I’ve create a ESPHome component for interacting with the Zehnder ComfoAir E300/E400 devices. The project is likely to work with the ComfoAir PRO 200/250/300 series as well, but this remains untested.
It works by connecting to an undocumented RS485 serial interface using Modbus RTU.
Current capabilities:
Fan speed control.
Read fan states (RPM, duty cycle, flow rate)
Read temperature & humidify (extract, supply, exhaust, intake).