Condensing Boilers
An increased efficiency boiler, the 'typical' non-condensing boiler is around 67-77% efficient, whereas with condensing boilers a figure of over 87% can be expected. This increased efficiency is due to the extraction of heat from the otherwise wasted flue gases.
Most boilers have a single combustion chamber enclosed by the waterways of the heat exchanger through which the hot flue gases can pass and be eventually expelled from the boiler into the flue at a temperature as high as 250 deg C. Condensing boilers, on the other hand, are designed to first allow the heat to rise upwards through a primary heat exchager; then at the top of the heater the flue gases are divided and turned 180 deg to pass back down over two secondary heat exchangers. These reduce the flue gas temperature to about 55 deg C, this reduction of temperature causes the water vapour, formed during the combustion of the fuel , to be condensed out thus releasing the latent heat which would otherwise escape with the flue gases. As the flue gas temperature is reduced the droplets of water formed fall by gravity to collect at the base of the flue manifold. From here a condensate drain allows the liquid to run off and the remaining gases are expelled to the outside environment through a fan assisted balanced flue The condensation produced within the appliance should be drained as necessary into the waste discharge pipework or externally into a purpose made soakaway.
| 
