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Thread: Electrical question: conduit and wiring

  1. #1
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    Electrical question: conduit and wiring

    Hi All, I'm about to relocate to a garage shop and have a question concerning EMT type conduit and NM 12/3 wire. Can you use this type wire inside metal conduit or do you have to use the separate wires? I've seen where people have done this in some situations but is there a problem with it? Thanks.
    Alan T. Thank God for every pain free day you live.

  2. #2
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    NM cable in EMT

    Alan,
    Talk about your loaded question.... The answer may depend on where you live and the code followed in your area. Based on the NEC there are at least two references concerning NM cable and EMT. Article 334-15(b) says that NM cable may be installed in EMT where required for physical protection. Article 373-5(c) is an exception to placing multiple NM cables in solid raceways connected to panels. Short answer (as if there ever was a short answer when talking about the NEC) if you're just using the conduit to protect the NM cable, you're OK. All the restrictions for NM cable remain in effect such as wet locations, GFCI etc.

    More appropriately, why would you want to run NM in conduit anyway? The cable is tough to pull and the jacket can get cut in fittings and it's generally not worth the extra trouble if you're going to run conduit anyway. Just curious.

    Jim
    Growing older is mandatory.
    Growing up is entirely optional.

    Remember; it's never too late to have a happy childhood.

  3. #3
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    I have used it to "protect" the NM as Jim mentions in my shop as I have installed electrical drops down the wall. (The NM cannot be left exposed and this was always retrofit work as I changed things around in the shop) But I also agree with his last comment...I wouldn't want to pull this stuff through conduit for any kind of distance or around bends. Using the proper loose conductors is so much easier and you can always transition to NM in a J-box where needed and appropriate.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  4. #4
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    Or better yet, why not use MC cable. This is flexible conduit with the conductors already inside. Allowed by the NEC for surface mount.

  5. #5
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    Personally, I would not. I could get into a diatribe or wind up being a boviator as ORielly calls them. I use EMT all the time and I see no need to stuff 12/3 into a conduit. Secondly, pulling a 12/3 safely through an EMT conduit may be very difficult resulting in damage to the wire. Why cann't you use THHN? That is my favorate wire!
    Last edited by Dev Emch; 02-10-2006 at 6:31 PM.
    Had the dog not stopped to go to the bathroom, he would have caught the rabbit.

  6. #6
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    When you install mn cable inside of conduit, it de-rates the conductors. The jacket is the wrong material, and the conductors are not as flexible as they should be. If the inspector is on top of things, it should not pass code.

    That being said, I've seen it done many times and it fact have it done this way for the AC unit for my shop. I needed some protection so I ran the romex in conduit for about 4'.

    Good luck.

  7. #7
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    Alan, Codewise there is no problem running 12/3 inside emt. Derating is not an issue with 1 or 2 cables. As Dev stated using type THHN wire inside of the conduit is easier and more practicle. What area of Maryland are you located?

    Charlie

  8. #8
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    Great ideas, thanks!

    Thanks guys, I can and will use the proper guage THNN. This sounds like the proper way to do it. I was thinking of Romex because it seems simpler to do i.e. one cable to pull instead of three. But the increased difficulty of pulling romex in conduit partly offsets the benifits. Thank you all very much.
    Alan T. Thank God for every pain free day you live.

  9. #9
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    Quote Originally Posted by Charlie Knauer
    Alan, Codewise there is no problem running 12/3 inside emt. Derating is not an issue with 1 or 2 cables. As Dev stated using type THHN wire inside of the conduit is easier and more practicle. What area of Maryland are you located?

    Charlie
    I'm in Rockville now just North of D.C. but will be moving to Raleigh soon hence my next post. Thanks.
    Alan T. Thank God for every pain free day you live.

  10. #10
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    Welcome to Raleigh

    Hi Alan, Welcome to NC and Raleigh. Hope you have a good move.

  11. #11
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    Thank you John

    Quote Originally Posted by john whittaker
    Hi Alan, Welcome to NC and Raleigh. Hope you have a good move.
    I appreciate the welcome . I used to be stationed at Camp Lejeune many moons ago and look forward to the slower pace in N.C.
    Alan T. Thank God for every pain free day you live.

  12. #12
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    Quote Originally Posted by Alan Tolchinsky
    Thanks guys, I can and will use the proper guage THNN. This sounds like the proper way to do it. I was thinking of Romex because it seems simpler to do i.e. one cable to pull instead of three. But the increased difficulty of pulling romex in conduit partly offsets the benifits. Thank you all very much.
    Quick tip to make life easier. Follow the minimal fill factor for EMT but if you think its going to be a hard pull, bump up the EMT size a bit. Secondly, set up your THHN spools to feed concurently into the pull. Tie up and tape off the end of *ALL* wires your going to pull. Then pull this run through the EMT while your wife, son, etc. monitors the proper feeding of the EMT at the entry end. Make sure you not chafing or scraping the wire on any sharp edges as its going in. Use pulling soap if you need to to lubricate the pull. Personally, I hate ROMEX. Actually I hate it because others love it. The others are those with large wearable front incisor teeth and they like romex jackets and insulation as a method to keep these choppers worn down and in check! If you know what I mean! Also Romex uses lots of paper and some romex actually uses a degradable cloth exterior (my home has some of this junk in it!).
    Had the dog not stopped to go to the bathroom, he would have caught the rabbit.

  13. #13
    Quote Originally Posted by Jim Becker
    NM cannot be left exposed
    The NEC permits NM to be used in both exposed exposed as well as concealed work; 336-6 specifies requirements for exposed work. Although, I'm with Dev and don't use NM in outbuildings due to the "rodent factor". I cringe when I see it run exposed in barns housing horses; 'just waiting for disaster IMHO.

  14. #14
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    BTW if you do decide to pull THHN and don't want to buy 3 spools of wire, you can go to the HD or other supplier and they will pre bundle them for you right off the rack with what ever colors you want ( I am always in 3 phase mode so I fool around with most colors except green and white/grey ). makes the pull easy

    lou

  15. #15
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    Quote Originally Posted by Dev Emch
    Quick tip to make life easier. Follow the minimal fill factor for EMT but if you think its going to be a hard pull, bump up the EMT size a bit. Secondly, set up your THHN spools to feed concurently into the pull. Tie up and tape off the end of *ALL* wires your going to pull. Then pull this run through the EMT while your wife, son, etc. monitors the proper feeding of the EMT at the entry end. Make sure you not chafing or scraping the wire on any sharp edges as its going in. Use pulling soap if you need to to lubricate the pull. Personally, I hate ROMEX. Actually I hate it because others love it. The others are those with large wearable front incisor teeth and they like romex jackets and insulation as a method to keep these choppers worn down and in check! If you know what I mean! Also Romex uses lots of paper and some romex actually uses a degradable cloth exterior (my home has some of this junk in it!).
    Dev, Thanks for the concise tutorial on this. I really appreciate it. Now I'm going to print this out in preparation for brain fade.
    Alan T. Thank God for every pain free day you live.

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