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Thread: Romex wire in conduit

  1. #1

    Default Romex wire in conduit

    I just installed some flood lights in my backyard and I ran the power source from an exisiting patio light.

    I used outdoor romex and fed it through PVC conduit. Yesterday, the local home center stated that I cannot feed romex through the conduit or it will cause "sweating" and might cause a fire. Is this true?

    Should I scap the PVC conduit an leave the out door romex exposed, or can I removed the romex covering and feed the electrical wires through the conduit?

    Any suggestions?

  2. #2


    Technically you can't run ROMEX in conduit except for short pieces for protection (like through walls or floors).

    You also technically can not simply strip the jacket of the wire and run it in the conduit (the wire is Romex are not LISTED for use).

    I've never heard of Romex wire causing sweating inside conduit. Any conduit underground will "sweat" inside. Since you ran outdoor Romex (Do you mean UF??) that would suggest it is water proof, and therfore being in a "sweaty" conduit shouldn't be a problem.

    Leaving romex exposed is never a good idea (weed wacker??). Personally I'd leave it as is. If you want to be to code, then you'll need to get some black, white, and green THHN/THWN wire and pull out the romex, and put this in its place.

  3. #3


    I will repectfully disagree with marako,
    Article 300.5 Underground Installations: does not limit the length of cable that can be pulled through several different types of conduit for the protection of the cable.
    Be sure you used UF type cable (not standard Romex or NM-b cable) so that it is rated for wet/underground installation, with or without conduit.

  4. #4

    Default Romex

    I agree with Ron. Just make sure you are using "UF" wire. Uf wire is the recognized wire for underground use-- in conduit, or not.

  5. #5
    Join Date
    Oct 2002


    you also need a minimum of 18" depth when using the PVC. SCH 40 fine for underground installation.Sch 80 required above ground IF subject to damage. Haven't seen Sch 80 in most DIY centers. 24" required depth if using UF cable only and again Sch 80 PVC when leaving trench vertically to whatever.(If subject to damage)

  6. Default

    The Home Depot in our area stocks both schedule 40 and schedule 80 pvc conduit. The Menards in our area also stocks both, but not quite so many sizes of the schedule 80. I suppose this varies by who runs the stores in each area,or something.


  7. #7


    OK, let me restate my answer... I rushed through the first one.

    You can't install Romex in conduit.... underground (Romex = NM-B). You can install Romex in conduit above ground, or as the others have said if you use UF which is water proof, you can put it in conduit even underground.

    My thought for the short peice was this: Generally running romex in coduit doesn't make sense. I belive you need to use 3/4" coduit for a single 12-2 w/g, and 1" for two peices of 12-2 w/g. This is because the width of the Romex determines to size of the conduit. So romex is about 3/8" wide. Anyway, I've seen where short peices of smaller conduit (1/2") would be used soley for protecting the romex on the way by/pass/through something.

    Sorry for the confusion.

  8. #8


    Code lets you bury UF cable directly in the ground, but you can also run conduit the length of the trench. If you do, you wont have to bury the cable quite as deep-12 inches instead of 24 inches as with the UF- in residential applications. You will, however, have to fish cable through the conduit. Contrary to what you may read on these forums running UF or other cable through conduit DOES meet code, but cable adds expense and the sheathing may make it difficult to fish. Most electricians feed three single wires, known as TW wires, through the conduit instead. If you do this run the conduit first, and glue the sections together if your dealing with PVC conduit. If your working with metal conduit besure to use compression fittings made specifically to keep water out. Once the conduit is in place, fish all three wires at once.

  9. #9
    Join Date
    Dec 2003
    Kent, WA


    You can only bury at 12" if the wire is breakered at 20A or less and it has GFCI protection before entering the earth. Conduit would allow the burial depth of direct bury cable to be reduced from 24" to 18" in most other cases.
    Kent, WA

  10. #10
    Join Date
    Dec 2003


    How did this old tread get re-born. I'm temped to close this tread!
    Learning brings success. While you are waiting, I'm getting better!

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