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#94204 07/17/05 11:31 AM
Joined: Mar 2005
Posts: 240
a friend asked me if a 125 amp sub panel would be ok for three water heaters that are 40 amps each.

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#94205 07/17/05 11:51 AM
Joined: Feb 2005
Posts: 693
Is the 40 amps the actual heater current, or the individual circuit ratings?

Larry Fine
Fine Electric Co.
#94206 07/17/05 11:56 AM
Joined: Mar 2005
Posts: 240
individual circuit ratings

#94207 07/17/05 12:30 PM
Joined: Jan 2005
Posts: 5,329
Cat Servant
Really comes down to the application.

If you're talking about water heaters used as household ones are....heating separate systems, and used occasionally for brief periods, the 125 amp panel should be fine.

If these are used together, as in supplying hot water to a production process, and use continuously, than you have to treat the loads as continuous, and have that 25% "buffer' added in to both your panel and the wire supplying it.
(Use the KW ratings of the heaters for your calcs).

#94208 07/17/05 06:24 PM
Joined: Feb 2005
Posts: 693
At max proper circuit loading, which would be (40a. x 80%) 32a. each, that's 96 a. total.

Another way, 3 x 40a. = 120a. Either way, you're okay.

Larry Fine
Fine Electric Co.

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