Determining Service size for house with two main panels

[wwhitney]

230.90(A) Exception 3 allows two 150A breakers on a 200A service so long as the load calc is 200A or less.

This is the correct answer. Given the above exception, if there is more than one service disconnect on a single service, adding the disconnect sizes does not give you the service size. Rather, you need to investigate all the equipment from the service point to the point where the service conductors divide, and use the lowest rating of those conductors/equipment.

Cheers, Wayne

 

[wwhitney]

There might be an issue with having two panelboards with 150 A mains as the protection for a 200 A rated cable

This is allowed per the above exception, and in this case the only overload protection for the 200A service conductors is the load calculation.

Cheers, Wayne