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#26055 - 05/28/03 08:03 PM Breakers that don't trip/ Fire hazard  
Electric Eagle  Offline
Member
Joined: Apr 2002
Posts: 914
Alpharetta, GA
Why is it that a breaker would hold with a dead short on it?

Recently we had a customer with a lightning strike. One circuit would not reset. I went on the troubleshoot with a helper. After taking a look around and unplugging everything on the circuit, I tried to close the breaker and it tripped. It was an old Westinghouse breaker, so just for kicks I replaced it with a new Seimens breaker and went in search of the problem. I took appart what I thought was the first j-box(switch) and told the helper to go reset the breaker. He did and came back saying it held, but was buzzing. I IMMEDIATELY went to the panel to turn it off. As I got there another breaker on the same phase tripped, but this circuit wasn't buzzing anymore and was still on. The wire was smoking. We traced the wire through the attic and found the wire melted throughout the circuit. We found one section where the wire was burned in half, thus why the breaker wasn't buzzing anymore.

This incedent scared me pretty bad. It made me tell everyone in the company to turn off a breaker if it buzzes. We rewired the entire circuit and all is well there, but it could've been very bad.

Today I tried to turn on a breaker on a new installation(15 amp GE). The breaker buzzed, but didn't trip. I had to turn it off. Someone had a ground touching a screw on a receptacle. Why aren't these breakers working???????

[This message has been edited by Electric Eagle (edited 05-28-2003).]


Work Gear for Electricians and the Trades

#26056 - 05/28/03 10:36 PM Re: Breakers that don't trip/ Fire hazard  
Joe Tedesco  Offline
Member
Joined: Oct 2000
Posts: 2,749
Boston, Massachusetts USA
This type of problem should be brought to the attention of the testing agency.

On a humorous note, perhaps this equipment was designed by those who designed the following products?

[Linked Image]
[Linked Image]


Joe Tedesco, NEC Consultant

#26057 - 05/28/03 10:52 PM Re: Breakers that don't trip/ Fire hazard  
CRW  Offline
Member
Joined: Feb 2001
Posts: 159
Bethlehem, PA USA
maybe it wasn't really a "dead short", but instead an arcing fault--not enough steady current to trip the breaker.


#26058 - 05/29/03 07:04 AM Re: Breakers that don't trip/ Fire hazard  
Redsy  Offline
Member
Joined: Mar 2001
Posts: 2,056
Bucks County PA
As CRW said, it sounds like a high resistance fault. Next time, try to get a meter on it.


#26059 - 05/29/03 11:15 AM Re: Breakers that don't trip/ Fire hazard  
Active 1  Offline
Member
Joined: Feb 2003
Posts: 687
Grayslake IL, USA
Maybe a poor ground path with high resistance not alowing enough current in the short to trip the breaker.

With EMT it could be loose lock nuts and set screws.


#26060 - 05/29/03 06:53 PM Re: Breakers that don't trip/ Fire hazard  
sparky  Offline
Member
Joined: Oct 2000
Posts: 5,308
Breaker 'hum' is a curious thing, the fact that noise is produced as a byproduct of load....
Other than motor starts i would also side with CRW.


#26061 - 05/29/03 07:03 PM Re: Breakers that don't trip/ Fire hazard  
Gwz  Offline
Member
Joined: Apr 2002
Posts: 197
By the replies, I guess it is not possible to have a defective CB.


#26062 - 05/29/03 08:19 PM Re: Breakers that don't trip/ Fire hazard  
sparky  Offline
Member
Joined: Oct 2000
Posts: 5,308
better chance than a defective fuse Glenn


#26063 - 05/29/03 10:10 PM Re: Breakers that don't trip/ Fire hazard  
harold endean  Offline
Member
Joined: Feb 2002
Posts: 2,233
Boonton, NJ
GEE JOE,

Are you saying that maybe one of those red handled type breakers have a problem with tripping? LOL I have seen that problem first hand before. I shorted out a circuit, burnt a locknut and screw driver tip, but the breaker held. It did not trip. I have heard of one job in the past few years of inspecting where that type of circuit breaker panel actuall caused the fire in the building. That was the word of one of the people who went in after the he fire to clean out the building.


#26064 - 05/31/03 11:12 PM Re: Breakers that don't trip/ Fire hazard  
Scott35  Offline

Broom Pusher and
Member
Joined: Oct 2000
Posts: 2,707
Anaheim, CA. USA
The non-trip situation may have been from numerous factors.

<OL TYPE=1>

[*] Load current stayed within the tolerance of the unit's trip characteristics - like not exceeding 20 amps on a 20 amp breaker, or rising briefly to only about 40 amps, then dropping back to 20 amps,
[*} Arc fault - as mentioned by others,

[*] Faulty unit or fried contacts,

[*] exceeded the AIC of the unit - highly unlikely in Residential or without a corresponding explosion of the frame!

[*] The parallel circuitry result of two branch circuits originating from the same line / phase allowed divided current levels to flow across each breaker - so each frame only saw ½ the current level flowing.
</OL>

Just thinking and typing outloud! [Linked Image]

Now if the situation was on the above mentioned and shown FPE equipment, or possibly on Zinsco type P / FP equipment, that is the exception [Linked Image]

No need to use trip-free type breakers if using FPE or Zinsco FP/Ps! They came factory stock as trip-free!
[Linked Image]

It's been a long time since I have flamed out towards FPE and Zinsco!

BTW, not all of the FPE or Zinsco line is like this. Only certain devices are the ones with the "Sucks For Overload / Overcurrent Protection" characteristics! Unfortunately, the ones that suck were very commonly used, which is why everyone in the trade makes so much fun of them.

Scott


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

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