BoilerFaultCodesTechnical description
Primary temperature 94°C (until 84°C) - shut down burner. Water over 89°C - shut-down. Gas valve OFF.
What causes this fault?
This fault occurs when water inside the boiler cannot flow away quickly enough, causing it to rapidly overheat and trigger a safety shutdown. The most common reasons are a seized internal pump that isn't pushing water around the system, or a blockage such as trapped air or a build-up of sludge. In some cases, a faulty sensor may simply be misreading the temperature even if the water itself is fine.
This issue often appears when the heating is first turned on after summer, as the pump can seize up during long 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.