Zinsco Electric, which manufactured electrical panels, circuit breakers, bus ducts, and transformers from 1891 to 1984 through its Zinsco brand name has been identified as having a design flaw that can result in hazard risks associated with the systems they serve.
Due to a nationwide copper shortage in the 1960s, Zinsco Electric changed from a copper bus to an aluminum bus in its manufacturing process. The aluminum selected for the change (Alloy 6061, first developed in 1935), was ultimately found to be prone to electrical oxidation along with tremendous expansion and contraction issues. Oxidation of aluminum creates aluminum oxide, which insulates rather than conducts electricity. This caused numerous fires, outlet burn-outs, and deaths per the NFPA.
Zinsco electrical equipment is now considered obsolete due to the above mentioned design flaw which leads to the circuit breaker’s connection to the bus bar becoming 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, resulting in a potential fire hazard.
Zinsco products produced prior to the mid-1970s do not meet current safety codes and would not receive the UL listing required for safe installation and use. Therefore, Zinsco circuit breakers and busbars do not meet the current UL requirements.
Zinsco labels are blue and white, green and white, or blue and silver. However the label on the circuit breaker or panelboard may or may not have the “Zinsco” name. The label may have an embossed “Magnatrip” logo which was the brand name of Zinsco products from the 1940s to the 1970s. Still, some circuit breakers do not exhibit any of these markers and may simply be a solid color designating the amperage of the circuit breaker.
In many locations, the Authority Having Jurisdiction (AHJ) does not allow the use of old Zinsco products. When the existing Zinsco electrical equipment requires modification, the AHJ mandates either replacing the existing Zinsco equipment with new UL approved electrical equipment or recertifying the existing Zinsco electrical equipment with UL.
Due to safety concerns, many property insurance companies also mandate replacing the old Zinsco electrical equipment with new UL approved electrical equipment.
Consistent with these AHJs and insurance companies, Elara Engineering continues to recommend the replacement of the old Zinsco electrical equipment with new UL approved electrical equipment. This recommendation is based on our experience as well as discussions with the City of Chicago and Chicagoland AHJs during the execution of multiple current and past projects.
For more information or to discuss possible next steps, please contact Principal Bhupendra Tailor (btailor@elaraeng.com).
Bhupendra Tailor
Principal
Electrical Practice Leader
btailor@elaraeng.com
