Hey, whats up? I posted this in the Beginners thread, but I realized I might get a better response here, anyway, I'm planning my first grow with some guys right now. We're trying to figure out what kind of CFM we would like from our fans and if we should run an intake/exhaust or just an exhaust. Our setup will include 250w HPS/MH Light Kit from HTG and a 36" x 33" x 40" (W x D x H) grow box. We were also considering a carbon scrubber as well. I read you want air to circulate 5x per min, if this is the case would we want to run a fan somewhere around 137 cfm (Grow Box is 27.5 cu. ft. x 5 = 137)? And should an intake be added as well, if so what CFM should I look for there? We're still in the planning stages so if you want to suggest anything feel free. Thanks in advance!
A 12 inch exaughst and 10 inch intake would be what your after. You always want to have negative pressure within your tent. Ie air always sucked in disregarding your intake. Thats a rather small space to be looking to have a grow in. P
Thanks for the response! So we'll run a bigger intake and a smaller exhaust, but what CFM should these fans be at? Would ~140 cfm intake, ~100 cfm exhaust work out??? As for the space, we're trying to grow about 4 plants, and we are restricted to a closet. Would you still recommend a larger growing area?
No no no your after negative pressure a lager exaughst than intake. Not to mention a carbon filter on the end of the exaught. You want all air to exit through your extraction and filtered to surpress smell come the time. I thought you were growing one plant in that space never mind four. You may want to reconsider your area, well if you want to have any bud worth the time spent. And if your are planning to grow four plants you will need a more powerfull light.IMO
Thanks for the clarification, sorry. As for the size we can run a box about 4.5' x 3.5' x 3.5' (Hx D x L), like I said we are pushed for size. Would this suffice for maybe 3 plants?
The light that you guys have would be ideal for two plants, and in that small of a space i'd probably only do two anyways.
If we bumped up to a 400w HPS/MH kit would it get too hot in that small box or can we compensate with more powerful fans? We have the option to get the 400w as well, we were just worried about overheating. This is the light were looking at from HTG: High Tech Garden Supply
Don't think this is right! All the stuff i read from the people that know say a larger intake is what gives you negative pressure.
Dont make the mistake that more plants equal more bud.... You can get as much but in most cases more bud from one plant that has space to grow and develop than 3-4 plants cramed into the same sapce. P
Ehh how can a bigger intake give negative pressure? Extraction is what creats negative pressure. The more air that is extracted the lesser the pressure, Ie smell/air is extracted rather than forced. So if you have more air forced in (intake) at a greater volume than the extraction (exaughst) can handle, the smell will be forced out though airgaps/zips rather than only through the extraction/carbon filter. Dont make me bring out the thermodynamics eqautions, Just wiki it!!!