Why Didn’t My Circuit Breaker Trip?

melted receptacle
Over the years I have advised customers to get rid of Sylvania, Zinsco and Federal Pacific Electrical Panels. The most serious reason is that often the breakers won’t trip. Last week we had a Zinsco 20 Amp Circuit Breaker that did not trip on a dead short. We were able to shut it off but only after several seconds. Smoke was everywhere and the wire insulation and the receptacles were melted. (The wire and receptacles had to be replaced) Please get rid of these panels!