As a solar system is designed you need to select the correct size conductor. The following tables will help in that selection. This information is based on the following:
- National Electric Code (NEC) Table 310.16
- Conductors rated 0 to 2000 V
- Not more than 3 current carrying conductors in raceway, cable or direct buried
- Ambient Temp 30C (86F)
Allowable Ampacity of Aluminum Conductors
| Size AWG or kcmil | Conductor Temp 60C (140F) | Conductor Temp 75C (167F) | Conductor Temp 90C (194F) |
|---|---|---|---|
| 12* | 20 | 20 | 25 |
| 10* | 25 | 30 | 35 |
| 8 | 30 | 40 | 45 |
| 6 | 40 | 50 | 60 |
| 4 | 55 | 65 | 75 |
| 3 | 65 | 75 | 85 |
| 2 | 75 | 90 | 100 |
| 1 | 85 | 100 | 115 |
| 1/0 | 100 | 120 | 135 |
| 2/0 | 115 | 135 | 150 |
| 3/0 | 130 | 155 | 175 |
| 4/0 | 150 | 180 | 205 |
| 250 | 170 | 205 | 230 |
| 300 | 190 | 230 | 255 |
| 350 | 210 | 250 | 280 |
| 400 | 225 | 270 | 305 |
| 500 | 260 | 310 | 350 |
*12 AWG Maximum overcurrent = 15 amps
*10 AWG Maximum overcurrent = 25 amps
Correction Factors for Different Ambient Temperatures
For ambient temperatures other than 30C (86F) the following are multipliers used to adjust the above ampacity. As the temperature of a conductor increases the amount of current the conductor can safety carry is reduced.
| Ambient Temperature (C) | Conductor Temp 60C (140F) | Conductor Temp 75C (167F) | Conductor Temp 90C (194F) | Ambient Temperature (F) |
|---|---|---|---|---|
| 21-25 | 1.08 | 1.05 | 1.04 | 70-77 |
| 26-30 | 1 | 1 | 1 | 78-86 |
| 31-35 | 0.91 | 0.94 | 0.96 | 87-95 |
| 36-40 | 0.82 | 0.88 | 0.91 | 96-104 |
| 41-45 | 0.71 | 0.82 | 0.87 | 105-113 |
| 46-50 | 0.58 | 0.75 | 0.82 | 114-122 |
| 51-55 | 0.41 | 0.67 | 0.76 | 123-131 |
| 56-60 | 0 | 0.58 | 0.71 | 132-140 |
| 61-70 | 0 | 0.33 | 0.58 | 141-158 |
| 71-80 | 0 | 0 | 0.41 | 159-179 |
