I am considering adding a 50A-60A sub-panel in my 6ft basement/crawlspace, to increase number of branch circuits I can run, and ease the running of some dedicated circuits. I am probably at least going to consult with a licensed electrician for this, if not having them install, but I like to have some idea of what I am talking about before doing this.

(I have done this before (30A) in a different situation). For this situation, I have an older 120A main, that has only a few spaces left (space for 1 larger double pole breaker (above the main shut off), and space for one smaller double pole breaker (slave to main shut off)).

A few questions: if the breaker for the sub-panel is "above the main", does it matter if my overall load (sub plus main) exceeds that of the main (that is, if I have a full main, and then a 60A sub, this is OK?)

Second, the sub will basically be there to run a bunch of kitchen branch circuits: ventilation, hot water, disposal, dishwasher, 240V steam oven. I could also put a built-in oven on it (needs 30A 120/240 connection to panel), if that were possible. What are the rules for determining what/how much I can have on this sub? What devices are considered "ON", verses a % usage?

thanks for the input.