Calculated Single phase loads with 3 phase panel

[Dennis Alwon]

This has been discussed in a closed thread. I have a question. The load calculated out as Phase A= 416, B=375 and C= 375. According to Charlie's post we should add all 3 loads and divide by 3 and we get 388 amps. Why would we not use the highest load. In theory if we installed a 400 amp breaker isn't phase by going to cause a problem.

 

[GoldDigger]

I agree.
If you are only going to use the amp value in a upstream KVA calculation of single core transformer size, then using 388 makes some sense.
But for the purpose of sizing conductors and OCPD, you need to use the larger value.

Tapatalk!

 

[kwired]

I read charlies post as saying the 388 amps is the average for all three phases, which I agree with. It doesn't tell us individual load on each phase. One could throw the balance off even further by changing connection of some heaters to different phases and you would still have a 388 average.

 

[Dennis Alwon]

Well it was interesting because the value the OP got was 388 even with rounding off. I guess I was confused and thought they were saying 388 is the size-- didn't make sense that is why I asked.

 

[kingpb]

This has been discussed in a closed thread. I have a question. The load calculated out as Phase A= 416, B=375 and C= 375. According to Charlie's post we should add all 3 loads and divide by 3 and we get 388 amps. Why would we not use the highest load. In theory if we installed a 400 amp breaker isn't phase by going to cause a problem.

388 Amps is average. Not sure what that gets you, or is even useful. I have never used average amps for a 3 phase panel before.

Everything on a panel for sizing should be based on first determining KVA, (individual branch, phase, and total) then calculating the amps.

Now, your question, yes, if you used the information above, the breaker would need to be based on the 416A.