Does anyone have experience with waste heat recovery units (HRUs)? Basically heat exchanges with a water pump that take heat from the compressor outlet and transfer it to the hot water tank.
My new home has a heat-pump (w/reversing valve) cooling/heating HVAC unit and a traditional electric hot water tank. Was thinking of getting one of these HRUs to save money. Google directed me to "doucetteindustries".
Unfortunately, the control system appears very crude. I'm concerned that it will only be usable in the summer so the ROI will be much longer than advertised.
In the summer, I assume it operates as expected with abundant waste heat and straight forward controls. The water pump simply activates when the compressor turns on. A 140°F switch turns the water pump off to prevent scalding.
But I'm confused how it's controlled the rest of the year.
If it's very cold outside (<20F), does the heatpump compressor outlet temp get hot enough (>120F) or does it just slowly get the entire tank warm before activating the heating elements which finish the job? How does it know how long to wait before turning on the heating elements?
If it's just a little chilly outside, the house might not need heat. Does it activate the heatpump compressor based on water temp or does it just let the hot-water tank stay cold until the house demands heat? How long does it wait before giving up on all of that and just turning on the hotwater heating elements?
I would assume that there's a seasonal day where the house doesn't need heat but running the heat pump for hot water is still more efficient than using the heating elements. Are the fans disabled when the house doesn't need heat but the hot water tank does?
Thank you for any experience you might have.
My new home has a heat-pump (w/reversing valve) cooling/heating HVAC unit and a traditional electric hot water tank. Was thinking of getting one of these HRUs to save money. Google directed me to "doucetteindustries".
Unfortunately, the control system appears very crude. I'm concerned that it will only be usable in the summer so the ROI will be much longer than advertised.
In the summer, I assume it operates as expected with abundant waste heat and straight forward controls. The water pump simply activates when the compressor turns on. A 140°F switch turns the water pump off to prevent scalding.
But I'm confused how it's controlled the rest of the year.
If it's very cold outside (<20F), does the heatpump compressor outlet temp get hot enough (>120F) or does it just slowly get the entire tank warm before activating the heating elements which finish the job? How does it know how long to wait before turning on the heating elements?
If it's just a little chilly outside, the house might not need heat. Does it activate the heatpump compressor based on water temp or does it just let the hot-water tank stay cold until the house demands heat? How long does it wait before giving up on all of that and just turning on the hotwater heating elements?
I would assume that there's a seasonal day where the house doesn't need heat but running the heat pump for hot water is still more efficient than using the heating elements. Are the fans disabled when the house doesn't need heat but the hot water tank does?
Thank you for any experience you might have.
source https://hvac-talk.com/vbb/threads/2235466-Opinions-on-compressor-waste-heat-recovery-to-hot-water-units?goto=newpost
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