Branch Circuits & Feeders第 20 / 120 题
A 277-volt feeder supplies three continuous lighting loads of 12, 15 and 18 amperes. What is the minimum standard feeder overcurrent device rating?
a.50 amperes
b.45 amperes
c.60 amperes
d.70 amperes
解析
Total the loads first: 12 + 15 + 18 = 45 A, all continuous, so the device must be at least 45 x 1.25 = 56.25 A and the next standard rating is 60 A. The 45 A answer omits the continuous-load factor, 50 A is below the calculated minimum, and 70 A overshoots the next standard size.
法律依据: 2023 NEC §215.3免费刷完整 120 道题库 — 无需注册。
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