A09
Ferroli
Domestic Hot Water (DHW) NTC Sensor Fault (on combi-style furnace/boiler units)
Ferroli furnace shows A09; may be associated with rapid cycling or incorrect temperature readings.
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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 Ferroli DHW NTC sensor, Scale buildup on DHW sensor pocket, Loose or broken sensor wiring
How to Fix / Troubleshooting
Safety: Turn off power and close water isolation valves before removing any DHW components.
Steps:
- Locate DHW NTC: Usually fitted on the DHW outlet pipe or within the plate heat exchanger assembly on Ferroli combi units.
- Check wiring and connector: Inspect for damage, corrosion, or loose fit. Reseat the connector.
- Descale sensor pocket (if accessible): If there is visible limescale, carefully clean the area. Severe scaling may require removal and descaling of the plate heat exchanger by a professional.
- Reset and test: Restore power, open valves, and reset the unit. Run hot water and observe operation.
Professional help: If A09 remains, the DHW NTC or control board input must be tested and replaced by a technician.
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Repair Difficulty
Medium
3/5
Required Part
DHW NTC Temperature Sensor
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