Restricted Use of Equipment Grounding Conductors (250.121)

[00crashtest]

If it is specifically designed as a raceway and is listed for use as an EGC it falls under 250.118.

However, wouldn't an box/cylindrical beam/column that is designed to be both a raceway and a structural framing member and used as both not be allowed to be used as an EGC because it conflicts with 250.121(B) and no exception is given there for structural members that meet the requirements of 250.118? Was 250.121(B) specifically written to prevent the doubling-up of function, or was it erroneous in that they forget to add an exception given how many typos there are in this book?

 

[roger]

250.52(A)(2) only lists a type of grounding electrode and not a "groubding electrode conductor" as defined in Article 100, Part I.

This is where you have to dig further, see 250.68(C)(2)

 

[00crashtest]

This is where you have to dig further, see 250.68(C)(2)

I've read 250.68(C)(2), and it allows metal structural frames to be GECs. 250.52(2) also allow them to be grounding electrodes if in direct contact with the soil for at least 3.0 m vertically, such as in a basement. So, a basement frame made of stainless steel or other corrosion-resistant metals and in direct contact with the soil for at least 3.0 m will be both a grounding electrode and a GEC. 250.121(A) only prohibits an EGC from being used as a GEC, and does not prohibit GECs or grounding electrodes from being used as EGCs. So, any GEC or grounding electrode can be used as an EGC under all rules in this reply so far. It may seem like 250.121(B) prohibits structural metal frames from being used as an EGC.

However, since the NEC 2020 considers this basement metal frame as both a grounding electrode and a GEC, is it allowed to be used in essence as an EGC (for the section between the short dedicated EGC and the short GEC wire connecting it with the panelboard neutral busbar) if an EGC listed under 250.118 were bonded to it?

Also, if the same frame extended upwards to form the superstructure, but the superstructure were made of a different metal such as regular iron (which is weathering steel for the base-model option nowadays AFAIK), would the NEC 2020 still consider the superstructure to be both a grounding electrode and a grounding electrode conductor? If not, what would the NEC 2020 consider it to be? Also, would this superstructure be allowed to be used in essence as an EGC under the same conditions as the substructure besides being above-ground?

 

[don_resqcapt19]

This also means that the listing of 250.121(B) prohibiting the use of metal frame of building/structure as an equipment grounding conductor is superfluous, because a box beam does not fit the definition of "raceway" defined in Article 100, rigid metal conduit defined in 344.2, intermediate metal conduit defined in 342.2, or electrical metallic tubing defined in 358.2.

The prohibition you speak of was in 250.136 and was relocated. It is a clarification to the permission found in 250.136. That permission is very specific but some wanted to say it permitted the building structure to be used as the EGC. The code does not permit that and this is just a clarification. It probably should have remained in 250.136.

 

[don_resqcapt19]

...

Also, if the same frame extended upwards to form the superstructure, but the superstructure were made of a different metal such as regular iron (which is weathering steel for the base-model option nowadays AFAIK), would the NEC 2020 still consider the superstructure to be both a grounding electrode and a grounding electrode conductor? If not, what would the NEC 2020 consider it to be? Also, would this superstructure be allowed to be used in essence as an EGC under the same conditions as the substructure besides being above-ground?

If it is not in contact with the earth is is not a grounding electrode. 250.68(C) permits some things that are not actual conductors of the wire type to be used as GECs.
Again, the structure would never be permitted to be an EGC and neither would a metal water pipe.

 

[00crashtest]

If it is not in contact with the earth is is not a grounding electrode. 250.68(C) permits some things that are not actual conductors of the wire type to be used as GECs.
Again, the structure would never be permitted to be an EGC and neither would a metal water pipe.

But in this case, the frame is in contact with the earth for 3 m in the basement.

 

[don_resqcapt19]

But in this case, the frame is in contact with the earth for 3 m in the basement.

The part that is not in contact with the earth is permitted to be used as a grounding electrode conductor, but is not a grounding electrode.

 

[00crashtest]

The prohibition you speak of was in 250.136 and was relocated. It is a clarification to the permission found in 250.136. That permission is very specific but some wanted to say it permitted the building structure to be used as the EGC. The code does not permit that and this is just a clarification. It probably should have remained in 250.136.

It's obvious in 250.136 (via its referenced 250.134(1) in combination with 250.118 (2) through (14)) that the equipment secured to grounded metal supports cannot use ~ regular building frame as an EGC because the building frame does not meet the requirements of 250.118, not even (1). However, what of the building frame met the requirements of 250.118 (2) through (14)? Will it then be allowed or does the prohibition formerly in 250.136 (now in 250.121(B)) still override 250.118 to cause the overall rule to prohibit it?

 

[00crashtest]

The part that is not in contact with the earth is permitted to be used as a grounding electrode conductor, but is not a grounding electrode.

Does that mean the above-ground portion of a purposely-made grouding electrode such as a rod not count as a grounding electrode? If so, may you show me the article item that does not permit it?

 

[don_resqcapt19]

Does that mean the above-ground portion of a purposely-made grouding electrode such as a rod not count as a grounding electrode? If so, may you show me the article item that does not permit it?

That is my opinion, and I really don't care if you agree or not....I am done responding to your nonsense.

 

[00crashtest]

That is my opinion, and I really don't care if you agree or not....I am done responding to your nonsense.

How is that nonsense? I just want to know exactly how the Code works. By above-ground portion of a grounding rod, I mean that it is a very long one (6 ft for example) has been driven mostly into the ground, deep enough to be more than compliant with the NEC, with maybe 2 feet remaining above the ground for convenience purposes. Also, why are you responding in opinion if I'm asking about the technical specifics of the Code?

 

[roger]

Also, why are you responding in opinion if I'm asking about the technical specifics of the Code?

The answers you get here will be opinions, no different than the NECH commentary. With that said this thread has run it's course. If there are local code courses in your area it may behoove you to look into taking one.

 

[GoldDigger]

It turns out, posts cannot be deleted on Mike Holt's Forum, so I will continue this thread here.

How do I edit or delete a post.

I have read faq concerning edit/delete post but I cannot find button located next to post. :( thank you

forums.mikeholt.com

Individual posts can be moved from one thread to another and deleted completely by a Moderator. Members should be able to delete their own posts, at least during the Edit time window. With more manual operation the content of posts can be copied and then the original edited or deleted.
Once there is no reason to keep a thread, I believe a Moderator can delete the entire thread by deleting the first post in the thread.