BoilerFaultCodesTechnical description
Flue thermostat sensor tripped (lockout)
What causes this fault?
This fault occurs when the temperature of the exhaust gases exceeds safe limits, triggering a safety sensor to prevent the plastic internal components from melting. The most common cause is a buildup of debris or lime-scale inside the heat exchanger, which prevents heat from being transferred to the water and pushes it out through the flue instead. It can also be caused by a damaged internal insulation panel or a faulty sensor giving an incorrect reading.
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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