Pc Fans For Small Grow Tent?

Discussion in 'Growing Marijuana Indoors' started by Buds245, May 27, 2013.

  1. Hello, I just ordered a GrowLab 60 tent which is 24 inches x 24 x 63. I was trying to stay on the cheap side and just throw some pc fans in there. The total cubic feet is 21.2, so in my mind a pc fan that moves 75 cfm would do the job plenty, I'm not putting a carbon filter on them or anything just trying to vent it, also I plan on only using 120 actual watts of cfls so it shouldn't be too hot.. I have a 74cfm 120mm fan and two 35cfm 100mm fans, would I put the 74 out take and two 34's intake or should I make a duct vent with all thre fans inline and exhausting and just have passive?
  2. Anyone have any opinions?
  3. You need to calculate how much airflow you need in relation to the size of your tent. Dont ask me the specifics rather ask google "how much airflow required for marijuana", but basically your plants require that a specific amount of air is completely replaced in a specific amount of time in a specific size space. You can then multiply that amount with your tent size, which will tell you if your fan setup is circulating the air quick enough. Theres an article on it out there i know I've read up on it. But more ventilation is better. Try to get the intake more or less the same as the exhaust but its not a train smash if they not. If be, have the exhaust stronger than the intake.

    Apart from the plants themselves requiring airflow to provide them with fresh air, circulation is also used to regulate temperature.

    Theres a chart here which tells you how much regulation can be achieved.


    You dont really ever require a duct inside the tent unless you want to provide an inline type sealed reflector hood with its own circulation to reduce heat, such as in cases with HID lamps.
  4. #5 GoldGrower, May 28, 2013
    Last edited by a moderator: May 28, 2013
    two 100mm fans will move more air than the single 120mm so I would use the two 100mm for exhaust and the 120mm for an intake. with fans like this that do not handle load very well you will need an intake almost to the power of the exhaust. don't use ducting otherwise the fans will struggle. however those three will easily handle the heat off those cfls.

    have a look here...


    I have 100watts of CFL cooled by two 120mm pc fans and the inside of the box is 2 degrees higher than the outside of the box
  5. Well the cfm is plenty, I just feel like pc fans barely have any pull, should I put the two 100mm in a row in one vent sock or separate it?
  6. side by side will work better, you don't have any sort of ducting do you? ducting will slow it right down, especially if there are bends or filters
  7. I won't need ducting for a sock hole will I? I'm going to be growing autos so light leaks aren't any concern
  8. No ducting required. If you put two fans on top op each other they will only have the airflow of one fan. if you put them next to each other they will double the airflow. Same for a duct. A duct with two fans at 190m/h in a duct will have a 190m airflow, not double that. if you have only one fan in the duct the flow will reduce as the duct adds resistance and the fan now has to suck in all the air and push it out. with two fans, one at each end, it reduces your resistance inside the duct and then your first fan will suck everything in and the second will push it all out. 

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