Running NM type Cable in Conduit

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  #1  
Old 12-13-04, 08:56 AM
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Running NM type Cable in Conduit

I have noticed a couple of posts in this forum that indicate not to run NM type cable in conduit, due to heating effects. Is this true?

I have used NMWU 12/3 (NM-B in the US?) to my unfinished garden shed. It’s direct buried from the house to the shed, regular ¾” PVC conduit into the shed and in ¾” blue flexible conduit inside the shed. Is this ok? I don’t “need” the conduit inside the shed, but wanted to provide some extra protection.

BTW, the circuit is solely for a pool pump and filter, nothing else is attached.
 
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Old 12-13-04, 09:43 AM
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I have used NMWU 12/3 (NM-B in the US?)
So I'm assuming you're from somewhere other than the US, so I can't say whether you can do it or not. In the US NM-B is not allowed in conduit.
 
  #3  
Old 12-13-04, 09:58 AM
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In the US your installation would not be allowed.

There are two separate issues:

1) Installing NM in conduit. This issue is subject to debate, because the code is actually unclear on the issue. You are clearly allowed to put NM into isolated lengths of conduit for protection from physical damage. What is not clear is if you can run NM from junction box to junction box; at the same time there is generally no good reason to do this in the first place; normally you run separate conductors in conduit.

2) Installing NM in wet locations. There is no debate on this issue. You cannot install NM in a wet location. An underground conduit is considered a wet location. So with absolute certainty your install is not permitted.

-Jon
 
  #4  
Old 12-13-04, 10:58 AM
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Point 2) is not a problem. NMWU is rated for concealed or exposed wiring in dry or wet locations. Also where exposed to weather or direct earth burial.
 
  #5  
Old 12-13-04, 11:53 AM
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So, the only question is 1) is NMWU allowed in junction box to junction box conduit?


Looks like I should have just left the short lengths of PVC conduit where the cable leaves the house, and enters the shed in place, and remove the flexible conduit inside the shed. (the cable is directly buried, no conduit in the trench)
 
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