Building a diy system with hybrid elec water heaters

Discussion in 'General Discussions' started by Ben Rogers, Apr 25, 2018.

  1. Ben Rogers

    Ben Rogers New Member

    New here. Some context:

    • Contractor. Have my own equipment.
    • I've installed/plumbed several Toyotomi boilers where all the controls run off 15 dollar RIB relays.
    • Building a super-insulated house in Traverse City Mi. (to Alaska standards).
    • DIY absolutely required. Hiring other people takes all the fun out of it.
    • I'd like to use simple, commoditized products with low tech controls.

    I'll likely be putting together a combi system of geo, solar thermal, solar elec, wind with a 5000 gallon heat store. My research is leading me to believe the system may easily supply my radiant heat and even hot tub needs 9 months out of the year. However, I might need geo in the winter. In addition to my thermal store tank, I'll have loops under the leach field and couple elsewhere, but the house is located on 130' bluff which is basically a sand dune so I'm not anticipating great ground source results (thus my tank).

    What I'm wondering is whether using 2-3 hybrid elec water heaters are a viable alternative to a standard heat pump. For example, see https://www.homedepot.com/catalog/pdfImages/c3/c368aa74-8dc3-42fd-a905-a94642a47939.pdf.

    These are cheap, easy to install, have self contained controls, don't require a professional to tweak, etc. So according to the spec, the 80 gallon version has a 29 gal recovery rate at 90 degree temp raise. My calcs lead me to believe that 29x8.33x90 = 21,700 BTUs/hr is possible. Two of these is more than enough to to heat the house and hot water. I'd be drawing from my thermal store of course to boost input air temp and I'll have a pre heated buffer tank with elec backup into which I can dump wind/solar energy if needed.

    So, what are the drawbacks of using these prepackaged hybrid heaters in tandem like this?

    Thanks,

    Ben
     
  2. nc73

    nc73 Member

    English please
     
  3. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    Generally codes require any dual usage appliance (domestic water, radiant) be rated as a dual usage appliance. These don't look to be rated dual usage.

    A dual usage boiler basically prevents cross contamination of the domestic water stream.

    Technically, you would require a tri-usage boiler if you want the hot tub on the same appliance. Don't think those exist.
     

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