210.23 and lighting circuits over 20 amp

[kwired]

This section mentions fixed lighting units "with heavy duty lampholders" for 30, 40 and 50 amp branch circuits.

Done this a few times with HID high bay luminaires, but these days T5 fluorescent are the more popular choice for these locations.

I never questioned the application of this article to HID luminaires, but typical linear fluorescent of about any design does not have the lampholder connected directly to branch circuit conductors. Are these luminaires acceptable on 30 - 50 amp branch circuits?

I feel the "heavy duty lampholder" was intended to apply to luminaires where the lampholder is connected directly to branch circuit conductors, and may not even directly apply to HID luminaires. The words "or other utilization equipment in same section likely means you can still connect these luminaires to a 30 - 50 amp branch circuit.

What does anyone else have to say on this?

 

[kwired]

I seen this asked in DEC 2012 Electrical Contractor magazine in the code FAQ's section. The authors opinion was that the lampholders in the fluorescent luminaire would qualify as heavy duty lampholders and the luminaires can not be on a 30 amp circuit (in the question asked in the magazine). I don't disagree with them not qualifying as heavy duty lampholders, but would argue that they are part of a separately derived system within the luminaire and are not connected to the branch circuit either, making the lampholder issue a mute point on this type of luminaire.

I question the responses to a couple other questions in that article and may start new threads where we can discuss each of those topics.

 

[ramsy]

I never questioned the application of this article to HID luminaires, but typical linear fluorescent of about any design does not have the lampholder..

Seems to me the Handbook agrees with you.

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
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 mediumbase
screw shell lampholders on branch circuits that are in excess of 20 amperes.

 

[kwired]

Seems to me the Handbook agrees with you.

Appears to me the handbook disagrees with my opinion on this, at least right now. I need more reasoning before my opinion will change.

First the branch circuit does not supply the lampholders any more than the utility supplies the premises wiring. These lampholders are on the load side of the ballast and if you short out the load side leads of the ballast I bet you never get any current at levels higher than the lampholders are rated for. I even question this some with typical HID luminaires, even though one output lead of these often is common to an input lead, but those lampholders typically do still meet the "heavy duty" requirement and make the question disappear anyway.

Is it possible that the real load as far as the branch circuit is concerned is the ballast, and it is "other utilization equipment" instead of a lampholder?

 

[ramsy]

Appears to me the handbook disagrees with my opinion on this, at least right now. I need more reasoning before my opinion will change.

Math is one universal form of reasoning that can breach some NEC language corruption.

1) One recurring variable found in the NEC is "Ambiguity".

Postulating cross-referenced authorities, listings, Handbooks, Building & Energy codes, local amendments, etc.., the following formula is derived:

Where A=Ambiguity, A+A‡A (Multiple Ambiguities do not always remain Ambiguous where a referee exists)

2) Those proficient enough to recognize properly cited authority realize agreeing on the variables, or the steps to proof NEC code, is far less important that agreeing with the Authority Having Jurisdiction (AHJ), since the AHJ has no mandate to justify subjective interpretations with any further authority.

 

[Smart $]

...

Is it possible that the real load as far as the branch circuit is concerned is the ballast, and it is "other utilization equipment" instead of a lampholder?

I agree with your technical assessment of the requirement... but I see it as poorly worded for the intent given by the Handbook. If that is the intent, it should be stated something like: "Where a luminaire is connected to a branch circuit having a rating in excess of 20 amperes, lampholders shall be of the heavy-duty type."

 

[iwire]

Who is putting T5s on circuits greater than 20 amps?:?

 

[kwired]

Who is putting T5s on circuits greater than 20 amps?:?

I could see, possibly retrofitting existing HID's on a 30 amp circuit with T5's, but they likely draw low enough current you could simply replace the 30 amp breaker with a 20.

I also just wanted opinions on whether or not that would be acceptable. I have done several shop buildings with just enough luminaires that you could get them all on a 30 amp circuit, but I have always split them into two circuits because I wasn't really sure if a 30 amp circuit is allowed. I do have a couple upcoming buildings where same issue will likely be there.