What I have is an added 2 car garage with a game room added and connected to the main house. Problem is the main service had to be moved to the exterior of the new garage. I picked up this job after someone else bailed on it. Anyway its been decided to put all the existing circuits into a 200a sub about 50ft from the main service. Also the main has been upped to a 400a panel with a 300a main breaker. That's what the inspector came up with due to previous load calc on the old service.

Question: does this sound reasonable and if so what size feeder should I use? What size breaker do I use at the main? This is a 2200 sq ft home and a 1200 sq ft addition. All new homeruns will come from the new main. Inspector also said to put a 200a main lug breaker on the sub. Help.

If I follow this correctly, the calcs show that he existing circuits need a 200 amp panel, with a 200 amp breaker at the meter/main, leaving 100 amps capacity for the new addition.

The 200 amp sub can use #4/0 aluminum, 4 wire SER cable, as a feeder.

Next you need branch circuit capacity at the meter/main for the remaining 100 amps to be used for the new addition.

Did I interpret this correctly?

Are you an electrician?