Building a cooling system with well water

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Old 07-30-16, 10:35 AM
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Building a cooling system with well water

I have a water-source heat pump that pulls the water for the heat exchanger from a well and discharges the water out into the wooded area behind the house. The water coming from the heat exchanger changes only a few degrees from the in-ground temp. The discharge water pipe exiting the HVAC unit runs across the back wall of the garage. If I can run the water through finned pipes or something similar and then blow air across them, I can heat/cool my garage with a simple system. I need suggestions on low cost finned pipe or something similar that can be used to easily create a compact, low flow resistance radiator. The discharge pipe is 1 1/2 PVC and I don't want to add much more back pressure for the well pump to push. It is a 100' well with a 40' run to the internal HVAC unit and the discharge pipe is an additional 80'. I would consider adding a pressure pump to the discharge pipe if necessary.

Any and all suggestions are appreciated. I am sure someone has already solved this problem.

Ed
Perry, GA
 
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Old 07-30-16, 11:03 AM
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My first thought is an OLD car radiator, something from the 1950s or earlier as they had large radiators with large passages. Large passages are necessary to reduce the pressure drop through the radiator which would reduce the flow. You have to be careful to not reduce the flow rate as it will have a detrimental effect upon the primary heat pump unit. To move the air a simple three-speed box fan is the least expensive option. You could add a line-voltage thermostat to the fan and be able to control the temperature in the garage to some degree.

Of course the radiator would need to be clean and not leak.
 
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Old 07-30-16, 11:25 AM
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Thanks for the suggestion. I considered that but auto radiators have a lot of back pressure. On the plus side they are an easy, ready-made solution. I would have to add a pump to force water through the radiators. Don't know if that would cause a problem with well pump regulation due to pressure differential between the discharge pressure and the inlet pressure. I considered a water reservoir to collect the water and then pipe it through the radiators but that requires discharging the water outside and then bringing it back in.
 
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Old 07-30-16, 11:33 AM
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pulls the water for the heat exchanger from a well and discharges the water out into the wooded area behind the house.
Really. Sounds like a terrible waste of water.
 
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Old 07-30-16, 11:34 AM
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Which is why I suggested an OLD radiator, they had larger passages back then and consequently less back pressure.

You COULD try taking a branch off the exit piping with a secondary pump to force the water through a more restrictive radiator and then pipe the radiator outlet back into the discharge piping. It's more work but definitely an easier to locate radiator.

Another option, if you can find a used one for a decent price, is a "unit heater" that already has the fan mounted to it. The larger the heater the less the back pressure but these don't find their way to junk yards all that often and buying a new one is prohibitively expensive for just messing around with.
 
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Old 07-30-16, 11:39 AM
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I would put a secondary pump on it and run it through an actual Water to Air Heat Exchanger. You can then put what ever kind of fan you want behind it.

Really. Sounds like a terrible waste of water.
I would agree, but some places of the country have gobs of water available.
 
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Old 07-30-16, 11:52 AM
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Depending on the depth of the aquifer it may not be wasting much water at all. Pump from a shallow well and discharge to a boggy area that returns to the aquifer in a matter of hours.
 
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Old 07-30-16, 05:21 PM
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The amount of water I use compared to the surrounding farm irrigation systems is tiny. I'm in GA and we sit on a huge aquifer. During the summer we often discharge the water onto the lawn or around the shrubs. It is on my to do list to catch the water for a sprinkler system.
 
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Old 07-30-16, 05:41 PM
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Accurate. The water exits into very loamy soil and disappears after 5 feet. 30 yards down the hill is swamp.
 
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Old 07-30-16, 05:44 PM
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Is that cost effective for small home project? Are those usually commercial units or are some sized for home use?
 
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Old 07-30-16, 08:36 PM
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Are those usually commercial units or are some sized for home use?
If that question is directed at my reply, yes. There are many home heat exchangers and normally run less then $200.

Only thing I should point out is when using it for cooling you will also need a catch basin because you will need to collect the condensation that forms on the exchanger or it will make a big mess.
 
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Old 07-31-16, 07:20 AM
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You would likely do well using a coil designed for the purpose as suggested.

A radiator would be fairly efficient if it was clean and the fins were in good shape.
The problem with it however is a rad is normally designed for 15 psi whereas a circulating pump for your heat pump could exceed that by many times.

Another concern with using well water to air-condition is that unless you are in a hot and dry climate a coil using well water will take very little humidity out of the air which in many climates is half the cooling load.
 
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