I have seen a few examples on here of boxfill calculations but not one where the box is directly attached to a light. So if possible please verify if these calculations are correct:

3 14/2 nm romex cables coming into the box = 3 * 2 * 2 + 1 (grounds) = 14

Lamp Yoke = 4 = 4

Total 18

The lamp head itself is what is throwing me off. It has two screws that hold this lamp to the box but doesn’t really have a strap or yoke like an outlet or switch but instead is like the cover to the box with a light on it. I plan to add one more 14/2 Romex to this box and pigtail the whites together so there is no double wire for single terminal as shown. However I was recently told pigtails don’t impact the box fill calculation so I should Be good on that front. Just need to figure out that lamp aspect and then add in these extra conductors from the wire to see if I fall under the 20.8 cubic in limit of this box.

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According to what I am reading from the 2020 NEC Handbook, you're good. The only question would be about the fixture if it is inside the box or outside, but you do have it covered when you added the lamp yoke.

If you would like to verify this yourself. If you find the Commentary Table 314.1 "Summary of Items Contributing to Box Fill". Remember this is in the 2020 NEC Handbook. Not the NEC. I select the 2020 since it should have the strictest interpretation. This table might be posted online somewhere as a stand alone.

Hope this helps.

  • 1
    Thanks for response. The lamp sits on top like a lid so it’s unclear if a yoke even applies. Isn’t the yoke the metal clamps at the top and bottom of a receptacle that screw to the box and is typically considered conductor hence the reason it is counted? This lamp is porcelain and really sits flush with top of box so I’m thinking the yoke might not count? Because if the yoke counts I’m at 18 so adding one more 14/2 wire would put me at a total fill of 22 which is over my 20.8 limit. So this yoke is killing me ha! I may purchase this handbook to keep around the house. Thanks for reference. Jan 11 at 13:03

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