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Old 04-28-15, 11:29 PM   #1
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Location: Oxford, MS USA
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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.
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. Iím 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 donít use with have a 120 volt 1,800 watt element for when the heat pump canít keep up (I hope that never happens).
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 shouldnít 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. Iíll 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 yaílls thoughts on how deep the bore hole is? What diameter DX coil, Iím thinking ľ 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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