Equipment grounding conductor definition

[cppoly]

The definition of the equipment grounding conductor in the 2011 NEC is:

"The conductive path(s) installed to connect normally non-current-carrying metal parts of equipment together and to the system grounded conductor or to the grounding electrode conductor, or both."

Using the word 'or' is what my question is about. If the EGC connects only to the grounding electrode (and not to the grounded conductor at the service equipment), wouldn't this create an unsafe condition since the fault current would return to the source via the ground which will not trip the overcurrent device since the earth is not a low impedance path back to the source?

 

[Smart $]

The definition includes the possibility of an ungrounded supply configuration... which would require a ground [fault] detector.

 

[charlie b]

. . . wouldn't this create an unsafe condition since the fault current would return to the source via the ground which will not trip the overcurrent device since the earth is not a low impedance path back to the source?

Not at all. The fault current would flow to the ground rod, and from there to the Grounding Electrode Conductor, and from there to the neutral bus at the service equipment. That completes the circuit for the ground fault, and the resulting high current would trip one or more breakers within the distribution system, thus terminating the event in a fraction of a second.

 

[charlie b]

Let me put it another way:

If the EGC connects only to the grounding electrode (and not to the grounded conductor at the service equipment). . . .

The EGC is a low impedance path from the grounding electrode to the grounded conductor at the service equipment.

 

[cppoly]

Let me put it another way: The EGC is a low impedance path from the grounding electrode to the grounded conductor at the service equipment.

Charlie, yes but according to the definition it says the EGC connects to the grounded conductor (neutral at the service) OR the GEC OR or both. Since it uses the word 'or', to me that means the connection to the neutral at the service is optional.

 

[david luchini]

Charlie, yes but according to the definition it says the EGC connects to the grounded conductor (neutral at the service) OR the GEC OR or both. Since it uses the word 'or', to me that means the connection to the neutral at the service is optional.

The connection of the EGC to the grounded conductor at the Service is NOT optional. It is required by 250.28.

As Smart$ pointed out, the definition uses "or" because not all services are grounded.

 

[cppoly]

The connection of the EGC to the grounded conductor at the Service is NOT optional. It is required by 250.28.

As Smart$ pointed out, the definition uses "or" because not all services are grounded.

Yes I understand that for ungrounded systems. However, just strictly looking at this definition, it is misleading without further explanation. There should at least be an information note referring to the different systems because without this explanation the definition by itself is false because it doesn't differentiate the different systems.

 

[ggunn]

Charlie, yes but according to the definition it says the EGC connects to the grounded conductor (neutral at the service) OR the GEC OR or both. Since it uses the word 'or', to me that means the connection to the neutral at the service is optional.

Those "or's" don't mean that the code does not care which you do, just that which it is connected to are determined by other sections of the code.

 

[Smart $]

Charlie, yes but according to the definition it says the EGC connects to the grounded conductor (neutral at the service) OR the GEC OR or both. Since it uses the word 'or', to me that means the connection to the neutral at the service is optional.

The definition is not a requirement statement, either prohibitive or permissive.... but it does have to cover the possibilities of requirements, which includes ungrounded systems with no MBJ or SBJ.

In reality it should be rewritten. It is always connected to the GES (grounding electrode system) but not necessarily to the GEC or the grounded neutral. For example, at the service the GEC is connected to the neutral, and those are in turn connected to the equipment grounding system by an MBJ... so technically the EGC does not connect to either the neutral or the GEC.

 

[cppoly]

Those "or's" don't mean that the code does not care which you do, just that which it is connected to are determined by other sections of the code.

I should be able to read a definition in article 100 and it should be fully correct. If I have to refer to another section for a correct definition, then it is wrong in my opinion. Unless it is covered by an information note.

 

[david luchini]

the definition by itself is false because it doesn't differentiate the different systems.

The definition is not false. It is true for BOTH grounded and ungrounded systems.

 

[charlie b]

Charlie, yes but according to the definition it says the EGC connects to the grounded conductor (neutral at the service) OR the GEC OR or both.

But if you chose to make the connection between the EGC and the GEC, where in the NEC does it say that that connection has to take place at the service equipment? I think it could take place at the grounding electrode, and still not violate what the definition is telling us.

 

[ggunn]

I should be able to read a definition in article 100 and it should be fully correct. If I have to refer to another section for a correct definition, then it is wrong in my opinion. Unless it is covered by an information note.

It is not incorrect, it's just a definition. If you see a wire that is connected from an equipment chassis to the grounded conductor or to the GEC or to both of them, it's defined as an EGC. The definition of the term does not try to tell you which it should be connected to; that is situational and covered by different articles in the code. You would not, for example, connect an EGC to both the GEC and the grounded conductor in a subpanel, would you?

 

[Smart $]

Another possibility is connecting an EGC to the GEC of an Auxiliary Grounding Electrode under 250.54.

 

[cppoly]

But if you chose to make the connection between the EGC and the GEC, where in the NEC does it say that that connection has to take place at the service equipment? I think it could take place at the grounding electrode, and still not violate what the definition is telling us.

Maybe this is where I'm getting caught up. Does the GEC by code have to terminate at the neutral bar in the service equipment? If yes, then if the EGC terminates at the GEC, then of course it will be connected to the neutral conductor.

If the GEC is permitted to terminate at enclosure of the service equipment only, then in I'm figuring there is no fault path back to the transformer except through earth ground.

 

[ggunn]

Maybe this is where I'm getting caught up. Does the GEC by code have to terminate at the neutral bar in the service equipment? If yes, then if the EGC terminates at the GEC, then of course it will be connected to the neutral conductor.

If the GEC is permitted to terminate at enclosure of the service equipment only, then in I'm figuring there is no fault path back to the transformer except through earth ground.

Correct, and in, for example, an ungrounded system, that's fine because the circuit conductors do not touch or reference ground at any other point, so earth ground is not a fault path in any case. Again, the "or's" do not mean that the alternatives are optional; it's just a definition. It is not trying to tell you what you can connect an EGC to, it's telling you that if it's connected here, or there, or both, it's an EGC. Where you need to connect a particular EGC is determined by other variables.

You aren't holding your mouth right when you are reading this stuff.

 

[cppoly]

Thanks!

 

[cppoly]

Question, if it's an ungrounded system we're talking about, why would there be a GEC in the first place? Wouldn't that mean there wouldn't be a connection of the EGC to the GEC?

 

[kwired]

Maybe this is where I'm getting caught up. Does the GEC by code have to terminate at the neutral bar in the service equipment? If yes, then if the EGC terminates at the GEC, then of course it will be connected to the neutral conductor.

If the GEC is permitted to terminate at enclosure of the service equipment only, then in I'm figuring there is no fault path back to the transformer except through earth ground.

250.64(D)(3) allows for connection anywhere on supply side of service disconnecting means for cases where there are multiple service disconnecting means. I could swear this was permitted even for a single disconnecting means, but am having trouble finding any code section that supports it.

Question, if it's an ungrounded system we're talking about, why would there be a GEC in the first place? Wouldn't that mean there wouldn't be a connection of the EGC to the GEC?

Ungrounded systems still need all non current carrying metallic components bonded together to form and equipment grounding system and needs to have a grounding electrode at the service, separately derived source or first disconnecting means. This is to provide a reference to ground on all these bonded items and prevent having any voltage between those items.

See 250.24(E) for the requirement to have a grounding electrode system for an ungrounded service.

 

[Smart $]

Maybe this is where I'm getting caught up. Does the GEC by code have to terminate at the neutral bar in the service equipment? If yes, then if the EGC terminates at the GEC, then of course it will be connected to the neutral conductor.

If the GEC is permitted to terminate at enclosure of the service equipment only, then in I'm figuring there is no fault path back to the transformer except through earth ground.

250.64(D)(3) allows for connection anywhere on supply side of service disconnecting means for cases where there are multiple service disconnecting means. I could swear this was permitted even for a single disconnecting means, but am having trouble finding any code section that supports it.

...

Do not confuse the connection of the GEC to the Grounded Conductor (neutral) with the Main Bonding Jumper...