F15
Saunier Duval
Flue Gas Temperature Sensor Fault / Overtemperature
Furnace displays F15, unit may shut down unexpectedly, sometimes after long operation
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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 flue gas NTC sensor,Blocked or partially blocked flue,Incorrect burner setting causing high flue temperature,Loose sensor connection
How to Fix / Troubleshooting
Safety first: Turn off power and gas. Flue work must comply with regulations; consult a qualified technician.
- Inspect flue terminal: Check outside that the flue outlet is clear of obstructions. Remove any debris or ice buildup.
- Check flue gas sensor: Locate the flue gas temperature sensor on the flue hood or in the flue path. Inspect wiring and connector for damage or looseness.
- Measure sensor resistance: With the sensor disconnected and cooled to room temperature, measure resistance and compare to the NTC specification. Replace if out of range.
- Combustion check: A gas engineer should verify burner pressure and combustion values. Excessive flue temperature may indicate overfiring or poor combustion.
- Flue inspection: Have the entire flue system inspected for blockages, incorrect slope, or condensate accumulation that could restrict flow.
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Repair Difficulty
Hard
4/5
Required Part
Flue Gas Temperature Sensor
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