Zinsco Electrical Panel & GTE-Sylvania-Zinsco Circuit Breakers Failure Mechanisms
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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

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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 (see ZINSCO OVERHEAT IR PHOTOS), 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 electrical panel overheating (Jon Bolton) - infrared photographs - see ZINSCO OVERHEAT IR PHOTOS.
Photo 2: A Zinsco panel bus, showing scratch and oxidation marks
Photo 3: A Zinsco double pole breaker in-place, with the electrical panel bus exposed
Photo 4: A Zinsco breaker side blowout, exposed breaker contact exposed in the electrical panel
Photo 5: A Zinsco breaker side blowout-2, exposed breaker contact exposed in the electrical panel
Photo 6: A Zinsco electrical panel bus bar burn marks, exposed by partial-removal of circuit breaker
Photo 7: A Zinsco burned panel bus bar, blown-out circuit breaker, and arcing debris on other circuit breakers - partial disassembly
Photo 8: A Zinsco main panel , below you can read the case report April 25, 2003 below
Photo 9: A Zinsco burned circuit breaker , case report April 25, 2003 below
Photo 10: A Zinsco double-pole thin style breaker, light green toggles
Photo 11: A Zinsco copper bus bar burn, in a Zinsco electric panel using copper busses
Photo 12: A Zinsco circuit breaker with burned contacts , closeup
Photo 13: A Zinsco circuit breaker with burned case, closeup side view
Photo 14: A Zinsco circuit breaker with burn and arcing flash marks, side view at the Zinsco electric panel
Photo 15: A Zinsco circuit breaker with burned, broken case, closeup
Photo 16: A Zinsco circuit breaker with burned, broken case , "clothes dryer quit working"
Photo 17: A Zinsco electric panel bus details , with what looks like a circuit breaker contact trapped on the bus
Photo 18: A Zinsco circuit breaker case damage, interior view
Photo 19: A Zinsco circuit breaker with burn and arcing flash marks,, side view at the electric panel
Photo 20: A Zinsco electric panel bus bar, showing pitting and burn marks
Photo 21: Zinsco burnt up main breaker -1
Photo 22: Zinsco burnt up main breaker -2
Photo 23: Zinsco burnt up main breaker -3
Photo 24: Zinsco burnt up main breaker -4
Photo 25: Zinsco main circuit breaker and buss damage -1
Photo 26: Zinsco main circuit breaker and buss damage-2
Photo 27: Zinsco breaker burn marks at copper bus damage
Photo 28: Bad copper bus damage behind a full size Zinsco breaker -1
Photo 29: Bad copper bus damage behind a full size Zinsco breaker -2
Photo 30: Zinsco breaker partly disassembled at site of copper panel bus damage
Photo 31: Burned outlet, Zinsco breaker no-trip-exterior, below you can read the case report May 04, 2005
Photo 32: Burned outlet, Zinsco breaker no-trip-interior-1, case report May 04, 2005
Photo 33: Burned outlet, Zinsco breaker no-trip-interior-2-burned wires, case report May 04, 2005
Photo 34: Zinsco Main Panel, case report May 04, 2005
Photo 35: Burned outlet, Zinsco breaker no-trip-burned wall at outlet, case report May 04, 2005
Photo 36: Burned outlet, Zinsco breaker no-trip-burned wall - 2, case report May 04, 2005
Photo 37, burned electrical wiring and receptacle, Zinsco circuit breaker did not trip, case report 2/20/2007 J. Shuma
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.

Zinsco burnup bus (C) D Friedman J Weissman

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ELECTRICAL INSPECTION, DIAGNOSIS, REPAIR
ZINSCO SYLVANIA ELECTRICAL PANELS
ADVICE FOR ZINSCO OWNERS
  ZINSCO SAFETY PRECAUTIONS
  SIGNS OF ZINSCO GTE SYLVANIA TROUBLE
IDENTIFY ZINSCO ELECTRICAL PANELS
IDENTIFY GTE SYLVANIA-ZINSCO PANELS
IDENTIFY ZINSCO SYLVANIA METER BASE
IDENTIFY KEARNEY PANELS
GTE-SYLVANIA-ZINSCO FAILURE MECHANISM
ZINSCO FAILURE PHOTOGRAPHS
ZINSCO FAILURE REPORTS
ZINSCO OVERHEAT IR PHOTOS
ZINSCO FAILURE REPORT PROCEDURE
  REPORT TO WEB AUTHOR
  REPORT TO THE US CPSC
  ZINSCO INSPECTION REPORT LANGUAGE
ZINSCO REPAIR ELECTRICIANS
ZINSCO REPLACEMENT PANELS
REPLACEMENT PANEL COSTS
ZINSCO WARRANTY & CONTACT INFO
REPAIR ELECTRICIANS

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 Jon Bolton, professional home inspector in central Florida, the INSPECTAGATOR for field photographs of Zinsco electrical panels and circuit breakers, including the no-trip burnup Zinsco photo used in this article. Mr. Bolton can be contacted at 407-678-HOME (4663) or by email jon@inspectagator.com. Mr. Bolton uses infrared imaging equipment in field investigations.

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

Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.

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)

* Safety Hazards and Safe Inspection Procedures for Electrical and Home Inspectors at Residential Electric Panels

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.

Ampacity of an Electrical Service: How to determine the electrical service size or ampacity entering a building

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.

Lightning Strike Risk Assessment, Protection Systems & Services

Multi-wire branch circuit inspection and defects

Rust and Corrosion in Electrical Panels, A Study and Report on Frequency and Cause for Electrical and Home Inspectors at Residential Electric Panels

"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.

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FAILURE MECHANISM - Failure Mechanisms for Zinsco or Zinsco-Sylvania Electric Panels and Circuit Breakers

Types of Zinsco Panel and Circuit Breaker Failures

FAILURE PHOTOGRAPHS - Zinsco Sylvania Electric Panel and Breaker Field Failure Photographs

Questions & Answers regarding this article

Ask a Question or Search InspectAPedia

Technical Reviewers & References

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair