Thread: Micro Heat Pump
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Old 12-17-19, 12:24 PM   #1
Helper EcoRenovator
Join Date: Dec 2019
Location: Northern Utah
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Default Micro Heat Pump

New member here and new to heat pumps. I do have some refrigerant experience with a freeze dry I built years back and feel confident about building a heat pump.

I have a greenhouse where I move heated water through an inground grow bed. I have been heating the water with wood and occasionally a 1K watt heating element. It would be nice to just use a small heat pump instead.

With the 1K watt heater it is able to increase the water temp in the tank above what I need over time. I have a small compressor that I believe is 1/10 HP. I'm hoping to be able to get about 300-400 watt equivalent heat output. It will be a water to water setup. I have a ground water source that can go up to 2 gallons a minute at 55F. Pumping height is 15-18 feet under load, so pumping wattage is low. Water would be returned to a cold storage well 50 ft away.

The pump is salvaged from a water cooler and was R134a. I would use the pump and cap tube. I would initially charge it with R134a and eventually 75/25 nButane/Propane.

For heat exchangers, I was thinking some 1/4 copper tubing coiled up inside about 20" or so of 1" PVC pipe. The well water and circulation water for the grow beds would pass through the PVC and around the copper coils placed inside.

I could use a temperature controller based off of the exit water temp to keep it from freezing. It may not be necessary with such a low power compressor

My first question is can this pump run 24/7 and survive? I use to run my freeze dryer pump for about 3-5 days strait. It used propane and mineral oil. It would get warm to the touch but not hot.

compressor and possible refrigerant


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