108
Ariston
Floor Overtemperature Protection Triggered
Error 108 appears; thermostat reports that the floor temperature is too high and heating is disabled.
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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
Faulty floor NTC sensor reading too low resistance, Floor heating output stuck on due to relay fault, Incorrect maximum floor temperature setting, Sensor not embedded correctly in floor
How to Fix / Troubleshooting
Safety: Turn off power to the underfloor heating circuit before inspection.
- Check floor temperature: Touch the floor surface. If it is only mildly warm, the sensor may be faulty. If it is very hot, leave the system off and allow it to cool.
- Verify settings: In the thermostat installer menu, check the maximum floor temperature limit (often 27–35°C). Adjust to manufacturer-recommended values for your floor covering.
- Test sensor resistance: Disconnect the floor sensor at the thermostat and measure its resistance. Compare with the Ariston chart. Replace the sensor if readings are out of range.
- Check relay operation: If the floor remains hot even when the thermostat output is off, the output relay or actuator may be stuck closed. This requires replacement by a qualified technician.
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Repair Difficulty
Hard
4/5
Required Part
Ariston Floor NTC Sensor
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