Boiler shows E15, may indicate domestic hot water flow sensor or turbine fault on combi models

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

• Check symptom: Open a hot tap. If the boiler does not recognise demand and E15 appears, the DHW flow sensor is suspect.
• Clean inlet filter (engineer task): Remove and clean the cold inlet filter screen to the boiler to ensure adequate flow.
• Inspect flow sensor/turbine: On Sime combis, the flow sensor is usually on the cold inlet manifold. Remove it carefully and check for debris or limescale preventing rotation. Clean or replace as needed.
• Check wiring: Ensure the sensor harness is intact and firmly connected to the PCB.