This Zinsco electrical panel article 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.
We include advice on how to identify Zinsco, Sylvania Zinsco, and Kearney electrical panels and circuit breakers, and repair or replacement advice for those products.
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Limited test results reported by Dr. Jess Aronstein (who is cited further at REFERENCES) indicate that the central Zinsco electrical panel and circuit breaker failure problem appears to be burn ups at the clip-to-bus connections such as shown in our photo of a burned Zinsco electrical panel bus and breaker. A circuit breaker whose bus connection burns can lead to overheating damage to the circuit breaker itself, rendering it non-functional.
For a summary of Zinsco and UBI-Zinsco-Replacement circuit breaker test results to date, see ZINSCO CIRCUIT BREAKER TEST REPORT - separate article.
Also see ZINSCO FAILURE REPORTS where we indicate that nearly 32% of the Zinsco circuit breakers tested to date failed to trip as required by the UL testing standard. A very small sample of UBI-brand replacement circuit breakers for Zinsco panels also failed to trip.
Photo at page top of a burned and failed Zinsco main circuit breaker, courtesy of J. P. Simmons - Mr. Electric. Simmons adds: "In this case the failure damaged the main wire to a mobile home also (you can see the melted wire to the left of the main). This is a good example of why I do not like to see anyone remove these breakers. You can not tell how bad they are damaged by looking at them.
Dr. Aronstein has agreed to perform independent overload and trip testing on Zinsco circuit breakers that may be contributed by electricians or homeowners.
In order to obtain a valid Zinsco circuit breaker set for testing, specifically wanted are circuit breakers from Zinsco electrical panels at which no field failure has previously been reported.
Such circuit breakers may be obtained from Zinsco electrical panels that are being replaced out of homeowner concern for potential hazards, obsolescence, or the need to install a new, higher capacity electrical panel - a "heavy-up" job. The circuit breakers should be left un-touched, that is, don't switch them off and on, just un-plug them from the electrical panel.
Contact: Dr. Jess Aronstein, "Dr. Jess Aronstein" <firstname.lastname@example.org>
With the exception of the more seriously failing FPE Stab-Lok electrical panels, we have not received any significant number of field failure reports concerning other electrical panel brands that also use aluminum parts and that are or were priced in the same range as Zinsco.
This means homes with this equipment may be at greater risk of fire or other electrical hazard.
Where Zinsco electrical panels and Zinsco circuit breakers are in use, arcing, contact-point burn, and even circuit breaker case blow-out have been observed in the field.
We do not have statistically solid data that supports an unequivocal argument to replace Zinsco electrical panels.
However, based on field reports to-date and preliminary tests, where Zinsco and Zinsco-Sylvania electrical panels are discovered in buildings a homeowner should consider replacing the panel to reduce fire and shock hazards and owners should be careful to avoid overloading their electrical circuits where this equipment is installed.
Building owners or electricians encountering problems with this equipment are asked to contact us to add that information to our electrical failure data base in an effort to develop accurate safety information which is then shared with appropriate federal and state agencies. Thanks to Mr. James Simmons, a licensed electrician with extensive field experience and the contributor of most of the photos and case reports at this web page.
Our photo (above left) illustrates a burned-up electrical receptacle whose circuit was protected by a Zinsco circuit breaker that failed to trip and in fact had burned itself in the panel.
A principal Zinsco™ circuit breaker (or Sylvania™ or GTE-Sylvania™ or Kearney™ electrical panel using this circuit breaker) point of failure appears to be at the point of contact where the circuit breaker contacts clip onto the electrical panel bus, combined with the use of an aluminum electrical panel bus.
As described at ZINSCO FAILURE REPORT PROCEDURE, expert testing on this equipment has shown that circuit breakers do not trip about 25% of the time when exposed to overcurrent - risking overheating, fire and other hazards. The failure rate of competitive-brand circuit breakers is much less than 1%.
In addition to advice on identifying Zinsco™ panels, inspecting Zinsco electrical panels, and repair/replacement
advice, we provide field photographs of
circuit breaker failures: overheating, burnups, failures to trip, overcurrent protection failure.
This document includes field reports of failures and additional
See ZINSCO FAILURE PHOTOGRAPHS and ZINSCO FAILURE REPORTS.
Repair advice (replace the equipment) is provided
at ZINSCO REPLACEMENT PANELS and
at REPAIR ELECTRICIANS we list electricians who have informed us that they have specific experience with this equipment. Lots of other licensed electricians are also qualified to replace electrical panels; it's best if your electrician is one who is familiar with this issue.
Replacement Zinsco circuit breakers and replacement copper-plated bus bars for Zinsco / Zinsco-Sylvania electrical panels are advertised. Without evidence of a design change in the product or support from independent expert testing, the effectiveness of these replacements is not clear.
As a not-for-profit activity, we have been collecting information and field failure reports for Zinsco/Sylvania electrical components since 1996 in an effort to develop credible failure-rate information which is then shared with the U.S. CPSC and with other electrical failure researchers and educators.
Manufacturers or vendors of Zinsco-style circuit breakers include
Mike Holt has provided excerpts of a history of Zinsco Electric quoting the company founder's great-grandaughter Heather Hill (un-dated). - http://codeforum.mikeholt.com/
Continue reading at GTE-SYLVANIA-ZINSCO FAILURE MECHANISM or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.
Or see this
Zinsco Electrical Panel Article Series
- ZINSCO SYLVANIA ELECTRICAL PANELS - home
- GTE-SYLVANIA-ZINSCO FAILURE MECHANISM
- IDENTIFY GTE SYLVANIA-ZINSCO PANELS
- IDENTIFY KEARNEY PANELS
- IDENTIFY ZINSCO ELECTRICAL PANELS
- IDENTIFY ZINSCO SYLVANIA METER BASE
- OK to USE ZINSCOS?
- ZINSCO CIRCUIT BREAKER INDEPENDENT TESTS - Notice: Zinsco circuit breakers are wanted for testing
- ZINSCO CIRCUIT BREAKER TEST REPORT
- ZINSCO FAILURE PHOTOGRAPHS
- ZINSCO FAILURE REPORTS
- ZINSCO OVERHEAT IR PHOTOS
- ZINSCO FAILURE REPORT PROCEDURE
- ZINSCO REPLACEMENT PANELS
- ZINSCO REPLACEMENT PANEL COSTS
- ZINSCO SAFETY PRECAUTIONS
- ZINSCO SUMMARY PAGE for Reproduction
- ZINSCO WARRANTY & CONTACT INFO
Or use the SEARCH BOX found below to Ask a Question or Search InspectApedia
Try the search box below or CONTACT US by email if you cannot find the answer you need at InspectApedia.
I am selling my house and just had an inspection done. I have a zinsco circuit breaker panel and would like to know is every model the same and are all of the circuit breaker panels a fire hazard risk? - Suzanne
Thanks for the important Zinsco breaker model question. We don't know if there are Zinsco-brand circuit breakers whose design is different from the ones discussed here (I don't think so), and we don't yet know if there are age or model differences among Zinsco circuit breakers and their performance, because not enough Zinsco breaker testing has yet been completed.
However it is reasonable to note that because the Zinsco failure reports we've received and physical inspection of that equipment focus attention on the bus and breaker-to-bus-connection design, unless your electrical panel uses a different circuit breaker and bus connection design than the models shown here, it would be prudent to treat your panel as a potential electrical fire and safety hazard.
I appreciate that nobody likes to have any question come up when selling a home. Fortunately, for this particular question, the costs unambiguous - they are confined to the electrical panel and circuit breakers.
House prices vary by region in the U.S. but taking the lowest current average price of $125,000, the cost of a replacement electrical panel should run around one percent or less of the home value - certainly that's not a cost issue that is substantial enough that it should jeopardize the sale.
How do I know if my Sylvania electrical breaker is a Zinsco? - Marie
How do I know if my Sylvania electrical panel is bad? - Wallace
Wallace: unfortunately it is not possible nor even safe to try to assure the safety of certain electrical problems by visual inspecting (you can't see hidden problems behind or even inside the circuit breaker) nor by testing in place the circuit breakers (you risk starting a building fire, and even a "tests-ok" breaker may fail the next time it is subjected to an overcurrent). Worse, testing in some cases (FPE in particular) can significantly INCREASE the chances that in the future the breaker will fail to trip.
For that reason, experts recommend replacement of FPE equipment. IN the case of Sylvania equipment, ... it depends. If your panel is Zinsco brand, previous burn-ups of breakers are physically visible on disassembly and inspection by an electrician where bus burns and breaker burns can be seen. But that inspection is no assurance that an un-burned component will work as needed in the future. For that reason we also suggest replacing Zinsco panels.
Marie: see IDENTIFY ZINSCO ELECTRICAL PANELS for help in identifying Zinsco brand electrical panels and circuit breakers.
Have a zinsco 100 amp service, turn the main off but still get power have very little cash. So I can't replace it at this time, if I replace the main, is it safe to still use this panel? Is it safe to add new breakers? - Tim
If you still have power when the main electric panel disconnect is in the "OFF" position then this is a VERY dangerous condition as you cannot, using normal homeowner controls, turn off electrical power in an emergency, and more, it is likely that the main disconnect is not going to trip on a large overcurrent and so is not protecting the equipment and building from an electrical fire.
I'd like to see photos of the equipment and all identifying labels and markings. Use the CONTACT link found at page top, left, or bottom to send us photographs.
Presuming that you don't have a back-fed panel from a second electrical source then you immediately need a licensed electrician to replace the faulty circuit breaker or as I would recommend, replace the entire panel.
"Replacement" Zinsco circuit breakers are certainly sold as well as entire panel bus assembly replacement parts using copper-plated bus bars that might perform better than the original aluminum bus bars - we have not seen any independent supporting study data that confirms that anticipated improvement.
A key ingredient in some Zinsco breaker burn-ups is arcing at the bus to breaker connection. It is difficult or impossible to see the arcing burns before the equipment fails, as disassembly would be required, and because every time a breaker is pulled and removed the bus and even a copper plated bus surface is cut and scratched further, we worry about increasing the arcing and failure rate by examining or plugging breakers in and out.
We might be tempted to say go ahead and replace breakers onto an unused bus position but as you have ALREADY had a very serious fail-to-trip in your Zinsco panel, continuing to use it doesn't sound safe to me. Also see DIRECTORY OF ELECTRICIANS - FPE Zinsco for electricians who assert that they are familiar with Zinsco electrical panel hazards.
I have a Sylvania panel on an exterior wall that simply has 100 amp service to the main breaker and then a single 100 amp breaker on the branch that leads to a new GE panel inside the house with its own 100 amp main breaker.
All power comes off of the GE panel. That being said, this seems safe as to take out the Sylvania I would just have a wire from the meter to the GE panel, which would provide no overcurrent protection anyway. With the Zinsco/Sylvania I have two additional breakers to try to trip if for some reason the 100 amp main in the GE failed, plus I can kill power to the GE panel from the outside if ever I needed to in case of a fire.
Does this sounds fine or is the Sylvania still a problem? - Bob Welderman
If I understand correctly, because you find that the outside Zinsco/Sylvania panel simply duplicates the main breaker on the inside panel you figure it's safe to leave it in place.
Here are some concerns with that approach:
1. The outside panel and breaker is protecting the SEC feeder wire between the meter and the inside panel. Depending on the inside panel distance from the meter and location and wire routing, that protection could be important and even code required. So you want that protection to be reliable. Though a problem with an indoor individual circuit is more likely, failures do occur on the SEC wire, including shorts and overheating that can lead to a fire.
2. Leaving in place a circuit breaker that has frequent bus arcing and overheating could be more dangerous than just the point above: the product you leave in place can not just fail to respond to an overcurrent, it can initiate a problem by overheating, arcing, burning itself.
First off. Thank you for the response. To be more specific. The wire from the meter to the Sylvania is about 4 feet and then the one from the Sylvania to the GE is about 4-6 feet as it is just on the other side of the wall. The breaker from the Sylvania to the GE is a brand new refurbished one that was tested by the electrical supplier about a year ago. - Bob.
Bob, in the arrangement you've described, it is the SEC between the Zinsco-Sylvania breaker and the new GE panel that is left unprotected should a short occur in that wire or should the main breaker in the GE panel fail to trip. I agree that the risk that remains in those components is likely to be lower in frequency than risks of the need to trip a circuit breaker protecting an individual branch circuit in the building. However, because of the chances of a higher current draw at a major failure in a panel or in an SEC, the protection of that wiring is very important. Indeed we attended a house fire that occurred in just those circumstances - an SEC or main panel short.
Just to be clear, the main switch protects equipment that is downstream from itself.
At this point, if I understand your schema, the service entry cable passes from meter to Zinsco-Sylvania breaker and from there to a main panel of another brand. So the risk of a no-trip or burnup in the service panel is less than before when Zinsco breakers were in use in that location.
Nevertheless, it's the main switch that does the heavy lifting when safety and shorts are concerned.
looking for two electric panel covers for zinsco 14" w x 20 L - Hank Vance
Hank, take a look at the article ZINSCO REPLACEMENT PANELS - This article describes replacement electrical panels and covers.
Sylvania Panel GRTE, 390-205-08, 380-025-15, e-52977, albiz (20-20)-c. Home Inspection comments this could be a recall item. Please advise 650-576-0777 Thank you, B Oliveira - 12/19/11
Brenda, I'm not sure what advice you are asking; please be sure to read the above articles on the hazards of Zinsco and Zinsco-Sylvania electrical panels and circuit breakers. Simply deciding on the presence or absence of a safety hazard based on whether or not there was a product recall is unreliable.
What is Sylvania-Zinsco's responsibility for a faulty product? Were there any recall notices? Is there any compensation for their faulty product? - G Butler 5/7/12
The assignment of responsibility for product defects is a legal and technical question that we InspectAPedia do not directly address. We report on building and environmental inspection, diagnosis, and repair topics with as much impartiality as possible. I agree that it's a fair question nevertheless, and as with other controversial product defects such as the FPE Stab-Lok hazard, we will report if there are product recalls or legal actions in the matter.
Keep in mind that in all fields there can be defective or hazardous products notwithstanding the existence of regulatory bodies and the court structure. By comparison, crimes occur even though there are law enforcement and a legal justice system.
Where to find licensed electrician for zinsco panel in my area - David Rue 5/16/12
David, ANY licensed electrician can replace a Zinsco electrical panel. The reason we like to use electricians who know about the Zinsco hazard is to avoid wasting time with someone who makes the mistake of telling you there is no possible hazard.
At DIRECTORY OF ELECTRICIANS we list some, not all, electricians who assert that they have experience with Aluminum wiring, FPE, and Zinsco electrical equipment repairs or replacements. There are no listing fees and InspectApedia has no business nor other financial relations with any topic or service provider discussed here.
I am a Master Electrician in Florida. I recently received a call from a customer who was having a new central A/C installed. The Installer told him that the Main 100A Zinsco breaker was turned off, but the house still had power. I assessed the situation, and told the homeowner he needed a service change. I would not even attempt to touch the service disconnect. I had the Power Company disconnect the power at the transformer, before I started.
When it was safe, I attempted to remove the old Zinsco breaker, and it crumbled in my hands. If someone had attempted to work the breaker they would have been subject to a terrific arc flash - burn - explosion. I,m glad I took the safety first approach. Hank Kline DeBary FL. - Hank Kline 7/15/2012
Thanks so much for your important Zinsco field failure report Hank. It illustrates how one real-world experience is worth a dozen arm-waving speculations from a few writers who think we've made the whole thing up. Glad you knew to be safe.
Indeed, though it was from a different root cause, a GA electrician was killed simply in the course of removing the cover from an electrical panel. The release of the cover screws allowed faulty components in that panel to move, shorting and causing an arc explosion that blew the cover and panel parts into him. I've also received reports of workers burned from situations such as the one you described.
If you come across iffy products like this again and have an opportunity to take a photo to show other readers it'd be helpful; also we welcome questions & content suggestions from everyone, but from an experienced master electrician your views are particularly helpful.
Is there a recall or some recourse from the company that manufactured the faulty Zinsco Electric Panel / Circuit Breaker? Do you have a contact for the company? Thanks! - Cynthia 7/23/12
Sorry, Cynthia, no.
I have a Zinsco Panel it is listed as a Sylvania but looks exactly like the photo above. I have a friend that is a electrician and told me he would replace the panel with a new square D 200 amp service. If I have the power company turn my meter off then no power will be running through the panel how is this job still dangerous? - Ryan 8/23/2012
If your electrician friend is qualified and knows what s/he is doing, and if power is dropped at the meter, the job MIGHT be not dangerous. I say might because an electrician who failed to confirm that power was off risks being killed by electrocution, and a time or two I've found that electrical power was not off when we thought it was.
The second hazard would be if wiring were not done correctly - which is therefore unsafe.
In sum, if the work is done by someone qualified and properly then the job is being handled properly.
We suggested they immediately get a licensed electrician to come out and replace the panel, but they just wanted to replace the breaker, worryingly enough.
The truly scary part, though, is that apparently this breaker was not the one that originally failed, it was set on fire by the failure of the adjacent breaker. One can only imagine what that one must have looked like, if there was anything left of it.
Feel free to include the photos in the Zinsco section of the website, if you'd like. I think I may end up making a display case in the store for this and a similarly failed FPE breaker. Maybe it'll give people a hint as to why we recommend that they replace these panels.
On a somewhat related note, I regularly recommend your site to customers with electrical safety questions, as does my father (a licensed electrician with over 40 years in the industry). Thanks for all the work you've put into it, and for trying to bring electrical safety issues to people's attention. - A.K.
Thank you for the Zinsco burn-up photos and the case report of another Zinsco circuit breaker failure. Your report is a reminder of Aronstein's frequent caveat that unless the remains of a fire are examined by a very expert forensic expert, we can not always be sure exactly what went wrong.
Nevertheless in the case you describe, and considering that based on an impartial review of the history of Zinsco product failures and field reports, our OPINION is that the product is defective, suffering from both design and performance issues.
What that fancy talk means in plain English is that simply installing a "replacement breaker" into a Zinsco panel is not a safe repair since it does nothing to address the design and product failure issues in the product. As with a few other replacement circuit breaker lines like FPE, there is unfortunately not a shred of independent test data nor field data that would support just replacing the breaker. Replacing the panel is what one should recommend.
The stumbling block for electricians and their customers is that too often all the customer has noticed is that power has been lost on one or two circuits in the building (where a breaker melted or failed to trip until the circuit wiring burned up). The customer figures that "all I need is a new $7.00 circuit breaker" and treats with suspicion the electricians's suggestion that the panel should be replaced.
To offer impartial assistance in problems like this you are welcome to provide your customers with printed copies of InspectApedia articles that you find helpful, and for a few cases listed just below we also provide special web pages that can be freely copied to other websites so long as they are not modified without our permission. Your email prompted us to make a new hazard summary page for Zinsco, Kearney, Zinsco-Sylvania electrical panels & circuit breakers
CONTACT US if you have suggestions for that material or if you have questions or content suggestions about other material at InspectApedia. Working together we're smarter than working alone. Thanks again, Daniel
(Mar 8, 2014) Tom Hons said:
Would doing a voltage drop measurement from the screw terminal of a Zinsco circuit breaker to the busbar it is attached to while putting a load on that circuit, tell the condition of the breaker's connection to the busbar? I measured it with no load and it was .005volts and with a load of 3 portable 120volt heaters on, it was 0.131 to .149volt.
Also, how quickly and at what amps should a 20 amp breaker trip? Thanx
That's an interesting question, Tom. I'm not sure of the answer, as there could be multiple explanations for a voltage drop including a defect inside the breaker itself, a poor wire-to-screw connection, etc. Worse I have no confidence that the type of measurement you are making is at all reliable in testing the safety of a circuit breaker.
Breakers are tested by experts by applying a known load or overcurrent to determine the trip point of the breaker under various conditions.
Measurements of resistance (which means taking the panel off line) between various points can be an indicator of trouble: oxidation or other poor connection problems;
The trip curves for circuit breakers are a function of time and current. At higher overcurrents the time to trip gets shorter and shorter until at a dead short the trip time is in milliseconds. DO NOT try these tests on an installed system - the risk is burning down the building or getting shocked.
But absence of a measurement of voltage drop nor increased resistance is definitely no assurance that a breaker will necessarily perform as needed.
(Aug 5, 2014) Tony B. said:
HI i think i may have a zinsco panel at least the outside metal cover says it is but how would i actually tell if the internals are Zinsco or not can you help me identify this please.
In the More Reading article links above see
IDENTIFY GTE SYLVANIA-ZINSCO PANELS
IDENTIFY KEARNEY PANELS
IDENTIFY ZINSCO ELECTRICAL PANELS
IDENTIFY ZINSCO SYLVANIA METER BASE
for photos and text that help you identify Zinsco equipment. You will see that the breaker connectors and bus bars onto whichg they clamp are not like other electrical panel designs.
You are also welcome to use the email found at our CONTACT link to send us photos of your electrical equipment for comment.
Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.
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