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 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 Badger Construction & Maintenance Electrician Massachusetts
Do you think the fixture canopy has any allowance?
The total box volume is determined by adding the individual volumes of the box components. The components include the box itself plus any attachments to it, such as a plaster ring, an extension ring, or a dome cover.
Q: Domed Fixture Canopy [314.16(B)(1), Ex.]. A round 4 x 1/2 in. box has a total volume of 7 cubic inches and has factory internal cable clamps. Can this pancake box be used with a lighting luminaire that has a domed canopy? The branch-circuit wiring is 14/2 nonmetallic-sheath cable and the luminaire has three fixture wires and one ground wire all smaller than 14 AWG. (a) Yes (b) No
(Check the link for answer )
******** EDIT: iwire...seems the proper term is a DOMED fixture CANOPY
[This message has been edited by Celtic (edited 04-03-2006).]
On another "point of discussion" - this has been ongoing discussion for a while on several jobs.....
The ground wire. tie to the pancake, or to the fixture bar, or both? Fixture bar gets connected to the pancake, so no need to to take bare ground to pancake, just loop the braided "luminere" [sic] ground wire to the fixture bar, nut it to the 14/2 NM ground, and done......