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For EC&M Magazine
By Mike Holt, NEC® Consultant
Here's the follow-up to yesterday's newsletter.
This includes the answers to the questions sent, so you can see how you did.
Note: The answers to these questions are based on the 2017 NEC.
Q1. What does the Code allow for the connection of electric-discharge and LED luminaires when they are supported independently of the outlet box?
A1. Electric-discharge and LED luminaires supported independently of the outlet box must be connected to the branch circuit with a raceway, or with Types MC, AC, NM cable, or flexible cord installed per 410.62(B) or (C) [410.24(A)]. Figure 01
Author's Comment:
• Electric-discharge luminaires can be cord-connected if the luminaires are provided with internal adjustments to position the lamp [410.62(B)].
• Electric-discharge luminaires can be cord-connected if the flexible cord is visible for its entire length, is plugged into a receptacle, and the installation complies with 410.62(C).
Q2. What are the requirements for installing surface mounting electric-discharge and LED luminaires over a concealed outlet box?
A2. When an electric-discharge luminaire or LED luminaire is surface mounted over a concealed outlet box, and not supported by the outlet box, the luminaire must be provided with suitable openings that permit access to the branch-circuit wiring within the outlet box [410.16(B)].
Q3. What are the Code requirements when using poles as luminaire supports?
A3. Luminaires and lampholders must be securely supported [410.30(A)].
Poles are permitted to be used to support luminaires and as a raceway to enclose supply conductors where the following conditions are met [410.30(B)]:
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. Š
(1) The pole must have an accessible 2 in. × 4 in. handhole with a cover suitable for use in wet locations that provides access to the supply conductors within the pole. Š
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. Š
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)]. Š
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 protection device won't open and clear the ground fault, and the metal pole will become and remain energized by the circuit voltage. Š
(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)].
Q4. What does the NEC require for support means of luminaires?
A4. Outlet boxes designed for the support of luminaires must be supported by any of the following methods [410.36 (A)]:
- 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)]. Š
- 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 luminaire's 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 installed in a suspended ceiling that isn't fire-rated; however, building codes often do. Š
• Raceways and cables within a suspended ceiling must be supported in accordance with 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 [314.23(D)].
Trees can be used to support luminaires, but they aren't permitted to be used to support overhead conductor spans [225.26, 410.36(G)].
Q5. What are the Code required methods of grounding luminaires?
A5. The metal parts of luminaires must be connected to an equipment grounding conductor of a type recognized in 250.118. If the equipment grounding conductor is of the wire type, the conductor must be sized in accordance with 250.122, based on the rating of the overcurrent protection device [410.44].
Ex 1: If an equipment grounding conductor isn't present in the outlet box, the luminaire must be made of insulating material and not have any exposed conductive parts.
Ex 2: Replacement luminaires can be installed in an outlet box that doesn't contain an equipment grounding conductor if the luminaire is connected to any of the following [250.130(C)]:
(1) The grounding electrode system [250.50],
(2) The grounding electrode conductor,
(3) The panelboard equipment grounding terminal,
(4) An equipment grounding conductor that's part of a different circuit, if both circuits originate from the same panel, or
(5) The service neutral conductor.
Ex 3: GFCI-protected replacement luminaires aren't required to be connected to an equipment grounding conductor if no equipment grounding conductor exists at the outlet box.
Author's Comment:
This is similar to the rule for receptacle replacements in locations where an equipment grounding conductor isn't present in the outlet box [406.4(D)(3)].
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