Didn't expect the heat pump to eat that much power on defrost

Started by btu_frank · · 1 reply
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#1
Been running the AquaCal alongside the gas heater this cold snap, mostly to save on gas since it wasn't crazy cold. Watched the amp draw on defrost cycles kick in more than I figured, has to reverse and melt frost off the coil when ambient dips near freezing and humidity's up off the ocean here. Adds up over a few hours if the compressor's cycling through it every twenty minutes or so. Not a knock on the unit, mine's been fine for four seasons, just didn't do the math on defrost load when I sized the electric side of this dual fuel setup. Below about 45 with damp air the gas heater just makes more sense, in the trade we'd call that the crossover point. FN

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#2
No heat pump here so I can't argue the numbers, but that crossover point thing makes sense, same reason my sand filter isn't worth backwashing below a certain pressure diff, at some point the fix costs more than the problem. Good info for anyone about to size a dual fuel setup though.