celain insulators. No switches or fusible cut-outs will be allowed where exposed to inflammable gases or dust, or to flyings of combustible material. e. Must be protected when passing through floors, walls, partitions, timbers, etc., by waterproof, non-combustible, insulating tubes, such as glass or porcelain. 22. INTERIOR CONDUITS*:-(See Definitions). . a. Must be continuous from one junction box to another, or to fixtures, and must be of material that will resist the fusion of the wire or wires they contain without igniting the conduit. b. Must not be of such material or construction that the insulation of the conductor will ultimately be injured or destroyed by the elements of the composition. *The object of a tube or conduit is to facilitate the insertion or extraction of the conductors to protect them from mechanical injury, and, as far as possible, from moisture. Tubes or conduits are to be considered merely as raceways, and are not to be relied on for insulation between wire and wire, or between the wire and the ground. c. Must be first installed as a complete conduit system, without conductors, strings, or anything for the purpose of drawing in the conductors, and the conductors then to be pushed or fished in. The conductors must not be placed in position until all mechanical work on the building has been, as far as possible, completed. d. Must not be so placed as to to be subject to mechanical injury by saws, chisels, or nails. e. Must not be supplied with a twin conductor, or two separate conductors, in a single tube. (See page 198, Rule 22). f. Must have all ends closed with good adhesive material, either at junction boxes or elsewhere, whether such ends are concealed or exposed. Joints must be made air-tight and moisture proof. g. Conduits must extend at least one inch beyond the finished surface of walls or ceilings until the mortar or other similar material be entirely dry, when the projection may be reduced to half an inch. 23. DOUBLE POLE SAFETY CUT-OUTS: a. Must be in plain sight or enclosed in an approved box readily accessible. (See Definitions). b. Must be placed at every point where a change is made in the size of the wire (unless the cut-out in the larger wire will protect the smaller). c. Must be supported on bases of non-combustible, insulating, moistureproof material. d. Must be supplied with a plug (or other device for enclosing the fusible strip or wire) made of non-combustible and moisture-proof material, and SO constructed that an arc cannot be maintained across its terminals by the fusing of the metal. e. Must be so placed that on any combination fixture no group of lamps requiring a current of six amperes or more shall be ultimately dependent upon one cut-out. Special permission may be given in writing by the Inspector for departure from this rule in case of large chandeliers. f. All cut-out blocks must be stamped with their maximum safe-carrying capacity in amperes. 24. SAFETY FUSES: a. Must all be stamped or otherwise marked with the number of amperes they will carry indefinitely without melting. b. Must have fusible wires or strips (where the plug or equivalent device is not used), with contact surfaces or tips of harder metal, soldered or otherwise, having perfect electrical connection with the fusible part of the strip. c. Must all be so proportioned to the conductors they are intended to protect that they will melt before the maximum safe-carrying capacity of the wire is exceeded. 25. TABLE OF CAPACITY OF WIRES: It must be clearly understood that the size of the fuse depends upon the size of the smallest conductor it protects, and not upon the amount of current to be used on the circuit. Below is a table showing the safe-carrying capacity of conductors of different sizes in Brown & Sharpe gauge, which must be followed in the placing of interior conduct NOTE.-By "open work" is meant construction which admits of all parts of the surface of the insulating covering of the wire being surrounded by free air. The carrying capacity of 16 and 18 wire is given, but no wire smaller than 14 is to be used except as allowed under Rules 18 (a) and 27 (d). 26. SWITCHES: a. Must be mounted on moisture |
