(A) Boxes at Luminaire Outlets. Boxes used at luminaire or lampholder outlets in a ceiling shall be designed for the purpose and shall be required to support a luminaire weighing a minimum of 23 kg (50 lb). Boxes used at luminaire or lampholder outlets in a wall shall be designed for the purpose and shall be marked on the interior to indicate the maximum weight of the luminaire that is permitted to be supported by the box in the wall, if other than 23 kg (50 lb). At every outlet used exclusively for lighting, the box shall be designed or installed so that a luminaire may be attached.
Exception: A wall-mounted luminaire weighing not more than 3 kg (6 lb) shall be permitted to be supported on other boxes or plaster rings that are secured to other boxes, provided the luminaire or its supporting yoke is secured to the box with no fewer than two No. 6 or larger screws.
(B) Maximum Luminaire Weight. Outlet boxes or fittings designed for the support of luminaires and installed as required by 314.23 shall be permitted to support a luminaire weighing 23 kg (50 lb) or less. A luminaire that weighs more than 23 kg (50 lb) shall be supported independently of the outlet box unless the outlet box is listed and marked for the maximum weight to be supported.