Desuperheater to storage tank to tankless finisher

Discussion in 'Geothermal Heat Pump Applications' started by Brad, May 22, 2018.

  1. Brad

    Brad New Member

    First, let me preface this first post by giving a big thank you to the industry experts and members who dedicate their knowledge and time to inform and stimulate learning and discussion. Like many, I am coming here as a novice on geothermal technology but am considering making a sizable investment in it and therefore want to be as informed as possible. Again, I really appreciate what you've all shared.

    I've been in discussions w/ a local geo contractor who strongly encourages using the geo desuperheater capability to pre-heat water in storage tank (unpowered) that then has this pre-heated water available to a propane-fired tankless heater which acts as the finishing heater. This all makes logical sense to me and according to the contractor, his clients pay beans in propane to make the system run throughout the year. Importantly, I'm in Massachusetts, so the heat pump gets a good workout where I live. As best I can see, the only downside to this is the upfront cost to set all this up (desuperheater option, preheat storage tank, tankless system, plus parts and install = ~$9k) and having a propane tank onsite.

    I searched on this setup on these forums and really didn't come up with any that seemed to be the same. Figured I'd share and get others' perspectives. Thank you for reading and for any comments.
  2. ChrisJ

    ChrisJ Active Member Forum Leader

    I went with the un-powered storage tank going into a heat pump water heater, so no propane tank, but I have a big generator.

    I have a 100 lbs propane tank which will only get me a couple days in a power outage.

    For your situation I would have you think about whether or not you are going to someday add a generator, Also be sure the tankless can handle hot water being fed to it. I have read somewhere that some don't do well with hot water entering, but if the contractor does it often he must install one that works.

    Good luck, welcome to the forum.
    Brad likes this.
  3. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    Why don't you put in an electric tank as a second tank?

    Or skip the entire DSH setup and put in a dedicated hot water geo heat pump? Which then can make you entire hot water with the efficiency of the geo system.
  4. Brad

    Brad New Member

    Huh. I didn't know about dedicated hot water geo heat pumps. That's very interesting.

    As it stands now, I'm holding off on the system because I've realized that given the way the rebates are processed, we can't afford this contractor. Dandelion Energy is coming to MA supposedly next year though (they're a lot cheaper comparatively), and they do the two tank setup so my expectation is to go with them and that setup.

    Back to the dedicated hot water geo pump though... very cool. I expect you'd just need to boost the length of your ground loop accordingly to supply the hot water heat pump. That said, wouldn't you still want to use the desuperheater function of your climate control heat pump since that is, in essence, free heat? Or is there no storage tank when you're using the dedicated hot water geo heat pump?

    Thanks for the response, Doc.
  5. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    Your loop capacity is not really much more since you are not extracting much more heat from the ground. The desuperheater extracts already extracts a large portion of the energy. There is no such thing as free heat, the argument can only be made (to a limited degree) in the summer, but with MA climate, the A/C runtime is limited anyway.
    Yes, dedicated Hot water has a storage tank.
    Brad likes this.

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