Remeha Unstable DHW temperature control

Boiler runs but hot water temperature fluctuates or goes cold then hot

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

Partially blocked plate heat exchanger, Faulty DHW NTC sensor, Modulating gas valve not responding correctly, Inadequate flow rate through boiler

Safety first: Water can become very hot unexpectedly. Take care when testing taps or showers.

Check flow rate: Open the hot tap fully. Very low flow can cause temperature swings; ensure filters and aerators on taps are not blocked.
Test multiple outlets: See if the issue occurs at all taps or only one, which may indicate a local plumbing issue.
Engineer tasks: Clean or replace the plate heat exchanger, verify DHW sensor readings, check gas valve modulation and combustion, and ensure correct minimum and maximum outputs are set.

Hard 4/5

Plate Heat Exchanger

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