A boiler is a closed vessel in which water is heated. The heated water exits the boiler for use in various processes or heating applications. In this hub, we only discuss domestic boilers which provide heating and hot water for a home.
Boilers vary considerably in detail and design. Most boilers may be classified and described in terms of a few basic features, or the design and structure of the boilers. They can be classified into gas boilers, oil boilers, electric boilers and solid fuel boilers, wood gasification boilers, back boilers and fire fronts, in terms of the source of heat.
But when you ask an boiler installation engineer, you may get such names as "Combi", "Regular" (or "traditional" or "conventional" ) and "System" in terms of a its basic structures and features, or such long name as "A-rated high energy efficiency condensing boiler". These names can lead to confusion and wrong decisions.
Condensing Boilers are a fairly new and harness money saving technology.
Off course, the most efficient boilers are know as condensing boilers. Basically, a condensing boiler recycles the hot gases back into the boiler, making the boiler work less hard, they extract more of the heat energy than non-condensing boilers and also recycle it into heat. therefore making the boiler a 'High Efficiency Boiler'
Condensing boilers are available for Gas Boilers and Oil Boilers. Electric Boilers do not have any exhaust fumes and in recent years have become a real cost effective alternative to gas and oil.
A typical conventional system incorporates a boiler and extended controls, a feed and expansion cistern, and a hot water cylinder (usually in the airing cupboard) which is often fed by a cold water storage cistern located in the loft.
The Combination Boiler
Combination or Combi boilers are sometimes confused with condensing boilers, they are very different. Combi boilers take cold water straight from the mains and heat it directly, giving a continuous flow of hot water, although the water pressure is generally not as high as it may be with some other boilers.
The high efficiency condensing combi or combination boiler is an ingenious space-saving idea, and an increasingly popular choice in domestic heating. In fact, combis now account for well over half of all the new domestic boilers installed in Britain every year.
The major difference between a combi and any other type of boiler is that a combi eliminates the need to store hot water - so no hot water cylinder in the airing cupboard. It is both a high-efficiency water heater and central heating boiler, combined (hence the name) within one compact unit which usually sits in the kitchen or utility room, or sometimes in the airing cupboard. The space savings result from the fact there is no hot water storage cylinder, cold water storage cistern or other familiar components of a regular (conventional) heating system.
The further benefits of this are a significant saving on hot water costs, and the fact that hot water is delivered through your taps or shower at mains pressure. So you can enjoy powerful showering without the need for a pump. Another combi benefit is that it can generally save you money on installation time and costs, since no tank in the roof space means less pipe work and a shorter installation time.
System boilers are designed primarily to make the installers lives easier. The system boiler contains an expansion vessel and circulation pump that is built in to them, saving installers fitting all the different components separately. A system boiler will eliminate the need for a cold water tank because it heats the water straight from the mains similar to a combi boiler.
Unlike a combi, both a system boiler and a regular (conventional) boiler work on the principle of stored hot water - but a system boiler differs from a regular boiler in some important respects.
Firstly, many of the major individual components of the heating and hot water system are built in, which means that installation is quicker, neater, easier and more efficient.
Secondly, the hot water is pumped from the boiler through the system to the radiators and hot water cylinder, resulting in a fast response and more economical running costs. The system boiler removes the need for a feed and expansion cistern.
Back boilers are no longer as popular as they once were but some homes do still have back boilers behind their chimneys, installing a new model or a new type of boiler could save you a lot of money on your heating bills. Back boilers are generally not installed unless it is too complicated or expensive to install a condensing boiler.