[amakarevic]

i noticed that MC cable comes with a few red plastic bushings. i don't know what they are for and whether they must be used. so far, i've only been putting MC cable into the BX type clamp connectors at the box and tightening the screw. wondering what those bushings do...

thanks

 

[nap]

first, you need to make sure if you are using MC cable or AC cable. AC cable has a bare binding wire laying in the inside of the metal sheath. MC doesn't.


so, to the insulators. If you are using actual MC cable, they are not required to be used although most guys I know use them anyway. They fit in the cut end of the metal sheath between the conductors and the metal sheath.

If you are using AC cable, those insulators are required unless the fittings you are using have a built in insulator (red plastic bushing built into the fitting which will fit in between the metal armor and the conductors.


the reason I say something about AC cable is; different areas of the country tend to use one or the other for general use and along with that, I know a lot of guys that call AC cable MC. There is a difference and it makes a difference.

 

[amakarevic]

it is simple MC cable i am using

 

[Saturday Cowboy]

"red heads" are not required but I like to use them

 

[SD515]

NEC doesn't mention that they have to be used on MC cable, but the manufacturers instructions may require them per their listing. I know...who ever reads the carton/tag on a roll of wire....:huh:

That aside, I always like to use them. Remember, the code is the minimum...you can always exceed the code.

 

[sparks1up]

If you get a bag of them attached to the roll when you buy it, the manufacturer is saying they should be used. Personally I use them on either cable.

What are you using to cut the cable? An armored cable (BX) stripper or a pair of ****'s?

 

[NJMarine]

NEMA

2.1.6 Cable Fittings
The combination of listed Type MC cable and listed MC cable fitting designs are such that the use of antishort
bushings is not required by the NEC®. MC cable fittings have a shoulder to protect the conductors
from any sharp edge that may be present on the cut edge of the armor. Bushings may be used however
(See Appendix A, or go to NEMA Engineering Bulletin 90).

Appendix A
NEMA ENGINEERING BULLETIN 90
Use of Anti-Short Bushings for Terminating Type MC Cable
There has been much confusion within the installation and inspection communities regarding the use of
anti-short bushings for terminating Type MC cable. 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.
Fittings used with Type MC cable are required to be listed per 330.40 of the NEC®. NEMA supports the
use of listed fittings for MC cable. The design of these fittings may or may not include an insulated throat.
However, they are required to be provided with a smooth, rounded end stop so that the metal sheath of
the cable will not pass through and the wires will not be damaged in passing over the end stop. Whether
or not an insulated throat is part of the listed product, these listed MC fittings do not require an additional
anti-short bushing. Anti-short bushings that may be supplied by MC cable manufacturers are for optional
use by the installer. However they are not required.

ROP #7-116 from the May 2001 Report on Proposals (ROP) for the 2002 NEC® was a proposal seeking
to require anti-short bushings on all MC cable termination installations. The following is an excerpt from
the Panel statement rejecting the proposal:
“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.”
NEMA supports the uniform adoption and enforcement of the NEC® and recommends that local
authorities having jurisdiction follow the requirements of NEC® Section 330.40, Boxes and Fittings for MC
Cable. Section 330.40 requires that the fitting be listed, but does not mandate the use of an anti-short
bushing.


© Copyright 2008 by the National Electrical Manufacturers Association

 

[nap]

wish we could do multiple thanks. Excellent information NJMarine:thumbsup::thumbsup:

 

[amakarevic]

If you get a bag of them attached to the roll when you buy it, the manufacturer is saying they should be used. Personally I use them on either cable.

What are you using to cut the cable? An armored cable (BX) stripper or a pair of ****'s?

to just cut the cable, i use the big bolt cutters the kind you would use to cut through a padlock or something. then to strip the metal of the end i use a wheel cutter.

 

[nap]

be careful the wheel does not cut the insulation on the conductors. I have seen some that allowed you to over cut quite easily resulting in a slice in the insulation.

 

[amakarevic]

be careful the wheel does not cut the insulation on the conductors. I have seen some that allowed you to over cut quite easily resulting in a slice in the insulation.

true that however the cable i got has a coat of nylon under the armoring layer and above the individual wires, which it wraps. not a hell of protection against that but better than nothing.

 

[SD515]

Plastic lining or not, if the cutter is set too deep, it can still cut into the wire. Trust me, I've repaired them.