BoilerFaultCodesYour boiler has detected an issue with how exhaust gases are leaving the flue or a problem with the air-fuel mixture, causing it to shut down for safety.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Flue blockage – due to chimney and combustion values – the boiler may need a calibration.
What causes this fault?
This fault occurs when the boiler's internal sensors detect that exhaust gases are not escaping the building correctly or the burner isn't receiving the right mix of air and gas. It often happens if there is a physical obstruction in the flue pipe or if the gas valve has drifted out of its safe operating parameters. To prevent the build-up of dangerous gases, the boiler automatically shuts down until the combustion levels are recalibrated.
This fault can sometimes appear during periods of high winds, which can cause back-draughts or pressure fluctuations that interfere with the boiler's ability to vent exhaust gases properly.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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