diy geothermal for garage

Discussion in 'HVAC Heating & Cooling' started by katherine1962, Jul 19, 2011.

  1. katherine1962

    katherine1962 New Member

    Jul 19, 2011
    Fairfield, Ohio
    I will be having a new furnace installed in my house. My old one has a fairly new replaced cooling coil heat exchanger in it (1.5 ton). i was considering running a couple hundred feet of cooling line buried approximately 5 ft in my backyard and having a glychol medium pumped through the line and through the cooling coil. i would have an appropriate sized fan to blow air across the coil. should something like this be sufficient for heating and cooling a 2 car garage that i use for woodworking. provided i have my garage adequately insulated. Thanks in advance for any information.
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    If the a/c unit is not a heat pump, I don't think you would be able to get it to work. Also, a couple of hundred feet may not be enough volume/length to extract much heat. A ground source heat pump system can be quite efficient, but the setup costs can be fairly expensive and the engineering required to make it all work well are not trivial.
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  4. Runs with bison

    Runs with bison Member

    Aug 23, 2009
    Since you aren't planning to have a refrigeraton loop (the normal geothermal heat pump arrangement) the best you can hope for is an approach (differential) to ground temperature. Fin efficiencies aren't all that great and I doubt you will want to use a high volume air source--further depressing the heat transfer coefficient. Plus this will be primarily a non-condensing mode. Condensation can increase heat transfer coefficients, but without refrigeration or a particularly cold source, this is an unlikely mode for the operation of your loop. Jim's comments about the length also are relevant as a cap--since the heat must be conducted away through the soil as source. The input power of the pump also comes into play, but I assume the pump would be before the ground coil so it's heat would be dissipated to the ground. (A monster pump would be a bad idea. I suspect a powerful fan/blower would also be bad as they might introduce more heat than can be removed or at least exceed the point of diminishing returns for their energy input.)

    To put it in easier to understand terms: don't expect much. It should give some cooling due to temperature differential. It will not give you any dehumidification. That might be all that you require, but I suspect that some dehumidification is what you really need in Summer in Ohio.
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