected to the raceways. Metallic 
enclosures shall be grounded. 

(C) Splices. Direct burial cables shall be permitted to be 
spliced or tapped without the use of splice boxes, provided 
they are installed using materials suitable for the appUca- 
tion. The taps and splices shall be watertight and protected 
from mechanical damage. Where cables are shielded, the 
shielding shall be continuous across the splice or tap. 

Exception: At splices of an engineered cabling system, 
metallic shields of direct-buried single-conductor cables 
with maintained spacing between phases shall be permitted 
to be interrupted and overlapped. Where shields are inter- 
rupted and overlapped, each shield section shall be 
grounded at one point. 

(D) Backfill. Backfill containing large rocks, paving materi- 
als, cinders, large or sharply angular substances, or corrosive 
materials shall not be placed in an excavation where materials 
can damage or contribute to the corrosion of raceways, cables, 
or other substructures or where it may prevent adequate com- 
paction of fill. 

Protection in the form of granular or selected material 
or suitable sleeves shall be provided to prevent physical 
damage to the raceway or cable. 

(E) Raceway Seal. Where a raceway enters from an un- 
derground system, the end within the building shall be 
sealed with an identified compound so as to prevent the 
entrance of moisture or gases, or it shall be so arranged to 
prevent moisture from contacting live parts. 



i., ... ,: Gonduc^prs^ior. Gekeral "^ 

310.1 Scope. This article covers general requirements for 
conductors and their type designations, insulations, mark- 
ings, mechanical strengths, ampacity ratings, and uses. 
These requirements do not apply to conductors that form an 
integral part of equipment, such as motors, motor control- 
lers, and similar equipment, or to conductors specifically 
provided for elsewhere in this Code. 

FPN: For flexible cords and cables, see Article 400. For 
fixture wires, see Article 402. 



310.2 Conductors. 

(A) Insulated. Conductors shall be insulated. 

Exception: Where covered or bare conductors are specifi- 
cally permitted elsewhere in this Code. 

FPN: See 250. 1 84 for insulation of neutral conductors of a 
solidly grounded high-voltage system. 

(B) Conductor Material. Conductors in this article shall 
be of aluminum, copper-clad aluminum, or copper unless 
otherwise specified. 

310.3 Stranded Conductors. Where installed in raceways, 
conductors of size 8 AWG and larger shall be stranded. 

Exception: As permitted or required elsewhere in this Code. 

310.4 Conductors in Parallel. Aluminum, copper-clad 
aluminum, or copper conductors of size 1/0 AWG and 
larger, comprising each phase, polarity, neutral, or 
grounded circuit conductor, shall be permitted to be con- 
nected in parallel (electrically joined at both ends). 

Exception No. 1: As permitted in 620.12(A)(1). 

Exception No. 2: Conductors in sizes smaller than 
1/0 AWG shall be permitted to be run in parallel to 
supply control power to indicating instruments, contac- 
tors, relays, solenoids, and similar control devices, pro- 
vided all of the following apply: 

(a) They are contained within the same raceway or 
cable. 

(b) The ampacity of each individual conductor is suf- 
ficient to carry the entire load current shared by the paral- 
lel conductors. 

(c) The overcurrent protection is such that the ampac- 
ity of each individual conductor will not be exceeded if one 
or more of the parallel conductors become inadvertently 
disconnected. 

Exception No. 3: Conductors in sizes smaller than 
1/0 AWG shall be permitted to be run in parallel for fre- 
quencies of 360 Hz and higher where conditions (a), (b), 
and (c) of Exception No. 2 are met. 

Exception No. 4: Under engineering supervision, grounded 
neutral conductors in sizes 2 AWG and larger shall be permit- 
ted to be run in parallel for existing installations. 

FPN: Exception No. 4 can be used to alleviate overheating 
of neutral conductors in existing installations due to high 
content of triplen harmonic currents. 

The paralleled conductors in each phase, polarity, neu- 
tral, or grounded circuit conductor shall comply with all of 
the following: 

(1) Be the same length 

(2) Have the same conductor material 



2005 Edition 



NATIONAL ELECTRICAL CODE 



70-133 



310.5 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



(3) Be the same size in circular mil area 

(4) Have the same insulation type 

(5) Be terminated in the same manner 

Where run in separate raceways or cables, the raceways 
or cables shall have the same physical characteristics. 
Where conductors are in separate raceways or cables, the 
same number of conductors shall be used in each raceway 
or cable. Conductors of one phase, polarity, neutral, or 
grounded circuit conductor shall not be required to have the 
same physical characteristics as those of another phase, 
polarity, neutral, or grounded circuit conductor to achieve 
balance. 

FPN: Differences in inductive reactance and unequal divi- 
sion of current can be minimized by choice of materials, 
methods of construction, and orientation of conductors. 

Where equipment grounding conductors are used with 
conductors in parallel, they shall comply with the require- 
ments of this section except that they shall be sized in 
accordance with 250.122. 

Conductors installed in parallel shall comply with the 
provisions of 310.15(B)(2)(a). 

310.5 Minimum Size of Conductors. The minimum size 
of conductors shall be as shown in Table 310.5, except as 
permitted elsewhere in this Code. 

Table 310.5 Minimum Size of Conductors 



Conductor 

Voltage Rating 

(Volts) 



Minimum Conductor Size (AWG) 



Copper 



Aluminum or Copper-Clad 
Aluminum 



0-2000 
2001-8000 
8001-15,000 
15,001-28,000 
28,001-35,000 



14 
8 
2 
1 

1/0 



12 
8 
2 
1 

1/0 



310.6 Shielding. Solid dielectric insulated conductors op- 
erated above 2000 volts in permanent installations shall 
have ozone-resistant insulation and shall be shielded. All 
metallic insulation shields shall be grounded through an 
effective grounding path meeting the requirements of 
250.4(A)(5) or 250.4(B)(4). Shielding shall be for the pur- 
pose of confining the voltage stresses to the insulation. 

Exception: Nonshielded insulated conductors listed by a 
qualified testing laboratory shall be permitted for use up to 
2400 volts under the following conditions: 

(a) Conductors shall have insulation resistant to elec- 
tric discharge and surface tracking, or the insulated con- 



ductor(s) shall be covered with a material resistant to 
ozone, electric discharge, and surface tracking. 

(b) Where used in wet locations, the insulated conduc- 
tor(s) shall have an overall nonmetallic jacket or a continu- 
ous metallic sheath. 

(c) Insulation and jacket thicknesses shall be in accor- 
dance with Table 310.63. 

310.7 Direct Burial Conductors. Conductors used for di- 
rect burial applications shall be of a type identified for such 
use. 

Cables rated above 2000 volts shall be shielded. 

Exception: Nonshielded multiconductor cables rated 2001- 
5000 volts shall be permitted if the cable has an overall me- 
tallic sheath or armor. 

The metallic shield, sheath, or armor shall be grounded 
through an effective grounding path meeting the require- 
ments of 250.4(A)(5) or (B)(4). 

FPN No. 1: See 300.5 for installation requirements for 
conductors rated 600 volts or less. 

FPN No. 2: See 300.50 for installation requirements for 
conductors rated over 600 volts. 

310.8 Locations. 

(A) Dry Locations. Insulated conductors and cables used in 
dry locations shall be any of the types identified in this Code. 

(B) Dry and Damp Locations. Insulated conductors and 
cables used in dry and damp locations shall be Types FEP, 
FEPB, MTW, PFA, RHH, RHW, RHW-2, SA, THHN, 
THW, THW-2, THHW, THHW-2, THWN, THWN-2, TW, 
XHH, XHHW, XHHW-2, Z, or ZW. 

(C) Wet Locations. Insulated conductors and cables used 
in wet locations shall be 

(1) Moisture-impervious metal- sheathed; 

(2) Types MTW, RHW, RHW-2, TW, THW, THW-2, THHW, 
THHW-2, THWN, THWN-2, XHHW, XHHW-2, ZW; or 

(3) Of a type fisted for use in wet locations. 

(D) Locations Exposed to Direct Sunlight. Insulated con- 
ductors or cables used where exposed to direct rays of the 
sun shall comply with one of the following: 

(1) Cables fisted, or listed and marked, as being sunfight 
resistant 

(2) Conductors listed, or fisted and marked, as being sun- 
light resistant 

(3) Covered with insulating material, such as tape or sleev- 
ing, that is listed, or listed and marked, as being sun- 
fight resistant 



• 



70-134 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



310.11 



• 



310.9 Corrosive Conditions. Conductors exposed to oils, 
greases, vapors, gases, fumes, liquids, or other substances 
having a deleterious effect on the conductor or insulation 
shall be of a type suitable for the application. 

310.10 Temperature Limitation of Conductors. No con- 
ductor shall be used in such a manner that its operating tem- 
perature exceeds that designated for the type of insulated con- 
ductor involved. In no case shall conductors be associated 
together in such a way, with respect to type of circuit, the 
wiring method employed, or the number of conductors, that 
the limiting temperature of any conductor is exceeded. 

FPN No. 1: The temperature rating of a conductor (see 
Table 310.13 and Table 310.61) is the maximum tempera- 
ture, at any location along its length, that the conductor can 
withstand over a prolonged time period without serious 
degradation. The allowable ampacity tables, the ampacity 
tables of Article 310 and the ampacity tables of Annex B, 
the correction factors at the bottom of these tables, and the 
notes to the tables provide guidance for coordinating con- 
ductor sizes, types, allowable ampacities, ampacities, ambi- 
ent temperatures, and number of associated conductors. 

The principal determinants of operating temperature 
are as follows: 

(1) Ambient temperature — ambient temperature may vary 
along the conductor length as well as from time to time. 

(2) Heat generated internally in the conductor as the result 
of load current flow, including fundamental and har- 
monic currents. 

(3) The rate at which generated heat dissipates into the 
ambient medium. Thermal insulation that covers or sur- 
rounds conductors affects the rate of heat dissipation. 

(4) Adjacent load-carrying conductors — adjacent conduc- 
tors have the dual effect of raising the ambient tempera- 
ture and impeding heat dissipation. 

FPN No. 2: Conductors installed in conduit exposed to 
direct sunlight in close proximity to rooftops have been 
shown, under certain conditions, to experience a tempera- 
ture rise of 17°C (30°F) above ambient temperature on 
which the ampacity is based. 

310.11 Marking. 

(A) Required Information. All conductors and cables 
shall be marked to indicate the following information, us- 
ing the applicable method described in 310.11(B): 

(1) The maximum rated voltage 

(2) The proper type letter or letters for the type of wire or 
cable as specified elsewhere in this Code 

(3) The manufacturer's name, trademark, or other distinc- 
tive marking by which the organization responsible for 
the product can be readily identified 

(4) The AWG size or circular mil area 

FPN: See Conductor Properties, Table 8 of Chapter 9, for 
conductor area expressed in SI units for conductor sizes 
specified in AWG or circular mil area. 



(5) Cable assemblies where the neutral conductor is smaller 
than the ungrounded conductors shall be so marked 

(B) Method of Marking. 

(1) Surface Marking. The following conductors and 
cables shall be durably marked on the surface. The AWG 
size or circular mil area shall be repeated at intervals not 
exceeding 610 mm (24 in.). All other markings shall be 
repeated at intervals not exceeding 1.0 m (40 in.). 

(1) Single-conductor and multiconductor rubber- and 
thermoplastic-insulated wire and cable 

(2) Nonmetallic-sheathed cable 

(3) Service-entrance cable 

(4) Underground feeder and branch-circuit cable 

(5) Tray cable 

(6) Irrigation cable 

(7) Power-limited tray cable 

(8) Instrumentation tray cable 

(2) Marker Tape. Metal-covered multiconductor cables 
shall employ a marker tape located within the cable and 
running for its complete length. 

Exception No. 1: Mineral-insulated, metal-sheathed cable. 

Exception No. 2: Type AC cable. 

Exception No. 3: The information required in 310.11(A) 
shall be permitted to be durably marked on the outer non- 
metallic covering of Type MC, Type ITC, or Type PLTC 
cables at intervals not exceeding 1.0 m (40 in.). 

Exception No. 4: The information required in 310.11(A) 
shall be permitted to be durably marked on a nonmetallic 
covering under the metallic sheath of Type ITC or Type 
PLTC cable at intervals not exceeding 1.0 m (40 in.). 

FPN: Included in the group of metal-covered cables are 
Type AC cable (Article 320), Type MC cable (Article 330), 
and lead-sheathed cable. 

(3) Tag Marking. The following conductors and cables 
shall be marked by means of a printed tag attached to the 
coil, reel, or carton: 

(1) Mineral-insulated, metal-sheathed cable 

(2) Switchboard wires 

(3) Metal-covered, single-conductor cables 

(4) Type AC cable 

(4) Optional Marking of Wire Size. The information re- 
quired in 310.11(A)(4) shall be permitted to be marked on 
the surface of the individual insulated conductors for the 
following multiconductor cables: 

(1) Type MC cable 

(2) Tray cable 

(3) Irrigation cable 



2005 Edition NATIONAL ELECTRICAL CODE 



70-135 



310.12 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



(4) Power-limited tray cable 

(5) Power-limited fire alarm cable 

(6) Instrumentation tray cable 

(C) Suffixes to Designate Number of Conductors. A type 
letter or letters used alone shall indicate a single insulated 
conductor. The letter suffixes shall be indicated as follows: 

(1) D — For two insulated conductors laid parallel within 
an outer nonmetallic covering 

(2) M — For an assembly of two or more insulated con- 
ductors twisted spirally within an outer nonmetallic 
covering 

(D) Optional Markings. All conductors and cables con- 
tained in Chapter 3 shall be permitted to be surface marked 
to indicate special characteristics of the cable materials. 
These markings include, but are not limited to, markings 
for limited smoke, sunlight resistant, and so forth. 

310.12 Conductor Identification. 

(A) Grounded Conductors. Insulated or covered grounded 
conductors shall be identified in accordance with 200.6. 

(B) Equipment Grounding Conductors. Equipment 
grounding conductors shall be in accordance with 250.119. 

(C) Ungrounded Conductors. Conductors that are intended 
for use as ungrounded conductors, whether used as a single 
conductor or in multiconductor cables, shall be finished to be 
clearly distinguishable from grounded and grounding conduc- 
tors. Distinguishing markings shall not conflict in any manner 
with the surface markings required by 310.11(B)(1). Branch- 
circuit ungrounded conductors shall be identified in accor- 
dance with 210.5(C). Feeders shall be identified in accordance 
with 215.12. 

Exception: Conductor identification shall be permitted in 
accordance with 200.7. 

310.13 Conductor Constructions and Applications. In- 
sulated conductors shall comply with the applicable provi- 
sions of one or more of the following: Table 310.13, Table 
310.61, Table 310.62, Table 310.63, and Table 310.64. 

These conductors shall be permitted for use in any of the 
wiring methods recognized in Chapter 3 and as specified in 
their respective tables or as permitted elsewhere in this Code. 

FPN: Thermoplastic insulation may stiifen at temperatures 
lower than -10°C (+14°F). Thermoplastic insulation may also 
be deformed at normal temperatures where subjected to pres- 
sure, such as at points of support. Thermoplastic insulation, 
where used on dc circuits in wet locations, may result in elec- 
troendosmosis between conductor and insulation. 

310.14 Aluminum Conductor Material. Solid aluminum 
conductors 8, 10, and 12 AWG shall be made of an AA-8000 
series electrical grade aluminum alloy conductor material. 



Stranded aluminum conductors 8 AWG through 1000 kcmil 
marked as Type RHH, RHW, XHHW, THW, THHW, THWN, 
THHN, service-entrance Type SE Style U and SE Style R 
shall be made of an AA-8000 series electrical grade aluminum 
alloy conductor material. 

310.15 Ampacities for Conductors Rated 0-2000 Volts. 

(A) General. 

(1) Tables or Engineering Supervision. Ampacities for 
conductors shall be permitted to be determined by tables as 
provided in 310.15(B) or under engineering supervision, as 
provided in 310.15(C). 

FPN No. 1: Ampacities provided by this section do not 
take voltage drop into consideration. See 210.19(A), FPN 
No. 4, for branch circuits and 215.2(A), FPN No. 2, for 
feeders. 

FPN No. 2: For the allowable ampacities of Type MTW 
wire, see Table 13.5.1 in NFPA 79-2002, Electrical Stan- 
dard for Industrial Machinery. 

(2) Selection of Ampacity. Where more than one calcu- 
lated or tabulated ampacity could apply for a given circuit 
length, the lowest value shall be used. 

Exception: Where two different ampacities apply to adja- 
cent portions of a circuit, the higher ampacity shall be 
permitted to be used beyond the point of transition, a dis- 
tance equal to 3.0 m (10 ft) or 10 percent of the circuit 
length figured at the higher ampacity, whichever is less. 

FPN: See 110.14(C) for conductor temperature limitations 
due to termination provisions. 

(B) Tables. Ampacities for conductors rated to 2000 volts 
shall be as specified in the Allowable Ampacity Table 310.16 
through Table 310.19, and Ampacity Table 310.20 and Table 
310.21 as modified by (B)(1) through (B)(6). 

FPN: Table 310.16 through Table 310.19 are application 
tables for use in determining conductor sizes on loads calcu- 
lated in accordance with Article 220. Allowable ampacities 
result from consideration of one or more of the following: 

(1) Temperature compatibility with connected equipment, 
especially the connection points. 

(2) Coordination with circuit and system overcurrent 
protection. 

(3) Compliance with the requirements of product listings 
or certifications. See 110.3(B). 

(4) Preservation of the safety benefits of established indus- 
try practices and standardized procedures. 

(1) General. For explanation of type letters used in tables 
and for recognized sizes of conductors for the various conduc- 
tor insulations, see 310.13. For installation requirements, 
see 310.1 through 310.10 and the various articles of this 
Code. For flexible cords, see Table 400.4, Table 400.5(A), 
and Table 400.5(B). 



• 



• 



70-136 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



310.15 



Table 310.13 Conductor Application and Insulations 



# 



• 





Type 


Maximum 
Operating 






Thickness of Insulation 














Trade Name 


Letter 


Temperature 


Application Provisions 


Insulation 


AWG or kcmil 


mm 


mils 


Outer Covering' 


Fluorinated ethylene 


FEPor 


90°C 


Dry and damp locations 


Fluorinated 


14-10 


0.51 


20 


None 


propylene 


FEPB 


194°F 

200°C 
392°F 


Dry locations — special 
applications^ 


ethylene propylene 

Fluorinated 

ethylene propylene 


8-2 


0.76 


30 






14-8 


0.36 


14 


Glass braid 








6-2 


0.36 


14 


Glass or other 


















suitable braid 


















material 


Mineral insulation 


MI 


90°C 


Dry and wet locations 


Magnesium oxide 


18-16^ 


0.58 


23 


Copper or alloy steel 


(metal sheathed) 




194°F 






16-10 


0.91 


36 








250°C 
482°F 


For special applications^ 




9-4 
3-500 


1.27 
1.40 


50 
55 




Moisture-, heat-, and 


MTW 


60°C 
140°F 


Machine tool wiring in 
wet locations 


Flame-re tardant 
moisture-, heat-. 




(A) (B) 


(A) (B) 


(A) None 


oil-resistant thermo- 






(B) Nylon jacket or 


plastic 




90°C 
194°F 


Machine tool wiring in 

dry locations. 
FPN: See NFPA 79. 


and oil -resistant 
thermo- 
plastic 


22-12 

10 

8 

6 

4-2 

1^/0 

213-500 

501-1000 


0.76 0.38 
0.76 0.51 
1.14 0.76 
1.52 0.76 
1.52 1.02 
2.03 1.27 
2.41 1.52 
2.79 1.78 


30 15 
30 20 
45 30 
60 30 
60 40 
80 50 
95 60 
110 70 


equivalent 


Paper 




85°C 
185°F 


For underground service 
conductors, or by 
special permission 


Paper 








Lead sheath 


Perfluoro-alkoxy 


PFA 


90°C 
194°F 


Dry and damp locations 


Perfluoro-alkoxy 


14-10 
8-2 


0.51 
0.76 


20 
30 


None 






200°C 


Dry locations — special 




M/0 


1.14 


45 








392°F 


applications'^ 












Perfluoro-alkoxy 


PFAH 


250°C 


Dry locations only. Only 


Perfluoro-alkoxy 


14-10 


0.51 


20 


None 






482°F 


for leads within 
apparatus or within 
raceways connected to 
apparatus (nickel or 
nickel-coated copper 
only) 




8-2 
1-4/0 


0.76 
1.14 


30 
45 




Thermoset 


RHH 


90°C 


Dry and damp locations 




14-10 


1.14 


45 


Moisture-resistant, 






194°F 






8-2 

1-4/0 

213-500 

501-1000 

1001-2000 

For 601-2000 

see Table 

310.62. 


1.52 
2.03 
2.41 
2.79 
3.18 


60 
80 
95 
110 

125 


flame-retardant, 
nonmetallic 
covering' 


Moisture-resistant 


RHW^ 


75°C 


Dry and wet locations 


Flame-retardant, 


14-10 


1.14 


45 


Moisture-resistant, 


thermoset 




167°F 




moisture- resistant 


8-2 


1.52 


60 


flame-retardant. 










thermoset 


1^/0 
213-500 
501-1000 
1001-2000 
For 601-2000, 
see Table 
310.62. 


2.03 
2.41 
2.79 
3.18 


80 
95 
110 
125 


nonmetallic 
covering^ 


Moisture-resistant 


RHW-2 


90°C 


Dry and wet locations 


Flame-retardant 


14-10 


1.14 


45 


Moisture-resistant, 


thermoset 




194°F 




moisture-resistant 


8-2 


1.52 


60 


flame-retardant. 










thermoset 


1-4/0 

213-500 

501-1000 

1001-2000 

For 601-2000, 

see Table 310.62. 


2.03 
2.41 
2.79 
3.18 


80 
95 
110 
125 


nonmetallic 
covering^ 



2005 Edition NATIONAL ELECTRICAL CODE 



(Continues) 

70-137 



310.15 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



Table 310.13 Continued 





Type 


Maximum 
Operating 






Tliicl(nes$ of Insulation 














Trade Name 


Letter 


Temperature 


Application Provisions 


Insulation 


AWG or kcmil 


mm 


mils 


Outer Covering^ 


Silicone 


SA 


90°C 


Dry and damp locations 


Silicone rubber 


14-10 


1.14 


45 


Glass or other 






194°F 






8-2 


1.52 


60 


suitable braid 






200°C 
392°F 


For special application^ 




1-4/0 
213-500 
501-1000 
1001-2000 


2.03 
241 
2.79 
3.18 


80 
95 
110 
125 


material 


Thermoset 


SIS 


90°C 


Switchboard wiring only 


Flame-retardant 


14-10 


0.76 


30 


None 






194°F 




thermoset 


8-2 
1^/0 


1.14 

241 


45 
95 




Thermoplastic and 


TBS 


90°C 


Switchboard wiring only 


Thermoplastic 


14-10 


0.76 


30 


Flame-retardant, 


fibrous outer braid 




i94°F 






8 
6-2 
1-^/0 


1.14 
1.52 
2.03 


45 
60 
80 


nonmetallic 
covering 


Extended poiytetra- 


VVh. 


250°C 


Dry locations only. Only 


Extruded polytetra- 


14-10 


0.51 


20 


None 


fluoro-ethylene 




482°F 


for leads within 
apparatus or within 
raceways connected to 
apparatus, or as open 
wiring (nickel or 
nickel-coated copper 
only) 


fluoro-ethylene 


8-2 
1^/0 


0.76 
1.14 


30 

45 




Heat-resistant 


THHN 


90°C 


Dry and damp locations 


Rame-retardant, 


14-12 


0.38 


15 


Nylon jacket or 


thermoplastic 




194°F 




heat-resistant 
thermoplastic 


10 

8-6 

4-2 

1-4/0 

250-500 

501-1000 


0.51 
0.76 
1.02 
1.27 
1.52 
1.78 


20 
30 
40 
50 
60 
70 


equivalent 


Moisture- and 


THHW 


75°C 


Wet location 


Rame-retardant, 


14-10 


0.76 


30 


None 


heat-resistant 




167°F 




moisture- and 


8 


1.14 


45 




thermoplastic 




90°C 
194°F 


Dry location 


heat-resistant 
thermoplastic 


6-2 

1^/0 

213-500 

501-1000 


1.52 
2.03 
241 
2.79 


60 
80 
95 
110 




Moisture- and 


THW^ 


75°C 


Dry and wet locations 


Flame-retardant, 


14-10 


0.76 


30 


None 


heat-resistant 




167''F 




moisture- and 


8 


1.14 


45 




thermoplastic 




90°C 
194°F 


Special applications within 
electric discharge 
lighting equipment. 
Limited to 1000 
open-circuit volts or 
less, (size 14-8 only as 
permitted in 410.33) 


heat-resistant 
thermoplastic 


6-2 

1-4/0 

213-500 

501-1000 

1001-2000 


1.52 
2.03 
241 
2.79 
3.18 


60 
80 
95 
110 

125 




Moisture- and 


THWN'' 


75°C 


Dry and wet locations 


Flame-retardant, 


14-12 


0.38 


15 


Nylon jacket or 


heat-resistant 




167°F 




moisture- and 


10 


0.51 


20 


equivalent 


thermoplastic 








heat-resistant 
thermoplastic 


8-6 

4-2 

1-4/0 

250-500 

501-1000 


0.76 
1.02 
1.27 
1.52 
1.78 


30 
40 
50 
60 
70 




Moisture-resistant 


TW 


60°C 


Dry and wet locations 


Flame-retardant, 


14-10 


0.76 


30 


None 


thermoplastic 




140°F 




moisture- resistant 
thermoplastic 


8 

6-2 

1-4/0 

213-500 

501-1000 

1001-2000 


1.14 
1.52 
2.03 
241 
2.79 
3.18 


45 
60 
80 
95 
110 
125 





• 



70-138 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



310.15 



Table 310.13 Continued 





Type 


Maximum 
Operating 






Thickness of Insulation 














Trade Name 


Letter 


Temperature 


Application Provisions 


Insulation 


AWG or kcmil 


mm 


mils 


Outer Covering' 


Underground feeder 


UF 


60°C 


See Article 340. 


Moisture-resistant 


14-10 


1.52 


60* 


Integral with 


and branch-circuit 




140°F 






8-2 


2.03 


SO'* 


insulation 


cable — single 




75°C 




Moisture- and 


1^/0 


2.41 


95* 




conductor (for Type 




167°F' 




heat-resistant 










UF cable employing 


















more than one 


















conductor, see Article 


















340.) 


















Underground service- 


USE'* 


75°C 


See Article 338. 


Heat- and moisture- 


14-10 


1.14 


5 


Moisture-resistant 


entrance cable — 




167°F 




resistant 


8-2 


1.52 


60 


nonmetallic 


single conductor (for 










1^/0 


2.03 


80 


covering (See 


Type USE cable 










213-500 


2.41 


95« 


338.2.) 


employing more than 










501-1000 


2.79 


110 




one conductor, see 










1001-2000 


3.18 


125 




Article 338.) 


















Thermoset 


XHH 


90°C 


Dry and damp locations 


Flame-retardant 


14-10 


0.76 


30 


None 






194°F 




thermoset 


8-2 

1-4/0 

213-500 

501-1000 

1001-2000 


1.14 
1.40 
1.65 
2.03 
2.41 


45 
55 
65 
80 
95 




Moisture-resistant 


XHHW* 


90°C 


Dry and damp locations 


Flame-retardant, 


14-10 


0.76 


30 


None 


thermoset 




194°F 




moisture-resistant 
thermoset 


8-2 
1^/0 


1.14 
1.40 


45 
55 








75°C 


Wet locations 




213-500 


1.65 


65 








167°F 






501-1000 
1001-2000 


2.03 
2.41 


80 
95 




Moisture-resistant 


XHHW-2 


90°C 


Dry and wet locations 


Flame-retardant, 


14-10 


0.76 


30 


None 


thermoset 




194°F 




moisture-resistant 
thermoset 


8-2 

1^/0 

213-500 

501-1000 

1001-2000 


1.14 
1.40 
1.65 
2.03 
2.41 


45 
55 
65 
80 
95 




Modified ethylene 


Z 


90°C 


Dry and damp 


Modified ethylene 


14-12 


0.38 


15 


None 


tetrafluoro-ethylene 




194°F 


locations 


tetrafluoro- ethylene 


10 


0.51 


20 








150°C 


Dry locations — 




8^ 


0.64 


25 








302°F 


special applications^ 




3-1 
1/0-4/0 


0.89 
1.14 


35 
45 




Modified ethylene 


ZW^ 


75°C 


Wet locations 


Modified ethylene 


14-10 


0.76 


30 


None 


tetrafluoro-ethylene 




167°F 

90°C 
194°F 

150°C 
302°F 


Dry and damp locations 

Dry locations — 
special applications^ 


tetrafluoro-ethylene 


8-2 


1.14 


45 





' Some insulations do not require an outer covering. 

^ Where design conditions require maximum conductor operating temperatures above 90°C (194°F). 
^ For signaling circuits permitting 300-volt insulation. 

'^ Listed wire types designated with the suflBx "2," such as RHW-2, shall be permitted to be used at a 
continuous 90°C (194°F) operating temperature, wet or dry. 
^ Some rubber insulations do not require an outer covering. 
^ Includes integral jacket. 
^ For ampacity limitation, see 340.80. 

^ Insulation thickness shall be permitted to be 2.03 mm (80 mils) for listed Type USE conductors that have 
been subjected to special investigations. The nonmetallic covering over individual rubber-covered conduc- 
tors of aluminum-sheathed cable and of lead-sheathed or multiconductor cable shall not be required to be 
flame retardant. For Type MC cable, see 330.104. For nonmetallic-sheathed cable, see Article 334, Part III. 
For Type UF cable, see Article 340, Part III. 



2005 Edition NATIONAL ELECTRICAL CODE 



70-139 



310.15 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



(2) Adjustment Factors. 

(a) More Than Three Current-Carrying Conductors in 
a Raceway or Cable. Where the number of current-carrying 
conductors in a raceway or cable exceeds three, or where 
single conductors or multiconductor cables are stacked or 
bundled longer than 600 mm (24 in.) without maintaining 
spacing and are not installed in raceways, the allowable 
ampacity of each conductor shall be reduced as shown in 
Table 310.15(B)(2)(a). Each current-carrying conductor of 
a paralleled set of conductors shall be counted as a current- 
carrying conductor. 

FPN No. 1: See Annex B, Table B.310.11, for adjustment 
factors for more than three current-carrying conductors in a 
raceway or cable with load diversity. 

FPN No. 2: See 366.23(A) for correction factors for con- 
ductors in sheet metal auxiliary gutters and 376.22 for cor- 
rection factors for conductors in metal wireways. 

Exception No. 1: Where conductors of different systems, 
as provided in 300.3, are installed in a common raceway or 
cable, the derating factors shown in Table 310.15(B)(2)(a) 
shall apply only to the number of power and lighting con- 
ductors (Articles 210, 215, 220, and 230). 

Exception No. 2: For conductors installed in cable trays, 
the provisions of 392. 11 shall apply. 

Exception No. 3: Derating factors shall not apply to con- 
ductors in nipples having a length not exceeding 600 mm 
(24 in.). 

Exception No. 4: Derating factors shall not apply to un- 
derground conductors entering or leaving an outdoor 
trench if those conductors have physical protection in the 
form of rigid metal conduit, intermediate metal conduit, or 
rigid nonmetallic conduit having a length not exceeding 
3.05 m (10 ft) and if the number of conductors does not 
exceed four 

Exception No. 5: Adjustment factors shall not apply to 
Type AC cable or to Type MC cable without an overall 
outer jacket under the following conditions: 

(1) Each cable has not more than three current-carrying 
conductors. 

(2) The conductors are 12 AWG copper 

(3) Not more than 20 current-carrying conductors are 
bundled, stacked, or supported on "bridle rings. " 

A 60 percent adjustment factor shall be applied where the 
current-carrying conductors in these cables that are 
stacked or bundled longer than 600 mm (24 in.) without 
maintaining spacing exceeds 20. 

(b) More Than One Conduit, Tube, or Raceway. 
Spacing between conduits, tubing, or raceways shall be 
maintained. 



Table 310.15(B)(2)(a) Adjustment Factors for More Than 
Three Current-Carrying Conductors in a Raceway or Cable 





Percent of Values in Tables 


Number of 


310.16 through 310.19 as 


Current-Carrying 


Adjusted for Ambient 


Conductors 


Temperature if Necessary 


4-6 


80 


7-9 


70 


10-20 


50 


21-30 


45 


31-40 


40 


41 and above 


35 



(3) Bare or Covered Conductors. Where bare or covered 
conductors are used with insulated conductors, their allow- 
able ampacities shall be limited to those permitted for the 
adjacent insulated conductors. 

(4) Neutral Conductor. 

(a) A neutral conductor that carries only the unbal- 
anced current from other conductors of the same circuit 
shall not be required to be counted when applying the pro- 
visions of 310.15(B)(2)(a). 

(b) In a 3-wire circuit consisting of two phase wires 
and the neutral of a 4-wire, 3-phase, wye-connected sys- 
tem, a common conductor carries approximately the same 
current as the line-to-neutral load currents of the other con- 
ductors and shall be counted when applying the provisions 
of 310.15(B)(2)(a). 

(c) On a 4-wire, 3-phase wye circuit where the major 
portion of the load consists of nonlinear loads, harmonic 
currents are present in the neutral conductor; the neutral 
shall therefore be considered a current-carrying conductor. 

(5) Grounding or Bonding Conductor. A grounding or 
bonding conductor shall not be counted when applying the 
provisions of 310.15(B)(2)(a). 

(6) 120/240- Volt, 3-Wire, Single-Phase Dwelling Ser- 
vices and Feeders. For individual dwelling units of one 
family, two-family, and multifamily dwellings, conductors, 
as Usted in Table 310.15(B)(6), shall be permitted as 
120/240-volt, 3-wire, single-phase service-entrance con- 
ductors, service lateral conductors, and feeder conductors 
that serve as the main power feeder to each dwelling unit 
and are installed in raceway or cable with or without an 
equipment grounding conductor. For application of this sec- 
tion, the main power feeder shall be the feeder(s) between 
the main disconnect and the lighting and appliance branch- 
circuit panelboards(s). The feeder conductors to a dwelling 
unit shall not be required to have an allowable ampacity 
rating greater than their service-entrance conductors. The 
grounded conductor shall be permitted to be smaller than 
the ungrounded conductors, provided the requirements of 
215.2, 220.61, and 230.42 are met. 



70-140 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



310.60 



Table 310.15(B)(6) Conductor Types and Sizes for 
120/240- Volt, 3- Wire, Single-Phase Dwelling Services and 
Feeders. Conductor T^pes RHH, RHW, RHW-2, THHN, 
THHW, THW, THW-2, THWN, THWN-2, XHHW, 
XHHW-2, SE, USE, USE-2 



Conductor (AWG or kcmil) 




Aluminum or 






Copper-Clad 


Service or Feeder 


Copper 


Aluminum 


Rating (Amperes) 


4 


2 


100 


3 


1 


110 


2 


1/0 


125 


1 


2/0 


150 


1/0 


3/0 


175 


2/0 


4/0 


200 


3/0 


250 


225 


4/0 


300 


250 


250 


350 


300 


350 


500 


350 


400 


600 


400 



• 



(C) Engineering Supervision. Under engineering supervi- 
sion, conductor ampacities shall be permitted to be calcu- 
lated by means of the following general formula: 



/ = 



TC-{TA + ATD) 
RDC{1 + YC)RCA 



where: 
TC = conductor temperature in degrees Celsius (°C) 
TA = ambient temperature in degrees Celsius (°C) 
ATD = dielectric loss temperature rise 
RDC = dc resistance of conductor at temperature TC 
YC = component ac resistance resulting from skin 
effect and proximity effect 
RCA = effective thermal resistance between conductor 
and surrounding ambient 

FPN: See Annex B for examples of formula applications. 



310.60 Conductors Rated 2001 to 35,000 Volts. 

(A) Definitions. 

Electrical Ducts. As used in Article 310, electrical ducts 
shall include any of the electrical conduits recognized in 
Chapter 3 as suitable for use underground; other raceways 
round in cross section, listed for underground use, and em- 
bedded in earth or concrete. 

Thermal Resistivity. As used in this Code, the heat trans- 
fer capability through a substance by conduction. It is the 
reciprocal of thermal conductivity and is designated Rho 
and expressed in the units °C-cm/watt. 

(B) Ampacities of Conductors Rated 2001 to 35,000 
Volts. Ampacities for sohd dielectric-insulated conductors 
shall be permitted to be determined by tables or under en- 
gineering supervision, as provided in 310.60(C) and (D). 

(1) Selection of Ampacity. Where more than one calcu- 
lated or tabulated ampacity could apply for a given circuit 
length, the lowest value shall be used. 

Exception: Where two different ampacities apply to adja- 
cent portions of a circuit, the higher ampacity shall be 
permitted to be used beyond the point of transition, a dis- 
tance equal to 3.0 m (10 ft) or 10 percent of the circuit 
length figured at the higher ampacity, whichever is less. 

FPN: See 110.40 for conductor temperature limitations 
due to termination provisions. 



2005 Edition 



NATIONAL ELECTRICAL CODE 



70-141 



310.60 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



Table 310.16 Allowable Ampacities of Insulated Conductors Rated Through 2000 Volts, 60°C Through 
90°C (140°F Through 194°F), Not More Than Three Current-Carrying Conductors in Raceway, Cable, 
or Earth (Directly Buried), Based on Ambient Temperature of 30°C (86°F) 





Temperature Rating of Conductor (See Table 310.13.) 












60°C 










60°C (140°F) 


75°C (167°F) 


90°C (194°F) 


(140°F) 


75°C (167°F) 


90°C (194°F) 










Types TBS, SA, SIS, 
















FEP, FEPB, MI, RHH, 






Types TBS, SA, SIS, 










RHW-2, THHN, 






THHN, THHW, 








Types RHW, 


THHW, THW-2, 




Types RHW, 


THW-2, THWN-2, 








THHW, THW, 


THWN-2, USE-2, 




THHW, THW, 


RHH, RHW-2, USE-2, 








THWN, XHHW, 


XHH, XHHW, 


Types 


THWN, 


XHH, XHHW, 






Types TW, UF 


USE, ZW 


XHHW-2, ZW-2 


TW, UF 


XHHW, USE 


XHHW-2, ZW-2 




Size AWG or 














Size AWG or 


kcmil 




COPPER 




ALUMINUM OR COPPER-CLAD ALUMINUM 


kcmil 


18 
16 

14* 


— 


— 


14 
18 

25 


— 


— 


— 


— 


20 


20 














12* 


25 


25 


30 


20 


20 


25 


12* 


10* 


30 


35 


40 


25 


30 


35 


10* 


8 


40 


50 


55 


30 


40 


45 


8 


6 


55 


65 


75 


40 


50 


60 


6 


4 


70 


85 


95 


55 


65 


75 


4 


3 


85 


100 


110 


65 


75 


85 


3 


2 


95 


115 


130 


75 


90 


100 


2 


1 


110 


130 


150 


85 


100 


115 


1 


1/0 


125 


150 


170 


100 


120 


135 


1/0 


2/0 


145 


175 


195 


115 


135 


150 


2/0 


3/0 


165 


200 


225 


130 


155 


175 


3/0 


4/0 


195 


230 


260 


150 


180 


205 


4/0 


250 


215 


255 


290 


170 


205 


230 


250 


300 


240 


285 


320 


190 


230 


255 


300 


350 


260 


310 


350 


210 


250 


280 


350 


400 


280 


335 


380 


225 


270 


305 


400 


500 


320 


380 


430 


260 


310 


350 


500 


600 


355 


420 


475 


285 


340 


385 


600 


700 


385 


460 


520 


310 


375 


420 


700 


750 


400 


475 


535 


320 


385 


435 


750 


800 


410 


490 


555 


330 


395 


450 


800 


900 


435 


520 


585 


355 


425 


480 


900 


1000 


455 


545 


615 


375 


445 


500 


1000 


1250 


495 


590 


665 


405 


485 


545 


1250 


1500 


520 


625 


705 


435 


520 


585 


1500 


1750 


545 


650 


735 


455 


545 


615 


1750 


2000 


560 


665 


750 


470 


560 


630 


2000 



CORRECTION FACTORS 



Ambient Temp. 

(°C) 


For ambient temperatures other than 30°C (86°F), multiply the allowable ampacities shown above by the appropriate 

factor shown below. 


Ambient Temp. 

(°F) 


21-25 


1.08 


1.05 


1.04 


1.08 


1.05 


1.04 


70-77 


26-30 


1.00 


1.00 


1.00 


1.00 


1.00 


1.00 


78-86 


31-35 


0.91 


0.94 


0.96 


0.91 


0.94 


0.96 


87-95 


36^0 


0.82 


0.88 


0.91 


0.82 


0.88 


0.91 


96-104 


41-45 


0.71 


0.82 


0.87 


0.71 


0.82 


0.87 


105-113 


46-50 


0.58 


0.75 


0.82 


0.58 


0.75 


0.82 


114-122 


51-55 


0.41 


0.67 


0.76 


0.41 


0.67 


0.76 


123-131 


56-60 




0.58 


0.71 


_ 


0.58 


0.71 


132-140 


61-70 




0.33 


0.58 


_ 


0.33 


0.58 


141-158 


71-80 


— 


— 


0.41 


— 


— 


0.41 


159-176 



* See 240.4(D). 



70-142 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



310.60 



Table 310.17 Allowable Ampacities of Single-Insulated Conductors Rated Through 2000 Volts 
in Free Air, Based on Ambient Air Temperature of 30°C (86°F) 



• 



• 





Temperature Rating of Conductor (See Table 310.13.) 






60°C (140°F) 


75°C (167°F) 


90°C (194°F) 


60°C (140°F) 


75°C (167°F) 


90°C (194°F) 










Types TBS, SA, SIS, 






Types TBS, SA, SIS, 










FEP, FEPB, MI, RHH, 






THHN, THHW, 








T^-pes RHW, 


RHW-2, THHN, THHW, 




lypes RHW, 


THW-2, THWN-2, 








THHW, THW, 


THW-2, THWN-2, 




THHW, THW, 


RHH, RHW-2, USE-2, 








THWN, 


USE-2, XHH, XHHW, 




THWN, 


XHH, XHHW, 






Types TW, UF 


XHHW, ZW 


XHHW-2, ZW-2 


Types TW, UF 


XHHW 


XHHW-2, ZW-2 




Size AWG or 














Size AWG or 


kcmil 




COPPER 


ALUMINUM OR COPPER-CLAD ALUMINUM 


kcmil 


18 






18 










16 


— 


— 


24 


— 


— 


— 


— 


14* 


25 


30 


35 


— 


— 


— 


— 


12* 


30 


35 


40 


25 


30 


35 


12* 


10* 


40 


50 


55 


35 


40 


40 


10* 


8 


60 


70 


80 


45 


55 


60 


8 


6 


80 


95 


105 


60 


75 


80 


6 


4 


105 


125 


140 


80 


100 


110 


4 


3 


120 


145 


165 


95 


115 


130 


3 


2 


140 


170 


190 


110 


135 


150 


2 


1 


165 


195 


220 


130 


155 


175 


1 


1/0 


195 


230 


260 


150 


180 


205 


1/0 


2/0 


225 


265 


300 


175 


210 


235 


2/0 


3/0 


260 


310 


350 


200 


240 


275 


3/0 


4/0 


300 


360 


405 


235 


280 


315 


4/0 


250 


340 


405 


455 


265 


315 


355 


250 


300 


375 


445 


505 


290 


350 


395 


300 


350 


420 


505 


570 


330 


395 


445 


350 


400 


455 


545 


615 


355 


425 


480 


400 


500 


515 


620 


700 


405 


485 


545 


500 


600 


575 


690 


780 


455 


540 


615 


600 


700 


630 


755 


855 


500 


595 


675 


700 


750 


655 


785 


885 


515 


620 


700 


750 


800 


680 


815 


920 


535 


645 


725 


800 


900 


730 


870 


985 


580 


700 


785 


900 


1000 


780 


935 


1055 


625 


750 


845 


1000 


1250 


890 


1065 


1200 


710 


855 


960 


1250 


1500 


980 


1175 


1325 


795 


950 


1075 


1500 


1750 


1070 


1280 


1445 


875 


1050 


1185 


1750 


2000 


1155 


1385 


1560 


960 


1150 


1335 


2000 



CORRECTION FACTORS 



Ambient 
Temp. (°C) 


For ambient temperatures other than 30°C (86°F), multiply the allowable ampacities shown above by the 

appropriate factor shown below. 


Ambient 
Temp. 

(°F) 


21-25 


1.08 


1.05 


1.04 


1.08 


1.05 


1.04 


70-77 


26-30 


1.00 


1.00 


1.00 


1.00 


1.00 


1.00 


78-86 


31-35 


0.91 


0.94 


0.96 


0.91 


0.94 


0.96 


87-95 


36-40 


0.82 


0.88 


0.91 


0.82 


0.88 


0.91 


96-104 


41-45 


0.71 


0.82 


0.87 


0.71 


0.82 


0.87 


105-113 


46-50 


0.58 


0.75 


0.82 


0.58 


0.75 


0.82 


114-122 


51-55 


0.41 


0.67 


0.76 


0.41 


0.67 


0.76 


123-131 


56-60 


— 


0.58 


0.71 


— 


0.58 


0.71 


132-140 


61-70 


— 


0.33 


0.58 


— 


0.33 


0.58 


141-158 


71-80 


— 


— 


0.41 


— 


— 


0.41 


159-176 



* See 240.4(D). 



2005 Edition NATIONAL ELECTRICAL CODE 



70-143 



310.60 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



Table 310.18 Allowable Ampacities of Insulated Conductors Rated Through 2000 Volts, 150°C Through 250°C (302°F 
Through 482°F). Not More Than Three Current-Carrying Conductors in Raceway or Cable, Based on Ambient Air 
Temperature of 40°C (104°F) 





Temperature Rating of Conductor (See Table 310.13.) 






150°C (302°F) 


200°C (392°F) 


250°C (482°F) 


150°C (302°F) 








Types FEP, FEPB, 










TypeZ 


PFA, SA 


Types PFAH, TFE 


TypeZ 








NICKEL OR 


ALUMINUM OR 








NICKEL-COATED 


COPPER-CLAD 




Size AWG or kcmil 


COPPER 


COPPER 


ALUMINUM 


Size AWG or kcmil 


14 


■34 


36 


39 




14 


12 


43 


45 


54 


30 


12 


10 


55 


60 


73 


44 


10 


8 


76 


83 


93 


57 


8 


6 


96 


110 


117 


75 


6 


4 


120 


125 


148 


94 


4 


3 


143 


152 


166 


109 


3 


2 


160 


171 


191 


124 


2 


1 


186 


197 


215 


145 


1 


1/0 


215 


229 


244 


169 


1/0 


2/0 


251 


260 


273 


198 


2/0 


3/0 


288 


297 


308 


227 


3/0 


4/0 


332 


346 


361 


260 


4/0 



CORRECTION FACTORS 



Ambient Temp. (°C) 


For ambient temperatures other than 40°C (104°F), multiply the allowable ampacities shown 
above by the appropriate factor shown below. 


Ambient Temp. (°F) 


41-50 


0.95 


0.97 


0.98 


0.95 


105-122 


51-60 


0.90 


0.94 


0.95 


0.90 


123-140 


61-70 


0.85 


0.90 


0.93 


0.85 


141-158 


71-80 


0.80 


0.87 


0.90 


0.80 


159-176 


81-90 


0.74 


0.83 


0.87 


0.74 


177-194 


91-100 


0.67 


0.79 


0.85 


0.67 


195-212 


101-120 


0.52 


0.71 


0.79 


0.52 


213-248 


121-140 


0.30 


0.61 


0.72 


0.30 


249-284 


141-160 





0.50 


0.65 


— 


285-320 


161-180 





0.35 


0.58 


— 


321-356 


181-200 








0.49 


— 


357-392 


201-225 


— 


— 


0.35 


— 


393-437 



• 



• 



70-144 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



310.60 



Table 310.19 Allowable Ampacities of Single-Insulated Conductors, Rated Through 2000 Volts, 150°C Through 250°C 
(302°F Through 482°F), in Free Air, Based on Ambient Air Temperature of 40°C (104°F) 



• 





Temperature Rating of Conductor (See Table 310.13.) 






150°C (302°F) 


200°C (392°F) 


250°C (482°F) 


150°C (302°F) 








Types FEP, 










TypeZ 


FEPB, PFA, SA 


Types PFAH, TFE 


TypeZ 










ALUMINUM OR 








NICKEL, OR 


COPPER-CLAD 




Size AWG or kcmil 


COPPER 


NICKEL-COATED COPPER 


ALUMINUM 


Size AWG or kcmil 


14 


46 


54 


59 




14 


12 


60 


68 


78 


47 


12 


10 


80 


90 


107 


63 


10 


8 


106 


124 


142 


83 


8 


6 


155 


165 


205 


112 


6 


4 


190 


220 


278 


148 


4 


3 


214 


252 


327 


170 


3 


2 


255 


293 


381 


198 


2 


1 


293 


344 


440 


228 


1 


1/0 


339 


399 


532 


263 


1/0 


- 2/0 


390 


467 


591 


305 


2/0 


3/0 


451 


546 


708 


351 


3/0 


4/0 


529 


629 


830 


411 


4/0 



CORRECTION FACTORS 



Ambient Temp. (°C) 


For ambient temperatures other than 40°C (104°F), multiply the allowable ampacities shown 
above by the appropriate factor shown below. 


Ambient Temp. (°F) 


41-50 


0.95 


0.97 


0.98 


0.95 


105-122 


51-60 


0.90 


0.94 


0.95 


0.90 


123-140 


61-70 


0.85 


0.90 


0.93 


0.85 


141-158 


71-80 


0.80 


0.87 


0.90 


0.80 


159-176 


81-90 


0.74 


0.83 


0.87 


0.74 


177-J94 


91-100 


0.67 


0.79 


0.85 


0.67 


195-212 


101-120 


0.52 


0.71 


0.79 


0.52 


213-248 


121-140 


0.30 


0.61 


0.72 


0.30 


249-284 


141-160 





0.50 


0.65 





285-320 


161-180 


— 


0.35 


0.58 





321-356 


181-200 








0.49 





357-392 


201-225 


— 


— 


0.35 


— 


393^37 



2005 Edition 



NATIONAL ELECTRICAL CODE 



70-145 



310.60 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



Table 310.20 Ampacities of Not More Than Three Single Insulated Conductors, Rated Through 2000 Volts, 
Supported on a Messenger, Based on Ambient Air Temperature of 40°C (104°F) 





Temperature Rating of Conductor (See Table 310.13.) 






75°C (167°F) 


90°C (194°F) 


75°C (167°F) 


90°C (194°F) 








Types MI, THHN, 












THHW, THW-2, 












THWN-2, RHH, 




Types THHN, THHW, 






Types RHW, THHW, 


RHW-2, USE-2, 


Types RHW, THW, 


RHH, XHHW, RHW-2, 






THW, THWN, 


XHHW, XHHW-2, 


THWN, THHW, 


XHHW-2, THW-2, 






XHHW, ZW 


ZW-2 


XHHW 


THWN-2, USE-2, ZW-2 




Size AWG or kcmil 


COPPER 


ALUMINUM OR COPPER-CLAD ALUMINUM 


Size AWG or kcmil 


8 


57 


66 


44 


51 


8 


6 


76 


89 


59 


69 


6 


4 


101 


117 


78 


91 


4 


3 


118 


138 


92 


107 


3 


2 


135 


158 


106 


123 


2 


1 


158 


185 


123 


144 


1 


1/0 


183 


214 


143 


167 


1/0 


2/0 


212 


247 


165 


193 


2/0 


3/0 


245 


287 


192 


224 


3/0 


4/0 


287 


335 


224 


262 


4/0 


250 


320 


374 


251 


292 


250 


300 


359 


419 


282 


328 


300 


350 


397 


464 


312 


364 


350 


400 


430 


503 


339 


395 


400 


500 


496 


580 


392 


458 


500 


600 


553 


647 


440 


514 


600 


700 


610 


714 


488 


570 


700 


750 


638 


747 


512 


598 


750 


800 . 


660 


773 


532 


622 


800 


900 


704 


826 


572 


669 


900 


1000 


748 


879 


612 


716 


1000 



• 







CORRECTION FACTORS 






Ambient Temp. (°C) 


For ambient temperatures other than 40°C (104°F), multiply the allowable ampacities shown 
above by the appropriate factor shown below. 


Ambient Temp. (°F) 


21-25 


1.20 


1.14 


1.20 


1.14 


70-77 


26-30 


1.13 


1.10 


1.13 


1.10 


79-86 


31-35 


1.07 


1.05 


1.07 


1.05 


88-95 


36^0 


1.00 


1.00 


1.00 


1.00 


97-104 


41^5 


0.93 


0.95 


0.93 


0.95 


106-113 


46-50 


0.85 


0.89 


0.85 


0.89 


115-122 


51-55 


0.76 


0.84 


0.76 


0.84 


124-131 


56-60 


0.65 


0.77 


0.65 


0.77 


133-140 


61-70 


0.38 


0.63 


0.38 


0.63 


142-158 


71-80 


— 


0.45 


— 


0.45 


160-176 



70-146 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



310.60 



Table 310.21 Ampacities of Bare or Covered Conductors in Free Air, Based on 40°C (104°F) Ambient, 
80°C (176°F) Total Conductor Temperature, 610 mm/sec (2 ft/sec) Wind Velocity 



• 





Copper 


Conductors 






AAC Aluminum Conductors 






Bare 




Covered 




Bare 


Covered 


AWGor 




AWGor 




AWGor 




AWGor 




kcmil 


Amperes 


kcmil 


Amperes 


kcmil 


Amperes 


kcmil 


Amperes 


8 


98 


8 


103 


8 


76 


8 


80 


6 


124 


6 


130 


6 


96 


6 


101 


4 


155 


4 


163 


4 


121 


4 


127 


2 


209 


2 


219 


2 


163 


2 


171 


1/0 


282 


1/0 


297 


1/0 


220 


1/0 


231 


2/0 


329 


2/0 


344 


2/0 


255 


2/0 


268 


3/0 


382 


3/0 


401 


3/0 


297 


3/0 


312 


4/0 


444 


4/0 


466 


4/0 


346 


4/0 


364 


250 


494 


250 


519 


266.8 


403 


266.8 


423 


300 


556 


300 


584 


336.4 


468 


336.4 


492 


500 


773 


500 


812 


397.5 


522 


397.5 


548 


750 


1000 


750 


1050 


477.0 


588 


477.0 


617 


1000 


1193 


1000 


1253 


556.5 


650 


556.5 


682 


— 


— 


— 


— 


636.0 


709 


636.0 


744 


— 


— 


— 


— 


795.0 


819 


795.0 


860 


— 


— 


— 


— 


954.0 


920 


— 


— 


— 


— 


— 


— 


1033.5 


968 


1033.5 


1017 


— 


— 


— 


— 


1272 


1103 


1272 


1201 


— 


— 


— 


— 


1590 


1267 


1590 


1381 


— 


— 


— 


— 


2000 


1454 


2000 


1527 



(C) Tables. Ampacities for conductors rated 2001 to 
35,000 volts shall be as specified in the Ampacity Table 
310.67 through Table 310.86. Ampacities at ambient tem- 
peratures other than those shown in the tables shall be de- 
termined by the formula in 310.60(C)(4). 

FPN No. 1: For ampacities calculated in accordance with 
310.60(B), reference ffiEE 835-1994 (IPCEA Pub. No. P-46- 
426), Standard Power Cable Ampacity Tables, and the refer- 
ences therein for availability of aU factors and constants. 

FPN No. 2: Ampacities provided by this section do not take 
voltage drop into consideration. See 210.19(A), FPN No. 4, 
for branch circuits and 215.2(A), FPN No. 2, for feeders. 

(1) Grounded Shields. Ampacities shown in Table 310.69, 
Table 310.70, Table 310.81, and Table 310.82 are for cable 
with shields grounded at one point only. Where shields are 
grounded at more than one point, ampacities shall be adjusted 
to take into consideration the heating due to shield currents. 

(2) Burial Depth of Underground Circuits. Where the 
burial depth of direct burial or electrical duct bank circuits 
is modified from the values shown in a figure or table, 
ampacities shall be permitted to be modified as indicated in 
(C)(a) and (C)(b). 

(a) Where burial depths are increased in part(s) of an 
electrical duct run, no decrease in ampacity of the conduc- 
tors is needed, provided the total length of parts of the duct 
run increased in depth is less than 25 percent of the total 
run length. 



(b) Where burial depths are deeper than shown in a 
specific underground ampacity table or figure, an ampacity 
derating factor of 6 percent per 300-mm (1-ft) increase in 
depth for all values of rho shall be permitted. 

No rating change is needed where the burial depth is 
decreased. 

(3) Electrical Ducts in Figure 310.60. At locations where 
electrical ducts enter equipment enclosures from under 
ground, spacing between such ducts, as shown in Figure 
310.60, shall be permitted to be reduced without requiring 
the ampacity of conductors therein to be reduced. 

(4) Ambients Not in Tables. Ampacities at ambient tem- 
peratures other than those shown in the tables shall be de- 
termined by means of the following formula: 



/,=/, 



TC-TA^-ATD 
rC-TA-ATD 



where: 

/^ = ampacity from tables at ambient TA^ 
I2 = ampacity at desired ambient TA2 
TC = conductor temperature in degrees Celsius (°C) 
TA^ = surrounding ambient from tables in degrees 

Celsius (°C) 
TA2 = desired ambient in degrees Celsius (°C) 
ATD = dielectric loss temperature rise 



2005 Edition NATIONAL ELECTRICAL CODE 



70-147 



310.60 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 






Detail 1 

290 mm x 290 mm 
(11.5 in. X 11 .5 in.) 
Electrical duct bank 
One electrical duct 




190 mm (7.5 in.) 

Detail 2 

475 mm x 475 mm 
(19in.x 19 in.) 
Electrical duct bank 
Three electrical ducts 
or 



m£- 



190 mm 
(7.5 in.) 



190 mm 
(7.5 in.) 



675 mm x 290 mm 
(27 in. X 11.5 in.) 
Electrical duct bank 
Three electrical ducts 







N ■ 


° ^ ,' 



190 mm (7.5 in.) 

Detail 3 

475 mm x 675 mm 
(19 in. X 27 in.) 
Electrical duct bank 
Six electrical ducts 
or 




190 mm 
(7.5 in.) 



190 mm 
(7.5 in.) 



675 mm x 475 mm 
(27 in. X 19 in.) 
Electrical duct bank 
Six electrical ducts 



# 



• 

Detail 5 

Buried 3 

conductor 

cable 



600 mm 



(24 in.) 

Detail 6 

Buried 3 

conductor 

cables 



190 mm 190 mm 
(7.5 in.) (7.5 in.) 



Detail 9 

Buried single-conductor 
cables (1 circuit) 



••• 

Detail 7 

Buried triplexed 
cables (1 circuit) 



190 mm 190 mm 
(7.5 in.) (7.5 in.) 



.f 



600 mm 



600 mm 



(24 in.) 



I 



(24 in.) 

Detail 10 

Buried single-conductor 
cables (2 circuits) 



Detail 8 

Buried triplexed 
cables (2 circuits) 



190 mm 190 mm 
(7.5 in.) (7.5 in.) 

->+< — 



Note: Minimum burial depths to top electrical ducts or cables shall be 
in accordance with Section 300.50. Maximum depth to the top 
of electrical duct banks shall be 750 mm (30 in.) and maximum 
depth to the top of direct buried cables shall be 900 mm (36 in.). 



Legend 

|°a"',°| Backfill (earth or concrete) 
(3 Electrical duct 
• Cable or cables 



Figure 310.60 Cable Installation Dimensions for Use with Table 310.77 Through Table 310.86. 



(D) Engineering Supervision. Under engineering supervi- 
sion, conductor ampacities shall be permitted to be calcu- 
lated by means of the following general formula: 



/ = 



TC-{TA + ATD) 
RDC{l + YC)RCA 



where: 
TC = conductor temperature in °C 
TA = ambient temperature in °C 

ATD = dielectric loss temperature rise 



RDC= dc resistance of conductor at 

temperature TC 
YC = component ac resistance 

resulting from skin effect and 
proximity effect 
RCA = effective thermal resistance 
between conductor and 
surrounding ambient 

FPN: See Annex B for examples of formula applications. 



70-148 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



310.60 



Table 310.61 Conductor Application and Insulation 





Maximum 




Operating 




Type Tempera- Application Outer 


Trade Name 


Letter tare Provision Insulation Covering 



Medium voltage MV-90 90°C 
solid dielectric MV-105* 105°C 



Dry or wet Thermo- Jacket, 

locations plastic or sheath, or 

rated 2001 thermo- armor 

volts and setting 
higher 



• 



*Where design conditions require maximum conductor temperatures 
above 90°C. 



Table 310.62 Thickness of Insulation for 601- to 2000- Volt 
Nonshielded Types RHH and RHW 



Conductor Size 
(AWG or kcmil) 



14-10 

8 

6-2 

1-2/0 

3/0^/0 

213-500 

501-1000 

1001-2000 



Column A^ 



Column B^ 



mm 


mils 


mm 


mils 


2.03 


80 


1.52 


60 


2.03 


80 


1.78 


70 


2.41 


95 


1.78 


70 


2.79 


110 


2.29 


90 


2.79 


110 


2.29 


90 


3.18 


125 


2.67 


105 


3.56 


140 


3.05 


120 


3.56 


140 


3.56 


140 



'Column A insulations are limited to natural, SBR, and butyl rubbers. 
^Column B insulations are materials such as cross-linked polyethyl- 
ene, ethylene propylene rubber, and composites thereof. 



Table 310.63 Thickness of Insulated Conductors Rated 2400 Volts and Jacket for Nonshielded 
Solid Dielectric Insulation 









Dry Locations, Single 


Conductor 








Wet or 


Dry Locations 






Without 
Jacket 




With Jacket 






Single 


Conductor 


























Multiconuuciur 


Conductor Size 


Insulation 


Insulation 


Jacket 


Insulation 


Jacket 


Insulation* 


























(AWG or kcmil) 


mm 


mils 


mm 


mils 


mm 


mils 


mm 


mils 


mm 


mils 


mm 


mils 


8 


2.79 


110 


2.29 


90 


0.76 


30 


3.18 


125 


2.03 


80 


2.29 


90 


6 


2.79 


110 


2.29 


90 


0.76 


30 


3.18 


125 


2.03 


80 


2.29 


90 


4-2 


2.79 


110 


2.29 


90 


1.14 


45 


3.18 


125 


2.03 


80 


2.29 


90 


1-2/0 


2.79 


110 


2.29 


90 


1.14 


45 


3.18 


125 


2.03 


80 


2.29 


90 


3/0-4/0 


2.79 


110 


2.29 


90 


1.65 


65 


3.18 


125 


2.41 


95 


2.29 


90 


213-500 


3.05 


120 


2.29 


90 


1.65 


65 


3.56 


140 


2.79 


110 


2.29 


90 


501-750 


3.30 


130 


2.29 


90 


1.65 


65 


3.94 


155 


3.18 


125 


2.29 


90 


751-1000 


3.30 


130 


2.29 


90 


1.65 


65 


3.94 


155 


3.18 


125 


2.29 


90 



*Under a common overall covering such as a jacket, sheath, or armor. 



• 



Table 310.64 Thickness of Insulation for Shielded Solid Dielectric Insulated Conductors 
Rated 2001 to 35,000 Volts 





2001-5000 
Volts 




5001-8000 volts 






8001-15,000 volts 




15,001-25,000 volts 


Conductor 

Size 

(AWG 

or kcmil) 


100 

Percent 

Insulation 

Level ' 

mm mils 


133 

Percent 

Insulation 

Level ^ 


173 

Percent 

Insulation 

LeveP 


100 

Percent 

Insulation 

Level^ 


133 

Percent 

Insulation 

Level^ 


173 

Percent 

Insulation 

LeveP 

mm mils 


100 

Percent 

Insulation 

Level' 

mm mils 


133 

Percent 

Insulation 

LeveP 


173 

Percent 

Insulation 

LeveP 




mm mils 


mm mils 


mm 


mils 


mm mils 


mm 


mils 


mm mils 


mm mils 


8 

6^ 

2 

1 

1/0-2000 


2.29 90 
2.29 90 
2.29 90 
2.29 90 
2.29 90 


2.92 115 
2.92 115 
2.92 115 
2.92 115 


3.56 140 
3.56 140 
3.56 140 
3.56 140 


4.45 
4.45 
4.45 
4.45 


175 
175 
175 
175 


4.45 175 
4.45 175 
4.45 175 


5.59 
5.59 
5.59 


220 
220 
220 


6.60 260 
6.60 260 
6.60 260 


6.60 260 
6.60 260 


8.13 320 
8.13 320 


10.67 420 
10.67 420 


2005 Edition 


NATIONAL ELECTRICAL CODE 


















(continues) 
70-149 



310.60 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



Table 310.64 Continued 



25,001-28000 volts 



28,001-35,000 volts 



Conductor 

Size 

(AWG 



,2001-5000 
Volts 



100 

Percent 

Insulation 

Level ^ 



133 

Percent 

Insulation 

Level ^ 



173 

Percent 

Insulation 

LeveP 



100 

Percent 

Insulation 

Level^ 



133 

Percent 

Insulation 

LeveP 



173 

Percent 

Insulation 

Level^ 



or kcmil) 


mm 


mils 


mm 


mils 


mm 


mils 


mm 


mils 


mm 


mils 


mm 


mils 


mm 


mils 


1 
1/0-2000 


2.29 
2.29 


90 
90 


7.11 
7.11 


2.80 
2.80 


8.76 
8.76 


345 
345 


11..30 
11.30 


445 
445 


8.76 


345 


10.67 


420 


14.73 


580 



Notes: 

'lOO Percent Insulation Level. Cables in this category shall be permitted to be applied where the system is provided with relay protection such 

that ground faults will be cleared as rapidly as possible but, in any case, within 1 minute. While these cables are applicable to the great majority 

of cable installations that are on grounded systems, they shall be permitted to be used also on other systems for which the application of cables is 

acceptable, provided the above clearing requirements are met in completely de-energizing the faulted section. 

^133 Percent Insulation Level. This insulation level corresponds to that formerly designated for ungrounded systems. Cables in this category shall 

be permitted to be appUed in situations where the clearing time requirements of the 100 percent level category cannot be met and yet there is 

adequate assurance that the faulted section will be de-energized in a time not exceeding 1 hour. Also, they shall be permitted to be used in 

100 percent insulation level apphcations where additional insulation is desirable. 

■'173 Percent Insulation Level. Cables in this category shall be permitted to be apphed under all of the following conditions: 

(1) In industrial establishments where the conditions of maintenance and supervision ensure that only qualified persons service the installation 

(2) Where the fault clearing time requirements of the 133 percent level category cannot be met 

(3) Where an orderly shutdown is essential to protect equipment and personnel 

(4) There is adequate assurance that the faulted section will be de-energized in an orderly shutdown 

Also, cables with this insulation thickness shall be permitted to be used in 100 or 133 percent insulation level applications where additional 
insulation strength is desirable. 



• 



Table 310.67 Ampacities of Insulated Single Copper 
Conductor Cables Triplexed in Air Based on Conductor 
Temperatures of 90°C (194°F) and 105°C (221 °F) and 
Ambient Air Temperature of 40°C (104°F) 



Table 310.68 Ampacities of Insulated Single Aluminum 
Conductor Cables Triplexed in Air Based on Conductor 
Temperatures of 90°C (194°F) and 105°C (221°F) and 
Ambient Air Temperature of 40°C (104°F) 





Temperature Rating of Conductor (See Table 310.61.) 




Temperature 


Rating of Conductor (See Table 310.61.) 




2001-5000 Volts 


5001-35,000 Volts 




2001-5000 Volts 


5001-35,000 Volts 




Ampacity 


Ampacity 


Conductor 


Ampacity 


Ampacity 


Conductor 




105°C 




105°C 




105°C 




105°C 


Size 


90°C 


(221°F) 


90°C 


(221°F) 


Size 


90°C 


(221°F) 


90°C 


(22rF) 


(AWG 


(194°F) 


Type 


(194°F) 


Type 


(AWG 


(194°F) 


Type 


(194°F) 


Type 


or kcmil) 


Type MV-90 

65 


MV-105 

74 


Type MV-90 


MV-105 


or kcmil) 


Type MV-90 


MV-105 


Type MV-90 


MV-105 


8 


8 


50 


57 






6 


90 


99 


100 


110 


6 


70 


77 


75 


84 


4 


120 


130 


130 


140 


4 


90 


100 


100 


110 


2 


160 


175 


170 


195 


2 


125 


135 


130 


150 


1 


185 


205 


195 


225 


1 


145 


160 


150 


175 


1/0 


215 


240 


225 


255 


1/0 


170 


185 


175 


200 


2/0 


250 


275 


260 


295 


2/0 


195 


215 


200 


230 


3/0 


290 


320 


300 


340 


3/0 


225 


250 


230 


265 


4/0 


335 


375 


345 


390 


4/0 


265 


290 


270 


305 


250 


375 


415 


380 


430 


250 


295 


325 


300 


335 


350 


465 


515 


470 


525 


350 


365 


405 


370 


415 


500 


580 


645 


580 


650 


500 


460 


510 


460 


515 


750 


750 


835 


730 


820 


750 


600 


665 


590 


660 


1000 


880 


980 


850 


950 


1000 


715 


800 


700 


780 



• 



• 



70-150 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



310.60 



• 



Table 310.69 Ampacities of Insulated Single Copper 
Conductor Isolated in Air Based on Conductor Temperatures 
of 90°C (194°F) and 105°C (221 °F) and Ambient Air 
Temperature of 40°C (104°F) 



Table 310.71 Ampacities of an Insulated Three-Conductor 
Copper Cable Isolated in Air Based on Conductor 
Temperatures of 90°C (194°F) and 105°C (221°F) and 
Ambient Air Temperature of 40°C (104°F) 



• 





Temperature Rating of Conductor (See Table 310.61.) 




Temperature 


Rating of Conductor (See Table 310.61.) 




2001-5000 Volts 


5001- 


-15,000 


15,001 


-35,000 




2001-5000 Volts 


5001-35,000 Volts 




Ampacity 


Volts Ampacity 
90°C 105°C 


Volts Ampacity 
90°C 105°C 


Conductor 


Ampacity 


Ampacity 


Conductor 


90°C 


105°C 




105°C 




105°C 


Size 


(194°F) 


(221°F) 


(I94°r) 


(221°F) 


(194°F) 


(221°F) 


Size 


90°C 


(221°F) 




(221°F) 


(AWG 


Type 


Type 


Type 


Type 


Type 


Type 


(AWG 


(194°F) 


Type 


90°C (194°F) 


Type 


or kcmil) 


MV-90 


MV-105 


MV-90 


MV-105 


MV-90 


MV-105 


or kcmil) 


Type MV-90 


MV-105 


Type MV-90 


MV-105 


8 


83 


93 














8 


59 


66 








6 


110 


120 


110 


125 


— 


— 


6 


79 


88 


93 


105 


4 


145 


160 


150 


165 


— 


— 


4 


105 


115 


120 


135 


2 


190 


215 


195 


215 


— 


— 


2 


140 


154 


165 


185 


1 


225 
260 


250 
290 


225 
260 


250 
290 


225 
260 


250 
290 


1 


160 


180 


185 


210 


1/0 


1/0 


185 


205 


215 


240 


2/0 


300 


330 


300 


335 


300 


330 


2/0 


215 


240 


245 


275 


3/0 


345 


385 


345 


385 


345 


380 


3/0 


250 


280 


285 


315 


4/0 


400 


445 


400 


445 


395 


445 


4/0 


285 


320 


325 


360 


250 


445 


495 


445 


495 


440 


490 


250 


320 


355 


360 


400 


350 


550 


615 


550 


610 


545 


605 


350 


395 


440 


435 


490 


500 


695 


775 


685 


765 


680 


755 


500 


485 


545 


535 


600 


750 


900 


1000 


885 


990 


870 


970 


750 


615 


685 


670 


745 


1000 


1075 


1200 


1060 


1185 


1040 


1160 


1000 


705 


790 


770 


860 












1250 


1230 


1370 


1210 


1350 


1185 


1320 












1500 


1365 


1525 


1345 


1500 


1315 


1465 












1750 


1495 


1665 


1470 


1640 


1430 


1595 


Table 310.72 Ampacities of an Insulated Three-Conductor 


2000 


1605 


1790 


1575 


1755 


1535 


1710 


Aluminum Cable Isolated in Air Based on Conductor 
Temperatures of 90°C (194°F) and 105°C (221°F) and 






























Ambient Air Temperature of 40°C (104°F) 




Table 310.70 Ampacities of Insulated Sinoip 


Aluminum 












Conductor Isolated in Air Based or 


— •&— '--" — "- 

I Conductor Temperatures 




Temperature Rating of Conductor (See Table 310.61.) 


of 90°C (194°F) and 105°C (221°F) and Ambient Air 














Temperati 


jre of 40°C (104°F) 








Conductor 


2001-5000 Volts Ampacity 
105°C 


5001-35,0( 
Ampa 


)0 Volts 
city 




Temperature Rating of Conductor (See Table 310.61.) 


105°C 
















Size 


90°C 


(221°F) 


90° C 


(221°F) 




2001-5000 Volts 


5001- 


15,000 


15,001- 


-35,000 


(AWG 


(194°F) 


Type 


(194°F) 


Type 




Ampacity 


Volts Ampacity 
90°C 105°C 


Volts Ampacity 
90°C 105°C 


or kcmil) 


Type MV-90 


MV-105 


Type MV-90 


MV-105 




90°C 


105°C 




Conductor 


8 


46 


51 






Size 


(194°F) 


(221°F) 


(194°F) 


(221°F) 


(194°F) 


(22rF) 


6 


61 


68 


72 


80 


(AWG 


Type 


Type 


Type 


Type 


Type 


Type 


4 


81 


90 


95 


105 


or kcmil) 


MV-90 


MV-105 


MV-90 


MV-105 


MV-90 


MV-105 


2 


110 


120 


125 


145 




64 


71 










1 


125 


140 


145 


165 


8 












6 


85 


95 


87 


97 


— 


— 


1/0 


145 


160 


170 


185 


4 


115 


125 


115 


130 


— 


— 


2/0 


170 


185 


190 


215 


2 • 


150 


165 


150 


170 


— 


— 












1 


175 


195 


175 


195 


175 


195 


3/0 
4/0 


195 

225 


215 
250 


220 
255 


245 
















285 


1/0 


200 


225 


200 


225 


200 


225 












2/0 


230 


260 


235 


260 


230 


260 


250 


250 


280 


280 


315 


3/0 


270 


300 


270 


300 


270 


300 


350 


310 


345 


345 


385 


4/0 


310 


350 


310 


350 


310 


345 


500 

750 


385 
495 


430 
550 


425 
540 


475 
















600 


250 


345 


385 


345 


385 


345 


380 


1000 


585 


650 


635 


705 


350 


4'^n 


480 


4'^n 


480 


4'^n 


475 












500 


545 


605 


535 


600 


530 


590 












750 


710 


790 


700 


780 


685 


765 












1000 


855 


950 


840 


940 


825 


920 




1250 


980 


1095 


970 


1080 


950 


1055 












1500 


1105 


1230 


1085 


1215 


1060 


1180 












1750 


1215 


1355 


1195 


1335 


1165 


1300 












2000 


1320 


1475 


1295 


1445 


1265 


1410 













2005 Edition 



NATIONAL ELECTRICAL CODE 



70-151 



310.60 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



Table 310.73 Ampacities of an Insulated Triplexed or Three 
Single-Conductor Copper Cables in Isolated Conduit in Air 
Based on Conductor Temperatures of 90°C (194°F) and 
105°C (221°F) and Ambient Air Temperature of 40°C 
(104°F) 





Temperat 


Lire Rating of Conductor (See 


Table 310.61.) 




2001- 


5000 Volts 


5001-35,000 Volts 




Ampacity 


Ampacity 


Conductor 


90°C 




90°C 




Size 


(194°F) 


105°C 


(194°F) 


105°C 


(AWG 


Type 


(221°F) Type 


Type 


(221°F) Type 


or kcmil) 


MV-90 


MV-105 


MV-90 


MV-105 


8 


55 


61 






6 


75 


84 


83 


93 


4 


97 


110 


110 


120 


2 


130 


145 


150 


165 


1 


155 


175 


170 


190 


1/0 


180 


200 


195 


215 


2/0 


205 


225 


225 


255 


3/0 


240 


270 


260 


290 


4/0 


280 


305 


295 


330 


250 


315 


355 


330 


365 


350 


385 


430 


395 


440 


500 


475 


530 


480 


535 


750 


600 


665 


585 


655 


1000 


690 


770 


675 


755 



Table 310.74 Ampacities of an Insulated Triplexed or Three 
Single-Conductor Aluminum Cables in Isolated Conduit in 
Air Based on Conductor Temperatures of 90° C (194°F) and 
105°C (221°F) and Ambient Air Temperature of 40°C 
(104°F) 

Temperature Rating of Conductor (See Table 310.61.) 



2001-5000 Volts 
Ampacity 



5001-35,000 Volts 
Ampacity 



Conductor 90°C 

Size (AWG (194°F) 
or kcmil) Type MV-90 



105°C 

(221°F) 

Type 
MV-105 



90°C 

(194°F) 

Type MV-90 



105°C 

(221°F) 

Type 
MV-105 



43 
58 
76 
100 
120 



48 

65 

85 

115 

135 



65 



115 
130 



72 

94 

130 

150 



1/0 
2/0 
3/0 
4/0 



140 
160 
190 
215 



155 
175 
210 
240 



150 
175 
200 
230 



170 
200 
225 
260 



250 
350 
500 
750 
1000 



250 
305 
380 
490 
580 



280 
340 
425 
545 
645 



255 
310 
385 
485 
565 



290 
350 
430 
540 
640 



Table 310.75 Ampacities of an Insulated Three-Conductor 
Copper Cable in Isolated Conduit in Air Based on 
Conductor Temperatures of 90°C (194°F) and 105°C (221°F) 
and Ambient Air Temperature of 40°C (104°F) 

Temperature Rating of Conductor (See Table 310.61.) 



2001-5000 Volts Ampacity 

Conductor 105°C 

Size 90°C (221°F) 

(AWG (194°F) Type 

or kcmil) Type MV-90 MV-105 



5001-35,000 Volts 
Ampacity 



90°C 

(194°F) 

Type MV-90 



105°C 

(221°F) 

Type 
MV-105 



52 

69 

91 

125 

140 



58 

77 

100 

135 

155 



83 
105 
145 
165 



92 
120 
165 
185 



1/0 
2/0 
3/0 
4/0 



165 
190 
220 

255 



185 
210 

245 
285 



195 
220 
250 
290 



215 
245 
280 
320 



250 
350 
500 
750 
1000 



280 
350 
425 
525 
590 



315 
390 
475 
585 
660 



315 
385 
470 
570 
650 



350 
430 
525 
635 

725 



Table 310.76 Ampacities of an Insulated Three-Conductor 
Aluminum Cable in Isolated Conduit in Air Based on 
Conductor Temperatures of 90°C (194°F) and 105°C (221°F) 
and Ambient Air Temperature of 40°C (104°F) 

Temperature Rating of Conductor (See Table 310.61.) 



2001-5000 Volts 
Ampacity 



5001-35,000 Volts 
Ampacity 



Conductor 105°C 

Size 90°C (221°F) 

(AWG (194°F) Type 

or kcmil) Type MV-90 MV-105 



90°C 

(194°F) 

Type MV-90 



105°C 

(221°F) 

Type 
MV-105 



41 
53 
71 
96 
110 



46 

59 

79 

105 

125 



64 

84 

115 

130 



71 

94 

125 

145 



1/0 
2/0 
3/0 
4/0 



130 
150 
170 
200 



145 
165 
190 

225 



150 
170 
195 

225 



170 
190 
220 

255 



250 
350 
500 
750 
1000 



220 
275 
340 
430 
505 



245 
305 
380 
480 
560 



250 
305 
380 
470 
550 



280 
340 
425 
520 
615 



• 



70-152 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



310.60 



Table 310.77 Ampacities of Three Single-Insulated Copper 
Conductors in Underground Electrical Ducts (Three 
Conductors per Electrical Duct) Based on Ambient Earth 
Temperature of 20°C (68°F), Electrical Duct Arrangement 
per Figure 310.60, 100 Percent Load Factor, Thermal 
Resistance (RHO) of 90, Conductor Temperatures of 90°C 
(194°F) and 105°C (221°F) 



Table 310.78 Ampacities of Three Single-Insulated 
Aluminum Conductors in Underground Electrical Ducts 
(Three Conductors per Electrical Duct) Based on Ambient 
Earth Temperature of 20°C (68°F), Electrical Duct 
Arrangement per Figure 310.60, 100 Percent Load Factor, 
Thermal Resistance (RHO) of 90, Conductor Temperatures 
of 90°C (194°F) and 105°C (221 °F) 





Temperature Rating of Conductor (S 


ee Table 




Temperature Rating of Conductor (See Table 






310.61.) 








310.61. 


) 






2001-5000 Volts 


5001-35,000 Volts 


2001-5000 Volts 


5001-35,000 Volts 




Ampacity 


Ampacity 


Conductor 


Ampacity 


Ampacity 


Conductor 


90°C 


105°C 


90°C 


105°C 


90°C 


105°C 


90°C 


105°C 


Size 


(194°F) 


(221°F) 


(194°F) 


(22rF) 


Size 


(194°F) 


(221°F) 


(194°F) 


(221°F) 


(AWG 


Type 


Type 


Type 


Type 


(AWG 


Type 


Type 


Type 


Type 


or kcmil) 


MV-90 


MV-105 


MV-90 


MV-105 


or kcmil) 


MV-90 


MV-105 


MV-90 


MV-105 


One Circuit (See Fig 


ure 








One Circuit (See 


Figure 








310.60, Detail 1.) 










310.60, Detail 1.) 








8 


64 


69 








8 


50 


54 








6 


85 


92 


90 


97 


6 


66 


71 


70 


75 


4 


110 


120 


115 


125 


4 


86 


93 


91 


98 


2 


145 


155 


155 


165 


2 


115 


125 


120 


130 


I 


170 


180 


175 


185 


1 


130 


140 


135 


145 


1/0 


195 


210 


200 


215 


1/0 


150 


160 


155 


165 


2/0 


220 


235 


230 


245 


2/0 


170 


185 


175 


190 


3/0 


250 


270 


260 


275 


3/0 


195 


210 


200 


215 


4/0 


290 


310 


295 


315 


4/0 


225 


245 


230 


245 


250 


320 


345 


325 


345 


250 


250 


270 


250 


270 


350 


385 


415 


390 


415 


350 


305 


325 


305 


330 


500 


470 


505 


465 


500 


500 


370 


400 


370 


400 


750 


585 


630 


565 


610 


750 


470 


505 


455 


490 


1000 


670 


720 


640 


690 


1000 


545 


590 


525 


565 


Three Circuits (See Figure 








Three Circuits (See Figure 








310.60, Detail 2.) 










310.60, Detail 2.) 








8 


56 


60 








8 


44 


47 








6 


73 


79 


77 


83 


6 


57 


61 


60 


65 


4 


95 


100 


99 


105 


4 


74 


80 


77 


83 


2 


125 


130 


130 


135 


2 


96 


105 


100 


105 


1 


140 


150 


145 


155 


1 


110 


120 


110 


120 


1/0 


160 


175 


165 


175 


1/0 


125 


135 


125 


140 


2/0 


185 


195 


185 


200 


2/0 


145 


155 


145 


155 


3/0 


210 


225 


210 


225 


3/0 


160 


175 


165 


175 


4/0 


235 


255 


240 


255 


4/0 


185 


200 


185 


200 


250 


260 


280 


260 


280 


250 


205 


220 


200 


220 


350 


315 


335 


310 


330 


350 


245 


265 


245 


260 


500 


375 


405 


370 


395 


500 


295 


320 


290 


315 


750 


460 


495 


440 


475 


750 


370 


395 


355 


385 


1000 


525 


565 


495 


535 


1000 


425 


460 


405 


440 


Six Circuits (See Figure 








Six Circuits (See 


Figure 








310.60, Detail 3.) 










310.60, Detail 3.) 








8 


48 


52 








8 


38 


41 








6 


62 


67 


64 


68 


6 


48 


52 


50 


54 


4 


80 


86 


82 


88 


4 


62 


67 


64 


69 


2 


105 


110 


105 


115 


2 


80 


86 


80 


88 


1 


115 


125 


120 


125 


1 


91 


98 


90 


99 


1/0 


135 


145 


135 


145 


1/0 


105 


110 


105 


110 


2/0 


150 


160 


150 


165 


2/0 


115 


125 


115 


125 


3/0 


170 


185 


170 


185 


3/0 


135 


145 


130 


145 


4/0 


195 


210 


190 


205 


4/0 


150 


165 


150 


160 


250 


210 


225 


210 


225 


250 


165 


180 


165 


175 


350 


250 


270 


245 


265 


350 


195 


210 


195 


210 


500 


300 


325 


290 


310 


500 


240 


255 


230 


250 


750 


365 


395 


350 


375 


750 


290 


315 


280 


305 


1000 


410 


445 


390 


415 


1000 


335 


360 


320 


345 



2005 Edition 



NATIONAL ELECTRICAL CODE 



70-153 



310.60 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



Table 310.79 Ampacities of Three Insulated Copper 
Conductors Cabled Within an Overall Covering 
(Three-Conductor Cable) in Underground Electrical Ducts 
(One Cable per Electrical Duct) Based on Ambient Earth 
Temperature of 20°C (68°F), Electrical Duct Arrangement 
per Figure 310.60, 100 Percent Load Factor, Thermal 
Resistance (RHO) of 90, Conductor Temperatures of 90°C 
(194°F) and 105°C (221°C) 



Table 310.80 Ampacities of Three Insulated Aluminum 
Conductors Cabled Within an Overall Covering 
(Three-Conductor Cable) in Underground Electrical Ducts 
(One Cable per Electrical Duct) Based on Ambient Earth 
Temperature of 20°C (68°F), Electrical Duct Arrangement 
per Figure 310.60, 100 Percent Load Factor, Thermal 
Resistance (RHO) of 90, Conductor Temperatures of 90°C 
(194°F) and 105°C (221°C) 





Temperature Rating of Conductor (S 


ee Table 




Temperature Rating of Conductor (See Table 






310.61.) 




- 




310.61.) 






2001-5000 Volts 


5001-35,000 Volts 


2001-5000 Volts 


5001-35,000 Volts 




Ampacity 


Ampacity 


Conductor 


Ampacity 


Ampacity 


Conductor 


90°C 


105°C 


90°C 


105°C 


90°C 


105°C 


90°C 


105°C 


Size 


(194°F) 


(221°F) 


(194°F) 


(221 °F) 


Size 


(194°F) 


(221°F) 


(194°F) 


(22rF) 


(AWG 


Type 


Type 


Type 


Type 


(AWG 


Type 


Type 


Type 


Type 


or kcmil) 


MV-90 


MV-105 


MV-90 


MV-105 


or kcmil) 


MV-90 


MV-105 


MV-90 


MV-105 


One Circuit (See Figure 








One Circuit (See Figure 








310.60, Detail 1.) 










310.60, Detail 1.) 










8 


59 


64 








8 


46 


50 








6 


78 


84 


88 


95 


6 


61 


66 


69 


74 


4 


100 


110 


115 


125 


4 


80 


86 


89 


96 


2 


135 


145 


150 


160 


2 


105 


110 


115 


125 


1 


155 


165 


170 


185 


1 


120 


130 


135 


145 


I/O 


175 


190 


195 


210 


1/0 


140 


150 


150 


165 


2/0 


200 


220 


220 


235 


2/0 


160 


170 


170 


185 


3/0 


230 


250 


250 


270 


3/0 


180 


195 


195 


210 


4/0 


265 


285 


285 


305 


4/0 


205 


220 


220 


240 


250 


290 


315 


310 


335 


250 


230 


245 


245 


265 


350 


355 


380 


375 


400 


350 


280 


310 


295 


315 


500 


430 


460 


450 


485 


500 


340 


365 


355 


385 


750 


530 


570 


545 


585 


750 


425 


460 


440 


475 


1000 


600 


645 


615 


660 


1000 


495 


535 


510 


545 


Three Circuits (See 


Figure 








Three Circuits (See 


Figure 








310.60, Detail 2.) 










310.60, Detail 2.) 










8 


53 


57 








8 


41 


44 








6 


69 


74 


75 


81 


6 


54 


58 


59 


64 


4 


89 


96 


97 


105 


4 


70 


75 


75 


81 


2 


115 


125 


125 


135 


2 


90 


97 


100 


105 


1 


135 


145 


140 


155 


1 


105 


110 


110 


120 


1/0 


150 


165 


160 


175 


1/0 


120 


125 


125 


135 


2/0 


170 


185 


185 


195 


2/0 


135 


145 


140 


155 


3/0 


195 


210 


205 


220 


3/0 


155 


165 


160 


175 


4/0 


225 


240 


230 


250 


4/0 


175 


185 


180 


195 


250 


245 


265 


255 


270 


250 


190 


205 


200 


215 


350 


295 


315 


305 


325 


350 


230 


250 


240 


255 


500 


355 


380 


360 


385 


500 


280 


300 


285 


305 


750 


430 


465 


430 


465 


750 


345 


375 


350 


375 


1000 


485 


520 


485 


515 


1000 


400 


430 


400 


430 


Six Circuits (See Figure 








Six Circuits (See Figure 








310.60, Detail 3.) 










310.60, Detail 3.) 










8 


46 


50 





— 


8 


36 


39 








6 


60 


65 


63 


68 


6 


46 


50 


49 


53 


4 


77 


83 


81 


87 


4 


60 


65 


63 


68 


2 


98 


105 


105 


110 


2 


77 


83 


80 


86 


1 


110 


120 


115 


125 


1 


87 


94 


90 


98 


1/0 


125 


135 


130 


145 


1/0 


99 


105 


105 


110 


2/0 


145 


155 


150 


160 


2/0 


110 


120 


115 


125 


3/0 


165 


175 


170 


180 


3/0 


130 


140 


130 


140 


4/0 


185 


200 


190 


200 


4/0 


145 


155 


150 


160 


250 


200 


220 


205 


220 


250 


160 


170 


160 


170 


350 


240 


270 


245 


275 


350 


190 


205 


190 


205 


500 


290 


310 


290 


305 


500 


230 


245 


230 


245 


750 


350 


375 


340 


365 


750 


280 


305 


275 


295 


1000 


390 


420 


380 


405 


1000 


320 


345 


315 


335 



• 



70-154 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



310.60 



Table 310.81 Ampacities of Single Insulated Copper 
Conductors Directly Buried in Earth Based on Ambient 
Earth Temperature of 20°C (68°F), Arrangement per Figure 
310.60, 100 Percent Load Factor, Thermal Resistance (RHO) 
of 90, Conductor Temperatures of 90°C (194°F) and 105°C 
(221°C) 



Table 310.82 Ampacities of Single Insulated Aluminum 
Conductors Directly Buried in Earth Based on Ambient 
Earth Temperature of 20°C (68°F), Arrangement per Figure 
310.60, 100 Percent Load Factor, Thermal Resistance (RHO) 
of 90, Conductor Temperatures of 90°C (194°F) and 105°C 
(221°F) 



• 





Temperature Rating of Conductor (See Table 




Temperature Rating of Conductor (S 


ee Table 






310.61.) 








310.61) 






2001-5000 Volts 


5001-35,000 Volts 




2001-5000 Volts 


5001-35,000 Volts 




Ampa 


city 


Ampacity 




Ampacity 


Ampacity 


Conductor 


90°C 


105°C 


90°C 


105°C 


Conductor 


90°C 


105°C 


90°C 


105°C 


Size 


(194°F) 


(221°F) 


(194°F) 


(221°F) 


Size 


(194°F) 


(221°F) 


(194°F) 


(221°F) 


(AWG 


Type 


Type 


Type 


Type 


(AWG 


Type 


Type 


Type 


Type 


or kcmil) 


MV-90 


MV-105 


MV-90 


MV-105 


or kcmil) 


MV-90 


MV-105 


MV-90 


MV-105 


One Circuit, 










One Circuit, Three 










Three Conductors (See 








Conductors (See Figure 








Figure 










310.60, Detail 9.) 










310.60, Detail 9.) 






























8 


85 


90 


— 


— 


8 


110 


115 


— 


— 


6 


110 


115 


100 


110 


6 


140 


150 


130 


140 


4 


140 


150 


130 


140 


4 


180 


195 


170 


180 


2 


180 


195 


165 


175 


2 


230 
260 


250 
280 


210 
240 


225 
260 


1 


205 


220 


185 


200 


1 


1/0 


230 


250 


215 














230 


1/0 


295 


320 


275 


295 


2/0 


265 


285 


245 


260 


2/0 


335 


365 


310 


335 


3/0 


300 


320 


275 


295 


3/0 


385 
435 


415 
465 


355 
405 


380 
435 


4/0 


340 


365 


315 


340 


4/0 


250 


370 


395 


345 














370 


250 


470 


510 


440 


475 


350 


445 


480 


415 


450 


350 


570 


615 


535 


575 


500 


540 


580 


510 


545 


500 


690 


745 


650 


700 


750 


665 


720 


635 


680 


750 


845 
980 


910 
1055 


805 
930 


865 
1005 


1000 


780 


840 


740 


795 


1000 


Two Circuits, Six 






















Two Circuits, 










Conductors (See Figure 








Six Conductors (See Figure 








310.60, Detail 10.) 










310.60, Detail 10.) 






























8 


80 


85 


— 


— 


8 


100 


110 


— 


— 


6 


100 


110 


95 


100 


6 


130 


140 


120 


130 


4 


130 


140 


125 


130 


4 


165 


180 


160 


170 


2 


165 


180 


155 


165 


2 


215 
240 


230 
260 


195 

225 


210 
240 


1 


190 


200 


175 


190 


1 


1/0 


215 


230 


200 














215 


1/0 


275 


295 


255 


275 


2/0 


245 


260 


225 


245 


2/0 


310 


335 


290 


315 


3/0 


275 


295 


255 


275 


3/0 


355 
400 


380 
430 


330 

375 


355 
405 


4/0 


310 


335 


290 


315 


4/0 


250 


340 


365 


320 














345 


250 


435 


470 


410 


440 


350 


410 


440 


385 


415 


350 


520 


560 


495 


530 


500 


495 


530 


470 


505 


500 


630 


680 


600 


645 


750 


610 


655 


580 


625 


750 
1000 


775 
890 


835 
960 


740 
855 


795 
920 


1000 


710 


765 


680 


730 













2005 Edition 



NATIONAL ELECTRICAL CODE 



70-155 



310.60 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



Table 310.83 Ampacities of Three Insulated Copper 
Conductors Cabled Within an Overall Covering 
(Three-Conductor Cable), Directly Buried in Earth Based on 
Ambient Earth Temperature of 20°C (68°F), Arrangement 
per Figure 310.60, 100 Percent Load Factor, Thermal 
Resistance (RHO) of 90, Conductor Temperatures of 90°C 
(194°F) and 105°C (221°F) 



Table 310.84 Ampacities of Three Insulated Aluminum 
Conductors Cabled Within an Overall Covering 
(Three-Conductor Cable), Directly Buried in Earth Based on 
Ambient Earth Temperature of 20°C (68°F), Arrangement 
per Figure 310.60, 100 Percent Load Factor, Thermal 
Resistance (RHO) of 90, Conductor Temperatures of 90°C 
(194°F) and 105°C (221°F) 





Temperature Rating of Conductor (See Table 




Temperature Rating of Conductor (S 


Be Table 






310.61.) 








310.61.) 






2001-5000 Volts 


5001-35,000 Volts 


2001-5000 Volts 


5001-35,000 Volts 




Ampacity 


Ampacity 


Conductor 


Ampacity 


Ampacity 


Conductor 


90°C 


105°C 


90°C 


105°C 


90°C 


105°C 


90°C 


105°C 


Size 


(194°F) 


(221°F) 


(194°F) 


(221°F) 


Size 


(194°F) 


(221°F) 


(194°F) 


(221°F) 


(AWG 


Type 


Type 


Type 


Type 


(AWG 


Type 


Type 


Type 


Type 


or kcmil) 


MV-90 


MV-105 


MV-90 


MV-105 


or kcmil) 


MV-90 


MV-105 


MV-90 


MV-105 


One Circuit (See Fig 


ure 








One Circuit (See Figure 








310.60, Detail 5.) 










310.60, Detail 5.) 










8 


85 


89 








8 


65 


70 








6 


105 


115 


115 


120 


6 


80 


88 


90 


95 


4 


135 


150 


145 


155 


4 


105 


115 


115 


125 


2 


180 


190 


185 


200 


2 


140 


150 


145 


155 


1 


200 


215 


210 


225 


1 


155 


170 


165 


175 


1/0 


230 


245 


240 


255 


1/0 


180 


190 


185 


200 


2/0 


260 


280 


270 


290 


2/0 


205 


220 


210 


225 


3/0 


295 


320 


305 


330 


3/0 


230 


250 


240 


260 


4/0 


335 


360 


350 


375 


4/0 


260 


280 


270 


295 


250 


365 


395 


380 


410 


250 


285 


310 


300 


320 


350 


440 


475 


460 


495 


350 


345 


375 


360 


390 


500 


530 


570 


550 


590 


500 


420 


450 


435 


470 


750 


650 


700 


665 


720 


750 


520 


560 


540 


580 


1000 


730 


785 


750 


810 


1000 


600 


650 


620 


665 


Two Circuits (See Figure 








Two Circuits (See Figure 








310.60, Detail 6.) 










310.60, Detail 6.) 










8 


80 


84 








8 


60 


66 








6 


100 


105 


105 


115 


6 


75 


83 


80 


95 


4 


130 


140 


135 


145 


4 


100 


110 


105 


115 


2 


165 


180 


170 


185 


2 


130 


140 


135 


145 


1 


185 


200 


195 


210 


1 


145 


155 


150 


165 


1/0 


215 


230 


220 


235 


1/0 


165 


180 


170 


185 


2/0 


240 


260 


250 


270 


2/0 


190 


205 


195 


210 


3/0 


275 


295 


280 


305 


3/0 


215 


230 


220 


240 


4/0 


310 


335 


320 


345 


4/0 


245 


260 


250 


270 


250 


340 


365 


350 


375 


250 


265 


285 


275 


295 


350 


410 


440 


420 


450 


350 


320 


345 


330 


355 


500 


490 


525 


500 


535 


500 


385 


415 


395 


425 


750 


595 


640 


605 


650 


750 


480 


515 


485 


525 


1000 


665 


715 


675 


730 


1000 


550 


590 


560 


600 



70-156 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



310.60 



Table 310.85 Ampacities of Three Tripiexed Single Insulated 
Copper Conductors Directly Buried in Earth Based on 
Ambient Earth Temperature of 20°C (68°F), Arrangement 
per Figure 310.60, 100 Percent Load Factor, Thermal 
Resistance (RHO) of 90, Conductor Temperatures 90°C 
(194°F) and 105°C (221°F) 



Table 310.86 Ampacities of Three Tripiexed Single Insulated 
Aluminum Conductors Directly Buried in Earth Based on 
Ambient Earth Temperature of 20°C (68°F), Arrangement 
per Figure 310.60, 100 Percent Load Factor, Thermal 
Resistance (RHO) of 90, Conductor Temperatures 90°C 
(194°F) and 105°C (221°F) 



• 





Temperature Rating of Conductor (See Table 




Temperature Rating of Conductor (See Table 






310.61. 


) 




- 




310.61.) 






2001-5000 Volts 


5001-35,000 Volts 


2001-5000 Volts 


5001-35,000 Volts 




Ampacity 


Ampacity 


Conductor 


Ampacity 


Ampacity 


Conductor 


90°C 


105°C 


90°C 


105°C 


90°C 


105°C 


90°C 


105°C 


Size 


(194°F) 


(221°F) 


(194°F) 


(22rF) 


Size 


(194°F) 


(22rF) 


(194°F) 


(221°F) 


(AWG 


Type 


Type 


Type 


Type 


(AWG 


Type 


Type 


Type 


Type 


or kcmil) 


MV-90 


MV-105 


MV-90 


MV-105 


or kcmil) 


MV-90 


MV-105 


MV-90 


MV-105 


One Circuit, Three 










One Circuit, Three 










Conductors (See Figure 








Conductors (See 


Figure 








310.60, Detail 7.) 










310.60, Detail 7.) 










8 


90 


95 








8 


70 


75 


_ 


_ 


6 


120 


130 


115 


120 


6 


90 


100 


90 


95 


4 


150 


165 


150 


160 


4 


120 


130 


115 


125 


2 


195 


205 


190 


205 


2 


155 


165 


145 


155 


1 


225 


240 


215 


230 


1 


175 


190 


165 


175 


I/O 


255 


270 


245 


260 


1/0 


200 


210 


190 


205 


2/0 


290 


310 


275 


295 


2/0 


225 


240 


215 


230 


3/0 


330 


360 


315 


340 


3/0 


255 


275 


245 


265 


4/0 


375 


405 


360 


385 


4/0 


290 


310 


280 


305 


250 


410 


445 


390 


410 


250 


320 


350 


305 


325 


350 


490 


580 


470 


505 


350 


385 


420 


370 


400 


500 


590 


635 


565 


605 


500 


465 


500 


445 


480 


750 


725 


780 


685 


740 


750 


580 


625 


550 


590 


1000 


825 


885 


770 


830 


1000 


670 


725 


635 


680 


Two Circuits, Six 










Two Circuits, Six 










Conductors (See Figure 








Conductors (See 


Figure 








310.60, Detail 8.) 










310.60, Detail 8.) 










8 


85 


90 








8 


65 


70 


_ 


_ 


6 


110 


115 


105 


115 


6 


85 


95 


85 


90 


4 


140 


150 


140 


150 


4 


110 


120 


105 


115 


2 


180 


195 


175 


190 


2 


140 


150 


135 


145 


1 


205 


220 


200 


215 


1 


160 


170 


155 


170 


1/0 


235 


250 


225 


240 


1/0 


180 


195 


175 


190 


2/0 


265 


285 


255 


275 


2/0 


205 


220 


200 


215 


3/0 


300 


320 


290 


315 


3/0 


235 


250 


225 


245 


4/0 


340 


365 


325 


350 


4/0 


265 


285 


255 


275 


250 


370 


395 


355 


380 


250 


290 


310 


280 


300 


350 


445 


480 


425 


455 


350 


350 


375 


335 


360 


500 


535 


575 


510 


545 


500 


420 


455 


405 


435 


750 


650 


700 


615 


660 


750 


520 


560 


485 


525 


1000 


740 


795 


690 


745 


1000 


600 


645 


565 


605 



2005 Edition NATIONAL ELECTRICAL CODE 



70-157 



312.1 



ARTICLE 312 — CABINETS, CUTOUT BOXES, AND METER SOCKET ENCLOSURES 



ARTICLE 312 

Cabinets, Cutout Boxes, and Meter 

Socket Enclosures 



312.1 Scope. This article covers the installation and con- 
struction specifications of cabinets, cutout boxes, and meter 
socket enclosures. 

I. Installation 

312.2 Damp, Wet, or Hazardous (Classified) Locations. 

(A) Damp and Wet Locations. In damp or wet locations, 
surface-type enclosures within the scope of this article shall be 
placed or equipped so as to prevent moisture or water from 
entering and accumulating within the cabinet or cutout box, 
and shall be mounted so there is at least 6-mm ('/4-in.) airspace 
between the enclosure and the wall or other supporting sur- 
face. Enclosures installed in wet locations shall be weather- 
proof. For enclosures in wet locations, raceways or cables 
entering above the level of uninsulated five parts shall use 
fittings fisted for wet locations. 

Exception: Nonmetallic enclosures shall be permitted to 
be installed without the airspace on a concrete, masonry, 
tile, or similar surface. 

FPN: For protection against corrosion, see 300.6. 

(B) Hazardous (Classified) Locations. Installations in 
hazardous (classified) locations shall conform to Articles 
500 through 517. 

312.3 Position in Wall. In walls of concrete, tile, or other 
noncombustible material, cabinets shall be installed so that 
the front edge of the cabinet is not set back of the finished 
surface more than 6 mm ('A in.). In walls constructed of 
wood or other combustible material, cabinets shall be flush 
with the finished surface or project therefrom. 

312.4 Repairing Plaster and Drywall or Plasterboard. 

Plaster, drywall, or plasterboard surfaces that are broken or 
incomplete shall be repaired so there will be no gaps or 
open spaces greater than 3 mm (Vs in.) at the edge of the 
cabinet or cutout box employing a flush-type cover. 

312.5 Cabinets, Cutout Boxes, and Meter Socket Enclo- 
sures. Conductors entering enclosures within the scope of 
this article shall be protected from abrasion and shall com- 
ply with 312.5(A) through (C). 

(A) Openings to Be Closed. Openings through which con- 
ductors enter shall be adequately closed. 



(B) Metal Cabinets, Cutout Boxes, and Meter Socket 
Enclosures. Where metal enclosures within the scope of 
this article are installed with messenger supported wiring, 
open wiring on insulators, or concealed knob-and-tube wir- 
ing, conductors shall enter through insulating bushings or, 
in dry locations, through flexible tubing extending from the 
last insulating support and firmly secured to the enclosure. 

(C) Cables. Where cable is used, each cable shall be se- 
cured to the cabinet, cutout box, or meter socket enclosure. 

Exception: Cables with entirely nonmetallic sheaths shall 
be permitted to enter the top of a surface-mounted enclo- 
sure through one or more nonflexible raceways not less 
than 450 mm (18 in.) and not more than 3.0 m (10 ft) in 
length, provided all of the following conditions are met: 

(a) Each cable is fastened within 300 mm (12 in.), 
measured along the sheath, of the outer end of the raceway. 

(b) The raceway extends directly above the enclosure 
and does not penetrate a structural ceiling. 

(c) A fitting is provided on each end of the raceway to 
protect the cable(s) from abrasion and the fittings remain 
accessible after installation. 

(d) The raceway is sealed or plugged at the outer end 
using approved means so as to prevent access to the enclo- 
sure through the raceway. 

(e) The cable sheath is continuous through the race- 
way and extends into the enclosure beyond the fitting not 
less than 6 mm (V4 in.). 

(f) The raceway is fastened at its outer end and at 
other points in accordance with the applicable article. 

(g) Where installed as conduit or tubing, the allowable 
cable fill does not exceed that permitted for complete con- 
duit or tubing systems by Table 1 of Chapter 9 of this Code 
and all applicable notes thereto. 

FPN: See Table 1 in Chapter 9, including Note 9, for allow- 
able cable fill in circular raceways. See 310.15(B)(2)(a) for 
required ampacity reductions for multiple cables installed in a 
common raceway. 

312.6 Deflection of Conductors. Conductors at terminals 
or conductors entering or leaving cabinets or cutout boxes 
and the like shall comply with 312.6(A) through (C). 

Exception: Wire-bending space in enclosures for motor 
controllers with provisions for one or two wires per termi- 
nal shall comply with 430.10(B). 

(A) Width of Wiring Gutters. Conductors shall not be 
deflected within a cabinet or cutout box unless a gutter 
having a width in accordance with Table 312.6(A) is pro- 
vided. Conductors in paraflel in accordance with 310.4 
shall be judged on the basis of the number of conductors in 
parallel. 



• 



70-158 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 312 — CABINETS, CUTOUT BOXES, AND METER SOCKET ENCLOSURES 



312.9 



Table 312.6(A) Minimum Wire-Bending Space at Terminals and Minimum Width of Wiring Gutters 



• 















Wires per 


Terminal 














1 




2 






3 




A 


1 


< 


) 


Wire Size (AWG or 


















































kcmil) 


mm 




m. 


mm 


m. 


mm 




m. 


mm 


m. 


mm 


m. 


14-10 


Not 


specified 




























8-6 


38.1 




V/2 


— 


— 


— 




— 


— 


— 


— 


— 


4-3 


50.8 




2 


— 


— 


— 




— 


— 


— 


— 


— 


2 


63.5 




Vh 


— 


— 


— 




— 


— 


— 


— 


— 


1 


76.2 




3 


— 


— 


— 




— 


— 


— 


— 


— 


1/0-2/0 


88.9 




3'/2 


127 


5 


178 




7 














3/0^/0 


102 




4 


152 


6 


203 




8 


— 


— 


— 


— 


250 


114 




41/2 


152 


6 


203 




8 


254 


10 


— 


— 


300-350 


127 




5 


203 


8 


254 




10 


305 


12 


— 


— 


400-500 


152 




6 


203 


8 


254 




10 


305 


12 


356 


14 


600-700 


203 




8 


254 


10 


305 




12 


356 


14 


406 


16 


750-900 


203 




8 


305 


12 


356 




14 


406 


16 


457 


18 


1000-1250 


254 




10 


— 


— 


— 




— 


— 


— 


— 


— 


1500-2000 


305 




12 


— 


— 


— 




— 


— 


— 


— 


— 



Note: Bending space at terminals shall be measured in a straight line from the end of the lug or wire 
connector (in the direction that the wire leaves the terminal) to the wall, barrier, or obstruction. 



(B) Wire-Bending Space at Terminals. Wire-bending 
space at each terminal shall be provided in accordance with 
312.6(B)(1) or (B)(2). 

(1) Conductors Not Entering or Leaving Opposite Wall. 

Table 312.6(A) shall apply where the conductor does not 
enter or leave the enclosure through the wall opposite its 
terminal. 

(2) Conductors Entering or Leaving Opposite Wall. 

Table 312.6(B) shall apply where the conductor does enter or 
leave the enclosure through the wall opposite its terminal. 

Exception No. 1: Where the distance between the wall and 
its terminal is in accordance with Table 312.6(A), a con- 
ductor shall be permitted to enter or leave an enclosure 
through the wall opposite its terminal, provided the con- 
ductor enters or leaves the enclosure where the gutter joins 
an adjacent gutter that has a width that conforms to Table 
312.6(B) for the conductor 

Exception No. 2: A conductor not larger than 350 kcmil 
shall be permitted to enter or leave an enclosure containing 
only a meter socket(s) through the wall opposite its termi- 
nal, provided the distance between the terminal and the 
opposite wall is not less than that specified in Table 
312.6(A) and the terminal is a lay-in type, where the termi- 
nal is either of the following: 

(a) Directed toward the opening in the enclosure and 
within a 45 degree angle of directly facing the enclosure 
wall 



(b) Directly facing the enclosure wall and offset not 
greater than 50 percent of the bending space specified in 
Table 312.6(A) 

FPN: Offset is the distance measured along the enclosure 
wall from the axis of the centerline of the terminal to a line 
passing through the center of the opening in the enclosure. 

(C) Conductors 4 AWG or Larger. Installation shall com- 
ply with 300.4(F). 

312.7 Space in Enclosures. Cabinets and cutout boxes 
shall have sufBcient space to accommodate all conductors 
installed in them without crowding. 

312.8 Enclosures for Switches or Overcurrent Devices. 

Enclosures for switches or overcurrent devices shall not be 
used as junction boxes, auxiliary gutters, or raceways for 
conductors feeding through or tapping off to other switches 
or overcurrent devices, unless adequate space for this pur- 
pose is provided. The conductors shall not fill the wiring 
space at any cross section to more than 40 percent of the 
cross-sectional area of the space, an«li the conductors, 
splices, and taps shall not fill the wiring space at any cross 
section to more than 75 percent of the cross-sectional area 
of that space. 

312.9 Side or Back Wiring Spaces or Gutters. Cabinets 
and cutout boxes shall be provided with back-wiring 
spaces, gutters, or wiring compartments as required by 
312.11(C) and (D). 



2005 Edition 



NATIONAL ELECTRICAL CODE 



70-159 



312.10 



ARTICLE 312 — CABINETS, CUTOUT BOXES, AND METER SOCKET ENCLOSURES 



Table 312.6(B) Minimum Wire-Bending Space at Terminals 







Wires per Terminal 


Wire Size (AWG or kcmil) 


1 


2 


3 


4 or 


More 




Compact 




















Stranded 




















AA-8000 




















Aluminum 




















Alloy 


















All Other 


Conductors 


















Conductors 


(See Note 3.) 


mm 


in. 


mm 


in. 


mm 


in. 


mm 


in. 


- 14-10 


12-8 


Not 


specified 





— 


— 




— 


— 


8 


6 


38.1 


11/2 


— 


— 


— 




— 


— 


6 


4 


50.8 


2 


— 


— 


— 




— 


— 


4 


2 


76.2 


3 


— 


— 


— 




— 


— 


3 


1 


76.2 


3 


— 


— 


— 




— 


— 


2 


1/0 


88.9 


3'/2 


— 


— 


— 




— 


— 


1 


2/0 


114 


4'/2 


— 


— 


— 




— 


— 


1/0 


3/0 


140 


5'/2 


140 


5'/2 


178 


7 








2/0 


4/0 


152 


6 


152 


6 


190 


7 J/2 


— 


— 


3/0 


250 


165^^ 


6'/2'' 


165=^ 


6'/2" 


203 


8 


— 


— 


4/0 


300 


178" 


7b 


190" 


7'/2" 


216^^ 


8'/2^ 


— 


— 


250 


350 


216" 


8'/2'' 


229" 


8'/2" 


254*^ 


9b 


254 


10 


300 


400 


254^ 


10" 


254" 


10" 


279" 


11" 


305 


12 


350 


500 


305^ 


12" 


305" 


12" 


330" 


13" 


356" 


14" 


400 


600 


330" 


13" 


330" 


13" 


356" 


14" 


381" 


15" 


500 


700-750 


356*= 


14" 


356" 


14" 


381" 


15" 


406" 


16" 


600 


800-900 


38 r 


15" 


406" 


16" 


457" 


18" 


483" 


19" 


700 


1000 


406^ 


16" 


457" 


18" 


508" 


20" 


559" 


22" 


750 


— 


432^ 


17" 


483" 


19" 


559" 


22" 


610" 


24" 


800 


_ 


457 


18 


508 


20 


559 


22 


610 


24 


900 


— 


483 


19 


559 


22 


610 


24 


610 


24 


1000 


— 


508 


20 


— 


— 


— 




— 




1250 


— 


559 


22 


— 


— 


— 




— 




1500 


— 


610 


24 


— 


— 


— 




— 




1750 


— 


610 


24 


— 


— 


— 




— 




2000 


— 


610 


24 


— 


— 


— 




— 





1. Bending space at terminals shall be measured in a straight line from the end of the lug or wire connector 
in a direction perpendicular to the enclosure wall. 

2. For removable and lay-in wire terminals intended for only one wire, bending space shall be permitted to 
be reduced by the following number of millimeters (inches): 

^ 12.7 mm {V2 in.) " 50.8 mm (2 in.) 

" 25.4 mm (I in.) " 76.2 mm (3 in.) 

" 38.1 mm (1/2 in.) 

3. This column shall be permitted to determine the required wire-bending space for compact stranded 
aluminum conductors in sizes up to 1000 kcmil and manufactured using AA-8000 series electrical grade 
aluminum alloy conductor material in accordance with 310.14. 



• 



II. Construction Specifications 

312.10 Material. Cabinets, cutout boxes, and meter socket 
enclosures shall comply with 312.10(A) through (C). 

(A) Metal Cabinets and Cutout Boxes. Metal enclosures 
within the scope of this article shall be protected both in- 
side and outside against corrosion. 



FPN: For information on protection against corrosion, see 
300.6. 

(B) Strength. The design and construction of enclosures 
within the scope of this article shall be such as to secure 
ample strength and rigidity. If constructed of sheet steel, the 
metal thickness shall not be less than 1.35 mm (0.053 in.) 
uncoated. 



70-160 



NATIONAL ELECTRICAL CODE 2005 Edidon 



ARTICLE 3 14 — OUTLET, DEVICE, PULL, AND JUNCTION BOXES; CONDUIT BODIES; FITTINGS; AND HANDHOLES 314.3 



• 



(C) Nonmetallic Cabinets. Nonmetallic cabinets shall be 
listed, or they shall be submitted for approval prior to 
installation. 

312.11 Spacing. The spacing within cabinets and cutout 
boxes shall comply with 312.11(A) through (D). 

(A) General. Spacing within cabinets and cutout boxes 
shall be sufficient to provide ample room for the distribu- 
tion of wires and cables placed in them and for a separation 
between metal parts of devices and apparatus mounted 
within them as follows. 

(1) Base. Other than at points of support, there shall be an 
airspace of at least 1.59 mm (0.0625 in.) between the base 
of the device and the wall of any metal cabinet or cutout 
box in which the device is mounted. 

(2) Doors. There shall be an airspace of at least 25.4 mm 
(1.00 in.) between any Uve metal part, including live metal 
parts of enclosed fuses, and the door. 

Exception: Where the door is lined with an approved in- 
sulating material or is of a thickness of metal not less than 
2.36 mm (0.093 in.) uncoated, the airspace shall not be less 
than 12.7 mm (0.500 in.). 

(3) Live Parts. There shall be an airspace of at least 
12.7 mm (0.500 in.) between the walls, back, gutter parti- 
tion, if of metal, or door of any cabinet or cutout box and 
the nearest exposed current-carrying part of devices 
mounted within the cabinet where the voltage does not 
exceed 250. This spacing shall be increased to at least 
25.4 mm (1.00 in.) for voltages of 251 to 600, nominal. 

Exception: Where the conditions in 312.11(A)(2), Excep- 
tion, are met, the airspace for nominal voltages from 251 to 
600 shall be permitted to be not less than 12.7 mm 
(0.500 in.). 

(B) Switch Clearance. Cabinets and cutout boxes shall be 
deep enough to allow the closing of the doors when 30- 
ampere branch-circuit panelboard switches are in any posi- 
tion, when combination cutout switches are in any position, 
or when other single-throw switches are opened as far as 
their construction permits. 

(C) Wiring Space. Cabinets and cutout boxes that contain 
devices or apparatus connected within the cabinet or box to 
more than eight conductors, including those of branch circuits, 
meter loops, feeder circuits, power circuits, and similar cir- 
cuits, but not including the supply circuit or a continuation 
thereof, shall have back-wiring spaces or one or more side- 
wiring spaces, side gutters, or wiring compartments. 

(D) Wiring Space — Enclosure. Side-wiring spaces, side 
gutters, or side-wiring compartments of cabinets and cutout 
boxes shall be made tight enclosures by means of covers, 



barriers, or partitions extending from the bases of the de- 
vices contained in the cabinet, to the door, frame, or sides 
of the cabinet. 

Exception: Side-wiring spaces, side gutters, and side- 
wiring compartments of cabinets shall not be required to be 
made tight enclosures where those side spaces contain only 
conductors that enter the cabinet directly opposite to the 
devices where they terminate. 

Partially enclosed back-wiring spaces shall be provided 
with covers to complete the enclosure. Wiring spaces that 
are required by 312.11(C) and are exposed when doors are 
open shall be provided with covers to complete the enclo- 
sure. Where adequate space is provided for feed-through 
conductors and for splices as required in 312.8, additional 
barriers shall not be required. 



ARTICLE 314 

Outlet, Device, Pull, and Junction Boxes; 

Conduit Bodies; Fittings; and Handhole 

Enclosures 

I. Scope and General 

314.1 Scope. This article covers the installation and use of 
all boxes and conduit bodies used as outlet, device, junc- 
tion, or pull boxes, depending on their use, and handhole 
enclosures. Cast, sheet metal, nonmetallic, and other boxes 
such as FS, FD, and larger boxes are not classified as con- 
duit bodies. This article also includes installation require- 
ments for fittings used to join raceways and to connect 
raceways and cables to boxes and conduit bodies. 

314.2 Round Boxes. Round boxes shall not be used where 
conduits or connectors requiring the use of locknuts or 
bushings are to be connected to the side of the box. 

314.3 Nonmetallic Boxes. Nonmetallic boxes shall be per- 
mitted only with open wiring on insulators, concealed knob- 
and-tube wiring, cabled wiring methods with entirely nonme- 
tallic sheaths, flexible cords, and nonmetallic raceways. 

Exception No. 1: Where internal bonding means are pro- 
vided between all entries, nonmetallic boxes shall be permit- 
ted to be used with metal raceways or metal-armored cables. 

Exception No. 2: Where integral bonding means with a 
provision for attaching an equipment bonding jumper in- 
side the box are provided between all threaded entries in 
nonmetallic boxes listed for the purpose, nonmetallic boxes 
shall be permitted to be used with metal raceways or metal- 
armored cables. 



2005 Edition 



NATIONAL ELECTRICAL CODE 



70-161 



314.4 ARTICLE 314 — OUTLET, DEVICE, PULL, AND JUNCTION BOXES; CONDUIT BODIES; FITTINGS; AND HANDHOLES 



314.4 Metal Boxes. All metal boxes shall be grounded in 
accordance with the provisions of Article 250. 

314.5 Short-Radius Conduit Bodies. Conduit bodies such 
as capped elbows and service-entrance elbows that enclose 
conductors 6 AWG or smaller, and are only intended to 
enable the installation of the raceway and the contained 
conductors, shall not contain splices, taps, or devices and 
shall be of sufficient size to provide free space for all con- 
ductors enclosed in the conduit body. 

II. Installation 

314.15 Damp, Wet, or Hazardous (Classified) Locations. 

(A) Damp or Wet Locations. In damp or wet locations, 
boxes, conduit bodies, and fittings shall be placed or 
equipped so as to prevent moisture from entering or accu- 
mulating within the box, conduit body, or fitting. Boxes, 
conduit bodies, and fittings installed in wet locations shall 
be listed for use in wet locations. 

FPN No. 1: For boxes in floors, see 314.27(C). 

FPN No. 2: For protection against corrosion, see 300.6. 

(B) Hazardous (Classified) Locations. Installations in 
hazardous (classified) locations shall conform to Articles 
500 through 517. 

314.16 Number of Conductors in Outlet, Device, and 
Junction Boxes, and Conduit Bodies. Boxes and conduit 
bodies shall be of sufficient size to provide free space for 
all enclosed conductors. In no case shall the volume of the 
box, as calculated in 314.16(A), be less than the fill calcu- 
lation as calculated in 314.16(B). The minimum volume for 
conduit bodies shall be as calculated in 314.16(C). 

The provisions of this section shall not apply to termi- 
nal housings supplied with motors. 

FPN: For volume requirements of motor terminal hous- 
ings, see 430.12. 

Boxes and conduit bodies enclosing conductors 4 AWG 
or larger shall also comply with the provisions of 314.28. 

(A) Box Volume Calculations. The volume of a wiring 
enclosure (box) shall be the total volume of the assembled 
sections and, where used, the space provided by plaster 
rings, domed covers, extension rings, and so forth, that are 
marked with their volume or are made from boxes the di- 
mensions of which are listed in Table 314.16(A). 

(1) Standard Boxes. The volumes of standard boxes that 
are not marked with their volume shall be as given in Table 
314.16(A). 

(2) Other Boxes. Boxes 1650 cm"' (100 in."') or less, other 
than those described in Table 314.16(A), and nonmetallic 



boxes shall be durably and legibly marked by the manufac- 
turer with their volume. Boxes described in Table 
314.16(A) that have a volume larger than is designated in 
the table shall be permitted to have their volume marked as 
required by this section. 

(B) Box Fill Calculations. The volumes in paragraphs 
314.16(B)(1) through (B)(5), as applicable, shall be added 
together. No allowance shall be required for small fittings 
such as locknuts and bushings. 

(1) Conductor Fill. Each conductor that originates outside 
the box and terminates or is spliced within the box shall be 
counted once, and each conductor that passes through the 
box without splice or termination shall be counted once. A 
looped, unbroken conductor not less than twice the mini- 
mum length required for free conductors in 300.14 shall be 
counted twice. The conductor fill shall be calculated using 
Table 314.16(B). A conductor, no part of which leaves the 
box, shall not be counted. 

Exception: An equipment grounding conductor or conduc- 
tors or not over four fixture wires smaller than 14 AWG, or 
both, shall be permitted to be omitted from the calculations 
where they enter a box from a domed luminaire (fixture) or 
similar canopy and terminate within that box. 

(2) Clamp Fill. Where one or more intemal cable clamps, 
whether factory or field suppUed, are present in the box, a 
single volume allowance in accordance with Table 314.16(B) 
shall be made based on the largest conductor present in the 
box. No allowance shall be required for a cable connector with 
its clamping mechanism outside the box. 

(3) Support Fittings Fill. Where one or more luminaire 
(fixture) studs or hickeys are present in the box, a single 
volume allowance in accordance with Table 314.16(B) 
shall be made for each type of fitting based on the largest 
conductor present in the box. 

(4) Device or Fquipment Fill. For each yoke or strap con- 
taining one or more devices or equipment, a double volume 
allowance in accordance with Table 314.16(B) shall be 
made for each yoke or strap based on the largest conductor 
connected to a device(s) or equipment supported by that 
yoke or strap. 

(5) Equipment Grounding Conductor Fill. Where one or 
more equipment grounding conductors or equipment bond- 
ing jumpers enter a box, a single volume allowance in ac- 
cordance with Table 314.16(B) shall be made based on the 
largest equipment grounding conductor or equipment bond- 
ing jumper present in the box. Where an additional set of 
equipment grounding conductors, as permitted by 250.146(D), 
is present in the box, an additional volume allowance shall be 
made based on the largest equipment grounding conductor in 
the additional set. 



• 



70-162 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 314 — OUTLET, DEVICE, PULL, AND JUNCTION BOXES; CONDUIT BODIES; FITTINGS; AND HANDHOLES 314.17 



Table 314.16(A) Metal Boxes 



Box Trade Size 


Minimum 
Volume 


Maximum Number of Conductors* 


mm 


in. 




cm^ 


in.^ 


18 


16 


14 


12 


10 


8 


6 


100 X 32 
100 X 38 
100 X 54 


(4x 11/4) 
(4x 11/2) 
(4 X 2'/8) 


round/octagonal 
round/octagonal 
round/octagonal 


205 
254 
353 


12.5 
15.5 
21.5 


8 

10 
14 


7 

8 

12 


6 

7 
10 


5 
6 
9 


5 
6 
8 


5 
5 
7 


2 
3 
4 


100 X 32 
100 X 38 
100 X 54 


(4x VA) 
(4 X 1 Vi) 
(4 X 21/8) 


square 
square 
square 


295 
344 
497 


18.0 
21.0 
30.3 


12 
14 
20 


10 
12 
17 


9 
10 
15 


8 

9 

13 


7 

8 

12 


6 

7 
10 


3 
4 
6 


120 X 32 
120 X 38 
120 X 54 


(4"/i6X VA) 
(4'yi6X l'/2) 

(4"/l6X21/8) 


square 
square 
square 


418 
484 
689 


25.5 
29.5 
42.0 


17 
19 
28 


14 
16 

24 


12 
14 
21 


11 
13 
18 


10 
11 
16 


8 

9 

14 


5 
5 
8 


75 X 50 X 38 
75 X 50 X 50 
75 X 50 X 57 
75 X 50 X 65 
75 X 50 X 70 
75 X 50 X 90 


(3x2x1 1/2) 
(3x2x2) 
(3 X 2 X 2/4) 
(3 X 2 X 2'/2) 
(3 X 2 X 23/4) 
(3 X 2 X 3'/2) 


device 
device 
device 
device 
device 
device 


123 
164 
172 
205 
230 
295 


7.5 
10.0 
10.5 
12.5 
14.0 
18.0 


5 
6 
7 
8 
9 
12 


4 
5 
6 
7 
8 
10 


3 
5 
5 
6 
7 
9 


3 
4 
4 
5 
6 
8 


3 
4 
4 
5 
5 
7 


2 
3 
3 
4 
4 
6 


1 
2 
2 
2 
2 
3 


100 X 54 X 38 
100 X 54 X 48 
100 X 54 X 54 


(4 X 2/8 X 1 V2) 
(4 X 2'/8 X VA) 
(4 X 2'/8 X 21/8) 


device 
device 
device 


169 

213 
238 


10.3 
13.0 
14.5 


6 
8 
9 


5 
7 
8 


5 
6 

7 


4 
5 
6 


4 
5 
5 


3 
4 
4 


2 
2 
2 


95 X 50 X 65 
95 X 50 X 90 


(33/4 X 2 X 2/2) 
(33/4 X 2 X 3/2) 


masonry box/gang 
masonry box/gang 


230 
344 


14.0 
21.0 


9 

14 


8 
12 


7 
10 


6 
9 


5 
8 


4 
7 


2 
4 


min. 44.5 depth 
min. 60.3 depth 


FS — single cover/gang (PA) 
FD — single cover/gang (23/8) 


221 
295 


13.5 
18.0 


9 

12 


7 
10 


6 
9 


6 

8 


5 
7 


4 
6 


2 
3 


min. 44.5 depth 
min. 60.3 depth 


FS — multiple 
FD — multiple 


cover/gang (PA) 
cover/gang (23/8) 


295 
395 


18.0 
24.0 


12 
16 


10 

13 


9 

12 


8 
10 


7 
9 


6 

8 


3 
4 



*Where no volume allowances are required by 314.16(B)(2) through (B)(5). 



Table 314.16(B) Volume Allowance Required per Conductor 





Free Space Within Box for Each 






Conductor 




Size of Conductor 














(AWG) 


cm^ 




in.^ 


18 


24.6 




1.50 


16 


28.7 




1.75 


14 


32.8 




2.00 


12 


36.9 




2.25 


10 


41.0 




2.50 


8 


49.2 




3.00 


6 


81.9 




5.00 



(C) Conduit Bodies. 

(1) General. Conduit bodies enclosing 6 AWG conductors 
or smaller, other than short-radius conduit bodies as de- 
scribed in 314.5, shall have a cross-sectional area not less 
than twice the cross-sectional area of the largest conduit or 
tubing to which it is attached. The maximum number of 



conductors permitted shall be the maximum number per- 
mitted by Table 1 of Chapter 9 for the conduit or tubing to 
which it is attached. 

(2) With Splices, Taps, or Devices. Only those conduit 
bodies that are durably and legibly marked by the manufac- 
turer with their volume shall be permitted to contain 
splices, taps, or devices. The maximum number of conduc- 
tors shall be calculated in accordance with 314.16(B). Con- 
duit bodies shall be supported in a rigid and secure manner. 

314.17 Conductors Entering Boxes, Conduit Bodies, or 
Fittings. Conductors entering boxes, conduit bodies, or fit- 
tings shall be protected from abrasion and shall comply 
with 314.17(A) through (D). 

(A) Openings to Be Closed. Openings through which con- 
ductors enter shall be adequately closed. 

(B) Metal Boxes and Conduit Bodies. Where metal boxes 
or conduit bodies are installed with messenger supported 



2005 Edition NATIONAL ELECTRICAL CODE 



70-163 



314.19 ARTICLE 314 — OUTLET, DEVICE, PULL, AND JUNCTION BOXES; CONDUIT BODIES; FITTINGS; AND HANDHOLES 



wiring, open wiring on insulators, or concealed knob-and- 
tube wiring, conductors shall enter through insulating bush- 
ings or, in dry locations, through flexible tubing extending 
from the last insulating support to not less than 6 mm 
('/4 in.) inside the box and beyond any cable clamps. Except 
as provided in 300.15(C), the wiring shall be firmly secured 
to the box or conduit body. Where raceway or cable is 
installed with metal boxes or conduit bodies, the raceway 
or cable shall be secured to such boxes and conduit bodies. 

(C) Nonmetallic Boxes and Conduit Bodies. Nonmetallic 
boxes and conduit bodies shall be suitable for the lowest 
temperature-rated conductor entering the box. Where non- 
metallic boxes and conduit bodies are used with messenger 
supported wiring, open wiring on insulators, or concealed 
knob-and-tube wiring, the conductors shall enter the box 
through individual holes. Where flexible tubing is used to 
enclose the conductors, the tubing shall extend from the last 
insulating support to not less than 6 mm ('A in.) inside the 
box and beyond any cable clamp. Where nonmetallic- 
sheathed cable or multiconductor Type UF cable is used, 
the sheath shall extend not less than 6 mm (V4 in.) inside 
the box and beyond any cable clamp. In all instances, all 
permitted wiring methods shall be secured to the boxes. 

Exception: Where nonmetallic- sheathed cable or multi- 
conductor Type UF cable is used with single gang boxes 
not larger than a nominal size 57 mm x 100 mm (2 'A in. 
X 4 in.) mounted in walls or ceilings, and where the cable 
is fastened within 200 mm (8 in.) of the box measured along 
the sheath and where the sheath extends through a cable 
knockout not less than 6 mm ('A in.), securing the cable to 
the box shall not be required. Multiple cable entries shall 
be permitted in a single cable knockout opening. 

(D) Conductors 4 AWG or Larger. Installation shall com- 
ply with 300.4(F). 

FPN: See 110.12(A) for requirements on closing unused 
cable and raceway knockout openings. 

314.19 Boxes Enclosing Flush Devices. Boxes used to en- 
close flush devices shall be of such design that the devices 
will be completely enclosed on back and sides and substan- 
tial support for the devices will be provided. Screws for 
supporting the box shall not be used in attachment of the 
device contained therein. 

314.20 In Wall or Ceiling. In walls or ceihngs with a 
surface of concrete, tile, gypsum, plaster, or other noncom- 
bustible material, boxes employing a flush-type cover or 
faceplate shall be installed so that the front edge of the box, 
plaster ring, extension ring, or listed extender will not be 
set back of the finished surface more than 6 mm (}A in.). 

In walls and ceilings constructed of wood or other com- 
bustible surface material, boxes, plaster rings, extension 



rings, or listed extenders shall be flush with the finished 
surface or project therefrom. 

314.21 Repairing Plaster and Dry wall or Plasterboard. 

Plaster, drywall, or plasterboard surfaces that are broken or 
incomplete around boxes employing a flush-type cover or 
faceplate shall be repaired so there will be no gaps or open 
spaces greater than 3 mm (Vs in.) at the edge of the box. 

314.22 Exposed Surface Extensions. Surface extensions 
from a flush-mounted box shall be made by mounting and 
mechanically securing an extension ring over the flush box. 
Equipment grounding and bonding shall be in accordance 
with Article 250. 

Exception: A surface extension shall be permitted to be 
made from the cover of a flush-mounted box where the 
cover is designed so it is unlikely to fall off or be removed 
if its securing means becomes loose. The wiring method 
shall be flexible for a length sufficient to permit removal of 
the cover and provide access to the box interior, and ar- 
ranged so that any bonding or grounding continuity is in- 
dependent of the connection between the box and cover 

314.23 Supports. Enclosures within the scope of this ar- 
ticle shall be supported in accordance with one or more of 
the provisions in 314.23(A) through (H). 

(A) Surface Mounting. An enclosure mounted on a build- 
ing or other surface shall be rigidly and securely fastened in 
place. If the surface does not provide rigid and secure sup- 
port, additional support in accordance with other provisions 
of this section shall be provided. 

(B) Structural Mounting. An enclosure supported from a 
structural member of a building or from grade shall be 
rigidly supported either directly or by using a metal, poly- 
meric, or wood brace. 

(1) Nails and Screws. Nails and screws, where used as a 
fastening means, shall be attached by using brackets on the 
outside of the enclosure, or they shaU pass through the interior 
within 6 mm (!/4 in.) of the back or ends of the enclosure. 
Screws shaU not be permitted to pass through the box unless 
exposed threads in the box are protected using approved 
means to avoid abrasion of conductor insulation. 

(2) Braces. Metal braces shall be protected against corro- 
sion and formed from metal that is not less than 0.51 mm 
(0.020 in.) thick uncoated. Wood braces shall have a cross 
section not less than nominal 25 mm x 50 mm (1 in. 
X 2 in.). Wood braces in wet locations shall be treated for 
the conditions. Polymeric braces shall be identified as being 
suitable for the use. 

(C) Mounting in Finished Surfaces. An enclosure 
mounted in a finished surface shall be rigidly secured 



• 



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Article 314 — outlet, device, pull, and junction boxes; conduit bodies; fittings; and HANDHOLES 314.23 



thereto by clamps, anchors, or fittings identified for the 
application. 

(D) Suspended Ceilings. An enclosure mounted to struc- 
tural or supporting elements of a suspended ceiling shall be 
not more than 1650 cm^ (100 in."^) in size and shall be 
securely fastened in place in accordance with either (D)(1) 
or (D)(2). 

(1) Framing Members. An enclosure shall be fastened to 
the framing members by mechanical means such as bolts, 
screws, or rivets, or by the use of clips or other securing 
means identified for use with the type of ceiling framing 
member(s) and enclosure(s) employed. The framing mem- 
bers shall be adequately supported and securely fastened to 
each other and to the building structure. 

(2) Support Wires. The installation shall comply with the 
provisions of 300.11(A). The enclosure shall be secured, 
using methods identified for the purpose, to ceiling support 
wire(s), including any additional support wire(s) installed 
for that purpose. Support wire(s) used for enclosure support 
shall be fastened at each end so as to be taut within the 
ceiling cavity. 

(E) Raceway Supported Enclosure, Without Devices, 
Luminaires (Fixtures), or Lampholders. An enclosure 
that does not contain a device(s) other than splicing devices 
or support a luminaire(s) [fixture(s)], lampholder, or other 
equipment and is supported by entering raceways shall not 
exceed 1650 cm^ (100 in.-^) in size. It shall have threaded 
entries or have hubs identified for the purpose. It shall be 
supported by two or more conduits threaded wrenchtight 
into the enclosure or hubs. Each conduit shall be secured 
within 900 mm (3 ft) of the enclosure, or within 450 mm 
(18 in.) of the enclosure if all conduit entries are on the 
same side. 

Exception: Rigid metal, intermediate metal, or rigid nonme- 
tallic conduit or electrical metallic tubing shall be permitted 
to support a conduit body of any size, including a conduit 
body constructed with only one conduit entry, provided the 
trade size of the conduit body is not larger than the largest 
trade size of the conduit or electrical metallic tubing. 

(F) Raceway Supported Enclosures, with Devices, Lu- 
minaires (Fixtures), or Lampholders. An enclosure that 
contains a device(s), other than splicing devices, or supports a 
luminaire(s) [fixture(s)], lampholder, or other equipment and 
is supported by entering raceways shall not exceed 1650 cm^ 
(100 in.^) in size. It shall have threaded entries or have hubs 
identified for the purpose. It shall be supported by two or more 
conduits threaded wrenchtight into the enclosure or hubs. 
Each conduit shall be secured within 450 mm (18 in.) of the 
enclosure. 

Exception No. 1: Rigid metal or intermediate metal con- 
duit shall be permitted to support a conduit body of any 



size, including a conduit body constructed with only one 
conduit entry, provided the trade size of the conduit body is 
not larger than the largest trade size of the conduit. 

Exception No. 2: An unbroken length(s) of rigid or interme- 
diate metal conduit shall be permitted to support a box used 
for luminaire (fixture) or lampholder support, or to support a 
wiring enclosure that is an integral part of a luminaire (fix- 
ture) and used in lieu of a box in accordance with 300.15(B), 
where all of the following conditions are met: 

(a) The conduit is securely fastened at a point so that 
the length of conduit beyond the last point of conduit sup- 
port does not exceed 900 mm (3 ft). 

(b) The unbroken conduit length before the last point 
of conduit support is 300 mm (12 in.) or greater, and that 
portion of the conduit is securely fastened at some point not 
less than 300 mm (12 in.) from its last point of support. 

(c) Where accessible to unqualified persons, the lumi- 
naire (fixture) or lampholder, measured to its lowest point, 
is at least 2.5 m (8 ft) above grade or standing area and at 
least 900 mm (3 ft) measured horizontally to the 2.5 m (8 ft) 
elevation from windows, doors, porches, fire escapes, or 
similar locations. 

(d) A luminaire (fixture) supported by a single conduit 
does not exceed 300 mm (12 in.) in any direction from the 
point of conduit entry. 

(e) The weight supported by any single conduit does 
not exceed 9 kg (20 lb). 

(f) At the luminaire (fixture) or lampholder end, the 
conduit(s) is threaded wrenchtight into the box, conduit 
body, or integral wiring enclosure, or into hubs identified 
for the purpose. Where a box or conduit body is used for 
support, the luminaire (fixture) shall be secured directly to 
the box or conduit body, or through a threaded conduit 
nipple not over 75 mm (3 in.) long. 

(G) Enclosures in Concrete or Masonry. An enclosure 
supported by embedment shall be identified as suitably pro- 
tected from corrosion and securely embedded in concrete or 
masonry. 

(H) Pendant Boxes. An enclosure supported by a pendant 
shall comply with 314.23(H)(1) or (H)(2). 

(1) Flexible Cord. A box shall be supported from a mul- 
ticonductor cord or cable in an approved manner that pro- 
tects the conductors against strain, such as a strain-relief 
connector threaded into a box with a hub. 

(2) Conduit. A box supporting lampholders or luminaires 
(fighting fixtures), or wiring enclosures within luminaires 
(fixtures) used in lieu of boxes in accordance with 
300.15(B), shall be supported by rigid or intermediate 
metal conduit stems. For stems longer than 450 mm 
(18 in.), the stems shall be connected to the wiring system 



2005 Edition 



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70-165 



314.24 ARTICLE 314 — OUTLET, DEVICE, PULL, AND JUNCTION BOXES; CONDUIT BODIES; FITTINGS; AND HANDHOLES 



with flexible fittings suitable for the location. At the lumi- 
naire (fixture) end, the conduit(s) shall be threaded 
wrenchtight into the box or wiring enclosure, or into hubs 
identified for the purpose. 

Where supported by only a single conduit, the threaded 
joints shall be prevented from loosening by the use of set- 
screws or other effective means, or the lumiiiaire (fixture), 
at any point, shall be at least 2.5 m (8 ft) above grade or 
standing area and at least 900 mm (3 ft) measured horizon- 
tally to the 2.5 m (8 ft) elevation from windows, doors, 
porches, fire escapes, or similar locations. A luminaire (fix- 
ture) supported by a single conduit shall not exceed 
300 mm (12 in.) in any horizontal direction from the point 
of conduit entry. 

314.24 Depth of Outlet Boxes. No box shall have an in- 
ternal depth of less than 12.7 mm (Vi in.). Boxes intended 
to enclose flush devices shall have an internal depth of not 
less than 23.8 mm (^Vie in.). 

314.25 Covers and Canopies. In completed installations, 
each box shall have a cover, faceplate, lampholder, or lu- 
minaire (fixture) canopy, except where the installation com- 
plies with 410.14(B). 

(A) Nonmetallic or Metal Covers and Plates. Nonmetal- 
lic or metal covers and plates shall be permitted. Where 
metal covers or plates are used, they shall comply with the 
grounding requirements of 250.110. 

FPN: For additional grounding requirements, see 410.18(A) 
for metal luminaire (fixture) canopies, and 404.12 and 
406.5(B) for metal faceplates. 

(B) Exposed Combustible Wall or Ceiling Finish. Where 
a luminaire (fixture) canopy or pan is used, any combus- 
tible wall or ceiling finish exposed between the edge of the 
canopy or pan and the outlet box shall be covered with 
noncombustible material. 

(C) Flexible Cord Pendants. Covers of outlet boxes and 
conduit bodies having holes through which flexible cord 
pendants pass shall be provided with bushings designed for 
the purpose or shall have smooth, well-rounded surfaces on 
which the cords may bear. So-called hard rubber or com- 
position bushings shall not be used. 

314.27 Outlet Boxes. 

(A) Boxes at Luminaire (Lighting Fixture) Outlets. 

Boxes used at luminaire (Ughting fixture) or lampholder out- 
lets shall be designed for the purpose. At every outiet used 
exclusively for lighting, the box shall be designed or installed 
so that a luminaire (fighting fixture) may be attached. 

Exception: A wall-mounted luminaire (fixture) weighing 
not more than 3 kg (6 lb) shall be permitted to be supported 



on other boxes, or plaster rings that are secured to other 
boxes, provided the luminaire (fixture) or its supporting 
yoke is secured to the box with no fewer than two No. 6 or 
larger screws. 

(B) Maximum Luminaire (Fixture) Weight. Outlet boxes 
or fittings installed as required by 314.23 shall be permitted 
to support luminaires (lighting fixtures) weighing 23 kg 
(50 lb) or less. A luminaire (lighting fixture) that weighs 
more than 23 kg (50 lb) shall be supported independently of 
the outlet box unless the outlet box is listed for the weight 
to be supported. 

(C) Floor Boxes. Boxes listed specifically for this applica- 
tion shall be used for receptacles located in the floor. 

Exception: Where the authority having jurisdiction judges 
them free from likely exposure to physical damage, mois- 
ture, and dirt, boxes located in elevated fioors of show 
windows and similar locations shall be permitted to be 
other than those listed for floor applications. Receptacles 
and covers shall be listed as an assembly for this type of 
location. 

(D) Boxes at Ceiling-Suspended (Paddle) Fan Outlets. 

Outlet boxes or outlet box systems used as the sole support of 
a ceiling-suspended (paddle) fan shaU be listed, shall be 
marked by their manufacturer as suitable for this purpose, and 
shall not support ceiling-suspended (paddle) fans that weigh 
more than 32 kg (70 lb). For outlet boxes or outlet box sys- 
tems designed to support ceiling-suspended (paddle) fans that 
weigh more than 16 kg (35 lb), the required marking shall 
include the maximum weight to be supported. 

314.28 Pull and Junction Boxes and Conduit Bodies. 

Boxes and conduit bodies used as pull or junction boxes 
shall comply with 314.28(A) through (D). 

Exception: Terminal housings supplied with motors shall 
comply with the provisions of 430.12. 

(A) Minimum Size. For raceways containing conductors 
of 4 AWG or larger, and for cables containing conductors of 
4 AWG or larger, the minimum dimensions of pull or junc- 
tion boxes installed in a raceway or cable run shall comply 
with (A)(1) through (A)(3). Where an enclosure dimension 
is to be calculated based on the diameter of entering race- 
ways, the diameter shall be the metric designator (trade 
size) expressed in the units of measurement employed. 

(1) Straight Pulls. In straight pulls, the length of the box 
shall not be less than eight times the metric designator 
(trade size) of the largest raceway. 

(2) Angle or U Pulls. Where splices or where angle or U 
pulls are made, the distance between each raceway entry 
inside the box and the opposite wall of the box shall not be 
less than six times the metric designator (trade size) of the 



70-166 



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ARTICLE 314 — OUTLET, DEVICE, PULL, AND JUNCTION BOXES; CONDUIT BODIES; FITTINGS; AND HANDHOLES 314.40 



• 



largest raceway in a row. This distance shall be increased 
for additional entries by the amount of the sum of the di- 
ameters of all other raceway entries in the same row on the 
same wall of the box. Each row shall be calculated indi- 
vidually, and the single row that provides the maximum 
distance shall be used. 

Exception: Where a raceway or cable entry is in the wall 
of a box or conduit body opposite a removable cover, the 
distance from that wall to the cover shall be permitted to 
comply with the distance required for one wire per terminal 
in Table 312.6(A). 

The distance between raceway entries enclosing the 
same conductor shall not be less than six times the metric 
designator (trade size) of the larger raceway. 

When transposing cable size into raceway size in 
314.28(A)(1) and (A)(2), the minimum metric designator 
(trade size) raceway required for the number and size of 
conductors in the cable shall be used. 

(3) Smaller Dimensions. Boxes or conduit bodies of di- 
mensions less than those required in 314.28(A)(1) and 
(A)(2) shall be permitted for installations of combinations 
of conductors that are less than the maximum conduit or 
tubing fill (of conduits or tubing being used) permitted by 
Table 1 of Chapter 9, provided the box or conduit body has 
been listed for, and is permanently marked with, the maxi- 
mum number and maximum size of conductors permitted. 

(B) Conductors in Pull or Junction Boxes. In pull boxes 
or junction boxes having any dimension over 1.8 m (6 ft), 
all conductors shall be cabled or racked up in an approved 
manner. 

(C) Covers. All pull boxes, junction boxes, and conduit bod- 
ies shall be provided with covers compatible with the box or 
conduit body construction and suitable for the conditions of 
use. Where used, metal covers shall comply with the ground- 
ing requirements of 250.110. An extension from the cover of 
an exposed box shall comply with 314.22, Exception. 

(D) Permanent Barriers. Where permanent barriers are 
installed in a box, each section shall be considered as a 
separate box. 

314.29 Boxes, Conduit Bodies, and Handhole Enclo- 
sures to Be Accessible. Boxes, conduit bodies, and hand- 
hole enclosures shall be installed so that the wiring con- 
tained in them can be rendered accessible without removing 
any part of the building or, in underground circuits, without 
excavating sidewalks, paving, earth, or other substance that 
is to be used to establish the finished grade. 

Exception: Listed boxes and handhole enclosures shall be 
permitted where covered by gravel, light aggregate, or non- 
cohesive granulated soil if their location is effectively iden- 
tified and accessible for excavation. 



314.30 Handhole Enclosures. Handhole enclosures shall 
be designed and installed to withstand all loads likely to be 
imposed. 

FPN: See ANSI/SCTE 77-2002, Specification for Under- 
ground Enclosure Integrity, for additional information on 
deliberate and nondeliberate traffic loading that can be ex- 
pected to bear on underground enclosures. 

(A) Size. Handhole enclosures shall be sized in accordance 
with 314.28(A) for conductors operating at 600 volts or 
below, and in accordance with 314.71 for conductors oper- 
ating at over 600 volts. For handhole enclosures without 
bottoms where the provisions of 314.28(A)(2), Exception, 
or 314.71(B)(1), Exception No. 1, apply, the measurement 
to the removable cover shall be taken from the end of the 
conduit or cable assembly. 

(B) Wiring Entries. Underground raceways and cable as- 
semblies entering a handhole enclosure shall extend into, 
the enclosure, but they shall not be required to be mechani- 
cally connected to the enclosure. 

(C) Handhole Enclosures Without Bottoms. Where 
handhole enclosures without bottoms are installed, all en- 
closed conductors and any splices or terminations, if 
present, shall be listed as suitable for wet locations. 

(D) Covers. Handhole enclosure covers shall have an identi- 
fying mark or logo that prominently identifies the function of 
the enclosure, such as "electric." Handhole enclosure covers 
shall require the use of tools to open, or they shall weigh over 
45 kg (100 lb). Metal covers and other exposed conductive 
surfaces shall be bonded in accordance with 250.96(A). 

HI. Construction Specifications 

314.40 Metal Boxes, Conduit Bodies, and Fittings. 

(A) Corrosion Resistant. Metal boxes, conduit bodies, 
and fittings shall be corrosion resistant or shall be well- 
galvanized, enameled, or otherwise properly coated inside 
and out to prevent corrosion. 

FPN: See 300.6 for limitation in the use of boxes and 
fiuings protected from corrosion solely by enamel. 

(B) Thickness of Metal. Sheet steel boxes not over 
1650 cm^ (100 in.-^) in size shall be made from steel not 
less than 1.59 nam (0.0625 in.) thick. The wall of a mal- 
leable iron box or conduit body and a die-cast or 
permanent-mold cast aluminum, brass, bronze, or zinc box 
or conduit body shall not be less than 2.38 mm (%2 in.) 
thick. Other cast metal boxes or conduit bodies shall have a 
wall thickness not less than 3.17 mm (Vs in.). 

Exception No. 1: Listed boxes and conduit bodies shown 
to have equivalent strength and characteristics shall be 
permitted to be made of thinner or other metals. 



2005 Edition 



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70-167 



314.41 ARTICLE 314 — OUTLET, DEVICE, PULL, AND JUNCTION BOXES; CONDUIT BODIES; FITTINGS; AND HANDHOLES 



Exception No. 2: The walls of listed short radius conduit 
bodies, as covered in 314.5, shall be permitted to be made 
of thinner metal. 

(C) Metal Boxes Over 1650 cm^ (100 in.^). Metal boxes 
over 1650 cm"^ (100 in.^) in size shall be constructed so as 
to be of ample strength and rigidity. If of sheet steel, the 
metal thickness shall not be less than 1.35 mm (0.053 in.) 
uncoated. 

(D) Grounding Provisions. A means shall be provided in 
each metal box for the connection of an equipment ground- 
ing conductor. The means shall be permitted to be a tapped 
hole or equivalent. 

314.41 Covers. Metal covers shall be of the same material 
as the box or conduit body with which they are used, or 
they shall be lined with firmly attached insulating material 
that is not less than 0.79 mm ('/sa in.) thick, or they shall be 
listed for the purpose. Metal covers shall be the same thick- 
ness as the boxes or conduit body for which they are used, 
or they shall be listed for the purpose. Covers of porcelain 
or other approved insulating materials shall be permitted if 
of such form and thickness as to afford the required protec- 
tion and strength. 

314.42 Bushings. Covers of outlet boxes and conduit bod- 
ies having holes through which flexible cord pendants may 
pass shall be provided with approved bushings or shall 
have smooth, well-rounded surfaces on which the cord may 
bear. Where individual conductors pass through a metal 
cover, a separate hole equipped with a bushing of suitable 
insulating material shall be provided for each conductor. 
Such separate holes shall be connected by a slot as required 
by 300.20. 

314.43 Nonmetallic Boxes. Provisions for supports or 
other mounting means for nonmetaUic boxes shall be out- 
side of the box, or the box shall be constructed so as to 
prevent contact between the conductors in the box and the 
supporting screws. 

314.44 Marking. All boxes and conduit bodies, covers, 
extension rings, plaster rings, and the like shall be durably 
and legibly marked with the manufacturer's name or 
trademark. 



IV. Pull and Junction Boxes for Use on Systems Over 
600 Volts, Nominal 

314.70 General. Where pull and junction boxes are used 
on systems over 600 volts, the installation shall comply 
with the provisions of Part IV and also with the following 
general provisions of this article: 
(1) Part I, 314.2, 314.3, and 314.4 



(2) Part II, 314.15; 314.17; 314.20; 314.23(A), (B), or (G); 
314.28(B); and 314.29 

(3) Part III, 314.40(A) and (C) and 314.41 

314.71 Size of Pull and Junction Boxes. Pull and junction 
boxes shall provide adequate space and dimensions for the 
installation of conductors, and they shall comply with the 
specific requirements of this section. 

Exception: Terminal housings supplied with motors shall 
comply with the provisions of 430.12. 

(A) For Straight Pulls. The length of the box shall not be 
less than 48 times the outside diameter, over sheath, of the 
largest shielded or lead-covered conductor or cable entering 
the box. The length shall not be less than 32 times the 
outside diameter of the largest nonshielded conductor or 
cable. 

(B) For Angle or U Pulls. 

(1) Distance to Opposite Wall. The distance between each 
cable or conductor entry inside the box and the opposite 
wall of the box shall not be less than 36 times the outside 
diameter, over sheath, of the largest cable or conductor. 
This distance shall be increased for additional entries by the 
amount of the sum of the outside diameters, over sheath, of 
all other cables or conductor entries through the same wall 
of the box. 

Exception No. 1: Where a conductor or cable entry is in 
the wall of a box opposite a removable cover, the distance 
from that wall to the cover shall be permitted to be not less 
than the bending radius for the conductors as provided in 
300.34. 

Exception No. 2: Where cables are nonshielded and not 
lead covered, the distance of 36 times the outside diameter 
shall be permitted to be reduced to 24 times the outside 
diameter 

(2) Distance Between Entry and Exit. The distance be- 
tween a cable or conductor entry and its exit from the box 
shall not be less than 36 times the outside diameter, over 
sheath, of that cable or conductor. 

Exception: Where cables are nonshielded and not lead 
covered, the distance of 36 times the outside diameter shall 
be permitted to be reduced to 24 times the outside diameter 

(C) Removable Sides. One or more sides of any pull box 
shall be removable. 

314.72 Construction and Installation Requirements. 

(A) Corrosion Protection. Boxes shall be made of mate- 
rial inherently resistant to corrosion or shall be suitably 
protected, both internally and externally, by enameling, gal- 
vanizing, plating, or other means. 



• 



70-168 



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ARTICLE 320 — ARMORED CABLE: TYPE AC 



320.30 



(B) Passing Through Partitions. Suitable bushings, shields, 
or fittings having smooth, rounded edges shall be provided 
where conductors or cables pass through partitions and at 
other locations where necessary. 

(C) Complete Enclosure. Boxes shall provide a complete 
enclosure for the contained conductors or cables. 

(D) Wiring Is Accessible. Boxes shall be installed so that 
the wiring is accessible without removing any part of the 
building. Working space shall be provided in accordance 
with 110.34. 

(E) Suitable Covers. Boxes shall be closed by suitable 
covers securely fastened in place. Underground box covers 
that weigh over 45 kg (100 lb) shall be considered meeting 
this requirement. Covers for boxes shall be permanently 
marked "DANGER — HIGH VOLTAGE — KEEP OUT." 
The marking shall be on the outside of the box cover and 
shall be readily visible. Letters shall be block type and at 
least 13 mm (Vi in.) in height. 

(F) Suitable for Expected Handling. Boxes and their 
covers shall be capable of withstanding the handling to 
which they are likely to be subjected. 



ARTICLE 320 
Armored Cable: Type AC 



I. General 

320.1 Scope. This article covers the use, installation, and 
construction specifications for armored cable. Type AC. 

320.2 Definition. 

Armored Cable, Type AC. A fabricated assembly of insu- 
lated conductors in a flexible metallic enclosure. See 320.100. 



II. Installation 

320.10 Uses Permitted. Type AC cable shall be permitted 
as follows: 

(1) In both exposed and concealed work 

(2) In cable trays 

(3) In dry locations 

(4) Embedded in plaster finish on brick or other masonry, 
except in damp or wet locations 

(5) To be run or fished in the air voids of masonry block or 
tile walls where such walls are not exposed or subject 
to excessive moisture or dampness 

FPN: The "Uses Permitted" is not an all-inclusive list. 



320.12 Uses Not Permitted. Type AC cable shall not be 
used as follows: 

(1) Where subject to physical damage 

(2) In damp or wet locations 

(3) In air voids of masonry block or tile walls where such 
walls are exposed or subject to excessive moisture or 
dampness 

(4) Where exposed to corrosive fumes or vapors 

(5) Embedded in plaster finish on brick or other masonry 
in damp or wet locations 

320.15 Exposed Work. Exposed runs of cable, except as 
provided in 300.11(A), shall closely follow the surface of 
the building finish or of running boards. Exposed runs shall 
also be permitted to be installed on the underside of joists 
where supported at each joist and located so as not to be 
subject to physical damage. 

320.17 Through or Parallel to Framing Members. 

Type AC cable shall be protected in accordance with 
300.4(A), (C), and (D) where installed through or parallel 
to framing members. 

320.23 In Accessible Attics. Type AC cables in accessible 
attics or roof spaces shall be installed as specified in 
320.23(A) and (B). 

(A) Where Run Across the Top of Floor Joists. Where 
run across the top of floor joists, or within 2.1 m (7 ft) of 
floor or floor joists across the face of rafters or studding, in 
attics and roof spaces that are accessible, the cable shall be 
protected by substantial guard strips that are at least as high 
as the cable. Where this space is not accessible by perma- 
nent stairs or ladders, protection shall only be required 
within 1.8 m (6 ft) of the nearest edge of the scuttle hole or 
attic entrance. 

(B) Cable Installed Parallel to Framing Members. Where 
the cable is installed parallel to the sides of rafters, studs, or 
floor joists, neither guard strips nor running boards shall be 
required, and the installation shall also comply with 
300.4(D). 

320.24 Bending Radius. Bends in Type AC cable shall be 
made such that the cable is not damaged. The radius of the 
curve of the inner edge of any bend shall not be less than 
five times the diameter of the Type AC cable. 

320.30 Securing and Supporting. 

(A) General. Type AC cable shall be supported and se- 
cured by staples, cable ties, straps, hangers, or similar fit- 
tings, designed and installed so as not to damage the cable. 



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70-169 



320.40 



ARTICLE 322 — FLAT CABLE ASSEMBLIES: TYPE PC 



(B) Securing. Unless otherwise provided, Type AC cable 
shall be secured within 300 mm (12 in.) of every outlet 
box, junction box, cabinet, or fitting and at intervals not 
exceeding 1.4 m (4 '72 ft) where installed on or across fram- 
ing members. 

(C) Supporting. Unless otherwise provided. Type AC cable 
shall be supported at intervals not exceeding 1.4 m (41/2 ft). 

Horizontal runs of Type AC cable installed in wooden 
or metal framing members or similar supporting means 
shall be considered supported where such support does not 
exceed 1.4-m (4V2-ft) intervals. 

(D) Unsupported Cables. Type AC cable shall be permit- 
ted to be unsupported where the cable complies with any of 
the following: 

(1) Is fished between access points through concealed 
spaces in finished buildings or structures and support- 
ing is impracticable 

(2) Is not more than 600 mm (2 ft) in length at terminals 
where flexibility is necessary 

(3) Is not more than 1.8 m (6 ft) in length from the last 
point of cable support to the point of connection to a 
luminaire(s) [lighting fixture(s)] or other electrical 
equipment and the cable and point of connection are 
within an accessible ceiling. For the purposes of this 
section. Type AC cable fittings shall be permitted as a 
means of cable support. 

320.40 Boxes and Fittings. At all points where the armor 
of AC cable terminates, a fitting shall be provided to protect 
wires from abrasion, unless the design of the outlet boxes 
or fittings is such as to afford equivalent protection, and, in 
addition, an insulating bushing or its equivalent protection 
shall be provided between the conductors and the armor. 
The connector or clamp by which the Type AC cable is 
fastened to boxes or cabinets shall be of such design that 
the insulating bushing or its equivalent will be visible for 
inspection. Where change is made from Type AC cable to 
other cable or raceway wiring methods, a box, fitting, or 
conduit body shall be installed at junction points as re- 
quired in 300.15. 

320.80 Ampacity. The ampacity shall be determined by 
310.15. 

(A) Thermal Insulation. Armored cable installed in ther- 
mal insulation shall have conductors rated at 90°C (194°F). 
The ampacity of cable installed in these apphcations shall 
be that of 60°C (140°F) conductors. The 90°C (194°F) rat- 
ing shall be permitted to be used for ampacity derating 
purposes, provided the final derated ampacity does not ex- 
ceed that for a 60°C (140°F) rated conductor. 

(B) Cable Tray. The ampacity of Type AC cable installed in 
cable tray shall be determined in accordance with 392.11. 



III. Construction Specifications 

320.100 Construction. Type AC cable shall have an armor 
of flexible metal tape and shall have an internal bonding 
strip of copper or aluminum in intimate contact with the 
armor for its entire length. 

320.104 Conductors. Insulated conductors shall be of a 
type listed in Table 310.13 or those identified for use in this 
cable. In addition, the conductors shall have an overall 
moisture-resistant and fire-retardant fibrous covering. For 
Type ACT, a moisture-resistant fibrous covering shall be 
required only on the individual conductors. 

320.108 Equipment Grounding. Type AC cable shall pro- 
vide an adequate path for equipment grounding as required 
by 250.4(A)(5) or 250.4(B)(4). 

320.120 Marking. The cable shall be marked in accor- 
dance with 310.11, except that Type AC shall have ready 
identification of the manufacturer by distinctive external 
markings on the cable sheath throughout its entire length. 



H Flat Cable Assembliei^: T)l^ 

I. General 

322.1 Scope. This article covers the use, installation, and 
construction specifications for flat cable assemblies, Type FC. 

322.2 Definition. 

Flat Cable Assembly, Type FC. An assembly of parallel 
conductors formed integrally with an insulating material 
web specifically designed for field installation in surface 
metal raceway. 

II. Installation 

322.10 Uses Permitted. Flat cable assemblies shall be per- 
mitted only as foUows: 

(1) As branch circuits to supply suitable tap devices for light- 
ing, small appUances, or small power loads. The rating of 
the branch circuit shall not exceed 30 amperes. 

(2) Where installed for exposed work. 

(3) In locations where they will not be subjected to physical 
damage. Where a flat cable assembly is installed less than 
2.5 m (8 ft) above the floor or fixed working platform, it 
shall be protected by a cover identified for the use. 



• 



70-170 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 324 — FLAT CONDUCTOR CABLE: TYPE FCC 



324.2 



• 



(4) In surface metal raceways identified for the use. The 
channel portion of the surface metal raceway systems 
shall be installed as complete systems before the flat 
cable assembhes are pulled into the raceways. 

322.12 Uses Not Permitted. Flat cable assemblies shall 
not be used as follows: 

(1) Where subject to corrosive vapors unless suitable for 
the application 

(2) In hoistways or on elevators or escalators 

(3) In any hazardous (classified) location 

(4) Outdoors or in wet or damp locations unless identified 
for the use 

322.30 Securing and Supporting. The flat cable assem- 
blies shall be supported by means of their special design 
features, within the surface metal raceways. 

The surface metal raceways shall be supported as re- 
quired for the specific raceway to be installed. 

322.40 Boxes and Fittings. 

(A) Dead Ends. Each flat cable assembly dead end shall 
be terminated in an end-cap device identified for the use. 

The dead-end fitting for the enclosing surface metal 
raceway shall be identified for the use. 

(B) Luminaire (Fixture) Hangers. Luminaire (fixture) 
hangers installed with the flat cable assemblies shall be 
identified for the use. 

(C) Fittings. Fittings to be installed with flat cable assem- 
blies shall be designed and installed to prevent physical 
damage to the cable assemblies. 

(D) Extensions. All extensions from flat cable assemblies 
shall be made by approved wiring methods, within the 
junction boxes, installed at either end of the flat cable as- 
sembly runs. 

322.56 Splices and Taps. 

(A) Splices. Splices shall be made in listed junction boxes. 

(B) Taps. Taps shall be made between any phase conduc- 
tor and the grounded conductor or any other phase conduc- 
tor by means of devices and fittings identified for the use. 
Tap devices shall be rated at not less than 15 amperes, or 
more than 300 volts to ground, and shall be color-coded in 
accordance with the requirements of 322.120(C). 

III. Construction 

322.100 Construction. Flat cable assemblies shall consist 
of two, three, four, or five conductors. 



322.104 Conductors. Flat cable assemblies shall have 
conductors of 10 AWG special stranded copper wires. 

322.112 Insulation. The entire flat cable assembly shall be 
formed to provide a suitable insulation covering all the 
conductors and using one of the materials recognized in 
Table 310.13 for general branch-circuit wiring. 

322.120 Marking. 

(A) Temperature Rating. In addition to the provisions of 
310.11, Type FC cable shah have the temperature rating 
durably marked on the surface at intervals not exceeding 
600 mm (24 in.). 

(B) Identification of Grounded Conductor. The grounded 
conductor shall be identified throughout its length by means 
of a distinctive and durable white or gray marking. 

FPN: The color gray may have been used in the past as an 
ungrounded conductor. Care should be taken when working 
on existing systems. 

(C) Terminal Block Identification. Terminal blocks iden- 
tified for the use shall have distinctive and durable mark- 
ings for color or word coding. The grounded conductor 
section shall have a white marking or other suitable desig- 
nation. The next adjacent section of the terminal block shall 
have a black marking or other suitable designation. The 
next section shall have a red marking or other suitable 
designation. The final or outer section, opposite the 
grounded conductor section of the terminal block, shall 
have a blue marking or other suitable designation. 



ARTICLE 324 
Flat Conductor Cable: Type FCC 

I. General 

324.1 Scope. This article covers a field-installed wiring sys- 
tem for branch circuits incorporating Type FCC cable and 
associated accessories as defined by the article. The wiring 
system is designed for installation under carpet squares. 

324.2 Definitions. 

Bottom Shield. A protective layer that is installed between 
the floor and Type FCC flat conductor cable to protect the 
cable from physical damage and may or may not be incor- 
porated as an integral part of the cable. 

Cable Connector. A connector designed to join Type FCC 
cables without using a junction box. 



2005 Edition 



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70-] 71 



324.6 



ARTICLE 324 — FLAT CONDUCTOR CABLE: TYPE FCC 



FCC System. A complete wiring system for branch circuits 
that is designed for installation under carpet squares. The FCC 
system includes Type FCC cable and associated shielding, 
connectors, terminators, adapters, boxes, and receptacles. 

Insulating End. An insulator designed to electrically insu- 
late the end of a Type FCC cable. 

Metal Shield Connections. Means of connection designed to 
electrically and mechanically connect a metal shield to another 
metal shield, to a receptacle housing or self-contained device, 
or to a transition assembly. 

Top Shield. A grounded metal shield covering under-carpet 
components of the FCC system for the purposes of provid- 
ing protection against physical damage. 

Transition Assembly. An assembly to facilitate connection 
of the FCC system to other wiring systems, incorporating 
(1) a means of electrical interconnection and (2) a suitable 
box or covering for providing electrical safety and protec- 
tion against physical damage. 

Type FCC Cable. Three or more flat copper conductors 
placed edge-to-edge and separated and enclosed within an 
insulating assembly. 

324.6 Listing Requirements. Type FCC cable and associ- 
ated fittings shall be listed. 

II. Installation 
324.10 Uses Permitted. 

(A) Branch Circuits. Use of FCC systems shall be permit- 
ted both for general-purpose and appliance branch circuits 
and for individual branch circuits. 

(B) Branch-Circuit Ratings. 

(1) Voltage. Voltage between ungrounded conductors shall 
not exceed 300 volts. Voltage between ungrounded conduc- 
tors and the grounded conductor shall not exceed 150 volts. 

(2) Current. General-purpose and apphance branch circuits 
shall have ratings not exceeding 20 amperes. Individual 
branch circuits shall have ratings not exceeding 30 amperes. 

(C) Floors. Use of FCC systems shall be permitted on hard, 
sound, smooth, continuous floor surfaces made of concrete, 
ceramic, or composition flooring, wood, and similar materials. 

(D) Walls. Use of FCC systems shall be permitted on wall 
surfaces in surface metal raceways. 

(E) Damp Locations. Use of FCC systems in damp loca- 
tions shall be permitted. 



(F) Heated Floors. Materials used for floors heated in ex- 
cess of 30°C (86°F) shall be identified as suitable for use at 
these temperatures. 

(G) System Height. Any portion of an FCC system with a 
height above floor level exceeding 2.3 mm (0.090 in.) shall 
be tapered or feathered at the edges to floor level. 

(H) Coverings. Floor-mounted Type FCC cable, cable con- 
nectors, and insulating ends shall be covered with carpet 
squares not larger than 914 mm (36 in.) square. Carpet squares 
that are adhered to the floor shall be attached with release-type 
adhesives. 

(I) Corrosion Resistance. Metal components of the system 
shall be either corrosion resistant, coated with corrosion- 
resistant materials, or insulated from contact with corrosive 
substances. 

(J) Metal-Shield Connectors. Metal shields shall be con- 
nected to each other and to boxes, receptacle housings, 
self-contained devices, and transition assembhes using 
metal-shield connectors. 

324.12 Uses Not Permitted. FCC systems shall not be 
used in the foUowing locations: 

(1) Outdoors or in wet locations 

(2) Where subject to corrosive vapors 

(3) In any hazardous (classified) location 

(4) In residential, school, and hospital buildings 

324.18 Crossings. Crossings of more than two Type FCC 
cable runs shall not be permitted at any one point. Cross- 
ings of a Type FCC cable over or under a flat communica- 
tions or signal cable shafl be permitted. In each case, a 
grounded layer of metal shielding shall separate the two 
cables, and crossings of more than two flat cables shall not 
be permitted at any one point. 

324.30 Securing and Supporting. All FCC system com- 
ponents shall be firmly anchored to the floor or wall using 
an adhesive or mechanical anchoring system identified for 
this use. Floors shall be prepared to ensure adherence of the 
FCC system to the floor until the carpet squares are placed. 

324.40 Boxes and Fittings. 

(A) Cable Connections and Insulating Ends. Ah Type 
FCC cable connections shall use connectors identified for their 
use, installed such that electrical continuity, insulation, and 
sealing against dampness and liquid spillage are provided. AH 
bare cable ends shall be insulated and sealed against dampness 
and liquid spillage using listed insulating ends. 

(B) Polarization of Connections. All receptacles and con- 
nections shall be constructed and installed so as to maintain 
proper polarization of the system. 



70-172 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 324 — FLAT CONDUCTOR CABLE: TYPE FCC 



324.120 



• 



(C) Shields. 

(1) Top Shield. A metal top shield shall be installed over 
all floor-mounted Type FCC cable, connectors, and insulat- 
ing ends. The top shield shall completely cover all cable 
runs, comers, connectors, and ends. 

(2) Bottom Shield. A bottom shield shall be installed be- 
neath all Type FCC cable, connectors, and insulating ends. 

(D) Connection to Other Systems. Power feed, grounding 
connection, and shield system connection between the FCC 
system and other wiring systems shall be accomplished in a 
transition assembly identified for this use. 

(E) Metal-Shield Connectors. Metal shields shall be con- 
nected to each other and to boxes, receptacle housings, 
self-contained devices, and transition assemblies using 
metal-shield connectors. 

324.41 Floor Coverings. Floor-mounted Type FCC cable, 
cable connectors, and insulating ends shall be covered with 
carpet squares not larger than 914 mm (36 in.) square. 
Carpet squares that are adhered to the floor shall be at- 
tached with release-type adhesives. 

324.42 Devices. 

(A) Receptacles. All receptacles, receptacle housings, and 
self-contained devices used with the FCC system shall be 
identified for this use and shall be connected to the Type FCC 
cable and metal shields. Connection from any grounding con- 
ductor of the Type FCC cable shall be made to the shield 
system at each receptacle. 

(B) Receptacles and Housings. Receptacle housings and 
self-contained devices designed either for floor mounting or 
for in-wall or on-wall mounting shall be permitted for use 
with the FCC system. Receptacle housings and self- 
contained devices shall incorporate means for facilitating 
entry and termination of Type FCC cable and for electri- 
cally connecting the housing or device with the metal 
shield. Receptacles and self-contained devices shall comply 
with 406.3. Power and communications outlets installed 
together in common housing shall be permitted in accor- 
dance with 800.133(A)(1)(c), Exception No. 2. 

324.56 Splices and Taps. 

(A) FCC Systems Alterations. Alterations to FCC sys- 
tems shall be permitted. New cable connectors shall be 
used at new connection points to make alterations. It shall 
be permitted to leave unused cable runs and associated 
cable connectors in place and energized. All cable ends 
shall be covered with insulating ends. 



(B) Transition Assemblies. All transition assembhes shall 
be identified for their use. Each assembly shall incorporate 
means for facilitating entry of the Type FCC cable into the 
assembly, for connecting the Type FCC cable to grounded 
conductors, and for electricaUy connecting the assembly to the 
metal cable shields and to equipment grounding conductors. 

324.60 Grounding. All metal shields, boxes, receptacle 
housings, and self-contained devices shall be electricaUy 
continuous to the equipment grounding conductor of the 
supplying branch circuit. All such electrical connections 
shall be made with connectors identified for this use. The 
electrical resistivity of such shield system shall not be more 
than that of one conductor of the Type FCC cable used in 
the installation. 

III. Construction 

324.100 Construction. 

(A) Type FCC Cable. Type FCC cable shall be listed for 
use with the FCC system and shall consist of three, four, or 
five flat copper conductors, one of which shall be an equip- 
ment grounding conductor. 

(B) Shields. 

(1) Materials and Dimensions. All top and bottom shields 
shall be of designs and materials identified for their use. 
Top shields shall be metal. Both metallic and nonmetaI%c 
materials shall be permitted for bottom shields. 

(2) Resistivity. Metal shields shall have cross-sectional areas 
that provide for electrical resistivity of not more than that of 
one conductor of the Type FCC cable used in the installation. 

324.101 Corrosion Resistance. Metal components of the 
system shall be either corrosion resistant, coated with 
corrosion-resistant materials, or insulated from contact with 
corrosive substances. 

324.112 Insulation. The insulating material of the cable 
shall be moisture resistant and flame retardant. All insulating 
materials in the FCC systems shaU be identified for their use. 

324.120 Markings. 

(A) Cable Marking. Type FCC cable shall be clearly and 
durably marked on both sides at intervals of not more than 
610 mm (24 in.) with the information required by 
310.11(A) and with the following additional information: 

(1) Material of conductors 

(2) Maximum temperature rating 

(3) Ampacity 

(B) Conductor Identification. Conductors shall be clearly 
and durably identified on both sides throughout their length 
as specified in 310.12. 



2005 Edition 



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70-173 



326.1 



ARTICLE 326 — INTEGRATED GAS SPACER CABLE: TYPE iGS 



integrated (Sai^Sp^c^rfc 



I. General 

326.1 Scope. This article covers the use, installation, and 
construction specifications for integrated gas spacer cable, 
Type IGS. 

326.2 Definition. 

Integrated Gas Spacer Cable, Type IGS. A factory assem- 
bly of one or more conductors, each individually insulated and 
enclosed in a loose fit, nonmetallic flexible conduit as an in- 
tegrated gas spacer cable rated through 600 volts. 



326.80 Ampacity. The ampacity of Type IGS cable shall 
not exceed the values shown in Table 326.80. 



Table 326.80 Ampacity of Type 


IGS Cable 




Size (kcmil) 


Amperes 


Size (kcmil) 


Amperes 


250 


119 


2500 


376 


500 


168 


3000 


412 


750 


206 


3250 


429 


1000 


238 


3500 


445 


1250 


266 


3750 


461 


1500 


292 


4000 


476 


1750 


344 


4250 


491 


2000 


336 


4500 


505 


2250 


357 


4750 


519 



• 



II. Installation 

326.10 Uses Permitted. Type IGS cable shall be permitted 
for use under ground, including direct burial in the earth, as 
the following: 

(1) Service-entrance conductors 

(2) Feeder or branch-circuit conductors 

326.12 Uses Not Permitted. Type IGS cable shall not be 
used as interior wiring or be exposed in contact with buildings. 

326.24 Bending Radius. Where the coilable nonmetallic 
conduit and cable is bent for installation purposes or is 
flexed or bent during shipment or installation, the radii of 
bends measured to the inside of the bend shall not be less 
than specified in Table 326.24. 

Table 326.24 Minimum Radii of Bends 



Conduit Size 



Minimum Radii 



Metric Designator Trade Size 



53 

78 

103 



600 

900 

1150 



24 
35 
45 



326.26 Bends. A run of Type IGS cable between pull boxes 
or terminations shall not contain more than the equivalent of 
four quarter bends (360 degrees total), including those bends 
located immediately at the pull box or terminations. 

326.40 Fittings. Terminations and splices for Type IGS 
cable shall be identified as a type that is suitable for main- 
taining the gas pressure within the conduit. A valve and cap 
shall be provided for each length of the cable and conduit 
to check the gas pressure or to inject gas into the conduit. 



III. Construction Specifications 

326.104 Conductors. The conductors shall be solid alu- 
minum rods, laid parallel, consisting of one to nineteen 
12.7 mm (Vi in.) diameter rods. The minimum conductor 
size shall be 250 kcmil, and the maximum size shall be 
4750 kcmil. 

326.112 Insulation. The insulation shall be dry kraft pa- 
per tapes and a pressurized sulfur hexafluoride gas (SFg), 
both approved for electrical use. The nominal gas pres- 
sure shall be 138 kPa gauge (20 pounds per square inch 
gauge). The thickness of the paper spacer shall be as 
specified in Table 326.112. 

Table 326.112 Paper Spacer Thickness 



Thickness 


Size (kcmil) 


mm 


in. 


250-1000 
1250-4750 


1.02 
1.52 


0.040 
0.060 



326.116 Conduit. The conduit shall be a medium density 
polyethylene identified as suitable for use with natural gas 
rated pipe in metric designator 53, 78, or 103 (trade size 2, 
3, or 4). The percent fill dimensions for the conduit are 
shown in Table 326.116. 

The size of the conduit permitted for each conductor 
size shall be calculated for a percent fill not to exceed those 
found in Table 1, Chapter 9. 

326.120 Marking. The cable shall be marked in accor- 
dance with 310.11(A), 310.11(B)(1), and 310.11(D). 



70-174 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 330 — METAL-CLAD CABLE: TYPE MC 



330.10 



Table 326.116 Conduit Dimensions 



Conduit Size 



Metric Trade 

Designator Size 



Actual Outside 
Diameter 



m. 



Actual Inside 
Diameter 



53 


2 


60 


2.375 


49.46 


1.947 


78 


3 


89 


3.500 


73.30 


2.886 


103 


4 


114 


4.500 


94.23 


3.710 



ARTICLE 328 
5 Medium Voltage Cable: Type MV J 

I. General 

328.1 Scope. This article covers the use, installation, and 
construction specifications for medium voltage cable. 
Type MV. 

328.2 Definition. 

Medium Voltage Cable, Type MV. A single or multicon- 
ductor solid dielectric insulated cable rated 2001 volts or 
higher. 

II. Installation 

328.10 Uses Permitted. Type MV cable shall be permitted 
for use on power systems rated up to 35,000 volts nominal 
as follows: 

(1) In wet or dry locations 

(2) In raceways 

(3) In cable trays as specified in 392.3(B)(2) 

(4) Direct buried in accordance with 300.50 

(5) In messenger-supported wiring 

FPN: The "Uses Permitted" is not an all-inclusive list. 

328.12 Uses Not Permitted. Unless identified for the use. 
Type MV cable shall not be used as follows: 

(1) Where exposed to direct sunlight 

(2) In cable trays, unless specified in 392.3(B)(2) 

(3) Direct buried, unless in accordance with 300.50 

328.80 Ampacity. The ampacity of Type MV cable shall 
be determined in accordance with 310.60. The ampacity of 
Type MV cable installed in cable tray shall be determined 
in accordance with 392.13. 



III. Construction Specifications 

328.100 Construction. Type MV cables shaU have copper, 
aluminum, or copper-clad aluminum conductors and shall 
comply with Table 310.61 and Table 310.63 or Table 310.64. 

328.120 Marking. Medium voltage cable shall be marked 
as required by 310.11. 



ARTICLE 330 
Metal-Clad Cable: Type MC 

I. General 

330.1 Scope. This article covers the use, installation, and 
construction specifications of metal-clad cable. Type MC. 

330.2 Definition. 

Metal Clad Cable, Type MC. A factory assembly of one 
or more insulated circuit conductors with or without optical 
fiber members enclosed in an armor of interlocking metal 
tape, or a smooth or corrugated metallic sheath. 

II. Installation 

330.10 Uses Permitted. 

(A) General Uses. Type MC cable shall be permitted as 
follows: 

(1) For services, feeders, and branch circuits 

(2) For power, lighting, control, and signal circuits 

(3) Indoors or outdoors 

(4) Exposed or concealed 

(5) To be direct buried where identified for such use 

(6) In cable tray where identified for such use 

(7) In any raceway 

(8) As aerial cable on a messenger 

(9) In hazardous (classified) locations as permitted 

(10) In dry locations and embedded in plaster finish on brick 
or other masonry except in damp or wet locations 

(11) In wet locations where any of the following conditions 
are met: 

a. The metallic covering is impervious to moisture. 

b. A lead sheath or moisture-impervious jacket is pro- 
vided under the metal covering. 

c. The insulated conductors under the metallic cover- 
ing are listed for use in wet locations. 

(12) Where single-conductor cables are used, all phase 
conductors and, where used, the neutral conductor 
shall be grouped together to minimize induced voltage 
on the sheath. 



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70-175 



330.12 



ARTICLE 330 — METAL-CLAD CABLE: TYPE MC 



(B) Specific Uses. Type MC cable shall be permitted to be 
installed in compliance with Parts 11 and EI of Article 725 and 
770.52 as applicable and in accordance with 330.10(B)(1) 
through (B)(4). 

(1) Cable Tray. Type MC cable installed in cable tray shall 
comply with 392.3, 392.4, 392.6, and 392.8 through 392.13. 

(2) Direct Buried. Direct-buried cable shall comply with 
300.5 or 300.50, as appropriate. 

(3) Installed as Service-Entrance Cable. Type MC cable 
installed as service-entrance cable shall be permitted in ac- 
cordance with 230.43. 

(4) Installed Outside of Buildings or as Aerial Cable. 

Type MC cable installed outside of buildings or as aerial 
cable shall comply with 225.10, 396.10, and 396.12. 

FPN: The "Uses Permitted" is not an all-inclusive list. 

330.12 Uses Not Permitted. Type MC cable shall not be 
used where exposed to the following destructive corrosive 
conditions, unless the metalUc sheath is suitable for the con- 
ditions or is protected by material suitable for the conditions: 

(1) Where subject to physical damage 

(2) Direct burial in the earth 

(3) In concrete 

FPN to (3): MC cable that is identified for direct burial appli- 
cations is suitable for installation in concrete. 

(4) Where subject to cinder fills, strong chlorides, caustic 
alkalis, or vapors of chlorine or of hydrochloric acids 

330.17 Through or Parallel to Framing Members. 

Type MC cable shall be protected in accordance with 
300.4(A), (C), and (D) where installed through or parallel 
to framing members. 

330.23 In Accessible Attics. The installation of Type MC 
cable in accessible attics or roof spaces shall also comply 
with 320.23. 



(B) Interlocked-Type Armor or Corrugated Sheath. 

Seven times the external diameter of the metallic sheath. 

(C) Shielded Conductors. Twelve times the overall diam- 
eter of one of the individual conductors or seven times the 
overall diameter of the multiconductor cable, whichever is 
greater. 

330.30 Securing and Supporting. 

(A) General. Type MC cable shall be supported and se- 
cured by staples, cable ties, straps, hangers, or similar fit- 
tings or other approved means designed and installed so as 
not to damage the cable. 

(B) Securing. Unless otherwise provided, cables shall be se- 
cured at intervals not exceeding 1.8 m (6 ft). Cables contain- 
ing four or fewer conductors sized no larger than 10 AWG 
shall be secured within 300 mm (12 in.) of every box, cabinet, 
fitting, or other cable termination. 

(C) Supporting. Unless otherwise provided, cables shall 
be supported at intervals not exceeding 1.8-m (6-ft) 

Horizontal runs of Type MC cable installed in wooden 
or metal framing members or similar supporting means 
shall be considered supported and secured where such sup- 
port does not exceed 1.8-m (6-ft) intervals. 

(D) Unsupported Cables. Type MC cable shall be permit- 
ted to be unsupported where the cable: 

(1) Is fished between access points through concealed spaces 
in finished buildings or structures and supporting is im- 
practical; or 

(2) Is not more than 1.8 m (6 ft) in length from the last 
point of cable support to the point of connection to a 
luminaire (lighting fixture) or other piece of electrical 
equipment and the cable and point of connection are 
within an accessible ceiling. For the purpose of this 
section, Type MC cable fittings shall be permitted as a 
means of cable support. 



330.24 Bending Radius. Bends in Type MC cable shall be 
so made that the cable will not be damaged. The radius of 
the curve of the inner edge of any bend shall not be less 
than required in 330.24(A) through (C). 

(A) Smooth Sheath. 

(1) Ten times the external diameter of the metallic sheath for 
cable not more than 19 mm (% in.) in external diameter 

(2) Twelve times the external diameter of the metallic 
sheath for cable more than 19 mm {V4 in.) but not more 
than 38 mm (I'/a in.) in external diameter 

(3) Fifteen times the external diameter of the metallic sheath 
for cable more than 38 mm (V/i in.) in external diameter 



330.31 Single Conductors. Where single-conductor cables 
with a nonferrous armor or sheath are used, the installation 
shall comply with 300.20. 

330.40 Boxes and Fitting. Fittings used for connecting 
Type MC cable to boxes, cabinets, or other equipment shall 
be fisted and idenrified for such use. 

330.80 Ampacity. The ampacity of Type MC cable shall be 
determined in accordance with 310.15 or 310.60 for 14 AWG 
and larger conductors and in accordance with Table 402.5 for 
18 AWG and 16 AWG conductors. The installation shall not 
exceed the temperature ratings of terminations and equipment. 



70-176 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 332 — MINERAL-INSULATED, METAL-SHEATHED CABLE: TYPE MI 



332.17 



(A) Type MC Cable Installed in Cable Tray. The am- 
pacities for Type MC cable installed in cable tray shall be 
determined in accordance with 392.11 and 392.13. 

(B) Single Type MC Conductors Grouped Together. 

Where single Type MC conductors are grouped together in 
a triangular or square configuration and installed on a mes- 
senger or exposed with a maintained free airspace of not 
less than 2.15 times one conductor diameter (2.15 x O.D.) 
of the largest conductor contained within the configuration 
and adjacent conductor configurations or cables, the ampac- 
ity of the conductors shall not exceed the allowable am- 
pacities in the following tables: 

(1) Table 310.20 for conductors rated through 2000 volts 

(2) Table 310.67 and Table 310.68 for conductors rated 
over 2000 volts 



III. Construction Specifications 

330.104 Conductors. The conductors shall be of copper, 
aluminum, or copper-clad aluminum, solid or stranded. 
The minimum conductor size shall be 18 AWG copper 
and 12 AWG aluminum or copper-clad aluminum. 

330.108 Equipment Grounding. Where Type MC cable is 
used for equipment grounding, it shall comply with 
250.118(10) and 250.122. 

330.112 Insulation. Insulated conductors shall comply 
with 330.112(A) or (B). 

(A) 600 Volts. Insulated conductors in sizes 18 AWG and 16 
AWG shall be of a type listed in Table 402.3, with a maximum 
operating temperature not less than 90°C (194°F) and as per- 
mitted by 725.27. Conductors larger than 16 AWG shall be of 
a type listed in Table 310.13 or of a type identified for use in 
Type MC cable. 

(B) Over 600 Volts. Insulated conductors shall be of a type 
listed in Table 310.61 through Table 310.64. 

330.116 Sheath. Metallic covering shall be one of the fol- 
lowing types: smooth metallic sheath, corrugated metallic 
sheath, interlocking metal tape armor. The metallic sheath 
shall be continuous and close fitting. A nonmagnetic sheath 
or armor shall be used on single conductor Type MC. 
Supplemental protection of an outer covering of corrosion- 
resistant material shall be permitted and shall be required 
where such protection is needed. The sheath shall not be 
used as a current-carrying conductor. 

FPN: See 300.6 for protection against corrosion. 



ARTICLE 332 

Mineral-Insulated, Metal-Sheathed 

Cable: Type MI 

I. General 

332.1 Scope. This article covers the use, installation, and 
construction specifications for mineral-insulated, metal- 
sheathed cable. Type MI. 

332.2 Definition. 

Mineral-Insulated, Metal-Sheathed Cable, Type MI. A 

factory assembly of one or more conductors insulated with 
a highly compressed refractory mineral insulation and en- 
closed in a liquidtight and gastight continuous copper or 
alloy steel sheath. 

II. Installation 

332.10 Uses Permitted. Type MI cable shall be permitted 
as follows: 

(1) For services, feeders, and branch circuits 

(2) For power, lighting, control, and signal circuits 

(3) In dry, wet, or continuously moist locations 

(4) Indoors or outdoors 

(5) Where exposed or concealed 

(6) Where embedded in plaster, concrete, fill, or other 
masonry, whether above or below grade 

(7) In any hazardous (classified) location 

(8) Where exposed to oil and gasoline 

(9) Where exposed to corrosive conditions not deteriorat- 
ing to its sheath 

(10) In underground runs where suitably protected against 
physical damage and corrosive conditions 

(11) In or attached to cable tray 

FPN: The "Uses Permitted" is not an all-inclusive list. 

332.12 Uses Not Permitted. Type MI cable shall not be 
used under the following conditions or in the following 
locations: 

(1) In underground runs unless protected from physical 
damage, where necessary 

(2) Where exposed to conditions that are destructive and 
corrosive to the metallic sheath, unless additional pro- 
tection is provided 

332.17 Through or Parallel to Framing Members. 

Type MI cable shall be protected in accordance with 300.4 
where installed through or parallel to framing members. 



2005 Edition 



NATIONAL ELECTRICAL CODE 



70-177 



332.24 



ARTICLE 334 — NONMETALLIC-SHEATHED CABLE: TYPES NM, NMC, AND NMS 



332.24 Bending Radius. Bends in Type MI cable shall be 
so made that the cable will not be damaged. The radius of 
the inner edge of any bend shall not be less than required as 
follows: 

(1) Five times the external diameter of the metalhc sheath for 
cable not more than 19 mm (¥4 in.) in external diameter 

(2) Ten times the external diameter of the metallic sheath 
for cable greater than 19 mm (¥4 in.) but not more than 
25 mm (1 in.) in external diameter 

332.30 Securing and Supporting. Type MI cable shall be 
supported and secured by staples, straps, hangers, or similar 
fittings, designed and installed so as not to damage the 
cable, at intervals not exceeding 1.8 m (6 ft). 

(A) Horizontal Runs Through Holes and Notches. In 

other than vertical runs, cables installed in accordance with 
300.4 shall be considered supported and secured where 
such support does not exceed 1.8 m (6 ft) intervals. 

(B) Unsupported Cable. Type MI cable shall be permitted 
to be unsupported where the cable is fished between access 
points through concealed spaces in finished buildings or 
structures and supporting is impracticable. 

(C) Cable Trays. All MI cable installed in cable trays 
shall comply with 392.8(B). 

332.31 Single Conductors. Where single-conductor cables 
are used, all phase conductors and, where used, the neutral 
conductor shall be grouped together to minimize induced 
voltage on the sheath. 

332.40 Boxes and Fittings. 

(A) Fittings. Fittings used for connecting Type MI cable to 
boxes, cabinets, or other equipment shall be identified for 
such use. 

(B) Terminal Seals. Where Type MI cable terminates, an 
end seal fitting shall be installed immediately after stripping 
to prevent the entrance of moisture into the insulation. The 
conductors extending beyond the sheath shall be individu- 
ally provided with an insulating material. 

332.80 Ampacity. The ampacity of Type MI cable shall be 
determined in accordance with 310.15. The conductor tem- 
perature at the end seal fitting shall not exceed the tempera- 
ture rating of the listed end seal fitting, and the installation 
shall not exceed the temperature ratings of terminations or 
equipment. 

(A) Type MI Cable Installed in Cable Tray. The ampaci- 
ties for Type MI cable installed in cable tray shall be deter- 
mined in accordance with 392.11. 

(B) Single Type MI Conductors Grouped Together. 

Where single Type MI conductors are grouped together in a 
triangular or square configuration, as required by 332.31, 



and installed on a messenger or exposed with a maintained 
free air space of not less than 2.15 times one conductor 
diameter (2.15 x O.D.) of the largest conductor contained 
within the configuration and adjacent conductor configura- 
tions or cables, the ampacity of the conductors shall not 
exceed the allowable ampacities of Table 310.17. 

III. Construction Specifications 

332.104 Conductors. Type MI cable conductors shall be 
of solid copper, nickel, or nickel-coated copper with a re- 
sistance corresponding to standard AWG and kcmil sizes. 

332.108 Equipment Grounding. Where the outer sheath 
is made of copper, it shall provide an adequate path for 
equipment grounding purposes. Where made of steel, an 
equipment grounding conductor shall be provided. 

332.112 Insulation. The conductor insulation in Type MI 
cable shall be a highly compressed refractory mineral that 
provides proper spacing for all conductors. 

332.116 Sheath. The outer sheath shall be of a continu- 
ous construction to provide mechanical protection and 
moisture seal. 



Nonmetallic-Sheathed Cable: Types MM, 

..... . 0-:NMG, and NMS;^ ::-. .-■ 

I. General 

334.1 Scope. This article covers the use, installation, and 
construction specifications of nonmetallic-sheathed cable. 

334.2 Definitions. 

Nonmetallic-Sheathed Cable. A factory assembly of two 
or more insulated conductors enclosed within an overall 
nonmetallic jacket. 

Type NM. Insulated conductors enclosed within an overall 
nonmetallic jacket. 

Type NMC. Insulated conductors enclosed within an over- 
all, corrosion resistant, nonmetallic jacket. 

Type NMS. Insulated power or control conductors with 
signaling, data, and communications conductors within an 
overall nonmetallic jacket. 

334.6 Listed. Type NM, Type NMC, and Type NMS cables 
shall be listed. 



• 



70-178 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 334 — NONMETALLIC-SHEATHED CABLE: TYPES NM, NMC, AND NMS 



334.15 



• 



II. Installation 

334.10 Uses Permitted. Type NM, Type NMC, and 
Type NMS cables shall be permitted to be used in the 
following: 

(1) One- and two-family dwellings. 

(2) Multifamily dwellings permitted to be of Types III, IV, 
and V construction except as prohibited in 334.12. 

(3) Other structures permitted to be of Types III, IV, and V 
construction except as prohibited in 334.12. Cables 
shall be concealed within walls, floors, or ceilings that 
provide a thermal barrier of material that has at least a 
15-minute finish rating as identified in listings of fire- 
rated assemblies. 

FPN No. 1 : Types of building construction and occupancy 
classifications are defined in NFPA 220-1999, Standard on 
Types of Building Construction, or the applicable building 
code, or both. 

FPN No. 2: See Annex E for determination of building 
types [NFPA 220, Table 3-1]. 

(4) Cable trays in structures permitted to be Types III, IV, 
or V where the cables are identified for the use. 

FPN: See 310.10 for temperature limitation of conductors. 

(A) Type NM. Type NM cable shall be permitted as follows: 

(1) For both exposed and concealed work in normally dry 
locations except as prohibited in 334.10(3) 

(2) To be installed or fished in air voids in masonry block 
or tile walls 

(B) Type NMC. Type NMC cable shall be permitted as 
follows: 

(1) For both exposed and concealed work in dry, moist, 
damp, or corrosive locations, except as prohibited by 
334.10(3) 

(2) In outside and inside walls of masonry block or tile 

(3) In a shallow chase in masonry, concrete, or adobe pro- 
tected against nails or screws by a steel plate at least 
1.59 mm (Vie in.) thick and covered with plaster, adobe, 
or similar finish 

(C) IVpe NMS. Type NMS cable shall be permitted as 
follows: 

(1) For both exposed and concealed work in normally dry 
locations except as prohibited by 334.10(3) 

(2) To be installed or fished in air voids in masonry block 
or tile walls 

334.12 Uses Not Permitted. 

(A) Types NM, NMC, and NMS. Types NM, NMC, and 
NMS cables shall not be permitted as follows: 
(1) In any dwelling or structure not specifically permitted 
in 334.10(1), (2), and (3) 



(2) Exposed in dropped or suspended ceilings in other 
than one- and two-family and multifamily dwellings 

(3) As service-entrance cable 

(4) In commercial garages having hazardous (classified) 
locations as defined in 511.3 

(5) In theaters and similar locations, except where permit- 
ted in 518.4(B) 

(6) In motion picture studios 

(7) In storage battery rooms 

(8) In hoistways or on elevators or escalators 

(9) Embedded in poured cement, concrete, or aggregate 

(10) In hazardous (classified) locations, except where per- 
mitted by the following: 

a. 501.10(B)(3) 

b. 502.10(B)(3) 

c. 504.20 

(B) Types NM and NMS. Types NM and NMS cables 
shall not be used under the following conditions or in the 
following locations: 

(1) Where exposed to corrosive fumes or vapors 

(2) Where embedded in masonry, concrete, adobe, fill, or 
plaster 

(3) In a shallow chase in masonry, concrete, or adobe and 
covered with plaster, adobe, or similar finish 

(4) Where exposed or subject to excessive moisture or 
dampness 

334.15 Exposed Work. In exposed work, except as pro- 
vided in 300.11(A), cable shall be installed as specified in 
334.15(A) through (C). 

(A) To Follow Surface. Cable shall closely follow the sur- 
face of the building finish or of running boards. 

(B) Protection from Physical Damage. Cable shall be 
protected from physical damage where necessary by rigid 
metal conduit, intermediate metal conduit, electrical metal- 
he tubing. Schedule 80 PVC rigid nonmetallic conduit, or 
other approved means. Where passing through a floor, the 
cable shall be enclosed in rigid metal conduit, intermediate 
metal conduit, electrical metallic tubing. Schedule 80 PVC 
rigid nonmetallic conduit, or other approved means extend- 
ing at least 150 mm (6 in.) above the floor. 

Where Type NMC cable is installed in shallow chases 
in masonry, concrete, or adobe, the cable shall be protected 
against nails or screws by a steel plate at least 1.59 mm 
(V]6 in.) thick and covered with plaster, adobe, or similar 
finish. 

(C) In Unfinished Basements. Where cable is run at 
angles with joists in unfinished basements, it shall be per- 
missible to secure cables not smaller than two 6 AWG or 



2005 Edition 



NATIONAL ELECTRICAL CODE 



70-179 



334.17 



ARTICLE 334 — NONMETALLIC-SHEATHED CABLE: TYPES NM, NMC, AND NMS 



three 8 AWG conductors directly to the lower edges of the 
joists. Smaller cables shall be run either through bored 
holes in joists or on running boards. NM cable used on a 
wall of an unfinished basement shall be permitted to be 
installed in a listed conduit or tubing. Conduit or tubing 
shall utilize a nonmetallic bushing or adapter at the point 
the cable enters the raceway. Metal conduit and tubings and 
metal outlet boxes shall be grounded. 

334.17 Through or Parallel to Framing Members. 

Types NM, NMC, or NMS cable shall be protected in 
accordance with 300.4 where installed through or paral- 
lel to framing members. Grommets used as required in 
300.4(B)(1) shall remain in place and be listed for the 
purpose of cable protection. 

334.23 In Accessible Attics. The installation of cable in ac- 
cessible attics or roof spaces shall also comply with 320.23. 

334.24 Bending Radius. Bends in Types NM, NMC, and 
NMS cable shall be so made that the cable will not be 
damaged. The radius of the curve of the inner edge of any 
bend during or after installation shall not be less than five 
times the diameter of the cable. 

334.30 Securing and Supporting. Nonmetallic-sheathed 
cable shall be supported and secured by staples, cable ties, 
straps, hangers, or similar fittings designed and installed so 
as not to damage the cable, at intervals not exceeding 1 .4 m 
(4'/2 ft) and within 300 mm (12 in.) of every outlet box, 
junction box, cabinet, or fitting. Flat cables shall not be 
stapled on edge. 

Sections of cable protected from physical damage by race- 
way shall not be required to be secured within the raceway. 

(A) Horizontal Runs Through Holes and Notches. In 

other than vertical runs, cables installed in accordance with 
300.4 shall be considered to be supported and secured 
where such support does not exceed 1.4-m (4l/2-ft) intervals 
and the nonmetallic-sheathed cable is securely fastened in 
place by an approved means within 300 mm (12 in.) of 
each box, cabinet, conduit body, or other nonmetallic- 
sheathed cable termination. 

FPN: See 314.17(C) for support where nonmetallic boxes 
are used. 

(B) Unsupported Cables. NonmetaUic-sheathed cable 
shall be permitted to be unsupported where the cable: 

(1) Is fished between access points through concealed 
spaces in finished buildings or structures and support- 
ing is impracticable. 

(2) Is not more than 1.4 m (4'/2 ft) from the last point of 
cable support to the point of connection to a luminaire 
(lighting fixture) or other piece of electrical equipment 
and the cable and point of connection are within an 
accessible ceiling. 



(C) Wiring Device Without a Separate Outlet Box. A 

wiring device identified for the use, without a separate out- 
let box, and incorporating an integral cable clamp shall be 
permitted where the cable is secured in place at intervals 
not exceeding 1.4 m (4'/2 ft) and within 300 mm (12 in.) 
from the wiring device wall opening, and there shall be at 
least a 300 mm (12 in.) loop of unbroken cable or 150 mm 
(6 in.) of a cable end available on the interior side of the 
finished wall to permit replacement. 

334.40 Boxes and Fittings. 

(A) Boxes of Insulating Material. Nonmetallic outlet 
boxes shall be permitted as provided by 314.3. 

(B) Devices of Insulating Material. Switch, outlet, and tap 
devices of insulating material shall be permitted to be used 
without boxes in exposed cable wiring and for rewiring in 
existing buildings where the cable is concealed and fished. 
Openings in such devices shall form a close fit around the 
outer covering of the cable, and the device shall fully enclose 
the part of the cable from which any part of the. covering has 
been removed. Where connections to conductors are by 
binding-screw terminals, there shall be available as many ter- 
minals as conductors. 

(C) Devices with Integral Enclosures. Wiring devices 
with integral enclosures identified for such use shall be 
permitted as provided by 300.15(E). 

334.80 Ampacity. The ampacity of Types NM, NMC, and 
NMS cable shall be determined in accordance with 310.15. 
The ampacity shall be in accordance with the 60°C (140°F) 
conductor temperature rating. The 90°C (194°F) rating 
shall be permitted to be used for ampacity derating pur- 
poses, provided the final derated ampacity does not exceed 
that for a 60°C (140°F) rated conductor. The ampacity of 
Types NM, NMC, and NMS cable installed in cable tray 
shall be determined in accordance with 392.11. 

Where more than two NM cables containing two or 
more current-carrying conductors are bundled together and 
pass through wood framing that is to be fire- or draft- 
stopped using thermal insulation or sealing foam, the al- 
lowable ampacity of each conductor shall be adjusted in 
accordance with Table 310.15(B)(2)(a). 

III. Construction Specifications 

334.100 Construction. The outer cable sheath of 
nonmetallic-sheathed cable shall be a nonmetallic material. 

334.104 Conductors. The 600 volt insulated conductors 
shall be sizes 14 AWG through 2 AWG copper conductors 
or sizes 12 AWG through 2 AWG aluminum or copper-clad 
aluminum conductors. The signaling conductors shall com- 
ply with 780.5. The communication conductors shall com- 
ply with Part V of Article 800. 



70-180 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 336 — POWER AND CONTROL TRAY CABLE: TYPE TC 



336.24 



• 



334.108 Equipment Grounding. In addition to the insu- 
lated conductors, the cable shall have an insulated or bare 
conductor for equipment grounding purposes only. 

334.112 Insulation. The insulated power conductors shall be 
one of the types listed in Table 310.13 that are suitable for 
branch circuit wiring or one that is identified for use in these 
cables. Conductor insulation shall be rated at 90°C (194°F). 

FPN: Types NM, NMC, and NMS cable identified by the 
markings NM-B, NMC-B, and NMS-B meet this requirement. 

334.116 Sheath. The outer sheath of nonmetallic-sheathed 
cable shall comply with 334.116(A), (B), and (C). 

(A) Type NM. The overall covering shall be flame retar- 
dant and moisture resistant. 

(B) Type NMC. The overall covering shall be flame retar- 
dant, moisture resistant, fungus resistant, and corrosion re- 
sistant. 

(C) Type NMS. The overall covering shall be flame retar- 
dant and moisture resistant. The sheath shall be applied so 
as to separate the power conductors from the communica- 
tions and signaling conductors. The signaling conductors 
shall be permitted to be shielded. An optional outer jacket 
shall be permitted. 

FPN: For composite optical cable, see 770.9 and 770.133. 



(5) For Class 1 circuits as permitted in Parts II and III of 
Article 725. 

(6) For non-power-limited fire alarm circuits if conductors 
comply with the requirements of 760.27. 

(7) In industrial establishments where the conditions of 
maintenance and supervision ensure that only qualified 
persons service the installation, and where the cable is 
continuously supported and protected against physical 
damage using mechanical protection, such as struts, 
angles, or channels, Type TC tray cable that complies 
with the crush and impact requirements of Type MC 
cable and is identified for such use with the marking 
Type TC-ER shall be permitted between a cable tray 
and the utilization equipment or device. The cable shall 
be secured at intervals not exceeding 1.8 m (6 ft). 
Equipment grounding for the utilization equipment 
shall be provided by an equipment grounding conduc- 
tor within the cable. In cables containing conductors 
sized 6 AWG or smaller, the equipment grounding con- 
ductor shall be provided within the cable or, at the time 
of installation, one or more insulated conductors shall 
be permanently identified as an equipment grounding 
conductor in accordance with 250.119(B). 

(8) Where installed in wet locations. Type TC cable shall 
also be resistant to moisture and corrosive agents. 

FPN: See 3 10. 10 for temperature limitation of conductors. 



2 ARTICLE 336 :■ 
iNDwier and Contol iVay (5abie: Type TC 



I. General 

336.1 Scope. This article covers the use, installation, and con- 
stmction specifications for power and control tray cable, Type TC. 

336.2 Definition. 

Power and Control Tray Cable, Type TC. A factory as- 
sembly of two or more insulated conductors, with or with- 
out associated bare or covered grounding conductors, under 
a nonmetallic jacket. 

II. Installation 

336.10 Uses Permitted. Type TC cable shall be permitted 
to be used as follows: 

(1) For power, lighting, control, and signal circuits. 

(2) In cable trays. 

(3) In raceways. 

(4) In outdoor locations supported by a messenger wire. 



336.12 Uses Not Permitted. Type TC tray cable shall not 
be installed or used as follows: 

(1) Installed where it will be exposed to physical damage 

(2) Installed outside a raceway or cable tray system, except 
as permitted in 336.10(7) 

(3) Used where exposed to direct rays of the sun, unless 
identified as sunlight resistant 

(4) Direct buried, unless identified for such use 

336.24 Bending Radius. Bends in Type TC cable shall be 
made so as not to damage the cable. For Type TC cable 
without metal shielding, the minimum bending radius shall 
be as follows: 

(1) Four times the overall diameter for cables 25 mm 
(1 in.) or less in diameter 

(2) Five times the overall diameter for cables larger flian 
25 mm (1 in.) but not more than 50 mm (2 in.) in diameter 

(3) Six times the overall diameter for cables larger than 
50 mm (2 in.) in diameter 

Type TC cables with metallic shielding shall have a 
minimum bending radius of not less than 12 times the cable 
overall diameter. 



2005 Edition 



NATIONAL ELECTRICAL CODE 



70-18] 



336.80 



ARTICLE 338 — SERVICE-ENTRANCE CABLE: TYPES SE AND USE 



336.80 Ampacity. The ampacity of Type TC tray cable shall 
be determined in accordance with 392.11 for 14 AWG and 
larger conductors, in accordance with 402.5 for 18 AWG 
through 16 AWG conductors where installed in cable tray, and 
in accordance with 310.15 where installed in a raceway or as 
messenger supported wiring. 

III. Construction Specifications 

336.100 Construction. A metallic sheath or armor as de- 
fined in 330.116 shall not be permitted either under or over 
the nonmetallic jacket. Metallic shield(s) shall be permitted 
over groups of conductors, under the outer jacket, or both. 

336.104 Conductors. The insulated conductors of Type 
TC tray cable shall be in sizes 18 AWG through 1000 kcmil 
copper and sizes 12 AWG through 1000 kcmil aluminum 
or copper-clad aluminum. Insulated conductors of sizes 
14 AWG and larger copper and sizes 12 AWG and larger 
aluminum or copper-clad aluminum shall be one of the 
types listed in Table 310.13 or Table 310.62 that is suit- 
able for branch circuit and feeder circuits or one that is 
identified for such use. 

(A) Fire Alarm Systems. Where used for fire alarm sys- 
tems, conductors shall also be in accordance with 760.27. 

(B) Thermocouple Circuits. Conductors in Type TC cable 
used for thermocouple circuits in accordance with Part III 
of Article 725 shall also be permitted to be any of the 
materials used for thermocouple extension wire. 

(C) Class I Circuit Conductors. Insulated conductors of 
18 AWG and 16 AWG copper shall also be in accordance 
with 725.27. 

336.116 Jacket. The outer jacket shall be a flame-retardant, 
nonmetalUc material. 

336.120 Marking. There shall be no voltage marking on a 
Type TC cable employing thermocouple extension wire. 



ServicerEntrance Cable;; Types SE 



I. General 

338.1 Scope. This article covers the use, installation, and 
construction specifications of service-entrance cable. 

338.2 Definitions. 

Service-Entrance Cable. A single conductor or multicon- 
ductor assembly provided with or without an overall covering, 
primarily used for services, and of the following types: 



Type SE. Service-entrance cable having a flame-retardant, 
moisture-resistant covering. 

Type USE. Service-entrance cable, identified for under- 
ground use, having a moisture-resistant covering, but not 
required to have a flame-retardant covering. 

II. Installation 
338.10 Uses Permitted. 

(A) Service-Entrance Conductors. Service-entrance cable 
shall be permitted to be used as service-entrance conductors 
and shall be installed in accordance with 230.6, 230.7, and 
Parts II, III, and IV of Article 230. 

Type USE used for service laterals shall be permitted to 
emerge from the ground outside at terminations in meter 
bases or other enclosures where protected in accordance 
with 300.5(D). 

(B) Branch Circuits or Feeders. 

(1) Grounded Conductor Insulated. Type SE service- 
entrance cables shall be permitted in wiring systems where 
all of the circuit conductors of the cable are of the rubber- 
covered or thermoplastic type. 

(2) Grounded Conductor Not Insulated. Type SE 
service-entrance cable shall be permitted for use where the 
insulated conductors are used for circuit wiring and the 
uninsulated conductor is used only for equipment ground- 
ing purposes. 

Exception: Uninsulated conductors shall be permitted as 
a grounded conductor in accordance with 250.140, 250.32, 
and 225.30 through 225.40. 

(3) Temperature Limitations. Type SE service-entrance 
cable used to supply appliances shall not be subject to con- 
ductor temperatures in excess of the temperature specified 
for the type of insulation involved. 

(4) Installation Methods for Branch Circuits and Feeders. 

(a) Interior Installations. In addition to the provisions 
of this article. Type SE service-entrance cable used for in- 
terior wiring shall comply with the installation require- 
ments of Parts I and II of Article 334, excluding 334.80. 

FPN: See 3 10. 10 for temperature limitation of conductors. 

(b) Exterior Installations. In addition to the provisions 
of this article, service-entrance cable used for feeders or 
branch circuits, where installed as exterior wiring, shall be 
installed in accordance with Part I of Article 225. The cable 
shafl be supported in accordance with 334.30, unless used 
as messenger-supported wiring as permitted in Part II of 
Article 396. Type USE cable installed as underground 
feeder and branch circuit cable shall comply with Part II of 



• 



70-182 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 340 — UNDERGROUND FEEDER AND BRANCH-CIRCUIT CABLE: TYPE UF 



340.80 



• 



Article 340. Where Type USE cable emerges from the 
ground at terminations, it shall be protected in accordance 
with 300.5(D). Multiconductor service-entrance cable shall 
be permitted to be installed as messenger-supported wiring 
in accordance with 225.10 and Part II of Article 396. 

338.24 Bending Radius. Bends in Types USE and SE cable 
shall be so made that the cable will not be damaged. The 
radius of the curve of the inner edge of any bend, during or 
after installation, shall not be less than five times the diameter 
of the cable. 

III. Construction 

338.100 Construction. Cabled, single-conductor. Type USE 
constructions recognized for underground use shall be permit- 
ted to have a bare copper conductor cabled with the assembly. 
Type USE single, parallel, or cabled conductor assemblies rec- 
ognized for underground use shall be permitted to have a bare 
copper concentric conductor applied. These constructions shall 
not require an outer overall covering. 

FPN: See 230.41, Exception, item (2), for directly buried, 
uninsulated service-entrance conductors. 

Type SE or USE cable containing two or more conduc- 
tors shall be permitted to have one conductor uninsulated. 

338.120 Marking. Service-entrance cable shall be marked 
as required in 310.11. Cable with the neutral conductor 
smaller than the ungrounded conductors shall be so marked. 



\r Underground Feeder and BranchHCircuit 

li ■.^..a;:.^:l..i■€able::]5ype.UF ,. -:,. ~x: ■.^^■:- :[ 

I. General 

340.1 Scope. This article covers the use, installation, and 
construction specifications for underground feeder and 
branch-circuit cable. Type UF. 

340.2 Definition. 

Underground Feeder and Branch-Circuit Cable, Type UF. 

A factory assembly of one or more insulated conductors 
with an integral or an overall covering of nonmetallic ma- 
terial suitable for direct burial in the earth. 

340.6 Listing Requirements. Type UF cable shall be Usted. 



II. Installation 

340.10 Uses Permitted. Type UF cable shall be permitted 
as follows: 

(1) For use underground, including direct burial in the 
earth. For underground requirements, see 300.5. 

(2) As single-conductor cables. Where installed as single- 
conductor cables, all conductors of the feeder grounded 
conductor or branch circuit, including the grounded 
conductor and equipment grounding conductor, if any, 
shall be installed in accordance with 300.3. 

(3) For wiring in wet, dry, or corrosive locations under the 
recognized wiring methods of this Code. 

(4) Installed as nonmetallic-sheathed cable. Where so 
installed, the installation and conductor requirements 
shall comply with Parts II and III of Article 334 and 
shall be of the multiconductor type. 

(5) For solar photovoltaic systems in accordance with 690.31. 

(6) As single-conductor cables as the nonhealing leads for 
heating cables as provided in 424.43. 

(7) Supported by cable trays. Type UF cable supported by 
cable trays shall be of the multiconductor type. 

FPN: See 310.10 for temperature limitation of conductors. 

340.12 Uses Not Permitted. Type UF cable shall not be 
used as follows: 

(1) As service-entrance cable 

(2) In commercial garages 

(3) In theaters and similar locations 

(4) In motion picture studios 

(5) In storage battery rooms 

(6) In hoistways or on elevators or escalators 

(7) In hazardous (classified) locations 

(8) Embedded in poured cement, concrete, or aggregate, 
except where embedded in plaster as nonheating leads 
where permitted in 424.43 

(9) Where exposed to direct rays of the sun, unless iden- 
tified as sunlight resistant 

(10) Where subject to physical damage 

(11) As overhead cable, except where installed as messenger- 
supported wiring in accordance with Part 11 of Article 396 

340.24 Bending Radius. Bends in Type UF cable shall be 
so made that the cable is not damaged. The radius of the 
curve of the inner edge of any bend shall not be less than 
five times the diameter of the cable. 

340.80 Ampacity. The ampacity of Type UF cable shall be 
that of 60°C (MOT) conductors in accordance with 310.15. 



2005 Edition 



NATIONAL ELECTRICAL CODE 



70-183 



340.104 



ARTICLE 342 — INTERMEDIATE METAL CONDUIT: TYPE IMC 



III. Construction Specifications 

340.104 Conductors. The conductors shall be sizes 14 AWG 
copper or 12 AWG aluminum or copper-clad aluminum 
through 4/0 AWG. 

340.108 Equipment Grounding. In addition to the insu- 
lated conductors, the cable shall be permitted to have an 
insulated or bare conductor for equipment grounding pur- 
poses only. 

340.112 Insulation. The conductors of Type UF shall be 
one of the moisture-resistant types listed in Table 310.13 
that is suitable for branch-circuit wiring or one that is iden- 
tified for such use. Where installed as a substitute wiring 
method for NM cable, the conductor insulation shall be 
rated 90°C (194°F). 

340.116 Sheath. The overall covering shall be flame retar- 
dant; moisture, fungus, and corrosion resistant; and suitable 
for direct burial in the earth. 



ARTICLE 342 
Intermediate Metal Conduit: Type IMC 

I. General 

342.1 Scope. This article covers the use, installation, and 
construction specifications for intermediate metal conduit 
(IMC) and associated fittings. 

342.2 Definition. 

Intermediate Metal Conduit (IMC). A steel threadable 
raceway of circular cross section designed for the physical 
protection and routing of conductors and cables and for use 
as an equipment grounding conductor when installed with 
its integral or associated coupling and appropriate fittings. 

342.6 Listing Requirements. IMC, factory elbows and cou- 
plings, and associated fittings shall be listed. 

II. Installation 
342.10 Uses Permitted. 

(A) All Atmospheric Conditions and Occupancies. Use 

of IMC shall be permitted under all atmospheric conditions 
and occupancies. 

(B) Corrosion Environments. IMC, elbows, couplings, 
and fittings shall be permitted to be installed in concrete, in 
direct contact with the earth, or in areas subject to severe 
corrosive influences where protected by corrosion protec- 
tion and judged suitable for the condition. 



(C) Cinder Fill. IMC shah be permitted to be installed in 
or under cinder fill where subject to permanent moisture 
where protected on all sides by a layer of noncinder con- 
crete not less than 50 mm (2 in.) thick; where the conduit is 
not less than 450 mm (18 in.) under the fill; or where 
protected by corrosion protection and judged suitable for 
the condition. 

(D) Wet Locations. All supports, bolts, straps, screws, and 
so forth, shall be of corrosion-resistant materials or pro- 
tected against corrosion by corrosion-resistant materials. 

FPN: See 300.6 for protection against corrosion. 

342.14 Dissimilar Metals. Where practicable, dissimilar 
metals in contact anywhere in the system shall be avoided 
to eliminate the possibility of galvanic action. 

Aluminum fittings and enclosures shall be permitted to 
be used with IMC. 

342.20 Size. 

(A) Minimum. IMC smaller than metric designator 16 (trade 
size Vi) shaU not be used. 

(B) Maximum. IMC larger than metric designator 103 (trade 
size 4) shall not be used. 

FPN: See 300.1(C) for the metric designators and trade 
sizes. These are for identification purposes only and do not 
relate to actual dimensions. 

342.22 Number of Conductors. The number of conduc- 
tors shall not exceed that permitted by the percentage fill 
specified in Table 1, Chapter 9. 

Cables shall be permitted to be installed where such use 
is not prohibited by the respective cable articles. The num- 
ber of cables shall not exceed the allowable percentage fill 
specified in Table 1, Chapter 9. 

342.24 Bends — How Made. Bends of IMC shaU be, so 
made that the conduit will not be damaged and the internal 
diameter of the conduit will not be effectively reduced. The 
radius of the curve of any field bend to the centerUne of the 
conduit shall not be less than indicated in Table 2, Chapter 9. 

342.26 Bends — Number in One Run. There shall not be 
more than the equivalent of four quarter bends (360 degrees 
total) between pull points, for example, conduit bodies and 
boxes. 

342.28 Reaming and Threading. All cut ends shall be 
reamed or otherwise finished to remove rough edges. Where 
conduit is threaded in the field, a standard cutting die with a 
taper of 1 in 16 {V4 in. taper per foot) shall be used. 

FPN: See ANSI/ASME B. 1.20.1-1983, Standard for Pipe 
Threads, General Purpose (Inch). 



• 



• 



70-184 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 344 — RIGID METAL CONDUIT: TYPE RMC 



344.10 



• 



342.30 Securing and Supporting. IMC shall be installed 
as a complete system in accordance with 300.18 and shall 
be securely fastened in place and supported in accordance 
with 342.30(A) and (B). 

(A) Securely Fastened. Each IMC shall be securely fas- 
tened within 900 mm (3 ft) of each outlet box, junction box, 
device box, cabinet, conduit body, or other conduit termina- 
tion. Fastening shall be permitted to be increased to a distance 
of 1.5 m (5 ft) where structural members do not readily permit 
fastening within 900 mm (3 ft). Where approved, conduit shall 
not be required to be securely fastened within 900 mm (3 ft) of 
the service head for above-the-roof termination of a mast. 

(B) Supports. IMC shall be supported in accordance with 
one of the following: 

(1) Conduit shall be supported at intervals not exceeding 3 m 
(10 ft). 

(2) The distance between supports for straight runs of conduit 
shall be permitted in accordance with Table 344.30(B)(2), 
provided the conduit is made up with threaded couplings 
and such supports prevent transmission of stresses to ter- 
mination where conduit is deflected between supports. 

(3) Exposed vertical risers from industrial machinery or 
fixed equipment shall be permitted to be supported at 
intervals not exceeding 6 m (20 ft) if the conduit is 
made up with threaded couplings, the conduit is sup- 
ported and securely fastened at the top and bottom of 
the riser, and no other means of intermediate support is 
readily available. 

(4) Horizontal runs of IMC supported by openings through 
framing members at intervals not exceeding 3 m (10 ft) 
and securely fastened within 900 mm (3 ft) of termina- 
tion points shall be permitted. 

342.42 Couplings and Connectors. 

(A) Threadless. Threadless couplings and connectors used 
with conduit shall be made tight. Where buried in masonry or 
concrete, they shall be the concretetight type. Where installed 
in wet locations, they shall comply with 314.15(A). Thread- 
less couplings and connectors shall not be used on threaded 
conduit ends unless Listed for the purpose. 

(B) Running Threads. Running threads shall not be used 
on conduit for connection at couplings. 

342.46 Bushings. Where a conduit enters a box, fitting, or 
other enclosure, a bushing shall be provided to protect the 
wire from abrasion unless the design of the box, fitting, or 
enclosure is such as to afford equivalent protection. 

FPN: See 300.4(F) for the protection of conductors 4 
AWG and larger at bushings. 



342.56 SpHces and Taps. SpUces and taps shall be made 
in accordance with 300.15. 

342.60 Grounding. IMC shall be permitted as an equip- 
ment grounding conductor. 

III. Construction Specifications 

342.120 Marking. Each length shall be clearly and dura- 
bly marked at least every 1.5 m (5 ft) with the letters IMC. 
Each length shall be marked as required in 110.21. 

342.130 Standard Lengths. The standard length of IMC 
shall be 3.05 m (10 ft), including an attached coupling, and 
each end shall be threaded. Longer or shorter lengths with 
or without coupling and threaded or unthreaded shall be 
permitted. 



ARTICLE 344 
Rigid Metal Conduit: Type RMC 

L General 

344.1 Scope. This article covers the use, installation, and 
construction specifications for rigid metal conduit (RMC) 
and associated fittings. 

344.2 Definition. 

Rigid Metal Conduit (RMC). A threadable raceway of 
circular cross section designed for the physical protection 
and routing of conductors and cables and for use as an 
equipment grounding conductor when installed with its in- 
tegral or associated coupling and appropriate fittings. RMC 
is generally made of steel (ferrous) with protective coatings 
or aluminum (nonferrous). Special use types are silicon 
bronze and stainless steel. 

344.6 Listing Requirements. RMC, factory elbows and 
couplings, and associated fittings shall be listed. 

II. Installation 
344.10 Uses Permitted. 

(A) All Atmospheric Conditions and Occupancies. Use 

of RMC shall be permitted under all atmospheric condi- 
tions and occupancies. Ferrous raceways and fittings pro- 
tected from corrosion solely by enamel shall be permitted 
only indoors and in occupancies not subject to severe cor- 
rosive influences. 



2005 Edition 



NATIONAL ELECTRICAL CODE 



70-185 



344.14 



ARTICLE 344 — RIGID METAL CONDUIT: TYPE RMC 



(B) Corrosion Environments. RMC, elbows, couplings, 
and fittings shall be permitted to be installed in concrete, in 
direct contact with the earth, or in areas subject to severe 
corrosive influences where protected by corrosion protec- 
tion and judged suitable for the condition. 

(C) Cinder Fill. RMC shall be permitted to be installed in 
or under cinder fill where subject to permanent moisture 
where protected on all sides by a layer of noncinder con- 
crete not less than 50 mm (2 in.) thick; where the conduit is 
not less than 450 mm (18 in.) under the fill; or where 
protected by corrosion protection and judged suitable for 
the condition. 

(D) Wet Locations. All supports, bolts, straps, screws, and 
so forth, shall be of corrosion-resistant materials or pro- 
tected against corrosion by corrosion-resistant materials. 

FPN: See 300.6 for protection against corrosion. 

344.14 Dissimilar Metals. Where practicable, dissimilar 
metals in contact anywhere in the system shall be avoided 
to eliminate the possibility of galvanic action. Aluminum 
fittings and enclosures shall be permitted to be used with 
steel RMC, and steel fittings and enclosures shall be per- 
mitted to be used with aluminum RMC where not subject to 
severe corrosive influences. 

344.20 Size. 

(A) Minimum. RMC smaller than metric designator 16 (trade 
size Vi) shall not be used. 

Exception: For enclosing the leads of motors as permitted 
in 430.245(B). 

(B) Maximum. RMC larger than metric designator 155 (trade 
size 6) shall not be used. 

FPN: See 300.1(C) for the metric designators and trade 
sizes. These are for identification purposes only and do not 
relate to actual dimensions. 

344.22 Number of Conductors. The number of conduc- 
tors shall not exceed that permitted by the percentage fill 
specified in Table 1, Chapter 9. 

Cables shall be permitted to be installed where such use 
is not prohibited by the respective cable articles. The num- 
ber of cables shall not exceed the allowable percentage fill 
specified in Table 1, Chapter 9. 

344.24 Bends — How Made. Bends of RMC shall be so 
made that the conduit will not be damaged and so that the 
internal diameter of the conduit will not be effectively re- 
duced. The radius of the curve of any field bend to the 
centerhne of the conduit shall not be less than indicated in 
Table 2, Chapter 9. 



344.26 Bends — Number in One Run. There shall not be 
more than the equivalent of four quarter bends (360 degrees 
total) between pull points, for example, conduit bodies and 
boxes. 

344.28 Reaming and Threading. All cut ends shall be 
reamed or otherwise finished to remove rough edges. 
Where conduit is threaded in the field, a standard cutting 
die with a 1 in 16 taper (y4-in. taper per foot) shall be used. 

FPN: See ANSI/ASME B. 1.20.1-1983, Standard for Pipe 
Threads, General Purpose (Inch). 

344.30 Securing and Supporting. RMC shall be installed 
as a complete system in accordance with 300.18 and shall 
be securely fastened in place and supported in accordance 
with 344.30(A) and (B). 

(A) Securely Fastened. RMC shall be securely fastened 
within 900 mm (3 ft) of each outlet box, junction box, device 
box, cabinet, conduit body, or other conduit termination. Fas- 
tening shall be permitted to be increased to a distance of 1.5 m 
(5 ft) where structural members do not readily permit fasten- 
ing within 900 mm (3 ft). Where approved, conduit shall not 
be required to be securely fastened within 900 mm (3 ft) of the 
service head for above-the-roof termination of a mast. 

(B) Supports. RMC shafl be supported in accordance with 
one of the following: 

(1) Conduit shall be supported at intervals not exceeding 3 m 
(10 ft). 

(2) The distance between supports for straight runs of conduit 
shall be permitted in accordance with Table 344.30(B)(2), 
provided the conduit is made up with threaded couplings, 
and such supports prevent transmission of stresses to ter- 
mination where conduit is deflected between supports. 

(3) Exposed vertical risers from industrial machinery or fixed 
equipment shaU be permitted to be supported at intervals 
not exceeding 6 m (20 ft) if the conduit is made up with 
threaded couplings, the conduit is supported and securely 
fastened at the top and bottom of the riser, and no other 
means of intermediate support is readily available. 

(4) Horizontal runs of RMC supported by openings through 
framing members at intervals not exceeding 3 m (10 ft) 
and securely fastened within 900 mm (3 ft) of termination 
points shaU be permitted. 

344.42 Couplings and Connectors. 

(A) Threadless. Threadless couplings and connectors used 
with conduit shall be made tight. Where buried in masonry or 
concrete, they shall be the concretetight type. Where installed 
in wet locations, they shall comply with 314.15(A). Thread- 
less couplings and connectors shall not be used on threaded 
conduit ends unless listed for the purpose. 



• 



70-186 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 348 — FLEXIBLE METAL CONDUIT: TYPE FMC 



348.20 



Table 344.30(B)(2) Supports for Rigid Metal Conduit 





Maximum Distance 




Between Rigid Metal 


Conduit Size 


Conduit Supports 


Metric 




Designator Trade Size 


m ft 


16-21 1/2-3/4 


3.0 10 


27 1 


3.7 12 


35^1 11/4-11/2 


4.3 14 


53-63 2-21/2 


4.9 16 


78 and larger 3 and larger 


6.1 20 



(B) Running Threads. Running threads shall not be used 
on conduit for connection at couplings. 

344.46 Bushings. Where a conduit enters a box, fitting, or 
other enclosure, a bushing shall be provided to protect the 
wire from abrasion unless the design of the box, fitting, or 
enclosure is such as to afford equivalent protection. 

FPN: See 300.4(F) for the protection of conductors sizes 4 
AWG and larger at bushings. 

344.56 Splices and Taps. Splices and taps shall be made 
in accordance with 300.15. 

344.60 Grounding. RMC shall be permitted as an equip- 
ment grounding conductor. 

III. Construction Specifications 

344.120 Marking. Each length shall be clearly and dura- 
bly identified in every 3 m (10 ft) as required in the first 
sentence of 110.21. Nonferrous conduit of corrosion- 
resistant material shall have suitable markings. 

344.130 Standard Lengths. The standard length of RMC 
shall be 3.05 m (10 ft), including an attached coupling, and 
each end shall be threaded. Longer or shorter lengths with 
or without coupling and threaded or unthreaded shall be 
permitted. 



'Cm ■,; article ,348.;;^. 
Flexible Sletal (ionauiti Type FMC 



I. General 

348.1 Scope. This article covers the use, installation, and 
construction specifications for flexible metal conduit 
(FMC) and associated fittings. 



348.2 Definition. 

Flexible Metal Conduit (FMC). A raceway of circular 
cross section made of helically wound, formed, interlocked 
metal strip. 

348.6 Listing Requirements. FMC and associated fittings 
shall be listed. 



II. Installation 

348.10 Uses Permitted. FMC shall be permitted to be used 
in exposed and concealed locations. 

348.12 Uses Not Permitted. FMC shall not be used in the 
following: 

(1) In wet locations unless the conductors are approved for 
the specific conditions and the installation is such that 
liquid is not likely to enter raceways or enclosures to 
which the conduit is connected 

(2) In hoistways, other than as permitted in 620.21(A)(1) 

(3) In storage battery rooms 

(4) In any hazardous (classified) location other than as per- 
mitted in 501.10(B) and 504.20 

(5) Where exposed to materials having a deteriorating ef- 
fect on the installed conductors, such as oil or gasoline 

(6) Underground or embedded in poured concrete or aggre- 
gate 

(7) Where subject to physical damage 

348.20 Size. 

(A) Minimum. FMC less than metric designator 16 (trade 
size V2) shall not be used unless permitted in 348.20(A)(1) 
through (A)(5) for metric designator 12 (trade size Vb). 

(1) For enclosing the leads of motors as permitted in 
430.245(B) 

(2) In lengths not in excess of 1.8 m (6 ft) for any of the 
following uses: 

a. For utilization equipment 

b. As part of a listed assembly 

c. For tap connections to luminaires (lighting fixtures) 
as permitted in 410.67(C) 

(3) For manufactured wiring systems as permitted in 
604.6(A) 

(4) In hoistways as permitted in 620.21(A)(1) 

(5) As part of a listed assembly to connect wired luminaire 
(fixture) sections as permitted in 410.77(C) 

(B) Maximum. FMC larger than metric designator 103 (trade 
size 4) shall not be used. 

FPN: See 300.1(C) for the metric designators and trade 
sizes. These are for identification purposes only and do not 
relate to actual dimensions. 



2005 Edition NATIONAL ELECTRICAL CODE 



70-187 



348.22 



ARTICLE 348 — FLEXIBLE METAL CONDUIT: TYPE FMC 



348.22 Number of Conductors. The number of conduc- 
tors shall not exceed that permitted by the percentage fill 
specified in Table 1, Chapter 9, or as permitted in Table 
348.22, or for metric designator 12 (trade size Vs). 

Cables shall be permitted to be installed where such use 
is not prohibited by the respective cable articles. The num- 
ber of cables shall not exceed the allowable percentage fill 
specified in Table 1, Chapter 9. 

348.24 Bends — How Made. Bends in conduit shall be 
made so that the conduit is not damaged and the internal 
diameter of the conduit is not effectively reduced, Bends 
shall be permitted to be made manually without auxiliary 
equipment. The radius of the curve to the centerline of any 
bend shall not be less than shown in Table 2, Chapter 9 
using the column "Other Bends." 

348.26 Bends — Number in One Run. There shall not be 
more than the equivalent of four quarter bends (360 degrees 
total) between pull points, for example, conduit bodies and 
boxes. 

348.28 Trimming. All cut ends shall be trimmed or other- 
wise finished to remove rough edges, except where fittings 
that thread into the convolutions are used. 

348.30 Securing and Supporting. FMC shall be securely 
fastened in place and supported in accordance with 348.30(A) 
and (B). 

(A) Securely Fastened. FMC shall be securely fastened in 
place by an approved means within 300 mm (12 in.) of 
each box, cabinet, conduit body, or other conduit termina- 
tion and' shall be supported and secured at intervals not to 
exceed 1.4 m (4V2 ft). 

Exception No. 1: Where FMC is fished. 

Exception No. 2: At terminals where flexibility is required, 
lengths shall not exceed the following: 



(1) 900 mm (3 ft) for metric designators 16 through 35 
(trade sizes 'h through I'M) 

(2) 1200 mm (4 ft) for metric designators 41 through 53 
(trade sizes IV2 through 2) 

(3) 1500 mm (5 ft) for metric designators 63 (trade size 
2V2) and larger 

Exception No. 3: Lengths not exceeding 1.8 m (6 ft) from a 
luminaire (fixture) terminal connection for tap connections to 
luminaires (light fixtures) as permitted in 410.67(C). 

Exception No. 4: Lengths not exceeding 1.8 m (6 ft) from 
the last point where the raceway is securely fastened for 
connections within an accessible ceiling to luminaire(s) 
[lighting fixture(s)] or other equipment. 

(B) Supports. Horizontal runs of FMC supported by open- 
ings through framing members at intervals not greater than 
1.4 m {AVi ft) and securely fastened within 300 mm (12 in.) 
of termination points shall be permitted. 

348.42 Couplings and Connectors. Angle connectors 
shall not be used for concealed raceway installations. 

348.56 Splices and Taps. Splices and taps shall be made 
in accordance with 300.15. 

348.60 Grounding and Bonding. Where used to connect 
equipment where flexibility is required, an equipment ground- 
ing conductor shall be installed. 

Where flexibility is not required, FMC shall be permit- 
ted to be used as an equipment grounding conductor when 
installed in accordance with 250.118(5) . 

Where required or installed, equipment grounding con- 
ductors shall be installed in accordance with 250.134(B). 

Where required or installed, equipment bonding jump- 
ers shall be installed in accordance with 250.102. 



Table 348.22 Maximum Number of Insulated Conductors in Metric Designator 12 (Trade Size %) Flexible Metal Conduit* 













Types TFN 


THHN, 


Types FEP, FEBP, PF, 




Types RFH-2, SF-2 


Types TF, XHHW, TW 
Fittings Fittings 


THWN 


PGF 




Fittings 


Fittings 


Fittings 


Fittings 


Fittings 


Fittings 




Inside 


Outside 


Inside 


Outside 


Inside 


Outside 


Inside 


Outside 


Size (AWG) 


Conduit 


Conduit 


Conduit 


Conduit 


Conduit 


Conduit 


Conduit 


Conduit 


18 


2 


3 


3 


5 


5 


8 


5 


8 


16 


1 


2 


3 


4 


4 


6 


4 


6 


14 


1 


2 


2 


3 


3 


4 


3 


4 


12 


— 


— 


1 


2 


2 


3 


2 


3 


10 


— 


— 


1 


1 


1 


1 


1 


2 



"In addition, one covered or bare equipment grounding conductor of the same size shall be permitted. 



70-11 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 350 — LIQUIDTIGHT FLEXIBLE METAL CONDUIT: TYPE LFMC 



350.42 



• 



Liqiiidtight Flexible Metal Gonjduit: ^ ^ 

i' I " " l ■::TypetF^c" j..:',. J.^ 1 

I. General 

350.1 Scope. This article covers the use, installation, and 
construction specifications for liquidtight flexible metal 
conduit (LFMC) and associated fittings. 

350.2 Definition. 

Liquidtight Flexible Metal Conduit (LFMC). A raceway 
of circular cross section having an outer liquidtight, non- 
metallic, sunlight-resistant jacket over an inner flexible 
metal core with associated couplings, connectors, and fit- 
tings for the installation of electric conductors. 

350.6 Listing Requirements. LFMC and associated fit- 
tings shall be listed. 

II. Installation 

350.10 Uses Permitted. LFMC shall be permitted to be 
used in exposed or concealed locations as follows: 

(1) Where conditions of installation, operation, or mainte- 
nance require flexibility or protection from liquids, va- 
pors, or solids 

(2) As permitted by 501.10(B), 502.10, 503.10, and 504.20 
and in other hazardous (classified) locations where spe- 
cifically approved, and by 553.7(B) 

(3) For direct burial where listed and marked for the purpose 

350.12 Uses Not Permitted. LFMC shall not be used as 
follows: 

(1) Where subject to physical damage 

(2) Where any combination of ambient and conductor tem- 
perature produces an operating temperature in excess 
of that for which the material is approved 

350.20 Size. 

(A) Minimum. LFMC smaller than metric designator 16 (trade 
size Vi) shall not be used. 

Exception: LFMC of metric designator 12 (trade size Vs) 
shall be permitted as covered in 348.20(A). 

(B) Maximum. The maximum size of LFMC shall be met- 
ric designator 103 (trade size 4). 

FPN: See 300.1(C) for the metric designators and trade 
sizes. These are for identification purposes only and do not 
relate to actual dimensions. 



350.22 Number of Conductors or Cables. 

(A) Metric Designators 16 through 103 (Trade Sizes V2 
through 4). The number of conductors shall not exceed 
that permitted by the percentage fill specified in Table 1, 
Chapter 9. 

Cables shall be permitted to be installed where such use 
is not prohibited by the respective cable articles. The num- 
ber of cables shall not exceed the allowable percentage fifl 
specified in Table 1, Chapter 9. 

(B) Metric Designator 12 (Trade Size Vs). The number of 
conductors shall not exceed that permitted in Table 348.22, 
"Fittings Outside Conduit" columns. 

350.24 Bends — How Made. Bends in conduit shall be so 
made that the conduit will not be damaged and the internal 
diameter of the conduit will not be effectively reduced. 
Bends shall be permitted to be made manually without aux- 
iliary equipment. The radius of the curve to the centerline 
of any bend shall not be less than required in Table 2, 
Chapter 9 using the column "Other Bends." 

350.26 Bends — Number in One Run. There shall not be 
more than the equivalent of four quarter bends (360 degrees 
total) between pull points, for example, conduit bodies and 
boxes. 

350.30 Securing and Supporting. LFMC shall be se- 
curely fastened in place and supported in accordance with 
350.30(A) and (B). 

(A) Securely Fastened. LFMC shall be securely fastened 
in place by an approved means within 300 mm (12 in.) of 
each box, cabinet, conduit body, or other conduit termina- 
tion and shall be supported and secured at intervals not to 
exceed 1.4 m (Wi ft). 

Exception No. 1: Where LFMC is fished. 

Exception No. 2: Lengths not exceeding 900 mm (3 ft) at 
terminals where flexibility is necessary. 

Exception No. 3: Lengths not exceeding L8 m (6 ft) from 
a luminaire (fixture) terminal connection for tap conductors 
to luminaires (lighting fixtures), as permitted in 410.67(C). 

Exception No. 4: Lengths not exceeding 1.8 m (6 ft) from 
the last point where the raceway is securely fastened for 
connections within an accessible ceiling to luminaire(s) 
[lighting fixture(s)] or other equipment. 

(B) Supports. Horizontal runs of LFMC supported by 
openings through framing members at intervals not greater 
than 1.4 m (4'/2 ft) and securely fastened within 300 mm 
(12 in.) of termination points shall be permitted. 

350.42 Couplings and Connectors. Angle connectors 
shall not be used for concealed raceway installations. 



2005 Edition 



NATIONAL ELECTRICAL CODE 



70-189 



350.56 



ARTICLE 352 — RIGID NONMETALLIC CONDUIT: TYPE RNC 



350.56 Splices and Taps. Splices and taps shall be made 
in accordance with 300.15. 

350.60 Grounding and Bonding. Where used to connect 
equipment where flexibihty is required, an equipment ground- 
ing conductor shall be installed. 

Where flexibility is not required, LFMC shall be per- 
mitted to be used as an equipment grounding conductor 
when installed in accordance with 250.118(6). 

Where required or installed, equipment grounding con- 
ductors shall be installed in accordance with 250.134(B). 

Where required or installed, equipment bonding jump- 
ers shall be installed in accordance with 250.102. 

FPN: See 501.30(B), 502.30(B), and 503.30(B) for types 
of equipment grounding conductors. 



III. Construction Specifications 

350.120 MarJiing. LFMC shall be marked according to 
110.21. The trade size and other information required by 
the listing shall also be marked on the conduit. Conduit 
suitable for direct burial shall be so marked. 



ARTICLE 352 
Rigid Nonmetallic Conduit: Type RNC 

I. General 

352.1 Scope. This article covers the use, installation, and 
construction specifications for rigid nonmetallic conduit 
(RNC) and associated fittings. 

352.2 Definition. 

Rigid NonmetalHc Conduit (RNC). A nonmetaUic race- 
way of circular cross section, with integral or associated 
couplings, connectors, and fittings for the installation of 
electrical conductors and cables. 

352.6 Listing Requirements. RNC, factory elbows, and 
associated fittings shall be listed. 

II. Installation 

352.10 Uses Permitted. The use of RNC shall be permit- 
ted in accordance with 352.10(A) through (H). 

FPN: Extreme cold may cause some nonmetallic conduits 
to become brittle and therefore more susceptible to damage 
from physical contact. 

(A) Concealed. RNC shall be permitted in walls, floors, 
and ceilings. 



(B) Corrosive Influences. RNC shall be permitted in lo- 
cations subject to severe corrosive influences as covered in 
300.6 and where subject to chemicals for which the mate- 
rials are specifically approved. 

(C) Cinders. RNC shall be permitted in cinder fill. 

(D) Wet Locations. RNC shall be permitted in portions of 
dairies, laundries, canneries, or other wet locations and in lo- 
cations where walls are frequently washed, the entire conduit 
system including boxes and fittings used therewith shall be 
installed and equipped so as to prevent water from entering the 
conduit. All supports, bolts, straps, screws, and so forth, shall 
be of corrosion-resistant materials or be protected against cor- 
rosion by approved corrosion-resistant materials. 

(E) Dry and Damp Locations. RNC shall be permitted 
for use in dry and damp locations not prohibited by 352.12. 

(F) Exposed. RNC shall be permitted for exposed work 
where not subject to physical damage if identified for 
such use. 

(G) Underground Installations. For underground installa- 
tions, see 300.5 and 300.50. 

FPN: Refer to Article 353 for High Density Polyethylene 
Conduit: Type HOPE. 

(H) Support of Conduit Bodies. Rigid nonmetallic con- 
duit shall be permitted to support nonmetallic conduit bod- 
ies not larger than the largest trade size of an entering 
raceway. These conduit bodies shall not support luminaires 
(fixtures) or other equipment and shall not contain devices 
other than splicing devices as permitted by 110.14(B) and 
314.16(C)(2). 

352.12 Uses Not Permitted. RNC shall not be used under 
the following conditions. 

(A) Hazardous (Classified) Locations. 

(1) In hazardous (classified) locations, except as permitted in 
503.10(A), 504.20, 514.8 Exception No. 2, and 515.8 

(2) In Class I, Division 2 locations, except as permitted in 
501.10(B)(3) 

(B) Support of Luminaires (Fixtures). For the support of 
luminaires (fixtures) or other equipment not described in 
352.10(H). 

(C) Physical Damage. Where subject to physical damage 
unless identified for such use. 

(D) Ambient Temperatures. Where subject to ambient tem- 
peratures in excess of 50°C (122°F) unless listed otherwise. 



• 



• 



70-190 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 352 — RIGID NONMETALLIC CONDUIT: TYPE RNC 



352.60 



(E) Insulation Temperature Limitations. For conductors 
or cables operating at a temperature higher than the RNC 
listed operating temperature rating. 

Exception: Conductors or cables rated at a temperature 
higher than the RNC listed temperature rating shall be 
permitted to be installed in RNC, provided they are not 
operated at a temperature higher than the RNC listed tem- 
perature rating. 

(F) Theaters and Similar Locations. In theaters and simi- 
lar locations, except as provided in 518.4 and 520.5. 

352.20 Size. 

(A) Minimum. RNC smaller than metric designator 16 (trade 
size Vi) shall not be used. 

(B) Maximum. RNC larger than metric designator 155 (trade 
size 6) shall not be used. 

FPN: The trade sizes and metric designators are for iden- 
tification purposes only and do not relate to actual dimen- 
sions. See 300.1(C). 

352.22 Number of Conductors. The number of conduc- 
tors shall not exceed that permitted by the percentage fill 
specified in Table 1, Chapter 9. 

Cables shall be permitted to be installed where such use 
is not prohibited by the respective cable articles. The num- 
ber of cables shall not exceed the allowable percentage fill 
specified in Table 1, Chapter 9. 

352.24 Bends — How Made. Bends shall be so made that 
the conduit will not be damaged and the internal diameter of 
the conduit will not be effectively reduced. Field bends shall 
be made only with bending equipment identified for the pur- 
pose. The radius of the curve to the centerline of such bends 
shall not be less than shown in Table 2, Chapter 9. 

352.26 Bends — Number in One Run. There shall not be 
more than the equivalent of four quarter bends (360 degrees 
total) between pull points, for example, conduit bodies and 
boxes. 

352.28 Trimming. All cut ends shall be trimmed inside 
and outside to remove rough edges. 

352.30 Securing and Supporting. RNC shall be installed 
as a complete system as provided in 300.18 and shall be 
fastened so that movement from thermal expansion or con- 
traction is permitted. RNC shall be securely fastened and 
supported in accordance with 352.30(A) and (B). 

(A) Securely Fastened. RNC shall be securely fastened 
within 900 mm (3 ft) of each outlet box, junction box, 
device box, conduit body, or other conduit termination. 
Conduit listed for securing at other than 900 mm (3 ft) shall 
be permitted to be installed in accordance with the listing. 



(B) Supports. RNC shall be supported as required in 
Table 352.30(B). Conduit listed for support at spacings 
other than as shown in Table 352.30(B) shall be permitted 
to be installed in accordance with the listing. Horizontal 
runs of RNC supported by openings through framing mem- 
bers at intervals not exceeding those in Table 352.30(B) 
and securely fastened within 900 mm (3 ft) of termination 
points shall be permitted. 



Table 352.30(B) Support of Rigid Nonmetallic 
Conduit (RNC) 



Conduit Size 


Maximum Spacing 
Supports 


Between 


Metric 
Designator 


Trade Size 


mm or m 


ft 


16-27 

35-53 

63-78 

91-129 

155 


1/2-1 
11/4-2 

21/2-3 

31/2-5 

6 


900 mm 
1.5 m 
1.8 m 
2.1 m 

2.5 m 


3 
5 
6 
7 
8 



352.44 Expansion Fittings. Expansion fittings for RNC 
shall be provided to compensate for thermal expansion and 
contraction where the length change, in accordance with 
Table 352.44(A) or Table 352.44(B), is expected to be 
6 mm (1/4 in.) or greater in a straight run between securely 
mounted items such as boxes, cabinets, elbows, or other 
conduit terminations. 

352.46 Bushings. Where a conduit enters a box, fitting, or 
other enclosure, a bushing or adapter shall be provided to 
protect the wire from abrasion unless the box, fitting, or 
enclosure design provides equivalent protection. 

FPN: See 300.4(F) for the protection of conductors 4 
AWG and larger at bushings. 

352.48 Joints. All joints between lengths of conduit, and 
between conduit and couplings, fittings, and boxes, shall be 
made by an approved method. 

352.56 Splices and Taps. Splices and taps shall be made 
in accordance with 300.15. 

352.60 Grounding. Where equipment grounding is re- 
quired, a separate equipment grounding conductor shall be 
installed in the conduit. 

Exception No. 1: As permitted in 250.134(B), Exception 
No. 2, for dc circuits and 250. 134(B), Exception No. 1, for 
separately run equipment grounding conductors. 

Exception No. 2: Where the grounded conductor is used to 
ground equipment as permitted in 250. 142. 



2005 Edition 



NATIONAL ELECTRICAL CODE 



70-191 



352.60 



ARTICLE 352 — RIGID NONMETALLIC CONDUIT: TYPE RNC 



Table 352.44(A) Expansion Characteristics of PVC Rigid Nonmetallic Conduit Coefficient 
of Thermal Expansion = 6.084 x 10"^ mm/mm/°C (3.38 x 10"^ in./inV°F) 





Length Change of 




Length Change of 






Temperature 


PVC Conduit 


Temperature 


PVC Conduit 


Temperature 


Length Change of PVC 


Change (°C) 


(mm/m) 


Change (°F) 


(in./100 ft) 


Change (°F) 


Conduit (in./100 ft) 


5 


0.30 


5 


0.20 


105 


4.26 


10 


0.61 


10 


0.41 


110 


4.46 


15 


0.91 


15 


0.61 


115 


4.66 


20 


•■ 1.22 


20 


0.81 


120 


4.87 


25 


■•:.1.52 


25 


1.01 


125 


5.07 


30 


1.83 


30 


1.22 


130 


5.27 


35 


2.13 


35 


1.42 


135 


5.48 


40 


2.43 


40 


1.62 


140 


5.68 


45 


2.74 


45 


1.83 


145 


5.88 


50 


3.04 


50 


2.03 


150 


6.08 


55 


3.35 


55 


2.23 


155 


6.29 


60 


3.65 


60 


2.43 


160 


6.49 


65 


3.95 


65 


2.64 


165 


6.69 


70 


4.26 


70 


2.84 


170 


6.90 


75 


4.56 


75 


3.04 


175 


7.10 


80 


4.87 


80 


3.24 


180 


7.30 


85 


5.17 


85 


3.45 


185 


7.50 


90 


5.48 


90 


3.65 


190 


7.71 


95 


5.78 


95 


3.85 


195 


7.91 


100 


6.08 


100 


4.06 


200 


8.11 



Table 352.44(B) Expansion Characteristics of Reinforced TNri-mosetting Resin Conduit 
(RTRC) Coefficient of Thermal Expansion = 2.7 x 10"^ mm/mm/°C (1.5 x 10"^ in./in./°F) 





Length Change of 




Length Change of 




Length Change of 


Temperature 


RTRC Conduit 


Temperature 


RTRC Conduit 


Temperature 


RTRC Conduit 


Change (°C) 


(mm/m) 


Change (°F) 


(in./100 ft) 


Change (°F) 


(in./100 ft) 


5 


0.14 


5 


0.09 


105 


1.89 


10 


0.27 


10 


0.18 


110 


1.98 


15 


0.41 


15 


0.27 


115 


2.07 


20 


0.54 


20 


0.36 


120 


2.16 


25 


0.68 


25 


0.45 


125 


2.25 


30 


0.81 


30 


0.54 


130 


2.34 


35 


0.95 


35 


0.63 


135 


2.43 


40 


1.08 


40 


0.72 


140 


2.52 


45 


1.22 


45 


0.81 


145 


2.61 


50 


1.35 


50 


0.90 


150 


2.70 


55 


1.49 


55 


0.99 


155 


2.79 


60 


1.62 


60 


1.08 


160 


2.88 


65 


1.76 


65 


1.17 


165 


2.97 


70 


1.89 


70 


1.26 


170 


3.06 


75 


2.03 


75 


1.35 


175 


3.15 


80 


2.16 


80 


1.44 


180 


3.24 


85 


2.30 


85 


1.53 


185 


3.33 


90 


2.43 


90 


1.62 


190 


3.42 


95 


2.57 


95 


1.71 


195 


3.51 


100 


2.70 


100 


1.80 


200 


3.60 



70-192 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 353 — HIGH DENSITY POLYETHYLENE CONDUIT: TYPE HDPE CONDUIT 



353.24 



• 



• 



• 



III. Construction Specifications 

352.100 Construction. RNC and fittings shall be com- 
posed of suitable nonmetallic material that is resistant to 
moisture and chemical atmospheres. For use above ground, 
it shall also be flame retardant, resistant to impact and 
crushing, resistant to distortion from heat under conditions 
likely to be encountered in service, and resistant to low 
temperature and sunlight effects. For use underground, the 
material shall be acceptably resistant to moisture and cor- 
rosive agents and shall be of sufficient strength to withstand 
abuse, such as by impact and crushing, in handling and 
during installation. Where intended for direct burial, with- 
out encasement in concrete, the material shall also be ca- 
pable of withstanding continued loading that is likely to be 
encountered after installation. 

352.120 Marking. Each length of RNC shall be clearly 
and durably marked at least every 3 m (10 ft) as required in 
the first sentence of 110.21. The type of material shall also 
be included in the marking unless it is visually identifiable. 
For conduit recognized for use above ground, these mark- 
ings shall be permanent. For conduit limited to under- 
ground use only, these markings shall be sufficiently du- 
rable to remain legible until the material is installed. 
Conduit shall be permitted to be surface marked to indicate 
special characteristics of the material. 

FPN: Examples of these markings include but are not 
limited to "limited smoke" and "sunlight resistant." 



ARTICLE 353 

High Density Polyethylene Conduit: 

Type HDPE Conduit 

I. General 

353.1 Scope. This article covers the use, installation, and 
construction specifications for high density polyethylene 
(HDPE) conduit and associated fittings. 

353.2 Definition. 

High Density Polyethylene (HDPE) Conduit A nonmetaUic 
raceway of circular cross section, with associated couplings, 
connectors, and fittings for the installation of electrical con- 
ductors. 

353.6 Listing Requirements. HDPE conduit and associ- 
ated fittings shall be listed. 

n. Installation 

353.10 Uses Permitted. The use of HDPE conduit shall be 

permitted under the following conditions: 

(1) In discrete lengths or in continuous lengths from a reel 



(2) In locations subject to severe corrosive influences as 
covered in 300.6 and where subject to chemicals for 
which the conduit is listed 

(3) In cinder fill 

(4) In direct burial installations in earth or concrete 

FPN to (4): Refer to 300.5 and 300.50 for underground 
installations. 

353.12 Uses Not Permitted. HDPE conduit shall not be 
used under the following conditions: 

(1) Where exposed 

(2) Within a building 

(3) In hazardous (classified) locations, except as permitted 
in 504.20 

(4) Where subject to ambient temperatures in excess of 
50°C (122°F) unless listed otherwise 

(5) For conductors or cables operating at a temperature higher 
than the HDPE conduit Usted operating temperature rating 

Exception: Conductors or cables rated at a temperature 
higher than the HDPE conduit listed temperature rating 
shall be permitted to be installed in HDPE conduit, pro- 
vided they are not operated at a temperature higher than 
the HDPE conduit listed temperature rating. 

353.20 Size. 

(A) Minimum. HDPE conduit smaller than metric desig- 
nator 16 (trade size Vt) shall not be used. 

(B) Maximum. HDPE conduit larger than metric designa- 
tor 103 (trade size 4) shall not be used. 

FPN: The trade sizes and metric designators are for iden- 
tification purposes only and do not relate to actual dimen- 
sions. See 300.1(C). 

353.22 Number of Conductors. The number of conduc- 
tors shall not exceed that permitted by the percentage fill 
specified in Table 1, Chapter 9. 

Cables shall be permitted to be installed where such use 
is not prohibited by the respective cable articles. The num- 
ber of cables shall not exceed the allowable percentage fill 
specified in Table 1, Chapter 9. 

353.24 Bends — How Made. Bends shall be so made 
that the conduit will not be damaged and the internal 
diameter of the conduit will not be effectively reduced. 
Bends shall be permitted to be made manually without 
auxiliary equipment, and the radius of the curve to the 
centerline of such bends shall not be less than shown in 
Table 354.24. 



2005 Edition NATIONAL ELECTRICAL CODE 



70-193 



353.26 



ARTICLE 354 — NONMETALLIC UNDERGROUND CONDUIT WITH CONDUCTORS: TYPE NUCC 



353.26 Bends — Number in One Run. There shall not be 
more than the equivalent of four quarter bends (360 degrees 
total) between pull points, for example, conduit bodies and 
boxes. 

353.28 Trimming. All cut ends shall be trimmed inside and 
outside to remove rough edges. 

353.46 Bushings. Where a conduit enters a box, fitting, or 
other enclosure, a bushing or adapter shall be provided to 
protect the wire from abrasion unless the box, fitting, or 
enclosure design provides equivalent protection. 

FPN: See 300.4(F) for the protection of conductors 4 
AWG and larger at bushings. 

353.48 Joints. All joints between lengths of conduit, and 
between conduit and couplings, fittings, and boxes, shall be 
made by an approved method. 

353.56 Splices and Taps. Splices and taps shall be made 
in accordance with 300.15. 

353.60 Grounding. Where equipment grounding is re- 
quired, a separate equipment grounding conductor shall be 
installed in the conduit. 

Exception No. 1: The equipment grounding conductor 
shall be permitted to be run separately from the conduit 
where used for grounding dc circuits as permitted in 
250.134, Exception No. 2. 

Exception No. 2: The equipment grounding conductor 
shall not be required where the grounded conductor is used 
to ground equipment as permitted in 250.142. 

III. Construction Specifications 

353.100 Construction. HDPE conduit shall be composed 
of high density polyethylene that is resistant to moisture 
and chemical atmospheres. The material shall be resis- 
tant to moisture and corrosive agents and shall be of 
suflBcient strength to withstand abuse, such as by impact 
and crushing, in handling and during installation. Where 
intended for direct burial, without encasement in con- 
crete, the material shall also be capable of withstanding 
continued loading that is likely to be encountered after 
installation. 

353.120 Marking. Each length of HDPE shall be clearly and 
durably marked at least every 3 m (10 ft) as required in 
110.21. The type of material shall also be included in the 
marking. 









I. General 



354.1 Scope. This article covers the use, installation, and 
construction specifications for nonmetallic underground 
conduit with conductors (NUCC). 

354.2 Definition. 

Nonmetallic Underground Conduit with Conductors 

(NUCC). A factory assembly of conductors or cables inside a 
nonmetalUc, smooth wall conduit with a circular cross section. 

354.6 Listing Requirements. NUCC and associated fit- 
tings shall be listed. 

II. Installation 

354.10 Uses Permitted. The use of NUCC and fittings 
shall be permitted in the following: 

(1) For direct burial underground installation (For mini- 
mum cover requirements, see Table 300.5 and Table 
300.50 under Rigid Nonmetallic Conduit.) 

(2) Encased or embedded in concrete 

(3) In cinder fill 

(4) In underground locations subject to severe corrosive influ- 
ences as covered in 300.6 and where subject to chemicals 
for which the assembly is specifically approved 

354.12 Uses Not Permitted. NUCC shall not be used in 
the following: 

(1) In exposed locations 

(2) Inside buildings 

Exception: The conductor or the cable portion of the assem- 
bly, where suitable, shall be permitted to extend within the 
building for termination purposes in accordance with 300.3. 

(3) In hazardous (classified) locations except as permitted 
by 503.10(A), 504.20, 514.8, and 515.8, and in Class I, 
Division 2 locations as permitted in 501.10(B)(3) 

354.20 Size. 

(A) Minimum. NUCC smaller than metric designator 16 (trade 
size Vj) shall not be used. 

(B) Maximum. NUCC larger than metric designator 103 (trade 
size 4) shall not be used. 

FPN: See 300.1(C) for the metric designators and trade 
sizes. These are for identification purposes only and do not 
relate to actual dimensions. 



• 



• 



# 



70-194 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 356 — LIQUIDTIGHT FLEXIBLE NONMETALLIC CONDUIT: TYPE LFNC 



356.2 



• 



354.22 Number of Conductors. The number of conduc- 
tors or cables shall not exceed that permitted by the per- 
centage fill in Table 1, Chapter 9. 

354.24 Bends — How Made. Bends shall be manually 
made so that the conduit will not be damaged and the in- 
ternal diameter of the conduit will not be effectively re- 
duced. The radius of the curve of the centerline of such 
bends shall not be less than shown in Table 354.24. 



Table 354.24 Minimum Bending Radius for Nonmetallic 
Underground Conduit with Conductors (NUCC) 







Minimum 


Bending 


Conduit Size 




Radius 




Metric 












Designator 


Trade Size 


mm 






in. 


16 


'/. 


250 






10 


21 


% 


300 






12 


27 


1 


350 






14 


35 


l'/4 


450 






18 


41 


l'/2 


500 






20 


53 


2 


650 






26 


63 


21/2 


900 






36 


78 


3 


1200 






48 


103 


4 


1500 






60 



354.26 Bends — Number in One Run. There shall not be 
more than the equivalent of four quarter bends (360 degrees 
total) between termination points. 

354.28 Trimming. For termination, the conduit shall be 
trimmed away from the conductors or cables using an ap- 
proved method that will not damage the conductor or cable 
insulation or jacket. All conduit ends shall be trimmed in- 
side and out to remove rough edges. 

354.46 Bushings. Where the NUCC enters a box, fitting, or 
other enclosure, a bushing or adapter shall be provided to 
protect the conductor or cable from abrasion unless the design 
of the box, fitting, or enclosure provides equivalent protection. 

FPN: See 300.4(F) for the protection of conductors size 
4 AWG or larger. 

354.48 Joints. All joints between conduit, fittings, and 
boxes shall be made by an approved method. 

354.50 Conductor Terminations. All terminations between 
the conductors or cables and equipment shall be made by an 
approved method for that type of conductor or cable. 

354.56 Splices and Taps. Splices and taps shall be made 
in junction boxes or other enclosures. 



354.60 Grounding. Where equipment grounding is required, 
an assembly containing a separate equipment grounding con- 
ductor shall be used. 

III. Construction Specifications 
354.100 Construction. 

(A) General. NUCC is an assembly that is provided in 
continuous lengths shipped in a coil, reel, or carton. 

(B) Nonmetallic Underground Conduit. The nonmetallic 
underground conduit shall be Usted and composed of a mate- 
rial that is resistant to moisture and corrosive agents. It shall 
also be capable of being suppUed on reels without damage or 
distortion and shall be of sufficient strength to withstand 
abuse, such as impact or crushing, in handUng and during 
installation without damage to conduit or conductors. 

(C) Conductors and Cables. Conductors and cables used 
in NUCC shall be listed and shall comply with 310.8(C). 
Conductors of different systems shall be installed in accor- 
dance with 300.3(C). 

(D) Conductor Fill. The maximum number of conductors 
or cables in NUCC shall not exceed that permitted by the 
percentage fill in Table 1, Chapter 9. 

354.120 Marking. NUCC shall be clearly and durably 
marked at least every 3.05 m (10 ft) as required by 110.21. 
The type of conduit material shall also be included in the 
marking. 

Identification of conductors or cables used in the assem- 
bly shall be provided on a tag attached to each end of the 
assembly or to the side of a reel. Enclosed conductors or 
cables shall be marked in accordance with 310.11. 



'p H Uiquidtight: Flexible Nonmetallic 
AS:.-'r^:- :;;C9iidiiit:;:iype LFNC . 

I. General 

356.1 Scope. This article covers the use, installation, and 
construction specifications for liquidtight flexible nonme- 
tallic conduit (LFNC) and associated fittings. 

356.2 Definition. 

Liquidtight Flexible Nonmetallic Conduit (LFNC). A race- 
way of circular cross section of various types as follows: 
(1) A smooth seamless inner core and cover bonded together 
and having one or more reinforcement layers between the 
core and covers, designated as Type LFNC-A 



2005 Edition NATIONAL ELECTRICAL CODE 



70-195 



356.6 



ARTICLE 356 — LIQUIDTIGHT FLEXIBLE NONMETALLIC CONDUIT: TYPE LFNC 



(2) A smooth inner surface with integral reinforcement 
within the conduit wall, designated as Type LFNC-B 

(3) A corrugated internal and external surface without integral 
reinforcement within the conduit wall, designated as 
LFNC-C 

LFNC is flame resistant and with fittings and is ap- 
proved for the installation of electrical conductors. 

FPN: FNMC is an alternative designation for LFNC. 

356.6 Listing Requirements. LFNC and associated fit- 
tings shall be fisted. 

n. Installation 

356.10 Uses Permitted. LFNC shall be permitted to be 
used in exposed or concealed locations for the following 
purposes: 

FPN: Extreme cold may cause some types of nonmetallic 
conduits to become brittle and therefore more susceptible to 
damage from physical contact. 

(1) Where flexibility is required for installation, operation, 
or maintenance 

(2) Where protection of the contained conductors is re- 
quired from vapors, liquids, or solids 

(3) For outdoor locations where listed and marked as suit- 
able for the purpose 

(4) For direct burial where listed and marked for the purpose 

(5) Type LFNC-B shafi be permitted to be instaUed in 
lengths longer than 1.8 m (6 ft) where secured in ac- 
cordance with 356.30 

(6) Type LFNC-B as a listed manufactured prewired as- 
sembly, metric designator 16 through 27 (trade size V2 
through 1) conduit 

356.12 Uses Not Permitted. LFNC shafi not be used as 
follows: 

(1) Where subject to physical damage 

(2) Where any combination of ambient and conductor tem- 
peratures is in excess of that for which the LFNC is 
approved 

(3) In lengths longer than 1.8 m (6 ft), except as permitted 
by 356.10(5) or where a longer length is approved as 
essential for a required degree of flexibility 

(4) Where the operating voltage of the contained conduc- 
tors is in excess of 600 volts, nominal, except as per- 
mitted in 600.32(A) 

(5) hi any hazardous (classified) location other than as per- 
mitted in 50L 10(B), 502.10(A) and (B), 503.10(A), and 
504.20 



356.20 Size. 

(A) Minimum. LFNC smaller than metric designator 16 (trade 
size V2) shall not be used unless permitted in 356.20(A)(1) 
through (A)(3) for metric designator 12 (trade size Vs). 

(1) For enclosing the leads of motors as permitted in 
430.245(B) 

(2) In lengths not exceeding 1.8 m (6 ft ) as part of a listed 
assembly for tap connections to luminaires (lighting 
fixtures) as required in 410.67(C), or for utilization 
equipment 

(3) For electric sign conductors in accordance with 600.32(A) 

(B) Maximum. LFNC larger than metric designator 103 (trade 
size 4) shall not be used. 

FPN: See 300.1(C) for the metric designators and trade 
sizes. These are for identification purposes only and do not 
relate to actual dimensions. 

356.22 Number of Conductors. The number of conduc- 
tors shall not exceed that permitted by the percentage fill 
specified in Table 1, Chapter 9. 

Cables shall be permitted to be installed where such use 
is not prohibited by the respective cable articles. The num- 
ber of cables shall not exceed the allowable percentage fill 
specified in Table 1, Chapter 9. 

356.24 Bends — How Made. Bends in conduit shall be so 
made that the conduit is not damaged and the internal di- 
ameter of the conduit is not efifectively reduced. Bends shall 
be permitted to be made manually without auxiliary equip- 
ment. The radius of the curve to the centerline of any bend 
shall not be less than shown in Table 2, Chapter 9 using the 
column "Other Bends." 

356.26 Bends — Number in One Run. There shall not be 
more than the equivalent of four quarter bends (360 degrees 
total) between pull points, for example, conduit bodies and 
boxes. 

356.28 Trimming. All cut ends of conduit shall be 
trimmed inside and outside to remove rough edges. 

356.30 Securing and Supporting. Type LFNC-B shall be 
securely fastened and supported in accordance with one of 
the following: 

(1) Where installed in lengths exceeding 1.8 m (6 ft), the 
conduit shall be securely fastened at intervals not exceed- 
ing 900 mm (3 ft) and within 300 mm (12 in.) on each 
side of every outlet box, junction box, cabinet, or fitting. 

(2) Securing or supporting of the conduit shall not be re- 
quired where it is fished, installed in lengths not ex- 
ceeding 900 mm (3 ft) at terminals where flexibility is 
required, or installed in lengths not exceeding 1.8 m 
(6 ft) from a luminaire (fixture) terminal connection for 
tap conductors to luminaires (fighting fixtures) permit- 
ted in 410.67(C). 



• 



70-196 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 358 — ELECTRICAL METALLIC TUBING: TYPE EMT 



358.12 



(3) Horizontal runs of LFNC supported by openings through 
framing members at intervals not exceeding 900 mm 
(3 ft) and securely fastened within 300 mm (12 in.) of 
termination points shall be permitted. 

(4) Securing or supporting of LFNC-B shall not be required 
where installed in lengths not exceeding 1.8 m (6 ft) from 
the last point where the raceway is securely fastened for 
connections within an accessible ceiling to luminaire(s) 
[lighting fixture(s)] or other equipment. 

356.42 Couplings and Connectors. Only fittings listed for 
use with LFNC shall be used. Angle connectors shall not be 
used for concealed raceway installations. Straight LFNC 
fittings are permitted for direct burial or encasement in 
concrete. 

356.56 Splices and Taps. Splices and taps shall be made 
in accordance with 300.15. 

356.60 Grounding and Bonding. Where used to connect 
equipment where flexibility is required, an equipment 
grounding conductor shall be installed. 

Where required or installed, equipment grounding con- 
ductors shall be installed in accordance with 250.134(B). 

Where required or installed, equipment bonding jump- 
ers shall be installed in accordance with 250.102. 

III. Construction Specifications 

356.100 Construction. LFNC-B as a prewired manufactured 
assembly shall be provided in continuous lengths capable of 
being shipped in a coil, reel, or carton without damage. 

356.120 Marking. LFNC shall be marked at least every 
600 mm (2 ft) in accordance with 110.21. The marking 
shall include a type designation in accordance with 356.2 
and the trade size. Conduit that is intended for outdoor use 
or direct burial shall be marked. 

The type, size, and quantity of conductors used in 
prewired manufactured assemblies shall be identified by 
means of a printed tag or label attached to each end of the 
manufactured assembly and either the carton, coil, or reel. 
The enclosed conductors shall be marked in accordance 
with 310.11. 









I. General 

358.1 Scope. This article covers the use, installation, and 
construction specifications for electrical metallic tubing 
(EMT) and associated fittings. 



358.2 Definition. 

Electrical Metallic T\ibing (EMT). An unthreaded thin- 
wall raceway of circular cross section designed for the 
physical protection and routing of conductors and cables 
and for use as an equipment grounding conductor when 
installed utilizing appropriate fittings. EMT is generally 
made of steel (ferrous) with protective coatings or alumi- 
num (nonferrous). 

358.6 Listing Requirements. EMT, factory elbows, and 
associated fittings shall be fisted. 

II. Installation 
358.10 Uses Permitted. 

(A) Exposed and Concealed. The use of EMT shall be 
permitted for both exposed and concealed work. 

(B) Corrosion Protection. Ferrous or nonferrous EMT, el- 
bows, couplings, and fittings shall be permitted to be installed 
in concrete, in direct contact with the earth, or in areas subject 
to severe corrosive influences where protected by corrosion 
protection and judged suitable for the condition. 

(C) Wet Locations. All supports, bolts, straps, screws, and 
so forth shall be of corrosion-resistant materials or pro- 
tected against corrosion by corrosion-resistant materials. 

FPN: See 300.6 for protection against corrosion. 

358.12 Uses Not Permitted. EMT shall not be used under 
the following conditions: 

(1) Where, during installation or afterward, it will be sub- 
ject to severe physical damage 

(2) Where protected from corrosion solely by enamel 

(3) In cinder concrete or cinder fill where subject to per- 
manent moisture unless protected on all sides by a 
layer of noncinder concrete at least 50 mm (2 in.) thick 
or unless the tubing is at least 450 nun (18 in.) under 
the fill 

(4) In any hazardous (classified) location except as permit- 
ted by 502.10, 503.10, and 504.20 

(5) For the support of luminaires (fixtures) or other equip- 
ment except conduit bodies no larger than the largest 
trade size of the tubing 

(6) Where practicable, dissimilar metals in contact any- 
where in the system shall be avoided to eliminate the 
possibihty of galvanic action 

Exception: Aluminum fittings and enclosures shall be per- 
mitted to be used with steel EMT where not subject to 
severe corrosive influences. 



2005 Edition NATIONAL ELECTRICAL CODE 



70-197 



358.20 



ARTICLE 360 — FLEXIBLE METALLIC TUBING: TYPE FMT 



358.20 Size. 

(A) Minimum. EMT smaller than metric designator 16 (trade 
size V2) shall not be used. 

Exception: For enclosing the leads of motors as permitted 
in 430.245(B). 

(B) Maximum. The maximum size of EMT shall be metric 
designator 103 (trade size 4). 

FPN: See 300.1(C) for the metric designators and trade 
sizes. These are for identification purposes only and do not 
relate to actual dimensions. 

358.22 Number of Conductors. The number of conduc- 
tors shall not exceed that permitted by the percentage fill 
specified in Table 1, Chapter 9. 

Cables shall be permitted to be installed where such use 
is not prohibited by the respective cable articles. The num- 
ber of cables shall not exceed the allowable percentage fill 
specified in Table 1, Chapter 9. 

358.24 Bends — How Made. Bends shall be made so that 
the tubing is not damaged and the internal diameter of the 
tubing is not effectively reduced. The radius of the curve of 
any field bend to the centerline of the tubing shall not be 
less than shown in Table 2, Chapter 9 for one-shot and full 
shoe benders. 

358.26 Bends — Number in One Run. There shall not be 
more than the equivalent of four quarter bends (360 degrees 
total) between pull points, for example, conduit bodies and 
boxes. 

358.28 Reaming and Threading. 

(A) Reaming. All cut ends of EMT shall be reamed or 
otherwise finished to remove rough edges. 

(B) Threading. EMT shall not be threaded. 

Exception: EMT with factory threaded integral couplings 
complying with 358.100. 

358.30 Securing and Supporting. EMT shall be installed 
as a complete system in accordance with 300.18 and shall 
be securely fastened in place and supported in accordance 
with 358.30(A) and (B). 

(A) Securely Fastened. EMT shall be securely fastened in 
place at least every 3 m (10 ft). In addition, each EMT run 
between termination points shall be securely fastened within 
900 mm (3 ft) of each outlet box, junction box, device box, 
cabinet, conduit body, or other tubing termination. 

Exception No. 1: Fastening of unbroken lengths shall be 
permitted to be increased to a distance of 1.5 m (5 ft) where 
structural members do not readily permit fastening within 
900 mm (3 ft). 



Exception No. 2: For concealed work in finished buildings 
or prefinished wall panels where such securing is imprac- 
ticable, unbroken lengths (without coupling) of EMT shall 
be permitted to be fished. 

(B) Supports. Horizontal runs of EMT supported by open- 
ings through framing members at intervals not greater than 
3 m (10 ft) and securely fastened within 900 mm (3 ft) of 
termination points shall be permitted. 

358.42 Couplings and Connectors. Couplings and connec- 
tors used with EMT shall be made up tight. Where buried in 
masonry or concrete, they shall be concretetight type. Where 
installed in wet locations, they shall comply with 314.15(A). 

358.56 Splices and Taps. Splices and taps shall be made 
in accordance with 300.15. 

358.60 Grounding. EMT shall be permitted as an equip- 
ment grounding conductor. 

III. Construction Specifications 

358.100 Construction. Factory-threaded integral couplings 
shall be permitted. Where EMT with a threaded integral cou- 
pling is used, threads for both the tubing and coupling shall be 
factory-made. The coupling and EMT threads shall be de- 
signed so as to prevent bending of the tubing at any part of the 
thread. 

358.120 Marking. EMT shall be clearly and durably marked 
at least every 3 m (10 ft) as required in the first sentence of 
110.21. 



ARTICLE 360 
Flexible Metallic Tubing; Type FMT 

I. General 

360.1 Scope. This article covers the use, installation, and 
construction specifications for flexible metallic tubing 
(FMT) and associated fittings. 

360.2 Definition. 

Flexible Metallic T\ibing (FMT). A raceway that is circu- 
lar in cross section, flexible, metallic, and liquidtight with- 
out a nonmetallic jacket. 

360.6 Listing Requirements. FMT and associated fittings 
shall be listed. 



70-198 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 360 — FLEXIBLE METALLIC TUBING: TYPE FMT 



360.120 



• 



II. Installation 

360.10 Uses Permitted. FMT shall be permitted to be used 
for branch circuits as follows: 

(1) In dry locations 

(2) Where concealed 

(3) In accessible locations 

(4) For system voltages of 1000 volts maximum 

360.12 Uses Not Permitted. FMT shall not be used as 
follows: 

(1) In hoist ways 

(2) In storage battery rooms 

(3) In hazardous (classified) locations unless otherwise 
permitted under other articles in this Code 

(4) Under ground for direct earth burial, or embedded in 
poured concrete or aggregate 

(5) Where subject to physical damage 

(6) In lengths over 1.8 m (6 ft) 

360.20 Size. 

(A) Minimum. FMT smaller than metric designator 16 (trade 
size V2) shaU not be used. 

Exception No. 1: FMT of metric designator 12 (trade size 
Vs) shall be permitted to be installed in accordance with 
300.22(B) and (C). 

Exception No. 2: FMT of metric designator 12 (trade size 
Vs) shall be permitted in lengths not in excess of 1.8 m (6 ft) 
as part of an approved assembly or for luminaires (lighting 
fixtures). See 410.67(C). 

(B) Maximum. The maximum size of FMT shall be metric 
designator 21 (trade size %). 

FPN: See 300.1(C) for the metric designators and trade 
sizes. These are for identification purposes only and do not 
relate to actual dimensions. 



(B) FMT — Metric Designator 12 (Trade Size ^/s). The 
number of conductors in metric designator 12 (trade size 
Ys) shall not exceed that permitted in Table 348.22. 

360.24 Bends. 

(A) Infrequent Flexing Use. Where FMT may be infre- 
quently flexed in service after installation, the radii of 
bends measured to the inside of the bend shall not be less 
than specified in Table 360.24(A). 

Table 360.24(A) Minimum Radii for Flexing Use 

Minimum Radii for Flexing 
Use 

Metric 

Designator Trade Size 



mm 



m. 



12 


3/8 


25.4 


10 


16 


1/2 


317.5 


12^/2 


21 


3/4 


444.5 


17 '/2 



(B) Fixed Bends. Where FMT is bent for installation pur- 
poses and is not flexed or bent as required by use after 
installation, the radii of bends measured to the inside of the 
bend shall not be less than specified in Table 360.24(B). 

Table 360.24(B) Minimum Radii for Fixed Bends 

Minimum Radii for Fixed 
Bends 



Metric 
Designator 



Trade Size 



mm 



m. 



12 


3/8 


88.9 


3'/2 


16 


1/2 


101.6 


4 


21 


3/4 


127.0 


5 



360.40 Boxes and Fittings. Fittings shall effectively close 
any openings in the connection. 



360.22 Number of Conductors. 

(A) FMT — Metric Designators 16 and 21 (Trade Sizes 

V2 and %). The number of conductors in metric designators 
16 (trade size V2) and 21 (trade size Va) shall not exceed 
that permitted by the percentage fill specified in Table 1, 
Chapter 9. 

Cables shall be permitted to be installed where such use 
is not prohibited by the respective cable articles. The num- 
ber of cables shall not exceed the allowable percentage fill 
specified in Table 1, Chapter 9. 



360.56 Splices and Taps. Splices and taps shall be made 
in accordance with 300.15. 

360.60 Grounding. FMT shall be permitted as an equip- 
ment grounding conductor where installed in accordance 
with 250.118(7). 



III. Construction Specifications 

360.120 Marking. FMT shall be marked according to 
110.21. 



2005 Edition 



NATIONAL ELECTRICAL CODE 



70-199 



362.1 



ARTICLE 362 — ELECTRICAL NONMETALLIC TUBING: TYPE ENT 



ARTICLE 362 

Electrical Nonmetallic Ttibing: 

Type ENT 



I. General 

362.1 Scope. This article covers the use, installation, and 
construction specifications for electrical nonmetallic tubing 
(ENT) and associated fittings. 

362.2 Definition. 

Electrical Nonmetallic TVibing (ENT). A nonmetallic pli- 
able corrugated raceway of circular cross section with inte- 
gral or associated couplings, connectors, and fittings for the 
installation of electric conductors. ENT is composed of a 
material that is resistant to moisture and chemical atmo- 
spheres and is flame retardant. 

A pliable raceway is a raceway that can be bent by hand 
with a reasonable force but without other assistance. 

362.6 Listing Requirements. ENT and associated fittings 
shall be listed. 



II. Installation 

362.10 Uses Permitted. For the purpose of this article, the 
first floor of a building shall be that floor that has 50 per- 
cent or more of the exterior wall surface area level with or 
above finished grade. One additional level that is the first 
level and not designed for human habitation and used only 
for vehicle parking, storage, or similar use shall be permit- 
ted. The use of ENT and fittings shall be permitted in the 
following: 

(1) In any building not exceeding three floors above grade 
as follows: 

a. For exposed work, where not prohibited by 362.12 

b. Concealed within walls, floors, and ceilings 

(2) In any building exceeding three floors above grade, 
ENT shall be concealed within walls, floors, and ceilings 
where the walls, floors, and ceilings provide a thermal 
barrier of material that has at least a 15-minute finish 
rating as identified in listings of fire-rated assemblies. The 
15-minute-finish-rated thermal barrier shall be permitted 
to be used for combustible or noncombustible walls, 
floors, and ceiUngs. 

Exception to (2): Where a fire sprinkler system(s) is in- 
stalled in accordance with NFPA 13-2002, Standard for the 
Installation of Sprinkler Systems, on all floors, ENT shall 
be permitted to be used within walls, floors, and ceilings, 
exposed or concealed, in buildings exceeding three floors 
above grade. 



FPN: A finish rating is established for assemblies contain- 
ing combustible (wood) supports. The finish rating is de- 
fined as the time at which the wood stud or wood joist 
reaches an average temperature rise of 121°C (250°F) or an 
individual temperature of 163°C (325°F) as measured on 
the plane of the wood nearest the fire. A finish rating is not 
intended to represent a rating for a membrane ceiling. 

(3) In locations subject to severe corrosive influences as 
covered in 300.6 and where subject to chemicals for 
which the materials are specifically approved. 

(4) In concealed, dry, and damp locations not prohibited by 
362.12. 

(5) Above suspended ceiUngs where the suspended ceilings 
provide a thermal barrier of material that has at least a 
15-minute finish rating as identified in hstings of fire-rated 
assemblies, except as permitted in 362.10(l)(a). 

Exception to (5): ENT shall be permitted to be used above 
suspended ceilings in buildings exceeding three floors above 
grade where the building is protected throughout by a fire 
sprinkler system installed in accordance with NFPA 13-2002, 
Standard for the Installation of Sprinkler Systems. 

(6) Encased in poured concrete, or embedded in a concrete 
slab on grade where ENT is placed on sand or ap- 
proved screenings, provided fittings identified for this 
purpose are used for connections. 

(7) For wet locations indoors as permitted in this section or 
in a concrete slab on or below grade, with fittings listed 
for the purpose. 

(8) Metric designator 16 through 27 (trade size Vi through 1) 
as Usted manufactured prewired assembly. 

FPN: Extreme cold may cause some types of nonmetallic 
conduits to become brittle and therefore more susceptible to 
damage from physical contact. 

362.12 Uses Not Permitted. ENT shall not be used in the 
following: 

(1) In hazardous (classified) locations, except as permit- 
ted by 504.20 and 505.15(A)(1) 

(2) For the support of luminaires (fixtures) and other 
equipment 

(3) Where subject to ambient temperatures in excess of 
50°C (122°F) unless listed otherwise 

(4) For conductors or cables operating at a temperature 
higher than the ENT listed temperature rating 

Exception to (4): Conductors or cables rated at a tempera- 
ture higher than the ENT listed temperature rating shall be 
permitted to be installed in ENT, provided they are not 
operated at a temperature higher than the ENT listed tem- 
perature rating. 

(5) For direct earth burial 

(6) Where the voltage is over 600 volts 



70-200 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 362 — ELECTRICAL NONMETALLIC TUBING: TYPE ENT 



362.120 



• 



(7) In exposed locations, except as permitted by 362.10(1), 
362.10(5), and 362.10(7) 

(8) In theaters and similar locations, except as provided in 
518.4 and 520.5 

(9) Where exposed to the direct rays of the sun, unless 
identified as sunlight resistant 

(10) Where subject to physical damage 

362.20 Size. 

(A) Minimum. ENT smaller than metric designator 16 (trade 
size Vi) shall not be used. 

(B) Maximum. ENT larger than metric designator 53 (trade 
size 2) shall not be used. 

FPN: See 300.1(C) for the metric designators and trade 
sizes. These are for identification purposes only and do not 
relate to actual dimensions. 

362.22 Number of Conductors. The number of conduc- 
tors shall not exceed that permitted by the percentage fill in 
Table 1, Chapter 9. 

Cables shall be permitted to be installed where such use 
is not prohibited by the respective cable articles. The num- 
ber of cables shall not exceed the allowable percentage fill 
specified in Table 1, Chapter 9. 

362.24 Bends — How Made. Bends shall be so made that 
the tubing will not be damaged and the internal diameter of 
the tubing will not be effectively reduced. Bends shall be 
permitted to be made manually without auxihary equip- 
ment, and the radius of the curve to the centerline of such 
bends shall not be less than shown in Table 2, Chapter 9 
using the column "Other Bends." 

362.26 Bends — Number in One Run. There shall not be 
more than the equivalent of four quarter bends (360 degrees 
total) between pull points, for example, conduit bodies and 
boxes. 

362.28 Trimming. All cut ends shall be trimmed inside 
and outside to remove rough edges. 

362.30 Securing and Supporting. ENT shall be installed 
as a complete system in accordance with 300.18 and shall 
be securely fastened in place and supported in accordance 
with 362.30(A) and (B). 

(A) Securely Fastened. ENT shall be securely fastened at 
intervals not exceeding 900 mm (3 ft). In addition, ENT 
shall be securely fastened in place within 900 mm (3 ft) of 
each outlet box, device box, junction box, cabinet, or fitting 
where it terminates. 

Exception No. 1: Lengths not exceeding a distance of 1.8 m 
(6 ft) from a luminaire (fixture) terminal connection for tap 
connections to lighting luminaires (fixtures) shall be permitted 
without being secured. 



Exception No. 2: Lengths not exceeding L8 m (6 ft) from 
the last point where the raceway is securely fastened for 
connections within an accessible ceiling to luminaire(s) 
[lighting fixture(s)] or other equipment. 

(B) Supports. Horizontal runs of ENT supported by open- 
ings in framing members at intervals not exceeding 900 mm 
(3 ft) and securely fastened within 900 mm (3 ft) of termina- 
tion points shall be permitted. 

362.46 Bushings. Where a tubing enters a box, fitting, or 
other enclosure, a bushing or adapter shall be provided to 
protect the wire from abrasion unless the box, fitting, or 
enclosure design provides equivalent protection. 

FPN: See 300.4(F) for the protecUon of conductors size 4 
AWG or larger. 

362.48 Joints. All joints between lengths of tubing and 
between tubing and couplings, fittings, and boxes shall be 
by an approved method. 

362.56 Splices and Taps. Splices and taps shall be made 
only in accordance with 300.15. 

FPN: See Article 314 for rules on the installation and use 
of boxes and conduit bodies. 

362.60 Grounding. Where equipment grounding is required, 
a separate equipment grounding conductor shall be installed in 
the raceway. 

III. Construction Specifications 

362.100 Construction. ENT shall be made of material that 
does not exceed the ignitibility, flammability, smoke gen- 
eration, and toxicity characteristics of rigid (nonplasticized) 
polyvinyl chloride. 

ENT, as a prewired manufactured assembly, shall be 
provided in continuous lengths capable of being shipped in 
a coil, reel, or carton without damage. 

362.120 Marking. ENT shall be clearly and durably marked 
at least every 3 m (10 ft) as required in the first sentence of 
110.21. The type of material shaU also be included in the 
marking. Marking for limited smoke shall be permitted on die 
tubing that has limited smoke-producing characteristics. 

The type, size, and quantity of conductors used in 
prewired manufactured assemblies shall be identified by 
means of a printed tag or label attached to each end of the 
manufactured assembly and either the carton, coil, or reel. 
The enclosed conductors shall be marked in accordance 
with 310.11. 



2005 Edition NATIONAL ELECTRICAL CODE 



70-201 



366.1 



ARTICLE 366 — AUXILIARY GUTTERS 



' A;i^niar^; :Gutters : 



I. General 



366.1 Scope. This article covers the use, installation, and 
construction requirements of metal auxiliary gutters and 
nonmetallic auxiliary gutters and associated fittings. 

366.2 Definitions. 

Metallic Auxiliary Gutters. Sheet metal enclosures with 
hinged or removable covers for housing and protecting 
electric wires, cable, and busbars in which conductors are 
laid in place after the wireway has been installed as a com- 
plete system. 

Nonmetallic Auxiliary Gutters. Flame retardant, non- 
metallic enclosures with removable covers for housing and 
protecting electric wires, cable, and busbars in which con- 
ductors are laid in place after the wireway has been in- 
stalled as a complete system. 

366.6 Listing Requirements. 

(A) Outdoors. Nonmetallic auxiliary gutters installed out- 
doors shall comply with the following: 

(1) Be listed as suitable for exposure to sunlight 

(2) Be listed as suitable for use in wet locations 

(3) Be listed for maximum ambient temperature of the 
installation 

(B) Indoors. Nonmetallic auxiliary gutters installed in- 
doors shall be listed for the maximum ambient temperature 
of the installation. 

II. Installation 

366.10 Uses Permitted. Auxiliary gutters shall be permitted 
to supplement wiring spaces at meter centers, distribution cen- 
ters, switchboards, and similar points of wiring systems and 
may enclose conductors or busbars. 

(A) Sheet Metal Auxiliary Gutters. 

(1) Indoor and Outdoor Use. Sheet metal auxiliary gut- 
ters shall be permitted for indoor and outdoor use. 

(2) Wet Locations. Sheet metal auxiliary gutters installed 
in wet locations shall be suitable for such locations. 

(B) Nonmetallic Auxiliary Gutters. Nonmetallic auxil- 
iary gutters shall be listed for the maximum ambient tem- 
perature of the installation and marked for the installed 
conductor insulation temperature rating. 



(1) Outdoors. Nonmetallic auxiliary gutters shall be per- 
mitted to be installed outdoors where listed and marked as 
suitable for the purpose. 

FPN: Extreme cold may cause nonmetallic auxiliary gut- 
ter to become brittle and therefore more susceptible to dam- 
age from physical contact. 

(2) Indoors. NonmetaUic auxiliary gutters shall be permit- 
ted to be installed indoors. 

366.12 Uses Not Permitted. Auxihary gutters shall not be 
used under the following conditions: 

(1) To enclose switches, overcurrent devices, appliances, 
or other similar equipment. 

(2) To extend a greater distance than 9 m (30 ft) beyond 
the equipment that it supplements. 

Exception: As permitted in 620.35 for elevators, an aux- 
iliary gutter shall be permitted to extend a distance greater 
than 9 m (30 ft) beyond the equipment it supplements. 

FPN: For wireways, see Articles 376 and 378. For busways, 
see Article 368. 

366.22 Number of Conductors. 

(A) Sheet Metal Auxiliary Gutters. The sum of the cross- 
sectional areas of all contained conductors at any cross section 
of a sheet metal auxiliary gutter shall not exceed 20 percent of 
the interior cross-sectional area of the sheet metal auxiliary 
gutter. The derating factors in 310.15(B)(2)(a) shall be applied 
only where the number of current-carrying conductors, includ- 
ing neutral conductors classified as current-carrying under the 
provisions of 310.15(B)(4), exceeds 30. Conductors for signal- 
ing circuits or controller conductors between a motor and its 
starter and used only for starting duty shall not be considered 
as current-carrying conductors. 

(B) Nonmetallic Auxiliary Gutters. The sum of cross- 
sectional areas of all contained conductors at any cross 
section of the nonmetallic auxihary gutter shall not exceed 
20 percent of the interior cross-sectional area of the non- 
metallic auxiliary gutter. 

366.23 Ampacity of Conductors. 

(A) Sheet Metal Auxiliary Gutters. Where the number of 
current-carrying conductors contained in the sheet metal 
auxiliary gutter is 30 or less, the correction factors specified 
in 310.15(B)(2)(a) shall not apply. The current carried con- 
tinuously in bare copper bars in sheet metal auxiliary gut- 
ters shall not exceed 1.55 amperes/mm^ (1000 amperes/in.^) 
of cross section of the conductor. For aluminum bars, the cur- 
rent carried continuously shall not exceed 1.09 amperes/mm^ 
(700 amperes/in.^) of cross section of the conductor. 



• 



70-202 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 366 — AUXILIARY GUTTERS 



366.120 



(B) Nonmetallic Auxiliary Gutters. The derating factors 
specified in 310.15(B)(2)(a) shall be appUcable to the current- 
carrying conductors in the nonmetallic auxiliary gutter. 

366.30 Securing and Supporting. 

(A) Sheet Metal Auxiliary Gutters. Sheet metal auxiliary 
gutters shall be supported throughout their entire length at 
intervals not exceeding 1.5 m (5 ft). 

(B) Nonmetallic Auxiliary Gutters. Nonmetallic auxil- 
iary gutters shall be supported at intervals not to exceed 
900 mm (3 ft) and at each end or joint, unless listed for 
other support intervals. In no case shall the distance be- 
tween supports exceed 3 m (10 ft). 

366.44 Expansion Fittings. Expansion fittings shall be in- 
stalled where expected length change, due to expansion and 
contraction due to temperature change, is more than 6 mm 
(0.25 in.). 

366.56 Splices and Taps. Splices and taps shall comply 
with 366.56(A) through (D). 

(A) Within Gutters. Splices or taps shall be permitted 
within gutters where they are accessible by means of re- 
movable covers or doors. The conductors, including splices 
and taps, shall not fill the gutter to more than 75 percent of 
its area. 

(B) Bare Conductors. Taps from bare conductors shall 
leave the gutter opposite their terminal connections, and 
conductors shall not be brought in contact with uninsulated 
current-carrying parts of different potential. 

(C) Suitably Identified. All taps shall be suitably identi- 
fied at the gutter as to the circuit or equipment that they 
supply. 

(D) Overcurrent Protection. Tap connections from con- 
ductors in auxiliary gutters shall be provided with overcur- 
rent protection as required in 240.21. 

366.58 Insulated Conductors. 

(A) Deflected Insulated Conductors. Where insulated 
conductors are deflected within an auxiliary gutter, either at 
the ends or where conduits, fittings, or other raceways or 
cables enter or leave the gutter, or where the direction of 
the gutter is deflected greater than 30 degrees, dimensions 
corresponding to one wire per terminal in Table 312.6(A) 
shall apply. 

(B) Auxiliary Gutters Used as Pullboxes. Where insu- 
lated conductors 4 AWG or larger are pulled through an 
auxiliary gutter, the distance between raceway and cable 
entries enclosing the same conductor shall not be less 



than that required in 314.28(A)(1) for straight pulls and 
314.28(A)(2) for angle pulls. 

366.60 Grounding. Metal auxiliary gutters shall be 
grounded. 

III. Construction Specifications 
366.100 Construction. 

(A) Electrical and Mechanical Continuity. Gutters shall 
be constructed and installed so that adequate electrical and 
mechanical continuity of the complete system is secured. 

(B) Substantial Construction. Gutters shall be of substan- 
tial construction and shall provide a complete enclosure for 
the contained conductors. All surfaces, both interior and 
exterior, shall be suitably protected from corrosion. Corner 
joints shall be made tight, and where the assembly is held 
together by rivets, bolts, or screws, such fasteners shall be 
spaced not more than 300 mm (12 in.) apart. 

(C) Smooth Rounded Edges. Suitable bushings, shields, 
or fittings having smooth, rounded edges shall be provided 
where conductors pass between gutters, through partitions, 
around bends, between gutters and cabinets or junction 
boxes, and at other locations where necessary to prevent 
abrasion of the insulation of the conductors. 

(D) Covers. Covers shall be securely fastened to the gutter. 

(E) Clearance of Bare Live Parts. Bare conductors shall 
be securely and rigidly supported so that the minimum 
clearance between bare current-carrying metal parts of dif- 
ferent potential mounted on the same surface will not be 
less than 50 mm (2 in.), nor less than 25 mm (1 in.) for 
parts that are held free in the air. A clearance not less than 
25 mm (I in.) shall be secured between bare current- 
carrying metal parts and any metal surface. Adequate pro- 
visions shall be made for the expansion and contraction 
of busbars. 

366.120 Marking. 

(A) Outdoors. Nonmetallic auxiliary gutters installed out- 
doors shall have the following markings: 

(1) Suitable for exposure to sunlight 

(2) Suitable for use in wet locations 

(3) Installed conductor insulation temperature rating 

(B) Indoors. NonmetalHc auxiliary gutters installed in- 
doors shall have the following markings: 

(1) Installed conductor insulation temperature rating 



2005 Edition 



NATIONAL ELECTRICAL CODE 



70-203 



368.1 



ARTICLE 368 — BUSWAYS 



ARTICLE 368 
Busways 



I. General Requirements 

368.1 Scope. This article covers service-entrance, feeder, 
and branch-circuit busways and associated fittings. 

368.2 Definition. 

Busway. A grounded metal enclosure containing factory- 
mounted, bare or insulated conductors, which are usually 
copper or aluminum bars, rods, or tubes. 

FPN: For cablebus, refer to Article 370. 



II. Installation 

368.10 Uses Permitted. Busways shall be permitted to be 
installed where they are located in accordance with 368.10(A) 
through (C). 

(A) Exposed. Busways shall be permitted to be located in 
the open where visible, except as permitted in 368.10(C). 

(B) Concealed. Busways shall be permitted to be installed 
behind access panels, provided the busways are totally en- 
closed, of nonventilating-type construction, and installed so 
that the joints between sections and at fittings are accessible 
for maintenance purposes. Where installed behind access 
panels, means of access shall be provided, and either of the 
following conditions shall be met: 

(1) The space behind the access panels shall not be used 
for air-handling purposes. 

(2) Where the space behind the access panels is used for 
environmental air, other than ducts and plenums, there 
shall be no provisions for plug-in connections, and the 
conductors shall be insulated. 

(C) Through Walls and Floors. Busways shall be permit- 
ted to be installed through walls or floors in accordance with 
(C)(1) and (C)(2). 

(1) Walls. Unbroken lengths of busway shall be permitted 
to be extended through dry walls. 

(2) Floors. Floor penetrations shall comply with (a) and (b): 

(a) Busways shall be permitted to be extended verti- 
cally through dry floors if totally enclosed (unventilated) 
where passing through and for a minimum distance of 1.8 
m (6 ft) above the floor to provide adequate protection from 
physical damage. 



(b) In other than industrial estabUshments, where a ver- 
tical riser penetrates two or more dry floors, a minimum 
100-mm (4-in.) high curb shall be installed around all floor 
openings for riser busways to prevent liquids from entering 
the opening. The curb shall be installed within 300 mm 
(12 in.) of the floor opening. Electrical equipment shall be 
located so that it will not be damaged by liquids that are 
retained by the curb. 

FPN: See 300.21 for information concerning the spread of 
fire or products of combustion. 

368.12 Uses Not Permitted. 

(A) Physical Damage. Busways shall not be instaUed where 
subject to severe physical damage or corrosive vapors. 

(B) Hoistways. Busways shall not be installed in hoistways. 

(C) Hazardous Locations. Busways shah not be installed 
in any hazardous (classified) location, unless specifically 
approved for such use. 

FPN: See 501.10(B). 

(D) Wet Locations. Busways shall not be instaUed outdoors 
or in wet or damp locations unless identified for such use. 

(E) Working Platform. Lighting busway and trolley 
busway shall not be installed less than 2.5 m (8 ft) above 
the floor or working platform unless provided with a cover 
identified for the purpose. 

368.17 Overcurrent Protection. Overcurrent protection 
shall be provided in accordance with 368.17(A) through (D). 

(A) Rating of Overcurrent Protection — Feeders. A 

busway shall be protected against overcurrent in accor- 
dance with the allowable current rating of the busway. 

Exception No. 1: The applicable provisions of 240.4 shall 
be permitted. 

Exception No. 2: Where used as transformer secondary 
ties, the provisions of 450.6(A)(3) shall be permitted. 

(B) Reduction in Ampacity Size of Busway. Overcurrent 
protection shall be required where busways are reduced in 
ampacity. 

Exception: For industrial establishments only, omission of 
overcurrent protection shall be permitted at points where 
busways are reduced in ampacity, provided that the length 
of the busway having the smaller ampacity does not exceed 
15 m (50 ft) and has an ampacity at least equal to one-third 
the rating or setting of the overcurrent device next back on 
the line, and provided that such busway is free from contact 
with combustible material. 



70-204 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 368 — BUSWAYS 



368.214 



(C) Feeder or Branch Circuits. Where a busway is used 
as a feeder, devices or plug-in connections for tapping off 
feeder or branch circuits from the busway shall contain the 
overcurrent devices required for the protection of the feeder 
or branch circuits. The plug-in device shall consist of an 
externally operable circuit breaker or an externally operable 
fusible switch. Where such devices are mounted out of 
reach and contain disconnecting means, suitable means 
such as ropes, chains, or sticks shall be provided for oper- 
ating the disconnecting means from the floor. 

Exception No. 1: As permitted in 240.21. 

Exception No. 2: For fixed or semifixed luminaires (light- 
ing fixtures), where the branch-circuit overcurrent device is 
part of the luminaire (fixture) cord plug on cord-connected 
luminaires (fixtures). 

Exception No. 3: Where luminaires (fixtures) without 
cords are plugged directly into the busway and the overcur- 
rent device is mounted on the luminaire (fixture). 

(D) Rating of Overcurrent Protection — Branch Cir- 
cuits. A busway used as a branch circuit shall be protected 
against overcurrent in accordance with 210.20. 

368.30 Support. Busways shall be securely supported at 
intervals not exceeding 1.5 m (5 ft) unless otherwise de- 
signed and marked. 

368.56 Branches from Busways. Branches from busways 
shall be permitted to be made in accordance with 368.56(A), 
(B), and (C). 

(A) General. Branches from busways shall be permitted to 
use any of the following wiring methods: 

(1) Type AC armored cable 

(2) Type MC metal-clad cable 

(3) Type MI mineral-insulated, metal-sheathed cable 

(4) Type IMC intermediate metal conduit 

(5) Type RMC rigid metal conduit 

(6) Type FMC flexible metal conduit 

(7) Type LFMC liquidtight flexible metal conduit 

(8) Type RNC rigid nonmetalhc conduit 

(9) Type LFNC liquidtight flexible nonmetal conduit 

(10) Type EMT electrical metallic tubing 

(11) Type ENT electrical nonmetallic tubing 

(12) Busways 

(13) Strut-type channel raceway 

(14) Surface metal raceways 

(15) Surface nonmetallic raceways 



Where a separate equipment grounding conductor is 
used, connection of the equipment grounding conductor to 
the busway shall comply with 250.8 and 250.12. 

(B) Cord and Cable Assemblies. Suitable cord and cable 
assemblies approved for extra-hard usage or hard usage, 
and listed bus drop cable shall be permitted as branches 
from busways for the connection of portable equipment or 
the connection of stationary equipment to facilitate their 
interchange in accordance with 400.7 and 400.8 and the 
following conditions: 

(1) The cord or cable shall be attached to the building by 
an approved means. 

(2) The length of the cord or cable from a busway plug-in 
device to a suitable tension take-up support device shall 
not exceed 1.8 m (6 ft). 

(3) The cord and cable shall be installed as a vertical riser 
from the tension take-up support device to the equip- 
ment served. 

(4) Strain reUef cable grips shall be provided for the cord 
or cable at the busway plug-in device and equipment 
terminations. 

Exception to (B)(2): In industrial establishments only, 
where the conditions of maintenance and supervision en- 
sure that only qualified persons service the installation, 
lengths exceeding 1.8 m (6 ft) shall be permitted between 
the busway plug-in device and the tension take-up support 
device where the cord or cable is supported at intervals not 
exceeding 2.5 m (8 ft). 

(C) Branches from Trolley-Type Busways. Suitable cord 
and cable assemblies approved for extra-hard usage or hard 
usage and listed bus drop cable shall be permitted as 
branches from trolley-type busways for the connection of 
movable equipment in accordance with 400.7 and 400.8. 

368.58 Dead Ends. A dead end of a busway shall be closed. 

368.60 Grounding. Busway shall be grounded. 

III. Construction 

368.120 Marking. Busways shall be marked with the volt- 
age and current rating for which they are designed, and 
with the manufacturer's name or trademark in such a man- 
ner as to be visible after installation. 



IV. Requirements for Over 600 Volts, Nominal 

368.214 Adjacent and Supporting Structures. Metal- 
enclosed busways shall be installed so that temperature rise 
from induced circulating currents in any adjacent metallic 
parts will not be hazardous to personnel or constitute a fire 
hazard. 



2005 Edition NATIONAL ELECTRICAL CODE 



70-205 



368.234 



ARTICLE 370 — CABLEBUS 



368.234 Barriers and Seals. 

(A) Vapor Seals. Busway runs that have sections located 
both inside and outside of buildings shall have a vapor seal 
at the building wall to prevent interchange of air between 
indoor and outdoor sections. 



Exception: 
cooled bus. 



Vapor seals shall not be required in forced- 



(B) Fire Barriers. Fire barriers shall be provided where 
fire walls, floors, or ceilings are penetrated. 

FPN: See 300.21 for information concerning the spread of 
fire or products of combustion. 

368.236 Drain Facilities. Drain plugs, filter drains, or simi- 
lar methods shall be provided to remove condensed moisture 
from low points in busway run. 

368.237 Ventilated Bus Enclosures. Ventilated busway 
enclosures shall be installed in accordance with Article 110, 
Part III, and 490.24. 

368.238 Terminations and Connections. Where bus en- 
closures terminate at machines cooled by flanmiable gas, 
seal-off bushings, baffles, or other means shall be provided 
to prevent accumulation of flammable gas in the busway 
enclosures. 

All conductor termination and connection hardware shall 
be accessible for installation, connection, and maintenance. 

368.239 Switches. Switching devices or disconnecting 
links provided in the busway run shall have the same mo- 
mentary rating as the busway. Disconnecting links shall be 
plainly marked to be removable only when bus is de- 
energized. Switching devices that are not load-break shall 
be interlocked to prevent operation under load, and discon- 
necting link enclosures shall be interlocked to prevent ac- 
cess to energized parts. 

368.240 Wiring 600 Volts or Less, Nominal. Secondary 
control devices and wiring that are provided as part of the 
metal-enclosed bus run shall be insulated by fire-retardant 
barriers from all primary circuit elements with the excep- 
tion of short lengths of wire, such as at instrument trans- 
former terminals. 

368.244 Expansion Fittings. Flexible or expansion con- 
nections shall be provided in long, straight runs of bus to 
allow for temperature expansion or contraction, or where 
the busway run crosses building vibration insulation joints. 

368.258 Neutral. Neutral bus, where required, shall be 
sized to carry all neutral load current, including harmonic 
currents, and shall have adequate momentary and short- 
circuit rating consistent with system requirements. 



368.260 Grounding. Metal-enclosed busway shall be 
grounded. 

368.320 Marking. Each busway run shall be provided 
with a permanent nameplate on which the following infor- 
mation shall be provided: 

(1) Rated voltage. 

(2) Rated continuous current; if bus is forced-cooled, both 
the normal forced-cooled rating and the self-cooled 
(not forced-cooled) rating for the same temperature rise 
shall be given. 

(3) Rated frequency. 

(4) Rated impulse withstand voltage. 

(5) Rated 60-Hz withstand voltage (dry). 

(6) Rated momentary current. 

(7) Manufacturer's name or trademark. 

FPN: See ANSI C37.23-1987 (R1991), Guide for Metal- 
Enclosed Bus and Calculating Losses in Isolated- Phase 
Bus, for construction and testing requirements for metal- 
enclosed buses. 






370.1 Scope. This article covers the use and installation 
requirements of cablebus and associated fittings. 

370.2 Definition. 

Cablebus. An assembly of insulated conductors with fit- 
tings and conductor terminations in a completely enclosed, 
ventilated protective metal housing. Cablebus is ordinarily 
assembled at the point of installation from the components 
furnished or specified by the manufacturer in accordance 
with instructions for the specific job. This assembly is de- 
signed to carry fault current and to withstand the magnetic 
forces of such current. 

370.3 Use. Approved cablebus shall be permitted at any 
voltage or current for which spaced conductors are rated 
and shall be installed only for exposed work, except as 
permitted in 370.6. Cablebus installed outdoors or in cor- 
rosive, wet, or damp locations shall be identified for such 
use. Cablebus shall not be installed in hoistways or hazard- 
ous (classified) locations unless specifically approved for 
such use. Cablebus shall be permitted to be used for branch 
circuits, feeders, and services. 



• 



• 



70-206 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 372 — CELLULAR CONCRETE FLOOR RACEWAYS 



372.2 



• 



Cablebus framework, where bonded, shall be permitted to 
be used as the equipment grounding conductor for branch 
circuits and feeders. 

370.4 Conductors. 

(A) Types of Conductors. The current-carrying conduc- 
tors in cablebus shall have an insulation rating of 75°C 
(167°F) or higher and be an approved type suitable for the 
application. 

(B) Ampacity of Conductors. The ampacity of conduc- 
tors in cablebus shall be in accordance with Table 310.17 
and Table 310.19, or with Table 310.69 and Table 310.70 
for installations over 600 volts. 

(C) Size and Number of Conductors. The size and num- 
ber of conductors shall be that for which the cablebus is 
designed, and in no case smaller than 1/0 AWG. 

(D) Conductor Supports. The insulated conductors shall 
be supported on blocks or other mounting means designed 
for the purpose. 

The individual conductors in a cablebus shall be supported 
at intervals not greater than 900 mm (3 ft) for horizontal runs 
and 450 mm (IVi ft) for vertical runs. Vertical and horizontal 
spacing between supported conductors shall not be less than 
one conductor diameter at the points of support. 

370.5 Overcurrent Protection. Cablebus shall be protected 
against overcurrent in accordance with the allowable ampacity 
of the cablebus conductors in accordance with 240.4. 

Exception: Overcurrent protection shall be permitted in 
accordance with 240.100 and 240.101 for over 600 volts, 
nominal. 

370.6 Support and Extension Through Wails and Floors. 

(A) Support. Cablebus shall be securely supported at in- 
tervals not exceeding 3.7 m (12 ft). 

Exception: Where spans longer than 3.7 m (12 ft) are 
required, the structure shall be specifically designed for the 
required span length. 

(B) Transversely Routed. Cablebus shall be permitted to 
extend transversely through partitions or walls, other than 
fire walls, provided the section within the wall is continu- 
ous, protected against physical damage, and unventilated. 

(C) Through Dry Floors and Platforms. Except where 
firestops are required, cablebus shall be permitted to extend 
vertically through dry floors and platforms, provided the 
cablebus is totally enclosed at the point where it passes 
through the floor or platform and for a distance of 1.8 m 
(6 ft) above the floor or platform. 



(D) Through Floors and Platforms in Wet Locations. 

Except where firestops are required, cablebus shall be per- 
mitted to extend vertically through floors and platforms in 
wet locations where (1) there are curbs or other suitable 
means to prevent waterflow through the floor or platform 
opening, and (2) where the cablebus is totally enclosed at 
the point where it passes through the floor or platform and 
for a distance of 1.8 m (6 ft) above the floor or platform. 

370.7 Fittings. A cablebus system shall include approved 
fittings for the following: 

(1) Changes in horizontal or vertical direction of the run 

(2) Dead ends 

(3) Terminations in or on connected apparatus or equip- 
ment or the enclosures for such equipment 

(4) Additional physical protection where required, such as 
guards where subject to severe physical damage 

370.8 Conductor Terminations. Approved terminating 
means shall be used for connections to cablebus conductors. 

370.9 Grounding. A cablebus installation shall be grounded 
and bonded in accordance with Article 250, excluding 250.86, 
Exception No. 2. 

370.10 Marking. Each section of cablebus shall be marked 
with the manufacmrer's name or trade designation and the 
maximum diameter, number, voltage rating, and ampacity of 
the conductors to be installed. Markings shall be located so as 
to be visible after installation. 



%M,.,X .ARTICLE. 372 
ijeilular Concrete Floor Raceways 



372.1 Scope. This article covers cellular concrete floor 
raceways, the hollow spaces in floors constructed of precast 
cellular concrete slabs, together with suitable metal fittings 
designed to provide access to the floor cells. 

372.2 Definitions. 

Cell. A single, enclosed tubular space in a floor made of 
precast cellular concrete slabs, the direction of the cell be- 
ing parallel to the direction of the floor member. 

Header, Transverse metal raceways for electric conduc- 
tors, providing access to predetermined cells of a precast 
cellular concrete floor, thereby permitting the installation 
of electric conductors from a distribution center to the 
floor cells. 



2005 Edition NATIONAL ELECTRICAL CODE 



70-207 



372.4 



ARTICLE 374 — CELLULAR METAL FLOOR RACEWAYS 



372.4 Uses Not Permitted. Conductors shall not be installed 
in precast cellular concrete floor raceways as follows: 

(1) Where subject to corrosive vapor 

(2) In any hazardous (classified) locations except as permitted 
by 504.20, and in Class I, Division 2 locations as permit- 
ted in 501.10(B)(3) 

(3) In commercial garages, other than for supplying ceiling 
outlets or extensions to the area below the floor but not 
above 

FPN: See 300.8 for installation of conductors with other 
systems. 

372.5 Header. The header shall be installed in a straight 
line at right angles to the cells. The header shall be me- 
chanically secured to the top of the precast cellular concrete 
floor. The end joints shall be closed by a metal closure 
fitting and sealed against the entrance of concrete. The 
header shall be electrically continuous throughout its entire 
length and shall be electrically bonded to the enclosure of 
the distribution center. 

372.6 Connection to Cabinets and Other Enclosures. 

Connections from headers to cabinets and other enclosures 
shah be made by means of listed metal raceways and listed 
fittings. 

372.7 Junction Boxes. Junction boxes shall be leveled to 
the floor grade and sealed against the free entrance of water 
or concrete. Junction boxes shall be of metal and shall be 
mechanically and electrically continuous with the header. 

372.8 Markers. A suitable number of markers shall be 
installed for the future location of cells. 

372.9 Inserts. Inserts shall be leveled and sealed against the 
entrance of concrete. Inserts shaU be of metal and shall be 
fitted with grounded-type receptacles. A grounding conductor 
shaU connect the insert receptacles to a positive ground con- 
nection provided on the header. Where cutting through the ceU 
wall for setting inserts or other purposes (such as providing 
access openings between header and cells), chips and other 
dirt shall not be allowed to remain in the raceway, and the tool 
used shall be designed so as to prevent the tool from entering 
the cell and damaging the conductors. 

372.10 Size of Conductors. No conductor larger than 
1/0 AWG shall be installed, except by special permission. 

372.11 Maximum Number of Conductors. The com- 
bined cross-sectional area of all conductors or cables shall 
not exceed 40 percent of the cross-sectional area of the cell 
or header. 



372.12 Splices and Taps. Splices and taps shall be made 
only in header access units or junction boxes. 

For the purposes of this section, so-called loop wiring 
(continuous unbroken conductor connecting the individual 
outlets) shall not be considered to be a splice or tap. 

372.13 Discontinued Outlets. When an outlet is aban- 
doned, discontinued, or removed, the sections of circuit 
conductors supplying the outlet shall be removed from the 
raceway. No splices or reinsulated conductors, such as would 
be the case of abandoned outiets on loop wiring, shall be 
allowed in raceways. 

372.17 Ampacity of Conductors. The ampacity adjust- 
ment factors, provided in 310.15(B)(2), shall apply to con- 
ductors installed in cellular concrete floor raceways. 



Geliuitar Metil ftloor Kaceways 



374.1 Scope. This article covers the use and installation 
requirements for cellular metal floor raceways. 

374.2 Definitions. 

Cellular Metal Floor Raceway. The hollow spaces of cel- 
lular metal floors, together with suitable fittings, that may 
be approved as enclosures for electric conductors. 

Cell. A single enclosed tubular space in a cellular metal 
floor member, the axis of the cell being parallel to the axis 
of the metal floor member. 

Header. A transverse raceway for electric conductors, pro- 
viding access to predetermined cells of a cellular metal 
floor, thereby permitting the installation of electric conduc- 
tors from a distribution center to the cells. 

374.3 Uses Not Permitted. Conductors shall not be in- 
stalled in cellular metal floor raceways as follows: 

(1) Where subject to corrosive vapor 

(2) In any hazardous (classified) location except as permit- 
ted by 504.20, and in Class I, Division 2 locations as 
permitted by 501.10(B)(3) 

(3) In commercial garages, other than for supplying ceiling 
outlets or extensions to the area below the floor but not 
above 

FPN: See 300.8 for installation of conductors with other 
systems. 



• 



70-208 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 376 — METAL WIREWAYS 



376.12 



I. Installation 

374.4 Size of Conductors. No conductor larger than 
1/0 AWG shall be installed, except by special permission. 

374.5 Maximum Number of Conductors in Raceway. 

The combined cross-sectional area of all conductors or 
cables shall not exceed 40 percent of the interior cross- 
sectional area of the cell or header. 

374.6 Splices and Taps. Splices and taps shall be made 
only in header access units or junction boxes. 

For the purposes of this section, so-called loop wiring 
(continuous unbroken conductor connecting the individual 
outlets) shall not be considered to be a splice or tap. 

374.7 Discontinued Outlets. When an outlet is aban- 
doned, discontinued, or removed, the sections of circuit 
conductors supplying the outlet shall be removed from the 
raceway. No splices or reinsulated conductors, such as 
would be the case with abandoned outlets on loop wiring, 
shall be allowed in raceways. 

374.8 Markers. A suitable number of markers shall be 
installed for locating cells in the future. 

374.9 Junction Boxes. Junction boxes shall be leveled to 
the floor grade and sealed against the free entrance of water 
or concrete. Junction boxes used with these raceways shall 
be of metal and shall be electrically continuous with the 
raceway. 

374.10 Inserts. Inserts shall be leveled to the floor grade and 
sealed against the entrance of concrete. Inserts shall be of 
metal and shall be electrically continuous with the raceway. In 
cutting through the cell wall and setting inserts, chips and 
other dirt shall not be aUowed to remain in the raceway, and 
tools shall be used that are designed to prevent the tool from 
entering the ceU and damaging the conductors. 

374.11 Connection to Cabinets and Extensions from 
Cells. Connections between raceways and distribution centers 
and wall outlets shall be made by means of liquidtight flexible 
metal conduit, flexible metal conduit where not installed in 
concrete, rigid metal conduit, intermediate metal conduit, elec- 
trical metallic tubing, or approved fittings. Where there are 
provisions for the termination of an equipment grounding con- 
ductor, nonmetallic conduit, electrical nonmetallic tubing, or 
hquidtight flexible nonmetalUc conduit shaU be permitted. 
Where instaUed in concrete, liquidtight flexible nonmetallic 
conduit shall be listed and marked for direct burial. 

FPN: Liquidtight flexible metal conduit and liquidtight 
flexible nonmetallic conduit that is suitable for installation 
in concrete is listed and marked for direct burial. 



374.17 Ampacity of Conductors. The ampacity adjust- 
ment factors in 310.15(B)(2) shall apply to conductors in- 
stalled in cellular metal floor raceways. 

II. Construction Specifications 

374.100 General. Cellular metal floor raceways shall be 
constructed so that adequate electrical and mechanical con- 
tinuity of the complete system will be secured. They shall 
provide a complete enclosure for the conductors. The inte- 
rior surfaces shall be free from burrs and sharp edges, and 
surfaces over which conductors are drawn shafl be smooth. 
Suitable bushings or fittings having smooth rounded edges 
shall be provided where conductors pass. 



I. General 

376.1 Scope. This article covers the use, installation, and 
construction specifications for metal wireways and associ- 
ated fittings. 

376.2 Definition. 

Metal Wireways. Sheet metal troughs with hinged or re- 
movable covers for housing and protecting electric wires 
and cable and in which conductors are laid in place after 
the wireway has been installed as a complete system. 

II. Installation 

376.10 Uses Permitted. The use of metal wireways shall 
be permitted in the following: 

(1) For exposed work 

(2) In concealed spaces as permitted in 376.10(4) 

(3) In hazardous (classified) locations as permitted by 
501.10(B) for Class I, Division 2 locations; 502.10(B) 
for Class II, Division 2 locations; and 504.20 for intrin- 
sically safe wiring. Where installed in wet locations, 
wireways shall be listed for the purpose. 

(4) As extensions to pass transversely through walls if the 
length passing through the wall is unbroken. Access to the 
conductors shall be maintained on both sides of the wall. 

376.12 Uses Not Permitted. Metal wireways shall not be 
used in the following: 

(1) Where subject to severe physical damage 

(2) Where subject to severe corrosive environments 



2005 Edition NATIONAL ELECTRICAL CODE 



70-209 



376.21 



ARTICLE 378 — NONMETALLIC WIREWAYS 



376.21 Size of Conductors. No conductor larger than that 
for which the wireway is designed shall be installed in any 
wireway. 

376.22 Number of Conductors. The sum of the cross- 
sectional areas of all contained conductors at any cross 
section of a wireway shall not exceed 20 percent of the 
interior cross-sectional area of the wireway. The derating 
factors in 310.15(B)(2)(a) shall be appUed only where the 
number of current-carrying conductors, including neutral 
conductors classified as current-carrying under the provi- 
sions of 310.15(B)(4), exceeds 30. Conductors for signaling 
circuits or controller conductors between a motor and its 
starter and used only for starting duty shall not be consid- 
ered as current-carrying conductors. 

376.23 Insulated Conductors. Insulated conductors installed 
in a metallic wireway shall comply with 376.23(A) and (B). 

(A) Deflected Insulated Conductors. Where insulated con- 
ductors are deflected within a metallic wireway, either at 
the ends or where conduits, fittings, or other raceways or 
cables enter or leave the metallic wireway, or where the 
direction of the metallic wireway is deflected greater than 
30 degrees, dimensions corresponding to one wire per ter- 
minal in Table 312.6(A) shall apply. 

(B) Metallic Wirevv'ays Used as Pull Boxes. Where insu- 
lated conductors 4 AWG or larger are pulled through a wire- 
way, the distance between raceway and cable entries enclosing 
the same conductor shall not be less than that required by 
314.28(A)(1) for straight pulls and 314.28(A)(2) for angle 
pulls. When transposing cable size into raceway size, the mini- 
mum metric designator (trade size) raceway required for the 
number and size of conductors in the cable shall be used. 

376.30 Securing and Supporting. Metal wireways shall 
be supported in accordance with 376.30(A) and (B). 

(A) Horizontal Support. Wireways shall be supported 
where run horizontally at each end and at intervals not to 
exceed 1.5 m (5 ft) or for individual lengths longer than 1.5 m 
(5 ft) at each end or joint, unless Usted for other support inter- 
vals. The distance between supports shaU not exceed 3 m 
(10 ft). 

(B) Vertical Support. Vertical runs of wireways shall be 
securely supported at intervals not exceeding 4.5 m (15 ft) 
and shall not have more than one joint between supports. 
Adjoining wireway sections shall be securely fastened to- 
gether to provide a rigid joint. 

376.56 Splices, Taps, and Power Distribution Blocks. 

(A) Splices and Taps. Splices and taps shall be permitted 
within a wireway, provided they are accessible. The con- 
ductors, including spHces and taps, shall not fill the wire- 
way to more than 75 percent of its area at that point. 



(B) Power Distribution Blocks. 

(1) Installation. Power distribution blocks instafled in 
metal wireways shall be listed. 

(2) Size of Enclosure. In addition to the wiring space re- 
quirement in 376.56(A), the power distribution block shall 
be installed in a wireway with dimensions not smaller than 
specified in the installation instructions of the power distri- 
bution block. 

(3) Wire Bending Space. Wire bending space at the termi- 
nals of power distribution blocks shaU comply with 312.6(B). 

(4) Live Parts. Power distribution blocks shall not have 
exposed live parts in the wireway after installation. 

376.58 Dead Ends. Dead ends of metal wireways shaU be 
closed. 

376.70 Extensions from Metal Wireways. Extensions 
from wireways shall be made with cord pendants installed 
in accordance with 400.10 or with any wiring method in 
Chapter 3 that includes a means for equipment grounding. 
Where a separate equipment grounding conductor is em- 
ployed, connection of the equipment grounding conductors 
in the wiring method to the wireway shall comply with 
250.8 and 250.12. 



III. Construction Specifications 

376.120 Marking. Metal wireways shall be so marked that 
their manufacturer's name or trademark will be visible after 
installation. 






I. General 



378.1 Scope. This article covers the use, installation, and 
construction specifications for nonmetallic wireways and 
associated fittings. 

378.2 Definition. 

Nonmetallic Wireways. Flame retardant, nonmetallic 
troughs with removable covers for housing and protect- 
ing electric wires and cables in which conductors are laid 
in place after the wireway has been installed as a com- 
plete system. 



70-210 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 378 — NONMETALLIC WIREWAYS 



378.60 



• 



• 



378.6 Listing Requirements. Nonmetallic wireways and 
associated fittings shall be listed. 

11. Installation 

378.10 Uses Permitted. The use of nonmetallic wireways 
shall be permitted in the following: 

(1) Only for exposed work, except as permitted in 378.10(4). 

(2) Where subject to corrosive environments where identi- 
fied for the use. 

(3) In wet locations where listed for the purpose. 

FPN: Extreme cold may cause nonmetallic wireways to 
become brittle and therefore more susceptible to damage 
from physical contact. 

(4) As extensions to pass transversely through walls if the 
length passing through the wall is unbroken. Access to the 
conductors shall be maintained on both sides of the wall. 

378.12 Uses Not Permitted. Nonmetallic wireways shall 
not be used in the following: 

(1) Where subject to physical damage 

(2) In any hazardous (classified) location, except as permit- 
ted in 504.20 

(3) Where exposed to sunlight unless listed and marked as 
suitable for the purpose 

(4) Where subject to ambient temperatures other than those 
for which nonmetallic wireway is listed 

(5) For conductors whose insulation temperature limitations 
would exceed those for which the nonmetaUic wireway is 
listed 

378.21 Size of Conductors. No conductor larger than that 
for which the nonmetallic wireway is designed shall be in- 
stalled in any nonmetaUic wireway. 

378.22 Number of Conductors. The sum of cross-sectional 
areas of all contained conductors at any cross section of the 
nonmetallic wireway shall not exceed 20 percent of the inte- 
rior cross-sectional area of the nonmetallic wireway. Conduc- 
tors for signaling circuits or controller conductors between a 
motor and its starter and used only for starting duty shall not 
be considered as current-carrying conductors. 

The derating factors specified in 310.15(B)(2)(a) shall 
be applicable to the current-carrying conductors up to and 
including the 20 percent fill specified above. 

378.23 Insulated Conductors. Insulated conductors in- 
stalled in a nonmetallic wireway shall comply with 
378.23(A) and (B). 

(A) Deflected Insulated Conductors. Where insulated con- 
ductors are deflected within a nonmetallic wireway, either 
at the ends or where conduits, fittings, or other raceways or 



cables enter or leave the nonmetaUic wireway, or where the 
direction of the nonmetallic wireway is deflected greater 
than 30 degrees, dimensions corresponding to one wire per 
terminal in Table 312.6(A) shall apply. 

(B) Nonmetallic Wireways Used as Pull Boxes. Where 
insulated conductors 4 AWG or larger are puUed through a 
wireway, the distance between raceway and cable entries en- 
closing the same conductor shall not be less than that required 
in 314.28(A)(1) for straight puUs and in 314.28(A)(2) for 
angle pulls. When transposing cable size into raceway size, the 
minimum metric designator (trade size) raceway required for 
the number and size of conductors in the cable shaU be used. 

378.30 Securing and Supporting. Nonmetallic wireway 
shaU be supported in accordance with 378.30(A) and (B). 

(A) Horizontal Support. Nonmetallic wireways shall be 
supported where run horizontally at intervals not to exceed 
900 mm (3 ft), and at each end or joint, unless listed for 
other support intervals. In no case shall the distance be- 
tween supports exceed 3 m (10 ft). 

(B) Vertical Support. Vertical runs of nonmetallic wire- 
way shall be securely supported at intervals not exceeding 
1.2 m (4 ft), unless listed for other support intervals, and 
shaU not have more than one joint between supports. Ad- 
joining nonmetallic wireway sections shall be securely fas- 
tened together to provide a rigid joint. 

378.44 Expansion Fittings. Expansion fittings for nonme- 
tallic wireway shaU be provided to compensate for thermal 
expansion and contraction where the length change is ex- 
pected to be 6 mm (0.25 in.) or greater in a straight run. 

FPN: See Table 352.44(A) for expansion characteristics of 
PVC rigid nonmetallic conduit. The expansion characteris- 
tics of PVC nonmetallic wireway are idendcal. 

378.56 Splices and Taps. Splices and taps shall be permit- 
ted within a nonmetallic wireway, provided they are acces- 
sible. The conductors, including splices and taps, shall not 
fill the nonmetallic wireway to more than 75 percent of its 
area at that point. 

378.58 Dead Ends. Dead ends of nonmetallic wireway 
shall be closed using listed fittings. 

378.60 Grounding. Where equipment grounding is re- 
quired, a separate equipment grounding conductor shall be 
installed in the nonmetallic wireway. A separate equipment 
grounding conductor shall not be required where the 
grounded conductor is used to ground equipment as permit- 
ted in 250.142. 



2005 Edition NATIONAL ELECTRICAL CODE 



70-211 



378.70 



ARTICLE 382 — NONMETALLIC EXTENSIONS 



378.70 Extensions from Nonmetallic Wireways. Exten- 
sions from nonmetallic wireway shall be made with cord 
pendants or any wiring method of Chapter 3. A separate 
equipment grounding conductor shall be installed in, or an 
equipment grounding connection shall be made to, any of 
the wiring methods used for the extension. 

III. Construction Specifications 

378.120 Marking. Nonmetallic wireways shall be marked 
so that the manufacturer's name or trademark and interior 
cross-sectional area in square inches shall be visible after in- 
stallation. Marking for limited smoke shall be permitted on the 
nonmetallic wireways that have Umited smoke-producing 
characteristics. 






I. General 



382.1 Scope. This article covers the use, installation, and 
construction specifications for nonmetalhc extensions. 

382.2 Definition. 

Nonmetallic Extension. An assembly of two insulated 
conductors within a nonmetallic jacket or an extruded ther- 
moplastic covering. The classification includes surface ex- 
tensions intended for mounting directly on the surface of 
walls or ceilings. 



380.1 Scope. This article covers the use and installation 
requirements for multioutlet assemblies. 

380.2 Use. 

(A) Permitted. The use of a multioutlet assembly shall be 
permitted in dry locations. 

(B) Not Permitted. A multioutlet assembly shall not be 
installed as follows: 

(1) Where concealed, except that it shall be permissible to 
surround the back and sides of a metal multioutlet as- 
sembly by the building finish or recess a nonmetallic 
multioutlet assembly in a baseboard 

(2) Where subject to severe physical damage 

(3) Where the voltage is 300 volts or more between con- 
ductors unless the assembly is of metal having a thick- 
ness of not less than 1.02 mm (0.040 in.) 

(4) Where subject to corrosive vapors 

(5) In hoistways 

(6) In any hazardous (classified) locations except Class I, 
Division 2 locations as permitted in 501.10(B)(3) 

380.3 Metal Multioutlet Assembly Through Dry Parti- 
tions. It shall be permissible to extend a metal multioutlet 
assembly through (not run within) dry partitions if arrange- 
ments are made for removing the cap or cover on all ex- 
posed portions and no outlet is located within the partitions. 



II. Installation 

382.10 Uses Permitted. Nonmetallic extensions shall be 
permitted only in accordance with 382.10(A), (B), and (C). 

(A) From an Existing Outlet. The extension shall be from 
an existing outlet on a 15- or 20-ampere branch circuit. 

(B) Exposed and in a Dry Location. The extension shall 
be run exposed and in a dry location. 

(C) Residential or OfiBces. For nonmetalhc surface exten- 
sions mounted directly on the surface of walls or ceilings, 
the building shall be occupied for residential or of&ce pur- 
poses and shall not exceed three floors above grade. 



FPN No. 1 
conductors. 



See 310.10 for temperature limitation of 
FPN No. 2: See 362.10 for definition oi first floor. 



382.12 Uses Not Permitted. Nonmetallic extensions shall 
not be used as follows: 

(1) In unfinished basements, attics, or roof spaces 

(2) Where the voltage between conductors exceeds 150 volts 
for nonmetallic surface extension and 300 volts for aerial 
cable 

(3) Where subject to corrosive vapors 

(4) Where run through a floor or partition, or outside the 
room in which it originates 

382.15 Exposed. One or more extensions shall be permit- 
ted to be run in any direction from an existing outlet, but 
not on the floor or within 50 mm (2 in.) from the floor. 

382.26 Bends. A bend that reduces the normal spacing be- 
tween the conductors shall be covered with a cap to protect 
the assembly from physical damage. 



• 



70-212 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 384 — STRUT-TYPE CHANNEL RACEWAY 



384.30 



382.30 Securing and Supporting. Nonmetallic surface 
extensions shall be secured in place by approved means at 
intervals not exceeding 200 mm (8 in.), with an allowance 
for 300 mm (12 in.) to the first fastening where the connec- 
tion to the supplying outlet is by means of an attachment 
plug. There shall be at least one fastening between each two 
adjacent outlets supplied. An extension shall be attached to 
only woodwork or plaster finish and shall not be in contact 
with any metal work or other conductive material other 
than with metal plates on receptacles. 

382.40 Boxes and Fittings. Each run shall terminate in a 
fitting that covers the end of the assembly. All fittings and 
devices shall be of a type identified for the use. 

382.56 Splices and Taps. Extensions shall consist of a con- 
tinuous unbroken length of the assembly, without splices, 
and without exposed conductors between fittings. Taps 
shall be permitted where approved fittings completely cov- 
ering the tap connections are used. Aerial cable and its tap 
connectors shall be provided with an approved means for 
polarization. Receptacle-type tap connectors shall be of the 
locking type. 






. .:|RTICLEf 84|; ;;T ::5 ^M-M 

I. General 

384.1 Scope. This article covers the use, installation, and 
construction specifications of strut-type channel raceway. 

384.2 Definition. 

Strut-Type Channel Raceway. A metallic raceway that is 
intended to be mounted to the surface of or suspended from 
a structure, with associated accessories for the installation 
of electrical conductors and cables. 



(5) As power poles. 

(6) In Class I, Division 2 hazardous (classified) locations 
as permitted in 501.10(B)(3). 

(7) As extensions of unbroken lengths through walls, par- 
titions, and floors where closure strips are removable 
from either side and the portion within the wall, parti- 
tion, or floor remains covered. 

(8) Ferrous channel raceways and fittings protected from cor- 
rosion solely by enamel shall be permitted only indoors. 

384.12 Uses Not Permitted. Strut type channel raceways 
shall not be used as foflows: 

(1) Where concealed. 

(2) Ferrous channel raceways and fittings protected from 
corrosion solely by enamel shall not be permitted where 
subject to severe corrosive influences. 

384.21 Size of Conductors. No conductor larger than that 
for which the raceway is listed shall be installed in strut- 
type channel raceways. 

384.22 Number of Conductors. The number of conduc- 
tors permitted in strut-type channel raceways shall not ex- 
ceed the percentage fill using Table 384.22 and applicable 
outside diameter (O.D.) dimensions of specific types and 
sizes of wire given in the tables in Chapter 9. 

The derating factors of 310.15(B)(2)(a) shall not apply 
to conductors installed in strut-type channel raceways 
where all of the following conditions are met: 

(1) The cross-sectional area of the raceway exceeds 
2500 mm^ (4 in.^). 

(2) The current-carrying conductors do not exceed 30 in 
number. 

(3) The sum of the cross-sectional areas of all contained 
conductors does not exceed 20 percent of the interior 
cross-sectional area of the strut-type channel raceways, 
calculated in accordance with the following formula for 
wire fill: 



384.6 Listing Requirements. Strut-type channel raceways, 
closure strips, and accessories shall be listed and identified 
for such use. 



II. Installation 

384.10 Uses Permitted. The use of strut-type channel 
raceways shall be permitted in the following: 

(1) Where exposed. 

(2) In dry locations. 

(3) In locations subject to corrosive vapors where pro- 
tected by finishes judged suitable for the condition. 

(4) Where the voltage is 600 volts or less. 



where: 
n = number of wires 
ca = channel area in square inches 
wa = wire area 

384.30 Securing and Supporting. 

(A) Surface Mount. A surface mount strut-type channel 
raceway shall be secured to the mounting surface with reten- 
tion straps external to the channel at intervals not exceeding 3 
m (10 ft) and within 900 mm (3 ft) of each outlet box, cabinet, 
junction box, or other channel raceway termination. 



2005 Edition 



NATIONAL ELECTRICAL CODE 



70-213 



384.56 



ARTICLE 386 — SURFACE METAL RACEWAYS 



Table 384.22 Channel Size and Inside Diameter Area 





Area 


40% 


4rea* 


25% 


Area** 


Size 


























Channel 


in.^ 


mm^ 


in.^ 


mm^ 


in.^ 


mm^ 


IVS X '3/16 


0.887 


572 


0.355 


229 


0.222 


143 


P/s X 1 


1.151 


743 


0.460 


297 


0.288 


186 


IVs X 13/8 


1.677 


1076 


0.671 


433 


0.419 


270 


P/s X lYs 


2.028 


1308 


0.811 


523 


0.507 


327 


15/8 X 2yi6 


3.169 


2045 


1.267 


817 


0.792 


511 


P/g X 3'/4 


4.308 


2780 


1.723 


1112 


1.077 


695 


1 1/2X3/4 


0.849 


548 


0.340 


219 


0.212 


137 


1I/2X l'/2 


1.828 


1179 


0.731 


472 


0.457 


295 


V/2 X P/s 


2.301 


1485 


0.920 


594 


0.575 


371 


1 '/2 X 3 


3.854 


2487 


1.542 


995 


0.964 


622 



*Raceways with external joiners shall use a 40 percent wire fill cal- 
culation to determine the number of conductors permitted. 
**Raceways with internal joiners shall use a 25 percent wire fill cal- 
culation to determine the number of conductors permitted. 



(B) Suspension Mount. Strut-type channel raceways shall 
be permitted to be suspension mounted in air with approved 
appropriate methods designed for the purpose at intervals 
not to exceed 3 m (10 ft) and within 900 mm (3 ft) of 
channel raceway terminations and ends. 

384.56 Splices and Taps. Splices and taps shall be permit- 
ted in raceways that are accessible after installation by hav- 
ing a removable cover. The conductors, including splices 
and taps, shall not fill the raceway to more than 75 percent 
of its area at that point. All splices and taps shall be made 
by approved methods. 

384.60 Grounding. Strut-type channel raceway enclosures 
providing a transition to or from other wiring methods shall 
have a means for connecting an equipment grounding con- 
ductor. Strut-type channel raceways shall be permitted as 
an equipment grounding conductor in accordance with 
250.118(14). Where a snap-fit metal cover for strut-type 
channel raceways is used to achieve electrical continuity in 
accordance with the listing, this cover shall not be permit- 
ted as the means for providing electrical continuity for a 
receptacle mounted in the cover. 

III. Construction Specifications 

384.100 Construction. Strut-type channel raceways and 
their accessories shall be of a construction that distinguishes 
them from other raceways. Raceways and their elbows, cou- 
phngs, and other fittings shall be designed such that the sec- 
tions can be electrically and mechanically coupled together 
and installed without subjecting the wires to abrasion. They 
shaU comply with 384.100(A), (B), and (C). 



(A) Material. Raceways and accessories shall be formed 
of steel, stainless steel, or aluminum. 

(B) Corrosion Protection. Steel raceways and accessories 
shall be protected against corrosion by galvanizing or by an 
organic coating. 

FPN: Enamel and PVC coatings are examples of organic 
coatings that provide corrosion protection. 

(C) Cover. Covers of strut-type channel raceways shall be 
either metallic or nonmetallic. 

384.120 Marking. Each length of strut-type channel race- 
ways shall be clearly and durably identified as required in 
the first sentence of 110.21. 



I. General 

386.1 Scope. This article covers the use, installation, and 
construction specifications for surface metal raceways and 
associated fittings. 

386.2 Definition. 

Surface Metal Raceway. A metallic raceway that is in- 
tended to be mounted to the surface of a structure, with 
associated couplings, connectors, boxes, and fittings for the 
installation of electrical conductors. 

386.6 Listing Requirements. Surface metal raceway and 
associated fittings shall be listed. 

II. Installation 

386.10 Uses Permitted. The use of surface metal race- 
ways shall be permitted in the following: 

(1) In dry locations. 

(2) In Class I, Division 2 hazardous (classified) locations 
as permitted in 501.10(B)(3). 

(3) Under raised floors, as permitted in 645.5(D)(2). 

(4) Extension through walls and floors. Surface metal race- 
way shaU be permitted to pass transversely through dry 
walls, dry partitions, and dry floors if the length passing 
through is unbroken. Access to the conductors shall be 
maintained on both sides of the wall, partition, or floor. 

386.12 Uses Not Permitted. Surface metal raceways shall 
not be used in the following: 



70-214 



NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 388 — SURFACE NONMETALLIC RACEWAYS 



388.12 



(1) Where subject to severe physical damage, unless other- 
wise approved 

(2) Where the voltage is 300 volts or more between con- 
ductors, unless the metal has a thickness of not less 
than 1.02 mm (0.040 in.) nominal 

(3) Where subject to corrosive vapors 

(4) In hoistways 

(5) Where concealed, except as permitted in 386.10 

386.21 Size of Conductors. No conductor larger than that 
for which the raceway is designed shall be installed in surface 
metal raceway. 

386.22 Number of Conductors or Cables. The number of 
conductors or cables installed in surface metal raceway 
shall not be greater than the number for which the raceway 
is designed. Cables shall be permitted to be installed where 
such use is not prohibited by the respective cable articles. 

The derating factors of 310.15(B)(2)(a) shall not apply 
to conductors installed in surface metal raceways where all 
of the following conditions are met: 

(1) The cross-sectional area of the raceway exceeds 
2500 mm^ (4 in.^) 

(2) The current-carrying conductors do not exceed 30 in 
number 

(3) The sum of the cross-sectional areas of all contained 
conductors does not exceed 20 percent of the interior 
cross-sectional area of the surface metal raceway 

386.30 Securing and Supporting. Surface metal raceways 
shall be supported at intervals in accordance with the 
manufacturer's installation instructions. 

386.56 Splices and Taps. Splices and taps shall be permit- 
ted in surface metal raceways having a removable cover 
that is accessible after installation. The conductors, includ- 
ing splices and taps, shall not fill the raceway to more than 
75 percent of its area at that point. Splices and taps in 
surface metal raceways without removable covers shall be 
made only in boxes. All splices and taps shall be made by 
approved methods. 

Taps of Type FC cable installed in surface metal race- 
way shall be made in accordance with 322.56(B). 

386.60 Grounding. Surface metal raceway enclosures pro- 
viding a transition from other wiring methods shall have a 
means for connecting an equipment grounding conductor. 

386.70 Combination Raceways. When combination sur- 
face metallic raceways are used for both signahng and for 
lighting and power circuits, the different systems shall be 
run in separate compartments identified by stamping, im- 
printing, or color coding of the interior finish. 



III. Construction Specifications 

386.100 Construction. Surface metal raceways shall be of 
such construction as will distinguish them from other race- 
ways. Surface metal raceways and their elbows, couplings, 
and similar fittings shall be designed so that the sections 
can be electrically and mechanically coupled together and 
installed without subjecting the wires to abrasion. 

Where covers and accessories of nonmetallic materials 
are used on surface metal raceways, they shall be identified 
for such use. 



C^|;l:y'';r=;")^iCLE'388 ;. 

I. General 

388.1 Scope. This article covers the use, installation, and 
construction specifications for surface nonmetallic race- 
ways and associated fittings. 

388.2 Definition. 

Surface Nonmetallic Raceway. A nonmetallic raceway 
that is intended to be mounted to the surface of a structure, 
with associated couplings, connectors, boxes, and fittings 
for the installation of electrical conductors. 

388.6 Listing Requirements. Surface nonmetallic raceway 
and associated fittings shall be listed. 

II. Installation 

388.10 Uses Permitted. Surface nonmetallic raceway shall 
be permitted as follows: 

(1) The use of surface nonmetallic raceways shall be per- 
mitted in dry locations. 

(2) Extension through walls and floors shall be permitted. 
Surface nonmetallic raceway shall be permitted to pass 
transversely through dry walls, dry partitions, and dry 
floors if the length passing through is unbroken. Access 
to the conductors shall be maintained on both sides of 
the wall, partition, or floor. 

388.12 Uses Not Permitted. Surface nonmetallic raceways 
shall not be used in the following: 

(1) Where concealed, except as permitted in 388.10(2) 

(2) Where subject to severe physical damage 

(3) Where the voltage is 300 volts or more between con- 
ductors, unless listed for higher voltage 

(4) In hoistways 



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388.21 



ARTICLE 390 — UNDERFLOOR RACEWAYS 



(5) In any hazardous (classified) location except Class I, 
Division 2 locations as permitted in 501.10(B)(3) 

(6) Where subject to ambient temperatures exceeding those 
for which the nonmetalhc raceway is listed 

(7) For conductors whose insulation temperature limitations 
would exceed those for which the nonmetallic raceway is 
listed 

388.21 Size of Conductors. No conductor larger than that 
for which the raceway is designed shall be installed in 
surface nonmetallic raceway. 

388.22 Number of Conductors or Cables. The number of 
conductors or cables installed in surface nonmetallic race- 
way shall not be greater than the number for which the 
raceway is designed. Cables shall be permitted to be in- 
stalled where such use is not prohibited by the respective 
cable articles. 

388.56 Splices and Taps. Splices and taps shall be permit- 
ted in surface nonmetallic raceways having a removable 
cover that is accessible after installation. The conductors, 
including splices and taps, shall not fill the raceway to more 
than 75 percent of its area at that point. Splices and taps in 
surface nonmetalhc raceways without removable covers 
shall be made only in boxes. All splices and taps shall be 
made by approved methods. 

388.60 Grounding. Where equipment grounding is re- 
quired, a separate equipment grounding conductor shall be 
installed in the raceway. 

388.70 Combination Raceways. When combination sur- 
face nonmetallic raceways are used both for signaling and 
for lighting and power circuits, the different systems shall 
be run in separate compartments identified by stamping, 
imprinting, or color coding of the interior finish. 

III. Construction Specifications 

388.100 Construction. Surface nonmetallic raceways shall 
be of such construction as will distinguish them from other 
raceways. Surface nonmetalhc raceways and their elbows, 
couphngs, and similar fittings shall be designed so that the 
sections can be mechanically coupled together and installed 
without subjecting the wires to abrasion. 

Surface nonmetallic raceways and fittings are made of 
suitable nonmetallic material that is resistant to moisture 
and chemical atmospheres. It shall also be flame retardant, 
resistant to impact and crushing, resistant to distortion from 
heat under conditions likely to be encountered in service, 
and resistant to low-temperature effects. 

388.120 Marking. Surface nonmetalhc raceways that have 
limited smoke-producing characteristics shall be permitted 
to be so identified. 



390.1 Scope. This article covers the use and installation 
requirements for underfloor raceways. 

390.2 Use. 

(A) Permitted. The installation of underfloor raceways 
shall be permitted beneath the surface of concrete or other 
flooring material or in office occupancies where laid flush 
with the concrete floor and covered with linoleum or 
equivalent floor covering. 

(B) Not Permitted. Underfloor raceways shall not be in- 
stalled (1) where subject to corrosive vapors or (2) in any 
hazardous (classified) locations, except as permitted by 
504.20 and in Class I, Division 2 locations as permitted in 
501.10(B)(3). Unless made of a material judged suitable for 
the condition or unless corrosion protection approved for 
the condition is provided, ferrous or nonferrous metal un- 
derfloor raceways, junction boxes, and fittings shall not be 
installed in concrete or in areas subject to severe corrosive 
influences. 

390.3 Covering. Raceway coverings shall comply with 
390.3(A) through (D). 

(A) Raceways Not Over 100 mm (4 in.) Wide. Half- 
round and flat-top raceways not over 100 mm (4 in.) in 
width shall have not less than 20 mm (¥4 in.) of concrete or 
wood above the raceway. 

Exception: As permitted in 390.3(C) and (D) for flat-top 
raceways. 

(B) Raceways Over 100 mm (4 in.) Wide But Not Over 
200 mm (8 in.) Wide. Flat-top raceways over 100 mm 
(4 in.) but not over 200 mm (8 in.) wide with a minimum of 
25 mm (1 in.) spacing between raceways shall be covered 
with concrete to a depth of not less than 25 mm (1 in.). 
Raceways spaced less than 25 mm (1 in.) apart shall be 
covered with concrete to a depth of 38 mm (IV2 in.). 

(C) Trench-Type Raceways Flush with Concrete. Trench- 
type flush raceways with removable covers shall be permit- 
ted to be laid flush with the floor surface. Such approved 
raceways shall be designed so that the cover plates provide 
adequate mechanical protection and rigidity equivalent to 
junction box covers. 

(D) Other Raceways Flush with Concrete. In office oc- 
cupancies, approved metal flat-top raceways, if not over 
100 mm (4 in.) in width, shall be permitted to be laid flush 
with the concrete floor surface, provided they are covered 



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NATIONAL ELECTRICAL CODE 2005 Edition 



ARTICLE 392 — CABLE TRAYS 



392.3 



with substantial linoleum that is not less than 1.6 mm (Vie 
in.) thick or with equivalent floor covering. Where more 
than one and not more than three single raceways are each 
installed flush with the concrete, they shall be contiguous 
with each other and joined to form a rigid assembly. 

390.4 Size of Conductors. No conductor larger than that 
for which the raceway is designed shah be installed in 
underfloor raceways. 

390.5 Maximum Number of Conductors in Raceway. 

The combined cross-sectional area of all conductors or 
cables shall not exceed 40 percent of the interior cross- 
sectional area of the raceway. 

390.6 Splices and Taps. Splices and taps shall be made 
only in junction boxes. 

For the purposes of this section, so-called loop wiring 
(continuous, unbroken conductor connecting the individual 
outlets) shall not be considered to be a splice or tap. 

Exception: Splices and taps shall be permitted in trench- 
type flush raceway having a removable cover that is acces- 
sible after installation. The conductors, including splices 
and taps, shall not fill more than 75 percent of the raceway 
area at that point. 

390.7 Discontinued Outlets. When an outlet is aban- 
doned, discontinued, or removed, the sections of circuit 
conductors supplying the outlet shall be removed from the 
raceway. No splices or reinsulated conductors, such as 
would be the case with abandoned outlets on loop wiring, 
shall be allowed in raceways. 

390.8 Laid in Straight Lines. Underfloor raceways shall 
be laid so that a straight line from the center of one junction 
box to the center of the next junction box coincides with 
the centerline of the raceway system. Raceways shall be 
firmly held in place to prevent disturbing this alignment 
during construction. 

390.9 Markers at Ends. A suitable marker shall be in- 
stalled at or near each end of each straight run of raceways 
to locate the last insert. 

390.10 Dead Ends. Dead ends of raceways shall be closed. 

390.13 Junction Boxes. Junction boxes shall be leveled to 
the floor grade and sealed to prevent the free entrance of 
water or concrete. Junction boxes used with metal raceways 
shall be metal and shall be electrically continuous with the" 
raceways. 

390.14 Inserts. Inserts shall be leveled and sealed to prevent 
the entrance of concrete. Inserts used with metal raceways 
shall be metal and shall be electrically continuous with the 



raceway. Inserts set in or on fiber raceways before the floor is 
laid shall be mechanically secured to the raceway. Inserts set 
in fiber raceways after the floor is laid shall be screwed into 
the raceway. When cutting through the raceway wall and set- 
ting inserts, chips and other dirt shall not be allowed to remain 
in the raceway, and tools shall be used that are designed so as 
to prevent the tool from entering the raceway and damaging 
conductors that may be in place. 

390.15 Connections to Cabinets and Wall Outlets. Con- 
nections from underfloor raceways to distribution centers 
and wall outlets shall be made by approved fittings or by 
any of the wiring methods in Chapter 3, where installed in 
accordance with the provisions of the respective articles. 

390.17 Ampacity of Conductors. The ampacity adjust- 
ment factors, in 310.15(B)(2), shall apply to conductors 
installed in underfloor raceways. 



ARTICLE 392 

Cable Trays 



392.1 Scope. This article covers cable tray systems, in- 
cluding ladder, ventilated trough, ventilated channel, solid 
bottom, and other similar structures. 

FPN: For further information on cable trays, see 
ANSI/NEMA-VE 1-1998, Metal Cable Tray Systems; 
NEMA-VE 2-1996, Metal Cable Tray Installation Guide- 
lines; and NEMA-FG-1998, Nonmetallic Cable Tray Systems. 

392.2 Definition. 

Cable Tray System. A unit or assembly of units or sections 
and associated fittings forming a structural system used to 
securely fasten or support cables and raceways. 

392.3 Uses Permitted. Cable tray shall be permitted to be 
used as a support system for service conductors, feeders, 
branch circuits, communications circuits, control circuits, 
and signaling circuits. Cable tray installations shall not be 
limited to industrial establishments. Where exposed to di- 
rect rays of the sun, insulated conductors and jacketed 
cables shall be identified as being sunlight resistant. Cable 
trays and their associated fittings shall be identified for the 
intended use. 

(A) Wiring Methods. The wiring methods in Table 392.3(A) 
shall be permitted to be installed in cable tray systems 
under the conditions described in their respective articles 
and sections. 



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392.4 



ARTICLE 392 — CABLE TRAYS 



Table 392.3(A) Wiring Methods 



Wiring Method 


Article Section 


Armored cable 


320 


Communication raceways 


800 


Electrical metallic tubing 


358 


Electrical nonmetallic tubing 


362 


Fire alarm cables 


760 


Flexible metal conduit 


348 


Flexible metallic tubing 


360 


Instrumentation tray cable 


727 


Intermediate metal conduit 


342 


Liquidtight flexible metal 


350 


conduit 




Liquidtight flexible nonmetallic 


356 


conduit 




Metal-clad cable