What is the ampacity of each 12 AWG conductor in a 4-conductor metal-clad cable supplying dedicated 20-ampere computer circuits in a temperature of 32°C?

To determine the ampacity of a 12 AWG conductor, we must consider the standard ampacity ratings as determined by the National Electrical Code (NEC) and factors such as the number of conductors in a cable and the ambient temperature.

For a single 12 AWG copper conductor, the typical ampacity is around 20 amperes at an ambient temperature of 30°C. However, when conductors are grouped together—such as in a 4-conductor metal-clad cable—the ampacity may need to be adjusted due to the increased heat buildup. The NEC allows for derating conductors under specific conditions where multiple conductors are bundled.

In this scenario, with four conductors in the cable, a derating factor of approximately 80% is applied to accommodate for heat dissipation. Therefore, the calculation for the adjusted ampacity becomes:

Initial ampacity (20 A) multiplied by the derating factor (0.80) results in:

20 A × 0.80 = 16 A

However, since the original ampacity is higher and the ambient temperature is slightly above 30°C, we must account for a rounding adjustment. After applying the necessary calculations and considering the 32°C ambient temperature, the final