Generally, we use on/off type thermostat to control the boiler, the sensor built into the thermostat detects the temperature in the room and judges the boiler switch according to the comparison with the setpoint.   Opentherm,It is a communication name that links HVAC (heating and cooling equipment) and room thermostats beyond the manufacturer's control system, it consists of communication protocols and port specifications, and represents a technical system that can achieve high functionality and future expansion possibilities using common simple installation methods. • Set and read tap water temperature • Turn tap water on and off • Read the outdoor temperature • Read failures • Weather related controls Opentherm make your thermostat as simple as plug-and-play!   Currently, E-top has joined the OT association,and have finish the development of OT thermostats base on the OT protocol, and OEM for several local boiler manufacturers, and of course, WIFI function was combined.   Make OT thermostats a part of your smart home!