metal clad cable

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catskills

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can anyone direct me to the section of the NEC or from their general experience when and where mc cable needs to be used? Everything you can tell me would be greatly appreciated.
 
I'm just looking to find where it is required to be used as opposed to nm cable. I know of places of assembly, commercial locatiobs, buidlings over 3 stories, etc. i can't find anything that spells out exactly where you need to use it.
 
catskills said:
....i can't find anything that spells out exactly where you need to use it.
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I don't think you'll find much that will tell you where you MUST use it. You will, however, find prohibited locations for type NM cable. MC is the first choice for locations where type NM cable is prohibited. You might want to read about NM prohibited locations, and that will give you a head's up on where to use MC.
 
catskills said:
thanks Marc. do you know what section lists the prohibited use of nm?
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Indeed. Article 334 is all about NM cable, and 334.12 covers the uses not permitted. If there is a location in 334.12 that is not permitted for NM cable and it's not listed in 330.12 (prohibited locations for type MC cable), MC cable would be a good first choice. You can always use a better method (EMT, IMC, RMC), but certain economic realities begin to prevail.
 
catskills said:
I'm just looking to find where it is required to be used as opposed to nm cable. I know of places of assembly, commercial locatiobs, buidlings over 3 stories, etc. i can't find anything that spells out exactly where you need to use it.
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No simple answer to your question. :) If you're contemplating using MC instead of or in place of NM, for example, I would begin at Article 330: Metal Clad Cable MC and look at 330.10 uses permitted and say for example you wanted to use it outdoors. 330.10(3) says "indoors or outdoors", so then you'd check out 330.12 Uses Not Permitted. at 330.12(2) you'd see that direct burial was not permitted. You'd look for an exception to this and not find one. However at 330.12(3) you'd see that the FPN (fine print note) to (3) concrete mentions cable identified for direct burial applications is suitable for installation in concrete. If you're like me, you'd wonder why on earth there wasn't a FPN or better yet an exception to 330.12(2) that clarified that listed direct burial MC would be better under 330.10 Uses Permitted. :-?

Anyway, when you get done scratching your head on this one, there are zillions more just like it. :) :grin:

It's more like process of elimination than anything to solve for allowable wiring methods. :)
 
I think I can pin down the question more accurately by stating one of my corporate policies. "MC cable shall be used in concealed locations prohibited by 334.12, but not prohibited by 330.12, were no other print spec or local prohibition exists."
 
We all look at it different ways.:)

I look at it like MC is allowed almost everywhere.
Exposed, concealed, most any occupancy.

There are very few places MC is not allowed.
 
catskills said:
I'm just looking to find where it is required to be used as opposed to nm cable. I know of places of assembly, commercial locatiobs, buidlings over 3 stories, etc. i can't find anything that spells out exactly where you need to use it.
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What year NEC is your area using? (You're in Catskills, NY?)

Comm. locations and buildings of 3+ stories may have changed for you....NM *might* be allowed.

A well-established means of codifying fire protection and fire safety requirements is to classify buildings by types of construction, based on materials used for the structural elements and the degree of fire resistance afforded by each element. The five fundamental construction types used by the model building codes are Type I (fire resistive), Type II (noncombustible), Type III (combination of combustible and noncombustible), Type IV (heavy timber), and Type V (wood frame). Types I and II basically require all structural elements to be noncombustible, whereas Types III, IV, and V allow some or all of the structural elements to be combustible (wood).
The selection of building construction types is regulated by the building code, based on the occupancy, height, and area of the building. The local code official or the architect for a building project can be consulted to determine the minimum allowable (permitted) construction type for the building under consideration. When a building of a selected height (in feet or stories above grade) and area is permitted to be built of combustible construction (i.e., Types III, IV, or V), the installation of nonmetallic sheathed cable is permitted. The common areas (corridors) and incidental and subordinate uses (laundry rooms, lounge rooms, etc.) that serve a multifamily dwelling occupancy are also considered part of the multifamily occupancy, thereby allowing the use of nonmetallic sheathed cable in those areas.
If a building is to be of noncombustible construction (i.e., Type I or II) by the owner's choice, even though the building code would permit combustible construction, the building is allowed to be wired with nonmetallic sheathed cable. In such an instance, nonmetallic sheathed cable may be installed in the noncombustible building because the Code would have permitted the building to be of combustible construction.
Annex E provides charts and other explanatory information to assist the user in understanding and categorizing the exact types of construction under consideration. A table to cross reference building types to the various building code types of construction is provided in Annex E also.
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2005 NECH, commentary following 334.10

Check the FPN No.2 to 334.10:
FPN No. 2:See Annex E for determination of building types [NFPA 220, Table 3-1].
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The "old" way of no NM in comm. and 3+ stories has changed to something a bit different...now based on building "type".
 
iwire said:
There are very few places MC is not allowed.
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Very true. There are locations where NM is also permitted, which would be cheaper. There are locations where MC would be permitted, where EMT is more traditionally installed. That one's a toss-up. Looks/tradition versus ease of install. Just because type MC cable is permitted in certain locations doesn't necessarily mean that it's a good idea.
 
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wbalsam1 said:
It's more like process of elimination than anything to solve for allowable wiring methods. :)
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That's the basis for us so often saying that we're allowed to do that which is not prohibited.
 
I work in industrial type locations and use a lot of PVC jacketed MC cable. Its class 1 Div 2 rated, and direct burial rated. Its a good alternative to RMC.
For office buildings, I don't like MC as it leaves no future additions as EMT does.
If I was using MC cable, I would use the new MC-AP cable which is a cross between AC and MC. MC-AP saves about 30% time on install as it does not the EGC needing termination as MC does. I would predict the eventually AC cable will no longer be mfg, as the MC-AP can be mfg in a health care version.
 
tom baker said:
For office buildings, I don't like MC as it leaves no future additions as EMT does.
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I can often add a new circuit in MC in an office building faster with MC then by hunting down a raceway with extra space, opening all the boxes etc.

That does not even take into account that you will be working in raceways with other conductors that must remain on.

Oh sure, sometimes a raceway is a major help but IMO not enough to justify every office building being done in EMT from the start.

JMO, Bob
 
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