Breaker tripped and I don't know why.

[JES2727]

Hello,
I was called to an office building today that had lost all their parking lot lights. I quickly discovered that the breaker had tripped. The lights are 480 volt, so I didn't want to be too hasty to reset the breaker. I disconnected the feeds from the contactor and used my Fluke to check for a short or a ground fault. I found none, though I did measure some ohms between phases, as I expected. I reconnected the feeds, reset the breaker, turned on the switch at the time clock and the lights came on. They burned for about an hour until I turned them off and left the site. Any ideas as to why a breaker trips for no apparent reason? I suspect a bad ballast, but only because I can't think of any thing else. Is there a better troubleshooting method to follow? Thanks for any help.

P.S. : I know someone will ask : No, I wasn't wearing any PPE when I reset the breaker and turned on the lights.

[petersonra]

I suspect an intermittant problem.

It should be worth about 15 service calls before it becomes mittant enough to figure out.

[dSilanskas]

Maybe water is getting into one of the lights?

[brian john]

A. Breakers DO NOT TRIP FOR NO REASON.
B. What size CB?
C. Use a megger..........


Proper tool for the job, if you do not have a megger contact a firm that does.

[Pierre C Belarge]

My thoughts are it may be a high ristance fault. Which could take up to days to trip again. As Brian has stated, get a megger and start testing.

[JES2727]

It's a 30 amp breaker. Each wire was pulling about 9 amps while the lights were on, except for during start-up. The ambiant temp in the area around the panel is over 90 degrees F.
If the problem persists I will use my megger. I presume I would have to open all splices and meg each wire in every direction, correct?

[mdshunk]

If the problem persists I will use my megger. I presume I would have to open all splices and meg each wire in every direction, correct?
Maybe it will come to that, but you can start with phase to ground, and see how that hashes out.

[growler]

Did you check the current draw of the circuit with an Amp meter? At this time of year it colder and the breakers with take longer to trip if they are drawing just a little over the current rating. Did you check the termination in the panel for loose connection ( if this is an exterior house panel there could be a bad connection, corosion).

Edit: a day late and a dollar short here.

[growler]

It's a 30 amp breaker. Each wire was pulling about 9 amps while the lights were on, except for during start-up. The ambiant temp in the area around the panel is over 90 degrees F.

9 Amps doesn't power very many pole lights. Were all the lights back on when you reset the circuit?

[mdshunk]

9 Amps doesn't power very many pole lights. Were all the lights back on when you reset the circuit?
Hey, that's using the old noodle. I know that a ballast can fail in such a way that it will trip the breaker. Reset the breaker, and the fixture is now dead and has declared itself. If it's an installation you're not famaliar with, however, it is always up in the air as to what fixtures might have been failed or had bad lamps for some time, and which may have failed concurrently with the breaker tripping.

[480sparky]

Sounds like an intermittent short. The only way to trace this down is to 'divide and conquer'. Remove a portion of the circuit and see if the problem is solved or persists.

What happens is there is a bare hot wire near a ground. When the wires are not used, there is no short. But turn them on, and heat starts to build up, and things start moving. After a while, Boom!

Case in point from the last time I experienced this:

http://i214.photobucket.com/albums/cc172/480sparky/DSC05328a.jpg

http://i214.photobucket.com/albums/cc172/480sparky/DSC05329a.jpg

School had an exterior lighting circuit with this same problem. I kept disconnecting parts of the circuit until I found it... an intermittent short in an in-ground HID for the flag out front. Sometimes it would trip in a couple minutes, sometimes after several hours.

[JES2727]

Did you check the current draw of the circuit with an Amp meter?
Yes. 9 amps per leg.
9 Amps doesn't power very many pole lights. Were all the lights back on when you reset the circuit?

This particular circuit feeds 8 pole lights. Last time I visited the site, 7 poles were lit. I don't have a bucket truck so I didn't make the repair, and neither did anyone else. Today, 6 poles were lit.
I know that a ballast can fail in such a way that it will trip the breaker. Reset the breaker, and the fixture is now dead and has declared itself.
That's what I'm thinking....

[brian john]

If the breaker is off when I get there or I can turn off the power the megger is in use. while there are cases, especially with pole lights with PVC, where a meggger might miss a fault, in my expierence, if there is an intermittent short in PVC due to moisture, carbon ect the megger will be a vast improvement over other test methods.

[nakulak]

i meg my wires, but haven't megged anything with devices attached - never knew if I would damage anything. You meg with the fixtures and all attached ?

[220/221]

It's kinda hard to fix when it aint broke huh?

I have seen a ballast that would not trip till it was on for quite a while.

I've also seen faulty undergound wiring in PVC that would take a while to trip.

I usually take the "wait and see" approach.

[growler]

This particular circuit feeds 8 pole lights. Last time I visited the site, 7 poles were lit. I don't have a bucket truck so I didn't make the repair, and neither did anyone else. Today, 6 poles were lit.


Jes2727, I don't have a bucket truck either ( don't really want one ) but I have the next best thing. I have used a company for years that does nothing other than outdoor ( mostly parking lot ) lighting. They have plenty of trucks that are stocked with all the right parts and techs. with the right experience to repair any parking lot lighting. I just give the customer their card. This company doesn't do anything other than lighting so if they run into a problem that requires any inside wiring then they throw that my way. We all get to do the work that we are best trained for and everyone stays happy.

Send these suckers an invoice and recommend a lighting contractor, find a good lighting contractor. Doctors charge to send you to a specialist all the time.

[cowboyjwc]

I once had a problem like this. Would get a call every few days that the sign wasn't working and I would check it and reset the breaker and sit there for a half hour or so and all would be fine. One night I happened to be there a little longer when it finally tripped. Turns out that someone had added some exterior lights to the same circuit, but on a different timer and when they would come on it would be just enough to trip the circuit. No real problem other than to many amps.

[-=PEAKABOO=-]

Hello,
I was called to an office building today that had lost all their parking lot lights. I quickly discovered that the breaker had tripped. The lights are 480 volt, so I didn't want to be too hasty to reset the breaker. I disconnected the feeds from the contactor and used my Fluke to check for a short or a ground fault. I found none, though I did measure some ohms between phases, as I expected. I reconnected the feeds, reset the breaker, turned on the switch at the time clock and the lights came on. They burned for about an hour until I turned them off and left the site. Any ideas as to why a breaker trips for no apparent reason? I suspect a bad ballast, but only because I can't think of any thing else. Is there a better troubleshooting method to follow? Thanks for any help.

P.S. : I know someone will ask : No, I wasn't wearing any PPE when I reset the breaker and turned on the lights.


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.

[hardworkingstiff]

Lots of good guesses here.

Have you ever heard the conductors slapping against the pole when the wind was blowing?

Maybe a wire with a nic?

[480sparky]

Have you ever heard the conductors slapping against the pole when the wind was blowing?

Maybe a wire with a nic?

I've seen make-ups in the poles with split-bolts because they're wired with #6s or larger, and the original installer skimped on the tape wrapping them up. After a few years, the bouncing around wore through the tape and would short out to the inside of the poles.

This is an easy fix, but time-comsuming. Just buy a log of quality tape and open every hand-hole....

[JES2727]

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.

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.

[JES2727]

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.

[quogueelectric]

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.

[Pierre C Belarge]

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.

This is all very good advice.

[quogueelectric]

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.

[JES2727]

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.

[little sparkie]

How old is the breaker and has it tripped a lot? Every time a breaker trips it loses a little of its rated capacity.

[stickboy1375]

Every time a breaker trips it loses a little of its rated capacity.


Where does it go? :roll:

[SeanKelly]

spliced fuses worked well for me also on occasions like this.

[brian john]

Every time a breaker trips it loses a little of its rated capacity.


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.

[220/221]

I assumed the pipe had broken, but I had no difficulty snaking it and pulling in new wire

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.

[guschash]

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?

[JES2727]

How old is the breaker and has it tripped a lot? Every time a breaker trips it loses a little of its rated capacity.
I'm guessing the breaker is at least 20 years old. I have no idea how many times it's been tripped.

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?
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.

[guschash]

Jes2727, Thanks for your relpy back. Glad it worked out for you. Good trouble shooting!

[JES2727]

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......

[quogueelectric]

at the risk of repeating myself. put pigtail fuses in the handholes at each pole it is a better installation.

[LawnGuyLandSparky]

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.

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.

[220/221]

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?

[LawnGuyLandSparky]

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.

[JES2727]

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.

[LawnGuyLandSparky]

I wouldn't "offer" to fuse the poles - I'd even lie about it and say it's required by code. Then, fuse each pole AND fuse each downstream feed out so that you will be able to diagnose exactly which section or pole has the fault. You can tell them that because this wasn't done during the initial installation is the reason why you have to keep coming back.

[guschash]

jese2727, can you keep us posted on this. I would like to know if you do rewirer, what you find when the old wires are removed. Maybe you find one of the fixtures has a loose wire or the whole fixture is bad.

[JES2727]

jes2727, can you keep us posted on this.

guschash ( and anyone else that's interested),
I revisited the site today. The circuit has not tripped since I moved the wires to the other breaker. I'm relieved.