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#94204 - 07/17/05 11:31 AM h20 heaters  
watersparkfalls  Offline
Member
Joined: Mar 2005
Posts: 220
Washington...Not DC
a friend asked me if a 125 amp sub panel would be ok for three water heaters that are 40 amps each.


2017 / 2014 NEC & Related Books and Study Guides

#94205 - 07/17/05 11:51 AM Re: h20 heaters  
Larry Fine  Offline
Member
Joined: Feb 2005
Posts: 693
Richmond, VA
Is the 40 amps the actual heater current, or the individual circuit ratings?


Larry Fine
Fine Electric Co.
fineelectricco.com

#94206 - 07/17/05 11:56 AM Re: h20 heaters  
watersparkfalls  Offline
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Joined: Mar 2005
Posts: 220
Washington...Not DC
individual circuit ratings


#94207 - 07/17/05 12:30 PM Re: h20 heaters  
renosteinke  Offline
Cat Servant
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Joined: Jan 2005
Posts: 5,316
Blue Collar Country
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 Re: h20 heaters  
Larry Fine  Offline
Member
Joined: Feb 2005
Posts: 693
Richmond, VA
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.
fineelectricco.com


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