Trouble shooting gfci

[brother]

Had a call about a gfci tripping. Well at first I thought it was the 'equipment' that was the problem. The gfci works ok with other tools.

What they had was a '2 prong (no ground prong)' work light, mostly plastic. I think the light is a 'led' every time they turn it on, it 'trips' the gfci. I saw this myself.

i know a gfci can work without a ground, it just senses an imbalance of current between the 'hot' and neutral.

Is the light (led) it self causeing something here?? I dont see any way for their to be any 'leakage ' here. any help would be appreciated. I told the guys the gfci will stay because it works with other tools. I admit I have not check the wiring/polarity of the gfci, but my understanding is that the 'new' ones will not reset if wired incorrectly. This is a fairly new install, (within the last year).

Also they said they tested the led work light at another gfci and it worked fine. Maybe its just a manufacturer type/style problem, wont know until tommorrow. Any suggestions would be greatly appreciated.

 

[ELA]

GFCI's in the the past have been known to be sensitive to "electrical noise".
Some brands are more immune than others.
From what you described it sounds like noise (switching regulator for LED) or possibly inrush current and not actual leakage.

If you have access to an oscilloscope(current probe) you could view the current waveform at turn on in a non protected circuit to diagnose.

Otherwise it looks like changing the brand might help as you pointed out it worked on another GFCI brand.

 

[cowboyjwc]

Just because the light worked on another GFCI outlet doesn't mean that the lights not bad, it could be that GFCI is bad. You could change it out and see if that works, but I still wouldn't rule out the fixture.