Having Lighting Issues. Please Help!!

az electrician

First off I lurk on here all of the time to gain information. Great forum with very smart people and Im taking this opportunity to thank all the people who have helped me without even knowing it.

Ok so heres my problem. My company wired a boutique with 10 low volt track lights. There are 2 circuits feeding these lights, 5 tracks each, with approximately 1200 watts per circuit on 20 amp Square D QO breakers. Both circuits feed a 240v 2 pole, single throw switch. These lights randomly trip breakers when you hit the switch, sometimes one circuit, sometimes the other, sometimes not at all. If I reset the breaker or both breakers, they will work fine and stay on all night, but maybe next time you go to turn them on something trips. And sometimes the lights turn on fine with no problems. My first troubleshoot session was to isolate the problem by disconnecting the tracks one at a time. On the first set of 5, I managed to keep 2 of these track lights on with no issues. If I hook up any of the other 3 the breaker trips. On the second set of 5, I only manage to keep 1 track on with no issues. The lighting company says its impossible for 7 of the 10 lights to be bad. On a side note, I noticed the white wire is the fused wire on all of these lights on the line side before the transformer. I thought that was weird. We don't normally do a whole lot of commercial work but this one seemed simple. I in particular had nothing to do with the wiring and the guy who did has since been fired for other reasons and I have to admit I haven't opened any j-boxes yet because this problem was not a direct short. I hope my post is somewhat easy to understand and I look forward to reading fellow electricians thoughts.
Also if there is something Im not catching thats extremely stupid feel free to let me have it. I THINK my troubleshooting was the right way to go but I've been known to be wrong before.:

Thanks
Josh

goose134

I know this may sound dumb, and I'm not sure if I understand your setup exactly. But, have you tried taking a few track heads off of each circuit? The other thing you may want to try is running a seperate neutral for each circuit.

Bubbles

I'm going to ponder on that today and check back. But one thing for sure, I agree you should get another neutral for that circuit. It's probably being overloaded to hell. Real quick it is sounding like an overload problem to me only since it sometimes happens and sometimes not. Did you take a meter on the circuits to see the actual load or did you calc. from bulbs? Track lights are a pain in the arse half the time. Take a measurement of the neutral when they are all working as well and see what you get. I'm checking back later to see what everyone else says.

Later

Speedy Petey

I'm not sure why both of you say to add another neutral. I fail to see how the one neutral can be overloaded and how adding a new one will help this situation. MWBC's are the norm in commercial lighting circuits.

If both these circuits are controlled by a single double-pole switch then a two-pole breaker MUST be used. See 210.4(B)

I have a suspicion that there is a line to line "semi-short". As the wiring heats up it expands and "makes" the short. This is why one or the other breaker will trip.
The same thing can happen with a poor splice. It can create so much resistance that it fools the breaker into tripping.

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220/221

Dumb question but I gotta ask.

Are the breakers on opposite phases?

Magnettica

Even if both circuits were on the same phase, neither breaker would trip because the added current would only be on the neutral. I would start by isolating sections of the circuit (transformer, trackheads, tracks,) to try and find the problem that way. And since you didn't do the original work, I would also get up and check those junction boxes.

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mdshunk

This is one of those deals where a megger sure would come in handy. I feel pretty good about guessing that you have a scuffed wire someplace on that circuit.

I do have one question, though. What are you using for a transformer? Is it integrated in each head, or is it a single transformer remote mounted someplace for each circuit?

The fact that it's the branch breaker tripping makes me believe the trouble is on the primary side of the xfmr. Have you taken amp draw measurements yet, to make sure that jives with what you'd expect for 1200 watts?

220/221

Eh..I would bet money on that. Couldn't more amperage on the neutral equal more resistance and therefore equal more amps?

Lectricity is funny like that.

Step 1, phase properly.

Step 2, install 2 SP switches

Step 3. check make up.

Step 4, read amp draw

Step 5, wait and see what happens.

az electrician

Im going back tomorrow to open everything on those 2 circuits. I havent taken an amp draw yet but I will tomorrow before doing anything else. The track lights have individual transformers for each seperate track integrated in the canopy of the light. If I did have a scuffed wire somewhere wouldnt it only trip the circuit that was scuffed and instantly instead of random trips between both breakers? These are on different phases, matter of fact they are circuits 2 and 4, top right 2. As I mentioned in my original post Ive individually disconnected these tracks as my first troubleshoot session which was cut short but tomorrow hopefully I figure something out. My only option now is to open EVERYTHING. I was trying to pin the problem on the lighting company but I better check everything out first. Thanks guys!

Sparky Joe

A new take on ohms law; A=R x (more)

with that new law fit this one in; (more)R=A x (more)

It seems we have a never ending circle and a for sure explosion of infinite porportion, so take care everyone while on the job tommorrow because with these new laws you'll need all the luck you can get

220/221

Hey, cut me some slack. I barely finished high school.

All I know for sure is that I often say "How the hell did THAT happen?"

Case in point: A few years ago I ran some conduit, pulled in some circuits, installed some outlets and was terminating at the panel. I did the EGC first and got an arc from the ground buss.

WTF?

Bubbles

Can't wait to see what you find AZ. I think one of those tips above will be the problem. 221...you gotta watch it on here. It's brutal. If you slip with one word people are are all over you. I'm on your side. Leading to the neutral topic. If everyone and their brother down the road would leave the the 2 circuits on the 2 pole breaker there wouldnt ever be a neutral problem, but in reality its another thing.

2 cents

az electrician

I still havent been back but will tomorrow. Ill fill all of you in on what I find.

Sparky Joe

One wrong word and I'll be on it like stink on .......
As for taking sides, I prefer to stand alone and everyone else probably prefers me standing that way also.

But i will say "electrician's" that don't know Ohm's Law are few and far between.

220/221

As opposed to apprentices who think they know everything.

HVAC_NW

I'm not in this trade, yet I have always expected them to know the theory behind what they're doing. I guess you're one of those red wire goes on here, and through here, connect these and they work type worker.

I honestly expected all electricians to know beyond scripts learned from experience and know the theory behind it.

220/221

That's quite an assumption to make after reading a couple posts dontcha think?


Maybe your expectations are too high. The theory behind electricity is really very simple. It goes in one end and comes out the other. Pretty much like water but you can't see it.

goose134

I don't know about anybody else, but I am dying to know what happened. I keep looking and waiting but nothing. The reason that I suggested running a seperate neutral was simply because of the electronic transformers. Now I realize that this sort of thing wouldn't always trip a breaker the way AZ describes, but they tend to act sort of funny when you get a bunch of them in a circuit. I realize that MWBC are the rule in commercial. When I have them ready, I'll post some pictures of our last project. Still waiting for the results!!

Bubbles

Whats going on AZ? THis is like a thriller novel. Don't leave us hanging like this. What happend??

Sparky Joe

So how do you explain AC theory where it goes in both ends and comes out both ends?