100 Amp Breaker

stickboy1375

Senior Member
Location
Litchfield, CT
So the other day a plumber decided to cut through a #2 AL. SER cable supplied by a 100 amp 2pole GE breaker... the thing that disturbs me the most is that the breaker never tripped as he cut through the entire wire... What is up with that? I met up with the plumber today and he showed me pics of his sawzall blade... I should have had him send me a copy.... Unbelievable though.
 

SG-1

Senior Member
Breakers do not trip because a circuit goes open. The saw blade was damaged because the circuit tried to use it to bridge the gap that was just made. Maybe a series arc fault breaker might have tripped.
 

stickboy1375

Senior Member
Location
Litchfield, CT
Breakers do not trip because a circuit goes open. The saw blade was damaged because the circuit tried to use it to bridge the gap that was just made. Maybe a series arc fault breaker might have tripped.
I'm pretty sure this would be a dead short, no? what are the odds he cut each wire individually in a SER type cable assembly?
 

texie

Senior Member
Location
Fort Collins, Colorado
Occupation
Electrician, Contractor, Inspector
So the other day a plumber decided to cut through a #2 AL. SER cable supplied by a 100 amp 2pole GE breaker... the thing that disturbs me the most is that the breaker never tripped as he cut through the entire wire... What is up with that? I met up with the plumber today and he showed me pics of his sawzall blade... I should have had him send me a copy.... Unbelievable though.
Probably not enough of a short to fall in the TCC of the breaker. It happens.
 

mbrooke

Batteries Not Included
Location
United States
Occupation
*
FWIW, I never liked GE breakers they always seem to be the least responcive to an overcurrent situation. Ive seen drill ins on seu and NM on older ge breakers tripping the main but not the branch itself. How old is this breaker? I would replace it just in case it is defective.
 

SG-1

Senior Member
I'm pretty sure this would be a dead short, no? what are the odds he cut each wire individually in a SER type cable assembly?
When we think think about faults we usually visualize a text book bolted fault with a low impedance source. This is seldom the case in the real world. I misunderstood your OP when it stated that he cut through the entire wire. You meant cable & I did not pick up on that. As others have stated the fault current through the moving saw blade was insufficient to trip the breaker. At times I am sure it spiked well into the pickup range.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Electrical Contractor
I can't imagine that he cut thru the entire cable while watching sparks fly etc. Wow. I believe I would replace that breaker just to be sure.
 

hurk27

Senior Member
Many reasons could come into play as to why the breaker didn't trip, to not blame the breaker right off bat is how long is the service from the transformer, how long was this run from the breaker, is there a loose or weak connection, how fast did the blade go through the wire, is the breaker thermo magnetic, thermo only can take a while to trip.

Many forget resistance is current limiting and a long service run while providing enough current for the loads on it might be limited as to how much current can pass through it, if it was close to the breakers trip curve it might never trip add the resistance of the arcing as the blade goes through the wire and again it may never trip, I have seen people cut through branch circuits fast enough with strippers that never trip the breaker or even arc the blades, all depends upon how much fault current is available at the point of the short and how long the short is made.
 

templdl

Senior Member
Location
Wisconsin
All too often when we would have expected a breaker to trip because of a given even it doesn't trip.
Remember that a breaker is designed and calibrated to respond to a specific TC curve. If the event doesn't present the time/current to fall within that curve the breaker will not trip. We can make all of the suppositions that we can but that's all they are suppositions. There is no way that we can regard them as facts. As one of the others stated even the dynamics of the cable as well as the fault current available can influence the results. Everything is a variable as no facts regarding the even can be provided and the circuit breaker is the only given and its easy to blame the breaker. The breaker should have could have would have tripped is only based on assumtions.

The bottom line is that there are no definites. You don't have a control case here where you would have the ability to control all of the the variables.
 

liquidtite

Senior Member
Location
Ny
ive seen branchcircuits were a guy caused a short when the bc arked two times in a row and it never triped the ge breaker.ive had it happen to me too were i caused a short seen it ark and it never triped. and had other people tell me the same.So when i read the post i wasnt surprised,But dosnt it also matter how far the circuit is from the transformer that is what someone told me aswell
 
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kwired

Electron manager
Location
NE Nebraska
The wire was exposed the entire length too, I have no idea how he did it, He used a cordless sawzall otherwise I'm sure his saw would have stopped. :)
Why? At most he just energizes any metal components but does not effect the power circuit of the saw itself unless the feeder being cut also supplies the circuit supplying the saw.
 

stickboy1375

Senior Member
Location
Litchfield, CT
Why? At most he just energizes any metal components but does not effect the power circuit of the saw itself unless the feeder being cut also supplies the circuit supplying the saw.
If you must know, all the temporary receptacles were fed off this feeder that he so inclined to cut in half. :)
 
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