Thermostat shows F6 and schedules or setpoints are not applied to the boiler

Safety: No high-voltage work is required for this check, but do not open the boiler casing.

• Manual time set: Enter the thermostat settings and manually set the correct date and time. Save and check if schedules now run correctly.
• Internet sync: If the thermostat is Wi‑Fi enabled, ensure it is connected to the internet so it can sync time from Saunier Duval servers or NTP.
• Power cycle: Turn the thermostat off (remove from base or disconnect power) for 1 minute, then power back on.
• Firmware update: In the app or thermostat menu, check for firmware updates and install them.

If F6 persists and time drifts quickly or resets after short outages, the internal clock hardware is likely defective and the thermostat should be replaced.