Saunier Duval Poor Temperature Regulation / Overshoot

Room temperature overshoots the setpoint by several degrees before boiler turns off

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Possible Causes

Thermostat installed near heat source or in draught, Incorrect control algorithm settings (hysteresis, TPI), Slow-response radiators with high water temperature, Faulty internal temperature sensor calibration

How to Fix / Troubleshooting

Safety: No electrical work required for basic checks.

  • Check location: Ensure the thermostat is mounted on an interior wall, about 1.5 m above floor, away from radiators, direct sunlight, and draughts.
  • Adjust settings: In the installer menu, reduce hysteresis or enable TPI/modulating control if available to improve regulation.
  • Lower flow temperature: On the boiler, reduce the central heating flow temperature to reduce overshoot.
  • Relocate thermostat: If installed in a poor location, have it moved to a representative room.

If overshoot remains excessive, the internal sensor may be out of calibration and the thermostat may need replacement.

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Repair Difficulty

Easy 2/5
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