Your fan should be able to maintain the temperatures in normal conditions if installed correctly. You are not saying what size of hole or pipe you are using for your exhaust. Your exhaust should be at the top of your box, preferably right smack between your lights. You are also not saying what the ambient temperature is outside of your box where you are drawing the air from. You will have a temperature difference with your 800 watts of 10 to 15 degrees higher than the temperature is from air being drawn in. 800W produce 2500 btu's of heat and there is no way you will ever get the temperature in your box the same as the ambient air outside just using a fan.
Good Luck
SpaceNeedle


If my doors are open, does this mean that the fan is not running the way it should and if the doors are closed i will get better air circulation thus decreasing my temps?

Is the size of the fan adequate at 375CFM for a box this size?

What else can I do to lower the tepms?

Thanks in advance as always.[/QUOTE]
SpaceNeedle Reviewed by SpaceNeedle on . Manging temperature in a 4x4x8 box Hi all. I have a 4w x 4h x 8L box and i am having a hard time getting my temperatures down to the high 70's. Running 2 x 400HPS They were over 100f and I have installed a 375CFM fan with a carbon sock and the temps are now running about 85f. There are 4 small 4" fans inside the box and two 4"x6" opening cut into the bottom as passive intake. Rating: 5