16%
KLE6 1 RIQ> JjJ^H
THE KLAWITERS
1 61 56 A lei ma Avenue
'acific Palisades, California
Making knot.
The knot made.
Connecting socket. Spare wire end to be cut off.
PLATE I.
WIRING HOUSES
FOR THE
ELECTRIC LIGHT
TOGETHER WITH
SPECIAL REFERENCES TO L( )\V VOLTAGE
BATTERY SYSTEMS
BY
NORMAN H. SCHNEIDER
Author of Electrical Instruments and Testing: Management
of Electric Power Plants; Induction Coils
and Coil Making; &c, &c.
SECOND EDITION REVISED AND ENLARGED
NEW YORK :
SPON & CHAMBERLAIN, 123 LIBERTY ST.
LONDON :
E. & F. X. SPOX, Ltd, 57 HAYMARKET, S. W.
1916
(No. 33)
Copyright, 1911,
By Spon & Chamberlain-.
Copyright, 1916,
By Spon & Chamberlain.
ALL RIGHTS OF FOREIGN TRANSLATIONS ARE RESERVED
Tress of Barr & Hay field, 12 Dutch Street, New York, U. S. A.
SRLF
URL
PREFACE TO SECOND EDITION
A supply of electric current in the house for light-
ing, cooking, and for the operation of the labor-
saving household appliances is no longer looked on
as a luxury.
Electricity in the house is a necessity.
The wiring of the house therefore is a subject
awakening vast interest and the second edition of
this book has become necessary in order to keep
abreast of the constantly arriving improvements in
electrical work.
Although many farms and isolated dwellings are
installing low voltage plants of their own, operated
by a gasoline engine, there exists no reason why
the wiring itself should not be as safe as that re-
quired for the higher voltage of the Public Service
lines. Therefore, the directions in the succeeding
pages are devoted to first class work only, and that
suitable for all ordinary household voltages.
The rules of the National Board of Fire Under-
writers have been freely consulted, an extensive
digest with notes is given in a complete chapter of
this edition.
In addition to practically all the information con-
tained in the former edition, there has been added
thirty-two new pages on conduit wiring and con-
centric wiring and a number of full-page plates.
Condulets and other fittings for conduit work
have been described, together with BX armored
cable and the handling of it.
• • •
111
IV PREFACE
Concentric wiring, a system of wiring much used
abroad is treated on, several illustrations of the wire
and the new line of fittings being developed by the
General Electric Company being shown through the
courtesy of the latter company.
There exists some opposition in the United States
to this concentric wiring due solely to the fact that
it is supposed to be a rival of the present systems,
and its adoption to entail great losses to invest-
ments in tools and machinery devoted to the manu-
facture of the ordinary fittings. This is not logical.
Concentric wiring is an addition to the modern
methods and has its field in the less pretentious
dwellings. It is not likely to supplant any other
form of wiring to any extent for years to come
other than small circuits in open work or moulding.
It does, however, present a new additional line
of convenient fittings to be likened to the condulet
and BX lines.
The author wishes to thank the following for
illustrations or information :
The Bryant Electric Mfg. Company and The H.
T. Paiste Company for electric fittings. The
Sprague Electric for illustrations of BX armored
wire and multilets, the Crouse Hinds Company for
illustrations of condulets, the Western Electric
Company for illustrations from their book "Bright-
ening up the Farm," and to the General Electric
Company for illustrations and information on their
new line of concentric wiring appliances.
Also he expresses his appreciation to Mr. R. S.
Hale for information on concentric wiring, to Mr.
John Deegan for reading manuscript and to Mr.
Alfonso Ciani for the excellent photographs.
Norman H. Schneider.
Jersey City, N. J.
CONTENTS
CHAPTER I.
Introduction.
Lamp ho>cfers. The circuit defined.
CHAPTER II.
Planning the Wiring.
The plan to be followed. Material needed. Laying
out the work. Centering ceiling outlets. Marking
outlets with the bit. Wiring plans. Pockets.
Boring and tubing. Running the wires. Knobs
and their use. Wire. Making fast to the knobs.
Joints. Splicing, soldering and taping. Ceiling
boards. Finishing wiring 7
CHAPTER IIL
Completing the Installation
The service switch and its installation. Switch box.
Cut-outs. Iron box and fused switch 37
CHAPTER IV.
Installing the Lights.
The outlet wires. Installing the light*. Rosettes.
Making up drop lights. Fixtures. Wiring single
pole switches. Hall lights. Wiring three way
switch 46
VI CONTENTS
CHAPTER V.
Other Methods of Wiring.
Open or cleat work. Wiring in wooden moulding.
Moulding taps and cross overs. The wall moulding
method. Outdoor service. Bringing in the service
through iron pipe 60
CHAPTER VI.
Materials and Notes.
Estimating the material required. Loom, knobs,
split knobs, screws and nails. Mouldings. Bits.
Tapes. Table of copper wire. Figuring the size
of wire required 75
CHAPTER VII.
Conduit and Protected Wiring.
Conduit work safer. Armored cables. Installing
armored cables. Pipe conduit. Concentric wiring.. 84
CHAPTER VIII.
Underwriters Rules and Notes.
The National Code. General suggestions. Inside
work. Wires. Appliances. Conduit work 100
LIST OF ILLUSTRATIONS
FIG. PAGE
1 Weatherproof s. icket
2 Brass socket 3
3 Floor showing joists 1 1
4 Plan of house circuits 12
5 Plan " " 14
6 Plan " " 16
7 Plan " " 16
S Cutting floor board 17
9 Raising floor board 18
10 Floor showing tubing and wiring 20
11 View of pockets and wiring 23
12 Hitching wire to knob 25
13 Tying wire to knob 25
14 Protecting crossing circuit 27
15 Method of splicing 28
16 Making a tap 29
17 Placing ceiling boards 33
18 Main cut-out 40
19 Cut-out box with wires at top and bottom 41
20 Cut-out box with wires at top 4-
21 D. P. vS. T. Knife switch. Fused 43
22 D. P. Panel switch 43
23 Cut-out box for 2 circuits 44
24 Iron box and service switch 45
25 Wiring an outlet 46
26 Rosette for concealed work 48
27 Moulding rosette 48
28 Cleat work rosette 49
29 Unfused rosatte 49
vii
Vlll LIST OF ILLUSTRATIONS
FIG. PAGE
30 Making up drop light 50
31 Fixture, two lights 52
32 Wiring a switch 54
33 Single pole switch 55
34 Wiring single pole switch 56
35 Wiring three way switch 58
36 Turning corner. Cleat work 61
37 Paiste taplet 64
38 Paiste cross-over 65
39 Plan for wall moulding system 67
40 Wiring switch for wall moulding 68
41 Iron pipe for service 71
43 Service from pole 73
43 Tie and insulator 74
44 Insulator and iron, bracket 74
45 How to cut armored cable 89
LIST OF PLATES. face
PAGE
Plate L— Making up a Socket Frontispiece
Plate II. — Receptacle and switch 3
Plate III. — Making splices and taps 38
Plate IV. — Making up a drop light 50
Plate V.— Sprague BX and fittings 87
Plate VI. — Some typical Condulets 91
Plate VII. — General Electric Concentric wiring ap-
pliances 95
Plate VIII. — General Electric Concentric wiring ap-
pliances 97
Plate IX.— Example of pipe conduit wiring '. . 99
CHAPTER I.
Introduction.
Before light can be obtained from the in-
candescent lamp it must be placed in a suitable
receptacle or socket and connected to wires leading
from the battery.
The socket consists of a shell having insulated
contacts of brass, into which the lamp screws and
makes connection between its base and the con-
tacts in the socket.
The wires having been attached to this socket
convey the current through these contacts to the
filament in the lamp and the filament becomes white
hot, giving the desired illumination.
It is of vital importance that the wires carrying
current shall not touch each other when bared
or the current will flow through such point of
contact and cause a short circuit which is a sudden
rush of uncontrolled current.
Such a short circuit would very likely have dis-
astrous results if not guarded against. This is
done by covering the wires with a covering or in-
sulation which prevents the passage of electricity.
All metal parts which are to carry current are also
insulated either by hard rubber, porcelain or by
ae other suitable means.
WIRING HOUSES
One of the simplest sockets to hold the lamp is
shown in Fig. 1 having two short wires protruding
from the upper part which are to be spliced or
tapped on to the main wires of the circuit. The
socket being of porcelain is especially adapted for
use outdoors or in damp places. The wires may
be of any length desired if specially ordered but
usually they are a few inches in length. The
copper wire is stranded giving greater flexibility
and less likelihood of breaking off when the socket
is swayed by the wind.
Fig. 1.
In attaching to the circuit wires, the socket wires
are to be bared of insulation for about three inches,
scraped bright and twisted on. A good plan is to
divide the strands in each wire into two parts,
bending them at right angles so as to form the letter
T. The» each half is twisted around the circuit
wire separately in opposite directions which
ensures a good support for the socket and less
liability of breaking at the point of connection.
Receptacle
for lamp
directly con-
nected to
circuit.
The same receptacle for
lamp controlled by a
single pole snap switc-h.
Note loom protection
where wire crosses — a
tube also may be used
and is preferable where
two opposite circuits
cross.
PLATE II.
INTRODUCTION 3
As stated elsewhere all such connections should be
well soldered and taped.
Such an arrangement of a weatherproof socket
tapped on to a wire is of use in its place, that is in
damp locations, but for a dwelling house where
something more convenient and ornamental is
desired brass sockets are used as illustrated in
Fig. 2. These having no permanent wires for
ready connection like the weatherproof socket must
be attached by means of other pieces of wire, or
by flexible incandescent lamp cord.
Fig. 2.
These brass sockets are provided with a key pro-
truding from the side by means of which the current
may be turned on or off as desired thus controlling
the light. The key operates a switch in the socket,
which switch is a device consisting of fixed and of
movable contacts through which the current passes
when the switch is turned on. Turning off the
switch or key separates these contacts and the
current can no longer pass until the key is again
turned.
4 WIRING HOUSES
Switches are also made in a great variety for lo-
cation in cases where it is desired to turn on or off
the lights without reaching up to the socket. And
sockets are made as in the weatherproof socket
without keys or switches contained in them.
A combination of wires and lamps with their
accessories is known as a circuit.
Circuits. The simplest practical circuit would
consist of a pair of insulated wires leading from the
battery to a key socket holding the lamp. The
key of the socket being turned would either light
or extinguish the lamp. The essential parts then
of a circuit are the wires to carry the current, the
socket or holder for the lamp and the switch or key
to control the light. The wires would be insulated,
that is, covered with some substance which is not
a conductor of electricity to prevent a contact of
the metallic portion of the wires and thereby a
" short circuit."
In a simple circuit a few feet long the insulation
on the wires would be deemed sufficient to protect
the wires but where the wires are to be extended for
a distance they would have to be supported on
insulated supports.
The latter are of glass or porcelain, being gen-
erally called insulators, except the porcelain ones,
to which the common name of " knobs " is usually
given.
Other control of the light than by means of the
key in the socket would probably be unnecessary.
INTRODUCTION 5
Going a step farther a fuse would be added to
prevent the copper wire becoming dangerously hot
should an accidental short circuit or metallic con -
tact be made. This fuse would be a piece of special
lead alloy wire and would melt, opening the circuit
when the current became too strong. Lead alloys
are used because they melt at a lower temperature
than copper without becoming hot enough to do
damage before melting. Aluminum wire is also
employed for fuses but principally in the high
ranges of current. Other forms of fuses will be
treated of in their place.
Then another light might be added or perhaps
two by means of wires leading from the main wires.
These circuits extending for considerable distances
and being most probably permanent would be on
insulators or otherwise safely supported.
The next improvement would be switches to
control the lights and a main switch to cut off the
battery fTom all connection with the wires. The
main swicch and the porcelain fuse block should be
enclosed in an iron box or a wooden one lined with
asbestos.
Elaborations will of course suggest themselves
such as the installation of more lights, special
means of control, fixtures and methods of running
the wires to meet special requirements.
It is assumed that a house is ready for wiring and
the details of the number, location and size of the
lights have been decided upon.
While the scope of these pages is more particu-
WIRING HOUSES
larly directed to the wiring for low voltage lighting
from storage batteries, the methods described will
be suitable for regular 110 volt installations. In
the latter case the local rules affecting wiring should
be consulted, and if insurance is to be carried, the
insurance rules should be consulted. It is im-
possible to give in a book all the rules which are
often different in each State and town. So far as
possible all general rulings have been consulted in
preparing these directions and the methods to be
described are safe.
CHAPTER II.
Wiring A House.
Before starting to wire a house the plan or specifi-
cations should be decided upon showing the num-
ber and wattage of the lamps and the location of
the lamp outlets. (It is customary to use the term
outlet instead of lamp, as for, example, a house
would be wired for ten outlets, not for ten lights) .
The location of the switches should also be set-
tled as well as the point of entrance for the service,
that is where the wires from the electric light mains
or battery shall come in.
If a small private plant it may be located in the
cellar in which case the main switch or service
switch will be in the cellar. But if the plant is
located in an outhouse, then the wires must come
in the same as those from an electric light company
in most cases leading to insulators fastened to the
walls at a height from the ground but may lead
from there into the cellar if desired.
The exact location should be settled before wiring
as all wires to the lighting circuits in the house
must run to the service or main switch so that they
may be more conveniently controlled.
Material Required. It will be better to read
7
8 WIRING HOUSES
generally through the directions for wiring given
here and then survey the job before attempting to
figure out what material is required if the operator
is inexpert. For this reason much of the de-
scription of material has been left to a later chapter
and described separately. It then becomes a
simple matter to measure with a rule the amount
of wire wanted and the other supplies will be in
proportion. Of course such things as sockets and
switches depend upon the actual lighting require-
ments.
Laying Out the Job. Suppose it is desired to
conceal the wiring in a finished frame house. The
first thing is to lay out the outlets or points where
the lights are to go and mark the walls or ceiling
with a pencil cross at the spot, also marking in the
loeation of switches if any.
Where outlets are required in the centre of a room
the ceiling must be marked at the centre spot.
This may be done in two ways. The width of the
floor is first measured and the result divided in
half, a long line than being penciled on the floor
at this point, or a stick laid down at right angles to
the width of the room. The length of the room is
then measured and likewise halved, the place
where the half length and the half width meet is
the centre of the room. The center of the ceiling
may be readily found by means of a plumb bob
or a weight on a string held to the ceiling and shifted
until the plumb bob hangs directly over the mark.
WIRING A HOUSE 9
Where the string touches the ceiling marks the
center.
Another and quicker method usually followed
by the regular wireman is to procure a stick about
half the width of the room in length and standing on
a chair or step ladder shove one end of the stick
against the wall near the ceiling and mark on the
ceiling where the other end reaches. Then put it
against the other side of the room near the ceiling
and mark again in like manner. This is done four
times when the four marks on the ceiling being
all of equal distance from the walls can be used to
get the exact centre by means of a foot rule.
The stick must be held straight each time parallel
to the wall or the measurement will be off. Where
rooms are of irregular shape the centre or location
for the ceiling outlet may be decided arbitrarily.
In the case of a bay window, the latter is not to be
taken as included in the dimensions of the room,
but is to be ignored.
A long thin bit about one quarter of an inch in
diameter and say eighteen inches long is fastened
in a brace and carefully driven up through the mark
on the ceiling until it comes through the flooring of
the upstairs room.
The little hole in the floor will show whereto
take up the board later on. It is very rare that the
center of a floor will correspond with the centre
of the ceiling right below it as the upstairs rooms
are often laid out differently than those down stairs
For this reason it would be very hard to locate the
10 WIRING HOUSES
exact spot where the floor board should be removed
or the pocket cut in order to get exactly over the
ceiling outlet, unless this above method was pur-
sued. The hole bored by the small bit is hardly
noticeable in the flooring, except it be looked for.
Where a partition comes exactly over the bored
hole, the skirting or mop board must be removed.
This is best done by driving in the nails with a nail
punch and then lifting off the mop board. If it is
attempted to pry it off, it will be surely split and
the plaster may come off in patches. But having
driven in the nails there is nothing holding the
board in place but the edges of the plaster and the
fit with the floor.
Having drilled all the outlets and marked where
the switches are to go, the next thing is to figure out
the easiest and shortest route for the wires. This
will not only save labor and mistakes when the
work is under way but will enable a list to be made
of the material needed.
Taking the case of a two story frame dwelling
house with the service or battery plant in the
cellar, the outlets on the first floor will be wired
through holes or " pockets " cut temporarily in
the floor above. The bed rooms may probably
be wired from the attic which if not floored will
facilitate the wiring operations.
In the first place look which way the floor joists
lie and arrange to have as many of the circuits as
possible run in the same direction to avoid boring
holes transversely through the joists.
WIRING A HOUSE
11
This is well illustrated in Fig. 3 which represents
a portion of a floor with part of the boards cut
away. The joists run in the direction of arrow B
while the flooring runs like arrow A .
If the circuit is to run in the direction of arrow A ,
the joists must be bored and porcelain insulating
Fig. 3.
tubes inserted in the holes as will be described later.
In order to bore the holes in every joist the entire
board or two boards covering the route must be
taken up.
But where the wires run in the direction of arrow
B it is not necessary to bore any joists as the wires
will lie between them, and the entire board need
12
WIRING HOUSES
not be taken up but only a small portion as will be
seen later.
Wiring Plans. In the following four plans are
shown some typical arrangements of wiring. The
/ \
Z2
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X-
K
X-
H
B
CP-— SJ
ZJ
L_
Fig. 4.
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T
-XL
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X —
G
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-ell
plans are those of the first floor and show the out-
lets of that floor, but the wiring is as it would ap-
pear when viewed from the second floor under
which it is located.
WIRING A HOUSE 13
In order not to complicate these plans no clothes
closets, bathrooms or the usual details of house
construction are shown. The idea is merely to
show in a brief manner the direction which the
wiring would take, the two wires being indicated
by a single firm line or dotted line.
The arrows indicate the direction of the joists
and floor boards, arrow A pointing in the direction
of the floor boards and arrow B in the direction
of the joists.
The heavy lines show where it is necessary to
take up complete boards and to bore and tube the
joists. The dotted lines show where the wires
are run between the joists.
It is thus possible to see at a glance the best
path for the wires.
The circle C is at the place where the wire from
the service or main switch will come up in the wall
to feed the circuit.
Consider first Fig. 4. The flooring will be taken
up between points E and F in the manner to be
■described later.
The branch wires to outlets D, K, H and G
will be joined or " tapped " on to the circuit
between E and F and the wires to the service down
the wall at C will be also tapped on. This ta'pping
will only require pockets to be taken up at in-
tervals possibly one at D, K, H and G, and one or
two between L and K and between M and H.
The point at C will probably be opened by re-
moving a portion of the mop board or skirting.
14
WIRING HOUSES
In Fig. 5 is another layout of the same job where
it will be noticed that there will be more boards
to remove and more boring as shown by the
heavy lines.
f \
^p--^
r
c_
1
-£
X
m
b
eL
Fig. 5.
The labor is greater in this scheme and nothing is
gained thereby.
In Fig. 6 is a plan of another house drawn in the
same manner the boards running like arrow A
WIRING A HOUSE 15
and the joists like arrow B. Here the boring
through the joists will take the direction of heavy
lines, but the wires may be continued past outlet D
and down in the wall to the cellar.
Outlets E and F and G will require branch wires
run to them.
In Fig. 7 is another house plan where the wires
run in a complete circuit from outlet F to outlet D
and the service wires tapped on at C where they go
down in the partition. If the partition is not
handy the main wires may continue to the point
E and there go to the service.
Each house presents its own conditions but a
little study will disclose the best and most handy
route for the wiring.
As the simplest of these circuits, the last one will
be considered and the operations more particularly
referred thereto although most of the directions
given will be general in application.
Pockets. The first operation in wiring will be to
open pockets at intervals in the floor or to remove
floor boards in order to gain access to the space
beneath.
The pockets will be spaced where the knobs are
to come and above all outlets in the ceiling.
In order not to complicate the directions at this
point, it will be better to read to the end of this
chapter before actually cutting any flooring. In
this way the exact points where the knobs are to
come will be better understood.
^F
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X
G
i
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X
F
FIG. 6
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X
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F
R
i-£
FIG. 7
A
-X-
-«««
X
D
B
WIRING A HOUSE
17
The exact places where the ceiling outlet pockets
are to be taken up will be found marked by the bit
which was driven up through the ceiling, but the
other points will have to be determined on survey-
ing the route and will be determined by the dis-
tance between outlets as is explained in the para-
graphs on knobs and their use.
The manner of opening a pocket in a matched
wood floor is first to bore a one quarter inch hole
for the keyhole saw through the joint between two
Fig. 8.
boards and as near the joist as possible. The
joist may be located by the nails through the
flooring.
If blind nailed bore a hole by guess after tapping
the floor and locating as near to the joist by the
dull sound. Then bend a short length of wire and
inserting it through the hole fish around for the
joist. A little practice will reveal to the touch
the distance of the joist by the resistance to the
bent wire.
Having bored the small hole, force in the end of a
is
WIRING HOUSES
key hole saw and cut across the board at an angle
as shown by the dotted lines in Fig. 8. This is
to permit of the board being replaced neatly after
the wiring is completed. Having sawed across the
piece of board at both ends in a similar manner it
may be pried out using a chisel as shown at B
in Fig. 9. If it be a hard wood floor it is better to
saw first down with the grain between the boards
cutting off the tongue of the adjacent board as
shown at B. This makes it easier to pry the
-'©||KH*WJJiMJJJ|Uliii\
Fig. 9.
board up without splitting off the top tongue C
of board D as would be the case if the chisel were
bent down hard at A.
When taking up a complete board insert the
chisel always on the side B and leave a second
chisel in to act as a wedge when removing the first
chisel to pry at a new place further along. Some-
times several flat wedges or chisels may be used
in this manner or an assistant can be of service.
Taking up the first board in every case is the
hardest, a second adjacent board is easier to take
WIRING A HOUSE 19
up than the first. Always lay the pieces near the
hole from which they are taken or mark them so
that they may be put back again. The chisel
used should be at least one inch broad and better if
it is wider as the distribution of leverage will ensure
lighter markings on the edges of the boards.
When all pockets are open and all necessary
boards taken up, the boring and tubing of the holes
through the joists may be undertaken.
Boring and Tubing. In boring the holes through
the joists they should be located about two inches
from the top of the joist. As they will be bored
from above they will slant a trifle but this cannot
be helped and will only require a little more wire
and be harder to pull the wires through than if the
holes could be bored straight and level.
These holes should be bored with an %i inch
Ford bit or other single cutter bit so that they will
accomodate tubes % inches outside and jjjg inch
hole. If a tighter fit is desired use f inch bit. It
is better to have the tubes fit tight as they will
not slip out through jarring or when pulling the
wires through them. The latter is usually done so
that the pulling wire tends to pull the tube head
into the hole and not the other way. The matter
of bits is taken up in the later section on tools and
material. There will be probably a lot of holes
to bore but a clean sharp bit and application will
finish the job.
In boring these joist holes an extension is a handy
20
WIRING HOUSES
tool, this is a steel rod which fits into the brace
and holds the bit lengthening the latter. These
extensions may be bought of several convenient
lengths.
The two holes for one circuit should not be closer
Fig. 10.
than five inches to one another and better if still
further apart.
The appearance of a portion of the floor with the
tubes and wires installed is shown in Fig. 10.
There being two wires it is necessary here to take
up two boards in order to have room enough to
WIRING A HOUSE 21
work in. A is a joist, T T two tubes and W W
two wires while B and C are the boards continuing
those which have been taken up. The wires being
pulled in the direction of the arrow pull the tubes
into the holes the heads being on the side of the
joists not shown. If pulled against the direction
of the arrow there is a liability of pulling out the
tubes. Of course it is a small job to push them
back again but doing so means handling the wires
after they have been stretched and this is not to
be done more often than is necessary by one in-
expert in wiring work.
Where two joists come together as where the end
of one overlaps the end of another, a long tube
must be used sufficiently long enough to pass com-
pletely through both joists. Details such as these
will readily suggest themselves to the careful worker
who studies the work as it progresses.
Running the Circuits. Having now bored all
the holes and tubed those in the joists, place the
knobs after which the actual running of the wires
may be proceeded with.
Nails and Nail-heads. For fastening knobs
to the wood work, screws may be used but
stout wire nails are cheaper quicker and satis-
factory.
In order to avoid hitting the" porcelain with the
hammer while driving the nail home, leather
nail-heads arc slipped on the nail. These are small
22 AVI RING HOUSES
washers of belt leather and lying under the head
of the nail act as a cushion between the hammer
and the porcelain. Leather nail-heads may be
purchased from any electrical supply store or cut
from a piece of old leather.
Knobs and Their Use. The form of porcelain
insulator or knob used in this class of wiring is
known as the No. 5 or 5| and is described and shown
in the section on materials. What are known as
split knobs are also there described.
The general spacing between knobs along the
joists is 4| feet but will vary according to cir-
cumstances. The pockets intended for use in plac-
ing knobs between outlets are taken up in ac-
cordance with this spacing but may vary. Some-
times by extending this spacing a trifle only one
knob is needed between two outlets and only one
pocket is therefore required.
A study of this condition will save work and
knobs but remember not to save labor and ma-
terial to the detriment of the job. A portion of
the floor showing three pockets with the knobs
and wire installed is given in Fig. 1 1 .
There is no attempt in these diagrams to give
exact distances or measurements as the width of
floor boards and other conditions vary.
Wire. The copper wire used in wiring inside
the house must be rubber covered and protected
by a cotton braid and of the size to be selected
WIRING A HOUSE
23
according to the data given elsewhere. This wire
is suitable to use in moulding or concealed in the
flooring when strung between porcelain knobs, or
pulled in between walls having first been incased
in some form of flexible tube such as Circular Loom
or Flcxduct.
It must not be used outdoors where it will be
exposed to rain or snow but the so-called weather-
proof wire with a braided covering used in its
Fig. 11.
stead. Although the latter form of insulation is
never as good as rubber yet outdoors it does not
crack or rot. It is never run in wood mouldings
but is always supported on knobs or glass insu-
lators.
Details of wire are given in the section on
materials.
The best method of handling the wire is to take
the coil and divide it into two equal coils. This
24 WIRING HOUSES
enables both sides of the circuit to be run practi-
cally at the same time.
For the present leave these two coils at the point
where it is intended to drop the two service ends
down in the wall to the service switch in the
cellar.
Take two ends from each coil, or one at a time
as preferred and with care so that they do not
kink, start these ends under the floor through
the nearest pocket and under the floor from pocket
to pocket and through the tubes until the extreme
end of the circuit is reached. Considering Fig. 7,
the coils will be left at D (or at E) and the ends
run under the floor past each outlet until outlet F
is reached. Then making fast at F, the wires may
be stretched and fastened to the knobs returning
along the route until the other end of the circuit
at D or E is reached, there being then the re-
mainder of the wire lying in two coils.
They will not be pulled down into the cellar at E
yet but at a later time as will be seen farther
on.
The ends at the farther ceiling outlets F may be
left long enough to pass down through the ceiling
hole and leave at least 8 inches for connection to
the fixture.
On straight runs or when running one circuit it
is a good plan to place all the knobs first then the
wires can be pulled tight from the extreme end
knob and fastened to the knobs as the circuit is
followed.
WIRING A HOUSE
25
The run will be past each outlet as far as possible
but no outlet wires will be tapped on yet, this will
be done when the entire length of wire has been
fastened under the floor to the knobs.
Making Fast. When making fast from knob to
knob the wire may either be given a turn around
the intermediate knobs being held tight at the end
knobs by a dead-end hitch or what is better be
Figs. 12 and 13.
tched at each knob as shown in Fig. 12. This
lakes more wire and a little more practice but keeps
the wire tight between ail knobs instead of only
between those to which it is dead-ended or hitched.
The principal objection to these methods as against
tie wires is that should the wire come off the knob
the hitched or twisted part would slacken and
allow the wire to touch the woodwork.
26 WIRING HOUSES
A good method is to fasten a few knobs on a.
board and practice the hitches and other methods
of securing wires the advantages of the several
methods will then be apparent and the practice
useful when actually engaged in wiring up the
house.
The method of tying a wire to a knob using tie
wires is shown in Fig. 13 from a photograph. The
tie wire is a separate piece about fifteen inches long
and is first tied around the knob and main wire so
as to secure the latter to the knob. The loose ends
are then twisted around the main wire one end on
each side of the knob. The hitch or tie is made by
using the middle portion of the tie wire leaving two
ends of about the same length.
Another method which is not so good is to merely
wrap the tie wire around the main wire and the
knob and twist on the ends. The hitch although
taking more wire and more time is to be preferred
in all cases.
Where a circuit ends at an outlet two methods
may be pursued. The wires may be dead ended
and short pieces for the outlet be tapped on,
this makes a firm job but requires a soldered
joint. Or the ends of the wire may be left long
enough to reach down through the outlet after the
wires have been stretched and made fast by means
of the dead-end method elsewhere illustrated.
The latter is the usual method where the wires can
be ended near the outlet but sometimes it is not
practicable to end them near the outlet.
WIRING A HOUSE
27
Where two circuits cross each other or where
one wire of a tap crosses the other main wire, a
porcelain tube should be slipped over the crossing
wire or wires as shown in Fig. 14. There should
be placed two knobs each side of the crossed wires
as shown in order to secure the crossing wire and
the tubes. These knobs are often omitted and
the tubes merely held fast to the wire upon which
they are slipped by means of tape but the above
is preferable.
Fig. 14.
All branch or tap wires must be secured to a knob
at the point where they are led off from the main
circuit as at outlets, these knobs however need
not be installed now but when making the
taps.
Joints. The two joints used in electrical
wiring are the splice and the tap. The splice as its
name implies is used where two pieces of wire
are to be joined together in the direction of their
28
WIRING HOUSES
length. The tap is used where a branch wire is to
be run of! another wire at right angles to it.
There are two methods of making splices, by-
twisting the wires together and by using patent
screw unions or Dossert joints. Taps are also
made by twisting one wire on to the other or by
Dossert taps. Furthermore there are several
pieces of apparatus such as fuse blocks and cutouts
Fig. 15.
in which wires are joined through screw connections
or under screwed lugs and several ingenious de-
vices for special conditions.
The first and simplest methods of twisting wires
will be described here.
The illustrations showing splices and the methods
of fastening wires have been made from photo-
graphs of the actual work making the operations
clearer than could be done by drawings.
Making a splice joint.
The splice ready for solde
A tap ready for soldering.
PL \TK 111.
WIRING A HOUSE 29
In Fig. 15 is the method of making a splice. The
wire is bared of its insulation for three inches and
the two pieces laid together and bent as shown.
Then the two bare wires are twisted together the
ends shown loose being either worked in with the
pliers or cut off close. A method often pursued
is to twist the wires tighter together each turn
lying close up to its neighbor, but the looser twist
gives a better means for applying the solder. With
Fig. 16.
the close coiling the solder is liable not to penetrate
the wire turns but where the turns are well apart
it can enter more readily.
The method of making a tap is shown in Fig. 16
from a photograph. A knob is placed where the
tap wire is to lead off from the main wire. The
latter is then bared of its insulation a few inches
from this knob and scraped bright.
The tap wire is also bared and scraped bright
for three or four inches at its end and fastened
30 WIRING HOUSES
around the knob so as to hold the main wire to the
insulator. This is done by making a hitch with
the tap wire while putting it in place. The loose
(Mid is wrapped around the insulated portion of the
main wire and twisted around the bare spot as
shown .
This method secures the main wire to the knob,
secures the tap wire to the knob and to the main
wire before it gets to the bare spot and takes all
strain off the joint and the main wire. The hitch
is not drawn tight in the illustration to better show
the details of the operation.
In the same figure is illustrated the best method
of making a dead-end. This is the end of this
circuit and the end of the wire is hitched around
the knob, then the loose end wrapped around the
tight wire. This is better than merely giving the
wire a turn or two around the knob and twisting
up the ends.
Soldering. All joints made in wires which are to
carry current should be soldered in order to make
good electrical contact. Unsoldered joints are
both dangerous and unreliable. In the first place
unsoldered joints will corrode from dampness and
by reducing the bare clean copper surface raise
the resistance of the joint so that it may become
fieated. In the case of 110 volt installations the
resistance of a poor joint might not be apparent
in the light but where the voltage is low the resist-
ance of the poor joint is a serious matter.
WIRING A HOUSE 31
Poor joints are the cause of fires in many cases
and it must be impressed here that all joints carry-
ing current must be above reproach. Remember
that an unsoldered joint or any poor work in fact
does not improve with time but becomes worse,
As there will be a number of joints to solder in
wiring up a house, it is best to leave them until as
many as possible are ready for soldering. It is
then a quick job to go from joint to joint and solder
up. The soldering torch need not be lighted and
extinguished more often than necessary.
The soldering torch used will depend upon what
is available unless it is desired to buy one. If none
is at hand a small alcohol torch or blowpipe may
be bought for about a dollar and will answer all
practical purposes. A flame that gives smoke
will not do to solder with, alcohol or gasoline used
in a proper torch are the best.*
Together with the lamp will be needed some wire
solder or shoestring solder and some kind of flux.
There are several good kinds on the market called
generally " soldering paste " and any electrical or
hardware store can supply them. So called solder-
ing salts made of muriatic acid and zinc should
never be used as unless the last trace has been
washed off the joint it will surely corrode in
time.
A small quantity of the paste should first be put
on the joint which is then h'eated with the torch
* See Thatcher, Simple Soldering both Hard and Soft.
32 WIRING HOUSES
flame and the solder held to it until it melts and
runs thoroughly into all the crevices of the joint.
If the wire is not hot and the solder run in well, the
joint will be bad and surely cause trouble. Try the
first job as soon as the solder is set and if it peels
off either the paste was not sufficient or the wire was
not hot enough. Soldering with a clean joint,
good paste and a hot flame is by no means a diffi-
cult process.
Taping. After soldering the joint, or tap, it
must be covered with an insulation equal to that
removed for a weak spot of insulation at any point
is bad.
A few inches of the rubber tape is cut off the
roll and twisted tightly around the joint while it is
hot. If it has cooled it should be again heated.
It will be found that the heat will melt the rubber
and it will adhere to the joint to which it is to be
moulded with the fingers. Then the friction or
adhesive tape is wound over the joint covering the
wire entirely from a few inches back of the joint to
an inch or so beyond it.
No bare spots may show at any place but all
metal must be covered neatly with rubber tape
and with friction tape.
Ceiling Outlets. In order to have a secure hold
for the screws used in fastening up the fixtures,
ceiling boards, B, Fig. 17 are placed at every
WIRING A HOUSE
33
ceiling outlet. A piece of f board, soft pine pre-
ferably is cut just long enough to fit between the
joists / J and about 6 inches wide. Wire nails are
then driven part way through the board near the
edge in a diagonal direction and the board laid in
place so that its centre comes just over the small
hole made by the bit. It is then nailed fast using
great care not to hit it so that the plaster falls from
the ceiling C.
Fig. 17.
It is not hard to fix these ceiling boards if the
nails are driven carefully and diagonally, using a
nail not over one inch and a half or two inches long.
A little experimenting first will show the correct
way to nail the board, it is easy after the correct
way is learned but pages of directions would not
make it any clearer.
Having put ceiling boards in place at every out-
let, go down stairs and with the bit used in boring
34 WIRING HOUSES
for the tubes, bore up through the ceiling at the
point where the small bit went through. Two
holes must be bored but each diagonally upwards
in such manner that they make two diagonal
holes through the ceiling board but enly one hole
in the ceiling plaster below. The idea is that the
two pieces of loom each covering one wire are to
start down through practically separate holes in
the ceiling board but to come together through one
hole in the ceiling. This is shown in a later il-
lustration (Fig. 25).
After studying this out it will be seen to be very
simple as the loom is flexible and two ends can be
flattened a trifle to come out through one % inch
hole in the plaster. If the operator prefers he may
bore one hole straight up and cut the board away
to allow the two pieces of loom to pass through,
or bore the ceiling hole first, then make a large
hole in the ceiling board before nailing it in place.
But the first method is the best and really the
simplest.
It may be remarked here that the wires coming
down through the ceiling outlets for the fixtures
will be separate pieces cut to length and tapped on
to the circuit separately except perhaps at the
extreme end where enough may be allowed when
tying to drop down at this one outlet.
After having installed the ceiling boards, pieces
of lumber say one inch thick and two inches wide,
are nailed on along the joist just below the opening
as shown at 5 S. These pieces are to hold the
WIRING A HOUSE 35
pieces of flooring when the latter are relaid as is
shown in a later illustration (Fig. 25).
Looming the Wire. Having now reached the
coiled wire measure enough to reach clear down
into the cellar and leave enough additional to
reach the switchboard, then cut loom encugh to
cover the wires from the last knob upstairs to the
entrance into the cellar and slip it on the wires.
This of course applies to both wires of the circuit.
This loom or " circular loom " is a flexible in-
sulating tube made in several varieties and called
by various trade names. Circular loom and
Flcxduct are the two best known and are suitable
for use here. They are costly however and
measurements should be made before buying, the
average cost being about 5 cents a foot or 10 cents
for the two wires.
The wire is inserted in the tube and should be
shoved in little by little taking a grip on the wire
between the first finger and the thumb a few inches
from the opening of the loom. At first the wire
will slip in easily but after a while it may stick,
when the loom should be shaken as a terrier shakes
a rat. If an assistant holds the far end of the loom
when feeding in long wires, he can shake it con-
tinually and the wire will slip in the more easily.
The sizes of loom suitable for different wires are
given in the section on materials.
Wiring in Attics. The wiring for the fixtures on
36 WIRING HOUSES
the second floor will be done in the attic. Wiring
in attics is done with consideration as to whether
there is any possibility of the attic being used for
other than a space between the roof and the ceiling.
Where the attic is too small for other use and there
is no possibility of persons entering it except for
stringing wires, or where it cannot be used for
storage purposes, as in many bungalows, the wiring
may be installed on the floor beams without boring
or tubing them but by running the wires on knobs.
But where there is any possibility of the attic being
used the wires should be installed by boring and
tubing.
The installation of the wiring for the second
floor then will probably be easier than that for the
first floor as there will be less cutting of boards and
perhaps none. The layout can be made easily as
here will be no partitions to obstruct the view and
the flooring if any will not be hard wood matched
but plain boards.
The ends of this circuit may either be tapped on
to the circuit on the floor below or what is better
in a large house, run clear to the service and there
connected to a separate cut-out or switch, details
of which will be given in the section on service
switches.
CHAPTER III.
Completing the Installation.
Wiring to the Service Switch. The service or
main switch will in the majority of cases be in the
cellar or lower part of the house. The ends of the
circuit wires which have been measured, cut and
protected by loom are now ready to be pulled down
for attachment to this switch. This may be done
now or after the outlet wires have been tapped on.
Whatever will save time labor and going up and
down stairs is worthy of consideration and will
determine the time for each operation.
In frame houses there will be found a space be-
tween the lath and plaster of the walls and the
outside boards of the house in which space the
wires may be pulled down. Generally this space
extends clear from the attic floor to the cellar
ceiling and a lead weight called a mouse tied on a
stout cord may be dropped clear down to the cellar
from above. In some houses where the floor has
been laid in continuous lengths the space will be
blocked but removal of the mop board and the
boring of a couple of holes will remedy this. A
joist or " plate " will also be frequently found
blocking the way and must be bored.
Having dropped the weight down in this space
37
38 WIRING HOUSES
and secured the free end of the cord to the wires,
the weight may be found down in the cellar prob-
ably resting on top of the cellar wall and the wires
pulled down by its aid.
It is a hard job for a novice to pull wires down
alone and an assistant is of service upstairs who can
feed the loomed wires down and keep them from
kinking while they are being pulled down. It is a
peculiar fact that if there is a nail or any projection
upstairs any where near the wires while they are
being pulled down that they are almost sure to
catch on it. The pull should be steady and careful
as although the loomed wire will stand a consid-
erable strain there is no need of using more force
than necessary.
The wires having been pulled into the cellar are
ready for attachment to the service switch.
Where the service is in the attic the weight is to
be dropped down in the same manner and the wires
pulled up. As this is a harder job, sometimes it is
better to pull down a separate pair of wires and tap
them on to the main circuit which is first dead-
ended.
The Service or Main Switch. Where the bat-
tery plant and the switchboard are located in the
house the circuit wires will probably be led di-
rectly to this switchboard and controlled from it
by means of a switch or switches. But if the plant
is in another building the wires leading from it will
then run to a main or service switch located in the
COMPLETING THE INSTALLATION 39
house to which likewise the house circuit wires will
also connect.
Considering then that the battery or service
wires are run in from outside it is best to install
a service switch and fuse block. As also in the
case of a large house the wiring will be divided into
perhaps two or more circuits, there will be neces-
sary more than one fuse block and if desired a
switch to control each circuit. The service wires
will run to the service switch and cut-out first.
The best plan is to make up a box to hold the
switches and fuse blocks.
The size of the box will depend upon what it is
to hold of course but it must be large enough to
hold all the apparatus with the switches either open
or closed. It should be made from § inch lumber
and be not less than 3| inches deep, provided with
a door which should be hinged from above so that
the weight of the lid will always keep it closed.
After having been well painted within and without
with a good moisture repelling paint, it should be
lined entirely on the inside with either sheet iron
or sheet asbestos and the asbestos again painted.
This will keep it dry and prevent any liability of
fire from a blown fuse or from other causes. The
holes through which the wires pass should be
bushed with porcelain tubes, loom is sometimes used
but is not suitable in damp places.
The usual form of main switch is known as a
double pole, single throw, knife switch and of an
ampere carrying capacity as required. Generally
40 WIRING HOUSES
for a small house with a few lights this switch will
be of 15 to 25 ampere capacity but a larger one is
no detriment.
The fuse block or cut-out may be one with cart-
ridge fuses or what is suitable for the low voltage
circuits, with Edison screw plug fuses as in Fig. 18.
The wires from the battery should go to the fuse
block or cut-out first and the house circuit wires to
the switch. This allows the fuses to protect the
entire circuit and the switch, if the switch should
happen to be short circuited by accident, it having
Fig. 18.
bare metal parts, the cut-out fuses would blow.
But if the outside wires led first to the switch, a
short circuit on the switch would not blow the
fuses there but those at the battery if there were
any. Note here and in all cases that a knife
switch must be fastened so that it opens downwards
and not upwards. This is so that it cannot drop
shut after being left open.
In Fig. 19 is shown a diagram of a service switch
and box where C is the cut-out with its fuses and
S the switch. The wires from the source of elec-
COMPLETING THE INSTALLATION
41
tricity here come in at the top of the box and the
house circuit wires leave from the bottom. This
Fig. 19.
is the simplest arrangement of a cut-out and
switch.
In Fig. 20 is another diagram where the house
42
WIRING HOUSES
circuit wires and the service wires all lead out at
the top. This is sometimes an advantage as the
wires may be led away directly along the cellar
ceiling beams.
A very convenient form of 25 ampere service
switch for this class of work is that shown in Fig. 21 .
Fig. 20.
It is self-contained with both the switch and the
cut-out and its fuses mounted on one base. This
form of switch may be installed on an asbestos
covered board, or even on a board painted with
moisture repelling paint providing the location
COMPLETING THE INSTALLATION
43
is not damp. But a cut-out box is easy to make,
and is by far a safer and neater job, a lock and key
Fig. 21.
Fig. 22.
being added giving greater protection against any
tampering with the main switch.
Where the house is a large one and it is best to
44
WIRINC, HOUSES
divide the lights into several separate circuits
each running to the cut-out box, the form of com-
bined switch and cut-out shown in Fig. 22 is very
suitable although for a cheaper job separate cut-
outs and switches may be used.
The arrange-
A_J,
Fig. 23.
ment shown has snap switches but is also made with
knife switches in a slightly different pattern. The
one illustrated is neat enough to use where it is
exposed should it be desired to put the switches
controlling such separate circuits in a prominent
place upstairs.
COMPLETING THE INSTALLATION
45
A service switch box made up with the self-con-
tained switch before described is in Fig. 23. This
box is arranged for two house circuits but more ma y
be added as desired.
Fig. 24.
The form of service switch installed in an iron
box shown in Fig. 24 is very convenient and ready
for attachment to the wires. The switch is self-
contained having plug fuses.
CHAPTER IV.
Installing Lights.
The Outlet Wires. The outlet wires may be
tapped on now that the wires are in place and
secured fast. Pieces of wire long enough to reach
Fig. 25.
down through the outlet holes about eight inches
and wrap around the knob and the main wire are
cut off from the coil or odd short pieces are used.
Before cutting them it will be well to fully under-
46
INSTALLING LIGHTS 47
stand how they are placed so that they may be cut
to suit the location.
As in Fig. 25 the outlet wire is tied around the
knob K, the short end bared and tapped on to the
main wire and a piece of loom slipped on after
which it is ready to be thrust down through the
outlet hole. Tying it in this manner secures both
the short piece and the main wire and takes the
strain off the joint. Leave the piece too long rather
than short. In cutting the outlet wire cut it long
enough as it is easier to push up the slack from
below or cut a piece off, than to splice a short
wire.
Installing the Lights. Every joint having been
soldered and taped and all wires in place the next
operation is the last, that of connecting on the
sockets or the fixtures. This is done after all
wires are ready and the floor boards back in place,
being generally a quick job.
Whether there will be regular fixtures or merely
drop lights is a matter to be decided by the reader,
but as the drop light is the cheaper and used very
generally they will be next considered.
Drop Lights. In many places such as bath-
rooms, bedrooms and the kitchen, a drop light will
suffice and save the cost of a fixture. Drop lights
are made up in two ways, with fuses and without.
The best plan is to make them up unfused and
have the fuses in the cut-out box.
48
WIRING HOUSES
A drop light comprises three parts, the rosette,
the cord and the socket, to which of course must
be added the lamp. The rosette is the device
by which the cord is attached to the main wires and
also which supports the cord and lamp. It is of
porcelain and has screws and lugs for attachment
of the cord and the main wires, the fused rosettes
being made in two readily separable parts.
The form of rosette shown in Fig. 26 is made to
Fig. 26.
Fig. 27.
take a fuse and is used in concealed work where
the wires come through the ceiling.
Another type for moulding work is shown in
Fig. 27 and a cleat type used where the wires are
run on cleats or otherwise -exposed is shown in
Fig. 28.
An unfused rosette is shown in Figs. 29. Making
up rosettes is done the same way as with sockets
INSTALLING LIGHTS 49
in that a knot must be made in the cord to take the
strain off the cord at the connecting clamps or
screws.
Making up a Drop Light. The cord may be
covered with cotton, silk or mohair as selected
the twisted cotton covered being the kind most
used. For low voltage lighting it is suitable but is
not used in good work for regular 110 volt lighting.
The sizes most used for single drop lights are No. 16
Fig. 28. Fig. 29.
and No. 18 B. & S. The former will be better
for low voltage work as its resistance per foot is
less. For lengths of over 10 feet No. 14 should be
employed.
The first operation is to measure the length of
cord necessary so that the light will hang at the
desired height. It should not be left too long as
although there are plenty of cord adjusting de-
vices for sale they all look unsightly.
50 WIRING II: lUSES
Having cut the cord to the right length take a
socket apart as in Fig. 30. Some sockets require
that screws be loosened before the shell can be
removed, others of more modern design are so made
that a pressure on the shell near the point where it
is slipped in the cap will loosen it so that it readily
comes apart.
A hard rubber socket bushing is screwed into
the hole in the cap to prevent the insulation of the
cord becoming abraded.
Having separated the socket into its three parts
the cord may be untwisted for a few inches and the
copper wires bared for about three-quarters of an
inch on each part. The easiest way to do this is to
lay the cord on the table and scrape off the cotton
and rubber insulation. Then twist up the loose
copper strands on both pieces so that they will not
stray but lie neatly like a solid wire.
A knot is then made about an inch and a half
from the end.
Loosen the screws on each side of the socket B
— Rosette base-
'j — Rosette cap —
— Socket cap
and bushing-
— Knot
-Bared
Wires
Wires
connected-
— Socket sbell —
PLATE IV
INSTALLING LIGHTS 51
and twist the wires under them once around.
Twist in the same direction as the screw will turn
when being tightened so that the turning of the
screw will not push out the wires.
Tighten up the screws and twist any loose ends
around the wire above the screw.
Then slip the cap A over the other end of the
cord and the shell C on to the lower part of the
socket. Press them together and it will be found
that the knot will take the strain off the screws
inside by catching against the inside collar of the
cap.
Great care must be taken that no loose strands
of wire are left inside the socket or a short circuit
will result, loose strands must be looked for before
closing up the socket.
Having made up the socket take the rosette
apart and thread the cord through the hole in the
cap. The cord must be inserted bearing in mind
that the cap will be head downward from the
ceiling. The top end of cord is then untwisted and
its ends bared as before, knotted and made fast
under the screws in the rosette cap.
All the drop lights for a job may be made up and
put up at one time if preferred which is the usual
way on large jobs.
When ready to put up the drop light the wires in
the ceiling are threaded through the holes in the
rosette base and the latter screwed fast to the
ceiling. Where ceiling boards have been in-
stalled screws long enough should be used so that
rig. 31.
INSTALLING LIGHTS 53
they penetrate it, a number 6 screw is heavy
enough. The wires are then cut to length and
scraped clean and fastened under the screw
heads or lugs in the rosette base.
Fixtures. The selection of fixtures is a matter
of taste. A simple design is shown in Fig. 31.
The recent introduction of high candlepower
lamps with high intrinsic brilliancy has starfed a
craze for what is termed indirect illumination, the
light being reflected from the ceiling and the
upper part of the walls, and not directly from the
lamp.
This system is all very well where the expen-
diture of electricy is of little account, or where
special effects are desired, but is out of place in
the home where the cost of current is an item.
The underlying idea is that the direct light
hurts the eyes, but no heed is taken of the fact
that the straining from the poor quality of this
reflected light is often worse.
Unless the candlepower of the light be very
great, or there be many lights, the light reflected
from the ordinary ceiling is almost always in-
sufficient for reading, specially if the reader has
any weakness of the sight, or has failing eyesight
due to advancing years.
Switches. Switches are made in man}' styles
and types to suit all conditions and will be treated
of in their place. It is, however, most likely that
54
WIRING HOUSES
Section through ceiling and wall.
Fig. 32. — Wiring a drop light and single pole switch.
Dotted line is second main wire.
INSTALLING LIGHTS 55
there will be one or more single pole switches in-
stalled to control some of the lights and the
operation of installing them will be next treated of.
The simple form of single pole snap switch is shown
in Fig. 33 without its cover, and may be procured
in many finishes to suit the fixtures, the most used
finish for general purposes being nickel plate.
Switch Wires. The running of switch wires
where simple single pole switches are used to
control a light from only one place as in Fig. 34
is as follows:
At the outlet in the ceiling or wherever the light
is to be located, only one piece of wire A is brought
down through the hole from the main circuit for
the fixture.
Another piece of wire B is cut long enough
to reach from the fixture up through the hole,
fasten to the knob and run clear along the floor
down to the switch outlet with enough left to make
connection to the switch.
56
WIRING HOUSES
A third piece C is cut and run from the other
side of the circuit at the outlet, that is from the
main wire other than the one to which the outlet
wire is connected. This second piece also runs
clear down to the switch.
It will be seen then that the current passing down
Fig. U.
through the first short piece A through the fixture
flows along the second length B through the switch
and back to the circuit by the wire C.
Pulling down Switch Wires. To cut the loom
for the switch outlets measure the distance from
INSTALLING LIGHTS 57
the switch outlet to the ceiling which should be the
same for all switch outlets on the first floor. Then
allow enough for the thickness of the ceiling or
beam under the floor, and also be sure that the
loom will reach in one piece from the outlet to the
knob at the point where the switch wire leaves
the joist to run down the wall. Then slip the
switch wires into the loom and pull through the
ends, bare the copper for a few inches and twist the
ends together ready for attachment to the fish
line.
The switch outlet having been cut in the wall
through the lath and plaster the mouse is dropped
down from above pulling the string along with it
all but the loop end which is tied tightly to the
twisted end of the switch wires.
A piece of hooked wire is then run in the outlet
hole down-stairs and the fish line pulled through.
Pulling on the line soon brings out the twisted
ends of the switch wires, if they stick, they must be
helped from above, it is very helpful here to have
an assistant who can guide the wires down. The
twisted ends arc then loosed from the fish line and
left for connection to the switch later on.
Hall Lights. It is often very convenient to
locate a light in a hallway for instance so that by
means of two switches it can be controlled from
two places. A person desiring to go down-stairs
at night can then light the lamp in the down-stairs
hall before descending, by means of the switch
58
WIRING HOUSES
up-stairs; and then after having descended can
extinguish the lamp from the switch down -stairs.
Or it may be lighted from down-stairs and extin-
Fig. 35.
guished from up-stairs. Either switch will light
or extinguish the lamp.
The wiring for this arrangement is not com-
INSTALLING LIGHTS 59
plicated but needs two special switches called
" three way switches."
A diagram of the wiring is in Fig. 35. The
rosette of the hall light L is connected on one side A
to the circuit as shown and the other side of the
rosette is connected to the single binding post on
the switch S up-stairs. This binding post is quite
easily distinguished as it is strapped to another
which has no hole and screw for a wire. The same
binding post on the switch down-stairs is connected
B to the circuit but not to the same side of the circuit
as the top switch rosette wire. Then two wires
are run, one between each of the two remaining
binding posts of the switches as shown.
Where there is an available circuit both up-stairs
and down -stairs or the same circuits runs near each
switch as shown, the wires may be attached to
each taking care that they go to different sides of
the circuit. But where there is no circuit down-
stairs the lower switch wire must be run upstairs
and tapped on to the same circuit as the rosette.
A study of the illustration will make this clearer
than pages of explanation. It really is very simple.
What happens is as follows: When the button
of one switch is turned it connects one live wire
to one of the two switch-wires and the current
flows along through the second switch and out
through the lamp to the other live wire lighting
the lamp. Now if the second switch is turned, it
changes the lamp wire to the other switch-wire
and the lamp goes out.
CHAPTER V.
Other Methods of Wiring.
Open Work or Cleat Work. Where appearance
is no object the wires may be run on knobs or
held by cleats on the ceiling or walls of the room.
In the case of barns, outhouses and even in cellars
this class of wiring may suffice. But it is not neat
and even moulding work is better and more
symmetrical.
The general directions for open work are not
much different than for running wires between the
floors except that cleats holding two wires may be
used. The wire should be rubber covered and
stretched tight between the knobs or cleats. Wires
must be kept apart at all times and a generous
use of knobs or cleats is recommended to that end.
Where a long run of open work is to be made,
the two extreme ends of the circuit should be
stretched tight first, that is of course on a straight
run such as the whole length of a hallway or cellar.
The end knobs or cleats being in place it is easier
to put up the intermediate ones straight.
In general wires should be supported by cleats
or knobs at least at every 4i feet but often it is
better to space them closer.
60
OTHER METHODS OF WIRING
61
This class of work is a little hard for the be-
ginner as the wires must be stretched tight in order
to look neat. An assistant would be of use to
help stretch the wire and hold it tight while it is
being cleated and the screws driven home.
When the circuit turns at an angle the wires
may be fastened as in Fig. 36 which shows the
arrangement of the cleats although where the wire
is stiff enough the middle cleat may be dispensed
Fig. 36.
with. The cleats used are porcelain and come in
pairs, some being interchangeable top and bottom.
This class of work should not be installed out-
doors or where it is damp. The wiring of damp
places is best done on knobs, and outdoors, except
under cover, on glass insulators.
Where money is less an object than time or
labor, loom may be used throughout dispensing
with knobs almost entirely. Pockets are opened
€2 WIRING HOUSES
only at the outlets and at a few other places such
as where the wires run down in the walls. The
wire then being encased in loom for its entire
length is pulled under the floors for the entire
distance being left without loom at the outlets for
a short space in order to make fast to the knob.
Knobs are used at the outlets of course to secure
the wires for the lights and the switches.
A snake wire of steel is useful to pull the loomed
wires from outlet to outlet. This snake wire is of
flat steel and one end being bent to prevent it
catching in projections beneath the floor it is
pushed under the floor boards and as it reaches
an outlet the wires made fast at its other end are
pulled along by its aid.
In some types of house construction there will
be found a space between the joists and the plaster
allowing the wires to be fished without boring the
joists. Otherwise the joists must be bored and
tubed as usual.
Wiring in Wooden Moulding. In buildings
where it is not desired to wire on the plans de-
scribed the wires are run in wooden moulding
fastened to the ceilings or to the walls. This
moulding consists of two parts, the backing which is
a flat strip having grooves cut in it for the wires to
lie in, and the capping, a thin lath which is nailed
over the wires to hold them in place and to conceal
them.
This moulding should be painted with a moisture
OTHER METHODS OF WIRING 63
repelling paint inside and out and the wire used
must be rubber covered.
Under no circumstances should this moulding be
used outdoors or in damp places.
In wiring with moulding, the backing is first
nailed in place, the wire laid in the grooves and
held temporarily in place by brads which are
removed when the capping is nailed on. It is
better to use screws instead of nails to fasten the
capping as it may then be the easier removed when
necessary. Whether nails or screws be used, they
are to be driven through the central rib of the back-
ing and not through the bottom of the grooves.
It is best to plan so that there are no splices
in the wires, but have them continuous through-
out.
When taps are necessary they may be made as
usual, by twisting the tap wires on and soldering
them but a better plan is to use one of the tap
devices described later on.
When the circuit turns at an angle, the moulding
should be neatly cut and mitred as in a picture
frame. This class of work is one where the me-
chanical skill of the operator becomes apparent
as it is really joiners work and the neat fitting of
the pieces in their place and the straightness with
which the moulding is run are very noticeable.
A great amount of ingenuity and taste may be
displayed in the manner with which the work is
done and a job of moulding may be either an
eyesore or an ornament. Sometimes it is nice
64
WIRING HOUSES
to continue the moulding beyond where the wires
stop in order to gain symmetry of design.
Although it is often quicker to use moulding all
the way, switch wires may be often pulled down
inside the walls in loom and out at the switch outlet.
Moulding Taps. Where a tap is to be taken
off a run of moulding one of the tap wires will
naturally cross the main wires and the moulding.
The crossing tap wire is led out through a slot cut
in the main wire moulding capping and crosses
outside this capping which is thus interposed
between the wires and keeps them apart. The
other tap wire is led out of a slot cut in the outside
wall of the main moulding and into the groove of
the tap moulding.
OTHER METHODS OF WIRING 65
A neater and better plan is to use the tap device
shown in Fig. 37 which is made by the H. T.
Paiste Co. of Philadelphia. It can be bought at
almost any electrical supply store and is simple
in attachment the illustration showing sufficiently
well its application.
Where two circuits have to cross each other, a
cross over device made by the same company is
used as illustrated in Fig. 38.
Fig. 38.
The moulding of the crossing wires is butted up
to the main run of moulding, a piece of capping cut
from the latter and the device installed as in the
illustration. This interposes a solid base of porce-
lain between the two circuits.
Wall Moulding Method. One of the slowest and
hardest jobs in wiring houses is the boring of in-
66 WIRING HOUSES
numerable holes through the floor joists to ac-
commodate the circuit wires which run through
them. In a house of six or eight rooms there may
easily be a hundred of these holes and the boring
of a hundred j^ inch holes through floor joists with
a brace and bit is no light task. Then the tubes
must be inserted and the wires pulled through all
of which may be saved if the operator is skillful
and there is no objection to moulding on the side
walls. This moulding may be of a special kind
resembling picture moulding or it may be the
regular electric wire wooden moulding as de-
sired.
In this side wall moulding method the wires that
otherwise would run through the holes in the joists
up-stairs are run in moulding on the side walls
down-stairs.
For example the main circuit that would run
from the front of a house to the rear necessitating
boring and tubing the whole distance may be run
in moulding on the wall of the room below as shown
by the heavy dotted line in Fig. 39. It may not
run as straight as by the other plan but will only
require a few feet more wire.
Taps for ceiling outlets H, K, D, L and M are
taken off and fished up-stairs in loom then run as
usual between the joists.
The number of pockets is also very much re-
duced and it is probable that there will be no need
to take up an entire board anywhere.
The outlet at G can be run in moulding on the
OTHER METHODS CF WIRING
67
ceiling being fed by wires coming through tubed
holes in the wall of the next room.
Where no picture moulding has been installed
this special moulding or the regular kind is run
Fig. 39.
about 10 or 12 inches below the ceiling or to suit
personal taste and the wall paper border.
As in the case of kitchen outlet G at partitions
between two rooms the partition wall is bored and
68
WIRING HOUSES
the wires pulled through in loom or tubes then con-
tinued on to the end of the circuit.
The ends for attachment to the cut-out box down-
Fig. 40.
stairs or to the main switch are encased in loom and
pulled up or down inside the walls, according as the
service is up-stairs or down-stairs.
OTHER METHODS OF WIRING 69
Taps running to ceiling outlets are to be run be-
tween the joists to a point as nearly above the
moulding as possible then holes being bored through
both moulding and wall the ends of these taps may
be fished down and through them and soldered
on to the wire in the moulding.
In the case of the live wire running from the
main wires to a switch, this is easily pulled down
to the outlet from a point in the moulding directly
above it. Of course it should be loomed first.
This makes a shorter run than in the ordinary
method as the switch live wire may be taken from
a near point right above it perhaps, whereas in the
other method it has to run generally clear to the
ceiling outlet. The wiring of a switch is clearly
shown in Fig. 40 where R is the rosette, M
the wall moulding and 5 the switch on the
wall.
There is no practical difficulty about this system
of wiring except that incurred by the appearance
of the moulding or on account of the down-stairs
wall running irregularly. It puts the wires
where they may be tapped on for additional
lights or wall brackets in a more accessible posi-
tion.
Outdoor Service. When the battery is to be
located in a separate building the wires leading to
the house from the battery switchboard must be
properly put up so as to withstand all weather
conditions.
70 WIRING HOUSES
In the first case the wire must be weatherproof,
triple braid the weights and sizes being given in
Table 1. Sizes larger than No. 12 B. & S. should
be stranded as they are then easier to handle and
less liable to fracture when bent.
The insulators will be of glass and mounted on
pins or brackets of wood or iron as may be decided-
Porcelain knobs should not be used to carry
main wires where they will be exposed to rain or
snow. In fact it is better to use glass insulators
exclusively outdoors except of course where
running a line for a light on the porch or inasimilar
case.
Before running an outdoor line, the route
should be first surveyed. It should be run in as
straight a direction to economize wire and must
be supported at frequent intervals to allow for
the weight of snow which accumulates on wires
in the winter, and for the strain of heavy winds.
In running long outdoor lines it is customary to
allow at least a pole at each 125 feet but in the
present ease it will be better to keep well within
this distance.
Although the wire itself may be exposed to the
weather when properly supported on insulators,
it is necessary to guard against rain running along
it and entering the house by way of the entrance
holes. This not only would damage the wall but
would seriously endanger the insulation at the
point of entrance. This contingency is guarded
against by fastening the wires below the entrance
^^M^^^^
Fig. 41.
72 WIRING HOUSES
holes, giving them a loop from which the water can
drip or by a combination of both.
The entrance holes must be bushed with porce-
lain tubes which are made for this purpose with a
curve, which curve is to be turned downwards.
In regular 110 volt work, an iron pipe about
10 feet long is bent at its lower end so that it will
enter the cellar, equipped with a proper bushing at
the top and the wires pulled through. After this
it is fastened up upright against the outside wall.
Fig. 41. Two insulators on iron brackets are lo-
cated at each side of the pipe at the top which
should be at least 10 feet from the ground de-
pending upon whether wagons are liable to pass
near it and the angle with which the wires come
down to enter it. The service wires leading from
the battery or plant being then fastened to the
insulators may be led in to the cut-out box or
service switch.
It is generally easier to make up the pipe with
two wires long enough to reach from the service
switch up the pipe and leave enough free ends to
connect to the wires coming from the plant.
Where suitable bushings are not used to close
the end of the pipe outdoors, it should be filled
with tape and a few wooden wedges driven in to
keep out dampness. The wires, however, must be
guarded against any possible cutting on the edges
of the pipe. Bushings such as described are
cheaper in the long run.
Where the wires come down from a pole set back
74
WIRING HOUSES
of the 'house, one insulator will be mounted above
the other so as to keep the wires apart as in Fig. 42,
Where the service wires come in up-stairs in the
attic for example the pipe is dispensed with and
insulators and tubes used. This method requires
the use of a ladder unless the entrance can be
located near a window.
Fig. 43. — How to tie a wire onto a glass insulator.
Fig. 44. — 'Dead ending a wire on a glass insulator and iron
bracket — showing drip loop and inclined porcelain tube.
CHAPTER VI.
Notes on Materials.
Estimating the Material Required. To estimate
the material required a careful survey must be
made of the job after having digested the wiring
directions already given.
The number of porcelain tubes will depend upon
the number of joists and the wires running through
them to which is to be added about 25% for use in
odd places. Often from 150 to 200 will be re-
quired in a frame house of 7 or 8 rooms wired on
the concealed knob and tube plan.
Knobs may be estimated at about 1 to each 3 feet
of wire needed which allowance should be sufficient
for most jobs.
The wire itself may be figured by measuring the
route to be followed but a generous allowance
should be made for ties or twisting around the knobs
and also for the irregular manner in which it will
run through the tubes in the joists. As wire is
useful to have on hand allow 50% more than the
estimate. This applies to small jobs, large jobs
may be calculated to close figures and the wire
bought in stock coils.
Flexible conduit or loom being somewhat ex
75
76 WIRING HOUSES
pensive can be estimated somewhat closer if suffi-
cient measurements are made. There will be two
lengths for each single pole switch reaching from
the switch to the space between the floor joists.
This will average 12 feet per switch in rooms of
ordinary height. For ceiling outlets short pieces
a foot or less in length will suffice. From the cir-
cuit up-stairs to the cellar ceiling (or the attic floor)
in the case of the service will be easy of measure-
ment.
A roll of friction tape and one of rubber tape
will be sufficient for quite a large job.
Other supplies such as nails or screws will be
easy to figure.
Material Required in Wiring. No. 5 porcelain
knobs for No . 12 or No. 14 wire have a groove ^ inch
wide to hold the wire, measure 1| inch from the
top to the surface upon which the insulator is
fastened and have a \ inch hole for the nail or
screw. No. 5| porcelain knobs are similar except
that they hold the wire higher from the surface
wired over being \% inches high.
Porcelain tubes should be unglazed and will vary
in length according to circumstances. But in
general for floor joists and most other woodwork in
the house they may be 3 to 4 inches long measuring
under the head. For places where two joists come
together they should be probably 6 inches long.
The inside diameter for wires not larger than
No. 12 B. & S. should be ^ inch and the outside
NOTES ON MATERIALS 77
diameter % inch. A tube f inch inside and % inch
outside is preferable for No. 12 B. & S. wire, as
it will be easier to pull through a lot of tubes when
in the joists.
Split Knobs. Split knobs are porcelain insula-
tors made in two pieces the wire being held tightly
between the upper and lower portions when the
screw through the center of the knob is tightened.
Nails and nail heads should not be used with split
knobs. For the latter reason it is very hard work
to use split knobs under a floor and in similar
places as there is not often enough room to handle
a screw driver. Moreover there is a greater lia-
bility for one inexpert to insufficiently tighten the
screw and the wire will be loose. And the breakage
is liable to be greater.
In the solid knob method if the knob is not abo-
lutely immovable on the joist it will at any rate
hold the wire as the latter is not dependent upon
the centre nail or screw. But with split knobs the
screw has to perform the double function of holding
the wire and holding the knob.
For wiring in exposed places where the screw
driver can be used readily, split knobs are prefer-
able as they make a neat job and the screw
being the easier driven allows no excuse for loose
wires.
Screws and Nails. Screws for switches and
rosettes will be generally Flat Head Bright wood
78 WIRING HOUSES
screws, No. 6 and from 1 inch to 2 inches in
length, according to whether they are to be used in
ceiling boards or only in lath and plaster.
Where screws are used for the knobs they should
be also Flat Head Bright wood screws. For No. 5
and No. 5h, If inch and 2 inch No. 8 are suitable
although 2 and 2\ give a firmer hold.
Wire nails are suitable for knobs, using nail
heads as mentioned before.
Screws and not nails are needed where wooden
moulding is run on plaster ceilings as nails will
not hold.
Moulding. The wooden moulding ordinarily
used in wiring is made of hard wood and painted
with moisture repelling paint or varnish. The
back as well as the grooves should be painted or
varnished and the whole outside may be painted
any desired color after being installed on the wall
or ceiling.
The size for No. 12 to No. 14 wire is No. A-2
and has grooves J2 inch wide. For Nos. 8 and 10
wire the size is No. B-l with grooves -fa inch wide.
The size of the grooves should be specified in order-
ing special mouldings or the number of the wire
given.
Bits. Bits used in boring holes for tubes or
outlets will of course follow the size of the hole
desired. If neat holes are desired use double cutter
bits, if a lot of holes are needed such as under the
NOTES ON MATERIALS 79
floor and through the joists the work is much easier
with single cutter bits such as the Ford bit.
Tubes really should fit tight but it is the general
rule to use a bit a trifle larger than the tube and
depend upon the fact that there is no motion to the
wire to make the tube stay in place. For a loose
fit use an l}& inch bit for tubes with an outside
diameter of % inch and a % inch bit for tubes with
an outside diameter of %. The rl inch bit will
also be suitable for the outlets and the x/i inch loom.
In locating the first holes in the ceiling for
marking outlets a \ inch Syracuse bit is best, and
may be as long as convenient one 18 inches long
being most generally useful.
Tape. The real insulating tape is a rubber
compound and must be put on with heat. It is
best applied immediately after soldering a joint
when it will adhere best but the joint may of
course be heated later on and the tape applied.
This rubber tape should not be confounded with
the sticky or friction tapes. These are used merely
to cover the rubber tape and protect it although
often wrongly used for insulation.
The insulation at a joint should be at least as good
as that on the wire itself.
Taped joints outdoors should be painted with
P. & B. paint which is a rubber compound and not
an asphaltum mixture. Failing genuine P. & B.
a good grade of asphaltum paint is better than
nothing.
80 WIRING HOUSES
TABLE 1.
Copper Wire Properties.
Weatherproof insulation Rubber
No.
Lbs. per
Carrying
insulation:
B. & S.
Circular
thousand
capacity
Carrying
gauge
mils
feet
amperes
capacity
00
133,325
522
220
150
0
105,625
425
185
127
1
83,694
328
156
107
2
66,373
270
131
90
4
41,742
170
92
65
6
26,250
115
65
46
8
16,509
78
46
33
10
10,381
53
32
24
12
6,530
35
23
17
14
4,107
25
16
12
16
2,583
16
8
6
18
1,624
12
5
3
Figuring the Size of Wire. The size of wire used
depends upon the amount of current to be carried
and the distance it will travel.
Although a good conductor of electricity, copper
presents some resistance. A wire that would carry
5 amperes without loss would not be suitable for 10
amperes if both currents were to travel the same dis-
tance. The results of resistance will be shown in a
dimming of the lights. Moreover, if the wire be too
small for the current carried it will get dangerously
hot. Fuses will be used to take care of this excess-
current when it arises from a short circuit but for
normal conditions the wire should be figured large
enough.
NOTES ON MATERIALS 81
The safe carrying capacity of copper wire is
shown in the Table I. The lower limits for rubber
covered wire is due to the fact that such wire is
generally used enclosed where the heating would
be more pronounced and also because rubber
deteriorates more than the weatherproof wire
insulation on being heated.
Although the carrying capacity will determine
the safe size of the wire, it will not ensure its being
large enough to carry the current without a loss.
In low voltage lighting this loss must be con-
sidered, as for example a loss of 3 volts would be
worse on a circuit of 30 volts and affect the lights
more than would the same loss on a wire where the
voltage was 110, being a greater proportion.
The resistance of a foot of copper wire one cir-
cular mil or one circular thousandth of an inch
in area is about 11 ohms.
It is a fundamental rule of electricity that the
voltage expended in carrying a given current a
given distance depends upon the resistance in the
circuit. It would actually need an expenditure of
11 volts to cause one ampere to pass through this
circular mil foot of wire. Therefore supposing the
voltage of the plant was 30, there would only be
19 volts left for the lamp.
Of course a wire so small would never be used,
it would burn up with the current but it is used as
an illustration.
In order therefore to have the wire of the right
area it must have the proper number of circular
82 WIRING HOUSES
mils which is determined by a simple calculation.
Referring to Table I No. 12 B. & S. has an area of
6530 circular mils so it is clear that a foot of this
would only expend 1/6530 of the 11 volts for the
same one ampere for its area having been in-
creased would have correspondingly reduced the
resistance.
Applying these facts to a simple arithmetical
formula gives a rule to calculate the size of wire
for any current and any distance.
Take the entire length of the wire, both sides of
the circuit L. Multiply this in feet by the am-
peres A to be carried and then multiply the result
by 11, or the ohms in a mil foot of copper wire.
The answer will give the size of wire in circular
mils to carry the current the required distance, and
a reference to Table I will show the numerical
size of wire needed. This allows a lose of one volt.
If more or less loss is allowed divide the above
answer by the loss allowable.
For example, suppose 10 amperes is to be
carried 200 feet and one volt loss allowed. Then
the entire wire length will be 400 feet and 400 times
10 times 11 equals 44,000 circular mils. The
nearest size of wire in the table is No. 4 B. & S.
with 41,742.
Another example, 12 amperes a distance of
240 feet with a loss of 2 volts. In this case perhaps
the voltage at the battery in a distant building
is 32, and 30 is required at the lamps. Then the
entire wire length will be 480 feet and the multi-
NOTES ON MATERIALS 83
plying together of 12,480 and 11 equals 63,360.
This divided by 2 equals 31,680. The nearest
in the table is again No. 4. A number 5 wire is
made, but the extra area is an advantage.
As a formula the rule would be stated as follows.
LXAX11 ,..,.,
— : = Area in circular mils.
volts loss
These rules apply to all voltages. For example, in
the last calculation, the loss would be 2 volts, whe-
ther the line voltage was 32,110, or even 220 volts.
But the percentage would of course be different,
and therefore the effect on the light would vary.
A loss of 2 volts in 32, would be worse than a loss
of 2 volts in a circuit of 110 volts.
The formula gives the actual volts loss for a given
number of amperes, a given distance and a wire of
a given diameter. It is evident that with a higher
voltage the current through the same resistance
would be greater, but increasing the current in the
wire would naturally increase the figure correspond-
ing to the amperes in the formula.
Where it is desired to get the loss in a given size
of wire, substitute the circular mils for the loss in
the formula.
LXAXH
— ~7^\r — Loss in volts.
Example, find the loss in a wire 31,680 circular
mils, carrying 12 amperes a distance of 240 feet
single wire, or 480 feet actual. Then 480 multi-
plied by 12 multiplied by 11 equals 63,360. This
divided by the circular mils, or 31,680 equals 2 volts.
CHAPTER VII.
Conduit or Protected Wiring.
The safest and most substantial methods of
wiring are those in which the conductors are pro-
tected by metal tape (armored cable), enclosed
in iron pipe (conduit), and which make use of
iron boxes to enclose all joints, switches or re-
ceptacles.
It is no more difficult to install these systems
of wiring than to install the open work or knob
and tube systems described previously. In fact
in many ways it is easier. The first cost is greater
and the cutting and threading of soft iron pipe
or the cutting of the armored cables perhaps re-
quires more physical labor. The pipe or the
armored cable however may be laid with less
labor and in shorter time, thus restoring the bal-
ance.
There exists no doubt of the greater safety and
general superiority of iron pipe or armored con-
duit wiring systems over knob and tube work.
They are as fireproof and damage-proof as any
system can be.
84
CONDUIT OR PROTECTED WIRING 85
Armored Cables. There are several makes of
armored cables on the market, sold under the
trade names of "Flex Steel" — BX, etc. All the
illustrations here are of work done with BX.
In the BX flexible steel armored cable, the wire
conductors are insulated separately and then the
two insulated conductors are held together by
further insulation.
Outside of these insulated conductors is wound
spirally, a convex and a concave shaped metal
strip, hot galvanized with zinc, and also a strip
of moisture repelling material laid between the
metal strips so as to keep out all moisture.
BX may be had with one, two, or three con-
ductors and in all the usual wire sizes.
These armored cables may be run practically
anywhere except of course under water or where
they would be subjected to the continuous action
of excessive dampness or chemical fumes. Where
likely to be exposed to moisture a lead covering
is placed between the outer braid of the con-
ductors and the armor.
The main requirements as laid down in the
National Electrical Code of the National Board
of Fire Underwriters require :
(a-) That the cable be continuous from out-
let to outlet — which means that where-
ever a splice becomes necessary it is
to be made in an approved metal box.
86 WIRING HOUSES
(b) That the armor of the cable must prop-
erly enter and be secured to all fittings,
which is done by clamps elsewhere
shown.
(c) That the cable be mechanically secured
in position, usually done by means of
metal pipe straps.
The code also requires that the metal armor be
permanently and effectually grounded to water
piping, or to other suitable ground connection.
The entire conduit or armored cable constitut-
ing the wiring system of one building must have
its iron pipe or armor effectually grounded. This
is usually done by seeing that good connection
is made at all breaks in the lines, such as at junc-
tion or switch boxes, and that a ground wire
clamp is properly secured to the conduit and to
an adjacent water pipe.
W here a gas pipe is used, the ground connec-
tion must be on the street side of the meter.
Where there is no gas or water pipe, an arti-
ficial ground is made consisting of a sheet of cop-
per with a copper wire soldered to it, and buried
in the ground where there is continuous moisture.
The idea is that there shall be a first class path
along the armor into the earth for any electricity
that hits the armor. It is self evident then that
rusty joints, poorly made connections and even
only one break in the continuity of the ground
connection will utterly destroy the value.
Malleable Iron Panel Box Connector.
^^'*#iKiW!*S»&**- giBHiy.*
Combination Coupling Joining Flexible Conduit to
Rigid Conduit. -~
Stamped Steel Panel Box Connector and Locknut
on BX.
\ \ :r~~f* ^^5^'^---
^BLkAfl.
Sprague BX Steel Armored Conductors.
Showing How Panel Box Connectors are Used with
BX and Rigid Conduit. Also Two Multilets.
PLATE V.
88 WIRING HOUSES
Although it may be true that where the voltage
is low, as in the low voltage home lighting plants,
there is less danger than where it is higher, it is
better to wire as if for 110 volts even if 32 are
only going to be used.
Good wiring is good insurance in itself.
Installing Armored Cables. The actual in-
stalling of BX or other cable is by no means
complicated. It may be pulled under the floors
or clown in the walls wherever desired.
The securing of the BX to the joists or beams
is done with pipe straps which may be nailed
or screwed fast, gripping the cable so that it
cannot shift. In no case is the strain of a wire
or cable to come directly upon a screw terminal,
such as in a socket or on a switch. The cable is
always made fast before the wires are connected.
At all places where a tap, joint or splice is to
be made or a switch, socket or receptacle is to be
attached, an approved iron box must be used.
This is to still farther carry out the idea of pro-
tecting the appliances against breakage and pre-
venting accidental contact with bare metal carry-
ing current. Examples of details are shown in
the illustrations.
The end of the BX is stripped of its armor and
the two inside wires separated (but not bared of
their own insulation) for 6 inches or so dependent
upon the distance between where they enter the
box and the connection screw.
CONDUIT OK PROTECTED WIRING
89
In cutting BX and all similar armored wires,
the saw cuts must be made across the metal tape
as shown in the second figure, never in a groove
as in the first figure. Otherwise, the saw will
jam and break. Care must always be taken not
to saw beyond the metal tapes and into the in-
sulation. A little practice will help. Having
sawed the first metal tape, it may be bent back
and broken off with the pliers and the second
tape also removed. Then, the braid and insula-
tion protecting the two inside insulated wires are
Wrong way to cut Right wav to cut
BX cable. BX cable.
FIG. 45.
cut away. Do not cut off any of the insulation of
the two inside wires until finally making the con-
nection or splice.
There are cutting tools made for stripping
armored cable, which are a great help.
The end being now ready, a malleable iron
panel box connector is slipped over the armor
(the free ends of the cable projecting from the
threaded end), and the clamp collar tightened.
The threaded end is now thrust through one of
90 WIRING HOUSES
the holes in the iron box and a lock nut screwed
on to draw the connector up tight.
This is where a sheet iron box is used, having'
discs of metal or knockouts closing the holes
around the box sides. These knockouts are driven
out by a hammer blow wherever entrance is de-
sired.
Cast iron boxes or condulets have threaded
nipples, in which case the threaded end of the
panel box connector is screwed in tight first, and
then the wire and armor are inserted and clamped.
The clamping of the armor in this manner not
only secures it, but by making a good connection
between the iron armor and the iron box, insures
that the ground circuit will be unbroken at that
point.
These operations are really not complicated.
A study of the illustrations and, wherever pos-
sible, a look at some actual armored cable wiring
will give the instruction necessary.
Conduit Wiring in Pipe. Iron pipe or" rigid
conduit work is the safest form of wiring in that
when properly installed, the wire is protected by
a rigid iron pipe against moisture, gases and
mechanical injury. The iron pipe or conduit is
coated either with black varnish or in the more
modern forms by a coating of zinc. Either coat-
ing admits of the pipe being bent without flaking
off, which would quickly permit rust and conse-
quent destruction of the pipe, the zinc coating
Condulet Type YC with cov-
er sealed, showing Plug
Fuse Cut-out.
Type J
Norbitt Conduletto Recepta-
cle with Shade Holder
Groove.
Type YL
With Plug Fuse Cut-out.
Condulet Type YD
With Plug Fuse Cut-out.
Type YS with Cartridge
Fuse Cut-out.
PLATE VI.
92 WIRING HOUSES
being preferable. Rigid conduit is installed com-
plete with all the iron boxes to contain the
switches, receptacles and other appliances, before
the wire is drawn in. For this reason it admits-
of changes, a wire being easily removed or re-
placed without in any way disturbing the pipe.
The installing of iron conduit and the iron boxes
is merely a mechanical operation involving the
cutting and threading of pipe and the setting of
the fittings. The conduit itself is fastened up by
pipe straps. Condulets, as they are generally
termed, are metal fittings of almost every con-
ceivable kind made to screw on the pipe. Ex-
amples are shown in the illustration. They in-
clude tees with porcelain bushings through which
the wires emerge, elbows, splice boxes, iron switch
boxes, receptacle boxes, and cutout boxes. Where
sheet iron boxes are used, the threaded conduit
is held in holes in them by locknuts and bushings..
In the condulets locknuts are not necessary as
threaded lugs or nipples form part of the box
itself. It will be evident that wire ends coming
out of the end of an iron pipe would be liable to
injury on the sharp edges. To prevent this in-
jury the pipe is reamed out and bushings with
rounded edges used. Sharp edges in the pipe are
always to be avoided. Even when two pipes are
joined together with couplings the pipes are
reamed out and drawn together by the coupling.
Wherever possible, the switches, receptacles or
CONDUIT OR PROTECTED WIRING 93
cutouts are installed in iron boxes forming part
of the pipe system, the pipe entering these boxes
and being secured thereto. But where it becomes
necessary to lead off a pair of wires or a flexible
cord a fitting made to screw on the pipe is neces-
sary.
A system of iron conduit, just like the armor
of a flexible armored wire or BX for example,
must be a continuous metallic structure. This is
to insure the proper grounding of the system, and
is insured by carefully scraping paint or rust off
all threads so that at all junctions there is a per-
fect metal to metal contact. Bends in the system
are obtained in two ways, by bending the pipe or
by using fittings, an example of the latter being
shown in the full page illustration of a switch
and ceiling light installation. In order to prevent
strain on the wire when being pulled in, only
1<>ur cpiarter bends are allowed by the code in any
one run. ^Yhere more bends become necessary,
a drawing in box must be used between each four
bends so that the wire has only this maximum
between its point of entry and where the pulling
strain is applied.
Concentric Wiring. A system of wiring much
used abroad for several years is that known as
concentric wiring. The wire itself from which
the name is derived is duplex, the conductors be-
ing made up together. The inner wire conductor
is insulated in the regular manner, but outside
!l 1 WIRING HOUSES
of this insulation a spiral or tape of copper or
alloy is wrapped, forming the second conductor.
This outer conductor is not insulated on the
outside but is bare. The outer conductor is how-
ever thoroughly grounded and therefore there
being no difference of potential (Voltage) be-
tween this bare conductor and the ground, no
danger ensues.
The grounding must be well performed and a
continuous contact must be assured at all joints
or boxes. These contacts are not made with
solder but with clamp sleeves.
Special fittings, sockets, switches, etc., are re-
quired as it is evident that the mode of construc-
tion of the two conductors would not admit of
the ordinary kind being used.
The General Elecric Company, some of whose
fittings for concentric wiring are shown here, fur-
nish a bare concentric wire with the outer con-
ductor or sheath of tinned sheet copper, folded
longitudinally around the inner insulated wire,
with a full lap. This tin sheath is then soldered
where it laps, making it continuous electrically
and mechanically, and at the same time gas tight
and water tight.
It will be noted on referring to the illustrations
that there is a clamp which fits over and makes
the contact with the sheath, and a screw connector
for the inner wire. This is most clearly shown in
the view of the back of the receptacle.
Concentric Wire, Outer Conductor Partly Cut and
Bent Out.
Wheel Bending Tool.
Xo. 171445
Switch and Plug Cut-out, 3 Wire to 2 Wire.
Xo. 171463
Key Receptacle.
Xo. 171456.
Sub-base for Receptacle.
PLATE VII.
96 WIRING HOUSES
Owing to the impracticability of making taps
or splices by twisting together wires, various
fittings have been designed for these purposes.
The No. 171446 Junction Box for example is
used where a tap or a switch leg is to be taken
off a circuit, the main wire passing through the
center of the block.
The Xo. 171448 inside junction box is used
where the service or main wire runs up or down
in the angle of a wall which in this form of wiring
is the most logical place for a riser. This box
located in the upper angle of the corner, takes
the wire from above op below and distributes
both ways along the walls of the room.
Switch No. 171445 is for a three wire service
to the top screws in ordinary wire, the two cir-
cuits of concentric wire joining to the connecting
clamp on each side of the lower part of the switch.
A ground wire is run from the middle lower
connection, which through the transverse clamp,
effectually grounds the sheaths of both the right
and left hand circuits.
The wire is bent to fit corners with a special
grooved roller tool shown in the illustration. In
the method of installation most in vogue this con-
centric wire is merely strapped to the walls or
supports with metal straps and screws.
Where the wire passes through the floor or
partitions it is protected by iron pipe, otherwise
it is not covered in any wav.
No. 171447.
Four Way Branch
Junction Box.
No. 171446.
Three Way Branch
Junction Box.
No. 171449
Outside corner
Junction Box.
No. 171452
Sub -base for
S. P. Snap Switch.
No. 171450.
Snap Switch
Junction Box.
No. 171448.
Inside Corner
Junction Box.
PLATE VIII.
98 WIRING HOUSES
It will be seen then that concentric wiring is
simple. Its cost of construction would approxi-
mate the cheaper kinds of open work, but at
greater safety and speed of installation.
The safety of this form of wiring is evident.
Owing to the perfect ground connection, the bare
outer wire may be touched with impunity. If
the ground is broken at any point the current
would fail as the continuity of the circuit would
also be broken.
Current is brought to the meter in the usual
Avay, the concentric wire being usually installed
for the actual house circuits alone.
Concentric wiring will be widely introduced
into the United States in the course of time.
It is a logical and well tried system of house
wiring for inexpensive, safe installations, and
although it may not entirely supplant the present
cumbersome methods, it will find a wide field of
application in the electric wiring of moderate
sized homes and business places.
For some time to come, however, the immense
investment in the older form of wires, sockets,
and fittings in general, and the tools or plant
necessary to make them, will necessitate time for
readjustment before concentric wiring becomes
general.
Rigid pipe conduit using
condulets to make bends.
PLATE IX.
CHAPTER VIII.
The National Code.
This Code comprises over 200 pages detailing
how electrical wiring should be done to be safe.
It should be studied and followed by everyone
doing electrical wiring.
It may be obtained from the National Board
Headquarters in most large cities, being furnished
free to interested parties.
The following extracts will assist the operator
in the installation of inside wiring for not ex-
ceeding 250 volts.
Under the head of General Suggestions the
Xational Board of Fire Underwriters in the
National Electrical Code make the following
valuable recommendations :
"In all electrical work, conductors, however well insu-
lated, should always be treated as bare, to the end that
under no conditions, existing or likely to exist, can a
ground or short circuit occur, and so that all leakage from
conductor to conductor, or between conductor and ground,
may be reduced to the minimum.
In all wiring special attention should be paid to the me-
chanical execution of the work. Careful and neat running,
connecting, soldering, taping of conductors, and securing
and attaching of fittings, are specially conducive to security
and efficiency, and are strongly advised.
In laying out an installation, except for constant current
systems, every reasonable effort should be made to secure
distribution centers located in easily accessible places, at
which points the cut-outs and switches controlling the
several branch circuits can be grouped for convenience
and safety of operation. The load should be divided as
evenly as possible among the branches, and all complicated
and unnecessary wiring avoided.
The use of wire-ways for rendering concealed wiring
100
THE NATIONAL CODE 101
permanently accessible is most heartily endorsed and recom-
mended; and this method of accessible concealed con-
struction is advised for general use."
Class C.
INSIDE WORK
{Including All Work for Light, Power and Heat Protected
by Service Cut-out and Switch.)
General Rules.
16. Wires.
a. Must not be of smaller size than No. 14 B. & S. gage,
except as allowed for fixture work andi pendant cord.
This is not only on account of carrying capacity, but also for
mechanical strength.
b. Conductors of size No. 8 B. & S. gage or over used
in connection with solid knobs must be securely tied there-
to. If wires are used for tying they must have an insula-
tion of the same type as the conductors they confine. Solid
knobs or strain insulators must be used for all wires at
the end of runs where conductors are terminated. Split
knobs or cleats must be used for the support of conductors
smaller than No. 8 B. & S. gage, except at the end of runs.
Knobs or cleats which are arranged to grip the wire,
must be fastened by either screws or nails. If nails are
used, they must be long enough to penetrate the woodwork
not less than one-half the length of the knob and fully the
thickness of the cleat, and must be provided with washers
which will prevent under reasonable usage, injury to the
knobs or cleats.
Leather nail heads are pieces of leather on nail just below
bead to take impact of hammer.
Splice should be open to allow solder to penetrate. See a
previous page.
c. Must be so spliced or joined as to be both mechanically
and electrically secure without solder. The joints must
then be soldered unless made with some form of approved
splicing device, and covered with an insulation equal to
that o?i the conductors.
Stranded wires (except in flexible cords) must be
soldered before being fastened under clamps or binding
screws, and whether stranded or solid, when they have a
conductivity greater than that of No. 8 B. & S. gage they
must be soldered into lugs for all terminal connections,
except where an approved solderless terminal connector
is used.
102 WIRING HOUSES
d. Must be separated from contact with walls, floors,
timbers or partitions through which they may pass by non-
combustible, non-absorptive, insulating tubes, such as glass
or porcelain, except at outlets where approved flexible
tubing is required.
Bushings must be long enough to bush the entire length
of the hole in one continuous piece, or else the hole must
first be bushed by a continuous waterproof tube. This
tube may be a conductor, such as iron pipe, but in that
case an insulating bushing must be pushed into each end
of it, extending far enough to keep the wire absolutely
out of contact with the pipe.
c. Where not enclosed in approved conduit, moulding
or armored cable and where liable to come in contact with
gas, water, or other metallic piping or other conducting
material, must be separated therefrom by some continuous
and firmly fixed non-conductor creating a permanent sep-
aration. Must not come nearer than two (2) inches to
any other electric lighting, power or signaling wire, not
enclosed as above, without being permanently separated
therefrom by some continuous and firmly-fixed non-con-
ductor. The non-conductor used as a separator must be
in addition to the regular insulation on the wires. Where
tubes are used, they must be securely fastened at the ends
to prevent them from moving along the wire.
Note. — This applies to wires not in conduit or armored cable.
Conduit work is cheaper in the long run.
Deviations from this rule may, when necessary, be al-
lowed by special permission.
/. Must be so placed in wet places that an air space will
be left between conductors and pipes in crossing, and the
former must be run in such a way that they cannot come
in contact with the pipe accidentally. Wires should be
run over, rather than under, pipes upon which moisture
is likely to gather or which, by leaking, might cause trouble
on a circuit.
g. The installation of electrical conductors in moulding,
or on insulators, in elevator shafts will not be approved,
but conductors may be installed in such shafts if encased
in approved metal conduits, or armored cables.
18. Table of Allowable Carrying Capacities of Wires.
</. The following table, showing the allowable carryjng
capacity of copper wires and cables of ninety-eight per
cent conductivity, according to the standard adopted by
THE NATIONAL CODE 103
18. Allowable Carrying Capacities of Wires — continued.
the American Institute of Electrical Engineers, must be
followed in placing interior conductors.
For insulated aluminum wire the safe carrying capacity
is eighty-four per cent of that given in the following tables
for copper wire with the same kind of insulation.
Table A Table B
Rubber Other
Insulation Insulations Circular
B. & S. G. Amperes Amperes Mils
18 3 5 1,624
16 6 10 2,583
14 15 20 4,107
12 20 25 6,530
10 25 30 10,380
8 35 50 16,510
6 50 70 26,250
5 55 80 33,100
4 70 90 41,740
3 80 100 52,630
2 90 1:.':. 66,370
1 100 150 83,690
0 125 200 105,500
00 150 225 133,100
000 175 275 167,800
0000 225 325 211,600
Circular Mils
200,000 200 300
300,000 275 400
400,000 325 500
500,000 400 600
600,000 450 680
700,000 500 760
800,000 550 840
900,000 600 920
1,000,000 650 1,000
1,100,000 690 1,080
1 ,200,000 730 1 ,1 50
1, .100,000 770 1,220
1,400,000 810 1,290
1,500,000 850 1,360
1,600,000 890 1 ,430
1. 700,000 930 1,490
i ,800,000 970 l ,:,:*)
1,900,000 1,010 1,610
2,000,000 1 ,050 1 .670
KM WIRING HOUSES
19. Switches, Cut-outs, Circuit-Breakers, Etc.
a. On constant potential circuits, all service switches and
all switches controlling circuits supplying current to motors
or heating devices, and all fuses, unless otherwise provided,
must be so arranged that the fuses will protect and the
opening of the switch will disconnect all of the wires;
that is, in the two-wire system the two wires, and the
three-wire system the three wires, must be protected by
the fuses and disconnected by the operation of the switch.
When installed without other automatic overload pro-
tective devices automatic overload circuit breakers must
have the poles and trip coils so arranged as to afford
complete protection against overloads and short circuits,
and if also used in place of the switch must be so ar-
ranged that no one pole can be opened manually without
disconnecting all the wires.
b. Must not be placed where exposed to mechanical in-
jury nor in the immediate vicinity of easily ignitible stuff
or where exposed to inflammable gases or dust or to fly-
ings of combustible material.
Where the occupancy of a building is such that switches,
cut-outs, etc., cannot be located so as not to be exposed
as above, they must be enclosed in approved dust-proof
cabinets with self-closing doors, except oil switches and
circuit breakers which have dust-tight casings.
c. Must, when exposed to dampness, either be enclosed
in a moisture-proof box or mounted on porcelain knobs.
The cover of the box must be so made that no moisture
which may collect on the top or sides of the box can enter
it.
23. Automatic Cut-outs.
c. Must be in plain sight, or enclosed in an approved
cabinet, and readily accessible. They must not be placed
in the canopies or shells of fixtures.
Link fuses may be used only when mounted on approved
bases and must be enclosed in dust-tight, fire-proofed
cabinets, except on switchboards.
d. Must be so placed that no set of incandes-
cent lamps, whether grouped on one fixture or on several
fixtures or pendants (nor more than 16 sockets or recep-
tacles) requiring more than 660 watts, will be dependent
upon one cut-out.
There are exceptions allowed individually for particular cases.
THE NATIONAL CODE 105
e. The rated capacity of fuses must not exceed the allow-
able carrying capacity of the wire as given in No. 18
The idea of a fuse is primarily to protect the wiring wherein
the greatest fire danger exists.
Fixture wire or flexible cord of No. 18 B. & S. gage,
will be considered as properly protected by 10 ampere fuses.
This is a miximum and does not mean that a lower fuse may
not be used.
For circuits having a maximum capacity greater than
that for which enclosed fuses are approved circuit breakers
alone will be approved.
26. Wires.
General Rules.
a. Where entering cabinets must be protected by ap-
proved bushings, which fit tightly the holes in the box
and are well secured in place. The wires should com-
pletely fill the holes in the bushings so as to keep out the
dust, tape being used to build up the wires if necessary.
On concealed knob and tube work approved flexible tub-
ing will be accepted in lieu of bushings, provided it shall
extend from the last porcelain support into the cabinet.
b. Must not be laid in plaster, cement or similar finish,
and must never be fastened with staples.
c. Must not be fished — pulled dozmi in walls or under
flooring — fbr any great distance, and only in places where
the inspector can satisfy himself that the rules have been
complied with.
d. Twin wires must never be used, except in conduits,
or where flexible conductors are necessary.
e. Must, where exposed to mechanical injury, be suitably
protected. When crossing floor timbers in cellars, or in
rooms where they might be exposed to injury, wires must
be installed in approved conduit or armored cable or be
attached by their insulating supports to the under side of
a wooden strip, not less than one-half inch in thickness,
and not less than three inches in width. Instead of the
running boards, guard strips on each side of and close
to the wires will be accepted. These strips to be not less
than seven-eighths of an inch in thickness and at least
as high as the insulators.
Protection on side walls must extend not less than seven
feet from the floor and must consist of substantial boxing,
retaining an air space of one inch around the conductors.
106 WIRING HOUSES
closed at the top (the wires passing through bushed holes)
or approved metal conduit pipe of equivalent strength.
When metal conduit or pipe is used, the insulation of
each wire must be reinforced by approved flexible tubing
extending from the insulator next below the pipe to the
one next above it.
This acts as a non-shiftable extra insulation through the metal
pipe.
The two or more wires of a circuit each with its flexible
tubing (when required), if carrying alternating current
must, or if direct current, may be placed within the same
pipe.
Here the flexible tubing is merely extra insulation. In all cases
it is preferable to put both wires of a circuit in the same metal
conduit. It must be done when alternating current is used on
account of the danger of the iron pipes heating if two were used.
This refers to metal conduit only.
In damp places the wooden boxing may be preferable
because of the precautions which would be necessary to
secure proper insulation if the pipe were used. With this
exception, however, iron piping is considered preferable
to the wooden boxing, and its use is strongly urged. It
is especially suitable for the protection of wires near belts,
pulleys, etc.
/. When run in unfinished attics, or roof spaces, will be
considered as concealed, and when run in close proximity
to water tanks or pipes, will be considered as exposed to
moisture.
In unfinished attics, or roof spaces, wires are considered
as exposed to mechanical injury, and must not be run on
knobs on upper edge of joints.
Special Rules.
For Open Work.
In dry places.
g. Must have an approved rubber slow-burning weather-
proof, or slow-burning insulation.
h. Must be rigidly supported in non-combustible, non-
absorptive insulators, which will separate the wires from
each other and from the surface wired over in accordance
with the following table :
THE NATIONAL CODE 107
Distance from Distance between
Voltage. Surface. Wires.
0 to 300 y2 inch 2l/2 inch
301 to 550 1 inch 4 inch
Rigid supporting requires under ordinary conditions,
where wiring along fiat surfaces, supports at least every
four and one-half feet. If the wires are liable to be dis-
turbed, the distance between supports must be shortened
In buildings of mill construction, mains of not less than
No. 8 B. & S. gage, where not liable to be disturbed, may
be separated about six inches, and run from timber to
timber, not breaking around, and may be supported at
each timber only.
Must not be "dead-ended" at a rosette, socket or re-
ceptacle unless the last support is within twelve inches of
the same.
For Moulding Work (Wooden and Metal).
Note. — Wooden moulding is practically obsolete and not al-
lowed in most places.
Metal mouldings must not be used for circuits requiring
more than 1,320 watts of energy.
For Conduit Work.
n. Must have an approved rubber insulating covering
(Type Letter R. D.), and must within the conduit tubing
be without splices or taps.
o. Must not be drawn in until all mechanical work on
the building has been, as far as possible, completed.
Conductors in vertical conduit risers must be supported
within the conduit system in accordance with the follow-
ing table :
Xo. 14 to 0 every 100 feet.
Xo. 00 to 0000 every 80 feet.
0000 to 350,000 C. M. every 60 feet.
350,000 C M. to 500,000 C. M. every 50 feet.
.•.0(1,000 C. M. to 750,000 C. M. every 40 feet.
750,000 C. M. every 35 feet.
For Concealed "Knob and Tube" Work.
q. Must have an approved rubber insulating covering.
r. Must be rigidly supported on non-combustible, non-
absorptive insulators which separate the wire at least one
inch from the surface wired over. Should preferably be
108 WIRING HOUSES
run singly on separate timbers, or studding, and must be
kept at least five inches apart.
Must be separated from contact with the walls, floor
timbers and partitions through which they may pass by
non-combustible, non-absorptive, insulating tubes, such as
glass or porcelain. Wires passing through cross timbers
in plastered partitions must be protected by an additional
tube extending at least four inches above the timber.
Rigid supporting requires, under ordinary conditions,
where wiring along flat surfaces, supports at least every
four and one-half feet. If the wires are liable to be dis-
turbed the distance between supports must be shortened.
At distributing centers, outlets or switches where space
is limited and the five-inch separation cannot be maintained,
each wire must be separately encased in a continuous length
of approved flexible tubing.
s. When in a concealed knob and tube system, it is im-
practicable to place the whole of a circuit on non-com-
bustible supports of glass or porcelain, that portion of the
circuit which cannot be so supported must be installed
with approved metal conduit, or approved armored cable,
except that if the difference of potential between the wires
is not over 300 volts, and if the wires are not exposed to
moisture, they may be fished if separately encased in ap-
proved flexible tubing, extending in continuous legths from
porcelain support to porcelain support, from porcelain sup-
port to outlet, or from outlet to outlet.
t. .When using either conduit or armored cable in mixed
concealed knob and tube work, the requirements for con-
duit work or armored cable work must be complied with
as the case may be.
u. Must at all outlets, except where conduit is used,
be protected by approved flexible tubing, extending in con-
tinuous lengths from the last porcelain support to at least
one inch beyond the outlet
When the surface at any outlet is broken, it must be
repaired so as to leave no holes or open spaces at such
outlet.
For Fixture Work.
v. Must be not smaller than No. 18 B. & S. gage, and
must have an approved rubber insulating covering.
THE NATIONAL CODE 109
27. Armored Cables.
a. Must be continuous from outlet to outlet or to junc-
tion boxes or cabinets, and the armor of the cable must
properly enter and be secured to all fittings, and the entire
system must be mechanically secured in position.
In case of service connections and main runs, this in-
volves running such armored cable continuously into a
main cut-out cabinet or gutter surrounding the panel board,
as the case may be.
b. Must be equipped at every outlet with an approved
outlet box or plate, as required in conduit work.
For concealed work in walls and ceilings composed of
plaster on wooden joist or stud construction, outlet boxes
or plates and also cut-out cabinets must be so installed
that the front edge will not be more than one-fourth inch
back of the finished surface of the plaster, and if this
surface is broken or incomplete it shall be repaired so that
it will not show any gaps or open spaces around the edges
of the outlet box or plate or of the cut-out cabinet. On
wooden walls or ceilings, outlet boxes or plates and cut-
out cabinets must be so installed that the front edge will
either be flush with the finished surface or project there-
from. This will not apply to concealed work in walls or
ceilings composed of concrete, tile or other non-combustible
material.
In buildings already constructed where the conditions-
are such that neither outlet box nor plate can be installed,
these appliances may be omitted by special permission, pro-
vided the armored cable is firmly and rigidly secured in
place.
c. Must have the metal armor of cables permanently
and effectually grounded to water piping, gas piping or
other suitable grounds, provided that when connections
are made to gas piping, they must be on the street side of
the meter. Tf the armored cable system consists of several
separate sections, the sections must be bonded to each
ether, and the system grounded, or each section may be
separately grounded, as required above.
The armor of cables and gas pipes must be securely
fastened in outlet boxes, junction boxes and cabinets, so
as to secure good electrical connection.
The clamp connectors illustrated elsewhere take care of this.
110 WIRING HOUSES
27. Armored Cables — continued.
If armor of cables and metal of couplings, outlet boxes,
junction boxes, cabinets or fittings baving protective coat-
ing of non-conducting material, such as enamel are used,
such coating must be thoroughly removed from threads
of both couplings and the armor of cables, and from
surfaces of the boxes, cabinets and fittings where the
armor of cables or ground clamp is secured in order to
obtain the requisite good connection. Grounded pipes must
be cleaned of rust, scale, etc., at place of attachment of
ground clamp.
Connections to grounded pipes and to armor of cables
must be exposed to view or readily accessible, and must
be made by means of approved ground clamps.
Ground wires must be of copper, at least No. 10 B. & S.
gage (where largest wire contained in cable is not greater
than No. 0 B. & S. gage), and need not be greater than
No. 4 B. & S. gage (where largest wire contained in cable
is greater than No. 0 B. & S. gage). They shall be pro-
tected from mechanical injury.
The ground for the armored cable system is not to be
considered as a ground for a secondary system.
d. When installed in so-called fireproof buildings in
•course of construction or afterwards if exposed to mois-
ture, or where it is exposed to the weather, or in damp
places, such as breweries, stables, etc., the cable must have
a lead covering placed between the outer braid of the con-
ductors and the steel armor.
The lead covering is not to be required when the cable
is run against brick walls or laid in ordinary plaster walls
unless same are continuously damp.
e. Where entering junction boxes, and at all other out-
lets, etc., must be provided with approved terminal fittings
which will protect the insulation of the conductors from
abrasion, unless such junction or outlet boxes are specially
designed and approved for use with the cable.
/. Junction boxes must always be installed in such a
manner as to be accessible.
g. For alternating current systems must have the two
or more conductors of the circuit enclosed in one metal
armor.
h. All bends must be so made that the armor of the
cable will not be injured. The radius of the curve of the
inner edge of any bend not to be less than iy2 inches.
THE NATIONAL CODE 111
28. Interior Conduits.
a. No conduit smaller than one-half inch electrical trade
size shall be used.
_ b. Must be continuous from outlet to outlet or to junc-
tion boxes or cabinets, and the conduit must properly
enter, and be secured to all fittings and the entire system
must be mechanically secured in position.
In case of service connections, and main runs, this in-
volves running each conduit continuously into a main cut-
out cabinet or gutter surrounding the panel board, as the
case may be.
Departure from this rule may be authorized in case of
underground services by special permission.
c. Must be first installed as a complete conduit system,
without the conductors.
d. Must be equipped at every outlet with an approved
outlet box or plate. At exposed ends of conduit (but not
at fixture outlets) where wires pass from the conduit sys-
tem without splice, joint or tap, an approved fitting having
separately bushed holes for each conductor must be used.
Departure from this rule may be authorized by special
permission.
Outlet plates must not be used where it is practicable
to install outlet boxes. . . .
In buildings already constructed where the conditions
are such that neither outlet box nor plate can be installed,
these appliances may be omitted, providing the conduit
ends are bushed and secured.
It is suggested that outlet boxes and fittings having con-
ductive coatings be used in order to secure better electrical
contact at all points throughout the conduit system.
This refers to the zinc coated conduit as being better than
enameled conduit.
e. Metal conduits where they enter junction boxes, and
at all other outlets, etc., must be provided with approved
bushings or fastening plates fitted so as to protect wire
from abrasion, except when such protection is obtained by
the use of approved nipples, properly fitted in boxes or
devices.
/. Must have the metal of the conduit permanently and
effectually grounded to water piping, gas piping or other
suitable grounds, provided that when connections arc made
112 WIRING HOUSES
28. Interior Conduits — continued.
to gas piping, they must be on the street side of the meter.
If the conduit system consists of several separate sections,
the sections must be bonded to each other, and the
system 'grounded, or each section may be separately
grounded, as required above. Where short sections of
conduit (or pipe of equivalent strength) are used for the
protection of exposed wiring on side walls, and such con-
duit or pipe and wiring is installed as required by No,
26 c, the conduit or pipe need not be grounded.
Conduits and gas pipes must be securely fastened in
outlet boxes, junction boxes and cabinets, so as to secure
good electrical connections.
Taken care of by lock nuts and bushings or by condulets
where the pipe is held by a threaded nipple.
If conduit, couplings, outlet boxes, junction boxes, cabi-
nets or fittings, having protective coating ot non-conduct-
ing material such as enamel are used, such coating must
be thoroughly removed from threads of both couplings and
conduit, and such surfaces of boxes, cabinets and fittings
where the conduit or ground clamp is secured in order to
obtain the requisite good connection. Grounded pipes
must be cleaned of rust, scale, etc., at place of attachment
of ground clamp.
Connections to grounded pipes and to conduit must be
exposed to view or readily accessible, and must be made
by means of approved ground clamps
Ground wires must be of copper, at least No. 10 B. & S.
gage (where largest wire contained in conduit is not greater
than No. 0 B. & S. gage), and need not be greater than
No. 4 B. & S. gage (where largest wire contained in con-
duit is greater than No. 0 B. & S. gage). They shall be
protected from mechanical injury.
The ground on the conduit system is not to be considered
as a g'/ound for a secondary system (see No. 15).
g. Junction boxes must always be installed in such a
manner as to be accessible.
h. All elbows or bends must be so made that the con-
duit will not be injured. The radius of the curve of the
inner edge of any elbow not to be less than three and
one-half inches. Must have not more than the equivalent
of four quarter bends from outlet to outlet, the bends at
the outlets not being counted.
UC SOUTHERN REGIONAL LIBRARY FACILITY
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