A hydronic heating system consists of five components:
The boiler heats water to a thermostatically controlled temperature. Boilers can use natural gas, LPG, off-peak electricity, or can be wood fired.
The piping, usually made of copper/plastic or multilayer and carries the heated water from the boiler to the radiators/ convectors, and back again for reheating.
A pump circulates the water through the piping.
Radiators or convectors transfer the heat into the room (several types of radiators and convectors are available).
Programmable wall thermostats ideally control the heat levels (or room temperature) to optimise comfort throughout the house.