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What are the chemicals used in GeoExchange?

Louisa Murray-Bergquist | Posted in Green Products and Materials on

Specifically, what are some common fluids used for circulation through the loops, and why? what properties make these liquids good for this purpose? Also, what are the refrigerants used for heat transfer from the liquid being circulated to the heat pump?

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  1. User avatar GBA Editor
    Martin Holladay | | #1

    Louisa,
    First of all, the word "Geoexchange" is a registered trademark used by an industry organization called the Geothermal Exchange Organization. The technical name for the type of heating and cooling system that your are thinking of is a ground-source heat pump.

    There are many types of ground-source heat pumps. Some have an "open loop" that circulates pond water or water from a vertical drilled well. Others have a "closed loop" that circulates ordinary water or a water and antifreeze solution through horizontal looped tubing (tubing buried in a trench) or through vertical tubing (tubing inserted in a drilled vertical borehole).

    If antifreeze is used -- it is optional, not required -- the two most common products are ethylene glycol and propylene glycol. Of these two products, propylene glycol is less hazardous to humans if accidentally consumed.

    Still another type of ground-source heat pump -- a so-called direct exchange system -- circulates a refrigerant through buried copper tubing. The heat pump industry uses several different refrigerants; if you want to know the specific refrigerant used in a system that you are considering installing, contact the equipment manufacturer and ask the company which refrigerant they use.

    For more information on these systems, see this article in the GBA encylopedia: Heat Pumps: The Basics.

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