I am buying a house and at some point in the past they installed or upgraded the HVAC. I think because they ran out of room in the two panels in the basement, instead of upping the number of circuits in the boxes they tied in a stand alone for just that one item on the supply/service side of the main breaker. I have looked in uglies but it only covered past the main in the rules.

Do I just need to have the elec cut for a day and upgrade the two panels to larger and then run the HVAC on a regular line? I'm comfortable enough with wiring it all up just not sure if it is good as is or must change since the HVAC technically isn't behind the main breaker.