Page 2 of 2 FirstFirst 12
Results 11 to 18 of 18

Thread: What am I missing... Romex not outside?

  1. #11
    Join Date
    Feb 2003
    Location
    New Jersey
    Posts
    3,384
    No ridicule. This topic comes up often. The problem with NM cable is that the wire ratings are marked on the outer sheath and as such can only be installed inside walls and in dry locations (and JB's for switches and receptacles with device covers on in bathrooms are still considered dry locations). The internal wiring in NM is also wrapped in a cardboard-like paper. It is possible that condensation could weep through the jacket and dampen the paper wrap and possibly corrode the wire over time. Now, if you look at MC cable, in contrast, the individual wires are marked before the armor goes on. So, my gripe is with manufacturers, and I'm sure it's a cost of production thing, but why can't they mark the wires or use THHN II before installing the sheathing ? That way, if you run the internal wiring say to an AC disconnect you can then use the same wires inside the whip to the unit.

    Anyway, I would say that if you intend to install wiring in PVC on the outside of the house, use UF cable to solve that problem.

  2. #12
    Join Date
    Feb 2003
    Location
    Massachusetts
    Posts
    60,020
    Here is the code section for aboveground.

    300.9 Raceways in Wet Locations Abovegrade. Where
    raceways are installed in wet locations abovegrade, the interior
    of these raceways shall be considered to be a wet location.
    Insulated conductors and cables installed in raceways in wet
    locations abovegrade shall comply with 310.1 O(C).
    In other words, if the raceway is in a wet location the NEC considers the conductors inside it to also be in a wet location.

    And while I am at it here is the section for underground

    300.5 Underground Installations.

    (B) Wet Locations.
    The interior of enclosures or raceways
    installed underground shall be considered to be a wet location.
    Insulated conductors and cables installed in these enclosures
    or raceways in underground installations shall comply
    with 310.10(C). Any connections or splices in an underground
    installation shall be approved for wet locations.

  3. #13
    Join Date
    Mar 2017
    Location
    Varnville
    Posts
    4

    THWN

    Quote Originally Posted by ActionDave View Post
    Critical distinction right there. No telling how many rolls of straight THHN left that we need to watch out for. If you see something say something.
    What do you mean by your statement?
    No telling how many rolls of straight THHN left that we need to watch out for. If you see something say something.
    Thanks
    Ron

  4. #14
    Join Date
    Jun 2015
    Location
    texas
    Posts
    1,569
    Quote Originally Posted by ronalddunbar@comcast.net View Post
    What do you mean by your statement?
    No telling how many rolls of straight THHN left that we need to watch out for. If you see something say something.
    Thanks
    Ron
    What ActionDave means is that straight plain vanilla THHN is not listed for wet locations.

  5. #15
    Join Date
    Jul 2003
    Location
    New Jersey
    Posts
    23,764
    Quote Originally Posted by user 100 View Post
    What ActionDave means is that straight plain vanilla THHN is not listed for damp/ wet locations.
    And that there isn't too much of it (straight rated THHN) around anymore, most modern insulation is dual rated THHN/THWN.
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

  6. #16
    Join Date
    Feb 2003
    Location
    Wisconsin
    Posts
    9,788
    Quote Originally Posted by infinity View Post
    And that there isn't too much of it (straight rated THHN) around anymore, most modern insulation is dual rated THHN/THWN.
    I don't think I have ever seen single rated THHN. It is probably a regional thing, but up north here I think everything has been dual rated for at least 35 years.
    Just because you can, doesn't mean you should.

  7. #17
    Join Date
    Jun 2015
    Location
    texas
    Posts
    1,569
    Quote Originally Posted by jim dungar View Post
    I don't think I have ever seen single rated THHN. It is probably a regional thing, but up north here I think everything has been dual rated for at least 35 years.
    I ended up editing my post earlier (thats why it appears different) after double checking the book on thhn- it seems it is listed for damp, not wet. Just never have given it much thought because I havent needed to. Usually do nm (which is run only in dry) or UF and when doing wire in pipe (which is rare)- its the dual rated stuff.

    Seems that "damp only rated" single THHN conductors would actually be kind of useless- who wants to keep another product laying around when you have other stuff that covers that and more.

  8. #18
    Join Date
    Apr 2006
    Location
    Simi Valley, CA
    Posts
    8,190
    Quote Originally Posted by wrobotronic View Post
    How is a bathroom not at least damp? There are several rules for fixtures above tubs for example.

    So then what I am ascertaining here is that drywall, tape and mud will then make the cavity in which the NM is ran a dry location?

    However, the reference to the pipe definition is helpful and clears up the reason for the need for THHN...

    Again, thank you....


    Sent from my SM-G930V using Tapatalk
    Then why wouldn't all exterior walls be considered at least a damp location?
    I can build anything you want if you draw a picture of it on the back of a big enough check.

    There's no substitute for hard work....but that doesn't mean I'm going to give up trying to find one.

    John Childress
    Electrical Inspector
    IAEI / CEI / C10
    Certified Electrical Inspector

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •