I'm interested to see what the data logger picks up. Please keep us posted Reno...
Seeing as how you're burning out control devices, I would suggest putting a contactor in the control circuit. Electronic timers can be pretty pricey (intermatics, anyway) and the 25A photcells are about $22 too, so you can save yourself some service calls and waranty work by taking the HID load off of those items. I go through a lot of 25A cells whenever they are running without a contactor, especially on ballasted fixtures.
I want to say harmonics sound like a possible culprit, based on the HID factor, but the logger should bring the problem to the surface.
Good Luck!
