I found this. It should help.....

Ga Grown!

Anyone that has more than two 1000 watt lights in their home has probably run into the problem of how to supply power and turn them on and off. A standard 120 volt circuit in your home has a 15 amp rating, that means one light. Note: I will be using the term "120 volt" and "240 volt" to describe the two different types of circuits we will be working with only because that's the term the ballast manufactures use. They are often referred to as "110 volt" or "220 volt", actually if you measured the voltage with an accurate meter a 120 volt circuit often will be less than that an can vary. A 1000 watt light draws about 9.2 amps at 120 volts (1100 watts / 120 volts = 9.17 amps). See this page for other ballast wattages. On a 240 volt circuit the amperage is 4.6 amps (1100 watts / 240 volts = 4.58 amps), so when running multiple light systems, it's easier to wire them for 240 because you can use smaller wire.

In a 120 volt circuit, the power cords have three wires; a black, a white and a green. The black is the "power" or 120 volts, the white is the "common" or "return" and the green is the ground. In a three wire 240 volt circuit, like we use for grow lights, there is also a black, white and green. The black and white are both 120 volts (180 degrees out of phase with each other) and the green is the common and ground. In a 240 circuit we are splitting the load between two wires.

The problem for most of you is that you just can't go out and buy a timer that you can "plug in" four lights. I have looked at many different lighting controllers for the hydroponics industry and found that most are $200 to $300 for what amounts to a $30 relay in a box with some outlets. I know many of you like to build this stuff on your own, so I setout to build one of these with safety and low price in mind and to get as much of it from Home Depot as I could. I know that some of you have built controllers based on the Intermatic T103 timers like this one, they will work for four lights but what do you do when you have eight or twelve lights and you want them to turn on at the same time? The answer is a relay.

A relay works like a light switch, it connects and disconnects two wires. The difference is that instead of flipping the switch with your finger, a relay has a coil that when power is applied, it makes the connection. The advantage of this is that the coil requires only minimal current. The one I am using draws 85 milliamps. That means I can control quite a few of these relays with one 15 amp timer. 15 amps / .085 (85 milliamps) = 176, or 176 four light controllers. I don't know if anyone has 704, 1000 watt lights, but if you did you could turn them all on with a $10 Home Depot timer! One problem though, you still need 176 different 30 amp circuits..... On with the project.