MC connector

al hildenbrand

Senior Member
Location
Minnesota
Occupation
Electrical Contractor, Electrical Consultant, Electrical Engineer
Are you asking why the Armor Grounding Wire -- a specific designed product for working as GEC – needs additional bonding at both ends? Obviously if such product already meets the code, that it is already having the conduit bonded at both ends to the inside copper conductor, then it should meet the code. But in practice I would think many cases people buy a 30 ft armor wire and only use a fraction of the length for the job, meaning they cut the cable to length, which means the cut end needs to be bonded.

Here is a good article to explain the choking effect: http://www.ecmag.com/section/codes-standards/guardian-ground

“The magnetic field’s strength increases in proportion to the amount of current in the conductor. In many cases, the magnetic lines of force in the conductor are induced into the conduit enclosing the grounding electrode conductor; they can even surpass the saturation point of the steel raceway. At the point where the grounding electrode conductor exits the conduit, the magnetic lines of force generated by the fault current in the conductor will try to be induced on the end of the conduit, creating a saturation point that exceeds the conduit’s capacity. The steel conduit, in this instance, acts like a steel core of a coil to concentrate the magnetic lines of force. This condition is often referred to as the “choke effect” because it is actually the restriction of a grounding electrode conductor from performing its function. Because of this, specific bonding requirements are necessary for ferrous metal raceways that contain grounding electrode conductors. This is not a concern for grounding electrode conductors that are installed in PVC conduit or other nonferrous metal raceways such as aluminum or brass conduit.”
Respectfully, you are missing the point. Armored grounding wire is NOT a bare copper conductor inside a raceway (conduit).

And the listing, as KDER - Grounding and Bonding Equipment, puts it outside of Armored Cable or Metalclad Cable. So I doubt that it is even a cable.

The Code is silent about bonding the armor of Armored Grounding Wire to the wire contained in the armor.
 
Respectfully, you are missing the point. Armored grounding wire is NOT a bare copper conductor inside a raceway (conduit).

And the listing, as KDER - Grounding and Bonding Equipment, puts it outside of Armored Cable or Metalclad Cable. So I doubt that it is even a cable.

The Code is silent about bonding the armor of Armored Grounding Wire to the wire contained in the armor.
I used "raceway" in a general way to describe any metal enclosure that houses one or more conductors, including RC, EMT, flex conduit, and the steel armor of the "Armor grounding wire".

What do you think the name “cable armor” below means? If it is not the specially designed single conductor enclosed by the flexible steel armor for GEC purpose that you were referring to, then what else this “cable armor” is for? It says the armor needs to be bonded (to the inside conductor).

“250.64(E) Enclosures for Grounding Electrode Conductors. Ferrous metal enclosures for grounding electrode conductors shall be electrically continuous from the point of attachment to cabinets or equipment to the grounding electrode and shall be securely fastened to the ground clamp or fitting.
Nonferrous metal enclosures shall not be required to be made electrically continuous. Ferrous metal enclosures that are not physically continuous from cabinets or equipment to the grounding electrode shall be made electrically continuous by bonding each end of the raceway or enclosure to the grounding electrode conductor. Bonding methods in compliance with 250.92(B) for installations at service equipment locations and with 250.92(B)(2) through (B)(4) for other than service equipment locations shall apply at each end and to all intervening ferrous raceways, boxes, and enclosures between the cabinets or equipment and the grounding electrode. The bonding jumper for a grounding electrode conductor raceway or cable armor shall be the same size as, or larger than, the enclosed grounding electrode conductor.”

From link: http://www.iqelectricaltraining.com/archived-newsletters
 

al hildenbrand

Senior Member
Location
Minnesota
Occupation
Electrical Contractor, Electrical Consultant, Electrical Engineer
The NFPA Glossary of Terms 2014 defines "Cable" as used in NFPA 70 (the National Electrical Code) as:
A factory assembly of two or more conductors having an overall covering.
Armored grounding wire is not cable.
 
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Come on, we were discussing about the rule of bonding GEC ferrous enclosure, not the definition of cable armor. I wanted to say that the name "cable armor" in the article and your "Armor grounding wire" are interchangeable, they refer to the same device.
 

al hildenbrand

Senior Member
Location
Minnesota
Occupation
Electrical Contractor, Electrical Consultant, Electrical Engineer
Come on, we were discussing about the rule of bonding GEC ferrous enclosure, not the definition of cable armor.
Actually, if you go back to the Opening Post (OP) and go through the first ten posts you will see that the discussion is very much about what Armored Grounding Wire actually is and where, in the Rules of the enforceable Code does and don'ts are printed.

I wanted to say that the name "cable armor" in the article and your "Armor grounding wire" are interchangeable, they refer to the same device.
So, you are claiming, the NFPA published definition of "cable" also includes (silently) something to the effect that any single bare conductor inside an overall outer covering is also two or more conductors. . . I suspect that this is because you "want" it to. . . not because of hard evidence of how an Armored Grounding Wire chokes unbalanced current, compared to a naked bare copper wire or compared to a bare copper wire in raceway bonded at both ends of a ferrous raceway.

Here's my point. The complete assembly of Armored Grounding Wire as a manufactured listed Category KDER product IS grounding and bonding equipment, wire AND armor. Armored Grounding Wire is manufactured to a NRTL standard, it is not field assembled by the rules of the NEC by an electrician. Any NEC rules that apply to the field assembly of a grounding wire inside an enclosure apply to a field electrician sliding the copper wire into the armor . . . the Armored Grounding Wire is assembled in a factory under a NRTL standard, not the NEC rules.
 
I agreed that the article is better off using the standard terminology, i.e Armor grounding wire instead of cable armor in the context, for less confusing. My point is that even if a legitimate Armor Grounding Wire was used for GEC, and only the bare copper wire was clamped to the grounding electrode, then it is a violation. Only when the steel armor and the copper wire were clamped together at both ends – bonding the armor to the copper wire – then this is compliant.

NEC says:
1) Armor grounding Wire: the steel armor must be bonded to the copper wire at both ends
2) GEC with steel conduit: the steel conduit must be bonded to the copper wire at both ends
 

al hildenbrand

Senior Member
Location
Minnesota
Occupation
Electrical Contractor, Electrical Consultant, Electrical Engineer
My point is that even if a legitimate Armor Grounding Wire was used for GEC, and only the bare copper wire was clamped to the grounding electrode, then it is a violation.
A violation of what? Please cite chapter and verse.

Only when the steel armor and the copper wire were clamped together at both ends – bonding the armor to the copper wire – then this is compliant.
And where is this written in the NEC specifically with respect to Armored Grounding Wire?

NEC says:
1) Armor grounding Wire: the steel armor must be bonded to the copper wire at both ends
Please provide actual citations from the NEC instead of a paraphrase.
 

al hildenbrand

Senior Member
Location
Minnesota
Occupation
Electrical Contractor, Electrical Consultant, Electrical Engineer
I agreed that the article is better off using the standard terminology, i.e Armor grounding wire instead of cable armor in the context, for less confusing.
"standard terminology" . . . i.e. what you claim it should mean. I understand that you want different words in the NEC than are there. But the words that are there are the legally adopted and enforceable words. . . period.

What you are being shown is what I understand as a "Code silence". Armored Grounding Wire, KDER, is not spoken of with respect to bonding of armor to conductor or to enclosure, either DO or NOT DO.
 

peter d

Senior Member
Location
New England
Talk about making a mountain out of a molehill. I've only encountered this armored ground conductor once and I used a regular MC cable clamp for it. Thankfully it's extremely uncommon in my area and really serves no purpose.
 
1)
http://www.ospmag.com/issue/article/032012-McCarty
From NEC 2011, 250.64 Grounding Electrode Conductor Installation.
“ it shall be protected in rigid metal conduit (RMC), intermediate metal conduit, (IMC) rigid polyvinyl conduit (PVC), reinforced thermosetting resin conduit (RTRC), electrical metallic tubing (EMT), or cable armor.”

2)
https://www.mikeholt.com/videodisplaynew.php?pageid=4139
(E) Enclosures for Grounding Electrode Conductor. Ferrous (iron/steel) raceways, boxes, and enclosures containing the grounding electrode conductors must have each end of the ferrous metal raceway, box, and enclosure bonded to the grounding electrode conductor [250.92(A)(3)]. Figure 250.115

From (1) I interpret cable armor as an enclosure for GEC. And (2) says it must have each end bonded to the GEC.

Enough to satisfy everyone? For me I think this is more than enough to say that Al's Armored Grounding Wire must have each end of the armor bonded to GEC, unless Al can show that said armored grounding wire assembled at the factory already having each end of the steel armor bonded to the inside conductor.
 

al hildenbrand

Senior Member
Location
Minnesota
Occupation
Electrical Contractor, Electrical Consultant, Electrical Engineer
1)
http://www.ospmag.com/issue/article/032012-McCarty
From NEC 2011, 250.64 Grounding Electrode Conductor Installation.
“ it shall be protected in rigid metal conduit (RMC), intermediate metal conduit, (IMC) rigid polyvinyl conduit (PVC), reinforced thermosetting resin conduit (RTRC), electrical metallic tubing (EMT), or cable armor.”

2)
https://www.mikeholt.com/videodisplaynew.php?pageid=4139
(E) Enclosures for Grounding Electrode Conductor. Ferrous (iron/steel) raceways, boxes, and enclosures containing the grounding electrode conductors must have each end of the ferrous metal raceway, box, and enclosure bonded to the grounding electrode conductor [250.92(A)(3)]. Figure 250.115

From (1) I interpret cable armor as an enclosure for GEC.
Please read the Article 100 Definition of "Enclosure". I have already shown you the NFPA Glossary definition of "Cable". . . you are absolutely grasping at straws and need to settle into the fundamental definitions.

And (2) says it must have each end bonded to the GEC.
Yes (2) does say that for boxes, enclosures and raceways, NONE of which is Armored Grounding Wire, KDER.

Enough to satisfy everyone? For me I think this is more than enough to say that Al's Armored Grounding Wire must have each end of the armor bonded to GEC, unless Al can show that said armored grounding wire assembled at the factory already having each end of the steel armor bonded to the inside conductor.
All the Code you are struggling with is old and settled. Armored Grounding Wire, KDER, is an old and understood product. There is a reason the Code is silent. The Armor and the bare Grounding wire, TOGETHER, are Grounding and Bonding Equipment. As a case in point of that, your reference to the MVP99 clamp includes the instructions:

11. No need for Armor removal from the wire.
 
"The Code is silent about bonding the armor of Armored Grounding Wire to the wire contained in the armor."

The code was not created to deal with a brand device. The code says all ferrous metallic enclosure must be bonded at each end to the GEC, regardless if General Electric or Lockheed made the enclosures. The AHJ is there to decide your Armored Grounding wire was properly bonded or not. We can do it right the first time, or fix it the next time.
 
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