anti-short bushings

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tilk

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Can anyone tell me why anti-short bushings are not required for MC Cable? I always install them by habit from using AC Cable plus seems like a safer installation. :confused:
Thank You for any opinions.
 
Re: anti-short bushings

If (and they usually do) come with the mc and instructions say use them then its a must.Personally there is no chance that i would not use them.
 
Re: anti-short bushings

Here is what NEMA has said about it.

We can all make up our own minds.

NEMA
ENGINEERING DEPARTMENT

BULLETIN No. 90

August 14, 2002

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 theuse of an anti-short bushing.


Distribution List:
Standards and Conformity Assessment Policy Committee
Codes and Standards Committee
NEMA Executive Staff
Click to expand...
 
Re: anti-short bushings

Call it mc or as it was called years ago BX yes it didn`t have a grounding conductor :D so no runs less than 5 ft :eek:
 
Re: anti-short bushings

I have worked in alot of healthcare places and have always used anti short bushings with mc cable.
 
Re: anti-short bushings

Originally posted by jdelectric:
I have worked in alot of healthcare places and have always used anti short bushings with mc cable.
Click to expand...
That was not MC cable. It was probably Type HCF, which is AC cable and anti-short bushings are required.
 
Re: anti-short bushings

When I think of BX I think of 2 conductors and the armor casing was the grounding system.(OK I am showing my age :eek: )
 
Re: anti-short bushings

It's my opinion that more shorts are caused by the over-tightening of saddle type ac/mc/bx connectors. The snap/snap connectors have not only
increased install time, but have eliminated most
shorts at termination points. I realize ther are
situations where you must use an alternative to a snap/snap fitting, but the anti-short does not negate a poor strip and install of metallic cable.
 
Re: anti-short bushings

Originally posted by magicdog:
It's my opinion that more shorts are caused by the over-tightening of saddle type ac/mc/bx connectors. The snap/snap connectors have not only
increased install time, but have eliminated most
shorts at termination points. I realize ther are
situations where you must use an alternative to a snap/snap fitting, but the anti-short does not negate a poor strip and install of metallic cable.
Click to expand...
I tend to agree. I think there is a right way and a wrong way to strip MC cable.

A hacksaw or rotozips do a nice job but you have to be careful not to cut right into the conductors, especially with the hacksaw.

I cringe when I see someone doing a "bend and snap" on MC cable. I have seen nothing but butchered cable and sharp edges from this "method."

Overtightening the connector is a no-brainer. Connector too tight = short. I would hope most electricians could grasp this concept.
 
Re: anti-short bushings

Thanks Peter, You're previous reply was so correct. I'm tired of hearing "Hospital Grade MC".
It is in fact AC cable.
 
Re: anti-short bushings

Is there such a thing as an anti-short bushing for FMC? I'm guessing not, and the code says to trim the FMC, which seems like an odd term. What's the best method to remove the sharp edges? Also, why is a set screw connector more commonly used than a screw in connector which wouldn't require 'trimming' the FMC. My guess is the former looks better.

(Sorry for the hijacking of the topic, but it is related :) )
 
Re: anti-short bushings

Paul 32,
I usually get stuck with having to use the screw in type of flex connectors. The problem is that these reduce the internal diameter of the flex which makes it hard to pull.
To "trim the ends of the flex, you use aviation snips to do the trimming. It may be helpful to have both a green pair and a red pair depending on which end you are working on. There is also a tool made to hold a hacksaw blade at 90? sort of like a miter box for flex.
~Peter
 
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