The room thermostat surface mount 24 h mode 5 up to 35 c homexpert by honeywell thr840d is a comfortable room thermostat suitable for centralized control of a heating or cooling system including electric heaters actuator controls thermal actuators and combi boilerthe universal wall thermostat for convenient and economical heating operation it can control both the central heating boiler or electric heating up to 18 kw and floor distributor with thermostatic radiator valves or connection