120/240V 1ph PNL with 120/208V

[ron]

Is there a problem with a 120/240V single phase panel be served with (2) ungrounded, (1) grounded and (1) grounding conductors from a 120/208V three phase source. There will be only 1 pole breakers installed (with no handle ties).
This is an odd situation in which the client already installed the 120/240V panels thinking that the service would match, but it doesn't.

 

[480sparky]

I don't see a problem, other than you only have 120/208 instead of 120/240.

 

[220/221]

It would also tend to put a disproportionate load on two phases.


Is it legal????? Beats me..... probably.

 

[jim dungar]

Is it legal????? Beats me..... probably.

Of course it is acceptable. Panels are listed with a maximum voltage Line-Line and a separate maximum voltage Line-Ground (the slash voltage). As long as you do not exceed either of these ratings the equipment is suitable for the system. As long as the panel is wired like a multi-wire branch circuit there is no problem with overloading the phase or neutral buses.

edited: grammar

 

[ron]

480sparky,
Since there will only be 1 pole breakers, it shouldn't be an issue.

220/221,
Since there will be several 120/240V panels, the two phases used for the panels will be alternated so as to try and balance the overall load at the main distribution panelboard.

 

[Jim W in Tampa]

Nothing wrong with it and saves money.I would suggest a label on it saying
120/208

 

[480sparky]

Nothing wrong with it and saves money.I would suggest a label on it saying
120/208

Add "Single Phase" as well, lest someone try to get 3-phase out of it.

 

[Smart $]

Of course it is acceptable. Panels are listed with a maximum voltage Line-Line and a separate maximum voltage Line-Ground (the slash voltage). As long as you do not exceed either of these ratings the equipment is suitable for the system. As long as the panel is wired like a multi-wire branch circuit there is no problem with overloading the phase or neutral buses.

What about 408.30 [NEC 2005] where, "Panelboards shall be durably marked by the manufacturer with the voltage and the current rating and the number of phases for which they are designed..." [Note this requirement has been moved to 408.58 in NEC 2008 edition]

120/208 1? 3W is a standard voltage and the panelboard needs to be marked by the manufacturer for this voltage, not as a 120/240 1? 3W panelboard.

 

[jim dungar]

120/208 1? 3W is a standard voltage and the panelboard needs to be marked by the manufacturer for this voltage, not as a 120/240 1? 3W panelboard.

Panelboards are labeled with the maximum voltage so they are allowed to be used on lower voltages. In 30 years I have never seen a 2 pole circuit breaker labeled for 208V.

 

[don_resqcapt19]

Smart,

120/208 1? 3W is a standard voltage and the panelboard needs to be marked by the manufacturer for this voltage, not as a 120/240 1? 3W panelboard.

Then what panels do we use when the utility supplies two hots and a grounded conductor from a 208/120Y system to a dwelling unit?
Don

 

[tom baker]

This type of installation is allowed, but you can not reduce the size of the neutral, it has to be the same size as the ungrounded conductors. Mike Holt has the math in one of his books, I can find it and post the graphic if needed.

 

[frenchelectrican]

It is allowed to use the 208/120 on 1? panels but Keep in your mind do not reduce the netural at all.

The reason why i mention do not reduce it because it will not shift the voltage at 180? therefore with 208/120 networks it common to find voltage shifted at 120? just like convetal 3? wye connected system is sans one phase.

Merci, Marc

 

[iwire]

Then what panels do we use when the utility supplies two hots and a grounded conductor from a 208/120Y system to a dwelling unit?

A very common situation in the city of Boston. :smile:

 

[e57]

Very common here too - have yet to see a single phase panel marked 208 or do I see a problem with it. Or for that matter a 3 phase wye service in a panel marked 3 phase 240/120. Although in that case I would be more inclined to re-mark it while labeling it.

 

[Jim W in Tampa]

I would hope that any electrician adding circuits or repairing one would be smart enough to use a volt meter and know what he is working on.If he assumes he has 240 then he needs to find other employment.