The allowable ampacity of a 4 AWG THHN conductor is 95 amperes.If we have four 4 AWG THHN conductors, what is the adjusted ampacity?
A)48
B)63
C)76
D)95

Question

Quizplus · Accepted Answer

When calculating the adjusted ampacity for multiple conductors, we use a derating factor. According to the NEC table 310.15(B)(3)(a), when there are between 3 and 6 current-carrying conductors in a raceway or cable, we must apply a derating factor of 80%. Therefore, the adjusted ampacity for four 4 AWG THHN conductors would be 95 amps x 0.8 = 76 amps. Choice C is the correct answer.

The Allowable Ampacity of a 4 AWG THHN Conductor Is