Services, Grounding & BondingCâu 40 / 120
A service uses two parallel sets of 750 kcmil copper per phase. Using the 12.5 percent rule, what is the minimum copper main bonding jumper?
a.250 kcmil
b.3/0 AWG
c.4/0 AWG
d.2/0 AWG
Giải thích
Where the ungrounded service conductors exceed 1,100 kcmil of copper, the main bonding jumper must be at least 12.5 percent of that area: 2 x 750 = 1,500 kcmil, and 1,500 x 0.125 = 187.5 kcmil. The smallest standard conductor with at least that area is 4/0 AWG at 211.6 kcmil; 3/0 at 167.8 kcmil falls short and 250 kcmil is larger than the calculated minimum.
Trích dẫn luật: 2023 NEC §250.28(D)(2)Luyện miễn phí toàn bộ 120 câu hỏi — không cần đăng ký.
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