Holy cow, it took a minute to realize what I was seeing there. An old panel used as a junction box! I wonder what the derating factor on all those conductors coming through the back should have been! What a mess. Glad to see it look like someone is going to clean it up.
Just my observation...those wires into the original panel look like they've taken quite a beating. I see a couple of spots where the insulation has been scraped off. I wonder if a J-box somewhere nearby for these circuits is in order, with new runs to the new panel? At least it would hold down the wire-nut count in the new panel.
BTW, In my part of the world, I have never seen a split-bus panel such as this with two separate lighting/appliance sections. Were these very common? Was there some kind of advantage to having a panel such as this, or is this just an older technology?
#168262 - 08/30/0712:05 PMRe: Johnny, show 'em what's behind panel number 1!
150 amp and larger split bus panels were available with two separate lighting sections, but they were not very common. I've only seen maybe a dozen of them in my 30 years in the business and they were usually being removed. Split bus panels have become so rare nowadays, that newcomers to the industry have never seen them. That's probably a good thing. I tend to think that most of these panels were 100 amp with a single lighting section. Many people who aren't familiar with them often question why they were ever made. On that note, I'll throw in my two cents worth about them:
The real reason for split bus panels was to reduce the cost. 60 amp breakers and below are relatively inexpensive in comparison to 100 amp and above. By using a 60 amp "lighting main", plus the various five other two-pole breakers in the "main" section, the need for a large main breaker is eliminated. Remember that it's legal to have up to six disconnecting means on a service. This setup makes the other two-pole breakers become service disconnects instead of branch breakers. Again, it was all just an effort to eliminate the cost of a main breaker.
Supposedly, the only breakers that were allowed to be in the main section were ones for larger loads, such as ranges, air conditioning, heating, dryers, etc. The problem with these panels was that Harry Homeowners would see these vacant spaces and assume that they could use them for their own branch circuits. By using single-pole breakers in these spaces, it was possible to have as many as ten disconnects (branch circuits) IN ADDITION to the two-pole lighting main.
Then, there was also the misconception that turning off the "lighting main" killed power to the house. People didn't realize that all breakers in the upper section of the panel had to be turned off to truly kill the power.
Ed: Thanks for the information you gave. I'm familiar with the the "six throw" rule, It's just that I assume the intent of the rule is to allow the homeowner a means of quickly shutting off power in an emergent situation. I wonder if the homeowner would easily know which breakers to open, given the circumstances. And, as you said, someone not knowing what's legal could fill up the remainder of that upper section with single pole breakers (and maybe even tandem breakers at that?) and throw the rule out the window.
The modern method of employing a single main disconnect is quite an advance in several ways.
#168297 - 08/31/0710:25 AMRe: Johnny, show 'em what's behind panel number 1!
I'm with you on that, Mike. A homeowner may understand a single main, but not a split bus panel. It's a bit much to expect in my opinion. If there was an emergency, are they really going to sit there and study the panel legend to find out which breakers are mains? I think not.
Gosh, I don't even want to think of the main section filled with tandems!