Protherm Unstable DHW Temperature Control

Domestic hot water temperature fluctuates between hot and cold during use

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 or partially blocked plate heat exchanger, Faulty DHW NTC sensor, Sticking diverter valve, Inadequate flow rate through boiler

Safety: Turn off power and gas before opening the boiler. Water may be hot.

Steps:

Check that the cold water inlet filter is clean and that the flow rate is within Protherm’s specified range.
Inspect and, if necessary, chemically clean or replace the DHW plate heat exchanger if scale is suspected.
Test the DHW NTC sensor and replace if readings are unstable.
Check the diverter valve for smooth operation; replace the valve or motor head if it sticks between positions.

Hard 4/5

DHW Plate Heat Exchanger

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