Fan placment
 

So I'm getting ready to set the new tank up. I have a retro fit light to go in the canopy. It will be running a 175MH and 2 75w vhos. My question is how should I mount the fans on the canopy? I have two 4 inch fans and don’t know what way would be best to place them.
Would one on each end with one pushing in and the other out or both out or both on the same side. As you can see i have a large canopy.


[IMG]http://i82.photobucket.com/albums/j264/mrkook_nyc/newtank004.jpg[/IMG]

Opposite sides, 1 pulling in fresh air the other blowing out warm air from the canopy..definitely the most efficient way to go.

Thanks thats what i thought just wanted to dub check

Fans work best with both blowing in, one on each end. With one in and one out you have the CFM volume of only one fan, you could stack 100 in a row but the last one will only move the same amount of air fed to it by the first one. With both blowing in you have the CFM of two fans. I have my canopy completely enclosed on all sides with a single Vantc Stealth 120mm fan in each end powered by variable voltage DC power supplies so I can vary the speed with a turn of a dial. The exit holes are in the top of the canopy above the MH reflectors so heat gets out but light does not. This takes advantage of convection as well as forced air to remove heat.
Also fans sucking air out fail much faster since you are passing hot damp salty air over them and the gum up. Fans blowing in move cooler drier air and last much longer.

what he said