Building regulations that came into force on April 1st, 2007 state that any replacement or new oil boiler must be a condensing boiler. Rare exceptions can apply.

Condensing Boilers

Condensing boilers are high efficiency because they convert water vapour (or steam) traditionally expelled through the flue into the atmosphere into useable heat.

The vapour is condensed (hence the name of ‘condensing boiler’) into a liquid condensate within which is latent heat that can be harnessed and used to warm your home.

This process means condensing boilers are considerably more efficient than the old-style conventional boilers that came before. Most condensing boilers state that they have a SEDBUK rating of ‘A’ – this means they convert 90 per cent or more of the fuel they use into heat.

Click here to find out more about boiler efficiency and SEDBUK ratings

Condensing boilers come in three types:

A combination or ‘combi’ boiler heats a home’s water supply and central heating system from one combined unit (hence the name). There is no separate hot water cylinder or tank needed, meaning the combi has the benefit of saving space in your home.  Therefore a combi is a good choice for homes where space is at a premium.

From the one unit, combis deliver hot water on demand to your taps and central heating system when you want it, however one small disadvantage of instant hot water is that, for example, it may not be possible to fill a bath and a kitchen sink simultaneously. You may need to fill one, then the other.

Having just one unit generally saves installation time and money, since there is no tank to install and less pipe work needed.

A further benefit of a combi boiler is the fact that water is delivered at mains pressure, so you can enjoy a hot powerful shower without the need for an additional pump.

Combi boilers are available in a range of power ratings that can be matched your home’s requirements. Our Domestic and General heating engineers will be able to advise you on the correct power rating for your home.

Traditional boiler (also known as regular or conventional)

Boilers of this type are known by three names – traditional, regular and conventional. As you may expect these type of boilers are traditional in the sense that they require a tank to store water. The chances are that if you have an older style boiler, it is traditional.

As well as needing a tank to store water (usually in the loft), a traditional boiler also requires cold water cistern (also usually located in the loft). The requirement for room to store these elements of a traditional boiler system must be a consideration when choosing a type of boiler.

The main advantages of traditional boilers are that the hot water flow rate will tend to be higher than that of combi boilers, as the hot water is stored within the hot water tank ready for use rather than being heated on demand. If you find that your family often have several hot water taps on at the same time, say a shower running in the bathroom and hot water running in the kitchen, then this stored hot water can be an advantage.

Another matter to consider is that a combi boiler needs a minimum water pressure from the mains to deliver your hot water flow, and this may not be available in all areas.

System Boiler

A system boiler is very similar in theory to a traditional boiler; they both work on the principle of stored hot water.

However, the main difference is that a system boiler does not require a cold water cistern, as well as a hot water tank, which saves space. Instead, system boilers take a direct feed from the cold water mains and store water in a small tank built into the boiler. Having components built into the boiler in this way has the benefit of cutting down installation time whilst at the same time reducing the number of components to maintain.

Furthermore, the hot water is pumped from the system boiler through the heating system to the radiators and hot water cylinder, resulting in a fast response to your hot water needs.

Domestic and General’s heating engineers will be able to advise you on all the various types of oil boilers and recommend the best one for your home and needs.