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I'm buying my first house (1000 sq ft) and it has an old, unused water well. It has a central furnace but no central AC, only window units.

I want to use geothermal to condition the air, but only to cool the house in the summer and supplementing the window units.

Here's my question:

What if I rigged up a geothermal system that simply takes the 55°F well water (open loop system), run it through a car radiator or something, and blow air over it? Won't that give me chilled air?? Now I can blast that air through the existing vents. Right?

  • Sounds like a neat idea. Try it and see. If it works out for you post something on instructables.com. – Octopus Dec 6 '16 at 6:29
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    Before you invest, you might do some calculations based on how much water you expect your well could produce and thus how much heat the water stream could absorb. You might find it to be less than you expect. – Daniel Griscom Dec 6 '16 at 11:55
  • Alright thanks guys. I was hoping this was a common use of geothermal and there would be products and systems ready for this, but it appears that I will have to figure something out myself and that starts with spinning the ol hamster wheel inside the head. The first consideration might be this: A/C units don't "chill" the air, they remove heat from the air and transfer it the refrigerant. Next I'll have to figure out what exactly a heat pump does and why its used, and how a geothermal system could operate without one...... – Dan Mantyla Dec 6 '16 at 15:24
  • I've often thought that the most effective use of this would be to mist / fog the outside part of the air conditioner - which would obviously be easier to arrange with a split system or whole house unit than with window units. It's designed to operate out in the weather, so the water should not be a problem, and it would help the A/C reject heat more efficiently. Never tried it (yet) but I can't see a flaw... – Ecnerwal Dec 10 '16 at 2:32
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The first problem that the heat pump solves is the small differential between the ambient air temp and the temperature you'd expect to get out of such a system.

Let's say your home is at 80 degrees. Let's say (with only wild guesses at actual results) that the air that comes off your radiator is cooled to 65 degrees. (You're unlikely to get anywhere near 55 degrees, your water temperature, with a simple fin-contact radiator.) You now have an air temperature differential of 15 degrees. That's not much, and unless you move massive amounts of air it's not going to give the results you're hoping for. You may drop the room five degrees, or even ten, but that ignores the primary benefit of a true air conditioning system: humidity reduction.

This is the second problem a heat pump solves. By dropping the temperature in the room without a condensation stage, you've now effectively raised the relative humidity. This reduces the sensation of cooling you'll feel, and it could actually cause ugly side effects with respect to your home. Now your windows and walls may start showing condensation because they're cooler than outside, but also wetter.

Basically, if it was that simple, everyone would do it. Unfortunately, it isn't. I'd upgrade your window units or add another one. For the cost and effort you'll come out ahead. (Don't forget that a well uses electricity, too.)

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This type of system was used in the early 1900's as a crude form of air conditioning. It will work but it is not very effective. You will need a large (water to air) coil and also need to move a large amount of water. If you pull the water out of the well you should also have a reinjection well to dispose of the water. In many places it is not lawful to dump well water into a town's sewage system without the water supply being metered as what goes thru the meter helps determine the sewage bill.

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