Modern electrical construction; a reliable, practical guide for the beginner in electrical construction, showing the latest approved methods of installing work of all kinds according to the safety rules of the National board of fire underwriters (1905)
Horstmann, Henry C[harles], 1858- [from old catalog], Tousley, Victor Hugo, 1875- [from old catalog] joint author · Chicago, F. J. Drake & Co. · leaf 129
gure 71 will answer where only protection against acci-dental contacts is required. c. Must not be single pole when the circuits which theycontrol supply devices which require over 660 watts of energy,or when the difference of potential is over 300 volts. This rule allows the use of single pole… … ^mtmtm Figure 72 well if large enough. It will readily open the circuit and itoffers no opportunities for short circuits, as do double poleswitches. Where, however, three wire systems with groundedneutrals are used double-pole switches are preferable, for byreference to Figure 72 one can readily…
Electrical engineering
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