How much current is permissible for twelve 1 AWG THWN copper conductors in an ambient temperature of 101°F?

To determine the permissible current for twelve 1 AWG THWN copper conductors in an ambient temperature of 101°F, it is essential to understand both the base ampacity of the conductors and the adjustment factors that apply due to temperature.

1 AWG THWN copper conductors typically have a base ampacity of around 130 amps when installed in a standard environment (using the National Electrical Code (NEC) tables). However, when ambient temperature increases beyond the standard rating (which is typically around 86°F), adjustments must be made.

At 101°F, there is a need to apply a temperature correction factor. According to NEC standards, for temperature ratings above 86°F, the conductors need to be derated. The correction factor for 1 AWG THWN conductors at 101°F is approximately 0.83.

To find the adjusted ampacity, multiply the base ampacity by the correction factor:

• 130 A (base ampacity) × 0.83 (correction factor) = 107.9 A

This value gives the maximum permissible ampacity before considering the effect of grouping. Since there are twelve conductors, they must be further derated due to the number of conduct