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House next to deep rock quarry: How can I tap water below 12-16″ of ice for heat?

scout159 | Posted in Mechanicals on

We have 50′ deep water 50′ behind our house.Water is very clean with 20′ visibility at least-comes from limestone rock –no creeks or rivers–it is a hole in the water table. 8 acres. we have only 48″ of earth above flat limestone shelf that is entire area around us. It was a Quarry for limestone way back. the water is at top of shelf–about 48″ below the yard.

My minisplit is outside in 20 degree winter air while its 32 degree’s or above a short distance away?
We are planning an addition and would like to upgrade our heat and ac. We have a hot water baseboard and put in a minisplit for AC which worked well.

Any ideas?

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Replies

  1. Jon_R | | #1

    A couple of horizontal pipes 4' down to bring water to/from an open loop, water-to-water geothermal heat pump?

  2. scout159 | | #2

    I have not seen a water to water heat pump----any suggestions--about 100,000 heat btu is good.

  3. Jon_R | | #3

    Climatemaster and Waterfurnace come to mind.

    Run the numbers to see if the project is worth it - over the entire season, there might not be much difference.

  4. Expert Member
    MALCOLM TAYLOR | | #4
  5. user-2890856 | | #5

    I recommend not taking anything in this discussion Malcolm points to as anything other than a grain of salt . There are always horror stories , this is one . I advised these folks on what experts to contact closer to them than myself . This was a hack job of the highest magnitude , not a good example of anything other than Buyer Beware .

    Andrew ,

    Are these pictures of guages showing incoming and leaving water temps on the source side of your heat pump ? So this is not GeoThermal but in fact a GSHP , correct ?

    Did ypou know that ice stores 141 more BTUs per pound than 32* water ? Think about that .

  6. Jon_R | | #6

    I'd expect a good inverter mini-split with 20F outside air to be more efficient than a water-to-water heat pump using a 35F source and producing 135F output.

  7. SwitchgrassFarmer | | #7

    Richard, you are correct, I have a ground source heat pump system.

    I put the word "geothermal" in parenthesis after the description, as that is generally the layperson term for that type system. I will amend my comment to make that clearer.

  8. SwitchgrassFarmer | | #8

    As Jon R said, you will need to run a whole year Manual J heating and cooling load analysis and consequent construction and operating cost analysis. However, since you are in a heating dominated climate (an assumption made by the fact you have 12 - 16" of ice on your pond!), I question if a water-to-water heat pump will be cost effective. You might be using the system much more in the winter than in the summer. Your sub ice winter water temp is pretty low.

    During this winter's corner case cold snap, I managed to drive my ground source water-to-water heat pump input temps to the area you are talking about. (My system is deep well based, typically referred to as being "geothermal", although that isn't the "technically correct" description. I don't live in a region with an above average below ground heat source.)

    I can tell you first hand, a water-to-water heat pump runs and runs to make hot water when it is using input/source water at the freezing mark, the coefficient of performance is seriously reduced. Attached some well temp pix I took that morning; I was making 135 degrees or so water (it was below zero outside).

    Also note you are likely talking closed loop with anti-freeze. That cold day last month I actually went and double-checked what anti-freeze concentration we used versus the freeze point.

    As to utilizing your existing hot water baseboard, you would have to know what water temperatures you are making now, determine what you actually need, and compare them to what is possible with a water-to-water heat pump with an appropriately sized loop field in your pond.

    PS I think what you want to do is very cool, that is why I answered. Unfortunately I suspect this might be the most "encouraging" response you receive.

  9. GBA Editor
    Martin Holladay | | #9

    Scout,
    Briefly, here are some points:

    1. The type of system you are talking about is called a ground-source heat pump. Using a pond as a heat source for this type of heat pump isn't unusual; a mechanical engineer with experience designing ground-source heat pump systems should be able to help you if you decide to pursue this approach.

    2. Even though such systems exist, it's important to remember that such systems are rarely cost-effective. For a single-family home, it's almost always much less expensive to install one or more air-source heat pumps. For more information, see Are Affordable Ground-Source Heat Pumps On the Horizon?

  10. scout159 | | #10

    I am impressed by how there is a consensus of sorts that newer mini splits outperform every other mode of heating available.
    Would it make a difference if we restricted choice to water to air units? Currently, I may have the best heating solution now--Hot water tank on baseboard heat all rooms and 1 mini on 1st kitchen and upper master bed only as we put it in for Ac use over window units. It is way undersized but after some time it cools house to a point that most of it is very nice. We do not use for heat much. Does provide a backup function.

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