BoilerFaultCodesTechnical description
Permanent fault. Maximum safe temperature value reached, safety thermostat open-circuited, no circulation, sensor not or badly connected, bad connection or sensor fault.
What causes this fault?
This fault occurs when the boiler's internal water temperature exceeds a safe limit, causing the system to shut down to prevent damage. The most common reasons are a lack of water circulation caused by a failed pump, a blockage in the heat exchanger, or a faulty sensor providing an incorrect temperature reading.
This issue often surfaces when the heating is first turned on in autumn, as internal pumps can seize up after being idle throughout 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.