Wire capacity of service panel

[nizak]

What determines how many and what size conductors can be fit into a panel? I know that the lugs (mains, neutral bar, equipment ground bar) all have minimum and maximum sizes predetermined. My question is where in the code does it spell out the actual physical amount of conductors that can be in there.I am looking at using a hybrid 200A 120/240V single phase main breaker panel that incorporates an automatic transfer switch built right in it. The product spec sheet says that it is ETL listed and meets NEC wire bending space. My concern is that it will have (3) 2/0 conductors for the mains and neutral,(3) #3 conductors for the generator feed, (3) #3 conductors + EG for a sub feed to the basement and then the branch circuit conductors (approx. 20 NM cables #14-#10). I guess this question could be asked about any conventional panel as well. I had one person tell me that the neutral bar spaces determined the amount and size of the conductors, but with that being said you can purchase additional bars and add them into the spaces that are provided in the can. Any help appreciated.

 

[infinity]

If you have no splices or taps you can occupy 40% of the gutter space. IMO it's pretty hard to exceed 40%. {312.8}