How Many Wires are Allowed in a Recessed Light Box
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Installing and Wiring Recessed Light Fixtures: NEC 314.16 and Box Fill, What does it mean when a light fixture wire box specifies a maximum number of wires? © By: Dave Rongey |
Wiring Methods for Recessed Light Fixtures
Electrical Question: What does it mean when a light fixture wire box specifies a maximum number of wires?
Jay’s Recessed Lighting Project
- I am currently, completely renovating a 2nd home with complete new electrical system thru out the dwelling. Open floor plan with different ceilings heights in same open areas consisting of some vaulted, some 10 ft flat and 12 ft flat.
- Other rooms consist of standard 8 ft ,9 ft and tray. This info is to provide some idea of the challenges for lighting systems. Major contribution of ceiling light will be accomplished with 6″ recessed fixtures and a few chandeliers for the d?cor. Open areas are large enough that lots of 3 way and 4 way switching is needed.
- Currently I am drafting my circuits and due to the amount of 3 wire that would be needed I have been calculating my light circuits with 14/2 and 14/3. Each switched area has sets of 2, 3, or 4 recessed cans. Due to ceiling issues and switch locations, power will be at the fixture. Some switched sets are within a couple of feet of another set, so the power feed would continue to the next set. Load calculations on 14 GA wire at 80% = 1440 watts, so powering a dozen cans each rated for max 75 watts on a single breaker circuit should be no problem, correct? I am using cooper lighting HALO 6″ IC airtight cans that allow the maximum size lamps of 75 watt, PAR30. The installation sheet states the electrical connection is approved for use with 12-18 AWG wire.
- During the placement installation of some of the cans, I read the following on the wire box: “MAXIMUM OF 8 NO 12AWG THROUGH CIRCUIT BRANCH CONDUCTOR”.
- All of this complex detail has been to ask these specific question that may throw a kink in my circuit layout plans.
- What does this mean EXACTLY – “MAXIMUM OF 8 NO 12AWG THROUGH CIRCUIT BRANCH CONDUCTOR”?
- Does it mean max. 8 cans on a single breaker circuit branch regardless of how many sets those 8 make? or Does it mean a max. set of 8 cans that branch off of a single breaker circuit that serves multiple sets?
- The load calculations for 8- 75w fixtures = 600w. That seems grossly underused capacity using 12 AWG wire, when it should be able to handle three times that and still be at 80%.
Thank you and sorry for all the details,
Jay
This electrical wiring question came from Jay, in Jacksonville, North Carolina who also commented the following: Dave, Thank you for your web site of info and invited reader questions. I have a good understanding and practical experience of electrical circuits and residential wiring.
Dave’s Reply:
Thanks for your electrical wiring question Jay.
Installing Electric Wiring for Recessed Light Fixtures
National Electrical Code NEC 314.16 and Box Fill
- Jay, the statement that you are referring to in the Halo Recessed Light Fixture documentation is referring to the maximum number of wires that may be installed in the light fixture junction box. Specifically, the documentation states that the light fixture electrical junction box may accommodate up to eight 12 gauge copper wires.
- The light fixture specification has nothing to do with the lighting circuit load, however your 80% calculations are accurate when calculated with the maximum allowed amperage for the #14 gauge wire.
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