You would have been OK most likely if you had not been underground. NM is not wet rated.....underground pvc is considered a wet location in concrete or not. Inspector may also have been a stickler about conduit fill if you ran 12 in 1/2". I'm thinking you may have been just over the one wire fill (53%)but I haven't made the calculation to be sure.
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I think you meant thwn for this application but I'm being picky...
I was always told (by those who know it all) that nm conductors are thhn rated and do not carry the thwn-2 rating because the infused membrane (nylon) is not placed over the insulation. But there sure is a thin nylon covering or something from my experience....
But I've researched this quite a bit and to my knowledge NM-b conductors are the equivalent to thhn/thwn-2 conductors. I located a document that may lead to the answer or at least satisfy some of us. I found it in the Southwire technical library. So for what it is worth here it is and it is the best answer I can find as to why NM-b (modern nm) is rated for dry location and not wet and it has nothing to with the insulation or W rating or nylon coating. Why you can't strip off the outer sheath and paper wrapping and use the insulated conductors I have not found the answer.... other than there are no markings to show the rating on the insulation.... but... why would they do that if they cover the conducters with a sheath...saves time and money I suppose. But the ink doesnt change the wire for what it is....I suppose one just can't confirm what the wires/conductors are without markings. However, they also don't rate the cable or mark it on the outer sheath other than NM-b so UL and the manufacturer and the NEC are not wanting it rated as wet location applicable. So I guess you remove the outer sheath with a witness and and get a legal affidavit saying it was nm-b conductors....:thumbsup:
I was always told (by those who know it all
) that nm conductors are thhn rated and do not carry the thwn-2 rating because the infused membrane (nylon) is not placed over the insulation. But there sure is a thin nylon covering or something from my experience....But I've researched this quite a bit and to my knowledge NM-b conductors are the equivalent to thhn/thwn-2 conductors. I located a document that may lead to the answer or at least satisfy some of us. I found it in the Southwire technical library. So for what it is worth here it is and it is the best answer I can find as to why NM-b (modern nm) is rated for dry location and not wet and it has nothing to with the insulation or W rating or nylon coating. Why you can't strip off the outer sheath and paper wrapping and use the insulated conductors I have not found the answer.... other than there are no markings to show the rating on the insulation.... but... why would they do that if they cover the conducters with a sheath...saves time and money I suppose. But the ink doesnt change the wire for what it is....I suppose one just can't confirm what the wires/conductors are without markings. However, they also don't rate the cable or mark it on the outer sheath other than NM-b so UL and the manufacturer and the NEC are not wanting it rated as wet location applicable. So I guess you remove the outer sheath with a witness and and get a legal affidavit saying it was nm-b conductors....:thumbsup:
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Not me. Why would you accuse me of failing one of your jobs?
In your case here, PVC out to the island into a box (THHN/ THWN), and separate armored cables to each of your devices or appliances.
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