Dịch vụ & Phân phốiCâu 82 / 521
A concrete-encased electrode (Ufer) must consist of at least 20 ft (6.0 m) of:
a.Bare 4 AWG copper conductor or 1/2 in. (13 mm) rebar encased in concrete near the earth
b.12 AWG insulated wire in conduit
c.8 AWG aluminum in a wall
d.6 AWG copper stapled to a stud
Giải thích
Per 250.52(A)(3), a concrete-encased electrode is at least 20 ft of one or more 1/2 in. or larger steel reinforcing bars, or at least 20 ft of bare 4 AWG copper, encased in at least 2 in. of concrete in contact with the earth. The other options are not qualifying electrode materials or lengths.
Trích dẫn luật: 2023 NEC §250.52Luyện miễn phí toàn bộ 521 câu hỏi — không cần đăng ký.
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