Thermostat displays E20 and refuses to start heating or cooling due to safety lockout

Safety: No immediate wiring work is required, but do not repeatedly cycle breakers.

• Wait lockout period: Many Lux thermostats enforce a 3–5 minute compressor protection delay. Wait at least 5 minutes before expecting the system to restart.
• Check settings: In the installer menu, verify minimum off-time and minimum run-time settings are appropriate for your system.
• Avoid rapid changes: Do not switch quickly between heating and cooling modes; allow several minutes between changes.
• Monitor system: If E20 recurs frequently, have an HVAC technician check the compressor and outdoor unit for high current draw or short cycling.