nmc in conduit

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bennie

Esteemed Member
Re: nmc in conduit

Ask the inspectors to show the code section prohibiting the use of conduit.

The purpose of conduit is to protect the conductors under any circumstances or application. Otherwise we revert to knob and tube wiring methods.
 

hurk27

Senior Member
Re: nmc in conduit

Yes it is allowed, And is required when you pass through a floor.

334.15 Exposed Work.
(B) Protection from Physical Damage. The cable shall be protected from physical damage where necessary by conduit, electrical metallic tubing, Schedule 80 PVC rigid nonmetallic conduit, pipe, guard strips, listed surface metal or nonmetallic raceway, or other means. Where passing through a floor, the cable shall be enclosed in rigid metal conduit, intermediate metal conduit, electrical metallic tubing, Schedule 80 PVC rigid nonmetallic conduit, listed surface metal or nonmetallic raceway, or other metal pipe extending at least 150 mm (6 in.) above the floor.
 

bennie

Esteemed Member
Re: nmc in conduit

Hurk: You are more descriptive than I, but we resolved the issue. I hope the inspectors who oppose will change their perception.
 

tonyi

Senior Member
Re: nmc in conduit

Originally posted by bennie:
Hurk: You are more descriptive than I, but we resolved the issue. I hope the inspectors who oppose will change their perception.
If it were NOT allowed, cable assemblies (which includes Romex) would not be explicitly mentioned in Chapter 9 note (9).

If anyone is having trouble with an inspector, direct them to this chapter and note and ask'em how come. The fill table chapter language is very explicit.

I pipe Romex all the time because its sometimes a more convenient "package" to deal with when working solo. Never had any inspection issues.
 

pierre

Senior Member
Re: nmc in conduit

Because the NEC permits the use of raceways for protection of physical damage, note 9 in table 1 of chapter is there.

358.22 Number of Conductors.
(second paragraph)
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.

Article 334 permits the use of raceways for physical protection, but does not state that it can be used for any other purpose. There is no definition for physical protection, so this can be subject to interpretation, but whose interpretation?

IF you are runing from a switch to a light fixture on the ceiling in a masonary building, is that run subject to physical protection?

Why not run THHN conductors instead of NM cable?

When runing EMT to protect cable from physical damage, can it be a complete run say from box to box of more than one full length of EMT?

How do you make the connections? Do you use EMT fittings? Do you use NM connectors and not complete the raceway to the boxes, if so how do you bond the raceway if it is metallic? How would you conform to 334.30?

IF you do not complete the metallic raceway to the boxes, what happens to the ground fault current on the raceway/EGC of the NM cable?

Pierre

[ October 11, 2003, 11:25 PM: Message edited by: pierre ]
 

tonyi

Senior Member
Re: nmc in conduit

Originally posted by pierre:

...Why not run THHN conductors instead of NM cable?


A coil of Romex is easier to handle in many cases. IMO, the sheath also provides an added measure of abrasion protection an individual conductor pull would not have.


When runing EMT to protect cable from physical damage, can it be a complete run say from box to box of more than one full length of EMT?

Why not? I've never had a problem with it with metal boxes. Plastic I'd not go over 10' unbonded, but the code words here are vague.


How do you make the connections? Do you use EMT fittings?

If going into a [metal] box, yes.


Do you use NM connectors and not complete the raceway to the boxes

Halex makes a connector for this purpose.


, if so how do you bond the raceway if it is metallic? How would you conform to 334.30?

Flip the page to 334.30(B)(1) :D Fishing through pipe is fishing between "access points"


IF you do not complete the metallic raceway to the boxes, what happens to the ground fault current on the raceway/EGC of the NM cable?

Here the code is somewhat squishy using a term like "short runs" for what's allowable in ungrounded protective metallic raceway. What is short? I dunno, could vary by AHJ. My general rule of thumb has been if its more than one standard 10' length, then j-box it at the ends and bond. Halex has a press on insulation sleeve for EMT ends in 1/2 and 3/4 that is useful when sleeving strictly for protection. With rigid, I'll screw on a plastic bushing. With EMT, I'd think a connector and bushing would be in order if not using something like the Halex insulator.


Pierre
 
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