A pump circulates water through four radiators. The temperature of the radiators is set using thermostatic valves.
A digital controller keeps the room temperature constant by driving the four-way mixing valve. This valve sets the temperature of the boiler return flow and the feed flow. Cold water connections enable the heat generated to be dissipated. The differential pressure across the pipe system is limited using a relief valve. Temperatures can be read on bimetallic thermometers.