How to calculate wire size by Voltage dropping
Voltage drop can be calculated by ohms law in which E = R I. Where
E = voltage drop (Volts)
R = electrical resistance (Ohms)
I = current (Amps)
Example:
Voltage drop in a 100 ft power line: 2 x 100 ft, electrical resistance 1.02 Ohm/ 1000 ft, current: 10 Amps
E = 2 (0.00102 Ohm/ft) (100 ft) (10 Amps) = 2.04 Volts
Max wire feet @ 120 volts, 1 phase, 2% max voltage drop |
Amps | Volt-Amps | #14 | #12 | #10 | #8 | #6 | #4 | #2 | 1/0 | 2/0 | 3/0 |
1 | 120 | 450 | 700 | 1100 | 1800 | 2800 | 4500 | 7000 | - | - | - |
5 | 600 | 90 | 140 | 225 | 360 | 575 | 910 | 1400 | 2250 | 2800 | - |
10 | 1200 | 45 | 70 | 115 | 180 | 285 | 455 | 705 | 1100 | 1400 | 1800 |
15 | 1800 | 30 | 47 | 75 | 120 | 190 | 305 | 485 | 770 | 965 | 1200 |
20 | 2400 | - | 36 | 57 | 90 | 140 | 230 | 365 | 575 | 725 | 900 |
25 | 3000 | - | - | 45 | 72 | 115 | 180 | 290 | 460 | 580 | 720 |
30 | 3600 | - | - | 38 | 60 | 95 | 150 | 240 | 385 | 490 | 600 |
40 | 4800 | - | - | - | 45 | 72 | 115 | 175 | 290 | 360 | 440 |
50 | 6000 | - | - | - | - | 57 | 90 | 145 | 230 | 290 | 360 |
60 | 7200 | - | - | - | - | - | 76 | 120 | 190 | 240 | 305 |
70 | 8400 | - | - | - | - | - | 65 | 105 | 165 | 205 | 260 |
80 | 9600 | - | - | - | - | - | - | 90 | 144 | 180 | 230 |
Max wire feet @ 240 volts, 1 phase, 2% max voltage drop |
Amps | Volt-Amps | #14 | #12 | #10 | #8 | #6 | #4 | #2 | 1/0 | 2/0 | 3/0 |
1 | 240 | 900 | 1400 | 2200 | 3600 | 5600 | 9000 | - | - | - | - |
5 | 1200 | 180 | 285 | 455 | 720 | 1020 | 1750 | 2800 | 4500 | 5600 | 7000 |
10 | 2400 | 90 | 140 | 225 | 360 | 525 | 910 | 1400 | 2200 | 2800 | 3600 |
15 | 3600 | 60 | 95 | 150 | 240 | 350 | 605 | 965 | 1500 | 1900 | 2400 |
20 | 4800 | - | 70 | 110 | 180 | 265 | 455 | 725 | 1100 | 1400 | 1800 |
25 | 6000 | - | - | 90 | 144 | 210 | 365 | 580 | 920 | 1100 | 1440 |
30 | 7200 | - | - | 75 | 120 | 175 | 300 | 485 | 770 | 970 | 1200 |
40 | 5600 | - | - | - | 90 | 130 | 230 | 360 | 575 | 725 | 880 |
50 | 12000 | - | - | - | - | 105 | 180 | 290 | 460 | 580 | 720 |
60 | 14400 | - | - | - | - | - | 150 | 240 | 385 | 485 | 600 |
70 | 16800 | - | - | - | - | - | 130 | 205 | 330 | 415 | 520 |
80 | 19200 | - | - | - | - | - | - | 180 | 290 | 365 | 440 |
100 | 24000 | - | - | - | - | - | - | - | 230 | 280 | 360 |
150 | 36000 | - | - | - | - | - | - | - | 185 | 190 | 240 |
200 | 48000 | - | - | - | - | - | - | - | - | - | 180 |