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Improve efficiency: Avoid defrosts

My heat pump tends to need to defrost itself when it’s cold, as most heat pumps do.

This is pretty bad for efficiency because we consume power to pump water around to absorb heat from the house and then get going again.

My control algorithm that holds the flow temperature down tends to ease the demand on the heat pump and so it doesn’t defrost as often. Anecdotally it’s about half as often, but I don’t have enough data yet to confirm that.

Bear in mind that defrost exists for a reason though. When the heat pump was running on it’s own scheme we can see it was less efficient at 05:30 and that defrosted itself at 06:10 and then was more efficient afterwards.

In fact I’m starting to wonder if my algorithm should step in and do something when it sees efficiency start to drop. If ambient is above zero then shutting down the heat pump would give it a change to warm up on it’s own. However, the end-users might get cold so it’ll take a bit of pondering to decide what the right strategy is. I don’t think I can’t force a defrost.