Should I provide separate panels for lighting and A/C and heating loads?

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apelk

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I've had people tell me they design lighting on one panel and AC/Heating on its own panel because otherwise load-cycling causes lights to dim up/down. Is this a legitimate concern? Is that actually going to happen, or is it going to happen if there's shoddy workmanship (I've read up on loose neutrals a little bit). The panels are still powered by the same source, so if this was going to happen, wouldn't it happen between panels too?

I can see doing this for buildings where you've got several 277/480V panels anyway due to the large number of loads. Right now I'm designing a building where it's going from installing two panels to three panels if I had a separate lighting panel.

Thanks for expanding my knowledge....

Amy
 
School....

School....

It depends on the loads delivered. Make sure you do the neutral size calculation and use that as a minimum. With the use of more switching power supplies the neutral is getting hammered.
Also think of the coincidental loads. AC vs heat vs lighting. Lighting will be used whenever either of these loads are being used and are a lot of times off on a separate panel because the panel is transformed down from high voltage for the heating and cooling needs. If the transformer is not calculated to the correct size you will have a voltage drop on the far ends. Heating and cooling can be more efficient on higher voltages if delivered by the local utility on site. If you use 277 lighting it will increase the costs but get you a more skilled electrical contractor.
TO which there has been regulatory interest here (FL) requesting voltage drop calculations on circuits.
You will need to crunch some numbers but that is what you went to school for, right?:bye:
 
apelk said:
I've had people tell me they design lighting on one panel and AC/Heating on its own panel because otherwise load-cycling causes lights to dim up/down. The panels are still powered by the same source, so if this was going to happen, wouldn't it happen between panels too?

Amy
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Yes.
 
Most of the time, the lights blinking on heavy load startup is on the utility side, too long of run to transformer, too small of a transformer, Though if you do have a long run from the meter to the panel, or all of the heavy loads in one panel, it can be on the customer side also.
 
My designs always show separate panels for lighting and for mechanical loads. But not for the reason you mention. I do it in part for convenience. Lighting loads generally do not require large panelboards. I often use a 100 amp rated riser and a 100 amp panel on each floor. Since I don't put receptacle loads or mechanical loads on this riser, I have no trouble keeping the total load to under 100 amps. But nowadays the emphasis on measurement and verification, particularly for projects that are seeking LEED certification, requires us to be able to separately measure lighting loads, mechanical loads, and all other loads. Keeping the panels separate makes this easier.
 
Interesting solution, charlie b. Makes it easy to monitor lighting all in one place.

Thanks for the input everyone. Need to have a conversation with the higher-ups!
 
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