Condensing Boilers – Gas and Oil Condensing Combi and Regular Boilers

Standard non-condensing boilers have a single combustion chamber and single heat exchanger through which exhaust gases pass, before being expelled through the flue, at a temperature of around 180°C.

A condensing boiler, on the other hand, employs one or more larger heat exchangers and cools the products of combustion to a temperature of around 55°C. This causes the water vapour contained in the exhaust gases to liquify, forming the “condensate” which collects at the base of the flue manifold and must be drained away into an existing waste water outlet or a purpose-built soakaway.

The design of condensing boilers makes them the most energy efficient domestic central heating boilers available. Indeed a boiler replacement of the condensing type could result in a reduction of 875kg in carbon dioxide (CO2) emissions per annum in a typical domestic dwelling in the United Kingdom. Boilers generally account for some 60% of domestic CO2 emissions and, therefore, the effect that condensing boilers can have on your overall “carbon footprint” should not be underestimated.

The reduction in temperature of exhaust gases means that they are not naturally expelled through the flues of condensing boilers, so a fan must be incorporated to drive them out. Similarly larger or more numerous heat exchangers are most costly to manufacture. These factors mean that condensing boilers are typically more expensive at the outset than their standard non-condensing counterparts. However, efficient design equally means that reductions in fuel costs, in the long term, more than compensate for the extra initial cost of condensing boilers.