E11
Keston
DHW NTC Sensor Fault
Boiler shows E11, domestic hot water temperature unstable or excessively hot
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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
Failed DHW temperature sensor, Loose sensor connection, Scale build-up around sensor pocket, Wiring harness fault
How to Fix / Troubleshooting
Safety: Risk of scalding from hot taps. Warn occupants and avoid very hot water use until resolved.
User checks:
- Run a hot tap and observe if temperature swings from hot to cold. If E11 appears, stop using hot water and call an engineer.
Engineer checks:
- Locate the DHW NTC sensor on the Keston plate heat exchanger or DHW outlet pipe. Inspect for scale, corrosion, or loose wiring.
- Measure sensor resistance at a known water temperature and compare with Keston data; replace if out of tolerance.
- Check wiring continuity back to the PCB and reseat connectors.
- Descale the DHW side of the plate heat exchanger if heavy limescale is present, which can affect sensor response.
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Repair Difficulty
Medium
3/5
Required Part
DHW NTC Sensor
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