Oh dear. Immediately makes me think of that Finnish hack some time ago to turn down thermostats from the Inet. That is what you get when plumbers go IT … (excluding Vincent, of course ;-)).
Does Viessmann support EEBus by now ? Vaillant claims they do.
PS: @Walters sorry for capturing the thread, but your request does not seem to have anything to do with openHAB at all and lacks quite some required information anyway.
(see How to ask a good question / Help Us Help You - Tutorials & Examples - openHAB Community)