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NEC Questions and Answers - Based on 2011 NEC
September 2013
By Mike Holt for EC&M Magazine
Here’s the follow up to yesterday’s newsletter. This includes all of the answers to the questions sent, so you can see how you did.
Q1. What are the Code rules for luminaires installed in bathtub and shower areas?
A1. According to 410.10(D), no part of chain-, cable-, or cord-suspended luminaires, track luminaires, or ceiling paddle fans can be located within 3 ft horizontally and 8 ft vertically from the top of the bathtub rim or shower stall threshold.
Author’s Comment: See 404.4 for switch requirements and 406.9(C) for receptacle requirements within or near bathtubs or shower stalls.
Luminaires located within the actual outside dimensions of a bathtub or shower to a height of 8 ft from the top of the bathtub rim or shower threshold must be marked for damp locations. If subject to shower spray, the luminaires must be marked for wet locations.
Q2. What are the NEC rules regarding poles used to support luminaires?
A2. A pole can be used to support luminaires, and can be used as a raceway [410.30].
Author’s Comment: With security being a high priority, many owners want to install security cameras on existing parking lot poles. However, 820.133(A)(1)(b) prohibits the mixing of power and communications conductors in the same raceway.
In addition, they must comply with the following six requirements:
(1) The pole must have an accessible 2 in. x 4 in. handhole with a cover suitable for use in wet locations that provides access to the supply conductors within the pole.
Ex 1: The handhole isn’t required for a pole that’s 8 ft or less in height, if the supply conductors for the luminaire are accessible by removing the luminaire.
Ex 2: The handhole can be omitted on poles that are 20 ft or less in height, if the pole is provided with a hinged base.
(2) When the supply raceway or cable doesn’t enter the pole, a threaded fitting or nipple must be welded, brazed, or attached to the pole opposite the handhole opening for the supply conductors.
(3) A metal pole must have an equipment grounding terminal accessible from the handhole.
Ex: A grounding terminal isn’t required in a pole that’s 8 ft or less in height above grade if the splices are accessible by removing the luminaire.
(5) Metal poles used for the support of luminaires must be connected to an equipment grounding conductor of a type recognized in 250.118 [250.4(A)(5)].
DANGER: Because the contact resistance of an electrode to the earth is so high, very little fault current returns to the power supply if the earth is the only fault current return path. Result—the circuit overcurrent device won’t open and clear the ground fault, and the metal pole will become and remain energized by the circuit voltage.
(6) Conductors in vertical metal poles must be supported when the vertical rise exceeds 100 ft [Table 300.19(A)].
Author’s Comment: When provided by the manufacturer of roadway lighting poles, so-called J-hooks must be used to support conductors, as they’re part of the listing instructions [110.3(B)].
Q3. What does the Code require regarding Track Lighting installation?
A3. Track lighting must be permanently installed and permanently connected to the branch-circuit wiring [410.151(A)]. Lampholders for track lighting are designed for lamps only, so a receptacle adapter isn’t permitted [410.90].
The connected load on a lighting track must not exceed the rating of the track, and an overcurrent device whose rating exceeds the rating of the track must not supply the track [410.151(B)].
Note: The feeder or service load calculations of 220.43(B) don’t limit the number of feet of track on a circuit, nor do they limit the number of luminaires mounted on an individual track.
Track lighting must not be installed [410.151(C)]:
- If it’s likely to be subjected to physical damage.
- In wet or damp locations.
- If subject to corrosive vapors.
- In storage battery rooms.
- In any hazardous location.
- If concealed.
- If extended through walls, partitions, or floors.
- Less than 5 ft above the finished floor, except where protected from physical damage or where the track operates below 30V open-circuit voltage.
- Within 3 ft horizontally and 8 ft vertically from the top of a bathtub rim or shower space [410.4(D)].
Track lighting must be securely mounted to support the weight of the luminaires. A single track section 4 ft or shorter in length must have two supports, and, where installed in a continuous row, each individual track section of not more than 4 ft in length must have one additional support [410.154].
Q4. What restrictions does the NEC put on the installation of luminaires in commercial cooking hoods?
A4. Luminaires can be installed in commercial cooking hoods if all of the following conditions are met [410.10(C)]:
- The luminaire is identified for use within commercial cooking hoods.
- The luminaire is constructed so that all exhaust vapors, grease, oil, or cooking vapors are excluded from the lamp and wiring compartment.
- The luminaire is corrosion resistant, or protected against corrosion, and the surface must be smooth so as not to collect deposits and to facilitate cleaning.
- Wiring methods and materials supplying the luminaire must not be exposed within the cooking hood.
Author’s Comment: Standard gasketed luminaires must not be installed in a commercial cooking hood because accumulations of grease and oil can result in a fire caused by high temperatures on the glass globe.
Q5. What means of support does the Code allow for luminaires?
A5. Outlet boxes designed for the support of luminaires must be supported by one of the following methods [410.36]:
- Fastened to any surface that provides adequate support [314.23(A)].
- Supported from a structural member of a building or from grade by a metal, plastic, or wood brace [314.23(B)].
- Secured to a finished surface (drywall or plaster walls or ceilings) by clamps, anchors, or fittings identified for the application [314.23(C)].
- Secured to the structural or supporting elements of a suspended ceiling [314.23(D)].
- Supported by two intermediate metal conduits or rigid metal conduits threaded wrenchtight [314.23(E) and (F)].
- Embedded in concrete or masonry [314.23(G)].
- Outlet boxes for luminaires can support a luminaire that weighs up to 50 lb, unless the box is listed for the luminaries’ actual weight [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 [410.36(B)].
Author’s Comment:
- The NEC doesn’t require independent support wires for suspended-ceiling luminaires that aren’t installed in a fire-rated ceiling; however, building codes often do.
- Raceways and cables within a suspended ceiling must be supported in accordance with 300.11(A). 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 [314.23(D)].
Trees can be used to support luminaires, but they must not be used to support overhead conductor spans [225.26 and 410.36(G)].
For more NEC Practice, purchase Mike Holt's NEC Exam Practice Questions book based on the 2011 NEC.
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