Grrr... intermittent breaker trippage

[ericsherman37]

Excellent.

If your recording meter has clamps for both hot and neutral, do measure both, as that'll determine if your overcurrent is phase - neutral or phase - ground.

You're actually lucky (or perhaps just well equipped) to have a recording meter, they are reasonably rare in the contracting community, yet without one, tracing this type of mischief is harder than it need be.

And having reread the original post, I do not agree that the breaker is tripping "by magic"; theres always a reason for these things, albeit sometimes the reasons are a tad difficult to come by

Yep the recording meter has served me well in the past. Troubleshot a weird issue at the hospital with it a few years ago, and then an even weirder issue at the Aquarium with it last year. I just hope to death that no one formatted the hard drive of the computer with the uploading software on it.

Could be the same as having a loose wire. The breaker could be going out on thermal overload.
I had a situation where another elect. wanted to replace a panel that was only 1 year old. Every thing worked fine until the heat strips in the HVAC unit would run for about 20min. then the main would trip. PhA in the main was loose. It wasn't loose enough to arc but was loose enough to cause the main to heat up and trip on thermal. Torqued it down and it has been good for three years now.

Makes sense I suppose.... I'll tighten some things down.

 

[kwired]

This is a stab in the dark. From the OP I would infer that the lights on the breaker that is tripping are running through the contactor that is controlled by a photo cell by another circuit. The contactor is a link between the breaker and the lights. If the contacts are worn/pitted they could, over the course of the night, act as a loose connection causing the circuit to overheat.

The increase in heat will be in the contacts not in the breaker and resistance of the bad connection will lower the circuit current. Chattering contacts on an inductive load will raise circuit current because it will be inrush current everytime the conact closes again.

If OP wants to find a bad connection all he needs is a infared thermometer and turn the circuit on for a few minutes. FOP test across contactor to check contacts.

Now that I mentioned chattering contacts maybe the photocell is rapidly cycling either at starting or ending time. Simply covering it while testing would not make this happen as the cell sees full dark or full light when doing that. Also make sure the cell is not receiving light from luminaires it controls. If there is a bad connection causing problems I would think it is more likely in the control circuit and is causing contactor chatter if it were in the power circuit the OP would have found the problem right away as he would have had melted insulation at the bad connection.

I would replace the photocell and if you wish fuse each luminaire. Also inspect contactor if it type that can be disassembled, paying particular attention to springs that maintain contact pressure. If it is not type that is easily disassembled it is a cheap one and I would plan to replace it just to eliminate it from possible problems list.

 

[zog]

Megger the circuit
Test the breaker

Without any testing any guess at the cause is just speculation.

 

[ericsherman37]

Okie dokie so I went and did the ol' recording meter this morning. Here's what I got from it (click the link for image - may need to zoom in or full-size it or something to see details):

http://i1239.photobucket.com/albums/ff503/ericsherman37/UPSexteriorlightschart.jpg

The chart is a current measurement; I set the recording meter to take a reading every 5 seconds. So I got it running about 8:40 AM... you can see a bit of the exterior light circuit "warm-up" as the current steadily rises for a little while. After that it's pretty much solid at about 13.6 to 13.8 amps for several hours. Then around 12:45 PM it took a nose-dive to zero - the breaker tripped. This happened to occur during a fairly nasty little squall we had right around that time.... the biggest clue. What I glean from this chart is that there isn't an obvious overload or anything. Seems like the fault condition happened probably in the interval between readings; perhaps if I had it set at 1 second intervals or something I might have been able to pick up at least part of the current spike before the breaker tripped.

Does anyone else have some analysis of this thing for me? Thanks

 

[jim dungar]

If it tripped between two readings, at 5 sec intervals, then it was not a 'current spike', it was a short circuit. Very few, if any, small molded case breakers will not hold 5-8x current for less than 5 sec.

 

[dbuckley]

I concur, something fairly dramatic occured.

You could get the breaker curves to be more accurate over what level of overcurrent would be required to trip the breaker in 5 seconds.

You've had your head in the lights and you didn't see anything short circuitous (or evidence of past shorts). And you mentioned "squall". So I'm wondering what the wiring method is, and if mechanical activity is causing a short in the wiring with movement.

Have you meggered this setup?

 

[Jlarson]

Yep I say it's megger time too.

 

[LarryFine]

Yep I say it's megger time too.

That, and checking each fixture and its wall penetration for signs of water infiltration.

 

[Jlarson]

That, and checking each fixture and its wall penetration for signs of water infiltration.

Aw, I think moisture has been covered already, sorry I had to point it out :grin:

I went out (with more time) and opened up all the exterior lights, looking for things like moisture infiltration...

 

[ericsherman37]

If it tripped between two readings, at 5 sec intervals, then it was not a 'current spike', it was a short circuit. Very few, if any, small molded case breakers will not hold 5-8x current for less than 5 sec.

That's what I mean. If a short or ground fault occured between my 5 second readings, then that's why I didn't see the current reading skyrocket and then drop to zero when the breaker tripped. It happened too fast for my recorder thingie to pick it up at the intervals I had it set at.

I concur, something fairly dramatic occured.

You could get the breaker curves to be more accurate over what level of overcurrent would be required to trip the breaker in 5 seconds.

You've had your head in the lights and you didn't see anything short circuitous (or evidence of past shorts). And you mentioned "squall". So I'm wondering what the wiring method is, and if mechanical activity is causing a short in the wiring with movement.

Have you meggered this setup?

Wiring method is EMT inside, with a J-box and MC cable whips stubbed through the siding into the back of each light :roll:

Yep I say it's megger time too.

Perhaps, but...

That, and checking each fixture and its wall penetration for signs of water infiltration.

I think this will probably be the culprit. Over the last few weeks, there have been a few mornings where the work crew came in and the breaker was NOT tripped. I looked at the weather history for those days... consistently dry and clear with minimal wind. Now when we get the nasty rain storms and squalls, then the breaker is tripping, as I saw today. Given that I didn't see any obvious moisture issues inside any of the lights, I think I will heed your advice and check the wall penetrations. They're all MC cable stubbed out through metal siding :roll: It's possible that water is getting through the wall penetration and into a J-box somewhere. Not looking forward to that. Really difficult area to access inside.

 

[Jlarson]

Perhaps, but...

Didn't you already look in each fixture though

 

[LEO2854]

Have you replaced all the lamps? From what i understand you have 4 HP'S Lamps and 1 MH lamp

Allso Metal halide lamps do crazy things at end of life and that includes cycleing it may allso it could have a bad ballast or defective capsiter Remember MH lamp's have a longer cool down before restrike.

Change all the lamps then if the breaker trips disconect the MH fixture first and go on from there.

 

[kwired]

You really think water is conductive enough to raise current level to short circuit quantities? In less than 5 seconds on top of everything?

If water is entering and current is flowing through it, the amount of current probably is not very high and would only give breaker tripping problems to GFCI type breakers, at the same time the water would start to evaporate from current flow along with increased heat from the lamp and eventually dry out causing less problems from water. Severe water leak would result in obvious problems as fixture may have a lot of water in it or be completely filled.

If water is entering and causing this it is because of an insulation problem of a component, and conductive material being suspended in the water, not the water itself. A megohmmeter will find this problem.

 

[G0049]

I think this will probably be the culprit. Over the last few weeks, there have been a few mornings where the work crew came in and the breaker was NOT tripped. I looked at the weather history for those days... consistently dry and clear with minimal wind. Now when we get the nasty rain storms and squalls, then the breaker is tripping, as I saw today. Given that I didn't see any obvious moisture issues inside any of the lights, I think I will heed your advice and check the wall penetrations. They're all MC cable stubbed out through metal siding :roll: It's possible that water is getting through the wall penetration and into a J-box somewhere. Not looking forward to that. Really difficult area to access inside.

This might also be vibration related if the wind is a consistant factor. There could be an intermittant short caused by something rubbing when the lights move in the wind.

 

[emsges]

HID circuit breakers

HID circuit breakers

I recently sold two circuit breakers to an electrical contractor. These were a Siemens Q115HID and a Square D QO115HM. An electrical inspector told him these are the types of breakers needed for HID light fixtures he was installing. There is information for these breakers on the mfrs. websites.

 

[dbuckley]

This might also be vibration related if the wind is a consistant factor. There could be an intermittant short caused by something rubbing when the lights move in the wind.

That was my thought a few posts above. Can't see a bit of water making the current go from normal to breaker trip in a five second period.

And given its in conduit, its gonna be fun to find. A set of series fuses splitting the run into chunks should do it though.

Might be quicker to repull the lot!

 

[kwired]

I recently sold two circuit breakers to an electrical contractor. These were a Siemens Q115HID and a Square D QO115HM. An electrical inspector told him these are the types of breakers needed for HID light fixtures he was installing. There is information for these breakers on the mfrs. websites.

Read 240.83(D) SWD and HID marked breakers are to be used where the breaker is used as the switching device. If not used for switching then standard breakers are acceptable.

 

[CNC]

Did I miss this.... What kind and brand contractor?

 

[CNC]

Did I miss this... What kind/brand contactor? Test the capacitors when you opened the fixture? Being capacitors regulate the current in an HID fixture, isn't it possible a failed one cause this?
MH lamps can't short at the socket.... Can they? I thought the MH ballast was able to contact (lamp lead to common lead) and not fault. I have never had a lamp with an arc tube rupture, and short anything. I'm kind of jumping around... Being that you have eliminated some of these