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Zinsco failure photo (C) InspectApedia Adam Kranzel Zinsco Electrical Panel FAQs
Zinsco Circuit Breaker Q&A

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Questions & answers about Zinsco brand and Zinsco-Sylvania brand electrical panel and circuit breaker performance, hazards, safety.

In this article series we discuss: the hazards of Zinsco or Zinsco-Sylvania electric panels; Zinsco & Zinsco/Sylvania electrical panel identification guides & Kearney electrical panel identification guide. Independent testing of Zinsco breakers confirms failures.

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

Zinsco & Zinsco-Sylvania Electrical Panel Questions & Answers

Zinsco breaker burnup (C) J P Simmons & D J FriedmanZinsco and Zinsco-Sylvania circuit breakers of the design described here do not offer the level of overcurrent and fire protection provided by most other electrical panels and circuit breakers.

Watch out: OPINION: we do not recommend installing "replacement" Zinsco circuit breakers as there some indications that the performance and safety of those devices may be poor.

These questions and answers about Zinsco & Sylvania-Zinsco breakers and panels were posted originally at ZINSCO SYLVANIA ELECTRICAL PANELS.

Be sure to review that article.

On 2018-07-25 by (mod) - poor performance of circuit breakers for Zinsco

Thanks for the helpful field report and interesting OPINION on the reliability of antixoidant to avoid replacing a problem breaker, bus, and panel design, Bob.

Watch out: Readers beware that while Mr. Ford had success using an antioxidant to "save" a Zinsco circuit breaker we cannot recommend relying on this approach. The field performance history of these breakers and independent testing show that the panels and breakers should be replaced entirely.

See ZINSCO CIRCUIT BREAKER TEST REPORT

and

See CIRCUIT BREAKER FAILURE RATES

There's an underlying problem when a connector design like the Zinsco breaker clip gouges and cuts through plating on the bus bar to which it connects, damaging the plating and exposing reactive metal. We're not sure that this is the entire faiiure mechanism but it's an obvious one.

We agree that the replacement circuit breakers mentioned have not performed well in independent testing.

On 2018-07-25 by Bob Ford

Antioxidant Kopr Shield at InspectApedia.comAfter 30 years as a licensed electrician, contractor and inspector, I purchased a house (in the late 90's) and as my fellow inspectors and I had been discussing the Zinsco breaker issue, I came up the following procedure to "save" it... first I tested all the breakers to make sure they were still functional. Then I pulled the meter to de-energize the panel. Next I removed all the breakers, including the Main. I cleaned the busbars with steel wool and electrical contact cleaner. Then I applied a thin coating of copper-based anti-seize compound (T&B Kopr-Shield). Lastly, I installed all new, authentic Zinsco breakers which I still had in stock.
This repair has now lasted 20 years and upon periodic inspection, everything is functioning normally. I would not recommend this to be done with the "replacement" UBI breakers as they are truly an unknown quantity as far as reliability. My experience and conclusion is that there was nothing wrong with the Zinsco breakers themselves, other than the narrow and weak clips that go on the busbars. Its that weak connection that causes the overheating and failure. The copper coating method seems to alleviate the problem.

On 2018-05-18 by (mod) -

Curtis

Please attach some photos to some comments so that we can see the detail about which you speak along with a photo of any labeling or panel identification details

On 2018-05-17 by CURTIS PALACE

I have come across a zinsco 12 space panel that has a red hold down bar for the line side of the breaker. How is this released as both the line and load side are clamped. Any one seen this.

On 2018-05-02 by (mod) - Zinsco breaker did not trip.

David, try adding your image directly below a comment on this page.

On 2018-05-02 by David Vaughn

David Vaughn said:

Zinsco breaker did not trip.

On 2017-10-04 by Barbara Surian

I'm installing solar on my 3000+sq ft home and I have a 125amp Zinsco panel. The solar installers have decreased my amps to 100 to "keep the electrical system safe". I think this panel is inadequate and needs to be replaced, what is your opinion?

On 2017-05-11 by (mod) -

Phil,

While there are replacement circuit breakers for a Zinsco panel on the market, independent testing shows a very poor performance of those products, making them in my opinion unsafe.

It's surprising to read about a new Zinsco electrical panel installation, since those boxes have not been for sale as new equipment on the market for quite some time.

That's what made me start my comment by suggesting that someone may have installed what really was intended for replacement parts or an older piece of equipment.

Perhaps you can ask the electrician where he or she obtained the equipment, and please use the page top or bottom CONTACT link to send me some sharp photos of the panel cover, and all labels or markings, and a close up of the circuit breakers.

That may allow us to comment further..

On 2017-05-11 by Phyl

I am representing a buyer on a newly built townhome. The electrician has installed Zinsco panel box. Builder is going to consult with electrician on this. Does this apply to current product being installed today?

On 2017-02-15 by (mod) -

Shauna, As we're not the king nor queen, we cannot tell you that you're "required" to do a darn thing.

But the evidence of Zinsco performance issues is real, despite the absence of a panel recall. To claim that products that have had no recall are therefore guaranteed "safe" is as incorrect as to claim that because we have policemen there is no crime.

The "requirement" to replace a poor-performing or unsafe component on a home often comes during sale or re-sale when the buyer's lender says "well fine, but we won't issue a mortgage unless you fix or replaced XYZ"

When the defect is a life-safety hazard, fire hazard, or involves potentially high costs, and when a lender balks at its presence, you can as a seller figure that it's going to be an issue for most buyers with most lenders. Furthermore, deciding to wait for an all-cash buyer or one whose lender doesn't object to the same hazard by no means eliminates the hazard.

Worse, you've now been notified of it and so could face a failure-to-disclose lawsuit should, god forbid, a loss or injury later occurs.

I figure that the cost of a new electrical panel is typically less than 1% of the value of a home. When my sister, selling her home in St. Simons objected to a similar situation, I advised, "Linda, suete el gallo! that is, pay up. It's a trivial item to help assure the sale of your home and to avoid an injury or loss later."

I prefer to make an allowance and to let a buyer make repairs or replacements for items we agree upon, as that allows the buyer to be confident that the seller didin't take a shortcut, and it excuses the seller from a liability should the repair later be the subject of a gripe.

On 2017-02-14 by Shauna

I am selling my home and rumor of a inspection indicated my Zinsco panel was not safe . My panel is labeled with a silver and red sticker . Number on the bottom says 60-77 . If it is not recalled and just labeled as unsafe then I should not be required to replace it for someone to get a loan right ?

On 2017-01-05 by (mod) -

Gabe, Just use the page top or bottom CONTACT link to send us photos and I'll be glad to post it. I'd much appreciate having whatever details about the fire you can provide: city, state, country, date, observations.

On 2017-01-05 by Gabe

How can I share a picture I have of this panel that caught fire. I am a firefighter and we had one of these boxes cause a house fire. I also am a home inspector on my shifts off from the fire station.

On 2016-11-21 23:58:26.052358 by (mod) -

Thanks for asking Todd.

Absolutely. The electrical panel can be replaced without changing house wiring. If an electrician is telling you otherwise, ask him why other wires need changing and let me know what you were told. Such a claim would make me nervous.

On 2016-11-21 by Todd

Can you replace box without replacing all the wire in house

On 2016-08-31 by Anonymous

will they pay like auto co to replace panel

On 2016-07-28 by (mod) -

Also, these panels and breakers have been independently tested - see CIRCUIT BREAKER FAILURE RATES

Robert: there are tens of thousands of defective or unsafe products that are not recalled as well as very significant efforts by individuals or companies to prevent a product recall in instances where there is worry about grave liability that might ensue from such an admission.

To pretend that all products that have not been recalled are therefore "safe" is as specious as to claim that because we have police departments and the world's strongest military there is no street-crime and there are never mass shootings by people who are nuts.

On 2016-07-28 by (mod) -

Ian R said:
I replace these all the time. Some years ago the local power company furnished them with new services. If you have one please consider replacing it ASAP! Recall or not they are a safety hazard.

On 2015-10-23 by Robert

If these boxes are that unsafe why is there no mandated recall for safety? The insurance companies may just be requireing the owner to replace so their coverage is more protected but if a real fire hazard is present then where is the safety board to force a recall of faulty product?

On 2015-07-24 by (mod) -

Linda,

If you have a Zinsco electrical panel such as described above you can read about the hazards and field experience of people with this equipment installed. If it were in my home I'd replace the panel. The risk is not just loss of power but of a shock or fire.

Circuit breakers protect individual circuits. Only a very large overcurrent will cause the main breaker in an electrical panel to cut off.

I cannot mediate in a disagreement between you and your insurance company. Just what the company is obligated to do depends on the terms of your insurance policy.

I can give the OPINION that in general, insurance policies do not cover the replacement of obsolete or unsafe electrical equipment.

Watch out: some insurance companies, knowing that unsafe electrical panels can cause fire or injury losses, may cancel or refuse to issue fire protection at all for a building until the equipment has been replaced. I've certainly seen that with another unsafe electrical panel brand: FPE.

On 2015-07-23 by Linda Benson

Should this be replaced? I am having issues with my electrical items and appliances. nI have Old Republic Insurance they refuse to replace the breaker box. I am having issues with the appliances along with light flickeing. My lights shut down along with my TV

. I have issues with my cable box and computer. At christmas I had many lights added to the outside. The lights would go out but Not once did the brekers trip. I'd have to shut everything off at the breakers to find out which one was controling the lights that shut off. I called the insurance company but they refuse to pay to replace the board.

I realize the electicians they hire work to help them spend as little as possable, however this is not a typical fix it is a safty issue that needs to be addresed.

I have burt out extension cords and brunt out electric outlits I added to add extra items to each outlet. I just purchased GFCI outlets to install in the house with the hope that will help me to know which breaker is out. I don't understand why the breakers don't shut down at the box.

Please help me with my question about the insurance company who hold our policy. Should they be held accountable to fix this issue?

On 2015-06-21 by Diana Thornton

My home was built in 1982. The inspector for the buyer of my home wants the circuit breaker box replaced. It has performed fine for 30 years. Why would an inspector insist on replacement at this point in time? Diana

On 2015-06-10 by (mod) -

Hi Steve, nice to hear from you.

I would take a look at the side of one of the circuit breakers (I know it's not ASHI standard to pull a breaker - and generally not recommended, but peering up from below the bottom of the breaker stack in the panel we should be able to see the breaker side profile to determine if it's actually a Zinsco design.

Certainly there were Zinsco-design breakers sold with GTE-Sylvania labeled panels.

Please see IDENTIFY GTE SYLVANIA-ZINSCO PANELS at https://inspectapedia.com/electric/GTE_Sylvania_Zinsco_Identification.php for photos that will help identify the equipment for which you'd want to issue a warning.

There you'll see a photo from the bus bottom that makes clear that that panel is using a Zinsco design.

Let me know if any of that's unclear and I'll be glad to work further with you. And if you have photos of the panel you were inspecting send them along (My email is at the page bottom CONTACT link)

Daniel

On 2015-06-10 by Steve Smallman

Re: Sylvania panels - labeled "GTE-Sylvania" but no mention of Zinsco on label, are they the same as the Zinsco and need to be reported as unsafe?

Question: I am selling my house and it has a Zinsco electrical panel - are they all a fire hazard risk?

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

Reply:

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.

Question: How do I identify a Zinsco electrical Panel or a Sylvania Zinsco Panel & How do I know if My Panel is Bad?

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

Reply:

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.

Question: My Zinsco Main Breaker is in the "Off" Position but power is still on in my panel. Help?

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

Reply:

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.

Question: Single Breaker Zinsco-Sylvania 100A Main Service Switch feeds a new GE Panel. Isn't this OK?

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

Reply: The service entry cable between meter and new panel may be under-protected

Bob,

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.

Dan

Reader Follow-Up:

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.

Comment: testing by the electrical supplier? Unusual. But the basic electrical failure risk remains.

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.

  1. It is very unusual to read that an electrical supplier is performing testing on circuit breakers, and one is left wondering just what testing of tests were performed, to what standard, and with what scope and reliability. For example some electricians will "test" a breaker by applying a dead short and observing that it trips.

    Circuit breaker standards, including the partially inadequate (in my OPINION) UL 486 specify that circuit breakers are tested at different overcurrent levels. A breaker is given more time to trip at a lower overcurrent than at a higher one. I

    f your supplier is actually testing to standards the test might be reliable - we'd sure like to see any documentation on what is being done (use the CONTACT link found on any of our pages to send us that information if you can obtain it).
  2. Even if the breaker was tested and appeared to perform successfully, some important warnings pertain. Presuming we are talking about a Zinsco-Sylvania product, the failures that occur most often are at the breaker clip - to - panel bus bar connection. Arcing and overheating appears to occur there - hidden from easy view without disassembling the equipment.

    Therefore even if a breaker starts out in healthy good operating condition, the in-service conditions can create a serious failure whose point of origin is actually outside the breaker and inherent in the combination of materials used and design of the breaker-to-bus connector - not something that is adequately addressed by testing the breaker alone, nor would it be adequately addressed by a short term breaker test mounted in a panel. Rather, arcing that occurs at an in-use breaker and panel over time seems to be the failure source.

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.

Question: where can I buy replacement electrical panel covers for a Zinsco ?

looking for two electric panel covers for zinsco 14" w x 20 L - Hank Vance

Reply:

Hank, take a look at the article ZINSCO REPLACEMENT PANELS - This article describes replacement electrical panels and covers.

Question: was there a Sylvania Panel recall?

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

Reply:

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.

Question: What is Sylvania-Zinsco's responsibility for a faulty product?

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

Reply:

Mr Butler:

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.

Question: where do I find a licensed electrician to do Zinsco Panel Replacements?

Where to find licensed electrician for zinsco panel in my area - David Rue 5/16/12

Reply:

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.

Question: Zinsco Field Failure Report 7/15/12

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

Reply:

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.

Best, Daniel

Question: is there a recall on Zinsco Electrical Panels / Circuit Breakers - or recourse?

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

Reply:

Sorry, Cynthia, no.

Question: is it safe to replace a Zinsco-design electrical panel if I have the electric company drop power at the meter?

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

Reply:

Ryan,

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.

Question: Reader comment: burned-up Zinsco Circuit Breaker Photos

Zinsco breaker burnup photo (C) InspectAPedia Adam Kranzel I manage the electrical department at a hardware store, and a customer brought in the breaker in the photos, looking for a replacement.

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.

Reply:

Dear A.K.

Zinsco failure photo (C) InspectApedia Adam KranzelThank 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

. I've also added your Zinsco burn-up photos here and your report and photos appear also at ZINSCO FAILURE REPORTS as well as at ZINSCO Hazard Summary Page for Reproduction.

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

Question: does voltage drop between zinsco terminal and busbar indicate trouble?

(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

Reply:

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.

Question: The cover of my breaker panel says Zinsco but how would I actually know if its internal guts are ZInsco?

(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.

Reply:

Tony

In the More Reading article links at the end of this page 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.

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Continue reading at ZINSCO SYLVANIA ELECTRICAL PANELS - home, or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see CIRCUIT BREAKER FAILURE RATES

Or see IDENTIFY GTE SYLVANIA-ZINSCO PANELS

Or see this

Zinsco Electrical Panel Article Series

Suggested citation for this web page

ZINSCO SYLVANIA ELECTRICAL PANEL FAQs at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

INDEX to RELATED ARTICLES: ARTICLE INDEX to ELECTRICAL INSPECTION & TESTING

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