OpenTherm Gateway basic example
  • 8/7/2021
  • OpenTherm, Gateway

OpenTherm Gateway basic example

Today we will use an OpenTherm Wi-Fi gateway to monitor commands issued from OT enabled thermostat to the boiler. Also a simple example of override will be shown. You can use/extend this sample to temporary shutdown heating or set it to maximum bypassing wall unit. To store the history we will use a ThingSpeak cloud.

What is OpenTherm?

OpenTherm is communication protocol for Heating, Ventilation and Air Conditioning (HVAC) systems. Most often it is used in communication between a central heating boiler and a room thermostat. OpenTherm protocol is designed to control modulating heating appliances which allows to reach better efficiency and energy saving. It is simple but powerfull protocol with large set of commands which enable the manufacturer to build extra functions into their control devices. Check OpenTherm protocol specification v2.2 for more details.

OpenTherm Connection

OpenTherm Connection

ThingSpeak setup

If you would like to store a history (heating and DHW temperatures) - you can setup a ThingSpeak channel. This step is optional.

  • Navigate to ThingSpeak cloud
  • Create a free account
  • Create a channel
  • Go to the 'API keys' tab ant write down your Channel ID, Read/Write API Keys
ThingSpeak channel setup ThingSpeak channel setup

Web UI

A simple web-page on the device allows to view a history graph of heating temperatures as well as monitor all commands issued by wall unit to boiler in live mode. Also you have a simple switch to disable heating completely, bypassing wall unit commands. ESP32 Wi-Fi OpenTherm Thermostat Output

Code Sample

Please adjust your WiFi name, password ant ThingSpeak tokens in sketch. After uploading device's IP address can be found in the serial monitor. Sketch can be found on a github