NM in conduit

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daveb.inva

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Ive had a discussion about using NM in conduit where the conduit is for protection only.

The gentleman I have discussed this with states that when using NM in conduit that you must stop the conduit short of the box, staple the conduit, then terminate it to the box.

I maintain that the conduit is supporting the NM and that your last staple should be within 12" of entering the conduit. I think it looks more professional this way plus the NM is protected all the way into the box.

So who is correct and what is the absolute correct way to sleeve NM for physical protection. Feel free to site as many articles of the NEC as you wish.

[ May 02, 2004, 06:23 PM: Message edited by: daveb.inva ]
 
Re: NM in conduit

334.30 Securing and Supporting.
Nonmetallic-sheathed cable shall be secured by staples, cable ties, straps, hangers, or similar fittings designed and installed so as not to damage the cable at intervals not exceeding 1.4 m (41/2 ft) and within 300 mm (12 in.) of every cabinet, box, or fitting. Flat cables shall not be stapled on edge.
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IMO secure the NM within 12" of the fitting where the NM enters the raceway and you have satisfied the 12" rule.
 
Re: NM in conduit

Dave,
So who is correct
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IMO you are.

If it were not allowed in a complete conduit system, why would the ink be wasted for note # 9 in the "Notes to Tables" in chapter nine, it does not say "only for nipples, or partial runs of conduit".

Roger

[ May 02, 2004, 08:20 PM: Message edited by: roger ]
 
Re: NM in conduit

Note #9 could also apply to other cable systems as well. Type FC, MC, TC, etc... Its funny that these articles specifically state permitted use in raceways, whereas NM does not. :p

I wonder if installing a cable system within a raceway, the heat disipation effects are reduced? Meaning, does UL test cable assemblies within raceways under load conditions? :confused:

One additional question, 334.15(B) specifies several methods allowed to protect NM. Does the protective method necessarily have to be a conduit or raceway system recognized by the code? The section says conduit....guard strips...other means. It only requires listing requirements for the surface raceways. For example, can I use white PVC pipe?

[ May 02, 2004, 08:59 PM: Message edited by: bphgravity ]
 
Re: NM in conduit

Bryan,
Note #9 could also apply to other cable systems as well. Type FC, MC, TC, etc... Its funny that these articles specifically state permitted use in raceways, whereas NM does not.
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if you think that's funny, please take a shot at explaining why article 400 uses the ink to specifically prohibit this method yet 334 does not.

I wonder if installing a cable system within a raceway, the heat disipation effects are reduced? Meaning, does UL test cable assemblies within raceways under load conditions?
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Who cares, Note 9 tells us how to calculate for this.


As far as
One additional question, 334.15(B) specifies several methods allowed to protect NM. Does the protective method necessarily have to be a conduit or raceway system recognized by the code? The section says conduit....guard strips...other means. It only requires listing requirements for the surface raceways. For example, can I use white PVC pipe?
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certainly.

Roger

[ May 02, 2004, 11:03 PM: Message edited by: roger ]
 
Re: NM in conduit

Originally posted by roger:
if you think that's funny, please take a shot at explaining why article 400 uses the ink to specifically prohibit this method yet 334 does not.
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In my opinion, Article 400 applies specifically to the cords and cables listed in Table 400.4, and not necessarily those listed in Chapter 3.

The sections I think are more relative are the 3XX.22 requirements that state: "Cables shall be permitted to be installed where such use is permitted by the respective cable articles." As I have stated in an early post. Many of the cable articles do indeed give this allowance, however, NM or UF does not.

Again I think this is all trivial due to the fact that I cannot associate a potential hazard or danger with performing this type of installation. The code is simply not clear, and leads to the arguements and interpretations we are having and that Dave described. ;)
 
Re: NM in conduit

I think common sense should rule here, but technically here is the answer. Article 334.10 4a,b,and c, clearly say they can be used for concealed work. The NEC definations say raceways are considered concealed, even though they may become accessible by withdrawing them. Therefore they are allowed in raceways. In addition, chapter 9 notes 5 and 9 address multiconductor cable fill in raceways.
 
Re: NM in conduit

This means the raceway can be put in as a complete system, the raceway will be the support for the wire. If a raceway will support THHN, it will certainly support NM wire. The heat issue is clearly addressed in article 310.15 B2a adjustment factors for raceways and cables, adjust as needed.
 
Re: NM in conduit

Hey wouldn`t 312.5 come in to play here?That would prevent you from entering the conduit at bushing and running down emt to boxes right. Provided you were using a metal raceway.312.5c?Or does this only apply to panels meter enclosures?
 
Re: NM in conduit

Paul, I agree that common sense (if it hadn't died) is the real justification, but I am curious as to how you interpret the wording of 334.10 (A),(B), or (C)to pertain to raceways.


Roger
 
Re: NM in conduit

Reel-Break, that is true, how much more protection should NM have over THHN though. Whats good for one is good for the other.

Roger, read the defination of concealed in article 100. Wires in a raceway are considered a concealed location. Article 334 uses permitted allow the use of NM in concealed locations.
 
Re: NM in conduit

Paul, sorry but that has nothing to do with the wording of 334.10(A),(B,)or(C).

Wires in a raceway are considered a concealed location.
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Paul read the article and the definition again.

Roger
 
Re: NM in conduit

Your opinion, thats one of my interpertations and I respectively disagree, Its all how you read it. Besides that I would like to see clear language on this instead of trying to read between the lines. Some inspectors dont have a problem with it, and some do. If I want to sleeve an entire piece of rx in a conduit for physical protection provided its not a wet location, I just cannot see any justification why I cannot as long as I comply with proper derating as any other wire would be subject to. The whole reason you secure wires in place is so they dont fall out of the installation. I think in a conduit wire is pretty secure as long as the raceway is secured correctly.
 
Re: NM in conduit

I think that the NEC should take the easy way out of this question...adopt the Chicago code.
Don
 
Re: NM in conduit

Paul,
Is there a table that states the derating ???
Would that be through the enclosure (pipe) or through the nipple ??

If it were just for support, would you need nipples at the ends...

So many questions... Yet I see it all the time.. doesn't mean I do it !!!!

IMHO...
O
 
Re: NM in conduit

Derating is in article 310.15

This is all irrelavent anyways, the 2005 code is going to have the uses permitted in 334 deleted like it used to be. This means if it is not listed in uses not permitted you can do it if the inspector is ok with it. So wait until 2005 and put all the rx you want into emt.
 
Re: NM in conduit

Originally posted by cormier_paul:

This is all irrelavent anyways, the 2005 code is going to have the uses permitted in 334 deleted like it used to be. This means if it is not listed in uses not permitted you can do it if the inspector is ok with it. So wait until 2005 and put all the rx you want into emt.
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I thought that was going to the technical corralating commitee for the 2008. You sure seem to have a lot of inside info on the 2005...how is that?
 
Re: NM in conduit

You must not know what ROP's are. They are the NEC committee report on proposals. They are now avaliable through the NFPA if you are a member. They show all the proposed amendments for the 2005 NEC which is open to public review. Most of the proposals that have been accepted by the CMP (cod making panels) will be the changes to the 2005 NEC. ROP 7-99 removal of uses permitted has been accepted. In addition the exact question on NM in raceways has been addressed in ROP#7-110 in which the CMP said that the uses not permitted
does not prohibit this type of installation.

This is public information if you want to take the time to review it.
 
Re: NM in conduit

It seems like alot of people on these forums are very defensive. I thought the idea was to exchange information and opinions back and forth so we can all be better educated. The entire code book is subject to interpertation, thats why we need these forum's to help educate each other.
 
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