3 phase, residential

Large, 6000 sf home, had 5 separate service panels. (yes, they all appeared to be service, not distribution) Also had 2 meters, so two of the panels are 3 phase, from one of the meters. I have never dealt with this, is there anything I should be concerned about, or does this seem ok? Most of the 3 phase breakers are 20 and 30 amp.
I also dont see a main disconnect on the first panel…
Curious why the home would have both types of service on the same property?

Nothing really different with 3Ø, the circuit breakers would correspond to the conductor size or the equipment requirements even for the 3Ø, 20 and 30 amp circuits. The usual violations are present, double taps, no visible main bonding jumper, no main on the second panel, NM cables not entering in individual connectors, etc.

Did you happen to check the voltage? With no single pole circuit breakers on the B phase it appears that this may be a 3Ø, 4 wire, Delta system. Also how is the panel with no main fed from the meter, is it in a separate raceway?

Typically all the houses I have inspected that had 3-phase electric had some commercial equipment using large electric motors over 5hp. Was there any commercial size equipment in this house or workshop?

No, I didn’t check voltage. How would a delta system differ?
And the only raceway would be at the meter. They go in the wall through the back side of the meter, into the attic, and come down at two different locations in a large garage.
Also, is it an issue when one of the condensers is 208/230, but only using two phases, even though the disconnect has 3?

No, this house had 3 different several car garages, so maybe they did in the past, but nothing now

A Delta system would have a high leg where the voltage to ground/neutral would be 208 volts. That could be a surprise to someone connecting a single pole, 120 volt circuit breaker to the B phase and applying 208 volts to the 120 volt circuit.

Regarding a 2 pole CB for a single phase circuit there is no issue. The service entrance conductors leaving the meter and running through the attic unprotected is a major issue.

That is possible but not likely. If it is a corner grounded Delta, the grounded conductor is terminated on the wrong side and should be identified with green, not white, tape. There is no neutral in a corner grounded Delta. Though, I suppose it is possible that an electrician could have made that mistake, it is hard to imagine that it would have gotten past the local inspector. A corner grounded Delta would be very unusual in a house and would be impractical.

A center tapped Delta would make slightly more sense in a residence than a corner grounded Delta but there is no marking indicating a High Leg. Again, it is possible that an electrician could make such a mistake but that would be a rookie mistake and I certainly hope someone else would have caught it. Here again, it is hard to imagine that it would have gotten past the local inspector.

The most common residential three-phase system is 3ø4w Wye. That would allow running the equipment most common in homes and would provide 120V. Whether 120V is used is another matter. They still have the option for future additions.

The OP ought to have photographed the supply transformer. If it is a pad mount, he could have read the tag. If they are pole mounted, we could see the actual connections to see what the arrangement is.

It would have a high leg if it is a center tapped Delta. There is no high leg on a corner grounded Delta.

George, would you elaborate on this please. I am unfamiliar with the ‘High Leg’ and ‘Delta’ thing regarding electricity.


I don’t know where a corner grounded delta system entered into this discussion. No one mentioned a corner grounded system.

Experience dictates there is a main somewhere between this panel and the meter pan.

Yes, thanks for all the help as usual, Robert!

You’re welcome. :slightly_smiling_face:
We don’t see much 3Ø in residential so it was an interesting question.

You mentioned a Delta connection without saying whether you were referring to center-tapped or corner grounded Delta. I explained the difference.

Rather than YOU guess … OR listen to us guess, you have reasons visible to refer to a competent electrician … THEN ask buyer or seller to let you know when hes there / MEET him and ask him your questions

Post #2 and post #6 stated the system, nothing would indicate a corner ground system with the information given:

Gee, thanks for the advice! I guess we don’t even need this forum then, do we?
Isn’t that the point here? To gain knowledge while at the same time helping others gain knowledge as well?

I don’t know how you do your reports, but I don’t simply find one wrong issue and say “welp, better have an electrician look at your panel!” Why, what’s wrong? “Well, this neutral shouldn’t be under the same terminal as this neutral”… while in the meantime, there’s 20 other things that could burn the house down.
I like to give them as much information as possible… isn’t that what they hire us for??



Thanks for sharing, we are here to learn from each other. I have been at this for 36 years. I have yet to see it all and would never make a claim I knew it all.

I am a little late to this party and see most has been covered… nothing like one of these to keep the blood pumping!

Good luck with this “project”, you found a real Gem! :joy:

You don’t pay real good attention so again, you had multiple issues in need of professional repair.

At that point its perfectly obvious that you have questions YOU don’t have answers for AND are 2nd guessing yourself AND asking everyone here to guess for you. A very sensible thing to do is what I suggested … MANY times an inspector may see and recognize say 4 defects with something like an electric panel not realizing there are other things the professional electrician may observe.

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Who are you to say I don’t pay good attention? You obviously don’t either… Read the question again. I didn’t ask everyone to point out every problem in the panel for me. I KNEW there are multiple defects with the panels, some are pretty major. Everything that Robert pointed out for me I already knew about.
I was merely asking what concerns there are with a 3 phase system, especially when a home has both setups on the same property.
Not sure if you knew this, but 3 phase systems aren’t exactly that common in residential properties, and not something we see everyday.
Google my reviews if you don’t think I pay good attention…

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