Explanation of the Failure Mechanisms for Zinsco or Zinsco-Sylvania Electric Panels and Circuit Breakers
Zinsco Sylvania Electric Panel and Breaker Field Failure Photographs
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Here we outline the apparent failure mechanism involved with Zinsco and GTE-Sylvania-Zinsco electrical panels and circuit breakers. We include field photographs of Zinsco equipment failures from a variety of sources. This website discusses the electrical, fire, and shock hazards associated with Zinsco electrical components,
circuit breakers, electrical panels, including
certain Sylvania electrical panels and breakers which are in fact of the same product design and origin.
Our page top photo of a burned Zinsco main circuit breaker and burned greased Zinsco electrical panel bus was provided by Washington state electrician J. P. Simmons
FAILURE MECHANISM - Failure Mechanisms for Zinsco or Zinsco-Sylvania Electric Panels and Circuit Breakers
Our photo (left, courtesy of J. P. Simmons) shows the typical Zinsco or Zinsco-Sylvania electrical panel main bus damage from arcing.
Arcing and/or overheating, or a similar failure process occurs at the connection of the circuit breaker to the electrical panel bus damage the bus, the breaker, and the connection, making the
electrical contact unreliable and leading to equipment failure.
Circuit breakers become damaged by arcing or overheating. Damaged circuit breakers are unlikely to perform properly in response to
an overcurrent condition.
Aluminum electrical panel components appear to be an important factor in failures in this equipment
Moisture exposure appears to be a factor in failures in this equipment.
Types of Zinsco Panel and Circuit Breaker Failures
Circuit breakers may fail to trip in response to an overcurrent condition. This is a fire and shock risk.
Circuit breakers may "blow out" the side casing of the device in an electrical "arc explosion"
Circuit breakers may fail to drop power even when they are switched off [remains to be verified--DF] - that is, the breaker may appear
to be switched to the "off" position but internally it may still be conducting power to the circuit.
At OK to USE ZINSCOS? we report on a different viewpoint from a vendor who continues to market this equipment and feels that at its price point in the market this product is reasonable to use, and who opines that when Zinsco equipment fails (burnups, failures to trip) it is because it was "over-used" at too-demanding an amperage draw. Our view is that it is just under that condition that a circuit breaker should trip off.
FAILURE PHOTOGRAPHS - Zinsco Sylvania Electric Panel and Breaker Field Failure Photographs
Clicking on any of the thumbnails at left will display a larger photograph.
Zinsco failure photos #38 & 39: burned Zinsco circuit breaker, burned grey Zinsco circuit breaker with case side blowout, case reports Jeff Weissman, 3/7/2007 and 3/8/07. These photographs of Zinsco circuit breaker blowouts and bus connection burning in the Zinsco electrical panel make clear that a simple visual inspection of the panel, without disassembly, risks failure to discover damaged, unreliable components that may not be offering the overcurrent and fire protection intended.
SAFETY WARNING: only a licensed, trained electrician should remove electrical panel covers or remove and install electrical components in the panel.
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Additional technical contributors & reference sources for this article are listed below.
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Personal communication, J. Aronstein to D. Friedman, 3/6/2006
James P. Simmons: Personal communication and photographs used in this article series, J. Simmons to Daniel Friedman, 3/4/2006, 2/19/2008. Photographs contributed to this website by Jim P. Simmons, Mr. Electric, Licensed Master Electrician,
1320 Dayton Street SE, Olympia, WA 98501, 360-705-4225, Fax 360-705-0130 or by email to mrelectricoly@msn.com
Thanks to various electricians, home owners, and home inspectors for contributing the Zinsco Sylvania-Zinsco electric panel and circuit breaker field failure reports cited above.
Thanks to David Osborn, an alert home inspector, for helpful critique regarding the need for Zinsco/Sylvania electrical panel replacement, 4/27/06
Thanks to Joe Funderburk,
Alpha & Omega Home Inspections,
Hickory Grove, SC for his photos of a Kearney electrical panel. Mr. Funderburk is a NACHI member and home inspector who can be reached at jfunderburk@aohomeinspection.com or at www.aohomeinspection.com
Thanks to Texas electrician Jeff Weissman for contribution of photographs of burned Zinsco circuit breakers. 03/06/2007. Mr Weissman can be reached at jeffweissman@gmail.com or by telephone at 713-666-6605
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
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Recommended books on electrical inspection, electrical wiring, electrical problem diagnosis, and electrical repair can be found in the Electrical Books section of the InspectAPedia Bookstore. (courtesy of Amazon.com)
Aluminum Wiring Information WebsiteAluminum Electrical Wiring Hazards and Repairs: in-depth authoritative info, photos, documents including selection of proper vs. ineffective repair methods. E.g.: Ideal 65 "Twister" purple connector fails in field and lab testing with aluminum wire.
Circuit Breaker, a bad one fails to trip failure at aluminum bus-to-circuit breaker connection - field report and photographs
Electrical Panels, How to Inspect in Buildings, safety for electrical inspectors, electrical panel, fusing, wiring defects, defective products. Inspection Class Presentation
Federal Pacific Electric (FPE) Stab-Lok Circuit Breaker Panel Hazards Website - Latent fire hazards, in-depth authoritative research, documents, advice on Stab-Lok electric panel and circuit breaker failures and what to do when this equipment is found in buildings.
"Electrical System Inspection Basics," Richard C. Wolcott, ASHI 8th Annual Education Conference, Boston 1985.
"Simplified Electrical Wiring," Sears, Roebuck and Co., 15705 (F5428) Rev. 4-77 1977 [Lots of sketches of older-type service panels.]
"How to plan and install electric wiring for homes, farms, garages, shops," Montgomery Ward Co., 83-850.
"Electrical System Inspection Basics," Richard C. Wolcott, ASHI 8th Annual Education Conference, Boston 1985.
"Simplified Electrical Wiring," Sears, Roebuck and Co., 15705 (F5428) Rev. 4-77 1977 [Lots of sketches of older-type service panels.]
"How to plan and install electric wiring for homes, farms, garages, shops," Montgomery Ward Co., 83-850.
"Home Wiring Inspection," Roswell W. Ard, Rodale's New Shelter, July/August, 1985 p. 35-40.
"Evaluating Wiring in Older Minnesota Homes," Agricultural Extension Service, University of Minnesota, St. Paul, Minnesota 55108.
"Electrical Systems," A Training Manual for Home Inspectors, Alfred L. Alk, American Society of Home Inspectors (ASHI), 1987, available from ASHI. [DF NOTE: I do NOT recommend this obsolete publication, though it was cited in the original Journal article as it contains unsafe inaccuracies]
"Basic Housing Inspection," US DHEW, S352.75 U48, p.144, out of print, but is available in most state libraries.
Aluminum Wiring Information Website Aluminum Electrical Wiring Hazards and Repairs: in-depth authoritative info, photos,
documents including selection of proper vs. ineffective repair methods. E.g.: Ideal 65 "Twister" purple connector fails in field and lab testing with aluminum wire.
Electrical Panels, How to Inspect in Buildings, safety for electrical inspectors, electrical panel, fusing, wiring defects,
defective products. Inspection Class Presentation
InspectAPedia® Home & Site Map - Building & Environmental Inspection, Testing, Diagnosis, Repair, & Problem Prevention Advice: In-depth research & advice on diagnosing, testing, correcting, & preventing building defects & indoor environmental hazards. Unbiased information, no conflicts of interest.
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Photo 2: A Zinsco panel bus
Photo 3: A Zinsco double pole breaker in-place
Photo 4: A Zinsco breaker side blowout
Photo 5: A Zinsco breaker side blowout-2
Photo 6: A Zinsco electrical panel bus bar burn marks
Photo 7: A Zinsco burned panel bus bar, blown-out circuit breaker
Photo 8: A Zinsco main panel 
Photo 9: A Zinsco burned circuit breaker 
Photo 10: A Zinsco double-pole thin style breaker
Photo 11: A Zinsco copper bus bar burn
Photo 12: A Zinsco circuit breaker with burned contacts 
Photo 13: A Zinsco circuit breaker with burned case
Photo 14: A Zinsco circuit breaker with burn and arcing flash marks
Photo 15: A Zinsco circuit breaker with burned, broken case
Photo 16: A Zinsco circuit breaker with burned, broken case 
Photo 17: A Zinsco electric panel bus details 
Photo 18: A Zinsco circuit breaker case damage
Photo 19: A Zinsco circuit breaker with burn and arcing flash marks,
Photo 20: A Zinsco electric panel bus bar
Photo 21: Zinsco burnt up main breaker
Photo 22: Zinsco burnt up main breaker
Photo 23: Zinsco burnt up main breaker
Photo 24: Zinsco burnt up main breaker
Photo 25: Zinsco main circuit breaker and buss damage
Photo 26: Zinsco main circuit breaker and buss damage
Photo 27: Zinsco breaker burn marks at
Photo 28: Bad copper bus damage
Photo 29: Bad copper bus damage
Photo 30: Zinsco breaker partly disassembled 
Photo 31: Burned outlet, Zinsco breaker no-trip-exterior
Photo 32: Burned outlet, Zinsco breaker no-trip-interior-1
Photo 33: Burned outlet, Zinsco breaker no-trip-interior-2-burned wires
Photo 34: Zinsco Main Panel
Photo 35: Burned outlet, Zinsco breaker no-trip-burned wall at outlet
Photo 36: Burned outlet, Zinsco breaker no-trip-burned wall - 2
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