The manuals are available on the Diezel website, depending on the models the behavior is different, you'll have all the references there.
I can speak about the Hagen, that I own: there are 3 loops, in that order: 1 switchable serial loop, 1 non-switchable serial loop and 1 non-switchable parallel loop. There's no CC control, just PC. I think only the VHX has CC control, to be verified.