AskCodeMan

JP,

Seeking your observations about the historical concerns about Zinsco and/or Sylvania-Zinsco panels. (I believe Sylvania bought Zinsco toward their end).

Mostly problems related to the buss bars from what I understand and not a situation where "breakers" would fall out.

Hi Nolan,

Correct, Sylvania bought Zinsco, but I'm not sure how close to the end of Zinsco's time that was.

The problems with Zinsco panels are the bus bars, but not confined to the bus bars, the problem was a combination of the bus bars and the breakers and their contact with each other.

My best explanation I've come up with of a cause to the overall problem is two-fold:

1) The aluminum bus bars were plated or coated with a material which was too thin and failed prematurely.

2) The breakers with their long slots and contacts for the bus bars, combined with the angle metal bus bars, were made for the breakers being pushed straight onto the bus bars, however, because the breakers first had to be hooked under the retainer, the breakers had to be rotated onto the bus bars instead of being installed straight on. This cause/created unexpected premature wear of the breaker contacts and the bus bars, which caused arcing of both contacts points (the breaker contacts and the bus bar contact points), which would in many cases cause poor connection between the two leading to overheating of both, often resulting in the failure of both, with the bus bar melting/arcing/burning away. I have seen Zinsco bus bars burned mostly in two, and several burned complete in two, where someone (homeowner?) installed a breaker on each side of the burned through gap and fed the now isolated bus bar from one breaker on the hot bus bar to the other breaker on the isolated bus bar, acting as a back fed main for that isolated bus bar section thereby energizing the other part of the burned through isolated bus bar.

With FPE panels, the breakers are known to fall out when the dead front cover is removed.

With Zinsco panels, the breakers are known for sometimes only being able to be removed from the bus bar by breaking the breaker into pieces and peeling its contacts off the arced and burned up bus bar. I had one such Zinsco panel in a house I once owned, and every breaker 30 amps and higher rated could only be removed by breaking them apart and peeling them off the bus bar - after replacing the panel, of course. Naturally, the bus bar was in no condition to be reused.