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  1. #1
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    Geothermal Heat Pump GPM Requirements

    I am looking at a Bosch 4 Ton Water Source Geothermal Heat Pump (45,900 BTU, 13.0 EER). This will be serviced by an OPEN loop configuration (pump and dump). Bosch is telling me I need a water flow rate of 12 GPM, but that is their standard answer regardless of configuration. It's my understanding that an Open Loop system will use substantially less GPM than a Closed Loop. Is this correct?

  2. #2
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    If the manufacturer wants 3 GPM PER TON that’s what they want.

    BTW that’s the average water usage for water cooled!

  3. #3
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    Quote Originally Posted by CommanderDave View Post
    I am looking at a Bosch 4 Ton Water Source Geothermal Heat Pump (45,900 BTU, 13.0 EER). This will be serviced by an OPEN loop configuration (pump and dump). Bosch is telling me I need a water flow rate of 12 GPM, but that is their standard answer regardless of configuration. It's my understanding that an Open Loop system will use substantially less GPM than a Closed Loop. Is this correct?
    No, that's not correct. You need 3gpm per ton either way. Why are you trying to argue with the manufacturer and circumvent their instructions?

    By the way, pump and dump is usually a bad idea unless the water is very low in mineral content.
    Bob Boan


    ​You can choose to do what you want, but you cannot choose the consequences.

  4. #4
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    Depending on your model I believe it's recommended between 2.25 -3 gal/ton. Back in the day they recommended 1.5 for open loops, but if they say 2.25-3, then that's what you go by. If entering water temperature remains above 50° 1.5gpm is minimum to prevent freezing. If it ever falls below 50° minimum required is 2.0gpm. For rated capacity 3gpm is suggested.

    Interesting, their chart only shows rated capacities at 6 or 10 gpm for the 4 ton package unit. Pretty easy to calculate that stuff though.

    Looks like the CE049?

    Correction, their chart shows 6 or 12 gpm for your model. So anywhere in between. Their spec sheet shows 12 is suggested.
    Last edited by mgenius33; 08-15-2019 at 06:11 PM.
    "The only true wisdom is in knowing you know nothing" Socrates

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