[Electric engineering.] . ghout 5 minutes the application of an electro-motive force of 3,000 volts per -£T inch thickness ofinsulation under the following conditions: The source of alternating electromotive forceshall be a transformer of at least 1 kilowatt capac-ity. The application of the electromotive forceshall first be made at 4,000 volts for 5 minutes andthen the voltage increased by steps of not over3,000 volts, each held for 5 minutes, until the rup-ture of the insulation occurs. The tests for dielec-tric strength shall be made on a sample of wire thathas been immersed for 72 hours in
[Electric engineering.] . ghout 5 minutes the application of an electro-motive force of 3,000 volts per -£T inch thickness ofinsulation under the following conditions: The source of alternating electromotive forceshall be a transformer of at least 1 kilowatt capac-ity. The application of the electromotive forceshall first be made at 4,000 volts for 5 minutes andthen the voltage increased by steps of not over3,000 volts, each held for 5 minutes, until the rup-ture of the insulation occurs. The tests for dielec-tric strength shall be made on a sample of wire thathas been immersed for 72 hours in water, 1 foot ofwhich is submerged in a conducting liquid held in ametal trough, one of the transformer terminalsbeing connected to the copper of the wire and theother to the metal of the trough. Tests by the Underwriters are made on the products ofthe various manufacturers from time to time, and the namesof those wires that are acceptable, as complying with thisstandard, can be learned from them. 21 INTERIOR WIRING. 21. Fig. 6. CONCEALED KNOB-AND-TUBE AVORK. 21. The most common way of concealing wires in abuilding is to run them through the joists between thefloors and ceilings andthrough studding par-titions, and to insulatethem by means of por-celain knobs and tubes,as shown in Fig. holes should notbe closer together thanis allowed by the Un-derwriters rules, asgiven below, and thetubes should fit tight-ly in the holes. Whenthe holes are not hori-zontal, but are boredfrom above or belowobliquely, the tubes should be put in with their heads on thehigh side, so that they cannot fall or slide out; and whentubes are placed so that there is any strain upon them, theirheads must be so placed that the tubes cannot slip. Holesshould be bored of such a size that the tubes can be insertedby driving lightly. Do not make the holes too small orthere will be danger of breaking the tubes. Holes must bebored sufficiently far away from the floors and ceilings to beout of reach of nai
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Keywords: ., bookcentury1900, bookdecade1900, bookidelectricengi, bookyear1902
