Ventilation Help?

Discussion in 'First Time Marijuana Growers' started by GanjaGilbert, Apr 18, 2014.

  1. Hi all, just started building a grow cab sized at 24" X 24" X 18". I've got a Soler & Palau TD-100X for the inline fan for the exhaust. It's sized at 4" for the ducting (Haven't installed yet). I plan on creating a carbon scrubber.
     
    For the air intake hole, what size should I make it? I hear its suppose to be 1/3 the size of the exhaust to create a vacuum? Is this correct? The cabinet is constructed of steel so once I drill the holes that it. Theres no going back.
     
    Also, does it matter where the intake and exhaust are positioned? Can I have the exhaust at the bottom of the cab and the intake at the top? Or will this create problems? The inline fan is quite large and the cab is quite small so I'm trying to position it out of the way of the 24" t5 light fixture.
     
    Also, for the intake hole, can I put window screen over it to prevent pest infestation? Or will this reduce the airflow?
     
    Thanks all!

     
  2. Seriously? 143 views and nobody has anything to give as input? Will someone for gods sake give me a little guidance? I've tried the search tool but I can't find any relevant results.
     
    Even just posting an article for me to read would be greatly appreciated!
     
  3. A passive intake should be about twice the size of the exhaust
    position your vents opposite of each other top/bottom left/ right, whatever works for ya
    window screen will stop a cat - maybe,but not spider mites IME
    furnace filters provide good airflow, you just need to get creative on how to mount it
     
  4. So it wouldn't be a problem to have the exhaust inline fan and filter at the bottom of the cab and the intake towards the top?
    Thanks for the feedback!!!!
    :)
     
  5.  
    The exhaust at the bottom could possibly make it less effective, especially in terms or removing heat from your grow box. Maybe you can install the fan outside the box to save room inside for the lights? With such a small space, controlling excessive heat is something you will need to deal with. Turn on your light for a few hours and get an idea of what the temps are. Maybe you'll be okay, who knows.
     
    I agree with the furnace filter instead of window screen. I disagree about the intake size though. I would make it smaller, not twice as big. Having a smaller intake than exhaust will create a negative pressure in the box, making it much harder for mites to live in the first place.
     
  6. well how much smaller should it be than the exhaust hole?
     
  7.  
    Passive intakes should be bigger than the exhaust hole and they're saying you should cut (2) 4" passive intakes. I think that would do the job.
     
  8. Why is this such a contreversial question? So I need two holes the size of my exhaust? I thought I wanted to create negative pressure.
     
  9. Intake at the bottom, exhaust at the top. Otherwise you won't be removing hot air efficiently, you might even be bringing the hot exhausted air back in.
     
  10.  
    I did not mean two smaller holes. I meant what I said, and yes, doing it the way I suggested will create negative pressure.
     
  11. I'm so lost. You guys are literally telling me to do two opposite things.
     
     
    Your saying the intake should be SMALLER than the exhaust......
     
     
     
    Your saying the intake should be LARGER than the exhaust by nearly DOUBLE!
     
    Which is correct? I need NEGATIVE pressure to reduce smell and help plant.
     
    To me it seems to make sense that by evacuating the space of more exhaust than it can take in at a time would create a negative pressure. Am I wrong?
     
  12.  
    I don't know why Not Sure is telling you to make your intake larger than your exhaust. If you want to create negative pressure, make the intake half the size of the exhaust.
     
  13. Thank you! Now I do want negative pressure to prevent odor from escaping correct? This also helps prevent pests as well?
     
  14.  
    Yes. All of the growboxes I've built had passive intakes, the area of which amounts to about 15% of the cfm of the fan, in square inches. For example, my 2x2x4 has a 4" 160cfm exhaust fan with (8) 2" passive intakes for a total of 25 sq inches of passive intake. I would get the same surface area from (2) 4" passive intakes. Or with a 6" fan (2) 6" passive intakes.
     
     
    I meant the area of his intake should be larger than the area of his exhaust for better efficiency, I've never lost negative pressure under these circumstances.
     
  15. Alright so now that we've established I need two 4" passive intake holes at the bottom, ( Gonna put em on the back wall, on in each corner), I've realized that to have the exhaust at the top I need to have the fan and filter mounted at the top of the box in order to keep it hidden and not be in the way of everything in the cab (again size is 24" wide X 24" tall X 18" deep).
     
    Now in order to have the fan mounted at the top, I'm going to have to use a 90 degree elbow coming straight out of the top of the cab. Is this okay? Might I add this sucks either way because I have to push the air through filter now, not pull.
     
    As some more info on the situation, I have the TD-100X set on low (100cfm) since the cab size is very small.Will this still be fine with a 90 degree elbow on it?
     
  16. Well I went ahead and did the 90 degree elbow. Next question is on position of passive intake. I'm going to go against my better judgement for the sake of knowledge and post a few pics of the cab so you can all see what I'm talking about. I'll have em up shortly.
     
  17. Sorry for the delay getting the pictures uploaded but here they are.
     
    Here's my question. On either side of the cab there are a sheet metal elevation that was made to originally hold drawers. There is about an inch ga between it and the exterior wall as you can see.
     
    If I drilled a hole in the center of the exterior wall would there be enough space to draw fresh air in without any problems?
     
    Do you think that light would be visible from those holes considering the length of the sheet metal "plateau"?
     
    Thanks all.
     

    Attached Files:

  18. Can anyone give some input here? Should I drill a hole on either side of the cab in the center of these raised areas? Would I be able to get adequate airflow that way?
     
    HEEEELP!!!
     
  19. I wish i had answers for u bro...... bump!!!!!!!!!!!
     

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