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Electrical Wiring in the Home/Rheem air handler with 15 kw heater kit


I am installing a Rheem furnace with 15kw heater kit, the manual calls for a single 70/80 amp breaker max. The heater unit has 2 breakers which would require a single line jumper kit. I want to know if i can run 2 40 amp breakers with #6 wire. or do i need to stay with the manual specs and run a 80 amp breaker with #4 wire with a jumper kit.

It sounds reasonable that 2 40 amp breakers would add up to 80 amps, but that is not how it works.

Your 15kw heater divided by 220 volts is 15000/220 = 68.2 amps.

That is on a double pole breaker and your wire needs to be able to carry that amperage on each wire.

I know the #4 wire is expensive but you would trip the 40 amp breakers and burn up the #6.

How these work is it cycles on your heating elements. You probably have three 5kw heaters (or some combination that gets you to 15kw) and they come on one by one.

When your t-stat calls for extra heating it cycles on the first element. If the t-stat is still not satisfied in a certain amount of time the next element comes on and so on.

If your t-stat gets satisfied right after the first element comes on you probably will not see the second one getting powered.

But, you have to run the correct wire size and breaker to handle if all three do come on.

Hope that helps.
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Greg Hughes


Troubleshooting electrical including appliances and HVAC.


34 years of experience.

Both college and tech schools in this field.

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