GFI and fluorescents in garage.


I have an unattached garage that we wired for electricity a couple years ago. I had a semi retired electrician consult and it was all inspected and passed. I had three cheap fluorescent 4 foot fixtures in the ceiling. The lighting circuit is on a 15 amp breaker and a 15 amp GFI outlet. That's code and the inspector was fine with it.
Then last year one of the fixtures died and I replaced that setup with six four-foot units that were more durable, and filled 'em with T8 32W, daylight spectrum.
The light is great. Except now, after the lights are on for a while - more than two hours, I think - if I turn them off, and then right back on because I forgot something, the gfi trips. If I wait a few minutes it won't trip. If I turn off two or three of the fixtures, it's usually okay but sometimes still trips. I replaced the gfi outlet with one of HD's "Heavy Duty" units. That lasted a little longer.
From some experimenting, I thought I had it narrowed down to one fixture so I switched the bulbs out of that one with another, but now it seems to be random. If three fixtures are off, the gfi doesn't trip. It's hard to be sure because after a few minutes, the gfi doesn't trip any more. I've had them on all day and everything's fine unless I turn them off and then back on.
Anybody got any thoughts? I'm thinking I might have to run another wire on another 15 amp circuit, and have two switched banks of three fixtures each. But maybe I can get away with replacing all those fixtures. That would cost more money that running another circuit up there, but I'm not looking forward to crawling around running more wires and outlets and a new switch. But maybe that's the only way.
Think it's the fixtures? Or am I just running too many fluorescents for on gfi to handle?
Dan
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If the lights are on the "load" side of the GFCI outlet, remove them and install them on the "line" side. There is no NEC requirement to protect them through GFCI

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wrote in

Well that would certainly make it simple. :-)
And yes, they're on the load side. Okay, I'll do that tomorrow.
Thanks RBM.
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Lasted a little longer but also give you *less* protection.

Why not just connect the fixtures to the existing lighting circuit in the first place? Either connecting to the line side of the GFI, as RBM suggested, or to the lighting circuit will make the tripping go away but you still have a stray ground leak somewhere enough to trip the GFI. What you describe is not easy to troubleshoot. Its not your lamps and its not that you have too many fixtures connected either, assuming you have no other additional loads. Recheck you connections, the neutral in particular. Could also be a bad fixture.
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I don't understand. They ARE connected to the existing lighting circuit, installed by a licensed electrician.

No additional loads. Nothing but six fluorescents. To answer Dave's question, hey're new, and they're not very heavy. I don't know for sure whether they're all-electronic but suspect they are.
I used that little three-light tester on every outlet on that circuit, and it indicated the wiring was correct. I've run continuity checks on the ground wire (after disconnecting it from the box) and it all says the ground is connected, and there's no continuity between the ground and the other two leads.
I'm stumped in that regard. Not sure what to test now. I've got an amp meter and have been checking the amperage on the lamps. They're all running at about .5 amps.
When you say "a bad fixture", do you mean one of them could be leaking some voltage to ground only when warm and only after being turned off and then back on? That was my first thought, and I think I'll continue with that line.
Thanks.
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The way I read your original post, you had two circuits with one for lighting and one for receptacles that is protected by GFI. Perhaps I misread. In any case, its better to have lighting and receptacle loads on different circuits if its all practical. Easier to troubleshoot and you won't have a receptacle load take out your lights in the middle of the night.
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Agree. Take the fixtures off of the GFI; but be sure all of the fixtures are well grounded. What I think is happening is that one or more of the ballasts in the fixtures has a high impedance leak to ground. But, some leakage is normal and actually is required to start the lamps in some types of fluorescent circuits. If there is a failing ballast, grounding it will eventually solve the problem as the ballast will fail dead or trip the CB. Ballasts have internal thermal cut-outs; so there is minimal risk of overheating or fire as the ballast fails.
It sounds like the ballast fault may be temperature sensitive -- not a surprise if the fault involves a capacitor inside the ballast.
TKM
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I agree it certainly seems temp related. It only happens when the lights are on for at least a couple hours.
Going on the assumption that it's a faulty cap or transformer and that it's probably just one fixture out of the six, I'm going to buy a new fixture and begin swapping them out one at a time and see what happens. I installed them in a way that makes it easy to remove and replace each one. I should have done that before I posted here. Maybe I was looking for someone to agree that it sounded like a bad fixture. :-\\
I and that electrician I hired spent a lot of time installing that circuit. I was very careful, he made the final hookups, we put the tester on every outlet in the lighting circuit, and the inspector approved the setup. I will continue to look for faults in the grounding, but I took extra time to make sure the white, black, and ground wires were where they're supposed to be when we ran that circuit because I didn't want to go crawling around those garage rafters again, chasing problems. I think the chances of it being faulty wiring are slim.
Thanks all. Still open to suggestions. :-)
If one of the fixtures isn't the culprit, it will probably take a few weeks to know for sure because I won't be spending lots of time in that garage for a while. Would you like me to post back with what I come up with?
Dan
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Don't buy a whole new fixture. Just replace the ballast(s). Cheaper, and it's the only part in a flourescent light that might actually go bad.
I would get the electronic ballasts from a local electrical supply shop, not Home Cheapo or other big-box place. They are a little more expensive than magnetic ballasts (but cheaper than a whole new light), they are more efficient (hence run cooler) and start almost immediately with no flicker or buzz. However, cheap brand-x units sometimes do buzz. Good ones will not.
Also, since this is in a garage, make sure you get ballasts rated for the coldest temps you are likely to get.
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Dan wrote:

Could be on the re-light the load is a bit inductive, are these all-electronic ballasts or the heavy ones with a fair number of transformer windings?
Getting zapped by an overhead light is unlikely, but unlikely stuff happens, so leaving it connected through the GFCI is for me a no-brainer.
Dave
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It's not required by NEC, and if the lighting circuit is properly grounded, he's perfectly safe

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