Single phase 208 loads on a 3ph 4 wire panelboard

[somsudeep]

For one of my projects in the refinery, for Heat trace, I have 208 1 ph heat trace cable loads that are fed from a 3 ph, 4 wire 120 / 208 panelboard .

My total amperage at 208 1 ph is 264 A.
This means IAB+IBC+ICA = 264A ????

I now need to size the transformer 480 delta:120-208Y.

Something in this calc: 1.732*264*208 (unity PF) does not seem right??? Can someone help??

 

[david luchini]

Your load is single phase, you wouldn't use 1.732.

You have 264A * 208V = 54.9kVA. You'd want a 75kVA transformer.

 

[Smart $]

Your load is single phase, you wouldn't use 1.732.

You have 264A * 208V = 54.9kVA. You'd want a 75kVA transformer.

I think we have to question how he arrived at 264A. If he just arithmetically summed the currents of each heat trace (which it appears he has done), then your assessment would be correct.

My total amperage at 208 1 ph is 264 A.
This means IAB+IBC+ICA = 264A ????