If I enable The ViCare single room control solution, what is the master device? My heating unit or Vitoconnect?

When The ViCare single room control solution is enabled and working, the control over the temperature and Time Programs is realized by Vitoconnect and accessible via ViCare application. All changes made on the heating device will be overwritten by application settings whether the Internet connection is secured and working or not.

Only if Vitoconnect is disconnected from the heating device, the changes on the heating device are accepted. When connection is back, the settings will be back to what was set via your ViCare account.