WIRING OF BUILDINGS
In laying out the circuits for a dwelling house, the cut out cabinets
should be located first. In many houses only one cut out cabinet is
necessary, but in large houses it is convenient to have one on each
floor, with vertical mains running through them from the top to the
bottom of the house.
If only one distributing point be used, it should be either in the
cellar or attic and risers run to the different floors.
=Ques. How should the distributing centers or cut out cabinets be
located?=
Ans. They should be installed near a partition that is so located as
to make the running of risers easy, and should be on an inside wall to
guard against dampness.
=Ques. What instructions are usually given the electrician who does the
wiring?=
Ans. In many cases simply a plan showing the location and number of
lights, from which he must figure out how to install them using the
least amount of material and labor consistent with a good installation
that will pass inspection.
=Ques. What provision should be made in rooms where lamps are suspended
from the ceiling?=
Ans. A switch should be placed at a point where it will be convenient
for any one entering to turn on the light.
=Ques. Where are receptacles usually placed?=
Ans. In the baseboard.
A receptacle is a convenient device which permits any one to
connect a lamp to the electric lighting system by inserting a
plug which is connected by flexible cord to the lamp.
[Illustration: FIG. 991.—Ceiling button. If a lamp be needed not more
than 3 feet from the direct line of the wires, it can be hung where
required by means of a _ceiling button_, as shown in the figure, but
the lamp cord must not be used to run lamps in this way more than two
or three feet from the rosette.]
=Ques. What provision should be made in wiring a hallway?=
Ans. The switching arrangement should be so designed that the lights
may be turned on or off either from the hall or floor above.
=Ques. What is this arrangement called?=
Ans. _A two way switch_, as shown in fig. 992.
=Ques. How can a two way switch be distinguished?=
Ans. It has three binding screws, two on one end and one on the other.
[Illustration: FIG. 992.—Two way lighting circuit permitting control
from two points. This is the usual arrangement for hall when it is
desired that the lights may be turned on or off from either floor. The
circuit contains two two way switches connected by "travellers." From
the diagram it is seen that the light may be controlled from either
switch. It is a bad arrangement to have travellers and return wire
located near each other, as it is possible by this method to connect
two individual circuits together and possibly overload one of the two
feed wires of each circuit. However, should each feed wire run to a
fuse direct, without any other lamps than those contained in the three
way circuit being connected, it is not objectionable and becomes a
convenient method in many cases.]
[Illustration: FIG. 993.—Four way lighting circuit, permitting
control from three points. This arrangement consists of a four way
switch connected between two two way switches as shown. In making the
connections it should be noted that the travellers connecting one side
of the four way switch to the two way switches should be crossed. On
the opposite side of the four way switch, the connections are direct.
For the various positions of the switches, the corresponding circuits
through them are as follows: ABDGHJ—ABDEIJ—ACFGHJ—ACFEIJ.]
=Ques. How may a group of lights be controlled from three points?=
Ans. By the use of a 4 way switch and two 2 way switches connected as
shown in fig. 993.
=Ques. Before laying out the wiring system for a building, what should
be done?=
Ans. It is necessary to ascertain whether power will be supplied from
the central station, or whether a private plant is to be installed.
[Illustration: FIG. 994.—Two wire multiple system as used with
isolated plant.]
=Ques. What wiring system should be used with a private or isolated
plant?=
Ans. The two wire multiple system as shown in fig. 994.
=Ques. When the central station is to supply power as an auxiliary in
case of break down, how should the connection be made?=
Ans. The supply from the central station should be connected to the
wiring system through a double throw switch, as in fig. 995, so that
either source may be thrown into circuit.
=Ques. How are the connections made when the auxiliary supply is
brought in through a three wire system?=
Ans. A double throw three pole switch is used as shown in fig. 995.
[Illustration: FIG. 995.—Double throw switch for use in isolated
plants when auxiliary power is used from the central station in case of
breakdown.]
=Ques. When power from an outside source only is to be used what must
be determined before wiring?=
Ans. The system of wiring of the supply. If a three wire system be
used, the general arrangement will be as shown in fig. 997.
[Illustration: FIG. 996.—Double throw three pole switch for use in
isolated plants where auxiliary power is brought in through three wire
system. The side of the switch controlling the current is bridged as
shown.]
=Ques. Would it be expensive to change a regular three wire system to a
two wire system?=
Ans. It would require the reinforcement of all mains and feeders by an
additional wire. This wire would be connected with the neutral wire so
as to make the capacity of the neutral equal to the sum of the other
two. If a three wire two wire system had been originally installed, no
change in the wiring system would be necessary. The only change would
be at the service end of the switchboard, and the doubling of the size
of the center fuses.
[Illustration: FIG. 997.—Three wire convertible, or three wire
two wire system; used to advantage where power is supplied from an
outside source and brought in through the three wire system. The only
difference between the three wire convertible, and the straight three
wire system is that the center, or neutral, wire of the mains and
feeders should have a current capacity equal to the other two. The
reason for this is that it allows the system to be readily changed
over to a two wire system for use in connection with a private plant.
It sometimes happens that after using power from the local electric
illuminating company for some time, conditions arise which make it
expedient for the owners to install a private electric plant. If a
straight three wire system had been originally installed, the mains and
the feeders when used on a two wire system would not be heavy enough
by 25 per cent., as the neutral wire of a straight three wire system
is the same in size as one of the two outer wires, and theoretically
carries one-half the current or less.]
=Ques. Is a three wire system desirable with an isolated plant?=
Ans. It is more expensive to install than one for a two wire system, as
it is necessary to add a balancer in connection with a 240 volt dynamo.
This balancer set should have one-tenth the capacity of the plant. Such
an equipment has its advantages when 240 volt motors and 120 volt lamps
are connected to the system. With this plant no changes in the motors
are necessary, whereas in a straight 120 volt system, the motors would
have to be changed from 240 to 120 volt machines.
[Illustration: FIG. 998.—Diagram showing reinforcement of neutral
wire necessary to change regular three wire system to two wire system.
The capacity of the neutral wire must equal that of the sum of the two
other wires.]
=Ques. After deciding on the system of wiring to be used, how should
the electrician proceed with the work?=
Ans. He should lay out the mains, feeders and branches of the wiring
system. The outlets are first located and then the distributing
centers. There is no fixed rule or plan by which to go, but the current
density and source of supply are the main points to be considered in
locating these centers. He must also consider the construction of the
building and select runways and shafts which provide easy runs for
feeders.
=Ques. How should panel boards be placed?=
Ans. Panel boards in loft buildings or in any building requiring 8
to 10 circuits to a floor should be distributed one to a floor. In
private houses it is sometimes advisable to install only one panel for
the entire house. This is good practice for a three-story house not
requiring over twelve circuits.
[Illustration: FIG. 999.—Diagram showing current required on each
floor of building. A sketch of this kind is useful in laying out the
feeder system. In the building here shown it will be seen that the
basement and first floor require the most power. In such a case a
feeder is run for these floors, and a sub-feeder from the basement
to the first floor. It is not worth while to reduce the size of the
sub-feeder unless the amount of current used on the sub-feeder be a
small percentage of that used in the feeder. Another reason is that
in changing the size of a wire, the underwriters require a fuse to be
inserted. This makes it necessary to install a larger panel with larger
trim, etc., and the consequent expense easily offsets any gain made by
installing a smaller wire.]
In a building covering a large area it is often advisable to
install two panels or centers to a floor, with two sets of
feeders. It is advisable to keep circuit lengths down to 100
feet or less, and the judicious laying out of circuit centers
will save many feet of wiring.
=Ques. How should the arrangement of feeders for a large building be
determined?=
Ans. A good method is to draw an elevation of the building as in fig.
999, and note on each floor the current requirements.
The best plan is to furnish a feeder for every floor,
especially in large installations. In smaller installations one
or two feeders are sometimes all that are required.
[Illustration: FIG. 1,000.—Diagram showing arrangement of switches in
wiring system where provision is made that any circuit can be fed from
an outside source in case of overload or accident.]
=Ques. How should feeders for motors be installed?=
Ans. They should be independent of the lighting feeders.
=Ques. What is the largest size of feeder that should be used?=
Ans. Feeders requiring over 2 inch pipe should not be used. It is
better to subdivide them, especially if there be many bends or offsets,
since two inch pipe is about the limiting size for economical handling.
=Ques. How should feeders be arranged?=
Ans. They should radiate from a distributing panel, having a proper
sized switch and fuse for each feeder.
If the system of wiring be such that auxiliary power is taken
from a local lighting company, it is a good plan to have each
circuit controlled by a double throw switch so that in case of
overload any circuit can be fed from the illuminating company's
mains as in fig. 1,000.
[Illustration: FIG. 1,001.—Sectional view showing method of cutting a
pocket or opening in floor for the insertion of wires.]
=Ques. How should feeders and mains be run?=
Ans. It is advisable to install them in iron pipe even though the
circuit wires be run otherwise. Since the former carry the main supply
of current it is important to have them well protected as they usually
run up side walls.
The underwriters make numerous restrictions against open or
moulding work on brick walls and require good protection, and
this is an additional reason for piping the mains and feeders.
=Ques. How much load should be placed on the branch circuits?=
Ans. In laying out the branch circuits, it is not good practice to use
up the underwriters' circuit allowance of 660 watts.
[Illustration: FIG. 1,002.—View of outlet pocket showing base board,
and cover supports in position.]
If a circuit be wired with the full allowance of lamps, no
additions could be made without violating the underwriter's
requirements.
=Ques. If concealed wiring is to be installed in a finished building
what should be done first?=
Ans. The outlets should be marked on the ceilings and walls with a
pencil cross at the spot, marking also the location of switches, etc.
=Ques. If an outlet is to be placed at the center of a room, how is the
center of the ceiling located?=
Ans. It is first located on the floor, then transferred to the ceiling
by means of a plumb bob.
=Ques. What is the first operation in making a ceiling outlet?=
Ans. A small hole is bored through the ceiling and the bit pushed up
till it comes in contact with the flooring of the room above, this
flooring is also bored, as in fig. 1,001.
[Illustration: FIG. 1,003.—View of completed pocket and ceiling outlet
showing method of bringing out the wires.]
A long bit about ¼ inch in diameter and about 18 inches long
is used. The hole bored in the floor above will show where to
take up the board to install the wires.
=Ques. How is a pocket opened above the hole bored for ceiling outlet?=
Ans. One-quarter inch holes are bored to insert a keyhole saw through
the joint between two boards at each end of the pocket, and as near
the beams as possible, then the board is cut at an angle as indicated
in fig. 1,001. Having sawed across the board at both ends, it is pried
out with a chisel as shown.
=Ques. How are the holes bored through the beams for the tubes?=
Ans. They are bored about two inches from the top with a 9/16 inch bit,
slanting downward just enough to give clearance for the brace.
[Illustration: FIG. 1,004.—Device for examining partition interiors. A
pocket flash lamp and a little mirror are the only apparatus required
to inspect the interior of a wall or partition which would ordinarily
be inaccessible. For fishing wires, retrieving cable and inspecting
finished work, the lamp and mirror will be found most useful. The
mirror has only to be introduced in the outlet hole in the wall, the
flash lamp and eye being held behind it as illustrated. The mirror
reflects the light of the lamp onto the place to be illuminated, at
the same time reflecting the image back to the eye near the lamp. The
usefulness of this little device is as great as its simplicity.]
=Ques. How are the knobs fastened?=
Ans. Screws may be used but stout wire nails are satisfactory and are
inserted with less labor.
Leather nail heads are slipped on the nails to protect the
porcelain.
=Ques. How is a ceiling outlet completed after the work has reached the
stage shown in fig. 1,002?=
Ans. A baseboard is next installed as in fig. 1,003 to have a secure
hold for the screws used in fastening the fixtures. Two holes are then
bored diagonally with a 11/16 inch bit inserting the bit in the small
hole bored in the ceiling as in fig. 1,001. The outlet wires are then
tied around the knobs and the upper ends being bared and tapped on to
the main wire. A piece of loom is slipped on each outlet wire after
which it is thrust through the outlet as in fig. 1,003.
[Illustration: FIG. 1,005.—Plan showing one floor of a dwelling house
wired with conduits. The numbers on the various outlets indicate the
number of lamps supplied. The wiring is carried out on the loop system,
and it will be noticed that no branches are taken off between outlets.
Four circuits are used in order that there may not be more than ten
lamps on any one circuit.]
=Ques. How are the mains secured to the knobs?=
Ans. By taking a turn around the intermediate knobs and a dead end
hitch at the end knobs, or they may be hitched at each knob. The main
may be secured also by use of a tie wire.
=Ques. What is the difference between a splice and a tap?=
Ans. A splice is the joining of two wires at their ends; a tap is the
joining of the end of one wire with an intermediate point of another
wire.
[Illustration: FIG. 1,006.—Wiring for heating appliances in two story
house; plan of basement.]
=Ques. What precaution should be taken in making joints?=
Ans. All wires joined together should be soldered as this insures good
electrical contact.
Unsoldered wires are both unreliable and dangerous, since they
will corrode from dampness, thus increasing the resistance of
the joint so that it may become heated.
=Ques. How should joints be finished after soldering?=
Ans. They should be covered with rubber tape twisted tightly while it
is hot. When the rubber has melted it will adhere to the joint and
can be moulded with the fingers. Adhesive tape is then wound over the
rubber, the insulation thus being made equal to that which was removed
to unite the wires.
[Illustration: FIG. 1,007.—Wiring for heating appliances; plan of
first floor.]
=Wiring for Heating Appliances.=—There are now on the market a great
number of heating appliances which absorb such small amounts of energy
that they can be used readily on the lighting circuit. These appliances
include the coffee percolator, chafing dish, heating pad, small water
heater, cigar lighter and many other miscellaneous devices. By adapting
these smaller devices to the lighting circuit, not only is the cost of
wiring decreased, but the convenience and cleanliness of the electrical
system is secured.
[Illustration: FIG. 1,008.—Wiring for heating appliances; plan of
second floor.]
The location of the outlets for the heating appliances is not of the
least importance. For many purposes, the flush receptacle in the
baseboard of the room answers many requirements. In other places, for
instance, a receptacle placed beneath the bracket lamp in the bathroom
upon the same circuit as the lamp, is very convenient as a connection
for the electric shaving mug or the massage motor. Similarly, a
suitable outlet placed near the head of the bed is most convenient for
operating a heating pad as it does not necessitate unscrewing a lamp at
night.
The house illustrated in figs. 1,006 to 1,008 is an example of
the use of a single electric heating circuit with a restricted
use of the lighting circuit for heating purposes.
[Illustration: FIG. 1,009.—Diagram illustrating wiring with
combination of moulding, flexible tubing or conduit in non-fireproof
building, where wiring had not been originally installed. In such cases
the moulding may be run in a cornice in the hall. When objectionable to
have the work exposed in the rooms, taps may be made in the moulding
opposite each room and the circuit extensions from the moulding to the
center outlets in the rooms may be run in flexible conduit, fishing
the wires from the moulding to the ceiling outlet. The use of wooden
moulding in new buildings is not to be recommended for the reason
that it is not usually fireproof, and it would be better to run the
conductors concealed in some form of conduit; if the circuit work
were installed at the time the building is erected, it would cost but
little more than moulding, and would be much more substantial. In some
cases, however, wooden moulding might be provided in a new building on
the ceiling as a means of affording facilities for making connections
to outlets over desks, tables, etc., where it would be impossible to
locate the outlet exactly before the building was plastered. In such
cases, the moulding could be installed on the ceiling at a distance of
18 to 24 inches from the walls, forming a rectangle on the ceiling.]
[Illustration: FIG. 1,010.—Feeder system for large hotel. The cellar,
basement, and ground floors are supplied by separate feeders, because
of the importance of having continuous and uninterrupted lighting
service at these floors. The three distributing centers at the cellar
are supplied by a single feeder. Three of the eight distributing
centers at the basement floor serve to supply the outside lights, as
described above. The distributing center for the outside street lamps
is supplied by a separate feeder from the main switchboard. Five of
the distributing centers at the basement floor serve for the basement
lights only; they are fed by two separate feeders, one of which serves
two centers and the other three centers as shown. Each of the three
centers at the ground floor is supplied by a separate feeder. The
upper floors, from the first to the fourteenth inclusive, are divided
into two symmetrical sections. Each section has its own distributing
center, and its own set of supply feeders. The feeder terminates at
the middle center of a group of three, and is extended by mains to the
corresponding centers at the floors immediately above and below. Each
feeder from the first to the twelfth floor inclusive serves to supply
three distributing centers.]
As can be seen in the basement plan, the main supply circuit enters
the basement and from this the heating circuit and lighting circuits
branch, as shown by the arrows. The heating circuit runs direct to
the basement laundry, a branch running to the flat iron. Connections
are made with the kitchen on the first floor and with the dining room
by branch circuits running through the partitions to the respective
rooms. The heating circuit at the dining room is provided with flush
wall receptacles, to which connection is made for the chafing dish and
percolator.
In the kitchen the electric baking outfit is arranged as shown. This
electric outfit is used for auxiliary cooking, such as a gas range
would be, and the oven, placed by itself on the opposite side of the
coal range, is controlled from the main table.
Upstairs the heating circuit, upon which the dining room appliances
are operated, is extended to supply current to the electric luminous
radiator, either in the chamber or bathroom.
The arrangements for the lighting circuits are shown in the figures.
Landing and basement lights are controlled by three way switches to
make them convenient.
In the living room a flush floor receptacle is installed so that the
reading lamp, chafing dish or coffee percolator can be operated without
necessitating the use of a long cord. A few of the electrical outlets
suitable for the purposes mentioned are illustrated.
Where several heating circuits are used it is essential that an
appliance taking a large current be not placed on the regular lighting
circuit. To guard against this possibility, special receptacles should
be installed, constructed for plugs which will not fit any other
receptacle.