There are so many factors to account for when choosing what size fan to go with. It all depends on your setup. Spend some time researching ventilation setups and designs. I use a 100cfm fan to ventilate my 250watt that is on its own independent ducting, and a 300cfm fan on a controller to ventilate the entire cab through my carbon filter. There is lots of info out there, you just have to do some digging.
It isn't about the wattage of your fan, it is all about the square footage of your grow air that you are trying to evacuate x3.
some of the better manufacturers have a table that you fill in your numbers (i.e. sq. ft., light wattage etc.) and it'll suggest what cfm fan to use.
My problem is ive never used cooltubes or air cooled reflectors. Ive had heat issues in the past and this is my main concern along with noise. My grow area is a tent, 3x3x5 ambient room temp will be aprox 70 deg F Id like to maintain temps at 80 or less inside the tent. I just need advice from people who HAVE used cool tubes to know if i can get away exhausting the entire grow with a 4 inch inline or do i need a 6 ? Again im only running a 250 watt hps. Ill most likely be using a hydrofarm active air inline fan, but if i could go the mixed flow fan route such as S&P fans id certainly consider it to keep noise down. Ill be running my setup as follows : Carbon filter > reflector > fan > out of tent
i HAVE used cool tubes, didn't like em. they cool fine, but i didn't care for the footprint. for only a 250 watt light, 4" fan will prob. be fine. although, using that small a fan (depending on cfm) might pose a problem. using it with a carbon filter might over tax it. i'd set it up differently than what you have planned. i'd put the fan directly on the filter, and exhaust through the tube. i suggest vortex fans. you can keep some noise down by hanging it from bungee cords.
So pull through the filter and push through the tube.. i like that idea... As far as the footprint issue i dont think ill be having one.. the reflector the cooltube in is pretty nice, its not a bat wing piece of __...and i believe it was designed with maximum footprint in mind. I cant imagine the glass from the tube affecting the footprint ? ? Yea im back in forth with which fan to buy.. I LOVE the suncourt/sunleaves windtunnel models.. The 4 inch is 200CFM . Problem is they are literally twice as expensive.. The hydrofarm active air will def get the job done.. noise being the issue with these.. if i went that route id get the 6 inch brand new off ebay for 75.00 including shipping. Moves 400CFM so i could tune it down considerably with a speed controller. just looking for opinions before i pull the trigger on purchases. Thanks for your help!
Never use cool tubes if possible....flat glass is bad enough, bent glass is terrible But to each their own...I have a tube and hate it
Well i need to keep it cool off 1 exhaust fan so there is gonna be some glass. ive used reflectors with glass before and grew some decent buds, like my avatar. Guess maybe it could of been "better" but like i said, gotta keep it cool in the tent.
Just bumping an old thread because I'm having the same issue. Can work out what fan I need for the light and room size but problem is apparently I need a much bigger fan for the carbon filter? 150cfm (5inch fan) for the room and 440cfm (8 inch fan) for the filter. I really just want to run one fan, pulling through the carbon filter, then the light then venting. The fan will have to be outside the grow room. Will 150cfm be enough?