Mitsubishi mini split behaving very differently with external thermostat vs. without
I am able to monitor my home’s electricity use and I always thought it was a little weird that my Mitsubishi FE18NA heat pump seemed to constantly be spiking up and down, considering that the whole idea of the inverter-driven compressor is that it can run smooth and steady… fast forward to yesterday when I received my MHK1 thermostat and hooked it up. Suddenly, the power usage was steady as a rock.
The real reason I bought the thermostat was because the temperature sensor internal to the heat pump seems to be very inaccurate and we constantly had to tweak the set point on the remote when the outdoor temperature changed. The thermostat also fixed that issue, as now the heat pump can sense the real temperature in the room. This makes me think that perhaps the hot air from the heat pump was pooling around it, causing it to think the room was warmer than it really was, throttling down, until the air dissipated and it realized that it needed to heat again.
Can it really be so flawed by default?
The room it’s in is a small dining room, about 8×10 or so, but one side of this room is totally open to the living room, and the air flow of the heat pump shoots straight down a hallway to the bedrooms. The house does all stay pretty evenly heated, at least with doors left open. Other than having to fiddle with the set point, we’ve never had a comfort problem. The thermostat is actually sitting on a table just a few feet from the heat pump. But maybe those few feet make the difference, particularly not being stuck up by the ceiling in perhaps a pool of warm air.
Two screenshots are attached of the “lumpy” and “not lumpy” power use charts. The small lumps in the “not lumpy” are from the fridge, I believe.
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