How do I lock the thermostat screen so users cannot change settings?

Screen lock is configured via ISU 435, which offers three options: None (fully unlocked), Partial (user can modify only temperature settings), or Full (user cannot modify any settings). When fully locked, the screen is locked by a default factory code that is displayed briefly before locking — the manual advises noting this code in a safe place. The Screen Lock option is also accessible through the Advanced Menu.