AC Cable terminations

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ryan_618

Senior Member
I was always led to beleive that you simply cut off the small bonding strip in type AC cable. Upon further investigation, it appears that I am wrong.

Here is an E-mail I sent to a major manufacturer of both AC and MC Cables, and his reply:

When terminating type AC cable, your instructions specify that you must bend the bonding strip back over the cable armor. Why is that? It seems to me that the purpose of the bonding strip is to be in intimate contact with the cable armor, therefore providing an effective ground fault current path. With this said, once the bonding strip leaves the cable armor, it is doing nothing. Why would you need to wrap the bonding wire back over the cable armor, when the cable armor is already in contact with the bonding strip inside of it?

Response:

Dear Mr. Jackson:

Yes, you are correct. However, in the absence of any guidance from the NEC or the U.L. standard that the cable is manufactured to, we are left with best trade practices. When we first published installation guidance for armored cables we worked with James Stallcup. With his assistance we polled the electrical community and gathered information on the best trade practices used in the field for terminating the bond strip in Type AC cables. Overwhelmingly the responses all lead to the bond strip being "displayed" on the outside of the cable armor because the electrical inspectors demanded to see it for themselves during the inspection process. Apparently by being able to see the bonding strip, they could quickly ascertain that the proper cable type had been used. Therefore, when we began printing our installation publications we illustrated what we had learned.



But again, you are correct. Through the manufacturing process the bonding strip is placed tight up against the interior of the cable armor, in complete contact from end to end, thereby providing the armor/bond wire combination with a low impedance ground fault capability, which is tested prior to being put into the marketplace for use. Cutting the bond wire off at the end of the cable armor, although not nationally recognized as a best trade practice, would not impact the viability of the grounding means of the armor/bond wire combination. Further, traditionally the bond wire holds the mandated anti-short bushing in place.



I trust this information has been helpful in understanding the history of terminating Type AC cables.



Please tell Mike that I send my hearty greetings his way.



Marilou Newell

National Marketing and Technical Services Manager

AFC Cable Systems, Inc.
 

bphgravity

Senior Member
Location
Florida
I still don't think you wrong Ryan. The "best trade practice" is not always the required or even needed practice.

Manufacturer's have and are increasingly manipulating and maneuvering in the industry to get products and product installations as code. While I generally prefer to see manufacturer's provide safe products and materials so that wiring methods don't need to be made more stringent, in some cases, they take it to the far end of the spectrum.

I can't wait to see what happens with the 2008. It seems as the major proposals that have leaked to date are generally concerned with product requirements.
 

pierre

Senior Member
I would be curious to see if all of the manufacturers of AC cable have to say about this. I do not see it as a requirement to twist it around the cable sheath. I know most in our area use it to help hold in the Anti-short bushing.. redhead.

Practically speaking, do you think it would make a difference in the performance of the cable to perform in a ground fault situation?
 

ryan_618

Senior Member
I don't see it as making a difference at all, but the problem is, with this product it is required per 110.3(B). As you all know, the manufacturer's instructions, accodring to UL, are a part of the listing and labeling. :(
 

roger

Moderator
Staff member
Location
Fl
Occupation
Retired Electrician
Along the lines with Pierre, most manufacturers "recommend" using anti short bushings on their MC, they even furnish them with it, but that is not an instruction to do so and IMO a "recommendation" is certainly not a code issue.

Roger
 

raider1

Senior Member
Staff member
Location
Logan, Utah
Here is a quote from the installation instructions for AFC brand cables.
Terminating AC & MC Cables
When terminating or splicing at a junction, outlet or switch box, cut
the cable so that 6 inches of free conductor is left for connections
or splices. Use an approved connector and insure a proper bond by
firmly tightening the connectors to
both the box and the cable. Please
note: set screw connectors cannot
be used with aluminum armor
Type AC cable.
To terminate an AC cable, insert an
anti-short bushing and bend back
the exposed length of bonding wire.
The bonding wire can be bent back
before or after the bushing is inserted. There are several techniques
used for this procedure as pictured on this page.
Insert the cable into the connector and secure the connector into
the box. Be sure that the anti-short bushing is plainly visible in the
connector for easy inspection. The same procedure is followed for
MC cable with the exception that there is no bonding wire.
Although anti-short bushings are only required by the NEC for AC
cable, most manufacturers recommend their use with MC cable.

They do say that the anti-short bushings are "recommended" for use with MC cable but it seems that they are pretty specific about the bond wire.

Chris
 

roger

Moderator
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Location
Fl
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Chris, thanks, that pretty much covers their current position.

Roger
 

peter d

Senior Member
Location
New England
I deal with AC cable about twice a year. I always cut off the bonding strip, and I will continue to do so. Although this is not as common a trade practice as backwrapping the bonding wire, it's is still a trade practice nontheless. I don't see how one practice can trump another, as they are both legitimate. Furthermore, backwrapping serves no purpose in the performance of the cable.
 

raider1

Senior Member
Staff member
Location
Logan, Utah
I agree that backwrapping does not enhance the ability of the cable to effectively carry a fault current.

The big question is where we are required to backwrap the bond wire due to the installation instructions. As Ryan points out in an earlier post
I don't see it as making a difference at all, but the problem is, with this product it is required per 110.3(B). As you all know, the manufacturer's instructions, accodring to UL, are a part of the listing and labeling

Chris
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
The cable manufacturer in Ryan's OP said that they changed their instructions. Would this require the product to be re-listed since the original product listing did not require the bonding wire to be wrapped?
 

don_resqcapt19

Moderator
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Location
Illinois
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retired electrician
As you all know, the manufacturer's instructions, accodring to UL, are a part of the listing and labeling.
As long as UL classifies breakers, I will not accept the above statement.
Don
 

ryan_618

Senior Member
don_resqcapt19 said:
As you all know, the manufacturer's instructions, accodring to UL, are a part of the listing and labeling.
As long as UL classifies breakers, I will not accept the above statement.
Don

Don, I know your position on this, and I certainly see where you are coming from. I spoke with a gentleman from UL about this, and his position is that a "classification" acts as an adendum to the original listing. Therefore, a classified breaker can be used in a panel it is classified for, because the classification litarture amend the panel litarature.
 

don_resqcapt19

Moderator
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Location
Illinois
Occupation
retired electrician
Ryan,
If the information in the instructions was not used in the product testing, then it is not part of the listing and labeling information. If you come back and tell me that the only way this cable is tested is with it installed per the supplied instructions, then I will agree that they are listing and labeling instructions, but if that is not how the cable was tested, then they are not.
Don
 

iwire

Moderator
Staff member
Location
Massachusetts
From NEMA August 21, 2003

During the termination of Type AC cables, the bonding strip is not terminated in the same manner as an equipment grounding conductor. The bonding strip is not an equipment-grounding conductor according to either UL or the NEC and it is not necessary for it to be terminated. The best practices for terminating the bonding strip based on many years of trade experience with Type AC Cables include:

(a) wrapping the bonding strip around the exterior of the cable armor, or

(b) laying the bonding strip straight against the exterior of the armor.

The bonding strip however may also be completely cut and removed from the end of the armor.

http://www.nema.org/stds/eng-bulletins/upload/NEMA-Termination-of-Bonding-Strip-on-Type-AC-Cable.pdf


Looks like a suggestion not an instruction.
 

sandsnow

Senior Member
don_resqcapt19 said:
Ryan,
If the information in the instructions was not used in the product testing, then it is not part of the listing and labeling information. If you come back and tell me that the only way this cable is tested is with it installed per the supplied instructions, then I will agree that they are listing and labeling instructions, but if that is not how the cable was tested, then they are not.
Don

If I go along with you here, then how do I know which parts of the instructions are valid????
I don't think it's practical to try and second guess things here. I also don't want to call UL every time I see a new product to find out which items in the instructions are valid.
 

iwire

Moderator
Staff member
Location
Massachusetts
ryan_618 said:
UL Disagrees with you. :)

That does not mean Don is incorrect.

UL seems to have their head planted where the sun don't shine on the classified breaker issue. :lol:

sandsnow said:
If I go along with you here, then how do I know which parts of the instructions are valid

Have you ever seen AC cable arrive that had instructions from the manufacturer?

Aren't UL required instructions and labeling required to be shipped with the product?

Just like the required markings on terminals or the required markings on conductors?

My point is this.

If the UL listing requires the bonding strip to be back wrapped or just folded back instructions explaining that would be required to be shipped with the product.
 
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