De Dietrich Unstable DHW Temperature Control

Domestic hot water temperature fluctuates between too hot and too cold during shower

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 on De Dietrich combi boiler, Faulty DHW NTC sensor, Inadequate flow rate through boiler, 3‑way valve not fully diverting

Safety: Risk of scalding. Be cautious when testing hot water.

Steps:

Check flow rate: Ensure taps are fully open. Very low flow can cause temperature swings.
Clean inlet filters: Clean the cold water inlet filter to ensure stable flow.
Set DHW temperature: Adjust the DHW setpoint on the boiler to a moderate value (e.g., 50–55°C) to reduce extremes.

Professional help: A technician should descale or replace the plate heat exchanger and check sensors and diverter valve operation.

Medium 3/5

Plate Heat Exchanger

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