Thhn/nm

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  #1  
Old 12-19-04, 10:10 AM
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Thhn/nm

Hi all appologies if this topic has been discussed before .

1] Is it SAFE to run inside the house and dry conditions, a single 14/2 NM 30 feet line inside NMC 1/2 '' box to receptacle with a box for a light fixture in the midle? 2]Any advantage using either NMC or EMT?

3]What are the limitations ,in general terms, to run NM in dry locations inside conduit instead of THHN ? I understand that THHM has better heating disipation than cable and that would be a factor if running more than one line.
Thanks very much for clarifications,looking forward to learn from this great forum.
 
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Old 12-19-04, 03:10 PM
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Papi,

IMHO your question is one that generates lots of heat but very little light.

There is no good reason to run a cable assembly (nm cable) for a complete run in a raceway (conduit) as you describe. If your conduit extends from box to box, then you should just run individual THHN conductors. They will be easier to pull, will fit better in the conduit, and there is no debate at all about weather or not it meets code.

NM gets run in conduit for _physical protection_. A common example would be NM run exposed along the joists in a basement ceiling, then going into a length of conduit for the trip down the wall to an outlet box.

Lots of code weenies (myself included) spend lots of time arguing points such as 'is it okay to run NM in conduit for a complete run from one junction box to another'. It is one of those things where the NEC simply is not clear. As a room of electricians, and about half would say its okay, and the other half would say it isn't. But they would all agree that it is never necessary to do so. (Then someone will come up with an example that suggests that maybe in that one circumstance it would be a good idea ) But for the situation you describe, there is no reason.

-Jon
 
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Old 12-19-04, 04:52 PM
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Thanks so much
 
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