BoilerFaultCodesYour boiler has shut down because it is struggling to discharge exhaust fumes safely or is detecting a significant lack of air flow.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Burner blocked
What causes this fault?
This fault occurs when the boiler's internal sensors detect that exhaust gases cannot exit the building or fresh air cannot enter the system properly. It is usually caused by a heavy buildup of debris within the heat exchanger or a blockage in the flue pipe, which prevents the burner from firing safely. In some cases, a blocked condensate trap can also cause water to back up, effectively choking the combustion process.
This fault can be more frequent in autumn or during high winds, as fallen leaves or debris can obstruct the external flue terminal.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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A boiler cover plan would cover faults like 1B — no call-out fees, no surprises.
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Could it be time for a new boiler?
If repair costs are adding up, a new energy-efficient boiler could be the smarter long-term choice.
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