All (3) chillers have MCA=321A and MOP=450A.

I know that branch circuits to each chiller in new panelboard will require 450A breaker with 350MCM feeder.

For the new feeder circuit to this panel I know that the feeder calculation will require 125% of largest motor plus 100% of all other motors. Since the MCA value for each chiller already inclues the 125% of largest motor for each chiller would that not be overkill to use MCA for each chiller in feeder calculation since you'd in essence be including the 125% of largest motor (3) times?

I would think that the correct calculation for feeder would be to use the RLA of (2) of the chillers (100% motors) and then use the MCA of (1) of the chillers in order to account for the 125% of largest motor as well as 100% motors in 3rd chiller?

If the RLA of the chillers is not given would a conservative approach be to just use the MCA of each chiller in feeder calc? So new feeder would require 321A x 3= 936A. New Feeder circuit would require 950A with (2) sets of 750MCM (or (3) sets of 500 MCM)