A combi (or combination) boiler is an ingenious space-saving idea, and an increasingly popular choice in Irish homes. In fact, combis now account for well over half of all the new domestic boilers installed in Britain every year. A combi boiler is both a high-efficiency water heater and a central heating boiler, combined (hence the name) within one compact unit. Therefore, no separate hot water cylinder is required, offering space saving within the property.

Regular boilers heat your central heating system directly and produce hot water for your cylinder. Here’s an example of a central heating and hot water system layout using a regular boiler:

If you are replacing an older model of boiler, the chances are that you will have a regular (also known as ‘conventional’) boiler.

A typical regular boiler system incorporates a boiler, extended controls, a hot water cylinder which is often fed by a cold water storage cistern located in the loft and a feed and expansion cistern - also located in the loft

A system boiler heats your central heating system directly and produces hot water for your cylinder. An example of a central heating and hot water system layout using a system boiler with an open-vented hot water cylinde

An example of a central heating and hot water system layout using a system boiler with a pressurised unvented hot water cylinder:

An example of a central heating and hot water system layout using a system boiler with a pressurised unvented hot water cylinder:

A system boiler, just like a regular (conventional) boiler works on the principle of stored hot water. However, 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 into a system boiler, which means that installation is quicker, neater, easier and more efficient.