
Weird Primary Secondary Schematic
I know it doesn’t look like your typical arrangement, but can this work? Really the decoupler/bypass would make a lot more sense if it skipped the chiller headers entirely.
Orange highlight is what I see as the secondary loop. Blue is what has effectually become 3 isolate primary loops.
Ignore the black lines, they denote a physical separation where air cooled chillers were added to the system outside. Chiller 3 and P-1 thru P-4 all live in the mechanical room.