As I understand it Radiums are actually a 360 watt bulb either High pressure sodium or mercury vapour and they are run on 430 watt ballast that is designed to run the other of these two lights. Meaning, if the radium is a HPS then it's run on a MV ballast or if the radium is MV it's run on a HPS ballast. Either way it's overdriven by about 60 watts. I could be wrong, that's just the way it was explained to me.
Doug
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