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Heat pump water heater for radiant floor heat?

Clayton Hufford | Posted in General Questions on

I have a 190 sq ft basement pad for an addition that I would like to put in floor heat. Have been looking at various top of the line gas water heaters, but am curious about heat pump water heaters. Several good ones on the market specifically GE GeoSpringâ„¢ and Stiebel Eltron Accelera¯ 300.
Because of slow recover seems an 80 gallon tank would be best but just can’t find much info on whether one of these would be good for radiant floor heat and my domestic water. I live in Asheville, NC a zone 3 climate zone, so winter do get below 20 F in Jan and Feb.

Any thoughts or experience here?

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Replies

  1. GBA Editor
    Martin Holladay | | #1

    Clayton,
    1. The heat-pump water heaters you mention don't have enough capacity to provide space heating. In any case, they won't work if they are located indoors -- because you can't rob your indoor space of heat in order to provide space heating.

    2. The only air-source heat pump available in North America that can do what you suggest is the Daikin Altherma -- a unit that costs about $20,000 (installed price). That's a lot.

  2. Bill Dietze | | #2

    The only system?
    I'm not a professional builder or HVAC guy so I could be missing something but what about Unico? I remember than someone in Seattle used one: see https://www.greenbuildingadvisor.com/homes/net-zero-energy-house-125-square-foot and for cold weather specification see http://www.prostar-mechanical.com/heatpump/uni_chiller/uni_chiller_rc.htm. It does seem pricey, oversized and possibly noisy, but it seems like it would get the job done. If not I'd like to know why!

  3. Richard McGrath | | #3

    Tell us a bit more about this basement you want in floor in . Possibly the best source for this would be another type heater , that would have to be determined . maybe the HPWH could work sufficiently , let's find out .

    What are the dimensions , length and height of exposed wall/s , door and window sizes and types in those walls, R value of the walls , average depth below grade , water table within 6' of slab bottom , finish floor type and will this be embedded tube or other , Below slab insulation R Value ?
    This water heater may very well be able to perform the duties you are inquiring about . It must be determined though by evaluating what it is that you need .

  4. Jonah Griffith | | #4

    We added around 1000 sqft here in Seattle to our house which is being heated with pex radiant floor heat. We are using a 66gal AirGenerate HPHW in an outside utility closet that is insulated to power the system. Our house is insulated and built very tight. There are quite a few homes around the area that are using this approach. I would just recommend finding someone who has installed the system successfully and can calculate heat loads. Also, ours is a split system that serves domestic and the radiant. We are 1 year in...:)

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