Boiler shows E11; may occur during hot water use or heating, often with fluctuating temperatures.

Safety: Isolate power and close cold water inlet before removing any water components.

• Check water supply: Ensure the cold water isolation valve to the boiler is fully open and that other taps in the property have good flow.
• Clean inlet filter: Many Alpha combi boilers have a mesh filter on the cold inlet. A qualified person can isolate, remove, and clean this filter to restore flow.
• Flow sensor inspection: Locate the DHW flow switch or turbine assembly. Check for obvious debris or limescale. Clean or replace as necessary.
• Wiring check: Ensure the flow sensor connector is secure on the PCB and that the cable is not damaged.

If E11 continues, the flow sensor assembly may need replacement by a professional.