Minimum Clear Distance 110.26

[WJPhillips]

This project has a 480V switchboard lineup that was set at 36" from a 2 layer 5/8" gypboard on metal stud wall in accordance with Table 110.26(A)(1) Working Spaces. But the Inspector claimed this to be a grounded surface and the gear requires a 42" clearance. The NEC Handbook shows the three conditions for clearances in Exhibit 110.9. I am confused by the term "Effectively Insulated" which is what he based the requirement for the clearance which makes us move the switchboard

 

[raider1]

Welcome to the forum.

IMHO, a sheetrocked wall without any electrical equipment mounted on it would be a wall without any live or grounded parts and would fall under condition #1 from Table 110.26(A)(1).

Chris

 

[infinity]

I agree that sheetrock is not grounded so condition 1 would apply, 3'.

 

[Jim W in Tampa]

If it was me with my back touching drywall i would call it grounded enough to kill me. I side with inspector on this one.

 

[charlie b]

This could go either way. But I am inclined to side with the inspector as well. It should be noted that the NEC says that concrete, brick, and tile count as "grounded surfaces." It does not mention sheet rock. That is why I say it is open to interpretation. But I would call it as grounded as a tile surface would be.

If push comes to shove, there is another solution. It is cheaper than moving the gear, but it is ugly, and worse, inelegant! Remove one layer of the sheet rock (this may actually require you to remove it all and install a single layer). Then place a layer of rubber matting against the wall. It should be the entire height and width of the working space (6.5 feet tall, the same width as the gear). That will create a Condition 1 situation.