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Old 04-28-15, 11:29 PM   #1
MEMPHIS91
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Default Dxgshpwh (ground source heat pump water heater)

Howdy! I begin by saying thank you, thank you to all who take the time to read my thread, who comment on it, who give advice, who save me money by keeping me from making stupid mistakes, and those of you who just want to see something created. My name is Jake, (I am very bad Dyslexia so I apologize if things get mixed up) my project is a DXGSHPWH that in English is a Direct Expansion (DX) Ground Source (GS) Heat Pump (HP) Water Heater (WH). I will give as many details as I break this all down. My idea is to use an electric hot water heater with the HX coil from a window AC unit coiled inside, with the DX line running 30 feet deep into a 2 inch bore hole. My outline will be broken down into sections of the system as follows: Section 1 Water Heater, the tank, thermostat, HX coil, and back up elements; Section 2 Main AC Systems, heat pump, refrigerant, accumulator, expansion valves, housing, and controls; Section 3 DX System, bore hole drilling, DX coil, bore hole replacement medium, and thermometer.
Section 1 WATER HEATER
I have sourced a used 50 electric hot water heater. I would like to have to already existing thermostat control the compressor I have read on this forum about how to do that and fill like it should work fine. The HX coil is probably the biggest question mark in my head. Im thinking 25 feet or 3/8 refrigeration copper tubing coiled into either the top or bottom 1 inch element hole. If I can get it the coil correctly would do it in the bottom be best? Also the fitting like on the Air Tap A7 looks perfect but can I just buy that fitting somewhere? Should I consider coating the coil in something to keep it from building up with calcium and other terrible water things? I have seen people electroplate copper with Nickle before, comments? Whatever hole I dont use with have a 120 volt 1,800 watt element for when the heat pump cant keep up (I hope that never happens).
Section 2 MAIN AC SYSTEM
I am hoping to basically just cut existing lines to the heat exchangers and braze with 15% silver rods the coils going to the WH and the DX bore hole on. The only control I should need is the thermostat on the WH because I shouldnt have to deal with defrost. I was thinking about running a temperature probe to the bottom of the bore hole and if it drops below 45F or so to cut off the compressor until the ground can warm back up. I can easily get a 5,000-7,000 BTU window unit, what size would be best? I will be using BBQ propane frozen and then double line dry filtered as my refrigerant.
Section 3 DX SYSTEM
I plan to use 2 inch PVC pipe with a metal cutting head hooked to a 2 inch mud pump from my large pond, and add pipe until I get to 30 feet. I have done this before and gone to 36 feet. Ill post pictures as I drill and give a run down on the set up. Then I will feed the DX coil down and refill the hole. What are yalls thoughts on how deep the bore hole is? What diameter DX coil, Im thinking or 3/8? My biggest concern is the lubricant getting stuck at the bottom of the DX loop, could I just put a bigger compressor and get more flow if the first one is too small? It is much easier to replace a compressor than to bore another hole. Should I paint or electroplate the coil? What should I refill the hole with; I was thinking sand as it would let water in. Should I run a thermometer probe to the bottom? Should I cover the bore hole with concrete? Or should I maybe do 2 bore holes at 20 feet? I can hit water 75% of the year at less than 10 feet. Ground temperature is normally around 55-62F.
I will post some simple drawings and pictures as soon as I get a chance. Thank you again for reading

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Old 04-29-15, 08:48 AM   #2
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First off, welcome to the site!

Very interesting project Memphis91. I look forward to see what you come up with.
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Old 04-29-15, 12:00 PM   #3
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Quote:
Originally Posted by MEMPHIS91 View Post
...My idea is to use an electric hot water heater with the HX coil from a window AC unit coiled inside, with the DX line running 30 feet deep into a 2 inch bore hole...
Jake,

Regarding the vertical bore hole and the lubricant issue, when I cited it as a potential problem, I was acting as a 'devil's advocate', and was (am) trying to visualize possible problems. I was not saying that a 30 ft deep DX hole will not work... it might work just fine.

We have heard from other folks from MS here on EcoRenovator, and from all reports, making vertical boreholes is comparatively easy in MS, compared to some other parts of the country. So in that regard, nature has been very kind to you.

So, I guess what I'm trying to say is that I hope your project doesn't get tied up in knots over my comment about the possibility of lubricant starvation in a 30' vertical hole. Your initial vision is clear and good, and quite likely to work exactly as you originally envisioned it.

& & & & &

Having said all that, only if your vertical idea doesn't pan out, you might want to consider the illustration below:



This is a typical diagram of a DX loop field as it is often implemented commercially. I always thought that this method was used because it resulted in the minimum disturbance to a suburban landscape, which is a very common reason that many people do not want to do a GSHP installation, even knowing the much greater efficiency (my girlfriend being one of them).

But thinking about a potential lubrication issue, and remembering this diagram, I see that a horizontal borehole would give good exposure to the soil, and reduce the vertical vertical lift.

It would also be much harder to dig unless you had specialized diagonal digging equipment, as seen below:




& & & & &

Just in case you didn't see it already, I just came across a Wikipedia entry on DX heat pumps HERE that indicates that vertical DX boreholes have been drilled to depths as great as 100 ft. so do not be discouraged, do not be confused.

Push on!!

Best,

-AC
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Old 04-30-15, 08:26 AM   #4
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Thanks Doax!

AC,
Yeah you just pointed out my biggest concern at the very beginning. The show WILL go on.
Oh the ground here is AMAZING! Plus in about 40-50 feet from a large 2 acre pond. So hitting water will ALWAYS happen. I already have 500 feet for HDPE 3/4 poly pipe in the pond for a geothermal loop idea I was already working on to heat my greenhouse (aquaponics) in the winter.
I have about 10 hours of reading ahead of me. I did find some good sites though.
http://welldrillingschool.com/course...geothermal.pdf "copper has sq.ft-hr-F per inch of wall thickness, whereas that of HDPE pipe is only 2.7 Btu/sq.ft-hr-F per inch"
And another forum mentioned using a oil separator, i guess like this one 1 3 8" HVAC Oil Separator 559011 | eBay
Looks from what I can tell the line coming from the HX coil is larger on the way down and smaller on the way up. So I'm thinking 3/8 down, 5/16 up. I will try one 30 foot bore hole and if it doesn't work I'll just drill another hole.
Are there any people with experience with DX installs on this site?
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Old 04-30-15, 08:47 AM   #5
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Quote:
Originally Posted by MEMPHIS91 View Post
...Are there any people with experience with DX installs on this site?
I think that you are the first to do so here, so this is really an interesting project.

I just did some searching on the web, and on THIS page I found an interesting article, which had this picture:


The tubing sizes are different going up and down, and are used for a bigger compressor.

-AC
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Old 04-30-15, 08:55 AM   #6
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AC,
Yes I was just on that page myself. I love diagrams. Those bore holes are at 120 feet. Boy that is deep.
Random thought, if acid is the problem why can I not dump some powdered line into the bore hole as im filling it with sand? Maybe even some sea shells that will release lime over a long period of time?
DX - Direct Exchange Equipment Options This site claims it 25% better than water loops.
NO ONE does DX around my area even though we have awesome ground for it, strange.
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Old 04-30-15, 09:28 AM   #7
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Quote:
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AC,
Yes I was just on that page myself. I love diagrams. Those bore holes are at 120 feet. Boy that is deep.
Random thought, if acid is the problem why can I not dump some powdered line into the bore hole as im filling it with sand? Maybe even some sea shells that will release lime over a long period of time?
DX - Direct Exchange Equipment Options This site claims it 25% better than water loops.
NO ONE does DX around my area even though we have awesome ground for it, strange.
Really great ideas about dealing with PH.

I was also thinking about where your expansion device (cap tube) should go...

Maybe at the top of the hole, before the entire trip... maybe at the bottom of the hole, before the trip back to the top?

If you went for the bottom, the cap tube is pretty fragile, but once you were certain that there were no leaks, you could cast the bottom assembly in plastic or tar... concrete might be too corrosive.

-AC
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Old 12-09-16, 10:55 PM   #8
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Quote:
Originally Posted by MEMPHIS91 View Post
Thanks Doax!

AC,
Yeah you just pointed out my biggest concern at the very beginning. The show WILL go on.
Oh the ground here is AMAZING! Plus in about 40-50 feet from a large 2 acre pond. So hitting water will ALWAYS happen. I already have 500 feet for HDPE 3/4 poly pipe in the pond for a geothermal loop idea I was already working on to heat my greenhouse (aquaponics) in the winter.
I have about 10 hours of reading ahead of me. I did find some good sites though.
http://welldrillingschool.com/course...geothermal.pdf "copper has sq.ft-hr-F per inch of wall thickness, whereas that of HDPE pipe is only 2.7 Btu/sq.ft-hr-F per inch"
And another forum mentioned using a oil separator, i guess like this one 1 3 8" HVAC Oil Separator 559011 | eBay
Looks from what I can tell the line coming from the HX coil is larger on the way down and smaller on the way up. So I'm thinking 3/8 down, 5/16 up. I will try one 30 foot bore hole and if it doesn't work I'll just drill another hole.
Are there any people with experience with DX installs on this site?
AQUAPONICS , wow I love that, can you show us some photos or videos with your aquaponics setup ,I researched for years about earthships and aquaponics and dream to build my own farm totally off grid and self sufficient. I m planning on using sun as main energy source but not using commercial solar panels instead more advanced stuff combined with vertical wind generator, anyway this is a very long topic on its own.

About heating greenhouses in the winter you might better consider building buried greenhouses were just the roof is exposed to the elements and you took advantage of the constant earth temperature.... this model was arrived here in Romania from China in small scale and works wonderfully for growing tomatoes at -20 C .... combined with a aquaponics system were you also heat the water with a solar heat exchanger if you want to raise tilapia and supplement the water heating with a heat pump

In the race for efficiency we should first use the passive sources that cost just at the beginning when you do the design and construction of the greenhouse (example the buried greenhouses), after that use some extra solar power (adding solar water heater to add more heat exactly were we need it the most were are the fishes) and even thou we love them so much, we could use the heat pumps just for extreme needs so at the end our tomatoes don t have included in them some KW/h of electricity from the local coal powered electric plant
I mean it might fell strange in the plate for some .... joking
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Old 05-02-15, 10:26 PM   #9
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For the tubing, check Xringer's thread on the airtap A7 HPWH he installed. He successfully integrated a solar/ashp/oil furnace powered water heating rig into his house for hot water no matter what. Last I heard, his solar was doing most all of the water heating, with the Airtap kicking in during high demand. Since the tank was rigged in, he has burned very little fuel oil at all. Way down from thousands of dollars a year.

http://ecorenovator.org/forum/geothe...er-heater.html

Randen also turned a 5000 btu window aircon unit into an air-source water heat pump, with much custom work done throughout. He is just a mechanical master genius. Everything he does comes out looking awesome, even the stuff that doesn't work! I hate to see a good-looking piece of machinery destroy itself, but it looks ALMOST as good dead... kind of like taxidermy.

http://ecorenovator.org/forum/geothe...heat-pump.html

If you look at a larger split-unit install manual, the manufacturers have pictures and guidelines for where and when to put the oil traps in the lines. They work just like a p-trap in a drain. When the flow stops, the extra oil gets stuck in the trap instead of finding the bottom of the plumbing. When flow starts, the oil is carried back to the compressor much quicker.

Rather than jog the line laterally for the trap, you can loop it once for the same effect.

With natural refrigerants (propane, propylene, butane, etc.), the oil is much more soluble and miscible in the refrigerant, so oil flows much easier and better through the system than with "modern"(r134a, r410a, r407c, etc.) refrigerants. As a result, it is usually ok just to size the tubing small enough to get decent velocity, so the foamy froth can make it a decent way back up the tube before the gas and oil separate completely.
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Old 05-04-15, 07:22 PM   #10
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The lines in your sketch are backwards. As a general rule, the liquid line should be smaller than the suction line. In your sketch, the borehole loop is part of the suction line. It would be better to use 5/16" from the cap tube to the compressor muffler and 1/4" everywhere else, if you even need it. The only tubing I have used over 1/4" in my beasts has been used to adapt up in size to fit compressors and txv fittings. The situation changes rapidly with long distances and larger capacity systems.
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