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How heat only boilers work

A heat only boiler is also known as a conventional or regular boiler.  It is an open vented system and has two water tanks - a water storage tank and a small 'feed and expansion' tank - usually sited in the roof space of the house.

Cold water from the storage tank is fed to the hot water storage cylinder, which is usually in an airing cupboard. The boiler heats the water in the cylinder, providing the hot water to taps throughout the house.

The second tank in the loft, the feed and expansion tank, maintains the correct level of water for the heating system, and allows for the water expansion when the heating is switched on.  A pump, usually also installed in the airing cupboard, circulates hot water via pipes to heat the radiators.

Unlike most heat only boilers, Baxi's range of heat only boilers are unique because they don't require a pump overrun or permanent live. That means the installer does not need to run wires from the boiler to the pump, which often involves lifting carpet and floorboards, and then making good. Learn why not having to install a pump overrun or permanent live is so much easier for installers and homeowners.

An open vented system with a heat only boiler is most likely to be the existing system in most homes. Showers, taps and running baths can be drawn in any room at the same time, but if all the hot water is used, the cylinder will take a little time to reheat.

Information & advice

Our series of FAQs, technical advice articles and 'How to...' videos are designed to help you understand your boiler, provide helpful tips and even save you money.

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