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Old 04-27-15, 08:55 AM   #1731
MEMPHIS91
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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.

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Old 04-27-15, 01:32 PM   #1732
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Quote:
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.

Jake,

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.

-AC_Hacker
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Old 04-27-15, 07:29 PM   #1733
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Thanks for the encouragement. I got a free hot water heater tank today to do the prototyping on.
I believed I used the term DX correctly. I will in fact be running my evap coil (one long copper loop) in my 30 foot deep bore hole.
I had though about the ground being slightly acidic..... I used a garden soil tester and measured 6.5. Not bad but I have no idea what it is at 10, 20 or 30 feet. So I will for sure be coating/painting it.
Yes I planned on using some foam spacers to hold the tubing to the outer walls of the bore hole til I can fill it with sand/dirt.
1/4 inch was by ball park guess as well. I will do the math with the exact compressor once I find it laying in someone's junk pile.
Thank you for your advice, I will be starting my own thread when I get started. No defrost..... that sure does sound nice.
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Old 04-28-15, 12:33 PM   #1734
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Great idea!
I think you will be a bit short in hole depth unless maybe you are in ground water for a good portion of your 30 ft. It may be tho that since domestic hot water use is intermittant, your loop may have time to "recover" between runs.
A cool shower is not as bad there as here in winter!
If going deeper is not a huge problem while you're set up - I'd sure do that.
Of course if that didn't work you could always do another 30 footer and add on.
The other thing that I wonder about is the 60 ft plus of 1/4" evap tubing - thats a small diameter for that length even for 5000 btu.
Good luck and take pics!!!
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Old 04-28-15, 06:20 PM   #1735
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Ron I have made it to 36 feet deep before. So I think I can go deeper if I need to. I guess my main concern was the lube not flowing if I keep going deeper. Going to 3/8 tubing at 30ish feet might be best. I can go to 7,000 BTU system if need be (or larger). Window units are EVERYWHERE around here. And I was also planing a electric back up element if needed. Thanks for the advise.
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Old 04-28-15, 08:19 PM   #1736
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Quote:
Originally Posted by Ron342 View Post
Great idea!
I think you will be a bit short in hole depth unless maybe you are in ground water for a good portion of your 30 ft. It may be tho that since domestic hot water use is intermittant, your loop may have time to "recover" between runs.
A cool shower is not as bad there as here in winter!
If going deeper is not a huge problem while you're set up - I'd sure do that.
Of course if that didn't work you could always do another 30 footer and add on.
The other thing that I wonder about is the 60 ft plus of 1/4" evap tubing - thats a small diameter for that length even for 5000 btu.
Good luck and take pics!!!
Ron342,

He's in Mississippi. I've lived in MD, and also in MS. Spring comes very early in MS, and summer stays a long time. So, the average soil temperature can be a full 10 degrees F warmer than it is in MD. That makes a lot of difference.


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Old 04-28-15, 10:24 PM   #1737
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AC,
Yes soil is nice and warm. During 75% of the year I can hit water in less than 10 feet deep. Shallow wells are common for gardens and things.
I am writing up my thread now. Try to break this project down into sections and cover as many details as possible.
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Old 04-29-15, 01:51 AM   #1738
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...I am writing up my thread now. Try to break this project down into sections and cover as many details as possible.
MEMPHIS91,

Thanks for taking the trouble.

A lot of people (maybe hundreds, maybe more) will be able to learn from your example.

Sincerely,

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Old 04-29-15, 07:54 AM   #1739
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AC - you're right - he has a lot warmer ground temp and with the high water table he may not have to go so deep.
Memphis - after thinking about the lube flow it does seem like a potential problem. The oil has to fight gravity up 30 ft or more of tube so you wind up with a lot of oil hanging on the return and if you go with a narrow tube to increase flow rate you eat it in head loss.
There are guys here tho who know lots about oil flow and maybe they will chime in to help.
Theres also the possibility of a horizontal loop?
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Old 04-29-15, 08:01 AM   #1740
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AC,
No problem this is my first forum based project, I have always just used the information and not given back. Time to change that. The new thread is up http://ecorenovator.org/forum/geothe...html#post44809

Ron342,
Yes at that is the biggest design problem. It would be always to hear from people who know lots more about it than me.
Yes I have access to a mini excavator if needed, but have a lot of water lines and field lines from the septic tank right there too. That was in fact a idea I had of running the DX line in the bottom of my septic tank.

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