All references are based on the 2014 edition of the NEC.
I found an interesting surprise when I removed the cover for this splice box. The box was not directly behind the cover; instead it was recessed below these floor boards. In other words, the cover cannot be installed on the box without sandwiching the floor boards between the box and the cover. The cover was actually just screwed to the floor boards with some wood screws, rather than being attached to the box.
If this type of installation was made in a wall or on a ceiling, this box position would be a violation of Sec. 314.20, since boxes installed in walls or ceilings made of combustible material like wood must be installed flush with the finished surface or project out there from. But believe it or not, the position of this recessed box is NOT a violation of Sec. 314.20, because this box was not installed in a wall or ceiling but in a floor.
Related
Is the intent of the Code to specifically exclude boxes installed in floors from this requirement? I tend to think not. I think it would be logical to apply the same rules to floor boxes. The heat from any arcing or sparking splices won’t discriminate between combustible wall, floor, or ceiling surfaces that may be exposed between the box and the cover. That same fire hazard exists for each of those types of installations.
Are there other Code violations we could cite? Perhaps we could point to Sec. 110.12 and say that this installation is not “neat and workmanlike,” but I have a difficult time finding any words in the Code that specifically make this box position a violation. Another concern I can point out is the questionable way in which the installer attempted to bond and ground the cover for the box. Section 250.110 requires this cover to be connected to the equipment ground wire; however, the equipment ground wire was just wrapped around one of the cover mounting screws and pinched between the cover and the floorboards. We could say that this method of grounding and bonding is a violation of Sec. 250.4(A)(3), since it would be doubtful this
connection would create a low-impedance ground fault current path.
As is always the case, when you’re in doubt of any Code rules, you should consult with your local AHJ for his or her interpretation.