All questions and answers are based on the 2017 NEC.
Q. What does the NEC require for support means of luminaires?
A. Outlet boxes designed for the support of luminaires must be supported by any of the following methods [Sec. 410.36 (A)]:
• Fastened to any surface that provides adequate support [Sec. 314.23(A)].
• Supported from a structural member of a building or from grade by a metal, plastic, or wood brace [Sec. 314.23(B)].
• Secured to a finished surface (drywall or plaster walls, or ceilings) by clamps, anchors, or fittings identified for the application [Sec. 314.23(C)].
• Secured to the structural or supporting elements of a suspended ceiling [Sec. 314.23(D)].
• Supported by two intermediate metal conduits or rigid metal conduits threaded wrenchtight [Sec. 314.23(E) and (F)].
• Embedded in concrete or masonry [Sec. 314.23(G)].
Outlet boxes for luminaires can support a luminaire that weighs up to 50 lb, unless the box is listed for the luminaire’s actual weight [Sec. 314.27(A)(2)].
If framing members of suspended-ceiling systems are used to support luminaires, they must be securely fastened to each other and they must be securely attached to the building structure at appropriate intervals. Luminaires must be attached to the suspended-ceiling framing members with screws, bolts, rivets, or clips that are listed and identified for such use [Sec. 410.36 (B)] (Figure).
The NEC doesn’t require independent support wires for suspended-ceiling luminaires installed in a suspended ceiling that isn’t fire-rated; however, building codes often do.
Raceways and cables within a suspended ceiling must be supported in accordance with Sec. 300.11(B). Outlet boxes can be secured to the ceiling-framing members by bolts, screws, rivets, clips, or independent support wires that are taut and secured at both ends [Sec. 314.23(D)].
Trees can be used to support luminaires, but they aren’t permitted to be used to support overhead conductor spans [Sec. 225.26, Sec. 410.36(G)].
Q. What are the Code required methods of grounding luminaires?
A. The metal parts of luminaires must be connected to an equipment grounding conductor (EGC) of a type recognized in Sec. 250.118. If the EGC is of the wire type, the conductor must be sized in accordance with Sec. 250.122, based on the rating of the overcurrent protection device [Sec. 410.44].
Exception No. 1: If an EGC isn’t present in the outlet box, the luminaire must be made of insulating material and not have any exposed conductive parts.
Exception No. 2: Replacement luminaires can be installed in an outlet box that doesn’t contain an EGC if the luminaire is connected to any of the following [Sec. 250.130(C)]:
(1) The grounding electrode system [Sec. 250.50],
(2) The GEC,
(3) The panelboard equipment grounding terminal,
(4) An EGC that’s part of a different circuit, if both circuits originate from the same panel, or
(5) The service neutral conductor.
Exception No. 3: GFCI-protected replacement luminaires aren’t required to be connected to an EGC if no EGC exists at the outlet box.
This is like the rule for receptacle replacements in locations where an EGC isn’t present in the outlet box [Sec. 406.4(D)(3)].
These materials are provided to us by Mike Holt Enterprises of Leesburg, Fla. To view additional Code training materials offered by this company, visit www.mikeholt.com.
