Image from page 410 of "Cyclopedia of heating, plumbing and sanitation; a complete reference work" (1909)
Authors: American School (Chicago, Ill.)
Publisher: Chicago American School of Correspondence
Contributing Library: Gerstein - University of Toronto
Digitizing Sponsor: University of Toronto
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in placesparticularly exposed to lightning discharges, and at all points whereconnections are made to enter a building. The location and number 368 ELECTRIC WIRING 79 of lightning arresters will depend upon local conditions, the likelihoodand frequency of thunderstorms, etc. Where lightning arresters areprovided, it is essential that agood ground connection be obtained.The ground connection should bemade by a fairly good-sized insu-lated rubber conductor, not lessthan No. 6 B. & S. Gauge, con-necting either with a water pipeto which it should be clamped, orfastened in such a maimer as toobtain a good electric contact, orelse to a ground-plate of copperembedded in crushed charcoal orcoke. The neutral wire of a three-wire of both secondary alternating-current systems and direct-currentsystems, should be properlygrounded as required by the National Electric Code (see Mules 12,13, and 13-A). Lamps on Poles. Fig. 71 shows the method of wiring to andsupporting a lamp located on a pole.
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Fig. 71. Method f Wiring to and Sup-porting Lamp on Pole. UNDERGROUND LINEWORK In large cities, or in congested districts, or where the appearanceof overhead linework is objectionable, it is generally necessary toplace the conductors underground instead of overhead. The advantages of underground linework are—first, that ofappearance; second, it is more permanent and less liable to inter-ruption than overhead work. The principal disadvantage of underground work is the greaterfirst cost. In overhead linework, conductors having weatherproofinsulators consisting of cotton dipped in a special compound similarto pitch, are used, the cost of which is relatively small. For under-ground linework, however, the conductors must not only have rubberinsulation, but also a lead sheathing for mechanical protection. 369 80 ELECTRIC WIRING Furthermore, the cost of the duets, trenching, concrete work, layingthe ducts, etc., is much greater than the cost of poles, cross-arms, ete. As in the cas
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