Boiler troubleshooting guides

History The History of the Boiler and Central Heating
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Boiler losing pressure repeatedly (Worcester Bosch, Ideal & Vaillant)

Boiler pressure gauge keeps dropping below 1 bar, needing regular repressurising

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Boiler heats water but radiators stay cold (Worcester Bosch & Baxi)

Hot water works fine but the central heating radiators stay cold, or vice versa

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Boiler keeps locking out or won’t fire up (Ideal, Vaillant, Vokera, Glow-worm & Potterton)

Boiler shows a fault code or simply won't ignite when heating or hot water is called for

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Worcester Bosch EA fault code — boiler won’t ignite or loses flame

Display shows EA and the boiler won't ignite or loses flame during operation

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Worcester Bosch D5 fault code — condensate pipe or pump issue

Display shows D5 and the boiler has locked out

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Vaillant F.28 and F.29 fault codes — ignition failure or flame loss

Display shows F.28 or F.29 and the boiler has locked out

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Vaillant F.22 and F.75 fault codes — low pressure or pump sensor fault

Display shows F.22 or F.75

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Boiler making a loud banging or “kettling” noise (all brands)

Loud banging, rumbling, or kettle-like noise when the boiler fires

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The History of the Boiler and Central Heating

Central heating isn’t a modern idea — the Romans piped warm air under floors via the hypocaust system nearly two thousand years ago. But the boiler as we’d recognise it, a sealed unit heating water for radiators, is a much more recent British and European story, and one that’s changed enormously even within living memory. […]

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