Boiler shows A22, DHW priority fault, heating may be disabled

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

Stuck DHW flow turbine in Herz combi boiler, scaled DHW inlet filter, faulty DHW flow switch, wiring fault to DHW sensor

Safety: Close cold water inlet and relieve pressure before opening DHW components.

Clean inlet filter: Remove and clean the cold water inlet filter screen on the Herz boiler.
Inspect turbine: Access the DHW flow turbine or switch and check that it rotates freely. Remove scale or debris.
Check wiring: Ensure the DHW flow sensor cable is properly connected to the PCB.
Replace sensor: If the boiler does not detect DHW flow despite good water flow, replace the Herz DHW flow sensor/turbine.

Medium 3/5

Herz DHW flow sensor

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