2014 Article 250.121

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Dennis Alwon

Dennis Alwon

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So it seems like in 2011 the NEC installed a new section to art. 250

250.121 Use of Equipment Grounding Conductors. An equipment grounding conductor shall not be used as a grounding electrode conductor.
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Then in 2014 they added an exception

250.121 Use of Equipment Grounding Conductors. An equipment grounding conductor shall not be used as a grounding electrode conductor.


Exception: A wire-type equipment grounding conductor installed in compliance with 250.6(A) and the applicable requirements for both the equipment grounding conductor and the grounding electrode conductor in Parts II, III, and VI of this article shall be permitted to serve as both an equipment grounding conductor and a grounding electrode conductor.
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My question-- Does this exception seem to allow an equipment grounding conductor to be used as a grounding electrode conductor in most cases if it is sized properly? It seems to also not allow a metal conduit to be used as a grounding electrode conductor either.
 
It seems strange that they would have a section prohibiting an EGC to be used as a GEC only to have an exception that allows it pretty much everywhere. I wonder what the motivation for the add was?

I see this on PV systems a lot -- where they size up the EGC to a min #8 and simply use it as an EGC/GEC all the way back to the main service disconnect. As long as all splices are exothermic welds or irreversible crimps, that should be Code-compliant, no? And what if it passes through a subpanel ground bus on the way -- is that okay?
 
A place where I see it seemingly pointless to run separate GEC and EGC is where you have 480 volt service and equipment, but want a small KVA transformer for deriving 120 volts and it is literally only inches away from the 480 volt service equipment. Do we really need to run a separate GEC and EGC between these two pieces of equipment and tie them to same points on each end?
 
5-190 Log #3401 NEC-P05 Final Action: Reject
(250.121)
________________________________________________________________
Submitter: Scott Cline, Monterey Park, CA
Recommendation: Delete 250.121 entirely.
Substantiation: What is the physics hazard reason that the same conductor
should not function both as the GEC and the EGC? Please, if someone can,
give me a single example of an installation, meeting the requirements of the
2008 NEC, and presenting a hazard of any kind. By all the evidence shown to
me, 250.121 is an unjustified restriction to not allow a GEC to act as an EGC
and vice versa.
I have struggled with and pursued this problem for nearly two years now.
This issue has been extensively discussed with many NEC experts such as, and
including most of, CMP-5. Nobody... not anyone from a CMP, not any of the
NECA Code reps, not any of many Los Angeles area Code reps (including the
very conservative Chief Electrical Inspectors and plan checkers of both LA
City and LA County)... nobody has come up with so much as a single example
of an installation in full compliance with the 2008 NEC which presents a
hazard, not one. The only examples given were ones where the 2008 NEC was
not complied with.
I am not looking to get into a discussion about 250.30(A)(7) and/or
250.64(F) in general or 250.64(F)(3) specifically. I am not looking to point out
any errors in installation. As an installation example: what conceivable good is
it to be required to add a #8 copper EGC running in parallel with a #2 copper
GEC in the same PVC underground conduit between a 480Y/277V service/
distribution section and a 75 kVA, 3-Phase, 480V to 208Y/120V, transformer?
This installation can easily be done in full compliance with the 2008 NEC
using only the #2 conductor. The #2 GEC is far more than capable of carrying
the rare-occasion ground-fault current from the primary circuit. A single
conductor would always be the larger of the two required sizes, usually the
GEC size.
There are an infinite number of ways to incorrectly install a GEC or EGC.
They shall be installed legally in all circumstances. But there is no physicshazard
reason to not allow a correct installation to do both jobs. Nobody wants
installations which violate Code sections; that is not the issue here.
From the 2011 cycle imposing Section 250.121:
5-/85 Log #3915 NEC-P05 David Williams
Substantiation: The Code does not prohibit you from using the grounding
electrode conductor to also function as an equipment grounding conductor. The
grounding electrode conductor serves a specific purpose and has installation
requirements that would normally make this type of installation prohibited. The
use of the grounding electrode conductor for equipment grounding has been
attempted in the past and often leads to code violations due to the installation
requirements of the GEC.
What installation requirements would ?normally? make this type of installation
prohibited? What mutually exclusive requirement is there that would make use
of two conductors connected to exactly the same terminal points necessary?
Flawed installations are just that - flawed; this is not a justifiable reason to
disallow an installation which does satisfy all requirements of the 2008 NEC.
5-259 Log #4526 NEC-P05 Phil Simmons
Substantiation: This new section will clarify that grounding electrode
conductors and equipment grounding conductors serve a different purpose in
the electrical safety system, are sized differently and have different installation
requirements. Equipment grounding conductors do not normally carry current
while a grounding electrode conductor may normally carry current since it is
often in parallel with the neutral conductor.
(discussion specific to the previous Substantiation continues here)
They do have differing installation requirements, but they are not mutually
exclusive requirements under many if not most circumstances. They do have
different stated purposes, but these purposes are accomplished in the same
manner; their basic electrical function is identical - allowing transport of a
sufficient quantity of electrons in a relatively unimpeded fashion.
The only place I know where a GEC is commonly ?in parallel with the
neutral? is at the line-side of the service. I cannot imagine a condition where
there would also be a need for an EGC here, other than the conduit itself. As
far as I know, it is illegal for the neutral to be in parallel anywhere downstream
of any system?s main/disconnect.
(general discussion continues here)
I appreciate and respect the fact that both proposals were submitted by well
intentioned members of CMP-5. But as CMP members, we have a
responsibility to review our actions. I?m sorry for the circumstances, but there
was inadequate Substantiation given for the adoption of this Section -especially
when submitted by CMP members. Anecdotal statements without any
evidentiary real-life examples, without any indication of danger, or examples of
problem events, without any laboratory reports or physics conditions given,
simply do not meet the standard by which we should be imposing Code
requirements.
It has been said that my position on this is based only on cost, and that I am
promoting an incorrect installation. I have received insulting and incorrect
statements regarding my abilities and integrity. My whole purpose of doing all
the many hours of work involved with this volunteer code panel work, is to do
public good based on expertise and facts, and debated in polite discussion.
Cost-benefit balance must always be a part of our responsibility in writing
Code. We are the Public?s representatives for their safety and economic
interests. Our number one primary responsibility as CMP members is ?Practical
Safeguarding.? ?Practical? includes the cost of installation. No economy can
afford to require Space Shuttle level perfection, neither can we allow the
horrors of third-world freelancing. It is our job to find the balance. And I will
point out that my position everywhere in this discussion is that the 2008 Code
requirements must ALL be followed.
I believe that adopting 250.121 was an unjustified action in accordance with
the rules of Panei responsibilities. It should be removed from the NEC.
Panel Meeting Action: Reject
Panel Statement: The panel re-affirms the position that the GEC and EGC?s
70-260
Report on Proposals A2013 ? Copyright, NFPA NFPA 70
have different functions and shall not be used as both. The substantiation for
the proposal contains some of the reasons this proposal is not acceptable. This
includes the fact that the two conductors are installed for different purposes, are
sized differently and have different installation requirements. Here are a few
illustrations of why the rule needs to remain in the NEC.
(1) An equipment grounding conductor is required to be installed with the
circuit conductors to the transformer enclosure. 250.30(A)(4) requires the
grounding electrode to be ?as near as practicable to, and preferably in the same
area as the grounding electrode conductor connection?. These locations could
and often are widely separated.
(2) A feeder is installed from a source in a building to a transformer that is
located outdoors. 250.30(C) requires the grounding electrode connection to be
at the transformer that is the source of a separately derived system. A
combination grounding electrode conductor/equipment grounding conductor
run to the source location would not be acceptable.
(3) A supply to a transformer-type separately derived system is installed from
a sub-panel (feeder panelboard). Where would a combination grounding
electrode conductor/equipment grounding conductor be connected? To the
neutral terminal bar? A clear violation of 250.24(A)(5). To the equipment
grounding terminal bar? The equipment grounding conductor supplying the
panelboard may not be large enough.
Number Eligible to Vote: 16
Ballot Results: Affirmative: 14 Negative: 2
Explanation of Negative:
DOBROWSKY, P.: Accept the proposal in principle and add an exception
that permits a wire type equipment grounding conductor that complies with all
requirements for both grounding electrode conductors and equipment
grounding conductors.
PHILIPS, N.: The Panel should consider adding a proposed new exception.
This ballot comment is provided to introduce the Exception into the record at
the Proposal stage. A public comment will be submitted for review by the panel
at the comment stage as follows:.
Exception. A wire-type equipment grounding conductor installed in
compliance with 250.6(A) and the applicable requirements in Parts II, III and
VI of this article shall be permitted to serve as both an equipment grounding
conductor and a grounding electrode conductor.
Substantiation: Section 250.121 restricts all equipment grounding conductors
provided in 250.118 from being used as a grounding electrode conductor. This
is appropriate for all of the types with the exception of a wire type, per
250.188(1), if the wire type satisfies all applicable requirements for both the
EGC and the GEC simultaneously. Equipment grounding conductors installed
in accordance with this restrictive exception that do not carry current during
normal operating conditions can comply with 250.6(A).
 
Pharon said:
It seems strange that they would have a section prohibiting an EGC to be used as a GEC only to have an exception that allows it pretty much everywhere. I wonder what the motivation for the add was?

I see this on PV systems a lot -- where they size up the EGC to a min #8 and simply use it as an EGC/GEC all the way back to the main service disconnect. As long as all splices are exothermic welds or irreversible crimps, that should be Code-compliant, no? And what if it passes through a subpanel ground bus on the way -- is that okay?
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It does seem strange. It isn't allowed but it is.......... If that was the intent they should say it is allowed if the grounding electrode conductor is a wire type and properly sized -- end of story but I wasn't sure if there was more to it.
 
Even after reading the ROP, I'm still not clear if my questions are answered... aren't all conductors "wire type"? Or are they saying that you can't use a ground bus as part of the path?

If that's true, I'm not sure why it would be a problem...
 
Pharon said:
Even after reading the ROP, I'm still not clear if my questions are answered... aren't all conductors "wire type"? Or are they saying that you can't use a ground bus as part of the path?

If that's true, I'm not sure why it would be a problem...
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An equipment grounding conductor can be a conduit and not a wire. In that case you could not use the conduit (equipment grounding conductor) as a grounding electrode conductor. I think that is what it is saying
 
Neither the main rule nor that exception are needed in the code. The combination puts us right back where we were before there was a rule that said you can't use the EGC as a GEC. With the exception it is exactly as it was before 250.121 was added...that is you can do it as long as you meet all of the code requirements for both the GEC and EGC. It can be done, but you have to be very careful.
 
don_resqcapt19 said:
Neither the main rule nor that exception are needed in the code. The combination puts us right back where we were before there was a rule that said you can't use the EGC as a GEC. With the exception it is exactly as it was before 250.121 was added...that is you can do it as long as you meet all of the code requirements for both the GEC and EGC. It can be done, but you have to be very careful.
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Don can you elaborate on the being very careful part of your statement.
 
Dennis Alwon said:
Gotcha, I thought you had something different than that. :thumbsup:
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I think there is more than that. The GEC has to originate at the grounding electrode, but you will need an EGC tap to the grounding point of the circuit that needs the EGC. Even though you would have a fault clearing path via the other GECs, you would have a 110.3(B) issue unless you have a tap to the equipment grounding bus for the circuit conductors that require the EGC. I think there are other issues that make the use of a common conductor somewhat difficult.

The most common application that I can think of is where a common conductor is used as the EGC for the primary of a transformer and the same conductor is used as the GEC for the secondary of that same transformer.

For that application, assuming that the transformer is in the same building as the service equipment, I don't really see a need for the GEC to be any larger than the transformer supply EGC, but the code doesn't see it that way.
 
Dennis Alwon said:
An equipment grounding conductor can be a conduit and not a wire. In that case you could not use the conduit (equipment grounding conductor) as a grounding electrode conductor. I think that is what it is saying
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I didn't read it, didn't look like I wanted to strain my brain that much right now, but if it says what you said - I did notice it only took you maybe about 100 characters to write it and the ROP at least 1000 maybe even 2000:roll:
 
This scenario happens when a service rated transfer switch is installed between the meter and what was the first disconnect, as in a generator install in an existing home. It seems dumb to run a separate GEC with the now required 4 wire feed on the load side of this disconnect. Then isolate the previously GEC at this panel and then reconnect it to the remaining run to say a water main.

Also, can the said re-connection be made by way of the isolated ground bus bar or does it have to be made by an irreversible connections?
 
Michael15956 said:
This scenario happens when a service rated transfer switch is installed between the meter and what was the first disconnect, as in a generator install in an existing home. It seems dumb to run a separate GEC with the now required 4 wire feed on the load side of this disconnect. Then isolate the previously GEC at this panel and then reconnect it to the remaining run to say a water main.

Also, can the said re-connection be made by way of the isolated ground bus bar or does it have to be made by an irreversible connections?
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Michael I am confused by this. Generally with a generator I have seen the grounding electrode conductor just run separately back to the building and tie it to the existing rods or just have one rod at the generator per the instructions. I am not sure what the nec requires here. I was thinking of this section more in terms of a separate structure far from the building.
 
Dennis Alwon said:
So it seems like in 2011 the NEC installed a new section to art. 250



Then in 2014 they added an exception



My question-- Does this exception seem to allow an equipment grounding conductor to be used as a grounding electrode conductor in most cases if it is sized properly? It seems to also not allow a metal conduit to be used as a grounding electrode conductor either.
Click to expand...

Yes, you are reading it correctly.
 
Dennis Alwon said:
Michael I am confused by this. Generally with a generator I have seen the grounding electrode conductor just run separately back to the building and tie it to the existing rods or just have one rod at the generator per the instructions. I am not sure what the nec requires here. I was thinking of this section more in terms of a separate structure far from the building.
Click to expand...

Dennis, it is for both.
 
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