Geothermal heat pump water heater

[GaryS]

I am about to pour a concrete floor in an addition to my basement (about 13' x 24'). This room is adjacent to my electric water heater. I have bought a 9500 btu R-22 compressor which I plan to use to replace the electric element in my 50 gallon water heater. The condenser is the water heater tank where I have shoved about 50 feet of 3/8" copper tubing inside. The evaporator will be 3/8" copper tubing buried in the concrete floor.

Has anyone tried this before? How much tubing is enough for proper heat transfer? How should I circuit the tubing? Once the concrete is poured, my design will be "set in stone"!

 

[Kevin999]

I can't specifically answer YOUR question, but I'm interested in the answers you might get.

But - I had a question for you... have you thought about putting an evaporator coil in your HVAC so that in the summer you can use the power for heating your water to also cool your house?? You might need a crossover valve to switch it in the winter so that it gets the heat from the concrete rather than the house air, but at least for half the year you're getting a benefit with a one-time cost.

Are you putting the evap coils IN the concrete or UNDER the concrete? Have you also thought about how cold the floor will get and if that might present a comfort issue?

 

[GaryS]

I am somewhat concerned about the floor being cold. It will probably sweat in the summer. If it's too much of a problem I could still go back to resistance heat for water heating.

My current thinking is to enclose the copper tubing inside an antifreeze filled pvc pipe and have it inside the concrete. The concrete might crack but the tubing will be safe. The concrete is a better thermal conductor than dirt.

We don't use the HVAC much. Only on a few hot days in the summer

 

[Topher925]

Theres really no way to answer your questions with the information you provided. The temperature at 12-20 feet into the ground is still going to have a significant temperature change just like the surface. Most geothermal cooling/heating systems operate with much deeper wells.