Grounding fixture trips breaker

[Phrank308]

I am in the process of replacing the old fluorescent fixtures in my garage and have run into an issue with the last one I installed. When I ground the fixture, even without hot or neutral connected the breaker will trip immediately.

Some background:

Garage had old T12 strip fixtures which plugged into outlets installed in the ceiling. As most of these had died and I wanted more light I replaced them with T8 eight foot tandem fixtures. These fixtures are direct wire and I've connected them at the boxes which used to hold the outlets in the ceiling. I removed the outlets and will plate over the boxes once everything is working. These boxes are all wired together as well. The fixture that is causing a problem is at the end of the circuit. As I said if I attach only the ground with the other wires disconnected and secured with wire nuts the breaker will trip. The fixture is screwed to wood frame so I doubt that it is grounding out anywhere.

I'm not sure what to start checking to determine what to fix. Any recommendations of what to look at?

 

[Geobound]

So are you saying that all of the other fixtures work fine, it's just when you try and attach the last one that the breaker trips?

Have you crossed the black/white/green anywhere?

Have you overloaded the circuit?

Perhaps the ballast lead wires have been installed incorrectly?

 

[wyliesdiesels]

Is the breaker thats tripping a GFCI?

If so then it means u have neutral current leaking to ground through the chassis. It only trips when u hookup the ground wire because the leaking current is finding an alternate path back to the dource and the GFCI sees this as a ground fault....

 

[James-W]

Is the breaker thats tripping a GFCI?

If so then it means u have neutral current leaking to ground through the chassis. It only trips when u hookup the ground wire because that's the only alternate path....

I am not sure exactly what he is even talking about, He says he has no other wires connected to the light fixture, not the black wire nor the white wire, only the green wire. But when the green wire is attached to the body of the light fixture, the breaker trips. That makes no sense to me. How can the green wire cause the breaker to trip, even if he has crossed the green wire to the black wire? With only wire connected to the light fixture, how can there be a dead short, or any kind of short for that matter? Am I missing something?

 

[LS6 Tommy]

My question is, WHY IS HE WORKING ON IT WITH THE BREAKER ON??

Tommy

 

[kd3pc]

fixture mounting screw through the feed or switch leg???

 

[Fixin'Stuff]

fixture mounting screw through the feed or switch leg???

This would be my guess. One of the screws that mount the fixture pierced a power wire above the ceiling.

 

[APEowner]

fixture mounting screw through the feed or switch leg???

This, or one of the wires so shorted to the fixture where it enters the housing.

 

[Phrank308]

This, or one of the wires so shorted to the fixture where it enters the housing.

Shorting on the fixture was my best guess. Not sure how I would have done that when wiring this one up but not the other seven but I am skilled like that .

The romex comes in through a knockout in the middle of the fixture with one of those screw down pressure fit grommets. If I over tightened the grommet could it cut through the casing or am I more likely to have just been sloppy when cutting the outer casing and nicked the wires?

That said would a continuity tester identify if this is what's going on or would I be better off just pulling the wire and putting in new to see if that fixed it?


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[Zeke]

Do you have a GFCI breaker? They don't like neutrals and grounds that are tied together. It will work with only a neutral and hot or with them all separated as they should be.

 

[Geobound]

If you stripped too much of the outer jacket away, and the metal strain relief is touching any exposed wire, then yes that could be your problem.

Are you going out from one fixture into another with a wire lead?

If so and the other fixtures work, then just replace that one lead and see what happens.

Whatever your problem is, it is only tied to that last fixture if the others before it work.

Check the ballast and make sure you were supplied with the proper voltage.

Some ballasts come as a tri-tap ballast (Canada) as 120/277/347, and perhaps you've tied into the wrong leg?

The same would apply in the US, but likely only 120/277.

 

[Dirtydan69]

My question is, WHY IS HE WORKING ON IT WITH THE BREAKER ON??

Tommy

There would be absolutely no challenge when turning the power off. Besides if you make a mistake it will turn itself off. Problem solved.

 

[klassenl]

There would be absolutely no challenge when turning the power off. Besides if you make a mistake it will turn itself off. Problem solved.

This

 

[dslabuda]

There would be absolutely no challenge when turning the power off. Besides if you make a mistake it will turn itself off. Problem solved.

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[Zeke]

I think the problem is in the box above the light. He may have reversed some wires in the box before it. After all, the OP was removing all the outlets and hard wiring his new fixtures.

 

[rburke65]

Please let us know what you discover. Interested.....

 

[Phrank308]

So just pulled the wire that I had run from the box to the fixture. And sure enough it had shorted through. When I opened it up it looks like the wire got pinched from not laying right and me putting too many turns on the grommet. As you can see it arched right through the wire insulation and the casing.




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[Phrank308]

Ohh and if I don't have power going to the lights how am I supposed to see what I'm doing [emoji12]


No really the power is off while I'm working it blew the circuit immediately because I have a switch tied to the garage door so the light was live as soon as the breaker was flipped.


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