BoilerFaultCodesTechnical description
waiting time: no water in system, temperature (gradient error) rise flow / return sensor too high
What causes this fault?
This fault occurs when the boiler's internal sensors detect that the water temperature is rising far too quickly, indicating that heat isn't being carried away from the heat exchanger. The most common reason is a failed circulation pump or a significant blockage in the pipework preventing water flow. It can also be caused by a build-up of air or a lack of pressure within the system.
This fault is frequently seen in autumn when heating systems are turned on for the first time after summer, as pump components can seize 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.