Mike Holt Enterprises Electrical News Source

NEC Questions and Answers based on 2017 NEC - August 2018

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Figure 01

 

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.
Underlined text indicates a change in the rule for the 2017 NEC.

Q1. What is the NEC definition of closet storage space, in regard to luminaires?
A1. Closet Storage Space [410.2]. Storage space is defined as a volume bounded by the sides and back closet walls, extending from the closet floor vertically to a height of 6 ft or the highest clothes-hanging rod at a horizontal distance of 2 ft from the sides and back of the closet walls. Storage space continues vertically to the closet ceiling for a distance of 1 ft or the width of the shelf, whichever is greater. Figure 01

Author’s Comment:
This definition consists of approximately 125 words in one sentence, perhaps the longest sentence in the Code. Take a breath and don’t get lost when reading it!

 Q2. What does the Code require of luminaires to be installed in wet, damp, or corrosive locations?
A2. Luminaires in wet or damp locations must be installed in a manner that prevents water from accumulating in any part of the luminaire. Luminaires marked “Suitable for Dry Locations Only” must be installed only in a dry location; luminaires marked “Suitable for Damp Locations” can be installed in either a damp or dry location; and luminaires marked “Suitable for Wet Locations” can be installed in a dry, damp, or wet location [410.10(A)].

Author’s Comment:
See Article 100 definitions of “Location, Damp,” Location, Dry,” and Location, Wet.”

Luminaires installed in corrosive locations must be suitable for the location [410.10(B)].

Q3. Under what conditions does the Code allow luminaires to be installed in commercial cooking hoods?
A3. Luminaires can be installed in commercial cooking hoods if all the following conditions are met [410.10(C)]:  
(1) The luminaire is identified for use within commercial cooking hoods.
(2) The luminaire is constructed so that all exhaust vapors, grease, oil, or cooking vapors are excluded from the lamp and wiring compartment.
(3) 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.
(4) Wiring methods and materials supplying the luminaire aren’t permitted to be exposed within the cooking hood.

Author’s Comment:
Standard gasketed luminaires aren’t permitted to 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.

Q4. What are the NEC requirements for the installation of luminaires in bathtub and shower areas?
A4. 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 [410.10(D)].

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.

Q5. What does the Code require for the spacing of luminaires installed under metal-corrugated sheet roof decking?
A5. Luminaires installed under metal-corrugated sheet roof decking must be installed at least 1½ in. from the lowest surface of the roof decking measured from the bottom of the decking to the top of the luminaire [410.10(F)].

Q6. What are the NEC requirements for the installation of luminaires in clothes closets?
A6. Only the following types of luminaires are permitted to be installed in a clothes closet [410.16(A)]:
(1) Surface or recessed incandescent or LED luminaires with an enclosed light source.
(2) Surface or recessed fluorescent luminaires.
(3) Surface-mounted or recessed LED luminaires identified for use within the closet storage space.

Incandescent luminaires with open or partially open lamps and pendant-type luminaires aren’t permitted to be installed in a clothes closet [410.16(B)].  

Luminaires must maintain a minimum clearance from the closet storage space as follows [410.16(C)]:
(1) 12 in. for surface-mounted incandescent or LED luminaires with an enclosed light source.  
(2) 6 in. for surface-mounted fluorescent luminaires.
(3) 6 in. for recessed incandescent or LED luminaires with an enclosed light source.  
(4) 6 in. for recessed fluorescent luminaires.
(5) Surface-mounted fluorescent or LED luminaires are permitted within the closet storage space if identified for this use.  

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