Those duct boosters supposedly work fine, from what I've READ, not personal experience but most people seem to get the ones at home depot etc. I don't know if that's a good deal after shipping compared to local or not. Duct boosters are not expensive like real can fans are.
If you have short ducting I am pretty sure this would be fine, but who knows if it's loud or will last.
Duct boosters
DO NOT work fine, this from what I have personally ascertained, not from what I've read. I bought the 8" fan at HD (Exact same one as in the link). They will keep moving air moving, provided that there is NO restriction anywhere. The motors on them do not have enough torque to overcome much resistance or to move a significant amount of air on thier own. They all have a rating of how much air they move at a given static pressure (.000in, .025in, etc) This one moves 500cfm of moving air, but wont move 200cfm of still air on it's own. I would think that you could use them in a cool tube type application to cool a light, but again, you gotta watch any restrictions in airflow.
I had mine sucking air from the area above my lights and venting it under the house. It would not even create a negative pressure in the room. (no airflow/suction into the room under the door)
They might well work to cool lights (cool tubes) but as a room air exchanger they suck miserably.
La9, you cannot go from a 4" line to a 2" line with this kind of fan. You need a way more powerful motor behind it if you plan on restricting air flow. I had mine set up as an 8" inline fan on 6" duct. Farts move more air than one of these.
Best advise for real ventilation is go with a "squirrel cage" type blower fan. Here is the one I found used. Mine is wired for 120v, but it's the same model. Over 2000 CFM at pressure!!! That translates out to 2 complete air changes in my room per minute. Air flows INTO the room under the closed door, eliminating odor in the house. I had to add some intake vents to allow for free flow of air.
http://www.grainger.com/Grainger/items/7D630
They are high dollar if you buy new, but you should be able to find one used. I got one that almost implodes the room (Windows flex in, and ears will pop when it kicks on) that was used as an air exchange fan in a paint booth. I tinted the windows on dudes car for it. It's fucking HUGE, but really quiet considering its size. You cant hear it from outside the room. I had to do some south african engineering to connect it to the ductwork, but this sucker will straight up MOVE some air. Pics available for anyone who wants. I know it's big and probably overkill for a closet or stealthbox grow, but Grainger has about 400 blower fans to choose from. And a blower fan is most definately called for here. Just be sure that the rated CFM is not at 0.00in static pressure. The higher the static pressure the fan is rated, the more air it will move on its own. 500 or 750 CFM (0.00in) sound good until you get it home and find out it wont do shit at pressure.
