NM cable in conduit

[marinesgt0411]

Re: NM cable in conduit

put a J-Box on the end of the conduit run your nm into it change over to THHN in the conduit make your splice in J-Box bond box and it no longer becomes an issue.

 

[automaton]

Re: NM cable in conduit

Thats totally ironic, i was going to suggest that on my last post. I am glad that we all have come to some form of an agreement. That would indeed take care of everything. I will run NM through the boards in basement to a small j box and from the box I will run conduit outside to an external box for security light. Sounds good to me.

 

[LarryFine]

Re: NM cable in conduit

Originally posted by infinity:
So let's say that it's not a sleeve. Couldn't I simply remove the outer jacket from the portion of the wiring in the EMT and use a transition fitting on the end of the EMT that attaches to the conduit and the NM?

I did that last year for a roof-top HVAC installation (2 roofs, 2 units each) for both the compressor feeds and the WP receptacle.

The NM "terminated" where it entered the non-metallic flex, using a 2-screw cable clamp screwed into a glued-on female adapter. Inspector was happy with it.

 

[shortcircuit2]

Re: NM cable in conduit

This type of romex installation, although commonly done is not CODE compliant because 314.17(B) says,in part: "Where raceway or cable is installed with metal boxes or conduit bodies, the raceway or cable shall be secured to such boxes or conduit bodies."

This requires that the type NM cable be secured to the box, which is not possible because the cable is enclosed in EMT and there is no way to install an approved box connector on it.

There are only 2 places in the CODE where type NM cable can be connected to an enclosure without the use of a cable connector.

The 1st is the exception to 314.17(C) where type NM can enter a single gang nonmetallic box if the cable is supported within 8 inches of the box and the sheath extends into the box at least a 1/4 inch.

The 2nd would be the exception to 312.5(C) where a group of NM sheathed cables are permitted to enter the top or an enclosure through a raceway between 18 inches and 10 feet in length provided:

1)The cable sheath extends at least a 1/4 inch beyond the lower end of the raceway.

2)The raceway is properly supported.

3)The cables are fastened not more than 12 inches beyond the upper end of the raceway.

4)Conduit fill requirements are followed.

5)Fittings to protect the cable from abrasion are installed on both ends of the raceway.

6)The raceway is sealed to keep vermin and debris from entering the raceway.

7)Derating factors are applied.

The limitations of 312.5(C) give guidance to the allowable length of raceway used to protect type NM cable from damage.Therefore it is reasonable to say that the limit for the length of raceway used for physical protection of NM is 10 feet.If the need for protection exceeds 10 feet, a splice box should be inserted between the cable and the raceway, and a change in wiring methods must be made, as required by 300.15

shortcircuit2

 

[iwire]

Re: NM cable in conduit

Originally posted by shortcircuit2:
This type of romex installation, although commonly done is not CODE compliant because 314.17(B) says,in part: "Where raceway or cable is installed with metal boxes or conduit bodies, the raceway or cable shall be secured to such boxes or conduit bodies."

Well I disagree.

358.22 Number of Conductors.
The number of conductors shall not exceed that permitted by the percentage fill specified in Table 1, Chapter 9.

Cables shall be permitted to be installed where such use is permitted by the respective cable articles. The number of cables shall not exceed the allowable percentage fill specified in Table 1, Chapter 9.

314.17(B) is not in a cable article.

Can you point to a section in the cable article 334 that prohibits NM in EMT?

Remember it is a permissive code.

 

[ryan_618]

Re: NM cable in conduit

From the 2005:

334.30 Securing and Supporting.
Nonmetallic-sheathed cable shall be supported and 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 (4? ft) and within 300 mm (12 in.) of every outlet box, junction box, cabinet, or fitting. Flat cables shall not be stapled on edge.
Sections of cable protected from physical damage by raceway shall not be required to be secured within the raceway.

 

[LarryFine]

Re: NM cable in conduit

Looks to me like Ryan's post supports Iwire's position, not ShortCircuit's. I happen to agree with Iwire and Ryan.

In my example, the NM cable "ends" where it's clamped entering the NM flex, and the other end of the flex is connected to the enclosure.

 

[shortcircuit2]

Re: NM cable in conduit

Well I disagree...

First of all, as Ryan pointed out,under article 334.30, NM cable must be supported at approiate intervals unless sections of cable are installed in raceway for protection from physical damage.When short sections of EMT are installed for protection of NM, a connector and bushing are required to be installed on each end of the raceway where the cable enters and exits...300.15(C)

Then, 334.30(B) only allows installation of unsupported NM cable where fished in concealed spaces or connection of luminaires or other electrical equipment above drop ceilings.

Yes 314.17(B) is not a cable article, but it tells us that cables must be secured to boxes or conduit bodies. How can NM cable be secured to a box when installed inside EMT?

The only other permissive installation of NM within raceway appears in the 2005 NEC under 334.15(C), which allows NM in conduit or tubing on the walls in unfinished basements.

As for the .22 of the raceway articles of the 2005 NEC which seem to permit cables in raceway systems...the approiate cable articles should also add exceptions to there respective supporting rules where necessary. Such as a 334.30(B)(3) which would allow NM to be unsupported when installed in a listed raceway supported according to its article.

shortcircuit2

 

[iwire]

Re: NM cable in conduit

The cables enter the raceway not the box.

Once the cable is secured at the end of the raceway there is no need of it to be secured a second time at the box, it would serve no purpose.

I am not going to say anymore about securing it to the box, that IMO is a weak argument.

Originally posted by shortcircuit2:
As for the .22 of the raceway articles of the 2005 NEC which seem to permit cables in raceway systems...the approiate cable articles should also add exceptions to there respective supporting rules where necessary.

ShortC they do not add permissions to do things as needed, it is a permissive code.

Unless it says you can't.....you can.

[ August 14, 2005, 08:18 PM: Message edited by: iwire ]

 

[ryan_618]

Re: NM cable in conduit

I agree, this is a weak argument. I don't think the code could possibly be any more clear than it is.

 

[automaton]

Re: NM cable in conduit

So is it final? If Im running NM cable from a basement to an exterior light which will need approx 8-10' of exposed conduit outside that I can just keep the run NM and still be within code? Or should I include a J box and jump to THHN?

 

[ryan_618]

Re: NM cable in conduit

If the raceway is outside, I would say it would have to contain either UF or THWN (or another conductor with a W in it).

 

[jimwalker]

Re: NM cable in conduit

yep was just gonna post same thing.NM cant be outside or thhn.What most forget is your roll of thhn says thhn/thwn

 

[physis]

Re: NM cable in conduit

I remember the first time I wanted to be sure there was a W and NONE of my supply guys were aware that the THHN they sold was also TWHN, of course neither was I.

Edit: wrong UBB code

Edit: And, that should be THWN.

[ August 15, 2005, 10:22 PM: Message edited by: physis ]

 

[CaseyM]

Re: NM cable in conduit

Our local inspector in Washington has never complained about nm-b in conduit except when it runs underground or in another wet location as the wires in nm-b are thhn and not thwn. So for me the problem isn't nm-b in conduit but nm-b in an application where it could be exposed to moisture from seepage through fittings or from condensation, ie warm moist air from the basement condensing in the cool walls of an underground conduit. But if you were to run uf from your panel, through bushing protected connectors on your pipe and outside with the pipe terminating in a bushed emt connector then you would be safe in my book. And if you sprayed some expansion foam or caulking into your conduit then the bugs wouldn't be an issue either.

 

[CaseyM]

Re: NM cable in conduit

what I meant to say was, a bushed pvc connector as emt doesn't live long underground. Sorry.

 

[LarryFine]

Re: NM cable in conduit

Originally posted by shortcircuit2:
Yes 314.17(B) is not a cable article, but it tells us that cables must be secured to boxes or conduit bodies. How can NM cable be secured to a box when installed inside EMT?

As I described, NM enters the far end of the flex, where it is clamped by a screw-in-type of connector threaded into a female adapter (sans locknut), and then stripped.

In my mind, this is where the NM ends (i.e., ceases to be a cable assembly), and becomes individual conductors, which do not require clamping at the destination box.

 

[shortcircuit2]

Re: NM cable in conduit

But LarryFine, when you strip the NM sheath and expose the individual conductors, you have created another violation... marking is required on cables and conductors (310.11).

Final Comment...

I do not see this practice as a safety hazard, just a violation of the code. In fact 9 of 10 inspectors would not red tag such work.I believe that 358.22 contradicts what 314.17(B) says in part, that cables SHALL be secured to such boxes and conduit bodies. Shall being a mandatory rule under 90.5

Just my interpretation of the NEC...

shortcircuit2

 

[jim dungar]

Re: NM cable in conduit

Shortcircuit2,
How is any conductor (i.e. THHN) installed in conduit able to meet the requirements of 314.17(B)?

The last sentence is the answer. You have a choice the cable or raceway, but not both, must be secured to the box.

 

[LarryFine]

Re: NM cable in conduit

Originally posted by shortcircuit2:
But LarryFine, when you strip the NM sheath and expose the individual conductors, you have created another violation... marking is required on cables and conductors (310.11).

Then I would say that the lack of splices means (proves, actually) that the conductors are "marked" (identified) by virtue of their emergence unbroken from the marked sheath.

When we terminate NM cable in any box, especially for more than the mandantory 6" such as in a panel, why don't we have to splice the NM's conductors to marked conductors?