The NEC requirements for outlet boxes are outlined in Sec. 314.27(A) through (E). Outlet boxes are distinct from pull boxes, junction boxes, and conduit bodies [314.28].
Three of the outlet box rules address supporting some kind of equipment. In summary:
- To support a luminaire or lampholder, use boxes or fittings designed for that purpose and install them per Sec. 314.23 [314.27(A)].
- If using an outlet box for the sole support of a ceiling-suspended (paddle) fan, the outlet box must be listed and manufacturer-marked for this purpose. The weight limit here is 70 lbs [314.27(C)].
- If using an outlet box to support utilization equipment other than a ceiling-suspended (paddle) fan, apply Sec. 314.27(A) and treat that equipment as if it’s a luminaire of the same size and weight [314.27(D)].
An exception to this last rule is there’s a 6 lb limit for supporting equipment on other boxes or plaster rings secured to other boxes and the equipment or its supporting yoke must be secured with no fewer than two No.6 or larger screws.
Floor boxes must be listed [314.27(B)]. Outlet boxes can use separable attachment fittings [314.27(E)].
