Electrical service clarification

Commercial 1990 build. Overhead service drop. I concluded this is 120/208v 3 phase/4 wire service.

For my edification and verification. Is there a way to verify how this voltage is produced? Diagram A and B are two options I see. Also, if I am missing the mark completely, please advise.

Service drop

Single phase panel

Three phase panel, I did not remove the dead front

Was the transformer accessible?
If pad mounted, (some O/H drop down to pad mounted in my area), was there Data plate info that you could research for the type and design of transformer?

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Not accessible :smile:

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You don’t climbs poles? :rofl:


Not sure what you need, but perhaps this will assist your research.

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I suspect this is not a Delta transformer because I often see some indicator or label identifying the B phase “wild leg”. However, Sometimes I see this inside the panel (orange wire as well) and sometimes outside. Not being able to take the panel cover off the 3 phase panel is certainly limiting. And the service entrance conductors were not color coded.

I am beginning to answer my own questions, (I think) Do all Delta’s have a “wild leg” ?(high leg, stinger etc)

I like to identify the type of service, specifically if it is a Delta. I’ll report on what I can verify. Also, if the wild leg is not properly identified at the correct locations, it may be noteworthy.


Any assist George?

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Why? If you can’t identify it is this something you just came up with?

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I may not be understanding you. But, I want to know for my edification mainly. Also, as I stated here.

There is 3Ø, 3-wire and 3Ø, 4-wire Delta. The latter has the high leg. Easiest way to tell (besides testing with a meter) if there is a delta system without taking the cover off is look for single pole 120 volt circuit breaker on all three phases. If there are 120 volt single pole CB’s on all three phases then its most likely a Wye system.

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Can you tell from this photo?

I don’t see an single poles on the C phase so my guess is that it is indeed a 3 phase, 4-wire delta system.

Thanks Robert! What would visually indicate a single pole on the C phase without taking the cover off?

If you count down from the top on each side the phase arrangement is A-B-C-A-B-C etc. You’ll see the the C phase has no single pole circuit breakers connected for 120 loads. That because the high leg voltage is 208 to neutral.

Ah ha moment! Hence the knock-out covers on each C count!

And this caught my attention.

One appears to be on the A,B and the right side B,C. Is this significant in anyway?

Not significant in that those are 2 pole circuit breakers.


Thanks for the free education! Sincerely.

Happy to help. Just a quick thing about the 2-pole CB’s, if you look at the 3Ø, 4-wire Delta graphic in the OP you’ll see that any 2 poles will give you 208 volts so the fact that there is a high leg present in the system but that it doesn’t matter for 2 pole or 3 pole loads.


On the other two panels, would you normally use A,C legs and get 120/240? No way to tell?

I guess I am looking for available voltages, 120,208 and 240?