Boiler types
Most UK homes heat with one of three gas boiler layouts: a combi with no tank, a system boiler with a cylinder, or a regular boiler with a cylinder and loft tanks. These entries explain how to tell them apart and what the other parts do.
- Combi boiler
A combi boiler is a single appliance that runs the central heating and heats hot water as it is drawn, with no storage cylinder or loft tanks.
- System boiler
A system boiler heats the radiators and a separate hot water cylinder, and generally needs no tank in the loft to fill the system.
- Regular boiler
A regular boiler, also called a heat-only or conventional boiler, heats radiators and a hot water cylinder, usually with a cold water tank in the loft feeding the cylinder.
- Condensing boiler
A condensing boiler pulls extra heat from its flue gases before they leave, and drains away the water that condenses out.
- Which boiler have I got?
To tell which boiler you have, look for a hot water cylinder, tanks in the loft, a pressure gauge, and the model name on the label on the boiler.
- Hot water cylinder
A hot water cylinder stores water heated by a system or heat-only boiler and supplies it to the taps, and it can also have an electric immersion heater.
- Expansion vessel
An expansion vessel in a boiler is a small pressurised container that takes up the extra volume when heating water warms and expands.
- Oil and LPG boilers
An oil boiler or LPG boiler works much like a mains gas boiler but burns fuel stored on site in a tank or cylinders, which suits homes off the gas grid.
- Electric boiler
An electric boiler heats the water for radiators and taps with an element instead of burning fuel, and needs no flue.