ive 120 x120 grow groom got 600w light got one fan puting cold air in , should i put one taking out ?
If you have a temp problem, you need better ventilation. Fan capacity is measured in Cubic Feet per Minute (CFM). My rule is to exchange all the air in the tent at least once every 5 minutes. So, your tent is 10X10X8, or 800 cubic feet. A very common, cheap 6"
inline fan is about $30 and moves 240cfm. If you had one of those blowing in, and balanced it with one blowing out, you would be replacing all the air in your tent once every three minutes. Unless the ambient temperatures are very hot (say, above 80 degrees), your tent should be OK. Is your light in a cool tube? If so, make sure the airflow for the tube is outside-to-outside to completely eliminate it as a heat source. I'm in Florida, and my tents are in a non-air conditioned garage, and this setup keeps them cool. Your situation may vary, and others here on RIU may have different ideas. I'm just sharing what works for me. Peace!