Referring to picture provided, what is the best way to transition my SER cable from running with the ceiling joists to running perpendicular? I can't drill through every joist due to all the existing pipes, HVAC and wires. This 2-2-2-4 cable is feeding a sub panel in my attached garage, and where the cable is perpendicular through the last joist, it feeds directly straight into the garage.

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1 Answer 1


The picture provided does not need a hole in "every joist" it needed one more hole in one more joist.

The best way to treat that problem is to drill that hole, missing the one visible or possibly more pipes invisible there. For instance, run left along the face of the joist-with-hole until past the pipe, then drill through joist-with-awkwardly-attached-cable where the pipe is not in the way.

If you have a long run (not pictured) where you need to run through many joists and have too many obstacles, transitioning to conduit or a conduit protective sleeve attached to the bottom of the joists is one of many methods, or building a lumber protective structure under the joists (ultimately a soffit, if you finish the basement ceiling) is another.

However 334.15(c) permits direct attachment to the joists for that cable size without additional protective measures. It might not be best, but it's adequate for code purposes.

  • I mean, clearly one hole was drilled, seems like it'd be facile to drill another one!, right?
    – Huesmann
    Commented Nov 26, 2023 at 16:36
  • If I don't go crazy with the 90 degree direction change, I guess I could just run it along the joist in the picture that already has the hole drilled in it.
    – user149104
    Commented Nov 26, 2023 at 17:45
  • 334.17(B) specifies that minimum bend radius (not diameter) shall be 5 times the cable diameter so that's exactly how crazy you can go with the 90 degree bend.
    – Ecnerwal
    Commented Nov 26, 2023 at 19:01
  • 2
    That may be easiest if you run the cable on the invisible face of joist-with-awkwardly-attached-cable rather than the visible face of joist-with-hole allowing you to use the full width of the joist bay to make the turn.
    – Ecnerwal
    Commented Nov 26, 2023 at 19:42
  • Attaching cables such as that to the bottom of joists is not permitted by code where I live, because they are clearly "subject to damage".
    – kreemoweet
    Commented Nov 27, 2023 at 3:18

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