Stripping MC Cable & Inserting an Anti-Short Bushing

Popular Mechanics has a great step-by-step article on stripping MC Cable and inserting a plastic anti-short bushing. Using a Roto-Split from Seatekco, the picture shows how to slice the metal cladding and how it's good practice to then insert the anti-short bushing.

You have to scroll down halfway on the page to see MC Cable being stripped. To view the article, click here.

MC Cable

There is a lot of talk in the discussion forums online as to whether or not anti-short bushings should be used for MC Cable installations. Since so many electricians use them as a safety precaution and as a matter of habit, it seems like a moot point as to whether or not they are actually required on MC Cable. Many contractors just see them as added insurance against shorts. What do you think? I'd love to hear your comments. Take a look at this recent forum posting, and you'll see what they're talking about:

http://forums.mikeholt.com/archive/index.php/t-75924.html

Anti-Short Bushings on Wikipedia

A write-up about Anti-Short bushings is finally showing up on Wikipedia. Prior to now, they were considered a commercial product and any postings about anti-short bushings were promptly removed by the team over at Wikipedia. Because they are now so widely used given their obvious safety benefits and wide spread use for terminating both MC Cable and AC Cable, I guess the team finally recognizes them as mainstream. To view or add to the Wikipedia article click here http://en.wikipedia.org/wiki/Anti-Short_Bushing

Anti-Short Bushing Sizes

There are so many different sizes of plastic anti-short bushings that I thought I'd finally post them. If you know of any other sizes, please leave a comment on this post:

• No. 0 - 5/16" flexible conduit trade size
• No. 1 - 3/8" flexible conduit trade size
• No. 2 - 7/16" flexible conduit trade size
• No. 3 - 1/2" flexible conduit trade size
• No. 4 - 3/4" flexible conduit trade size
• No. 5 - 1" flexible conduit trade size
• No. 6 - 1-1/4" flexible conduit trade size
• No. 7 - 1-1/2" flexible conduit trade size
• No. 8 - 2" or 2-1/2" flexible conduit trade size

National Electrical Code Diagram

Parts of the National Electrical Code are now posted online. To view the NEC's installation diagram for Insulating (Anti-Short) Bushings, as shown in the second edition of the Illustrated Guide to the National Electrical Code, click here.

You'll have to scroll down on the page to view the whole diagram.

Using Anti-Short Bushings with MC Cable

Here's an animation showing the cutting of MC Cable and the insertion of a plastic anti-short bushing. You'll notice the animation doesn't use a roto-split. They use a bx cutter instead, which was used after many people stopped using a hacksaw. To view the animation, click here.

Installing an Anti-Short Bushing

Here's a handy guide to installing a plastic anti-short bushing (ie.Terminating AC & MC Cables). Of course, check with your local inspector first, but this shows an example from a cable manufacturer, with pictures, on page 22 of http://www.afcweb.com/pdfs/afcpocketguide.pdf . There is also another one under Learning Center at www.anti-shortbushing.com If you have a better picture for us to post, leave a comment or a link on this blog post.

IAEI News was established in 1928 as the official organ of International Association of Electrical Inspectors

Here's a great magazine that electrical inspectors read. Apparently it reaches authorities with power of product specification, approval and acceptance. Here's an article they posted on MC Cable and a brief discussion about the use of plastic anti-short bushings with MC Cable.

To view the article, click here click here Of course, your comments are always welcome, so feel free to post a comment on this post after you read it.

Standards in Development

According to their website, the National Electrical Installation Standards (NEIS) are "the first quality and performance standards for electrical construction". They are often developed with expert groups in a joint effort. Because they are quality and performance standards, they also often exceed NEC safety requirements. Here is list of standards in development.

Nicknames for The Anti-Short Bushing

You can't really afford a short. So most electricians say they use plastic anti-short bushings on MC Cable because they see them as backup insurance against a short, even if they happen to be told they aren't required on MC Cable for one reason or another.

Looking online, you can find many names for the anti-short bushing including "redheads", "redeyes", and even "red devils". You can also find many ways to spell anti-short bushing, including antishort bushing, anti short bushing, and the correct way which is anti-short bushing. The red color of the anti-short bushing helps inspectors easily find the bushing. If you have any other names or uses for them, feel free to post a comment.

NEMA's Take on MC Cable

In August of 2002 The National Electric Manufacturers Association (NEMA) posted a bulletin to clarify the use of a plastic anti-short bushing with cable installations. What's interesting is that they stated that it has been historical practice to use them on MC Cable.

In their words, "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." To see the actual "NEMA Engineering Department Bulletin No. 90, titled Use of Anti-Short Bushings for Terminating Type MC Cable", click here. Go ahead and leave your comments here on whether you feel they should be mandated for use in conjunction with MC Cable.

Do you think NEMA should mandate the use of anti-short bushing on MC Cable since they are already required for terminating AC Cable and since most electricians use them on MC Cable anyway? Leave your opinion as a comment to this post. I'd like to hear from you!

Survey on Anti-Short Bushings

We recently showed up at a local electrician's shop at 6 in the morning to do a survey on Anti-Short Bushings. The manager handed out the survey to his team of electricians and the general consensus was that redheads are a must with MC Cable. They feel it's a safety hazard to not use them, even if they are told they are not required. We're going to be posting the results soon, and we'll let you know when they are up..

To take the anonymous survey yourself, click here http://www.anti-shortsurvey.com/.

Anti-Short Bushings on This Old House TV Show

The TV Show This Old House actually had a video on how to install the anti-short bushing. If any of you electricians have any suggestions for the team at This Old House, feel free to post your comments after you watch the video.

http://www.thisoldhouse.com/toh/video/0,,20047018,00.html

Fiber Anti-Short Bushings

Anti-short bushings are made of polyethylene (plastic) and are designed to comply with CSA and UL requirements. Electricians use roto-splits to cut cable so there is a cleaner cut.

Anti-short bushings used to be made out of fiber. They also used to cut the cable with a hacksaw. Take a look at this old diagram of how the fiber bushings used to look by clicking here. Notice how the guy in the diagram is using a hacksaw to cut the cable, while using his knee to hold the cable taut. Leave your comments on this post if you have any specialized ways of cutting the cable.

Why Anti-Short Bushings Were Invented

Back in the 1940's, many fires were attributed to electrical sources, particularly to the use of armored cable. Apparently, the conductor insulation in the armored cable was being cut by the very sharp edges of the cut armor when terminations were being made. Two investigators found that the insertion of a hard, waxed fiber bushing between the armor and the insulated conductors would prevent damage to the insulation and the anti-short bushing was born.

The reality is, anti-short bushings were and still are a critical part of electrical safety. Do you agree? For a quick history of the the Anti-Short Bushing, click here www.anti-shortbushing.com