14 ga wire on a 20 amp lighting circuit

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goldstar

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An EC friend of mine recently asked me if he installed a 20 amp lighting circuit above a suspended ceiling in a commercial office would he be permitted to install 14 ga. whips from each junction point to the flourescent luminaires below. My answer was that he would have to continue to install 12 ga. wire to be Code compliant. After thinking about it the current draw on each luminaire is probably far less that an amp and the manufacturers of the lamps often use 16 or 18 ga. wire for their ballasts. In addition the wiring method is not a cascading type (in and out of a luminaire). Is there any reason 14 ga. whips wouldn't be allowed ? Thanks in advance.
 

Dennis Alwon

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I agree. I do not believe this applies to a lighting whip.
(Art. 402)

Are you saying 240.5 does not apply to fixture whips? If not we see whips all the time with 16 or 18 gauge from the manufacturer. Yes I know they have fixture wire in the whips but I am confused by the other statement
 

templdl

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Wisconsin
The pre-assembled whips typically have fixture wire in them, but usually also are a listed assembly.

The way that I see it is that is sort of a tsp. Instead of the tty so conductor terminating of anOCPD it terminate on a fixture that has a limited load, that load determining the wire size and wire rating of the wip conductor.
 

Dennis Alwon

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That is my interpretation. 240.5 does not apply to wiring methods not identified in 400 and 402 the way I read it.
I understand that but can I use 16 awg fixture wire from a jb in a ceiling to the fixture? If so it is odd that I cannot use 14 awg on the 20 amp circuit
 

luckylerado

Senior Member
I understand that but can I use 16 awg fixture wire from a jb in a ceiling to the fixture? If so it is odd that I cannot use 14 awg on the 20 amp circuit

Odd indeed:

402. 10 Uses Permitted
Fixture wires shall be permitted (1) for installation in luminaires
and in similar equipment where enclosed or protected
and not subject to bending or twisting in use, or (2) for connecting
luminaires to the branch-circuit conductors supplying
the luminaires.

Commentary:
Fixture wire is permitted to be used as a tap conductor to connect
a luminaire(s) to the branch-circuit conductors. The transition
from the branch-circuit wiring method to the fixture wire tap conductors
can be accomplished via a junction box or other fitting
that is allowed to contain splices.

I wonder if the intent is to limit the "tap" or "whip" to individual fixtures rather than feeding a room full of fixtures. Why wouldn't everyone make a "tap" at the switch?
 

luckylerado

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goldstar

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New Jersey
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THHN is not fixture wire. I would think those whips are only good for 15 amp circuits and are not covered in 240.5 which to Dennis' point makes no sense.
Understood. I just picked this one at random. They claim it's THHN but I don't see any UL listing. Does that mean that if the mfr. submits this whip to UL and it passes it's OK for them to use THHN ? What are the characteristics of fixture wire that sets it apart from THHN (aside from what the Code says) ?
 

GoldDigger

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Understood. I just picked this one at random. They claim it's THHN but I don't see any UL listing. Does that mean that if the mfr. submits this whip to UL and it passes it's OK for them to use THHN ? What are the characteristics of fixture wire that sets it apart from THHN (aside from what the Code says) ?
Fixture wire insulation has a much higher temperature rating, and the fixture-end terminations can take advantage of that to justify a higher ampacity in a smaller size wire than for more common wire types.
Not sure whether a manufacturer-supplied whip is UL tested or not. But the NEC allows for field use of fixture wire too.
 
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