Can a two wire dusk to dawn photo cell be used safely on a mercury vapor light, which uses a tranformer to step up voltage. The photo cell states 300watts max. and doesn't say tungsten lighting only. Will the transformer over heat by having a lower start up voltage until complete darkness.

Would a 2 wire photocell (triac type) work on a mercury vapor driveway light , instead of an relay or instant on. 120ac. Would the slow voltage increase as night fall approaches, under voltage the ballast and overheat it, such as a a/c motor running on a lower voltage such as what happens in the event of a long extension cord which is under rated for the amperage needed by the motor. Example given... Would be concrete mixer.