Dịch vụ & Phân phốiCâu 29 / 521
A service uses 3/0 copper conductors at 75 C (200 A ampacity) with a 200 A load. What is the correct standard OCPD?
a.225 A
b.250 A
c.175 A
d.200 A
Giải thích
The conductor ampacity (200 A) exactly matches a standard OCPD rating, so a 200 A device is used - the next-size-up rule of 240.4(B) does not apply when the ampacity equals a standard size. 175 A undersizes for the 200 A load, and 225/250 A overprotect the conductor.
Trích dẫn luật: 2023 NEC §240.6(A)Luyện miễn phí toàn bộ 521 câu hỏi — không cần đăng ký.
Câu hỏi liên quan cùng chủ đề
- Which of the following is NOT a standard ampere rating for a fuse or inverse-time breaker per 240.6(A)?
- A conductor has an allowable ampacity of 115 A that does not match a standard fuse size. The load is 112 A. What is the largest standard OCPD permitted?
- For circuits rated over 800 A, what is the rule for the overcurrent device relative to conductor ampacity?
- As a general rule, where must overcurrent protection for a conductor be located?
- Why is a service disconnect required to be readily accessible and located near the point of entrance of the service conductors?
- A branch circuit carries a continuous load of 80 A. What minimum OCPD rating is required?
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