multiple heat exhcangers

[Copperclad]

Hi all,
I have an install coming up, that will require a sub panel to feed the following:
(3) Heat exchangers, 40 FLA @ 208 volt single phase
(3) circulation pumps, 16 FLA @ 208 volt single phase
The loads will be not be continuous for the exchangers, but will be continuous for the circulation pumps.
Im trying to size the the sub feeders and subfeed OCP. Is there any way I can derate these particular loads?
Any help would be much apprecitated.

 

[petersonra]

Hi all,
I have an install coming up, that will require a sub panel to feed the following:
(3) Heat exchangers, 40 FLA @ 208 volt single phase
(3) circulation pumps, 16 FLA @ 208 volt single phase
The loads will be not be continuous for the exchangers, but will be continuous for the circulation pumps.
Im trying to size the the sub feeders and subfeed OCP. Is there any way I can derate these particular loads?
Any help would be much apprecitated.

what do you mean by "derate"? you have to size motor conductors according the the chart of FLA for such things. you can't get past it for any normal motor like this.

does the heat exchanger include loads that are not motors? or multiple motors? you might get the feeder down to a #6 that way. otherwise I think you are stuck with a #4 feeder.

 

[petersonra]

what do you mean by "derate"? you have to size motor conductors according the the chart of FLA for such things. you can't get past it for any normal motor like this.

does the heat exchanger include loads that are not motors? or multiple motors? you might get the feeder down to a #6 that way. otherwise I think you are stuck with a #4 feeder.

I misread the OP.

You have 3 each 40A loads and 3 each 16A loads at 208 V. A lot more than a #6 or #4 if you run just 2 wires like maybe you are thinking. that would be 168 + 10 = 178A ampacity required - that would be 3/0.

However if you were to run 3 phase as the feeder your total connected load would be about 97A. If the 40A load is a single motor you need to add 25% of that to the FLA to get the required feeder ampacity or 108A, which would be a #2.

choose your poison. two 3/0 or three #2.