Boiler displays E18; burner output is limited, or the boiler shuts down under high demand.

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

Possible Causes

Faulty DHW flow sensor, Excessive DHW flow rate, Partially blocked plate heat exchanger, Incorrect sensor wiring.

Safety first: Hot water may fluctuate; test carefully.

Reduce flow rate: Open hot taps less fully to reduce the flow and see if the boiler maintains operation without E18.
Clean aerators: Blocked aerators can cause unstable flow. Remove and clean tap and shower aerators.
Visual sensor check: On ACV combi models, the DHW flow sensor is usually on the cold inlet. Ensure its connector is secure, and there are no leaks.
Professional service: A technician should test or replace the DHW flow sensor and descale the plate heat exchanger if it is partially blocked.

Medium 3/5

DHW Flow Sensor

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