I am adding an external outlet to my house. I have come across a number of posts and articles on how to do this. For my AC unit I need to add an electrical disconnect on the outside of my house and also need to add a 110V outlet within 25' because of code.

What I'm not clear on is if I need to use outdoor rated cable when piercing the wall of my house to the external box. In all the other posts on this sites, it seems that outdoor rated electrical cable is only needed when burying or using cable in a raceway. In some pictures I've seen, it appears that indoor rated cable is being run through the wall to the outdoor box. Given that indoor rated cable is better in a fire, it seems that the indoor rated cable should pierce the wall. Then if there is any other runs outdoors, that the junction be made with outdoor rated cable. Is this correct?

  • 2
    If the cable goes directly into the box standard NM normally called romex (brand name) is ok.
    – Ed Beal
    Commented Oct 11, 2016 at 21:35

1 Answer 1


If the cable is concealed entirely within the wall, then non-metallic sheathed cable (NM) is fine -- the inside of a wall cavity is dry unless you have some serious problems with your house! You only need underground feeder cable (UF) if the cable's buried, put through an outdoor conduit that can get water inside it, baked in the sun, or otherwise exposed to the elements.

  • I agree+ Has to a direct connection with no exposed wire +
    – Ed Beal
    Commented Oct 12, 2016 at 0:33

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