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20:44:14:01. General definitions. Terms defined in SDCL 36-16-2 have 
the same meaning when used in this article. In addition, terms used in this 
article mean: 

(1) "Commission," the State Electrical Commission; 

(2) "Inspector's report procedure," a procedure that requires the installer 
to notify the inspector regarding the status of the corrections required, as listed 
on an inspector's report by the day specified; 

(3) "Correction order," a notice written by an inspector to the person 
responsible for the electrical installation, listing the violations of this article and 
stating the time allowed for correction; 

(4) "Doorknob card," a card that is left at the door by an inspector when 
no one is home, instructing the homeowner or installer to call the inspector and 
schedule the required inspection; 

(5) "Electrical lineman," a person with a minimum of four years of 
experience with electrical power distribution systems; 

(6) "Electrical school," as referred to in SDCL 36-16-2(4) . a four-year 
educational institution which grants an electrical engineering degree (BSEE) 
and which is accredited by a nationally recognized accreditation agency; 

(7) "Electrical wiring apprenticeship program," a classroom program 
supplemented by a minimum of 144 hours a year of electrical wiring instruction 
in conjunction with the normal 2,000 hours a year of actual electrical wiring 
on-the-job work experience of an apprentice electrician; 

(8) "License," a license issued to a person who qualifies under one of the 
classes defined in SDCL 36-16-2 or is granted reciprocity from another state; 

(9) "Local inspection system," a municipal government or power supplier 
that has complied with commission requirements and which provides local 
electrical inspections under the rules and direction of the commission and 
SDCL chapter 36-16: 

(10) "Modular home" or "modular structure," a home or other structure 
built on a factory assembly line or other construction site to Uniform Building 
Code specifications and transported to its destination in sections or as a 



manufactured home as defined in SDCL 32-7A-1 or a recreational vehicle; 



Contact HelD Privacy PoliCN 



South Dakota Homeoaae 



(11) "National Electrical Code," the National Electrical Code, copyright © 2008 South Dakota 
published by the National Fire Protection Association (2008 edition) with the Legislature, all rights reserved. 
following exceptions: 

(a) Article 100 - definitions - remove the new word "machinery" from 
the definition of "equipment"; 

(b) Eliminate the GFCI requirement for sump pumps, lift stations, 
garage door openers; 

(c) Eliminate GFCI and AFCI requirement for life support equipment 
and like/similar equipment as determined by Authority Having Jurisdiction; 

(12) "Owner's exemption," an exemption from licensure requirements in 
SDCL 36-16-13 for an individual owner who is personally installing electric 
wiring and fixtures in a residence or farmstead which is owned and resided in or 
on by the person installing the electrical wiring or fixtures; 

(13) "Point of service attachment," as referred to in SDCL 36-16-16(1) , 
that point where the power supplier's conductors connect to the consumer's 
conductors; 

(14) "Wiring permit," a form notifying the commission that a described 
electrical installation will be made in accordance with the requirements of this 
article at a described location: 



(15) "Wiring permit—Form B," a wiring permit to be used in an area 
where the commission has approved local inspection systems; 

(16) "Wiring school," a postsecondary school that teaches one or more 
courses in electrical wiring which lasts at least 18 months, consisting of 6 
quarters or 4 semesters. 

Source: SL 1975, ch 16, § 1; 4 SDR 37, effective January 1, 1978; 5 SDR 
1, effective July 20, 1978; 7 SDR 60, effective January 1, 1981; 10 SDR 62, 
effective January 1, 1984; 10 SDR 131, effective June 3, 1984; 12 SDR 92, 
effective January 1, 1986; 12 SDR 151, 12 SDR 155, effective July 1, 1986; 13 
SDR 75, 13 SDR 95, effective January 1, 1987; 16 SDR 153, effective March 
29, 1990; 19 SDR 155, effective April 14, 1993; 20 SDR 222, effective July 6, 
1994; transferred from §20:44:01:01, August 12, 1994; 23 SDR 2, effective 
July 16, 1996; 25 SDR 157, effective July 1, 1999; 28 SDR 83, effective 
December 19, 2001; 28 SDR 178, effective July 1, 2002; 32 SDR 37, effective 
September 1, 2005; 34 SDR 322, effective July 1, 2008. 

General Authority: SDCL 36-16-12. 

Law Implemented: SDCL 36-16-12. 

References: The National Electrical Code, 2008 Edition. National Fire 
Protection Association, Inc., One Batterymarch Park, Quincy, MA 02169-7471. 
Cost: $80. (Price subject to change). 



Uniform Building Code, International Conference of Building Officials. 



Back to 20:44:14 I 20:44:14:01 mM 



NATIONAL ELECTRICAL CODE' 

International Electrical Code® Series 







NFPM 



NFPA 70 



Copyright © 2007 

National Fire Protection Association® 

One Batterymarch Park 

Quincy, Massachusetts 02169-7471 

NFPA 70 is a trademark of the National Fire Protection Association. 

NFPA, National Fire Protection Association, National Electrical Code, and NEC 
are registered trademarks of the National Fire Protection Association. 



IMPORTANT NOTICE ABOUT THIS DOCUMENT 
Notice and Disclaimer of Liability Coeceming the Use of NFPA® Dociumeets 

NFPA codes, standards, recommended practices, and guides, of which the document 
contained herein is one, are developed through a consensus standards development 
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promote fairness in the development of consensus, it does not independently test, evaluate, 
or verify the accuracy of any information or the soundness of any judgments contained in 
its codes and standards. 

The NFPA disclaims liability for any personal injury, property or other damages of any 
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In issuing and making this document available, the NFPA is not undertaking to render 
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using this document should rely on his or her own independentjudgment or, as appropriate, 
seek the advice of a competent professional in determining the exercise of reasonable care 
in any given circumstances. 

The NFPA has no power, nor does it undertake, to police or enforce compliance with the 
contents of this document. Nor does the NFPA list, certify, test or inspect products, designs, 
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Important Notices and Disclaimers continue on inside back cover. 






\^. 



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Copyright © 2007, National Fire Protection Association®. All Rights Reserved 



• 



• 



Natioeal Eleclrkal Code 



® 



This edition of NFPA 70, National Electrical Code, was prepared by the National Electrical Code 
Committee and acted on by NFPA at its June Association Technical Meeting held June 3-7, 2007, in 
Boston, MA. It was issued by the Standards Council on July 26, 2007, with an effective date of August 
15, 2007, and supersedes all previous editions. 

This edition of NFPA 70 was approved as an American National Standard on August 15, 2007. 

History and Bevelopment 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 2005 
National Electrical Code was published by NFPA in July 2006. 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 2005 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. Following the close of the public conmient period, the 
Code-Making Panels met, acted on each comment, and reported their action to the Correlating Com- 
mittee. NFPA published the National Electrical Code Committee Report on Comments in March 2007, 
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 Coimnents were 
presented to the 2007 June 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. At the Electrical Section Codes and Standards 
Review Session held at the 2007 NFPA World Safety Conference and Exposition, Section members 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 2007 June Technical Session. 

This 51st 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, 2002, and 
2005. 

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 such as 
insurance underwriting, building and facilities construction and management, and product testing and 
certification. 

This^20Q8; editiOT 1^ 'the fbHoWiiig Usability feature^ other than 

pditOTial'ffle ffighlighidd for large blocks of 

changed or new text and for new tables and changed or newrfiguresv Where one or more complete 
paragraphs have been deleted, the deleMoh- is^Undicated by- a ibullet (•). between the paragraphs that 
rernain. The index how has dietionary-sty^^^^^ every index 

page; 



2008 Edition NATIONAL ELECTRICAL CODE 70-1 



CONTENTS 



Contents 



ARTICLE 

90 Introduction 70- 21 

Chapter 1 General 

100 Definitions 70- 24 

I. General 70- 24 

II. Over 600 Volts, Nominal 70- 31 

110 Requirements for Electrical Installations 70- 32 

I. Genera] 70- 32 

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 Electrical 
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- 52 

215 Feeders 70- 55 

220 Branch-Circuit, Feeder, and Service 

Calculations 70- 57 

I. General 70- 57 

II. Branch-Circuit Load Calculations 70- 58 

III. Feeder and Service Load Calculations .... 70- 60 

IV. Optional Feeder and Service Load 
Calculations 70- 62 

V. Farm Load Calculations 70- 66 

225 Outside Branch Circuits and Feeders 70- 67 

I. General 70- 67 

II. More Than One Building or Other 

Structure 70- 70 

m. Over 600 Volts 70-72 

230 Services 70- 73 

I. General 70- 73 

II. Overhead Service-Drop Conductors 70- 74 

III. Underground Service-Lateral 

Conductors 70- 75 

IV. Service-Entrance Conductors 70- 76 

V. Service Equipment — General 70- 78 

VI. Service Equipment — Disconnecting 

Means 70- 78 

VII. Service Equipment — Overcurrent 

Protection 70- 80 

VIII. Services Exceeding 600 Volts, 

Nominal 70- 81 

240 Overcurrent Protection 70- 83 

I. General 70- 83 

II. Location 70- 86 



ARTICLE 

m. Enclosures 70- 90 

IV. Disconnecting and Guarding 70- 90 

V. Plug Fuses, Fuseholders, and Adapters . . . 70- 90 

VI. Cartridge Fuses and Fuseholders 70- 91 

VII. Circuit Breakers 70- 91 

VIII. Supervised Industrial Installations 70- 92 

IX. Overcurrent Protection over 600 Volts, 

Nominal 70- 93 

250 Grounding and Bonding 70-94 

I. General 70- 94 

II. System Grounding 70- 97 

III. Grounding Electrode System and 

Grounding Electrode Conductor 70-104 

IV. Enclosure, Raceway, and Service 

Cable GGhhpctipns 70-109 

V Bonding "^*"::....y 70-109 

VI. Equipment Grounding and Equipment 

Grounding Conductors 70-113 

VII. Methods of Equipment Grounding 70- 117 

VIII. Direct-Current Systems 70-120 

IX. Instruments, Meters, and Relays 70-121 

X. Grounding of Systems and Circuits of 

1 kV and Over (High Voltage) 70-121 

280 Surge Arresters, OverrlikV 70-123 

I. General 70-123 

II. Installation 70-124 

III. Connecting Surge Arresters 70-124 

285 Surge^Protaciye^Deviees XSPDs)! T^KV, or 

i$ss^^^:::..!;.^ '::.:: :..'..'..'.:..;^y.:;::.:..r:. 70-124 

I. General 70-124 

IL Installation 70-125 

m. Connecting SPDs 70-125 

Chapter 3 Wiring Methods and Materials 

300 Wiring Methods 70-126 

I. General Requirements 70-126 

II. Requirements for over 600 Volts, 

Nominal 70-136 

310 Conductors for General Wiring 70-138 

312 Cabinets, Cutout Boxes, and Meter Socket 

Enclosures 70-164 

I. Installation 70-164 

II. Construction Specifications 70-165 

314 Outlet, Device, Pull, and Junction Boxes; 
Conduit Bodies; Fittings; and Handhole 
Enclosures 70-167 

I. Scope and General 70-167 

n. Installation 70-168 

III. Construction Specifications 70-174 

IV. Pull and Junction Boxes for Use on 

Systems over 600 Volts, Nominal 70-175 

320 Armored Cable: Type AC 70-175 

L General 70-175 

IL Installation 70-175 



• 



• 



70-2 



NATIONAL ELECTRICAL CODE 2008 Edition 



CONTENTS 



• 



ARTICLE 

ni. Construction Specifications 7(D— 177 

322 Flat Cable Assemblies: Type FC 70-177 

I. General 7(0)-177 

II. Installation 70-177 

III. Construction 70-178 

324 Flat Conductor Cable: Type FCC 70-178 

I. General 70-178 

II. Installation 70-178 

III. Construction 70-180 

326 Integrated Gas Spacer Cable: Type IGS 70-180 

I. General 70-180 

II. Installation 70-180 

III. Construction Specifications 70-181 

328 Medium Voltage Cable: Type MV 7(0^1 8 1 

I. General 70-181 

II. Installation 70-181 

III. Construction Specifications 70-182 

330 Metal-Clad Cable: Type MC 70-182 

I. General 70-182 

II. Installation 70-182 

III. Construction Specifications 70-183 

332 Mineral-Insulated, Metal- Sheathed Cable: 

Type MI 70-184 

I. General 70-184 

II. Installation 70-184 

III. Construction Specifications 70-185 

334 Nonmetallic-Sheathed Cable: Types NM, 

NMC, andNMS 70-185 

I. General 70-185 

II. Installation 70-185 

III. Construction Specifications 70-187 

336 Power and Control Tray Cable: Type TC ....70-188 

I. General 70-188 

II. Installation 70-188 

III. Construction Specifications 70-188 

338 Service-Entrance Cable: Types SE and 

USE 70-189 

I. General 70-189 

II. Installation 70-189 

III. Construction 70-190 

340 Underground Feeder and Branch-Circuit 

Cable: Type UF 70-190 

I. General 70-190 

II. Installation 70-190 

III. Construction Specifications 70-191 

342 Intermediate Metal Conduit: Type IMC 70- 1 9 1 

I. General 70-191 

II. Installation 70-191 

III. Construction Specifications 70-192 

344 Rigid Metal Conduit: Type RMC 70-192 

I. General 70-192 

II. Installation 70-193 

III. Construction Specifications 70-194 



ARTICLE 

348 Flexible Metal Conduit: Type FMC 70-194 

I. General 70-194 

II. Installation 70-195 

350 Liquidtight Flexible Metal Conduit: Type 

LFMC 70-196 

I. General 70-196 

II. Installation 70-196 

III. Construction Specifications 70-197 

352 Rigid Polyvinyl Chloride Conduit: Type 

PVC 70-197 

I. General 70-197 

II. Installation 70-197 

III. Construction Specifications 70-200 

353 High Density Polyethylene Conduit: Type 

HOPE Conduit 70-200 

I. General 70-200 

II. Installation 70-200 

III. Construction Specifications 70-201 

354 Nonmetallic Underground Conduit with 
Conductors: Type NUCC 70-201 

I. General 70-201 

II. Installation 70-201 

III. Construction Specifications 70-202 

355 Reinforced Thermosetting Resin Conduit: 
TypeRTRC : 70-203 

I. General 70-203 

II. Installation 70-203 

in. Construction Specifications 70-204 

356 Liquidtight Flexible Nonmetallic Conduit: 
TypeLFNC 70-205 

I. General 70-205 

II. Installation 70-206 

III. Construction Specifications 70-207 

358 Electrical Metallic Tubing: Type EMT 70-207 

I. General 70-207 

n. Installation 70-207 

III. Construction Specifications 70-208 

360 Flexible Metallic Tubing: Type EMT 70-208 

I. General 70-208 

II. Installation 70-209 

III. Construction Specifications 70-209 

362 Electrical Nonmetallic Tubing: Type ENT ...70-210 

I. General 70-210 

II. Installation 70-210 

III. Construction Specifications 70-211 

366 Auxiliary Gutters 70-212 

I. General 70-212 

II. Installation 70-212 

III. Construction Specifications 70-213 

368 Busways 70-214 

I. General Requirements 70-214 

II. Installation 70-214 

III. Construction 70-215 



2008 Edition NATIONAL ELECTRICAL CODE 



)-3 



CONTENTS 



ARTICLE 

IV. Requirements for Over 600 Volts, 

Nominal 70-216 

370 Cablebus 70-216 

372 Cellular Concrete Floor Raceways 70-217 

374 Cellular Metal Floor Raceways 70-2 1 8 

I. Installation 70-219 

II. Construction Specifications 70-219 

376 Metal Wireways 70-219 

I. General 70-219 

II. Installation 70-219 

III. Construction Specifications 70-220 

378 Nonmetallic Wireways 70-221 

I. General 70-221 

II. Installation 70-221 

III. Construction Specifications 70-222 

380 Multioutlet Assembly 70-222 

382 Nonmetallic Extensions 70-222 

I. General 70-222 

II. Installation 70-223 

ni- GDristraetionfSpeiinfic 
(Gbricealable: NorimetalUo 

sffl^f '^r^^t^"^." ^T^'7.'rr:r^*^! iz:~. :i'.7:'::! 70-224 

3 84 Strut-Type Channel Raceway 70-224 

I. General 70-224 

II. Installation 70-224 

III. Construction Specifications 70-225 

386 Surface Metal Raceways 70-226 

I. General 70-226 

II. Installation 70-226 

III. Construction Specifications 70-226 

388 Surface Nonmetallic Raceways 70-227 

I. General 70-227 

II. Installation 70-227 

III. Construction Specifications 70-227 

390 Underfloor Raceways 70-228 

392 Cable Trays 70-229 

394 Concealed Knob-and-Tube Wiring 70-235 

I. General 70-235 

II. Installation 70-236 

III. Construction Specifications 70-236 

396 Messenger-Supported Wiring 70-237 

I. General 70-237 

II. Installation 70-237 

398 Open Wiring on Insulators 70-237 

I. General 70-237 

II. Installation 70-238 

III. Construction Specifications 70-239 

Chapter 4 Equipment for General Use 

400 Flexible Cords and Cables 70-240 

I. General 70-240 



ARTICLE 

II. Construction Specifications 70-249 

III. Portable Cables Over 600 Volts, 

Nominal 70-250 

402 Fixture Wires 70-251 

404 Switches 70-255 

I. Installation 70-255 

II. Construction Specifications 70-258 

406 Receptacles, Cord Connectors, and 

Attachment Plugs (Caps) 70-258 

408 Switchboards and Panelboards 70-262 

I. General 70-262 

U. Switchboards 70-263 

III. Panelboards 70-263 

IV. Construction Specifications 70-264 

409 Industrial Control Panels 70-265 

I. General 70-265 

II. Installation 70-266 

III. Construction Specifications 70-266 

410 Luminaires, Lampholders, and Lamps 70-267 

I. General 70-267 

II. Luminaire Locations 70-268 

III. Provisions at Luminaire Outlet Boxes, 
Canopies, and Pans 70-269 

IV. Luminaire Supports 70-269 

V. Grounding 70-270 

VI. Wiring of Luminaires 70-271 

VII. Construction of Luminaires 70-272 

VIII. Installation of Lampholders 70-27 3 

IX. Construction of Lampholders 70-273 

X. Lamps and Auxiliary Equipment 70-274 

XI. Special Provisions for Flush and 

Recessed Luminaires 70-274 

XII. Construction of Flush and Recessed 

Luminaires 70-274 

XIII. Special Provisions for 
Electric-Discharge Lighting Systems of 

1000 Volts or Less 70-274 

XIV. Special Provisions for 
Electric-Discharge Lighting Systems of 

More Than 1000 Volts 70-276 

XV. Lighting Track 70-277 

XVI. Decorative Lighting and Similar 

Accessories 70-277 

411 Lighting Systems Operating at 30 Volts or 

Less 70-278 

422 Appliances 70-278 

I. General 70-278 

IL Installation 70-279 

III. Disconnecting Means 70-28 1 

IV. Construction 70-282 

V. Marking 70-283 

424 Fixed Electric Space-Heating Equipment 70-284 

L General 70-284 

n. Installation 70-284 

III. Control and Protection of Fixed 

Electric Space-Heating Equipment 70-284 

IV. Marking of Heating Equipment 70-286 



• 



• 



70^ 



NATIONAL ELECTRICAL CODE 2008 Edition 



CONTENTS 



ARTICLE 

V. Electric Space-Heating Cables 70-286 

VI. Duct Heaters 70-288 

VII. Resistance-Type Boilers 70-289 

VIII. Electrode-Type Boilers 70-290 

IX. Electric Radiant Heating Panels and 

Heating Panel Sets 70-290 

426 Fixed Outdoor Electric Deicing and 
Snow-Melting Equipment 70-292 

I. General 70-292 

II. Installation 70-293 

ni. Resistance Heating Elements 70-293 

IV. Impedance Heating 70-294 

V. Skin-Effect Heating 70-294 

VI. Control and Protection 70-295 

427 Fixed Electric Heating Equipment for 

Pipelines and Vessels 70-295 

I. General 70-295 

II. Installation 70-296 

III. Resistance Heating Elements 70-296 

IV. Impedance Heating 70-297 

V. Induction Heating 70-297 

VI. Skin-Effect Heating 70-298 

VII. Control and Protection 70-298 

430 Motors, Motor Circuits, and Controllers 70-298 

I. General 70-298 

II. Motor Circuit Conductors 70-304 

III. Motor and Branch-Circuit Overload 

Protection 70-306 

IV. Motor Branch-Circuit Short-Circuit 

and Ground-Fault Protection 70-3 1 

V. Motor Feeder Short-Circuit and 

Ground-Fault Protection 70-313 

VI. Motor Control Circuits 70-313 

VII. Motor Controllers 70-315 

VIII. Motor Control Centers 70-316 

IX. Disconnecting Means 70-317 

X. Adjustable-Speed Drive Systems 70-320 

XI. Over 600 Volts, Nominal 70-321 

XII. Protection of Live Parts — All 

Voltages 70-322 

XIII. Grounding — All Voltages 70-323 

XIV. Tables 70-324 

440 Air-Conditioning and Refrigerating 

Equipment 70-327 

I. General 70-327 

II. Disconnecting Means 70-329 

III. Branch-Circuit Short-Circuit and 
Ground-Fault Protection 70-330 

IV. Branch-Circuit Conductors 70-33 1 

V. Controllers for Motor-Compressors 70-331 

VI. Motor-Compressor and Branch-Circuit 

Overload Protection 70-332 

VII. Provisions for Room Air Conditioners .... 70-333 

445 Generators 70-334 

450 Transformers and Transformer Vaults 

(Including Secondary Ties) 70-335 

I. General Provisions 70-335 

II. Specific Provisions Applicable to 

Different Types of Transformers 70-339 



ARTICLE 

III. Transformer Vaults 70-341 

455 Phase Converters 70-342 

I. General 70-342 

II. Specific Provisions Applicable to 

Different Types of Phase Converters 70-343 

460 Capacitors 70-344 

I. 600 Volts, Nominal, and Under 70-344 

n. Over 600 Volts, Nominal 70-344 

470 Resistors and Reactors 70-345 

I. 600 Volts, Nominal, and Under 70-345 

II. Over 600 Volts, Nominal 70-346 

480 Storage Batteries 70-346 

490 Equipment, Over 600 Volts, Nominal 70-347 

I. General 70-347 

II. Equipment — Specific Provisions 70-347 

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

Assemblies 70-350 

IV. Mobile and Portable Equipment 70-352 

V. Electrode-Type Boilers 70-352 

Chapter 5 Special Occupamcies 

500 Hazardous (Classified) Locations, Classes 

I, n, and m. Divisions 1 and 2 70-354 

501 Class I Locations 70-362 

L General 70-362 

n. Wiring 70-363 

m. Equipment 70-368 

502 Class II Locations 70-372 

L General 70-372 

n. Wiring 70-372 

m. Equipment 70-374 

503 Class m Locations 70-378 

L General 70-378 

IL Wiring 70-378 

III. Equipment 70-379 

504 Intrinsically Safe Systems 70-380 

505 Class L Zone 0, 1, and 2 Locations 70-384 

506 Zone 20, 21, and 22 Locations for 
Combustible Dusts orTgnitibre: 

Fibere/Flyihgs !:7.:.:: '. .:.7^ 70-398 

510 Hazardous (Classified) Locations — 

Specific 70-404 

511 Commercial Garages, Repair and Storage .... 70-404 

513 Aircraft Hangars 70^07 

514 Motor Fuel Dispensing Facilities 70-410 

515 Bulk Storage Plants 70-414 

516 Spray Application, Dipping, and Coating 

Processes 70-419 

517 Health Care Facilities 70-425 

L General 70-425 



2008 Edition NATIONAL ELECTRICAL CODE 



7®-5 



CONTENTS 



ARTICLE 

II. Wiring and Protection 70^27 

III. Essential Electrical System 70-430 

IV. Inhalation Anesthetizing Locations 70-437 

V. X-Ray Installations 70^40 

VI. Communications, Signaling Systems, 

Data Systems, Fire Alarm Systems, 

and Systems Less Than 120 Volts, 

Nominal 70^41 

VII. Isolated Power Systems 70^42 

518 Assembly Occupancies 70-443 

520 Theaters, Audience Areas of Motion 
Picture and Television Studios, 
Performance Areas, and Similar Locations ... 70^44 

I. General 70^44 

II. Fixed Stage Switchboards 70^46 

III. Fixed Stage Equipment Other Than 
Switchboards 70^47 

IV. Portable Switchboards on Stage 70-448 

V. Portable Stage Equipment Other Than 

Switchboards 70^51 

VL Dressing Rooms 70^52 

VII. Grounding 70-453 

522 Control Systems for Permanent 

Amusement Attractions 70^53 

I. General 70^53 

II. Control Circuits 70-453 

III. Control Circuit Wiring Methods 70^54 

525 Carnivals, Circuses, Fairs, and Similar 

Events 70^55 

I. General Requirements 70-455 

IL Power Sources 70-455 

III. Wiring Methods 70-456 

IV. Grounding and Bonding 70-457 

530 Motion Picture and Television Studios 

and Similar Locations 70—457 

L General 70-457 

n. Stage or Set 70^58 

III. Dressing Rooms 70-460 

IV. Viewing, Cutting, and Patching Tables .... 70^60 
V Cellulose Nitrate Film Storage Vaults 70-460 

VL Substations 70^60 

540 Motion Picture Projection Rooms 70^61 

I. General 70^61 

II. Equipment and Projectors of the 

Professional Type 70^61 

III. Nonprofessional Projectors 70-462 

IV. Audio Signal Processing, 
Amplification, and Reproduction 

Equipment 70—462 

545 Manufactured Buildings 70-^62 

547 Agricultural Buildings 70-463 

550 Mobile Homes, Manufactured Homes, and 

Mobile Home Parks 70-466 

I. General 70-466 

II. Mobile and Manufactured Homes 70^67 

III. Services and Feeders 70-474 



ARTICLE 

551 Recreational Vehicles and Recreational 

Vehicle Parks 70-475 

L General 70-475 

II. Combination Electrical Systems 70^77 

m. Other Power Sources 70-477 

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

Systems 70-478 

V. Factory Tests 70-485 

VI. Recreational Vehicle Parks 70^85 

552 Park Trailers 70^88 

L General 70-488 

II. Low- Voltage Systems 70-488 

III. Combination Electrical Systems 70^89 

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

Systems 70^90 

V. Factory Tests 70-496 

553 Floating Buildings 70^97 

L General 70^97 

II. Services and Feeders 70-497 

III. Grounding 70-497 

555 Marinas and Boatyards 70-498 

590 Temporary Installations 70-501 

Chapter 6 Special Equipment 

600 Electric Signs and Outline Lighting 70-504 

I. General 70-504 

II. Field-Installed Skeleton Tubing and 

Wiring 70-508 

604 Manufactured Wiring Systems 70-509 

605 Office Furnishings (Consisting of Lighting 
Accessories and Wired Partitions) 70-5 1 

610 Cranes and Hoists 70-511 

I. General 70-511 

II. Wiring 70-512 

III. Contact Conductors 70-514 

IV. Disconnecting Means 70-515 

V. Overcurrent Protection 70-5 15 

VI. Control 70-516 

VIL Grounding 70-516 

620 Elevators, Dumbwaiters, Escalators, 
Moving Walks, Platform Lifts, and 
Stairway Chairlifts 70-517 

L General 70-517 

IL Conductors 70-519 

m. Wiring 70-520 

IV. Installation of Conductors 70-523 

V. Traveling Cables 70-523 

VI. Disconnecting Means and Control 70-524 

VII. Overcurrent Protection 70-526 

VIII. Machine Rooms, Control Rooms, 

Machinery Spaces, and Control Spaces .... 70-526 

IX. Grounding 70-527 

X. Emergency and Standby Power 

Systems 70-527 

625 Electric Vehicle Charging System 70-527 

L General 70-527 



• 



70-6 



NATIONAL ELECTRICAL CODE 2008 Edition 



CONTENTS 



ARTICLE 

II. Wiring Methods 7(D-528 

III. Equipment Construction 70-528 

IV. Control and Protection 70-529 

V. Electric Vehicle Supply Equipment 

Locations 7<[)-529 

626 Elecdified Truck Faffing Spaces 70-531 

I. General 70-531 

II. Electrified Truck Parking Spaces 

Electrical Wiring Systems 70-532 

III. Electrified Truck Parking Space Supply 
Equipment 70-533 

IV. Transport Refrigerated Units (TRUs) 70-535 

630 Electric Welders 70-536 

I. General 70-536 

II. Arc Welders 70-536 

III. Resistance Welders 70-537 

IV. Welding Cable 70-538 

640 Audio Signal Processing, Amplification, 

and Reproduction Equipment 70-538 

I. General 70-538 

II. Permanent Audio System Installations .... 70-542 
III. Portable and Temporary Audio System 

Installations 70-542 

645 Information Technology Equipment 70-544 

647 Sensitive Electronic Equipment 70-546 

650 Pipe Organs 70-547 

660 X-Ray Equipment 70-548 

I. General 70-548 

II. Control 70-549 

III. Transformers and Capacitors 70-549 

IV. Guarding and Grounding 70-549 

665 Induction and Dielectric Heating 

Equipment 70-550 

I. General 70-550 

n. Guarding, Grounding, and Labeling 70-55 1 

668 Electrolytic Cells 70-551 

669 Electroplating 70-554 

670 Industrial Machinery 70-555 

675 Electrically Driven or Controlled 

Irrigation Machines 70-556 

L General 70-556 

II. Center Pivot Irrigation Machines 70-55 8 

680 Swimming Pools, Fountains, and Similar 

Installations 70-558 

L General 70-558 

II. Permanently Installed Pools 70-56 1 

III. Storable Pools 70-568 

IV. Spas and Hot Tubs 70-568 

V Fountains 70-570 

VI. Pools and Tubs for Therapeutic Use 70-572 

VII. Hydromassage Bathtubs 70-572 

682 Natural and Artificially Made Bodies of 

Water 70-573 

L General 70-573 



ARTICLE 

n. Installation 70-573 

III. Grounding and Bonding 70-574 

685 Integrated Electrical Systems 70-575 

I. General 70-575 

n. Orderly Shutdown 70-575 

690 Solar Photovoltaic Systems 70-575 

I. General 70-575 

II. Circuit Requirements 70-578 

III. Disconnecting Means 70-580 

IV. Wiring Methods 70-581 

V Grounding 70-583 

VI. Marking 70-585 

VII. Connection to Other Sources 70-585 

Vm. Storage Batteries 70-587 

IX. Systems over 600 Volts 70-588 

692 Fuel Cell Systems 70-588 

I. General 70-588 

II. Circuit Requirements 70-589 

III. Disconnecting Means 70-589 

IV. Wiring Methods 70-590 

V. Grounding 70-590 

VL Marking 70-590 

VII. Connection to Other Circuits 70-590 

VIII. Outputs Over 600 Volts 70-591 

695 Fire Pumps 70-591 



Chapter 7 Special CoedHtlons 

700 Emergency Systems 70-596 

I. General 70-596 

II. Circuit Wiring 70-597 

III. Sources of Power 70-598 

IV Emergency System Circuits for 

Lighting and Power 70-600 

V. Control — Emergency Lighting 

Circuits 70-600 

VI. Overcurrent Protection 70-600 

70 1 Legally Required Standby Systems 70-60 1 

L General 70-601 

IL Circuit Wiring 70-602 

III. Sources of Power 70-602 

IV. Overcurrent Protection 70-603 

702 Optional Standby Systems 70-604 

I. General 70-604 

II. Circuit Wiring 70-605 

III. Grounding 70-605 

IV. Sources of Power 70-605 

705 Interconnected Electric Power Production 

Sources 70-605 

L General 70-605 

IL Utility-Interactive Inverters 70-608 

m. Generators 70-609 

(708 Critical Operations Power Systems 

(gM) :::.:..::..:.:;:..:..::.::.::... 70-609 

L General 70-609 

II. Circuit Wiring and Equipment 70-6 1 



2008 Edition NATIONAL ELECTRICAL CODE 



70-7 



CONTENTS 



ARTICLE 

III. Power Sources and Connection 70-6 1 2 

IV. Overcurrent Protection 70-613 

V. System Performance and Analysis 70-6 1 4 

720 Circuits and Equipment Operating at Less 

Than 50 Volts 70-614 

725 Class 1, Class 2, and Class 3 

Remote-Control, Signaling, and 

Power-Limited Circuits 70-614 

L General 70-614 

II. Class 1 Circuits 70-615 

III. Class 2 and Class 3 Circuits 70-617 

IV. Listing Requirements 70-622 

727 Instrumentation Tray Cable: Type ITC 70-624 

760 Fire Alarm Systems 70-625 

I. General 70-625 

II. Non-Power-Limited Fire Alarm 

(NPLFA) Circuits 70-626 

III. Power-Limited Fire Alarm (PLFA) 

Circuits 70-628 

IV. Listing Requirements 70-63 1 

770 Optical Fiber Cables and Raceways 70-63 3 

I. General 70-633 

IL CablesiOutsideianiiEntOT^ 

Bimdingi; "r..„...*r.7^^.7.. 70-634 

IIL Protection 70-635 

I^ GrouridinglCleras 70-635 

VJ InstaliSionfMethodsJp^i^ .... 70-636 
VI, Listing Requirements 70-638 

Chapter 8 Communications Systems 

800 Communications Circuits 70-640 

I. General 70-640 

II. Wires and Cables Outside and 

Entering Buildings 70-641 

III. Protection 70-642 

IV. Grounding Methods 70-644 

V. Installation; MetK^^^^^ ...70-645 

VI. Listing Requirements 70-647 

810 Radio and Television Equipment 70-649 

I. General 70-649 

II. Receiving Equipment — Antenna 

Systems 70-650 

III. Amateur Transmitting and Receiving 

Stations — Antenna Systems 70-652 

IV. Interior Installation — Transmitting 

Stations 70-653 

820 Community Antenna Television and Radio 

Distribution Systems 70-653 

I. General 70-653 

II. Coaxial Cables Outside and Entering 

Buildings 70-654 



ARTICLE 

m. Protection 70-655 

IV. Grounding Methods 70-656 

V. liistallatiorirMethOds. Within Buildings .... 70-657 

VI. Listing Requirements 70-659 

830 Network-Powered Broadband 

Communications Systems 70-660 

L General 70-660 

II. Cables Outside and Entering Buildings ... 70-662 

III. Protection 70-664 

IV. Grounding Methods 70-666 

V. Installatipri Methods Within Buildings .... 70-667 

VI. Listing Requirements 70-669 

TABLES 

Chapter 9 Tables 

1 Percent of Cross Section of Conduit and 

Tubing for Conductors 70-67 1 

2 Radius of Conduit and Tubing Bends 70-671 

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) 70-672 

5 Dimensions of Insulated Conductors and 

Fixture Wires 70-676 

5A Compact Coppeifahd Aluminum Building 

Wire Nominal Dimensions and Areas 70-680 

8 Conductor Properties 70-68 1 

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

Conductors in Conduit 70-682 

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

Power Source Limitations 70-684 

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

Source Limitations 70-684 

12(A) PLFA Alternating-Current Power Source 

Limitations 70-685 

12(B) PLFA Direct-Current Power Source 

Limitations 70-685 

AnnexA 70-686 

Annex B 70-689 

Annexe 70-703 

Annex D 70-763 

Annex E 70-773 

Annex F 70-774 

Annex G 70-776 

Annex H 70-778 

Index 70-785 



• 



70-8 



NATIONAL ELECTRICAL CODE 2008 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. 



Teclmkal Correlating Committee 



• 



James W. Carpenter, Chair 
International Association of Electrical Inspectors, TX [E] 

Mark W. Earley, Secretary 
National Fire Protection Association, MA 
(nonvoting) 

Jean A. O'Connor, Recording Secretary 
National Fire Protection Association, MA 
(nonvoting) 



James E. Brunssen, Telcordia Technologies, Inc., NJ [UT] 

Rep. Alliance for Telecommunications Industry Solutions 
Merton W. Bunker, Jr., U.S. Department of State, VA [U] 

(VL to Document: 110, Document: 111, Document: 70, 

Document: 70B, Document: 70E, Document: 79) 
WiMiam R. Drake, Marinco, CA [M] 
Palmer L. Hickman, National Joint Apprentice & Training 
Committee, MD [L] 

Rep. International Brotherhood of Electrical Workers 
John R. Kovacik, Underwriters Laboratories Inc., IL [RT] 
WiMiam M. Lewis, Martinsville, IN [U] 

Rep. American Chemistry Council 
Jim Pauley, Square D Company/Schneider Electric, KY [M] 

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

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

Rep. Electric Light & Power Group/EEI 
Robert G. Wilkinson, lEC Texas Gulf Coast, TX [IM] 

Rep. Independent Electrical Contractors, Inc. 

Alternates 

Jeffrey Boksiner, Telcordia Technologies, Inc., NJ [UT] 
(Alt. to J. E. Brunssen) 



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

(Alt. to J. Pauley) 
Stanley J. Folz, Morse Electric Company, NV [IM] 

(Alt. to M. D. Toman) 
David L. Hittinger, lEC of Greater Cincinnati, OH [IM] 

(Alt. to R. G. Wilkinson) 
Neil E LaBrake, Jr., National Grid, NY [UT] 

(Alt. to J. W. Troglia) 
Danny Liggett, Dupont Company, TX [U] 

(Alt. to W. M. Lewis) 
Mark C. Ode, Underwriters Laboratories Inc., NC [RT] 

(Alt. to J. R. Kovacik) 
Richard P. Ov^en, City of St. Paul, MN [E] 

(Alt. to J. W. Carpenter) 

Nonvoting 

David Mascarenhas, Canadian Standards Association, 
Canada [RT] 

Richard G. Biermann, Biermann Electric Company, Inc., 
lA [IM] 

(Member Emeritus) 
D. Harold Ware, Libra Electric Company, OK [IM] 

(Member Emeritus) 



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. 



CODE-MAKING PANEL NO. 1 

A, Amiex G 



John D. Minick, Chair 
National Electrical Manufacturers Association, TX [M] 



Michael A. Anthony, University of Michigan, MI [U] 

Rep. Association of Higher Education Facilities OfBcers 
Louis A. Barrios, Shell Global Solutions, TX [U] 

Rep. American Chemistry Council 
Kenneth F. Boyce, Underwriters Laboratories Inc., IL [RT] 
William T. Fiske, Intertek Testing Services NA, Inc., NY [RT] 
H. Landis Floyd, The DuPont Company, DE [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
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 Conu^actors, Inc. 
Neil F. LaBrake, Jr., National Grid, NY [UT] 

Rep. Electric Light & Power Group/EEI 
Randall R. McCarver, Telcordia Technologies, Inc., 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] 



2008 Edition 



NATIONAL ELECTRICAL CODE 



NATIONAL ELECTRICAL CODE COMMITTEE 



Alternates 

Mark Christian, IBEW Local Union 175, TN [L] 

(Alt. to P. L. Hickman) 
Benjamin F. Dunford, Ben Dunford Electric Company Inc. 
TN [IM] 

(Alt. to D. L. Hittinger) 
Ernest J. Gallo, Telcordia Technologies, Inc., NJ [U] 

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

(Alt. to L. G. McMahill) 
Donald H. McCullough, II, Washington Savannah River 
Company, SC [U] 

(Alt. to H. L. Floyd) 



Gil Moniz, National Electrical Manufacturers Association, 
MA[M] 

(Alt. to J. D. Minick) 
Alfredo M Ramirez, Underwriters Laboratories Inc., IL [RT] 

(Alt. to K. R Boyce) 
John W. Troglia, Edison Electric Institute, WI [UT] 

(Alt. to N. F. LaBrake, Jr.) 

Nonvoting 

Ark Tsisserev, City of Vancouver, Canada 

Rep. CSA/Canadian Electrical Code Committee 



CODE-MAKING PANEL NO. 2 
Articles 210, 215, 220, Annex D, Chapter 9 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, Inc., 
WA[U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Lawrence Brown, National Association of Home Builders, 
DC [U] 

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

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 
Robert L. LaRocca, Underwriters Laboratories Inc., NY [RT] 
Brian J. Nenninger, The Dow Chemical Company, TX [U] 

Rep. American Chemistry Council 
Jim Pauley, Square D Company/Schneider Electric, KY [M] 

Rep. National Electrical Manufacturers Association 
Ronald L. Purvis, Sharpsburg, GA [UT] 

Rep. Electric Light & Power Group/EEI 
Michael D. Toman, MEGA Power Electrical Services, Inc., 
MD [IM] 

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

Rep. Independent Electrical Contractors, Inc. 



Alternates 

James E. Degnan, SparUng, WA [U] 

(Alt. to R. W. Becker) 
David A. Dini, Underwriters Laboratories Inc., IL [RT] 

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

(Alt. to J. Pauley) 
William Ross McCorcle, American Electric Power, OK [UT] 

(Alt. to R. L. Purvis) 
William J. McGovern, City of Piano, TX [E] 

(Alt. to R. W. Weber) 
Clifford L Rediger, Independent Electrical Contractors 
Training Fund, CO [IM] 

(Alt. to R. G. Wilkinson) 
Janet D. Skipper, IBEW Local Union 606, FL [L] 

(Alt. to D. M. King) 
Joseph E. Wiehagen, National Association of Home 
Builders, MD [U] 

(Alt. to L. Brown) 

Nonvoting 

William Burr, Canadian Standards Association, Canada [RT] 
Douglas A. Lee, U.S. Consumer Product Safety 
Commission, MD [C] 

Andrew M. Trotta, U.S. Consumer Product Safety 
Commission, MD [C] 



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, Inc., OH [IM] 

Rep. Independent Electrical Contractors, Inc. 
Paul J. Casparro, Scranton Electricians JATC, 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, Inc. 
Thomas J. Guida, Underwriters Laboratories Inc., NY [RT] 
Ray R. R. Keden, ERICO, Inc., CA [M] 

Rep. Building Industry Consulting Services International 



Ronald E. Maassen, Lemberg Electric Company, Inc., 
WI [IM] 

Rep. National Electrical Contractors Association 
Juan C. Menendez, Southern California Edison Company, 
CA [UT] 

Rep. Electric Light & Power Group/EEI 
Steven J. Owen, Steven J. Owen, Inc., AL [IM] 

Rep. Associated Builders & Contractors, Inc. 
David A. Pace, Ohn Corporation, AL [U] 

Rep. American Chemistry Council 



70-10 



NATIONAL ELECTRICAL CODE 2008 Edition 



NATIONAL ELECTRICAL CODE COMMITTEE 



Melvin K. Sanders, Things Electrical Co., Inc. 
(TECo., Inc.), lA [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Johm E. Sleights, St. Paul Travelers, CT [I] 

Alternates 
Shame M. Clary, Bay Alarm Company, CA [M] 

(Alt. to S. E. Egesdal) 
Adam D. Corbimi, Corbin Electrical Services, Inc., NJ [IM] 

(Alt. to L. S. Ayer) 
Danny Liggett, Dupont Company, TX [U] 

(Alt. to D. A. Pace) 
T. David Mills, Bechtel Savannah River, Inc., SC [U] 

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

(Alt. to T. J. Guida) 



Roger S. Passmore, Davis Electrical Constructors, Inc., SC 
[IM] 

(Alt. to S. J. Owen) 
Marty L. Riesberg, IBEW Local Union 22, MD [L] 

(Alt. to P. J. Casparro) 
George A. Straniero, Tyco/AFC Cable Systems, Inc., NJ 
[M] 

(Alt. to L. Easter) 
Robert J. Walsh, City of Hayward, CA [E] 

(Alt. to R. R Owen) 

Nonvotinig 

Edv^ard C. Lawry, Oregon, WI [E] 
(Member Emeritus) 



James M. Naeghton, Chair 
IBEW Local Union 103, MA [L] 
Rep. International Brotherhood of Electrical Workers 



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

Rep. Electric Light & Power Group/EEI 
Malcolm Allison, Ferraz Shawmut, MA [M] 
Robert J. Deaton, The Dow Chemical Company, TX [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Howard D. Hughes, Hughes Electric Company Inc., AR [IM] 

Rep. National Electrical Contractors Association 
Mark C. Ode, Underwriters Laboratories Inc., NC [RT] 
James J. Rogers, Towns of Oak BluflFs, Tisbury, West 
Tisbury, MA [E] 

Rep. International Association of Electrical Inspectors 
John A. Sigmund, PPG Industries, Inc., LA [U] 

Rep. American Chemistry Council 
John W. Young, Siemens Energy & Automation, Inc., GA [M] 

Rep. National Electrical Manufacturers Association 
Vincent Zinnante, Advantage Electi-ic, Inc., TX [IM] 

Rep. Independent Electrical Contractors, Inc. 



Paul D. Barnhart, Underwriters Laboratories Inc., NC [RT] 

(Alt. to M. C. Ode) 
Mark D. Gibbs, BWXT Y-12, LLC, TN [U] 

(Alt. to R. J. Deaton) 
Kenneth W. Hengst, EAS Conti-acting, LP, TX [IM] 

(Alt. to V. Zinnante) 
Mark R. Hilbert, State of New Hampshire, NH [E] 

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

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

(Alt. to J. M. Naughton) 
Peter R. Walsh, Ferraz Shawmut, MA [M] 

(Alt. to M. Allison) 



• 



Ronald J. Toomer, Chair 
Toomer Electrical Company Inc., LA [IM] 
Rep. National Electrical Contractors Association 



JeiBfrey Boksiner, Telcordia Technologies, Inc., NJ [UT] 

Rep. Alliance for Telecommunications Industry Solutions 
David Brender, Copper Development Association, Inc., NY 
[M] 

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

Rep. American Iron and Steel Institute 
Paul Dobrowsky, Innovative Technology Services, NY [U] 

Rep. American Chemistry Council 
Dan Hammel, IBEW Local Union 704, lA [L] 

Rep. International Brotherhood of Electrical Workers 
G. Scott Harding, F. B. Harding, Inc., MD [IM] 

Rep. Independent Electrical Contractors, Inc. 
William J. Helfrich, U.S. Department of Labor, PA [E] 
Michael J. Johnston, International Association of Electrical 
Inspectors, TX [E] 
Chuck MeOo, Underwriters Laboratories Inc., WA [RT] 



Daleep C. Mohla, DCM Electrical Consulting Services, Inc., 
TX [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Gregory J. Steinman, Thomas & Betts Corporation, TN [M] 

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

Rep. Power Tool Institute, Inc 
Richard Temblador, Southwire Company, GA [M] 

Rep. The Aluminum Association 
C. Douglas White, CenterPoint Energy, Inc., TX [UT] 

Rep. Electric Light & Power Group/EEI 



Harold G. Alexander, American Electric Power, OH [UT] 

(Alt. to C. D. White) 
Ron D. Alley, Northern New Mexico lEC, NM [IM] 

(Alt. to G. S. Harding) 



2008 Edition NATIONAL ELECTRICAL CODE 



)-ll 



NATIONAL ELECTRICAL CODE COMMITTEE 



Joseph P. DeGregoria, Underwriters Laboratories Inc., NY 
[RT] 

(Alt. to C. Mello) 
Ronald Lai, FCI Electrical, NH [M] 

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

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

(Alt. to M. J. Brett, Jr.) 
Michael E. McNeil, FMC Corporation/Bio Polymer, ME [U] 

(Alt. to P. Dobrowsky) 
Nathan Philips, Integrated Electronic Systems, OR [IM] 

(Alt. to R. J. Toomer) 



Paul R. Picard, Tyco/AFC Cable Systems, Inc., MA [M] 

(Alt. to R. Temblador) 
Elliot Rappaport, Electro Technology Consultants, Inc., FL 
[U] 

(Alt. to D. C. Mohla) 
Phil Simmons, Simmons Electrical Services, WA [M] 

(Alt. to D. Brender) 
David A. Williams, Delta Charter Township, MI [E] 

(Alt. to M. J. Johnston) 

Nonvoting 

Robert A. Nelson, Canadian Standards Association, Canada 
[RT] 



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

Scott Cline, Chair 
McMurtrey Electric, Inc., CA [IM] 
Rep. National Electrical Contractors Association 



Samuel B. Friedman, General Cable Corporation, RI [M] 

Rep. National Electrical Manufacturers Association 
Robert L. Huddleston, Jr., Eastman Chemical Company, 
TN [U] 

Rep. American Chemistry Council 
G. W. "Jerry" Kent, Kent Electric & Plumbing Systems, 
TX [IM] 

Rep. Independent Electrical Contractors, Inc. 
William F. Laidler, South Shore VoTech/IBEW 223, MA [L] 

Rep. International Brotherhood of Electrical Workers 
L. Bruce McClung, Electrical Safety Consulting Services, 
Inc., WV [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Paul R. Picard, Tyco/ AFC Cable Systems, Inc., MA [M] 

Rep. The Aluminum Association 
Gran P. Post, Akron, OH [E] 

Rep. International Association of Electrical Inspectors 
Carl Timothy Wall, Alabama Power Company, AL [UT] 

Rep. Electric Light & Power Group/EEI 
Austin D. Wetherell, Underwriters Laboratories Inc., NY 
[RT] 
Joseph S. Zimnoch, The Okonite Company, NJ [M] 

Rep. Copper Development Association Inc. 



Alternates 

Jacob Benninger, IBEW Local Union 241 JATC, NY [L] 

(Alt. to W. F. Laidler) 
Peter E. Bowers, Satellite Electric Company, Inc., MD [IM] 

(Alt. to G. W. Kent) 
James M. Daly, General Cable, NJ [M] 

(Alt. to J. S. Zimnoch) 
Timothy Edwards, Alcan Cable Company, GA [M] 

(Alt. to R R. Picard) 
Richard A. Holub, E. I. DuPont de Nemours & Company, 
Inc., DE [U] 

(Alt. to R. L. Huddleston, Jr.) 
Lowell Lisker, American Insulated Wire Corporation, MA 
[M] 

(Alt. to S. B. Friedman) 
Harry J. Sassaman, Forest Electric Corporation, NJ [IM] 

(Alt. to S. Cline) 
Bradley J. Schmidt, Underwriters Laboratories Inc., IL [RT] 

(Alt. to A. D. Wetherell) 
John Stacey, City of St. Louis, MO [E] 

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

(Alt. to L. B. McClung) 



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 
Highland, UT [E] 
Rep. International Association of Electrical Inspectors 



Martin D. Adams, Adams Electric, Inc., CO [IM] 

Rep. National Electrical Contractors Association 
Harry C. Brown, IBEW Local Union 606, FL [L] 

Rep. International Brotherhood of Electrical Workers 
John J. Cangemi, Underwriters Laboratories Inc., NY [RT] 
James M. Daly, General Cable, NJ [M] 

Rep. National Electrical Manufacturers Association 
Timothy Edwards, Alcan Cable Company, GA [M] 

Rep. The Aluminum Association 
Chris J. Fahrenthold, Design Electric, TX [IM] 

Rep. Independent Electrical Contractors, Inc. 
Herman J. Hall, Austin, TX [M] 

Rep. Society of the Plastics Industry, Inc. 



Ronald G. Nickson, National Multi Housing Council, DC 

[U] 

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

Rep. Electric Light & Power Group/EEI 
Gregory L. Runyon, Eli Lilly and Company, IN [U] 

Rep. American Chemistry Council 
David E. Schumacher, Associated Builders & Contractors, 
Inc., lA [IM] 
H. R. Stewart, HRS Consulting, TX [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
George A. Straniero, Tyco/AFC Cable Systems, Inc., NJ 
[M] 

Rep. Copper Development Association Inc. 



70-12 



NATIONAL ELECTRICAL CODE 2008 Edition 



NATIONAL ELECTRICAL CODE COMMITTEE 



Alternates 

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

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

(Alt. to G. L. Runyon) 
Rogers Hester, Jr., Encore Wire Limited, TX [M] 

(Alt. to G. A. Straniero) 
James K. Hinrichs, State of Washington, WA [E] 

(Alt. to G. D Rogers) 
Jacob Killinger, Underwriters Laboratories Inc., IL [RT] 

(Alt. to J. J. Cangemi) 



Samuel R. LaDart, City of Memphis, TN [L] 

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

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

(Alt. to H. R. Stewart) 
Peter Pollak, The Aluminum Association, Inc., VA [M] 

(Alt. to T. Edwards) 
Thomas H. Wood, Cecil B. Wood Inc., IL [IM] 

(Alt. to M. D. Adams) 



CODE=MAK!NG PANEL NO. 8 

18, 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 throogli 4, Ameex C 

Julian R. Burns, Chair 
Burns Electrical/Quality Power Solutions, Inc., NC [IM] 
Rep. Independent Electrical Contractors, Inc. 



Joseph Dabe, City of St. Paul, MN [L] 

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

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

Rep. The Aluminum Association 
James T. Dwight, Sasol North America, Inc., LA [U] 

Rep. American Chemistry Council 
M. Shan Griffith, Kellogg, Brown & Root, Inc., TX [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
David G. Humphrey, County of Henrico, Virginia, VA [E] 

Rep. International Association of Electrical Inspectors 
David H. Kendall, Carlon, Lamson & Sessions, OH [M] 

Rep. Society of the Plastics Industry, Inc. 
Richard E. Loyd, R & N Associates, AZ [M] 

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

Rep. National Electrical Contractors Association 
George F. Walbrecht, Underwriters Laboratories Inc., IL [RT] 
Leslie R. Zielke, South Carolina Electric & Gas Company, 
SC [UT] 

Rep. Electric Light & Power Group/EEI 



Alternates 

Richard J. Berman, Underwriters Laboratories Inc., IL [RT] 

(Alt. to G. F. Walbrecht) 
Joyce Evans Blom, The Dow Chemical Company, CA [U] 

(Alt. to J. T. Dwight) 
Duane A. Carlson, PRS Consulting Engineers, WA [U] 

(Alt. to M. S. Grifdth) 
Charles W. Forsberg, Shaker Heights, OH [M] 

(Alt. to D. H. Kendall) 
James M. Imlah, City of Hillsboro, OR [E] 

(Alt. to D. G. Humphrey) 
Kevin J. Lippert, Eaton Corporation, PA [M] 

(Alt. to G. R. Dauberger) 
Gregory L. Maurer, Wheatland Tube Company, AR [M] 

(Alt. to R. E. Loyd) 
Gary W. Pemble, Montana Electrical JATC, MT [L] 

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

(Alt. to J. R. Burns) 
Richard Temblador, Southwire Company, GA [M] 

(Alt. to J. C. DoUins) 



Articles 312, 314, 404, 408, 450, 490 

Robert A. McCulIough, Chair 
Ocean County Construction Inspection Department, NJ [E] 
Rep. International Association of Electrical Inspectors 



Rodney D, BeSisJe, NECA-IBEW Electrical Training Trust, 
OR [L] 

Rep. International Brotherhood of Electrical Workers 
Billy Breitkreutz, Fluor Corporation, TX [U] 

Rep. Associated Builders & Contractors, Inc. 
Richard P. Fogarty, Consolidated Edison Company of New 
York, Inc., NY [UT] 

Rep. Electric Light & Power Group/EEI 
Frederic P. Hartwell, Hartwell Electrical Services, Inc., MA 
[SE] 
Thomas J. LeMay, LeMay Electric, Inc., GA [IM] 

Rep. Independent Electrical Contractors, Inc. 
Robert D. Osborne, Underwriters Laboratories Inc., NC [RT] 



Bradford D. Rupp, Allied Moulded Products, Inc., OH [M] 

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

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Monte Szendre, Wilson Construction Company, OR [IM] 

Rep. National Electrical Contractors Association 
Ralph H. Young, Eastman Chemical Company, TN [U] 

Rep. American Chemistry Council 

Alternates 
Charles L. Boynton, The DuPont Company, TX [U] 
(Alt. to R. H. Young) 



2008 Edition 



NATIONAL ELECTRICAL CODE 



70^13 



NATIONAL ELECTRICAL CODE COMMITTEE 



Kevin J. Breen, Breen Electrical Contractors Inc., NY [IM] 

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

(Alt. to B. D. Rupp) 
Kenneth L. McKinney, Jr., Underwriters Laboratories Inc., 
NC [RT] 

(Alt. to R. D. Osborne) 
James C. Missildine, Jr., Southern Company Services, Inc., 
AL [UT] 

(Alt. to R. R Fogarty) 



Paul W. Myers, Innovene LLC, OH [U] 

(Alt. to S. Sengupta) 
Donald R. Offerdahl, North Dakota State Electrical Board, 
ND [E] 

(Alt. to R. A. McCuUough) 
Rhett A. Roe, IBEW Local Union 26 JATC, MD [L] 

(Alt. to R. D. Belisle) 



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, 
Inc., MA [IM] 

Rep. InterNational Electrical Testing Association 
Madeline Borthick, lEC of Houston, Inc., TX [IM] 

Rep. Independent Electrical Contractors, Inc. 
Dennis M. Darling, Ayres, Lewis, Norris & May, Inc., MI [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Charles Eldridge, Indianapolis Power & Light Company, IN 
[UT] 

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

Rep. American Chemistry Council 
C. W. Kimblin, Eaton Electrical Corporation, PA [M] 

Rep. National Electrical Manufacturers Association 
John R. Kovacik, Underwriters Laboratories Inc., IL [RT] 
Robert W. Mount, Jr., Hussmann Corporation, MO [M] 

Rep. Air-Conditioning and Refrigeration Institute 
George J. Ockuly, O'Fallon, MO [M] 
Richard Sobel, Quantum Electric Corporation, NY [IM] 

Rep. National Electrical Contractors Association 
Gerald W. Williams, County of Ventura, California, CA [E] 

Rep. International Association of Electrical Inspectors 



Alternates 



Robert R. Gage, National Grid, NY [UT] 

(Alt. to C. Eldridge) 
Roderic Hageman, PRIT Service, Inc., IL [IM] 

(Alt. to C. K Blizard) 
Robert J. Kauer, Middle Department Inspection Agency, 
Inc., PA [E] 

(Alt. to G. W. WilUams) 
Frank G. Ladonne, Underwriters Laboratories Inc., IL [RT] 

(Alt. to J. R. Kovacik) 
Richard E. Lofton, II, IBEW Local Union 280, OR [L] 

(Alt. to J. T. Dollard, Jr.) 
Alan Manche, Square D Company/Schneider Electric, KY 
[M] 

(Alt. to C. W. Kimblin) 
Vincent J. Saporita, Cooper Bussmann, MO [M] 

(Alt. to G. J. Ockuly) 
Steve A. Struble, Freeman's Electric Service, Inc., SD [IM] 

(Alt. to M. Borthick) 
Steven E. Townsend, General Motors Corporation, MI [U] 

(Alt. to D. M. Darling) 



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

Wayne Brinkmeyer, Chair 
Britain Electric Company, TX [IM] 
Rep. National Electrical Contractors Association 



Rick L. Bunch, Tecumseh Products Company, MI [M] 

Rep. Air-Conditioning and Refrigeration Institute 
J. Ron Caccamese, Alterman Electric Co., Ltd., TX [L] 

Rep. International Brotherhood of Electrical Workers 
Terry D. Cole, Hamer Electric, Inc., WA [IM] 

Rep. Independent Electrical Contractors, Inc. 
Robert G. Fahey, City of Janesville, WI [E] 

Rep. International Association of Electrical Inspectors 
William D. Glover, PPG Industries, Inc., WV [U] 

Rep. American Chemistry Council 
Charles A. Goetz, Underwriters Laboratories Inc., IL [RT] 
Paul E. Guidry, Fluor Enterprises, Inc., TX [U] 

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

Rep. Electric Light & Power Group/EEI 



Paul S. Hamer, Chevron Energy Technology Company, CA 
[U] 

Rep. American Petroleum Institute 
Vincent J. Saporita, Cooper Bussmann, MO [M] 
Lynn F. Saunders, Brighton, MI [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Lawrence E. Todd, Intertek Testing Services NA, Inc., OR 
[RT] 
Ron Widup, Shermco Industries, Inc., TX [IM] 

Rep. InterNational Electrical Testing Association 
James R. Wright, Siemens Energy & Automation, Inc., IL 
[M] 

Rep. National Electrical Manufacturers Association 



70-14 



NATIONAL ELECTRICAL CODE 2008 Edition 



NATIONAL ELECTRICAL CODE COMMITTEE 



Alternates 

Larry W. Burns, Bums Electric, Inc., TX [IM] 

(Alt. to T. D. Cole) 
Ralph M. Esemplare, Consolidated Edison Company of 
New York, NY [UT] 

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

(Alt. to J. R. Caccamese) 
Stanley J. Folz, Morse Electric Company, NV [IM] 

(Alt. to W. Brinkmeyer) 
Barry G. Karnes, Underwriters Laboratories Inc., CA [RT] 

(Alt. to C. A. Goetz) 
Robert J. Keoegh, Emerson Motor Company, MO [M] 

(Alt. to J. R. Wright) 



Thomas E. Moore, City of North Royalton, OH [E] 

(Alt. to R. G. Fahey) 
Arthur S. Neubauer, Colonial Pipeline Company, GA [U] 

(Alt. to R S. Hamer) 
George J. Ockuly, O'Fallon, MO [M] 

(Alt. to V. J. Saporita) 
Charles L. Powell, Eastman Chemical Company, TN [U] 

(Alt. to W. D. Glover) 
Arthur J. Smith, III, Waldemar S. Nelson & Company, 
Inc., LA [U] 

(Alt. to L. F. Saunders) 
Mossell A. Tiffany, Johnson Controls, Inc., PA [M] 

(Alt. to R. L. Bunch) 



. 12 



mpUes 



Timothy M. Croushore, Chair 
Allegheny Power, PA [UT] 
Rep. Electric Light & Power Group/EEI 



Kent B. Givens, Alcoa, Inc., TX [M] 

Rep. The Aluminum Association 

(VL to 610, 625, 630, 645, 660, 665, 668, 669, 685) 
Thomas L. Hedges, Hedges Electric & Construction Inc., 
CA[IM] 

Rep. National Electrical Contractors Association 
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, Inc., 
TX [IM] 
Andy Juhasz, Kone, Inc., IL [M] 

Rep. National Elevator Industry Inc. 

(VL to 610, 620, 630) 
Todd Lottmann, Cooper Bussmann, MO [M] 

Rep. National Electrical Manufacturers Association 
Sam Marcovici, New York City Department of Buildings, 
NY[E] 
John H. Mortimer, Inductotherm Corporation, NJ [M] 

(VL to 610, 630, 665, 668, 669) 
Ralph C. Prichard, Hercules Incorporated, DE [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
David R. Quave, IBEW Local Union 903, MS [L] 

Rep. International Brotherhood of Electrical Workers 
Craig Sato, Underwriters Laboratories Inc., CA [RT] 
Arthur E. Schlueter, Jr., A. E. Schlueter Pipe Organ 
Company, GA [M] 

Rep. American Institute of Organ Builders 

(VL to 640, 650) 
Kenneth White, Olin Corporation, NY [U] 

Rep. American Chemistry Council 



Alternates 



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

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

(VL to 610, 620, 630) 

(Alt. to A. Juhasz) 
Thomas M. Burke, Underwriters Laboratories Inc., CA [RT] 

(Alt. to C. Sato) 
Jeffrey L. Holmes, IBEW Local Union 1 JATC, MO [L] 

(Alt. to D. R. Quave) 
Tim McClintock, Wayne County, Ohio, OH [E] 

(Alt. to R. L. Janikowski) 
Roger D. McDaniel, Georgia Power Company, GA [UT] 

(Alt. to T. M. Croushore) 
Peter Pollak, The Aluminum Association, Inc., VA [M] 

(VL to 610, 625, 630, 645, 660, 665, 668, 669, 685) 

(Alt. to K. B. Givens) 
Lori L. Tennant, Square D Company/Schneider Electric, NC 
[M] 

(Alt. to T. Lottmann) 
George S. Tidden, George's Electrical Service Inc., TX [IM] 

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

(Alt. to T. L. Hedges) 
Robert C. Turner, Oxford, MD [M] 

(VL to 610, 630, 665, 668, 669) 

(Alt. to J. H. Mortimer) 

Nonvoting 

Andre R. Cartal, Yardley, PA [E] 
(Member Emeritus) 



2008 Edition NATIONAL ELECTRICAL CODE 



70-15 



NATIONAL ELECTRICAL CODE COMMITTEE 



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

Thomas H. Wood, Chair 
Cecil B. Wood Inc., 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, NIVI [U] 

Rep. Solar Energy Industries Association 

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

Rep. American Chemistry Council 
George W. Flach, George W. Flach Consultant, Inc., LA 
[SE] 
Ernest J. Gallo, Telcordia Technologies, Inc., NJ [U] 

Rep. Alliance for Telecommunications Industry Solutions 

(VL to 445, 480, 690, 692) 
Robert J. Gustafson, Ohio State University, OH [U] 

Rep. American Society of Agricultural & Biological 

Engineers 
Banks Hattaway, Hattaway Brothers, Inc., AL [IM] 

Rep. Associated Builders & Contractors, Inc. 
Barry N. Hornberger, PECO Energy Company, PA [UT] 

Rep. Electric Light & Power Group/EEI 
Kenneth Krastins, Plug Power, Inc., 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, Inc., 
NY [RT] 

Elliot Rappaport, Electro Technology Consultants, Inc., FL 
[U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Duke W. Schamel, Electrical Service Solutions, Inc., CO 
[IM] 

Rep. Independent Electrical Contractors, Inc. 
Todd W. Stafford, National Joint Apprentice & Training 
Committee, TN [L] 

Rep. International Brotherhood of Electrical Workers 



Herbert V. Whittall, Electrical Generating Systems 

Association, FL [M] 

Timothy P. Zgonena, Underwriters Laboratories Inc., IL 

[RT] 

Alternates 

Paul D. Barnhart, Underwriters Laboratories Inc., NC [RT] 

(Alt. to T P Zgonena) 
Daniel Batta, Jr., Constellation Power Source Generation, 
Inc., MD [UT] 

(Alt. to B. N. Hornberger) 
Ron B. Chilton, North Carolina Department of Insurance, 
NC [E] 

(Alt. to T. L. Baker) 
Larry D. Cogburn, Cogbum Bros, Inc., FL [IM] 

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

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

(VL to 690, 692, 705) 

(Alt. to K. Krastins) 
John P. Goodsell, Hubbell Incorporated, CT [M] 

(Alt. to J. S. Nasby) 
Timothy D. Holleman, AC Corporation, NC [IM] 

(Alt. to D. W Schamel) 
Robert Swayne, P2S Engineering, Inc., CA [U] 

(Alt. to E. Rappaport) 
Dale A. Triffo, Shell Oil Products U.S., TX [U] 

(Alt. to D. L. L. Elkins) 
Robert H. Wills, Intergrid, LLC, NH [U] 

(VL to 690, 692, 705) 

(Alt. to W. I. Bower) 

Nonvoting 

David Mascarenhas, Canadian Standards Association, 
Canada [RT] 



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

Donald Cook, Chair 
Shelby County Development Services, AL [E] 
Rep. International Association of Electrical Inspectors 



Troy Beall, B & D Industries, Inc., NM [IM] 

Rep. National Electrical Contractors Association 
Marc J. Bernsen, IBEW Local Union 291, ID [L] 

Rep. International Brotherhood of Electrical Workers 
Edward M. Briesch, Underwriters Laboratories Inc., IL [RT] 
James D. Cospolich, Waldemar S. Nelson & Company Inc., 
LA[U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Mark Goodman, Jacobs Engineering Group, CA [U] 

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

Rep. Independent Electrical Contractors, Inc. 
Joseph H. Kuczka, Killark Electric Manufacturing 
Company, MO [M] 

Rep. National Electrical Manufacturers Association 



William G. Lawrence, Jr., FM Global, MA [I] 
L. Evans Massey, Rockwell Automation, SC [M] 

Rep. Instrumentation, Systems, & Automation Society 
Jeremy Neagle, Intertek ETL SEMKO, 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 
Mark C. Wirfs, R & W Engineering, Inc., OR [U] 

Rep. Grain Elevator and Processing Society 

Alternates 

Donald W. Ankele, Underwriters Laboratories Inc., IL [RT] 
(Alt. to E. M. Briesch) 



70-16 



NATIONAL ELECTRICAL CODE 2008 Edition 



NATIONAL ELECTRICAL CODE COMMITTEE 



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

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

(Alt. to M. C Wirfs) 
Dave Burns, Shell Exploration & Production Company, LA 
[U] 

(Alt. to M. Goodman) 
Larry E. Fuhrman, City of Titusville, PL [E] 

(Alt. to D. Cook) 
Richard A. Holub, E. I. DuPont de Nemours & Company, 
Inc., DE [U] 

(Alt. to D. B. Wechsler) 
Nicholas P. Ludlam, FM Global, United Kingdom [I] 

(Alt. to W. G. Lawrence, Jr.) 
Christopher P. O'Neil, NSTAR Electric & Gas Corporation, 
MA [UT] 

(Alt. to M. O'Meara) 



Ted H. Schnaare, Rosemount Incorporated, MN [M] 

(Alt. to L. E. Massey) 
John L. Simmons, Florida East Coast JATC, FL [L] 

(Alt. to M. J. Bernsen) 
Donald W. Zipse, Zipse Electrical Engineering Inc., PA [U] 

(Alt. to J. D. Cospolich) 

Nonvoting 

Timothy J. Pope, Canadian Standards Association, Canada 
[RT] 

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

Fred K. Walker, U.S. Department of the Air Force, FL [U] 
Rep. TC on Airport Facilities 



Artkks 517, 518, 520, 525, 530, 5^ 

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



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

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Ronald E. Duren, PacifiCorp, WA [UT] 

Rep. Electric Light & Power Group/EEI 
Douglas S. Erickson, American Society for Healthcare 
Engineering, VI [U] 

Mitchell K. Hefter, Entertainment Technology/Genlyte, TX 
[IM] 

Rep. Illuminating Engineering Society of North America 

(VL to 518, 520, 525, 530, 540) 
Kim Jones, Funtastic Shows, OR [U] 

Rep. Outdoor Amusement Business Association, Inc. 

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

Rep. International Alliance of Theatrical Stage Employees 

(VLto518, 520, 525, 530,540) 
Larry Lau, U.S. Department of Veterans Affairs, DC [U] 

(VL to 517, 518) 
Dennis W. Marshall, TAG Electric Companies, TX [IM] 

Rep. Independent Electrical Contractors, Inc. 
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 
Michael D. Skinner, CBS Studio Center, CA [U] 

Rep. Alliance of Motion Picture and Television Producers 

(VL to 518, 520, 525, 530, 540) 



Kenneth E. Vannice, Leviton Manufacturing Company Inc., 
OR [M] 

Rep. U.S. Institute for Theatre Technology 

(VLto518, 520, 525, 530, 540) 
Michael Velvikis, High Voltage Maintenance Corporation, 
WI [IM] 

Rep. InterNational Electrical Testing Association 
Andrew White, IBEW Local Union 3, NY [L] 

Rep. International Brotherhood of Electrical Workers 
James L. Wiseman, Square D Company/Schneider Electric, 
TN[M] 

Rep. National Electrical Manufacturers Association 

Alternates 

James L. Brown, Detroit Edison, DTE Energy, MI [UT] 

(Alt. to R. E. Duren) 
Matthew B, Dozier, IDesign Services, TN [U] 

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

(Alt. to J. L. Wiseman) 
Stephen M. Lipster, The Electrical Trades Center, OH [L] 

(Alt. to A. White) 
Joseph P. Murnane, Jr., Underwriters Laboratories Inc., NY 
[RT] 

(Alt. to D. J. Talka) 
Marcus M. Sampson, Minnesota Department of Labor & 
Industry, MN [E] 

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

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

(VL to 518, 520, 525, 530, 540) 

(Alt. to K. E. Vannice) 



2008 Edition NATIONAL ELECTRICAL CODE 



70-17 



NATIONAL ELECTRICAL CODE COMMITTEE 



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

S. D. Kahn, Chair 

Tri-City Electric Company, Inc., CA [IM] 

Rep. National Electrical Contractors Association 



J. Robert Boyer, GE Infrastructure, Security, 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 Inc. 
Roland W. Gubisch, Intertek Testing Services NA, Inc., MA 
[RT] 
Robert L. Hughes, The DuPont Company, GA [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, Inc. 
Harold C. Ohde, IBEW-NECA Technical Institute, IL [L] 

Rep. International Brotherhood of Electrical Workers 
Luigi G. Prezioso, M. C. Dean, Inc., VA [IM] 

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

Rep. Telecommunications Industry Association 
Susan L. Stene, Underwriters Laboratories Inc., CA [RT] 



Kyle E. Todd, Entergy Corporation, TX [UT] 
Rep. Electric Light & Power Group/EEI 

Alternates 

Terry C. Coleman, National Joint Apprentice & Training 
Committee, TN [L] 

(Alt. to H. C. Ohde) 
Timothy D. Cooke, Times Fiber Communications, Inc., VA 
[UT] 

(Alt. to S. C. Johnson) 
Bill Hopple, Tyco/SimplexGrinnell, CA [M] 

(Alt. to J. R. Boyer) 
Randolph J. Ivans, Underwriters Laboratories Inc., NY [RT] 

(Alt. to S. L. Stene) 
Stanley Kaufman, CableSafe, Inc./OFS, GA [M] 

(Alt. to G. L. Dorna) 
William J. McCoy, Verizon Wireless, TX [U] 

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

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

(Alt. to S. D. Kahn) 
David B. Schrembeck, DBS Communications, Inc., OH 
[IM] 

(Alt. to L. G. Prezioso) 



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

Don W. Jhonson, Chair 
Interior Electric, Inc., PL [IM] 
Rep. National Electrical Contractors Association 



Thomas V. Blewitt, Underwriters Laboratories Inc., NY [RT] 
Richard J. Cripps, Association of Home Appliance 
Manufacturers, VA [M] 

(VL to 422, 424) 
Paul Crivell, Camp, Dresser & McKee Inc., WA [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Larry M. Eils, National Automatic Merchandising 
Association, IL [M] 

(VL to 422) 
Christopher S. Gill, New York Board of Fire Underwriters, 
NY[E] 

Bruce R. Hirsch, Baltimore Gas & Electric Company, MD 
[UT] 

Rep. Electric Light & Power Group/EEI 
Robert M. Milatovich, Clark County Building Department, 
NV [E] 

Rep. International Association of Electrical Inspectors 
Jurgen Pannock, Whirlpool Corporation, TN [M] 

Rep. Air-Conditioning and Refrigeration Institute 

(VL to 422, 424) 
Marcos Ramirez, Hatfield-Reynolds Electric company, AZ 
[IM] 

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

Rep. National Electrical Manufacturers Association 



Kenneth M. Shell, Tyco Thermal Controls, CA [M] 

Rep. Copper Development Association Inc. 

(VL to 426, 427) 
Ronald Sweigart, E.I. duPont de Nemours & Company, Inc., 
DE [U] 

Rep. American Chemistry Council 

(VL to 422, 424, 426, 427, 682) 
Lee L. West, Balboa Instruments, Inc., 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 

Alternates 

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

(Alt. to M. Ramirez) 
Aaron B. Chase, Leviton Manufacturing Company, Inc., NY 
[M] 

(Alt. to B. E. Rock) 
James E. Maldonado, City of Tempe, AZ [E] 

(Alt. to R. M. Milatovich) 
Wayne E. Morris, Association of Home Appliance 
Manufacturers, DC [M] 

(VL to 422, 424) 

(Alt. to R. J. Cripps) 
Brian Myers, IBEW Local Union 98, PA [L] 

(Alt. to R. J. Yasenchak) 



70-18 



NATIONAL ELECTRICAL CODE 2008 Edition 



NATIONAL ELECTRICAL CODE COMMITTEE 



Ronald F. Schapp, Intertek Testing Services NA, Inc., OH 
[RT] 

(Voting Alt. to Intertek Rep.) 
Gary L. Siggins, Underwriters Laboratories Inc., CA [RT] 

(Alt. to T. V. Blewitt) 
Joel G. Solis, Air-Conditioning & Refrigeration Institute, VA 
[M] 

(VL to 422, 424) 

(Alt. to J. Pannock) 



Robert E. Wisenburg, Coates Heater Company, Inc., WA 
[M] 

(VL to 680) 

(Alt. to Lee L. West) 

Nonvoting 

Andrew M. Trotta, U.S. Consumer Product Safety 
Commission, MD [C] 

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



Michael N. Ber, Chair 
lEC, Houston, TX [IM] 
Rep. Independent Electrical Contractors, Inc. 



Charles L. Boynton, The DuPont Company, TX [U] 

Rep. American Chemistry Council 
Frederick L. Carpenter, Lithonia Lighting, GA [M] 

Rep. National Electrical Manufacturers Association 
Paul Costello, NECA and IBEW Local 90 JATC, CT [L] 

Rep. International Brotherhood of Electrical Workers 
Kenneth F, Kempel, Underwriters Laboratories Inc., NC 
[RT] 
Stephen G. KieflFer, Kiefifer & Company, Inc., WI [M] 

Rep. International Sign Association 

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

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Michael S. O'Boyle, Lightolier Division of Genlyte Group, 
MA[M] 

Rep. American Lighting Association 

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

Rep. International Association of Electrical Inspectors 
Jim F. Pierce, Intertek Testing Services NA, Inc., OR [RT] 
Michael W. Smith, Schaeffer Electric Company, MO [IM] 

Rep. National Electrical Contractors Association 
Sondra K. Todd, Westar Energy, Inc., KS [UT] 

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



Randall K. Wright, RKW Consulting, PA [SE] 

Alternates 

Steve Campolo, Leviton Manufacturing Company, Inc., NY 
[M] 

(Alt. to F. L. Carpenter) 
Robert T. Carlock, R. T. Carlock Company, TN [IM] 

(Alt. to M. N. Ber) 
Melvyn J. Kochan, Young Electric Sign Company, NV [M] 

(VL to 600) 

(Alt. to S. G. KieflFer) 
Charles S. Kurten, Underwriters Laboratories Inc., NY [RT] 

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

(Alt. to T. S. Owens) 
Terry K. McGowan, Lighting Ideas, Inc., OH [M] 

(VL to 410, 411) 

(Alt. to M. S. O'Boyle) 
Ronald Michaelis, South Bend Vicinity Electrical JATC, IN 
[L] 

(Alt. to R Costello) 
Ronald Sweigart, E.I. duPont de Nemours & Company, Inc., 
DE [U] 

(Alt. to C. L. Boynton) 



Articles 545, 547, 550, 551, 552, 553, 555, 604, 675, Annex D, Examples Dll and D12 

Leslie Sabin-Mercado, Chair 
San Diego Gas & Electric Company, CA [UT] 
Rep. Electric Light & Power Group/EEI 



Barry Bauman, AUiant Energy, WI [U] 

Rep. American Society of Agricultural & Biological 

Engineers 
William Bruce Bowman, Fox Systems, Inc., GA [IM] 

Rep. Independent Electrical Contractors, Inc. 
Roger L. Carlson, Monaco Coach Corporation, IN [M] 

(VL to 550, 551, 552) 
Monte R. Ewing, Wisconsin Department of Commerce, WI 
[E] 

Rep. International Association of Electrical Inspectors 
James W. Finch, Kampgrounds of America, Inc., MT [U] 

(VL to 550, 551,552, 555) 
Bruce A. Hopkins, Recreation Vehicle Industry Association, 
VA[M] 

(VL to 550, 551, 552) 



Thomas R. Lichtenstein, Underwriters Laboratories Inc., IL 

[RT] 

Linda J. Little, IBEW Local 1 Electricians JATC, MO [L] 

Rep. International Brotherhood of Electrical Workers 
Timothy P. McNeive, Thomas & Betts Corporation, TN [M] 

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

Rep. Manufactured Housing Institute 

(VL to 550, 551,552) 
Tug L. Miller, National Association of RV Parks & 
Campgrounds, CA [U] 

Rep. National Assn. of RV Parks & Campgrounds 

(VLto550, 551, 552) 
Kenneth Weakley, Mountain Electric, Inc., CA [IM] 

Rep. National Electrical Contractors Association 



2008 Edition 



NATIONAL ELECTRICAL CODE 



7©-19 



NATIONAL ELECTRICAL CODE COMMITTEE 



Michael L. Zieman, RADCO, CA [RT] 
(VLto545, 550, -551, 552) 

Alternates 

Glenn H. Ankenbrand, Delmarva Power, MD [UT] 

(Alt. to L. Sabin-Mercado) 
Steven J, Blais, EGS Electrical Group, IL [M] 

(Alt. to T. R McNeive) 
Joseph M. Bolesina, Pinellas County Building Inspections, 
FL[E] 

(Alt. to M. R. Ewing) 
William (Billy) E. Duggins, San Diego Electrical Training 
Center, CA [L] 

(Alt. to L. J. Little) 



David W. Johnson, CenTex lEC, TX [IM] 

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

(VLto550, 551,552) 

(Alt. to B. A. Hopkins) 
Michael J. Slifka, PES Corporation, WI [M] 

(VLto550, 551,552) 

(Alt. to J. Mikel) 
Raymond F. l\icker. Consulting Professional 
Engineer/RADCO, CA [RT] 

(VLto545, 550, 551, 552) 

(Alt. to M. L. Zieman) 
Eugene W. Wirth, Underwriters Laboratories Inc., WA [RT] 

(Alt. to T. R. Lichtenstein) 



CODE-MAKING PANEL NO. 20 
Articles 708 and Annexes F and G 



• 



Donald P. Bliss, Chair 
National Infrastructure Institute, NH [U] 



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

Rep. International Association of Electrical Inspectors 
Lawrence A. Bey, Cummins Power Generation, MN [M] 
Richard Bingham, Dranetz-BMI, NJ [M] 
Jeffrey Boksiner, Telcordia Technologies, Inc., NJ [UT] 

Rep. Alliance for Telecommunications Industry Solutions 
James C. Carroll, Square D Company/Schneider Electric, 
TN [M] 

Wayne G. Carson, Carson Associates, Inc., VA [SE] 
George R. Dauberger, Thomas & Betts Corporation, TN 
[M] 

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

Rep. International Brotherhood of Electrical Workers 
Ronald A. Keenan, M. C. Dean, Inc., VA [IM] 

Rep. Independent Electrical Contractors, Inc. 
Gil Moniz, National Electrical Manufacturers Association, 
MA[M] 

Wayne D. Moore, Hughes Associates, Inc., RI [SE] 
Timothy S. Owens, City of Santa Clara, CA [E] 

Rep. International Association of Electrical Inspectors 



Leslie Sabin-Mercado, San Diego Gas & Electric Company, 

CA [UT] 

Evangelos Stoyas, U.S. Army Corps of Engineers, VA [E] 

Timothy P. Zgonena, Underwriters Laboratories Inc., IL 

[RT] 

Alternates 

Paul J. Casparro, Scranton Electricians JATC, PA [L] 

(Alt. to P. L. Hickman) 
Robert Michael Forister, National Electrical Manufacturers 
Association, WY [M] 

(Alt. to G. Moniz) 
Peyton S. Hale, Jr., U.S. Army Corps of Engineers, VA [E] 

(Alt. to E. Stoyas) 
John R. Kovacik, Underwriters Laboratories Inc., IL [RT] 

(Alt. to T. P. Zgonena) 
Alan Manche, Square D Company/Schneider Electric, KY 
[M] 

(Alt. to J. C. Carroll) 
Stephen V. St. Croix, Primo Electric Company, Inc., MD 
[IM] 

(Alt. to R. A. Keenan) 



NFPA Electrical Engineering Division Technical Staff 

Mark W, Earley, Assistant Vice President/Chief Electrical 

Engineer 

Ernest W. Buss, Senior Electrical Engineer 

Mark Cloutier, Senior Electrical Engineer 

Jean A. O'Connor, Electrical Project Specialist/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 



Support Staff 
Carol Henderson 
Mary Warren-Pilson 
Kimberly Shea 

NFPA Staff Editors 
Joyce G. Grandy 
Pamela Nolan 
Kim Cervantes 



Note: Membership 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. 



70-20 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 90 — INTRODUCTION 



® 



This NFPA document is 
available for use subject to important notices and legal 
disclaimers. These notices and disclaimers appear in all 
publications containing this document and may be found 
under the heading "Important Notices and Disclaimers 
Concerning NFPA Documents." They can also be ob- 
tained on request from NFPA or viewed at 
www. nfpa.org/disclaimers. 



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 
substations 

(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. 



ARTICLE 90 
Introdettloii^ 



(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 wir- 
ing systems by methods or usage not in conformity with 
this Code. This occurs because initial wiring did not pro- 
vide for increases in the use of electricity. An initial ad- 
equate installation 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) Melatiom to Other Imteraationai 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. 



(A) Covered. This Code covers the installation of electri- 
cal conductors, equipment, and raceways; signaling and 



Covered. This Code does not cover the following: 

(1) Installations in ships, watercraft other than floating 
buildings, railway rolling stock, aircraft, or automotive 
vehicles other than mobile homes and recreational ve- 
hicles 

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 traihng 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 or 
rights-of-way designated by or recognized by public 
service commissions, utility commissions, or other 
regulatory agencies having jurisdiction for such in- 
stallations, 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. 

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 communi- 
cation systems (such as telephone, CATV, Internet, satellite, or 



2008 Edition NATIONAL ELECTRICAL CODE 



70-21 



90.3 



ARTICLE 90 — INTRODUCTION 



data services). Utilities may be subject to compliance with 
codes and standards covering their regulated activities as 
adopted under governmental law or regulation. Additional in- 
formation can be found through consultation with the appro- 
priate governmental bodies, such as state regulatory commis- 
sions, the Federal Energy Regulatory Commission, and the 
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 
introduction and nine chapters, as shown in Figure 90.3. 
Chapters 1, 2, 3, and 4 apply generally; Chapters 5, 6, and 7 
apply to special occupancies, special equipment, or other spe- 
cial 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 that are kpiplieiable^ip 
referenced. 

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



Chapter 1 — General 



Chapter 2 — Wiring and Protection 



Chapter 3 — Wiring Methods and Materials 



Chapter 4 — Equipment for General Use 



Applies generally 
• 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 
1 Chapters 1 through 7 except 
J where the requirements are 

specifically referenced in 

Chapter 8. 

Y Applicable as referenced 



Annex A through Annex H 



"jT Informational only; 



not mandatory 



Figure 90.3 Code Arrangement. 



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 estabhshing 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. 

90.5 Mandatory Rules, Permissive Rules, and Explana- 
tory 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 ex- 
tracted 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. 

90.6 Formal Interpretations. To promote uniformity of 
interpretation and application of the provisions of this 



70-22 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 90 — INTRODUCTION 



Code, formal interpretation procedures have been estab- 
lished and are found in the NFPA Regulations Governing 
Committee Projects. 



90.7 Examtnation of Eqeipmeet 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 facihties described in the preced- 
ing paragraph and that requires suitability for installation in 
accordance with this Code. 



FPN No. 1 
FPN No. 2 

FPN No. 3 



See requirements in 110.3. 

Listed is defined in Article 100. 

Annex A contains an informative list of prod- 



uct safety standards for electrical equipment. 



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. 



if Circeits m Enclosures. It is elsewhere 
provided in this Code that the number of wires and circuits 
confined 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. 



(A) Measurememt 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 Conversiom. 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 conver- 
sion. 

(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. 



2008 Edition NATIONAL ELECTRICAL CODE 



70-23 



CHAPTER 1 



ARTICLE 100 — DEFINITIONS 



Chapter 1 General 



rD^nitibris 






Scope. This article contains only those definitions essential 
to the proper application 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 vt^iring 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). An organization, 
office, or individual responsible for enforcing the require- 
ments of a code or standard, or for approving equipment, 
materials, an installation, or a procedure. 



FPN: The phrase "authority having jurisdiction," or its ac- 
ronym AHJ, is used in NFPA documents in a broad manner, 
since jurisdictions and approval agencies vary, as do their 
responsibilities. Where pubhc safety is primary, the author- 
ity having jurisdiction 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 depart- 
ment, or health department; building oflBcial; electrical in- 
spector; or others having statutory authority. For insurance 
purposes, an insurance inspection department, rating bureau, 
or other insurance company representative may be the author- 
ity having jurisdiction. In many circumstances, the property 
owner or his or her designated agent assumes the role of the 
authority having jurisdiction; at government installations, the 
commanding officer or departmental official may be the au- 
thority having jurisdiction. 

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. 

jBpiid6d^^<Midmg^J jEorffieScte^WestoM 
jSnuity ■ 'aM^':eon(iuctiwty: 

Bonding Jumper. A rehable conductor to ensure the re- 
quired electrical conductivity between metal parts required 
to be electrically connected. 

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

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

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

Branch Circuit, Appliance. A branch circuit that supplies 
energy to one or more outlets to which appliances are to be 



70-24 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 100 — DEFINITIONS 



CHAPTER 1 



• 



connected and that has no permanently connected lumi- 
naires that are not a part of an appliance. 



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



L A branch circuit that supplies 
only one utilization equipment. 



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. 

Brancli^Cimiit'Overciifrent'BSvlteo A'devic^'eapable'M 
pfdvidihg pnjtectiori- for service|ifeederf^ahd" tHfahch circuits 
^nd'equiprneht oyer the fu pf overeaMrentilbetweeh 

its rated current and ;its interruptirig rating. Braneh-circuit 
pvercuiTi^^^ devices are provided with ;^ 

liigrMingS; appropriate for th^ iil]tehded iise^biif iidvf6s§^ than 
5,000 aim^res^ 



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. 

Cablmet 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. 



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 
qualifying term indicating that no delay is purposely intro- 
duced 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. 

Clothes Closeto A non-habitable room or space intended 
prirnarily for storage of garments and apparel 

Communications Equipment. The electronic equipment 
that performs the telecommunications operations for the 
transmission of audio, video, and data, and includes power 
equipment (e.g., dc converters, inverters, and batteries) and 
technical support equipment (e.g., computers). 

Concealed. Rendered inaccessible by the structure or finish 
of the building. Wires in concealed raceways are consid- 
ered concealed, even though they may become accessible 
by withdrawing them. 



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. 



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



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 estab- 
lishes 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. 



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



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. 



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. 



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



jr-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 



2008 Edition 



NATIONAL ELECTRICAL CODE 



)-25 



CHAPTER 1 



ARTICLE 100 — DEFINITIONS 



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. 

Device. A unit of an electrical system that 'cHirrres or con- 
trol| electric energy i^ its pnnpipalifiiri^^ 

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, 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. 

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. 

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

Electric Power Production and Distribution Network. 

Power jpi^ductibnvdistti^^ 

arid faCiMtieiS, siich' a|'^^^ utihti^ S^^tepas Jithat dSl^^ 



electric* |)iower'^ tgi ;the xoKtiected'ldadsi; ffiaf "Efcre'external- ' id 

and not iC^rolled |^y^ai|iritei^Gti%;^ 

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 Tabl'eulip.SO for examples of enclosure types. 

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

Equipment. A general term, including material, fittings, 
devices, appliances, luminaires, apparatus, machinery, and 
the like used as a part of, or in connection with, an electri- 
cal 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. 



70-26 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 100 — DEFINITIONS 



FPN: For commercial garages, repair and storage, see 
Article 511. 



o The-:eartliv 



l). Connected (connecting) to 
ground or to a conductive body that ^tends the groiind 
connection. 

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

Groeeded Coeductor. A system or circuit conductor that 
is intentionally grounded. 

Groeed-Faiinlil Circeit leterrapter (GFCI). A device in- 
tended for the protection of personnel that functions to de- 
energize a circuit or portion thereof within an established 
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 is 6 mA or higher Md y 
when the current to ground is less than 4 mA. For further 
information, see UL 943, Standard for Ground-Fault Cir- 
cuit Interrupters. 



jmemto 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 de- 
vice. 



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



Coedector, Eqiiiinpmeinilt (EGC). The conduc- 
tivierpjatKjiihstalled to connect normally non-current- 
carrying metal parts of equipment together and to the sys- 
tem grounded conductor or to the grounding electrode 
conductor, or both. 

FPN- No.;]:;' It is ;fecognized that the equipment grounding 
conductor also performs bonding. 

FPN No, 2: : See 250.11 8 for a list of acceptable equipment 
grounding conductors. 



J. A conducting object through which 
a direct connection to earth is estabhshed. 



A conductor used to 
connect the system grounded conductor or the equipment to 
a grounding electrode or to a point on the grounding elec- 
trode system.' 



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. 



An accommodation combining living, sleep- 
ing, sanitary, and storage facilities within a compartment. 

Guest Sente. 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 facilities. 



jsere. An enclosure for use in underground 
systems, provided with an open or closed bottom, and sized 
to allow personnel to reach into, but not enter, for the pur- 
pose of installing, operating, or maintaining equipment or 
wiring or both. 



Any shaftway, hatchway, well hole, or other ver- 
tical opening or space in which an elevator or dumbwaiter 
is designed to operate. 



emilt). 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 
(listing and labeling), an inspection agency, or other orga- 
nizations concerned with product evaluation. 



In Sight From (Witlhie Siglit From, Withim Sight). 
Where this Code specifies that one equipment shall be "in 
sight from," "within sight from," or "within sight of," and 
so forth, another equipment, the specified equipment is to 
be visible and not more than 15 m (50 ft) distant from the 
other. 



. An electric power production system 
that is operating in parallel with and capable of delivering 
energy to an electric primary source supply system. 



Mmg Eating. 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. 



tem Bomdiiig Termleatioii. A device that pro- 
vides a means for connecting communications system(s) 
grounding conductor(s) and bonding conductor(s) at the 
service equipment or at the disconnecting means for build- 
ings or structures supplied by a feeder or branch circuit. 

Isolated (as applied to locatiom). Not readily accessible 
to persons unless special means for access are used. 



2008 Edition 



NATIONAL ELECTRICAL CODE 



70-27 



CHAPTER 1 



ARTICLE 100 — DEFINITIONS 



Kitchen; An areaiwith a^sihlcand'Jpem 
food preparation a|idi£;opkinf J 

Labeled. Equipment or materials to which has been at- 
tached a label, symbol, or other identifying mark of an 
organization that is acceptable to the authority having juris- 
diction and concerned with product evaluation, that main- 
tains periodic inspection of production of labeled equip- 
ment or materials, and by whose labeling the manufacturer 
indicates compliance with appropriate standards or perfor- 
mance in a specified manner. 

Lighting Outlet. An outlet intended for the direct connec- 
tion of a lampholder or luminaire. 

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 listing states that either 
the equipment, material, or service meets appropriate des- 
ignated 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 evaluation, 
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. 

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 bams, 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 underground or in concrete 
slabs or masonry in direct contact with the earth; in loca- 
tions subject to saturation with water or other Hquids, such 
as vehicle washing areas; and in unprotected locations ex- 
posed to weather. 

Luminaire. A""COn|pletis'li|hffi 

source "siich '-as ':a " laiTip'^ot; iaiiips^;: fc^ 

designed lo'pbsitiori' fhe ligM |soiirce;md' connect it J;o[^ 

pawer ' supply;' It}m^3^oliMu£i6;|)artsf W 'protect "^tte^|igh| 

30iirCi^brith^'baMas|j3fypHist^^ 

itselfis not a luminaire; 



Metal-Enclosed Povt^er Switchgear. A switchgear assem- 
bly completely enclosed on all sides and top with sheet 
metal (except for ventilating openings and inspection win- 
dows) and containing primary power circuit switching, in- 
terrupting 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, 
removable covers, or both. Metaljeiielosed Jpower Switch- 
g€^'MyiyaiiablHjin;.^npMa^ ■ ^^^i 

Ip^tip^s] 

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. 



|pUtr^;;..Cpriduc^ [pl|B;id5n|duGtGr'!#iin^ 

fiallppiiiFM c^iry^euftent under 

i^grm^-^iiffitioii&: 

Neuti^LPoiiii|3 Pi^i^dprnrnpni^PiM ^;^yey6oniieetit)n'=in 

a ~ppI55^ha$e [s^^sj^il^^ 

lystem^ j3iS mMpoi^ of .a Biphase 

Systein^ 

iF^jgrf^i Atl!Kneiitral^p<|mt^^ 

pf'We nomin'ai;;;^^^ 

system that .utilizis ' the jieutrki,; with' respect tp; the ' neutral 

fjmntliis^zierpfppteiitiali 

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 
Hghting, 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. 



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ARTICLE 100 — DEFINITIONS 



• 



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. 

Pamelboard. 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 Oiitleto 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). Interior and exterior wiring, 

including power, lighting, control, and signal circuit wiring 

together with all their associated hardware, fittings, and 

wiring devices, both permanently and temporarily installed. 

jrius~inc]irdes]Xa)^^ 

^btirce^^to^tlie 'Outlets^ or ^(^ and uicludiiig the 

po^^\^oij^cep;oj^ '>\^ere' tliere[i¥p(y^r^^c^i^^ 

Such wiring does not include wiring internal to appli- 
ances, luminaires, motors, controllers, motor control cen- 
ters, 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 
to recognize and avoid 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 
busbars, with additional functions as permitted in this 
Code. Raceways include, but are not limited to, rigid metal 
conduit, rigid nonmetallic conduit, intermediate metal con- 
duit, liquidtight flexible conduit, flexible metallic tubing, 
flexible metal conduit, electrical nonmetallic tubing, 
electrical metallic tubing, underfloor raceways, cellular 



concrete floor raceways, cellular metal floor raceways, 
surface raceways, wireways, and busways. 



f. Constructed, protected, or treated so as to pre- 
vent rain from interfering with the successful operation of 
the apparatus under specified test conditions. 



it. Constructed or protected so that exposure to a 
beating rain will not result in the entrance of water under 
specified test conditions. 



J. 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. 

An outlet where one or more recep- 



tacles are installed. 

Remote-Control Circeit. Any electrical circuit that con- 
trols any other circuit through a relay or an equivalent de- 
vice. 



Equipment enclosed in a case or 
cabinet that is provided with a means of sealing 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 conductors made up in the form of 



a cable. 



i. 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 
service conductors between the terminals of the service 
equipment and a point usually outside the building, clear of 
building walls, where joined by tap or splice to the service 
drop. 

Service-Emtrance Conductors, Underground System. 
The service conductors between the terminals of the service 
equipment and the point of connection to the service lateral. 



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ARTICLE 100 — DEFINITIONS 



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 
consisting of a circuit breaker(s) or switch(es) and fuse(s) 
and their accessories, connected to the load end of service 
conductors 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 utility and the premises wiring. 

SMort-Circuit'Ciirreiit^Katiri^ [The prospective synimefri^ 
cal Sialt ciii'iieht at a noii^rtafA^ltage td which- an ajpparatus 
or system is ableto be connected' without ;siistaihih^^ 
age exceeding defined'accep^nce criteria. 

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 electrical circuit that energizes sig- 
naling equipment. 

Solar Photovoltaic System. The total components and sub- 
systems that, in combination, convert solar energy into 
electric 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 spe- 
cific applications and utilization equipment such as lumi- 
naires and appliances. This limited protection is in addition 
to the protection provided in the required branch circuit by 
the branch circuit overcurrent protective device. 

Serge Arrester. A protective de\fice^foifliitutirig siirge A'olt-? 
age^^byi discharging or bj^assing; siirge^cuirentvit^alsQ pre- 
vents continued flow of follow current while remaining ca-^; 
pable of r'epeatiiig these fiihctioris/ 

Surge-Protective :^I)evice;XSPI5|^ 'M ■ prioteetiye- , device-lQr 
limiting transient /voltages by diverting or hmiting surg^ 



eiirrent; it llSot^pi-ei^ts^fcontiriued! flow 'of folldw'iftirrent 
while ;rernairiing-e^ble|ofi repeatihgrthese iiiriclipns^ and is 
designated MfoUows: 

T^pe il : JPermaheritl^^^ 
stallatiori l)etween the sepondary of the service transfpririer 
arid the ^irie' side of ' tie ^eiyicier di«ioriiieef ^^ o^ 
jdeyiee; 

Type^2^ Perinanentlyl cmrieictei^ 
SaUation iGrv;;the: load side ;b 

current device, ihcludingl SFDs Jloeated atfthe Branch .panel.; 
Ty^et3^riointof;iin]|zadon:SI^^ ~ 

1ype']4: Gonaponent iSPDs; iricluding discrete bbmpo-! 
fieiiti^ ;a^'; JwelMis? Mseiriblies: ' 

FPN: ; Fdf[further;ihfoi^Mion,^ 3i 

lecfiveiiDevieesl 

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. 



• 



GeneraI=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. 



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- 
trical circuit from the source of power. It has no interrupt- 
ing 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. 



• 



rmally 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. 



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ARTICLE 100 — DEFINITIONS 



• 



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. 

PiigroiiiMea^ Not ■ ^q|, j^g^^g^j- |^-;gj|;Q^jj^jj--;pj.- ^q ^alcondiietiAf e 
body that extends the. ground jeonnection J 

JtJtilily-ljitfer^tivi^ ; liivertfen Ah'Hh vdrtef ■ mtended;|oi:j- ijse 
in parallel With- an? electric uMityUo; supply i|ioriimori;loads 
that may; deUyer^l^^ 



Equipment that utilizes electric 
energy for electronic, electromechanical, chemical, heating, 
lighting, or similar purposes. 



Provided with a means to permit circulation of 
air sufficient to remove an excess of heat, fumes, or vapors. 



A flammable hquid 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 circisit). 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. 



L 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. 1-2006, Voltage Ratings for Electric 
Power Systems and Equipment (60 Hz). 



ige to Groeed. 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. 



_ it. 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 ful- 
fill the requirements for weatherproof where varying 
weather conditions other than wetness, such as snow, ice, 
dust, or temperature extremes, are not a factor. 



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. 



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. 



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. 

Controlled Vented Power Fuse. A fuse with provision for 
controlling discharge circuit interruption such that no solid 
material may be exhausted into the surrounding atmo- 
sphere. 

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 mem- 
bers 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 
recommendation s . 

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, hquids, or solid particles to the surrounding 
atmosphere during circuit interruption. 



2008 Edition 



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110,1 



ARTICLE 110 — REQUIREMENTS FOR ELECTRICAL INSTALLATIONS 



Multiple Fuse. An assembly of two or more single-pole 
fuses. 

Switching Device. A device designed to close, open, or 
both, one or more electrical circuits. 

Circuit Breaker. A switching device capable of making, 
carrying, and interrupting currents under normal circuit 
conditions, and also of making, carrying for a specified 
time, and interrupting currents under specified abnormal 
circuit conditions, 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 Means. A device, group of devices, or 
other means whereby the conductors of a circuit can be 
disconnected from their source of supply. 

Disconnecting (or Isolating) Switch (Disconnector, Isola- 
tor). A mechanical switching device used for isolating a 
circuit or equipment from a source of power. 

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. 



I Requiremeiris:l6r Electi^^ 

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 instal- 
lations. 

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, Examination, Identification, Installation, 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 idendfied by a 
description marked on or provided with a product to iden- 
tify 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 Kkely to come in contact with 
the equipment 

(B) Installation and Use. Listed or labeled equipment 
shall be installed and used in accordance with any instruc- 
tions included in the fisting 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 
nominal 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 Wiriiiig Integrity. Completed wiring installations 
shall be free from short circuits, grdiaiid/;:fjiuitey;Sr;=^h^ 



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ARTICLE 110 — REQUIREMENTS FOR ELECTRICAL INSTALLATIONS 



• 



connections to groujid otHer tjian as required or permitted 
elsewhere in this Cdde. 

110.8 Wirimig 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. 



tninig MaHflinig. 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. 

lldD.lO Circenl!; Impedamce and Ollher CIharaclter3§lt!c§. 
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. 

11(0). 11 Deterioraltieg Ageelts. 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, liquids, 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 materials used 
for insulating and structural applications in equipment. 

Equipment not identified for outdoor use and equipment 
identified only for indoor use, such as "dry locations," "in- 
door use bnly," "damp locatibnSj" or enclosure Types 1, 2, 
5,' 12, 12K, and/or 13, shall be protected against permanent 
damage from the weather during building construction. 

■FPN No. 3:- See Table 110.20 for appropriate enclosiire-type 
designatidrisJ 

IKU.ll Mechamkal ExecMtioini of Work. Electrical equip- 
ment shall be installed in a neat and workmanlike manner. 

FPN: Accepted industry practices are described in 
ANSI/NEC A 1-2006, Standard Practices for Good Work- 
manship in Electrical Contracting, and other ANSI- 
approved installation standards. 



(A) Ummiised Opemnmigs. Unused openings, other than those 
intended for the operation of equipment, those intended for 
mounting purposes, or those permitted as part of the design 
for listed equipment, shall be closed to afford protection 
substantially equivalent to the wall of the equipment. 
Where metallic plugs or plates are used with non metallic 
enclosures, they shall be recessed at least 6 mm ('/4 in.) 
from the outer surface of the enclosure. 

(B) letegrilty off EEectrkal Equipmeinilt and ComeectDomis. 
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 MoMiniltnmg amd Coolmg of EqenpmeiniL 

(A) Mouetieg. 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) Cooliing. 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 
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 instaUed so that walls or other obstructions do not 
prevent the free circulation of air through the equipment. 

110.14 EkctrkaE Cominiectfloiis. 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) Termnmais. Connection of conductors to terminal 
parts shall ensure a thoroughly good connection without 



2008 Edition 



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70-33 



110.15 



ARTICLE 110 — REQUIREMENTS FOR ELECTRICAL INSTALLATIONS 



damaging the conductors and shall be made by means of 
pressure connectors (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 
splicing devices identified for the use or by brazing, weld- 
ing, or soldering with a fusible metal or alloy. Soldered 
splices shall first be sphced or joined so as to be mechani- 
cally and electrically secure without solder and then be 
soldered. All splices and joints and the free ends of conduc- 
tors 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 termina- 
tion provisions of equipment shall be based on 
110.14(C)(1)(a) or (C)(1)(b). Unless the equipment is Usted 
and marked otherwise, conductor ampacities used in deter- 
mining 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, shall 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 
equipment is listed 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 fisted 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 Marking. 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. MeGtnbal^^qiiipiiieht^^'siich^j^^ 
switchboards, panelboards, industrial control panels, meter 
socket enclosures, and motor control centers, that are in 
other than dwelling occupancies, and are likely to require 
examination, adjustment, servicing, or maintenance while 
energized shall be field marked to warn qualified persons of 
potential electric arc flash hazards. The marking shall be 
located so as to be clearly visible to qualified persons be- 
fore examination, adjustment, servicing, or maintenance of 
the equipment. 

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 electrical equipment that in 
ordinary operation produce arcs, sparks, flames, or molten 
metal shall be enclosed or separated and isolated from all 
combustible 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. 



• 



• 



70-34 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 110 — REQUIREMENTS FOR ELECTRICAL INSTALLATIONS 



110.20 Enclpsdre--l]y.pes. EhGl;0suresr(other tKanisiiifouM-' 
ing jfenc^s W waii]^ 

tnaJ control "panels, iridtor control centers, nieteif soclcets^ 
krtd motor ccmtrolliei:^ rated Wt^(^ 600 volts Iriomlial^nd 
intended [^ for^ siieh , .lpcatiqns|; -shall .be marked ; ; ^yith;:;^ii; 
encrdsure-type nunibe^^^ 110.20. 

jTable 11;0:20 '. sliMl be used foF selefctmg -thes^ -isivclcy^ 
sures fob use in; isppific locations ^pther; ; thart ', haz^^ou s 

Table 110.20 Enclosure Selection 



(classified) locations. The enclosures are not intended to 
protect against conditions such as condensation, icing, cor- 
rosion, or contamination that may occur within the enclo- 
sure or enter via the conduit or unsealed openings. 



ag. The manufacturer's name, trademark, 
or other descriptive marking by which the organization 



Provides a Degree of 










For Outdoor Use 










Protection Against the 
Following Environmental 










Emclosmire 


•Type Number 










Conditions 


3 


3M 


3S 


3X 


3RX 


3SX 


4 


4X 


6 


6P 


Incidental contact with the 


X 


X 


X 


X 


X 


X 


X 


X 


X 


X 


enclosed equipment 






















Rain, snow, and sleet 


X 


X 


X 


X 


X 


X 


X 


X 


X 


X 


Sleet* 


— 


— 


X 


— 


— 


X 


— 


— 


— 


— 


Windblown dust 


X 


— 


X 


X 


— 


X 


X 


X 


X 


X 


Hosedown 


— 


— 


— 


— 


— 


— 


X 


X 


X 


X 


Corrosive agents 


— 


— 


— 


X 


X 


X 


— 


X 


— 


X 


Temporary submersion 


— 


— 


— 


— 


— 


— - 


— 


— 


X 


X 


Prolonged submersion 


— 


— 


— 


— 


— 


— 


— 


— 


— 


X 


Provides a Degree of 










For Indoor Use 










Protection Against the 
Following Environmental 










Enclosure-Type Number 










Conditions 


1 


2 


4 


4X 


5 


6 


6P 


12 


12K 


13 


Incidental contact with the 


X 


X 


X 


X 


X 


X 


X 


X 


X 


X 


enclosed equipment 






















Falling dirt 


X 


X 


X 


X 


X 


X 


X 


X 


X 


X 


Falling liquids and light 
splashing 


— 


X 


X 


X 


X 


X 


X 


X 


X 


X 


Circulating dust, lint, fibers, 
and flyings 


— 


— 


X 


X 


— 


X 


X 


X 


X 


X 


Settling airborne dust, lint, 
fibers, and flyings 


— 


— 


X 


X 


X 


X 


X 


X 


X 


X 


Hosedown and splashing 


— 


— 


X 


X 


— 


X 


X 


— 


— 


— 


water 






















Oil and coolant seepage 


— 


— 


— 


— 


— 


— 


— 


X 


X 


X 


Oil or coolant spraying and 
splashing 


— 


— 


— 


— 


— 


— 


— 


— 


— 


X 



Corrosive agents 
Temporary submersion 
Prolonged submersion 



*Mechanism shall be operable when ice covered. 

FPN: The term raintight is typically used in conjunction with Enclosure Types 3, 3S, 3SX, 3X, 4, 4X, 6, and 6P. The term rainproof \s typically 
used in conjunction with Enclosure Types 3R, and 3RX. The term watertight is typically used in conjunction with Enclosure Types 4, 4X, 6, 6P. 
The term driptight is typically used in conjunction with Enclosure Types 2, 5, 12, 12K, and 13. The term dusttight is typically used in conjunction 
with Enclosure Types 3, 3S, 3SX, 3X, 5, 12, 12K, and 13. 



2008 Edition 



NATIONAL ELECTRICAL CODE 



)-35 



110.22 



ARTICLE 110 — REQUIREMENTS FOR ELECTRICAL INSTALLATIONS 



responsible for the product can be identified shall be 
placed on all electrical equipment. Other markings that 
indicate voltage, 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. 

(jA) p^eiieral. Each disconnecting means shall be legibly 
marked to indicate its purpose unless located and arranged 
so the purpose is evident. The marking shall be of sufficient 
durability to withstand the environment involved. 

(B) Engineered Series GomWhationrSystems. Where-dr-- 
cuit breakersior fuses are applied 'in* compliahcew 
combination- ratings seleetedunder.eiigineeringjsupervisioii 
and marked on the equipfnent as directed :by the engineer^ 
the equipment ericlosure(s) shaH be legibly miarked inithe 
field to indicate the ^eqmprrient has-: beeriiapplied; with: -a 
series conibinatipn rating. The markirig- shall be readily iVis-j 
ible and statd the folio wing:- 

CAUTION — ENGINEERED SERIES COMBINA-: 
TION SYSTEM RATED: rM^iiT AMPERES. IDENTIC 
FIEp REPLACEMENT CpMiOTENTSREQUI^ 

FPNi'; See/r24Q. 86(A) for engineered ^series eqmbi nation 

systems. 

(C) Tested Series GomMnatipnTiSystemss. Where circuit 
breakers or fuses are applied in compliance with the series 
combination ratings marked on the equipment by the manu- 
facturer, the equipment enclosure(s) shall be legibly 
marked in the field to indicate the equipment has been 
applied 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 tested ;series' combination sys^^^^ 

110.23 Current Transformers. Unused current transform- 
ers associated with potentially energized circuits shall be 
short-circuited. 



II. 600 Volts, Nominal, or Less 

110.26 Spaces About Electrical Equipment. Sufficient 
access and working space shall be provided and maintained 
about all electrical equipment to permit ready and safe op- 
eration and maintenance of such equipment. 

(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) unless the requirements of 
110.26(A)(1)(a), (A)(1)(b), or (A)(1)(c) are met. Distances 
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 


914 mm (3 ft) 
914 mm (3 ft) 


914 mm (3 ft) 
1.07 m (3 ft 6 in.) 


914 mm 
1.22 m 


I (3 ft) 
(4 ft) 



Note: Where the conditions are as follows: 

Condition 1 — Exposed live parts on one side of the working space 

and no live 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 con- 
nections 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 work- 
ing 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- 
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 qualified 
persons who are authorized will service the installation. 

(2) Width of Working Space. The width of the working 
space in front of the electrical equipment shall be the width 
of the equipment or 7=62 mm (30 in.), whichever is greater. 



)-36 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 110 — REQUIREMENTS FOR ELECTRICAL INSTALLATIONS 



In all cases, the work space shall permit at least a 90 degree 
opening of equipment doors or hinged panels. 



dug 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) Emltramce to aefl. Egress Irom' Workiinig Space. 

(1) Minimem Required. At least one entrance of suffi- 
cient area shall be provided to give access to ahdlegress 
from working space about electrical equipment. 

(2) Large EquipmenL For equipment rated 1200 amperes 
or more and over; 1.8 m (6 ft) wide that contains overcur- 
rent devices, switching devices, or control devices, there 
shall be one entrance to and egress from the required work- 
ing space not less than 610 mm (24 in.) wide and 2.0 m 
(6^/2 ft) high at each end of the working space. 

A single entrance to and egress from the required work- 
ing space shall be permitted where either of the conditions 
in 110.26(C)(2)(a) or (C)(2)(b) is met. 

(a) Unobstructed Egress. Where the location permits a 
continuous and unobstructed way of egrSss 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 such 
that the distance from the equipment to the nearest edge of 
the entrance is not less than the minimum clear distance 
specified in Table 110.26(A)(1) for equipment operating at 
that voltage and in that condition. 

(3) Personnel Boors. Where eqiiipment rated 1200 A' or 
more that contains oVercurrent devices, switching devices, 
Or control devices is iiistalled^^and: there is a- parsonnel 
.door(s) intended for entrance to andjegress from the work-; 
ihg space less than 7.6 rh (25 ft)' from the nearest e<ige of 
the workiiig spaced the cl6biT(s)^ shall open in the difectitm of 
egress and be- equipped with :pah ie bars, pressure plates^ or 
other: devices that arC; normally ^ latched but ^operi under 
simple pressiire^ 

(D) Illemlnatioini. 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) Meadroom. The minimum headroom of working spaces 
about service equipment, switchboards, panelboards, or motor 
control centers shall be 2.0 m (6V2 ft). Where the electrical 
equipment exceeds 2.0 m (6'/4 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 Equipmeet Space. All switchboards, pan- 
elboards, 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) ledoor. 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 
similar ceiling that does not add strength to the building 
structure shall not be considered a structural ceiling. 

(2) Oetdoor. Outdoor electrical equipment shall be installed 
in suitable enclosures and shall be protected from accidental 
contact by unauthorized personnel, or by vehicular traffic, or 



2008 Edition 



NATIONAL ELECTRICAL CODE 



-37 



110.27 



ARTICLE 110 — REQUIREMENTS FOR ELECTRICAL INSTALLATIONS 



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. 

(G) Locked Electricar Equipment; Rdpnis^ otM^^ 
sures. EJeetrical equipiiient iropins of ehcldsijres' housing 
electrical apparatus: that areycoiitrolledrby ta lodk(s) shaB hB^ 
considered (accessible: to t^ 

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 quahfied 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 electri- 
cal equipment is likely to be exposed to physical damage, 
enclosures 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 five 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. 

in. 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 110.30 through 110.40, 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 
installations 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 qualified persons only. 
The type of enclosure used in a given case shall be 
designed and constructed according 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 
typical BIL ratings, see ANSI C2-2007, National Electrical Safety 
Code. 



FPN: See Article 450 for construction requirements for 
transformer vaults. 

(A) Fire Ee^istancfe 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. 

(B) 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 equip- 
ment shall be marked with appropriate caution signs. Open- 
ings in ventilated dry-type transformers or similar openings 
in other equipment shall be designed so that foreign objects 



70-38 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 110 — REQUIREMENTS FOR ELECTRICAL INSTALLATIONS 



inserted through these openings are deflected from energized 
parts. 

(2) Im Places Accessible to Quallied 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) OeMoor lestallatloms. 

(1) Ie Places Accessible to Umqualified Persons. Outdoor 
electrical installations that are open to unqualified persons 
shall comply with Parts I, II, and III of Article 225. 

(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 Unquallfled 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 ex- 
posed to physical damage from vehicular traffic, suitable 
guards shall be provided. NonmetaUic or metal-enclosed 
equipment located 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 nonmetallic or metal-enclosed equipment is acces- 
sible 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 meet- 
ing this requirement. 

110.32 Work Space Aboult Eqoipmemt. Sufficient space 
shall be provided and maintained about electrical equipment 
to permit ready and safe operation and maintenance of such 
equipment. Where energized parts are exposed, the minimum 
clear work space shall be not less than 2.0 m (6Y2 ft) high 
(measured vertically from the floor or platform) or not less 
than 9^ mm (3 ft) wide (measured parallel to the equipment). 
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 ^to'^Eii'dosures and Access to ^li^orMig 



(A) Entrance. At least one entrance to^ericlosuresjMfieli&GH 
tocal mMallafions,^!^^^^^ not less than 

610mm (24 in.) wide and 2.0 m (6 1/2 ft) high shall be 



provided to give access to the working space about electri- 
cal equipment. 

(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 work- 
ing space is twice that required by 110.34(A), a single en- 
trance 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. 

(3) Persohhel Doors. Where there is a personnel door(s) 
___j„^,^_^^__ ^^_^^ egress from the working space 

less,tHanl7.6 hi (25 ft) frorn the nearest edge of the working 
spac'ey the door(s) shall open in the direction of egress 
and :Jbe-*lequipped with panic; bars, pressure plates, or 
0therdeYices that are normally latched but open under 
simple "pfessure^^ 

(B) Access. Permanent ladders or stairways shall be pro- 
vided to give safe access to the working space around 
electrical equipment 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 
permitted in this Code, equipment likely to require ex- 
amiriatidh, adjustment, servicing, or maintenance while 
jenergized/shall have clear working space in the direction 
of access to live parts of the electrical equipment and 
shall be not 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 
working space of 762 mm (30 in.) horizontally shall be 
provided. 



2008 Edition NATIONAL ELECTRICAL CODE 



J-39 



110.36 



ARTICLE 110 — REQUIREMENTS FOR ELECTRICAL INSTALLATIONS 



Table 110.34(A) Minimum Depth of Clear Workimg 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 

25,001 V-75 kV 

Above 75 kV 


900 mm (3 ft) 
1.2 m (4 ft) 
1.5 m (5 ft) 
1.8 m (6 ft) 
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 

2.9 

2.9 m + 9.5 mm/kV 

above 35 


9 

9 ft 6 in. 
9 ft 6 in. + 
0.37 in./kV 

above 35 



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 Uve parts on both sides of the working space. 



(B) Separation from Low-Voltage Eqeipmemit. Where 
switches, cutouts, or other 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. 

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 permit- 
ted to be installed in the high-voltage vault, room, or en- 
closure without a partition, fence, or screen if accessible to 
qualified persons only. 

(C) Locked Rooms or Enclosures. The entrance to all 
buildings, vaults, rooms, or enclosures containing exposed 
live parts or exposed conductors operating at over 600 
volts, nominal, 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 live parts or other equipment. 

The points of control shall be located so that persons 
are not likely to come in contact with any live part or 
moving part of the equipment while turning on the lights. 



(E) Elevation off 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 re- 
quiring periodic maintenance or whose malfunction would 
endanger the operation of the electrical system shall not be 
located in the vicinity of the service equipment, metal- 
enclosed power switchgear, or industrial control assemblies. 
Protection shaU be provided where necessary to avoid damage 
from condensation leaks and breaks in such foreign systems. 
Piping and other facilities shall not be considered foreign if 
provided for fire protection of the electrical installation. 

110.36 Circuit Conductors. Circuit conductors shall be per- 
mitted 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 comply 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 if 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. 

11®.4(D 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. Tunnel Installations over 600 Volts, Nominal 



(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 



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NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 110 — REQUIREMENTS FOR ELECTRICAL INSTALLATIONS 



• 



as substations, trailers, cars, mobile shovels, draglines, 
hoists, drills, dredges, compressors, pumps, conveyors, un- 
derground excavators, and the like. 

(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. 

(C) Protection Against Physical DamagCo 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. 



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 Groendlng Condec- 



All non-current-carrying 
metal parts of electrical equipment and all metal raceways 
and cable sheaths shall be solidly 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 Groiindleg 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, mo- 
tors, rectifiers, and other equipment installed belowground 
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 trans- 
former supply conductors. The switch or circuit breaker for 
a motor shall comply with the applicable requirements of 
Article 430. 



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. 



ges 

110.70 General. Electrical enclosures intended for person- 
nel entry and specifically fabricated for this purpose shall 
be of sufl&cient size to provide safe work space about elec- 
trical equipment with live parts that is likely to require 
examination, adjustment, servicing, or maintenance while 
energized. Such enclosures shall have sufficient size to per- 
mit 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 electrical enclosures covered by Part V 
of this article are part of an industrial wiring system oper- 
ating 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 C2-2007, National Electrical Safety Code, 
for additional information on the loading that can be ex- 
pected to bear on underground enclosures. 



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 {IVi ft) 
where cables are only on one side. The vertical headroom 
shall be not less than 1.8 m (6 ft) unless the opening is 
within 300 mm (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 



2008 Edition NATIONAL ELECTRICAL CODE 



70-41 



110.73 



ARTICLE 110 — REQUIREMENTS FOR ELECTRICAL INSTALLATIONS 



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 760S21 

(3) Class 2 or Class 3 remote-control and signaling cir- 
cuits, or both, supplied in accordance with 725jl21\ 

110.73 Equipment Work Space. Where electrical equip- 
ment with live parts that is likely to require examination, ad- 
justment, servicing, or maintenance while energized is in- 
stalled 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 
considered 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 at 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 persons 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 be not 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 760.121 



(3) Class 2 or Class 3 remote-control and signaling cir- 
cuits, or both, supplied in accordance with 725^121 

(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 
located where they are not directly above electrical equip- 
ment or conductors in the enclosure. Where this is not prac- 
ticable, 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 TYinnels. 

(A) Location. Access openings for personnel shall be lo- 
cated where they are not directly above electrical equip- 
ment or conductors in the enclosure. Other openings shall 
be permitted over equipment to facilitate installation, main- 
tenance, 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 parts 
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. 



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NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 200 — USE AND IDENTIFICATION 



OF GROUNDED CONDUCTORS 



Cfliapteir 2 Wiirneg aied Protectroe 



-^- ^v=^A«TIC£E2W- ■■■■ v-f-.:h 
: ; : Use and .Ideiitlfieatipm ; . -^ =■;;;-■.: .^^ .' 
of Qropndec!, Conductors ■,„.., vL .:/':. i 

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. 



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 shall comply with 200.2(A) and (B). 

C4i) Iiisulatldii(. The grounded conductor, where insulated, 
shall have insulation that is (1) suitable, other than color, 
for any ungrounded conductor of the same circuit on cir- 
cuits 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 described in 250.184(A). 

(P) (EoFitmiilty. The continuity of -a gtounded^: conductor 
shall not ; depend ^oh a connection to aTmetaU ic enclosure,; 
raceway, pr cable armor. 



D Groimdled System. Premises wiring 
shall not be electrically connected to a supply system un- 
less the latter contains, for any grounded conductor of the 
interior system, a corresponding conductor that is 
grounded. For the purpose of this section, electrically con- 
nected shall mean connected so as to be capable of carrying 
current, as distinguished from connection through electro- 
magnetic induction. 

Exception: Listed utility-interdctive inverters identified for 
useindiSiri}miedMsoUrce^erii^rdti6n such as pRo- 

tqvoltaicandfue^^^^^ shall he permitted to 

be connected to premises wiring without a grounded con- 
ductor wKere pie 'WrOiected premises mring or utility '^5- 
tem inclwies^a^griiunxi^d conductor^ 



(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 Tliiami 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) Gromeded Comdiiictors of DifflFereeit Systems. Where 
grounded conductors of different systems are installed in 
the same raceway, cable, box, auxihary 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 (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. 



2008 Edition 



NATIONAL ELECTRICAL CODE 



70^3 



200.7 



ARTICLE 200 — USE AND IDENTIFICATION OF GROUNDED CONDUCTORS 



(3) Other and different means of identification as allowed 
by 200.6(A) or (B) that will distinguish each system 
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 
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. 1: 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 multicon- 
ductor varnished-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 (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 su- 
pervision ensure that only qualified persons service the in- 
stallations, terminals for grounded conductors shall be per- 
mitted to be permanently identified at the time of 
installation by a distinctive white marking or other equally 
effective means. 

200.10 Identification of Terminals. 

(A) Device Terminals. All devices, excluding panel- 
boards, provided with terminals for the attachment of con- 
ductors and intended for connection to more than one side 
of the circuit shall have terminals properly marked for iden- 
tification, unless the electrical connection of the terminal 
intended to be connected 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 am- 
peres, other than polarized attachment plugs and polarized 
receptacles for attachment plugs as required in 200.10(B). 

(B) Receptacles, Plugs, and Connectors. Receptacles, 
polarized attachment plugs, and cord connectors for plugs 



70^4 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 210 — BRANCH CIRCUITS 



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. 



(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 con- 
nected by (1) a permanent wiring method or (2) field- 
installed attachment plugs and cords with three or more 
wires (including the equipment grounding conductor), shall 
have means to identify the terminal for the grounded circuit 
conductor (if any). 

200.11 Polarity of Commections. No grounded conductor 
shall be attached to any terminal or lead so as to reverse the 
designated polarity. 



,^RTIC|E^^aiO.,. 
Braiicli Circiiits 



I. Gemeral 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. 



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 rat- 
ing for other than individual branch circuits shall be 15, 20, 
30, 40, and 50 amperes. Where conductors of higher am- 
pacity are used for any reason, the ampere rating or setting 
of the specified overcurrent device shall determine the cir- 
cuit rating. 

Exception: Multioutlet branch circuits greater than 50 am- 
peres shall be permitted to supply nonlighting outlet loads 
on industrial premises where conditions of maintenance 
and supervision ensure that only qualified persons service 
the equipment. 

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 of a]; multiwire branch circuit shall originate 
from the same panelboard or similar distribution equip- 
ment. 

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 currents on the neutral conductor. 



ose 

cults. Branch circuits shall comply with this article and also 
with the applicable provisions of other articles of this Code. 
The provisions for branch circuits supplying equipment 



(B) Disconnecting Means. Each multiwire branch circuit 
shall-, be priDvided with a means that will simultaneously 
disconnect all ungrounded conductors at the point where 
the bi^aiieliMrcuit originates . 

(C) Llne-to-Neetral 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. 

(D) Gf-bupiiig. The ungroiihded and grounded conductors 
(of each riiiiiltiwire branch circiiifsha^ by wire 
ties or- similar means in at least one location within the 
pahelb|)£ffd'^pr point of brigination. 

Exception: The YequiriemeM for grduping shall not apply if 
the ciric:uit,:^nters from a cable or raceway unique to the 
circuiiHhatjnakes the grouping obvious. 



2008 Edition NATIONAL ELECTRICAL CODE 



70-45 



ARTICLE 210 — BRANCH CIRCUITS 



Table 210.2 Specific-Purpose Branch CircMits 



Equipment 


Article 


Section 


Air-conditioning and 




440.6, 440.31, 


refrigerating equipment 




440.32 


Audio signal processing, 




640.8 


amplification, and 






reproduction equipment 






Busways 




368.17 


Circuits and equipment 


720 




operating at less than 






50 volts 






Central heating equipment 




422.12 


other than fixed electric 






space-heating equipment 






Class 1, Class 2, and Class 3 


725 




remote-control, signafing, 






and power-limited circuits 






Cranes and hoists 




610.42 


Electric signs and outline 




600.6 


lighting 






Electric welders 


630 




Electrified truck parking/space 


em 




Elevators, dumbwaiters. 




620.61 


escalators, moving walks. 






wheelchair lifts, and stairway 






chair fifts 






Fire alarm systems 


760 




Fixed electric heating 




427.4 


equipment for pipelines and 






vessels 






Fixed electric space-heating 




424.3 


equipment 






Fixed outdoor electrical 




426.4 


deicing and snow-melting 






equipment 






Information technology 




645.5 


equipment 






Infrared lamp industrial 




422.48, 424.3 


heating equipment 






Induction and dielectric 


665 




heating equipment 






Marinas and boatyards 




555.19 


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 




650.7 


Recreational vehicles and 


551 




recreational vehicle parks 






Switchboards and panelboards 




408.52 


Theaters, audience areas of 




520.41, 


motion picture and television 




520.52, 


studios, and similar locations 




520.62 


X-ray equipment 




660.2, 517.73 



210.5 Identifflcation for Branch Circuits. 

(A) Groimded Conductor. The grounded conductor of a 
branch circuit shall be identified in accordance with 200.6. 

(B) Eqeipmeut 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 
nominal voltage system, each ungrounded conductor of a 
branch circuit shall be identified by phase oi- line arid sys- 
tem at . all terminatipii,; eonnection, and splicQ ppintsj The 
means of identification shall be permitted to be by separate 
color coding, marking tape, tagging, or other approved 
means. The method utilized for conductors originating 
within^ :ek;h; braiieh-eireuit=^paneIboard or i^imilar brahchT 
circuit distribution equipment shall be docurnented in a 
manner^ that; is readily.'available^or shall be permanently 
posted at each branch-circuit panelboard or similar branch- 
circuit distribution equipment. 

21®.6 Branch=C5rcuit Voltage Limitations. The nominal 
voltage of branch circuits shall not exceed the values per- 
mitted by 210.6(A) through (E). 

(A) Occupancy Limitation. In dwelling units and guest 
rooms or guest suites of hotels, motels, and similar oc- 
cupancies, the voltage shall not exceed 120 volts, nomi- 
nal, between conductors that supply the terminals of the 
following: 

(1) Luminaires 

(2) Cord-and-plug-connected loads 1440 volt-amperes, 
nominal, or less or less than Vi 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 
utihzation 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 

(2) Listed incandescent luminaires, where supplied at 120 
volts or less from the output of a stepdown autotrans- 
former that is an integral component of the luminaire 
and the outer shell terminal is electrically connected to 
a grounded conductor of the branch circuit 



• 



70^6 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 210 — BRANCH CIRCUITS 



(3) Luminaires equipped with mogul-base screw shell 1am- 
pholders 

(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 where the 
luminaires are mounted in accordance 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 

(3) luAirwA^^ idiregt^current ^ystpMs ^where 
the lurnihaire cQtitaihs a listed, dc-rated ballast that jpro- 
yidesjisolatioriiibetween the^ dcrpower soured; -^d^ the 
iaiript;pircuit and prM^ electric^ Jshock \yhen 



ductors supplying those devices shall be provided at the 
point at which the branch circuits originate. 



FPN: See 410.[r31 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. 

(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 Requirements for D'eMCfe- €!,oiiiieiG= 
pibns ^aiid,. -Uqc^tidiis. 

(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- 



er 



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 

o (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. 

(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 

Q Exception 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. 

FPN; J iSee 760.41(B) and 760.121(B) for power supply 
requjrernents for fire alarm systems. 

Receptacles installed under the exception to 
210.8(A)(5) shall not be considered as meeting the 
requirements of 210.52(G). 

(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) K^^ehens 

(3) Rooftops 

(4) ©utddOTSi 



2008 Edition NATIONAL ELECTRICAL CODE 



7§-47 



210.9 



ARTICLE 210 — BRANCH CIRCUITS 



Exception No. 1 to (3) and (4): Receptacles that are not 
readily accessible and are supplied from a dedicated 
branch circuit for electric snow-melting or deicing equip- 
ment shall be permitted to be installed without :^FGI 
proieeliori. 



Exception No. 2 fa J4^/: LriftiidusMdllJest^ 
wJiere '■ fhe'cj^difit^^jof' 'em 

sure tHdt pnlyi qJ4alifie(k^P;e}^nn0}^ dre^iinyglved, ; :dn .. assu0^ 
pqUipment grounding 'tc^^ specifiM id 

'5^j5J^B^2){]sh£illf^e,l ^p^f^tted^^fd^KiiO^ 

i>Weis used^^ id Isuppl^l e0 that wduld-- create a 

g^dtier-fHdZttM'if^p0w 'a- desigfi, 

tJmt i^^t compatible^ 

(5) Sinks —^whlrere^^ 

p : fl|-qfi thei^siidfi:ieag^jof: tHe=^mk^ 

'Exceptibri'Ni^^ Wivn^sWjMilja^^ 

taeles iusedr^o sl^pplyjeguipinm^ removal of power 

'mmld^^'inM^ j>e 

insMiredwiiEoutlGE 

^Exf<spiii)hlW-^2'':ia'^^f{i Eorjj^c0idcie/s'loc^^ patient 
cjdiikafi^ icd^fmiUiies^ oiMb th&ft ihpse d<0m-ed 

wider 2rl not be[requiredj 

(C) Boat Hoists. GEGI protection shall be provided for 
outlets not^pe^diE^:2^0nvp that supply boat hoists in- 
stalled in dwelling unit locations. 

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. 

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 
qualified 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 systems, 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) 410.9J for double-pole switched lampholders 

(2) 41O.jI0^(B) for electric-discharge lamp auxiliary equip- 
ment switching devices 

(3) 422.31(B) for an appliance 

(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 apph- 
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 be required to be installed only 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. 



70-48 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 210 — BRANCH CIRCUITS 



• 



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 Dl(a), Dl(b), D2(b), and D4(a) in 
Annex D. 

210.12 Arc-Fault Circuit-Interrupter Protection. 

(A) Defioition: Arc-Fault Circuit Interrupter (AFCI|. 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 Wmis. All 120- volt, single phase, 15- and 
20-ampere branch circuits supplying outlets installed in 
dwelling unit familji^ rooms, dining jj-oorns,li^^ 
parlors^-liijraKe^^ ; ^bedreo^ 

rooiiiS, clic^s^hall^ shall be 

protected by a hsted arc-fault circuit interrupter, 
combination-type, installed to provide protection of the 
branch circuit. 

EPN^NSgllii; For information on types of arc-fault circuit 
interrupters, see UL 1699-1999, Standard for Arc-Fault 
Circuit Interrupters. 

F-vre A liaym-'Qpde^'0or ■ itif ofrtiation ■ relateid^ % rseeondary: 
po w|f "suppTy ■ fdrpsnioKe alarjiis Installefen 

;d^#lMgluhits^ 

™:jfGE3;;] §ge;f 6Q^1:(B) and 760.|12^(B) for power- 
supply requirements for fire alarm systems. 

Exception No. 1: ^}iet^VRMf^r'.Bi^ 

bable;-Typie^AC^m 

m^tdlcpuflet'dnd^jiin^^^ 

of thci^ branch Mrcu.it\ between itfie^ IfranchfcifcMit\ oy^rcufi 

'^rU deviM^)dnd^!}t}w shallWe permitted id, 

imtalt^jav^mbmatip^^ 

prbie([tidjn<fdf tlie^^ poQidn -of the brdiich Circuity 

Exception No. 2: yifj^eydi^fld^^^ 

sysiein'^~insiall£^r^ 'with^, {760:.W(B)x{dnd. 

mored^^ Qable,^^T^e^}^,A^C^x^ . ,*re^Mir^m^nte_. p/ 

250.118, ' with^ meMrpuUef^a^^ boxes^^^^ALpV^-Jf^^ 

tecti0'n:shdlf:}^i^^ 



5 Guest Rooms and Guest Suites. Guest rooms and 
guest suites that are provided with permanent provisions for 
cooking shall have branch circuits 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 



(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 No. 1: Where the assembly, including the over- 
current devices protecting the branch circuit(s), is listed for 
operation at 100 percent of its rating, the allowable ampac- 
ity of the branch circuit conductors shall be permitted to be 
not less than the sum of the continuous load plus the non- 
continuous load. 

Exception No. 2: Grourided cpnductors that are not con- 
nected iixan overcUrreht device shall be permitted to be 
size(f.i2t;ifQ0p(^reen^ and noncontinuous 

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 branch circuits as defined in 
Article 100, sized to prevent a voltage drop exceeding 
3 percent at the farthest 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 SV^ kW or 
more rating, the minimum branch-circuit rating shall be 40 
amperes. 

Exception No. 1: Conductors tapped from a 50-ampere 
pramh circuit supplying electric ranges, wall-mounted 
electric ovens, and counter-mounted electric cooking units 
shall have an ampacity of not less than 20 amperes and 
shall be sufficient for the load to be served. These tap con- 
ductors 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 servicing the appliance. 



2008 Edition NATIONAL ELECTRICAL CODE 



70-49 



210.20 



ARTICLE 210 — BRANCH CIRCUITS 



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 conductors 
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 with taps ex- 
tending not longer than 450 mm (18 in.) beyond any por- 
tion of the lampholder or luminaire. 

(b).A lupiindire having tap conductors as provided in 

4io.m 

(c) Individual outlets, other than receptacle outlets, 
with taps not over 450 mm (IS 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. 

(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 permit- 
ted 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- 



• 



• 



70-50 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 210 — BRANCH CIRCUITS 



Table 210.21(B)(2) Maximum Cord-and-Ptag-Connected 
Load to Receptacle 



Circuit Rating 

(Amperes) 



Receptacle Rating 

(Amperes) 



Maximum Load 
(Amperes) 



15 or 20 
20 
30 



15 
20 
30 



12 
16 

24 



and-plug-connected load in excess of the maximum 
specified in Table 210.21(B)(2). 

(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 410J^fC). 

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. 

(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-Pleg-Coenected 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, shall not exceed 50 percent of the branch- 
circuit ampere rating where lighting 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 Branch Circuits in' BuOdings with More Than 
One : Occiiparicy:. 

(A) Dwe!linguPniti-Branch'?Cireuit§. Branch circuits in 
each dwelling umt shall supply only loads within that dwelling 
unit or loads associated only with that dweUing unit. 

(B) t^mniori -Area Branch Circuits. Branch circuits re- 
quired for the purpose of lighting, central alarm, signal, 
communications, or other needs for public or common ar- 
eas of a two-family dwelling^ a miirtifarnily dwelling, or a 
5[inultp0(xuf^anc^b^^ shall not be supplied from equip- 
ment that supplies an individual dwelling unit or tenant 
space] 



2008 Edition 



NATIONAL ELECTRICAL CODE 



70-51 



210.50 



ARTICLE 210 — BRANCH CIRCUITS 



Table 210.24 Summary of Branch-Circuit Requirements 



Circuit Rating 


ISA 


20 A 


30 A 


40 A 


50 A 


Conductors (min. size): 
Circuit wires ^ 
Taps 

Fixture wires and cords 
— see 240.5 


14 
14 


12 
14 


10 

14 


8 
12 


6 

12 


Overcurrent 
Protection 


ISA 


20 A 


30 A 


40 A 


50 A 


Outlet devices: 
Lampholders 

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 


ISA 


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, see 410.30(C). 



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. 

(C) Appliance Receptacle Outlets. Appliance receptacle 
outlets instaUed in a dwelhng 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 re- 
ceptacle outlets. The;'rS^epta^le$ required by this section 
shall be in addition to any receptacle that is: 

( 1 ) Part, ctf ja. liiminaifec^ appliartce, or 

(2) iC^ohtrolled'?-b)^^|a': wallJl^iteK ■■■ irv v acpprdarice-;lwith 
2py70<^)(il^^lxp|ti(:a^ 

(3) I:Xicated;W 

(4) Lpcated mbre than |^7 irv^(5y^)^boye thepoqr 

Permanently instaUed electric baseboard heaters equipped 
with factory-installed receptacle outlets or outlets provided as 
a separate assembly by the manufacturer shall be permitted as 
the required outlet or outlets for the wall space utilized by 



such permanently installed heaters. Such receptacle outlets 
shaU 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 shall be installed in accor- 
dance with the general provisions specified in 210.52(A)(1) 
through (A)(3). 

(1) Spacing. Receptacles shall be installed such 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 oudets 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 



70-52 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 210 — BRANCH CIRCUITS 



210.52 



• 



• 



• 



unit, the two or more 20-ampere small-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 re- 
ceptacle outlets in the kitchen and other rooms specified in 
210.52(B)(1). No small-appliance branch circuit shall serve 
more than one kitchen. 

(C) Countertops. In kitchens, pEffipes^breakfa^^^^ 
jdihit^^rdonS^:^ of dwelling units, recep- 

tacle outlets for ^imWrtpp spaces shall be installed in ac- 
cordance with 2i0.52(C)(l) through (C)(5). 

P(|iereva^|autig^v^b 
is installed Injap jslffi 

widthi'of 'ffi^OTtpertop'l^lM 

j:poKng jwit,^x)i;; sin)^ js^^iessr^^^aj^ the 

rajflgeFcciLnterr^mq or sink' fe ; coMidef ed 

jtcTcffikad^'pi^ 

§pac«s'as''dpniiJ'mW03S^ 

space*-sh[aIl«cQm|lpWtKMe 

2m52 (C f" 

(1) Wall ^Gipiimtertopi Spaces. A receptacle outlet shall be 
installed at each wall CGuhf^itop 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, Wpm&fmoMie 

unifl or sink in the installation described in figure 

2m52(^)(% 



Outlet within _j. 

600 mm (24 in.) 



Space exempt from wall 
line if X< 300 mm (12 in.) 



_ Outlet within _ 
600 mm (24 in.) 



Range, counter-mounted cooking unit extending 
from face of counter 



Space exempt from wall line 
if X< 450 mm (18 in.) 



Outlet within 600 mm (24 in.) 




Range, counter-mounted cooking unit mounted in corner 

Figure 210.52(C)(1) Determination of Area Behind a Range, 
or Counter-Mounted Cooking Unit or Sink. 



(2) Island J^6^ngfto| Spaces. At least one receptacle 
shall be installed at each island 'cbufitertop space with a 
long dimension of 600 mm (24 in.) or greater and a short 
dimension of 300 mm (12 in.) or greater. 

(3) Peninsular EMriteFtqp^ Spaces. At least one recep- 
tacle outlet shall be installed at each peninsular countertop 
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. 

(4) Separate Spaces. Countertop spaces separated by 
rangetops, refrigerators, or sinks shall be considered as 



2008 Edition 



NATIONAL ELECTRICAL CODE 



70-53 



210.60 



ARTICLE 210 — BRANCH CIRCUITS 



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 apphances 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, orinstalled on the side or face of 
the basin cabinet not;rnoreJ^hah30OTmm (12 in^^below the 
countertop: 

(E) Outdoor Outlets. Outdoor ;receptacle outlets shall be 
installed in acGordance with (E)(1)' through (E)(3). [See 
2J0.8(A)(3l.] 

(1) One-FarnUy, and 1>vo-FaiTiily DweUin For a one- 
family dwelling and each unit of a two-family dwelling that 
is at grade level, at least one receptacle outlet accessible 
while standing at grade level and located not more than 
2.0 m (6'/2 ft) above grade shall be installed at the front and 
back of the dwelling. 

(2) Multifamily Dwellings. For each dwelling 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. 

(3) Bakpnies, Pecks, and Porches. Balconies^, decks, and 
porches that are accessible frQiTi inside the dweUihg unit 
shall ? have at least one receptacle outlet instal led within- the 
perimeter of the balcony, deck, or porch. The receptacle 



shall not; be located more than ,2,0 m (6 '/2 ft) above; the' 
balicbny,ldeck,, oi^ poreh ^u^ 

Exceptidn to -(3}: Balconies, decks, or fporche^ with crius- 
able area, of, less than 1^86 m^ (20; ft^)- are, not, required to 
have a receptacle installed. 

(F) Laundry Areas. In dwelling 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, 
!the;^llowing;pix)vjsipns;shalf apply: 

(1) At least one receptacle outlet, in addition to those for 
specifie equipment,' shall be installed in each basement, 
in each attached garage, and in each detached garage 
with electric power. 

(2) Where a portion of the basement is finished into one or 
more habitable rooms, each separate unfinished portion 
shall have a receptacle outlet installed in accordance 
with this section. 

(H) Hallways. In dwelling 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. 

210.60 Guest Rooms, Guest Suites, pormitbries, arid 
Similar Occupancies. 

(A) General. Guest rooms or guest suites in hotels, motels, 
sleeping rooms in dormitories, and similar occupancies 
shall have receptacle outlets installed in accordance with 
210.52(A) and 210.52(D). Guest rooms or guest suites pro- 
vided with permanent provisions for cooking shall have 
receptacle outlets installed in accordance 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 



• 



• 



70-54 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 215 — FEEDERS 



• 



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 iwithih 450 rnim |p irf;) of^the vtop of ^ 
show window for each 3.7 linear m (12 linear ft) or major 
fraction thereof of show window area measured horizon- 
tally at its maximum width. 

210.63 Heating, Air-Conditioning, and Mefrigeratioim 
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 evaporative 
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 lighting 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, in stairways, and at outdoor entrances, remote, cen- 
tral, 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 wall 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 allows 
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. 



p"'V'Y T ''Article 215' 

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). 



2008 Edition NATIONAL ELECTRICAL CODE 



70-55 



215.2 



ARTICLE 215 — FEEDERS 



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 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 allowable ampacity of 
the feeder conductors shall be permitted to be not less than 
the sum of the continuous load plus the noncontinuous 
load. 



Exception No. 2: Xj^vUnded.';^ 

necied id. idri oyercufrintl Memce^ sifidllrfbe permitted ^o be 

si^ct[ Mi ; 100 ipemeni: ^.oj^thei ■^Of^tinuous- and fngncontinuous 
toadl 

The size of the feeder circuit grounded conductor shall 
not be smaller than that required by 250.122, except that 
250.122(F) shall 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 outlet of power, heating, and lighting 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, will provide rea- 
sonable efficiency 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 
shall be in accordance with 310.15 and 310.60 as appli- 
cable. Where installed, the size of the feeder-circuit 
grounded conductor shall not be smaller than that required 
by 250.122, except that 250.122(F) shall not apply where 



grounded conductors 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 
Equipment. 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 quaUfied 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 thefeeder(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 GbnidiictOr. 

(A) Feeders with Common Neutral. Up to three sets of 
3-wire feeders or two sets of 4-wire or 5-wire feeders shall 
be permitted to utilize a common neutral. 

(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 pondWctor shall be en- 
closed within the same raceway or other enclosure as re- 
quired in 300.20. 



70-56 



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ARTICLE 220 — BRANCH-CIRCUIT, FEEDER, AND SERVICE CALCULATIONS 



220.3 



• 



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 E||iiipmeii| Grounding Conductor. Where 
a feeder supplies branch circuits in which equipment 
grounding conductors are required, the feeder shall include 
or provide an l|uip|nent grounding p(mductor in accor- 
dance with the provisions of 250.134, to which the equip- 
ment grounding conductors of the branch circuits shall be 
connected. Where the 'feeder' supplies a separate building' or 
sfira(^r^,J^ 

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 
neutral 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 health care 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 if ground-fault protection of equipment is provided on 
the supply side of the feeder mid on the load side o^ any 
if^isforineWUp^ thi^'f^edet, 

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 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 
qualified 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 systems, without the connection to a similar 
grounded conductor 

215.12 Identiication 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 supphed from more than one nominal 
voltage system, each ungrounded conductor of a feeder 
shall be identified by phase or line and system at all termi- 
nation,: cQnheption,:^^ splice points. The means of identi- 
fication shall be permitted to be by separate color coding, 
marking tape, tagging, or other approved means. The 
inethbd utilized for conductors originating within each 
feeder panelboard or similar feeder distribution equipment 
shall ibe ^documented in a manner that is readily available or 
shall be permanently posted at each feeder panelboard or 
similar feeder distribution equipment. 



^- :ARTICLE220 
Branch-Circuit, Feeder, 
and Service Calculations 



I. General 

220.1 Scope. This article provides requirements for calcu- 
lating branch-circuit, feeder, and service loads. Part I pro- 
vides for general requirements for calculation methods. Part 
n provides calculation methods for branch-circuit loads. Parts 
in and rV provide calculation methods for feeders and ser- 
vices. Part V provides calculation methods for farms. 

FPN: See Figure 220.1 for information on the organization 
of Article 220. 



of Other Articles. In other articles 
applying to the calculation of loads in specialized applica- 
tions, there are requirements provided in Table 220.3 that 



2008 Edition 



NATIONAL ELECTRICAL CODE 



70-57 



220.5 



ARTICLE 220 — BRANCH-CIRCUIT, FEEDER, AND SERVICE CALCULATIONS 



Part I General 



Part II Branch-circuit load calculations 



Part III 
Feeder and 
service load 
calculations 



220.61 
Neutral 
Loads 



Part IV 

Optional 

feeder and 

service load 

calculations 



Farm dwellings 
only 



Farm dwellings 
only 



Part V Farm load calculations 



Figure 220.1 Branch-Circuit, Feeder, and Service Calculation 
Methods. 



are in addition to, or modifications of, those within this 
article. 

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 



• 



Table 220.3 Additional Load Calculation References 



Calculation 


Article 


Section (or Part) 


Air-conditioning and refrigerating equipment, branch-circuit 


440 


Part IV 


conductor sizing 






Cranes and hoists, rating and size of conductors 


610 


610.14 


Electric welders, ampacity calculations 


630 


630.11, 630.31 


Electrically driven or controlled irrigation machines 


675 


675.7(A), 675.22(A) 


Electrified I truck parking jspa^^^^ 


626 




Electrolytic cell lines 


668 


668.3(C) 


Electroplating, branch-circuit conductor sizing 


669 


669.5 


Elevator feeder demand factors 


620 


620.14 


Fire pumps, voltage drop (mandatory calculation) 


695 


695.7 


Fixed electric heating equipment for pipelines and vessels, 


427 


427.4 


branch-circuit sizing 






Fixed electric space-heating equipment, branch-circuit sizing 


424 


424.3 


Fixed outdoor electric deicing and snow-melting equipment, 


426 


426.4 


branch-circuit sizing 






Industrial machinery, supply conductor sizing 


670 


670.4(A) 


Marinas and boatyards, feeder and service load calculations 


555 


555.12 


Mobile homes, manufactured homes, and mobile home parks, 


550 


550.18(B) 


total load for determining power supply 






Mobile homes, manufactured homes, and mobile home parks, 


550 


550.31 


allowable demand factors for park electrical wiring systems 






Motion picture and television studios and similar locations - 


530 


530.19 


sizing of feeder conductors for television studio sets 






Motors, feeder demand factor 


430 


430.26 


Motors, multimotor and combination-load equipment 


430 


430.25 


Motors, several motors or a motor(s) and other load(s) 


430 


430.24 


Over 600-volt branch-circuit calculations 


210 


210.19(B) 


Over 600-volt feeder calculations 


215 


215.2(B) 


Phase converters, conductors 


455 


455.6 


Recreational vehicle parks, basis of calculations 


551 


551.73(A) 


Sensitive electrical equipment, voltage drop (mandatory 


647 


647.4(D) 


calculation) 






Solar photovoltaic systems, circuit sizing and current 


690 


690.8 


Storage-type water heaters 


422 


422.11(E) 


Theaters, stage switchboard feeders 


520 


520.27 



• 



70-58 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 220 — BRANCH-CIRCUIT, FEEDER, AND SERVICE CALCULATIONS 



220.14 



• 



occupancies specified therein shall constitute the minimum 
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 


DweUing units" 


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 


1/4 


In any of the preceding 






occupancies except 






one-family dwellings and 






individual dwelUng units of 






two-family and multifamily 






dwellings: 






Assembly halls and 


11 


] 


auditoriums 






Halls, corridors, closets, 


6 


1/2 


stairways 






Storage spaces 


3 


'/4 


"See 220.I4(J). 






^See 220.14(K). 







• 



220.14 Other Loads — All Occupancies. In all occupan- 
cies, the minimum load for each outlet for general-use 
receptacles 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 he 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 appliances. 

(C) Motor Loads. Outlets for motor loads shall be calcu- 
lated in accordance with the requirements in 430.22, 
430.24, and 440.6. 

(D) Luminaires. An outlet supplying luminaire(s) shall be 
calculated based on the maximum volt-ampere rating of the 
equipment and lamps for which the luminaire(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 outhne 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 appliances 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 



2008 Edition NATIONAL ELECTRICAL CODE 



1^59 



220.16 



ARTICLE 220 — BRANCH-CIRCUIT, FEEDER, AND SERVICE CALCULATIONS 



than 180 volt-amperes for each single or for each multiple 
receptacle on one yoke. A single piece of equipment con- 
sisting of a multiple receptacle comprised of four or more 
receptacles shall be calculated at not less than 90 volt-amperes 
per receptacle. This provision shall not be applicable to the 
receptacle 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 lighting 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 calculated load from 220.14(1) 

(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 dwelling 
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 
dwelling 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 cal- 
culated in accordance with either 220.12 or 220.14, as ap- 
plicable. 

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 utihzation 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 Part III or 
IV or required by Part V have been applied. 

FPN: See Examples Dl(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 Genera! 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. 1 4(H) and (I) shall be permitted to be made subject to 
the demand factors given in Table 220.42 or Table 220.44. 



70-60 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 220 — BRANCH-CIRCUIT, FEEDER, AND SERVICE CALCULATIONS 



220.55 



Table 220.42 Lighting Load Demand Factors 



a 





Portion of Lighting 






Load to Which 






Demand Factor 




Type of 


Applies 


Demand 


Occupancy 


(Volt-Amperes) 


Factor (%) 


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 
50,000 at 



40 
20 



Hotels and motels, 
including 
apartment houses 
without provision 
for cooking by 
tenants* 



First 20,000 or less at 


50 


From 20,001 to 




100,000 at 


40 


Remainder over 




100,000 at 


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 
Demand Factor Applies 
(Volt-Amperes) 



Demand Factor (%) 



First 10 kVA or less at 
Remainder over 10 kVA at 



100 
50 



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. 



.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 SmaBl=Appliaince and Laundry Loads — Dweli- 



Ilance Circuit Load. In each dwelling unit, 
the load shall be calculated at 1500 volt-amperes for each 
2-wire small-appliance branch circuit as covered 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 permitted 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 covered 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 Unst(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 
supplied 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. Kilovolt- 
amperes (kVA) shall be considered equivalent to kilowatts 
(kW) for loads calculated in this section. 

220.55 Electric Manges 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 PA kW shall be permitted to be calcu- 
lated in accordance with Table 220.55. Kilovolt-amperes 



2008 Edition NATIONAL ELECTRICAL CODE 



70-61 



220.56 



ARTICLE 220 — BRANCH-CIRCUIT, FEEDER, AND SERVICE CALCULATIONS 



Table 220.54 Demand Factors for Household Electric 
Clothes Dryers 



Number of 
Dryers 






Demand Factor 

(%) 


1^ 

5 

6 

7 

8 

9 
10 
11 






100 

85 
75 
65 
60 
55 
50 
47 


MM 


¥M 


jniinusp l;%?|for !ei^l pyeKpteeedingl M 




WiM 


mnu5 




24-42 


; W5^ 5 fpi: =ea^fi;^rj(^ :exdpe^n§j2S 


43 and over 






25% 



(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. 

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 Kitchen Equipment — 
Other Than Dwelling Unit(s) 



Number of Units of 


Demand Factor 


Equipment 


(%) 


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 eonduc- 
|q| and any one ungrounded conductor. 

Exception: For 3-wire, 2-phase or 5-wire, 2-phase systems, 
the maximum unbalanced load shall be the maximum net 
calculated load between the neutral Wnduc0f',:arM any one 
ungrounded 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 
amperes 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 iin^- 
g|pMdg(|||0E^j^ and the neutral |indue]tGu^ of a 
4-wire, 3-phase, wye-connected system 

(2) That portion consisting of nonhnear loads supplied 
from a 4-wire, wye-connected, 3-phase system 

FPN No. 1: See Examples Dl(a), Dl(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-eofflfuetor 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. 



• 



70-62 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 220 — BRANCH-CIRCUIT, FEEDER, AND SERVICE CALCULATIONS 



220.80 



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 (%) (See Notes) 



Number of 
liances 



Column A 

(Less than 

Wz kW Rating) 



Column B 
(3V2 kW Ihrougts 
m* kW Rating) 



Column C 
Maximum Demand (kW) (See 
over 12 kW Rating) 



80 
75 
70 
66 
62 



80 
65 

55 
50 
45 



11 

14 
17 
20 



6 
7 
8 
9 
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 



39 
38 
37 
36 

35 



28 
28 
28 
28 
28 



31 
32 
33 
34 
35 



21 

22 
23 
24 
25 



34 
33 
32 
31 
30 



26 
26 
26 
26 
26 



36 
37 
38 
39 
40 



26-30 
31^0 



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 + 3/4 kW for each range 



• 



Notes: 

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 SV4 kW through 27 kW ranges of unequal ratings. For ranges individually rated more than 8% 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 1% kW through B'A 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 1% kW but not more than 8^/4 kW and multiply the sum by the demand factors specified in Column A or 
Column B for the given number of appliances. Where the rating of cooking appliances 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 shall also apply to household cooking appliances rated over iy4 kW and used in instructional programs. 



2008 Edition NATIONAL ELECTRICAL CODE 



70-63 



220.82 



ARTICLE 220 — BRANCH-CIRCUIT, FEEDER, AND SERVICE CALCULATIONS 



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 ch- 
cuit eoyered:in ;2 ID • H=(G)^1i ffl^ 

(3) The nameplate rating of the;follGwing:; 

ai All appliances that are fastened in place, permanently 
connected, or located to be on a specific circuit 

hi Ranges, wall-mounted ovens, counter-mounted 
cooking units 

ip] Clothes dryers that ;a^;nbt:t0hridGtedito th^ 
braiich;Circuit'speeified;iil 

(1; Water heaters 

(4) The nameplate ampere or kVA rating of all perma- 
nently connected motors not included in item (3). 

(C) Heating and Air-Conditioning Load. The largest of 
the following six selections (load in kVA) shall be in- 
cluded: 

(1) 100 percent of the nameplate rating(s) of the air condi- 
tioning and cooling. 

(2) 100 percent of the nameplate rating(s) of the heat; pump 
when the heat pump is used without any supplemental 
electric heating. 

(3) 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. 

(4) 65 percent of the nameplate rating(s) of electric space 
heating if less than four separately controlled units. 



(5) 40 percent of the nameplate rating(s) of electric space 
heating if four or more separately controlled units. 

(6) 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). 

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 cal- 
culate 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 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 ck- 
cuit covered inr:2imp^G)C|);;a^^ 

(3) Th^'-nim^^late; rating; M^ 

'al Air ■ iapplian^es ttthat ": Jar^;Tfa§tei^;-inJiplaeeJV:pe;riha^ 

nently; Jcoiiiject^d; : or ?lpeat^;ia:be;]on 'a [sjiecifiCfeii^ 

ciiit 
b'i Ranges,;] waU-riiQunted cpunter-mouiited"; copk-| 

ing^iiriits 
e: Clotps['dryer^,'that'att^;]^ 

brai)Gh;cifcuif spec^ified;;iii!?iK^ni; (2) 
d; W^ter:heatei^ 

(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 


100 


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 



70-64 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 220 — BRANCH-CIRCUIT, FEEDER, AND SERVICE CALCULATIONS 



220.86 



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 i?p>^ed|iifp: lg;^f)E-;^ ;a^^^ 

(3) |'h^:naiii^ate;tating;5of-t^^ 

E. j^U;;^^|plilnees^;tMt^ 

nehl|y'iC)G^neGted^^Qf^^c^^ 

emit 
W^ Rahgp|[|JiwaUfmbTOted*H^0^ 

GooMri^iiiiiit^ 
ft^ Glc^es^dryers; that? am^tj ^c^neeted; tp;p 

branch? !ci]^OT^e^ified ^n ; (^2) 
W V^ter theaters 

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) Hoose 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- 
appHance branch circuit and each laundry branch cir- 
cuit i(weredi^n:il;j3^;H;(G^ 

(3) The nameplate rating of ffleifollowijig^ 

11 All appUances that are fastened in place, permanently 
connected, or located to be on a specific circuit 



Table 220.84 Optional Calculations — Demand Factors for 
Three or More Multifamily Dwelling Units 



Number of 


Demand Factor 


Dwelling Units 


(%) 


3-5 


45 


6-7 


44 


8-10 


43 


11 


42 


12-13 


41 


14-15 


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 


43-45 


27 


46-50 


26 


51-55 


25 


56-61 


24 


62 and over 


23 


b: Ranges, wall-mounted 


ovens, counter-mounted 


cooking units 





c: Clothes dryers that are^vriot.e6hrieGte;d^^ 

branch: tireuitisjpeeiiied 
dy Water heaters 

(4) The nameplate ampere or k\p rating of all peirma- 
p.ntly;:d<)pWecte^^^ motors not included in item (3) 

(5) The larger of the air-conditioning load or the fixed elec- 
titc space-heating load 

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. 



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70-65 



220.87 



ARTICLE 220 — BRANCH-CIRCUIT, FEEDER, AND SERVICE CALCULATIONS 



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. 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 III 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. 

Table 220.86 Optional Method — Demand Factors for 
Feeders and Service 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 lieu 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 Calculations 

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 
dwelling 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 loads 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- 



Table 220.88 Optional Method — Permitted Load Calculations for Service and Feeder Conductors for New Restaurants 



Total Connected 
Load (kVA) 



All Electric Restaurant 
Calculated Loads (kVA) 



Not All Electric Restaurant 
Calculated Loads (kVA) 



0-200 
201-325 
326-800 
Over 800 



80% 
10% (amount over 200) + 160.0 
50% (amount over 325) + 172.5 
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. 



70-66 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 225 — OUTSIDE BRANCH CIRCUITS AND FEEDERS 



225.4 



Table 220.102 Method for Calculating Farm Loads for 
Other Than Dwelling Unit 



Table 225.2 Other Articles 



Ampere Load at 
240 Volts Maximum 



jmand Factor 
(%) 



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 loads 



100 



50 

25 



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 220.103 Method for Calculating Total Farm Load 



Individual Loads Calculated in 
Accordance with Table 220.102 



jmand Factor 
(%) 



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 electrical equip- 
ment 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 C2-2007, National Electrical Safety Code. 

225.2 Other Articks. Application of other articles, includ- 
ing additional requirements to specific cases of equipment 
and conductors, is shown in Table 225.2. 



Equipment/Conductors 



Branch circuits 

Class 1, Class 2, and Class 3 

remote-control, signaling, 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 



I. General 

225.3 CalculatloM 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 111 of Article 220. 

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. 



2008 Edition 



NATIONAL ELECTRICAL CODE 



70-67 



225.5 



ARTICLE 225 — OUTSIDE BRANCH CIRCUITS AND FEEDERS 



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: 

(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 spans 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 Ar- 
ticle 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 ppnductoi' and all un- 
grounded conductors 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 
for illumination of outdoor areas of industrial establish- 
ments, office buildings, schools, stores, and other commer- 
cial or public buildings where the luminaires are not less 
than 900 mm (3 ft) from windows, 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, || 
Wyi^>03^::eQ!b\^^ as Type MI cable, as messenger-supported 
wiring, in rigid metal conduit, in intermediate metal con- 
duit, in rigid nonmetallic conduit, in cable trays, as cable- 
bus, in wireways, in auxiliary gutters, in electrical metallic 
tubing, in flexible metal conduit, in liquidtight flexible 
metal conduit, in liquidtight flexible nonmetallic conduit, 
and in busways. Circuits of over 600 volts, nominal, shall 
be installed as provided 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 mm (4 in.). 

(D) Conductors on Poles. Conductors on poles shall have 
a separation of not less than 300 nam (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 con- 
ductors: 



a. 300 volts or less 

b. Over 300 volts - 



- 600 mm (24 in.) 
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. 



• 



• 



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NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 225 — OUTSIDE BRANCH CIRCUITS AND FEEDERS 



• 



(B) Means of Attadimeiit. 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. 



• 



225.18 Clearance fo^f^^Qverlwaa^nflGoM 
;Ca|fl(e|. Overhead spans of open conductors and open mul- 
ticonductor 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 Usted 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 Moofs. 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 
arranged, where practicable, so that a clear space (or zone) 
at least 1.8 m (6 ft) wide will be left either adjacent to the 
buildings or beginning not over 2.5 m (8 ft) from them to 
facilitate 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. 



2008 Edition ' NATIONAL ELECTRICAL CODE 



70-69 



225.21 



ARTICLE 225 — OUTSIDE BRANCH CIRCUITS AND FEEDERS 



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. 

225.24 Outdoor Lampholders. Where outdoor lamphold- 
ers are attached as pendants, the connections to the circuit 
wires shall be staggered. Where such lampholders have 
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 Ughting 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. 

II. 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 suf&ciently 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 lighting 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 utihzed. 

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- 



• 



70-70 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 225 — OUTSIDE BRANCH CIRCUITS AND FEEDERS 



225.39 



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) Siogle-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 
equipped with idisltifited handle ties or a master handle to 
disconnect all ungrounded conductors with no more than 
six operations of the hand. 

225.34 Grouping of Dtsconiiects. 

(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 per- 
mitted 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 minimize 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 pass- 
ing 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 power 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 section 
of the switchboard, provided any such switchboard section 
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 



2008 Edition NATIONAL ELECTRICAL CODE 



70-71 



225.40 



ARTICLE 225 — OUTSIDE BRANCH CIRCUITS AND FEEDERS 



ealciilateid load to be supplied, determined in accordance 
with Parts I and II of Article 220 for branch circuits, Part III 
or IV of Article 220 for feeders, or Part V of Article 220 for 
farm loads. Whei^;^tfe;l5ra^ 
irigil meansu GonsiMsu C)f ^ ^moteUSbaii ;:Gfl^ ^s^ 
breailcer^';a& ;^ ;225 ;33^ ; i^mMiiin^ itheHratiiigs *bf 

all; th^ Jswirt^chfe^: Oit'^ b^eaKepi^ ;fGK id^termiriing; tljei jratp 

iiighof^'thdidi^cdnnecrtiiigv'^ 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. 

225.40 Access to Overcurrent Protective Devices. Where 
a feeder overcurrent device is not readily accessible, 
branehTGireuit 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 over- 
current device. 

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 vis- 
ible break contacts and meeting the requirements of 
230.204(B), (C), and (D) shall be installed on the supply side 
of the disconnecting means and all associated equipment. 

Exception: The isolating switch shall not be required 
where the disconnecting means is mounted on removable 
truck panels 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 con- 
ductors and live parts up to 22 kV, nominal, to ground or less 
shall be not less than the values shown in Table 225.60. 

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 


5.6 


18.5 


lots, 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 


5.2 


17.0 


boating 







(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 
be engineered considering the special circumstances and 
shall be approved by the authority having jurisdiction. 

FPN: For additional information, see ANSI C2-2007, Na- 
tional Electrical Safety Code. 

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. 



• 



70-72 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 230 — SERVICES 



230.2 



• 



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 



(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 C2-2007, A^a- 
tional Electrical Safety Code. 



ARTICLE 230 
Services 



230.1 Scope. This article covers service conductors and 
equipment for control and protection of services and their 
installation requirements. 



FPN: See pg]Bjp^n230:lj. 



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 



General Part I 

Overhead Service-Drop Conductors Part II 

Underground Service-Lateral Conductors Part III 

Service-Entrance Conductors Part IV 

Service Equipment— General Part V 

Service Equipment— Disconnecting Means Part VI 

Service Equipment— Overcurrent Protection Part VII 

Services Exceeding 600 Volts, Nominal Part VIII 



Source 



Part II 
230.24 



Overhead 
Last pole 

Service drop 
Clearances 

Service head 



□ 



Service-entrance 
conductors 



Service equipment— general 
Grounding and bonding 

Disconnecting means 
Overcurrent protection 



Underground 
Street main 



Service lateral 

Depth of burial 
and protection 



Terminal box, 
meter, or other 
enclosure 



Part III 
230.49 



Part IV 



Part V 
Article 250 

Part VI 
Part VII 



Branch circuits 
Feeders 



Articles 210, 225 
Articles 215, 225 



■MgujFe-:i2'3().^li Services. 

(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 Mequirements. 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 



2008 Edition NATIONAL ELECTRICAL CODE 



J-73 



230.3 



ARTICLE 230 — SERVICES 



(D) Different Characteristics. Additional services shall 
be permitted for different voltages, frequencies, or phases, 
or for different uses, such as for different rate schedules. 

(E) Identification. Where a building or structure is sup- 
plied by more than one service, or any combination of 
branch circuits, 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 

(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 cle^irance 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 con- 
ductors. 



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 sufficient 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 



• 



70-74 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 230 — SERVICES 



230.31 



maintained 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 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 service 
drop is attached to the side of a building. 

(B) Vertical Clearance ffor;iSeirVft«i-13ropf[;C^ 
Service-drop conductors, 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 electrical service entrance to 
buildings, also at the lowest point of the drip loop of 
the building electrical entrance, and above areas or 
sidewalks 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 

(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 pubhc 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 Insulatloji. 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 di- 
rect 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. 



2008 Edition NATIONAL ELECTRICAL CODE 



-75 



230.32 



ARTICLE 230 — SERVICES 



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 dam- 
age in accordance with 300.5. Service-lateral conductors 
entering a building shall be installed in accordance with 
230.6 or protected 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 wiMmote^t 
shall be permitted to have one set of service-entrance con- 
ductors 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. 

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(5) or 230.82(6). 

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 PartTn;;!"^ 
or:Wof^MtMe;!23XiiM^ Ampacity shall be deter- 
mined 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 smallef 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 metalHc tubing 

(6) Electrical nonmetallic tubing (ENT) 



70-76 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 230 — SERVICES 



• 



(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 betvs/een 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. GdhUiWrdyji 

}^dMm:g ^]^^^v0(Erv0mt^ The ] ilabel^j :sMll 

Tt^qded^itfjtmi^gJi^l^^ }irayl 

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. 

230.50 Protection Against Physical Damage. 

(A) Underground SeryiCjfefEntra Under- 

ground service-entrance conductors shall be protected 
against physical damage in accordance with 300.5. 

(P) AIlFpihe^lSeJFvie^EnlTa^ Af ;:oth^ 

^iM£|;^iir^(S^rfQo^ ^Mti! m&^xpjGm^ 

pSe^trance^^Qiplub^^ shall be protected against physi- 
cal damage as specified in ^|0^50pl)(l?):.Qi|fBp). 

(1) 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 m;Q conduit 



(4) Electrical metallic tubing 

(5) Other approved means 

(|) Otiier Tliae 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 
physical damage or where protected in accordance with 
300.5(D). 

230.51 Mounting Supports. Cables or individual open 
service 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.). 



Cables that are not approved for 
mounting in contact with a building or other structure shall 
be mounted on insulating supports installed at intervals not 
exceeding 4.5 m (15 ft) and in a manner that maintains a 
clearance 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 
bushings 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. 



.53 Racevyays to Drain. Where exposed to the 
weather, raceways enclosing service-entrance conductors 
shall be sui^le^f^i^ispniffl^p^y and arranged to 

drain. Where embedded in masonry, raceways shall be ar- 
ranged to drain. 

230.54 Overhead Service Locations. 

(A) Service Head, Service raceways shall be equipped 
with a service head at the point of connection to service- 
drop conductors. nnie*^ei^iee7h|adl;shai with the 
ropirment 



2008 Edition NATIONAL ELECTRICAL CODE 



70-77 



230.56 



ARTICLE 230 — SERVICES 



Table 230.51(C) Supports 





Maximum Distance 


Minimum Clearance 












Maximum 


Between Supports 


Between Conductors 


From Surface 










Volts 


m ft 


mm in. 


mm 


in. 


600 


2.7 9 


150 6 


50 


2 


600 


4.5 15 


300 12 


50 


2 ■ 


300 


14 41/2 ~ 


75 3 


50 


2 


600* 


14* 41/2* 


65* 2'/2* 


25* 


1* 



*Where not exposed to weather. 

(B) Service Cable Equipped with Service Head or 
Gooseneck. Service cables shall be equipped with a service 
head. pi^VseiryiGe tiead, ^Ktiall^ = tMreguii^eriierit 
f6r^fittuigs;ifl^.314;iw^ 

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. 

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 
Ground. 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. En- 
ergized parts of service equipment shall be enclosed as 
specified in 230.62(A) or guarded as specified in 
230.62(B). 

(A) Enclosed. 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 
installed 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. 



• 



70-78 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 230 — SERVICES 



230.79 



(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 No. 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 dis- 
connects per service grouped in any one location. 

For the purpose of this section, disconnecting means wH 
i^aUed;|af;^attic^:li^ used solely for thd 

follqwing:'|shaU^ 
rrie^: 

(1) Power monitoring equipment 

(2) Surge-protective device(s) 

(3) Control circuit of the ground-fault protection system 

(4) Power-operable 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 identifiea handle ties or a master handle to 
disconnect all conductors of the service with no more than 
six operations of the hand. 

FPN: See 4G8.^^HExc^ron'l^::;3t;;ana;;E^(^ 

for service equipment in Geirtain 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. 

(B) Additional Service Disconnecting Means. The one or 
more additional service disconnecting means for fire 
pumps, emergency systems, legally required standby, or op- 
tional standby services permitted by 230.2 shall be installed 
remote from the one to six service disconnecting 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 elec- 
tric service and electrical maintenance are provided by the 
building management and where these are under continu- 
ous building management supervision, the service discon- 
necting means supplying more than one occupancy shall be 
permitted to be accessible to authorized management per- 
sonnel only. 

230.74 Simultaneous Opening of Poles. Each service dis- 
connect 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 calcpated load to be carried, determined in accordance 
with Patt^inp^i^'vO^ 220, as applicable: In no 



2008 Edition 



NATIONAL ELECTRICAL CODE 



70-79 



230.80 



ARTICLE 230 — SERVICES 



case shall the rating be lower than specified in 230.79(A), 
(B), (C), or (D). 

(A) One-Circuit Installations. 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 
disconnecting means shall have a rating of not less than 30 
amperes. 

(C) One-Family Dwellings. 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 dis- 
connecting 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 in act^ordaiicevwith^ 

and ;bOiided; in ■accordarice^^^ 

(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 in accordance with Part VII and 
bonded ihvacbbrdariGe^- Avith Part -V 'Of^y^tiele; :250; ; A 
rileter -idisoOTrieet ; s be 'capable^ ^of iiitemipt-^ 
ing- :the/ 16acl^:s^ryed; 

(4) Instrument transformers (current and voltage), imped- 
ance shunts, load management devices, surge arresters, 
and;!Iy|)e:I;'sii^ 

(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 Typ^e'^^Vsurg^-, 
pro^etiya- deyieesv where installed as part of listed 
equipment, if suitable overcurrent protection and dis- 
connecting means are provided. 

YII. Service Equipment — Overcurrent Protection 

230.90 Where Required. Each ungrounded service con- 
ductor shall have overload protection. 

(A) Ungrounded Conductor. Such protection shall be 
provided by an overcurrent device in series with each un- 
grounded service conductor that has a rating or setting not 
higher than the allowable ampacity of the conductor. A set 
of fuses shall be considered all the fuses required to protect 
all the ungrounded conductors of a circuit. Single-pole cir- 
cuit breakers, grouped in accordance with 230.71(B), shall 
be considered as one protective device. 

Exception No. 1: For motor- starting currents, ratings that 
comply with 430.52, 430.62, and 430.63 shall be permitted. 

Exception No. 2: Fuses and circuit breakers with a rating 
or setting that complies 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 comply 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 Conductor. 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 



• 



70-80 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 230 — SERVICES 



230.200 



• 



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 ar- 
resters, l^p^jrjlijjsurg^rp^ surge -protective 
capacitors, and instrument transformers (current and volt- 
age) shall be permitted to be connected and installed on the 
supply side of the service disconnecting means as permitted 
by 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 solidly 
grounded wye electric 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 solidly grounded wye system 
shall be connected directly to ground thrau^hia-Jgroiinding 
jel^rc^ssrystern;^^ without inserting 
any resistor or impedance 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: The ground-fault protection provisions of this 
section shall not apply to a service disconnect for a con- 
tinuous industrial process where a nonorderly shutdown 
will introduce additional or increased hazards. 

(A) Setting. The ground-fault protection system shall op- 
erate to cause the service disconnect to open all ungrounded 
conductors 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. 

(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 
coordination. Additional installations of ground-fault pro- 
tective equipment may be needed on feeders and branch 
circuits where maximum continuity of electric service is 
necessary. 

FPN No. 3: Where ground-fault protection is provided for 
the service disconnect and interconnection is made with 
another supply system by a transfer device, means or de- 
vices 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. 



VIIL 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. 



2008 Edition 



NATIONAL ELECTRICAL CODE 



70-81 



230.202 



ARTICLE 230 — SERVICES 



FPN: For clearances of conductors of over 600 volts, 
nominal, see ANSI C2-2007, 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 he 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) Connection jtq: Gi!Oiiiid. Isolating switches shall be 
provided with a means for readily connecting the load side 
conductors toi'l^^igilmmdiTig^^elee^^ 
gr0und::busbar;:{0r;!groun^ when discon- 
nected from the source of supply. 

A means for grounding the load side conductors ,t<3-;a 
grounditig ■: iepGtroiffe; iSpterh i i ;^ 

pr^rouii^dfed^stmtti^^ 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. 

E^:eitKe5r;^<);v^h^ 
tiqiii \ systems i: on' ;piwate:i|Jropeit^^ 



shall be permitted to be locat(ed:ih::a^l(>Gatiph;;th^^^^ 
readily accessible. 

(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 con- 
tribute to the fault-closing rating of the disconnecting 
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. 

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 de- 
vice shall be capable of detecting and interrupting all val- 
ues of current, in excess of its trip setting or melting point, 
that can occur at its location. A fuse rated in continuous am- 
peres 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 conductors, 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 Article 
490, Part II. 

(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. 



# 



70-82 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 240 — OVERCURRENT PROTECTION 



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. 



(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 ofBces, warehouses, garages, 
machine 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. 



ARTICLE 240 
Overcurrent Protection 



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. 



I. General 

240.1 Scope. Parts I through VII of this article provide the 
general requirements for overcurrent protection and over- 
current protective devices not more than 600 volts, nomi- 
nal. Part VIII covers overcurrent protection for those por- 
tions of supervised industrial installations operating at 
voltages of not more than 600 volts, nominal. Part IX cov- 
ers overcurrent protection over 600 volts, nominal. 

FPN: Overcurrent protection for conductors and equipment 
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 re- 
quirements for interrupting radngs and 110.10 for require- 
ments 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 ac- 
tivities, or both, as calculated in accordance with Ar- 
ticle 220. 



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-handling mag- 
net circuit or fire pump circuit. Short-circuit protection 
shall be provided. 

FPN: See NFPA 20-2007, 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. 



2008 Edition NATIONAL ELECTRICAL CODE 



70-83 



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 Class 3 


725 


remote-control, signaling, and 




power-limited circuits 




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 chairlifts 




Emergency systems 


700 


Fire alarm systems 


760 


Fire pumps 


695 


Fixed electric heating equipment for 


427 


pipeUnes 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, lampholders, and lamps 


410 


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 



(D) Small Conductors. Unless specifically permitted in 
240.4(E) or (G), the overcurrent protection shall not exceed 
that required by (D)(1) through (D)(7) iMj^r-afi^^ 
faetors^lor^^inbieht ;t«n^ \ n^fn t>^ -of jeonductors 

hav^ been ^applied. 

(I) l:8;MV(T3Goppejr. 7^^amperes,;;prewi,ded;:2^^ 
ingl'cpnditions^^are^riiet: 



(1) Goiitinuous;:lqads d0:^ri6^ 

(2) Ov&iimjMii^0^ 
Idwir^: 

ai; Branch^eiiruit-rated ^ ;:cireuit;y ^breakei-s ; ■ ;listed:-^K;aM 
inailllid^ipniiS^! ?w 8;l?^Glc^SppCTl w|r^ 

bl RrMiqh^dd^it^at^pis^ 
witli ■ IS ^;(^"G; ep^er -wir& 

e; !ClaLSsiGGi'Oass\J!^^6i^Glasis;T^ 

(2) ;l^A^<J5Cbpper. lp-ainp&es,'^rovided;^ 

jHg.^(:(Omlitioii$;\arfe:r^ 

( 1 ) Gpntiiiuoiis^^i^ 

(2) OS^cMircnt iprotea^ M^|>rovided;;by ; -c»^ ^- 
Ibwing; 

a; Btancjh^cif(?mt:36a^ 

mafl!:ed:-for;\ise;witW'4;6' 
bv Rranchnjircuit^t^ 

witfe' 16; ;^^\^ ;GOppe^^ 
e: ClassXG,^Xi}lass:Jv:^or:Glass;^ir;^ 

(3) 14;^^!G;dGopper. 4:5i;amp§:es 

a5;:amp^s 

(5) :l2;^p;G<)pper. m^am^§ies 

(6) 10;:i^G;iAJuihihum 

25=:-aiT^i^s 

(7) mm^^^mppm. so^ampei^s 

(E) Tap Conductors. Tap conductors shall be permitted 
to be protected against overcurrent in accordance with 
the following: 

(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) Transformer Secondary Conductors. Single-phase 
(other than 2-wire) and multiphase (other than delta-delta, 
3-wire) transformer secondary conductors shall not be con- 
sidered to be protected by the primary overcurrent protec- 
tive device. Conductors supplied by the secondary side of a 
single-phase transformer having a 2-wire (single-voltage) 
secondary, or a three-phase, delta-delta connected trans- 
former having a 3-wire (single-voltage) secondary, shall be 
permitted to be protected by overcurrent protection pro- 
vided on the primary (supply) side of the transformer, pro- 
vided this protection is in accordance with 450.3 and 
does not exceed the value determined by multiplying the 



• 



70-84 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 240 — OVERCURRENT PROTECTION 



240.6 



• 



secondary conductor ampacity by the secondary-to- 
primary transformer voltage ratio. 

(G) Overcurrent Protection for Specific Conductor Ap- 
plications. Overcurrent protection for the specific conduc- 
tors shall be permitted to be provided as referenced in Table 
240.4(G). 

Table 240.4(G) Specific Conductor AppMcatioins 



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 


760.43, 760.45, 


circuit conductors 




760.121, and Chapter 9, 
Tables 12(A) and 12(B) 


Motor-operated 


422, Part II 




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 


725.43, 725.45, 


signaling, and 




725.121, and Chapter 9, 


power-limited 




Tables 11(A) and 11(B) 


circuit conductors 






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 overcur- 
rent in accordance with its ampacity as specified in Table 
402.5. Supplementary overcurrent protection, as covered 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)(3), or (B)(4). ||xtuiieHwireN|haU^ 



t€:cte4^?fwheie:suppM^ 

(1) Supply Cord of Listed Appliance or Luminaire. 
Where flexible cord or tinsel cord is approved for and used 
with a specific listed appliance or lUminaire, it shall be 
considered to be protected when applied within the appUance 
or liiiTiinaire listing requirements. For^pe purposes sec- 
tion ; ^ a; lumnamfe- ;^ 

(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 hsted ex- 
tension cord sets shall be considered to be protected when 
applied within the extension cord fisting 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. 

(C) Restricted Access Adjustable-Trip Circuit Break- 
ers. A circuit breaker(s) that has restricted access to the 
adjusting means shall be permitted to have an ampere rat- 
ing(s) that is equal to the adjusted current setting (long-time 
pickup setting). Restricted access shall be defined as lo- 
cated behind one of the following: 



2008 Edition 



NATIONAL ELECTRICAL CODE 



70-85 



240.8 



ARTICLE 240 — OVERCURl^NT PROTECTION 



(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 over- 
current due to short circuits or ground faults, but the use of 
such devices shall be permitted to protect motor branch- 
circuit conductors from overload if protected in accordance 
with 430.40. 

240.10 Supplementary Overcurrent Protection. Where 
supplementary overcurrent protection is used for lumi- 
naires, appliances, and other equipment or for internal cir- 
cuits 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 or- 
derly shutdown is required to minimize the hazard(s) to 
personnel and equipment, a system of coordination based 
on the following 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 shut- 
down, 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 



240.15 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 mi,mB)(l), (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 protec- 
tion for each ungrounded conductor for hne-to-line con- 
nected loads for single-phase circuits or 3 -wire, direct- 
current circuits. 

(3) 3-Phase and 2-Phase Systems. For Hne-to-line loads 
in 4-wire, 3-phase systems or 5-wire, 2-phase systems hav- 
ing a grounded neutral point and no conductor operating at 
a voltage greater than permitted in 210.6, individual single- 
pole circuit breakers with identified handle ties shall be 
permitted as the protection for each ungrounded conductor. 

(C) Closed-Loop Power 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 (H). (ndndiicl 
toirs supplied under the provisions of 240.21(A) through (H) 
shall riot supply another conductor except through an overcur- 
rent protective device meeting the requirements of 240.4. 

(A) Branch-Circuit Conductors. Branch-circuit tap con- 
ductors meeting the requirements specified in 210.19 shall 
be permitted to have overcurrent protection as specified in 

(B) Feeder Taps. Conductors shall be permitted to be 
tapped, without overcurrent protection at the tap, to a feeder as 



70-86 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 240 — OVERCURRENT PROTECTION 



240.21 



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 panel- 
boards, see ?^0,8;3;6. 

(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 limit the load to the ampac- 
ity of the tap conductors. This device shall be permitted 
to supply any number of additional overcurrent 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 con- 
ductors supply a transformer and comply with all the fol- 
lowing 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 
ceilings. 

(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: 

(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. 



2008 Edition NATIONAL ELECTRICAL CODE 



70-87 



240.21 



ARTICLE 240 — OVERCURRENT PROTECTION 



(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. ■^rS&tyOf:--&^, 

||g||||j|i||||||i|j||||p||i|i|||)^ 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 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. 

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 complies 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 

(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. 



(4) f^rv fields iiStajUalixjiis^-v^ 

leaye^^h&'enelosureudr^-vault;^ 

iiection^isAittade:^ : 0e|^ra^ ; (^^the = jSvCTct^ 

prdteetirigjthd priiria^ 

tiie!,ppnm^r}^Uito: ; ^iecoiida^ 

shall^not ■ exteed;ll;0 = tin^ 

aryi^ohdiictoft 

FPN: For overcurrent protection requirements for panel- 
boards, see 408 .:36. 

(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 ) (SpifviitiorisVGf ^m^ 
pnly--;qualifi^ed;persoiis'serwce;^ 

(2) 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. 

(3) All overcurrent devices are grouped. 

(4) 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. 

(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: 



70-88 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 240 — OVERCURRENT PROTECTION 



240.24 



• 



• 



(1) The secondary conductors shall have an ampacity that 
is not less than the value of the primary-to-secondary 
voltage ratio multiplied by one-third of the rating of the 
overcurrent device protecting the primary of the trans- 
former. 

(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 conductors shall be per- 
mitted to be protected by overcurrent devices in accordance 
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. 

(H) B^rt^yfC^iiducAors. Oyere^in^Jtt 

j)igmitted^to;fe^ii^^ 

ag0l|^#r)^ite]iMna^ 

fion|s|Ml^MsO;be;|^ernu 

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 follow- 
ing applies: 

(1) For busways, as provided in 368.17(C). 

(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, uiiless-othe^^ permitted in 240.24(B)(1) 

arKi;^^(2).: 

(l) Service ;;aiid?;^ede# Overcurrent Devices. Where 
electric service and electrical maintenance are provided by 
the building management and where these are under continu- 
ous building management supervision, the service overcurrent 
devices and feeder overcurrent devices supplying more than 
one occupancy shall be permitted to be accessible only to 
authorized management personnel in the following: 

(1) Multiple-occupancy buildings 

(2) Guest rooms or guest suites 

(2) BtancftHCircui|;0 Where electric 

service and electrical maintenance are provided by the 
building management and where these are under continu- 
ous building management supervision, the branch-circuit 
overcurrent devices supplying any guest rooms or guest 
suites \yithbiit;;perteahe^^ shall be 

permitted to be accessible only to authorized management 
personnel. 

(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 dwelhng 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. 

(F) ;Not:LoGated";Oyer Steps. Overcurrent devices shall not 

be^loeated/^oyerTsteips;!©^^ 



2008 Edition 



NATIONAL ELECTRICAL CODE 



70-89 



240.30 



ARTICLE 240 — OVERCURRENT PROTECTION 



III. 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 

(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. 

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. Cartridge fuses 
in circuits of any voltage where accessible to other than 
qualified persons, and all fuses in circuits over 150 volts to 
ground, shall be provided with a disconnecting means on 
their supply side 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 point 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 
adapters 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. 



70-90 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 240 — OVERCURRENT PROTECTION 



240.85 



240.54 Type S Fuses, Adapters, and Feseliolders. 

(A) To Fit Edison-Base FusehoSders. 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. 

(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 Fuscss and Fuseholders 
240.60 General. 

(A) Maximum Voll;age — 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) Nonintercliangeable — 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 v^'hich 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 be permitted to be used only for replace- 
ment in existing installations where there is no evidence of 
overfusing or tampering. 



240.61 Classification. Cartridge fuses and fuseholders 
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 
currents 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 



2008 Edition NATIOI^JAL ELECTRICAL CODE 



)-91 



240.86 



ARTICLE 240 — OVERCURllENT PROTECTION 



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(|)-3([) to indicate such 
suitability. 

A circuit breaker with a slash rating, such as I20/240V 
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 
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, particu- 
larly on comer grounded delta systems, considers the cir- 
cuit 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. 

For I icalciflated ; tappficatipp's;^ ;;iJb!e^ 1 :e;iigineieii'; :shall j^ens^ 
thkt:;thei^Q>ra5trfeainydr^ 
series G^^ 
period^^b'f ^heUine^-^ide ;^lly i raf |d^;CUCTent 

(B) 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. 

EPN;tip::(;A)i;and;(B):. See :l;lpj^2:^r=maiMtig :of jsOTM^oprnhi- 
natipiniisystems: 

(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 shall 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 (E). 

(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(p), (C), (D), or (E). 

(R) I'^cii-frap^. FGr;fee^lt^s;i^f>eeifi^lm;|^^ 

|EtK35)I':anC|B)^);;vthetti^ 

stizeidM : a^oixismc^ 

(C) Transformer Secondary Conductors of Separately 
Derived Systems. Conductors shall be permitted to be con- 
nected to a transformer secondary of a separately derived 
system, without overcurrent protection at the connection, 
where the conditions of 240.92(C)(1), (C)(2), and (C)(3) 
are met. 

(1) Short-Circuit and Ground-Fault Protection. The 

conductors shall be protected from short-circuit and 
ground-fault conditions by complying with one of the fol- 
lowing 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 ex- 
ceed 150 percent of the value determined by 
multiplying the secondary conductor ampacity by the 
secondary-to-primary transformer voltage ratio. 

(2) The conductors are protected by a difl^crential relay 
with a trip setting equal to or less than the conductor 
ampacity. 

FPN: A differential 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 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. 



70-92 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 240 — OVERCURRENT PROTECTION 



240. 



• 



Table 240.92(B) Tap Conductor Short-Circuit Current 
Ratings. 

Tap conductors are considered to be protected under 
short-circuit conditions when their short-circuit temperature 
limit is not exceeded. Conductor heating under short-circuit 
conditions is determined by (1) or (2): 

(1) Short-Circuit Formula for Copper Conductors 

(lVA^)t = 0.0297 logio [(7^2 + 234)(ri + 234)] 

(2) Short-Circuit Formula for Aluminum Conductors 

il2/A2)t = 0.0125 log,o [(7^2 + 228)/(ri + 228)] 
where: 

/ = short-circuit current in amperes 

A = conductor area in circular mils 

t = time of short circuit in seconds (for times less than or equal 
to 10 seconds) 

T] = initial conductor temperature in degrees Celsius. 

T2 = final conductor temperature in degrees Celsius. 

Copper conductor with paper, rubber, varnished cloth insulation, 
T2 = 200 

Copper conductor with thermoplastic insulation, T2= 150 

Copper conductor with cross-linked polyethylene insulation, T2 
= 250 

Copper conductor with ethylene propylene rubber insulation, T2 
= 250 

Aluminum conductor with paper, rubber, varnished cloth 
insulation, T2 = 200 

Aluminum conductor with thermoplastic insulation, T2 = 150 

Aluminum conductor with cross-linked polyethylene insulation, 
T2 = 250 

Aluminum conductor with ethylene propylene rubber insulation, 
T2 = 250 

(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 hmit the load to the conductor ampacity. 

(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) Overcurrent relaying is connected [with a current trans- 
former(s), if needed] to sense all of the secondary con- 
ductor current and Hmit 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. 

(3) Physical Protection. The secondary conductors are 
protected from physical damage by being enclosed in an 
approved raceway or by other approved means. 

(D) 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 

(E) Protection by Primary Overcerreet 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, multiplied by the maximum effective primary-to- 
secondary transformer voltage ratio, effectively protects the 
secondary conductors. 

IX. Overcurrent Protecition 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 



2008 Edition NATIONAL ELECTRICAL CODE 



J-93 



240.101 



ARTICLE 250 — GROUNDING AND BONDING 



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. Cir- 
cuit 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 cir- 
cuit, shall be permitted to replace the residual relay element 
and one of the phase-conductor current transformers. 
Where the neutral cqiidiieitOT is not regrounded on the load 
side of the circuit as permitted in 250.184(B), the current 
transformer shall be permitted to link all 3-phase conduc- 
tors 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. 

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 de- 
vice where that overcurrent device also protects the tap 
conductor. 



ARTICLE 250 
Grounding and Bonding 



I. General 



250.1 Scope. This article covers general requirements for 
grounding and bonding of electrical installations, and the 
specific 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 

FPNii; See Figuren250:l; for information on the organiza- 
tion of Article 250 cpv^rmg Hgixmn^gllM^H 
requireinents^- 



Part I General 



Part II System 
grounding 



Part VIII 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 Equipment 

grounding and equipment 

grounding conductors 




• 



Part V Bonding 



Part VII Methods of 
equipment grounding 



Part IX Instruments, 
meters, and relays 



Figiirie 25Q;1 Grounding and Bonding. 



• 



70-94 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 250 — GROUNDING AND BONDING 



250.2 Definitions. 



• 



• 



Ponding.; Jumper, Sj^stem;' The connection between the 
grounded circuit conductor and the equipment grounding 
conductor at a separately derived system. 

Efifective Ground-Fault Current Path. An intentionally 
constructed, low-impedance electrically conductive 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 facilitates 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 electri- 
cal circuit and the normally non-current-carrying conduc- 
tors, metallic enclosures, metallic raceways, metallic equip- 
ment, 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 consist 
of any combination of equipment grounding conductors, 
metallic raceways, metallic cable sheaths, electrical equip- 
ment, and any other electrically conductive material such as 
metal water and gas piping, steel framing members, stucco 
mesh, metal ducting, reinforcing steel, shields of commu- 
nications cables, and the earth itself. 

250.3 Application of Other Articles. For other articles 
applying to particular cases of installation of conductors 
and equipment, groutidingpriif'^bohding requirements are 
identified in Table 250.3 that are in addition to, or modifi- 
cations of, those of this article. 

250.4 General Requirements for Grounding and Bond- 
ing. 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 re- 
quirements 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. 

FPN:h Aniinpprtanrc6nsideration:fof limiting the irhgised 

yoltagq is; the :ipuUn^ of bonding; a^rid^round 

so that they 'are hot! any longer than necessary to coifiplete 

the connection, w disturbing the. permanent parts; of 

the inst'aiiatipri arid ^so; that ^unnecessary :bericls and loops, arb 

avoided.' 



(2) Grounding of Electrical Equipment. Normally non- 
current-carrying conductive materials enclosing electrical 
conductors or equipment, or forming part of such equip- 
ment, shall be connected to earth so as to hmit the voltage 
to ground on these materials. 

(3) Bonding of Electrical Equipmemt. Normally non- 
current-carrying conductive materials enclosing electrical 
conductors or equipment, or forming part of such equip- 
ment, shall be connected together and to the electrical sup- 
ply source in a manner that establishes an effective ground- 
fault current path. 

(4) Bonding off Electrically Conductive Materials and 
Other Equipment. Normally non-current-carrying elec- 
trically conductive materials that are likely to become 
energized shall be connected together and to the electri- 
cal supply source in a manner that establishes an effec- 
tive 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 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. 

(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 materials. 

(2) Bonding of Electrical Equipment. Non-current- 
carrying conductive materials enclosing electrical conduc- 
tors or equipment, or forming part of such equipment, shall 
be connected together and to the supply system grounded 
equipment in a manner that creates a 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 low-impedance path for ground-fault current 
that is capable of carrying the maximum fault current likely 
to be imposed on it. 



2008 Edition 



NATIONAL ELECTRICAL CODE 



70-95 



250.4 



ARTICLE 250 — GROUNDING AND BONDING 



Table 250.3 Additional Grounding arid|B6jn(ling 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 chairlifts 
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 and fighting equipment 
Luminaires, 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 
Natural- land^ditifici^^ 
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 



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 



427.29, 427.48 

426.27 

400.22, 400.23 

553.8, 553.10, 553.11 

406.9 



# 



500-517 
517 
665 
670 



410 
550 



430 
682 



• 



650 
810 

551 
230 

680 



200 
660 



645.15 

504.50 

410.40, 410.42, 410.46, 410.155(B) 

555.15 

530.20, 530.64(B) 

mim:-6smmm^32i^6S23s 

"""■■"'*""" "'S 14.4,' 3 14.25~'"^~"*" 
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 



70-96 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 250 — GROUNDING AND BONDING 



150.2& 



• 



(4) Patli for Fault Cerrerat. Electrical equipment, wiring, 
and other electrically conductive material likely to become 
energized shall be installed in a manner that creates a low- 
impedance circuit from any point on the wiring system to 
the electrical supply source to facilitate the operation of 
overcurrent devices should a second grofniid fault from a 
differentl'phase occur on the wiring system. The earth shall 
not be considered as an effective fault-current path. 



250.8 Coimectlon of Groundneg and Bonding 



(A) Arrangement to Prevent Objectionable Current. 
The grounding of electrical systems, circuit conductors, 
surge arresters, sti^^nJ^OJ^Sti^^-Jd^^iG^^ and conductive 
i|iOiTOall^ non-current-carrying metMn:|]!^S;|jof equipment 
shall be installed and arranged in a manner that will prevent 
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 ippsin)g;tie^|pye^^ 

(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 faults, shall not be classified 
as objectionable current for the purposes specified in 
250.6(A) and (B). 



rmisslble 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 '0bMecte^d:rto:ran;*e^ 
grpMdiiigHiGG^^ as required by this article. Currents 

that introduce noise or data errors in electronic equipment 
shall not be considered the objectionable currents addressed 
in this section. 

(E) Isolation of Objectionable Direct-Cerrent Gromind 
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 Gonduetc>E path to provide an effec- 
tive return path for ac ground-fault current while blocking 
dc current. 



(M) PeFi|utted;M^tWods, ©rounding- coridMctc^ 
ing; jumpers!^ sliyi'fl^^ 

(1) Iiisted;pr^sMr&=ec^ 

(2) TIptmiBal^l^s 

(3) K6^Ui^liconne^tG^Sv;lis^^ bonding 
equipment 

(4) isQtheiiriic^M^lcffig^'l^^ 

(5) ^stehiiie: sbrfewHypeifaSterieS^^^^ than 
iwo;|hi^ds^p: : af e ^saS^ 

(6) Opflr^^ciffpriiM^jin^ les^ 

thanijt\A^?|Srea^ 

(7) C0nftepi<)ri^jth^t^ 

(8) M^^^StddMi^ 

(K) B|et!iW§p:Qtt*]Ppmi|t(Ei. GpniiectiiOTiyeyices or fit- 



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 coatings (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. 



II. System GroBindIng 

250.20 Alternating-Cnrrent Systems to Be Grounded. 
Alternating-current systems shall be grounded as provided 
for in 250.20(A), (B), (C), (Mrx3^I;(E|. Other systems shall 
be permitted 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 SO 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 



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70-97 



250.21 



ARTICLE 250 — GROUNDING AND BONDING 



(2) Where supplied by transformers, if the transformer sup- 
ply system is ungrounded 

(3) Where installed outside as overhead conductors 

(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 eohduttpr 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(A). Wligre; an;Mternate;:so^ 

ajri : 'oiifsite) ;geiiqratpi^ '^li ; ^ovi^ed -jwith: itranSfet; ieqUip^ 
that;infeludes;:aJ^rounded ;epn^tMpnthai^ps^hbt; sOlicIly; inter-j 
Connected ?t0 ;the^ service;-supphed; ground^: :t^ '. jlie 

alternated source ;(den\^d;;systeiTi) iyiallbe^gj^ aci 

FPN No. 1: An alternate ac power source such as an on- 
site generator is not a separately derived system if the 
grounded ^conductor is solidly interconnected to a service- 
supplied system grounde^idonduGtoi\;An;e^ 
situatioh's ;is: ^hei-e; alternate source; transter^equiprnent ;dQes 
notiincliade; a: switching actipii: .irijjthe: grounded; conductor 
and : iailow s ■ it! to ; remain; . splidlyj iconiieGted ; to; ?the ] serv ice^ 
supplied ;grOunided ; conductor^ when ; the; alternate; -SQurce is 
pperati cinal jaiid su pp^^^^ 

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. 

(H) g|i||i|. The following ac systems of 50 volts to 1000 
volts shall be permitted to be grounded but shall not be 
required to be grounded: 
(1) Electrical 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 in- 
stallation. 

c. Continuity of control power is required. 

(4) Other systems that are not required to be grounded in 
accordance with the requirements of 250.20(B) 

(B) GrQuip^d|#etec1;di;S. IJngrpiitidejdp^iltef^^ 
systeiTi^lasupeiMtled m 250.2 1 (A)p|; through; (Ai^4);^|»er^ 
atiir^TM; Mt ; ^ess-; "thaB;^ 1 20 : :w^ 
yplts ^sWali: have; jgrPuiid; Jdetectors; installed; on- Ihei ;sy sterril 

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) 

(5) Seooft^ary; ciimiits of ligM 
68()|3(fe(2); 

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 grouiiding electrPde^'eon connec- 
tion shall be made at any accessible point from the load end 
of the service drop or service lateral to and including the 
terminal or bus tP which the grounded service conductor is 
connected at the service disconnecting 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. 



• 



70-98 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 250 — GROUNDING AND BONDING 



250.24 



• 



Exception: The additional grounding elisbiwdeMoj^dudtof 
connection shall not be made on high-impedance grounded 
neutral systems. The system shall meet the requirements of 
250.36. 

(3) Duall-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 coHdUctOT connection to the tie 
point of the grounded conductor(s) from each power source 
shall be permitted. 

(4) Male 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=Slde Grounding Connections. A gfouSded- coS 
(du^Qii^^allimMi^^^cQ^ 

fcaiT5^in^;ih£itHl:^ ^f ietpipmeiit;^ pc^ ©quip fgrounding 
^iidu|it^p;s)l|Q|;l^;ifC(^^ on the load side 

of the service disconnecting means except as otherwise per- 
mitted 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. 



Jumper. For a grounded system, an 
unspliced 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 Equip- 
ment. 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 

&c^iipl;te^jtq^ ^eachf discoM&Gtmgi ^i^i^shs; ^:ncni^@edrfiqndB^ 
toii(s)ienffinpS]3bu^ ^pifflecft 

iie-^gf0iinded;}ty^ 

fheaiiis enclosure. The grounded conductor(s) shall be in- 
stalled in accordance with 250.24(C)(1) through (C)(3). 



Exception: Where more than one service disconnecting 
means are located in 'di^ir(gj.e assembly listed for use as 
service equipment, it shall be permitted to run the grounded 
conductor(s) to the assembly cpmmon gtourided conduc- 

tpri^s^A^efminqV^ ;^M5: t^e;|^^em^^:5:/?a//:;mc/w<ie a main 
bimdmg^T^^ c&imic conductor(s) 

to the assembly enclosure. 

(1) Mooting 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 kc- 
mil copper or 1750 kcmil aluminum, the grounded conduc- 
tor shall not be smaller than 12V2 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 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 service-entrance conductor in the raceway but not 
smaUer 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. Thi^; coiidiictor-^haUiM 

\vith;;250;66v " "~ 

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. 



2008 Edition 



NATIONAL ELECTRICAL CODE 



70-99 



250.26 



ARTICLE 250 — GROUNDING AND BONDING 



250.26 Conductor to Be Grounded — Alternating-Current 
Systems. For ac premises wiring systems, the conductor 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 other corrosion-resistant ma- 
terial. 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 cbniieGted in the manner specified by 
the applicable provisions of 250.8. 

(D) Size. MajSH^Pon^^ 
jiiMpfiii--:|h£^ 
thfepfiijDjal' 

(1) General. Main bonding jumpers and system bonding 
jumpers shall not be smaller than the sizes shown in 
Table 250.66. Where the supply conductors are larger 
than 1100 kcmil copper 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 conductors 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 
equivalent to that of the installed phase conductors. 

(2) Maiiii^jQiiding^ JlujjnpeM^ §lieryieei witli' More 
On^'Enclpsure. WKereM: $^ipe;icomist^ ;of :mtire:;ffiaii;;a 
smglfe:Jeii(dxDsu^^ 

ing jtitfip^l Kff[:eMti;-;eiiclosure:^lM M^; j^iz^ lS,a<ic^G^daE^ 

;^?ifh/250J8(©^(l^)lba^ 

coiiduetpr ; ^yiiig:^hat jeiicloSure; 

(3) Sep^rat^ivPeny'^ft 

EnClf^ure. 5®^Sm;S;isfepSffatel3^ivde^^ 



mor^-; iihaii^ -a i^npe; eiiuslosure; ■ ^the^/sj^tbmJ^bo^diri^ 

fJOT V ;J^^h^ ; en^losufe^ ; ;s^ 

25P;^8(I55(;1) ;basedj;on-^^ 

diictxDf H^erying : &ai i&m % =saiigle^?system 

jiimli^iishail ; be; iristaUed: :at i tiie ^ ?spiirCeJ 'anif '^ 

iiaii§|ji^ith^250;28^ 

laiies|;SUjpply];C^4^^ 

ffi^jarfeaSibf ;the.^ Cpn:esppiiding;ic»Mui^^ 

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). p^e^ptuM^!.Qthemise^;p^^ 
gi^iidSdr;t6HduGto;r;:S^ 

mfep;g:rt)]U&(Mg:C<^ l^ejreepnnectedjM 

the^i load ; ;side :;of ; ;thej i ppiiit;; of ngEoundiiig ; ^of i^Kseparatelj^ 
denyed^sySenir 

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. 

Exception No. 3: The size of the system bonding jumper for 
a system that supplies a Class 1, Class 2, or Class 3 



• 



• 



70-100 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 250 — GROUNDING AND BONDING 



25©.30 



• 



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) Eqelpmeet Bondleg Jumper Size. Where aiit'eiq.uipj 
ment bonding jumper of the wire type is run with the de- 
rived phase conductors from the source of a separately de- 
rived system to the first disconnecting means, it shall be 
sized in accordance 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 e^jiinectef i 

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 gwmidMg bus internal to the equipment is 
not smaller than the required grounding electrode conduc- 
tor for the separately derived system, the grounding elec- 
trode connection for the separately derived system shall be 
permitted 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). pis "con-; 
hjBbjfipn'M^lt'Mima^ 'the ' separately; 

deiiyedpsySt^in^\^i^^ .jumper ' "is " in^ 

staled;- 

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 sys- 
tem 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. 

(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 {Va in. x 2 in.). Where alu- 
minum busbars are used, the installation shall comply 
with 250.64(A). 

(3) 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. 



2008 Edition NATIONAL ELECTRICAL CODE 



)-101 



250.32 



ARTICLE 250 — GROUNDING AND BONDING 



(5) Installation. The installation of all grounding electrode 
conductors shall comply with 250.64(A), (B), (C), and (E). 

(6) Bonding. Structural steel and metal piping shall be 

coniiectedj;tO; jthe j ^poiinded: ^conductor • ©f ; k ■separately' I dfeH 
Ktvedlsystem 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 sys- 
tem. 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 connection; is not 
located at the source of the separately derived system, 
250.30(A)(8)(a), (A)(8)(b), and (A)(8)(c) shall 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 12V2 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 
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 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 un- 
grounded 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 
ghall 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 a 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 Part; III: ^ofiiAitiGleJSSQi^ The grounding 
electrode conductor(s) shall be connected in accordance 
with 250.32(B) or (C). Where. there is no existing ground- 
ing 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, includingJM^^ 
^mrichlcircmt^ supplies the building or structure and the 
branch circuit includes an equipment grounding conductor 
for grounding the normally non— current-carrying metal 
parts of equipment. 

(B) Grounded Systems. For a grounded system at the 
separate building or structure, ah equipment grounding con- 
ductor as described in 250.118 shall be run with the supply 
conductors and jbe connected to the building or structure 
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 with 250.122. 
Any installed grounded conductor shall not bq connected 
to the equipment grounding conductor or to the ground- 
ing electrode(s). 

Exception: E&r:^existing ■pr^m^ieSy^^^ the 

grounded ciMdMft&t run ; with ; the ■ supply' W/fhW-Buirding^vr 
stmciureishdU: be. pefmiited to; Ueicdniiected^ to W^ibuildiwg 
OT:} istrmtm^^-iidisc^^ jafidiltp\l}thMgrpm 

el0i^trQde(s^dnd:sHalh lye'mMfqrigm d^f^ofidw^of 



• 



70-102 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 250 — GROUNDING AND BONDING 



(1) An equipment grounding conductor is not run with the 
supply to the building or structure. 

(2) There are no continuous metallic paths bonded to the 
grounding system in each building or structure involved. 

(3) Ground-fault protection of equipment has not been in- 
stalled on the supply side of the feeder(s). 

Wfiemlthel jgmimd£^il(imd^ -M^MsMliM. f^&jMtfMwMfi 
M^0fc^nce-{!y^^ 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) Umgroended Systems. The grounding electrode(s) 
shall be connected to the building or structure disconnect- 
ing means. 



• 



or Strectere oe 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 No. 1 and No. 2, UM^M^I^., 
[^f l|fa)^^^|jdij/i^()2;ai;^ all of the following conditions 
shall be met: 

(1) The connection of the grounded conductor to the 
grounding electrode, tiQ:jfipMiH]|y 10 

metal^ilpM; of ifequipmeiit ; : oif f to : tM^ei^iiipmettf ^ g|Mfld| 
ingjGQjiductor at a separate building or structure shall 
not be made. 

(2) An equipment grounding conductor for grounding and 
bondmg any normally non-current-carrying metal parts 
;e^f equipment, interior metal piping systems, and build- 
ing or structural metal frames is run with the circuit 
conductors to a separate building or structure and ccpl 
ne.dtgd 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) p3hSvoonneetmnl6et>^^ the equipment grounding con- 
ductor anjii the grounding electrode at a separate build- 
ing or structure shall be made in a junction box, panel- 
board, 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 Fart III of this article. 

250.34 Portable and Vehkle-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 nomjaUy non-current-carrying metal parts of equip- 
ment and the equipment grounding conductor terminals of 
the receptacles are cofiiiee'ted 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 ni6nnffly non-current-carrying metal parts of 
equipment and the equipment grounding conductor ter- 
minals of the receptacles are connected to the generator 
frame. 

(C) Grounded Conductor Bonding. A system conductor 
that is required to be grounded by 250.26 shall be ton- 
ijMt^M to the generator frame where the generator is a com- 
ponent of a separately derived system. 

FPN: For grounding portable generators supplying fixed 
wiring systems, see 250.20(D). 

250i35 EeniiMflitll'pffisSlle^ A" (conductor 

tiwdt^prtr^i^S^an e|^^ shall be 

ii^tAUedjfWJlte-the'^u 

imtalledi^^inSatc^ in 

^c^c^ande0^^i|la^](^^ 

(A) Separa|«l3l'P^ree^;^y$f!em p^er^-'the-'gi^erator is 
iiisf|ll0d'-s^^a?^eparal^y the ..requirements in 

ppiBoihaiiTiipji"'" " ' " "' ' " ' 

(B) Mons^araleljI'Mei^^ Wh^feTthe generator 

|sjipHii$talled<;as^ ;.a;sep^ately;^'derfved' ^systerh,' an equip- 
|pf|iit|MiM^rig^|ja^^ genera- 

toEy;^quipm|i)|gg^^ -'{md- the equipment 



2008 Edition NATIONAL ELECTRICAL CODE 



70-103 



250.36 



ARTICLE 250 — GROUNDING AND BONDING 



equipment; t)0a^ pn the suppl^^sMe: of; each; gen-^ 

emtOT: pViei^urreiit; dpiee ^ shall; ;1je: isiz&dm ajccordme^i^>^\^ 
250ilG2(G): based; ;on the isize of the; conductors s^ ;by 
the;^riera:tor; 

(2) Eo^^;^iae;;pf^Geiieratpri0^ The 

equipraenti grounding; ;C ;on ■ theH load- side of ;?each 

geii^^f^^0S0m ^d^yice ; ^hap; ;b^; si^zed; ^iit ; accordance 

\vithp25C)J|Q2(]])); ; l^iased 
device isuppheii 

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 quahfied persons service the installation. 

(2) Ground detectors are installed on the system. 

(3) 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 point. Where a neutral 
poiht is not available, the grounding impedance shall be 
installed between the grounding electrode conductor and 
the neutral point derived from a grounding transformer. 

(B) i|rt)uhd^; System Conductor. The grbundi^j^j/sterii 
conductor from the neutral point of the transformer or gen- 
erator to its connection point to the grounding impedance 
shall be fully insulated. 

The grdunded ^system conductor shall have an ampacity 
of not less than the maximum current rating of the ground- 
ing impedance. In no case shall the grounded;: syste^ con- 
ductor be smaller than 8 AWG copper or 6 AWG aluminum 
or copper-clad aluminum. 

(C) System .Grounding Connection. The system 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 Pd5nt-;to.Grouridm^^ Conductor 
Routing. The conductor connecting the neutral point of the 
transformer or generator to the grounding impedance shall 
be permitted to be installed in a separate raceway fi:pmjthB 
uhgrouhded-Cond^^^ It shall not be required to run this 
conductor with the phase conductors to the first system 
disconnecting 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 Connected 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)(fl^ 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)(8) shall be installed and used. 

Exception: Concrete-encased electrodes of existing buildings 
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 



• 



70-104 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 250 — GROUNDING AND BOND^G 



• 



• 



(10 ft) or more (including any metal well casing bonded to 
the pipe) and electrically continuous (or made electrically 
continuous by bonding around insulating joints or insulat- 
ing pipe) to the points of connection of the grounding elec- 
trode 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 conductor to interconnect 
electrodes that are part of the grounding electrode system. 

Exception: In industrial, commercial, and 'institMipnM 
buildings or structures where conditions of maintenance 
and supervision ensure that only qualified persons service 
the installation, 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 perpendicu- 
larly 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 Structmre. The metal 
frame of the building or structure tliM;is;|G|onn^ctpd^ 
eaMK;b}^^any Jof Ihe ^follJQ^^yir^jmetMd^ 

(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) jEkliiM&ipiig the structural metal frame tgijftieijeiiifw^in^ 
^^s;:JjG]^:!a;^;coinicFet6rienc^^ 
250;52|i^)(;3^^or;gFou^^ 

(3) BSndri^etlieOstmctoa^ 
^hfej^puiiding^Mectra to f 25(p!2(;jA^(5J){XM 

(4) Other approved means of establishing a connection to 
earth 

(3) Concrete-Eiracased Electrode. An electrode encased 
by at least 50 mm (2 in.) of concrete, located horizoiitally 
near the bottom or;yertix:Mj^;:apl;wit^ 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 
{V2 in.) in diameter, or consisting of at least 6.0 m (20 ft) of 
bare copper conductor not smaller than 4 AWG. Reinforc- 
ing bars shall be permitted to be bonded together by the 
usual steel tie wires or other effective means. WHerepfniil;- 
ti|?lgj -COiier^te^epi^sed^ ;|^ese!iit j at \ a^j&ipdmg 

ttte^groiini^ 

(4) GrouMd Rimg, 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 ElectrodeSo Rod and pipe electrodes 
shall not be less than i2.'44 m (8 ft) in length and shall 
consist of the following materials. 

(a) Grourtditigiel^tJxM of pipe or conduit shall not 
be smaller than metric designator 21 (trade size Va) and, 
where of steel, shall have the outer surface galvanized or 
otherwise metal-coated for corrosion protection. 

(b) GrpuMing^etrodes ipf stainless :steel and copper 
dfi^zinc5;cQat«l steel shall be at least 15.87 mm (% in.) in 
diameter, unless listed and not less than p-2:7D mm {Vi in.) 
in diameter. 

(S) 0iSieEi;pste«|jp(s^tirod<^. <Me|;Wsted:poundihg'elec- 

t|wj|^;^!iajl!ibe:permitted 

(7) 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 ('/4 in.) 
in thickness. Electrodes of nonferrous metal shall be at least 
1.5 mm (0.06 in.) in thickness. 

(§) Other Local Metal Underground Systems or Strac- 
teres. Other local metal underground systems or structures 
such as piping systems, underground tanks, and under- 
ground metal well casings that are not bonded to a metal 
water pipe. 

(B) Not Permitted for ils:e:^!as Groending Electrodes. 
The following systeriSlindrmaten shall not be used as 
grounding electrodes: 

(1) Metal underground gas piping system| 

(2) Aluminum 

FPN: See 250.104(B) for bonding requirements of gas 
piping. 



FPN: See 547.9 and 547.10 for special grounding and 
bonding requirements for agricultural buildings. 

(A) Mod, Pipe, and Plate Electrodes. Where practicable, 
rod, pipe, and plate electrodes shall be embedded below 
permanent 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)(7) 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 bonded 
together shall be considered a single grounding electrode 
system. 



2008 Edition NATIONAL ELECTRICAL CODE 



)-105 



250.54 



ARTICLE 250 — GROUNDING AND BONDING 



(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)(8). 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 conduc- 
tor, 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 
electrode, that portion of the bonding jumper that is the sole 
connection 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 
2.44 m (8 ft) except that, where rock bottom is encoun- 
tered, the electrode shall be driven at an obUque angle not 
to exceed 45 degrees from the vertical or, where rock bot- 
tom is encountered at an angle up to 45 degrees, the elec- 
trode 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 above- 
ground end and the grounding electrode conductor attach- 
ment 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 Auxiliary Grounding Electrodes. Oh^i-Qhiimore 
grounding electrodes shall be permitted to be connected to 
the equipment grounding conductors specified in 250.118 
and shall not be required to comply with the electrode 
bonding requirements of 250.50 or 250.53(C) or the resis- 
tance 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)(4) through (A)(;8):. 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 bonded to- 
gether 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 equipment. This provision shall not prohibit the re- 
quired bonding together of grounding electrodes of differ- 
ent systems. 

FPN No. 1: See 250.106 for spacing from air terminals. 
See 800.100(D), 810.2I(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, alumi- 
num, or copper-clad aluminum. The material selected shall 
be resistant to any corrosive condition existing at the instal- 
lation or shall be suitably protected against corrosion. The 
conductor shall be solid or stranded, insulated, covered, or 
bare. 



• 



• 



70-106 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 250 — GROUNDING AND BONDING 



Grounding electrode conductors ajEf;fHelis^\^(;^|^it^;;eaGK 

}^iiMdmg3tQi^ 

JSrMeH^pireiS shall be 

installed as specified in 250.64(A) through (F). 

(A) Aleminem or Copper-Clad Alammem 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 en- 
closure shall be securely fastened to the surface on which it 
is carried. A 4 AWG or larger copper or aluminum ground- 
ing 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 per- 
mitted to be run along the surface of the building construc- 
tion without metal covering or protection where it is se- 
curely fastened to the construction; otherwise, it shall be in 
rigid metal conduit, intermediate metal conduit, rigid non- 
metallic conduit, electrical metalhc tubing, or cable armor. 
Grounding electrode conductors smaller than 6 AWG shall be 
in rigid metal conduit, intermediate metal conduit, rigid non- 
metallic conduit, electrical metallic tubing, or cable armor. 

(C) Continuoes. Grounding electrode conductor(s) shall 
be installed in one continuous length without a splice or 
joint except as permitted in (1) and (2): 

(1) Splicing shall be permitted only by irreversible 
compression-type connectors listed as grounding and 
bonding equipment or by the exothermic welding pro- 
cess. 

(2) Sections of busbars shall be permitted to be connected 
together to form a grounding electrode conductor. 

(D) §ei?Y»cf:WltIlI|^Mp 

'sWtWi' ^?Piei^j^fservic^ 

p|Qpren;as;:p^mutt^ 

pohneGtK)hs:':sKall::^bie;iMadenM:;M 

(i) ^i^pfflJIngai^ecipiij W|i§ti;|I|6 

^^icei^;iinstall^;p||>e^ 1? jf n230^^ iExc^^tiQi|;|R|^: 

^|a|ccpiiiiffi?|i^^ 

e^leetrodescqiidlL^ 

grQundiiTig;jeje|CJ^^ 

with ' j2S0^6^f jbapdv on/ tl^ ?area|of 

th&"; jpffgesf ^: mjigrQi^^ I ^ondi;cto*(s)^ 

Wli^gt|piepicefeirtr^ii^i;o^^ 



ti^f;;edhd|i<^c^ Table^ 

250M§|^$^Qtej; Kv^; jtipjxiG^^ the Insidd 

grotpdiiig:si|ecftBd|po^^ 

daricei;wMn25CSS6;^r|th&0ai the 

m^pduMjeiKlq^u^^^^ to 

jtheJfj&Srnft^ exothermic 

jW^ldmg :OT: V<^^ 

^[i||rment^ii^ eleci 

lode^coiidi^^ 

(i) iiffivliial;ni|ijiiiiiiflg'^^ lAj 

gi^ndi|igi^lect3?pdel^ be connected between! 

theigrc^nd#iicffluc^^ equiprnent disconnect- 

pgI|ffl^Ss'j^tpJd^ system] 

pa(|||gFOurffi in accor^ 

d^ce^ with^250i(56i^ tiiei":sei^icetentrance 
^upplyirigj||iW 

shailr ;be]Goniiqc|ted^lo^ ^ -set^/ice ; c6nductor(s) ' in 

af?fv#|wpt^^^^qtli^mcoe^^i^ side 

p|^;ffie;iseM(p^di|G6in^^ ' shall 

^'!mldi6^piplpc>the^ eoiffiedtoi^listed' a^ 

g3fQuiMirig^;aSc||J^^ elec-i 

txiode;icb|iduct^ 

baisiedtdiiath^^fery^ common 

locatjiqh ^ wKire^he?cm M- W^M¥l 

(E) Enclosures for Groending Electrode Conductors. 
Ferrous metal enclosures for grounding electrode conduc- 
tors shall be electrically continuous from the point of at- 
tachment to cabinets or equipment to the grounding elec- 
trode and shall be securely fastened to the ground clamp or 
fitting. Nonferrous metal enclosures shall not be required to 
be electrically continuous. Ferrous metal enclosures that are 
not physically continuous from cabinets or equipment to 
the grounding electrode shall be made electrically continu- 
ous by bonding each end of the raceway or enclosure to the 
grounding electrode conductor. Bonding shall apply at each 
end and to all intervening ferrous raceways, boxes, and 
enclosures between the cabinT^WrSr 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 enclosed grounding elec- 
trode 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) Ip^iaiatfoi to Electrode(s). Grounding electrode con- 
ductor|s|faiidi*b^di|ig^3ffira|^ 

BlectftJdeS;;s|^lf|^ (1), (2), or 

(3). The grounding electrode conductor shall be sized for 
the largest grounding electrode conductor required among 
all the electrodes connected to it. 



2008 Edition 



NATIONAL ELECTRICAL CODE 



70-107 



250.66 



ARTICLE 250 — GROUNDING AND BONDING 



( 1 ) il|ie i^6iihdirig;:decitrod^ be ; jjerm jtted 
to: be run to any convenient grounding electrode avail- 
able in the grounding electrode system where ; the otliejF 
electTode<:s|^Mfi any^T ar^-cbnne 

pQrr!§m53M- ' ' ■■ ' 

(2) GroundMg el^tte^ be 
rtiii to one or more grounding electrode(s) individually. 

(3) B6ftding;jim]pgE(s) ; 
l>emitfed^lQlbe;CG^^ 
bar^iTOt^l^sjSf^thah 

busbar- ^hall ;be Jsecmiely vft^tened ^an ^hHllJt^- :instoUedi iii 

aiiiiacee^spDleploc^bn;^ 

listed yoOTMectOT;^^ 

1Mq\ groiiiidiiig: j electrdde : qtmduetor shall be ; peniiittey: ;to 

b^ Jnjir^;fQ5thie: busbaij:]Where;;^ 

the ;instaIljaKbn -shall ;co 

250.66 Size of Alternating-Current Grounding Elec- 
trode Conductor. The size of the grounding electrode con- 
ductor at^ithe^Wvicej :at;eaeh;buildi^ 
supplibdi:by^Jia = |^c^r(s); ^r; ^branch- :Circuii;(s); ;<)r ; iaf JW^sepa!- 
mtely^den>^d;system of a grounded or ungrounded ac sys- 
tem 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. 

(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)(7), that portion of the conductor that is the sole connec- 
tion 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. 

250.68 Grounding Electrode Conductor and Bonding 

Juniper Connection to Grounding Electrodes. The ■Gortj 

n0Gti0h;0f;a;gi:Quhdirig{§[ec^^ 

gach'buii|ing;"or ;s&TiGtiute;-^ 

braiK^lciMuif^^^:P^^ 

;SGciatedl' liffiihdingH jimpei'(s)?!;SK£a 

|Si8(>fc):!St-(i)v^'''" 



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) 



Size of Grounding 

Electrode Conductor 

(AWG/kcmil) 



Copper 



Aluminum or 

Copper-Clad 

Aluminum 



Copper 



Aluminum 

or 

Copper-Clad 

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 there are no service-entrance conductors, the grounding 
electrode 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) Accessibility. Mfjrheehanicaf 'elei^^^^ 

niate-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: EjcotMmuc 

cmnecti0SvUsM ■ at\ \feirnimticmsWt0 -^WiyMeyM^^^ 

ctimw^o^-rm 

p^wqfed-sii^ ] whetheriiof^^m^ 

mednsi W-^ reyefsiblei - sfidll^liof^e Wqfiired^tp. lbe}aeMs.i:if?W 

(B) Effective Grounding Path. The connection of a 
grounding electrode conductor or bonding jumper to a 
grounding electrode shall be made in a manner that will 
ensure an effective grounding' path. Where necessary to 



70-108 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 250 — GROUNDING AND BONDING 



ensure the grounding path for a metal piping system used as 
a grounding electrode, bonding shall be provided around 
insulated joints and around any equipment likely to be dis- 
connected for repairs or replacement. Bonding jumpWs shall 
be of sufficient length to permit removal of such equipment 
while retaining the integrity of the grpuhiflpig'pathl 

250.70 Methods of Grpunding and Bomdiimg 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, 
hsted 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 Usted 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 

IV. Enclosure, Raceway, and Service Cable 



250.80 Service Raceways and Enclosures, Metal enclo- 
sures and raceways for service conductors and equipment 
shall be Gonneete(i-^5Silii^{gro 
iSl.eetiTC^^systeM'is;ig^ 
c^riducit|Ef6r;M0ctnc£^ 

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 

Wrm0ii§fiM>. \ thM^mUMM ^?y^t^^ WMucfQn^r'. grqtifidiM^ 

•etectwdei^cm 

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 conniscted to the grounded system 
icondiuitdr|oSitK^-cJ^^ shall not be required to be 

ieqnKepdUb;JJT^ grounded system;;eoiiduGtpr at the building 



or structure. The sheath or armor shall be permitted to be 
insulated from the interior metal raceway or piping. 

(B) Underground Service Raceway Containing Cable; 
An underground metal service raceway that contains a 
metal-sheathed or armored cable connected to the grounded 
system epriductpr shall not be required to be connected to 
the grounded systeM^S^iducli^ at the building or structure. 
The sheath or armor shall be permitted to be insulated from 
the ihterior metal raceway or piping. 

250.86 Oth^r Conductor Enclosures and Raceways. Ex- 
cept as permitted by 250.112(1), metal enclosures and race- 
ways for other than service conductors shall be Connected 

toJMieJeipjpiiiishtfgBo^ 

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 Cpniieptie'd^^^^^ 

c&ftdJM^or where these enclosures or wiring methods com- 
ply 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 C(mn^tediW;tf^ tdnducior. 

Exception No. 3: A metal elbow shall not be required to be 
8(ijm£ci^ 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. 

V. Bonding 

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. 

250.9^ Services. 

(A) Bonding of Services. The non-current-carrying metal 
parts of equipment indicated in 250.92(A)py and (A)(2) 
shall be bonded together. 

(1) The service raceways, cable trays, cablebus framework, 
auxiliary gutters, or service cable armor or sheath ex- 
cept as perrnitted in 250.84 

(2) All service enclosures containing service conductors, 
including ineter fittings, boxes, or the like, interposed 
in the service raceway or armor 



2008 Edition NATIONAL ELECTRICAL CODE 



7(J-109 



250.94 



ARTICLE 250 — GROUNDING AND BONDING 



(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 locknuts, 
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. ^M^j^iiit^sy^eiti 

bdndh^^Setrcanafc^ 

atndjgrouiiding tcondpctofs JrequiiMi ^ 

jbcvpi^ided^extem 

jaad iaS -the- di^corin^^ng imesa]^ IfOTiany Jaddlt^ 

aGc|$^ible^:iPaF; ;(loniiectibni|md; liispeetioiivj fife 

fejGUidiiigifei^^ 

|of ; ]^p| ;lessf:fian thi|fe^ 

pMsysteSntvlfe^ 

If iM JSpMflpg ; atjseMce^^i iiriesteimgrequipi^^ 

|lf^; |nteisystem;il^^ 

folowingf 

( 1 ) i'i^is^itMtermirialSi^ure 

siii^ -arid ; electriea}lyj -cpniiec^ed^ to; thesii^^^ lenGlc^iwe; 

Wh6. ^temiMals' ^haUi^; iisted;is ; gro^ 

esqiiipmentv 

(2) i^^'5bc)ndihgUbar giqar;-^ 

iheteii {jent^^imire;; ;_it^^ :!^&rvici : :coidu^rsJ 

The>;b0hdiig;bar; shall ; be;]cxmnedteid j-y^^ minimttfri 
^tj^ikWCj', copper Jep^ 
Gonductdi^s^ in jthe ; s^\^it^ -eqiuppenfe^dlos^ = W^^^ 

(3) ]^fb(OTdiiT^^ait.3teaJiffie 
flpe^^bondifagr^bp ^sha^j 1^^^ 
l^eefficMei;©^^ 

Exception: IjiXjex^mg^ibmM^ 

fxistj] 'imtoMati^: 'ojvtlw nnters^stepji^M '^efmmnMorf^^ 
W0JiPequireM An accessible means external to enclosures 
for connecting intersystem bonding and grounding elec- 



trode conductors shall be pe7miited}M the service equip- 
ment and at the disconnecting means for any additional 
buildings or structures by at least one of the following 
means: 

(1) Exposed nonfiexible metallic raceways 

(2) An 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 nonfiexible 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, pxGe|>tioiiTitem' (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 
conductors, with or without the use of supplementary 
equipment grounding conductors, shall be bonded where 
necessary to ensure electrical continuity and the capacity to 
conduct 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 insMl^d for the 
reduction of electrical noise (electromagnetic interference) 
on the grounding circuit, an equipment enclosure supplied 
by a branch circuit shall be permitted to be isolated from a 
raceway containing circuits supplying only that equipment 
by one or more listed nonmetalhc raceway fittings located at 
the point of attachment of the raceway to the equipment en- 
closure. The metal raceway shall comply with provisions of 
this article and shall be supplemented by an internal insulated 
equipnient grounding conductor installed in accordance with 
250.146(D) to ground die 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 



70-110 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 250 — GROUNDING AND BONDING 



with concentric or eccentric knockouts is listed to provide a 
reliable Wmdmgicof^ 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 connec- 
tors, flexible metal conduit connectors, and cable con- 
nectors, with one locknut on the inside of boxes and 
cabinets 

(4) Listed fittings 

250.98 Bonding Loosely Joimted Metal Maceways. Ex- 
pansion fittings and telescoping sections of metal raceways 
shall be made electrically continuous by equipment bond- 
ing jumpers or other means. 



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 hazard- 
ous (classified) location as defined in 50015 shall be ensured 
by any of the bonding methods specified in 250.92(B)(2) 
through (B)(4). One or more of these bonding methods 
shall be used whether or not equipment grounding conduc- 
tors jof;jtKe;M?ir^ftyp6 are installed. 



• 



L 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) AttaclimeiniL 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) Ske — Equipment Bonding Jumper on Sepply Side 
of Service. The bonding jumper shall hot be smaller than 
the sizes shown in Table 250.66 for grounding electrode 
conductors. 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 121/2 
percent of the area of the largest phase conductor except 
that, where the phase conductors and the bonding jumper 
are of different materials (copper or aluminum), the mini- 
mum 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 equivalent to that 
of the installed phase conductors. 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 coimecl 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 a raceway, the equipment bonding jumper 
shall comply 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 purpose of bonding or grounding isolated sections of 
metal raceways or elbows installed in exposed risers of 
metal conduit or other metal raceway. 

2S(D.1§4 Bonding of Piping Systems and Exposed Strec- 



(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 
attached 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 suffi- 
cient size, or to the one or more grounding electrodes used. 
The bonding jumper(s) shall be sized in accordance with 
Table 250.66 except as permitted in 250.104(A)(2) and 
(A)(3). 



(2) Bnildirags 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 



2008 Edition 



NATIONAL ELECTRICAL CODE 



70-111 



250.104 



ARTICLE 250 — GROUNDING AND BONDING 



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, 
t|£ised^ on; ^h^ Ta^rig; M ^the' (5y§rcui^^ 
the.:ai^uit'suppl^ 

(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 
conductors, 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. 

(B) Other Metal Piping. Where installed in or attached to 
a building or structure, a 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 sufficient size, or the one or more grounding elec- 
trodes used. The bonding jumper(s) shall be sized in accor- 
dance with 250.122, using the rating of the circuit that is 
hkely to energize the piping system(s). The equipment 
grounding conductor for the circuit that is likely to energize 
the piping shall be permitted 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 likely 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 am:^;^^;^wa]^H^J^^:^}j5ifem 
isrik '{the-- -xired^^Seryed.i 

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 de- 
rived system. This connection shall be made at the same 
point on the separately derived system where the grounding 
electrode conductor is connected. Each bonding jumper 
shall be sized in accordance with Table 250.66 based on 
the largest ungrounded conductor of the separately de- 
rived 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 build- 
ing 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 sepa- 
rately derived system. 

(3) Common Grounding Electrode Conductor. Where a 
common grounding electrode conductor is installed for 
multiple separately derived systems as permitted by 
250.30(A)(4), and exposed structural metal that is intercon- 
nected 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. 



70-112 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 250 — GROUNDING AND BONDING 



25( 



250.1®6 Lightnieg Protectloe 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 780-2008, Standard for the Instal- 
lation of Lightning Protection Systems, which contains de- 
tailed information on grounding, bonding, and sideflash 
distance; from lightning protection systems. 

FPN No. 2: Metal raceways, enclosures, frames, and other 
non-current-carrying metal parts of electrical equipment in- 
stalled on a building equipped with a Ughtning protection sys- 
tem may require bonding or spacing from the hghtning pro- 
tection conductors in accordance with NFPA 780-2008, 
Standard for the Installation of Lightning Protection Systems. 



(Fixed). Exposed non- 
current-carrying metal parts of fixed equipment likely to 
become energized shall be cx)hne^^df;tpHthe;^ 
groiffldiiigipjoiiductoi; under any of the following conditions: 

(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 
equipment ground, except as permitted by 250.86, Ex- 
ception 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 appli- 
ances, 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 comMt^iwtKieli^^ Where 

such a system is employed, the equipment shall be distinc- 
tively marked. 

).112 Fastened m Place or Conmected by Permameitit 
rimg Methods (Fixed) — Specific. Except' jas: permitted 
iii;^5()5M2!(t); 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 con- 

iieGted;fo;the^iequipnlenf ;giD^^ regardless of 

voltage. 

(A) Switchboard Frames amd Structures, Switchboard 
frames and structures supporting switching equipment, ex- 
cept frames of 2-wire dc switchboards where effectively 
insulated from ground. 



Eirgaiis. Generator and motor frames in an elec- 
trically operated pipe organ, unless effectively insulated 
from ground and the motor driving it. 



(C) Motor 
430.242. 



. Motor frames, as provided by 



(D) Enclosures for Motor Controllers. Enclosures for 
motor controllers unless attached to ungrounded portable 
equipment. 

(E) Elevators and Cranes. Electrical equipment for eleva- 
tors and cranes. 



(F) Garages, Theaters, and Motion Picture Studios, 
Electrical 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 W&;^\. 



(H) Motion Picture Projection 
ture projection equipment. 



Bent. Motion pic- 



(I) Remote-Control, Signaling, and Fire Alarm Circuits. 
Eqiiif^meiit : su^plie jGlass- l:^ircuits shall/ibe grounded 
j^nle;s§;t>pera:Gmg:at^ Equipment supplied 

by Class 1 power-limited circuits, by Class 2 and Class 3 
remote-control and signahng circuits, and by fire alarm cir- 
cuits shall be grounded where system grounding is required 
by Part II or Part VIII of this article. 

(J) Luminaires. Luminaires as provided in Part V of Ar- 
ticle 410. 



(K) SMd=Mounted Equipment. Permanently mounted 
electrical equipment and skids shall be Gprihected to the 
equipment groipdiri^-:;i;(pduGtdr sized as required by 
250.122. 

(L) Motor=Operated Water Pumps, Motor-operated wa- 
ter pumps, including the submersible type. 



igs. Where a submersible pump is 
used in a metal well casing, the well casing shall be con- 
nected to the pump circuit equipment grounding conductor. 



2008 Edition 



NATIONAL ELECTRICAL CODE 



70-113 



250.114 



ARTICLE 250 — GROUNDING AND BONDING 



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 p)n|ieGted^t!^|M;eg^ipii^ 

Exception: Listed tools, listed appliances, and listed equip- 
ment covered in 250.114(2) through (4) shall not be re- 
quired to be c^mecteditpjmi^^j^ 

ibr where protected by a system of double insulation or its 
equivalent. Double insulated equipment shall be distinc- 
tively 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 re- 
quired to be CQinp^cted:Mm^ 

Exception No. 2: Metal frames of electrically heated appli- 
ances, exempted by special permission, shall not be re- 
quired to be ''cmMcte^^ 

tofj 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 

c. Hand-held motor-operated tools, stationary and 
fixed motor-operated tools, and 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, and 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 

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 lo- 
cations 



Exception: Tools and portable handlamps likely to be used 
in wet or conductive locations shall not be required to be 
tmimMed:{'iQ;^ where 

supplied through an isolating transformer with an un- 
grounded secondary of not over 50 volts. 

250.116 Nonelectrical Equipment. The metal parts of the 
following nonelectrical equipment described in this section 
shall be c^nnect^d^tp^;the;equi^i^ 

(1) Frames and tracks of electrically operated cranes and 
hoists 

(2) Frames of nonelectrically driven elevator cars to which 
electrical 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: 

FPNi;i JOTi'e^etiwei-;grouhd>^^ 
Pfefiiiitionj 

(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^*USlMtfittirig$^ 

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 lj^tid::fitting$. 

b. For metric designators 12 through 16 (trade sizes 
% through Vi), the circuit conductors contained in 
the conduit are protected by overcurrent devices 
rated at 20 amperes or less. 



• 



)-114 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 250 — GROUNDING AND BONDING 



250.120 



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 
Hquidtight flexible metal conduit in trade sizes 
metric designators 12 through 16 (trade sizes Vs 
through Vi) in the grounding path. 

d. The combined length of flexible metal conduit and 
flexible metaUic 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 listed, flttiiigs and meeting the following con- 
ditions: 

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. 

(10) Type MC cable where Usted 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 and 392.7. 

(12) Cablebus framework as permitted in 370.3. 

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

(14) Surface metal raceways listed for grounding. 



dectors. 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 shaU not be used for un- 
grounded or grounded circuit conductors. 



Exception: Ftmey-^lij^ cables 

cpntairjmg'Q 

^Ajjfi^iJMe^'i^ insulation for 

atHerlifu^ ^WuHdptg^pm^ 

(A) Condectors Larger Than 6 AWG. Equipment 
grounding 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 shaU 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 insulation or covering green at the ter- 
ffil^tibii 

c. Marking the insulation or covering with green tape 
or green adhesive labels atpthelteyriiiiSatiD^ 



J. Where the conditions of 
maintenance and supervision ensure that only qualified per- 
sons service the installation, one or more insulated conduc- 
tors in a multiconductor cable, at the time of installation, 
shall be permitted to be permanently identified as equipment 
grounding conductors at each end and at every point where the 
conductors are accessible by one of the foUowing 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 Eqeipmeist 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, Cablebes, 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 installed in 
accordance with the applicable provisions in this Code us- 
ing fittings for joints and terminations approved for use 



2008 Edition NATIONAL ELECTRICAL CODE 



J-115 



250.122 



ARTICLE 250 — GROUNDING AND BONDING 



with the type raceway or cable used. All connections, 
joints, and fittings shall be made tight using suitable tools. 

ar^:jpM^'^:an:r elect 1^ iftfptectiv^i ^y s^mj'on a ; fire^ 

r^ed^iGable; ;iiste:d; ittf ; piaintaM 'eircuiV integrity; 

(B) Aluminum and Copper-Clad Aluminum Conduc- 
tors. Equipment grounding conductors of bare or insulated 
aluminum or copper-clad aluminum shall be permitted. 
Bare conductors shall not come in direct contact with ma- 
sonry or the earth or where subject to corrosive conditions. 
Aluminum or copper-clad aluminum conductors shall not 
be terminated 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 race- 
way or cable armor except where run in hollow spaces of 
walls or partitions, where not subject to physical 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 itiniibjicase 
shall they be required to be larger than the circuit conduc- 
tors supplying the equipment. Where a cp»le*;|r^y, a race- 
way, 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 the 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, cable, brieabfe! tray, it shall be sized for the largest 
overcurrent device protecting conductors in the raceway, 
cable, pl^ble^^trayJ^mp^ 

stalBdl|ii ^cableitr^aprshall'irfleef M^miSiiniiipieijiiife^ 

bfpiiiiiii ...-^...........-....~.^>...,. ^. ...>....„ ~. 

(D) Motor Circuits. pqui|)iQe!nf:gipin^ 
inotGp^:Giii?uit^;ishaJU|^be^!S^ 



(f) p^heral.' ^hel^lsqufltnoMt^ 
Sha|t 'ilbjt ibei,^malfe 
oti'th^^|a;tihg^o|^t]^^ 
0uij^prote^v^JLe\a^ 

(2) IhMiitane^ 

S^rt-JCiix^uitlProtiettor. WIiireHthj^iOivejpeiirKS^ 



an^Mt^atpie^ 

sizedi;no|^|rii^eii:t]|^; tMngiyeti; :by :250vli22|A); ^tisihg ithe 

pnaxini]^ 

isel^tedjfpr;|)rai^ 

t^|Mim-;a&OTda^ 

(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. 

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. 

(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 
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 grounding 
conductor shall be identified by one of the following: 

(1) A green, not readily removable terminal screw with a 
hexagonal head. 

(2) green, hexagonal, not readily removable terminal nut. 

(3) A green pressure wire connector. If the terminal for 
the grounding conductor is not visible, the conductor 



70-116 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 250 — GROUNDING AND BONDING 



Table 250.122 Minimpm Size Eqiiipmeiit Groundiimg 
Condectors for Grounding Raceway and Equipment 



• 



Mating or Setting of 
Automatic Overcurreet 
Device in Circuit Ahead 
of Equipment, Conduit, 

etc., Not Exceeding 
(Amperes) 



Size (AWG or kcmil) 



Copper 



immum or 
ler-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) or (B)(4), the 

equipment grounding conductor shall be sized larger than given in this 

table. 

*See installation restrictions in 250.120. 

entrance hole shall be marked with the word green or 
ground, the letters G or GR, a grounding symbol, or 
otherwise identified by a distinctive green color. If 
the terminal for the equipment grounding conductor 
is readily removable, the area adjacent to the termi- 
nal shall be similarly marked. 

FPN: See FPN Figure 250.126. 



FPN Figure 250.126 One Example of a Symbol Used to Men- . 
tify the Grounding Termination Point for an Equipment 
Grounding Conductor. 



VII. Methods of Eqoipmeeit Groemdmg 



source of separately derived systems shall be made in ac- 
cordance with 250.30(A)(1). Equipment grounding conduc- 
tor connections at service equipment shall be made as in- 
dicated 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 installa- 
tions that do not have an equipment grounding conductor in 
the branch circuit, connections shall be permitted as indi- 
cated 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. 



s. The connection shall be 
made by bonding the equipment grounding conductor to the 
grounding electrode conductor. 

(C) Nomgroemdleg Receptacle Replacememt or Bramclh 
Circuit Extemsioiis. 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 conn^te^[toJTaS?e^i^^ 
gondiictpr in accordance with 250.134. 

250.134 Eqeipmeet Fastened in Place or Connected by 
Permanent Wiring Methods (Fixed) — Grounding. Un- 
less grounded by connection to the grounded circuit con- 
ductor 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 connected to an 
^ipiiis^Hp'^^hili]^|e^c^ by one of the methods 
specified in 250. 1 34(A) or (B) . 



tions. Equipment grounding conductor connections at the 



(A) Equipment Grounding Conductor Types. By con- 
neetiSgito any of the equipment grounding conductors per- 
mitted by 250.118. 



2008 Edition NATIONAL ELECTRICAL CODE 



J-117 



250.136 



ARTICLE 250 — GROUNDING AND BONDING 



(B) With Circuit Conductors. By tQii^eGtitigVte an equip- 
ment grounding conductor contained within the same race- 
way, cable, or otherwise run with the circuit conductors. 

Exception No. 1: As provided in 250.130(C), the equip- 
ment 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 250.102 and 250.168 for equipment bond- 
ing jumper requirements. 

FPN No. 2: See 400.7 for use of cords for fixed equipment. 

250.136 Equipment Considered Grounded. Under the 
conditions specified in 250.136(A) and (B), the nomicilly 
non-current-carrying metal parts of the equipment shall be 
considered 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 
cpiiriec^edrta-an?eq 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 Goriniected 
td;ara;e(giiipment^rcHin^ by one of the meth- 
ods 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 cbMet^teidftoarf 
groundiilgeohduG^^^^ by one of the methods in 250.138(A) 

or'(B)r" 

(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. 

Exception: The grounding contacting pole of grounding- 
type plug-in ground-fault circuit interrupters shall be per- 
mitted to be of the movable, self -re storing 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, 
Gonnected:to'an;:e^ pro- 

tected 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 apphances shall be 
conhfebtbdhtouthe ; ec^m^ 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 
amil£f:ted}iq the grounded circuit conductor if all the fol- 
lowing conditions are met. 

(1) The supply circuit is 1 20/240-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 sepa- 
rately 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 ov- 
ens, counter-mounted cooking units, and clothes dryers un- 
der the conditions permitted for existing installations by 



)-118 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 250 — GROUNDING AND BONDING 



250.148 



250.140 shall be permitted to be 'QQfin&fedifSHhe 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 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. 



le Circuit Coimectioims. Where equipment 
is grounded and is supplied by separate connection to more 
than one circuit or grounded premises wiring system, art 
ecjuipii^th^putodi^ shall be pro- 

vided for each such connection as specified in 250.134 and 
250.138. 

250.146 Corniectlng Receptacle Groeeding 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). 'ffie/epipMeitlroHc^^ 
iiiJaisGordance jW;^ lof tKs 

o^veiiCurrerft; deyijce' ^protecting; thej^ 

(A) Serface-Moented 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. 'A/listed 
(SJtpoie(fAS^r^ 

aiS|t)pridmgJSL^^ isNattEched;;toj the 

Q0yeciwith ; at4ea^^ 

asM; w^et|Jc«^ h^i-a- thpsad^teeloj^ TtieMs. 

and;l(2|^Wli6ff ilie: Goyen are; Jt)Gat(Bdi- oii; ia^flM 

rioh^aised? port|onHoCpe;;0o\^ 



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 installed 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 ieoniiectedjto an insulated equipment grounding 
conductor run with the circuit conductors. This equipment 
grounding conductor shall be permitted to pass through one 
or more panelboards without a connection to the panel- 
board grounding terminal bar as permitted in 408.40, Ex- 
ception, so as to terminate within the same building or 
structure directly at an equipment grounding conductor ter- 
minal of the applicable derived system or service. Where 
m^ta^Jed'inJ^CGOTdanee^yi^^ this section, 
tiu^^egiitj^e^ shall also be permitted 
ta;pass^;thrx3ij|h;b^ or t)ther enclosures with- 
oiW; ibe^ngrtejOnn^^ :'^rieljepires; 

FPN: Use of an isolated equipment grounding conductor 
does not relieve the requirement for grounding the raceway 
system and outlet box. 

25®.148 ComtfliniLiiity and Attachment of Equipment 



u Boxes. Where circuit conduc- 
tors are spliced within a box, or terminated on equipment 
within or supported by a box, any equipment grounding con- 
ductor(s) associated with those circuit conductors shall be con- 
nected 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 permitted 
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. 



is or Yokes. Contact devices or yokes 
designed and listed as self-grounding shall be permitted 



The arrangement of ground- 
ing connections shall be such that the disconnection or the 
removal of a receptacle, luminaire, 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, equiphfeht listed for' g^^ or a 

listed grounding device. 



2008 Edition 



NATIONAL ELECTRICAL CODE 



J-119 



250.160 



ARTICLE 250 — GROUNDING AND BONDING 



(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 
system 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 ampere 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. 

250.164 Point of Connection for Direct-Current Sys- 
tems. 

(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 the Direct-Current Grounding Elec- 
trode Conductor. The size of the grounding electrode con- 
ductor for a dc system shall be as specified in 250.166(A) 

aM;i3^|^ex?i^tras^^erpdd 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 (A)(7), that portion of the grounding elec- 
trode 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. 

(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 System Bonding Jumper. For 

dii¥i|e]KcuiTent:=s}^em^ 
bpndirig^ ■ jumj^rf;^h 
pCMidir^-c^iidu^ 

st)urce ; ior^ihe! ;fijret;^ystem: JdiStiOTnectirig "rn^ans ;^here Jthe 
sys^rn^is: grounded: The size of the bonding jumper shall 
not be smaller than the system grounding electrode conduc- 
tor specified in 250.166 ^idishaUJ^mplyiwit^^ 
«s;0f;25p;28|A),;|B^q^ 

250.169 Ungrounded Direct-Current Separately De- 
rived 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 Fait III of this article to provide for 
grounding of metal enclosures, raceways, cables, and ex- 
posed non-current-carrying metal parts of equipment. The 



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ARTICLE 250 — GROUNDING AND BONDING 



25t 



grounding electrode conductor connection shall be to the 
metal enclosure at any point on the separately derived sys- 
tem 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. 

The size of the grounding electrode conductor shall be 
in accordance with 250.166. 



250.170 Instrument Transformer Circuits. Secondary 
circuits of current and potential instrument transformers 
shall be grounded where the primary windings are con- 
nected to circuits of 300 volts or more to ground and, where 
on switchboards, shall be grounded irrespective of voltage. 

Exception No. 1: Circuits where the primary windings are 
connected to circuits of less than 1000 volts with no live 
parts or wiring exposed or accessible to other than quali- 
fied persons. 

Exception No. 2: 'Cu0:^r^rff^sf(^^ 
WectMi^mH^W^ierp 

250.172 Instrument Transformer Cases. Cases or frames 
of instrument transformers shall be iedmdeted^t^rtheJ^^^ 
mf^flfilgimnMig^ where accessible 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 coiin|ctedi;1X3(/j3lfe;;(^^ 
conducto| as specified in 250.174(A), (BJ, or (C). 

(A) Not on Switchboards. Instruments, meters, and relays 
not located on switchboards, operating with windings or 
working parts at 300 volts or more to ground, and acces- 
sible to other than qualified persons, shall have the cases 
and other exposed metal parts GOtiiijeGted;itpft|i^:^^ 
jgrofindliglcoiMuG 



Instruments, meters, 
and relays (whether operated from current and potential trans- 
formers or connected directiy in the circuit) on switchboards 
having no five parts on the front of the panels shall have the 
cases c§Mecte^^OiJEhe:e^ 

(C) On Live-Front Switchboards. Instruments, meters, 
and relays (whether operated from current and potential 
transformers or connected directly in the circuit) on switch- 



boards having exposed live parts on the front of panels 
shall not have their cases efthieefed* tq^the equipnient 
pounding;JfC<)nduet^^^^^ Mats of insulating rubber or other 
suitable floor insulation shall be provided for the operator 
where the voltage to ground exceeds 150. 



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 eoniiected to the 
Iquipirfent j ^u|dMgI^!Mu^t^^ 

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. 



The equip- 

inenl grounding conductor for secondary circuits of instru- 
ment transformers and for instrument cases shall not be 
smaller than 12 AWG copper or 10 AWG aluminum. Cases 
of instrument 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 equipment 
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 provisions 
of the preceding sections of this article and with 250.182 
through 250.190, which supplement and modify the preced- 
ing sections. 

250.182 Derived Neutral Systems. A system neutral pomt 
derived 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 neu- 
tral 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 conductor of the following: 

(1) S^iee^fitrd^ 

(2) 'Siejmfi£i\ldferdls 

(3) 'Dimc;t-lmnM/.p^^ 



2008 Edition NATIONAL ELECTRICAL CODE 



)-l2] 



250.186 



ARTICLE 250 — GROUNDING AND BONDING 



Exception No. 2: Bare conductors shall be permitted for 
the neutral bbftduct()jr}^jqf overhead portions installed 
outdoors. 

Exception No. 3: The gmmdeH{n^0m^ 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 sufficient 
ampacity for the load imposed on the conductor but not less 
than 33^3 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 |||l||||| System. Where a 
single-point grounded neutral system is used, the following 
shall apply: 

(1) A single-point grounded neutral system shall be permit- 
ted 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 multi- 
grounded neutral conductGr at the source of the 
single-point grounded neiitral 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 coMiictbr. 

(4) A bonding jumper shall connect the equipment ground- 
ing conductor to the grounding electrode conductor. 

(5) An equipment grounding conductor shall be provided 
to each building, structure, and equipment enclosure. 

(6) A neutral cpriductpr shall only be required where 
phase-to-neutral loads are supplied. 

(7) The neutral bonduetor, where provided, shall be insu- 
lated and isolated from earth except at one location. 

(8) An equipment grounding conductor shall be run with 
the phase conductors and shall 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 

(C) Multigrounded Neutral Systems. Where a multi- 
grounded neutral system is used, the following shall apply: 
(1) The neutral eonduetpr 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 following locations: 

a. Transformers supplying conductors to a building or 
other structure 



b. Underground circuits where the neutral Gohdiictor 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 grpunding electrode. 

(3) At least one grounding electrode shall be installed and 
connected to the multigrounded neutral conductor ev- 
ery 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 aU of the following conditions are met: 

(1) The conditions of maintenance and supervision ensure 
that only qualified persons 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 Goiiductoir Connection. The system 
neutral eonductpij 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 Go:puct6f grounded through an imped- 
ance. Where a delta-connected high-voltage system is used 



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ARTICLE 280 — SURGE ARRESTERS, OVER 1 kV 



to supply portable or mobile equipment, a system neutral 

poinfJaiM 4iJSSt)Ciafce(^ shall be derived. 

(B) Exposed Non-Cprrenlt-Carrymg 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 Cerremt, 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) Groend=Faelt 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. 

iguiplient 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 dis- 
tribution apparatus. 



280.1 Scope. This article covers general requirements, instal- 
lation requirements, and connection requirements for surge 
arresters installed on premises wiring systems ^ver 1 kV. 

2§§L2 ¥ses;^P#l?Perinftied. A'^ui-ge;arrfesterTshairnot be; 

m$taned/\vhere;the[| arrester is less than 

the:thaximjM 

ypltag;e; [mmMM^^i^Wi^, ;poiirt;^f 'ap{)licat^^ 



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. T.he-siffge:'fcesters shall 

egripl^§(it^;280if(A) and (B). 

(|A) Eatiiig. pie^mting^ ^i'lsurg&iarfe equal to 

|or igreaterj tli^n ;tlii?|iiaximum voltage 

amlablefat^th^Jpmnt 

(|0 SolidlyJiGrounjded The;maximum continuous 

fe^prpu%' voltage? Shall >^beKthe^ ; jphap-^OTgroimd ■ voltage of 

|he:sy$tpms 

(y2) lSopedanGie:iOr.-Wimgr^ [The' maximum 

eonffiupus ^o^ratin the phase-to-phase 

iMtage; ^f thq ^system- 



The rating of a silicon 
carbide-type surge arrester shall be not less than 125 per- 
cent of the ratings SpeGifipd;in 2^80; 

FPN No. 1: For further information on surge arresters, see 
ANSI/IEEE C62. 11-2005, Standard for Metal-Oxide Surge 
Arresters for Alternating-Current Power Circuits (>1 kV); 
and ANSI/IEEE C62.22-1997, Guide for the Application of 
Metal-Oxide Surge Arresters for Alternating-Current 
Systems. 

FPN No. 2: The selection of a properly rated metai 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 location. 

280^ IJstmg. A^lurge^^airestef^^ 



2008 Edition NATFONAL ELECTRICAL CODE 



)-123 



280.11 



ARTICLE 285 — SURGE-PROTECTIVE DEVICES (SPDs), 1 kV OR LESS 



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 GrpundingL'^^ohdii^^^^ 
tors. The conductor used to connect the surge arrester to 
Une, bus, or'^&gmpr^^ and tc^^iiVgixiuHdingjcon^^ 
nfection^oinf ^as^iH^oyi shall not be any longer 
than necessary and shall avoid unnecessary bends. 

III. Connecting Surge Arresters 

280.21 tponiieciitfri. The arrester grounding conductor 
shall be connected to one of the following: 

(1) Grounded service conductor 

(2) Grounding electrode conductor 

(3) Grounding electrode for the service 

(4) Equipment grounding terminal in the service equipment 

280.23 Surgef Arrester The conductor be- 
tween 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 irttemMfei^ The grounding conductor of a 
surge arrester protecting a transformer that supplies a sec- 
ondary distribution system shall be interconnected as speci- 
fied in 280.24(A), (B), or (C). 

(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) Additipnal^Gro^ The grounded 
conductor of the secondary has elsewhere a grounding con- 
nection to a continuous metal underground water piping 
system. In urban water-pipe areas where there are at least 
four water-pipe connections on the neutral GOiidUetor; and 
not fewer than four such connections in each mile of neu- 
tral CondiibtM, the metallic interconnection shall be permit- 
ted to be made to the secondary neutral iconductof with 
omission of the direct grounding connection at the surge 
arrester. 

(2) MxMgi(opMM The 
grounded conductor of the secondary system is a part of a 
niyltigrounded neutral system or static wire of which the 
primary neutral pOnductor or static wire has at least four 
grounding connections in each mile of line in addition to a 
grountlingTco^^^ at each service. 



(B) Through Spark Gap or Device. Where the surge ar- 
rester 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 inter- 
connection shall be made through a spark gap or listed 
device as required by (B)(1) or (B)(2): 

(1) Opgroiijn^a^:;Qr;;Unig^^ For 
ungrounded or unigrounded primary systems, the spark gap 
or listed device shall have a 60-Hz breakdown 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) Mffltlgrouhilfed^;Nieutr For multi- 
grounded 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 fi'om the surge-arrester grounding electrode. 

(C) By Special Permission. An interconnection of the 
surge-arrester ground and the secondary neutral condiidtorl 
other than as provided in 280.24(A) or (B), shall be permit- 
ted to be made only by special permission. 

280.25 Grounding Gpnduct^r;-€piinfecti!^ 
stires. Except as indicated in this article, surge-arrester 
grounding conduGtor connections shall be made as speci- 
fied in Article 250, Parts ;i|I^^nd;J5^?;Gn^rtpr^i^ 
m^^ledlm:Tnetal;;^ncl^3^^ iSKalf-Goraply rwith^ 250;64(]|| 



ARTICLE 285 

Surge-Protective Devices (SPDs), 
1 kY or Less 



I. General 

285.1 Scope. This article covers general requirements, in- 
stallation requirements, and connection requirements for 

^fp3|?tsu|geigiri^tiers^;an 

S0r^p(pl¥3^| permanently installed on premises wiring 

systems ;lf;KV';^or;leslsJ 

FPN ; Nd, J ;i: 1- Surge ^a&e$ters. ;less; ttiari { likVj -^el also l Mowii 

aremisey jMiio wji! WJ^j^- 2; and; fj^e ;3 ; SPBsl 

285.3 Uses Not Permitted. |/^^;^^p£n^^^;^iTp^;;o^ 
T¥SS) device shall not be installed in the following: 



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ARTICLE 285 — SURGE-PROTECTIVE DEVICES (SPDs), 1 kV OR LESS 



28S.28 



(1) Circuits exceeding MW^i 

(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 Si?E);pmigefaf^stej:ri(tt3^ 

is less than the maximum continuous phase-to-ground 
power frequency voltage available at the point of 
application 

FPN: For further information on SEDSi^f^W^SSs)^ see 
NEMA LS 1-1992, Standard for Low~Voltage Surge Sup- 
pression Devices. The selection of a properly rated SPD 
(OFYSS.)i i^ based on criteria such as maximum continuous 
operating voltage, the magnitude and duration of overvolt- 
ages at the suppressor location as affected by phase-to- 
ground faults, system grounding techniques, and switching 
surges. 



Where used at a point on a cir- 
cuit, the SPE^||urge^iffiFes]^if^^ shall be connected 
to each ungrounded conductor. 

285.5 Listing. An ^M5^;(|u^.ffi:estffiM^ shall be a 
listed device. 

285.6 Sliort-Circiiit Cerreet Rating. The SB|3;|slrgerar: 
|^te|^f^T^SS^ shall be marked with a short-circuit current 
rating arid 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. 



285.11 Location. SpG)fs'^(suxg^;aiTepei|^ shall be 

permitted to be located indoors or outdoors and shall be 
made inaccessible to unqualified persons, unless listed for 
installation in accessible locations. 



The conductors used to 
connect the S]PB'i(^surge: arrester ;ot^^ to the line or bus 

and to ground shall not be any longer than necessary and 
shall avoid unnecessary bends. 



(2) T^pe;;|[S|RD^;(^spge?arr8st^ 
c^MfeGfe<|;a&^S^^ 

(E) ;Mitlie}SCTM|^. |\Piin;ipta|]£d^i^|^yie(eO^ 

mf ^e||nduc^[pf jajT^j^f^li;^ one^of 

the^fqltSroing: 

(1) Gjtt|uii(|ed,]S^^ 

(2) GroMdihg!edee|^^ 

(3 ) Groutidingf plectra JfoteJthe: seiMce; 

(4) pqmpme[p|S;:gi:(|uh<^ : ihy:- ^Ihe; service 

gquipmeiit 

'm§m w^^mi§!^MMMWi^' M^IiSpps^crvsss) shaii 

beHnst^lM:iiRE:aeei^ 285.2^0^) through j(C): 



(M) Service-Sepplied BelMIng or Structure. Type "2 
SPKsf^Oli^SSs:^ shall be connected anywhere on the load 
side of a service disconnect overcurrent device required in 
230.91, unless installed in accordance with 230.82(8). 

(K) Feeder-Sopplled Buildlmg or Structure. Type "2 "SPDs 
I^^SS^ shall be connected ^ tM^BiMdingW strucmre 
an^;!^.lprl on the load side of the first overcurrent device at 
the building or structure. 

(§) Separately Derived System, The SPJD;;(TySS;»: shall 
be connected on the load side of the first overcurrent device 
in a separately derived system. 

2851^ l^^-f SPgi pgg§;SPI5^i(TVSS|l?im;be per- 

mltt»d;t^eaiist^^ 

igjfcfilit; Syeixjuircnt ^prot^ ?Hf)j1;ttpieT equ^ * served^ 

|i^3#3edf[the;j^nn^ ft) of 

GoiMuttcJE derived 

sptSffiMsGOMeM: 



}ke. Line and gfbuhd|ng conductors 
shall not be smaller than 14 AWG copper or 12 AWG 
aluminum. 



285,21 Connection, Where m;?S|^|<|itegeMMeste*^^^^ 
|?|fSS)pfyic| is installed, it shall comply with 285:^ 
through IsSigi 

^5^3 |^iil;:fS^r^rgfe;flrrfeprs). ^ypiJf^rSPEs 
shMM^^tnsilLlI^^I^^ 2.8^5(1^) anc}fj(®). 

(M) |i|s|aIIatlgS. p^{^|Of^?|?>sr;:(sp|e;f:§ps^)^^ 

mspHddi aljfollo^?! I 

(1) T^^ni|j^(3^pmfge:^^t^stes^ 

|^iipfedr|§|heB|^ |e^^e|discpiiri^ 
^s jp^p|tlMli|IP0iB2^^ ~ 



;285.j,^7; Connection Between Conductors, Ah" SPD' (surge 
alrester^JOgWSS^ shall be permitted to be connected be- 
tween 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 SPD (surge 
ariestitJcii^^P^S)' during a surge. 

sire|. ^^;c^t;|is;iridy[GMifd;^|Q 
^^^^^^„^^j^^^^^^_^^^^_^„_^^j^.^^^ "250,' Part 

i^t|jWrpiiMingn^0hiJw*^ 
shpi^pn^y:^tI|?P|^^ 



2008 Edition NATIONAL ELECTRICAL CODE 



-125 



CHAPTER 3 



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 utihzation equipment. 

(C) Metric Designators and Trade Sizes. Metric designa- 
tors and trade sizes for conduit, tubing, and associated fit- 
tings and accessories shall be as designated in Table 
300.1(C). 

Table 300.1(C) Metric Designators and Trade Sizes 



Metric 
Designator 



Trade 
Size 



12 

16 

21 

27 

35 

41 

53 

63 

78 

91 

103 

129 

155 



1/2 
3/4 

1 

l'/4 

1/2 

2 

2'/2 

3 

31/2 

4 
5 
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(JA) shall only be installed where part of a 
recognized wiring method of Chapter 3. 

Exception: Individual conductors shall be permitted where 
installed as separate overhead conductors in accordance 
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). 

(4) Enclosures. Where an auxiliary gutter runs between a 
column-width panelboard and a pull box, and the pull box 



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ARTICLE 300 — WIRING METHODS 



• 



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 aeJahdrde 
circuits, rated 600 volts, nominal, or less, shall be permitted 
to occupy the same equipment wiring enclosure, cable, or 
raceway. All conductors shall have an insulation rating 
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 725.136(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, sign, or out- 
line lighting enclosure as the branch-circuit conductors. 

(b) Primary leads of electric-discharge lamp ballasts in- 
sulated for the primary voltage of the ballast, where con- 
tained within the individual wiring enclosure, shall be per- 
mitted to occupy the same luminaire, sign, or outline 
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 (VA 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|s| or bushing^], at least 
1.6 mm (Vie 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 pro- 
tect 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 (Vi6 in.) thick that provides equal or better protec- 
tion against nail or screw penetration shall be permitted. 

(2) Notches m 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 (Vi6 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 pro- 
tect 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 (Vi6 in.) thick that provides equal or better protec- 
tion against nail or screw penetration shall be permitted. 



metallic Ikbing 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 pro- 
tected by listed bushings or listed grommets covering all 
metal edges that are securely fastened in the opening prior 
to installation of the cable. 

(2) Nonmetallic-Sheathed Cable and Electrical Nonme= 
tallic Tubing. Where nails or screws are likely to penetrate 
nonmetallic-sheathed cable or electrical nonmetallic tubing, 
a steel sleeve, steel plate, or steel clip not less than 1.6 mm 
(Vie in.) in thickness shall be used to protect the cable or 
tubing. 

Exception: 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. 

(C) Cables Through Spaces Behind Panels Designed to 
Access. Cables or raceway-type wiring methods. 



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300.5 



ARTICLE 300 — WIRING METHODS 



installed 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 (yi6 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 buildings, 
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 (Vi6 in.) thick that provides equal or better protec- 
tion against nail or screw penetration shall be permitted. 

(E) Cables ;^and \ Raceways^lIii^taUed^; ll^iid^ ©ieck- 
iiig. |fi.;]GabIe^ ;pr:f acewayyt^ ;wiMg yinethoc^ ■ m^ Hii 

^x|>psedJOT;Go^ sheet 

roof Jdeckihg,^ ^shall ; be ■ in^aHed; Jancl: supportedi ;^: ;the nearest 
|CHJ&Mei surface: bfffie^cable^ 
t J;V^! m^);|rom;tlte :nea^ 

after 5 the: ini ti al- race way :^^^^ ^and;; roofing ; installation 

and ; may i \ib ^penetrated; by . -flie screws; or- ;other; Inieehanical 
deyiees- fdesigfied; ;to: .provide: ri'ffold.Vdown" jstrengtHVof -the 
waterproof ^membran^^ or jQpf linsulating material 

Exception: W^iid}fmtal^:;C(^^ 

ct0duiti sHcjll \rtot:he': m^ir^ t^icomply, withi -SOQ^iE^^ 

(F) 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 fiiU 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. 

(G) Insulated Fittings. Where raceways cohtam 4 AWG 
or larger insulatediieireuitiepniuc^ 

enter a cabinet, box, enclosure, or raceway, the conductors 
shall be protected by a substantial fitting providing a 
smoothly rounded insulating 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 in- 
tegral part of a cabinet, box, enclosure, or raceway provide 
a smoothly rounded or flared 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) Wet^tocatioiis. Theiiite^iM'pf eiiclo 

ihStialledf ufldergrqiinil shall Ije cpnsixieredjto: Jbem ;wet llpca- 

tiohl Tftsi|iated; eondufetors: ;kiid- cable&^mstalled in ithese'eiii 

closujres^orT^ceway^ 

listed- ^ ioii ■ :use ■ uri;: ^Wet ; ■ locdtiiMs =; -ajHlL^-shaU ;; ; cpmplyU witi^ 

3p:t^ 8(jG); ? J^ny;; conriectiOns;^:or: ; spliced; irv?|aif^iindergixDurid 

iiistanationi ^shalltibe' approved :fpr ;\v^; loeatipWs^ 

(C) Underground Cables Under Buildings. Underground 
cable installed under a building shall be in a raceway. 

(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 
cables emerging from grade aiid;;apieoified5m(^Qlu|iii^ 
4i.o|i :Tablei30O;5 shall be protected by enclosures or. race- 
ways 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 



• 



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ARTICLE 300 — WIRING METHODS 



• 



Table 300.5 Minimum Cover RequBrements, to 600 Volts, Nominal, Berial in Millimeters (Inches) 





Type of Wiring Method or Circuit 
















Column 5 












Circuits for 










Column 4 


Control of 








Column 3 


Residential 


Irrigation and 








Nonmetallic 


Branch Circuits 


Landscape 








Raceways Listed 


Rated 120 Volts or 


Lighting Limited 








for Direct Burial 


Less with GFCI 


to Not More Than 






Column 2 


Without 


Protection and 


30 Volts and 




Column 1 


Rigid Metal 


Concrete 


Maximum 


Installed with 




Direct Burial 


Conduit or 


Encasement or 


Overcurrent 


Type UF or in 




Cables or 


Intermediate 


Other Approved 


Protection of 20 


Other Identified 




Conductors 


Metal Conduit 


Racevs^ays 


Amperes 


Cable or Raceway 


Location of Wiring Method 






















or Circuit 


mm nn. 


mm m. 


mm m. 


mm m. 


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 traflBc 








(direct burial) 


(direct burial) 


and the slab extending not 
less than 152 mm (6 in.) 








100 4 


100 4 


beyond the underground 








(in raceway) 


(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 hsted 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. 



2008 Edition 



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300.6 



ARTICLE 300 — WIRING METHODS 



identified 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 W^Q conduit, or equivalent. 

(E) Splices and Taps. Direct-buried conductors or cables 
shall be permitted to be spliced or tapped without the use of 
splice 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. 

Where necessary to prevent physical damage to the 
raceway or cable, protection shall be provided in the form 
of granular or selected material, suitable running boards, 
suitable 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 ne- 
cessitate sealing of underground conduits or raceways en- 
tering buildings. 

(H) Bushing. A bushing, or terminal fitting, with an inte- 
gral bushed opening shall be used at the end of a conduit or 
other raceway that terminates underground where the con- 
ductors or cables emerge as a direct burial wiring method. 
A seal incorporating 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 '^quipf. 
M^M. grounding conductors. 

Exception No. 2: Isolated phase, polarity, grounded con- 
ductor, and equipment grounding and bonding conductor 
installations 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) Earth 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 
armor, boxes, cable sheathing, cabinets, elbows, couplings, 
fittings, supports, and support hardware shall be of materi- 
als 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, couphngs, nipples, 
fittings, supports, and support hardware shall be suitably 
protected against corrosion inside and outside (except 
threads at joints) by a coating of approved corrosion- 
resistant material. Where corrosion protection is necessary 
and the conduit is threaded in the field, the threads shall be 
coated with an approved 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. 



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300.11 



• 



(B) MumMum Metal Equipment. :^lU;mintifn raceways, 
cable trays, cablebus, auxiliary gutters, cable armor, boxes, 
cable sheathing, cabinets, elbows, couplings, nipples, fit- 
tings, supports, and support hardware embedded or encased 
in concrete or in direct contact with the earth shall be pro- 
vided with supplementary corrosion protection. 

(C) Nonmetallk Equipment. Nonmetallic raceways, 
cable trays, cablebus, auxiliary gutters, boxes, cables with a 
nonmetallic outer jacket and internal metal armor or jacket, 
cable sheathing, cabinets, elbows, couplings, nipples, fit- 
tings, supports, and support hardware shall be made of ma- 
terial approved for the condition and shall comply with 
(C)(1) and (C)(2) as applicable to the specific installation. 

(1) Exposed to Senlight 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 
chemicals based on their listing or be identified for the 
specific 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 frequently 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 (^A-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. 



• 



ling. 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 interior to the 
exterior of a building, the raceway or sleeve shall be filled 
with an approved material to prevent the circulation of warm 
air to a colder section of the raceway or sleeve. An explosion- 
proof seal shall not be required for this purpose. 



sion Fittings. Raceways shall be provided with 
expansion fittings where necessary to compensate for ther- 
mal expansion and contraction. 

FPN: Table 352.44 and Tpme!35p4|5t provide the expan- 
sion information for polyvinyl chloride (PVC) arid for re- 
inforced f th^ifipsejHing' ;resm Jc^mdutt !^RrRG)iy ra^ vel y. 
A nominal number for steel conduit can be determined by 
multiplying the expansion length in fTable 352,44 by 0.20. 
The coefiScient of expansion for steel electrical metallic 
tubing, intermediate metal conduit, and rigid conduit is 
ira^Tt^faO^^ (0.0000117 mm per mm of conduit for each 
°C iri temperature change) [0.650 x 10";^: (0.0000065 in. per 
inch of conduit for each °F in temperature change)]. 

ASpminalrriurnb^^ conduit and alumi- 

niffi^sjectrical^me^ by multi- 

pl)^nj^^the/eXpaiis^ by 0.40. The 

epQffeieifti0f;;^pm^ electrical metallic 

tubing I faiid'ial^^ is 2.34 x 10"^ 

(0!:0p0O2M|mrn^p^r?mm^p^ each °C in tempera- 

tuip^bKii||||lpD;>^i}^ per inch of conduit 

Wt. jeadh; ^F|m Jteraparature; ^change]'^ 



M Installation of Conductors witli Other Systems. 
Raceways or cable trays containing electrical conductors 
shall not contain any pipe, tube, or equal for steam, water, 
air, gas, drainage, or any service other than electrical. 

WBM: Raceways -inliWeti to Grade. Where 

f^v^§uareiinsta|leS^il:w§t^ the in- 

tefi|tf?^f;]th^e;S£^ to' be' a^ wet 

loGa|]K^J;lnsyllat©d!^^ installed in race- 

pf yf|;m?^i wetyjlf^atpns^^ ^comply'^ w^th 



D) Electrical Contimuily of Metal Raceways and 
Enclosures. Metal raceways, cable armor, and other metal 
enclosures for conductors shall be metallically joined to- 
gether into a continuous electrical conductor and shall be 
connected to all boxes, fittings, and cabinets so as to pro- 
vide effective electrical continuity. Unless specifically per- 
mitted elsewhere in this Code, raceways and cable assem- 
bUes shall be mechanically 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. 



(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- 



2008 Edition 



NATIONAL ELECTRICAL CODE 



70-131 



300.12 



ARTICLE 300 — WIRING METHODS 



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 251-2006, Standard Methods of 
Tests of Fire Resistance of Building Construction and 
Materials. 

(2) Non-Fire-Rated Assemblies. Wiring located within 
the cavity of a non-fire-rated floor-ceiling or roof-ceiling 
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 and 
sliafl;be: permitted^ to.-bej ^ijtabhe ^assembly; 

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. 

(B) Raceways Used as Means of Support. Raceways 
shall be used only as a means of support for other race- 
ways, cables, or nonelectrical 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 in accordance with 410.36(E) 

(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, 
fittings, or other enclosures or outlets. 

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 mechanically 
continuous. 

Exception No. 2: Raceyyays.m 

Wfttam^^-^p^ii^^h 

Wotpr^cofi^^c 

efSiYSJiMlvriot-M^ 

equipmenh 



).13 Mechanical and Electrical Continuity — Con- 
ductors. 

(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 splices or the 
connection of luminaires 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, outlet 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, 



• 



70-132 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 300 — WIRING METHODS 



300.18 



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. 



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. 



II 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) letegraE 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), Excep- 
tion 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- 
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. A box or conduit body shall not be re- 
quired where a luminaire is used as a raceway as permitted 
in 410.64 and 410.65. 



A box or conduit body shall not be re- 
quired for splices where conductors are embedded as per- 
mitted in 424.40, 424.41(D), 426.22(B), 426.24(A), and 
427.19(A). 

(L) Manholes and Handhole Enclosures. A box or con- 
duit body shall not be required for conductors in manholes 



or handhole enclosures, except where connecting to electri- 
cal equipment. The installation shall comply with the pro- 
visions of Part V of Article 110 for manholes, and 314.30 
for handhole enclosures. 



A box shall 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, Eoiitfiiit :B;oidy,;:or:iFitfiiig. A box, 'eoiduit body, 
or terminal fitting having a separately bushed hole for each 
conductor shall be used wherever a change is made from 
conduit, electrical metallic 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 splices and shall not be used at luminaire 
oudets. i^^imduit^bodymsad'^^ contain 

rM^ps ji^ -^plldes^:!^ 



ag. 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. 



J.17 Number and Size of Conductors in 
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: intermediate 
metal conduit, 342.22; rigid metal conduit, ?>AA21\ flexible 
metal conduit, 348.22; liquidtight flexible metal conduit, 
350.22; FS^C conduit, 352.22; pDi^»Gonduit,;,353.22; 
RTRG,;; 355,22;; liquidtight nonmetallic flexible conduit, 
356.22; electrical metallic tubing, 358.22; flexible metallic 
tubing, 360.22; electrical nonmetallic tubing, 362.22; cellu- 
lar concrete floor raceways, 372.11; cellular metal floor 
raceways, 374.5; metal wireways, 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); eleva- 
tors, 620.33; audio signal processing, amplification, and re- 
production equipment, 640.23(A) and 640.24; Class 1, 
Class 2, and Class 3 circuits. Article 725; fire alarm cir- 
cuits, Article 760; and optical fiber cables and raceways. 
Article 770. 



Raceways, other than busways or ex- 
posed raceways having hinged or removable covers, shall 



2008 Edition 



NATIONAL ELECTRICAL CODE 



70-133 



300.19 



ARTICLE 300 — WIRING METHODS 



be installed complete between outlet, junction, or splicing 
points prior to the installation of conductors. Where re- 
quired to facilitate the installation of utilization equipment, 
the raceway shall be permitted to be initially installed with- 
out a terminating connection at the equipment. Prewired 
raceway assemblies shall be permitted only where specifi- 
cally permitted in this Code for the applicable wiring 
method. 

Exception: Short sections of raceways used to contain con- 
ductors or cable assemblies for protection from physical 
damage shall not be required to be installed complete be- 
tween 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. 

(R) EireTRated::CaMes:yan^^ Smpportjmeths 

■ ods;and;^paemgdntei^s 
toi;s: ^hall jeSffiqplyHMthmy'i^M ffl-lj^?: ^^?!^ 

Table 300.19(A) Spacings for Conductor Supports 



iiijg^lhe;;e|eGtFioal^c]^^ 

case::sKa|I; ^exce^ dp ;Tabl^^300vJ9||<i'^ 

(p) 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 
insulating supports are installed and secured in a satis- 
factory manner to withstand the weight of the conduc- 
tors attached thereto, the boxes being provided with 
covers. 

(3) In junction boxes, by deflecting the cables not less than 
90 degrees and carrying 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 EerrouS Metal Enclosures 

or Fercoos Metal Raceways. 

(A) Conductors Grouped Together. Where conductors 
carrying alternating current are installed in ferrous metal 
enclosures or ferrous metal raceways, they shall be ar- 
ranged so as to avoid heating the surrounding feitOus metal 
by induction. To accomplish this, all phase conductors and, 
where used, the grounded conductor and all equipment 
grounding conductors 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). 



Size of Wire 



Conductors 



Support of 

Conductors in 

Vertical 

Raceways 



Aluminum or 

Copper-Clad 

Aluminum 



ft 



Copper 



ft 



18 AWG through 8 AWG Not greater than 30 

6 AWG through 1/0 AWG Not greater than 60 

2/0 AWG through 4/0 AWG Not greater than 55 

Over 4/0 AWG through 350 kcmil Not greater than 41 

Over 350 kcmil through 500 kcmil Not greater than 36 

Over 500 kcmil through 750 kcmil Not greater than 28 

Over 750 kcmil Not greater than 26 



100 
200 
180 
135 
120 
95 
85 



30 
30 
25 
18 
15 
12 
11 



100 
100 
80 
60 
50 
40 
35 



70-134 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 300 — WIRING METHODS 



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. 



rs. 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 appa- 
ratus, the currents carried by the conductors are so small 
that the inductive heating effect can be ignored where these 
conductors 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 suflBcient 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 Combestloe. 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- 
resistive 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 separation that usually apphes 
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 m Ducts, 
Handling Spaces. The provisions of this section apply to 
the installation and uses of electrical 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 



shaft containing only such ducts, used for vapor removal or 
for ventilation of commercial-type cooking equipment. 

(B) Ducts or Plemums Used for Eeviroemental 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- 
taflic 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 shall be permitted. 

(C) Other Space Used for EmvlroEmeetal Air. This sec- 
tion apphes to space used for environmental air-handling 
purposes other than ducts and plenums as specified in 
300.22(A) and (B). It does not include habitable rooms or 
areas of buildings, 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 secdon 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 Umited 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, conductors, 
andlr^ewayg shall be ^i|m|te(|^[be installed in electrical 
metallic tubing, flexible metallic tubing, intermediate metal 
conduit, rigid metal conduit without an overafl nonmetallic 
covering, flexible metal conduit, or, where accessible, sur- 
face metal raceway or metal wireway with metal covers or 
solid bottom metal cable tray with solid metal covers. 

(2) EquipmeMt. Electrical equipment with a metal enclo- 
sure, or with a nonmetallic enclosure listed for the use and 



2008 Edition NATIONAL ELECTRICAL CODE 



70-135 



300.23 



ARTICLE 300 — WIRING METHODS 



having adequate fire-resistant and low-smoke-producing 
characteristics, 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. Electrical wir- 
ing in air-handling areas beneath raised floors for informa- 
tion 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 insulatioii. 

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- 
conductor 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 shall 
also be permitted. Busbars shall be permitted to be either 
copper or aluminum. 



300.39 Braid-Covered Insulated Conductors — Ex- 
posed Installation. Exposed runs of braid-covered insu- 
lated conductors shall have a flame-retardant braid. If the 
conductors 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, ac- 
cording 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. Metallic 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, shall be conriectedj ;tp;^$i 
grouin^ing^?cof!K3;iict6r^ graundirig 

elMtfOde^r 

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 listed raceways. Raceways 
installed on poles shall be of rigid metal conduit, interme- 
diate metal conduit. Schedule 80 pyG;;conduit,: or equiva- 
lent, 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 



70-136 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 300 — WIRING METHODS 



Table 300.50 Mimimum Cover" Requirements 





General Conditions (mot otherwise specified) 


Special Conditions (use if applicable) 










(4) 














Raceways 














Under 


(5) 












Buildings or 


Cables in 


(6) 










Exterior 


Airport 


Areas Subject to 








(3) 


Concrete 


Runways or 


Vehicular Traffic, 






(2) 


Rigid Metal 


Slabs, 100 mm 


Adjacent 


Such as 




(1) 


Rigid 


Conduit and 


(4 in.) 


Areas Where 


Thoroughfares 




Direct-Buried 


Nonmetallic 


Intermediate 


Minimum 


Trespass Is 


and Commercial 




Cables" 


Conduit'' 


Metal Conduit 


Thickness*' 


Prohibited 


Parking Areas 


Circuit VoStage 


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 



General 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. 

3^;Iii; Midusjteial ^establishments, : w^ere ;pMditipns;;of mauUeti^e ; ati(^;sup :tHat;qualified;persons ; w th^ installation, the 

minimum: cov^^^ rigid jmetalLconduit. landiintemediaV^mbtaf S^^ .p^firnitted; fo-;be. reduced l;50"miri (6 in.) 

fpr;eachf50;mm;^ 

Specific Footnotes: 

^ 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. 

^ 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. 

rt:pIndCTgrpund ;direct-b^ cables; that^ are: not^ei^sed^^;p^^ fcy]cpncrete ^nd: are ^l^^ :(3D in:); or -more below; gr^de shall have 

tiieiurilocationjito 



approved enclosure or raceway from the minimum cover 
depth to the point of entrance. Where direct-buried conduc- 
tors, raceways, or cables are subject to movement by settle- 
ment 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 applica- 
tion. The taps and splices shall be watertight and protected 
from mechanical damage. Where cables are shielded, the 
shielding shall be continuous across the sphce or tap. 

Exception: At splices of an engineered cabling system, me- 
tallic 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 mate- 
rials, cinders, large or sharply angular substances, or corro- 
sive materials shall not be placed in an excavation where 
materials can damage or contribute to the corrosion of race- 
ways, cables, or other substructures or where it may pre- 
vent adequate compaction 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. 



2008 Edition 



NATIONAL ELECTRICAL CODE 



70-137 



310,1 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



ARTICLE 310 
Conductors for General Wlrmg 



1.1 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 hare conductors are specifi- 
cally permitted elsewhere in this Code. , 

FPN: See 250.184 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. 

(A) General. 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 connected in parallel (electrically joined 
at both ends). 

Exception No. 1: Conductors in sizes smaller than 1/0 
AWG shall be permitted to be run in parallel to supply 
control power to indicating instruments, contactors, relays, 
solenoids, and similar control devices, prJi>r]frv0Wi^^ 
'3'60.'iH^'::Md]MgHefy, provided 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. 2: Under engineering supervision, 
grounded neutral conductors in sizes 2 AWG and larger 
shall be permitted to be run in parallel for existing 
installations. 

FPN tp.Exception -No; ;2; Exception No. 2 can be used to 
alleviate overheating of neutral conductors in existing installa- 
tions due to high content of triplen harmonic currents. 

(B) C^opduGtorrjC The paralleled conduc- 

tors in each phase, polarity, neutral, grounded circuit con- 
ductor, dP'equipaientHgi^M^^ shall comply 
with all of the following: 

(1) Be the same length 

(2) Have the same conductor material 

(3) Be the same size in circular mil area 

(4) Have the same insulation type 

(5) Be terminated in the same manner 

(G.) SepsH'ate^C^blesioi^^Rabevi^ Where run in separate 
cabjesjon raqoway s^ : the^cables ^.oriTaeeway^ wffli-|oS|iet^ 
shall have the same number ; of ccmdiictoi^ 
thfei:«amej;;electfic9.1i[;c^ Conductors of one 

phase, polarity, neutral, grounded circuit conductor, oc 
equipment ;:grqiindirig:^#hdue^^^^^ shall not be required to 
have the same physical characteristics as those of another 
phase, polarity, neutral, grounded circuit conductor, or 
equijjrheht grc)uridiiig=^ to achieve balance. 



(15) Ampacity'Adyustme^ Conductors installed in paral- 
lel shall comply with the provisions of 310.15(B)(2)(a). 

(E) Eflrapment:;Gi1i^ Whbr^;]F^ralle]i 

^^ _^^_^,^ ^^^^. ^_ ^ ^^^^^j^^_. ijgj^ ;^gg(j i^if^g^ l^hall ;fb6 

sijzed; -in; :aec^o^dMC(^^ ? ;with]; 2|^ 

grounding ; eortdiiptors; ;sm^aller ;:thah; ;i/0:AW'(3; ^hallJbe; perf 
ni i tited: In ■ mijltiGOiiduc^r cables m} aecOrdane^ :Mth i 31 0. 13|^ 
prOyidted 0e;C(Jmbiried pi^ 

piiefwiai;25G:122: 

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) 

Aluminum or Copper-Clad 
Copper 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 



• 



70-138 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



ling. 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 jE^nneetedJiafa'^^^ 
ingMeeteodei;^ 

eiectrjojdev Shielding shall be for the purpose of confining 
the voltage stresses to the insulation. 

Exception No. 1: 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 ^bM^^^M^-WiM)- 

Exception No. 2: Wjieref^emiiM^^ 



J Direct-Burial Conductors. Conductors used for 
direct-burial applications shall be of a type identified for 
such use. 

Cables rated above 2000 volts shall be shielded. 

Exception No. 1: Nonshielded multiconductor cables rated 
200 rf 24,00 volts shall be permitted if the cable has an 
overall metallic sheath or armor 

The metallic shield, sheath, or armor shall be eonnected 
to5^ igi^iMidiJng/iJe^^ 
gromdmgjelest^ 

Exception No. 2: Mffieldrlightiifg^able'^ 

cuits}fhM[Ufys}^^ 

re-gulatom. IsHalil beiperfmtfed^ M -be] HojiMieMed: 

PfIg;-te^?E?fce{)tiM?]No^ iMeral-"i^iaiKH|]^ 

(FA A;)^-Admory; ^GireiilarsV-^ AGs) t provide i additional > pi-aetiges 

ahdt m^tBodsHf orjaii^^^^ lighting: 

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. 



(A) Dry Locatloms. 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, THWN, THWN-2, TW, XHH, 
XHHW, XHHW-2, Z, or ZW. 



(C) Wet Locations. Insulated conductors and cables used 
in wet locations shall comply with one of the following: 

(1) Be moisture-impervious metal-sheathed 

(2) Be types MTW, RHW, RHW-2, TW, THW, THW-2, 
THHW, THWN, THWN-2, XHHW, XHHW-2, ZW 

(3) Be of a type listed for use in wet locations 

(D) Locations Exposed to Direct SunMglit. Insulated con- 
ductors or cables used where exposed to direct rays of the 
sun shall comply with I(1P>)j|;1^;jOT jcPi^2): 

(1) Conductors and cables shalf be listed, or listed and 
marked, as being sunlight resistant 

(2) ©otiyuGtor^faiidJbabM covered with insulating 
material, such as tape or sleeving, that is listed, or 
listed and marked, as being sunlight resistant 



1.9 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. 



ture Limitation of Conductors. No con- 
ductor shall be used in such a manner that its operating 
temperature exceeds that designated for the type of insu- 
lated conductor 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 con- 
ductors, that the limiting temperature of any conductor is 
exceeded. 

FPN: The temperature rating of a conductor [see Table 
31;0.I3(A) and Table 31 0.:13;(C)] 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. 

310.11 Marking. 



All conductors and cables 
shall be marked to indicate the following information, us- 
ing the applicable method described in 310.11(B): 



2008 Edition 



NATIONAL ELECTRICAL CODE 



70-139 



310.12 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



(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 assembUes 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 

(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 in- 
tended for use as ungrounded conductors, whether used as a 
single conductor or in multiconductor cables, shall be fin- 
ished to be clearly distinguishable from grounded and 
grounding conductors. 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 accordance 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 Table 310.13fA;) pKmi^iimMemi||df(|). 



• 



70-140 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



3110.13 



These conductors shall be permitted for use in any of 
the wiring methods recognized in Chapter 3 and as speci- 
fied 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 pressure, such as at points of support. Thermoplastic 
insulation, where used on dc circuits in wet locations, may 
result in electroendosmosis between conductor and 
insulation. 

Eqm|^ent::Jgfj>im to 

be:^tipned.jwitlunja;li|ted 

|H^^£(StobihicJ;;C^ 



Table 310.13i(;A)~ Condector Applications and Insulations ;MMed-;$WS¥o|t^ 



• 



• 







Maximum Operating 






Tliicl(ness of Insulation 














Trade Name 


Type Letter 


Temperature 


Application Provisions 


Insulation 


AWG or kcmil 


mm 


mils 


Outer Covering^ 


Fluorinated 


FEPor 


90°C 


Dry and damp locations 


Fluorinated ethylene 


14-10 


0.51 


20 


None 


ethylene 


FEPB 


194°F 




propylene 


8-2 


0.76 


30 




propylene 














200°C 
392°F 


Dry locations — special 
applications^ 


Fluorinated ethylene 
propylene 


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 


For special applications^ 




9^ 


1.27 


50 








482°F 






3-500 


1.40 


55 




Moisture-, heat-, 


MTW 


60°C 


Machine tool wiring in 


Flame-retardant 




(A) 


(A) 


(A) None 


and oil-resistant 




MOT 


wet locations 


moisture-, heat-, and 
oil-resistant 








(B) Nylon jacket or 


thermoplastic 






equivalent 






90°C 


Machine tool wiring in 


thermoplastic 


22-12 


0.76 


30 








194°F 


dry locations. 
FPN-. See NFPA 79. 




10 

8 

6 

4-2 

1-4/0 

213-500 

501-1000 


0.76 
1.14 
1.52 
1.52 
2.03 
241 
2.79 


30 
45 
60 
60 
80 
95 
110 




Paper 




85°C 
185°F 


For underground service 
conductors, or by special 
permission 


Paper 








Lead sheath 


Perfluoro-aikoxy 


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 




1^/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-^/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 


1.52 
2.03 
241 
2.79 
3.18 


60 
80 
95 
110 
125 


flame-retardant, 
nonmetallic covering' 


Moisture- 


RHW 


75°C 


Dry and wet locations 


Flame-retardant, 


14-10 


1.14 


45 


Moisture-resistant, 


resistant 




167°F 




moisture- 


8-2 


1.52 


60 


flame-retardant, 










resistant thermoset 


1-4/0 


2 03 


80 


nonmetaUic covering"; 




RHW^2 


90?G 






213-500 


241 


95 






;194?F 






501-1000 


2.79 


110 












1001-2000 


3.18 


125 




Sihcone 


SA 


90°C 


Dry and damp locations 


Silicone rubber 


14-10 


1.14 


45 


Glass or other suitable 






194°F 






8-2 
1-4/0 


1.52 
2.03 


60 
80 


braid material 






200°C 


For special application^ 




213-500 


241 


95 








392°F 






501-1000 
1001-2000 


2.79 
3.18 


110 

125 





(Continues) 



2008 Edition NATIONAL ELECTRICAL CODE 



70-141 



310.13 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



Table 310.13(Ai) Continued 







Maximum Operating 






Thickness of Insulation 














Trade Name 


T^pe Letter 


Temperature 


Application Provisions 


Insulation 


AWG or kcmil 


mm 


mils 


Outer Covering* 


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 

55. 




Thermoplastic and 


TBS 


90°C 


Switchboard wiring only 


Thermoplastic 


14-10 


0.76 


30 


Flame-retardant, 


fibrous outer 




194°F 






8 


1.14 


45 


nonmetaJlic covering 


braid 










6-2 
1-4/0 


1.52 
2.03 


60 
80 




Extended polytetra- 


TFE 


250°C 


Dry locations only. Only 


Extruded polytetra- 


14-10 


0.51 


20 


None 


fluoro- 




482°F 


for leads within 


fluoroethylene 


8-2 


0.76 


30 




ethylene 






apparatus or within 
raceways connected to 
apparatus, or as open 
wiring (nickel or 
nickel-coated copper 
only) 




1-4/0 


1.14 


45 




Heat-resistant 


THHN 


90°C 


Dry and damp locations 


Flame-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 


Flame-retardant, 


14-10 


0.76 


30 


None 


heat-resistant 




167°F 




moisture- and 


8 


1.14 


45 




thermoplastic 








heat-resistant 


6-2 


1.52 


60 








90°C 


Dry location 


thermoplastic 


1^/0 


2.03 


80 








194°F 






213-500 
501-1000 
1001-2000 


241 
2.79 

ill 


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 


Special applications 


heat-resistant 


6-2 


1.52 


60 








194°F 


within electric discharge 
lighting equipment. 
Limited to 1000 
open-circuit volts or 
less, (size 14-8 only as 
permitted in 410.33) 


thermoplastic 


1^/0 

213-500 

501-1000 

J0Q:ls2pOO 


2.03 
241 
2.79 

3718 


80 
95 
110 

;125. 






TH>V:2 


::90fG 


Dry ;and;wet: locations 








194^F 














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 


0.76 
1.02 


30 
40 














THWN?2 








1-4/0 
250-500 
501-1000 


1.27 
1.52 
1.78 


50 
60 
70 




Moisture- 


TW 


60°C 


Dry and wet locations 


Flame-retardant, 


14-10 


0.76 


30 


None 


resistant 




140°F 




moisture- 


8 


1.14 


45 




thermoplastic 








resistant 
thermoplastic 


6-2 

1^/0 
213-500 
501-1000 
1001-2000 


1.52 
2.03 
241 
2.79 
3.18 


60 
80 
95 
110 
125 




Underground feeder 


UF 


60°C 


See Article 340. 


Moisture- 


14-10 


1.52 


60.^ 


Integral with insulation 


and branch-circuit 




140°F 




resistant 


8-2 


2.03 


80^, 




cable — single 










1-4/0 


2.41 


95? 




conductor (for 


















Type UF cable 




■ 75°C 




Moisture- and 










employing more 




167°Fl 




heat-resistant 










than one 


















conductor, see 


















Article 340.) 



















• 



70-142 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



310.13 



• 



Table 310.13:(:A) Continued 





Type Letter 


Maximum Operating 
Temperature 


Application Provisions 


Insulation 


Tliickness of Insulation 




Trade Name 


AWG or kcmiJ 


mm 


mils 


Outer Covering^ 


Underground 


USE 


75°C 


See Article 338. 


Heat- and 


14-10 


1.14 


45 


Moisture-resistant 


service- 




167°F 




moisture-resistant 


8-2 


1.52 


60 


nonmetallic covering 


entrance cable — 










1-4/0 


2.03 


80 


(See 338.2.) 


single conductor 










213-500 


241 


95^ 




(for Type USE 










501-1000 


2.79 


110 




cable employing 










1001-2000 


3.18 


125 




more than one 


















conductor, see 


















Article 338.) 




















MSEf?; 


-:90''G 


Dry iand: wet Jocalions 




Thermoset 


XHH 


90°C 


Dry and damp locations 


Flame-retardant 


14-10 


0.76 


30 


None 






194'^F 




thermoset 


8-2 

1^/0 
213-500 
501-1000 
1001-2000 


1.14 
1.40 
1.65 
2.03 
241 


45 
55 
65 
80 
95 




Moisture- 


XHHW 


90°C 


Dry and damp locations 


Flame-retardant, 


14-10 


0.76 


30 


None 


resistant 




194°F 




moisture- 


8-2 


1.14 


45 




thermoset 




75°C 
167°F 


Wet locations 


resistant thermoset 


1-4/0 
213-500 
501-1000 
1001-2000 


1.40 
1.65 
2.03 
241 


55 
65 
80 
95 




Moisture- 


XHHW-2 


90°C 


Dry and wet locations 


Flame-retardant, 


14-10 


0.76 


30 


None 


resistant 




194°F 




moisture- 


8-2 


1.14 


45 




thermoset 








resistant thermoset 


1-4/0 
213-500 
501-1000 
1001-2000 


1.40 
1.65 
2.03 
241 


55 
65 
80 
95 




Modified ethylene 


Z 


90°C 


Dry and damp locations 


Modified ethylene 


14-12 


0.38 


15 


None 


tetrafluoro- 




194°F 




tetrafluoro- 


10 


0.51 


20 




ethylene 




150°C 
302°F 


Dry locations — special 
applications^ 


ethylene 


8-4 

3-1 

1/0-4/0 


0.64 
0.89 
1.14 


25 
35 
45 




Modified ethylene 


zw 


75°C 


Wet locations 


Modified ethylene 


14-10 


0.76 


30 


None 


tetrafluoro- 




167°F 




tetrafluoro- 


8-2 


1.14 


45 




ethylene 




90°C 
194°F 
150°C 
302°F 


Dry and damp locations 

Dry locations — special 
applications^ 


ethylene 












zw-g 


90''e 

;194°F 


Dry: and wet : locations 





' 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. 

* 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. 



• 



2008 Edition 



NATIONAL ELECTRICAL CODE 



70-143 



310.13 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



Table 310.13(B) Thickness of Insulation for Nonshielded 

Types RHH and RHW S.oHd.-DieliectriG; InsulatedLeondiictors 
Rated .lOOOi^tts 



• 





Column A* 


Column B^ 


Conductor Size 


















(AWG or kcmil) 


mm 


mils 


mm 


mils 


14-10 


2.03 


80 


1.52 


60 


8 


2.03 


80 


1.78 


70 


6-2 


2.41 


95 


1.78 


70 


1-2/0 


2.79 


110 


2.29 


90 


3/0^/0 


2.79 


110 


2.29 


90 


213-500 


3.18 


125 


2.67 


105 


501-1000 


3.56 


140 


3.05 


120 


1001-2000 


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 310.13(CJ Conductor Application and Insulation RiatedX20pipy61tS;:Md^ 



Trade 

Name 



Maximum Operating Application 

Type Letter Temperature Provision 



Insulation 



Outer Covering 



Medium voltage solid 


MV-90 


90°C 105°C 


Dry or wet locations Thermo- 


Jacket, sheath, or 


dielectric 


MV-105* 




plastic or thermo- 
setting 


armor 



*Where design conditions require maximum conductor temperatures above 90°C. 

Table 310.13(D) Thickness of Insulation and Jacket for Nonshielded Solid Dielectric psulated: Conductors: -:Ratedr.24^^^ 































Dry Locations, 


Single Conductor 






Wet or Dry Locations 








Without 
Jacket 




With Jacket 




Single Conductor 






















JVlUlUCUIIIUUClUl 




Insulation 


Insulation 


Jacket 


Insulation 


Jacket 


Insulation* 


Conductor Size 














































(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 


no 


2.29 


90 


1.14 45 


3.18 


125 


2.03 


80 


2.29 


90 


3/0-4/0 


2.79 


no 


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 


no 


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 


4001M250 


3L56 


il40 


2192 


=U5 


1165 65 


4v32 


170 


3.56 


140 


W2 


:115 


11251^1500 


3156 


140 


2;92 


115 


2^03 80 


43% 


17Q 


me 


140 


2.92 


115 


1501-2000 


3.56 


1;40 


2.92 


115 


2:03 80 


m^ 


170 


3;94 


155 


3.56 


;W0 



■= Under a common overall covering such as a jacket, sheath, or armor. 



70-144 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



310.1S 



Table 310.13(E) 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 




100 


100 


133 


173 


100 


133 


173 


100 


133 


173 




Percent 


Percent 


Percent 


Percent 


Percent 


Percent 


Percent 


Percent 


Percent 


Percent 


Conductor 


Insulation 


Insulation 


Insulation 


Insulation 


Insulation 


Insulation 


Insulation 


Insulation 


Insulation 


Insulation 


Size 


hevm" 


Level ^ 


Level 2 


LeveP 


Level^ 


LeveF 


LeveF 


LeveF 


LeveP 


LeveP 


(AWG 
















or kcmil) 


mm mils 


mm mils 


mm mils 


mm mils 


mm mils 


mm mils 


mm mils 


mm mils 


mm mils 


mm mils 



8 2.29 90 — — — — — — — — — — ____ __ __ 

6-4 2.29 90 2.92 115 3.56 140 4.45 175— — — — ____ __ __ 

2 2.29 90 2.92 115 3.56 140 4.45 175 4.45 175 5.59 220 6.60 260 — — — — — — 

1 2.29 90 2.92 115 3.56 140 4.45 175 4.45 175 5.59 220 6.60 260 6.60 260 8.13 320 10.67 420 

1/0-2000 2.29 90 2.92 115 3.56 140 4.45 175 4.45 175 5.59 220 6.60 260 6.60 260 8.13 320 10.67 420 







25,001-28,000 volts 






28,001-35,000 volts 




Conductor 

Size 


100 

Percent 
Insulation 

Level^ 


133 

Percent 

Insulation 

Level ^ 


173 

Percent 

Insulation 

Level' 


100 

Percent 
Insulation 

Level* 


133 

Percent 

Insulation 

LeveP 


173 

Percent 

Insulation 

Level' 


(AWG 
or kcmil) 


mm mils 


mm mils 


mm mils 


mm mils 


mm mils 


mm mils 


1 
1/0-2000 


7.11 280 
7.11 280 


8.76 345 
8.76 345 


11. .30 445 
11.30 445 


8.76 345 


10.67 420 


14.73 580 



' 100 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 applied 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 applications where additional insulation is desirable. 

■'its Percent Insulation Level. Cables in this category shall be permitted to be applied 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 apphcations where additional 
insulation strength is desirable. 



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 ma- 
terial. 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 Raited 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 79-2007, 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 



2008 Edition NATIONAL ELECTRICAL CODE 



70-145 



310.15 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



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 appUcation 
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 pro- 
tection. 

(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 con- 
ductor insulations, see Tabiej-jjSfpBpA) and Table 
310.13(6). 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). 

(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 iistajied 
J^Kput|tnairitmmhg^s^^ longer 

than 600 mm (24 in.) 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 con- 
ductor of a paralleled set of conductors shall be counted as 
a current-carrying conductor. 

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 


31^0 


40 


41 and above 


35 



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 adjustment factors for con- 
ductors in sheet metal auxiliary gutters and 3,7;6;22(B) for 
adJMtriient 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 conduc- 
tors 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. 

(c) CbndmtsjE^ W^f^P. 
coF^iicpts^ aax^'ii ipM!ednijiv;cciiiduits ^;&;^osed: -^to 
IdffireetJSuiilif ht? oiiior lal^ye^^rooftqps^ jthe jadfiist^ pOwn 
'^me:m&^S^^^ ;spll:i30 :aaaet;tQ?tli^;cw 
poij^efifxM^^erM^ ^pplk^alyle; ;amM£^ 
foKa;^picSiMi^f 

ppSjOTif'' "' ' ' '"'""" ---^-.-^ 

FPNir: Onel source Jfpr^the 'ayerag^jambieiitj tein^ 

vOTpusjlocatiomasp^ 



• 



70-146 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



Table 310.15(B)(2)(c) Ambient Temperature Adjustment for 
Conduits Exposed to Sunlight On or Above Rooftops 



• 



Distance Above Roof to Bottom of 
Conduit 



Temperature Adder 



°C 



- 13 mm ('/2 in.) 33 60 

Above 13 mm (Vi in.) - 90 mm (iVi in.) 22 40 

Above 90 mm (31/2 in.) - 300 mm (12 in.) 17 30 

Above 300 mm (12 in.) - 900 mm 14 25 
(36 in.) 



|P|gg||5M;531;pp5(g|;^)(f;- 3|ift! Mature; i^adm 

|3ab][eiM(|^|i^^|lc^^aSSIb^^ 

pSbi^]|teiiii^a^^ 

(3) Bare or Covered Conductors. Where bare or covered 
conductors are j^t^led with insulated conductors, t|ieltemf: 
jierat^fraS^iofS^ 
ei^'^lPll^llwepJptt^^ 

(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 ^bnduGr; 
tor| and the neutral coi^diftor of a 4-wire, 3-phase, wye- 
connected system, a common conductor carries approxi- 
mately the same current as the line-to-neutral load currents 
of the other conductors 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 cur- 
rents are present in the neutral conductor; the neutral einduGt 
tor 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) 12©/240-Volt, 3-Wire, Single-Phase Dwelling Ser= 
vices and Feeders. For individual dwelling units of one- 
family, two-family, and multifamily dwelhngs, conductors, 
as listed 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 between the 



main disconnect and the panelboard that'|uppliesreit^ b>^ 
pi^nfe|gc§Ci^ part 

ori'a^sE^g^clMtpjM The feeder conductors 

to a dwelling unit shall not be required to have an allowable 
ampacity rating greater than their service-entrance conduc- 
tors. The grounded conductor shall be permitted to be 
smaller than the ungrounded conductors, provided the re- 
quirements of 215.2, 220.61, and 230.42 are met. 



Table 310.15(B)(6) Conductor Types and Sizes for 
120/240- Volt, 3- Wire, Single-Phase Dwelling Services and 
Feeders. Conductor Types RHH, RHW, RHW-2, THHN, 
THHW, THW, THW-2, THWN, THWN-2, XHHW, 
XHHW-2, SE, USE, USE-2 



Conductor (AWG or kcmil) 



Service or Feeder 
Rating (Amperes) 



Copper 



Aluminum or 

Copper-Clad 

Aluminum 



100 
110 
125 
150 
175 
200 
225 
250 
300 
350 
400 



4 

3 

2 

1 

1/0 
2/0 
3/0 
4/0 
250 
350 
400 



2 

1 

1/0 
2/0 
3/0 
4/0 
250 
300 
350 
500 
600 



(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{l + 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. 



2008 Edition 



NATIONAL ELECTRICAL CODE 



70-147 



310.15 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRIN(j 



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(A).] 












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, 






Types TBS, SA, 










FEP, FEPB, MI, RHH, 






SIS, THHN, 










RHW-2, THHN, 






THHW, THW-2, 








Types RHW, 


THHW, THW-2, 




Types RHW, 


THWN-2, RHH, 








THHW, THW, 


THWN-2, USE-2, 




THHW, THW, 


RHW-2, USE-2, 




Size AWG or 




THWN, XHHW, 


XHH, XHHW, 


Types TW, 


THWN, XHHW, 


XHH, XHHW, 




kcmil 


Types TW, UF 


USE, ZW 


XHHW-2, ZW-2 


UF 


USE 


XHHW-2, ZW-2 












ALUMINUM OR COPPER-CLAD 








COPPER 






ALUMINUM 


Size AWG or kcmil 


18 


— 


— 


14 
18 

25 


— 


— 


— 


— 


14* 


20 


20 


z 


z 


_ 


_ 


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 


JIO 


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). 



70-148 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



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,^A).] 






60°C (140°F) 


75°C (167°F) 


90°C (194°F) 


60°C (140°F) 


75°C (UTF) 


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, 




Types 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 
16 

14* 


— 


— 


18 

24 
35 


— 


— 


— 


— 


25 


30 





_ 


_ 


_ 


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 


41^5 


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). 



2008 Edition 



NATIONAL ELECTRICAL CODE 



70-149 



310.15 



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(A).] 






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 



• 



70-150 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



310.1i 



Table 310.19 Allowable Ampacities of Single-Insulated Conductors, Rated Through 200§ 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(M] 






150°C (302°F) 


200°C (392°F) 


250°C (482°F) 


150°C (302°F) 








Types FEP, 










TypeZ 


FEPB, PFA, SA 


lypes PFAH, TFE 


lypeZ 












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 


177-194 


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 



2008 Edition NATIONAL ELECTRICAL CODE 



70-151 



310.15 



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 310.13i||.] 






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 kcmii 


COPPER 


ALUMINUM OR COPPERCLAD 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 


36-40 


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 



• 



70-152 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



3W.li 



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 


kcmll 


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 



2008 Edition NATIONAL ELECTRICAL CODE 



70-153 



310.60 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



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. 

(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 IEEE 835-1994 (IPCEA Pub. No. 
P-46-426), Standard Power Cable Ampacity Tables, and the 
references therein for availability of all 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)(2)(a) and (C)(2)(b). 

(a) Where burial depths are increased in part(s) of an 
electrical duct run, no decrease in ampacity of the conductors 
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 
TC-TA-ATD 



where: 

1 1 = ampacity from tables at ambient TA^ 

12 = ampacity at desired ambient TXj 

TC = conductor temperature in degrees Celsius (°C) 
7>\j = surrounding ambient from tables in degrees 

Celsius (°C) 
TA2 = desired ambient in degrees Celsius (°C) 
ATD = dielectric loss temperature rise 



• 



70-154 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 




Detail 1 

290 mm x 290 mm 
(11.5in. x1L5in.) 
Electrical duct bank 
One electrical duct 




190 mm (7.5 in.) 

Detail 2 

475 mm x 475 mm 
(19 in. X 19 in.) 
Electrical duct bank 
Three electrical ducts 
or 




190 mm 190 mm 
(7.5 in.) (7.5 in.) 

675 mm x 290 mm 
(27in. x11.5in.) 
Electrical duct bank 
Three electrical ducts 



A 


-® ® 


-® ® 


< > 



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 



600 mm 



Detail 5 

Buried 3 

conductor 

cable 

190 mm 
(7.5 in.) 



(24 in.) 

Detail 6 

Buried 3 

conductor 

cables 



600 mm 



190 mm 
(7.5 in.) 



Detail 7 

Buried triplexed 
cables (1 circuit) 



190 mm 190 mm 
(7.5 in.) (7.5 in.) 



(24 in.) 



Detail 8 

Buried triplexed 
cables (2 circuits) 



190 mm 190 mm 
600 mm J^ '") (''•^ '") 



Detail 9 

Buried single-conductor 
cables (1 circuit) 



(24 in.) 



Detail 10 

Buried single-conductor 
cables (2 circuits) 



Note: Minimum burial depths to top electrical ducts or cables shall be 
in accordance with 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 

Xj?\ Backfill (earth or concrete) 
O Electrical duct 
© Cable or cables 



Figure 310.60 Cable Installation Dimensions for Use with Table 310.77 Through Table 310.86, 



2008 Edition NATIONAL ELECTRICAL CODE 



)-155 



310.60 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



(D) Engineering Supervision. Under engineering supervi- 
sion, conductor ampacities shall be permitted to be calcu- 
lated by means of the following general formula: 



Table 310.68 Ampaciities 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) 



/ = 



TC-{TA + ATD) 
RDC{1 + 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. 



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) 

Temperature Rating of Conductor [See Table 
3mi3(C).] 





Temperature Rating of Conductor [Set 


; Table 






3Jft.l3(C;^.] 






2001-5000 Volts 


5001-35,000 Volts 




Ampacity 


Ampacity 


Conductor 




105°C 




105°C 


Size 


90°C 


(221°F) 


90°C 


(221°F) 


(AWG 


(194°F) 


Type 


(194°F) 


Type 


or kcmil) 


Type MV-90 


MV-105 


Type MV-90 


MV-105 


8 


50 


57 






6 


70 


77 


75 


84 


4 


90 


100 


100 


110 


2 


125 


135 


130 


150 


1 


145 


160 


150 


175 


1/0 


170 


185 


175 


200 


2/0 


195 


215 


200 


230 


3/0 


225 


250 


230 


265 


4/0 


265 


290 


270 


305 


250 


295 


325 


300 


335 


350 


365 


405 


370 


415 


500 


460 


510 


460 


515 


750 


600 


665 


590 


660 


1000 


715 


800 


700 


780 



Table 310.69 Ampacities of Insulated Single Copper 
Conductor Isolated in Air Based on Conductor Temperatures 





2001-5000 Volts 
Ampacity 


5001-35,000 Volts 
Ampacity 


of 90°C (194°F) and lOS^C (221°F) and Ambient Air 
Temperature of 40°C (104°F) 




Conductor 




105°C 




105°C 




Temperature Rating of Conductor [See 


! Table JJiqil3(€^.] 


Size 

(AWG 

or Itcmil) 


90°C 

(194°F) 

Type MV-90 

65 


(221°F) 

Type 

MV-105 


90°C 

(194°F) 

Type MV-90 


(221°F) 

Type 

MV-105 




2001-5000 Volts 
Ampacity 


5001-15,000 
Volts Ampacity 


15,001-35,000 
Volts Ampacity 


8 


74 




Conductor 


90°C 


105°C 


90°C 


105°C 


90°C 


105°C 


6 


90 


99 


100 


110 


Size 


(194°F) 


(221°F) 


(194°F) 


(221°F) 


(194°F) 


(221°F) 


4 


120 


130 


130 


140 


(AWG 


Type 


Type 


Type 


Type 


Type 


Type 


2 


160 


175 


170 


195 


or kcmil) 


MV-90 


MV-105 


MV-90 


MV-105 


MV-90 


MV-105 


1 


185 


205 


195 


225 


8 


83 


93 




















— 


1/0 


215 


240 


225 


255 


6 


110 


120 


110 


125 


— 


— 


2/0 


250 


275 


260 


295 


4 


145 


160 


150 


165 


— 


— 


3/0 


290 


320 


300 


340 


2 


190 


215 


195 


215 


— 


— 


4/0 


335 


375 


345 


390 


1 
1/0 


225 
260 


250 
290 


225 
260 


250 
290 


225 
260 


250 


250 


375 


415 


380 


430 


290 


350 


465 


515 


470 


525 


2/0 


300 


330 


300 


335 


300 


330 


500 


580 


645 


580 


650 


3/0 


345 


385 


345 


385 


345 


380 


750 


750 
880 


835 
980 


730 
850 


820 
950 


4/0 


400 


445 


400 


445 


395 


445 


1000 


250 
350 


445 
550 


495 
615 


445 
550 


495 
610 


440 
545 


490 
605 






















500 


695 


775 


685 


765 


680 


755 












750 


900 


1000 


885 


990 


870 


970 












1000 


1075 


1200 


1060 


1185 


1040 


1160 












1250 


1230 


1370 


1210 


1350 


1185 


1320 












1500 


1365 


1525 


1345 


1500 


1315 


1465 












1750 


1495 


1665 


1470 


1640 


1430 


1595 












2000 


1605 


1790 


1575 


1755 


1535 


1710 



70-156 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



Table 310.70 Ampacities of Insulated Single Aluminum 
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 310.72 Ampacities of an Insulated Three-Conductor 
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) 





Temperature Ratii 

2001-5000 Volts 
Ampacity 


[ig of Conductor [Se« 

5001-15,000 

Volts Ampacity 

90°C 105°C 
(194°F) (221°F) 

Type Type 
MV-90 MV-105 

87 97 
115 130 
150 170 
175 195 


; Table 310.13(G).] 

15,001-35,000 
Volts Ampacity 

90°C 105°C 
(194°F) (221°F) 

Type Type 
MV-90 MV-105 

175 195 


Conductor 

Size 

(AWG 

or kcmil) 


Temperature Rating of Conductor [See 

mmmA 


Table 




2001-5000 Volts Ampacity 

105°C 
90°C (221°F) 
(194°F) Type 
Type MV-90 MV-105 


5001-35,00 
Ampa( 


Volts 




90°C 
(194°F) 

Type 
MV-90 

64 

85 

115 

150 

175 


105°C 
(221°F) 

Type 
MV-105 

71 

95 

125 

165 

195 


:ity 


Conductor 

Size 

(AWG 

or kcmil) 


90°C 

(194°F) 

Type MV-90 


105°C 

(221°F) 

Type 
MV-105 


8 
6 
4 
2 
1 


8 
6 

4 

2 
1 


46 

61 

81 

110 

125 


51 

68 

90 

120 

140 


72 

95 

125 

145 


80 
105 
145 




200 
230 
270 
310 


225 
260 
300 
350 


200 
235 
270 
310 


225 
260 
300 
350 


200 
230 
270 
310 


225 
260 
300 
345 


165 


1/0 
2/0 
3/0 
4/0 


1/0 
2/0 


145 
170 


160 
185 


170 
190 


185 
215 


3/0 
4/0 


195 

225 


215 
250 


220 

255 




250 
350 
500 
750 


345 
430 
545 
710 


385 
480 
605 
790 


345 
430 
535 
700 


385 
480 
600 
780 


345 
430 
530 
685 


380 
475 
590 
765 


245 
285 


250 
350 
500 
750 
1000 


250 
310 
385 
495 
585 


280 
345 
430 
550 
650 


280 
345 
425 
540 
635 


315 
385 


1000 
1250 
1500 


855 

980 

1105 

1215 

1320 


950 
1095 
1230 
1355 
1475 


840 

970 

1085 

1195 

1295 


940 
1080 
1215 
1335 
1445 


825 

950 

1060 

1165 

1265 


920 
1055 
1180 
1300 
1410 


475 
600 
705 


1750 
2000 


TnhlP 11lrt.7 


"^ Aimir»nf>itips 


aiP itn Tnsiil!: 


it<»irfl TVinlpYPfi 


ni* Thrpp 



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 
310.13(C),] 



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) 

Temperature Rating of Conductor [See Table 
31.0^3(G).] 



2001-5000 Volts 
Ampacity 



Conductor 10S°C 

Size 90°C (221°F) 

(AWG (194°F) Type 

or kcmil) Type MV-90 MV-105 



5001-35,000 Volts 
Ampacity 

105°C 

(221°F) 
90°C (194°F) Type 
Type MV-90 MV-105 



2001-5000 Volts 
Ampacity 

Conductor 90°C 

Size (194°F) 105°C 

(AWG Type (221°F) Type 

or kcmil) MV-90 MV-105 



5001-35,000 Volts 
Ampacity 

90°C 
(194°F) 105°C 

Type (22rF) Type 
MV-90 MV-105 



59 

79 

105 

140 

160 



66 

88 
115 
154 
180 



93 
120 
165 
185 



105 
135 
185 
210 



55 

75 

97 

130 

155 



61 

84 

110 

145 

175 



83 
110 
150 
170 



93 
120 
165 
190 



1/0 
2/0 
3/0 
4/0 



185 
215 
250 
285 



205 
240 
280 
320 



215 
245 
285 
325 



240 
275 
315 
360 



1/0 
2/0 
3/0 
4/0 



180 
205 
240 
280 



200 
225 
270 
305 



195 
225 
260 
295 



215 
255 
290 
330 



250 
350 
500 
750 
1000 



320 
395 
485 
615 
705 



355 
440 
545 
685 
790 



360 

435 
535 
670 
770 



400 
490 
600 
745 
860 



250 
350 
500 
750 
1000 



315 
385 
475 
600 
690 



355 
430 
530 
665 
770 



330 
395 
480 
585 
675 



365 
440 
535 
655 
755 



2008 Edition NATIONAL ELECTRICAL CODE 



70-157 



310.60 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



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 



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) 













Conductor 
Size 

(AWG 
or kcmil) 


Temperature Rating of Conductor [Set 
31pil3(C;).] 


! Table 




Temperature Rating of Conductor [Set 

3ip.i3(e).] 


; Table 






2001-5000 Volts 
Ampacity 


5001-35,00 
Ampat 






2001-5000 Volts 
Ampacity 


5001-35,000 Volts 
Ampacity 


10 Volts 
:ity 




90°C 

(194°F) 

Type MV-90 


105°C 

(221°F) 

Type 
MV-105 


90° C 

(194°F) 

Type MV-90 




Conductor 

Size (AWG 


90°C 

(194°F) 
Type MV-90 

43 

58 

76 
100 
120 


105°C 
(221°F) 

Type 
MV-105 

48 

65 

85 
115 
135 


90°C 

(194°F) 
Type MV-90 

65 

84 
115 
130 


105°C 

(221 °F) 

Type 

MV-105 

72 

94 
130 
150 


105°C 

(221°F) 

Type 
MV-105 


or kcmil) 

8 
6 

4 

2 


8 
6 

4 

2 
1 


41 
53 
71 
96 
110 


46 

59 

79 

105 

125 


64 

84 

115 

130 


71 

94 

125 

145 


1 


1/0 
2/0 
3/0 
4/0 


130 
150 
170 
200 


145 
165 
190 

225 


150 
170 
195 

225 




1/0 
2/0 
3/0 


140 
160 
190 

215 


155 
175 
210 
240 


150 
175 
200 
230 


170 
200 
225 
260 


170 
190 

220 

255 


4/0 


250 
350 
500 
750 
1000 


220 
275 
340 
430 
505 


245 
305 
380 
480 
560 


250 
305 
380 
470 
550 




250 
350 
500 
750 


250 
305 
380 
490 
580 


280 
340 
425 
545 
645 


255 
310 
385 
485 
565 


290 
350 
430 
540 
640 


280 
340 
425 
520 
615 


1000 













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 






Mtlliii-] 










5001-35,000 Volts 




2001-5000 Volts Ampacity 


Ampacity 


Conductor 




105°C 




105°C 


Size 


90°C 


(221°F) 


90°C 


(221°F) 


(AWG 


(194°F) 


Type 


(194°F) 


Type 


or kcmil) 


Type MV-90 


MV-105 


Type MV-90 


MV-105 


8 


52 


58 






6 


69 


77 


83 


92 


4 


91 


100 


105 


120 


2 


125 


135 


145 


165 


1 


140 


155 


165 


185 


1/0 


165 


185 


195 


215 


2/0 


190 


210 


220 


245 


3/0 


220 


245 


250 


280 


4/0 


255 


285 


290 


320 


250 


280 


315 


315 


350 


350 


350 


390 


385 


430 


500 


425 


475 


470 


525 


750 


525 


585 


570 


635 


1000 


590 


660 


650 


725 



• 



70-158 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



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 [See Table 




Temperature Rating of Conductor [See Table 






31<K13(C).] 








3ip:i3(e).] 






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) 


(22rF) 


(194°F) 


(221°F) 


Size 


(194°F) 


(22rF) 


(194°F) 


(221°F) 


(AWG 


IVpe 


Type 


IVpe 


TVpe 


(AWG 


l^Pe 


lype 


Type 


Type 


or kcmil) 


MV-90 


MV-105 


MV-90 


MV-105 


or kcmil) 
One Circuit (See 


MV-90 
Figure 


MV-105 


MV-90 


MV-105 


One Circuit (See Fig 


ure 










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 


1 


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 



2008 Edition 



NATIONAL ELECTRICAL CODE 



70-159 



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 






3iq,13(G).] 




- 




3i«:43(e).] 






2001-i 


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 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 


1/0 


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 
6 

4 
2 
1 


46 
60 
77 
98 
110 


50 

65 

83 

105 

120 


63 

81 

105 

115 


68 

87 

110 

125 


8 
6 

4 
2 
1 


36 
46 
60 

77 
87 


39 
50 
65 
83 
94 


49 
63 
80 
90 


53 
68 
86 
98 


1/0 
2/0 
3/0 
4/0 


125 
145 
165 
185 


135 
155 
175 
200 


130 
150 
170 
190 


145 
160 
180 
200 


1/0 
2/0 
3/0 
4/0 


99 
110 
130 
145 


105 
120 
140 
155 


105 
115 
130 
150 


110 
125 
140 
160 


250 
350 
500 
750 
1000 


200 
240 
290 
350 
390 


220 
270 
310 
375 
420 


205 
245 
290 
340 
380 


220 
275 
305 
365 
405 


250 
350 
500 
750 
1000 


160 
190 
230 
280 
320 


170 
205 
245 
305 
345 


160 
190 
230 

275 
315 


170 
205 
245 
295 
335 



70-160 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



Table 310.81 Ampacities of Single Insulated Copper 
Conductors Directly Buried in Earth Based on Ambient 
Earth Temperature of 2€i°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 Eating of Conductor [Si 


se Table 






3io:e(G).] 








MMm)^ 






2001-5000 Volts 


5001-35,000 Volts 




2001-5000 Volts 


5001-35,000 Volts 




Ampacity 


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 


lype 


Type 


lype 


Type 


(AWG 


Type 


Type 


l>pe 


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 9.) 










310.60, Detail 9.) 










8 


110 


115 








8 


85 


90 








6 


140 


150 


130 


140 


6 


110 


115 


100 


110 


4 


180 


195 


170 


180 


4 


140 


150 


130 


140 


2 


230 


250 


210 


225 


2 


180 


195 


165 


175 


1 


260 


280 


240 


260 


1 


205 


220 


185 


200 


1/0 


295 


320 


275 


295 


1/0 


230 


250 


215 


230 


2/0 


335 


365 


310 


335 


2/0 


265 


285 


245 


260 


3/0 


385 


415 


355 


380 


3/0 


300 


320 


275 


295 


4/0 


435 


465 


405 


435 


4/0 


340 


365 


315 


340 


250 


470 


510 


440 


475 


250 


370 


395 


345 


370 


350 


570 


615 


535 


575 


350 


445 


480 


415 


450 


500 


690 


745 


650 


700 


500 


540 


580 


510 


545 


750 


845 


910 


805 


865 


750 


665 


720 


635 


680 


1000 


980 


1055 


930 


1005 


1000 


780 


840 


740 


795 


Two Circuits, 










Two Circuits, Six 










Six Conductors (Si 


ee Figure 








Conductors (See Figure 








310.60, Detail 10.) 










310.60, Detail 10.) 










8 


100 


110 








8 


80 


85 


_ 





6 


130 


140 


120 


130 


6 


100 


110 


95 


100 


4 


165 


180 


160 


170 


4 


130 


140 


125 


130 


2 


215 


230 


195 


210 


2 


165 


180 


155 


165 


1 


240 


260 


225 


240 


1 


190 


200 


175 


190 


1/0 


275 


295 


255 


275 


1/0 


215 


230 


200 


215 


2/0 


310 


335 


290 


315 


2/0 


245 


260 


225 


245 


3/0 


355 


380 


330 


355 


3/0 


275 


295 


255 


275 


4/0 


400 


430 


375 


405 


4/0 


310 


335 


290 


315 


250 


435 


470 


410 


440 


250 


340 


365 


320 


345 


350 


520 


560 


495 


530 


350 


410 


440 


385 


415 


500 


630 


680 


600 


645 


500 


495 


530 


470 


505 


750 


775 


835 


740 


795 


750 


610 


655 


580 


625 


1000 


890 


960 


855 


920 


1000 


710 


765 


680 


730 



2008 Edition NATIONAL ELECTRICAL CODE 



70-161 



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 [S 


lee Table 




Temperature Rating of Conductor [See Table 






310il3(e).] 








3ipj3(e).] 






2001-5000 Volts 


5001-35,000 Volts 


2001-i 


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 Figi 


ure 








One Circuit (See Figure 








310.60, Detail 5.) 










310.60, Detail S.) 










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 



• 



• 



70-162 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



310.(f 



Table 310.85 Ampacities of Three Triplexed 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 Triplexed 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 






mmm-i 








mm(m 






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 


10S°C 


90°c 


105°C 


90°C 


105°C 


Size 


(194°F) 


(221 °F) 


(194°F) 


(221 °F) 


Size 


(194°F) 


(22rF) 


(194°F) 


(221°F) 


(AWG 


.l^pe 


Type 


lype 


Type 


(AWG 


Type 


Type 


Type 


Type 


or kcmil) 


MV-90 


MV-IOS 


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 


1/0 


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 



2008 Edition 



NATIONAL ELECTRICAL CODE 



70-163 



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. 

L Installation 

312.2 I5affi^Hanp^;^l^llii^ In damp or wet loca- 
tions, surface-type enclosures within the scope of this ar- 
ticle 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 (V4-in.) airspace between the enclosure and the wall 
or other supporting surface. Enclosures installed in wet lo- 
cations shall be weatherproof. For enclosures in wet loca- 
tions, raceways or cables entering above the level of unin- 
sulated live parts shall use fittings listed 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. 

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 {Va in.). In walls constructed of 
wood or other combustible material, cabinets shall be flush 
with the finished surface or project therefrom. 

312.4 Repairing NoncombifetiblerSuifaefes. NondombusH 
tible surfaces that are broken or incomplete shall be re- 
paired so there will be no gaps or open spaces greater than 
3 mm ('/s 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 fi) 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 al- 
lowable cable fill in circular raceways. See 310.15(B)(2)(a) 
for required ampacity reductions for multiple cables in- 
stalled 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 shah not be 
deflected within a cabinet or cutout box unless a gutter having 
a width in accordance with Table 312.6(A) is provided. Con- 
ductors in parallel in accordance with 310.4 shall be judged on 
the basis of the number of conductors in parallel. 

(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 



• 



)-164 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 312 — CABINETS, CUTOUT BOXES, AND METER SOCKET ENCLOSURES 



312.10 



Table 312.6(A) Minimum Wire-Bending Space at Terminals and Minimum Width of Wiring Gutters 















Wires per 


' Terminal 














1 




2 






3 




4 


I 


5 


( 


Wire Size (AWG or 


















































kcmil) 


mm 




m. 


mm 


m. 


mm 




m. 


mm 


m. 


mm 


m. 


14-10 


Not 


specified 




























8-6 


38.1 




IVi 


— 


— 


— 




— 


— 


— 


— 


— 


4-3 


50.8 




2 


— 


— 


— 




— 


— 


— 


— 


— 


2 


63.5 




21/2 


— 


— 


— 




— 


— 


— 


— 


— 


1 


76.2 




3 


— 


— 


— 




— 


— 


— 


— 


— 


1/0-2/0 


88.9 




31/2 


127 


5 


178 




7 














3/0-4/0 


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. 



enter or leave the enclosure through the wall opposite its 
terminal. 



(2) Conductors Entering or Leaving Opposite 
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(G). 



312.7 Space in Enclosures. Cabinets and cutout boxes 
shall have sufl&cient 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 con- 
ductors feeding through or tapping off to other switches or 
overcurrent devices, unless adequate space for this purpose 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, and 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). 

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) StrengtSi. The design and construction of enclosures 
within the scope of this article shall be such as to secure 



2008 Edition NATIONAL ELECTRICAL CODE 



)-165 



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 


IV2 


— 


— 


— 




— 


— 


6 


4 


50.8 


2 


— 


— 


— 




— 


— 


4 


2 


76.2 


3 


— 


— 


— 




— 


— 


3 


1 


76.2 


3 


— 


— 


— 




— 


— 


2 


1/0 


88.9 


31/2 


— 


— 


— 




— 


— 


1 


2/0 


114 


41/2 


— 


— 


— 




— 


— 


1/0 


3/0 


140 


51/2 


140 


51/2 


178 


7 








2/0 


4/0 


152 


6 


152 


6 


190 


7'/2 


— 


— 


3/0 


250 


165" 


61/2'* 


165" 


61/2" 


203 


8 


— 


— 


4/0 


300 


178" 


7b 


190" 


7>/2" 


216" 


81/2" 


— 


— 


250 


350 


216'' 


SVi" 


229^^ 


81/2'* 


254" 


9b 


254 


10 


300 


400 


254^ 


10" 


254^* 


10** 


279" 


11" 


305 


12 


350 


500 


305^ 


12" 


305" 


12" 


330" 


13" 


356-^ 


14d 


400 


600 


330^ 


13" 


330" 


13" 


356" 


14" 


381" 


15" 


500 


700-750 


356^ 


14" 


356" 


14" 


381" 


15" 


406" 


16" 


600 


800-900 


38r 


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.) 
" 25.4 mm (1 in.) 
'^ 38.1 mm (11/2 in.) 
'' 50.8 mm (2 in.) 
" 76.2 mm (3 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. 



• 



70-166 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 314 — OUTLET, DEVICE, PULL, AND JUNCTION BOXES; CONDUIT BODIES; FITTINGS; AND HANDHOLES 



ample strength and rigidity. If constructed of sheet steel, the 
metal thickness shall not be less than 1.35 mm (0.053 in.) 
uncoated. 

(C) Noemetalllc Cabinets. Nonmetallic cabinets shall be 
listed, or they shall be submitted for approval prior to in- 
stallation. 

312.11 Spacing. The spacing within cabinets and cutout 
boxes shall comply with 312.11(A) through (D). 



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 in accordance with (A)(1), (A)(2), and (A)(3). 

(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 live metal part, including live metal 
parts of enclosed fuses, and the door. 

Exception: Where the door is lined with an approved insu- 
lating 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) Switcli 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 apparams 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. 



ARTI(E|E314 i 

Outlet, Device, Puli^j and Junction Boxes; 
Conduit BMies; Fittings; 
and Handliole Jinclosures 

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 
permitted only with open wiring on insulators, concealed 
knob-and-tube wiring, cabled wiring methods with en- 
tirely nonmetallic sheaths, flexible cords, and nonmetal- 
lic raceways. 

Exception No. 1: Where internal bonding means are pro- 
vided between all entries, nonmetallic boxes shall be per- 
mitted 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- 



2008 Edition NATIONAL ELECTRICAL CODE 



70-167 



314.4 ARTICLE 314 — OUTLET, DEVICE, PULL, AND JUNCTION BOXES; CONDUIT BODIES; FITTINGS; AND HANDHOLES 



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. 

314.4 Metal Boxes. I»^et^;^l3<)xe^ysh|i3jsb^ 

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 or Wet Locations. In damp or wet loca- 
tions, 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. 

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 0r;;generatorsi 

FPN: For volume requirements of motor origeiieratGE ter- 
minal housings, 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. 
Eaqh^lo^plxDf iaoill^Qf unbroken conductor not less than twice 
the minimum length required for free conductors in 300.14 
shall be counted twice. The conductor fill shall be calcu- 
lated 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 or similar 
canopy and terminate within that box. 

(2) Clamp Fill. Where one or more internal cable clamps, 
whether factory or field supplied, 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 
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 Equipment 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. A^d^wceior-iJ^lizMbi^ 
^|^gl^^!50;Mit||2; iiti^)^l§yi*?l Obfo^pat^f|estyHbed] -^^ P^j-e 
3>|4;l^P)Sshall;;ha*^;dpuble^ 

[Kr; -^^h^igangfeqii^ ;fopjiriy^iifingv 

(5) Equipment Grounding Conductor Fill. Where one 
or more equipment grounding conductors or equipment 
bonding jumpers enter a box, a single volume allowance 
in accordance with Table 314.16(B) shall be made based 
on the largest equipment grounding conductor or equip- 



70-168 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 314 — OUTLET, DEVICE, PULL, AND JUNCTION BOXES; CONDUIT BODIES; FITTINGS; AND HANDHOLES 314.17 



Table 314.16(A) Metal Boxes 



Box IVade Size 


1 

Minimum 
Volume 


Maximum Number of Conductors* 


mm 


in. 




cm^ 


in.^ 


18 


16 


14 


12 


W 


8 


6 


100 X 32 
100 X 38 
100 X 54 


(4 X VA) 
(4 X 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 11/4) 
(4x l'/2) 
(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 


(4H/16 X 11/4) 
(411/16 X 11/2) 
(411/16 X 21/8) 


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 


(3 x2x 11/2) 
(3x2x2) 
(3 X 2 X 21/4) 
(3 X 2 X 21/2) 
(3 X 2 X 23/4) 
(3 X 2 X 31/2) 


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 21/8 X 11/2) 
(4 X 21/8 X IVs) 
(4 X 21/8 X 2'/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 21/2) 
(33/4 X 2 X 31/2) 


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 (I3/4) 
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 cover/gang (I3/4) 
FD — multiple 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 Allovyance Required per Conductor 



• 





Free Space 


Within Box for Each 


Size of Conductor 




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 



ment bonding 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 allow- 
ance shall be made based on the largest equipment grounding 
conductor in the additional set. 



(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 they:;eahrib§ attached. The maximum num- 
ber of conductors permitted shall be the maximum number 
permitted by Table 1 of Chapter 9 for the conduit or tubing 
to which it is attached. 

(2) With Spikes, 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 



2008 Edition NATIONAL ELECTRICAL CODE 



)-169 



314.19 ARTICLE 314 — OUTLET, DEVICE, PULL, AND JUNCTION BOXES; CONDUIT BODIES; FITTINGS; AND HANDHOLES 



fittings 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 
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 in- 
stalled 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 (Vi 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 multicon- 
ductor Type UF cable is used with single gang boxes not 
larger than a nominal size 57 mm x 100 mm (2V4 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 (V4 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(G). 

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 ceilings with a sur- 
face of concrete, tile, gypsum, plaster, or other noncombus- 



tible 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 fisted extender will not be set back of the 
finished surface more than 6 mm (Vi 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 Drywall 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 {V% in.) at the edge of the box. 

314.22 Surface Extensions. Surface extensions shall be 
made by mounting and mechanically securing an extension 
ring over the box. Equipment grounding shall be in accor- 
dance with Bail. ;M of Article 250. 

Exception: A surface extension shall be permitted to be 
made from the cover of a 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 arranged so that any 
grounding continuity is independent of the connection be- 
tween 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 shall pass through the interior 
within 6 mm {Va in.) of the back or ends of the enclosure. 
Screws shall not be peiTnitted 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 



70-170 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 314 — OUTLET, DEVICE, PULL, AND JUNCTION BOXES; CONDUIT BODIES; FITTINGS; AND HANDHOLES 



• 



conditions. Polymeric braces shall be identified as being 
suitable for the use. 

(C) Mounting in Finislied Surfaces. An enclosure 
mounted in a finished surface shall be rigidly secured 
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 
ceihng cavity. 

(E) Raceway Supported Enclosure, Without Devices, 
Luminaires, or Lampholders. An enclosure that does not 
contain a device(s) other than splicing devices or support a 
luminaire(s), lampholder, or other equipment and is sup- 
ported 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 non- 
metallic conduit or electrical metallic tubing shall be permit- 
ted 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, or Lampholders. An enclosure that contains a 
device(s), other than splicing devices, or supports a lumi- 
naire(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 con- 
duits 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 inter- 
mediate metal conduit shall be permitted to support a box 
used for luminaire or lampholder support, or to support a 
wiring enclosure that is an integral part of a luminaire 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 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 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 or lampholder end, the conduit(s) 
is threaded wrenchtight into the box, conduit body, or inte- 
gral wiring enclosure, or into hubs identified for the pur- 
pose. Where a box or conduit body is used for support, the 
luminaire 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, 
or wiring enclosures within luminaires used in lieu of boxes 
in accordance with 300.15(B), shall be supported by rigid 



2008 Edition NATIONAL ELECTRICAL CODE 



)-171 



314.24 ARTICLE 314 — OUTLET, DEVICE, PULL, AND JUNCTION BOXES; CONDUIT BODIES; FITTINGS; AND HANDHOLES 



or intermediate metal conduit stems. For stems longer than 
450 mm (18 in.), the stems shall be connected to the wiring 
system with flexible fittings suitable for the location. At the 
luminaire 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 luminaire, 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 horizontally to the 
2.5 m (8 ft) elevation from windows, doors, porches, fire 
escapes, or similar locations. A luminaire supported by a 
single conduit shall not exceed 300 mm (12 in.) in any 
horizontal direction from the point of conduit entry. 

3Mi?4 Minjrnuiii^^ J)epth; ^;:R^ 

^d:XJ]tiUzatioii;Equ <^tlet-and;deyi(5e^l§)xjes^ 

hayensuffidie^ 

thenj;$G'y3ermpuiited; :|)r(^^ jwitli iswfficieiit|;l 

tQipi^enfl^ajfnajge^^t^ 

(A) Outlet^ Boxei^; Without ^Eiiclpsedi©(mces; ;or i IJtiliza^ 
tioii^;£^qai[:^m(ent. Np^^bbxi^shall^ave ;;^^|nteM2Ll.;.4!eptli:M 

(B) Oiirtl^tuaiidyBevide.; ffokes ■ ;mth;;EpCl<^ 
Mjs^sianitejiided; ta ^piicl^ 
tep^;jdef^Ko|'ii0tVie^ 

(G) lUlUizati6n:^E(quipmen(. Oiitlet^^andi'devieel'bp^ 

ertelosfi^^nizatiqn^^c^ 

nM:depth:thati.a(x:j^^ 

ieguipmerrt :tlie^eoiidUie^ 

egiii^raeiiE ;pie; ;iiitei^ 

that;,of ■ any^xtensioii^ 

pChe ^ toeriialide^ applicable iproyi? 

s&m;|>fi:(e)(;l|jthi^ 

(3:) Earge^^E^quipmeitt Kqxesr^Jthatj^^^clos^U^ 
e^uipraentilthat^ -pi^qjeats t -mo^: 0anH48:: mm; ; (JK^: :m;)iire^j 
ward^om^e^inouittiTig upland :of-thg^bojc;sha31^haAfe^(}^ 
thatlft; )Kit ^le|s; :thaffi t^ 

'iwmir'"'^ '"' ^ ' '^ ' "' 

(2) Conductptsltarger^Tli ]BOTes;thatleffi:ldse 
WtnizatiQir leqiaipftneffi ■l^ti^tj jthath^sl 
A^G : shal|;b!e adSMytiljed :fQr\ thsiri^^ecific ^fuiiQtiprii 

(3) Cc)iiductdi^^;8,ii6^[jor4 Boxes' ;thM^;anclpse^i^^ 
zatipfl j^^uipine^^ ^ha| 
haVe'attait^3iar 

(4) §!onduetcMhsi^|^iio^^ B0xes;^tKa|;e^Glosi^^iid^^^ 
xpc^nf I ecjitjipineiitn 

^alBihave 5 aii^ |ifteraM ^deptJa; ;that ;i^^notI^^^ ;tharv\3():2 j.inffi 



(l^f |h;)^^^here:t3ie.^e«|i^ Im^wstfi; pjiiS^the 

iiiQ|intiTig;^I)|aj^ 

bpx.;^^ ;]ipfe;|a^{i^ptKmbti 3ess^thaii;;that;xpf -the^ 

hay e ;:a^|rth ] thatus; ^ip^^ 

ExScepifqri^^ WtUmMom^qmpr^, 

314.25 Covers and Canopies, hi completed installations, 
each box shall have a cover, faceplate, lampholder, or lumi- 
naire canopy, except where the installation complies with 
410.a#(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 410.42(A) 
for metal luminaire canopies, and 404.12 and 406.5(B) for 
metal faceplates. 

(B) Exposed Combustible Wall or Ceiling Finish. Where 
a luminaire canopy or pan is used, any combustible wall or 
ceiling finish exposed between the edge of the canopy or 
pan and the outlet box shall be covered with noncombus- 
tible 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 Outlets. Boxes used at luminaire 
or lampholder outlets i^;a ceiling shall be designed for the 

purpose an(|^)Ml^b6*irequiredJ^ 

lampiMdier^'Qiffle^ in ; a: wall: sMllibe^designe^^ jfor; -the ;piii>i 

|)Os^^^£ffid.shMl.^b^ 

W-Ms9'^&M tliat^is;: peiina sup|:!e»rte{i; :b^^^;thei 

boxjjKthel^ptU^Hrfi At every outlet 

used exclusively for lighting, the box shall be designed or 

installed so that a luminaire may be attached. 

Exception: A wall-mounted luminaire 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, pro- 
vided the luminaire or its supporting yoke is secured to the 
box with no fewer than two No. 6 or larger screws. 



• 



70-172 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 314 — OUTLET, DEVICE, PULL, AND JUNCTION BOXES; CONDUIT BODIES; FITTINGS; AND HANDHOLES 314.29 



(B) Maximum Lemmaire Weight. Outlet boxes or fit- 
tings id(e^ign^|pKffie;supj? installed as 
required by 314.23 shall be permitted to support a/liirniH 
na'if^' weighing 23 kg (50 lb) or less. A luminaire that 
weighs more than 23 kg (50 lb) shall be supported indepen- 
dently of the outlet box unless the outlet box is listed m^. 
Marked for the |tt^|Enu^ 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 floors 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 Ceilieg=Suspended (Paddle) Fam Outlets. 
Outiet boxes or outlet box systems used as the sole support 
of a ceiling-suspended (paddle) fan shall be listed, shall be 
marked by their manufacturer as suitable for this purpose, 
and shall not support ceihng-suspended (paddle) fans that 
weigh more than 32 kg (70 lb). For outlet boxes or outlet 
box systems designed to support ceiling-suspended 
(paddle) fans that weigh more than 16 kg (35 lb), the re- 
quired marking shall include the maximum weight to be 
supported. 

(E) Ptpiiail|ditt^^wii^^ BoxeSfiKed^fOTJtKisu|^^ 
jJjffizatuDtf^uijgifl^ 
fffi|=pall^im^^;ttieJr^-^^ 
theMppoirt!iC)fi;S|L^^ 

Exception: "^tUizctiiGfi^&qi^^ '^t^l than 

Wfx^-^tf^ W'xesi: ^pyrW. 

'Mx'M}M^no^w€K thamltwo JA^lf^ ,^- ^^?^er ^j'c/ijw^.? 

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 that;are(:rp|[u|ceidite and for 

cables containing conductors of 4 AWG or larger, the mini- 
mum dimensions of pull or junction 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 raceways, 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 oj^Spicies. Where splices or where 
angle or U pulls are made, the distance between each race- 
way 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 largest raceway in a row. This distance shall be 
increased for additional entries by the amount of the sum of 
the diameters of all other raceway entries in the same row 
on the same wall of the box. Each row shall be calculated 
individually, 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. 



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 
bodies shall be provided with covers compatible with the 
box or conduit body construction and suitable for the con- 
ditions of use. Where used, metal covers shall comply with 
the grounding requirements of 250.110. 

(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 



2008 Edition NATIONAL ELECTRICAL CODE 



M73 



314.30 ARTICLE 314 — OUTLET, DEVICE, PULL, AND JUNCTION BOXES; CONDUIT BODIES; FITTINGS; AND HANDHOLES 



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 hkely to be 
imposed diiith^ni^ ;Piey - pKall^t)€i,adeIltiile^|■|c>i^ iise ^ijilundgf i^ 
grmiiid^!sy^temS; 

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) Enclosed li^iring. All enclosed conductors and any 
splices or terminations, if present, shall be listed as suitable 
for wet locations. 

(D) Covers. Handhole enclosure covers shall have an iden- 
tifying 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 
2S0:92(A^:|if;;the;lcc)ndu ih;:iatii^-;iiandhrale ^iatelsat^fe 
c6nduet0r§K^Gf 

torsi in; the li^ndJb©le^ajft^ l^fJeir jor ibi^chHcjmcuittcbnd^ 

III. 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 fit- 
tings 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 mm (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 (¥32 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. 

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 (Vsa 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 thiclcness 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 nonmetallic 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 



70-174 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 320 — ARMORED CABLE: TYPE AC 



320.10 



and legibly marked with the manufacturer's name or trade- 
mark. 



IV. Pull and Junction Boxes for Use on Systems over 
600 Volts, Nominal 



H 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. 

(B) Passing Through Partitions. Suitable bushings, 
shields, or fittings having smooth, rounded edges shall be 
provided where conductors or cables pass through parti- 
tions 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. 









L 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: 



2008 Edition 



NATIONAL ELECTRICAL CODE 



70-175 



320.12 



ARTICLE 320 — ARMORED CABLE: TYPE AC 



(1) FoTrif^djersJian^^ 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. 

(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 'A 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) or other electrical equipment and the cable 
and point of connection are within an accessible ceil- 
ing. 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. 



• 



• 



70-176 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 322 — FLAT CABLE ASSEMBLIES: TYPE FC 



(A) Thermal Insulation. Annored cable installed in ther- 
mal insulation shall have conductors rated at 90°C (194°F). 
The ampacity of cable installed in these applications 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|A)^ 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 ^^piiducior. Type AC 
cable shall provide an adequate path for piilti^^wsepi;^ 
reg|iJ^qci^by^|250;^ 

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. 



ARTICLE 322 

Flat Cable Assemblies: Type FC 



322.1 Scope. This article covers the use, installation, and 
construction specifications for flat cable assembhes, Type 
FC. 

322.2 Definition. 

Flat CaMe 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 follows: 



(1) As branch circuits to supply suitable tap devices for fight- 
ing, small appliances, 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 wiU 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. 

(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 assemblies are pulled into the raceways. 



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 Hangers. Luminaire 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. 



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 
assembly 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 



2008 Edition NATIONAL ELECTRICAL CODE 



J-177 



322.100 



ARTICLE 324 — FLAT CONDUCTOR CABLE: TYPE FCC 



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 assembhes 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 shall 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 
system 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. 

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 re- 
ceptacles. 

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 cir- 
cuits shall have ratings not exceeding 20 amperes. Indi- 
vidual branch circuits shall have ratings not exceeding 30 
amperes. 



70-178 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 324 — FLAT CONDUCTOR CABLE: TYPE FCC 



(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 simi- 
lar materials. 



5o 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. 

324.12 Uses Not Permitted. FCC systems shall not be 
used in the following 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 shall 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. 



tt 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. 



(A) Cable Connections and Insulating Ends. All Type 
FCC cable connections shall use connectors identified for 
their use, installed such that electrical continuity, insulation, 
and seahng against dampness and hquid spillage are provided. 
All 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. 

(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 ShneM, 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. 



(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 ground- 
ing conductor of the Type FCC cable shall be made to the 
shield system at each receptacle. 



igs. 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. AU transition assemblies 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 



2008 Edition 



NATIONAL ELECTRICAL CODE 



70-179 



324.60 



ARTICLE 326 — INTEGRATED GAS SPACER CABLE: TYPE IGS 



conductors, and for electrically 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 electrically 
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 nonmetallic 
materials shall be permitted for bottom shields. 

(2) Resistivity. Metal shields shall have cross-sectional ar- 
eas 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 insulat- 
ing materials in the FCC systems shall 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. 



ARTICLE 326 
Integrated Gas Spacer Cable: Type IGS 

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. 

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 


mm in. 


53 

78 

103 


2 
3 
4 


600 24 

900 35 

1150 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), includ- 
ing 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. 



70-180 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 328 — MEDIUM VOLTAGE CABLE: TYPE MV 



• 



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 


315 


4250 


491 


2000 


336 


4500 


505 


2250 


357 


4750 


519 



III. CoMstructlon SpecMcatioES 

326.104 Coeductors. The conductors shall be sohd alumi- 
num rods, laid parallel, consisting of one to nineteen 12.7 mm 
(Vz in.) diameter rods. The minimum conductor size shaU be 
250 kcmil, and the maximum size shall be 4750 kcmil. 

326.112 lesulatioe. The insulation shall be dry kraft paper 
tapes and a pressurized sulfur hexafluoride gas (SFg), both 
approved for electrical use. The nominal gas pressure shall be 
138 kPa gauge (20 pounds per square inch gauge). The thick- 
ness of the paper spacer shall be as specifiedin 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 Condett. 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. 

Table 326.116 Conduit Dimensions 



Conduit Size 



Actual 
Outside 
Diameter 



Actual Inside 



Metric Trade 
Designator Size 



53 

78 

103 



60 2.375 

89 3.500 

114 4.500 



49.46 
73.30 
94.23 



1.947 
2.886 
3.710 



ig. The cable shall be marked in accor- 
dance with 310.11(A), 310.11(B)(1), and 310.11(D). 






ARTICLE 3p;H:p|-r; 

Mediem \^ltage Cables j^pe'MV 



I. General 

328.1 Scope. This article covers the use, installation, and 
construction specifications for medium voltage cable. Type 

MV. 



fV. A single or multicon- 
ductor solid dielectric insulated cable rated 2001 volts or 
higher. 



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) Ii]|;pMyle;|Faysi!wHpe^ the use, in accor- 
iifc^'^WiS]^i3|3|i^ 

Exception: ^p^l^itca&ej,]thai^ metallic 

sMeqM mH l aml§Hn WsWMi'OffipU^ yi^^feqtii^pnents for 

^j^}M^-Miaj^M^&^:i^ 

pemiitiedi ^ Wffi fnsfhlM^iriI(^hleJtr^^ 'jrv: xiecpMance with 

m§3iBimr^ '''''-■'^'''""■^''-'""—-■-'--■-'^- 

(4) Direct buried in accordance with 300.50 

(5) In messenger-supported wiring iivacJ^OTdance] w^^ Part 
IJ!pApclftI^96 "^' ' 

(6) A|]expq^egfMfJinFac(^^ 

Exception: ^j^l^]^i:cdhl^:WHi^ 

'sh^atU ME WrriidXi I 'als0 ccmj^eM^^^ for 

Wyf>eiM(^}cafyle; lajri^imidmtifj^fl^^ '■ shall be 

P&miitedi\tgi 'bei ms0JJ^i\d^^i^^ 

FPN: The "Uses Permitted" is not an all-inclusive list. 

328.12 Uses Not Permitted, Type MV cable shall not be 
used whem^^po^dltfxMi]^^ for 

theiuse} 

328.80 Ampacity. The ampacity of Type MV cable shall 
be determined in accordance with 310.60. The ampacity of 



2008 Edition NATIONAL ELECTRICAL CODE 



70-181 



328.100 



ARTICLE 330 — METAL-CLAD CABLE: TYPE MC 



Type MV cable installed in cable tray shall be determined 
in accordance with 392.13. 



III. Construction Specifications 

328.100 Construction. Type MV cables shall have copper, 
aluminum, or copper-clad aluminum conductors and shall 
comply with W^M^MM and Table 310.13(D) or Table 
310.13(E). 

328.120 Marking. Medium voltage cable shall be marked 
as required by 310.11. 



ARTICLE 330 
Metal-Ciad 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 condi- 
tions 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 and:;a 
cori^s^n-i:e:5istahty^ 
tallic; stif ath.^ 
(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. 

(B) Specific Uses. Type MC cable shall be permitted to be 
installed in compliance with Parts II and III of Article 725 
and 770.133 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 Structure^^ or as 

Aerial Cable. Type MC cable installed outside of buildings 
OT;structures 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 undeft;eithfei^';Of-the:fo^ 

(1) Where subject to physical damage 

(2) Wh^emposeci't<|);m3ffpf?th^ 

ditions :iii(0 iW' (b) ■ Jtmless: ith^iffitj^^ 
Is; resistai^ to; the feOTd]tiohis;^;is[pQ^ 
resj^tanttgithe^ 

a: 0ireet;;:buried m'tJmleaiiiE^o^ 

ui^es^yidentified^pqt; ;dii^; burial 
b; Exposed; to iander^fill^inslr^ 

jcMisif^ctfiyapOT^'cx^ 

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. 

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). 



• 



70-182 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 330 — METAL-CLAD CABLE: TYPE MC 



(1) Ten times the external diameter of the metallic sheath 
for cable not more than 19 mm (Va 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 (I1/2 in.) in external diameter 

(3) Fifteen times the external diameter of the metallic 
sheath for cable more than 38 mm (IV2 in.) in external 
diameter 

(B) leterlocked-Type Armor or Comigated 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. 

330.3® Securing aed 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 support- 
ing is impractical; 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 
luminaire| or other electrical equipment and the cable 
and point of connection are within an accessible ceil- 
ing. For the purpose of this section. Type MC cable 
fittings shall be permitted as a means of cable support. 

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 listed and identified 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. 

(A) Type MC Calble 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. Conductors shall be of copper, alu- 
minum, copper-clad aluminum, mGkerip:{nickel-coated 
gO^ppi solid or stranded. The minimum conductor size 
shall be 18 AWG copper, mckel^;JM|5|ip:eil^pa^ 
and 12 AWG aluminum or copper-clad aluminum. 

330.108 Equipment Grounding WonSmiM' Where Type 
MC cable is used |^||r|pide5iH equipment grounding con- 
ductor, it shall comply wkhisb. 11 8(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 permitted by 725.49. Conductors larger than 
16 AWG shall be of a type listed in Table 310.13[A) 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 310.13(C): through Table 310.13(E). 



K116 Sheath. MetaUic covering shall be one of the fol- 
lowing types: smooth metallic sheath, corrugated metallic 
sheath, interlocking metal tape armor. The metallic sheath 



2008 Edition NATIONAL ELECTRICAL CODE 



70-183 



332.1 



ARTICLE 332 — MINERAL-INSULATED, METAL-SHEATHED CABLE: TYPE MI 



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 Ml 

L 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, T^pe MI. A 

factory assembly of one or more conductors insulated with 
a highly compressed refractory mineral insulation and en- 
closed in a liquidtight and gaslight 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 gasohne 

(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. 

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 metallic sheath 
for cable not more than 19 mm (Va- in.) in external 
diameter 

(2) Ten times the external diameter of the metallic sheath 
for cable greater than 19 mm (3/4 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. 



70-184 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 334 — NONMETALLIC-SHEATHED CABLE: TYPES NM, NMC, AND NMS 



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. 



Insulated conductors enclosed within an overall 
nonmetallic jacket. 



(B) Single Type MI Conductors 
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 .^oii^iiicMr.. Where the 
outer sheath is made of copper, it shall provide an adequate 
path t0;sei^e!;SS;^:equipi^ 

p^;^ (S(t|5t^i^he$th||s[;nfe ^pf;listeeli?ra| JseparalB 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 continuous 
construction to provide mechanical protection and moisture 
seal. 






Ll Scope. This article covers the use, installation, and 
construction specifications of nonmetallic-sheathed cable. 



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. 



1.6 Listed, Type NM, Type NMC, and Type NMS 
cables shall be listed. 



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 220-2006, 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 



Nonmetalllc-Sheathed Cable. A factory assembly of two 
or more insulated conductors enclosed within an overall 
nonmetallic jacket. 



'. 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 



2008 Edition 



NATIONAL ELECTRICAL CODE 



70-185 



334.12 



ARTICLE 334 — NONMETALLIC-SHEATHED CABLE: TYPES NM, NMC, AND NMS 



(C) Type 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) 

Exception: Type NM, NMC, and NMS cable shall he per- 
mitied in Type I and U construction when installed within 
raceways permitted to he installed in Type I and I! 
iX)iisp;uction. 

(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 5I^;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) Iii;.8yet;orrxi^nflp;|G^ 

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- 
lic tubing. Schedule 80 PVC 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 conduit, or 
other approved means extending at least 150 mm (6 in.) 
above the floor. 

Type NMC cable installed in shallow chases ;or[grQb>V:es 
in masonry, concrete, or adobe, shall be protected iii^accdrr; 
idariGe(iwithjjtJie?]i^G^ and covered with 

plaster, adobe, or similar finish. 

(C) In Unfinished Basements andCpmwli^^^es. Where 
cable is run at angles with joists in unfinished basements 
puiiei^lispac^i it shall be permissible to secure cables 
not smaller than two 6 AWG or three 8 AWG conductors 
directly to the lower edges of the joists. Smaller cables 
shaU be run either through bored holes in joists or on run- 
ning boards. NM cable mstalled on JtKe wall of an unfin- 
ished basement shall be permitted to be installed in a listed 
conduit or tubing or shall: b^lpOpE^d^aW^aCc^ 

3M^: Conduit or tubing shall be; /provided; i\yitli?:i^isui^ 

msufatingi bushing or adapter at the point the cable enters 

the raceway. llie;iN]S|;caMe;shea^ 

pioiiduit; 0r; It^bing^^^cl^into; theSlratjfet ^orjitfey^ ^l)o|Se^Uess 

than??6pniin;;(!4^^ini|i;;^^ 

3M); mm -tl2^;"inv)p o|^ jthel pMht- A\^hereptiie.] cable ; ;eriters: |hci 

mnf^^.m^Xibm^ Metal conduit, tubing, and metal outlet 

boxes shall be cbnne^d:^q;;an:;e(pij^^ 

ti!^or: 

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 parallel 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 
accessible 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 shafl 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 
(41/2 ft) and within 300 mm (12 in.) of every outlet box, 



70-186 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 334 — NONMETALLIC-SHEATHED CABLE: TYPES NM, NMC, AND NMS 



• 



junction box, cabinet, or fitting. Flat cables shall not be 
stapled on edge. 

Sections of cable protected from physical damage by 
raceway shall not be required to be secured within the 
raceway. 



(A) Horizontal Reus Through Holes amd 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 (4!/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. 



Nonmetallic-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 
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. 



(A) Boxes of lesulating Material. Nonmetallic outlet 
boxes shall be permitted as provided by 314.3. 

(B) Devices of iKisulatimg Material. Switch, outlet, and 
tap devices of insulating material shall be permitted to be 
used without boxes in exposed cable wiring and for rewir- 
ing 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 con- 
ductors are by binding-screw terminals, there shall be avail- 
able as many terminals 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). 



334.8® 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 instaired, without 
mSuMaiiiingfi^ same 

opemtig^i'n wood framing that is to be fire- or draft-stopped 
using thermal insulation, jcaiilkj or sealing foam, the allow- 
able ampacity of each conductor shall be adjusted in accor- 
dance with Table 310.15(B)(2)(a) indH^yfirp/^isioiis of 
310;|5:(AJ(^ppxcepHfemi5^^ 

^^i(ljfei^JiiioreJ-th!^ or 

t|i<?|^^ci^ent^^^ contact 

IwithSperfnafl^^ffist^^ fjjnaihtainiiigp^ be- 

twei^ ;^abl|s^p ^the; l Wmra^oWW^^ 



M Construction. The outer cable sheath of non- 
metallic-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 je^rrtiriumc^ conductors 

shall comply with Part V of Article 800. 

334.108 Equipment Grounding CottHuctiSr;. In addition 
to the insulated conductors, the cable shall have an insu- 
lated, ieoveped^ or bare ^liiprtteifltgiW^hdil^ 

334.112 Insulation. The insulated power conductors shall 
be one of the types listed in Table 310.13j(A)" that are suit- 
able 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. 



1.116 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. 



L The overall covering shall be flame re- 
tardant, moisture resistant, fungus resistant, and corro- 
sion resistant. 



2008 Edition NATIONAL ELECTRICAL CODE 



70-187 



336.1 



ARTICLE 336 — POWER AND CONTROL TRAY CABLE: TYPE TC 



(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 conductors. 



ARTICLE 336 
Power and Control Tray Cable: Type TC 

I. General 

336.1 Scope. This article covers the use, installation, and 
construction 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. 

(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 760.49. 

(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). 

Exception: WUem:not]'m^^ 

and). 'J?etween. I Gabl^ '■. imy.S. ionrfj WMMtti<M. M0:iip!tneht: W'j^^ 
vi^^s-''^6rXaXMptM^ 

^ijMim^i&'^suffj^rtH WJie. \ (}bM^j}shM^^ be \ mecHaiiwallyl mipi 
ported] 'where \ exiting] thei cuMei W0, ftp! \ "emure-; that f the iMinif. 
mitfm i>endmg:mdms iis- motiexce^ded;: 
(8) Where installed in wet locations. Type TC cable shall 
also be resistant to moisture and corrosive agents. 

FPN: See 310.10 for temperature limitation of conductors. 

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 than 
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. 

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 metalhc 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 cables' shall be in sizes 18 AWG t0 1000 kcmil copper. 



70-188 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 338 — SERVICE-ENTRANCE CABLE: TYPES SE AND USE 



338.12 



• 



nic]Mp]?^MMl^TQGa^ and sizes 12 AWG through 

1000 kcmil aluminum or copper-clad aluminum. Insulated 
conductors of sizes 14 AWG, and larger copper, ni|K^!'€i 
nJSkfelfpSatedffeopperl; and sizes 12 AWG thr(3Jj^;||i^Jk£g 
rml aluminum or copper-clad aluminum shall be one of the 
types listed in Table 310.13^| or 'g)^?3;ipa31B5 that is 
suitable 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 760.49- 

(B) Thermocouple Circeits. 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 1 Circmt Conductors. Insulated conductors of 
18 AWG and 16 AWG copper shall also be in accordance 
with 725.49. 



16 Jacket. The outer jacket shall be a flame- 
retardant, nonmetallic material. 

336.1201 MarMeg. There shall be no voltage marking on a 
Type TC cable employing thermocouple extension wire. 



ARTICLE 338 

Service-Entrance Cabk" 

Tj'pes SE and USE 



338.1 Scope. This article covers the use, installation, and 
construction specifications of service-entrance cable. 

338.2 Definitioms. 

Service-Entrance Cable. A single conductor or multicon- 
ductor assembly provided with or without an overall cov- 
ering, 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. 



conductors and shall be installed in accordance with 230.6, 
230.7, and Parts II, III, and IV of Article 230. 

(B) Branch Circeits 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 ihermb-: 
set 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 2^5d32 and 

^diJM)/: wHerej :f/ii?; iww^i^wZaitef^ grounded conductor of the 
table^mtgma^ 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 
Feeders. 



for Branch Circuits and 



338.10 Uses Permitted, 

(A) Service=Entrance Conductors. Service-entrance 
cable shall be permitted to be used as service-entrance 



(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 Part II of Article 334. 

FPN: See 310.10 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 
shall be supported in accordance with 334.30. Type USE 
cable instaUed as underground feeder and branch circuit 
cable shall comply with Part II of Article 340. 

(^ Serw^^E^ti^ S^m^-M&m€^}cable (SE) 

pallMQtJbe?me;d;iim in the 
following; locations: 

(1) B^re'5^tq^p0^|fiy^pi|pd|^^ in 
pprda|iG^;wifh;i250^5()pA) 

(2) lInder^ur)d'Wi|I||Hr|^ 

(3) Rons^xtmprjbjra^^ unless 
flieiri^aUpjMcbm^ of Part I of 
AffiGle^225^;|ffidu||^p|^^ with 334.30 
G|;M:used;^s'^sseiigerr^ as permitted 

M^SmM-M^jI'irm^ 



2008 Edition NATIONAL ELECTRICAL CODE 



70-189 



338.24 



ARTICLE 340 — UNDERGROUND FEEDER AND BRANCH-CIRCUIT CABLE: TYPE UF 



(B) Underground Service-Entrance Cable. LJnderground 
service-entrance cable (USE) shall nol be used under the 
foll(3wing conditions or in the following locations: 

(1) For interior wiring 

(2) For aboveground installations except where USE cable 
emerges from the ground and is terminated in an enclo- 
sure at an outdoor location and the cable is protected in 
accordance with 300.5(D) 

(3) As aerial cable unless it is a multiconductor cable iden- 
tified for use aboveground and installed as messenger- 
supported wiring in accordance with 225.10 and Part li 
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 
permitted to have a bare copper conductor cabled with the 
assembly. Type USE single, parallel, or cabled conductor as- 
sembUes recognized for underground use shall be permitted to 
have a bare copper concentric conductor applied. These con- 
structions 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. 



ARTICLE 340 

Underground Feeder and Branch-Circuit 

Cable: Type UF 

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 conduc- 



tors with an integral or an overall covering of nonmetallic 
material suitable for direct burial in the earth. 

340.6 Listing Requirements. Type UF cable shall be listed. 

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 in- 
stalled, 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 nonheating 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 ^aiiy hazardous (classified) locationi^;^?refepJaspothH 
eiwis^-^I^ermitted 

(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 
II 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 



70-190 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 342 — INTERMEDIATE METAL CONDUIT: TYPE IMC 



• 



curve of the inner edge of any bend shall not be less than 
five times the diameter of the cable. 



• 



[) Ampacity. The ampacity of Type UF cable shall be 
that of 60°C (140°F) conductors in accordance with 310.15. 

IIL Construction Specifications 



K104 Condectors. The conductors shall be sizes 14 
AWG copper or 12 AWG aluminum or copper-clad alumi- 
num through 4/0 AWG. 

340.108 Equipment Grounding M&n&mtm. In addition 
to the insulated conductors, the cable shall be permitted to 
have an insulated or bare ii|ui|^rrfeM:groimd conductor. 

340.112 Insulation. The conductors of Type UF shall be 
one of the moisture-resistant types hsted in Table 
SIO.ISjgA) that is suitable for branch-circuit wiring or one 
that is identified for such use. Where installed as a substi- 
tute wiring method for NM cable, the conductor insulation 
shall be rated 90°C (194°F). 



1.116 Sheath. The overall covering shall be flame retar- 
dant; moisture, fungus, and corrosion resistant; and suitable 
for direct burial in the earth. 



(B) Corrosion Environments. IMC, elbows, couphngs, 
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 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. 

342.14 Dissimilar Metals. Where practicable, dissimilar 
metals in contact anywhere in the system shall be avoided 
to ehminate the possibility of galvanic action. 

Aluminum fittings and enclosures shall be permitted to 
be used with IMC. 

342.20 Size. 



• 



ARTICLE 342 

Intermediate Metal Condoit; Type IMC 



342.1 Scope. This article covers the use, installation, and 
construction specifications for intermediate metal conduit 
(IMC) and associated fittings. 

342.2 Deinition. 

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. 



ig Requirements. IMC, factory elbows and 
couplings, and associated fittings shall be hsted. 



342.10 Uses Permitted. 

(A) All Atmospheric Conditions and Occupancies. Use 
of IMC shall be permitted under all atmospheric conditions 
and occupancies. 



urn. IMC smaller than metric designator 16 
(trade size V2) shall 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. 



Bends of IMC shall 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. 



2008 Edition NATIONAL ELECTRICAL CODE 



J-191 



342.28 



ARTICLE 344 — RIGID METAL CONDUIT: TYPE RMC 



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 (¥4 in. taper per foot) shall be used. 

FPN: See ANSUASME B. 1.20. 1-1983, Standard for Pipe 
Threads, General Purpose (Inch). 

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), oriperMtl^Jtefe'iM 
aecqrdii#f?^it!);i42i^Q(f). 

(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 
termination. 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 ap- 
proved, conduit shall not be required to be securely fas- 
tened within 900 nmi (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 con- 
duit shall be permitted in accordance with Table 
344.30(B)(2), provided the conduit is made up with 
threaded couplings and such supports prevent transmis- 
sion of stresses to termination where conduit is de- 
flected 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. 

(<S) l]nsuppwrt©d;Racew^§. ^\^em^er^i|?^<i;:<^n^ 

or eceenl^c; p£ri0§Kputs^are^ ;Typs IMX| slwM 

l>e i|)erimtted;;td 'jt)e ^iiMj^ited: ■ whi^i?^ irkeewayjiis ' Sfot 

morexthatf gfisp ^ynm;] (}l;^i^in;)^ | ^ and ;^ reoflaiiisyj m^ ;iim 

jtength$;^vvithbMicoii^ 

i^i^'l^petibo^ 

teMMiliOTt jat^ gach?^^ 



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. 
Threadless 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(G) for the protection of conductors 4 
AWG and larger at bushings. 

342.56 Splices and Taps. Splices 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 

I. 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 



• 



70-192 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 344 — RIGID METAL CONDUIT: TYPE RMC 



• 



• 



• 



is generally made of steel (ferrous) with protective coatings 
or aluminum (nonferrous). Special use types are tedr^brass; 
and stainless steel. 

344.6 Listing Reqesremefflis. RMC, factory elbows and 
couplings, and associated fittings shall be listed. 



344.1® Uses Permitted. 

(A) Atmospheric Comditioms and Occepamdes. 



(I) iG^Irafii2^n^te§?£y^;§tam jSara 

iiized|s|edi^dM^nl^^!steel RMC shall be permitted un- 
der all atmospheric conditions and occupancies. 

be jm|t||Ie^: |p|^|diiie^^ j|pd?swiifl^^ 

(§) ^IiwI^piil^TOp' ^uWM:iMf UsW01§^|^rm 

|o;|)e^msl|^le(lfwK^ 

I^gidgalupipSffiBcj^^ irndira|t 

e^ftaeit]:w|t|inth^yj#^ 

su§pl^nie|ifary;i|o^ 



(4) ]E'et|cps|;|li^&V^i Ferrous raceways 

and fittings protected from corrosion solely by enamel shall 
be permitted only indoors and in occupancies not subject to 
severe corrosive influences. 

(B) ^oj^dpy^ Emvlrommeets. 

(1) |Salf MiizeiHStael^nSMinl^^ 
ip/I|^j^Ep)^^J€dup^ S§lvaiiizediste#^ 
^tMn|^s;:StbfeI^:a|M^8d;^rass 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. 

(2) Supplementai^yl'Ero Aluj. 
minjM: RMCl shM; be; proyijited: 

jaj^y Ji^ri^sipii; gpro ^-^rc^gS jin ^ cpflcrete? 'ObM 

(C) Cnmder Fill. Galy3Size^|steel|^^ 

brass RMC shall be permitted to be installed in or under 
cinder fill where subject to permanent moisture where pro- 
tected on all sides by a layer of noncinder concrete 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 cor- 
rosion 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. 



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. 



(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). 



dmem. 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. 



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. 



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 
centerline of the conduit shall not be less than indicated in 
Table 2, Chapter 9. 



1.26 Bends — Numbeir ira One Rem. There shall not be 
more than the equivalent of four quarter bends (360 degrees 
total) between pull points, for example, conduit bodies and 
boxes. 



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). 



[) 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) or-permitted.to be unsupported in 

adgGiTdaiice^witW344^; 30(<3) . 



2008 Edition NATIONAL ELECTRICAL CODE 



70-193 



344.42 



ARTICLE 348 — FLEXIBLE METAL CONDUIT: TYPE FMC 



(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 termi- 
nation. 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 ap- 
proved, conduit shall not be required to be securely fas- 
tened within 900 mm (3 ft) of the service head for above- 
the-roof termination of a mast. 

(B) Supports. RMC 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 con- 
duit shall be permitted in accordance with Table 
344.30(B)(2), provided the conduit is made up with 
threaded couplings and such supports prevent transmis- 
sion of stresses to termination where conduit is de- 
flected between supports. 

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 


35-41 11/4-11/2 


4.3 


14 


53-63 2-21/2 


4.9 


16 


78 and larger 3 and larger 


6.1 


20 



(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 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 shall be permitted. 

(O) pn^ppaHed:R3^^^ ;Wli^ ;qye]^size4r tew|c^^ 

m iecGeritric ; ;lmockGiits\\:are ;\npt '■ jeiieounte^^^i Tj^f -iRIV^Q 

shall be iperrnitted; to beiunsuppOrted- wh£iK;the;j^cewiayj jis 

notmore ; thag; ^450; teiii ; ;(:IB! m)^;aiid(remams; jiiij ^nbroKen 

iMgtlis;'(Jwiffioiit;;(5^ 

ift aii^^iMrtletVbo^^^ "^iieMce^i^^^^^ 

termination! af jeach; end? of : thi; raeewayi 



344.42 Couplings and Connectors. 

(A) Threadless. Thieadless 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. 
Threadless 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. 

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(G) 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 thi-eaded. Longer or shorter lengths with 
or without coupling and threaded or unthreaded shall be 
permitted. 



ARTICLE 348 
Flexible Metal Conduit: 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. 



• 



• 



70-194 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 348 — FLEXIBLE METAL CONDUIT: TYPE FMC 



• 



• 



• 



• 



348.6 Listing Mequirememts. FMC and associated fittings 
shall be listed. 



348.1® Uses Permitted. FMC shall be permitted to be 
used in exposed and concealed locations. 

348.12 Uses Not Permittedo FMC shall not be used in the 
following: 

(1) I]ii^w0tl|0cati^ 

(2) In hoistways, other than as permitted in 620.21(A)(1) 

(3) In storage battery rooms 

(4) In any hazardous (classified) location ^s^pt^iiennit^ 
tbd^;by l^^tliS! ardfilfe^ -iifi^ thisr<I^j(^ 

(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 



Imum. FMC less than metric designator 16 (trade 
size Vt) shall not be used unless permitted in 348.20(A)(1) 
through (A)(5) for metric designator 12 (trade size Vs). 

(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 as permitted in 
410.^:P(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 
sections as permitted in 410.5l3^(C) 



imum. 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. 

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. 



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). 



Table 348.22 Maximum Number of Imsulated Conductors in Metric Designator 12 (Trade Size %) Flexible MetaJ Conduit* 





Types RFH 


-2, SF-2 


Types TF, XHHW, TW 
Fittings Fittings 


Types TFN, 


THHN, THWN 


Types FEP, F: 
Fittings 


EBP, PF, PGF 




Fittings 


Fittings 


Fittings 


Fittings 


Fittings 


Size 


Inside 


Outside 


Inside 


Outside 


Inside 


Outside 


Inside 


Outside 


(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 ihsuTated, covered, or bare equipment grounding conductor of the same size shall be permitted. 



2008 Edition 



NATIONAL ELECTRICAL CODE 



70-195 



348.42 



ARTICLE 350 — LIQUIDTIGHT FLEXIBLE METAL CONDUIT: TYPE LFMC 



Exception No. 1: Where FMC is fished betn^jefii-jac^ess 
poifuM':thmU^j!e^^ 

Exception No. 2: Where flexibility is ri^esmi^p^lfe^ 
Iqtipn, lengths shall not exceed the following: 

(1) 900 mm (3 ft) for metric designators 16 through 35 
(trade sizes V2 through IV4) 

(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 terminal connection for tap connections to lumi- 
naires as permitted in 410.1:Ii7{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) or 
other equipment. 

(B) Supports. Horizontal runs of FMC supported by open- 
ings through framing members at intervals not greater than 
1.4 m (41/2 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 afteiijiristal^tibn; an 
equipment grounding conductor shall be installed. 

Where flexibility is not required after in st^llatio^^ FMC 
shall be permitted 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. 



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 instaUation of electric conductors. 

350,6 Listing Requirements. LFMC and associated fit- 
tings shall be fisted. 

IL 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 shafl 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 V2) 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. 



• 



ARTICLE 350 

Liquidtight Flexible Metal Conduit: 

Type LFMC 



I. General 

350.1 Scope. This article covers the use, installation, and 
construction specifications for liquidtight flexible metal 
conduit (LFMC) and associated fittings. 



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 fill 
specified in Table 1, Chapter 9. 



• 



70-196 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 352 — RIGID POLYVINYL CHLORIDE CONDUIT: TYPE PVC 



352.1 



• 



(B) Metric Desigeator 12 (Trade Size %), The number of 
conductors shall not exceed that permitted in Table 348.22, 
"Fittings Outside Conduit" columns. 



350.56 Splices and Taps. Splices and taps shall be made 
in accordance with 300.15. 



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 Rue. There shall not be 
more than the equivalent of four quarter bends (360 degrees 
total) between pull points, for example, conduit bodies and 
boxes. 



g, 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 (41/2 ft). 

Exception No. 1: Where LFMC is fished 'BBMBkmqMt^,, 

Exception No. 2: Whef^!0exiMU0^ 
-Mi0y^Mgifis^0i^I^ 

(1) ^^O&mtM^ 

(2) U^Ox^mm^iC^^^^^fo^ 
'^Mi^M^SxT^'^th^ 

(3) jpi0C^»i;miJJ^;j(^;^ 

Exception No. 3: Lengths not exceeding L8 m (6 ft) from a 
luminaire terminal connection for tap conductors to lumi- 
naires, as permitted in 410JL1^C). 

Exception No. 4: 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) or 
other equipment. 



ts. Horizontal runs of LFMC supported by 
openings 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. 

350.42 Couplings and Connectors. Angle connectors 
shall not be used for concealed raceway installations. 



ng. Where used to connect 
equipment where flexibility is required after ihstaHation, an 
equipment grounding conductor shall be installed. 

Where flexibility is not required after installation, 
LFMC shall be permitted 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 50L30(B), 502.30(B), 503.30(B), |05^5(B), 
an(^j§06*.25(B) for types of equipment grounding conductors. 



350.120 Marking. 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. 



pii5^^;<Srt^n«ie^ Conduit: 



I. General 

352.1 Scope. This article covers the use, installation, and 
construction specifications for rigid ^lyyi§fTc|ilo^^ con- 
duit lEVCI and associated fittings. 

mf^ffiiig^I^KC^G(5n^ 



Rigid Eql|^yIrCilorii|s! Conduit I^C). A ri^idj nonme- 
tallic edidijif j|R=NC) of circular cross section, with integral 
or associated couplings, connectors, and fittings for the in- 
stallation of electrical conductors and cables. 



PVC conduit, factory el- 
bows, and associated fittings shall be hsted. 



352.10 Uses Permitted. The use of PVC conduit shall be 
permitted in accordance with 352.10(A) through (H). 



2008 Edition NATIONAL ELECTRICAL CODE 



70-197 



352.12 



ARTICLE 352 — RIGID POLYVINYL CHLORIDE CONDUIT: TYPE PVC 



FPN: Extreme cold may cause some nonmetallic conduits 
to become brittle and, therefore, more susceptible to dam- 
age from physical contact. 

(A) Concealed. p\^C:cpnduit shall be permitted in walls, 
floors, and ceilings. 

(B) Corrosive Influences. PYC'epJnduit shall be permitted 
in locations subject to severe corrosive influences as cov- 
ered in 300.6 and where subject to chemicals for which the 
materials are specifically approved. 

(C) Cinders. P¥(D?C(>ridiiit shall be permitted in cinder fill. 

(D) Wet Locations. PVG icbrigiuit shall be permitted in 
portions of dairies, laundries, canneries, or other wet loca- 
tions, and in locations 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 materi- 
als or be protected against corrosion by approved 
corrosion-resistant materials. 

(E) Dry and Damp Locations. P¥IC eoiiduit shall be per- 
mitted for use in dry and dainp locations not prohibited by 
352.12. 

(F) Exposed. PV(| ;coBdi.iit shall be permitted for exposed 
work. PV^i jcpiiduitjusedjexp^ tiaiWr 
a^vslmlUbie: idehlifiedifo)^ 

FPN: ]^e,@?nduit>^T^evvSGlie(^ 
areas ^f;physiciU;;da 

(G) Underground Installations. For underground installa- 
tions, homogehc^* ahd/nonhpnfiQ^enpi^ 

mittedJ r f6r:odipetiburial - ■ and : jundergroui^^ j^ M icphn 
crete^ See 300.5 and 300.50. . ' 

(H) Support of Conduit Bodies. PVC conduit shall be 
permitted to support nonmetallic conduit bodies not larger 
than the largest trade size of an entering raceway. These 
conduit bodies shall not support luminaires or other equip- 
ment and shall not contain devices other than splicing de- 
vices as permitted by 110.14(B) and 314.16(C)(2). 

352.12 Uses Not Permitted. p¥C;doiiduit shall not be used 
under the conditions specified in 352.12(A) through (F). 

(A) Hazardous (Classified) Locations. In any hazardous 

(classified) location, except as permitted b^^oth^; aiticle&pf 

(B) Support of Luminaires. For the support of luminaires 
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 
temperatures in excess of 50°C (122°F) unless listed 
otherwise. 

(E) Insulation Temperature Limitations. For conductors 
or cables operating at a temperature higher than the P^?(E; 
GOiiduit listed operating temperature rating. 

Exception: Conductors or cables rated at a temperature 
higher than the 'I^]{C^ conduit listed temperature rating shall 
be permitted to be installed in PVG -conduit^ provided they 
are not operated at a temperature higher than the PVC 
eonduit listed temperature 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. WCBf ePnduit smaller than metric designa- 
tor 16 (trade size Vi) shall not be used. 

(B) Maximum. PV C eoiidiiit 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 shah 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 
purpose. The radius of the curve to the centerUne 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. P^CiCpMuit shaU 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. PV;C eohduit shall be securely fastened 
and supported in accordance with 352.30(A) and (B) orp^r-J 
mtted;tia;be;itf^iLippc«te 



70-198 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 352 — RIGID POLYVINYL CHLORIDE CONDUIT: TYPE PVC 



352J6 



• 



• 



(A) Securely Fastemed. P^^G. conduit shall be securely fas- 
tened within 900 mm (3 ft) of each outlet box, junction box, 
device box, conduit body, or other conduit termination. Con- 
duit listed for securing at other than 900 mm (3 ft) shall be 
permitted to be installed in accordance with the listing. 

(B) Sepports. P¥G c'Ohdiiit shall be supported as required 
in iIablgl352;3|Q. Conduit listed for support at spacings 
other than as shown in Table 352.30 shall be permitted to 
be installed in accordance with the listing. Horizontal runs 
of PyCjcohduit supported by openings through framing 
members at intervals not exceeding those in \iM\Jsrf5230. 
and securely fastened within 900 mm (3 ft) of termination 
points shall be permitted. 

Table 352.3(1) Support of Rigid Poly vinyll Chloride Conduit 



(C) Dnsppgorted Raceways, ^iVhere oversized, concentric 
breccentric knoCkoiits are not^ e PVC conduit 

shaU be; permitted vtorbesurisupport^ the raceway is 

notrriore than 450 mm (18 in.) and remains in unbroken 
iehgthSi(^withoute6uplmg); Such raceway shall terminate in 
an ^outlet box, junjctiOT cabinet, or other 

termihatlbn at each end of the raceway. 



. Expansion fittings for PVC 
conduit shall be provided to compensate for thermal expan- 
sion and contraction where the length change, in accordance 
with Table 352.44, is expected to be 6 mm (V4 in.) or greater in 
a straight run between securely mounted items such as boxes, 
cabinets, elbows, or other conduit terminations. 



Maximemni Spacing Between 



Conduit Size 



Metric 








Designator 


Trade Size 


mmmi or im 


ft 


16-27 


1/2-1 


900 mm 


3 


35-53 


l'/4-2 


1.5 m 


5 


63-78 


21/2-3 


1.8 m 


6 


91-129 


3 1/2-5 


2.1 m 


7 


155 


6 


2.5 m 


8 



ngSo 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(G) for the protection of conductors 4 
AWG and larger at bushings. 



All joints between lengths of conduit, and 
between conduit and couplings, fittings, and boxes, shall be 
made by an approved method. 



Splices and taps shall be made 



Table 352.44 Expansion 
of Thermal Expansion = 



off PVC Rigid Nonm 
mEn/mm/X (3.38 x 1§"^ 



in accordance with 300.15. 

Conduit Coefficient 
m./°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 



2008 Edition NATIONAL ELECTRICAL CODE 



70-199 



352.60 



ARTICLE 353 — HIGH DENSITY POLYETHYLENE CONDUIT: TYPE HDPE CONDUIT 



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. 



FPN: : Refer to Articl^:352;for Rigid Polyvinyl Chloride 
GpnclCiit;' Type' iP VC "^nd- Artijel t-355, ^iov ? Rei Wforqed ■ Theiy 
rnQsefijhg Resiii Go tiduif. Type RTRC . 

353.2 Definition. 

High Density Polyethylene (HDPE) Conduit. A nonme- 
tallic raceway of circular cross section, with associated 
couplings, connectors, and fittings for the installation of 
electrical conductors. 



HI. Construction Specifications 

352;i00 jGohstfiittipii. I^Ci';C0hdiiitphall;'^b6;^ 
ngid^l^npnplasticized) ppjy ym^ ^C^Oivl 

diiit and fittings shall be composed of suitable nonmetallic 
material that is resistant to moisture and chemical atmo- 
spheres. For use aboveground, it shall also be flame retar- 
dant, resistant to impact and crushing, resistant to distortion 
from heat under conditions likely to be encountered in ser- 
vice, and resistant to low temperature and sunlight effects. 
For use underground, the material shall be acceptably resis- 
tant to moisture and corrosive agents and shall be of suffi- 
cient strength to withstand abuse, such as by impact and 
crushing, in handling and during installation. Where in- 
tended for direct burial, without encasement in concrete, 
the material shall also be capable of withstanding continued 
loading that is likely to be encountered after installation. 

352.120 Marking. Each length of P\^r ctHKlHil 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 aboveground, 
these markings shall be permanent. For conduit limited to 
underground use only, these markings shall be sufficiently 
durable 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 lim- 
ited to "limited smoke" and "sunlight resistant." 



T High Density PolJ^ethylene Conduit: : 

I. General 

353.1 Scope. This article covers the use, installation, and 
construction specifications for high density polyethylene 
(HDPE) conduit and associated fittings. 



353.6 Listing Requirements. HDPE conduit and associ- 
ated fittings shall be listed. 

II. 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. 

(5) i4t>G^! gF^PPfliJf^^f^s.proffibited 

jenca^d in riQmess^thaii;;50 ram"(2' iri.JI6f concreted 

353.12 Uses Not Permitted. HDPE conduit shall not be 
used under the following conditions: 

(1) Where exposed 

(2) Within a building 

(3) In any hazardous (classified) location, except as permit- 
ted Iryjc^er articles^ 

(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 listed operating tem- 
perature 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 Vi) shall not be used. 

(B) Maximum, HDPE conduit larger than metric designa- 
tor I55u(trad&isize^6) shall not be used. 



• 



• 



70-200 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 354 — NONMETALLIC UNDERGROUND CONDUIT WITH CONDUCTORS: TYPE NUCC 



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). 



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. 



J. 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 equip- 
ment, and the radius of the curve to the centerline of such 
bends shall not be less than shown in Table 354.24. 



III. Constmictiom Specifications 

353.100 Constractlom. HDPE conduit shall be composed 
of high density polyethylene that is resistant to moisture 
and chemical atmospheres. The material shall be resistant 
to moisture and corrosive agents and shall be of sufficient 
strength to withstand abuse, such as by impact and crush- 
ing, in handling and during installation. Where intended for 
direct burial, without encasement in concrete, the material 
shall also be capable of withstanding continued loading that 
is likely to be encountered after installation. 



ig. 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. 



L There shall not be 
more than the equivalent of four quarter bends (360 degrees 
total) between pull points, for example, conduit bodies and 
boxes. 



^^^:" ";'■"-" ".Article 354 ^ 

:fMonmetal!IC: /Underground Conduit with 
Z . Conductors^ Type NUCC 



• 



• 



ig. All cut ends shall be trimmed inside 
and outside to remove rough edges. 



353.46 BMShnmgs. 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(G) for the protection of conductors 4 
AWG and larger at bushings. 



353.48 JoflEts. All joints between lengths of conduit, and 
between conduit and couplings, fittings, and boxes, shall be 
made by an approved method. 

FPN: HDPE coiiduit can;;be joined using; eitlierr 
sibn, elecirbfusioh;; or mechanical i fittings: 

353.56 Splices and Taps. Splices and taps shall be made 
in accordance with 300.15. 

353.60 Grouedlng. 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. 



I. 

354.1 Scope. This article covers the use, installation, and 
construction specifications for nonmetallic underground 
conduit with conductors (NUCC). 



Noemetallic 

(NUCC). A factory assembly of conductors or cables inside 

a nonmetallic, smooth wall conduit with a circular cross 

section. 



354.6 Listing 
tings shall be listed 



s. NUCC and associated fit- 



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 
influences as covered in 300.6 and where subject to 
chemicals for which the assembly is specifically ap- 
proved 

(5) Aboy^gi^Guid, except- as prohibit^^ in 354712, "where 
encased in; not less than 50 mm (2 in.) of concrete. 



2008 Edition NATIONAL ELECTRICAL CODE 



70-201 



354.12 



ARTICLE 354 — NONMETALLIC UNDERGROUND CONDUIT WITH CONDLfCTORS: TYPE NUCC 



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 any hazardous (classified) location, except as permit- 
ted by other articles oTyMsiCpde 

354.20 Size. 

(A) Minimum. NUCC smaller than metric designator 16 
(trade size Vi) 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. 

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 


Vi 


250 


10 


21 


3/4 


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(G) 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 be- 
tween 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 re- 
quired, an assembly containing a separate equipment 
grounding conductor 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 listed and composed of a ma- 
terial that is resistant to moisture and corrosive agents. It 
shall also be capable of being supplied on reels without 
damage or distortion and shall be of sufficient strength to 
withstand abuse, such as impact or crushing, in handling 
and during installation without damage to conduit or con- 
ductors. 

(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. 



• 



• 



70-202 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 355 — REINFORCED THERMOSETTING RESIN CONDUIT: TYPE RTRC 



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. 



RiinfOTcedJTlierttibistettiiig 'l^sinf 



L 



355.1 Scope. This article covers the use, installation, and 
construction specification for reinforced thermosetting resin 
conduit (RTRC) and associated fittings. 

FPN: Refer to Article 352 for Rigid Polyvinyl Chloride 
Conduit: Type PVC, and Article 353 for High Density 
Polyethylene Conduit: Type HDPE. 



rigid nonmetallic conduit (RNC) of circular cross section, 
with integral or associated couplings, connectors, and fit- 
tings for the installation of electrical conductors and cables. 

355.6 Listing Reqeirememts, RTRC, factory elbows, and 
associated fittings shall be listed. 



355.1® Uses Permitted. The use of RTRC shall be permit- 
ted in accordance with 355.10(A) through (H). 

(A) Concealed. RTRC shall be permitted in walls, floors, 
and ceilings. 



i. RTRC 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. RTRC shall be permitted in cinder fill. 



Locations. RTRC shall be permitted in portions 
of dairies, laundries, canneries, or other wet locations, and 
in locations 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 pro- 
tected against corrosion by approved corrosion-resistant 
materials. 



(E) Dry and Damp Locations. RTRC shall be permitted 
for use in dry and damp locations not prohibited by 355.12. 

(F) Exposed. RTRC 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. 

(H) Support of Condeit Bodies. RTRC shall be permitted 
to support nonmetaUic conduit bodies not larger than the 
largest trade size of an entering raceway. These conduit 
bodies shall not support luminaires or other equipment and 
shall not contain devices other than splicing devices as 
permitted by 110.14(B) and 314.16(C)(2). 



355.12 Uses Not Permitted. RTRC shall not be used un- 
der the following conditions. 

(A) Hazardous (Classiied) Locations. 

(1) In any hazardous (classified) location, except as permit- 
ted by other articles in this Code 

(2) In Class I, Division 2 locations, except as permitted in 
501.10(B)(3) 

(B) Support of Luminaires. For the support of luminaires 
or other equipment not described in 355.10(H). 

(C) Physical Damage. Where subject to physical damage 
unless identified for such use. 

(D) Ambient Temperatures. Where subject to ambient 
temperatures in excess of 50°C (122°F) unless listed 
otherwise. 

(E) Insulation Temperature Limitations. For conductors 
or cables operating at a temperature higher than the RTRC 
listed operating temperature rating. 

Exception: Conductors or cables rated at a temperature 
higher than the RTRC listed temperature rating shall be 
permitted to be installed in RTRC, provided they are not 
operated at a temperature higher than the RTRC listed 
temperature rating. 

(F) Theaters and Similar Locations. In theaters and simi- 
lar locations, except as provided in 518.4 and 520.5. 

355.20 Size. 

(A) Minimum. RTRC smaller than metric designator 16 
(trade size V2) shall not be used. 



L RTRC larger than metric designator 155 
(trade size 6) shall not be used. 



2008 Edition NATIONAL ELECTRICAL CODE 



70-203 



355.22 



ARTICLE 355 — REINFORCED THERMOSETTING RESIN CONDUIT: TYPE RTRC 



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). 

355.22 Number of Coniductors. 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 respec- 
tive cable articles. The number of cables shall not exceed 
the allowable percentage fill specified in Table 1, Chapter 9. 

355.24 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 
purpose. The radius of the curve to the centerUne of such 
bends shall not be less than shown in Table 2, Chapter 9. 

355.26 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. 

355.28 Trimming. All cut ends shall be trimmed inside 
and outside to remove rough edges. 

355.30 Securing and Supporting. RTRC shall be installed 
as a complete system in accordance with 300.18 and shall 
be securely fastened in place and supported in accordance 
with 355.30(A) and (B) or permitted to be unsupported in 
accordance with 355.30(C). 

(A) Securely Fastened. RTRC 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. RTRC shall be supported as required in 
Table 355.30. Conduit Usted for support at spacing other 
than as shown in Table 355.30 shall be permitted to be 
installed in accordance with the listing. Horizontal runs of 
RTRC supported by openings through framing members at 
intervals not exceeding those in Table 355.30 and securely 
fastened within 900 mm (3 ft) of termination points shall be 
permitted. 

(C) Unsupported Raceways. Where oversized, concentric 
or eccentric knockouts are not encountered, Type RTRC 
shall be permitted to be unsupported \yhere the raceway is 
not more than 450 mm (18 in.) and remains in unbroken 
lengths (without coupling). Such raceways shall terminate 
in an outlet box, device box, cabinet, or other termination at 
each end of the raceway. 

355.44 Expansion Fittings. Expansion fittings for RTRC 
shall be provided to compensate for thermal expansion and 



Table 355.30 Support of Reinforced Thermosetting Resin 
Conduit (RTRC) 







Maximum Spacing 


Conduit Size 


Between Supports 


Metric 






Designator 


Trade Size 


mm or m ft 


16-27 


1/2-1 


900 mm 3 


35-53 


11/4-2 


1.5 m 5 


63-78 


21/2-3 


1.8 m 6 


91-129 


31/2-5 


2.1 m 7 


155 


6 


2.5 m 8 



contraction where the length change, in accordance with 
Table 355.44, is expected to be 6 mm QA in.) or greater in 
a straight run between securely mounted items such as 
boxes, cabinets, elbows, or other conduit terminations. 

355.46 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(G) for the protection of conductors 4 
AWG and larger at bushings. 

355.48 Joints. All joints between lengths of conduit, and 
between conduit and couplings, fitting, and boxes, shall be 
made by an approved method. 

355.56 Splices and Taps. Splices and taps shall be made 
in accordance with 300.15. 

355.60 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. 

III. Construction Specifications 

355.100 Construction. RTRC and fittings shall be com- 
posed of suitable nonmetallic material that is resistant to 
moisture and chemical atmospheres. For use aboveground, 
it sfiall 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 sulficient strength to withstand 
abuse, such as by impact and crushing, in handling and 



70-204 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 356 — LIQUIDTIGHT FLEXIBLE NONMETALLIC CONDUIT: TYPE LFNC 



TahSe 355.44 
Coefficient of 



Characternstacs of Rennforced Thermosetting Resin Conduit 
Expansion = 2.7 x 10"^ mm/mm/°C (1.5 x 10"^ in./in./°F) 





Length Change of 






Length Change of 






Temperatmre 


RTRC Conduit 




Temperature 


RTRC Conduit 


Temperature 


Length Change of RTRC 


Change (°C) 


(mm/m) 




Change (°F) 


(mJim ft) 


Change (°F) 


Conduit (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 


J 


100 


1.80 


200 


3.60 



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. 



355,120 Markimg. Each length of RTRC shall be clearly 
and durably rnarked 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 aboveground, 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 lim- 
ited to "limited smoke" and "sunlight resistant." 



,,;p,.,.,-: ^RTICLE.356 
Oquidtight Flexible Noemetallic 

=H|:i'^;Coiidiiltt:iype LFNC ^ 



I. General 

356.1 Scope. This article covers the use, installation, and 
construction specifications for liquidtight flexible nonme- 
talhc conduit (LFNC) and associated fittings. 



Liquidtlglit Flexible Noemetallic Condunt (LFNC). A race- 
way of circular cross section of various types as follows: 

(1) A smooth seamless inner core and cover bonded to- 
gether and having one or more reinforcement layers 
between the core and covers, designated as Type 
LFNC-A 

(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 in- 
tegral reinforcement within the conduit wall, desig- 
nated 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. 



2008 Edition NATIONAL ELECTRICAL CODE 



70-205 



356.6 



ARTICLE 356 — LIQUIDTIGHT FLEXIBLE NONMETALLIC CONDUIT: TYPE LFNC 



356.6 Listing Requirements. LFNC and associated fit- 
tings shall be listed. 

IL 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 pur- 
pose. 

(5) Type LFNC-B shall be permitted to be installed 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. 

(7) Foi;::ehcaisemeri^^ 

356.12 Uses Not Permitted. LFNC shall 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) In any hazardous (classified) location, |exeijp|t;^;^n|it^ 
ted^by other aiBicles^jiivM^^ 

356.20 Size. 

(A) Minimum. LFNC smaller than metric designator 16 
(trade size Vi) shall not be used unless permitted in 
356.20(A)(1) or (A)(2) 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 as required 
in 410.^117:(C), or for utilization equipment 

(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 effectively 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 shaU 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 ex- 
ceeding 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 terminal connection for tap con- 
ductors to luminaires permitted in 410.if^(C). 

(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 shafl not be re- 
quired where installed in lengths not exceeding 1.8 m 



• 



• 



70-206 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 358 — ELECTRICAL METALLIC TUBING: TYPE EMT 



(6 ft) from the last point where the raceway is securely 
fastened for connections within an accessible ceiling to 
luminaire(s) or other equipment. 

356.42 Couplings and Coeraectors. 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 asid 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. 



356.100 Construction. LFNC-B as a prewired manufac- 
tured assembly shall be provided in continuous lengths ca- 
pable of being shipped in a coil, reel, or carton without 
damage. 



ig. 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. 









358.1 Scope. This article covers the use, installation, and 
construction specifications for electrical metallic tubing 
(EMT) and associated fittings. 



• 



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 listed. 



Electrical Metallic Tubing (EMT). An unthreaded thin- 
wall raceway of circular cross section designed for the 



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 in- 
stalled in concrete, in direct contact with the earth, or in areas 
subject to severe corrosive influences where protected by cor- 
rosion 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 mm (18 in.) under 
the fill. 

(4) In any hazardous (classified) location except as permit- 
ted by dtlienIitiele|;a|i?tH^ 

(5) For the support of luminaires or other equipment ex- 
cept 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 
possibility 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. 

358.20 Size. 

(A) Minimum. EMT smaller than metric designator 16 
(trade size Vi) shall not be used. 



2008 Edition NATIONAL ELECTRICAL CODE 



)-207 



358.22 



ARTICLE 360 — FLEXIBLE METALLIC TUBING: TYPE FMT 



Exception: For enclosing the leads of motors as permitted 
in 430.245(B). 

(B) Maximum. The maximum size of EMT 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. 

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) or permi1:tedttf;be^uhsu^ 
acconjance \#th; 35S:.30(G) . 

(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. 

(p) llnsuppwle^^pacje^ays. Whi#re:©yersip;ea^^iphee^ 

or r|e^eentne;;;lmpckG^^ aren ihot? ^jeiicountered^ 

shall: be; jpemiitted \ to be lihsiippdtted wh^; the race way ; is 

np ' rnor^ : jffia^;450 ; mm; -(IS -Inv); ■ and ■ ;reniaiii(^^ rii; iunbrpkeii 

l6iipiSu(^itiiout;^^ 

iii:an;OutIet.b(i)X;;deyijpe;bp^^^ 

each Jepfid; of Jthe; jac^way^ 

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. 

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 cou- 
plings shall be permitted. Where EMT with a threaded in- 
tegral coupling is used, threads for both the tubing and 
coupling shall be factory-made. The coupling and EMT 
threads shall be designed 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 iMetallic 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. 



70-208 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 360 — FLEXIBLE METALLIC TUBING: TYPE FMT 



# 



• 



360.6 Listing RequiremeiratSo FMT and associated fittings 
shall be listed. 



[) 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 



rmitted. FMT shall not be used as 
follows: 

(1) In hoistways 

(2) In storage battery rooms 

(3) In hazardous (classified) locations unless otherwise 
permitted under other articles in this Code 

(4) Underground 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) 



FMT smaller than metric designator 16 
(trade size Vi) shall 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 Uv^lfst^d. assembly or for luminaires. See 
410.imC). 



n. The maximum size of FMT shall be metric 
designator 21 (trade size V4). 

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. 



(A) FMT — Metric Desigmators 16 amd 21 (Trade Sizes 
Vz 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. 



(B) FMT — Metric Designator 12 (Trade Size %). The 
number of conductors in metric designator 12 (trade size 
Vs) shall not exceed that permitted in Table 348.22. 



(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 36(]).24(A) Minimum Radii for Flexning Use 

Mnnimeimi Radii 
for FlexJmig Use 



Designator 


IVade Size 


minni 


in. 


12 


3/8 


254.0 


10 


16 


>/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 



Radii 
for Fixed Bends 



Designator 


Trade Size 


mi in 


in. 


12 


3/8 


88.9 


31/2 


16 


'/2 


101.6 


4 


21 


3/4 


127.0 


5 



i'ittiegs. Fittings shall effectively close 
any openings in the connection. 

36(01.56 Splices and Taps. Splices and taps shall be made 
in accordance with 300.15. 



ling. FMT shall be permitted as an equip- 
ment grounding conductor where installed in accordance 
with 250.118(7). 



g. FMT shall be marked according to 



110.21. 



2008 Edition NATIONAL ELECTRICAL CODE 



70-209 



362.1 



ARTICLE 362 — ELECTRICAL NONMETALLIC TUBING: TYPE ENT <■ 



ARTICLE 362 

Electrical Noninetallic Tubing: 

T>pe 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 Tbbing (ENT). A nonmetalhc, ph- 
able, corrugated raceway of circular cross section with in- 
tegral or associated couplings, connectors, and fittings for 
the installation of electrical conductors. ENT is composed 
of a material that is resistant to moisture and chemical 
atmospheres 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 ceil- 
ings where the waUs, 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 assem- 
blies. The 15-minute-fimsh-rated thermal barrier shall 
be permitted to be used for combustible or noncombus- 
tible walls, floors, and ceilings. 

Exception to (2): Where a fire sprinkler system(s) is in- 
stalled in accordance with NFPA 13-2007, 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 
abovegrade. 



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 ceihngs where the suspended ceil- 
ings provide a thermal barrier of material that has at 
least a 15-minute finish rating as identified in listings 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 13-2007, 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 belowgrade, with fittings listed 
for the purpose. 

(8) Metric designator 16 through 27 (trade size V2 through 
1) as listed 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 'iii\y hazardous (classified) location, except as per- 
mitted by GtheraiiHjefes^ffi 

(2) For the support of luminaires 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 



• 



• 



70-210 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 362 — ELECTRICAL NONMETALLIC TUBING: TYPE ENT 



(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 sunhght resistant 

(10) Where subject to physical damage 



um. ENT smaller than metric designator 16 
(trade size Vi) shall not be used. 



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. 



;. 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 auxiliary 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 m One Run. There siiall not be 
more than the equivalent of four quarter bends (360 degrees 
total) between pull points, for example, conduit bodies and 
boxes. 

362.28 Trlmmfljig. 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 terminal connection for tap connections 



to lighting luminaires 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) or 
Other equipment. 

Exception No. 3: Fpr: concealed work in finished buildings 
or prefinisKeW wall pariels where such securing is imprac- 
ticable;; unbivken^}!^^ coupling) of ENT shall 
be permitted to be fished. 

(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. 



igs. 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(G) for the protection of conductors size 4 
AWG or larger. 

362.48 Joints. All joints between lengths of tubing and 
between tubing aiid 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. 



Where equipment grounding is re- 
quired, a separate equipment grounding conductor shall be 
installed in the raceway in cornpliance wifh Article 250, 



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 shall also be in- 
cluded in the marking. Marking for limited smoke shall be 
permitted on the tubing that has limited smoke-producing 
characteristics. 



2008 Edition NATIONAL ELECTRICAL CODE 



-211 



366.1 



ARTICLE 366 — AUXILIARY GUTTERS 



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 

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 Gutter. ^^ sheet raetaliehclosureu^^^^ 

Su^lemeiit wirii^i. spa^s "ial meter tcenters^J-^^ 

tefs, switqhboafds, aM ^irmiS ppM of wMiig syStenisJ 

The ■ ehclQ^ure ;ha% hijrtgied^or!]^ 

9nd protecting electricEil wires;; cable; and busbars: The}enclo-; 

siLire;is designedifS 

the;eiricl6sufes have byeiii^installedi^a Cofi^ 

Nonmetallic Auxiliary Gutter. ^ffa^iMiskM!^^^ 

metallic ^closure" used Ib-^^iip^ ' spa^s^Tal 

fheter :centers^ ■ distnbutimr -eentersi j^^tcMtoardS • ' aiid rsirnifi 
lar' pointsTof winng systenisj Th'efencl^^^^ has Mng&3 or 

rempvable^n;<^vei^r 

y/ires, cable, and " busbars . ^THe ^enclosure is designed f 6i 
coiiductqrs- ■ to .beVlaidTlpr, ^sef'Jm; jplai^e ; :afiteF:jthe5';enclosures 
have been' installed as fa comjplete^pteM. 

366.6 Listing Requirements. 

(A) Outdoors. Nonmetallic auxiUary 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 auxihary gutters installed in- 
doors shall be listed for the maximum ambient temperature 
of the installation. 



II. Installation 

366.10 Uses Permitted. 

(A) Sheet Metal Auxiliary Gutters. 



(1) Indoor and Outdoor Use. Sheet metal auxihary 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- 
ters to become brittle and therefore more susceptible to 
damage from physical contact. 

(2) Indoors. Nonmetallic auxiliary gutters shall be permit- 
ted to be installed indoors. 

366.12 Uses Not Permitted. Auxiliary 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 auxil- 
iary 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 auxihary gutter. The derating factors in 310.15(B)(2)(a) 
shall be applied only where the number of current-carrying 
conductors, including neutral conductors classified as current- 
carrying under the provisions of 310.15(B)(4), exceeds 30. 
Conductors for signaling circuits or controller conductors be- 
tween a motor and its starter and used only for starting duty 
shall not be considered as current-carrying conductors. 

(B) Nonmetallic Auxihary Gutters. The sum of cross- 
sectional areas of all contained conductors at any cross 
section of the nonmetallic auxiliary 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 



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ARTICLE 366 — AUXILIARY GUTTERS 



auxiliary gutter is 30 or less, the adjustment factors specified 
in 310.15(B)(2)(a) shall not apply. The current carried continu- 
ously in bare copper bars in sheet metal auxiliary gutters shall 
not exceed 1.55 amperes/mm^ (1000 amperes/in.^) of cross 
section of the conductor. For aluminum bars, the current 
carried continuously shall not exceed 1.09 amperes/mm^ 
(700 amperes/in.'^) of cross section of the conductor. 

(B) NonmetalMc Aexlliary Gutters. The derating factors 
specified in 310.15(B)(2)(a) shall be applicable to the 
current-carrying conductors in the nonmetallic auxiliary 
gutter. 

366.30 Seciirieg and Supportlmg. 

(A) Slieet Metal Auxiliary Getters. Sheet metal auxiliary 
gutters shall be supported throughout their entire length at 
intervals not exceeding 1.5 m (5 ft). 



imetallic Auxiliary Getters. 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). 



msiom Fstttrngs. 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.). 



js. Splices and taps shall comply 
with 366.56(A) through (D). 



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 Comdectors. 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 Meaitified. All taps shall be suitably identi- 
fied at the gutter as to the circuit or equipment that they 
supply. 

(D) Overcurreut ProtectioE. Tap connections from con- 
ductors in auxiliary gutters shall be provided with overcur- 
rent protection as required in 240.21. 



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. 



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. 



[) Grounding. Metal auxiliary gutters shall be con- 
riSet©dEHto?;,Jirt to an 

|^tji|pent"¥oii to the grounded conductor 

phemlpSMtted or 250.142. 



loes 



(A) Electrical and Mecliaiiical 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. Comer 
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 Mounded 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 off 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 (1 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. 



(A) Outdoors. Nonmetallic auxiliary gutters installed out- 
doors shall have the following markings: 



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368.1 



ARTICLE 368 — BUSWAYS 



(1) Suitable for exposure to sunlight 

(2) Suitable for use in wet locations 

(3) Installed conductor insulation temperature rating 

(B) Indoors. Nonmetallic auxiliary gutters installed in- 
doors shall have the following markings: 
(1) Installed conductor insulation temperature rating 



ARTICLE 368 
Biasways 



I. General Requirements 

368.1 Scope. This article covers service-entrance, feeder, 
and branch-circuit bus ways 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 vertically 
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 Irom physical 
damage. 

(b) In other than industrial establishments, where a 
vertical 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 installed where 
subject to severe physical damage or corrosive vapors. 

(B) Hoistways. Busways shall not be installed in hoistways. 

(C) Hazardous Locations. Busways shall 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 installed 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 



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ARTICLE 368 — BUSWAYS 



15m (50ft) 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. 

(C) Feeder or Brancli ClrcMits. 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, where 
the branch-circuit overcurrent device is part of the lumi- 
naire cord plug on cord-connected luminaires. 

Exception No. 3: Where luminaires without cords are 
plugged directly into the busway and the overcurrent device 
is mounted on the luminaire. 

(D) Matieg of Overcerrent Protection — Branch Cir- 
cuits. A busway used as a branch circuit shall be protected 
against overcurrent in accordance with 210.20. 

368.3® Support. Busways shall be securely supported at 
intervals not exceeding 1.5 m (5 ft) unless otherwise de- 
signed and marked. 

368.56 Branclies from Besways. 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 I^MC:'n^dl|MJlyyin^lt?^ 

(9) Type R3|R(I!^Jmnfo^ 

( 1 0) TyfjpHK TJiNCD ;MquMtight; ■flexible; 'nonmetpic; ;^plMm^ 

(11) Type EMT electrical metallic tubing 

(12) Type ENT electrical nonmetallic tubing 

(13) Busways 

(14) Strut-type channel raceway 

(15) Surface metal raceway 



(16) Surface nonmetallic raceway 

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. 



lies. 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 inter- 
change in accordance with 400.7 and 400.8 and the follow- 
ing 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 relief 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 (6ft) 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 Eeds. A dead end of a busway shah be 
closed. 

368.60 Grounding. Busway shall be ppipebled' to an 

e^pHpmenf ground^ equipment bond- 

i|f g ujrnperj^ ;or; t&. jthe: gmUnded' cohd where permitted 

i?:-;5eqMifed;jby^2^^ 



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. 



2008 Edition NATIONAL ELECTRICAL CODE 



-215 



368.214 



ARTICLE 370 — CABLEBUS 



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. 

368.234 Barriers and Seals. 

(A) Vapor Seals. Bus way 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: Vapor seals shall not be required in forced- 
cooled bus. 

(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 
similar methods shall be provided to remove condensed 
moisture from low points in bus way 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 flammable 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 Coiidiictor. 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. 



ARTICLE 370 
Cablebus 

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 



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ARTICLE 372 — CELLULAR CONCRETE FLOOR RACEWAYS 



372.2 



• 



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. 

Cablebus framework, where bonded, shall be permitted 
to be used as the equipment grounding conductor for 
branch circuits and feeders. 



jes of Coedectors. 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 Comdectors. 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 sup- 
ported at intervals not greater than 900 mm (3 ft) for hori- 
zontal runs and 450 mm (IV2 ft) for vertical runs. Vertical 
and horizontal spacing between supported conductors shall 
not be less than one conductor diameter at the points of 
support. 



Cablebus shall be pro- 
tected 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 Ttirouglh Walls and 



(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 re- 
quired, 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) Tlhrougti 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) Througli 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. 



D.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 conduc- 
tors. 



A cablebus installation shall be 
grounded and bonded in accordance with Article 250, ex- 
cluding 250.86, Exception No. 2. 



Each section of cablebus shall be 
marked with the manufacturer'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. 



■iCIeliiilaf ; sGoiicfete 'Floor ' ] 



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 



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. 



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372.4 



ARTICLE 374 — CELLULAR METAL FLOOR RACEWAYS 



Header. Transverse metal raceways for electrical conduc- 
tors, providing access to predetermined cells of a precast 
cellular concrete floor, thereby permitting the installation of 
electrical conductors from a distribution center to the floor 
cells. 

372.4 Uses Not Permitted. Conductors shall not be in- 
stalled in precast cellular concrete floor raceways as follows: 

(1) Where subject to corrosive vapor 

(2) In any hazardous (classified) location, except as permit- 
ted by otheriaitfeleS;iii;tiiis G^ 

(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 
shall 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 nurhber 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 shall be of metal and shall 
be fitted with grounded-type receptacles. A grounding con- 
ductor shall connect the insert receptacles to a positive 
ground connection provided on the header. Where cutting 
through the cell wall for setting inserts or other purposes 
(such as providing access openings between header and 
cefls), 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 shaU 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 outlets on loop wiring, 
shall be allowed in raceways. 

372,17 Ampacity of Conductors. The ampacity adjust- 
ment factors, provided in 310.15(B)(2), shaU apply to con- 
ductors installed in cellular concrete floor raceways. 



ARTICLE 374 
Cellular Metal Floor Raceways 



374.1 Scope. This article covers the use and installation 
requirements for cellular metal floor raceways. 

374.2 Definitions. 

Cellular Metal Floor Raceway. The hoflow spaces of cel- 
lular metal floors, together with suitable fittings, that may 
be approved as enclosures for electrical 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 electrical conductors, 
providing access to predetermined cells of a cellular metal 
floor, thereby permitting the installation of electrical con- 
ductors 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 pherartiG^;^ 

(3) In commercial garages, other than for supplying ceiling 
outlets or extensions to the area below the floor but not 
above 



• 



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ARTICLE 376 — METAL WIREWAYS 



FPN: See 300.8 for installation of conductors with other 
systems. 



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 m 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. 



Splices aod 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. 



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. 



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. 



D 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 race- 
way. In cutting through the cell wall and setting inserts, chips 
and other dirt shall not be allowed 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 cen- 
ters 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, electrical metallic tubing, or approved fit- 
tings. Where there are provisions for the termination of an 
equipment grounding conductor, nonmetallic conduit, elec- 
trical nonmetallic tubing, or liquidtight flexible nonmetallic 
conduit shall be permitted. Where installed in concrete, liq- 
uidtight flexible nonmetallic conduit shall be hsted 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. 



The ampacity adjust- 
ment factors in 310.15(B)(2) shall apply to conductors in- 
stalled in cellular metal floor raceways. 



\)Q 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 shall be smooth. 
Suitable bushings or fittings having smooth rounded edges 
shall be provided where conductors pass. 



^ppfiGLE376 



L General 



.1 Scope. This article covers the use, installation, and 
construction specifications for metal wireways and associ- 
ated fittings. 



Wireways. Sheet metal troughs with hinged or re- 
movable covers for housing and protecting electrical wires 
and cable and in which conductors are laid in place after 
the wireway has been installed as a complete system. 



Q) 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. 



2008 Edition 



NATIONAL ELECTRICAL CODE 



70-219 



376.12 



ARTICLE 376 — METAL WIREWAYS 



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 

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 and Ampacity. Mejffitr 

ber i^f i ;CX)ndiictOTS:: ian(J; th^ir;: ampaSity, jya^l^ic 

376.'22(A)'aSd;(B)f; 

(A) E|rdiSs|-S©dipiml:;^ 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. 

(B) Adjustment; ::l'iac^^ The ad^iastrfieilt factors in 
310.15(B)(2)(a) shall be applied only where the number of 
current-carrying conductors, including neutral conductors 
classified as current-carrying under the provisions 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 considered as 
current-carrying conductors. 

376.23 Insulated Conductors. Insulated conductors in- 
stalled in a metallic wireway shall comply with 376.23(A) 
and (B). 

(A) Deflected Insulated Conductors. Where insulated 
conductors 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 rrietallic wireway is deflected greater than 
30 degrees, dimensions corresponding to one wire per ter- 
minal in Table 312.6(A) shall apply. 

(B) Metallic Wireways 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 puUs 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 listed for other support 



intervals. The distance between supports shall 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 splices 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 installed 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 ter- 
minals of power distribution blocks shall comply with 
312.6(B). 

(4) Live Parts. Power distribution blocks shall not have 

ttnffisulateid live parts exposed;5^^ffiin=-a:;i^n^ 
m\ pp^tfie ; wii^way ^ci6ver Is'instalied^ 

376.58 Dead Ends. Dead ends of metal wireways shall 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 

;37CI00 Constilicticra, 

(M pl|B^toie^i=^|i(i|iM^^ W^^ 

shalli-be; jdQn|tri^^ sd^ W^:M6[^^^ 

and- ;nie!diMi|M'^ffif ^ 

(B) SiBslantiiErtlConst^ Wirewapj"sIiMl;be;pffSi3t^ 

stantial^epn^^ j>ro\qde;^?c^^ 

for ^thfi^coflt^tiediccffldiicto^ ;boii iiiitmoK and 



• 



70-220 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 378 — NONMETALLIC WIREWAYS 



378.23 



• 



# 



jiMntS:J^KpBbe;Mfadeitig^ 
tg|ppf;bY?]Metig^^^^ 

tiqnsv ppindn tte^ 

376.120 Marklmg. Metal wireways shall be so marked that 
their manufacturer's name or trademark will be visible after 
installation. 






378.1 Scope. This article covers the use, installation, and 
construction specifications for nonmetallic wireways and 
associated fittings. 

378.2 Definition, 



Flame retardant, nonmetallic 
troughs with removable covers for housing and protecting 
electrical wires and cables in which conductors are laid in 
place after the wireway has been installed as a complete 
system. 

378.6 Listing Reqwirements. Nonmetallic wireways and 
associated fittings shall be listed. 



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 hsted 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 pennit- 
ted byf0the£;artip@|ii]tliisyG^ 

(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 nonmetalhc wireway is listed 

(5) For conductors whose insulation temperature limita- 
tions would exceed those for which the nonmetallic 
wireway is listed 

378.21 Size of Conductors, No conductor larger than that 
for which the nonmetallic wireway is designed shall be 
installed in any nonmetallic 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 per- 
cent of the interior cross-sectional area of the nonmetallic 
wireway. Conductors 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). 



Where insulated 
conductors are deflected within a nonmetallic wireway, ei- 
ther at the ends or where conduits, fittings, or other race- 
ways or cables enter or leave the nonmetallic 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. 



imetallic Wireways Used as Pull Boxes. Where 
insulated conductors 4 AWG or larger are pulled through a 
wireway, 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 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 conduc- 
tors in the cable shall be used. 



2008 Edition NATIONAL ELECTRICAL CODE 



)-221 



378.30 



ARTICLE 382 — NONMETALLIC EXTENSIONS 



378.30 Securing and Supporting. Nonmetallic wireway 
shall 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 
shall 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 shall 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 for expansion characteristics of 
PVC conduit. The expansion characteristics of PVC non- 
metallic wireway are identical. 

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. 

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 
installation. Marking for limited smoke shall be permitted 
on the nonmetaUic wireways that have limited smoke- 
producing characteristics. 



ARTICLE 380 
Multioutlet Assembly 

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) location, except as permit- 
ted b^=ptherigiitiele$;ijiUthis;;^ 

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. 



ARTICLE 382 
Nonmetallic Extensions 



I. General 

382.1 Scope. This article covers the use, installation, and 
construction specifications for nonmetallic extensions. 

382.2 Definitions. 

:Coiic^il|?|5l(e; ;NoiiroetaIIiciEx^e|isio AJ|ist^;^Sembl^;gf 

t?wpv:=three^nOT='fottr^ 

a<OTinetallic : jaekstj ; aii jexCrtided ;tHei^ = or 

a;:sealed;|ioipiMal|icAGO¥e^ 

|mfacp7^eiisiop^ 

stitfaee :of palis': ;Qr^ ceipngs,! iaiid; ;eoneea][j?ci Wfj^ jj^mp^i^, 

tiife^ jlqiiit ;eo^^ tale; ^wallipajtieling^ 

sir other ;siinilaf ni^iiais; 



• 



• 



70-222 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 382 — NONMETALLIC EXTENSIONS 



Nonmetallic Extensiom. 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. 

|32i§ SsliBgjRl^uii^eills. (^nceMlabl^jflon 

ten|ii)nssp[d^ 

3Phej ;Staftjiig/s6jff^ ] device ifor .;t|j^5e?ct^sioni Jshalf ; cphj; 

!tMif|;andppT0>a^^ 

(1) SUfjiplfemehMyJiGy^ 

(2) Ei(^v^l0f|)ix)fe^^ 

(3) E^v^i<i^:ipi^|ptiQ^ 

(4) piejaM:ic)adt^|id@itniSw 

(5) Pfoiwd^pm 



ing outlet, but not on the floor or within 50 mm (2 in.) from 
the floor. 



382.10 Uses Permitted. Nonmetallic extensions shall be 
permitted only in accordance with 382.10(A), (B), and (C). 



_ t. The extension shall be from 

an existing outlet on a 15- or 20-ampere branch circuit. 

^herp- j£tyS)iiC(2ala^^ l&gm 

isptoiiTTgpu^^ 

^\ih;§i|ip£i«S 

(B) Exposed and in a Dry Location. The extension shall 
be run exposedj^iJrilsone^alfedj^s^^^^ and in 
a dry location. 

(C) Residential or Offices. For nonmetallic surface exten- 
sions mounted directly on the surface of walls or ceilings, 
the building shall be occupied for residential or oflBce pur- 
poses and shall not exceed three floors abovegrade. jWhere 
peStiSed^loriifiei'i^ 

|KaU:ibejpmmtifed;:m^^ 

FPN No. 1: See 310.10 for temperature limitation of 
conductors. 

FPN No. 2: See 362.10 for definition of 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 extensions 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 



(B) GdeceaIatoIe:?Noemet^H .Where identi- 
fied^ foi-; the; tKe^inomne^^ may be concealed 
with |)ain1^^textOTe -jj^ plaster, wallpa- 
{)^i:^e,l;Wifll3;paneliHg^[0^^ and in- 



(:&) NopmfelalJIciiEp.e^^ A bend that reduces the nor- 
mal spacing between the conductors shall be covered with a 
cap to protect the assembly from physical damage. 



ms. Concealable 
exteiisibiiis rshalli 3e' pennitted to be folded back over them- 

sel>^s;a)tfdifla;ttened;a for ihstallattion. 

382.3® Securing and Supporting. 

(M) :M^itMete|icHllxtOT Nonmetallic surface exten- 

sions shall be secured in place by approved means at inter- 
vals not exceeding 200 mm (8 in.), with an allowance for 
300 mm (12 in.) to the first fastening where the connection 
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. 



All surface- 
mouhted^coriGealable^^n^^ extension components shall 
be fiiffily/aiichored to the; wall or ceihrig using aii adhesive or 
ittechaiiieaf JaAibhOT identified for this use. 



Bgs. Each run shall terminate in a 
fittingiIconj1etjtor,;k)r box that covers the end of the assem- 
bly. All fittings, connectors, and devices shall be of a type 
identified for the use. 



(jM) ^tiitt^tffll|jEK;Este|isic|ns. One or more extensions 
shall be permitted to be run in any direction from an exist- 



(iA) Pece-ptecfes. AUrrecep.tades,:rgceptadle-^ and 

self^cfontairf^ \ deyices^ u$ed ; \yith concealable nonmetallic 
exteiisibns^ shall ^Udentified 

(B) Me€eptac|<?s,!aBffi:Hoppinig§. pReceptiacle housings and 
self^c^OntMne(f;deyicesv design for surface or for 

reces^|d:,moun^^ use with conceal- 

ableriMrirhetall^^^^ and self- 

containedHdevices^^half incorporate means for facilitating 
eiitryTiaiDid; terihiMtibn of concealable nonmetallic exten- 
sionsrJind;!^^^^ housing or device. 

Rede^J^acle Jahd self-coritained devices shall comply with 
406.%' Power and: cornmum outlets installed together 



2008 Edition NATIONAL ELECTRICAL CODE 



70-223 



382.56 



ARTICLE 384 — STRUT-TYPE CHANNEL RACEWAY 



in* edmm^^^^^^ sliall; ;b;e ' jperfriitteid; an' : aceordance; yvMi 

382.56 Splices and Taps. Extensions shall consist of a 
continuous unbroken length of the assembly, without 
splices, and without exposed conductors between fittings| 
cpiiiieetoi^l :or Taps shall be permitted where ap- 

proved fittings completely covering 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. 

HI; €pnsitructipnf^ 

N(cmm0tal^^ only) 

382.100 Cbttstrticitiptt. GorlegalM^le;^;5ftpi^^ 

sipiis : ]sKall; ;^ ^a; fflultiia^er |la^ 

C)f ; a; -denter ; imgi^ounded ■ cdiiductpr'; lencliaisedrijy j a= 'sectteied 

|imiMeduGOfidut^ i^ahdfi^; idyerali i isectipiied; ; pG^dmg 

c^hduttdr. 



3^MW, Marking. 

(^) ^aftfe. iGpncepableu^ 

c]fe£trly rand durably; ifriarkei 0n;bdtiti : sides:;at;iiitei^als pf ;not 

rriQre; ^han : 6if) ;■ rani: ;(M Hn:)'; wit^; the; iiiifi)!^ 

byjj3IQ0t|A|i:ajO;(i 

tion: 

(1) Matenal-pfcdhdut^ 

(2) MaS^KnwTOpmpeifati^ 

(3) i^mpacity 

and ^abl^ s ideMfi^ 

^;^peeified;Hi3831fp4. 



ARTICLE 384 
Strut-Type Channel Raceway 



382^104 Flat;G|raductOrs. Gdhce^able:ffi)hmetalli^ 
siQns;i.sHall:]b€;iii?diistmct^ 
ecpiivalent^ftp: i |4; AWG 
eMstracted;pei^3;82(^^ (B), and (Q. 

(E) lJngrtJoiMed;;Cdnd^ Tleffiirir 

gri^deicf^fcohdi^^ 

grounded flartpdndu^^ and (C) 

and identified in accordance with 310.12(C). 

(B) Gmunded;GoiMu(^ Th^ 

giwndedpp^^ ^hall^ Gphsislj ^df it^ ; ^ectidfite^lnner' flat 
CdiidiiGtprSf , ^t^/iencl£>se; ; th^ ! ; cen^iWgrgpMM 

yyi ;the; seetiPiied; gtCTJ^^ 
eprdaiiee: jwith' 200:6.- 

(£) Grpuiiding; ; iGondiictpr:: ; (iQurferi : iSeclioned; ;;La^ers). 

TKe^gimriding^cdndue 

tidned jcpiidiictdrs; 3^ :cdiidtictdC:&d 

urigmundfed;^ j iCGiiducto 

250ijf(J^)f 5);^ Th^igmUhdiMg'^dndue^ ishair =be iid^ 

tififedj :b5f l^iiyj ^piie i of ;:the ; ifeUd whgjpetjpdsf 

(1) As;;p0rinitted;iHjpQ.li9 

(2) i^^idlear ^e¥)^ihg 

(3) 0ne:f or ^indre cdntMuPus;^en; stripie^ 

(4) Thej terMi [^qp|)merit-i(3rdiini:t^ regulat JintejH 
yalsJtlwstog^ 

382.112 InsulatibH. Tlte:.ungrpunded:;ahd;:gi^un^ 
conductor layers:^h^ 

wiiv^3iQJ310i/T'lie^ ; grpitfiding = ediiductdr ! shall; ;be? fidyered: p^ 
iiisiiMed; 



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. 

384.6 Listing Requirements. Strut-type channel race- 
ways, 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. 

(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. 



• 



70-224 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 384 — STRUT-TYPE CHANNEL RACEWAY 



• 



(8) Ferrous channel raceways and fittings protected from 
corrosion solely by enamel shall be permitted only 
indoors. 

384.12 Uses Not Permitted. Strut-type channel raceways 
shall not be used as follows: 

(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 Coedectors. No conductor larger than that 
for which the raceway is listed shall be installed in strut- 
type channel raceways. 



Table 384.22 Chanmel Size and Inside Cross-Sectional Area 



The number of conduc- 
tors permitted in strut-type channel raceways shall not ex- 
ceed the percentage fill using Table 384.22 and applicable 
'c|osSrsb6Mona^^ 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: 



where: 
n = number of wires 
ca = channel area in square inches 
wa = wire area 



584.30 Securmg and Supportimg. 



A surface mount strut-type channel 
raceway shall be secured to the mounting surface with re- 
tention straps external to the channel at intervals not ex- 
ceeding 3 m (10 ft) and within 900 mm (3 ft) of each outlet 
box, cabinet, junction box, or other channel raceway termi- 
nation. 



L 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. 



Size 


Area 


40% 


Area* 


25% Area** 














Channel 


in.^ 


mm^ 


in.2 


nuTB 


in.^ 


mm^ 


15/8 X 13/16 


0.887 


572 


0.355 


229 


0.222 


143 


15/8 X 1 


1.151 


743 


0.460 


297 


0.288 


186 


IVs X P/s 


1.677 


1076 


0.671 


433 


0.419 


270 


15/8 X 15/8 


2.028 


1308 


0.811 


523 


0.507 


327 


15/8 X 2716 


3.169 


2045 


1.267 


817 


0.792 


511 


15/8 X 31/4 


4.308 


2780 


1.723 


1112 


1.077 


695 


11/2 X 3/4 


0.849 


548 


0.340 


219 


0.212 


137 


11/2 X 11/2 


1.828 


1179 


0.731 


472 


0.457 


295 


I1/2X 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. 



384.56 Splices amd 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. 



I. 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(13)1 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. 



384.100 CoMstrectiom. Strut-type channel raceways and 
their accessories shall be of a construction that distin- 
guishes them from other raceways. Raceways and their el- 
bows, couplings, and other fittings shall be designed such 
that the sections can be electrically and mechanically coupled 
together and installed without subjecting the wires to abrasion. 
They shall comply with 384.100(A), (B), and (C). 

(A) Material. Raceways and accessories shall be formed 
of steel, stainless steel, or aluminum. 



1. Steel raceways and accessories 
shall be protected against corrosion by galvanizing or by an 
organic coating. 



2008 Edition NATIONAL ELECTRICAL CODE 



)-225 



384.120 



ARTICLE 386 — SURFACE METAL RACEWAYS 



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. 



ARTICLE 386 
Surface Metal Raceways 



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 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. 

386.12 Uses Not Permitted. Surface metal raceways shall 
not be used in the following: 

(1) Where subject to severe physical damage, unless oth- 
erwise 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). 

(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. SpUces 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 signaling 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 



70-226 



NATIONAL ELECTRICAL CODE 2008 Edition 



ARTICLE 388 — SURFACE NONMETALLIC RACEWAYS 



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. 



ARTICLE 388 
Surface Nonmetallic Raceways 



I, 

388.1 Scope. This article covers the use, installation, and 
construction specifications for surface nonmetallic race- 
ways and associated fittings. 

388.2 Deimtlom. 

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.