MEMPHIS91
This water heater project is probably the best bang for buck on any DIY home efficiency radar. My parents are saving a pile of money with the one I had built for them.
Its located in their finished basement an it purrs away in a small utility room. The heat it actually sequesters from the room is not at all noticeable. During the summer months when the air is humid they may get a quart of water (condensate) in a bucket beside the HPWH. But it evaporates as quickly as it collects. In fact there is a drain located only 4 ft. from the HPWH. But didn't bother to run the drain hose to it.
With your DX you will not encounter this small problem.
I have found that the amount of heat required by the evaporator is quite small (5000 BTU A/C window shaker) The amount of work required to drill the ground bore hole would be my issue. (As I age I'm getting lazy) However I'm on the edge of my seat to see how little energy you will use to heat the water as you have no need for a fan to force air through a finned HX. In fact it will be very quiet as well. I believe My creation ultimately used approx. 450 watts total. I know you will do a lot better with your efficiency not having the fan and only powering the compressor. I'm going to guess less that 300 watts!!!
To charge the system I used propane and slowly added to get an appropriate condenser temp approx. 140 deg. F As adding more refrigerant just raised the amount of power required and no more heat was produced. I believe the suction side was only 18 psi.
As far as the copper in the ground it will out-live both of us and 1/4" is all you will need there too. However if you are concerned HVAC suppliers (or Ebay) have a polyethylene coated copper tube that would last for an eternity in the ground.
Its a very rewarding project. More should do the same!!!
Randen
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