I would build my own if I was you. All you need is;
- dpdt relay (600V) x 1
- lampcord x 1
- receptacle x 2
- enclosure x 1
- compression fittings
- terminal lugs
- #8-32 nuts and bolts x 2
- tools
Are you using a digital ballast. You WILL need to shut off the digital ballast during each 12 hour flip cycle. Others will tell you you don't have to turn off the digital ballast and that their flips are built for digital ballasts, that's false. There is no difference in a flipbox for digital or c&c ballasts, it's all the same components.
This is a relay that will work for this application, I am picking up a couple today.
http://www.grainger.com/Grainger/DAYTON-Power-Relay-5X848
That has a 240V coil which doesn't seem practical. the coil is what connects to the timer or trigger and its a lot easier to use a 120 timer
the coil is the trigger and some run on 12v,24v,120v, and 240v. It may not be triggered by a timer all the time. Contactors can be triggered by sensors, when other items turn on etc so the different voltages are understandable.
Most contactors are rated up to 600V (The first one linked may not be 600V) capable and will switch ANY voltage up to that amount.
If using to power a ballast that is fine.
If using to switch the output of a ballast to a different bulb, you need one that is 600V because a 1000W ballast puts out 400-500 Volts.
Switching the ballast output has sparked many discussions on the proper relay to use due to the high voltage and arcing that occurs
no its a new idea. If you have a room with 4 hoods, and another room with 4 hoods, and only run two lights at a time, you do not gain yields IMO because you wont get as much if you had run all 4 hoods the whole cycle.