Turning on your gas boiler is the first step in start its functioning process. Once you have done this, a valve opens and allows gas to enter a sealed combustion chamber, this passes into a primary heat exchanger which is attached with a cold-water pipe. The hot gas is then transfers its energy into the water, heating it and circulating around the pipes and radiators within your home. This movement is worked powered by a pump.
The water that flow through pipes, gradually cools and is passed flow through a secondary exchanger, where it is reheated again by the gases and it can be condensate, which is then force drained from the boiler.
Because as the gases have already transferred their heat energy into the water, they have served their purpose and are no longer of use, then they are discarded out of the system via the flue. and then the remaining water that has already been heated and circulated around your radiator systems then flows back through the primary exchanger. Where the process recommences so that the radiators can continue to heat your unit. This cycle carries on until the thermostat detects that your home has reached the predefined temperature, or alternatively until the boiler is switched off manually.