Boiler displays A19, hot water temperature overshoots setpoint significantly

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, Sticking modulating gas valve, Faulty DHW NTC sensor, Incorrect parameter settings

Safety: Risk of scalding. Warn occupants and reduce DHW setpoint on the controller.

Technician steps:

Check DHW NTC sensor readings and replace if inaccurate.
Inspect the plate heat exchanger for limescale; chemically descale or replace if restricted.
Verify correct gas valve modulation and adjust using a flue gas analyser according to IVT data.
Review and correct control parameters for DHW temperature and anti-scald limits.

Hard 4/5

Plate Heat Exchanger

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