Termet Reduced DHW Output / Heat Transfer Limitation

Boiler runs for hot water but tap temperature is only lukewarm even at low flow.

Safety Warning

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

Heavily scaled plate heat exchanger on Termet combi boiler, Gas rate set too low or incorrect nozzle/orifice, Partially blocked DHW inlet filter, Faulty DHW temperature sensor misreading

How to Fix / Troubleshooting

User checks:

Reduce the flow at the hot tap to see if temperature increases.
Check that the cold water isolation valve to the boiler is fully open.

Technician checks:

Measure DHW flow rate and temperature rise; compare with Termet specifications.
Descale or replace the plate heat exchanger.
Check and clean the DHW inlet filter.
Verify gas input rate and adjust the gas valve if necessary.
Test the DHW NTC sensor for accuracy.

Restoring proper DHW output often requires descaling and combustion checks.

Repair Difficulty

Hard 4/5

Required Part

Plate Heat Exchanger

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