I am installing an electrical subpanel in my garage and have a 2" PVC conduit run up approximately 5 feet from the panel through the ceiling to the garage attic. In the conduit i ran 2 12/2 NM romex runs for 2 separate circuits.

The AHJ said that this is not permitted and that i would need to run individual wires. I plan on installing a junction box on the top of the conduit where i will make the connections between the NM cabling and the individual THHN wires i am running into the subpanel. My question is do i need to fasten the THHN cables in the junction box? The NM cables will have the plastic insert in the knockout. If it does need to be fastened, any ideas how? I could drill holes in the jbox and use strap ties but don't think that meets code.

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  • Are you going to a metal or a plastic junction box? Generally, the wires would just pass through a knockout with a hub to receive the conduit, which functions similarly to a cable clamp (where the cable sheathing is the "conduit").
    – Hari
    Apr 5, 2018 at 21:32
  • Hari, i was planning on using a PVC J box mounted to the top of the 2" conduit as the AJH told me that the conduit needs to have a nut on both ends. I don't think not fastening the THHN wires will cause an issue but i can't find any regulation that says either way..
    – overpar83
    Apr 5, 2018 at 22:48
  • A nut? I'm not entirely sure I understand, but regardless, I haven't seen wires in conduit fastened to anything before.
    – Hari
    Apr 5, 2018 at 22:52
  • Where does the sub panel receive its power? Apr 5, 2018 at 23:00
  • Also see my answer here . Apr 5, 2018 at 23:31

1 Answer 1


Fastening not needed

For a short run like yours, you do not need to fasten the wires to the boxes -- the NEC folks have worked this out, and for 12AWG wires, you can run 100' straight up in conduit before you need to put any support in. (This number comes from NEC table 300.19, by the way.)

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