How I Made a Non-Wi-Fi Mitsubishi AC Smart with an ESP32
I moved into a house with ducted ACs controlled by a wired wall thermostat without Wi-Fi. Instead of buying a $200 MelCloud adapter that sends data to Mitsubishi's servers, I used an ESP32 and the CN105 port to connect the AC to Home Assistant locally. The setup costs under €10, keeps full control of mode, fan speed, and temperature, and even adds energy monitoring and outdoor temperature sensors.
Mitsubishi cannot update the units remotely, so our configuration should remain valid (the units don’t have Wi-Fi connectivity).
- akifbayram
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.
- sippingabonedry
For anyone wondering why he would ever do this, it seems to be a type of hidden mini-split system used in euro-style shoebox flats, with a super-proprietary thermostat. Wi-Fi capability is an option at additional cost, but was not purchased.
In the USA, wired thermostats tend to use standardized 24V wiring schemes, or 208V/240V for mains voltage heaters (electric heat, common on the west coast, especially in shitty apartments, central hot water/steam heating with 24V controls is more common on the east coast).
- userbinator
My idea of HVAC is that it should be "set and forget", so "smart" is the polar opposite of what I want. The round Honeywell on the wall has been doing its job for the past few decades, and will likely last many more with only an occasional cleaning.
- nemosaltat
I did a similar thing, heavily aided by Claude, after seeing the protart modules posted here on HN last year. https://github.com/samstevenm/minisplit-local-public
Apologies for the Claudish, especially if anyone wades through the blog posts. I cringe when I reread them, but having some documentation on a working system is better than the ~none I was publishing before.
- llsf
Does anyone know if this could be used to "cap" the AC settings ? It could be useful in an airbnb place, where I want to limit the lowest (e.g. 18 degres Celsius) or hottest (e.g. 22 degres Celsius) the guest can set the AC.