They tend to have a higher purchase cost than non-condensing boilers although the efficiency savings pay back this extra investment in a few years depending upon the size of your property. It is recognised that a condensing gas boiler tends to have an efficiency of around 88% compared to non-condensing boiler of about 75%. Both these are significantly higher than old boilers which rate at between 55% -60%.
Types of Condensing Boilers
There are three types of condensing boilers, Combi boilers, system boilers and regular boilers. The main difference between these is the use, or elimination of, various parts within a typical system such as the hot water cylinder or the expansion tank. For more information see the relevant pages in this site.
Possible side effects
Condensing boilers are often noted for their ‘pluming’, a feature sometimes mistaken for ’steam’ coming out of the flue. This is caused by water droplets held in suspension in the flue gases condensing in the colder outside atmosphere. Although non-hazardous ‘pluming’ may be a nuisance if the condensation interferes with windows so care is needed in positioning the flue pipe to avoid this. Also a small pipe need to be run to a drain to allow the condensate to flow away.
The law in England & Wales changed in April 2005, which means only a condensing boiler can be fitted as a replacement boiler or complete new installation. There is a minor loophole to this law where, in exceptional circumstances, the local authority, can agree to an exemption certificate allowing a non-condensing boiler can be fitted.
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