208 Volt single phase available but Contractor installing 240 volt panelboard

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amendez

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I have an application where only 120/208 volt is available in the building, and the Contractor has supplied a 120/240 volt load center for a standby generator (aux equipment). Are there any code violations associated if we feed the load center with a 208 volt single phase feed and ALL loads connected to the 240 volt single phase load center are either 120 v or 208 volts single phase?
 

charlie b

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I think this is acceptable. Not ideal, necessarily, but acceptable. If someone later wants to connect a single phase 240 volt load, there might be an issue, and I am not sure how to prevent that from taking place. But we don't have to make present day decisions on the basis of the possibility that a future change might be done incorrectly.
 

augie47

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When I first read this I agreed with Charlieb, but upon re-reading, I may have a question (sorry charlieb).
If the utility supply to the building and to your panel is 208 and the generator being installed is 240, you may have a violation of 110.4 if any of the equipment connected to your panel is rated at 208v.
 

K8MHZ

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Michigan. It's a beautiful peninsula, I've looked
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if we feed the load center with a 208 volt single phase feed and ALL loads connected to the 240 volt single phase load center are either 120 v or 208 volts single phase?

I don't think I have ever seen a 120/208 single phase generator. I have seen some labeled 120/208-240 which would still really be a 120/240 single phase center tapped supply.

Are you talking about a 120/240 1 ph. generator feeding 120/208 loads or just using one phase of a 120/208 three phase generator?
 

amendez

Member
Let me just clarify...the load center is ONLY for the aux equipment furnished with the generator. The generator is 277/480 volts. The load center is part of the genset to feed the jacket water heater, battery charger etc. Our design has these items fed from the 208 volt panel directly, but since the genset comes with the load center, the Contractor is indicating that if we don't feed the aux equipment from the load center, it may (somehow) void the warranty.
 

charlie b

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Let me just clarify...the load center is ONLY for the aux equipment furnished with the generator.
That is what I had thought you meant (Sorry, Gus ;)), so I stand by my answer.

. . .the Contractor is indicating that if we don't feed the aux equipment from the load center, it may (somehow) void the warranty.
That is nonsense. The generator's auxiliary equipment needs power, and it does not matter where the power comes from. You can bring in a feed to the sub-panel that came with the generator, or you can feed individual circuits to each item of aux equipment from a panel of your own. Feel free to do it either way you want.


However, you do raise a question in my mind. If the aux panel that came with the generator is 120/240, how can you be sure that the loads are rated 120 or 208 volt single phase, and not 120 or 240 volt single phase? As I said before, if you supply 208 volts to a load that is rated for 240, you will have a problem. Do you know if there are any 200+ volt single phase loads at all?
 

amendez

Member
The engine jacket water heater comes either 240 or 208 volt single phase (all others are 120 v) and through the shop drawing submittal process, we have verified that the unit being furnished WILL BE 208 volt single phase. We have called on the gen manufacturer re: the warranty issue and are trying to work this out separately, but if push comes to shove...just needed to verify that other than the labeling on the load center, there were no other issues that I haven't been able to think of that would cause/create a problem.
 

charlie b

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I have to disagree here, we must follow the instructions or we may have trouble getting the warranty honored.
I don't have a problem with that. I just don't think it likely that the instructions will state that the power to the auxiliaries must come from a panel that the manufacturer provides.
 

iwire

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Massachusetts
I don't have a problem with that. I just don't think it likely that the instructions will state that the power to the auxiliaries must come from a panel that the manufacturer provides.

My thought is what they really want is to ensure is that the Aux equipment is supplied by a panel that is live when the generator is running, not a panel supplied from the 'other' source that would be dead.
 

charlie b

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Lockport, IL
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Of course. But I can supply the same loads from a standby panel in the electric room or even in the diesel room, without necessarily having them supply the panel. Indeed, the drawing I have open in AutoCAD on my other computer screen shows a standby panel (intended to be furnished and installed by the electrical contractor) that will be located within the diesel room, and that will supply its auxiliaries.
 
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