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.