BoilerFaultCodesYour boiler has switched itself off completely as a protective measure because its internal safety sensors have detected a critical operating fault.
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 internal components reach an unsafe temperature, triggering a complete shutdown to prevent damage. The most common reasons are a failure in the water circulation system, such as a faulty pump, or a defective sensor that is incorrectly reporting the heat levels to the control board.
This issue is more frequent during the first cold snap of winter when heating systems are suddenly pushed to run at high temperatures after being idle for months.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like E20 — 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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