Waterheater wiring


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Old 01-16-01, 06:38 PM
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I am installing a new waterheater and am wondering what wire size to use. There is about a 40 foot run. I feel that 12/2 would be OK but want to double check here at the forum. Thanks
 
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Old 01-16-01, 07:14 PM
J
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Well, I'm really glad you asked. You should never select wire size by what feels right. Use a minimum of 10 gauge copper wire for a water heater. 12 gauge copper isn't even enough for a 4500 watt heater.

Please consult the manual for your water heater for more information. If you don't have the manual, then investigate how many watts your heater is. 10 gauge copper wire will allow up to a 5700 watt heater. If your heater is above this, then drop down to 8 gauge copper.
 
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Old 01-17-01, 12:11 AM
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FontanaHorseman,
Since you wisely asked about the 12/2 before using it on a 220v water heater, and just to add my 2c to what John has already said, you need to use a 30 amp double-pole breaker on the 10/2, or a 40 amp, if you need to use 8 gauge.
Wire the bare ground to the green screw on the heater, of course, and the black and white to either of the red and black hots. (No neutral.)
Good Luck!
 
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Old 01-17-01, 09:13 AM
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I have an additional question involving the same waterhear wiring system. The house was built in 1922 and has 2 seperate 100 amp boxes with screw in fuses. The old heater was wired into 2 different fuses, one for each wire. The fuses are both 20 amp fuses. Should I replace each of these with a 15 amp fuse? The water heater is a 4500 watt model. Thanks for the above advice also.
 
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Old 01-17-01, 09:20 AM
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Q: Should I replace each of these with a 15 amp fuse?
A: Absolutely not. As OldGuy said, if you first make sure you have no wires smaller than 10 gauge copper on this circuit, you should install 30 amp fuses. To get 30 amps, you need two 30-amp fuses, not two 15-amp fuses. (P.S. If you've got 25-amp fuses, these would be better for a 4500 watt heater, but you are allowed to use 30-amp fuses as long as the water heater manual says so).
 
 

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