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Can Anyone Fill Me In On Pos/neg Pressure Pertaining To Tents?


rockinlespaul
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How do you go about figuring out how much air should be going in and how much should be going out? Can someone explain this postive and negative pressure thing?

 

My room is veg when you walk in, but I also have a large tent that I flower in as well. Well I opened it up last night to turn the lights on and it was 80 degrees and 80% humidity! :blink::o:blink:

 

I have a 6" 400 cfm pulling air out and a 6" 200 cfm blowing in. The 200 cfm is a can fan and it's pretty strong. I understand you don't want the tent to suck itself in and collapse, but is it ok if its the opposite somewhat? Because when they are going, the tent actually blows up a little. :unsure:

 

I usually don't have these two fans going when the tents zipped up and the lights are out. I just use a oscillating fan inside and another stand alone fan to blow air around as well, but now I'm gonna need to vent during darkness.

 

The weather is very challenging....thanks all.

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What kind of reflector do you have on your light? Is it enclosed? If it is I would personally run ducting from an intake hole, through the reflector to the 200cfm fan then out an exhaust. That will help cool things alot, secondly if you run a carbon filter hook the 400 up to that and then exhaust that as well. Most grow tents have long vent flaps along the bottom, open those and use them as a passive intake. that will create a "negative" pressure without collapsing the tent. The reason I put negative pressure in quotes is that the only air coming in is passive, thus meaning any possible air leaks are now intakes and the only air exhausting from the tent has to pass through the carbon filter and out. The lights intake/exhaust effects nothing inside of the tent, its strictly for cooling purposes.

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What kind of reflector do you have on your light? Is it enclosed? If it is I would personally run ducting from an intake hole, through the reflector to the 200cfm fan then out an exhaust. That will help cool things alot, secondly if you run a carbon filter hook the 400 up to that and then exhaust that as well. Most grow tents have long vent flaps along the bottom, open those and use them as a passive intake. that will create a "negative" pressure without collapsing the tent. The reason I put negative pressure in quotes is that the only air coming in is passive, thus meaning any possible air leaks are now intakes and the only air exhausting from the tent has to pass through the carbon filter and out. The lights intake/exhaust effects nothing inside of the tent, its strictly for cooling purposes.

 

 

Oh boy...I don't even know where to start here. :unsure:

 

Nope, the reflector is open, and it's a 1000 watts. The rig is ghetto(for lack of a better word). I do have the bottom vents your talking about though, but I usually keep them closed so I get no light leaks(the rest of the room is on with a 400 watt and T5).

 

The can fan is part of a filter combo I bought but have not gotten to use yet...just the fan, but it IS powerful. Seems more powerful than the 400 cfm fan. The can fan is my intake(just pulling air from the rest of the house and pushing in), and the 400 cfm fan is hanging inside the tent alone pulling the air out and venting it out and under the house.

 

I know I need a enclosed reflector, and like I said the setup is less than desired but these are issues when the lights out. I appreciate your input Jipo. I'd love to get this thing right and appreciate the help big time brother...

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Oh boy...I don't even know where to start here. :unsure:

 

Nope, the reflector is open, and it's a 1000 watts. The rig is ghetto(for lack of a better word). I do have the bottom vents your talking about though, but I usually keep them closed so I get no light leaks(the rest of the room is on with a 400 watt and T5).

 

The can fan is part of a filter combo I bought but have not gotten to use yet...just the fan, but it IS powerful. Seems more powerful than the 400 cfm fan. The can fan is my intake(just pulling air from the rest of the house and pushing in), and the 400 cfm fan is hanging inside the tent alone pulling the air out and venting it out and under the house.

 

I know I need a enclosed reflector, and like I said the setup is less than desired but these are issues when the lights out. I appreciate your input Jipo. I'd love to get this thing right and appreciate the help big time brother...

 

http://www.htgsupply.com/viewproduct.asp?productID=49541

 

Pickup something like that, their pretty cheap and do a lot of cooling. I would never recommend an open reflector on a 1kw :lol: I wouldn't sweat the infamous light leaks unless your in a room with a ton of lights on all the time. Those flaps are so close to the floor, you could put a flange in one of the sleeves that ducts will hook up to, but I would definitely recommend a passive intake, because however much exhaust your pushing out is going to draw more air, and since you're running a filter, its extremely beneficial to have enough power to draw all possible air leaks into the tent. The filter needs to be the exhaust for smell purposes, if anything from inside the tent is getting blow out without passing through the filter then its not really filtering anything. If you reversed the filter/fan as an exhaust and hung the 400cfm as close to the bulb as possible it will pull out alot of heat, but also unfiltered air. With the enclosed hood you could run cool air from outside through it and out of the tent without ever drawing in unfiltered air that passed over your plants.

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http://www.htgsupply.com/viewproduct.asp?productID=49541

 

Pickup something like that, their pretty cheap and do a lot of cooling. I would never recommend an open reflector on a 1kw :lol: I wouldn't sweat the infamous light leaks unless your in a room with a ton of lights on all the time. Those flaps are so close to the floor, you could put a flange in one of the sleeves that ducts will hook up to, but I would definitely recommend a passive intake, because however much exhaust your pushing out is going to draw more air, and since you're running a filter, its extremely beneficial to have enough power to draw all possible air leaks into the tent. The filter needs to be the exhaust for smell purposes, if anything from inside the tent is getting blow out without passing through the filter then its not really filtering anything. If you reversed the filter/fan as an exhaust and hung the 400cfm as close to the bulb as possible it will pull out alot of heat, but also unfiltered air. With the enclosed hood you could run cool air from outside through it and out of the tent without ever drawing in unfiltered air that passed over your plants.

 

Well the open reflector worked great thru the winter. Our heat bills were lower too... :lol:

 

I definetely will get a closed reflector asap. The filter itself has not been used yet, just the fan. I wanted to get everything right first before setting the filter up. It also says the charcoal filtering will not work corectly if the heat is above 80 degrees. Another reason I'm not using it yet.

 

The 400 cfm IS hanging right in front of the light pulling the hot air out. You kinda lost me there at the end. Sorry...but I do appreciate your input! :)

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I still say if theres any possible way you should add a window air to that room then you can control the enviroment im sure we could doctor it up and keep it remained hidden from the old bittys.

 

 

Right on brother.... :lol:

 

I was thinking a stand alone unit, but damz, the power bill is killing me as it is....

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Well the open reflector worked great thru the winter. Our heat bills were lower too... :lol:

 

I definetely will get a closed reflector asap. The filter itself has not been used yet, just the fan. I wanted to get everything right first before setting the filter up. It also says the charcoal filtering will not work corectly if the heat is above 80 degrees. Another reason I'm not using it yet.

 

The 400 cfm IS hanging right in front of the light pulling the hot air out. You kinda lost me there at the end. Sorry...but I do appreciate your input! :)

 

at the end I was just saying if you had a Enclosed reflector you would run the intake to it from outside the tent so it draws air from outside the tent, through the reflector and then out exhausts out of the tent. That way you didn't draw air that stinks like pot from inside your tent through the exhaust.

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at the end I was just saying if you had a Enclosed reflector you would run the intake to it from outside the tent so it draws air from outside the tent, through the reflector and then out exhausts out of the tent. That way you didn't draw air that stinks like pot from inside your tent through the exhaust.

 

Ah...gotcha. That makes total sense to me, lol. :)

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