E15
Termet
Return Temperature Sensor (Return NTC) Fault
Boiler displays E15, temperature readings jump or are inconsistent, boiler may cycle rapidly.
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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
Defective return NTC sensor on CH return pipe, Loose or corroded connector, Damaged sensor cable, Faulty PCB sensor input
How to Fix / Troubleshooting
Safety first: Isolate power and allow the boiler to cool before handling sensors.
User checks:
- Observe if the displayed temperature changes erratically without demand.
- Reset the boiler once. If E15 persists, a technician is required.
Technician checks:
- Locate the return NTC sensor on the return pipe to the heat exchanger.
- Measure resistance at known temperatures and compare with Termet charts.
- Inspect wiring and connectors for damage or moisture.
- Replace the return NTC sensor if readings are incorrect; otherwise, test the PCB.
Correct sensor operation is essential for proper modulation and efficiency.
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Repair Difficulty
Medium
3/5
Required Part
CH Return NTC Sensor
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