My experience with Mini-Split thermostats

Figured I would share here, in case someone else is looking for these. Thanks in advance for letting me nerd out on this one, as I did put some thought into it, and hopefully it helps someone.

I built a new house last year, with a Mitsubishi mini split heat pump system - four air handlers, with one unit. These are controlled with the standard remote controls. My previous home had a Fujitsu, controlled the same way, but Fujitsu includes Wi-Fi access with their own app for control. Mitsubishi offers something similar but around $200 per unit, and no home kit. Given the experience with many of these companies, their apps leave a LOT to be desired as well.

I am not particularly happy with the Mitsubishi remotes - they are kind of hard to read. I do not experience any significant temperature variation that some report.

Three big companies out there produce replacement thermostats for the remote, that essentially function as IR blasters that work the mini-split unit, and also give access to the controls remotely.

I started with the Cielo Breeze - What attracted me was the display of the temperature and the ability to set the temperature from the remote - No home kit compatibility natively. I figured that would not be a problem, enter home bridge. No, their API is NOT open, so you can’t do it. After a little trouble getting it connected, it has been working fine. I can set schedules, and all is OK. But no HomeKit.

I purchased the Sensibo Air - This has native HomeKit support (doesn’t support the fan only function with native HomeKit, supposedly the Homebridge plugin does, Tried it, been having trouble with it, and haven’t worked on it that much). This controls great using the app, as well as with the HomeKit integration. The app has a nice timer that lets you set the unit to turn off after a certain amount of time (can be handy with cooling, as that often is good to shut off, and at this time of year, we can use both heat and cool in one day.)

But one issue is a real turn off - there is NO way to set the temperature from the wall unit. None. No indicator. First, thinking of guests in the home, how will they work it? Yes, they can use Siri, but that isn’t always a good thing. And also, no matter how I can use my phone to do these things, there are times that I would rather walk over to the unit and turn it off. Period.

I ordered the Mysa unit to try. Native HomeKit compatibility. And, you can set the temperature from the unit itself. You can also set the mode (cool, dry, heat or off) from a button on the side of the unit. It uses a color coded LED for the modes to show which mode it is in, which may require some training and explanation for house guests, but a better option than having no controls.

They Mysa does not appear to have the turn it off after so many hours function, but this can be done with a dummy switch in HomeKit (turn on dummy switch - set automation to turn it off in 3 hours - automation when switch turns off, turn off HVAC.) so that should work. I can also run that with a bedtime scene.

Mysa also makes a HomeKit thermostat for floor heating, which I have in two bathrooms. The thermostats that came with these units are Wi-Fi with their own app, but in time, I may upgrade these thermostats to the Mysa to have HomeKit, plus one app to control them as well.

One of the features that everyone seems to rave about with these, is the ability to use “comfy” features where the unit turns on the AC when the temperature gets to a certain point, and off when it gets to another. While this sounds good in theory, you really are defeating much of the energy efficiency of a High efficiency variable compressor heat pump. These are designed to turn down when the temperature hits a certain point, and use much less energy, and last longer than the constant cycling. Plus, with winter temperatures sometimes getting very cold up here (below zero), you really don’t want to turn the heat off with geofencing in the winter (and there is real argument for if you should do that if you want to save energy anyway, instead opting for a few degree drop. With HomeKit, you can use Apple’s geofencing instead of the in-app geofencing if you want that.

Some controllers claim that they will bump the temperature up if the thermostat measured temperature is lower than what it is set for. Example - You have set the temp for 70 (in heat mode) and the sensor in your unit is reading 71 degrees, so the heat turns down. But the remote thermostat is reading 68 degrees, and sensing the heat is not increasing - they supposedly will turn the unit to, say, 74 degrees to get more heat, and then turn it back when it hits the set temperature for the wall thermostat of 70. This is a much smarter feature than the on and off feature. I haven’t observed it with either of the units I have. How do I know? I don’t get a ton of variance from what the unit reads and the wall thermostats (in my old house, there could be quite a shift - more due to insulation and design), so this feature would be largely un-necessary. But my units will beep whenever remote commands are sent, and I haven’t heard any beeping. So I don’t think that they are THAT smart.

Mysa claims their units do this, so should be nice to see.

My biggest use case for any of these, was the ability to control them remotely with my phone (a feature we liked in our old house), and to replace the hard to read stock remotes. If Sensibo allowed the settings to be changed from the wall, it would be a winner.

So these will all be within the 30 day return window, so I can make my decision.