I really don't know why you would want to control fluorescent lights with a dimmer controlling a relay. It is a convoluted way of replacing a single pole switch.Here is my original post regarding using Lutron dimmers with a circuit that is all fluorescent lights on it.
Can someone point me in the direction of wiring one of these? Also, will it be to code? Also, will it handle about 7 fluorescent tube ballasts?
"If you want to control the fluorescent lights with this dimmer, I'd suggest using a relay to control the power to the lights from the lutron dimmer. You can take the output from the dimmer to the relay coil input, then a constant power source to be switched for the lights. This would ensure a clean on/off for the fluorescent lights.
If you need help figuring out how to wire up this relay, just ask. Many of us around here have wired these up and can help you out.
The above is what you are asking to do.
A dimmer and fluorescent lights do no work together very well unless you have dimmable ballasts. Adding a relay in the mix does not solve anything.
The link provided is to a relay that is rated for controlling ballasts totaling up to 450VA. I don't know the ratings of your ballasts to even begin to say if it's compatible. The relay is NOT rated for electronic ballasts. The relay will accept either (10-30 volts either AC or DC) or (120V AC) to control the switching of the relay and the relay has a normally open and a normally closed set of contacts to supply your load.
If you don't understand relays, the basic principle is to use one source of power to switch another source of power. Typically used as 24V source switching 120V or 240V loads. Or also typically used as 24V or 120V source switching 480V loads.