Branch Circuits & FeedersCâu 24 / 120
A 200-ampere feeder uses THHN copper conductors, but the equipment terminations are rated 75 degrees C. What is the minimum conductor size?
a.4/0 AWG
b.2/0 AWG
c.3/0 AWG
d.250 kcmil
Giải thích
Because the terminations are listed for 75 degrees C, the final ampacity must be taken from the 75 degrees C column even though THHN is a 90 degrees C insulation. In that column 2/0 copper is 175 A and fails, while 3/0 copper is 200 A and matches the device. Reading the 90 degrees C column would wrongly allow 2/0, and 4/0 or 250 kcmil exceed the minimum.
Trích dẫn luật: 2023 NEC §110.14(C)(1)(b)Luyện miễn phí toàn bộ 120 câu hỏi — không cần đăng ký.
Câu hỏi liên quan cùng chủ đề
- For that same 45-ampere continuous lighting feeder, what is the minimum copper conductor size at 75 degrees C terminations?
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- Using the dwelling service and feeder conductor table, what is the minimum copper conductor size for a 200-ampere single-phase dwelling service?
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- 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?
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