Three phase panel used for single phase service. Violation?

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rambojoe said:
well at least one pipe has a overloaded neutral, and that's without clearly seeing all terminations... 11 breakers and 10 hots- and 4 nu=eutrals… not good
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I see at least six branch circuit neutral wires in the picture. Two from the far-left conduit, two from the middle and two from the right.(eta: the smaller conduits from the far left to the middle of the picture)

I have never come across this particular animal in the field, so I am at a loss at the moment to say if there are code violations in using a 3 phase panel for single phase or not. shot from the hip, I would think such an installation violates the listing of the panel.

The panel is full, even a tandem has been put in there. Time to put on your sales hat and sell an upgraded, single phase, panel.
 
jaggedben said:
I'm looking to see if there's consensus on whether the panel itself is a no-no.
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I don't think such an installation would pass inspection here in Livonia. At the very least, the inspector could cite an electrician for not doing the installation in a workmanlike manner (using an improper panel because he was too lazy to go and buy a proper one).
 
MAC702 said:
I can only see three of the conduits coming in, not counting the feeders. They each look normal, figuring likely MWBCs.
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some of them are trying to be mwbc- but most certainly some are black/red and 120volts. and the phasing (of course) remains a pretty black/ red across the panel.. about 100 kilometers south of normal!

consensus- never do this! sell them the right one- and tell the owner the welders are no longer allowed to do electrical work (the story of my life)
 
drcampbell said:
This might be a code violation (AND a hazard) if it's a service entrance and the B-phase conductor is "protected" by two breakers in parallel, which would allow double the B-phase conductor's ampacity to flow before tripping.

Even if not, it seems like a really bad idea. The next person to come along and add something will face several non-obvious opportunities for trouble. For example:
- The above-mentioned shared-neutral MWBC, which will seem to be OK when installed & tested but will eventually overheat the neutral.
- Trying to supply a three-phase device from this "three-phase" panel, which won't work and might damage a motor.
- Trying to supply a 208-volt single-phase load from the B & C phases, which won't work.
- Trying to supply a 208-volt single-phase load from the A & B phases, which might overheat on 240 volts, ...

At worst, the next person trying to add something might place a hex on the original installer, resulting in a lifetime of bad luck and torment.
(sorry, watching too many old Halloween Week movies)
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Next person trying to add something might have more to look at than just single or three phase. Even if it were supplied with three phase, doesn't mean they can add any load, still need to see if there is capacity for what they are adding. Not going to add a 100 kVA load to a 100 amp 208/120 panel and have it operate successfully.
 
jap said:
To me, this panelboard would be a violation of 408.58.

This panel is being used for a different number of phase conductors than for what it was designed.

JAP>
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That section requires it be marked with voltage/current rating and number of buses, doesn't say you must use a panel with three ungrounded buses for three phase supply.

If you need single phase or even two wire DC and are using an I line panel - you get a panel with three buses as that is all they make in that series. You just don't use one of the buses and order breakers that don't connect to the unused bus.
 
This topic is similar to using typical 120/240 panel on a 120 volt only supply line. It does happen occasionally, but they don't really make a panel designed specifically for just 120 volt two wire supply.
 
kwired said:
That section requires it be marked with voltage/current rating and number of buses, doesn't say you must use a panel with three ungrounded buses for three phase supply.

If you need single phase or even two wire DC and are using an I line panel - you get a panel with three buses as that is all they make in that series. You just don't use one of the buses and order breakers that don't connect to the unused bus.
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Actually that section requires it to be marked for the number of "Phases" not the number of "Buses".

There is not 3 phase inside the panel as the cover would suggest, therefore I would consider it a violation of this rule.

JAP>
 
jap said:
Actually that section requires it to be marked for the number of "Phases" not the number of "Buses".

There is not 3 phase inside the panel as the cover would suggest, therefore I would consider it a violation of this rule.

JAP>
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What about my mentioning of I -Line panels? They all have three buses, but if you need single phase or even two wire DC you just don't use one of the buses.

Not sure what actual markings on equipment says but looking in Square D catalog NQ panels are rated for 240 volts AC as well as 48 volts DC. Not seeing 48 VDC in the load center section of catalog, but seem to recall seeing that rating in the field.

Just because there are three buses doesn't necessarily mean you must use them or that you must supply them with "three phase". I think. Main thing is not to exceed maximum rated voltage and current.

Might be good design to make field markings of what is in there if not what one would typically expect.

One can go down similar path when it comes to presence of a grounded conductor bus in the assembly. For services you must run the grounded conductor, but for non service applications you don't need to run a grounded conductor if there is no loads utilizing a grounded conductor. Rarely have done this with 120/240, but has been a time or two where using a panelboard supplying straight 240 only loads. Done it even more often with 480/277 when there are no 277 volt loads - mostly just motors or other "power" loads.
 
kwired said:
What about my mentioning of I -Line panels? They all have three buses, but if you need single phase or even two wire DC you just don't use one of the buses.

Not sure what actual markings on equipment says but looking in Square D catalog NQ panels are rated for 240 volts AC as well as 48 volts DC. Not seeing 48 VDC in the load center section of catalog, but seem to recall seeing that rating in the field.

Just because there are three buses doesn't necessarily mean you must use them or that you must supply them with "three phase". I think. Main thing is not to exceed maximum rated voltage and current.

Might be good design to make field markings of what is in there if not what one would typically expect.

One can go down similar path when it comes to presence of a grounded conductor bus in the assembly. For services you must run the grounded conductor, but for non service applications you don't need to run a grounded conductor if there is no loads utilizing a grounded conductor. Rarely have done this with 120/240, but has been a time or two where using a panelboard supplying straight 240 only loads. Done it even more often with 480/277 when there are no 277 volt loads - mostly just motors or other "power" loads.
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I'm just reading what it says.

The above is a good example of the conversation that would more than likely take place if that rule was used in this instance. :)


JAP>
 
Thanks for the continued responses.

I believe there are three MWBCs in the panel, and then there would be the 240V circuit I want to add. So if the handle tie rule is enforced then, with two quad breakers, it would be just barely possible to make the panel compliant in all respects other than listing or workmanship. (A 12 space single phase panel would allow up to 7 quad breakers instead of only two.) However, there's other work happening on the property, too. Fortunately, the owners and other contractors involved seem amenable to replacing the thing. For which I'm thankful and keeping my fingers crossed.
 
LarryFine said:
A suitable 1ph panel can be bought for under $100, so I don't see the reason to keep this one.
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Not in the vocabulary of a cheapskate:)

Places I have seen three phase panels converted to single phase is existing installations where occupancy change/use has occurred and three phase is no longer needed or maybe not even available anymore. Can't say I ever seen someone install a three phase panel when there was never going to be three phase supplied, exception may be for very limited load applications and using something already on hand.
 
kwired said:
This topic is similar to using typical 120/240 panel on a 120 volt only supply line. It does happen occasionally, but they don't really make a panel designed specifically for just 120 volt two wire supply.
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Except in that case, the panel is single-phase in either instance, consistent in that regard to its labeling.
 
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