A combi or combination boiler controls your whole central heating system directly from one, compact unit.
Combi boilers are also an energy efficient option as all modern combi boilers are condensing so they use much more of the energy they produce and less is wasted. Condensing boilers make more use of the energy supplied by extracting heat from flue gasses that would have otherwise been lost by a non-condensing boiler. Combi boilers are usually quicker and cheaper to install, since there’s no requirement for a water cylinder meaning less pipe work is needed.
How do combi boilers work?
Combi boilers work by having one compact system heating both your hot water and radiators so there is no need to have an additional external cold-water tank or hot water cylinder. Combi boilers provide instant hot water, by constantly being on standby when there is no water demand. As soon as you turn the hot water tap, the boiler will kick in and the water will become hot very quickly. When the request for hot water is trigged by someone turning on the hot tap, this signals the boiler to start heating water inside of the system. The heat exchanger transfers the majority of the heat from the burnt gas inside the boiler to the cold water, and then delivers it to the taps as required.
Inside combi boilers, the control valves operate in different directions to either allow water to flow through the central heating system or divert it to the appropriate hot water tap as required — but never both at the same time. You can pre-set your desired temperature and the boiler will work with the room thermostat to ensure your home is heated as you like.