how do you use this?

what do u plug into this a fan or an A/C unit or what? http://htgsupply.com/viewproduct.asp?productID=51244

yes a fan or a/c unit. it will work like a thermostat and turn the fan or a/c on and off.

If you plug it into a fan it will most likely run 24/7
If you plug it into an A/C unit, it will work like a thermostat