OpenTherm Gateway

Finished device

High resolution photo

Board

Box for installation on DIN rail - D2MG, 2 DIN modules.
The 220V > 5V power supply is already on the board, so additional power supplies are not needed.
After manufacturing, the boards need to be divided into 2 parts - upper and lower.

Some components can be replaced with similar ones (for example use a fuse and led with legs). Some SMD components (for example optocouplers) can be replaced with similar SOT components.

Intro

Firmware

Once upon a time I started developing a simple Opentherm controller on esp8266 for personal use, which resulted in a full-fledged controller product for Home Assistant. I think it’s time to publish it.
The software is free, it develops as I have free time.

• DHW temperature control
• Heating temperature control
• Smart heating temperature control modes:
  • PID
  • Equithermic curves - adjusts the temperature based on indoor and outdoor temperatures
• Hysteresis setting (for accurate maintenance of room temperature)
• Ability to connect additional (external) sensors: Dallas (1-wire), NTC 10k, Bluetooth (BLE). Makes it possible to monitor indoor and outdoor temperatures, temperatures on pipes/heat exchangers/etc.
• Emergency mode. In any dangerous situation (loss of connection with Wifi, MQTT, sensors, etc) it will not let you and your home freeze.
• Ability of remote fault reset (not with all boilers)
• Diagnostics:
  • Displaying gateway status
  • Displaying the connection status to the boiler via OpenTherm
  • Displaying the fault status and fault code
  • Displaying the diagnostic status & diagnostic code
  • Display of the process of heating: works/does not work
  • Display of burner (flame) status: on/off
  • Display of burner modulation level in percent
  • Display of pressure in the heating system
  • Display of current temperature of the heat carrier
  • Display of return temperature of the heat carrier
  • Display of setpoint heat carrier temperature (useful when using PID or Equitherm)
  • Display of the process of DHW: working/not working
  • Display of current DHW temperature
  • And other information...
• Home Assistant integration via MQTT. The ability to create any automation for the boiler!

Links

• Project Repository
• Firmware releases
• Project documentation
• Web Flasher