are all pushmatic panels 100 amp and where to find that info on it ........second can it b replaced with a regulatory 100 amp service any guidance would b most appreciated
Welcome to the Forum.
A lot of Pushmatic panels were installed in the decades when the "split bus" design was very popular. This, in many ways, was a cost containment tactic developed as the required minimum service size was changed from 60 A to 100 A. The 100 A main breaker came at a premium price, compared to the commodity 15 - 60 A breakers prices.
The Split Bus panel has positions for up to six service disconnects. One is used to power the second section of the panel, the "Lighting Section", where most of the general lighting and small appliance circuits are located. Large double pole loads, such as the electric range, electric clothes dryer, electric water heater, central air, etc., would be installed in the "Service Disconnect" section.
The size of the service entrance conductors was determined by the calculation for the dwelling, plus whatever additional size the installer wanted to add above that minimum.
Upshot: If your client's panel is a Split Bus, no breaker or label on the panel will indicate the rated service entrance ampacity. One has to know the service entrance conductor guage and insulation class and date of Code that the installation was under to be able to look up the rated ampacity.
I've seen a lot of 125 Amp services over the years, in my geographic area, in the guise of a panel, that at first glance, appeared to be main lugs only, but upon closer examination had up to six service disconnects, none larger than 60 Amps.
