Supplemental vs Grounding Electrode

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walton

walton

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When is a supplemental grounding electrode (250.54) not considered supplemental? If I install a ground rod for a motor and terminate it on the motor skid is that supplemental? Yes. If I install a ground rod at a subpanel and terminate it on the ground bus is it supplemental? No?
 
A supplemental grounding electrode must supplement another electrode. If there are metal water pipes as an electrode then the other electrodes supplement the water pipe electrode. The supplemental electrode may be any of the items in 250.52(A)(2) thru (A)(8). Quite often it is a rod or a CEE.
 
What the OPer is referring too is now called an auxiliary grounding electrode (250.54) the name was changed in the 2008 NEC to to help clarify that this electrode is not a supplemental electrode as required in 250.52(D)(2) but is an extra electrode that is not required to meet the other requirements in Article 250.

Chris
 
Thanks. I see "connected to the equipment grounding conductors specified in 250.118" in 250.54 (2008).
So a ground rod installed at a subpanel that is terminated on the ground bus is not auxillary and must be connected to the GEC system.
 
A panel ground bus was not listed in 250.118. Then you are considering the bus as an equipment grounding conductor? It is the term point for the EGCs so that would apply.
 
walton said:
Thanks. I see "connected to the equipment grounding conductors specified in 250.118" in 250.54 (2008).
So a ground rod installed at a subpanel that is terminated on the ground bus is not auxillary and must be connected to the GEC system.
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iwire said:
No, that could be an auxiliary.
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Could also just be a grounding electrode if the subpanel is serving and located in another building... and is connected to (or is, or part of) the GES for that building.
 
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walton said:
A panel ground bus was not listed in 250.118. Then you are considering the bus as an equipment grounding conductor? It is the term point for the EGCs so that would apply.
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Is the subpanel located in the same building or structure as the equipment that it feeds it?

If it is in or of another building or structure, it is an EGC, but is permitted to be the bonding point for the local building or structure's GES.

If in the same building or structure, it is required to be connected to the GES, but if you connect it to the EGC at the subpanel, it is an auxiliary electrode and not required to be connected to the GES (this last part seems to be only implied and my interpretation).
 
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A previous thread "Building Steel used for Conductor" in a discussion about a ground rod at a subpanel the consensus was that it would be required to be connected to the grounding electrode system or be cut off or bounded in. If considered auxillary then the consensus was wrong.
That thread started me thinking, which is trouble in it's self, about auxillary grounds.
 
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walton said:
A previous thread "Building Steel used for Conductor" in a discussion about a ground rod at a subpanel the consensus was that it would be required to be connected to the grounding electrode system or be cut off or bounded in. If considered auxillary then the consensus was wrong.
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IIRC, the consensus was biased due to an [ignorant?] inspector "demanding" it be connected to the GES.
 
walton said:
A panel ground bus was not listed in 250.118. Then you are considering the bus as an equipment grounding conductor? It is the term point for the EGCs so that would apply.
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That is an interesting point, but 250.118 also does not list wire nuts, 'lugs' or 'clamps' so how would I connect the aux electrode to a conductor or EMT?
 
I would consider wire nuts, lugs and clamps to be methods of connection and not what is to be connected to. I do agree that the ground rod at a building subpanel could be auxillary. Thanks for all your input on this discussion.
 
Twoskinsoneman said:
:lol::lol:
I'm sorry but this comment was so off-the-wall/unrelated I literally laughed out loud in front on my PC.
:rotflmao:
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I did not think it was unrelated. There are many that think that is acceptable practice. The more they are reminded that it is not, the more likely it will sink in someday.
 
kwired said:
I did not think it was unrelated. There are many that think that is acceptable practice. The more they are reminded that it is not, the more likely it will sink in someday.
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Oh c'mon why so argumentative?
If I had said "Oh and also you shouldn't use cut-up sections of ground rods as fuses" it would have had the same relevance in this thread.
 
walton said:
When is a supplemental grounding electrode (250.54) not considered supplemental? If I install a ground rod for a motor and terminate it on the motor skid is that supplemental? Yes. If I install a ground rod at a subpanel and terminate it on the ground bus is it supplemental? No?
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Twoskinsoneman said:
Oh c'mon why so argumentative?
If I had said "Oh and also you shouldn't use cut-up sections of ground rods as fuses" it would have had the same relevance in this thread.
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I don't know what the experience level of the OP is. A ground rod for a motor? Not a common installation, but not a violation of NEC to have one either. Hopefully he is expreienced enough to know that he needs an EGC whether he installs the ground rod or not.

Besides ground rods do not fit very well in most fuseholders. 3/4 copper water pipe fits better:p
 
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