HOW YOUR SYSTEM WORKS

If you have a Combi boiler it is a combined water heater from which is connected the heating system. Cold water in, instantly heated and comes out of the taps. A different circuit is fitted with a pump which pumps the hot water around the heating system.

With a “normal” system that has a hot water tank it works as follows; -

Water, which is heated by the boiler, is pumped around to the hot water cylinder and, as required around the radiators.

 I have underlined “as required” because this is the key to the system.

The water is controlled by an electronic valve that opens the waterway to the heating (or hot water cylinder) as required. The thermostats on the wall or the cylinder usually determine this.

Sometimes there is a valve for each of the pipes, one for the radiators and one for the hot water. On other systems there is a “T” junction in which there is a change over paddle, blocking off one side or the other as required.

When both the hot water and the heating is up to temperature then the pump and the boiler are both turned off. On some boilers the pump will run for a little longer after it has been turned off to make use of the heat which is still in the boiler.

On older systems the hot water is heated without the need of a pump and it operates via thermal convection, in the same way that a hot air balloon takes off. Hot water rises, as it cools it falls back to the boiler to be re-heated. This is why, sometimes, upstairs radiators get hot when they are not supposed to.