Interlocking Armor Type MC Cable

[mc5w]

1) NEC section 330.40

2) Revised text indicated in square brackets

3) Proposal:

330.40 Boxes and Fittings. Fittings used for connecting [ smooth sheath and corrugated sheath ] Type MC cable to boxes, cabinets, or other equipment shall be listed and identified for such use. [ Fittings used with interlocking armor Type MC cable with a waterproofing sheath shall be listed and identified for such use. ] [ Interlocking armor Type MC cable without a nonmetallic waterproof covering shall be connected in accordance with 320.40 using antishort bushings and fittings listed for use with Type AC cable. Fittings that are listed for use with both Types MC and AC cable shall be permitted. ]

4) Substantiation: The difference in rules for interlocking armor Type MC and Type AC cable is a source of utter confusion and short circuits. Most electricians I know are incapable of knowing this difference. Most electrical inspectors cannot readily tell the difference between indoor interlocking armor Type MC cable and Type AC cable. Terminating both types of interlocking armor cables in the SAME manner will improve electrical safety by SIMPLFYING the rules.

There is also a Type MC interlocking armor cable on the market that uses a bare copper equipment grounding conductor that is in contact with the sheath. This product adds to the confusion.

An example is that in the summer of 2004 some buddies of mine were wiring a health care facility using type AC cable. When I got there my boss and his apprentices had installed a substatial amount of Type AC cable using type MC box connectors WITHOUT using any antishort bushings. This was because my boss thought that he was installing Type MC cable. I was the only person on the job who had spotted this error and I told my boss that next time he must use antishort bushings. Any terminations that I had to redo were redone with antishort bushings but I was not about to redo the whole installation since it was not my insurance policy that was on the line.

The electrical inspector did not catch this error either. Once Type AC cable and indoor Type MC cable is installed there is not a way for the inspector to tell the difference. There is no external marking. In the case of waterproof interlocking armor type MC cable the difference is obvious because of the nonmetallic sheath.

Some places have banned type AC cable because they have had problems in the past with making electricians install the antishort bushings. These places could also ban interlocking armor Type MC cable because of fear that Type AC cable could be sneaked in by claiming that it is Type MC.

To my knowledge, smooth sheath and corrugated sheath Type MC cable that is rated 600 volts or less is no longer made in the United States.

This difference in rules is a lot like how Abraham Lincoln once publically asked, "If you call a dog's tail a leg, how many legs does it have?" Similarly, interlocking armor indoor Type MC cable is like calling a dog's leg a tail and saying that is has 2 tails and 3 legs.

[ July 02, 2005, 02:06 PM: Message edited by: mc5w ]

 

[ryan_618]

Re: Interlocking Armor Type MC Cable

Do you have any dead bodies or fires to show me that would justify the use of anti-short bushings?

I think your substantiation is a matter of training and education, not a change to the rules. Sorry

 

[mc5w]

Re: Interlocking Armor Type MC Cable

The manufacturers of interlocking armor type MC cable supply it with antishort bushings and HIGHLY recommend using the antishort bushings. If they are not really needed why is the manufacturer spending an extra buck or 2 per 250 feet of cable to supply antishort bushings?

Also, how the h#!! does the inspector tell the difference between the 2 types of interlocking armor cable? Saying that one of them MUST use antishort bushing and for the other that antishort bushings are OPTIONAL just creates confusion.

Also, most electricians are not as smart as you and I are.

When we lived in New Jersey we rented a house where the original armored able started blowing out because there were ZERO antishort bushings in the armored cable. This happened in 1971 so it could have been wired right before licensing of electricians started in 1964 but at any rate there had to be almost nonexistent electrical inspection.

Now I feel a bit leery about this 2004 vintage health care facility also has type AC without antishort bushings. Maybe it will last indefinitely because type MC fitting with insulated throats were used, but since it was my boss's job it is his insurance.

 

[iwire]

Re: Interlocking Armor Type MC Cable

Originally posted by mc5w:
The manufacturers of interlocking armor type MC cable supply it with antishort bushings and HIGHLY recommend using the antishort bushings.

Do they?

I Think you need to look at NEMA Bulletin 89 or 90.

Originally posted by mc5w:
Also, how the h#!! does the inspector tell the difference between the 2 types of interlocking armor cable?

Perhaps he may look for a insulated green conductor or ask the electrician.

 

[iwire]

Re: Interlocking Armor Type MC Cable

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.

Distribution List:
Standards and Conformity Assessment Policy Committee
Codes and Standards Committee
NEMA Executive Staff

 

[mc5w]

Re: Interlocking Armor Type MC Cable

Hey Bob,

The type AC cable for use in health care facilites has both an insulated green equipment grounding conductor AND a #16 aluminum bonding strip for the armor. There is also an interlocking armor cable that has a bare #12 equipment grounding conductor

Unfortunately, in an installation that was one of my boss's jobs last year type AC cable for a health care facility was illegally installed WITHOUT antishort bushings. I was the only one who caught this error. This was because my boss and his people were mistakenly using the type MC rules. The electrical inspector did NOT catch this mistake. It may take 10 or 15 years for the installation to catch on fire and maybe the type MC box connectors will prevent that, but it is my boss's insurance, not mine that was on the line.

NEMA Engineering Bulletin 90 is pure BULL$#!+ because most electricians and electrical inspectors are totally confused as to when anitshort bushings are mandantory or when they are not needed.

If I were an electrical inspector I would just simply make people use BX connectors and anitshort bushings on ANY interlocking armor cable on the basis that there is not a way for me to tell the difference - there is no outer marking on the cable and there is not the much difference in the internal construction. If an electrical contractor wants to prove that only type MC cable was delivered to the job he can give me all of the packing slips and reel tags.

You are just trying to avoid the issue that most electricians and electrical inspectors are confused. If it looks like a duck, walks like a duck, quacks like a duck and most expecially SMELLS like a duck it must be a duck.

 

[iwire]

Re: Interlocking Armor Type MC Cable

Originally posted by mc5w:
Hey Bob,

The type AC cable for use in health care facilites has both an insulated green equipment grounding conductor AND a #16 aluminum bonding strip for the armor.

No kidding....

Originally posted by mc5w:
Unfortunately, in an installation that was one of my boss's jobs last year type AC cable for a health care facility was illegally installed WITHOUT antishort bushings. I was the only one who caught this error.

Thank God you where on the job to save the world.

Originally posted by mc5w:
NEMA Engineering Bulletin 90 is pure BULL$#!+ because most electricians and electrical inspectors are totally confused as to when anitshort bushings are mandantory or when they are not needed.

Really? I will trust NEMA engineering much more than mc5w ramblings.

Folks are you as confused as mc5w is as to what is MC and what is AC cable?

Sorry the electricians and inspectors I work with can tell the difference between MC and AC. They can also tell the difference between THHN and TW.

Originally posted by mc5w:
If I were an electrical inspector I would just simply make people use BX connectors and anitshort bushings on ANY interlocking armor cable on the basis that there is not a way for me to tell the difference -

Well here is where I would tell you to pound sand. If you can not tell the difference between MC and AC you would have no business being an inspector. You do realize that at the time you look at the rough you could look in the boxes.

Originally posted by mc5w:
You are just trying to avoid the issue that most electricians and electrical inspectors are confused.

By the way, we always use redheads.

[ July 19, 2005, 05:35 AM: Message edited by: iwire ]

 

[don_resqcapt19]

Re: Interlocking Armor Type MC Cable

Bob,
There is a much easier way to solve this problem...Ban both AC and MC
Don

 

[mc5w]

Re: Interlocking Armor Type MC Cable

Don,

That is not such a bad idea. Or, ban interlocking armor type MC cable and stipulate that it must be listed as type AC. Whatever it is, saying that one type interlocking cable MUST be used with antishort bushings and making antishort bushings optional for the other is a bit like calling a dog's tail a leg.

What is more interesting is that corrugated sheath type MC cable such as Corraclad and 5 KV type MC cable has never needed antishort bushings because of the difference in construction.

Also, what Bob said about the health care facilites type AC cable being green on the outside just further confuses the issues because the other type AC cable are either not painted on the outside or have colored stripes on the outside. In a lot of instances all that the colored stripes do is to help electricians who are too lazy to look at the end of a reel to see what wire colors are in there.

The electrical inspector should not have to carry around a bunch of manufacturer's catalogs because of all the crazy things that AFC, Alflex, etc. are doing. If the electrician wants to prove that interlokcing armor cable falls under the type MC rules they should have to prove ti to the electrical inspector.

Likewise, there are a lot of places around here where the minimum grounding electode conductor size is #4 solid copper or #2 stranded copper partly to SIMPLIFY enforcement - the number of house that have a GEC running crosswise to the ceiling beams in the basement or have a 200 amp service is so great that qualifying #6 copper is too much bother.

 

[mc5w]

Re: Interlocking Armor Type MC Cable

Don,

There are some places such as Cuyahoga Falls, Ohio that have banned interlocking armor type AC and MC cable because they had too hard of a time getting electricians to put antishort bushings into type AC.

 

[iwire]

Re: Interlocking Armor Type MC Cable

Originally posted by mc5w:
Don,

There are some places such as Cuyahoga Falls, Ohio that have banned interlocking armor type AC and MC cable because they had too hard of a time getting electricians to put antishort bushings into type AC.

Yeah....sure.... thats true. :roll:

mc5w few people on the forums get under my skin as far as you do.

Show us all some respect and when you post something like this provide some sort of reference to prove your point.

 

[iwire]

Re: Interlocking Armor Type MC Cable

Originally posted by mc5w:
Also, what Bob said about the health care facilites type AC cable being green on the outside just further confuses the issues because the other type AC cable are either not painted on the outside or have colored stripes on the outside. In a lot of instances all that the colored stripes do is to help electricians who are too lazy to look at the end of a reel to see what wire colors are in there.

I do not know where you are from but most electricians who have installed AC and MC can tell the difference.

If an electrician can not tell the difference between AC and MC they will probably have a real hard time with UF and NM. :roll:

Looks like it's time to ban NM also. :roll:

 

[roger]

Re: Interlocking Armor Type MC Cable

Bob, it looks to me like Mc5w and his cohorts need to get some experience with these materials before using them.

They would have a much better chance of installing them correctly.

Mc5w, it seems as though I remember you complaining in the past that you can't get a job in other areas due to finacial or time in the field reasons, are you sure there is not some other reason?


Roger

 

[pierre]

Re: Interlocking Armor Type MC Cable

There are a couple of answers to this topic.

From Ryan
1. I think your substantiation is a matter of training and education, not a change to the rules.

We should not ban anything, as proper training is the answer, and more of it needs to be had.

If the training does not work:
From Don
2. There is a much easier way to solve this problem...Ban both AC and MC

I will take this one step further and say ban all electrical work!!!

Then I can take the rest of the summer off

 

[don_resqcapt19]

Re: Interlocking Armor Type MC Cable

Bob,

I do not know where you are from but most electricians who have installed AC and MC can tell the difference.

I guess if you have used it that you should be able to tell the difference, but a lot of us live and work in the land of conduit and wire. What is this "cable" stuff you guys are always talking about?
Don

[ July 20, 2005, 07:19 AM: Message edited by: don_resqcapt19 ]

 

[sandsnow]

Re: Interlocking Armor Type MC Cable

Originally posted by mc5w:



There is also a Type MC interlocking armor cable on the market that uses a bare copper equipment grounding conductor that is in contact with the sheath. This product adds to the confusion.

Please tell us who makes this? I'd thought I'd seen every type out there.

 

[tom baker]

Re: Interlocking Armor Type MC Cable

Its called smart MC cable, but its not a copper bond wire, its aluminum. Its still new and in the approval process, consider it a cross between MC and AC cable.
Heres more info:
http://www.iaei.org/magazine/04_c/trainor.htm

 

[iwire]

Re: Interlocking Armor Type MC Cable

Originally posted by don_resqcapt19:
Bob,

I do not know where you are from but most electricians who have installed AC and MC can tell the difference.

I guess if you have used it that you should be able to tell the difference, but a lot of us live and work in the land of conduit and wire. What is this "cable" stuff you guys are always talking about?
Don

Well that was why I said most electricians who have installed these cables know the difference.

I will try to adapt to you wire and conduit guys.

Most electricians who have installed RMC, IMC and EMT can tell them apart.

 

[sandsnow]

Re: Interlocking Armor Type MC Cable

Originally posted by tom baker:
Its called smart MC cable, but its not a copper bond wire, its aluminum. Its still new and in the approval process, consider it a cross between MC and AC cable.
Heres more info:
http://www.iaei.org/magazine/04_c/trainor.htm

Thanks Tom.
I knew about that stuff. The copper through me.

 

[sandsnow]

Re: Interlocking Armor Type MC Cable

The more I think about this the more I wonder:

How can you call yourself an electrician or electrical inspector if you cannot identify common products recognized by the NEC??