akifbayram

Agreed. After the headache of getting them paired and dealing with repeated disconnections, I tried out a few bluetooth sensors and was pleasantly surprised. Specifically Govee H5074 and similar. No pairing troubles. They just work. Battery life is definitely over a year, possibly 2. A pack of three can be had for <$40.

Spot on. If you're using Home Assistant, you can push any temperature sensor available. Zigbee, Zwave, BLE, 433mhz rtl sdr, etc. At one point, I was using the proprietary temperature sensors that were paired with my ecobee thermostat (for my ancient natural gas fired hydronic boiler). For the BLE sensors, your HA server must have bluetooth capabilities. I use a bluetooth dongle attached to a short USB extension cord.

Thanks! I just took a look at AirTouch. It seems they have a nice ecosystem. Their Mitsubishi Electric offerings [1] use the CN105 port (like the OP's device).

I use the word zones on the Serin Multi Zone product page but it's interchangeable with indoor units. One indoor unit equals one zone.

You can override the room (intake) temperature per indoor unit/zone using a controller plugged into the CN105 port (like the OP wrote about). Depending on the controller, it can pair with a Bluetooth sensor or listen to any other type of sensor from Home Assistant. By going the ESP32 path, you can use simple, off the shelf $10 BLE sensors.

The Serin multi zone controller uses the centralized communication bus which isn't capable of overriding the indoor unit's room (intake) temperature. But if that is a must (which it is for ducted units), you can have both the multi-zone controller and a controller at every indoor unit without issue. So if you have an MHK2 thermostat on the wall and don't want to use their Kumo app anymore, the Serin multi zone controller will give you local control and you'll be able to retain the remote temperature sensor from the MHK2 thermostat.

[1] https://theairstore.com.au/product/airtouch-gateway-mitsubis...

From what I've read and experienced over the years, the indoor units of a Mitsubishi multi zone system never fully close their valves, so refrigerant flows through them even when they aren't actively heating or cooling. This becomes a problem when the indoor unit also runs the fan non-stop to get an accurate reading of the room temperature, since a thermostat with a remote temperature reading typically isn't available.

I got around this by disabling the fan from blowing when the indoor unit isn't actively calling for refrigerant. The refrigerant still flows through the indoor unit but since the fan isn't running, it isn't dumping conditioned air into the room. Every unit has a different way to disable the fan when it's not heating or cooling. My mini splits needed a jumper cut on the indoor control board but my air handler was configurable via a thermostat.

This raises the issue of getting a proper temperature reading of the room. Without the air flowing over the thermistor in the indoor unit, the reported indoor temperature becomes wildly inaccurate. To get around this, a thermostat with a temperature sensor is needed. Mitsubishi has a few off the shelf options. I went with the popular route of adding a Bluetooth sensor to my ESPHome builds and I sell a bundle including the controller and remote temperature sensor. More information here: https://serin-labs.com/controller/room-sensors.html

Awesome. I'm glad to hear that.

It's not possible to cross-flash a different firmware track over the air but since you're already using the Matter-compatible firmware, you can pair it directly with Home Assistant, fully local. It won't be as configurable as the ESPHome firmware, but it'll get you the controls you need.

I’ve been working on a similar setup using the M5Stack NanoC6 and AtomS3 Lite, and put together a parts list and wiring guide on my site: https://serin-labs.com/parts.html.

I also built a web flasher with firmware configured for those boards, so you can install directly from your browser without any fiddling or configuring. The ESPHome option uses the same echavet/MitsubishiCN105ESPHome project mentioned in the article. I also included a YAML generator for that project so you can more simply customize the config. There are also separate firmware options for HomeKit and Matter. https://serin-labs.com/flash.html https://serin-labs.com/esphome/generate-yaml.html

I run Serin Labs and sell assembled kits and the cable separately.

For anyone with City Multi, P series, or M series systems with a branch box, you may also be interested in a multi zone controller I’m developing: https://serin-labs.com/multi-zone-controller.html. It connects to the system’s communication bus, allowing one device to control all zones without needing a CN105 adapter at each indoor unit. It also exposes operating data such as refrigerant pressures, temperatures, power, compressor frequency, and fault codes, with everything running locally. Software is still in development.