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Solar Hot Water Tank supplying a radiant loop?

GCR Member Posts: 10
We are considering making an offer on a house but I have some concerns about the HVAC system. This is in the Washington DC area. Half of the house is heated by in-floor radiant. The in-floor radiant is supplied by a solar pre-heated electric water heater, A thermo-miser TM80HE installed about 10 years ago. Domestic hot water is supplied by a nearby gas on-demand hot water heater.

I'm a little concerned that a hot water heater is doing a boiler's job. I suppose in the future I could forget the solar and have a boiler do both DHW and serve the radiant. Who knows whether it makes sense to keep the solar and have an indirect tank serve the DHW. Any thoughts on how long this TM80HE should last me? It's a a few years out of warranty.


  • newagedawn
    newagedawn Member Posts: 586
    some radiant floors have so little btu load that a full size boiler is way oversized for the load, so some guys use WH to supply the heat demand which works, its not a common practice but does do the job nicely and the energy costs are lower, your in good shape
    "The bitter taste of a poor install lasts far longer than the JOY of the lowest price"
  • hot_rod
    hot_rod Member Posts: 22,254
    About how many square feet is 1/2 the house? How many collectors on the roof?
    That is not a bad way to heat using solar for a portion of the load. When there is no solar, you have basically electric resistance heat. Any data on power bills, mainly electric costs?

    If you have a boiler, when the solar tank fails you could consider an indirect solar tank, dual coil with both solar and boiler input.

    With small loads and no fresh water being added that solar tank could possibly last another 10 years. Unless the operating cost is excessive, I'd let it run and see how much you enjoy radiant comfort.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • GCR
    GCR Member Posts: 10
    Thanks all. Very helpful.