Wemos OpenTherm shield

OpenTherm shield for wemos d1 mini based on https://github.com/ihormelnyk/opentherm_library

Homeassistant configuration

Program the device with the shield disconnected

1. In the Homeassistant / ESPHome tab add a new device
2. Name it as you wish & press next button
3. Press skip this step, select the device esp8266 / esp32
4. On the congratulations tab press skip as well
5. Edit the newly created device

6. Insert the following code below the generated code

   
   external_components:
     - source: github://olegtarasov/esphome-opentherm
   
   opentherm:
     in_pin: 4
     out_pin: 5
   
   switch:
     - platform: opentherm
       ch_enable:
         id: ot_ch_enable
         name: "Central Heating enabled"
         restore_mode: RESTORE_DEFAULT_OFF
       dhw_enable:
         id: ot_dhw_enable
         name: "Hot Water enabled"
         restore_mode: RESTORE_DEFAULT_OFF
   
   number:
     - platform: opentherm
       t_set:
         id: ot_setpoint
         name: "Heating setpoint"
         min_value: 22
         max_value: 40
         restore_value: true
         initial_value: 25
   
       t_dhw_set:
         id: dhw_setpoint
         name: "Hot Water target temperature"
         min_value: 25
         max_value: 50
         restore_value: true
         initial_value: 42
   
   sensor:
     - platform: opentherm
       rel_mod_level:
         id: ot_rel_mod_level
         name: "Boiler Relative modulation level"
       t_boiler:
         id: boilotron_temperature_ch
         name: "Boiler Feed Temperature"
   
   binary_sensor:
     - platform: opentherm
       ch_active:
         id: ot_ch_active
         name: "Boiler Central Heating active"
       dhw_active:
         id: ot_dhw_active
         name: "Boiler Hot Water active"
       flame_on:
         id: ot_boiler_flame_on
         name: "Boiler Flame on"
   
   # Based on https://olegtarasov.me/opentherm-thermostat-esphome/

7. Press save and then install button
8. Press and hold the reset button and then plug in the wemos device esp8266 / esp32 via a USB cable
9. Press connect and select COM port of the connected device and press Connect
10. Assemble the shield, see #Assembly

Additional configuration options might be available, but it depends on the heating device For reference try https://github.com/arthurrump/esphome-opentherm/blob/main/examples/thermostat-pid-complete.yaml

Assembly

The shield should be assembled as a hat for ESP8266 / ESP wemos kits. The cable connector should align with USB socket. Please see for specific pinout.

Example shows wemos d1 v4 with USB C connector, for MicroUSB version please consult pinout

Boiler connection

OpenTherm is a 2 wire bus, you should connect the pins on the shield to corresponding pins in the boiler.

Disclaimer

By using this electronics project, you acknowledge and accept that there are inherent risks associated with working with electronic components, circuits, and devices. You agree to assume all such risks and agree to use appropriate safety precautions.

The creators and contributors to this project have made efforts to ensure the accuracy and reliability of the information provided. However, they cannot guarantee that the information is error-free or that the project will work as intended in every circumstance.

The shield project is provided on an "as-is" basis. The creators and contributors to this project make no representations or warranties, either express or implied, including but not limited to, any warranties of merchantability or fitness for a particular purpose.

In no event shall the creators, contributors, or sponsors of this project be liable for any direct, indirect, incidental, special, exemplary, or consequential damages (including, but not limited to, procurement of substitute goods or services; loss of use, data, or profits; or business interruption) arising in any way out of the use of the project.