# Inside a Zinsco breaker



## 480sparky (Sep 20, 2007)

The other day, I had a service call to replace a 100a 2P Zinsco breaker.

I brought the old one home, drilled out the pins, and just for S&Gs I took a pix of the innards of one.








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## Bkessler (Feb 14, 2007)

I 've done that a few times, I wondered if the specific working parts have names?


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## 480sparky (Sep 20, 2007)

Bkessler said:


> I 've done that a few times, I wondered if the specific working parts have names?


Yea, I'd say they do. :laughing:


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## BuzzKill (Oct 27, 2008)

480sparky said:


> Yea, I'd say they do. :laughing:


holy crap.
nice, I need to do that, instead of drink on a friday and...spend time on this web site, or as my wife calls it, "my chat room"


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## BuzzKill (Oct 27, 2008)

so that little brown thing to the upper right decides whether to trip or not


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## 480sparky (Sep 20, 2007)

BuzzKill said:


> so that little brown thing to the upper right decides whether to trip or not



No. that's the terminal.


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## Bkessler (Feb 14, 2007)

Good work 480, that's neat I am gonna print out a copy.


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## Toronto Sparky (Apr 12, 2009)

Nice clean Photo :thumbsup:


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## Bob Badger (Apr 19, 2009)

BuzzKill said:


> so that little brown thing to the upper right decides whether to trip or not


This is a thermal breaker only and the part that heats up and causes the trip is the silver unit on the bottom right.

A modern breaker also has a magnetic trip that lets the breaker respond much faster to short circuits.


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## McClary’s Electrical (Feb 21, 2009)

Zinsco was not popular in my area. I have only seen a few. I see Bryant and Crouse hinds by the boatload. Where do you get breakers? Did you replace just breaker or entire panel?


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## MarkyMark (Jan 31, 2009)

So, could you tell what the failure point was?


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## jwjrw (Jan 14, 2010)

MarkyMark said:


> So, could you tell what the failure point was?


 

Most of them here are loose and burn the bus on the panel up.Many houses here had zinsco


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## JTMEYER (May 2, 2009)

Never seen a zinsco, but it looks awfuly similar to an XO breaker. Is it?


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## 480sparky (Sep 20, 2007)

MarkyMark said:


> So, could you tell what the failure point was?





jwjrw said:


> Most of them here are loose and burn the bus on the panel up.Many houses here had zinsco


Not the case here. Bus bars looked like new.... nice & shiny. That's why I brought the old breaker home: to do an autopsy. So far, I haven't seen anything out of the ordinary.

HO said the main would trip for no apparent reason. With nothing more than a couple lights and the TV, it would open. No AC, dryer (gas water heater) running. I hooked up an ampmeter and took some temp readings. Amperage was between 11 and 23, all temp readings were low 80sF. So my guess was it was just a breaker that tripped at really low current levels.


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## 480sparky (Sep 20, 2007)

JTMEYER said:


> Never seen a zinsco, but it looks awfuly similar to an XO breaker. Is it?



No. This is an XO:


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## Bkessler (Feb 14, 2007)

There's tons of Zinsco's and XO's in Ca. I have never seen a overheating problem with an XO. But Zinsco's are very unstable.


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## william1978 (Sep 21, 2008)

Nice pic's Ken. Thanks for posting them.


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## oldtimer (Jun 10, 2010)

480sparky said:


> No. This is an XO:


 Are XO s still used??? We have'nt had them here since the sixties, or even before. They were not a good design,the bus bar clips were very weak.


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## 480sparky (Sep 20, 2007)

oldtimer said:


> Are XO s still used??? We have'nt had them here since the sixties, or even before. They were not a good design,the bus bar clips were very weak.


They're still out there, but they haven't been manufactured since the 60s.


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## Norcal (Mar 22, 2007)

XO's were replaced by the C-H type CH, and SQ D QO in the late 50's. BTW SQ D used to tool up once a year to build XO's up until the mid to late 70's.


Editerhaps should open up a damaged Zinsco (actually Sylvania) bolt-on 20A single pole that I tossed in the trash tonight & photograph it......


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