How to Properly Support Electrical Boxes

Every box must be adequately supported. And you’ll find the basic requirements in Sec. 314.23(A) through (H) of the National Electrical Code (NEC). You’re expected to exercise good judgment. For example, when surface mounting you need to determine whether the surface provides rigid and secure support.

Here are some highlights:

• You can use a structural member to support your enclosure directly, or you can use a brace made of wood, polymer, or metal [314.23(B)(1)].
• If you mount an enclosure in a finished surface, ensure that it’s rigidly secured using clamps, anchors, or fittings identified for the purpose [314.23(C)].
• Raceway-supported enclosures without devices, luminaires, or lamp holders have different support requirements from those that have these [314.23(E) vs. 314.24(F)]. The main difference is this: Because of the lower weight, you can use tubing as your raceway for raceway-supported enclosures without devices, luminaires, or lamp holders. If a raceway-supported enclosure has devices, luminaires, or lamp holders, then you must use conduit (and it has to be threaded).
• An enclosure supported by dint of being embedded in concrete must be identified as being suitably protected from corrosion [314.23(G)]. Installation errors can negate the protection.