Service Photos

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dvcraven0522!

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St. Louis
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Electrical Design
Good Morning. I did a site survey for an existing store about 70,000 sq.ft. The service is 2500 amp at 480/277V. If figured 1500kva total = 1806 amps for (3) at 500kva. I have attached a photo of a transformer bank on a platform. I believe these are (3) 500kva xfmrs. I guess my question is the physical wiring from transformers. I was expecting to see (4) taps for the 3-phase xfmr (A-B-C-N).

But maybe it does work that way. Your thoughts are greatly appreciated.
 

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It's a wye secondary. There are three 1ph transformers, and no 3ph units.

If it was a high-leg delta, one of the transformers would have a center tap.

The left bushings feed separate buses, and the right bushings feed one.

The three upper buses are the phases, and the lower bus is the neutral.

There is a conductor group at the far right end tied to the neutral bus.

There are four conductor groups across the very top of the photograph.
 
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Ok - I was thinking 1-phase transformer as well but, I don't see how (3) single phase 500kva xfmrs. can deliver anything close to a 2500 amp 3hase, 4wire distribution panel as the drawings claim.
 
The poco does not size transformers for the ocp rating, they size it accordingly to what they think the projected load will be. Also, as others have said, larger loads may have been added since original install. I have a job right now, the service is 600 amp, but the poco has #2 dropped from nearly 200’ away, with several other buildings on the same transformer. Cleaning up and moving the old service, new owners going total electric. Service is still sufficient, just needs poco upgrade. Met with the engineer, he is changing out the transformer, and changing the drop to 4/0.
 
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