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 the use of an anti-short bushing.
www.nema.org

A couple of years ago I contacted AFC (the manufacturer) re the bushings.
I was told that they were included only as an "added protection" for the cable terminations. The engineer said they were recommended, but not required...good enough for me. I still use them...S

OK, who are you and what have you done with Joe?!?!?!?!

Virgil:

ROTFL

Mr. Tedesco:

What cable types require the bushings? These are the "red heads," correct?

I recall a post on the board indicating that the bushing needs to be visible so the AHJ has no doubt that the bushing was installed.

Thinkgood, that is the wording of 320.40 which is type AC. Type MC 330.40 does not require these.

Roger

OK, now I understand sparky66wv's post above:
OK, who are you and what have you done with Joe?!?!?!?!

Is Type MC Cable used in WV?




[This message has been edited by Joe Tedesco (edited 02-22-2003).]

Required or not, I'd still use those red bushings - they're damned cheap and sold by the bagfull!

There's no such thing as too much protection.....

Good thing now I also know there's a specific connector for type MC cable. I thought MC and BX cable connectors were interchangeable - the DIY books never point THAT out!

[This message has been edited by SvenNYC (edited 02-21-2003).]

Yes, Joe, we use it on commercial jobs and when I have fluorescent lay-ins or for HVAC circuitry.

I always install the bushings, although I have seen those who did not, and I have mistakenly thought it would be a violation.

Of course, I just call MC Cable "BX".

[This message has been edited by sparky66wv (edited 02-22-2003).]

I got blasted on this by an inspector in San Diego, in pre-ECN days.
She made us cut the shear panel, replace the connectors and install bushings on an existing installation.
Then, the shear panel had to be repaired, per their other inspector.
In all, it cost about $800 or so.
That's just another reason I'm glad you're all here ...S

Whats a shear panel?
Bob

An older sparky that was my leadman on commercial jobs years ago would rap me on the hardhat and say " You make shore you use them reddevils boy".Old habits would be hard to break. Russell

I'm with you Russell, taught the same way, but, I have to laugh when a journeyman shows an apprentice how to install them with the sharp edge (from a "roto-split") exposed through the split in the bushing. (and thinks this is OK)

iwire:

Shear Panel refers to the plywood installed on an interior wall. Call them "Shear Walls".

Shear Walls are perpendicular to long walls. When a building is a long rectangle, there needs to be some support on
the "shorter" wall segments, in order to achieve a more stable frame.

The Shear Panel is load bearing, so it should not be crippled in any way - such as randomly cutting out segments of
plywood, like what Electure (Scott) was describing.

Electure:

That sounds like a lot of fun (please invert to not-fun!). Must have made the Framing Inspector a little ticked off?

Scott35 S.E.T.

I've always used them. The only problem I've had is the plastic "tape" inside. I would use that tape to "hitch" the bushing in place. It wouldn't take much to cause that bushing to fall out. The solution was found in a short piece of tie wire. I would slip about 4" of a 10" piece of tie wire into the end of the MC, and secure the bushing by winding the tie wire around the MC just like when using type AC cable. It really works well, and there is no harm done to the insulation. Necessity is the mother of invention.

Regards,
Doc

Scott35, Thanks I got it now, I was thinking something electrical not structural.
Bob

I was taught that tape could be used as an alternative to the bushings (push down jacket, tape wire, pull up jacket, continue tape around jacket).
I was also taught to use tape to hold the bushings in place.
In this matter, I treat MC and AC the same. Indeed, I sometimes wonder why the code differentiates between the to, and why AC is still made,

Just to be sure I've got this right...can I use those 2-screw connectors with the ring opening without the anti-short bushing? It seems to me that it would be ok, especially if the plastic sheathing passes through the opening, but I would prefer to use the MC connectors that have the red plastic ring opening, so that any wire bent against the opening won't short out.

Anyone accidently set a screw clamp down in the MC connector...only to find out that the clamp plate was missing, and the screw just punctured the MC armor? I had to go back to fix someone else's screw-up like that, and it was no fun.