Been a while since initial post/inquiry, so figured I'd update those interested .... "finally" after umpteen visits from umpteen HVAC techs we have a heated 20 x 24 family room that really is "heated". Were lucky enough to track down a Buderus "expert" that really knows this complicated system (w/o asking for my users manual). Most importantly, he listened to us & didn't act like we were talking crazy.
After a lot of looking, talking and photo taking, said the new boiler piping wasn't done properly and the hot water that was suppose to be flowing directly to the family room, was actually coming by way of the bedrooms, at times flowing in reverse. Has anyone ever hear of such a thing? He said its actually a fairly common mistake.
After a couple of hours of repair work - re-piping and a some kind of "flow valve" that prevents water flowing in reverse, we have a warm family room - tstat is set @ 68, room is 68, and stays @ 68. The upstairs bedrooms are now regulated by the main house tstat (as they should have been) - set @ 64 and they're at 64. He also adjusted the heating curve (said prior HVACs had it set incorrectly).
Amazing ......... now we'll see if this $$$ system saves any $$$ or not ... its only been 5+ years in the making.