Geothermal heat pump water heater

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Discussion Overview

The discussion revolves around the design and implementation of a geothermal heat pump water heater system, specifically focusing on integrating a compressor with a water heater and utilizing buried copper tubing in a concrete floor for heat exchange. Participants explore practical considerations, potential benefits, and challenges associated with this setup.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant describes their plan to replace the electric element in a water heater with a 9500 BTU R-22 compressor and seeks advice on the amount of tubing needed for effective heat transfer and the circuiting of the tubing.
  • Another participant suggests considering the integration of an evaporator coil in the HVAC system for dual functionality, raising questions about the placement of the evaporator coils and potential comfort issues related to cold floors.
  • A third participant expresses concern about the coldness of the floor and the possibility of sweating in summer, proposing the use of antifreeze-filled PVC pipes to protect the copper tubing within the concrete.
  • One participant challenges the feasibility of the proposed system, noting that typical geothermal systems operate with deeper wells and that the temperature at shallow depths may not provide stable heating or cooling.

Areas of Agreement / Disagreement

Participants express varying opinions on the effectiveness and practicality of the proposed geothermal heat pump system. There is no consensus on the optimal design or the adequacy of the proposed tubing setup, and concerns about temperature stability and comfort remain unresolved.

Contextual Notes

Participants highlight limitations related to the depth of tubing placement and the potential for temperature fluctuations. The discussion does not resolve these issues, leaving assumptions about thermal dynamics and system efficiency open to interpretation.

GaryS
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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"!
 
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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?
 
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
 
there's 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.
 

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