Fluorescent Luminaires on a 30A circuit

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George Stolz

George Stolz

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Is there a prohibition from having lights on a 30A circuit in a commercial setting?

Example: Existing 20A circuit breaker supplying 10 AWG CU conductors supplying fluorescent luminaires. Circuit is loaded to 19A continuously. Can the breaker be swapped out for a 30A?
 
George, here is the commentary from the 2008 Handbook.

The intent of 210.21(A) is to restrict a fluorescent lighting branch-circuit rating to not more than 20 amperes because most lampholders manufactured for use with fluorescent lights have a rating less than that required for heavy-duty lampholders (660 watts for admedium type or 750 watts for all other types).
Branch-circuit conductors for fluorescent electric-discharge lighting are usually connected to ballasts rather than to lampholders, and, by specifying a wattage rating for these lampholders, a limit of 20 amperes is applied to ballast circuits.
Only the admedium-base lampholder is recognized as heavy duty at the rating of 660 watts. Other lampholders are required to have a rating of not less than 750 watts to be recognized as heavy duty. The requirement of 210.21(A) prohibits the use of medium-base screw shell lampholders on branch circuits that are in excess of 20 amperes.
 
Curt, I thought that sounded wrong, so I started looking around. I could have sworn that there was a definition of "lampholder", but I can't seem to find one in the NEC. So, I looked to the White Book, and see their descriptions seem to jive with the handbook concept.

View attachment 3320

However, I have got to say, I still have an issue with their trying to apply a branch circuit wiring rule to something that is beyond the lighting outlet point of the circuit. The branch circuit conductors connect to a listed "fluorescent luminaire", and as far as applying the NEC to it goes, the story should end there, IMO.

It's a real stretch to say that this section applies to a lampholder connected to a ballast inside a fixture listed as a complete assembly, connected to a branch circuit.
 
Just a what if: What if each fixture had a fuse? Would the circuit become a feeder instead of a branch circuit??

But then you have to consider the rating of any switches.
 
I am currently working on some new class rooms in a hig-school. They spec 30Amp QO breakers with 10 wire feeding each class room.

I cant see there being any problem feeding them with 30amps if you can use 20amps, the fixture wire is usually like an 18awg anyway.
 
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