i just did CO2 and if you have a photo sensor you still need a monitor to measure CO2 ppm because if you have too much CO2 can hurt your plants. the thermostat really does nothing...you need a timer on your fan~off during light hours and on at dark...if you have your fan kick on just for temps then you are wasting your CO2:jointsmile:

you can still feel cool bro...you are right you need 2 timers...1 for your CO2 generator and 1 for your fan...i know you have an AC in your room that is where your thermostat comes in to keep your temps in check and not waste CO2 :smokin: