BoilerFaultCodesTechnical description
Max.water temperature: Flow temperature too high.
What causes this fault?
This fault occurs when the water leaving the boiler exceeds its safe temperature limit, causing the system to shut down for safety. The most common cause is a failed internal pump that isn't moving water away from the burner quickly enough, or a significant blockage within the heat exchanger that is restricting flow. It can also be triggered by a faulty sensor that is incorrectly reporting the water temperature as being too high.
This issue is more frequent in autumn when heating systems are switched back on after a long summer break, as internal pump components are prone to seizing during periods of inactivity.
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.