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Thread: How much negative pressure in my tent

  1. #1

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    Default How much negative pressure in my tent

    Up until now I’ve relied on a passive air intake in my 4x4 tent. My extraction fan is quite powerful and the sides of the tent billowed quit allot, so I obviously had good negative pressure. I want to bring some cooler air into the tent so have bought an in-line fan and speed controller.
    Without being to technical how much negative pressure do I want i.e. do I want the sides of the tent fairly taut or is just enough to see it’s negative?

    Thanks guys

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  3. #2

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    Just bowing in slightly is your lowest point.
    Touching in the middle is your highest point.

    Anywhere inbetween the two is fine

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  5. #3

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    If you want to be more technical...

    mutliply the 3 lengths of your tent together. then times that by 60. That tells you how much air you want to shift per hour

    For example a 2x1x2 tent = 2x1x2=4. 4x60 = 240m3 per hour

    If your fan and filter are rated 480m3 per hour for example you can run the fan at 50% and still achieve that 240m3 per hour with it.

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  7. #4

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    Also keep in mind that the carbon filter, if used, will reduce the air that the extraction fan will be able to move.

    You can always put some rigid sticks in the middle of the tent (horizontally) to avoid the sides taking plant space.

    Rigid metal core tutors are great for that.

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  9. #5

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    The idea is to have slightly more going out than in. Enough for tent sides to bow... but not collapse
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  11. #6

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    Quote Originally Posted by Mac View Post
    If you want to be more technical...

    mutliply the 3 lengths of your tent together. then times that by 60. That tells you how much air you want to shift per hour

    For example a 2x1x2 tent = 2x1x2=4. 4x60 = 240m3 per hour

    If your fan and filter are rated 480m3 per hour for example you can run the fan at 50% and still achieve that 240m3 per hour with it.
    Am I right in thinking. My tent 0.9x0.9x1.8 times 60 it says 87m3. Doesn’t seem like much.

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  13. #7

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    Quote Originally Posted by Uv123_4 View Post
    Am I right in thinking. My tent 0.9x0.9x1.8 times 60 it says 87m3. Doesn’t seem like much.
    Thats correct yes,. A fan rated 87m3 will replace the air once a minute, 43.5m3 will replace the air every 2 minutes etc.

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  15. #8

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    Can you have too much negative pressure. Does upping the air outtake cool down hps much. Had temps about 28 steady till we got a bit warmer and had 38 one day. I need to get new filter anyway so I’m goin to go from 4 to 6” and then even use the 4 for intake. Do you think it would bring them down much. Any idea?

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