Zinsco breaker

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catronics

catronics

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Nevada City, CA
Every once in awhile I find a Zinsco breaker that is hot when it's off and cold when it's on. What is that? I just got a brand new breaker and it's doing the same thing after just a few hours. I'm hoping I don't have to return this $126 breaker that I got by mail order.
 
It's probably cold because, when closed, the internal resistance of its metal parts is so low that it does not produce any heat. That's normal behavior.

If it is hot when "open," then I suspect a high resistance leakage path that is allowing current to flow (from where to where :? ) and building up internal heat. It could be in the breaker itself. But if it happens after you swap out the breaker I would tend to suspect the panel itself. I would look for a loose connection (wire to terminal, perhaps) or loose bus bar.
 
charlie b said:
It's probably cold because, when closed, the internal resistance of its metal parts is so low that it does not produce any heat. That's normal behavior.

If it is hot when "open," then I suspect a high resistance leakage path that is allowing current to flow (from where to where :? ) and building up internal heat. It could be in the breaker itself. But if it happens after you swap out the breaker I would tend to suspect the panel itself. I would look for a loose connection (wire to terminal, perhaps) or loose bus bar.
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I suspect when he says hot when off he really meant the contact is closed even though the handle is in the off position, and the opposite when he said cold when on.

My best guess is his "new" breaker is actually something that has been refurbished, or more like just cleaned up and then sold.
 
back-fed or double-breakered??

back-fed or double-breakered??

is the conductor hot? or is the breaker lug hot?
Occasionally the hot leg is powered up or backfed from another breaker.

two hots(same phase) are maybe tied together somewhere dowstream.

turnoff all other breakers, then check for hot.

turn on breakers one at a time to find other breaker.
 
It was my voltage tester

It was my voltage tester

It was operator error! Even though my voltage testers, all three of them, showed voltage when the breaker was off, when I put my multimeter on it and actually read the voltage, there was nothing there. So all of my voltage testers were reading the same thing, and it was wrong.

When I hooked my branch circuit wires to the breaker, the phenomenon stopped. All of the meters read correctly. It seems that when this breaker is unterminated, it has some kind of floating-ground type stray voltage associated with it that only the voltage testers pick up, and "no voltage" when the breaker is turned on! Weird! ?

This is a 100-amp breaker, and I saw the same thing happen with a 125 amp breaker in the same panel. However, this did not show up on the 15A and 20A breakers. When those were unterminated, all my testers read correctly - totally normal.

I seem to recall this happening once many years ago, where I was ready to send a breaker back to the manufacturer. But I forgot all about it - just another reminder to ALWAYS put a multimeter on stuff before freaking out! ?

Thank you all for your incredible expertise and help! ?
 
catronics said:
It was operator error! Even though my voltage testers, all three of them, showed voltage when the breaker was off, when I put my multimeter on it and actually read the voltage, there was nothing there. So all of my voltage testers were reading the same thing, and it was wrong.

When I hooked my branch circuit wires to the breaker, the phenomenon stopped. All of the meters read correctly. It seems that when this breaker is unterminated, it has some kind of floating-ground type stray voltage associated with it that only the voltage testers pick up, and "no voltage" when the breaker is turned on! Weird! ������

This is a 100-amp breaker, and I saw the same thing happen with a 125 amp breaker in the same panel. However, this did not show up on the 15A and 20A breakers. When those were unterminated, all my testers read correctly - totally normal.

I seem to recall this happening once many years ago, where I was ready to send a breaker back to the manufacturer. But I forgot all about it - just another reminder to ALWAYS put a multimeter on stuff before freaking out! ������

Thank you all for your incredible expertise and help! ������
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Are you talking non contact voltage testers?

Those work using capacitive coupling, any coupling for any reason can give you false impression of what is going on.
 
catronics said:
Yes, I have three non-contact voltage testers. They can be wacky sometimes.

Thanks for the help.
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Welcome to the forum.

I don't quite get the hot when off thing. Are you speaking of actual warmth? or Hot meaning live or on?
 
Sierrasparky said:
Welcome to the forum.

I don't quite get the hot when off thing. Are you speaking of actual warmth? or Hot meaning live or on?
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Seems to be non contact tester indicating live when it is not. But they are prone to doing that at times. They are sensing capacitive coupling, any kind of coupling going on can throw off what you think may be happening though the "capacitor" storing said energy has limited storage and is easily shorted out without producing any significant current.
 
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