b. Must be continuous from outlet to outlet or to junction boxes, 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 involves running each conduit continuously into a main cut-out cabinet or gutter surrounding the panel board, as the case may be (see No. 54).

When conduit is used every run of pipe must end in accessible outlet boxes. This box may be a cut-out center, switch outlet, fixture outlet or a junction box. If a mixed form of wiring is used, where part of a circuit is run in conduit and the balance with some other form of construction, such as

-Junction box

--lock nut

gas

•nipple

Figure 107.

concealed knob and tube work, for instance, the conduit must in all cases enter the box and be firmly attached to it, as shown in Figure 107. Cases are sometimes found where the

conduit is brought just to the box, but does not enter it, the wires being extended through holes into the box. This method of wiring is obviously wrong, as a wireman is apt to find if he ever has occasion to replace wires in such a system. The same holds true of cut-out centers. Here also every run of conduit must enter the box. The conduit should not simply be brought to the sides or the back of the cut-out center and the wires then carried to the cut-outs in flexible tubing, but every conduit should enter clear into the box so that when

the work is completed there will be no exposed wiring. In the case of main runs the conduit should enter the boxes and never be broken between the outlets. Sometimes it is necessary to install meters on the mains and the conduit is ended and the wires carried to the meters and then either extended

in conduit or carried into the cut-out center. This construction should be avoided. If a meter is to be installed near a cut-out center, the main conduit should be carried into the box and the necessary meter loops then brought out. In this way the quantity of wire outside of conduits is reduced to a minimum. If a meter is to be installed in some location along the mains other than at the cut-out center or service switch, a junction box should be provided and the meter loops brought out from that. This is shown in Figure 108, which also shows a cut-out box as used with conduit systems.

C. Must be first installed as a complete conduit system, without the conductors.

As fast as the conduit is installed, the ends of the pipes should be closed, using paper or corks. This does away with the liability of plaster or other substances entering the pipes and causing trouble when the wires are to be pulled in. The conductors should not be pulled in until all the mechanical work on the building is, as far as possible, finished. When a conduit system is ready for the wires, the "pulling in" may be done in various ways. For short runs, all that is necessary is to shove the wires in at one opening until they come out at the other. If a run is too long to be inserted in this way, what is known as a "fish wire" can be used. The ordinary fish wire is a flat band of steel about 5/32 inch wide and 1/32 inch thick. This wire can be forced through any ordinary length of pipe. Ordinary round steel wire of about No. 12 or 14 B. & S. gage can also be used, although this is not as good as the fish wire above described.

The end of the wire is first bent back so as to form a very small hook or eye; this will enable it to slide easily over obstructions in the pipe and also make it possible should it stick somewhere to engage it with another fish wire provided with

a suitable hook and entered from the other end of the pipe. This is very often necessary in runs having many bends. The fish wire, having been pushed through the pipe, is now fastened to the copper wire by means of a strong hook and the copper wire pulled into the pipe.

In pulling in the large size cables, it is often found advantageous to pull on the fish wire and at the same time push on the end of the cable entering the pipes. It is also well to remember that it is easier to pull down than to pull up, as, when pulling down, the weight of the cable assists. The use of soapstone facilitates the drawing in of the wires. The wire may either be covered with the powdered soapstone or the soapstone may be blown into the pipes. An elbow partly filled with soapstone is often found convenient for blowing the soapstone into the pipe, always blowing from the highest point.

Graphite or axle grease should never be used for this purpose, as the graphite is a conductor and the axle grease will rot the rubber insulating covering of the wire.

d. Must be equipped at every outlet with an approved outlet box or plate (see No. 49 A).

Outlet plates must not be used where it is practicable to install outlet boxes.

The outlet box or plate shall be so installed that it will be flush with the finished surface, and if this surface is broken it shall be repaired so that it will not show any gaps or open spaces around the edge of the outlet box or plate.

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 of the Inspection Department having jurisdiction, provided the conduit ends are bushed and secured.

The object of an outlet box is to hold the conduits firmly in place, to connect the various runs of conduit so that they form a continuous electrical path to the ground, and to afford a fireproof enclosure for the joints, switches, etc. Outlet

boxes are made in various designs to meet the requirements of the work on which they are to be used.

Where it is impossible to use an outlet box, an outlet plate can be used. These plates are fitted with set screws so that they hold the ends of the conduits firmly in position and make the metal of the system continuous. They do not afford a fireproof enclosure for the joints and for that reason should never be used when it is practicable to use an outlet box. If the conditions are such that neither an outlet box nor plate can be used, special permission can be obtained from the Inspection Department having jurisdiction to omit them. In this case the conduits should be bushed at the ends and the pipes. should be bonded together.

e. Metal conduits where they enter junction boxes, and at all other outlets, etc., must be provided with approved bushings, 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.

When a piece of conduit is cut with a pipe cutter, a sharp edge is left on the inside. This edge, if left on, would soon cut into the insulation of the wires. It should be removed by means of a pipe reamer. The bushing can now be screwed on as shown in Figure 107, a locknut having first been screwed onto the pipe. The locknut and bushing are then screwed up so that they are tight and form a good connection.

f. Must have the metal of the conduit permanently and effectually grounded.

It is essential that the metal of conduit systems be joined so as to afford electrical conductivity sufficient to allow the largest fuse or circuit breaker in the circuit to operate before a dangerous rise in temperature in the conduit system can occur. Conduits and gas pipes must be securely fastened in metal outlet boxes so as to secure good electrical connection. Where boxes used for centers of distribution do not afford good electrical connections, the conduits must be joined around them by suitable bond wires. Where sections of metal