T8 light trips GFCI

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480sparky

Senior Member
Location
Iowegia
Tack your pick:

1. There's a ground fault.
2. Defective GCI recep.


Why are you plugging in a fluorescent light?
emoticon_test_by_vampire_meme.gif
 

steve66

Senior Member
Location
Illinois
Occupation
Engineer
I have the same problem with the shop lights in my house. It only trips the GFCI once in a blue moon when I turn the lights on or off.

I think its caused by cheap ballasts that cause an inductive kick when the light switch interrupts the current flow. Some of that inductive kick must find some capacitive coupling to ground.

I would suggest trying fixtures with more expensive ballasts. Or for a band aid fix, try putting a GFCI at each fixture to limit the wiring lengths and loads on each GFCI device.

Steve
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
090113-1003 EST

yankj:

How often does the GFCI trip?
Does it trip when the light is turned on?
Or when turned off?
Does it trip at some other time than when the switch state is changed?
Is the metal structure of the light insulated from ground? Hanging from wood joists I would classify as insulated from ground.
Is there a 3 prong plug on the cord and an EGC from the plug to the sheetmetal of the light?
What is the brand and age of the GFCI?
Is there an RFI filter at the input to the light?

.
 

luggem

Member
T-8 light fixture

T-8 light fixture

090113-1003 EST

yankj:

How often does the GFCI trip?
Does it trip when the light is turned on?
Or when turned off?
Does it trip at some other time than when the switch state is changed?
Is the metal structure of the light insulated from ground? Hanging from wood joists I would classify as insulated from ground.
Is there a 3 prong plug on the cord and an EGC from the plug to the sheetmetal of the light?
What is the brand and age of the GFCI?
Is there an RFI filter at the input to the light?

.

It trips every time it is turned on. There was no ground hooked up because I was just bench testing it first. GFCI is good.
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
090115-1140 EST

yankj and luggem:

Using my test Leviton 7899-W device I have discussed in a different thread I got the following results:
1. 8 ft Slimline magnetic ballast and no RFI filter.
--- many tries and I could not trip the GFCI.
2. Same as (1) but includes an RFI filter.
--- tripped on the first try. Obviously this one has a EGC to the lamp and the filter has capacitors from the supply lines to the EGC.
The filter current to EGC is about 20 MA.

From looking at the Leviton circuit I think it is moderately immune to transients.

.
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
090115-1333 EST

Continuing:

I have a cheapie 4 ft with an electronic ballast. It has a 3 prong plug.

This won't trip my test GFCI with or without the EGC connected. Any current on the EGC is less than 10 microamps.

Get a Leviton of the same model number I used, 7899-W. See if your lamp trips this model device. I am not suggesting that this is any better or worse than others. It just happens that when I decided to run some tests this is what I bought first, and on which I have done the most analysis. Since it does not trip in my test it provides a frame of reference.

.
 

ELA

Senior Member
Occupation
Electrical Test Engineer
090115-1140 EST


2. Same as (1) but includes an RFI filter.
--- tripped on the first try. Obviously this one has a EGC to the lamp and the filter has capacitors from the supply lines to the EGC.
The filter current to EGC is about 20 MA.


.

Gar,
How old is that RFI filter. 20ma of leakage is substantially above what is normally allowed these days.
Older filters used larger caps and used to trip GFCIs but I have not encountered any modern RFI filters on commercial equipment that leaked this much?
 

bobsherwood

Senior Member
Location
Dallas TX
electronic ballast and GFCI

electronic ballast and GFCI

while doing an office remode, painters wanted lights connected for painting purposes. We had not had a scheduled shut down to install breakers for these circuits. We opened the 4sq that fed the 4 - 2 lamp 2X4's. We put a 3 prong cord cap on the lighting circuit and for extra safety my guy plugged it into a GFCI protected extension cord. It tripped everytime he tried to plug it up. I do not know why. I am tempted to open a ballast to see if there's an obvious reason.
 

glene77is

Senior Member
Location
Memphis, TN
Why does a 2 lamp T8 electronic ballast light trip a GFCI
that it's plugged into?

Yanky,

The T-8 ballast is Electronic,
a "switching power supply"
with auto (high voltage) starter circuitry
(puts lots of harmonic hash on the line during startup).

So, ?why? are you putting a light fixture on a GFCI ?
Could you bypass the GFCI? :confused:
 
Last edited:

glene77is

Senior Member
Location
Memphis, TN
Steve,

I agree that open/close the switch will trigger 'kicks' on the line.
If there is 'kick', then for a moment
the hot and neutral are out of phase (for that moment),
and that may be enough to trip the GFCI.

But, T-8 tubes require an electronic ballast, at least they come that way,
and with less mercury and more argon (etc) they can cycle at 10 KHz
and become much more efficient.
(That is a much higher cycling rate than the 120 Hz normally igniting a tube;
ie, that is two half phases per full cycle, with full ignition on each half phase.)

Disclaimer:
You may already know this,
the engineers surely do,
but I'm just reiterating it for the record. :smile:
 

PetrosA

Senior Member
I had a situation a few months back where I installed 4 Phillips LED strips in a closet activated by a occupancy sensor. It turned out the feed was from a GFCI breaker and every time the sensor turned the lights on the GFCI would trip two floors down in the basement. I called Phillips and their engineers set up the scenario in house and ran the experiment, no trip. I finally had to replace the breaker with a non-GFCI one and install GFCI recepts. in the powder rooms. Phillips' guys figure it has to do with the way electronic circuits start and interact with various GFCI devices.
 
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