Nest thermostat displays E20 and may not complete learning or scheduling

Note: E20 is typically related to the Nest's internal software rather than HVAC wiring.

• Reboot the thermostat: Press and hold the Nest display ring for about 10 seconds until it restarts.
• Check for firmware update: Once rebooted and connected to Wi‑Fi, go to Settings > Software and allow the thermostat to check for and install any pending updates.
• Ensure adequate ventilation: Make sure the Nest is not installed in a recessed box or covered location that could cause overheating.
• Factory reset if needed: If E20 persists, perform a full reset via Settings > Reset > All Settings and reconfigure the device.

If the error continues after a reset and update, the internal memory may be defective and the display module will likely need replacement.