BoilerFaultCodesTechnical description
Safety temperature limiter in CH flow or flue gas temperature limiter has operated
What causes this fault?
This fault occurs when the internal sensors detect that the water or exhaust gases have reached a dangerously high temperature. The most common reason is a lack of water circulation, often caused by a failed internal pump or a blockage in the system pipework that prevents heat from being carried away from the burner. It can also happen if there is an air lock in the heat exchanger or if the sensors themselves have developed a fault.
This fault often appears during the first cold spell of autumn when the heating is turned back on after months of inactivity, as internal pumps are prone to seizing during the summer.
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.