Service call today question

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nickelec

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Hey all so I was called out to a service call today for a dead circuit. So I find a tripped breaker an try to re set it and see a dead short . While doing so I saw an arc in a splice box so I opened it up fixed what I thought was the problem. It was BX into a 1900 coming out of the box was emt. So I tried to reset breaker and see an arc in a different spot. Them emt was leaning against a steam pipe and at the point there seemed to be some metal/arcing/welding lol. It seemed to me that it was looking for a ground. Arcing at several different locations. I reset breaker one more time to it held . The. I saw smoke coming out of the main disconnect it was a blown fuse . My initial thought was no ground to the building. Just a note its an old service fpe breakers no ground rod only a water main I think that the main ground to water main is most likely carroaded. Wat do you all think?

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nickelec said:
Hey all so I was called out to a service call today for a dead circuit. So I find a tripped breaker an try to re set it and see a dead short . While doing so I saw an arc in a splice box so I opened it up fixed what I thought was the problem. It was BX into a 1900 coming out of the box was emt. So I tried to reset breaker and see an arc in a different spot. Them emt was leaning against a steam pipe and at the point there seemed to be some metal/arcing/welding lol. It seemed to me that it was looking for a ground. Arcing at several different locations. I reset breaker one more time to it held . The. I saw smoke coming out of the main disconnect it was a blown fuse . My initial thought was no ground to the building. Just a note its an old service fpe breakers no ground rod only a water main I think that the main ground to water main is most likely carroaded. Wat do you all think?

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I think you have a short somewhere and you should have at least put an ohmmeter to the circuit before you turned the breaker back on. As for FPE breakers, now that you have reset it and it didn't trip and sent the damage elsewhere, it probably is set for life, and by that I mean it will no longer trip on a shorted or overloaded circuit.
 
There was definitely a short somewhere . It's the only ckt in a small apartment so I would have gotten a reading regardless

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Everything is so old and corrated and mostly a handyman special. The ckt in question ran through some emt up 2 stories into a handy box in an appartment then out of the box BARE silconed into the corner of a wall and some molding. I killed the ckt and told owner she needs to replace that SVC for starters and that ckt at a bare minimum

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I'm just trying to figure out why it was arching in different locations then it held and blew a main breaker

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Did you ask the resident what was happening when the circuit stopped working? Was there anybody else in the house? Did they try turning something on or off right before it went dead?

Seems like there were multiple issues, enough to finally blow the circuit. After you reset it a couple of times it held (malfunctioning), but there was still a short so because the circuit breaker wasn't tripping, there was enough current to cause the main to go.
 
mjf said:
Sounds like the BX jacket is live......in turn everything metal in the circuit is live.

Now the breaker is shot, so it's holding.
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If there was a good ground then that couldn't be possible correct?

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nickelec said:
If there was a good ground then that couldn't be possible correct?
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The over current device was operating so you had a good fault path, which seems to be over corroded metal. As long as the neutral and ground/metallic enclosures are bonded together at the main disconnect, you will have a fault path.
 
Just a side note: The fact that there was no ground rod and only a water pipe, has nothing to do with your short circuit. That is not the "ground" you are needing for a fault path.

I'm with the others, either the breaker (FPE) is shot or the path back to the source has burnt clear and you no longer have a path back to the panel for fault current.
 
FPE 1p Stab-Lock breakers arent nearly as notoriously unreliable as the 2p breakers are.

Sounds like there is a fault upstream of what you have seen, and multiple paths to ground. If the service/circuit was unbonded/ungrounded, there wouldnt be an OCPD-tripping fault, but eqpt sitting at 120V potential. That you are tripping breakers would indicate that all branch circuit wiring has a sufficient/low enough impedance path to ground/neutral/back to the source. A high impedance path would not allow >15/20+A to flow to trip the circuit's OCPD.

Please follow up and know what you find. :)
 
Break the circuit in half and determine which way the SC is. Then you have to keep breaking that circuit in half until you find the problem.
 
nickelec said:
There was definitely a short somewhere . It's the only ckt in a small apartment .
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Only circuit to a small apartment. Can you say overloaded boys and girls? :lol:

NO kidding I would guess that this circuit has been overloaded for some time and the breaker was not tripping. Happens a lot with FPE breakers but can happen with other brands. When a circuit is overload and a breaker doesn't trip the insulation of the wire heats up and melts. This is where a short comes in.

The home run will get the most damage and then to where overload or short occured.
 
growler said:
Only circuit to a small apartment. Can you say overloaded boys and girls?

NO kidding I would guess that this circuit has been overloaded for some time and the breaker was not tripping. Happens a lot with FPE breakers but can happen with other brands. When a circuit is overload and a breaker doesn't trip the insulation of the wire heats up and melts. This is where a short comes in.

The home run will get the most damage and then to where overload or short occured.
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This is probably the most likely scenario we come across this alot in this area. But I WILL get to the Bottom of this lol and let you guys know

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