equipment grounding conductors in NM box

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andrew

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Always up in the air about this. 2, 3, 4, gang nonmetallic cut-in, nail-on etc. any number of circuits any number of devices. A mixture of 15 and 20amp circuits lets just say NM as the wiring method. Must the equipment grounds ALL be spliced together or can the 14's and the 12's be seperate in the box. I was taught (and doesnt make it right) that all the EGC's go together and the largest is put on the devices. 250.148(D) is as close as I can come and I do not believe it actually states that. A code article would help.

Thanks
Andrew
 
Great question andrew.....I guess it depends on what the scenario is lets take a 3 gang with 2 switches and a standard receptacle in it.The grounding conductors must be together.Here is where it gets complex.If all circuits within this box are just standard circuits from non afci/gfci circuits no problem.But once you introduce afci or gfci protected devices into this same box the scenario changes.

Lets say that an afci circuit is fed from a receptacle under a switch for that room but its a 2 gang 1 sw. for a light in that room and one for a 3way for an exterior light.The 3 way goes into a non afci protected room,and in that 2 gang is the 3 way from the afci room and a switch for whatever is in that room(non afci protected)are in the same box.Well we all know that if you combine them as one the afci will trip when a load is applied.

Take a gfci circuit and add it into the equation now there is a 3 gang 2 standard non gfci switches and a gfci receptacle circuit within the same box.Can we join all the grounding conductors together no.The gfci will trip from the neutral to ground fault.But we are still required to attach all grounding conductors together aside from isolated receptacles as stated in 250 146 D and that requires an insulated grounding conductor.

As far as an article that permits us to seperate these circuits I haven`t found one but maybe some code guru here will give us the answer.I know that they will not work if all combined together,this is NM so all grounding conductors are bare copper.

Anyone have the proper article to deal with this ????
 
allenwayne said:
Great question andrew.....I guess it depends on what the scenario is lets take a 3 gang with 2 switches and a standard receptacle in it.The grounding conductors must be together.Here is where it gets complex.If all circuits within this box are just standard circuits from non afci/gfci circuits no problem.But once you introduce afci or gfci protected devices into this same box the scenario changes.

Lets say that an afci circuit is fed from a receptacle under a switch for that room but its a 2 gang 1 sw. for a light in that room and one for a 3way for an exterior light.The 3 way goes into a non afci protected room,and in that 2 gang is the 3 way from the afci room and a switch for whatever is in that room(non afci protected)are in the same box.Well we all know that if you combine them as one the afci will trip when a load is applied.

Take a gfci circuit and add it into the equation now there is a 3 gang 2 standard non gfci switches and a gfci receptacle circuit within the same box.Can we join all the grounding conductors together no.The gfci will trip from the neutral to ground fault.But we are still required to attach all grounding conductors together aside from isolated receptacles as stated in 250 146 D and that requires an insulated grounding conductor.

As far as an article that permits us to seperate these circuits I haven`t found one but maybe some code guru here will give us the answer.I know that they will not work if all combined together,this is NM so all grounding conductors are bare copper.

Anyone have the proper article to deal with this ????
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You lost me when you said that a AFCI or GFCI wouldn't work if their EGC's we connected together. My questions is why? If they're connected together at the panel why would a downstream connection make any difference? And how does the GFCI trip from a neutral to ground fault?
 
Trevor on the load side of an afci breaker if you had a non afci circuit tied in with the afci(after the breaker)when any load is applied the afci breaker would trip out.The grounded and grounding conductors have to be isolated from one another.Otherwise it is just like having a neutral to ground fault on a independent afci circuit.Apply any load the afci trips out.The breaker sees the fault and trips out.

Now on a gfci circuit on the load side the device sees a neutral to ground fault and trips out with or without a load.If you mix the grounding conductors on the load side of the device with a standard grounding conductor then the gfci sees this and trips out,since on a standard circuit the grounding conductors and the grounded conductors are one in the same back at the panel.They are not isolated from one another.If I am wrong someone show me how these devices can operate with a neutral to ground fault present.An afci trips with this fault when a load is applied and a gfci trips with this fault regardless of there being a load.
 
There is no reason to seperate the EGC, regardless of the type of CB - AFCI, GFCI. There is no current flow on these wires, so it just does not matter.

Connect the EGCs together and run the correct size wire to the device based on the branch circuit OCPD size (or larger).
 
petersonra said:
There is no reason to seperate the EGC, regardless of the type of CB - AFCI, GFCI. There is no current flow on these wires, so it just does not matter.
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I agree and go on to say that 250.148 requires the EGCs to be connected together.

If 250.148 didn't require all EGCs to be interconnected there would be no need for this exception directly under it

Exception: The equipment grounding conductor permitted in 250.146(D) shall not be required to be connected to the other equipment grounding conductors or to the box
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GFCI's, whether breakers or recepacles, function by measuring the verctor sum of the current flowing through the (one or more) ungrounded conductors it is used with, plus the grounded (white) conductor current. If this is enough above zero, for long enough, it trips. Whether this sum is non-zero because of GF current flow to the EGC, or someplace else (e.g., through a person), doesn't matter to the GFCI. The EGC plays no part in this function, is not connected to GF detection circuitry, and as Larry said its only connection in a GFCI receptacle is to the grounding poles and the yoke.
 
Allen, I distinctly remember you saying EGC's tied together would trip an AFCI, and distinctly remember you later realizing your mistake. I'd search for the thread, but I'm late for work.

I agree with the posters who say 250.148 requires all the conductors to be tied together. I've eaten crow on that before too. :)
 
petersonra said:
There is no reason to seperate the EGC, regardless of the type of CB - AFCI, GFCI. There is no current flow on these wires, so it just does not matter.

Connect the EGCs together and run the correct size wire to the device based on the branch circuit OCPD size (or larger).
Click to expand...


I guess I had to think on this....... I was mistaken and what I meant was that the grounded not the grounding conductors can`t be tied together.So pass me a plate of that delicious crow........ :)
 
LarryFine said:
An EGC has only one function when it comes to GFCI's: so a plug-in tester will work. ;)
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I believe you will find that some electronic equipment relies on that for connection of shields ad shielding cases to "ground".
 
GeorgeB said:
I believe you will find that some electronic equipment relies on that for connection of shields ad shielding cases to "ground".
Click to expand...
Yup, in order to form hum- and video-roll-inducing ground loops, that help keep electricians and engineers busy. ;)
 
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