Saw this strange identified device crop up the other day. I thought it kind of odd that it would repeat so regularly, running for 30min every hour, though not quite…some hours are skipped and there’s some skew where the start time changes by a few minutes over days.
This was all happening while I was on vacation, and nothing I could think of would be waking up so regularly (but imperfectly). My computers were off and draw much more power besides. The clock-based repeats didn’t feel like thermostat-derived, and the imperfect time keeping didn’t feel like a clock-based scheduler.
Then I turned my mini split heat pumps on remotely, and the 27W repeater stopped. After a day I turned them off again, and after a while the 28W repeater started up again. That seemed to indicate the heat pumps were the source, which I thought odd since the heat pumps draw on the order of 1kW normally.
But that gave me a hint; the mini splits must be using some bit of standby power, so why on a schedule? I did a search for “Mitsubishi mini splits standby power” and found a link from the DOE discussing exactly that, indicating some units draw 27W in standby mode…others up to 180W!
So Mitsubishi heat pumps use a bit of power to keep the condenser from freezing when not in use. 28W seems like not much power, but that must be it. The clock skew is probably from a timed process running on durations rather than clock time.
Now if only Sense would find the other heat pump modes I could get some real data to see how it stacks up to oil heat when it’s freezing outside.