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  1. #1
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    Question Geothermal Ground Loop Pressure and Efficiency?



    I have 3 x 300FT wells in series. My ground loop pressure keeps dropping, but my HVAC company says it's not concerning. They'll goose it up to 68 PSI, then over 6 months it'll drop to 20 PSI. Then they goosed it again to about 68 PSI, then drops down to 30 PSI over 6 months.

    I'm not concerned about a leak as it is a large ground loop to pressurize through. My question is how does that PSI equate (if at all) to efficiency? I bought a device to pump the pressure up myself so I can keep it close to 68 PSI all the time. My question is how much will that help my efficiency? (basically am I wasting my time to obsess over it being close to 68 PSI).

    FYI, my street water pressure is 68 PSI which is why I can only get it to there.

    Thanks,

    John



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    Re: Geothermal Ground Loop Pressure and Efficiency?

    Welcome to the forum John,

    As long as the pump circulating the water in your loop doesn't start to cavitate and you got proper circulation in the loop, the pressure will not affect your efficiency.
    Your heat pump (or chiller) doesn't care what pressure the waterloop is at, it will only be reducing it's efficiency when the mass of water going through it is reduced.

    However, regardless of system size, after all the air been vented out any constant drop in pressure means that there is a leak.


  3. #3
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    Quote Originally Posted by The Viking View Post
    Welcome to the forum John, As long as the pump circulating the water in your loop doesn't start to cavitate and you got proper circulation in the loop, the pressure will not affect your efficiency. Your heat pump (or chiller) doesn't care what pressure the waterloop is at, it will only be reducing it's efficiency when the mass of water going through it is reduced. However, regardless of system size, after all the air been vented out any constant drop in pressure means that there is a leak.
    ^^^ what he said the HP don't care

    Many a loop running without pressure gauges, some even just on a header bottle. Just be sure that if you have a antifreeze mix you don't dilute it too much adding water...depending on application of course

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    Re: Geothermal Ground Loop Pressure and Efficiency?

    .

    65psi seems excessive, 15 psi to a bar so that's over 4 bar?

    1 bar is enough and 2 bar (30psi) is more than enough.

    Why 4.5 bar (65psi)? is it in the manual as a recomended?

    Regrds

    Rob

    .
    .. ... -. .----. - / -- --- .-. ... . / -.-. --- -.. . / --. --- --- -..

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    Re: Geothermal Ground Loop Pressure and Efficiency?

    Many a loop running without pressure gauges, some even just on a header bottle. Just be sure that if you have a antifreeze mix you don't dilute it too much adding water...depending on application of course
    Last edited by frank; 21-10-2014 at 08:55 AM.

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    Re: Geothermal Ground Loop Pressure and Efficiency?

    Quote Originally Posted by The Viking View Post
    Welcome to the forum John,

    As long as the pump circulating the water in your loop doesn't start to cavitate and you got proper circulation in the loop, the pressure will not affect your efficiency.
    Your heat pump (or chiller) doesn't care what pressure the waterloop is at, it will only be reducing it's efficiency when the mass of water going through it is reduced.

    However, regardless of system size, after all the air been vented out any constant drop in pressure means that there is a leak.

    The Viking is right , as long as you gave enough pressure to circulate and the pumps dont cavitate with entrapped air you are set. The pressure drop surely points to a leak, somewhere. Best of luck.

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    Re: Geothermal Ground Loop Pressure and Efficiency?

    And don't forget, that 68 psi is at the top of the whole system. 300 ft down it is way more and there is no need for more pressure down there. As stated, 15 psi is all that is needed and if there is an expansion tank (not usual on GSHPs but I have seen them) keep it on the suction side of the pump. If it sits at 20psi and doesn't drop further, leave it there, but have the glycol percentage checked.

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