What is a condensing boiler?

imageA condensing boiler is a boiler that re-uses its waste heat that is produced when burning fuel (latent heat) to heat the cold water before it enters the boiler. Using this type of energy recycling, condensing boilers are far more efficient than their predecessors, the non-condensing boilers.

The reason for the name “condensing” is that as the water leaves the boiler through the flue is starts off as water vapour. The vapour then travels upwards along the flue until it cools and drips back down the flue into a condense trap. This waste water then leaves the boiler into a drain via a condense pipe.

Whereas older non-condensing boilers have a flue that projects at a downward angle, condensing boilers project slightly upwards so the water re-enters the boiler.

All new boilers are condensing to keep inline with SEDBUK (Seasonal Efficiency of Domestic Boilers in the UK) which states that a boiler should operate at 90% efficiency or above. Previously, non-condensing boilers were operating at around 70-80% efficiency.

If you would like to speak to Allserve Heating & Plumbing about upgrading to a condensing boiler or have a question, please call us on 01923 254173 or email us.




- Prevents boiler breakdown and impacts system efficiency. - Inhibits against corrosion, sludge and scale. - Ideal for new and existing systems. - Concentrated formulation. - Treats 100L / 10 x radiators. - Stops frequent venting of radiators. - Suitable for all water types and disposal to foul drain. - Compatible with all metals, inc. aluminium. - Independantly verified when used in conjunction with Fernox cleaner F3 up to 15% gas savings every time you heat your room - equivalent to 90kg CO2e per typical home per year.
List Price: £22.19 GBP
New From: £17.78 GBP In Stock
Used from: £16.00 GBP In Stock

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  • Sarah

    Is a condensing boiler the same as a combi?

    • http://www.ahpltd.com Allserve Heating & Plumbing

      Hi Sarah,
      All modern boilers are condensing boilers. ‘Condensing’ refers to the way in which they expel and re-use the waste energy through condensation. A combi, or combination boiler is a boiler that heats water as it passes through the boiler as and when it is needed (when the tap is turned on), thus doing away with the need for a hot water storage cylinder. Hope this helps.