We've got four 400W 220V metal halide pole mounted fixtures in our church parking lot that currently are being switched by a 15A 110V photocell (switching one side of the 220V). After 10 months of working, one of the ballasts has blown. I thought you should get several years out of these ballasts. My suspicion is that since the photocell is switching only 110, there is still 110V at the ballast all the time and thus leading to premature end of life. The original electrician who installed says it shouldn't matter and claims he checked with the ballast manufacturer on this. Would only switching one leg of the full voltage lead to a short ballast life?
