Breaker tripped and I don't know why.

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-=PEAKABOO=- said:
megohmmeter, put a meger on the circuit. There are various ways to do it but this tool will find everything from bad insulation on the feeder wires, bad insulation in the ballast to a wire nut setting in a box full of water.
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I just a bought a megger this past summer. Perhaps I need to learn more about it as to how to use it in a situation like this.
Thanks for all the advice.
 
Well, I got another call from this customer this afternoon. The parking lot lights are out again. Looks like I'll be learning more about my megger.
 
lots of things

lots of things

can go wrong with parking lot lights. you can start by installing inline spliced fuses in the handholes so the pole with the problem will only take out the pole with the problem. I would start to look for saw cuts in the parking lot and possiblydrainage pools installed after the lighting was installed. A jerk working a backhoe many times will hit underground wires and splice them back with romex and wirenuts which will rust out shortly if unprotected just long enough for the contractor to get paid and get lost.
 
quogueelectric said:
can go wrong with parking lot lights. you can start by installing inline spliced fuses in the handholes so the pole with the problem will only take out the pole with the problem. I would start to look for saw cuts in the parking lot and possiblydrainage pools installed after the lighting was installed. A jerk working a backhoe many times will hit underground wires and splice them back with romex and wirenuts which will rust out shortly if unprotected just long enough for the contractor to get paid and get lost.
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This is all very good advice.
 
Squirrel condition

Squirrel condition

I knew a guy who had a blue wirenut chewed by squirrels that he carried on his truck. He made thousands of dollars with that wirenut no joke. I could hardly keep my composure as he was explaining to the customer about the squirrel condition which they had to take care of asap. I would have to walk away to keep from laughing out loud. He would pull it out in a moments notice out of a handhole that was missing a cover. Not all of the actors are in Hollywood.
 
I returned to the sight today, hooked up my megger and in a short period of time I located some faulty underground wiring. I pulled the conductors out and they looked like they had been cooking there for quite some time. I assumed the pipe had broken, but I had no difficulty snaking it and pulling in new wire. The parking lot is lit again, all is well. Thanks to all for the good advice.
 
Every time a breaker trips it loses a little of its rated capacity.
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Circuit breakers can be a single trip device depending on the magnitude of the fault.

Circuit breakers can deteriorate due to carbon build up on the insulating material in the interior of the CB.

Circuit breakers can be damaged due to long term long term loose connections at the line to bus or load to conductor termination.

Circuit breakers can expierence metal fatigue from long term exposure to overloads and or high resistance connections.

But just not sure about the little bit of it's rating.
 
I assumed the pipe had broken, but I had no difficulty snaking it and pulling in new wire
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Underground failures are quite common even if there is no damage to the conduit.

The conduit is often filled with dirty water and.....stuff happens.
 
Jes2727 did you undo both ends of the wire or did leave the fixture attached? I know you ask about this but I did not see a reply. Whenever we use our megger, we have both ends open. With a megger aren't you just checking the condition of the insulation?
 
little sparkie said:
How old is the breaker and has it tripped a lot? Every time a breaker trips it loses a little of its rated capacity.
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I'm guessing the breaker is at least 20 years old. I have no idea how many times it's been tripped.

guschash said:
Jes2727 did you undo both ends of the wire or did leave the fixture attached? I know you ask about this but I did not see a reply. Whenever we use our megger, we have both ends open. With a megger aren't you just checking the condition of the insulation?
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This time I left the fixtures attached. I started at the time clock and meggered the entire circuit. It failed. I went to the first pole and opened up the splice. The circuit went off in two directions from here. I meggered both branches. One passed, one failed. From there it was easy to find the fault. I wasn't sure that this method would work because I had diffrent results a couple of weeks ago when I meggered some parking lot lights that were working fine. We were changing some lamps and I got my megger out just out of curiosity. I meggered the whole circuit and it failed instantly. I don't know why, there were no problems with the circuit. Last week I meggered some feeders to a transfer switch and it also failed instantly. I disconnected them from the switch and they passed. Meggered the switch and it failed. But it's working fine.
 
Just when I thought it was safe......
The customer called me this morning and reported that the parking lot lights were out again, and had been for several days. I went back to the sight and the breaker had tripped (!!). I meggered everything again, and everything seemed to be fine. I was reading about 20 megohms, but it held steady for 3 minutes. I'm guessing I'm getting some leakage through some of the lighting components.
The circuit is 480V single phase on a three pole 30A TED breaker. I moved the conductors to a spare 2 pole 20A, because I'm out of ideas......
 
JES2727 said:
I returned to the sight today, hooked up my megger and in a short period of time I located some faulty underground wiring. I pulled the conductors out and they looked like they had been cooking there for quite some time. I assumed the pipe had broken, but I had no difficulty snaking it and pulling in new wire. The parking lot is lit again, all is well. Thanks to all for the good advice.
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You found one problem. Nothing says there can't be another problem with the underground wiring that might pass a megger under the right circumstances, but still be intermittantly faulty.

Explain to the customer the only logical course of action is to install fuses at each pole, and remove & reinstall all underground wiring to eliminate the possibility that more of it is faulty.
 
Don't you just hate multiple problems?

It can make you look like you don't know what you are doing. You need to explain to the owner that because the wiring failed at point A, it is likely to fail at points B, C and D in the future.

You are going to have to be there when it's tripping. Putting fuses in will only eliminate the pole wiring/ballasts....right?
 
Maybe this happens when certian sprinklers come on. Maybe when the wind blows. Maybe when a garbage truck backs over a particular point. Maybe someone is vandalizing. Maybe there's a faulty ballast.

You can't visually inspect the wiring under the asphalt, nor can you sit there all night to wait for it to happen again. You don't have x-ray eyes and you're not a magician.

Because they're calling you back, AND they "claim" the lights have been out "for days" it leads me to wonder how accurate or truthful they're being. That said, it's time to shit or get off the pot. You see what you're up against. Offer a price to rewire the system, or tell them to lose your number.
 
Thanks for the advice, again. I'm not ready to burn any bridges with this customer, as they've been good to me in the past. But if the breaker trips again, I will take the advice and offer to rewire the entire circuit and fuse the poles, or just be done with it.
 
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