This "split-bus" panel typically has 6 double-pole breakers as the "power section" feeding the range, dryer, AC, etc. Also, a 50 or 60 amp breaker to feed the "lighting" section in the top half. Used in this manner, it would meet the "six operations of the hand" rule with regard to Servive Disconnect.
However, if it is considered a lighting & appliance panel (which it probablty is) it would require a main.
Correct?
