water heater (breaker size)

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kfenn

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I'm having a brain freeze...

a water heater with (2) 6,000 watt elements, both can run at the same time...to find out the breaker size; I add both elements together (12,000 w), divided it by the voltage 208 (Single Phase)...I get 57.69 amps. But to find the breaker size I need to divid by 2(since it is 208 single phase)and I get 29 amps.....So i need to put it on a 2p-40a breaker with #8 awg..

Does this sound right.....
 
Re: water heater (breaker size)

Is there a nameplate on this water heater?

The way I would figure it is this:
12000/208=57.69A
58*1.25=72.5
Next standard size up from 72.5 is 80A breaker
80 Breaker, 75 degree conductor (if terminals are listed as such) would be #4. 60 degree terminals (if applicable) would be #3.

This all seems very high to me, however. What does the nameplate say?

Edit to add code text:
422.13 Storage-Type Water Heaters.
A branch circuit supplying a fixed storage-type water heater that has a capacity of 450 L (120 gal) or less shall have a rating not less than 125 percent of the nameplate rating of the water heater.
Click to expand...

[ July 15, 2004, 12:35 PM: Message edited by: ryan_618 ]
 
Re: water heater (breaker size)

I think Ryan has it right. I' not sure why you are dividing by 2, Kfenn.

Steve
 
Re: water heater (breaker size)

no nameplate...For some reason I'm figuring that you will have 29 amps per line(hot) so you need to size the breaker per line not total amps..
 
Re: water heater (breaker size)

This is somewhat unusual to have both elements run at the same time.

Are you sure about this, is this a commercial water heater? Most times with only two elements there is a thermostat that choses the upper or lower element but not both.
 
Re: water heater (breaker size)

Willing to bet they are set up that only one at time runs.This is to keep from having cold spots.Put ohm meter on it then undo top element ,i bet it does not change reading.
 
Re: water heater (breaker size)

Simultaneous (pardon my spelling) heating elements is an option available on most commercial type "State" brand heaters. Our Mech. engineer specs. them like that a lot.

Steve
 
Re: water heater (breaker size)

Originally posted by steve66:
Simultaneous (pardon my spelling) heating elements is an option available on most commercial type "State" brand heaters. Our Mech. engineer specs. them like that a lot.
Steve
Click to expand...
You might remind him that his spec is nearly doubling the cost of the electrical installation. :)
 
Re: water heater (breaker size)

You might remind him that his spec is nearly doubling the cost of the electrical installation.
Click to expand...
Yes, but I think it nearly doubles the recovery rate also. Asking him to omit this would be like asking him to cut the size of an air conditioner in half just to reduce the electrical installation cost.

Steve :)
 
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