How do I lock the thermostat screen to prevent unauthorized changes?

Screen locking is configured via ISU 435 in the Installer Setup menu, with three options: None (fully unlocked), Partial (user can modify temperature settings only), 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 — you should note this code in a safe place for future reference. (Page 14)