Code Quiz

Aug 9, 2004 9:08 AM, By Steven Owen

                

According to 312.6 of the 2002 NEC, what's the minimum wire bending space required in a 200A rated panelboard, at the main circuit breaker terminals, where the main circuit breaker is fed with 4/0 AWG THHN/THWN insulated conductors? The 4/0 AWG conductors are installed in parallel -- two per phase. The conductors enter the enclosure on the wall directly opposite the circuit breaker lugs, i.e., through the top of the enclosure, in-line with the circuit breaker terminals.

A) 5 inches
B) 6 inches
C) 7 inches
D) 7.5 inches

Answer: D

Explanation: Refer to 312.6(B)(2) and Table 312.6(B). Look in the Wire Size column; find 4/0 AWG. Look at the top heading in the column Wires Per Terminal - 2 (wires per terminal). The minimum distance required from the terminal of the circuit breaker to the wall of the enclosure opposite the circuit breaker lug is 7.5 inches. If the manufacturer hasn't provided the minimum 7.5 inches (which is unlikely), the electrical installer may have to bring the 4/0 AWG conductors into the enclosure through a sidewall, or the bottom of the enclosure, or some other point that isn't directly opposite the lugs of the circuit breaker.

Owen is the owner and president of National Code Seminars and the holder of master electrician certifications in 46 states.

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