There are forced air in-wall heaters in my house which are quite noisy. I am considering to replace those with electric radiant floors. What would be the least invasive way to do it?

Current heater is 800W 240V. There are three rooms with such heaters all using the same circuit protected by 20A breaker. I presume I can go as high as 5A per room with this setup, i.e. 1200W. But again, if 800W forced air heater is enough to keep the room warm, equivalent power radiant floor should work just as well. Am I missing anything?

Anyway, my current idea is to reuse existing wiring: disconnect the in-wall heaters and use their wiring to power the radiant floors (installing additional junction boxes as needed). Is anything wrong with that plan? Would I be able to use existing thermostats that directly control power to the heater (i.e. no low voltage lines)?

Washington state, if that matters.

  • I am south of your location and my radiant floor in my bathroom draws more than 5 amps, it is only 10 x 6. Not sure that you will be able to do it with that small of a feeder for all 3 areas.
    – Ed Beal
    Commented Aug 13, 2019 at 15:08
  • @EdBeal, what temperature is your thermostat set to? I keep mine around 68 F.
    – n0rd
    Commented Aug 13, 2019 at 18:30
  • 72 feels warm and the one problem with radiant heat is the slow recovery time. I love it in the bathrooms but I had hydronic in my last place and if not zoned correctly it is almost impossible to turn off rooms with electric it should be easier to regulate each room with a line voltage thermostat.
    – Ed Beal
    Commented Aug 13, 2019 at 18:36

1 Answer 1


800 watts/room is 2,400 watts, drawing 10 amperes total at 240 VAC. Assuming you need to increase it by 50%, as you suggest, the maximum current is still just 15 amps, still within the 20 A circuit capability.

You must have a very mild climate and well insulated house if 800 W (about 2,700 BTU.hr) is sufficient to keep it warm... you're not up by Snoqualmie Pass. ;-)

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