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.
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 - 10/29/0604:56 PMRe: Breakers not tripping
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
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 - 10/30/0610:25 PMRe: Breakers not tripping
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 - 10/30/0611:08 PMRe: Breakers not tripping
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.