Clone 320.40 into 330

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tonyi

Senior Member
IMO, its goofy to think that MC armor won't somehow ding up insulation while AC's could...

I've always put anti-short bushings into MC ends, but I've seen some installations where they weren't used.
 

charlie

Senior Member
Location
Indianapolis
Re: Clone 320.40 into 330

Gentlemen, if you are using the correct connectors, you do not need the anti-shorts on MC cable any more than you need bushings on the EMT connectors for #12 wire. Workmanship or doing a good job has nothing to do with it. :D

Edited it so my answer made sense.

[ November 10, 2004, 08:21 PM: Message edited by: charlie ]
 

tonyi

Senior Member
Re: Clone 320.40 into 330

I disagree. I've seen the insulation damage.

Many prebushed MC/AC compatible connectors (ex. SpeedLock or Arlington L15A) displace the armor off-center as the saddle clamps down. The section of wire coming through the bushing is fine, but the wire right as it exits the armor gets shoved against the armor's edge. There's nothing you can do to in terms of "workmanship" to avoid this off-centering displacement on the smaller cable sizes like 14-2/12-2. Its somewhat less an issue with 12-3,10-2 or 10-3's as the diameter of the armor is larger and tends to center somewhat better as the saddle clamps down.

IMO, if bushings are somehow deemed REQUIRED for AC, then then they should logically be required for MC since the mechanical aspects of the connectors and armors are virtually identical.
 

roger

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Fl
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Electrician
Re: Clone 320.40 into 330

Tonyi, make a proposal.

Roger
 

charlie

Senior Member
Location
Indianapolis
Re: Clone 320.40 into 330

Tonyi, I don't think Roger was making a wise a** comment. If this is really a problem, that is what the proposal process is all about. This intent of this portion of the forum is to look at the language of a proposal and massage it so you will have a solid proposal to send in to the Code Making Panel and it having a chance to get passed.

Personally, I think this is a performance issue with a particular connector that should be brought to the attention of UL. If that is something that is going on with all brands, then I am with you. :D
 

rbalex

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Location
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Professional Electrical Engineer
Re: Clone 320.40 into 330

Originally posted by tonyi:
Real insightful Roger...
tonyi,

Roger's reply is "on point."

Please reread the "Welcome" to this forum.

Make a specific "Proposal" that you intend to submit to the NFPA. Then the members of this forum will "critique" it for you. It will give you a "sense of the consensus" and help you make a stronger "formal" Proposal, if you choose to do so.

It is not the purpose of this forum to make the proposals for you.
 

tonyi

Senior Member
Re: Clone 320.40 into 330

How's this then?

Clone 320.40 into 330 replacing all instances of the term "AC" with "MC".

If someone could explain to me how, by whatever mechanism, MC has some sort of immunity to damage from rough armor ends that AC somehow doesn't have, then I'll become a believer that everything is fine the way it is.
 

tonyi

Senior Member
Re: Clone 320.40 into 330

I guess I should give up - there's no logic at work here :eek:

If NEMA believes MC is fine without anti-short bushings, why not remove the anti-short language from 320.40 as being unnecessary?

Of course, there's the dreaded 90 degree connectors...that don't have insulated throats and pretty clearly allow the wire to rub against cut ends if someone starts yanking the wires around.
 

roger

Moderator
Staff member
Location
Fl
Occupation
Electrician
Re: Clone 320.40 into 330

Thanks Charlie and Bob. Tonyi, If it makes you feel better, do as Jim does and use the "Anti Short Bushings".

Seeing how NEMA, who sees a lot more installations than you or I do, does not see the need for "Anti Short Bushings" on MC, I would be looking at the individuals installing the MC around you if you are seeing this many problems.

We use T&B TITE-BITE insulated throat MC connectors, and have very few problems with or with out the Red Heads (slang).

BTW, we use alot of Arlington products also, especially in the over 3" category.

Roger
 

don_resqcapt19

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Location
Illinois
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retired electrician
Re: Clone 320.40 into 330

Tony,
The designs of the listed MC connectors and AC connectors are not the same. The listed MC connector will prevent conductor damage without the use of anti-short bushings. Note, just because the connector fits on the cable does not mean that it is the correct connector for that cable.
Don

[ November 11, 2004, 01:34 PM: Message edited by: don_resqcapt19 ]
 

rbalex

Moderator
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Location
Mission Viejo, CA
Occupation
Professional Electrical Engineer
Re: Clone 320.40 into 330

Originally posted by tonyi:
IMO, its goofy to think that MC armor won't somehow ding up insulation while AC's could...

I've always put anti-short bushings into MC ends, but I've seen some installations where they weren't used.
tonyi

CMP7 controls both Articles. I haven't set in on any of their deliberations but I know several members and I don't believe they would consider this an adequate substantiation.

However, your personal experience is still a valid place to begin your substantiation. If you have personally observed problems with conductor failures caused (or permitted) by connectors properly installed and listed for terminating MC cables - then you have a case and a solid proposal. If you simply think it?s a good idea, it probably won?t fly ? no matter how reasonable it may be.

One proposal I had accepted a while back resulted in what is now 300.18(B). It was simply based on my personal observation of damaged raceways and there was enough universal experience to validate it.
 

tonyi

Senior Member
Re: Clone 320.40 into 330

Originally posted by don_resqcapt19:
Tony,
The designs of the listed MC connectors and AC connectors are not the same.
Don
AMC-50/75, L15A, 8400's, 850's are all listed for both AC and MC. I'm sure I could find a dozens more similarly dual listed if I went looking for parts I don't buy on a regular basis.
 

roger

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Location
Fl
Occupation
Electrician
Re: Clone 320.40 into 330

Tonyi. of the connectors you listed which ones do you find are being used on the problems you frequently encounter?

We literally use 1000's a week at times and have very few problems.

Roger
 

tonyi

Senior Member
Re: Clone 320.40 into 330

Originally posted by roger:
Tonyi. of the connectors you listed which ones do you find are being used on the problems you frequently encounter?

We literally use 1000's a week at times and have very few problems.

Roger
Of those thousands, how many do you ever have occasion to take apart and inspect the result?

Have you ever done a post-install disassembly on something that passed inspection and appeared to work?

This is something people doing new installation aren't going to notice or realize is happening.

Any connector that saddles the cable off the connector throat centerline where the spiral armor's thickness is less than the distance from the throat bottom to the connector bottom will tend to drive the wires upward as the saddle clamps down.

Rather than jawing about it ad-nausaeum, why not just construct a couple and look at how the saddles clamp down. Install an AMC-50 on a some 14-2 MC. Look down the throat. The off center displacement of the connector is enough to allow for the cut armor end to rub on the wire insulation as the wires in the box are worked on.

Note: the AMC-50 is even prebushed and still exhibits the kind of issue I'm talking about due to the off-center displacement effect.

An ordinary 8400 with smallish diameter cable (AFC's 14-2 is the smallest I've seen)will exhibit the same offcentering and allowing wires to contact cut ends as they're worked.

[ November 11, 2004, 10:19 PM: Message edited by: tonyi ]
 

roger

Moderator
Staff member
Location
Fl
Occupation
Electrician
Re: Clone 320.40 into 330

Tonyi, you didn't answer the question, specifically. of the connectors you listed which ones do you find are being used on the problems you frequently encounter?

I would stop using these, and as Bob stated earlier, make a proper proposal and if the sustantiaion can show sufficient cause you may get your wish.

We simply don't have the problem you seem to be having.


Roger

[ November 12, 2004, 01:33 AM: Message edited by: roger ]
 

iwire

Moderator
Staff member
Location
Massachusetts
Re: Clone 320.40 into 330

Originally posted by tonyi:
Originally posted by roger:
Tonyi. of the connectors you listed which ones do you find are being used on the problems you frequently encounter?

We literally use 1000's a week at times and have very few problems.

Roger
Of those thousands, how many do you ever have occasion to take apart and inspect the result?

Have you ever done a post-install disassembly on something that passed inspection and appeared to work?

This is something people doing new installation aren't going to notice or realize is happening.

Tony I am sure like myself Roger hears about the job for at least a year after completion.

Seriously, and I am not being a wise guy, submit a proposal. :)

Bob
 
Re: Clone 320.40 into 330

For what it's worth I just finished a rather large commercial building and I did have several shorts where the MC conn was the problem.My opinion it's not the product it's the men putting it in.Every short in the building was MC connector screwed down too tight and/or stripped with something besides MC strippers. (dykes,lineman's pliers,etc.)
 
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