If I'm not mistaking, I think the pack 1 supply first the cockpit, and pack 2 the fwrd and aft cabin.
Then the air is sucked out of the different zones and recirculated via the cabin fan to the mixer unit.
I do agree that when looking at the AC diagram, it's a bit confusing. (not obvious at least)
(Don't pay attention to my above comment, I'm wrong)
Last edited by Feather44; 23rd Apr 2017 at 03:15.