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  1. #1
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    Any fundamental difference between geothermal and closed loop water cooled condenser?

    Hi, I've been scratching my header the past few hours trying to figure out why you need to spend thousands of dollars to replace a traditional hvac system with a geothermal one? It seems like fundamentally, all that is changing is that the condenser is now a liquid-liquid hx rather than liquid-air and that maybe a normal ac compressor isn't designed to be run in reverse i.e. the heat is usually supplied via lng or electrical. Otherwise the only other difference I've come across so far is that the geothermal units are packaged together whereas a traditional hvac system is broken up into the evaporator and condenser/compressor.

  2. #2
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    Well, if you lived in a very hot environment it just might be a big energy savings to use 55- 65F ground water vs 100F air temperature to cool your refrigerant.
    Also the compressors do not run in reverse. The refrigerant flow does.

  3. #3
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    I live in palmdale, CA so even in the winter it's getting up to 60-70 during the day, so odds are I'd never see any benefit with changing the heating side. So if we only focus on the cooling side, it seems like it should be pretty straightforward from an installation point of view... Just bypass the a/a hx with an wahx. Otherwise it's just a lot of digging.

    That's a good point in the flow reversal. I've never really gone past the extremely abstracted refrigeration cycle. Makes me think that you could add in a reversal valve relatively easily...does a full geothermal add much functionality beyond this? I'm tempted to make a mini version to cool my garage in the summer... Probably wouldn't be too hard to plumb in another mini heat exchanger into the water heater inlet...

  4. #4
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    The advantage of the closed loop is the water savings. Is your water free ?

  5. #5
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    The water is relatively cheap in the grand scheme of things, but it seemed like running tap water came with its own issues with corrosion and sediment. There was something like 1-4 gph/ton of cooling so an open system might use like 100 gallons a day? I could collect the water and use it for irrigation, and that would greatly reduce the labor. I think the most logical implementation would be to dump the waste water to the water heater with a bypass/overflow into the garden... Assuming it doesn't get too hot.

  6. #6
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  7. #7
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    I suppose this is basically the same thing. The only thing I'm wondering about is if the water loop is being kept at the system pressure (40-60 psig), then when the tank is full, you won't really get any flow through the heat exchanger, unless the drain valve opens when the ac is on or when there isn't enough flow?

  8. #8
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    I found my mistake... It's gpm not gph which changes things drastically. The other thing is that reducing the flow to get more temperature rise appears to defeat the purpose of reducing compressor load. It's seeming like maybe closed loop makes more sense?

    I also saw something about how buildings were making ice at night and using that to run the chillers during the day. That might be interesting...

  9. #9
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  10. #10
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    Laws generally prohibit 'wasting' the 'geothermal' water in any way. It usually has to be returned to where you got it - via a separated same-depth well.

    PHM
    -----------



    Quote Originally Posted by Engr010 View Post
    The water is relatively cheap in the grand scheme of things, but it seemed like running tap water came with its own issues with corrosion and sediment. There was something like 1-4 gph/ton of cooling so an open system might use like 100 gallons a day? I could collect the water and use it for irrigation, and that would greatly reduce the labor. I think the most logical implementation would be to dump the waste water to the water heater with a bypass/overflow into the garden... Assuming it doesn't get too hot.
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  11. #11
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    It reminds me a of a crazy idea I had to invent a mini split pool heater. I just always found it annoying that a house would have one unit heating the pool while a separate unit cools the house.

  12. #12
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    Quote Originally Posted by a4372302 View Post
    It reminds me a of a crazy idea I had to invent a mini split pool heater. I just always found it annoying that a house would have one unit heating the pool while a separate unit cools the house.
    One of the guys on the forum... a few years ago...

    Designed and built something similar to this... last I heard... it worked just fine!
    GA-HVAC-Tech

    Your comfort, Your way, Everyday!

  13. #13
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    Quote Originally Posted by Engr010 View Post
    I found my mistake... It's gpm not gph which changes things drastically. The other thing is that reducing the flow to get more temperature rise appears to defeat the purpose of reducing compressor load. It's seeming like maybe closed loop makes more sense?

    I also saw something about how buildings were making ice at night and using that to run the chillers during the day. That might be interesting...
    It's called a ice bank. Run a chiller all night making ice then let the ice chill the water to cool a building. The savings are in the demand charge from the electric company. Go back 60-70 years churches use to be cooled by ice bank. Take a 1/2 hp freezer unit freeze water for 3+ days blow air over the ice cool the church for Sunday service.

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