My main 200 amp panel has the neutral bus bar and the equipment ground bus bonded. I am running 2/2/2/4 al wire to the 100 amp sub panel. The neutral bus and the equipment ground bus are not bonded on the sub panel. Can the equipment ground bus bar be mounted directly to the metal panel box? Also, can the panel box be mounted directly to the metal building frame? The main panel and sub panel are on two seperste buildings.
If an inspector is particularly picky he can insist that only the ground bars listed on the panel instructions be used, mounted as instructions say.
The panel can be mounted on a metal building frame. You must create a grounding electrode system at the detached building and bond the metal structure to the electrode system.
At best #2 aluminum is only good for 90A, and only 75A if you have 60°C conditions. You can use a 100A (or larger) panel, but you will need to feed it with a smaller breaker.