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Zinsco was a manufacturer of circuit breakers and electrical distribution panels, founded by Emile Martin Zinsmeyer and his son Martin Emile Zinsmeyer in the early 1930s.


Zinsco was originally the West Coast division of the Frank Adam Electric Company, whose main facility was in St Louis, Missouri, the company became independent as the Zinsmeyer Company following the onset of the Great Depression. The younger Zinsmeyer took over the company from his father in 1943 and renamed it Zinsco.[1] The company was sold in 1973 to GTE-Sylvania, who continued to manufacture breakers and panels to the original Zinsco design for some years; this product line is now discontinued.

Zinsco electrical equipment is considered obsolete, due to a design flaw in which the circuit breaker's connection to the bus bar becomes loose, causing arcing and subsequent overheating. Long term exposure to this heat can cause the breaker to fuse to the bus bar, making it impossible to remove. Even worse, it can cause the breaker's contacts to fuse together, thus preventing the breaker from tripping even in an overcurrent situation, thereby causing a potential fire hazard.[2]

Aftermarket replacements for the Zinsco breakers are available; however, it may be more cost effective simply to replace the entire panel with a more modern and safer design from another manufacturer (such as Eaton, GE, Siemens, or Square-D), depending on the number of breakers to be replaced. If the bus bar shows signs of corrosion, or if any of the breakers show signs of overheating, the panel should be replaced entirely. Many electricians advocate replacement of the panel in any case, due to its historically poor reliability.

Manufactures of Zinsco Style Breakers:


3 How to Identify Zinsco Circuit Breakers with Pictures