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What is a condensing boiler?

This month we would like to explain the question that we are always asked:  what is a condensing boiler?  In short, a condensing boiler is a vessel that heats water using gas or oil.  They are efficient because the condense water vapour.

1) Are boilers only efficient when they are condensing?

No! Condensing boilers are made with larger heat exchangers which means that they are able to use the heat from the exhaust gases. They extract more heat from the fuel than a standard boiler can and not only when they are condensing. When a new condensing boiler is fitted, you can expect between 84% to 94% efficiency compared with an old non-condensing boiler (SEDBUK).

Annual Fuel Costs (SEDBUK)
Boiler TypeOld Gas BoilerNew Condensing Boiler
Gas unit price – 4.3p per KWh (April 2013)

2) Are condensing boilers much more expensive?

No! Although earlier condensing boilers were more expensive, over time, technology has improved and now the components required are relatively inexpensive. The cost of a condensing boiler is the same as a non-condensing boiler.

3) But are they are harder to maintain?

No! You just need to make sure that you get the Condense Line cleared when you have your annual service. That’s the only difference.

4) They can’t be fitted to an existing heating system?

Yes, they can! A good engineer will be able to fit a new condensing boiler to your heating system. The engineer will carry out a free survey for you and at that point, it can be decided what controls are required, where the boiler will be located (hopefully in the same place), whether a hot water cylinder is required.

5) The plume is annoying

Condensing boilers have to expel gases. They leave the boiler cool and look like a mist or water vapour. This is perfectly normal and shows that the boiler is working properly. Flues should be located away from doors and windows and away from neighbouring properties as much as possible.

6) The condensate is a problem

No! The condensate just connects onto a normal drain by a plastic overflow pipe. This is easy for a good engineer to locate for you.

Click here to find out more about installing boilers.If you have any questions about fitting your new boiler or about this blog, please call My Plumber on 020 3078 5920.

What is a condensing boiler?

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