Commercial Branch Lighting Circuits

[qopanel]

On a job today a discussion came up about lighting circuits. On a commercial branch lighting circuit (feeding lets say 2x4 fixtures) to be on a 15 amp circuit unless protected by an in line fuse holder in the fixture it self? I have always limited my lighting circuits to be on a 15 amp circuit, unless I had to put it on a 20, but installed fuse holders. I cant find a code to back myself up,so I might be wrong. Is it code or just an common practice that I use.

Thanks
Bob

 

[iwire]

Re: Commercial Branch Lighting Circuits

I could count on one hand the number of 15 amp breakers I have installed in commercial work, and I have only seen fuses in fixtures a few times.

We install hundreds of 20 amp 120 or 277 volt circuits for commercial lighting and never put in fuse at the fixtures

 

[robert]

Re: Commercial Branch Lighting Circuits

You don't have to put lights on a 15a cicuit. A 15 or 20a branch circuit can supply lighting units or other utilazation equitment or a combo of both.210.23(a). You can even use a 30-50a breaker were lights with heavy duty lamp holders are used. That is in other than dwelling units. As far as supplementary ocp, it is not required but does in some cases save your fixures. Just make sure your conductors are sized to 125%, and you only use 80% of you over current protection device. Hope this helps.

 

[flightline]

Re: Commercial Branch Lighting Circuits

The old Chicago Electrical Code had a code section that pretty much stated just that. Fluorescent fixtures had to be on 15 amp circuits, unless thay had an internal replaceable fuse. But that code section went away with the little tan book. When the Chicago Electrical Code was brought in line with the NEC, around '99 or 00, it was the same verbiage as the NEC. Since many of the surrounding suburbs along with the unincorporated areas of Cook county used the old code, it was likely that's where all this comes from.

 

[lady sparks lover]

Re: Commercial Branch Lighting Circuits

I've never used 15amp breakers, I feel it's a waste of time, when you can use a 20amp breaker. Nothing in the code that prohibits that.

[ March 14, 2003, 09:10 AM: Message edited by: lady sparks lover ]

 

[Ed MacLaren]

Re: Commercial Branch Lighting Circuits

A typical 277 volt, 2-lamp ballast draws .25 amps or less.
You could put 48 of them on a circuit and not exceed 12 amps, 80% of the 15 amp breaker's rating.

If I were a commercial/industrial facility owner, I would want the better protection afforded by the 15 amp breaker.

Ed

 

[bennie]

Re: Commercial Branch Lighting Circuits

Keep in mind that ballasts have a start up inrush.

 

[Ed MacLaren]

Re: Commercial Branch Lighting Circuits

And keep in mind that the magnetic trip in a standard thermal-magnetic breaker picks up at approximately 600% of rated current.

Ed

 

[toddb1963]

Re: Commercial Branch Lighting Circuits

article 100 defines a "continuous load as one that is on for three hours or more. commercial lighting is considered a continuous load. the number of fixtures should be adjusted for the ocp that you are providing whether or not it is a 15 or a 20 amp breaker. 48 fixtures at .25A a piece comes to 12A times 1.25 (125%) comes to 15A. a reduction in the number of fixtures is in order. i have heard people say that you can't use 15A breakers in commercial. i have yet to find this in the code but i do know that as long as the load to be served doesn't exceed the OCP device you are okay. please correct me if i am wrong.

 

[scott thompson]

Re: Commercial Branch Lighting Circuits

48 fixtures at .25A a piece comes to 12A
times 1.25 (125%) comes to 15A. a reduction in the number of fixtures is in order

Todd,

Ed already figured LCL for the Lighting Circuit in his example, so 48 fixtures is the maximum that could be connected to the 15 Amp circuit, and run continuously.

If the lights were only on for 179 Minutes, then turned off, a total of 60 Fixtures could be connected to the circuit.

Scott35

 

[rwp]

Re: Commercial Branch Lighting Circuits

20A circuit is OK.

 

[hurk27]

Re: Commercial Branch Lighting Circuits

If I have allot of fixtures in a given area I like to split them across two breakers or more so if I loose a breaker the workers wont be in total darkness

 

[toddb1963]

Re: Commercial Branch Lighting Circuits

scott you are correct. 60 ballasts at .25 amps a piece can be put on a 15 amp breaker. however, i would then put them on a 20 amp breaker. 60 ballasts on a 15 amp breaker, does that not exceed the 80% rating on that breaker and will you have problems with that breaker tripping because it is getting to hot. the breaker will hold but for how long? and then, the more it trips the weaker it gets, until it won't reset or it shorts out closed. and then you have no ocp. i think that i would rather have the 15 amp protection on the 48 ballasts with the 125% factored in all ready. as i read ed's reply i didn't see that in there so i apologize. but to assume that the lights will be turned off after 179 minutes in a commercial business is not very wise. i cannot base my load calculations on the assumption that they will turn the lights off after 179 minutes. i have to base it on the fact that the business will be open for more than 3 hours and that they will need lights for that length of time. therefore it is a continuous load and should be calculated as such

 

[luke warmwater]

Re: Commercial Branch Lighting Circuits

Is there a misconception that there is something wrong with 15amp breakers in commercial work?
Or is there a misconception that there is nothing wrong with 15amp breakers in commercial work?
In large-scale commercial work core wiring, #12 might be needed for voltage drop and may require a 15amp breaker. Otherwise, #10 might be needed to use a 20amp breaker.
And in tenant fit-out, what is the advantage of putting 6, 2x4 troffers with T-8 lamps on a 20amp breaker.?

 

[scott thompson]

Re: Commercial Branch Lighting Circuits

Todd,

The 80% derating factor is for a load's LCL - which would be for loads running 3 Hours or more (180 Minutes or more), AKA Continuous Loads.

If not Continuous Loads, the circuit can be run at 100% capacity. This is what I was getting at with the inclusion of the 60 Fixtures running for 179 Minutes, then turned off.
It was merely an example and FYI statement.

The 15 Amp Circuit Breaker will not trip if loaded past 12 Amps (unless it sucks!). If this was the case, they would be identified as 12 Amp Trips, instead of 15 Amp Trips.
Even if the 15 Amp breaker was to carry 100% rated current (15 Amps) for 3+ Hours, it would not trip (once again, unless it sucks!). This is where designing maximum current limits of circuits comes in.

As to loading a circuit up to 100% and running it for anything more than a few minutes, I would not do that either. I just posted that example as an FYI example.

As to LCL and Lighting circuits, for any projects I do Electrical Design/Engineering on, Lighting Circuits are figured to be LCL (Volt-Amps listed in Panel Schedules are 125% of actual connected VA) and the circuits are not loaded above 50% Capacity.
My projects are Commercial based (nearly all are Bank Branches or some type of Fin. Assoc. Clients), and involved in both Designing/Engineering of projects, plus the physical Installations (Power and Lighting, Comm/Data, CCTV/Security designs and installs).

Scott35

 

[toddb1963]

Re: Commercial Branch Lighting Circuits

breakers are not rated for 100% unles specifically designed for that purpose. bottom line is everyone does their job different. i design and build commercial/industrial lighting, power distribution. i double check all lighting and power calculations, including my own, to ensure that all loads are distributed properly and evenly and iaw the nec.

 

[iwire]

Re: Commercial Branch Lighting Circuits

I agree a 20-amp breaker on its own should not trip below 20 amps continuous or not.

But IMO if you have a panelboard with a few fully loaded breakers beside each other you may have tripping of breakers.

I find this with even quality bolt-on breakers for 120-volt circuits.

On using 15 amp breakers, on the jobs we do there will be no 15-amp breakers for lighting, I am not saying that's the only right way to do it, just in this area, that?s how we do it.

I find the 20 amp lighting circuits are only loaded to 9 to 12 amps, this is good for voltage drop and is great at the end of the job if some places need more light or when remodel comes the circuits have some room left.

We work from engineered prints 99% of the time, with panel schedules that show planed loads, so the customer has paid already for the "extra" circuits it takes to not load them to even 80%

A typical fixture we install is a 3-F32T8-lamp single ballast 277 volt .35 amp drop in; even at 12 amps loading we still get 34 of them on a circuit.

[ March 17, 2003, 07:28 AM: Message edited by: iwire ]

 

[scott thompson]

Re: Commercial Branch Lighting Circuits

breakers are not rated for 100% unles specifically designed for that purpose.

Todd,
Could you please verify this information and present data that will coordinate with the claim?

I believe you may have mistaken this a bit. It's MCCBs rated for 100% CONTINUOUS LOAD that you are referring to, not just a flat-out 100%.
If the frame is listed as able to handle 100% Load for Continuous Duty (>3 hours), then a 20 Amp MCCB would be allowed to run a full 20 Amp load for 3 to gazillion hours. If not listed / Identified as such, then defaults back to 80% (derated 20%)-which places the maximum Continuous load of a 20 Amp MCCB at 16 Amps.

Please verify your claim and post results here. If I have been misled in the past, would like to know!!!
Either paste a URL to a page which supports the claim, or snip the text (copy/paste) in your reply message body.

TIA.

Scott35

 

[toddb1963]

Re: Commercial Branch Lighting Circuits

scott, i am not your errand boy. you want that info research it yourself. i did, and that is what i base my findings on. you dont put a continuous load on a breaker at 100%. it is not good practice to do this. your breakers will overheat and trip eventually. give yourself some space when you size your loads and you won't lay awake at night wondering if the job you just did is going to burn down or not. like i said i do things my way you do things your way. i take my continuous load and multiply it by 125%, and with that value i assign it the ocpd that it requires. that is what i am required to do. are we clear?

 

[iwire]

Re: Commercial Branch Lighting Circuits

toddb1963,

Scott helps many people out at this forum he does not need an "Errand boy" maybe you could read some other posts and see how we treat each other here.

Most of us will try to provide a reference to help prove our points.

So if you have "findings" why not share them with the rest of us.