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What's Wrong Here?

May 16, 2008 4:02 PM, By Joe Tedesco, NEC Columnist

I recently ran across this unique installation. These pictures are from a newly renovated office space. Some offices were torn down to make room for a large conference room. They needed a new place to put the light switch, but since the outer wall sheet rock is screwed onto ½-inch metal rails with cinder block behind them, this did not leave much room for a switch box to be installed. So the maintenance guy came up with this idea, mount the switch in the open cavity of one of the structural steel columns. "Why not, he said? The wire fill capacity of an H beam is astronomical, right? I guess this would be more than up to Code if the metal switch-mounting tabs were grounded. Heck, when was the last time you saw a 3/8-inch-thick steel electrical box?"

Two sections of the Code can be cited on this installation.

As per 320.40 (Boxes and Fittings), “At all points where the armor of AC cable terminates, a fitting shall be provided to protect wires from abrasion, unless the design of the outlet boxes or fittings is such as to afford equivalent protection, and, in addition, an insulating bushing or its equivalent protection shall be provided between the conductors and the armor. The connector or clamp by which the Type AC cable is fastened to boxes or cabinets shall be of such design that the insulating bushing or its equivalent will be visible for inspection. Where change is made from Type AC cable to other cable or raceway wiring methods, a box, fitting, or conduit body shall be installed at junction points as required in 300.15.” As per 300.10 (Electrical Continuity of Metal Raceways and Enclosures), “Metal raceways, cable armor, and other metal enclosures for conductors shall be metallically joined together into a continuous electrical conductor and shall be connected to all boxes, fittings, and cabinets so as to provide effective electrical continuity. Unless specifically permitted elsewhere in this Code, raceways and cable assemblies shall be mechanically secured to boxes, fittings, cabinets, and other enclosures.”

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