BoilerFaultCodesTechnical description
Flue or high limit thermostat activated
What causes this fault?
This fault occurs when the internal temperature of the boiler rises above a safe limit, triggering a safety shut-off. The most common reasons are a failed pump that isn't moving water away from the heat exchanger quickly enough, or a build-up of sludge and debris creating a blockage in the system.
This code is often seen when central heating is first turned on after summer, as the pump can seize up from lack of use during the warmer months.
Engineer required
This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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