BoilerFaultCodesYour boiler has sensed that heat is rising too quickly because there isn't enough water moving through the system to carry the heat away.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical 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.
DIY fix possible
Check the pressure gauge on the front of the boiler or under the casing.If the pressure is below 1.0 bar, use the filling loop handles to top up the system to 1.5 bar.Ensure all radiator valves are fully open to allow water to flow.Reset the boiler using the power button or reset switch.
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