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#71388 - 10/29/06 01:33 AM Breakers not tripping  
skipr  Offline
Member
Joined: Jan 2005
Posts: 39
Huntington Beach, Ca.
I have a brand new installed "GE A-Series" panelboard. Bolt on THQB's. after a teacher somehow got a peice of jewrey stuck in an outlet.She claimed the breaker never tripped, after looking at the plug face and the jewlrey peice it had arced pretty bad. To test the theory I directly shorted circuit. The breaker did not trip, the jumper wire melted and caught fire. I tried another breaker, same thing. Brand new go figure.


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#71389 - 10/29/06 07:44 AM Re: Breakers not tripping  
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
Quote
To test the theory I directly shorted circuit. The breaker did not trip, the jumper wire melted and caught fire.


That was not 'testing a breaker', that was for lack of a better word stupid

I highly doubt you got two non-functional breakers in a row.

It is possible that the branch circuit has high impedance.

It is more likely that the jewelry and your jumper where not 'connected' to the circuit well enough to produce a magnetic trip.

That was a very bad idea, you should change your 'testing' procedures.


Bob Badger
Construction & Maintenance Electrician
Massachusetts

#71390 - 10/29/06 10:50 AM Re: Breakers not tripping  
Lostazhell  Offline
Member
Joined: Feb 2004
Posts: 1,431
Bakersfield, CA (Originally Or...
Ummm... Being a C-10, I hope you're kidding about the whole jumper idea... It's one thing to use some #10 and put a 28A load on a 20A breaker to see if it'll trip, but intentionally dead shorting a circuit in an uncontrolled environment is just a bad idea...

If you have doubts about your breaker(s) functioning, I can tell you 2 breaker houses in your area that'll put em on their test bench and let you know if they work.


#71391 - 10/29/06 04:56 PM Re: Breakers not tripping  
e57  Offline
Member
Joined: May 2003
Posts: 2,876
S.F.,CA USA
Oooooo, you're trouble now.....

I'm not going to go on the lecture circuit of arch flash and general electrical safety, but will say that the reasons that can happen under vary quite a bit. AIC rating for tranformer to OCP - OCP to fault distance. Circuit design and impedance. The trip current/time rating of the breaker I believe is this page?: I cant see it.... But may hold several thousand amps for a small amount of time, enough to clear the molten metal out of the path, slowing reaction time.
http://www.geindustrial.com/publibrary/checkout/38652.30055.31248.24184/PDF/GES-9920.pdf

Unfortunately ilegible... But can be found here: http://www.geindustrial.com/publibr...Id=8&pubType=Time%20Current%20Curves

Either way, you may have caused significant damage to the wiring between the short, and the breaker, and may have even damaged the breaker to boot. You may have to re-do that run....


Mark Heller
"Well - I oughta....." -Jackie Gleason

#71392 - 10/29/06 05:19 PM Re: Breakers not tripping  
Dave T  Offline
Member
Joined: Jan 2005
Posts: 155
Waukesha, WI, USA
TM breakers with trip because of an overload in response to I2t or magnetically (instantaneously). The must be current maintained for a given amount of time to fall within the thermal trip curve of the breaker in order for the breaker to trip thermally. If you were tat the breaker location when the breaker tripped more often than not the breaker can not be reset, latched and closed immediately as the thermal element must cool.
The magnetic element is often calibrated 7-10x the breaker rating for residential breakers and 10x for commercial and industrial breakers +20%. This means that a common 20at breaker would be calibrated at 200a but most likely is calibrated toward the high end at 240a. This means that a 20at breaker must see an instantaneous current of over 200a for it to call for a trip.
The question is if in fact the breaker saw 200+ amperes. Since the scenario as described was most likely resulted in an arcing fault it is highly doubtful that the breaker saw enough fault current to trip.
Such a situation is common in that we expect a breaker to trip. Because the breaker doesn't have eyes to actually see when we can, the breaker can only respond to the current values that it has been designed to respond to regardless of what is or has happened down stream on the circuit it protecting.
Since arcing faults often are L-G or end up to be so within a very short time a GFI breaker will with almost all certainty would have picked up the fault and opened the breaker.


#71393 - 10/30/06 10:25 PM Re: Breakers not tripping  
Theelectrikid  Offline
Member
Joined: Apr 2004
Posts: 810
Levittown, PA
The only time I'll jump an outlet is when I need to figure out which outlet goes to which cable; when there's no power to the house; in other words no power anywhere. For what you did though:

Ohh man you're in trouble. Just looking at a few past posts proves that.

Ian A.
Edited 'cause I kant spell!

[This message has been edited by Theelectrikid (edited 10-30-2006).]


Is there anyone on board who knows how to fly a plane?

#71394 - 10/30/06 10:36 PM Re: Breakers not tripping  
skipr  Offline
Member
Joined: Jan 2005
Posts: 39
Huntington Beach, Ca.
Ok I knew I was going to get a lecture or two on the way I tested it. That's not the question here.I don't use this as a general testing method, in fact I never had a breaker that refuses to trip.OK does anyone have anything useful to say? I got five reply's saying the same thing, but not one that comes close to explaining the problem.Can anyone address the breaker problem instead of my procedure problem?


#71395 - 10/30/06 11:08 PM Re: Breakers not tripping  
Tesla  Offline
Member
Joined: Jun 2004
Posts: 1,273
Sacramento, CA
Watch out for Black on Black/ Red on Red circuit 'crossovers'.

I can' speak to the residential situation but many's the time that my apprentices cross circuit 1 with circuit 7 in a three phase system.

Naturally, this permits the wire to draw across double breakers -- completely defeating their protection: #12 is now able to receive 40 continous amperes!

Could anything like that have happened to you?

This kind of circuit fault is just another reason why deliberately faulting circuits is so risky, especially troubled circuits.


Tesla

#71396 - 10/30/06 11:12 PM Re: Breakers not tripping  
Tesla  Offline
Member
Joined: Jun 2004
Posts: 1,273
Sacramento, CA
BTW, After MELTING my jumper... a free air conductor...I'd consider my in-the-wall Romex TOAST. It's wearing a fur coat... the jumper was wearing Bermuda shorts.


Tesla

#71397 - 10/30/06 11:43 PM Re: Breakers not tripping  
Active 1  Offline
Member
Joined: Feb 2003
Posts: 687
Grayslake IL, USA
I agree of the possability of 2 breakers feeding the same circuit.

Did you short the circuit hot to the Nutral or the equipment ground? If it was hot to EG then a question of the equipment ground integerty comes to mind. How far does the fault current need to travel to get to the incoming service? Is the EG conduit only? Could be loose connections at boxes or couplings creating resistance on the branch circuit or between a sub panel and service. You could look at the service equipment grounding.

The ideal suretest I never used myself but I believe it tests the EG for impedance.


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