Restricted Use of Equipment Grounding Conductors (250.121)

[00crashtest]

In the National Electric Code 2020 Edition, section 250.121 is titled Restricted Use of Equipment Grounding Conductors.

In its newly-added item of A, it prohibits an equipment grounding conductor from being used as a grounding electrode conductor, unless it meets the requirement of item 250.6(A) and Parts II, III, and VI of Article 250. The requirements for the grounding electrode conductor are stricter than those for the equipment grounding conductor.

Does this mean that an otherwise minimally compliant grounding electrode conductor is allowed to be used as an equipment grounding conductor?

Also, Article 250 makes no mention that a dedicated grounding electrode conductor be required. In fact, section 250.52 allows metal underground non-gas piping systems to be used as grounding electrodes. Item 250.118(2) also allows rigid and intermediate flexible metal conduit to be used as an equipment grounding conductor.

Since the NEC 2020 does not define conduit, and the common and all other technical definitions of conduit includes all pipes, does this mean that metallic water pipes are allowed to be used as an equipment grounding conductor? If that is the case, then would the metal water pipe be allowed to be used as an equipment grounding conductor (after a dedicated equipment grounding conductor has been attached to it from an electrical outlet, not necessarily a receptacle) AND a grounding electrode conductor [for the section between the short dedicated conductor (to bond the neutral bus bar of the electrical panelboard with it) and soil interface] AND a grounding electrode (for the underground section that is well over 6 feet long) at the same time?

Also, the NEC 2020 does not define what gas piping is. Does that mean a steam district heating pipe may not be used as a grounding electrode because steam is a gas as defined by the physical sciences? Also, what about pipes that carry refrigerant in the vapor-phase part of the refrigerant circuit? Also, since gasoline is colloquially shortened to gas, does that mean a gasoline pipe may not be used an a grouding electrode?



Also, item 250.121(B) prohibits the structural metal frame of a building or structure to be used as an equipment grounding conductor. The NEC 2020 in Article 100 defines a building as a type of structure, so that mention of building in 250.121(B) is needless. However, what if the structural component of the building acts as a rigid metallic conduit as a raceway that encloses the wires and has covers over the openings to prevent fingers from getting, such as an enclosed box beam with access panels? Will the box beams then be allowed to be used as an equipment grounding conductor?

Also, item 250.52(2) allows a metal in-ground support structure to be used as a grounding electrode. That is in direct conflict with 250.121(B) if the grounding electrode is also used as an equipment grounding conductor, because a metal in-ground support structure is a type of structural metal frame in the broad sense. So, does that mean that a metal-in ground support structure may not be used as an equipment grounding conductor for equipment located in the basement?

Also, the NEC 2020 does not define in Article 100 or anywhere else what a structural frame is. So, is rebar within a reinforced concrete column allowed to be used as an equipment grounding conductor, since the common definition and all other technical definitions consider it a concrete frame rather than a metal frame? Also, what if the ground-affixed structure were a custom-designed one (or even just a standard shipping container home) that is made of a body shell instead of a discrete frame like the portion of a vehicle above the chassis? Would the metal body shell then be allowed to be used as an equipment grounding conductor?

The NEC 2020 also does not precisely define what a structure is. It only says, "That which is built or constructed, other than equipment." It also only vaguely defines equipment as, "A general term, including fittings, devices, appliances, luminaires, apparatus, machinery, and the like used as a part of, or in connection with, an electrical installation." So, is an RV considered equipment under the NEC definition because it is an apparatus or machine (trailer, to be exact)? How about a motorhome (which may be considered an RV)? Does this allow the structural metal frame (chassis) of a trailer RV to be used as an equipment grounding conductor since the RV would be considered an equipment? In practice, does factory-installed wiring in non-motorhome RVs use the chassis or body shell as the equipment grounding conductor? Is the wiring, besides for the powertrain-related components, any different in motorhomes? Also, does the the NEC 2020 consider a floating home to be a structure or not, because it is not attached to the ground?

 

[00crashtest]

Also, does the NEC 2020 consider a floating home to be a structure or not, because it is not attached to the ground? Also, how are floating homes even able to have any conductor that meets the requirements of a grounding electrode, because they sit entirely on water and do not even touch the soil?

 

[tom baker]

This is a very long post and hard to follow. I suggest deleting and reposting in separate topics

 

[00crashtest]

This is a very long post and hard to follow. I suggest deleting and reposting in separate topics

okay, will do so.

 

[00crashtest]

okay, will do so.

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

 

[don_resqcapt19]

In general, nothing other than the items listed in 250.118 can be used as an EGC.

 

[00crashtest]

In general, nothing other than the items listed in 250.118 can be used as an EGC.

Of course! The main statement for the 250.118 includes the word "shall" without "be permitted", so it is a mandatory rule as stated in 90.5(A). But I'm asking about the indidivual listings under 250.118, because their wording is not specific enough, specifically items (2) and (3) because they do not define conduit.

 

[don_resqcapt19]

Of course! The main statement for the 250.118 includes the word "shall" without "be permitted", so it is a mandatory rule as stated in 90.5(A). But I'm asking about the indidivual listings under 250.118, because their wording is not specific enough, specifically items (2) and (3) because they do not define conduit.

Every list item in 250.118, with the exception of list item (1), is defined in the respective code article for that wiring method. List item (1) is defined within the list item itself.

Any time a word or term is used in the code, where that word or term is defined in the code, is used, the code definition is the only definition that applies.

Not only are "rigid metal conduit" and "intermediate metal conduit" defined in the xxx.2 sections of their respective articles (344 and 342), the xxx.6 section of those same articles requires that conduits be listed as such.

 

[00crashtest]

Every list item in 250.118, with the exception of list item (1) is defined in the respective code article for that wiring method. List item (1) is defined within the list item itself.

Any time a word or term is used in the code, where that word or term is defined in the code, is used, the code definition is the only definition that applies.

Not only are "rigid metal conduit" and "intermediate metal conduit" defined in the xxx.2 sections of their respective articles (344 and 342), the xxx.6 section of those same articles requires that conduits be listed as such.

I didn't know that. I thought all definitions not listed in Article 100: Definitions, would be listed in the article sections that mandate them to be used. Now I know that I have to look through all mentions of the terms in the book (locations shown in the glossary -- known as index in the NEC) to see if they are defined anywhere.

 

[don_resqcapt19]

I didn't know that. I thought all definitions not listed in Article 100: Definitions, would be listed in the article sections that mandate them to be used. Now I know that I have to look through all mentions of the terms in the book (locations shown in the glossary -- known as index in the NEC) to see if they are defined anywhere.

The 2023 code moves all definitions into Article 100....in my opinion a huge step backwards, but that was required by the NFPA Standards Council. It makes more sense to me, to have the definition of a raceway, within the article that covers the installation and use of that raceway.

For the 2020 and older codes, where there are definitions not in Article 100, they are found in the xxx.2 sections of the code articles.

 

[00crashtest]

The 2023 code moves all definitions into Article 100....in my opinion a huge step backwards, but that was required by the NFPA Standards Council. It makes more sense to me, to have the definition of a raceway, within the article that covers the installation and use of that raceway.

For the 2020 and older codes, where there are definitions not in Article 100, they are found in the xxx.2 sections of the code articles.

Actually, the 2023 Edition makes way more sense to me because reading about applications of the terminology in other articles will not require referring to so many other articles. Starting with that edition, readers will only have to refer to Article 100 for all definitions for the purposes of the NEC.

 

[00crashtest]

I didn't know that. I thought all definitions not listed in Article 100: Definitions, would be listed in the article sections that mandate them to be used. Now I know that I have to look through all mentions of the terms in the book (locations shown in the glossary -- known as index in the NEC) to see if they are defined anywhere.

So, metal water pipes are clearly not allowed to be used as an equipment grounding conductor because they do not fit the definition of any of the "conduit", "tubing", "raceways", or "gutters" items listed in 250.118, with their definitions listed in the articles that deal specifically with them. They also do not meet the requirement of conductor in (1) because pipes are not in the form of a wire of busbar.

 

[00crashtest]

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.

 

[roger]

So, metal water pipes are clearly not allowed to be used as an equipment grounding conductor because they do not fit the definition of any of the "conduit", "tubing", "raceways", or "gutters" items listed in 250.118, with their definitions listed in the articles that deal specifically with them. They also do not meet the requirement of conductor in (1) because pipes are not in the form of a wire of busbar.

Correct.

 

[roger]

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.

Also correct.

 

[00crashtest]

Also correct.

However, if a box beam is also designed explicitly "for holding wires, cables, or busbars" as stated in Article 100 Part I, then is it allowed as an equipment grounding conductor? This is the only possible exception where the existence of the listing of 250.121(B) might be superfluous.

Also, what if a frame formed by regular electrical metal conduits carrying wires to elevated lights were used to hold up a canopy? Would the conduits then still be allowed to be used as an equipment grounding conductor, or would the conduits now be considered a structural metallic frame of for the purposes of the NEC and prohibit them from being used as an EGC?

 

[roger]

However, if a box beam is also designed explicitly "for holding wires, cables, or busbars" as stated in Article 100 Part I, then is it allowed as an equipment grounding conductor?

If it is specifically designed as a raceway and is listed for use as an EGC it falls under 250.118. Structural parts of buildings may be used for GEC's if they meet the requirements

Also, what if a frame formed by regular electrical metal conduits carrying wires to elevated lights were used to hold up a canopy? Would the conduits then still be allowed to be used as an equipment grounding conductor, or would the conduits now be considered a structural metallic frame of for the purposes of the NEC and prohibit them from being used as an EGC?

In most cases conduit and tubing would not be permitted to "hold up a canopy" (see 358.12 (5) for example) but if the design allowed it and did not prohibit I don't see why it could not be an EGC

 

[00crashtest]

Structural parts of buildings may be used for GEC's if they meet the requirements

Did you mean GEC (grounding electrode conductor) or EGC (equipment grounding conductor)?

 

[roger]

GEC see 250.52(A)(2)

 

[00crashtest]

GEC see 250.52(A)(2)

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