CARRYING CAPACITY OF WIRES AND WEIGHT
| B. & S. Gauge No. | Weight 1,000 ft. Weatherproof (Pounds) | Carrying capacity Weatherproof (Amperes) | Carrying capacity rubber cov. (Amperes) |
| 0000 | 800 | 312 | 175 |
| 000 | 666 | 262 | 145 |
| 00 | 500 | 220 | 120 |
| 0 | 363 | 185 | 100 |
| 1 | 313 | 156 | 95 |
| 2 | 250 | 131 | 70 |
| 3 | 200 | 110 | 60 |
| 4 | 144 | 92 | 50 |
| 5 | 125 | 77 | 45 |
| 6 | 105 | 65 | 35 |
| 7 | 87 | 55 | 30 |
| 8 | 69 | 46 | 25 |
| 10 | 50 | 32 | 20 |
| 12 | 31 | 23 | 15 |
| 14 | 22 | 16 | 10 |
| 16 | 14 | 8 | 5 |
| 18 | 11 | 5 | 3 |
Since two wires are required for electrical transmission, the above formula is made simple by counting the distance only one way, in feet, and doubling the resistance constant, 10.6, which, for convenience is taken as 22, instead of 21.2.
Examples of Transmission Lines
As an example, let us say that Farmer Jones has installed a water-power electric plant on his brook, 200 yards distant from his house. The generator is a 5 kilowatt machine, capable of producing 45 amperes at 110 volts pressure. He has a 3 horsepower motor, drawing 26 amperes at full load; he has 20 lights of varying capacities, requiring 1,200 watts, or 10 amperes when all on; and his wife uses irons, toasters, etc., which amount to another 9 or 10 amperes—say 45 altogether. The chances are that he will never use all of the apparatus at one time; but for flexibility, and his own satisfaction in not having to stop to think if he is overloading his wires, he would like to be able to draw the full 45 amperes if he wishes to. He is willing to allow 5 per cent loss in transmission. What size wires will be necessary, and what will they cost? Substituting these values in the above formula, the result is:
Transmission wire on glass insulator
Referring to the table, No. 0 wire is 105,534 circular mills, and is near enough; so this wire would be used. It would require 1,200 feet, which would weigh, by the second table, 435.6 pounds. At 19 cents a pound, it would cost $82.76.