I am familiar with the type of panel you described, however this panel has 2 sets of 2 pole bars. It has a 100 amp double pole breaker on the left and a 100 amp double pole on the right. But come to think of it, does the 2nd set just bar over to the 1st? The 2nd 100 amp main would just more of a switch to service that side of the panel. I'll have to look at it again. I just seem to remember it having 2 independent 100 amp 2 pole bus bars. Thought maybe it was that erra's form of a 150 or 200 amp service. Currently 1 100 amp main contains an A/C, 1930's lighting panel, and general circuits. The 2nd 100 amp main has another A/C, an oven, Driveway heaters, and other general circuits. He wants to just swap for a main the size of the existing feeders. However with all those appliances it exceeds 100 amp estimated load. But with the way the existing panel is, the house has been fine but with the 2 double pole 100 amp breakers allowing over 100 amps to pass through. The wire has got to be bigger than 4, thought it was larger than 2. That's why I thought maybe #1 aluminum. But did they even have cloth covered aluminum wire in the past? Thanks

I remember helping someone replace a panel before I had any electrical experience myself who 'knew what they were doing.' They just taped the entrance cables and said 'that will be good enough' and when he was jerking.. I am not joking jerking on the old box to get it off the entrance cable the tape came off. We had been standing in a dark utility room area of the basement which became lit like like 1,000 of them flashing firecrackers. He called and had the meter pulled after that event.

If you "know the answer," what information are you seeking? Are you saying that your panel is simply so old that you can't find replacement breakers? I find that hard to believe. There are breakers out there someplace. If the panel and wiring inside are otherwise in good condition, forget the big box stores and go to an electrical supply house for breakers. Or are you saying that your electrical service capacity is inadequate? If that's the case, then you most certainly will need an electrician and/or an electrical permit and inspection. A service upgrade typically is NOT a job for even the most skilled DIY'er.

bob_the_farmer, similar here - I've been wearing my "electrician" hat quite a bit lately, but electronics would be my home field. Welcome to the world of career crossover. Today I also got to play carpenter. I hate pretending to be a plumber. :P General idea in all of this is that ground and neutral never get broken anywhere. If you turn off every switch in an entire building, all of the neutral wires will still be connected to each other, and same with the grounds. Only switch hots - ever. Actually I try to carry that over into electronics as well. :)