Does code permit small return current on ground?

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avhays

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Have a 208/240 device with an L6-20 plug (an L6 receptacle is hot-hot-ground).

This device has a built-in 110v GFCI outlet labelled ".5 amps max load". That's point five. I suspect the device is using the ground for return for 110v (but maybe they are generating 110v internally some how like a small transformer). Install instructions also state device must be externally grounded.

Does code permit this small return current on ground for 208/240 devices using L6 cordsets?

Thanks,
 
charlie b

charlie b

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It does not. And for what it is worth, let me mention that .1 amps (i.e., only 20% of the current you are talking about) is enough to cause a fatal shock.
 
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GoldDigger

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charlie b said:
It does not. And for what it is worth, let me mention that .1 amps (i.e., only 20% of the current you are talking about) is enough to cause a fatal shock.
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But, if the device uses an isolation transformer (i.e. very small SDS) to derive the "neutral" lead for the receptacle they would almost be compliant to bond that SDS terminal to the incoming EGC. But they would have to fuse or breaker protect that limited current source to protect the transformer and the wiring.
To achieve complete compliance they would probably have to have an external GEC as well instead of relying on the EGC as the ground source for the grounded 120 lead. More input on that please....
 
Smart $

Smart $

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Is this a listed device?

Is there a specific purpose for this outlet?

I'm leaning towards it having an SDS as mentioned by GD.... but the exceptions for grounding hinge on the transformer being a control transformer and an Article 725 "Class" circuit (but this could be superseded if the device is listed).
 
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Buck Parrish

Buck Parrish

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Location
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GoldDigger said:
So it is better to leave out the earth ground so that people will get shocked and call an electrician when a fault occurs?
I do not quite see the logic in that.
Click to expand...

No it's not. I too, don't see the logic in that.
Perhaps you miss understood me. In my case the fault current was taking any path available back to the source.

I was showing the importance on the earth ground.
I'll rewrite it.
Thanks
 
S

shortcircuit2

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South of Bawstin
Some electronic switches use the equipment grounding conductor for a return path for the standby current of the device. The acceptable amount of current tolerance is .05ma that a manufacturer can allow an electronic device to flow over the EGC...

The 2017 NEC 404.2(C) has language in an exception to allow 5 electronic devices on a branch circuit with a limit of 2.5ma and no more than 25 electronic devices on a feeder for a total of 12.5ma for a feeder. This is only allowed in existing conditions where no grounded conductor exists or can be extended to the switch location(s).

At least...thats how I read it.
 
Buck Parrish

Buck Parrish

Senior Member
Location
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Saturn_Europa said:
That is an impressive video. Hopefully they called you before someone got shocked!

What did you do to fix it?
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Yes, I called the power company thinking the neighbors may have lost there utilities ground.
But no. So we stuck a probe with a gauge in the ground near my outside main water pipes.

I had about 10 volts outside, 20 inside. We turned off each circuit breaker one at a time until the gauge went to almost zero. I traced that circuit back found the short. That solved the problem.
 
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shortcircuit2

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Location
South of Bawstin
GoldDigger said:
.05ma times 5 equals .25, not 2.5. Which is the typo? or are the two sections just setting very different standards?
Click to expand...

My mistake, the error was the .05 ,it is .5ma as the allowed current tolerance.

Info found in the 2017 IAEI Analysis pg188
5*.5 = 2.5ma (Branch Circuit)
15*.5 = 12.5ma (Feeder)

So it would take 8 feeder circuits with 15 lighting controls to get to that danger threshold charlie b stated. This wouldn't be a difficult situation to get to in a large commercial building with alot of lighting branch circuits. There is most likely many buildings out there with early generation lighting controls that used the EGC to power the standby electronics of the device.

Seems like alot of electrons flowing on the EGC...

So anyway, the article says this .5ma current tolerance is allowed for "manufacturer's of devices such as an appliance". I would say this is not a "Code Allowance" as the OP asked, but rather a "Listing Allowance" from a UL standard.
 
kwired

kwired

Electron manager
Location
NE Nebraska
avhays said:
Have a 208/240 device with an L6-20 plug (an L6 receptacle is hot-hot-ground).

This device has a built-in 110v GFCI outlet labelled ".5 amps max load". That's point five. I suspect the device is using the ground for return for 110v (but maybe they are generating 110v internally some how like a small transformer). Install instructions also state device must be externally grounded.

Does code permit this small return current on ground for 208/240 devices using L6 cordsets?

Thanks,
Click to expand...
if there is a control transformer in whatever you have there, that 110 V return is to the control transformer not to the main power supply neutral, so the EGC still doesn't carry current under normal conditions.
 
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