Ambient Temperature Correction Factors Based on 30°C (86°F)
To calculate the maximum current in an insulated wire when the temperature is not 30°C, first find the
maximum allowable current for a raceway or cable for 30°C,
then multiply that maximum current by the adjustment factor from the Adjustment Factors for Temperatures Other
than 30°C Chart below.
Chart of Maximum Current Adjustment Factors for Temperatures Other than 30°C
Ambient
Temperature
(°C) |
Temperature Rating of Conductor |
| 60°C |
75°C |
90°C |
| 10 or Less |
1.29 |
1.20 |
1.15 |
| 11 - 15 |
1.22 |
1.15 |
1.12 |
| 16 - 20 |
1.15 |
1.11 |
1.08 |
| 21 - 25 |
1.08 |
1.05 |
1.04 |
| 26 - 30 |
1.00 |
1.00 |
1.00 |
| 31 - 35 |
0.91 |
0.94 |
0.96 |
| 36 - 40 |
0.82 |
0.88 |
0.91 |
| 41 - 45 |
0.71 |
0.82 |
0.87 |
| 46 - 50 |
0.58 |
0.75 |
0.82 |
| 51 - 55 |
0.41 |
0.67 |
0.76 |
| 56 - 60 |
--- |
0.58 |
0.71 |
| 61 - 65 |
--- |
0.47 |
0.65 |
| 66 - 70 |
--- |
0.33 |
0.58 |
| 71 - 75 |
--- |
--- |
0.50 |
| 76 - 80 |
--- |
--- |
0.41 |
| 81 - 85 |
--- |
--- |
0.29 |
Table 310.15(B)(1), 2020 NEC®
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WARNING: When using this information to perform electrical work, call a licensed electrician and consult the NEC® for safety. All licensed
electricians have passed examinations covering the National Electric Code®, know state and local building codes, and may carry insurance to cover damages.