All references are based on the 2017 edition of the NEC, unless otherwise noted.
For the boxes in these photos, what is the requirement for the minimum luminaire weight they must be capable of supporting? Many installers would look to the requirements in Sec. 314.27(A)(2) for this answer. It states the boxes must be required “to support a luminaire weighing a minimum of 50 lb.” It goes on to say a luminaire weighing more than 50 lb must be supported independently of the box, unless the box is listed for the weight to be supported and the interior of the box is marked by the manufacturer to indicate the maximum weight. This would seem like the correct requirement to follow. But is this rule even applicable to the boxes in the photos?
These boxes are not actually installed on “ceilings;” therefore, Sec. 314.27(A)(2) would not be applicable, since the title of this Code Section is “Ceiling Outlets.” So is there another rule that might be applicable? It would not be Sec. 314.27(A)(1) either, because the title of that Code Section is “Vertical Surface Outlets.” These boxes obviously aren’t installed on vertical surfaces. Section 314.27(B) is irrelevant, since these are not floor boxes. The weight requirements of Sec. 314.27(C) are not applicable because these are not paddle fan outlets. Although Sec. 314.23 has lots of requirements for supporting and securing boxes, none of the rules found there specify the minimum weight that these boxes must be able to support.
So where does this leave us? Unfortunately, there are literally no Code rules that specify the minimum weight that these boxes must be capable of supporting. You should probably have a discussion with your AHJ about which rules might be best applied to boxes like these and installations that are neither “Ceiling Outlets” nor “Vertical Surface Outlets.”
Personally, I think the best option would be to apply the rules for “Ceiling Outlets” to these boxes. Weight and gravity would have the same effects on luminaires installed on these boxes as they would on boxes installed in horizontal ceilings. I think the intent of Sec. 314.27(A)(2) is to apply to boxes installed similarly to the ones in the photos, even if the literal wording may not quite fit.
