Branch Circuits & FeedersCâu 3 / 120
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.25 amperes
b.20 amperes
c.22.5 amperes
d.24 amperes
Giải thích
Start in the 90 degrees C column of Table 310.16, where 12 AWG THHN is 30 A, then apply the adjustment factor for 4 through 6 current-carrying conductors, which is 80 percent: 30 A x 0.80 = 24 A. The 22.5 A answer wrongly starts from the 75 degrees C value of 25 A, 25 A applies no adjustment at all, and 20 A is simply the 60 degrees C table value.
Trích dẫn luật: 2023 NEC §310.15(C)(1)Luyện 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?
- 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 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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