I ground MOST of my streetlights.........hes right...recommended....esp if one starts to burn out...and highly recommended for HPS or any pulse start ballasts....If one of the wires gets loose or something...SHOCK!!!
I don't know how. my M-400 always had trouble startign the lamps until i properly grounded it. I thought it was a ballast problem, but it was 'cause of no ground. The lamp would strobe dimly for about 20 seconds before the warm-up process started. The cooper HPS light worked fine without the ground wire. It had always had a 2-wire plug until about two weeks ago. I put the ground screw in for Niall because it didn't have a ground screw before.