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Old 04-27-15, 12:32 PM   #1732
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Originally Posted by MEMPHIS91 View Post
Howdy name is Jake,
I have been looking and looking and using all kinds of search tools, could be that I'm just overlooking something.
I'm planing a HPWH design with a 5,000 BTU (or larger if needed) AC window unit. I plan to use BBQ Propane (after freezing and running it through a few dryers). Its a 50 Gallon electric water tank and I plan to running copper tubing (maybe nickle electroplated?) into the tank. I plan to start my own thread but am just giving details so ya'll can answer this question better. My plan is to drill a 2" hole 30' feet deep (i've done it before, very easy) and running my DX line in a loop down and up again. Around here the soil temp stays about 58F. Is this possible? I understand with much larger systems you need a closed loop system. But would this work? Has it ever been tried? If not I'm standing by with the need recording devises to get accurate info during testing and will post my finds here. Just don't want to waste time and money if this has already failed. Thank you for your time.


Sounds like an amazing project.

So if I understand you, you are going to make a Ground Source Heat Pump water heater, and you are going to use direct refrigerant expansion (DX) in your single, 30 foot deep bore hole.

If I am understanding your plan correctly, it sound exceedingly interesting. Nobody on this forum has done exactly the configuration that you are describing.

You can find examples of successful DIY ASHP projects, which will be helpful to you, but you are breaking new ground with your project, and I think that your idea is awesome!

Some ideas that come to mind:
  • If your soil tends to be acidic, the life of your tubing will be more limited, but maybe long enough for your purposes. Painting the tubing might help a lot.
  • If the PH of your soil is neutral or alkaline, no problem.
  • You will want to maintain space between your tubes. I used plastic tubing and strips of inner tube. Once the dirt is put in, the dirt will do the work.
  • Any refrigerant line, and DX lines are no exception, need an optimum diameter to assure that the velocity of your refrigerant flow is high enough to keep the lubricant in suspension. In other words, bigger diameter = lower velocity (but less friction), smaller diameter = higher velocity (but more friction). My intuitive guess (with nothing to back it up) would be that 1/4" would be fine. It would probably be a good idea if you could get in touch with local DX heatpump people, or search the web for manuals on DX installation. I have come across that information before. But keep in mind that your compressor is pretty tiny, compared to commercial installations, and your tubing should be smaller.

Yeah, your DX water heater will avoid a lot of problems, like water pumps, anti-freeze, frost build-up on the evaporator coils.

Brilliant, just brilliant.

Take lots of photos as you go.

I'm not an HVAC technician. In fact, I'm barely even a hacker...
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