What is a Condensing Boiler?

Condensing boilers are now largely replacing earlier conventional designs in powering domestic central heating systems. Today there are over eight million homes with condensing boilers installed. The reason they are so popular is that they are far more effecient than ordinary boilers, and produce less carbon dioxide. Condensing boilers minimise heat loss through a series of design features. A condensing boiler uses the latent heat of water produced from burning gas to increase its efficiency. In other words condensing boilers reduce the amount of fuel being used by recycling the waste gasses as it were.

With a normal boiler, fuel like gas is burned which produces hot gases which get passed through a heat exchanger where most of the heat is transferred to water which rises the waters temperature.

One of these hot gasses is water vapour which comes from the burning of the hydrogen within the fuel. With non-condensing boilers this is normally wasted and ejected out of the flue. But with a condensing boiler, these gases are instead allowed to rise through the primary heat exchanger and then get go through a secondary heat exchanger which extracts more heat and has the effect of lowering the temperature of flue gas.

Modern condensing boilers usually are classed as 'A' rated, which means they are very efficient and economical. This means they use fuel at least 90% more economically to create the same about of heat.

A condensing boiler can be a system boiler, open vent boiler or even combi boiler and are suitable for any type of property. Many people think that a combi or combination means condensing, but this is not the case. You can get both condensing and non condensing combi boilers.

One of the most beneficial design features of a condensing boiler which allows them a lower work load is that they ‘modulate’. This simply means that rather than turn on and off to keep the right temperature, they simple slow down and tick over to keep the right temperature. This is a lot less work for the boiler.

This modulate feature combined with an optimising stat means it will monitor the temperature outside to see if the temperature is higher or lower than the day before. With this information it will work out how long it will take to warm up the house and make adjustments. It kind of learns at it goes along which is clever really.

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