NTI Unstable DHW Temperature

Domestic hot water temperature fluctuates or runs hot then cold during a 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, Faulty DHW sensor, Inadequate flow through DHW side, Mixing valve malfunction

Safety: Risk of scalding—test water temperature carefully.

Check flow rate: Ensure fixtures are providing steady flow; very low flow can cause cycling.
Clean inlet filter: Remove debris from the cold water inlet strainer on the NTI combi boiler.
Inspect mixing valve: If an external thermostatic mixing valve is installed, verify it is not stuck or scaled; replace if necessary.
Descale plate exchanger: Have a technician chemically descale or replace the DHW plate heat exchanger if scale buildup is suspected.

Medium 3/5

DHW Plate Heat Exchanger

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