What is the minimum size THHN copper conductor required for a load of 65 amperes in an ambient temperature of 110°F?

To determine the minimum size THHN copper conductor required for a load of 65 amperes at an ambient temperature of 110°F, you'll need to refer to the National Electrical Code (NEC) and conductor ampacity charts.

Under typical conditions, a 75°C rated THHN conductor can carry 65 amperes. According to the NEC, a 6 AWG copper conductor has an ampacity of 65 amperes when the temperature is at 30°C (86°F), but this must be adjusted for the higher ambient temperature of 110°F.

The NEC specifies derating for conductors when they are subjected to higher temperatures. For instance, if the ambient temperature exceeds 30°C, the ampacity of the conductors must be derated according to NEC tables.

At 110°F (approximately 43°C), the 6 AWG size maintains its rating without needing additional derating to handle the load of 65 amperes. Smaller conductor sizes, such as 8 AWG, 10 AWG, or 12 AWG, would not meet the required ampacity to safely handle 65 amperes at higher temperatures, making them unsuitable choices in this scenario.

Hence, a 6 AWG