CHAPTER XLI

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.

=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.

=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.

=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.

=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.

=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.

=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.

=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.

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.

=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.

=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.

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.

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.

=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.

=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.

=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.

=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.

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.

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.