Boilers and central heating
Central Heating Boilers
Following changes to Building Regulations condensing boilers will now be the norm, with few exceptions, when new or replacement boilers are installed.
Click here for more information on the Building Regulations.
Condensing Boilers (high efficiency)
Inside a condensing boiler
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Condensing boilers have very high efficiency in the order of 90-95%. They are available as both conventional and combination units. The increased efficiency, compared to standard boilers, means lower running costs and less carbon dioxide emitted. Condensing boilers can be installed as replacements for older standard efficiency boilers.
Either oil or gas fired they incorporate a larger or an additional heat exchanger to extract as much heat from the combustion process as possible.
A drain or soak away is required for the condensate that the boiler produces.
Use in a conventional system
A conventional heating system and boiler
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Condensing boilers can be used in conjunction with hot water cylinders, roof tanks and of course radiators. Gas boilers are usually wall hung with fan assisted flues. Oil boilers are usually floor standing with either balanced, low level discharge or conventional flues i.e.; into an existing chimney. Outdoor oil fired condensing boilers are also available.
When directly replacing a standard efficiency boiler, that is connected to an old gravity hot water and pumped heating system, it will be necessary to upgrade so both hot water and heating are pumped. Condensing boilers are not compatible with gravity circulation.
Diagram of a combination boiler and heating system
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Oil and gas condensing combination boilers, often referred to as combi boilers, provide both heating and hot water from one unit. They produce hot water instantaneously so there is no requirement for roof tanks or for hot water cylinders. As with gas and oil fired conventional boilers there are many flueing options. Outdoor oil fired combination boilers are also available, as are wall hung oil combis.
Consideration needs to be given to many aspects of the installation of new and replacement boilers. Among the most important are ventilation and flueing. Ventilation requirements depend on many factors, for example, is the boiler open flued or room sealed, in a compartment or in the garage? It is essential that the correct ventilation is provided.
The flue from a boiler and especially its termination are also important considerations. Many restrictions apply as to exactly where a flue can terminate.
Pluming also needs to be considered. This is the water vapour that is visible due to the low flue gas temperature. This should not be discharged where it is likely to be a nuisance.
The overall efficiency of the heating and hot water system needs to be taken into consideration. Click here for more information.
Variations on the three main types of boiler are usually additions to ease installation requirements. System boilers for example have a built in pressure vessel to eliminate the need for a heating header tank.
Check www.boilers.org.uk for more information on boiler efficiency ratings, running costs etc.
David Kearns © 2004 - 2008