BoilerFaultCodesTechnical description
Overtemperature protection intervention
What causes this fault?
This fault occurs when the internal temperature sensors detect that the heat exchanger has exceeded its safety limit, causing the boiler to shut down to prevent internal damage. The most common reason is a lack of water flow, often caused by a failing circulation pump or a blockage within the system that prevents heat from being carried away. In some cases, it can also be triggered by a buildup of limescale or debris inside the heat exchanger itself.
This fault is more frequent in autumn and winter when the heating is first turned on, as pumps can seize up after being idle during the summer 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.