What is the maximum gap allowed at a recessed electric panel box (flush mount) between the front of the box and the wall surrounding it?
Saturday, July 7, 2018
No gap is allowed between the front of a panel box and the wall surface that the dead front of a recessed panel will sit against in a regular wood stud (combustible) wall structure, but a 1/4” gap is acceptable in a noncombustible (steel stud or concrete) wall construction.
Also, the gap around the sides of the box cannot exceed 1/8” (NEC 312.3 and 312.4). The panel enclosure above, shown with the dead front removed, fails on both counts: it is almost an inch inset from the wall surface and the drywall was cut back too far around the box.
The reason for this rule is to keep any arcing that occurs inside the box from reaching the combustible materials nearby. A dead front should securely seal a panel box when it is closed. In the example above, the dead front screw was missing at that corner because it was not long enough to reach the box, and there were additional openings around the breakers because they sat back behind the dead front.
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