2014 NEC, 406.4(D)(2) Non–Grounding-Type Receptacles.

[NVF7777]

Possibly someone can help me answer a question I have regarding: NEC - ‘406.4(D)(2) Non–Grounding-Type Receptacles.”


My understanding of this code is that the old, not-grounded, 2-prong receptacles can be replaced with a GFCI receptacle, so long as the GFCI receptacle is marked, ” “GFCI Protected” and “No Equipment Ground.” This is clear.


Can someone help me understand the NEC rationale for sub-paragraph (c)?

Sub-paragraph (c) of this code states, “(c) .... Grounding-type receptacles supplied through the ground-fault circuit interrupter shall be marked “GFCI Protected” and “No Equipment Ground.” An equipment grounding conductor shall not be connected between the grounding-type receptacles.”


Sub-paragraph (c), I don’t get. Why does the NEC on one had allow “Grounding-type receptacles s supplied through the ground-fault circuit interrupter “ and on the other hand say, “An equipment grounding conductor shall not be connected between the grounding-type receptacles.”


Here’s my question: What’s the purpose for allowing grounding-type receptacles downstream from a non-grounded GFCI receptacle , if the NEC says you’re not permitted to plug a grounded 3-prong-plug (equipment grounding conductor ) into that receptacle? Why not just use 2-prong receptacles marked “GFCI Protected” downstream from the non-grounded GFCI receptacle since 3-prong plugs at those outlets are not permitted according to to my read of 406.4(D)(2)(c)?

Thanks for your feedback.

 

[augie47]

Note the exact wording of the section you quoted is:
An equipment grounding conductor shall not be connected from the ground-fault circuit interrupter type receptacle to any outlet supplied from the ground-fault circuit-interrupter receptacle.

It does not prohibit you from plugging a 3 wire cord into the receptacle

 

[don_resqcapt19]

... It does not prohibit you from plugging a 3 wire cord into the receptacle

But for some loads 250.114 says you can't plug the 3 wire cord into that receptacle.

 

[charlie b]

I think the intent recognizes that the first outlet in the string (i.e., the one that has the GFCI protection) does not have a ground wire coming in to it. The next part of the reasoning is that if you allow a ground wire to be run from that outlet to another outlet downstream, that ground wire will not be able to do its function (i.e., because there is no ground wire that goes all the way back to the panel). So why allow one to be installed, if it cannot do its job? Also (and I know this is weak), if a future installer sees a ground wire going into the second outlet, and it has been long enough since it was installed that all labels are lost or faded, how will they know there is no ground path back to the source? By not allowing a ground wire to be run from the first outlet to the second, a future installer will recognize right away (with or without seeing any labels) that there is not a complete ground path.

 

[LarryFine]

NV, welcome to the forum. One GFCI receptacle can be used to protect downstream receptacles in this case, too.


Charlie, I believe the reason for not interconnecting EGC terminals is to make sure that an accidental energization of one load's cabinet, and thus its EGC, does not energize another load's EGC, and thus its cabinet.

 

[charlie b]

Charlie, I believe the reason for not interconnecting EGC terminals is to make sure that an accidental energization of one load's cabinet, and thus its EGC, does not energize another load's EGC, and thus its cabinet.

That makes sense. Thanks, Larry.

 

[NVF7777]

Bad Read

Bad Read

Note the exact wording of the section you quoted is:
An equipment grounding conductor shall not be connected from the ground-fault circuit interrupter type receptacle to any outlet supplied from the ground-fault circuit-interrupter receptacle.

It does not prohibit you from plugging a 3 wire cord into the receptacle

I think you're right. I misread subparagraph (c). There is no prohibition in using a 3-wire cord/plug. The prohibition is running a ground from the not-grounded gfci receptacle to its down stream receptacles. Bad misread on my part. Thanks for the clarification !! :thumbsup:

 

[jap]

I think the intent recognizes that the first outlet in the string (i.e., the one that has the GFCI protection) does not have a ground wire coming in to it. The next part of the reasoning is that if you allow a ground wire to be run from that outlet to another outlet downstream, that ground wire will not be able to do its function (i.e., because there is no ground wire that goes all the way back to the panel). So why allow one to be installed, if it cannot do its job? Also (and I know this is weak), if a future installer sees a ground wire going into the second outlet, and it has been long enough since it was installed that all labels are lost or faded, how will they know there is no ground path back to the source? By not allowing a ground wire to be run from the first outlet to the second, a future installer will recognize right away (with or without seeing any labels) that there is not a complete ground path.

To me, all of this if very weak indeed.

The allowance of the GFI to be installed is because of the absence of an EGC in the first place.

What difference does it make if an EGC happens to be run from the load side of the first GFI protected outlet to the 2nd ? even if it cant do it's job.

Is that not what the GFI was installed for in the first place?

Also, what normal person is going to go read 250.114 before deciding whether or not they should plug their 3 wire cord into a perfectly accepting 3 wire receptacle ?

JAP>

 

[PaulMmn]

A GFCI does not need a ground wire in order to detect a ground fault, and break the circuit.

 

[LarryFine]

A GFCI does not need a ground wire in order to detect a ground fault, and break the circuit.

Agreed. It does require that the power source has a grounded conductor.

 

[PaulMmn]

Agreed. It does require that the power source has a grounded conductor.

Your comment bothers my Sense of Reality-- I thought the GFCI just sensed the difference between the outgoing current on the hot lead compared to the incoming current on the neutral lead. I didn't think it required a grounded conductor at the power source. :?

 

[jap]

Your comment bothers my Sense of Reality-- I thought the GFCI just sensed the difference between the outgoing current on the hot lead compared to the incoming current on the neutral lead. I didn't think it required a grounded conductor at the power source. :?

The neutral from the source is the Grounded Conductor and is required for proper operation of a Ground Fault Receptacle.


JAP>

 

[jap]

Don't confuse "Grounded Conductor" or Neutral with an "Equipment Grounding Conductor".

JAP>

 

[LarryFine]

Your comment bothers my Sense of Reality-- I thought the GFCI just sensed the difference between the outgoing current on the hot lead compared to the incoming current on the neutral lead. I didn't think it required a grounded conductor at the power source. :?

Without a grounded circuit conductor, a contact between a hot wire and a grounded surface will not create a current difference. The hot wire wouldn't carry more current than the neutral, because there is no pathway for current around the current-sensing ring that both line conductors pass through.

Remember why plug-in GFCI testers don't work on non-grounding receptacles? It's because the plug-in tester has no access to the neutral ahead of the current-sensing ring, so it can't create an artificial shock condition using a resistor like the one used for testing inside GFCI receptacles and breakers.

A GFCI device serves no purpose and will not function on a non-grounded power source.

 

[PaulMmn]

How about a 240 volt GFCI-- Only neutral involved is in the breaker box to power the electronics in the GFCI. Black wire out, black wire in; no neutral anywhere; neither black is grounded. GFCI still knows when there's a fault.

Several interesting threads from the fora:

From https://www.ecmweb.com/content/think-gfci

From closed thread https://forums.mikeholt.com/showthread.php?t=158467

From closed thread https://forums.mikeholt.com/showthread.php?t=102515

From closed thread https://forums.mikeholt.com/showthread.php?t=66292

 

[tom baker]

The Code Making panel determined it would be safer to have a non grounded outlet replaced by a GFCI than to have someone cut off the ground in the cord cap.

 

[jap]

How about a 240 volt GFCI-- Only neutral involved is in the breaker box to power the electronics in the GFCI. Black wire out, black wire in; no neutral anywhere; neither black is grounded. GFCI still knows when there's a fault.

Several interesting threads from the fora:

From https://www.ecmweb.com/content/think-gfci

From closed thread https://forums.mikeholt.com/showthread.php?t=158467

From closed thread https://forums.mikeholt.com/showthread.php?t=102515

From closed thread https://forums.mikeholt.com/showthread.php?t=66292

In that scenario the GFCI is monitoring the 2 phase conductors.


JAP>

 

[jap]

The Neutral connection in the Panel is needed to energize the electronics inside of it to allow it to do so.

JAP>

 

[PaulMmn]

The Neutral connection in the Panel is needed to energize the electronics inside of it to allow it to do so. JAP>

Yes, but neither of the conductors the GFCI is monitoring is grounded. The neutral in the panel is just for the electronics.

Likewise, for a 120 volt GFCI, it wouldn't care if either of the conductors it is monitoring are grounded or not. The 120 volt model wouldn't care if the electronics were powered by a 110-volt DC battery!

IMHO.

 

[MAC702]

The Neutral connection in the Panel is needed to energize the electronics inside of it to allow it to do so.

But that would just be a design issue of the electronics inside, not a fundamental function of how it works, right?