How is the ampacity adjusted when using 12 AWG THWN-2 conductors at an ambient temperature of 32°C?

When adjusting ampacity, it is crucial to consider the impact of ambient temperature on conductor performance. For THWN-2 conductors, the base ampacity value is determined at a standard temperature, typically around 30°C. As the operating temperature increases, the ampacity must be adjusted downward to account for the heat generated within the conductor, which could lead to insulation damage or reduced efficiency.

In this case, at an ambient temperature of 32°C, the adjustment involves a multiplicative factor to the base ampacity. The National Electrical Code (NEC) indicates that for each degree above the base reference temperature, there is a necessity for a slight reduction in ampacity.

Using a correction factor, specifically for 12 AWG THWN-2 conductors at 32°C, approximately a decrease to 96% of the base value is warranted, which corresponds to multiplying the base ampacity by 0.96. This adjustment accounts for the increase in ambient temperature and ensures the safe operation of the conductors without exceeding their thermal limits. Therefore, multiplying by 0.96 correctly reflects the necessary reduction in ampacity needed for safe installations in warmer conditions.