OpenTherm Thermostat.

This repository is for a feedback on using our OpenTherm Thermostat.

Here you can request a new feature or report an issue(s) experienced while using our Thermostats.

Original Firmware

If you have experimented with your thermostat, i.e. set up the wrong settings or loaded a custom firmware - you can restore the original one using our web flasher. You would not need an activation code if you use it with an original ESP32 bought from us in the thermostat bundle.

Firmware Versions

v2.1 (2024.12.09)

bugfixes

• CH schedule not working
• CH schedule payload and enable now are independent properties
• BLE connected mode - fixed battery percentage
• BLE connected mode - timeout reduced to 4 minutes
• Heating Action - take into account CHActive OpenTherm flag

changes

• state json properties rename
  • CHWaterPressure -> CHPressure
  • ReturnWaterTemperature -> CHRetTemp
  • OutsideTemperature -> OutsideTemp
  • ExhaustTemperature -> ExhaustTemp
• availability topic changed: ~/tele/LWT -> ~/avail (single topic / message for all entities)
• availability properties for BLE / OT / MQTT / Internal sensors

improvements / new features

• HA autodiscovery - device unique id added
• HA autodiscovery - diagnostics sensors added
• CH Boiler Limit / Boiler Max properties (and sensors) added
• OpenTherm messages log to the mqtt (~/otlog)
• Initial REST API implementation (/api/set endpoint), accepts JSON payload. Currently allows setting the room temperature (roomTemp property)

list of autodiscoverable sensors

• Flame Level

• Flame State

• CH Temperature

• CH Setpoint

• CH State

• CH Boiler Temp Limit

• CH Boiler Max Temp

• CH Water Pressure

• CH Return Temperature

• DHW State

• DHW Temperature

• DHW Temperature2

• Outdoor Temperature

• Exhaust Temperature

• Diagnostic

• Fault

• Fault Code

• OpenTherm Connection State

• PI factor I

• MQTT Sensor Temperature

• MQTT Sensor Connection State

• MQTT Sensor State

• MQTT Sensor Last Seen

• Internal Sensor Temperature

• Internal Sensor Connection State

• Internal Sensor State

• WiFi RSSI

• BLE Battery

• BLE Battery Voltage

• BLE RSSI

• BLE Loss Rate

• BLE Last Seen

• BLE Temperature

• BLE Humidity

v2.2 (2025.01.25)

bugfixes

• JSON messages corruption (invalid properties values)
• Thermostat2/3 model name as Thermostat 1 within HA autodiscovery

improvements / new features

• Equithermic regulation with hysteresis (weather dependent)
• Constant temp regulation with hysteresis (manually controlled boiler temperature)
• Outside temperature sources: diyless (using weatherapi), weatherapi, openweathermap
• sensors offset config
• room setpoint min/max config
• configurable room setpoint step
• HA sensors for outside temperature sources

v2.2.1 (2025.08.11) Thermostat3 only

bugfixes

• External (DS18B20) sensor not working as a room temperature source

v2.2.2 (2025.10.24)

bugfixes

• External mqtt sensor not working (#21)
• Relative modulation level command change (12)

improvements / new features

• 'Publish a temperature value to the topic_name...' hint improved to show full topic name (for mqtt / external mqtt sensors) (#27)
• display MQTT state & control (T2 / T3) (#4)
• uptime HA sensor (#17)
• config backup / restore (#24)
• ambient light sensor HA entity (T3)
• system page wifi rssi / ot stats display

v2.2.3 (WIP)

bugfixes

• display off button turns the screen on (if screen off timeout set to zero) (#4)
• HA logs flood because of a missing property in JSON (#24)
• CHMin + Curve combination does not work (#29)
• ntp server typo fix (#23 comment)

improvements / new features

• websocket scheme selector based on location.protocol (thermostat behind reverse proxy with SSL)

v2.3 (WIP)

bugfixes

• T3: first touch event on sleeping screen changes settings

improvements / new features

• DHW schedule
• kiosk mode
• Configurable HA discovery prefix