This box has a capacity of 150A. The breakers in the upper section are as follows:
Left side upper: RANGE 60A, AIR CONDITIONER 40A, MAIN 60A
Right side upper: MICROWAVE 20A, FRIDGE 15A, KITCHEN LIGHTS 15A, DRYER 40A ["dryer" circuit is actually unused since we got a gas dryer]
The bottom section of the panel is controlled by the 60A "MAIN" breaker, and contains all the general use circuits in the house (all 15A, I think).
I would like remove all the breakers on the upper right side, and replace them with two 100A breakers controlling two subpanels. So, there will be only 5 double breakers in the upper portion--the three currently on the left and the two new 100A breakers on the right.
One of the subpanels will hold the 3 smaller circuits currently on the top right of the main panel (Micro 20A, Fridge 15A, kit lights 15A) plus a dedicated 20A circuit for an electric fireplace insert and 3 or 4 additional 15A circuits for general lighting and plugs for a basement remodel.
The other subpanel will go in the garage and contain a 30A circuit (garage workshop heater that will have intermittent use only in the winter), a 40A circuit (electric vehicle charger--intermittent use, mostly during the wee hours), and a 20A general use circuit. I don't envision the 30A and the 40A ever being used at the same time.
So, based on that background, a few questions:
Given the load on the left side of the upper main panel (two 60A and one 40A), will the two proposed 100A subpanels overload the 150A main box? (Note that one of the 60A is for the range, which has intermittent use, and the 40A is for the AC, which will never be used at the same time as the 30A heater in the garage or the 20A electric fireplace insert.)
If the proposed 100A subpanels will overload the main box, can I use two 60A subpanel breakers instead, or will they overload the main box?
If I end up using a 60A subpanel for the garage, will the use proposed above (30A, 40A and 20A--with the 30A and 40A not used simultaneously) overload a 60A subpanel?
I appreciate any thoughts.