# MC cable and duplex connectors



## Rikki

I know that you supposedly don't have to use red heads with MC connectors, because they're supposed to be self-bushed. Do you need to use red heads when you're using a duplex MC connector? They don't seem like they have any way to bush each MC, and you might legitimately need to use a red head. I know some people are going to say -always use a red head- but I'm trying to figure out the real answer and not what a person might do. 

Thanks.


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## MDShunk

Always use a red head! (sorry, couldn't resist):jester: 

I don't know, but I see where you're coming from. Sounds like a question for NEMA, since that bulletin about not requiring anti-short bushings originally came from them. I have no idea how you ask NEMA a question, though.


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## Joe Momma

I've always known "red-heads" as a concrete anchor, but for MC I assume you mean "a$$holes", or as some fruity guy called them, "rose-buds".

I've only used anti-shorts with the type of MC connector that has a set-screw. The push in type; double or single barrel, I don't use them and have yet to see a problem.
Though I will point out that a quality installation depends on the installer.


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## raider1

> I know that you supposedly don't have to use red heads with MC connectors, because they're supposed to be self-bushed.


The reason that you don't need to use anti-short bushings on MC cable is that the listed connectors for use with MC cable come with bushings in the connector themselves.

I still always use the anti-short bushings on my MC cable. (a little extra protection goes a long ways.:thumbsup: )

Chris


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## ssandoval

*No anti-short needed?*

So am I correct in understanding that the NEC does not _require_ anti-shorts for MC? I know ART 320.40 is very specific about requiring them for AC cable, but isn't all MC cable inherently AC. What's difference between AC, MC and BX? Someone, please?


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## raider1

> but isn't all MC cable inherently AC.


No, the sheath of standard MC cable is not listed as EGC and the cable contains an insulated EGC. 

AC cable has a small aluminum bond wire run in direct contact with the interior of the cable sheath that will help the sheath provide a low impedance fault current path without an additional insulated EGC.

Also "BX" is a trade term for AC cable similar to the term "Romex" for NM cable.

Chris


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## electricalperson

a lot of guys use romex connectors for MC. i hate doing that makes me feel like peter d


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## B4T

electricalperson said:


> a lot of guys use romex connectors for MC. i hate doing that makes me feel like peter d


Peter D uses connectors?? :laughing:


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## raider1

electricalperson said:


> a lot of guys use romex connectors for MC. i hate doing that makes me feel like peter d


If the romex connector is not listed for MC cable that could be a big problem. The sheath of the MC cable must still be bonded and you need to use a connector that is listed for MC cable.

Chris


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## electricalperson

raider1 said:


> If the romex connector is not listed for MC cable that could be a big problem. The sheath of the MC cable must still be bonded and you need to use a connector that is listed for MC cable.
> 
> Chris


 only difference i see between an arlington MC connector and an arlington 3/8 romex connector is the bottom that sits inside the panel. the MC connector keeps all the wire in the center and a romex connector doesnt. i never looked up the UL listing of that stuff. i use MC connectors anyway:thumbsup:


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## manchestersparky

AC generally has the conductors wrapped in paper and MC generally has the conductors wrapped in plastic.


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## B4T

I think this is nit-picking.. put the  thing on.. the time it takes to accomplish this is seconds.

*Even* a HO could do this and the red heads are free :thumbsup:


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## jsb

is anyone out there using mcap?


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## LJSMITH1

Perhaps this will help explain where anti-shorts are to be used and why. MC is not the same as AC - even though it looks similar. 

As for Southwire's MCap, what exactly are you looking for as far as info?


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## LJSMITH1

raider1 said:


> If the romex connector is not listed for MC cable that could be a big problem. The sheath of the MC cable must still be bonded and you need to use a connector that is listed for MC cable.
> 
> Chris


 
Its a bit more than just a bonding requirement. There is also a cable stop requirement for AC/MC fittings. There is no similar requirement for NM.

Bottom line is always use fittings listed for the particular type and size cable/conduit you are using. The label on the box should tell you just about everything.


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## jsb

I have all the info I need I was just curious what parts of the country were using it


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## LJSMITH1

Typically any area where MC/AC cable is widely accepted (i.e. NOT Chicagoland). It certainly does reduce the time to wire a job. 

Be sure to use fittings listed for use with that cable.


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## zappy

Joe Momma said:


> I've always known "red-heads" as a concrete anchor, but for MC I assume you mean "a$$holes", or as some fruity guy called them, "rose-buds".
> 
> I've only used anti-shorts with the type of MC connector that has a set-screw. The push in type; double or single barrel, I don't use them and have yet to see a problem.
> Though I will point out that a quality installation depends on the installer.


And I always thought a a%#hole was a plastic bushing.


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## Termination

*Anti-Short*

The union guy has never had a problem, Because they don't call you to repair your problems, :laughing:


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## JohnJ0906

zappy said:


> And I always thought a a%#hole was a plastic bushing.


No, that's usually my helper.


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## SideWorker

Termination said:


> The union guy has never had a problem, Because they don't call you to repair your problems, :laughing:


Then who does the warranty work for a union contractor?


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## KayJay

Not sure what the hubbub is all about, but those Arlington duplex connectors are listed for NM, MC and BX, at least according to the box I have in front of me. If you use them with BX, you would need the redheads, hence the inspection holes, but not with MC cables. The clamp has nubs that grab and lock the NM sheath or spiral armor of the BX and MC. They also bond and prevent the sheath or armor from slipping in or out after installation. The connector throat is smooth inside to prevent abrasion and contoured to act as a cable end stop and redhead retainer.
I see these duplex connectors used with four NM’s cables stuck in them quite often, even though they are apparently only listed for two cables max of any type.


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## crazymurph

Then why does a coil of MC come with a bag of red heads?


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## Protech

Go back to post 14 and read the link


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## crazymurph

Protech said:


> Go back to post 14 and read the link


That explains nothing


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## Celtic

crazymurph said:


> Then why does a coil of MC come with a bag of red heads?



Perhaps because using a red head is considered "good practice" and has been installed "traditionally"...although it's use is not required.

The MFG probably doesn't care one way or the other....the cost just gets moved on down the line.


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## steelersman

raider1 said:


> The reason that you don't need to use anti-short bushings on MC cable is that the listed connectors for use with MC cable come with bushings in the connector themselves.



Umm, I don't think so. The standard single MC connectors (the ones that look just like romex connectors with the 2 screws that clamp down on the MC) don't have a bushing inside of them.


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## Celtic

steelersman said:


> Umm, I don't think so. The standard single MC connectors (the ones that look just like romex connectors with the 2 screws that clamp down on the MC) don't have a bushing inside of them.


I don't know what you mean by "standard".
Standard to you, might be something different to someone else.

Post a link so we are all talking about the exact same item.

Thanks :thumbsup:


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## steelersman

the kind mentioned here:

only difference i see between an arlington MC connector and an arlington 3/8 romex connector is the bottom that sits inside the panel. the MC connector keeps all the wire in the center and a romex connector doesnt. i never looked up the UL listing of that stuff. i use MC connectors anyway:thumbsup:


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## Celtic

steelersman said:


> the kind mentioned here:
> 
> only difference i see between an arlington MC connector and an arlington 3/8 romex connector is the bottom that sits inside the panel. *the MC connector keeps all the wire in the center* and a romex connector doesnt. i never looked up the UL listing of that stuff. i use MC connectors anyway:thumbsup:



That is why the need for a red head is not required.
The connector holds the conductors away from the sheath.


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## steelersman

Oh ok. I never thought about it like that.


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## LJSMITH1

Red Heads are not typically not required on MC due to the plastic sheathing between the outer sheath and the conductors. In AC cable, there is no plastic sheathing and only paper around the conductor insulation. This is why a red head is typically required to guard against abrasion from the cut edge of the metal sheathing. However, there have been some discussions in requiring these red heads for MC cable for the same reasons as AC cable. I have been told that some jurisdictions require the use of red heads on ANY AC/MC cable. 

As for the insulated throats on fittings for MC/AC, again, this is only required in some jurisdictions or when specified by the engineer. 

Regarding the difference between a Romex connector and an MC cable connector, the hole is there because UL514B requires a cable stop feature that will prevent the outer sheathing from passing through the fitting. It could be a round hole or a elongated hole. That is the primary reason. The NEMA document talks about centering the conductors, but I am not sure if that is accurate. How do the conductors remain 'centered' in a duplex fitting?...

The sight holes in many AC/AC fittings are there to allow the installer to see where the end of the sheath is prior to tightening the strap. The end of the sheath should be visible in the sight hole.

:thumbsup:


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## steelersman

Makes perfect sense to me.


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## Protech

Taken from the PDF:

"The confusion stems from the fact
that some MC cable manufacturers include anti-short bushings with their cable. The inclusion of
anti-short bushings with coils or reels of MC cable is based on historical practice relating to the
requirements of 320.40 of the NEC, which mandates the use of anti-short bushing or its​equivalent protection for Type AC Cable"

Further down:

"Whether or not an insulated throat is part of the listed product, these​listed MC fittings do not require an additional anti-short bushing."

What didn't you understand?
 


crazymurph said:


> That explains nothing


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## Celtic

LJSMITH1 said:


> Red Heads are not typically not required on MC ....



:blink:

So they are required?


:laughing:


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## LJSMITH1

Celtic said:


> :blink:
> 
> So they are required?
> 
> 
> :laughing:


 
Sometimes by the AHJ...:001_huh: They want them on ALL MC/AC cable installs. I think that's the primary reason why some cable Mfr's ship a little bag of them with every roll. It's cheap insurance that there won't be any complaints that they were not installed because there were none on the job site.:thumbsup:


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## MDShunk

LJSMITH1 said:


> Red Heads are not typically not required on MC due to the plastic sheathing between the outer sheath and the conductors. In AC cable, there is no plastic sheathing and only paper around the conductor insulation. This is why a red head is typically required to guard against abrasion from the cut edge of the metal sheathing.


I would buy that if there wasn't also type MC cable on the market that has no plastic around the conductors. I think it was on the back cover of this month's EC Mag.


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## EBFD6

My $0.02, use 'em if you got 'em. I almost always use red heads on MC, they are free and don't take any extra time to install. However, if I don't have one handy I won't make an extra trip to the truck just to get one, just install the connector. I've never lost a wink of sleep worrying about this issue.:thumbsup:


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## DayMan

MDShunk said:


> I would buy that if there wasn't also type MC cable on the market that has no plastic around the conductors. I think it was on the back cover of this month's EC Mag.


HCF MC has paper on it.


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## MDShunk

DayMan said:


> HCF MC has paper on it.


I was thinking of AFC Cable's MC-Quik, which has no plastic or paper. They also have HCF cable called MC-Stat with no plastic or paper on it.


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## JohnJ0906

DayMan said:


> HCF MC has paper on it.


If you are referring to "Health care MC", that stuff isn't MC - it's Type AC cable.

http://www.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheet164


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## LJSMITH1

MDShunk said:


> I would buy that if there wasn't also type MC cable on the market that has no plastic around the conductors. I think it was on the back cover of this month's EC Mag.


The new MCI-A cable on the market is made by AFC Cable. It has no separate wrap, but the conductors each have the same material "wrap" (Polypropylene) extruded over the THHN insulation. This is the difference that allows them to have a similar cable to Southwire's MCap.

http://www.afcweb.com/pdfs/AFC0903_QS_Cbl_Cat_web.pdf

:thumbsup:


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## LJSMITH1

JohnJ0906 said:


> If you are referring to "Health care MC", that stuff isn't MC - it's Type AC cable.
> 
> http://www.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheet164


 
There are four types of HCF cable available.

*HCF-AC* AC Cable construction certified for use in Health Care Facilities (Paper wrapped conductors)

*HCF-MC* MC Cable construction certified for use in Health Care Facilities (Polypropylene wrapped conductor bundle)

*HCF-MCAP* MCI-A Cable construction certified for use in Health Care Facilities (Polypropylene wrapped conductor bundle)

and now *HCF-MCQuick* MCI-A Cable construction certified for use in Health Care Facilities (Polypropylene wrapped conductors)
:thumbsup:


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## Fredman

MDShunk said:


> I would buy that if there wasn't also type MC cable on the market that has no plastic around the conductors. I think it was on the back cover of this month's EC Mag.


 
Additionally, I dont know how a thin layer of plastic could be counted on to stop sharp metal from cutting thru it...:001_huh:


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## LJSMITH1

Fredman said:


> Additionally, I dont know how a thin layer of plastic could be counted on to stop sharp metal from cutting thru it...:001_huh:


It can't, but its more cut resistant than the paper. :thumbsup:


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## Fredman

LJSMITH1 said:


> It can't, but its more cut resistant than the paper. :thumbsup:


Maybe just a _smidjon_ more. :blink:

I'll keep using the redheads. 





Run for your life! The word police are coming! Ahhhhh:laughing:


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## Shockdoc

Black4Truck said:


> Peter D uses connectors?? :laughing:


 I still prefer the old style one screw squeeze mc connectors, there hard to come by since all these suppliers out here like to push the cheap garbage.


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## tkb

Fredman said:


> Additionally, I dont know how a thin layer of plastic could be counted on to stop sharp metal from cutting thru it...:001_huh:


So putting red dye in the plastic makes it better?


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## Fredman

tkb said:


> So putting red dye in the plastic makes it better?


Right on TK!

And to think I thought nobody understood me. 


:blink:



:laughing:


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## lenco12

LJSMITH1 said:


> Perhaps this will help explain where anti-shorts are to be used and why. MC is not the same as AC - even though it looks similar.
> 
> As for Southwire's MCap, what exactly are you looking for as far as info?


Its a bit more than just a bonding requirement. There is also a cable stop requirement for AC/MC fittings. There is no similar requirement for NM.

Bottom line is always use fittings listed for the particular type and size cable/conduit you are using. The label on the box should tell you just about everything.


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## Shockdoc

EMT and greenfield, old school is always better


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## Frasbee

I typically make use of the plastic wrapping, as well as the "red devils", (amongst other terms I've heard for it).

I cut the aluminum off, and keep the wires wrapped in plastic, then put on the bushing, pull back the excess plastic and cut it before I push it into the connector.

But I've seen other guys just cut the plastic away without bothering to use a bushing, as well.


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## HARRY304E

Rikki said:


> I know that you supposedly don't have to use red heads with MC connectors, because they're supposed to be self-bushed. Do you need to use red heads when you're using a duplex MC connector? They don't seem like they have any way to bush each MC, and you might legitimately need to use a red head. I know some people are going to say -always use a red head- but I'm trying to figure out the real answer and not what a person might do.
> 
> Thanks.


Allways use redheads your better off and allway make sure your connectors are tite:thumbup:


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## LJSMITH1

lenco12 said:


> Its a bit more than just a bonding requirement. There is also a cable stop requirement for AC/MC fittings. There is no similar requirement for NM.
> 
> Bottom line is always use fittings listed for the particular type and size cable/conduit you are using. The label on the box should tell you just about everything.


 
Redheads have nothing to do with Cable Stops....


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## Shockdoc

So one can safely assume Tommic connectors are not approved for ac lite. Came across a 200 amp panel years back with all bx wires doubled in Tommic connectors. Guess the guy never heard of duplex connectors.


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## LJSMITH1

Shockdoc said:


> So one can safely assume Tommic connectors are not approved for ac lite. Came across a 200 amp panel years back with all bx wires doubled in Tommic connectors. Guess the guy never heard of duplex connectors.


 
The box label will tell you everything you need to know. Tommic connectors are only rated for NM only as there is no cable stop incorporated into the connector.


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## davidwilsoon

ssandoval said:


> So am I correct in understanding that the NEC does not _require_ anti-shorts for MC? I know ART 320.40 is very specific about requiring them for AC cable, but isn't all MC cable inherently AC. What's difference between AC, MC and BX? Someone, please?


No, the sheath of standard MC cable is not listed as EGC and the cable contains an insulated EGC. 

AC cable has a small aluminum bond wire run in direct contact with the interior of the cable sheath that will help the sheath provide a low impedance fault current path without an additional insulated EGC.


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## miller_elex

You don't have to use anti-shorts IF:

You have the arlington snap-ins with the red barbs,
AND, you use the roto-split.

This includes green mc.


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## Split Bolt

I'm sorry to drag this thread back from its resting place, but not one post mentioned the REAL name "red eyes!" I agree with one of the first replies that "red heads" are drop-in anchors. Here's how you can tell if you are dealing with MC. When you cut off the clear plastic layer and drop it off of your ladder, it should stick to your pants leg with static electricity! Then you know it is MC!:thumbsup:


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## Bob Badger

Split Bolt said:


> I'm sorry to drag this thread back from its resting place, but not one post mentioned the REAL name "red eyes!"


That is crazy talk. :jester:





> I agree with one of the first replies that "red heads" are drop-in anchors.


Redheads are anti shorts, drop in anchors are 'drop ins'. :laughing:


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## brian john

Bob Badger said:


> That is crazy talk. :jester:
> Redheads are anti shorts, drop in anchors are 'drop ins'. :laughing:


Red eyes around here are Anti-Short Bushings, the name I use to see on the bag, that comes with BX back in the day.

Red Heads are a brand name for drop in anchors in the 70's this was the only brand we saw. The power tool hammered and we had an attachment to spin back and forth the anchor.


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## djmessina

Joe Momma said:


> I've always known "red-heads" as a concrete anchor, but for MC I assume you mean "a$$holes", or as some fruity guy called them, "rose-buds".
> 
> I've only used anti-shorts with the type of MC connector that has a set-screw. The push in type; double or single barrel, I don't use them and have yet to see a problem.
> Though I will point out that a quality installation depends on the installer.


Ha I've always called them Red Devils idk why.


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