Cyclopedia of heating, plumbing and sanitation; a complete reference work . Porcelain Knob. 304 ELECTRIC WIRING 15 • Fibrous Tubing. Fibrous tubing is frequently used with knoband tube wiring, and the regulations governing its use are given inRule 24, Section S, of the National Electric Code. This tubing, asstated in this Rule,may be used where it is impossible and impracticableto employ knobs and tubes, provided the difference in potentialbetween the wires is not over 300 volts, and if the wires are not subs. Fig. 17. Flexible Tubing, Flexauct of National Metal Molding Co., Pitt
Cyclopedia of heating, plumbing and sanitation; a complete reference work . Porcelain Knob. 304 ELECTRIC WIRING 15 • Fibrous Tubing. Fibrous tubing is frequently used with knoband tube wiring, and the regulations governing its use are given inRule 24, Section S, of the National Electric Code. This tubing, asstated in this Rule,may be used where it is impossible and impracticableto employ knobs and tubes, provided the difference in potentialbetween the wires is not over 300 volts, and if the wires are not subs. Fig. 17. Flexible Tubing, Flexauct of National Metal Molding Co., Pittsburg, Pa. ject to moisture. The cost of wiring in flexible fibrous tubing isapproximately about the same as the cost of knob and tube conductors, or two wires together are not allowed in fibroustubing. Fibrous tubing is required at all outlets where conduit or armoredcable is not used (as in knob and tube wiring);and, as required by theRules, it must extend back from the last porcelain support to one inchbeyond the outlet. Fig. 17 shows one make of fibrous tubing. Table VIII gives the maximum sizes of conductors (double-braided) which may be installed in fibrous conduit. TABLE VIIISizes of Conductors in Fibrous Conduit OUTSIDE D AHETEB JlA METER One Wire in Tube 11 inch 11 inch No 12 2 1 ( 3 ti S fz \ << 6 H I a 1 1ft i it 2/0 l& l 250,000 C. M. 1A H 400,000 (. M. r. 750,000 CM. 21 11 1, C. M. 23 2 1,500,000 C M. • )-. — 8 -I 2,000,000 C. M. 305 1G ELECTRIC
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