| Gas Fired Boilers
The choices of gas boiler are conventional or combination boilers and these are both only available as condensing boilers.
Central Heating and Hot Water using Conventional Gas Fired Boilers
Conventional boilers heat your radiators and hot water when activated by a control. The hot water is then stored in a cylinder until it is needed. This type of system is most suitable for families or large houses where hot water is needed on demand and in significant quantities for heating, baths, washing machines, dishwashers and so on.
Combination (Combi) Gas Boilers
Combination boilers (Combi) provide hot water on demand, heated as required with no water storage. They heat your radiators when activated by a control similar to standard (or conventional) boiler systems. Combi boilers dispense with the need for the hot water cylinder in the airing cupboard, the large cold water cistern (tank) plus small header cistern (tank) in the loft which are otherwise needed in conventional vented heating systems. All the major components are housed in one unit which makes them very convenient to the installer and saving space for the householder.
Combi boiler systems are generally suitable for smaller households, flats and bungalows where there are a smaller number of users with modest heating and hot water demands although some of the latest combination boilers can suit larger households.
Condensing Gas Boilers
Both of these types of boilers are available as condensing boilers. Condensing boilers are designed to recycle heat with an extra heat exchanger so that the hot exhaust gases are used to pre-heat the water in the boiler system, therefore reducing energy consumption and bills.
See our condensing boilers page or our condensing boilers FAQ for more information or visit the SEDBUK (Seasonal Efficiency of Domestic Boilers in the UK) website for some useful facts and figures.
Condensing central heating boilers are the most energy efficient boilers available. All gas boilers fitted in both new and existing homes must be condensing boilers with an ‘A’ efficiency rating (A = greater than 90%).
Condensing boilers have now been in use for 20 years and are reliable – indeed most of the components are also used in non-condensing (conventional) boilers.
They will ALWAYS be more efficient than a new regular boiler whether in condensing mode or not. They can be up to 10% to 15% more efficient than a modern conventional boiler and up to 30% more efficient than older boilers so the energy saving and the impact on your fuel bills can be significant.
There is only a marginal benefit from over-sizing radiators. Larger radiators will allow slightly cooler water to return to the boiler and can increase the efficiency by a further 3%. However this is not considered to be cost effective and is often impractical.
They can be fitted to most new and old systems. Normal good practice must be followed which will include flushing of system and adding an inhibitor. As with any replacement boiler, an assessment of the effectiveness of the control system and type of hot water cylinder, should also be made.
The only real difference from a conventional non-condensing boiler is a drain for the condensed liquid which is like a plastic overflow pipe.
Up to 1 litre of condensed water per hour is produced. This has a pH of about 5 which is between rain water and cola. The condensed liquid is disposed of through a condense pipe connected to the drainage system.
The flue gases produced on non-condensing boilers cannot be seen due to their high temperature. The cooler flue gases from a condensing boiler produce a plume which can be seen. Therefore care should be taken locating any flue terminal to avoid the visible plume being a nuisance to neighbours, however numerous flue options are available.
Plants thrive on carbon dioxide!
Yes but the price difference has continued to reduce and is offset by the saving in fuel bills. Condensing boilers are the most efficient boilers available – the more efficient the boiler is, the less fuel it uses, the less carbon dioxide it produces and the less it costs to run.
See the SEDBUK (Seasonal Efficiency of Domestic Boilers in the UK) website for some useful facts and figures.