Thermostat displays B9 and cannot access certain configuration menus; installer lock is active.

Safety first: No electrical work is required.

• Enter installer PIN: If you are the installer or have been given the PIN, enter it to unlock the restricted menus.
• Use user menus only: For normal operation, use the standard user menus and app controls, which remain available even when installer lock is active.
• Reset PIN (installer only): If the PIN is lost, an installer may need to perform a factory reset or use Viessmann tools to reset access.
• Contact original installer: If you are the homeowner and do not have the PIN, contact the company that installed the system.