Error 08 displayed; unit may not detect water flow when a hot tap is opened, or may run pump without burner ignition.

Safety: Isolate electrical power and close the cold water inlet valve.

• Clean inlet filter: At the cold water inlet to the Immergas heater, remove the filter screen (if fitted) and rinse out debris. Reinstall carefully.
• Inspect flow sensor: The DHW flow sensor is usually on the cold inlet manifold. Remove it according to the manual. Check that the turbine spins freely under gentle water flow. Remove scale or debris.
• Check sensor wiring: Ensure the connector from the flow sensor to the control board is fully seated and the cable is not damaged.
• Test operation: Reassemble, open the inlet valve, bleed air from a hot tap, restore power, and open a hot tap to confirm that the unit now detects flow.

Note: If the sensor electronics (reed/Hall element) are defective, replace the complete Immergas flow sensor assembly.