BoilerFaultCodesYour boiler is automatically shutting down because it has detected dangerous exhaust fumes backing up into your home instead of escaping safely through the chimney.
Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now — this fault can be dangerous if ignored.
Technical description: If the unit continues to trip then the flue should be checked for spillage.
What causes this fault?
This fault occurs when a safety sensor detects that the hot exhaust gases are not rising correctly through the chimney and are instead spilling back into the room. The most common reason is a blockage in the flue, a damaged chimney liner, or poor atmospheric conditions that prevent the natural pull of the chimney. Because these fumes contain carbon monoxide, the boiler shuts down immediately to prevent a dangerous build-up in your home.
This issue is more common during particularly windy weather or high-pressure summer days when atmospheric conditions can push air back down the chimney, causing a 'down-draught'.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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