Surprised how much three cloudy mornings slowed my heat pump recovery

Started by btu_frank · · 1 reply
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#1
Been running the AquaCal for the shoulder season heat and never paid much mind to cloud cover till this week. Three overcast mornings in a row, ambient barely hit 60 by 10am instead of the usual mid 70s, and recovery from an overnight dip took almost twice as long. Makes sense once you think about it, heat pump output drops with ambient same as a heat pump on a house does, it's not pulling BTUs out of thin air, literally. At 12k gallons a one degree rise is right around 8,000-9,000 btus I need, and on a cold cloudy day the unit just can't push that fast. Didn't expect clouds alone to matter that much without a real temp drop. Anyone else notice their heat pump sulking on gray days even when it's not actually cold out. FN

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#2
Frank, you got it right about the ambient drop hurting output, but nobody's mentioned your flow rate through the unit while this is going on. If you've got a check valve or gate valve partially throttled down on that return line feeding the heater, you're already losing GPM before the heat pump even has to fight bad ambient air, and that compounds the slow recovery worse than the clouds alone would. Worth popping the lid and checking your flow switch is reading good flow, not just assuming the cloudy days are the whole story.