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Please take a look at attached pictures of my can light junction box. Outside says max 8 14 AWG conductors. It also says 10 cubic inch is J-Box volume.

Inside, there are 3 push in connectors (for hot, neutral and ground), each with 4 holes. 1 of the hole in each connector is occupied by internal wire which goes to bulb holder. It seems to me that I can connect 3 more 14 AWG NM cables given that 3 holes are available in each connector, but outside the junction box it says only 8 AWG conductors allowed. Each NM cable has 3 conductors (hot, neutral and ground) , so I am not sure if I can connect 3 NM cables with this can light. One for power source and 2 going to other cans.

Can someone tell me how many NM cables can be connected to this box ? There are 3 knockout holes in addition to 2 black clamps. If you can give explanation of how to interpret what it says outside junction box it would be helpful.

outside

inside

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    Wow. I have never seen a JB with such self-contradictory labeling on it before. Makes me wonder how the manufacturer crammed 8 14AWG or 6 12AWG conductors into a 10in3 box -- by Code, a 10in3 box should only be able to hold 5 14AWG or 4 12AWG conductors... Commented Nov 29, 2020 at 23:31
  • By code, the labeling on the box rules for that case, if the box is labelled and the device is listed/approved. Follow the manufacturers instructions.
    – Ecnerwal
    Commented Nov 30, 2020 at 2:09
  • Yup, if the device is not UL listed, do not install it. NEC 110.2. If it is UL listed, part of that listing is approved instructions which must be followed. NEC 110.3B. If the instructions say you can do it, then you can do it because UL said so. Commented Nov 30, 2020 at 3:06
  • @ThreePhaseEel is it because of the push-in connector block? Maybe the block itself isn't included in the in^3 calculation, so the "connector" count doesn't matter? I haven't a clue, just speculating...
    – FreeMan
    Commented Nov 30, 2020 at 16:05
  • They are sold at big box stores so I am sure they are UL listed, I believe I have used that brand in the past but don’t remember push in connectors with that said I would read the listing info just to be sure. The instructions should state wire type the tinned ground I would flag until reading the instructions to verify stranded wire is allowed. I do believe the OEM did that.
    – Ed Beal
    Commented Nov 30, 2020 at 19:39

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I think the most likely interpretation of the labeling would indicate since the NEC only requires the box fill calculation to count the ground once then you could have two 12/2, three 14/2, or two 14/3, but it could be argued that only one 12/2 or two 14/2 would be allowed.

The Code in section 314 specifies the volume (cm³ or in³) required per wire based on size of wire, and has a couple of details like counting certain types of fittings, only counting the largest ground once, not counting wires that start and end in the box. The confusing part is the Code also says installations shall comply with the UL (or other lab) Listing which includes the instructions supplied with products.

Normally the Listing is more restrictive, so following the Listing doesn't conflict with Code, but often light housing boxes like yours allow more fill than Code. I have always found Inspectors allow the Listing to overrule the Code. If an Inspector told me I would have to comply with both, meaning the tighter more restrictive standard I would have a hard time arguing against that, but I never have had to. Normally I do try to comply with the Code restrictions also to avoid arguments.

The size on the box is also relevant if using some combination of NM/AC/MC cable with smaller fixture whips.

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    You are forgetting the biggest part and the part that absolutely over rides code. if UL listed the mfg instructions Shall be followed NEC 110.3.B still the same in the 2020 code. The term Shall over rides all the box fill instructions if the device in this case is listed.
    – Ed Beal
    Commented Nov 30, 2020 at 19:34

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