OpenTherm is the name for a form of communication between the central heating module and room thermostats. The OpenTherm protocol sets the rules for how the module and thermostat should communicate and exchange information. If you install an OpenTherm boiler and an OpenTherm thermostat (such as the Honeywell Evohome and the R8810A1018 OpenTherm module), the thermostat will control the precise water temperature of your boiler and continuously maintain the temperature at the most efficient level. Compared to a classic On/Off heating system (even TPI-controlled systems), the water in the boiler is always set to a fixed preset temperature – which is not a very efficient way to control the boiler.

The common way to control a boiler is simple switching on and off at specified time intervals. OpenTherm allows for more precise control through the regulation of the gas valve. This enables the amount of heat provided by the boiler to meet more variable demands. By reducing the flow temperature at the boiler's output, OpenTherm modulation improves boiler efficiency by maintaining a low output temperature for longer intervals. This ensures that more heat is in the exchanger at condensing temperatures.

Imagine two cars standing side by side at traffic lights. When the light turns green, one car accelerates as fast as it can, while the other accelerates smoothly and sensitively. By the time they reach the next set of lights, the sensitive driver has caught up with the first driver but has used significantly less fuel, thus saving money. Unfortunately, the fast car did not benefit from the aggressive driving, as they are both in the same position again. In this case, the fast driver is represented by the classic On/Off control system, and the sensitive and efficient driver by the OpenTherm control.

• Increases heating system efficiency and reduces costs
• The ability to remotely control the boiler allows for future integration into remote heating system management
• Extra features
• No batteries
• Increases boiler lifespan
• Preparedness for future expansion
• Devices are easy to install (in most cases similar to existing On/Off devices)
• No configuration required
• Provides status information on the display
• Reduces energy bills

OpenTherm is not compatible with all boilers. We recommend always checking compatibility with your boiler's manufacturer. OpenTherm is not compatible with non-condensing boilers.

OpenTherm cannot work with standard voltages. Therefore, OpenTherm room thermostats do not have switches. Instead, they have a sensor that sends a signal to the boiler. This allows the boiler to be controlled more efficiently. Therefore, OpenTherm cannot work with standard boilers.