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Help for buying central heating cover

Please use the information below to help identify the type of central heating boiler you have. If you have any questions about cover for your boiler, please call us on 0800 197 0610.

Help with buying Home Emergency Response

Your central heating boiler

Do you have a cold water storage tank in your home?

It's usually in the loft. If you do, you probably have a conventional boiler or a condensing boiler.

If you don't have a water tank in the loft, you likely have a combination boiler.

The following descriptions provide further information.

Conventional boiler

In a conventional heating system a cold water tank situated high up in your home – usually in the loft – feeds a hot water storage cylinder. It is usually enclosed in an 'airing' cupboard. Heated by the boiler, the cylinder supplies hot water via a circulating pump to the radiators and taps.

If all of the water in the hot water storage cylinder has been used, or has cooled overnight, the heating process has to be restarted to produce a fresh supply of hot water.

Conventional boiler key features

  • Needs a cold water storage tank
  • Requires a hot water storage cylinder, usually in the airing cupboard
  • You sometimes have to wait for a fresh supply of hot water

A back boiler is a variation on the conventional boiler, and is installed behind an existing heat source, like a gas fire or wood burning stove. The back boiler heats water which is fed to a hot water storage cylinder (usually in the airing cupboard) and to radiators. This system also needs a cold water storage tank, which is often located in the loft.

Combination boiler

A combination boiler – or 'combi' boiler – heats water from the mains supply when a hot tap is turned on, as well as supplying hot water to the radiators.

Combination boiler key features

  • Heats water directly from the mains supply, so no hot water storage cylinder or airing cupboard
  • Doesn't require a cold water storage tank
  • You only get a decent flow of hot water from one tap at a time
  • Using a hot tap while the heating is on interrupts the flow of hot water to the radiators

Condensing boiler

Condensing boilers can be either 'conventional' or 'combination', as described above. However, they work more efficiently by using the hot flue gases – which are normally lost – to assist heating the water.

Condensing boiler key features

  • Reusing heat from flue gases is energy efficient, so gas fuel bills are lower

Since 1 April 2005 the Building Regulations have specified that new or replacement gas-fired boilers installed in England and Wales should normally be condensing boilers. If your boiler has been installed since then it is likely to be a condensing boiler.

Thermal storage cylinders

A thermal storage cylinder stores hot water. When a hot tap is turned on, a heat exchanger in the cylinder heats the mains water that passes through it.

The hot water stored in the cylinder can be pumped to radiators. This water never leaves the system, returning to the thermal storage cylinder to be re-heated.

Water in a thermal storage cylinder can be heated with an electric element, or with a gas or oil boiler.

Thermal storage key features

  • Hot water is supplied to taps at mains pressure
  • Provides hot water to taps and showers at the same time

Boiler summary

  • Conventional boiler
    Uses a cold water tank with hot water stored in a cylinder, usually in an airing cupboard
  • Back boiler
    Fitted in a fireplace, usually behind a gas fire, and operates like a conventional boiler
  • Combi boiler
    No storage tanks required, uses the mains water supply
  • Condensing boiler
    Can be conventional or combination and uses flue gases to assist heating the water, improving efficiency
  • Thermal storage
    Provides mains pressure hot water