  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.
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. 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. 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. 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. 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. 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 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. 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 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. 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.
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.
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.
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
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. Fig. 1,002.—View of outlet pocket showing base board, and cover supports in position.
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. Fig. 1,003.—View of completed pocket and ceiling outlet showing method of bringing out 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 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. 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.
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 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. 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.
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. 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, 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
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. 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. |
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