My co-worker and I were replacing some old wallpacks today with new. I was assembling fixtures while he put them up. He is working on the last fixture while I am cleaning up and I hear the building back-up genny fire up. Thought is was a weird time for a genny run at 3 in the afternoon. Next thing I know a women is asking me what is wrong. She explained the building lost power. My co-worker walks over and has slight arc burn on his arm. Said he was holding the fixture against the wall when it slipped down a little and the hot leg started crackling. Next thing he knew genny behind him was running. I went down to the elec room and the 1200a main is tripped. I reset the trip mechanism than reset the main switch. Everything is fine...genny cycles down and all is well. My thinking is that the lighting circuit has no, or a bad earth ground and caused the trip. Am I correct in this assessment? Theories?
