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 detects an unusually rapid rise in heat that cannot be carried away from the heat exchanger quickly enough. The most common reason is a lack of water flow, often caused by a failing internal pump, a physical blockage in the pipework, or air trapped within the system. Essentially, the boiler is shutting down to prevent itself from overheating because the heated water has nowhere to go.
This issue often surfaces at the start of autumn when heating systems are turned back on after being idle, which can cause internal pump parts to seize.
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.