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 a sudden, rapid spike in temperature because there is no water flow to carry the heat toward your radiators. The most common reasons are a seized internal pump, an air lock in the pipework, or a blockage that is preventing the water from circulating through the heat exchanger. Essentially, the boiler is protecting itself from overheating by shutting down when it senses the water is standing still.
This issue often surfaces in autumn when the heating is turned on for the first time after summer, as pump components 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.