im not sure what you mean by contactor,


if you mean the ballast, somtimes, like mine they have two plugs, one is the power supply for the light, and the other is for pluging into a timer, which is then plugged into a DIFFERENT wall socket to the power supply, this is a safety feature that prevents you overloading the timer, potentially breaking it and ruining your plants.

if you didnt mean any of the above, im not sure what you mean!