Branch Circuits & FeedersCâu 7 / 120
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?
a.8 AWG
b.14 AWG
c.12 AWG
d.10 AWG
Giải thích
Three percent of 120 volts is 3.6 volts, so the required area is CM = (2 x 12.9 x 12 x 120) / 3.6 = 37,152 / 3.6 = 10,320 circular mils. From Chapter 9, Table 8, 12 AWG has only 6,530 circular mils and fails, while 10 AWG has 10,380 circular mils and just satisfies the requirement. 8 AWG works electrically but is larger than the minimum asked for, and 14 AWG is far too small.
Luyện miễn phí toàn bộ 120 câu hỏi — không cần đăng ký.
Câu hỏi liên quan cùng chủ đề
- 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?
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