EGC wire and metal boxes

[crossman]

I would say you are holding on for dear life at this point.

Do you base that assessment on jobsite rumor, preconceived notions, what JW Billy has said, and what "ThE iNsPEcToR" has claimed?

Or do you base that assessment on a contemplative and thoughtful reading of 250.148 in its entirety?

There is no holding on for dear life here. It is as plain as day in the 2008 code.

2008 NEC 250.148(C): A connection shall be made between the one or more equipment grounding conductors and a metal box by means of.... equipment listed for grounding... .

I left out the other two "or" choices to limit the confusion. I am certain that in plain english, this means that equipment listed for grouding can be used to connect the box to the EGCs. If the EMT and fittings is listed for grounding, then they can be used to make the connection from the wire-type EGC to the box. Plain as day.

 

[frizbeedog]

I have met the literal requirements of 250.148(C).

Bob gave you this from the CMP ROP for 2002:

SUBSTANTIATION: The present requirement requires an
equipment grounding conductor pulled through a pull box to be
cut or tapped and connected to the box even though no similar
requirement applies to conduit bodies used for the same
purpose, and even though the other conductors running through
the box are permitted to be left intact. In the event that a metal
pull box is used with nonmetallic conduit or other wiring
methods that do not themselves provide for grounding of the box,
an equipment grounding conductor will be required to be run
with the circuit conductors and the box will be required to be
grounded by other provisions of Article 250, specifically 250-80 or
250-86 and Part F.

This is about as close as you'll get to an explanation from the CMP, from the ROP, for the wording change in 2008:

250.148 and 250.148(C): These changes clarify the present requirement in
more prescriptive language.

chris kennedy posted this commentary back in post #2 which I believe explains the present requirement. From the handbook? He didn't say.

Where a metal box is used in a metal raceway system and there is a wire-type equipment grounding conductor installed in the raceway, it is not required that the wire-type equipment grounding conductor be connected to the pull box, provided the box is effectively grounded by the metal raceway and the circuit conductors are not spliced or terminated to equipment in the metal box. An example of this provision would be where conductors are run unbroken through a pull box.

Anyhoo......I have seen interpratations from authors that match what chris has posted, I have read what the CMP has written about this, and I have read closely the code sections that trouble you and have been keeping you busy for the past few days. And I see no conflict with the wording of the code or the herd's interpratation, so to speak.

You being the minority opinon, have weathered the debate well.

However.....your scenario of where you think the present wording is confusing does not hold water in pratical application. Being convinced as you are that the conduit fittings are the method that was intended for this article.

Practically speaking, there would be no need for this article if it wasn't refering to a wire type equipment grounding conductor. Try reading it closely without thinking about a wire type equipment gounding conductor. Kind of like asking someone to not think of a pink elephant. Can't be done.

As I had said earlier, this article is not there just to address the needs of your scenario but others as well, where the box is suppplied by non metallic wiring methods, be they conduit or cable.

I don't see a loophole here.

 

[fondini]

Violation.

yes tis true

 

[crossman]

You being the minority opinon, have weathered the debate well.

I appreciate that.

However.....your scenario of where you think the present wording is confusing does not hold water in pratical application. Being convinced as you are that the conduit fittings are the method that was intended for this article.

Practically speaking, there would be no need for this article if it wasn't refering to a wire type equipment grounding conductor. Try reading it closely without thinking about a wire type equipment gounding conductor. Kind of like asking someone to not think of a pink elephant. Can't be done.

Several comments:

1) If the CMP intended 250.148(C) to apply only to wire-type EGCs, then they would have written it that way. They differentiate between raceway EGCs and wire EGCs in other sections, so why not here? I trust that the CMP members are highly skilled and competent, and that they labor for days to get the wording just right, and to mean exactly what they say. If we have to assume what they are intending, then we pretty much have carte blanche to make assumptions about every word written in the code.

2) Okay, we have to ask ourselves why the CMP added "equipment listed for grounding" to 250.148(C). The reason IMO for the change in 2008 is because they discovered the mistake in the 2005 Code as follows: 2005 NEC 250.148(C) - A connection shall be made between the one or more equipment grounding conductors and a metal box by means of a grounding screw that shall be used for no other purpose, or a listed grounding device.

This says that the EMT and fittings are not suitable for grounding the box because EMT and fittings, to me, is not a listed grounding device. Keyterm is device. An EMT fitting is equipment, not a device, according to Art 100 definitions. So by the 2005 code, to meet the requirements of 250.148(C), the EMT by itself could not be used to ground the box unless we used a grounding bushing and a jumper wire, where we would consider the grounding bushing to be a device.

So, to alleviate the mistake, the CMP added "equipment listed for grounding" to the methods of connecting the EGC or EGCs to the box. Now with the correction, the section includes EMT and fittings as a permissible connection.

You may think this is "way out there" but does anyone have a better explanation of why they added "equipment listed for grounding"?

I don't see a loophole here.

Yes, no loophole. They said exactly what they mean. Equipment listed for grounding can be used to connect the one or more EGCs to the box.

 

[crossman]

And everyone:

We can argue 'til the cows come home about what the CMP meant to say. My interest is in "what does the code actually say?"

 

[quogueelectric]

The CMP does not control how manufacturers ground equipment.

Are you telling me the manufacturers are not well represented in the code making process? They are listed right after the table of contents in the code book .

 

[quogueelectric]

And everyone:

We can argue 'til the cows come home about what the CMP meant to say. My interest is in "what does the code actually say?"

Allright you gotta crank my tail too!! Read the book and you will know what it says.

 

[crossman]

Allright you gotta crank my tail too!! Read the book and you will know what it says.

:grin: :grin:

I'll be out tomorrow, but Saturday all of you are at my mercy.... if anyone can still stomach my ramblings. Maybe I should make some drawings and post them, and pose some questions with yes or no answers to simplify thngs:roll:

 

[quogueelectric]

Take your time I like to crank your tail too.

 

[M. D.]

I trust that the CMP members are highly skilled and competent, and that they labor for days to get the wording just right, and to mean exactly what they say. If we have to assume what they are intending, then we pretty much have carte blanche to make assumptions about every word written in the code.

Here in ,..lies the problem:wink:

 

[chris kennedy]

chris kennedy posted this commentary back in post #2 which I believe explains the present requirement. From the handbook? He didn't say.

Where a metal box is used in a metal raceway system and there is a wire-type equipment grounding conductor installed in the raceway, it is not required that the wire-type equipment grounding conductor be connected to the pull box, provided the box is effectively grounded by the metal raceway and the circuit conductors are not spliced or terminated to equipment in the metal box. An example of this provision would be where conductors are run unbroken through a pull box.

Yes, this is commentary from the 08 NECHB.

 

[M. D.]

So, everyone:

If the connection must be made inside the box, then why does the main portion of 250.148 say "within the box or to the box..."?

250.148 Continuity and Attachment of Equipment
Grounding Conductors to Boxes. Where circuit conductors
are spliced within a box, or terminated on equipment

within or supported by a box, any equipment grounding conductor(
s) associated with those circuit conductors shall be connected
within the box or to the box with devices suitable for
the use in accordance with 250.148(A) through (E).
Exception: The equipment grounding conductor permitted
in 250.146(D) shall not be required to be connected to the
other equipment grounding conductors or to the box.
(A) Connections. Connections and splices shall be made
in accordance with 110.14(B) except that insulation shall
not be required.
(B) Grounding Continuity. The arrangement of grounding
connections shall be such that the disconnection or the
removal of a receptacle, luminaire, or other device fed from
the box does not interfere with or interrupt the grounding
continuity.
(C) Metal Boxes. A connection shall be made between the
one or more equipment grounding conductors and a metal
box by means of a grounding screw that shall be used for
no other purpose, equipment listed for grounding, or a
listed grounding device.

I think it says "to" the box because you could connect to the box individually with the one or more grounding conductors .

You have one grounding conductor (EMT) connection to the box now you need to connect the other (wire) grounding conductor to the box

 

[frizbeedog]

I think it says "to" the box because you could connect to the box individually with the one or more grounding conductors .

You have one grounding conductor (EMT) connection to the box now you need to connect the other (wire) grounding conductor to the box

Thanks for showing up. Took you long enough. :smile:

....and for adding more clarity to something that seems very clear already. For most that is.

 

[frizbeedog]

Several comments:

If we have to assume what they are intending, then we pretty much have carte blanche to make assumptions about every word written in the code.

No. We really don't.

Intention is everything, in all forms of communication. And in the written form even harder to convey, but intention of purpose is the goal. There are no facial expressions, no body language, no inflection of tone that may be percieved, and it isn't a document that entertains creative writing skills to drive the point home.

So the wording is not perfect and and we want to hold the CMP accountable for some misunderstandings of some of the recipients of the message?

How many times in your life have you been misunderstood for what you have said or written that was not what you intended. Find me the perfect communication method given all of it's forms and you will have resumed construction of the Tower of Babel.

So here's what I'm suggesting:

Re-write this section of the code. Post it here for review, or start a new thread, and lets see if we can come to an understanding of what the intention is for what you have written. Because in the end we really need to know what was intended, right? Don't answer that, because its true.

Find us the perfect wording.

....and good luck. :smile:

 

[crossman]

All I can do is go by what the code says. I do not have access to the inner thoughts of the individual CMP member's brains. I can only guess as to their intent. That is all that any of us can do without an official technical interpretation from the CMP. Therefore, I cannot reword the section because I do not know what the intent is.

However, I can tell you and show you what the code section says. Here is a diagram. If anyone can give a logical demonstration that this does not comply with what is written in the code, I would sure be thankful.

Now, to continue with some logic on safety:

Here is a diagram of a similar installation in which most of you will agree is okay. So the question is, what is the difference in safety between the two diagrams? The j-box is grounded/bonded by only the EMT in both applications. And the EMT is equipment which is listed for grounding in my scenario.

 

[rexowner]

So the question is, what is the difference in safety between the two diagrams?

If you look over the population of all electricians:
wirenut connections come apart more often than wire
insulation goes flying apart spontaneously.

 

[crossman]

If you look over the population of all electricians:
wirenut connections come apart more often than wire
insulation goes flying apart spontaneously.

In diagram 1: If the wire nut falls off or doesn't fall off, the box is still grounded/bonded by the EMT.

In diagram 2: If the insualtion stays intact or if it comes off, the box is still grounded/bonded by the EMT.

Same exact thing. If there is a need to make a connection to the wire-type EGC in diagram 1, the same argument holds for diagram 2. Ever seen a wire pinched in a cover? It probably happens as often as lil' johnny poking a knife into a receptacle.

 

[haskindm]

The code says what it says. However, if the installer or designer requires a wire equipment ground in addition to the EMT raceway, they are in effect stating that is their intention is that the raceway NOT serve as an equipment ground. In this case, I believe that it is within the scope and the responsibility of the AHJ to agree and say that "since the installer has opted not to rely on the raceway as an equipment ground, then I will not consider it as an equipment ground". In this case the AHJ may treat it just as if the EMT was replaced with PVC; the wire equipment ground becomes the only reliable equipment ground and must be installed accordingly. You should not be allowed to have it both ways, using the wire equipment ground when it is convenient and then using the EMT equipment ground when it is convenient. If you are going to use the EMT as the equipment ground, do not install an additional wire ground. If you are going to use a wire ground, then treat the EMT as if it were PVC and do not rely on it for ANY grounding. It is not unreasonable to make you pick one method or the other instead of a bastardized combination.

 

[crossman]

The code says what it says. However...

Does this mean that in your opinion, diagram 1 does meet a literal interpretation of the code?

 

[rexowner]

In diagram 1: If the wire nut falls off or doesn't fall off, the box is still grounded/bonded by the EMT.

In diagram 2: If the insualtion stays intact or if it comes off, the box is still grounded/bonded by the EMT.

Same exact thing. If there is a need to make a connection to the wire-type EGC in diagram 1, the same argument holds for diagram 2.

Ever seen a wire pinched in a cover? It probably happens as often as lil' johnny poking a knife into a receptacle.

Yes, I have. It can certainly happen whether the
wire is wirenutted or not. The chance of (a wirenut
connection failing + a pinched wire) is greater than
a pinched wire, so the wirenutted version has
a greater chance of fault. So, I think that is a
"difference in safety" to answer your question, although
I'm not sure that is the real question anyway.

I think the real question is still the interpretation of
connecting the ground wire "to" the box, and on that
question I believe a reasonable interpretation is that
it doesn't include the path back to the panel, bus
and back through the EMT.

Edit: Removed my extraneous point about redundant ground which was
not asked about by the poster.