Heat pump fan speed settings
Climate Zone 6, Southern Ontario. My apologies if the below is too verbose. Heat pumps excite me for reasons I have yet to quantify, which was great for thermodynamics class in Uni, but poor for brevity.
My nearly finished Net Zero house will have a Mitsubishi P-Series heat pump, with a multi-position air handler that feeds three different zones. The zoning should make the building more comfortable because the main floor has a lot of south facing glass that can easily lead to floor by floor temperature differences with a single zone solution.
They used an AirZone zoning system that knows how to control the Mitsubishi unit by setting a fan speed (1 – 5), and a target temperature for the air handler’s return air temperature. This controls the speed of the compressor.
The AirZone system is smart enough to increase the fan speed as more zones call for heat and has three self explanatory Modes: Quiet, Normal, and Powerful.
If my goal is optimal energy efficiency, do I want the air handler pushing as much air as possible at all times? This in theory lowers dT across the coil, provides better heat transfer from the refrigerant, and lowers pressures on the compressor, but you do spend some more energy on pushing air around. Do I perhaps more slower air speeds in the summer for dehumidifcation purposes? Or perhaps will this not make much of a difference, no matter what I do?
I can see that for A/C on minisplits I definitely want low fan speeds, but heating looks like a mixed bag. Anyone have any better data?
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