The box fill rules allow including additional volume from added sections.
314.16(A) Box Volume Calculations. The volume of a wiring enclosure (box) shall be the total volume of the assembled sections, and, where used, the space provided by plaster rings, domed covers, extension rings, and so forth, that are marked with their volume or are made from boxes the dimensions of which are listed in Table 314.16(A).
The people making the boxes do not
know ![[Linked Image]](https://www.electrical-contractor.net/ubb/wink.gif)
that the box will be used without a domed cover with a marked volume.
In the end it is up to the installer to use the boxes code compliantly.
Bob
