Well thanks for the response everyone, I have a follow up question.
I go to a house that has a 100 amp service that is in excellent shape, the load is OK but I do not have enough spaces for all the circuits.
Example 1) Why can't I just change the panel to a 200 amp 42 circuit panel leaving the 100 amp service conductors?
Example 2) By using 230.90(A)(1)Exception No. 3 I could leave the existing 100 amp panel and add one right beside it.
I do not understand the logic here?
How is example 2 any safer than example 1
Thanks, Bob
