I agree with you the formula isn't that easy to use. Also I can't really attest to its validity. But it worked for the original poster. Think of it as a starting point with a 20% margin of error maybe?
Bohbo - I made this thread a sticky and will be sending people asking ventilation questions here. Great thread by the way, Lots of good info.
hello have a question what fan would i need for room that is 3ft*9ft*9ft would a 6" inline duct fan work?
What is the purpose to exchange air? See formula first page Q: How big of a fan do I need for my room? Answer: Big Enough to replace the air in the room every 5 min. Explanation: The air needs to be replaced every 5 minutes if you are not using CO2, the leaves need fresh CO2 and the the roots need oxygen. Use this formuila Take your total cubic feet and divide by 5. LxWxH / 5 min 10'x10'x10' / 5 Min = 1000 ft^3 / 5 Min = 200 ft^3 / Min = 200 CFM NOTE: This is NOT a calculation meant to control heat, this is only for fresh air for the plants. 3x3x9 = 243 ft^3 /5 = 49 CFM MINIMUM Airflow not rating. If it was the math that was the problem there you go, if you just didn't read the first page, there you go. FAQ = Frequently asked questions. A suggestion for future forum use would be to read the first page of any thread before posting on it. Especially an information / how to type thread. If you plan to use a carbon filter double the CFM needed.
@bohbo thank you i did read the first page the math was what i was just checking update the fan would be use for a exhust fan and i would haVE a caRBON SCUBBER ON IT venting out of my dryer vent
I would use a 6" Vortex style fan, at the very least a 4", whatever fits your dryer vent really will most likely be best. My guess is you will need the static pressure for filter+pipe bends+distance.
yea im not going to have a inlet so i would be useing the neg pressure for the fresh air but i will have fan on the plants too.....i will strt a grow journaL but i hve to get my room up nd running witing on seeds to germ
I would like to update my growbox. The box is 2'x3'x6'. It has two 4" diameter passive intakes on the bottom and two 4" PC fans on the top for exhaust. I am currently growing with CFL's. About 330 watts. No oder control. I grow in soil and I like to get my girls to about 3 to 3 and a half feet tall before I harvest. I would like to run a 400 watt HPS with cooltube. I would also like to have a carbon filter. Can I cool my light and scrub the air with one fan? I would like to have the fan and filter outside of my box. Is this possible? What size fan and filter do I need? How would I set it up? I can patch old holes or cut new ones. Would a 6" system be better than a 4" system or would 6" be overkill for such a small box? Thanks.
I would do a 4" Centrifugal / Mix Flow (Vortex Style). That would provide enough static pressure for carbon filter and enough air exchange and cooling for 400W HPS.
Thanks Bohbo. How many CFM's should I be looking for? Could I draw air in through the passive intake into the open end of my cooltube, then out of the box, into the carbon filter, through the fan and out? BTW this sticky is really cool. Thanks for starting it.
Yes that would work. I would suggest the 4" TD-100X or the 4" Vortex CFN-400. Either of those will work around 150 CFM but both will have nice static pressure. And you are welcome, glad it's being utilized.
im putting together a grow cabinet and have been told (maybe by you, cant remember this was a couple months ago) that this is a good fan and scrubber combo. im getting closer to D day on buying a fan/scrubber and looking at this scrubber and similar others it seems to me that they are meant to be put in your grow space and "suck air through" the holes in the sides. if your familiar with this type of scrubber can you tell me if this is right? and if that is how it is supposed to work is there anyway i can rig it so that i could put the scrubber outside of my cabinet (working with small space). maybe doing exaughst hole, ducting out my cab, the scrubber somehow inside 8in ducting, airseal the ducting to the bottom rim of the scrubber (or maybe an 8" to 4" flange sealed to the outside of the 4" flange on the scrubber), then fan? theres gotta be a way i just dont know enough about ducting... thanks
Your plan is very doable, running scrubber in-line or at end of line not at start (if that makes sense). In my Carbon Filter DIY I have a couple mounting examples... now with that filter (I didn't suggest this one btw) although i have never used this one, It appears like it would be able to run start or end but not inline. I would put it at the end of your line and exhaust out of it. IE you push dirty air through it on the exit instead of pulling dirty air through it at entrance.
Ha! That's the very combo I ordered just 5 minutes ago. I have the same problem, not enough room in my cabinet. I'm hopeing to mount the fan and filter on top (outside) of my cabinet. We'll see.
You should be able to, Just mount fan and filter with filter on exhaust end of fan. Then duct into cab for the fan's intake. Inside cab make sure there are passive intake areas for air to get in, you may want to maintain a little bit of neg pressure IE door should have a little pull before breaking the air seal.
thanks for your help with my ventilation questions bohbo. check out the final product here. let me know what you think wait... i have another question . i noticed that by adding the necessary a/c, i have lost my negative pressure. in fact air is now blowing out of the cracks in the cab. could i fix this by cutting a few holes in my a/c intake ducting so that the exaughst fan is pulling enough air through the ducting. this might make more sence when you look at the pics in my thread. it seems like this would work to me but i dont want to go ruining my beautifully ghetto ducting for no reason.
Hey man, great thread. I'm just about finished with my build but I am having some issues with my ventilation. I have a small cabinet, 18L x 18W x 27H. I have a 120V 60CFM computer style fan that is just not cutting it. It works great cooling, but I intend to install a carbon filter and it just doesn't have the static pressure to draw air through the filter or any ducting. I have made 2 different filters but after some testing, the fan is not capable of pulling air through even nominal filter material. I have very limited space and stealth is an issue. I was considering this TD-100 fan. It's not the TD-100X that is listed in the original post but I'm hoping it will have the required static pressure to draw air through a filter. Even this fan is quite large for the build I'm looking at. Ideally, a computer style 120mm fan would suit my space requirements. There are plenty of high cfm 120mm fans on the market but I can't find any that with a decent static pressure rating. Do you have any suggestions? There's a link to my build in my signature. Any help would be most appreciated. Thanks!
Looked at your setup, I think poking holes would work. I would do a single hole near the AC unit to start (light leak reason). You could try an AC Media Center fan big one for a cab that small you may want to try an Axial Duct booster. But the Td100 would be more than enough in fact its overkill so if you can get away with a duct booster (stay 4" though) give that a try. You have around 6 cubic ft or less (head calc, may want to verify) I would think a 4" Axial could still pull enough air through a carbon filter. For that little space. How much wattage you running?
Thanks for the reply. I'm just running a 125 watt CFL. I'll look into those axial duct boosters. Is there one in particular that you would recommend?
I would say Inductor 6 In. In-Line Duct Booster Fan - DB206 at The Home Depot give that a try. Its 30W just like the 4" but has a better throughput. You should be able to return it without problems if it doesn't solve heat problems. EDIT:: you could always try the 4" version first, if it doesn't work near to what you want the 6" probably won't either. Maybe start here http://www.homedepot.com/h_d1/N-5yc...splay?langId=-1&storeId=10051&catalogId=10053