Question 1

What is ampacity in electrical work?

Accepted Answer

Ampacity is the maximum current (in amps) a conductor can carry continuously without exceeding its temperature rating. It is determined by wire gauge (AWG), insulation type, and installation conditions per NEC Table 310.16.

Question 2

How is ampacity calculated per NEC?

Accepted Answer

Ampacity is calculated using NEC Table 310.16 as the base, then applying correction factors for ambient temperature (310.15(B)(1)) and adjustment factors for conduit fill (310.15(C)(1)) when more than 3 current-carrying conductors are bundled.

Question 3

What wire size do I need for a 20-amp circuit?

Accepted Answer

Per NEC Table 310.16, a 20-amp circuit requires a minimum of 12 AWG copper conductor (with 90°C insulation in a 30°C ambient). Always verify with the full derating calculation if multiple conductors are bundled.