junction box

My can light junction box has 2 black clamps for NM cables and there are 3 metal knockout holes on 3 sides of junction box. (Picture shows one of these 3 knockouts).

Given the location of LINE wire and can light locations in celling, can I attach 3 NM (romex) cables with one can light ? Can light junction box has only 2 clamps , but can I use knockout hole ( metal) for 3rd cable? All cables are NM cables

1 LINE cable (through Knockout holes)

2 cables connecting to 2 other can lights. ( Through black clamps)

Take a look at diagram with red color can in question.

enter image description here

  • 3
    Is that box marked with a volume (cubic inches) anywhere? – ThreePhaseEel Nov 27 '20 at 16:34
  • I agree, I know the problem seems "solved" to you OP, but the "cubic inch" question is important, and may be a deal-killer. We need to know. – Harper - Reinstate Monica Nov 27 '20 at 19:01
  • It does say max 8 14 AWG conductors on junction box. – user2716454 Nov 27 '20 at 23:14

You have to use something when ever NM cable enters a metal box or enclosure to protect the cable from abrasion.

If you use a clamp for two cables, it must be rated for two cables of the applicable size. For example the Arlington NM94 is made for a 1/2" trade size knockout and can be used with one or two 14/2 or 12/2 NM cables.

Arlington NM94


Yes, you just need to add an appropriate clamp, like:

NM clamp

You should be able to get them at any hardware store/home improvement big box store/etc. An electrical supply house will be cheaper, but for an occasional clamp just go "anywhere".

  • I have one like this one already. Would it work ? Check out link. tinyurl.com/y5hyk7sa – user2716454 Nov 27 '20 at 16:16
  • That's a different style but perfectly fine. The only question is whether it matches the knockout size. – manassehkatz-Moving 2 Codidact Nov 27 '20 at 16:25
  • 2
    @user2716454 Yes, that clamp indicates it is meant for this purpose (securing NM-B cable in 1/2 knockout). – PhilippNagel Nov 27 '20 at 16:25
  • 1
    I am pretty sure the clamp in the picture is actually rated for just one cable. – batsplatsterson Nov 27 '20 at 17:39
  • 1
    @batsplatsterson Just read the question again: "can I use knockout hole ( metal) for 3rd cable" So my answer works. That being said, sometimes it is easier if the cables all enter through the same location, so your answer is good too. – manassehkatz-Moving 2 Codidact Nov 27 '20 at 18:07

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