Thermostat shows F19 and the boiler cycles rapidly on and off, ignoring anti‑short‑cycle settings.

Safety first: No direct electrical risk, but frequent cycling can damage the boiler.

• Adjust settings:
  • Increase temperature hysteresis (difference between on and off) in the installer menu.
  • Increase minimum burner on/off times if available.
• Improve thermostat location:
  • Ensure the thermostat is on an internal wall, away from drafts, direct sunlight, and heat sources.
  • Relocate if necessary.
• Check sensor stability:
  • Monitor the displayed room temperature; if it jumps quickly, there may be a sensor or placement issue.
• If F19 remains and cycling continues:
  • Update firmware or replace the Ferroli smart thermostat if the control logic is faulty.