Can someone explain to me the NEC rules on sub panels? What I want to know is the maximum amount of panels if any and maximum size(amps) of each. Example: 200A service and client wants 2 100A subs off of this. Can this be done this way and meet code? Please clarify Thanks
H2O, there is a "six switch rule" but that does not have any effect on the number of sub-panels allowed.
With a few exceptions the six switch rule means you must be able to kill the entire building by opening no more than six switches.
As an example if you had a building with a single 200 amp breaker as the service disconnect you would only have to open that one switch in order to kill the entire building regardless of how many sub panels where connected to it.
Think about a very large building, there may be hundreds of sub-panels located throughout the building. But at the service entrance there will be no more than six switches to kill the entire building.
Bob Badger Construction & Maintenance Electrician Massachusetts