venting for grow tents

Discussion in 'Grow Room Design & Setup' started by groder97, Jun 7, 2009.

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    groder97

    groder97 Member

    ok i have two grow tents they are the 4x4x6 tents one i have for vegging and one for flowering. i can not figure out how i need to have my fan set up for the veg tent. Do i want my fan pumping air in or out of it? Then do i need a carbon filter on it? Then the real problem i have is i cant figure out is my flowering tent. I have a 1000 watt hps with a daystar hood and i dont know how i need to run my ventilation. Do i run it into the tent to the hood then out the hood to the fan and then a carbon filter on the other side of the fan or reverse? i need some help plz
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    Hairy Bob

    Hairy Bob Well-Known Member

    Always suck air out of a growroom, fans work better this way, and any small air leaks will be pulling fresh air into the room, not blowing hot, smelly air out of it. Carbon filter on the veg tent is entirely down to how stealth you need it to be. Veg plants will smell somewhat, so if there's a chance of anyone getting near your exhaust, better to be safe than sorry.
    If you have an air cooled hood the best thing is to have that run on its own ventilation, again pulling the air through it, otherwise it will be intaking warm air from the tent an using it to cool the bulb, which makes the bulb, and growroom slightly warmer, and the cycle continues (what you said is right, btw, i was just trying to explain why).
    You could use a Y adapter to split ducting to a single fan exhausting from both tents, and blowing through a carbon filter. I have heard people say to suck through a filter, but mine sits after the fan and works well.
  3.  
    groder97

    groder97 Member

    thank u so much i thought no one would answer my q bc iam a newbi and dont have a high posting score. but ya it needs to be steath. it will be in a aptment. cool thanks. now u talk about a Y adapter pulling (sucking) air from both tents would a 6" can fan with a rating of 309 cfm would that be the right size and CFM rating for doing that and what size of carbon filter should i have at the end? also do u use a tent ur self?
  4.  
    Hairy Bob

    Hairy Bob Well-Known Member

    Each of your tents is 4x4x6 = 96 cubic feet = 192 total. Normally it's recommended to exchange the air about once a minute with HID lighting, but a kw is quite a big light for that size tent, so it can't hurt to go a bit overkill with the ventilation to make sure it stays cool.
    Plus the fact that a carbon filter, as well as any ducting, creates resistance and reduces the amount of air the fan can move below it's rating. To minimise this you should try to keep all ducting runs as short and straight as possible. If you have to put a bend in it try to make it as long and smooth as possible, rather than a sharp turn as that would slow airflow considerably.
    Carbon filters are normally rated by the amount of air they can flow in cfms (edit; a lot seem to be advertised rated on cubic metres per hour, but it's simple enough to convert, just type it into google ;-)), so try to match that to your fan as closely as possible, but it's better to have a carbon filter rated slightly higher than the fan, as opposed to the other way round if you can't find an exact match (though if, say, you had a choice of a 300 or a 350, go for the 300 as it's closest to the actual rating of the fan)
    I've never used a tent, or known anyone using one. I have a pretty low opinion of them myself, mainly based on looking at tents for sale and thinking 'I could build a fantastic cabinet for half that price' but have nothing against people using them as a quick setup solution, and obviously I see their merits, I just prefer to design and build things myself.
    The advice I've given is relevant, since the principles of airflow remain the same no matter if you grow in a tent, cupboard, attic, basement or wherever. You take hot air out from the top, leave a hole for cool, fresh air to come in near the bottom and match the fan and filter to the size of the room, and the heat generated by the lights.
    Anyroad, I think I've gone on long enough for one post, hit me back if you need any more info.

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