Am doing repairs to hot tub circuit, ten year old gfci breakers faulty, in doing panel work noticed that the GE 150 amp main backfed breaker wasn't fitting with cover, in a newer eaton panel. Solar panels were added last to this service, and its got a older 150 amp full width main from a ge panel. on number 2 copper.
I know sometimes the engineering might make exceptions to main sizing in order to not overdrive the buss. I am by no means a authority on solar reasoning, It may have been a loaded ge service without any room for a 2 pole solar breaker? they installed a 200 amp Eaton panel and used existing ? 150 amp backfed main breaker, was number two copper ever used for 150amp service riser conductors, work looks ok, nothing stands out except that the main doesn't sit flat and that it is not same brand as panel, will look into solar contractor. but was trying to see when ampacities may have changed. or other exceptions to solar installs, El Cerrito California