E11
Thermona
Flow Sensor / Turbine Fault (DHW Flow Detection)
Boiler intermittently locks out with E11, especially during hot water use, temperature fluctuates.
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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.
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Possible Causes
Sticking DHW flow turbine in Thermona flow sensor, Debris or scale in DHW inlet filter, Faulty Hall sensor on flow meter, Loose wiring to DHW flow sensor
How to Fix / Troubleshooting
Safety: Isolate power and close cold water inlet before removing any DHW components.
- Check DHW flow: Open a hot tap fully. If the boiler does not recognise flow (no flame symbol, no start), the flow sensor may be stuck.
- Clean inlet filter (engineer level): Close the cold inlet valve to the boiler. Remove and clean the Thermona DHW inlet filter screen of debris.
- Inspect flow sensor: Remove the DHW flow sensor/turbine assembly. Clean any scale or debris and ensure the turbine spins freely.
- Check wiring: Verify the flow sensor connector is secure on the PCB and that the cable is undamaged.
- Replace sensor: If cleaning does not restore reliable operation, replace the Thermona DHW flow sensor assembly.
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Repair Difficulty
Medium
3/5
Required Part
DHW Flow Sensor / Turbine
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