zinsco

[John Dirks Jr]

I found my first Zinsco. It was interesting. It had a 55amp main. The house was built in 1955. Just thought I'd share. I know it needs to be replaced but what are the specific issues with these?

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[Robert Jones]

The main issues with Zinsco/Sylvania is the possibility of arcing and contact point burn. Basically the breaker can get loose from the bus which, from what I have understood, is the main concern. That and most of the electric panel bus installed were aluminum.

[John Dirks Jr]

Wait a minute. The SEC is not connected at the top. It goes into a breaker in the middle. That looks weird. Any clues?

There was another abandoned SEC in the panel also. There must have been a problem with the original SEC so they disconnected it and fed a new one to the bus bar in the middle. ????

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[Robert Jones]

Usually when I see that, they have replaced the main feed(service drop) from the street. Was it an overhead service drop? Did you test those clipped wires? My guess would be they are the old ones and just not removed. Either way that service panel and more than likely the service drop, needs to be replaced/updated.

[John Dirks Jr]

It is overhead. The old portion of SEC was just left in the panel. It was removed from the outside portion. The old hole was there and had been patched. They just didn't pull all of the old cable out.

[Jim Katen]

I found my first Zinsco. It was interesting. It had a 55amp main. The house was built in 1955. Just thought I'd share. I know it needs to be replaced but what are the specific issues with these?

The specific issues are mostly what Rob said but also that the bus bars can be pitted in places that you can't see. In this regard, I'd be particularly suspicious of that backfed breaker.

Backfed breakers are supposed to be secured in place. I don't know how you'd do that in a Zinsco design, though I suppose that there must have been a way.

Also, there's a ton of anecdotal evidence that the breakers are unreliable. Unfortunately, there isn't any hard data or actual statistical proof that they're unreliable. In my area, the electrician's will pretty much always back up a call to replace these panels -- even the stubborn electricians who will argue about FPE.

- Jim Katen, Oregon

[Mr. Electric]

I have personally tested 20 amp (Zinsco) circuits with 30 amps on them that did not trip (see picture running 2 portable heaters and hairdryer at the same time). Jim K. is right in that there is not a lot of hard evidence on them except what you can find at http://www.inspect-ny.com/elec...sco.htm. I helped Daniel Friedman put this information together (most of the pictures are ones that I personally took). I don’t have time to log onto this site a lot. So if you have any specific questions I am at mrelectricoly@msn.com

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[Mike Lamb]

For some reason Mr. E's link came up broken for me. This might work.

http://www.inspect-ny.com/electric/Zinsco.htm