Branch Circuits & FeedersQuestion 27 of 120
Twelve current-carrying 12 AWG THHN copper conductors run in one raceway through a 38 degrees C ambient. What is the adjusted ampacity of each conductor?
a.15 amperes
b.13.65 amperes
c.12 amperes
d.10.9 amperes
Explanation
Start at the 90 degrees C ampacity of 30 A, apply the 36 to 40 degrees C correction factor of 0.91, then the 50 percent adjustment for 10 through 20 conductors: 30 x 0.91 x 0.50 = 13.65 A. Answers of 15 A and 12 A apply only one of the two factors, and 10.9 A uses the 45 percent bracket that begins at 21 conductors.
Law Reference: 2023 NEC §310.15Practice all 120 questions free — no signup required.
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