408.55(C) Back Wire-Bending Space.

Use NEC Tables 312.6(A) or 312.6(B) to determine minimum dimensions when raceways and cables enter the back of a panelboard enclosure. On a different note: Based on the wiring configuration of the panelboard, is this a service or a subpanel?
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Use NEC Tables 312.6(A) or 312.6(B) to determine minimum dimensions when raceways and cables enter the back of a panelboard enclosure. On a different note: Based on the wiring configuration of the panelboard, is this a service or a subpanel?

Code Change Summary: A new subsection was added with requirements on conductors entering the back of a panelboard enclosure.

In most panelboard installations, the feeders enter the top, bottom or side of the enclosure. The NEC® has code language for those type of situations. Once in a while the feeders enter the enclosure through the back, opposite the removable cover. Until now, the NEC® was silent on this, other than the exception in 314.28(A)(2).

Now, the 2014 NEC® address this. The new subsection allows the distance for “one wire per terminal” from Table 312.6(A) when a raceway or cable entry is in the wall of the enclosure opposite the removable cover. The distance is measured from the wall where the raceway enters to the back side of the cover.

As well, the distance between the center of the rear entry and the nearest termination for the entering conductors shall not be less than the distance given in Table 312.6(B).

Below is a preview of the NEC®.  See the actual NEC® text at NFPA.ORG for the complete code section. Once there, click on the “free access” tab and select the applicable year of NFPA 70 (National Electrical code).

2014 Code Language:

408.55(C) Back Wire-Bending Space. Where a raceway or cable entry is in the wall of the enclosure opposite a removable cover, the distance from that wall to the cover shall be permitted to comply with the distance required for one wire per terminal in Table 312.6(A). The distance between the center of the rear entry and the nearest termination for the entering conductors shall not be less than the distance given in Table 312.6(B).

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408.55(C) Back Wire-Bending Space.

Below is a Real Question from our Electrical Continuing Education Courses for Electrical License Renewal:

Which of the following is required for dimension “A” in the illustration?

A: Table 312.6(A) must be used based on one wire per terminal.
B: Table 312.6(B) must be used based on one wire per terminal.
C: Table 312.6(B) must be used.
D: Table 408.56 must be used to determine the wire bending radius.
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