BoilerFaultCodesTechnical description
Flue sensor overheating
What causes this fault?
This fault occurs when the internal temperature of the exhaust pipe exceeds safe limits, triggering an emergency shutdown to prevent damage to the plastic flue components. The most common reason is a buildup of limescale or debris inside the heat exchanger, which prevents heat from being transferred to the water and sends it out through the chimney instead. In some cases, it can also be caused by a faulty sensor sending an incorrect high-temperature reading to the main control board.
This fault often becomes more apparent during winter when the boiler is running at maximum capacity for long periods to heat a cold home.
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.