BoilerFaultCodesYour boiler has shut down automatically because it detected that the exhaust gases are getting too hot, which is a safety feature to prevent damage to the internal components.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Safety switch-off: Flue temp. too high - flue gas temperature too high
What causes this fault?
This fault occurs when the internal sensors detect that the exhaust gases are reaching dangerous temperatures that could melt or damage the boiler's components. The most common reason is a heavy buildup of limescale or debris inside the main heat exchanger, which prevents heat from being transferred to the water and pushes it out through the flue instead.
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 F.25 — 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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