Try this topic from the forumMoving heat up stairs
My pictures of my setup are there before my last upgrade which will soon follow. I now run the fan to the upstairs with a RIB Relay in a Box RIBU1C, which is hooked up to the cool contacts on my upstairs thermostat. The fan is conected to the N/C contacts, and when the cool set point on the thermostat is active the relay opens turning the fan off until the room cools and then the thermostat opens allowing the fan to come back on. Kind of reverse logic. Works great!
By the way I finally figured out how to link a previous post
and I am a computer guy