Is it allowed to use 3phase MSB for 1phase incomming service from utility service

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rahulch9

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The client for one of the project bought 400A-3phase-MSB and 125A-3phase panels but the utility service can provide only 1phase for this project.

Can we use this 3phase equipment for single phase service. if so can you let us know the approach of wiring it.

If we use 3phase equipment for 1phase service will there be any effect on breaker?
 
Depends on the equipment. If you want an I-line panel all you get is three phase versions, you just don't order breakers that utilize the unused bus if you only have single phase available.

Do that with typical miniature breaker panels and you lose 1/3 of the available breaker spaces and do need to watch which spaces you use for any 2-pole circuits.
 
Aside from probably overpaying for 3ph panels and wasting at least a third of the breaker spaces, I dont know of any NEC violations with wiring 3ph panels with one phase. If the panels have been bought already (and if Im reading correctly, they have) and cannot be returned (to be determined), you can wire your split phase to any two legs of those panels. If you go that route, keep it consistent (i.e., use A and C in all panels and B is blank/unused).

If there is any possibility in the future of 3ph service, or a potential need for it, wire for it now and just dont use the 3rd ungrounded conductor.

I do not know if it is legal to wire a 3ph panel with a second leg from a split phase service, i.e. ABA, or ABB. Istm you could possibly overload the neutral and/or xfmr if done carelessly. I'd avoid it either way.

eta: I initially wrote use A and B legs; amended to "use A and C". If you eventually acquired a high leg delta, it needs to be B phase. No need to move wiring around or repull feeders to accommodate that; simply hook up the existing unused conductor to B.
 
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I would think there would be a labeling issue.
All of the 3ph equipment if a neutral connection was present, would read 480/277, 120/208, 120/240 3ph, none of which would say 120/240v 1ph.

JAP>
 
Personally speaking I would not jump the phases (I.e AB or AC). Breaker panels are designed to alternate branch circuits on phases so that the possibility of over-loading the neutral is minimized (that doesn't mean you can't over-load it anyway). All the other opinions are valid points (waste of breaker spaces and waste of $$). Just because your customer purchased the wrong product doesn't mean you should have to come up with a workable solution for his error. If you're getting inspected your EI may have a problem with this.
 
jap said:
I would think there would be a labeling issue.
All of the 3ph equipment if a neutral connection was present, would read 480/277, 120/208, 120/240 3ph, none of which would say 120/240v 1ph.

JAP>
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I agree with that as well.
 
jap said:
I would think there would be a labeling issue.
All of the 3ph equipment if a neutral connection was present, would read 480/277, 120/208, 120/240 3ph, none of which would say 120/240v 1ph.

JAP>
Click to expand...
Again I will use I-Line panels as an example. They are all rated 600 volts, they all have three phase busing. You can get 240 volt breakers, 480 volt breakers, 600 volt breakers. You can get single, double or three pole breakers.

You can use for anything 600 volt AC and below, and I believe 250 volt DC, provided the breakers you use don't exceed their voltage rating.

Because of the bus design on this series, you can avoid needing to skip "spaces" should you only use it for single phase applications, you just order breakers with jaws installed on appropriate bus positions.

A factory assembled unit may get factory marked for 208/120 if that is what was specified, but it is still made with same components as if it were field assembled. Field assembled units the panelboard itself will be marked for 600 volts.

OP says MSB - main switchboard? I could see such a thing being rated 600 volts also, may have 240 volt components installed on 600 volt rated bus and may or may not have single/three phase bus options just like the I line.
 
kwired said:
Again I will use I-Line panels as an example. They are all rated 600 volts, they all have three phase busing. You can get 240 volt breakers, 480 volt breakers, 600 volt breakers. You can get single, double or three pole breakers.

You can use for anything 600 volt AC and below, and I believe 250 volt DC, provided the breakers you use don't exceed their voltage rating.

Because of the bus design on this series, you can avoid needing to skip "spaces" should you only use it for single phase applications, you just order breakers with jaws installed on appropriate bus positions.

A factory assembled unit may get factory marked for 208/120 if that is what was specified, but it is still made with same components as if it were field assembled. Field assembled units the panelboard itself will be marked for 600 volts.

OP says MSB - main switchboard? I could see such a thing being rated 600 volts also, may have 240 volt components installed on 600 volt rated bus and may or may not have single/three phase bus options just like the I line.
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To say that would be much like saying you could use a 125v rated cord connector for a 250v application simply because everyone knows the copper on the inside of the connector for both is made out of the same material right ?

Wrong.

The panel labeling needs to match what the voltage is and whether its single phase or 3 phase in my opinion.

And if your a professional in this industry you'd install it as such.

At least I would.

JAP>
 
jap said:
To say that would be much like saying you could use a 125v rated cord connector for a 250v application simply because everyone knows the copper on the inside of the connector for both is made out of the same material right ?

Wrong.

The panel labeling needs to match what the voltage is and whether its single phase or 3 phase in my opinion.

And if your a professional in this industry you'd install it as such.

At least I would.

JAP>
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What about using a 250 volt rated cord connector for 120 volt application?

There is nothing that prohibits using 600 volt gear for 120/240 or 208/120 supply. Can be some confusion but you haven't exceeded the voltage rating.

What about using said panel for 250 VDC?

Like I said if you have say an I-Line factory assembled for you - you might get one that is marked 208/120Y. If you order components from stock and field assemble it, the panelboard label itself likely will say 600 volts. You may save some cost by ordering breakers rated for 240 volts (and using them on a 208/120 system) instead of ordering 600 volt breakers that also fit the same panel. Get into 400 amp plus breakers and you still have a 600 volt rated breaker anyway even though you are using it on a 208 volt system. I even have had NQOD panels with a 400 amp "LAL" main installed - an LA breaker is a 600 volt breaker.
 
Safety switches typically only come in 240 volt and 600 volt ratings. You can apply a 240 or a 600 volt switch to a 208 or a 240 volt system. Over 240 volts you need to use a 600 volt switch, even though most of US only uses them on a 480 or 480/277 volt system.
 
kwired said:
What about using a 250 volt rated cord connector for 120 volt application?
Click to expand...

So You'd do that also?
Remind me not to ever follow up on one of your twistlock cord drop installations being fed by your 3 phase panels that are being fed with single phase power. :)


JAP>
 
kwired said:
Safety switches typically only come in 240 volt and 600 volt ratings. You can apply a 240 or a 600 volt switch to a 208 or a 240 volt system. Over 240 volts you need to use a 600 volt switch, even though most of US only uses them on a 480 or 480/277 volt system.
Click to expand...

Now we're starting to see things as they should be.
Because It makes sense.
Just like the configurations of the panelboards voltage and phase orientation should relate to the voltage and phase orientation of the power that is feeding it should.

Point is, don't let someone else's error con you into doing something that you wouldn't normally do in the first place.

JAP>
 
jap said:
So You'd do that also?
Remind me not to ever follow up on one of your twistlock cord drop installations being fed by your 3 phase panels that are being fed with single phase power. :)


JAP>
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I normally wouldn't install 240 volt cord connectors on a 120 volt circuit, but also think it could be more acceptable then the other way around.
 
jap said:
So You'd do that also?
Remind me not to ever follow up on one of your twistlock cord drop installations being fed by your 3 phase panels that are being fed with single phase power. :)


JAP>
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You should follow him up. Get to charge 400$ for changing a NEMA L21 plug and receptacle when otherwise you'd get a quarter that putting on the right stuff. Imma start using twistlock 480V plugs for everything! :happysad:

Valid point tho. The worst offenses Ive seen with this are using 5-20 receptacles with 6-20 plugs; the ground pin was cut off and the plug flipped upside down. Must be in the "Maintenance for Hotels" handbook.
 
I believe if you do this, the unused phase should be required to be part of the EGC otherwise its unbonded. This is stupid but so is getting 3 phase panels for a single phase service.
 
ActionDave said:
This makes no sense. Phases, used or unused, don't get bonded to anything.
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Well it's an unbonded piece of the electrical system... The code does not address this so I'm not wrong. Just playing Devils advocate because technicially this bus could store charge and be a shock hazard

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