BoilerFaultCodesYour boiler has shut itself down for safety because a critical fault has been detected that requires a manual reset.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: The safety devices have been activated (lockout)
What causes this fault?
This fault occurs when the boiler's safety sensors detect a failure in the ignition process or a consistent loss of flame during operation. The system shuts down to prevent unburnt gas from building up, often triggered by a worn-out ignition spark, a faulty gas supply, or a communication error within the internal electronics.
This fault can be more frequent during the first cold snap of winter when components that have sat idle all summer are suddenly put under high operational stress.
DIY fix possible
Locate the reset button or selector switch on the control panelTurn the selector to the 'RESET' position for 5-10 secondsRelease the switch and wait for the boiler to attempt to restart; if the code returns or happens frequently, call an engineer
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A boiler cover plan would cover faults like E21 — 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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