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Why are Zinsco and Sylvania-Zinsco electric panels a problem?

Sunday, July 29, 2018

Zinsco panels, like the one shown above, use a clip-on connection between the breakers and aluminum bus bar. They have a higher than usual rate of failure, due most often to loosening of the connection between bus bar and breaker. When this happens, it causes arcing and overheating in the area, which leads to melting of the metal, with breaker permanently welded to bus bar and impossible to remove. Secondary problems are failure of the breakers to trip under an overcurrent event and cases of a tripped breaker continuing to be energized.

    The Zinsco company was sold to GTE-Sylvania in 1973, which continued to manufacture the Zinsco panel design under the name of Sylvania-Zinsco.  It was also sold under the Kearney brand name. But the design was eventually discontinued, and later Sylvania panels do not have the problematic Zinsco design.

    There have been no recalls of the Sylvania-Zinsco panel, and it has not been made for many years now. We occasionally see these panels, still in use and not experiencing any problems after we examine them with an infrared camera for hot spots. However the high failure rate means that most home inspectors (including us) recommend that any of them still in service be examined by an electrician for defects, which are not visible unless the deadfront (front cover plate) is removed, along with multiple breakers, in order to examine the bus bar and back of breakers. We DO NOT recommend that you attempt to examine the interior of the panel yourself. You might also consider replacement of a Zinsco panel as a safety precaution, based on its checkered history, and that is what some experts recommend.

   Another panel of the same era, the “Stab-Lok” made by Federal Pacific, was found to have fraudulently obtained UL-approval of their panel design and eventually went out of business due to lawsuits related to fires caused by equipment failures. Although Sylvania-Zinsco panels should have a safety examination, the standard recommendation for Stab-Lok panels is replacement. See our blog post “Who is the manufacturer of those ‘bad’ electric panels” for more information.

    Challenger brand panels have also gone on the uninsurable list in the last few years, due to overheating of the bus bars. See our blog post Why are Challenger electrical panels not insurable? for more on this.

Here’s links to a collection of our other blog posts about ELECTRIC PANELS:

What causes copper wires to turn green or black in an electric panel?  

What is the maximum number of circuit breakers allowed in an electric panel?

When should a corroded or damaged electric panel cabinet or disconnect box be replaced? 

What is a tandem circuit breaker? 

When did arc fault circuit interrupter (AFCI) breakers first become required?

Can an electric panel be located in a closet? 

Can an electric panel be located in a bathroom? 

Can you add circuit breakers by different manufacturers to an electric panel if they fit?

My circuit breaker won't reset. What's wrong?  

What is a split bus electric panel?

How do I identify a combination AFCI (CAFCI) circuit breaker? 

What does a circuit breaker with a yellow or white test button indicate? 

What is the maximum gap allowed between the front of a recessed electric panel box and the wall surface surrounding it? 

What are the requirements for NM-cables entering an electric panel box?

Why is a fuse box/panel an insurance problem for homebuyers? 

Why is bundled wiring in an electric panel a defect?

What is the difference between GFCI and AFCI circuit breakers? 

Why are old electrical components not always "grandfathered" as acceptable by home inspectors?

What happens when you press the "TEST" button on a circuit breaker in an electric panel?

What is a Dual Function Circuit Interrupter (DFCI)? 

What is the difference between a Combination Arc Fault Circuit Interrupter (CAFCI) and an Arc Fault Circuit Interrupter (AFCI) circuit breaker?  

What is the difference between "grounded" and "grounding" electrical conductors? 

What does it mean when a wire is "overstripped" at a circuit breaker?

Why is an old fuse panel dangerous?  

Who is the manufacturer of those "bad" electric panels?

Why is the circuit breaker stuck in the middle? 

What is a double tap at a circuit breaker?

   Visit our ELECTRIC PANELS page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles. 

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