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richinok 06-21-2008 07:21 PM

Adding Geothermal heat exchanger to window unit
Anyone heard of adding a geothermal heat exchanger to a window AC unit? I was thinking about simply adding intake and outlet manifolds around the outside of a window unit's case, then running some pipe from the intake side into a suitably long and deep trench and then back to the outlet side, using one or two 12v inline fans to circulate the air through the pipe. Would this increase the efficiency of the unit? That is, since the outlet side is normally trying to release heat into the ambient hot air, would I get some gain releasing the heat into significantly cooler air (from the ground-cooled piped air flow)? All this because the cost of trenching is mostly labor, a solar panel can run the 12v fans and charge a battery for nightime use, and PE pipe is pretty cheap still but utilities prices just keep going up...

sgthvac 06-21-2008 08:59 PM

WHY??? would you put all the time and effort into a window unit? To answer your question, no. I've been in the business 20 yrs and never heard of nor seen anyone attempt it.

richinok 06-22-2008 04:17 PM

Well, a central air unit to cool the 900 sq. ft. apartment on the end of my shop will cost about $3000 installed, and I can get a window unit big enough to do the job for a little less than a third of that. In this part of Oklahoma, we run an AC for about 5 months a year. Since the added cost of the geothermal "remodel" is only about $200 plus 2 days labor, it may be worth it if I can get a big enough increase in efficiency. The window unit as-is will cool the apartment, but if I can increase the efficiency of the heat exchange I get a lower operating cost, too.

8 Ball 06-22-2008 04:26 PM

If you mean drawing air thru the geo coil then thru the condensor, and discharging to the atmosphere, yes, you will gain some capacity. Will you gain, due to the increased cost of running a fan to circulate the air, and the addition power required to overcome the static created by the coil.

In order to gain efficiency, you would need to reduce power consumption, not add to it.

The engineering indicates an awfuly long run, and alot of cfm in order to make the heat transfer viable. If your serious about trying it, use water. Even then, theres no economic advantage.

geo fan 06-23-2008 06:59 PM

please do not spend all that time money and thought into a window unit.
the real benifit to direct source geo thermal is the heating side . put in a ductless split unit with an inveter these are very eff and will give you heat as well

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