Branch Circuits & Feeders第 23 / 120 题
The rule permitting the next higher standard overcurrent device rating above the conductor ampacity may be applied only where that device rating does not exceed what value?
a.400 amperes
b.600 amperes
c.1,000 amperes
d.800 amperes
解析
The round-up allowance stops at 800 amperes; above that rating the overcurrent device must not exceed the ampacity of the conductors it protects. The other values are not thresholds in 240.4(B), and choosing 600 A would needlessly restrict legitimate designs in the 601 to 800 A range.
法律依据: 2023 NEC §240.4(B)免费刷完整 120 道题库 — 无需注册。
同考点相关题目
- A 277-volt feeder supplies three continuous lighting loads of 12, 15 and 18 amperes. What is the minimum standard feeder overcurrent device rating?
- For that same 45-ampere continuous lighting feeder, what is the minimum copper conductor size at 75 degrees C terminations?
- What is the smallest conductor size generally permitted to be installed in parallel?
- A 200-ampere feeder uses THHN copper conductors, but the equipment terminations are rated 75 degrees C. What is the minimum conductor size?
- Using the dwelling service and feeder conductor table, what is the minimum copper conductor size for a 200-ampere single-phase dwelling service?
- What is the allowable ampacity of 4/0 AWG copper THWN in the 75 degrees C column?