Im installing one 400 amp MCC and one  later in the year. I want to run 4" emt to a junction box and catch the first MCC with 3" emt out of the first junction box. I will then run 3" emt to the other MCC later. The wire sizing that I come up with is 250 mcm paralleled for each phase. The first 100 feet of  emt will have both MCC conductors then will branch out to each MCC.
	
		
			
		
		
	
				
			 
				
 
 
		 
 
		 
 
		 
 
		