Geothermal Heat - Old house is it worth it?

Discussion in 'HVAC Heating & Cooling' started by shluffer, Sep 23, 2008.

  1. shluffer

    shluffer Member

    Apr 23, 2008
    I have an old house with poor insulation in CT. I am trying to figure out if it is worth installing, and if it will work. My understanding is that I will have to run ducts. I have a couple of other things I am trying to figure out:

    1) What is maintenance on this thing like? How much does it cost?

    2) How long are these things supposed to last?

    3) Where is the heat exchanger? Is it buried at the bottom of the well?

    4) Is there anything else at the bottom of these wells to break? Drilling is expensive and I only want to do it once.

    5) Will it produce enough heat to warm a poorly insulated house? I should be able to run extra ducts to provide more hat (and a larger system in general to produce the heat) but at some point it is no longer cost effective.

    Lastly, can anyone tell me what the temperture difference is between the air produced by a oil system and a geothermal? I have heard it is around 120 on the geo, but that may be specific to the system I was asking about.

    Thanks for the help!
  2. Bill Arden

    Bill Arden Computer Programmer

    Sep 30, 2006
    computer programmer
    MN, USA
    I don't know of any Hot Geothermal heat sources in CT, so I am going to assume you mean a ground source heat pump.

    1. "Closed loop" systems just need the same maintenance that a furnace would need. Air filters and occasional cleaning.

    "Open loop" systems need to be flushed with a cleaner once a year or so. It's not expensive, but messy.

    2. The Heat pump itself lasts decades, and the "closed loop" pipes are estimated to last over 100 years.

    "Open loop" systems last about 5 to 10 years depending on water quality

    3. In a "closed loop" system the ground heat exchanger is a series of pipes in the wells or pipes in a trench.

    "open loop" systems just use one well and draw up ground water.

    Either way there is a freon to water heat exchanger in the heat pump and a second freon to air or hot water heat exchanger for the output.

    4. in a "closed loop" system there is nothing but pipes in the ground and they hardly ever have problems.
    There is a well pump in a "open loop" system.

    5. Yes. Where's your wallet?

    Heat pumps are great in that you can just keep adding more as you need.


    A Heat pumps efficiency is reduced as it's output air temperature is increased. For example you could produce 180 F air or water, but that would be about half the efficiency that you would get at 110F

    Heat pump efficiency decreases as you increase the temperature difference between the ground water and the output water. So doubling this temperature difference cuts the efficiency in half. (or more based on the design of the unit)

    For comparison: The efficiency of an oil system decreases more slowly as it's output temperature increases since it's based on the ratio of the flame temperature to the output temperature.
    0% efficiency is achieved when the output air flow slows to the point where the output temperature equals the flame temperature. Note: most heat exchangers would melt before this point :p
    Last edited: Sep 23, 2008
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