If you have a Federal Pacific breaker box in your home you need to be aware that this breaker system was poorly designed from the beginning thus they did not survive very long in the market place. They have a history of not tripping at their rated values. They were very inconsistence and some would not trip even when the steady state current was as high as 150% of its rated value. Not good!
There is a lot of information on the internet about this problem that goes both ways so you need to read up on it and make your own judgment to replace your system with a modern one or not. Even though it can be costly to replace, please keep in mind when you are making your decision that the main function of the breaker box in your home or office is to shut down when a problem is present to prevent equipment damage and or fire. Given the track record of the Federal Pacific Stab-Lok breakers, this is nothing I would want in my home or any member of my family.
So take a look at these breakers and if yours look like or similar to these, consider budgeting the money to get it replaced before it’s too late.
Zinsco Breakers also known as Challenger or Sylvania are included in this list. They are not quite as bad as the Federal Pacific when comparing trip values but they still do not always trip when and where they should.
The more serious problem they suffer from is a very soft connection point and soft main bus. This causes arcing to the point that a solid electrical connection can’t always be maintained and they heat up, self destruct and destroy the main buss at the same time. Once that occurs, that breaker location on the buss will never be able to be used again.
Here is a picture of Zinsco breakers. As with the Federal Pacific, you might not want them in your home since they are not 100% safe.