Determine the ampacity of a 3-conductor 8 AWG copper Type MC cable at an ambient temperature of 96°F.

To determine the correct ampacity of a 3-conductor 8 AWG copper Type MC cable at an ambient temperature of 96°F, it is essential to reference the National Electrical Code (NEC) ampacity tables and consider the impact of temperature on conductor performance.

For a standard 8 AWG copper conductor, the base ampacity at a standard temperature of 86°F is typically around 50 A in a dry location. However, when considering higher temperatures, adjustments must be made according to NEC tables, which include derating factors for ambient temperature increases above 86°F.

At an ambient temperature of 96°F, which is 10°F above the standard reference temperature, an adjustment factor is applied. Generally, the adjustment for temperatures above the standard will reduce the ampacity. The ampacity decrease for copper conductors usually starts to reflect with an increasing temperature, and thus a proper calculation or reference to a derating table is necessary to arrive at the final ampacity.

Taken from the tables, it becomes clear that for the conditions given—specifically for 3-conductor configurations—using the proper adjustment factor could lead to an ampacity of 40 A. However, recognizing that some practices may round it or not apply the