MC cable connectors

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Ralphie said:
Are fiber bushings( red heads ) required for terminating MC cable when using connectors with insulated throats ?
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No, they are not, see article 330.40 for MC cable and see article 320.40 for type AC cable (BX)..
 
MC cable doesn't even require the use of a bushing, AC cable does - but no one seems to know why they are different with this requirement. This is generally true for the spiral tape style sheath versions anyhow, other sheath types may have different requirements.
 
Most of the manufactures (us included) will provide them regardless of being AC or MC. We do this because of the very nature of this question. Rather than have an inspector debate the issue of knowing how to satisfy Section 320.40, where anti-shorts are required and confusing it with Section 330.40 where anti-shorts are not required, we simply provide both and give the installer the option to use them when not required as well.

What is quite interesting is that Section 330.40, which requires no anti-shorts does require that it's fittings be listed and identified for use, (Will be listed and labeled in the 2017 NEC BTW) but dos not have the same language in Section 320.40 requiring this listed and identified statement. However, that is not the genesis of the anti-short requirement.

The following is an excerpt from the Panel statement rejecting proposal ROP #7-116 from the May 2001 Report on Proposals (ROP) for the 2002 NEC. This proposal was seeking to require anti-short bushings on all MC Cable termination installations.


?Anti-short bushings are not required for Type MC cable in accordance with the listing for the product. The termination fittings approved for use with Type MC cables are designed such that the wires will not come in contact with the cut edge of the armor; the throat of the fitting is small enough to prevent contact with the armor. Type MC termination fittings perform the same function for Type MC cable as Type AC terminations plus the anti-short bushing do for Type AC cable.?

The origins are in the different requirements for the fittings construction.
 
MasterTheNEC said:
Most of the manufactures (us included) will provide them regardless of being AC or MC. We do this because of the very nature of this question. Rather than have an inspector debate the issue of knowing how to satisfy Section 320.40, where anti-shorts are required and confusing it with Section 330.40 where anti-shorts are not required, we simply provide both and give the installer the option to use them when not required as well.

What is quite interesting is that Section 330.40, which requires no anti-shorts does require that it's fittings be listed and identified for use, (Will be listed and labeled in the 2017 NEC BTW) but dos not have the same language in Section 320.40 requiring this listed and identified statement. However, that is not the genesis of the anti-short requirement.

The following is an excerpt from the Panel statement rejecting proposal ROP #7-116 from the May 2001 Report on Proposals (ROP) for the 2002 NEC. This proposal was seeking to require anti-short bushings on all MC Cable termination installations.


?Anti-short bushings are not required for Type MC cable in accordance with the listing for the product. The termination fittings approved for use with Type MC cables are designed such that the wires will not come in contact with the cut edge of the armor; the throat of the fitting is small enough to prevent contact with the armor. Type MC termination fittings perform the same function for Type MC cable as Type AC terminations plus the anti-short bushing do for Type AC cable.?

The origins are in the different requirements for the fittings construction.
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I can understand that last sentence as being a reason for a difference in requiring the bushings, but every new connector I can recall ever using for the last 25 years or so is listed for both AC and MC cable, and cable sheaths are of very similar if not the same design when it comes to spiral tape type sheath. Still kind of leaves questions as to why one is acceptable without a bushing and the other is not.
 
kwired said:
I can understand that last sentence as being a reason for a difference in requiring the bushings, but every new connector I can recall ever using for the last 25 years or so is listed for both AC and MC cable, and cable sheaths are of very similar if not the same design when it comes to spiral tape type sheath. Still kind of leaves questions as to why one is acceptable without a bushing and the other is not.
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I agree both are made the same way and cut the same creating the same sharp edge that the anti short is supposed to cover.
 
kwired said:
MC cable doesn't even require the use of a bushing, AC cable does - but no one seems to know why they are different with this requirement. This is generally true for the spiral tape style sheath versions anyhow, other sheath types may have different requirements.
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The difference between the two cable types is.. The jacket for AC cable is listed as its ground while the jacket of MC cable is not. That's why AC cable has no EGC and MC cable does.
 
AdamS said:
The difference between the two cable types is.. The jacket for AC cable is listed as its ground while the jacket of MC cable is not. That's why AC cable has no EGC and MC cable does.
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I don't think the EGC has anything to do with the plastic bushing.
 
AdamS said:
The difference between the two cable types is.. The jacket for AC cable is listed as its ground while the jacket of MC cable is not. That's why AC cable has no EGC and MC cable does.
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Except a couple of years ago MCap came out and that is MC with jacket listed for grounding.
 
AdamS said:
The difference between the two cable types is.. The jacket for AC cable is listed as its ground while the jacket of MC cable is not. That's why AC cable has no EGC and MC cable does.
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edward said:
I don't think the EGC has anything to do with the plastic bushing.
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I agree the EGC has nothing to do with the plastic bushing requirement. As far as using the cable sheath as the EGC, the sheath alone is not acceptable, the bonding wire that is just under and in fairly intimate contact with the sheath is what makes it acceptable to use the sheath for equipment grounding, and as mentioned they have in recent years started applying same method to certain types of MC cable - again making the two products even more the same.
 
AdamS said:
The difference between the two cable types is.. The jacket for AC cable is listed as its ground while the jacket of MC cable is not. That's why AC cable has no EGC and MC cable does.
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That is common knowledge but as iwire has stated companies have come out with MC SG (Smartground) and MCap as well. Also the thickness of the actual spiral sheathing is slightly different between the two products as well.
 
kwired said:
I agree the EGC has nothing to do with the plastic bushing requirement. As far as using the cable sheath as the EGC, the sheath alone is not acceptable, the bonding wire that is just under and in fairly intimate contact with the sheath is what makes it acceptable to use the sheath for equipment grounding, and as mentioned they have in recent years started applying same method to certain types of MC cable - again making the two products even more the same.
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It comes down to the termination fittings. The fittings for MC are designed to keep the conducters from coming in contact with the cut edge of the sheath. They perform the same function as the term fittings for ac cable with a bushing.
 
AdamS said:
It comes down to the termination fittings. The fittings for MC are designed to keep the conducters from coming in contact with the cut edge of the sheath. They perform the same function as the term fittings for ac cable with a bushing.
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Can you name a newer fitting that is listed MC or AC only, only ones I know of are listed for both.
 
As I understand it, when using M-cap or MC-SG, when you terminate the cable into the listed fitting you just cut off that extra wire at the end of the spiral jacket (use of red heads is not required and is optional). Now, when that cable assembly (or assemblies) and fitting(s) are connected into and out of the JB, that JB is effectively grounded. Now, if we assume that we are using a 4" square JB with a 1-gang mud ring to install a receptacle, the mud ring is effectively grounded via its mechanical connection and the use of a self grounding receptacle requires no additional ground wire to the JB. Seems like better method than using std. MC where you have 2 insulated green wires (1 in-1 out) + 1 bonded to the JB. Even though all the grounds are counted in box fill calculations it's still a lot of wires to jam into the JB IMHO.
 
MC fittings on AC cable

MC fittings on AC cable

Why are we not allowed to use the MC cable connectors on AC and thus avoid using the anti short bushings? That seems to be the question.
 
Greg1707 said:
Why are we not allowed to use the MC cable connectors on AC and thus avoid using the anti short bushings? That seems to be the question.
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Well it is possible to cross use the connectors that are evaluated for that purpose and many are....but the little issue of Section 320.40 makes a statement to require the bushings while Type MC in 330.40 does not.
 
kwired said:
Can you name a newer fitting that is listed MC or AC only, only ones I know of are listed for both.
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Yes, there are many.....The Snap In MC/MCI-A Connector # 560MCIA from Bridgeport for example...is listed only for those uses and not AC.
 
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