Is there any consensus on whether fluorescent lights might normally
cause nuiscance gfci trips? And if so, is there anything that can be
done? These are the long, 48'' dual-bulb overhead lights, on a 20A GFCI
outlet.

Some background on the problem:
The lights (3 sets of them) are hanging in a detatched garage, and
plugged into a string of outlets on the ceiling, which are connected
through a single wall switch.

The _entire_ garage circuit is fed from a dedicated 20A GFCI
receptacle-but-not-a-receptacle (looks just like a receptacle, but
missing the outlets, and has just the GFCI part) in the basement of the
house, about 15' away. The wire runs underground using UF cable to the
garage, with ground wire, then to the problematic lighting run and a
few unswitched wall outlets.

I think I have narrowed down the tripping to the lighting outlets. The
ground path could be in the outlets themselves, the plugs/cords for the
lights, or somewhere internal to the fluorescent lights (the
ballast/filter, I am guessing).

Previous owner had chopped off all of the ground prongs on the lights,
so no tripping, but the lights didn't turn on reliably. I put the
prongs back on, so now I get reliable lights, but frequent gfci
tripping.

Thanks,
-kevin

I don't know anything about fluorescent lights, but the obvious work around
is to remove the GFCI and reinstall it just before the wall outlets. (or
toss it and buy a GFCI outlet.)

"kevin" wrote in message
ups.com...
Is there any consensus on whether fluorescent lights might normally
cause nuiscance gfci trips? And if so, is there anything that can be
done? These are the long, 48'' dual-bulb overhead lights, on a 20A GFCI
outlet.

Some background on the problem:
The lights (3 sets of them) are hanging in a detatched garage, and
plugged into a string of outlets on the ceiling, which are connected
through a single wall switch.

The _entire_ garage circuit is fed from a dedicated 20A GFCI
receptacle-but-not-a-receptacle (looks just like a receptacle, but
missing the outlets, and has just the GFCI part) in the basement of the
house, about 15' away. The wire runs underground using UF cable to the
garage, with ground wire, then to the problematic lighting run and a
few unswitched wall outlets.

I think I have narrowed down the tripping to the lighting outlets. The
ground path could be in the outlets themselves, the plugs/cords for the
lights, or somewhere internal to the fluorescent lights (the
ballast/filter, I am guessing).

Previous owner had chopped off all of the ground prongs on the lights,
so no tripping, but the lights didn't turn on reliably. I put the
prongs back on, so now I get reliable lights, but frequent gfci
tripping.

Thanks,
-kevin

GFCI tripping when fluorescent lights are on the protected circuit is fairly
common especially if the ballasts powering the lights are the older
electromagnetic type. The reason is that there is a fairly large capacitor
inside the ballast and current is induced to ground during operation and
particularly during turn on or off. My GFCI usually tripped when I turned
the lighting fixture off. It was just one fixture with a 2-lamp ballast
powering two 4-foot lamps.

Removing the ground from the fixtures reduced the induced current to below
the tripping point (about 5 milliamps) for the GFCI; but, as you say,
starting became a problem. That's because your fluorescent lamp system is
designed to have the lamps about 1/2 inch away from a grounded piece of
metal when starting. Otherwise, starting is slow to slower. Fluorescent
systems are highly engineered for efficiency and long life, but they have
strict requirements.

What can you do?

1. Bypass the GFCI with a feed just for the lighting fixtures and hard wire
the fixtures so you'll meet code requirements. Make sure you have a good
ground.

2. Replace the ballasts in the fixtures with the newer high-frequency
electronic type. You might as well go with a high-efficiency system too; so
use T8 rather than T12 lamps (F32T8). They will fit into your existing
fixtures.

3. Mount the GFCI where it's easy to reach and live with the occasional
tripping.

TKM

Thanks for the responses. Unfortunately most aren't doable...

... remove the GFCI and reinstall it just before the wall outlets.

The GFCI is protecting all of the outdoor outlets, which are required
to have GFCI. I would have to run a new cable back to the panel just
for this part of the circuit. And worse, I think that the GFCI is
required on the house-side of the (very shallow) underground run.

1. Bypass the GFCI with a feed just for the lighting fixtures
3. Mount the GFCI where it's easy to reach

Same problem -- underground run is shallow, so I think it might need
the GFCI (in the house basement) for protection, and hence very
inconvenient to the garage, in the dark, on the other side of the
house.

2. Replace the ballasts in the fixtures with the newer
high-frequency...

I will look into this one -- it sounds promising. These balasts are
indeed quite old.

Regards,
-Kevin

Kevin,

The lights are obviously causing or contributing to your
problem. This seems obvious from the fact that restoring
the proper grounding of the lights led to the GFCI tripping
plus the fact that the previous owner removing the ground
plugs for a reason.

I believe that even with newer ballast systems, some
fluorescent light systems can confuse GFCI circuitry due
to the small capacitive losses created between the bulbs
themselves and the metal reflectors which are in close
proximity to the bulbs. This is a nuisance ground fault -
a genuine loss of current to ground but not a safety issue.

The problem is that background nuisance ground faults
are cummulative and they can create nuisance GFCI
tripping. If they don't trip the GFCI, then they increase
its sensitivity by preloading it with some small level
of ground fault.

Before you invest in new ballasts or new fixtures, I'd
suggest doing some research to be certain that it is not
just the starting cycle of the lights which contributes to
the ground faults. Hopefully you'll get some good advise
on this newsgroup on the issue of capacitive losses
during fluorescent light operation. If not, there is probably
a lot of information which can be located with "Google".

Good luck,
Gideon

=======================

Kevin wrote:
Is there any consensus on whether fluorescent lights might normally
cause nuiscance gfci trips? And if so, is there anything that can be
done? These are the long, 48'' dual-bulb overhead lights, on a 20A GFCI
outlet.

Some background on the problem:
The lights (3 sets of them) are hanging in a detatched garage, and
plugged into a string of outlets on the ceiling, which are connected
through a single wall switch.

The _entire_ garage circuit is fed from a dedicated 20A GFCI
receptacle-but-not-a-receptacle (looks just like a receptacle, but
missing the outlets, and has just the GFCI part) in the basement of the
house, about 15' away. The wire runs underground using UF cable to the
garage, with ground wire, then to the problematic lighting run and a
few unswitched wall outlets.

I think I have narrowed down the tripping to the lighting outlets. The
ground path could be in the outlets themselves, the plugs/cords for the
lights, or somewhere internal to the fluorescent lights (the
ballast/filter, I am guessing).

Previous owner had chopped off all of the ground prongs on the lights,
so no tripping, but the lights didn't turn on reliably. I put the
prongs back on, so now I get reliable lights, but frequent gfci
tripping.

Thanks,
-kevin