BoilerFaultCodesTechnical description
Flue sensor overheating
What causes this fault?
This fault occurs when the internal temperature of the exhaust fumes exceeds safe limits, triggering a safety cutout to prevent damage to the plastic flue components. The most common reasons include a buildup of limescale or debris inside the main heat exchanger, which prevents heat from being transferred to the water effectively, or a faulty sensor sending incorrect readings to the control board.
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.
Find a Gas Safe engineer
Search the official register →