50 or 75 KVA transformer

[hardworkingstiff]

I am looking at a dock with one section having five 50-amp receptacles not individually metered. 555.12 says I can use a .9 multiplier for service calculations. 250*.9 = 225-amps. 225*240-volts = 54KVA (single-phase) transformer (we are feeding the dock w/480-volts).

Question, transformers go from 50KVA to 75KVA. Do you think 50KVA is OK (I think it's fine)? Do you know if the NEC will allow the 50KVA in this instance (I don't know)?

Thanks,

 

[GISdude]

XFRM sizing

XFRM sizing

POCO's routinely size THEIR XFRM (either commercial or residential) 120-150% of the capacity of the XFRM due to diversification. Is this for 1 customer only?

One more thing, are you REALLY going to serve this 480-1ph? Usually for this we would serve 3ph 480.

 

[don_resqcapt19]

I would not use the 50 kVA. Look at the FPN for this section.

FPN: These demand factors may be inadequate in areas of extreme hot or cold temperatures with loaded circuits for heating, air-conditioning, or refrigerating equipment.