KVA off Pole Bolted XFORMER

[GISdude]

HI all.
I am trying to calc the the KVA of a 100A service off a 25 kVA transfomer. I am using 3 1/0 Al for a total run of about 200'. It's a 120/240 system set up as a delta connected load side.

In order to get the kVA, would I just multiply 100A X 240V and then divide by 1000? This would be 24 kVA, which would be too much for this XFORMER, right?

The load is for the phone company(ATT) and I would venture a guess that there is no way they are going to be using the full 100A.

TIA

 

[micromind]

If this is a 25KVA single phase xfmr, the current at 120/240 is 104 amps. More than enough for a 100A breaker. It wouldn't bother me a bit to protect it with a 125, and load it to 100.

It's stated that it's a 120/240 system set up as a delta connected load side. A delta connection is 3PH. I've never seen a 25KVA 3PH xfmr. I've seen 22 1/2's, and 30's, but not 25's. Is it 3 25's delta connected? If so, we'd call it a 75. It would be good for 180 amps per leg.

Either way, you're safe with a 100A breaker.

If this xfmr is owned by the local utility, and you've given them the load calc., they'll size it as they see fit. If it burns up, it's their problem, and they'll have to fix it at no cost to you.

 

[GISdude]

load

load

Thx micromind.
I am a designer here for the local utility. I am just trying to make sure this load doesn't burn the xfmr that's currently used. I do have 2 1500 sq ft houses coming off the xfrmr, that is what I'm concerned with.
It seems that these "b-boxes" that ATT has, draw very little current, but I just want to calc it out to be on the safe side.

Thx again.