The Golden State: Where & How to Live, Secure, Visit, Enjoy and Thrive in California
Practical Electricity And House Wiring
Wiring With Conduit
In this chapter we will wire the same house that we discussed in Chapters 13 and 14, except that instead of using cable, we are going to use conduit. Most of the essentials of conduit wiring were covered in Chapter 11, where we installed the service wires, but at the risk of unnecessary repetition, these points will be here again covered.
If the completed installation is for Alternating Current, as over 99% of all installations are, then the Code provides that all the conductors of a circuit shall be placed within one conduit. This simply means that both the black and white wire to any outlet must run inside the same conduit. For example, if a large motor required a pair of No. 2 wires, both must be inside 11/4 inch conduit; it would not be permissible to run the black wire inside a 3/4 inch conduit, the white wire in a separate 3/4 inch conduit.
This does not mean that wires for two or more different circuits may not be within one conduit. For example, if your fuse cabinet provides for four circuits, the four pairs of wires for the four circuits may all be contained within one conduit up to the point where it is desirable to separate them.
Definition of Conduit.—Conduit is shown in Fig. 161. It is really steel pipe, differing from water pipe in several respects.
It is particularly smooth inside, lest the insulation of wire be damaged in pulling it into the conduit. It is softer so it will bend easily, and enameled or galvanized to prevent rusting. The galvanized is the more common finish.
Installing Conduit.—Only the conduit itself (with outlet and switch boxes) is installed as the house is built; the wires are pulled into the conduit after the house is built and plastered. Spliced wires are not permitted inside conduit: one continuous piece must be used from one outlet to the next. The bends must be gradual, so that if a length of conduit were bent into a complete circle, the diameter would not be less than 12 times the diameter of the conduit itself. In larger sizes, factory bent elbows are generally used. Any "run" of conduit (from one outlet to another) may contain not over four quarter bends, for a greater number of bends might make it too difficult to pull in the wire, with possible damage to the insulation.
