MC cable/Places of Assembly/518.4

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infinity

infinity

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I was wondering if the new MC cable with it's cable armor that is a listed EGC would be permitted in places of assembly? It seems as though this article was written when interlocking type MC only contained an insulated EGC. Since it requires AC cable to have an insulated EGC within the cable it would seem likely that the requirement would be the same for MC cable as well. But the literal wording of 518.4 seems to allow the new MC cable without an insulated EGC. Any thoughts?
 
IMO 518.4 says "or type AC cable with an insulated ground". Type AC and MC are two different birds and to me it doesn't say that type MC has to have an insulated ground.
 
Chris6245 said:
IMO 518.4 says "or type AC cable with an insulated ground". Type AC and MC are two different birds and to me it doesn't say that type MC has to have an insulated ground.
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So does that make MC okay or verboten?
 
Chris6245 said:
IMO 518.4 says "or type AC cable with an insulated ground". Type AC and MC are two different birds and to me it doesn't say that type MC has to have an insulated ground.
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Chris,518.4 does say mc and ac needs to have an insulated ground and sized to 250.122.

518.4 Wiring Methods
(A) General The fixed wiring methods shall be metal raceways, flexible metal raceways, nonmetallic raceways encased in not less than 50 mm (2 in.) of concrete, Type MI, MC, or AC cable containing an insulated equipment grounding conductor sized in accordance with Table 250.122.
Rick
 
Ahj

Ahj

I believe since this cable assembly is so new that the code would leave it to the AHJ to decide whether the cable assembly is acceptable. I imagine that it has been UL approved and listed. But it is not carried by either of the local supply houses yet in CT.
 
infinity said:
I was wondering if the new MC cable with it's cable armor that is a listed EGC would be permitted in places of assembly? .....Any thoughts?
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MC ap (all purpose) cable manufactured by Southwire and others would be acceptable IMO. The all purpose rating means that dual use(ac/ mc) is permitted because the armor of MC ap is listed and identified as a suitable equipment grounding path, unlike conventional MC. There's a full-sized aluminum grounding conductor run on the outside of the mylar-wrapped conductors which is in direct contact with the interlocked armor for the entire length of the cable. I know "Armorlite" MC, "Duraclad" MC, and "Armorlite IG" MC are all rated for 518.4. There are many others, too.:)
 
RUWired said:
Chris,518.4 does say mc and ac needs to have an insulated ground and sized to 250.122.

518.4 Wiring Methods
(A) General The fixed wiring methods shall be metal raceways, flexible metal raceways, nonmetallic raceways encased in not less than 50 mm (2 in.) of concrete, Type MI, MC,or AC cable containing an insulated equipment grounding conductor sized in accordance with Table 250.122.
Rick
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I would say if the "OR" was "AND" then it would be required to have an insulated ground. JMO.
 
I think the question that would answer this is, does MI cable come with an insulated EGC? If so, I'd say all the wiring methods in the section require an insulated EGC.

Here's a question: Why must we have enhanced grounding in assembly occupancies? :-?
 
georgestolz said:
I think the question that would answer this is, does MI cable come with an insulated EGC? If so, I'd say all the wiring methods in the section require an insulated EGC.

Here's a question: Why must we have enhanced grounding in assembly occupancies? :-?
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The MI cable I have used has a copper jacket that is used for the grounding. You can even order "single conductor" MI Cable. But it's been a few years since I've done any explosion proof work so things may have changed?
 
RUWired said:
Chris,518.4 does say mc and ac needs to have an insulated ground and sized to 250.122.

Rick
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I agree with Chris. The use of the word or in the sentence does not include MC cable as requiring an insulated EGC.
 
I went to southwires web site an it does list mc ap for places of assemblies and where standard ac/mc was allowed. It was my opinion that an aluminum sheath with an aluminum ground would not be allowed in a fire rated area.
Rick
 
This is really confusing to me.

I don't understand why AC would require an insulated EGC, while MC could be bare.

I've not seen a bare EGC in MC cable, but from what I read in the White Book (and in flipping around the NEC) a bare or covered EGC is permitted in MC cable just like NM.

So why the extra requirement for AC?
 
I don't think a bare copper ground with an aluminum sheath mc cable was ever made.Atleast i haven't seen it.The al sheath would have to to be rated alcu.
Rick
 
JohnJ0906 said:
It's possible this article doesn't take the new style MC into account. Perhaps it is assumed that the MC used would HAVE an insulated EGC?
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That's the precise reason I started this thread. I'm guessing that the original intent was for a cable to have an insulated EGC. With this new MC cable there isn't an insulated EGC within the cable. The code article as written permits this new stuff because it only requires AC cable to have the insulated EGC.
 
I just done a job with alot of mc cable and all that i used had a insulated ground in it,but i always thought that plastic covering had do with the fire rating.
 
The 2008 NEC will address this:

518.4 Wiring Methods.
(A) General. The fixed wiring methods shall be metal raceways, flexible metal raceways, nonmetallic raceways encased in not less than 50 mm (2 in.) of concrete, Type MI, MC, or AC cable. The wiring method shall itself qualify as an equipment grounding conductor according to 250.118, or shall containing an insulated equipment grounding conductor sized in accordance with Table 250.122. [ROP 15–109]

Exception: Fixed wiring methods shall be as provided in
(a) Audio signal processing, amplification, and reproduction equipment — Article 640
(b) Communications circuits — Article 800
(c) Class 2 and Class 3 remote-control and signaling circuits — Article 725
(d) Fire alarm circuits — Article 760
 
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