Ferroli Incorrect Control Algorithm / PID Settings

Thermostat shows large temperature swings; room feels alternately too hot and too cold.

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Possible Causes

Thermostat set to simple on/off instead of modulating mode for compatible Ferroli boiler, Hysteresis set too wide, Underfloor heating controlled like radiators, Poorly tuned weather compensation curve

How to Fix / Troubleshooting

Safety first: Control adjustments only.

  • Enable modulation:
    • If your Ferroli boiler supports OpenTherm/BUS, set the thermostat to modulating mode instead of on/off.
  • Adjust hysteresis:
    • Reduce the on/off differential to 0.3–0.5 °C for more stable temperature.
  • Optimize for system type:
    • Select the correct system type (radiators vs underfloor) in the installer menu.
    • For underfloor, use lower flow temperatures and slower response settings.
  • Tune weather compensation:
    • Adjust the heating curve slope and offset based on comfort feedback.
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Repair Difficulty

Easy 2/5
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