powerful currents are used, must be made of some incombustible substances that will withstand the heat of the arc when the switch is changed. Motors.-Wires for motors should be run exactly as for lamps on similar circuits. On low-tension circuits, where motors are run in multiple, safety catches must be used on each side of the circuit. On high-tension circuits the same restrictions apply as for arc lamps, and suitable cut-outs must be provided. Motors must be treated as dynamos as regards insulation, flyings, dampness, etc. NOTE. If the regulations of the Underwriters' Association are not followed in wiring buildings, the wiring is liable to be condemned by the Insurance Inspectors and the policy canceled. EQUIVALENT SECTIONAL AREA OF WIRES, B. & S. GAUGE. The above table indicates the number of smaller wires required to give a sectional area equal to one larger size wire, the figures between the horizontal lines corresponding to each other. For example: It requires two wires, No. 0, or 4 wires, No. 3, etc., to give a sectional area equal to 1 wire, No. 0000. Again: it requires two wires, No. 13, or 4 wires, No. 16; or 2 wires, 1 No. 12 plus 1 No. 14, to give a sectional area equal to 1 No. 19. |