art. 690.47(D) ex. #2

[elohr46]

Trying to get a clear understanding of 690.47(D) ex. #2. 2008NEC Situation; roof mounted solar array on a commercial one story building, building steel and steel bar joist is the grounding electrode system, is "on the roof" considered to be within 6' of the premises wiring electrode? We were going to run a GEC from the array down to building steel but not certain this is necessary, the metal conduit is being used as the equipment ground.