F03
Ferroli Overheat Thermostat Trip

F03 appears, burner shuts down, sometimes accompanied by very hot outlet water.

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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 overheat thermostat, Poor water circulation, Severely scaled heat exchanger, Pump failure (if fitted)

How to Fix / Troubleshooting

Safety: Allow the heater to cool fully. Do not bypass safety thermostats.

  • 1. Manual reset: Some Ferroli overheat stats have a reset button. Press gently to reset. If it trips again, investigate the cause.
  • 2. Check for scale: In hard water areas, arrange for a professional descaling of the heat exchanger.
  • 3. Verify pump operation: On models with an internal pump, listen and feel for pump running during demand. If silent or very hot to touch, it may be seized and require replacement.
  • 4. Replace thermostat: If the thermostat is open-circuit at normal temperature, replace it with the correct Ferroli part.
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Repair Difficulty

Hard 4/5

Required Part

Overheat Thermostat
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