Central MVHR with peak lopping

[PennyCarey]

Hi all,

So I'm modelling a Passivhaus project so I have a central MVHR system providing constant fresh air at various rates to a number of zones (this I can control no problem individually), however, I have transfer ducts between zones and I'm extracting from different zones than I'm supplying to and they all go back to the central MVHR unit to allow and overall balanced system.

HVAC deals with individual zones very easily when you supply and extract to the same zone, but I can't think of the best way to model the common CAV system which has a peak lopping cooling coil available on it and supplying and extracting from different zones. I've tried it just using ApSys, but it's almost definitely oversizing the losses and I want to be able to control the flows correctly. Any ideas anyone?

Thanks
Penny