I'm replacing my hot water heater with a tankless heater the breaker needs to be 80amps I currently have 2 20 amp breakers tied together can I replace those 2 with 1 100 amp breaker and change the wiring also to 8 gauge?

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Originally Posted by Kneedeep11

I'm replacing my hot water heater with a tankless heater the breaker needs to be 80amps i currently have 2 20 amp breakers tied together can i replace those 2 with 1 100 amp breaker and change the wiring also to 8 guage?

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The changeover will need revising to match the product manufacturer's installation specifications requirements. The load may be considered continuous, thus NEC code will require increased conductor and breaker sizing. Again, without guessing, see the manufacturer listed product requirements. nmwirez

Yes, two single pole breakers can be removed and replaced with a 2 pole 80 Amp breaker.


You state that the new water heater needs a 80 amp breaker, why do you mention a 100 Amp breaker?

No, #8 wire cannot be served by a 100 amp breaker, nor an 80 Amp fot that matter.

#8 copper wire, if NM-B (Romex) cable can have a maximum breaker of 40 Amp, and if THHN pulled in conduit or in MC cable, max CB is 50 Amp.

What you need to be most concerned about is if the existing service can handle this large additional load.

And do not use #8 wire on an 80 or 100 amp circuit breaker.