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tankless water heaters for radiant heat

Jim T
Jim T Member Posts: 4
I'm thinking of using a tankless heater to heat 2 bathrooms that are going on an extention. It will be used for radiant floor heating. Am I wrong in thinking this will be alright since radiant heating does not have to get that hot?
Also, can anyone explain why constant circulation is better than the circ. pump going on and off as heat is needed? Wouldn't the pump be pushing cold water through the system, thus making it necessary for the heater to constantly call for heat.


  • Al Letellier
    Al Letellier Member Posts: 781
    tankless water heater

    You can use a tankless for your heat source, but most of them are variable input and it sounds like your load will be quite light. The unit will rarely ramp up to max input and cause some operational problems.
    Constant circ is great when used with reset control or a floor sensor. It keeps the floor warm at all times and is more even and efficient and will keep heat from "pooling" under throw rugs, etc. We use primary/secondary setups with this kind of system and it work great, especially for the baths.

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  • Paul Rohrs
    Paul Rohrs Member Posts: 357
    Check out...

    a few threads down. Titled, I wish I had a testing lab.

    It dovetails with your request.

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