Branch Circuits & FeedersCâu 4 / 120
Four current-carrying 8 AWG THWN-2 copper conductors run in a raceway through a 48 degrees C ambient. What is the adjusted ampacity of each conductor?
a.36 amperes
b.44 amperes
c.40 amperes
d.33 amperes
Giải thích
Begin with the 90 degrees C ampacity of 8 AWG copper, 55 A, then correct for the 46 to 50 degrees C ambient range at 0.82 and adjust for four current-carrying conductors at 0.80: 55 x 0.82 x 0.80 = 36 A. Answers of 40 A and 44 A apply only one of the two required factors, and 33 A comes from starting in the 75 degrees C column, which is not required when a 90 degrees C conductor is used as the derating base.
Trích dẫn luật: 2023 NEC §310.15Luyện miễn phí toàn bộ 120 câu hỏi — không cần đăng ký.
Câu hỏi liên quan cùng chủ đề
- A 208-volt, single-phase branch circuit supplies a continuous load of 24 amperes. What is the minimum standard overcurrent device rating permitted?
- For that same 24-ampere continuous load, what is the minimum size copper branch-circuit conductor, assuming 75 degrees C terminations and THWN insulation?
- Six current-carrying 12 AWG THHN copper conductors are installed in a single EMT run at a 30 degrees C ambient. What is the adjusted ampacity of each conductor before termination limits are applied?
- A 120-volt circuit carries 20 amperes through 12 AWG copper (6,530 circular mils) to a load 100 feet away. Using K = 12.9, what is the approximate voltage drop?
- A 480-volt, three-phase feeder carries 40 amperes 250 feet using 6 AWG copper (26,240 circular mils). Using K = 12.9, what is the approximate voltage drop?
- A 120-volt branch circuit must carry 12 amperes 120 feet with voltage drop held to 3 percent. Using K = 12.9 for copper, what is the smallest conductor that meets the target?
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