F. H. Richardson's bluebook of projection (1935)

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64 RICHARDSON'S BLUEBOOK OF PROJECTION rated capacity of a wire is, for all practical purposes, the same — the rise in temperature is too slight to be a factor. Mil Foot Standard (13) Calculation of resistance in electrical conductors is based upon what is known as the "mil foot," (14) which is the resistance of a wire of the same characteristics as the one to be calculated, and which is one mil (1/1000 of an inch) in diameter and one foot long. TABLE NO. 3 STANDARDIZED STRANDING Strands ■s 1 7/25 7/ 32 7/40 7/ 51 7/ 64 7/ 81 7/ 91 7/102 19/ 64 19/ 72 19/ 81 19/ 91 19/107 19/114 37/ 91 37/ 97 37/102 37/116 61/102 61/107 61/114 61/121 61/128 91/114 91/128 127/114 127/128 Cable Allowable Carrying Capacities in Amperes 6 OS o Outside Dia. over Copper < S »— i Table B Varnished Cloth Insulation 22 4,490 .075 15 18 20 7,150 .096 20 25 18 11,370 .120 25 30 16 18,080 .153 35 40 14 28,740 .192 50 60 12 45,710 .253 70 85 11 58,000 .273 80 95 10 72,680 .306 90 110 14 78,030 .320 100 120 13 98,380 .360 125 150 12 124,900 .405 150 180 11 157.300 .455 175 210 * 217,500 .540 225 270 9 248,700 .570 250 300 11 306,400 .637 275 330 * 347,500 .679 300 360 10 381,200 .714 325 390 * 484,300 .798 400 480 10 633,300 .918 475 565 * 698,000 .963 500 600 9 788,500 1.030 550 660 * 893,100 1.090 600 720 8 1,007,000 1.150 650 780 9 1,191,000 1.250 725 870 8 1,502,000 1.410 850 1020 9 1,660,000 1.480 900 1100 8 2,097,000 1.660 1100 1300 4, JJ'-S 3-5-2 20 25 35 50 70 90 110 130 150 175 210 250 325 350 400 450 500 600 700 750 825 900 1000 1125 1350 1460 1700 *These individual S. Wire Tables. strands are odd sizes not listed in the American or B. (15) The resistance of one mil foot wire made of commercial copper is 10.5 ohms at normal temperature of 75 degrees Fahrenheit. Resistance of Copper Circuits (16) In applying the mil foot standard we will assume a circuit to be of No. 6 wire and that it is 200 feet in length, having 400 feet of wire. If one foot of