Thermostat displays E17 and schedules or settings are lost unexpectedly

Safety: No high-voltage work is required, but avoid opening the thermostat case.

• Stabilize power: Ensure the HVAC breaker is not tripping and that there are no frequent power outages. Consider using a surge protector on the furnace circuit.
• Firmware update: Use the Lux app to check for and install the latest firmware, which may address memory handling issues.
• Factory reset: Perform a full factory reset and then reprogram schedules. Monitor whether E17 recurs.
• Replace thermostat: If E17 continues and settings keep resetting, the internal memory is failing and the thermostat should be replaced.