Negative pressure creating smaller grow space....

Discussion in 'Growing Marijuana Indoors' started by TUK5150, Jun 27, 2019.

  1. a couple of you may know ive been struggling with lights off and lights on temps, both being around 2 degrees c to high (24c lights off & 30.0c lights on), Now I've come across an issue...yeah another one.....becusee of the heat of the room with the sun hitting it for a few hours a day, it raises the room temps which in exchange raises my grow tent temps with a knock on effect making my extractor run harder, Now when it fully kicks in to keep the temps in range which it's struggling to do for some reason as it was the best fan in the shop (6inch rhino Thermostatic adjustable extractor), but I've noticed it sucks my tent right in on all 4 sides, ive measured it and worked out im losing more than half a meter from my grow space and my grow space is only 1.2meters x 1.2 x I'm growing in less than half my grow space when temps raise to high, Would this affect the airflow coming in? Rather than it coming in filling the tent with coolish air and then exiting thru the the extractor just tugging away directly at the fresh air? With it being so small i couldn't see if filling the tent correctly? I am considering side support bars to stop it sucking in but the point to this thread is......could this problem be contributing to my heat problems with the growing space going from.1.2 meters squared to say half that? So 600mm of growing space? My head is all over with this I cannot put my finger in enough pies to figure this out as a newbie grower!!! Driving me crazy!!!:mad:
  2. Do you have your intake vents open? You may actually need an intake fan rather than just passive vents.

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  3. Hey man, no I don't as when lights off its light here my timing is 6pm till 12pm the following day so 18 hours on 6 hours off, so I can't leave any vents open to cool it or it'll let light in, real shit situation, I can't move the tent anywhere else, I can't extract air in from anywhere else nor can I vent out anywhere other than the attick which it's already venting to there, I'm trying some frozen bottles in the intake ducting inside to keep things cooler on the inside, if it works then great but I'm just curious to wether the shrinking of my tent could be helping to keep it warmer
  4. If plants don't get enough fresh air, growth is harmed.
    Temps out of whack, and growth is harmed.
    Tent walls getting sucked in means overworking and shortening the life of your fan.
    Damage from light leaks is over rated, and is non-existent with autos.

    Open some bottom tent vents, and cover with dark material if needed.
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  5. These aren't autos these bro there photoperiod so light getting in on a dark period as far as I'm aware is a massive no no...

    As for the tent walls sucking in they all do that with powerful fans but as I said will it make the room hotter with it being half the size adding to the temps rising? If so ill get some side support bars to stop it sucking in, thus in affect should suck more fresh air thru the existing intake ducting which is mounted To my window wufjin directly from outside so fresh air is getting in there
  6. Afew feet of Aluminum ducting should help keep the light out since it's not just an open hole.
  7. Lighting bounces up and down aliuminum ducting lol lit my garden up like a Christmas tree at night because of that so had to improvise and make a vent so it dampened the light coming out of the ducting, so I presume if it can bounce out it'll bounce in won't it? Light I mean?
  8. Sure, if you're shining a flashlight in it. I have a duct that runs down the side of my tent and lays on the floor, no leak. Where there's a will there's a way. You got it!
  9. I really hope so man, it is doable I'm just trying to figure it out without it costing me an arm n a leg to fix, as I say the temps only rise for an hour before lights on and for an hour after when the lights come on, as soon as the sun gets off my room everything runs more than perfect, I just need to fix those few hours of harsh temp rises before I get into bud!! As I want this the best as possible as it's for me and for me only
  10. The ducting us usually pretty cheap, but replacing that negative pressure with fresh air should do wonders for ya.
  11. There already is fresh air mate, it's connected directly to an opening on my window, it's because its hot outside it's potentially sucking warm fresh air from outside whilst the sun is on the window, that's my issue haha
  12. #12 Han-Bolo, Jun 27, 2019
    Last edited: Jun 27, 2019
    So are you saying that this is an issue at night only because you have to close the side vents due to light leakage? Most tents have two holes up top for ducting. Run one as the intake and one for exhaust. Run the intake ducting from the top into the tent. Let the duct hang over the backside towards the bottom where its darker, surround it with some a blanket to stop the light. No need for a fan, the negative pressure should do the rest. This should save the tent from being sucked in so much. If you are already getting fresh air from outside but the tent is still sucking in then is the intake that much smaller than the exhaust or is it restricted? I would not pull in fresh air from outside because its hot and the risk of bugs. Just pull it in from outside the tent. If you have it filtered to stop bugs, that might explain the restriction causing the tent to suck up. Ideally you want the negative pressure to balance out and just keep that tent cycling the fresh air and old air out. Seems like your restricted somewhere.
  13. I see .You said the issue was because the sun was hitting the room, meaning the room is hot, and making your exhaust fan suck in the sides...if the air your putting through it, is hot as balls, there's nothing much you can do but get an ac unit. Opening the intake vent will allow more air in and through it, but if that air is hot, the tent will stay hot.
    • Agree Agree x 1
  14. I would recommend rotating light hours to make them come on after the 2 or 3 hours of extreme temps to minimize the heat for that stretch of time.
    • Agree Agree x 1
  15. agreed, he defintely needs to run his night hours during the hottest time of day. still wont matter if his source of fresh air is restricted and hot. needs more cooler, unrestricted flow to equalize what his exhaust is pulling out.
    • Agree Agree x 2
  16. Well this is my temps right now, out is in the tent, and in is in the bedroom where it all is, i l just got back and my lights off temps was fuckin sky high at nearly 26 degrees c!!!! So I put s frozen bottle of water inside the duct on the inside of the tent to cool air, and moved my vent from my window to just at the side of my bed away from the window and I have managed to drop it to 24c, my fan is set to 21 degrees c now and has been since 12pm this afternoon, I'll turn it back up to 28.5 when lights come on in a couple hours, if I made my intake duct bigger to like 8inch or 10ich would this help to cool the lights off temps? As it's nearly 4pm here now, Would also the side support bars help increase airflow with the space being bigger inside the tent? As when my fan kicks in proper I lose half a meter of growing space in a tent that's only 1.2 meters square, I'm losing my mind!!!

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  17. Open the vents until there is no negative pressure, whatever it takes be it a 8" or 10" vent, then you can pinpoint the difference in temps with and without the negative pressure being the air temp your pulling is the same for both. Without an ac unit, replacing all of the air in the tent several times in a few minutes will be the best you'll be able to get it. While having more room for more air would seem better, it's more about the air temp. Being you have the negative pressure means more fresh air is possible, but then its the factor of more hot air or less hot air....
  18. I still dont understand why the exhaust is out doing the intake so much. What diameter is the exhaust set up? what type of fan are you running? also, what is the diameter of your current intake? Have you tried pulling in air from outside the tent instead of outside yet?
  19. I think bigger intake ducting to 10inch will help pull more fresh air in than it already is, that'll help with the negative pressure being so hard I think, I have just moved the intake end of the vent for the intake away from the window and sat it on a unit at the side of my bed and it has sorta declined to my room temp with is 24 degrees c right now with the help of a frozen bottle of water down the duct on the inside of the tent to cool the air even more, that's the best I can do now until payday tomorrow lol, on my list is get side support bars to stop it sucking in so much, some 10inch ducting for the intake to bring a bigger load of air into the tent, and see where that gets me, If that doesn't work it'll have to be an air cooler or air conditioner which doesn't help my pocket any more :confused_2:
  20. Because the exhaust out and fan is only 6inch, but I was told the fan alone would be overkill for my size tent which was a good thing to have on the side, I have a 6inch exhaust and extractor fan (6inch rhino Thermostatic extractor fan), have 6inch ducting running from my tent to my window to pull in air? So there the same size? Should I increase my intake ducting to 10inch?

    I have just moved my vent that I built to be stealthy and sit to my window and moved it to in the room just aside my bedside unit, that's dropped the temps to the room temp which is 24 degrees c? So it has helped I suppose if I had an air cooler in my bedroom near the tip of the intake would that help? Or should I place it in my tent?

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