LED lighting fixtures and GFCI's

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Ingenieur

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coal mines are starting to install LED fixtures
most are having issues with nuisance tripping on the legally required GFCI circuits (our law, all cord connected lighting must be on GFCI unless hard wired)
the wiring is MSHA approved SO type cable
they want to use plugs but eliminate the GFCI due to having to move the lights as the operation continuously advances

I actually went to few mines and measured the I on the G, it varied from 20-50 mA, so the tripping was valid

is this common with LED/GFCI?
 
I don't know why there would be that much current on the ground. The driver should be converting the LED supply to DC, so I would expect less leakage to ground than on fluorescent lights.

Can you post a brand and model number? I'd be asking the manufacturer.
 
steve66 said:
I don't know why there would be that much current on the ground. The driver should be converting the LED supply to DC, so I would expect less leakage to ground than on fluorescent lights.

Can you post a brand and model number? I'd be asking the manufacturer.
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I have seen it in several different mines, different manufacturers
I'm trying to get data sheets for a few of them

I'm guessing the DC convertor is referenced to ground
 
Ingenieur said:
I have seen it in several different mines, different manufacturers
I'm trying to get data sheets for a few of them

I'm guessing the DC convertor is referenced to ground
Click to expand...

Sure, it's probably referenced to ground, but the actual supply current would be through the neutral, and since its DC, there shouldn't be any leakage current through any stray capacitance or inductance. (Or does this just happen when they are switched?)

Do they have integral controls? Occupancy sensors? Surely they aren't using the exception that wall switch controls have for using the ground as a CCC??

It would be interesting to put one of these fixtures on the bench and find out whats going on.
 
steve66 said:
Sure, it's probably referenced to ground, but the actual supply current would be through the neutral, and since its DC, there shouldn't be any leakage current through any stray capacitance or inductance. (Or does this just happen when they are switched?)

Do they have integral controls? Occupancy sensors? Surely they aren't using the exception that wall switch controls have for using the ground as a CCC??

It would be interesting to put one of these fixtures on the bench and find out whats going on.
Click to expand...

this is a coal mine, underground, acutally in the working face section
no swtches (only the disconnect/cb)
no occupancy sensor

Did not believe it until I measured it
120 vac, doubt much coupling capacitance
it is a damp environment and some runs are long
use #10 several hundred feet (10 is the smallest allowed)
I'm going to try to set-up some tests next week underground, not sure the bench would tell us much, imo it's the conditions

I should have measured at a few points
source, 1/4 of the run, 1/2....last fixture
only messued at source

thinking about allowing them to use a gfep device set next step above ambient i
set at 100 mA most trip at 65

the personnel protection is important (obviously)
but 65 should provide some 120 v / 1000 Ohm ~ 120 mA, should trip fast)
well below the Dalziel curve
besides not handled often and should always be de-energized
it also provides fire protection
a non gfci/gfep device may allow a crushed cable l-l-g fault to arc/spark/smolder for a while as long as below 20 A
not good along a roof made of coal
 
If the runs are that long, in wet and damp locations, are you sure its not just the wiring causing the leakage?
 
steve66 said:
If the runs are that long, in wet and damp locations, are you sure its not just the wiring causing the leakage?
Click to expand...

nope, not sure
could be
I'll try to test for that
Begining and end of long runs with close to full loading

but not much can be done about it

on a 15 A ngr on a 1 MVA 480/3 load center feeding equip via cables we may see 2-3 A
8-10 ckts anywhere from a few hundred to 1000' runs
 
Are you using GFCI breakers or receptacles?

Is it possible to substitute for equipment rated GFPE circuit breakers? The equipment rated breakers offer a higher mA trip setting compared to receptacle based ones.
 
shoon said:
Are you using GFCI breakers or receptacles?

Is it possible to substitute for equipment rated GFPE circuit breakers? The equipment rated breakers offer a higher mA trip setting compared to receptacle based ones.
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all gfci now
mixed cb and recept

that is one option mentioned above
gfep cb's set at the next setting > the residual current

one issue is gfci is the law
if I grant a variance I must justify in a technical report
narrow/limited in scope
mine/application specific
or it may be interpreted to set precedent and creep into other areas
I do not like decreasing the level of safety
is it offset by better illumination?
that must be established
 
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