BoilerFaultCodesYour boiler has shut itself down for safety because a internal limit was exceeded, likely due to overheating or a lack of water circulation.
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 temperature rises too quickly or exceeds a safe limit, causing the system to shut down to prevent damage. The most common reasons are a pump failure that stops water from moving or a buildup of debris and sludge that creates a blockage within the heat exchanger. This lack of circulation means the heat produced by the burner has nowhere to go, triggering the safety sensors.
This issue often appears when the heating is first turned on after summer, as pump components can seize up during long periods of inactivity.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
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A boiler cover plan would cover faults like E18 — 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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