Danger of fire from an electric current comes from the "short circuit," partial or complete; and it is against this danger that the rules guard one. The amount of electricity flowing through a short circuit is limited only by the fuse protecting that line; and since there is no substance known that can withstand the heat of the electric arc, short circuits must be guarded against. Happily the current is so easily controlled that the fire hazard is eliminated entirely—something which cannot be done with oil lamps.
In house-wiring for farm plants, the wire should be rubber-covered, and not smaller than No. 14 B. & S. gauge. This is the wire to use on all lamp circuits. It costs about $0.85 cents per 100 feet. There are four kinds of wiring permitted, under the insurance code:
(1) Flexible armoured cable: This consists of two-wire cable, protected with a covering of flexible steel. It is installed out of sight between the walls, and provides suitable outlets for lamps, etc., by means of metal boxes set flush with the plaster. It is easily installed in a house being built, but requires much tearing down of plaster for an old house. Since its expense prohibits it in the average farm house, this system will not be described in detail here.
(2) Rigid and flexible conduit: As the name implies this system consists of iron pipe, in connection with flexible conduit, run between the walls. It differs from the above system, in that the pipes with their fittings and outlet boxes are installed first, and the wires are then "fished" through them. Duplex wires—the two wires of the circuit woven in one braid—are used; and a liberal amount of soapstone, and occasionally kerosene, are used to make the wires slip easily into place. This is the most expensive system, and the best; but it is difficult to install it in an old house without tearing down a good deal of plaster. It has the advantage of being absolutely waterproof and fireproof.
(3) Wooden moulding: This is simply moulding, providing two raceways for the insulated wires to run in, and covered with a capping. It is nailed or screwed firmly to the wall, on top of the plaster; and when the wires have been installed in their respective slots and the capping tacked on, the moulding is given a coat of paint to make it in harmony with the other moulding in the room. This system is cheap, safe, and easily installed, and will be described in detail here.
Detail of wooden moulding
(4) Open wiring: In open wiring, the wires are stretched from one support to another (such as beams) and held by means of porcelain cleats, or knobs. It is the simplest to install; but it has the objection of leaving the wires unprotected, and is ugly. It is very satisfactory in barns or out-buildings however.