Boiler intermittently shows A19, hot water temperature unstable, sometimes too hot.

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

Scaled plate heat exchanger, Faulty DHW NTC sensor, Sticking diverter valve, PCB modulation control issue

Safety: Beware of scalding water when testing hot taps.

Run hot water at a single tap: Open one tap fully and observe temperature stability. Avoid mixing with cold during testing.
Technician – descale plate heat exchanger: Remove and chemically descale the Beretta plate heat exchanger or replace if heavily scaled.
Check DHW NTC: Test and replace the DHW temperature sensor if readings are erratic.
Inspect diverter valve: Ensure the diverter valve moves freely between CH and DHW positions and is not partially stuck.

Hard 4/5

Plate Heat Exchanger

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