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What is a condensing boiler?

Image of Martyn Bridges

Q: I need to replace my old boiler, I’ve heard people talking about ‘condensing’ boilers but what’s the difference and why should I choose a condensing model?

A: Martyn Bridges, director of technical support at Worcester, Bosch Group says;

In line with the Government’s commitment to reduce the UK’s energy consumption and emissions of harmful, climate-changing greenhouse gases, such as carbon dioxide, a new Building Legislation has been put into place which means condensing boilers are the only models permitted for all new domestic installations and boiler replacements, where gas and oil is used.

A condensing boiler is a high efficiency modern boiler that incorporates either a larger heat exchanger or even a second heat exchanger. It produces lower flue gas temperatures, lower flue gas emissions, and reduced fuel consumption. By recovering and using heat that would otherwise be lost up the flue all of Worcester’s condensing boilers are over 90% efficient, which means they use over 90% of the produced fuel to heat the home. Whereas a standard efficiency boiler, those over 10 years old, are usually only around 60 - 70% efficient meaning that every pound you put in up to 30 pence is wasted - making condensing boilers extremely economical. You could even repay the initial installation costs in fuel savings.

According to the Energy Saving Trust, if everyone in the UK with gas central heating installed a high efficiency condensing boiler, we would save enough energy to heat 3.3 million homes for a whole year and save around 12.5 million tonnes of CO2 emissions.

Date published: 12th August, 2008

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