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  1. #1
    Join Date
    Jul 2008
    Central VA
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    Need help with load calc and your thoughts

    We just got the results last week. It looks like the heat loss (62,022 BTUH) is over twice that of the heat gain (29,842 BTUH). Is this average, or is it just part of having a 165 year old house?

    Given those numbers, our geo guy is telling me that we need to couple the geo system with a backup heat system. Now, I've never heard of geo needing a backup. I'm assuming that because of the load calc, if we size the unit for cooling, we won't have enough tonnage to provide the necessary heat? And if we size it for heat, it'll be waaay oversized for cooling, yes?

    We currently have an ancient oil furnace with separate AC. I'm wondering if that's why. Geo's expensive enough that I want it to be able to heat and cool without backup.

    What do you all think?

  2. #2
    Join Date
    Jun 2008
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    That heat loss is possible, but without knowing where you're located, living volume (square footage & ceiling heights), insulation, door and window counts and types, shade and southerly exposure, etc., there's now way to know if that heat loss is correct.

    What is your geo guy saying you'll get for worst-case BTUs?

    Somehow you'll need to meet those heat loss BTUs or you'll be cold.

  3. #3
    Join Date
    Mar 2004
    Vancouver, BC
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    Or look at your budget for the geo, and see how much money you can spend out of that with upgraded high performance windows, police up all the infiltration and cracks, add more roof and wall insulation, and use a heat recovery ventilator to pre-heat the ventilation air for the house, and see if you can get your heat losses down to close to equal what your heat gains are, and then you can get away with a much smaller geo system, AND have a balanced load.

    It is a fundamental alw of physics that in a heating dominated climate, you will have more heat loss than heat gain and the most economical application for a geo-exchange system is to have a balanced heating and cooling load. Supplemental heat is used for many geo systems all the time in many climate zones of North America where the heat losses exceed the heat gains.

    Or, as I've stated above, spend $$ on reducing the heat losses to try to balance the heating and cooling needs and it's a win-win: lower energy bills, smaller geo system, more comfort.

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