F18
Ferroli
Zone Control Output Fault
Thermostat shows F18 and underfloor heating zone valves do not open when there is demand.
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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
Incorrect wiring of zone valve outputs on Ferroli zone controller, Overloaded output channels driving too many actuators, Blown internal fuse on zone control board, Faulty Ferroli zone control module
How to Fix / Troubleshooting
Safety first: Zone controllers may switch mains voltage to actuators. Isolate power before opening.
- Verify wiring:
- Check that each underfloor heating actuator is wired to the correct zone output on the Ferroli controller.
- Ensure common/neutral connections are correct.
- Check load per channel:
- Count the number of actuators per output and compare with the controller's rated maximum.
- Inspect fuses:
- With power off, check any replaceable fuses on the zone controller PCB and replace with identical ratings if blown.
- Test individual zones:
- Use the thermostat to call for heat in one zone at a time and listen for valve actuation.
- If F18 persists:
- The zone controller board may be damaged.
- Replace the Ferroli zone control module.
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Repair Difficulty
Hard
4/5
Required Part
Ferroli Zone Control Module
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