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NEED HELP WITH POSITIVE/negative pressure in grow tents.

  • Thread starter Thread starter danielbmk97
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NEED HELP WITH POSITIVE/negative pressure in grow tents.

danielbmk97 17 Replies 4,188 Views
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danielbmk97

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#1
hey guys. I have two 4x4 grow tents with one 6” inline fans exhausting outside thru window. Each tent also has a fan on the inside of tent to move air around but there is no real “intake as rest of tent is sealed up. Exhaust comes on when temp hits 75f. Issues is the tent is sucking in hard. And I have seen mixed reviews about weather this is good or bad. Just trying to get some expert advice. (I understand it has negative pressure and why but not sure if this is ok. Every other forum I read says it should be positive pressure the other half say it should be .PLEASE HELP!
 

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#2
I don't have rigorous science to back this up, but I don't want my fans fighting for air. They'll wear out faster. I run 6" fans in my 4x4s, and have enough vents open to provide fresh air to pull in. I make baffles out of ducting or cardboard so light doesn't leak into my intake vents.
 
#3
ArtfulCodger said:
I don't have rigorous science to back this up, but I don't want my fans fighting for air. They'll wear out faster. I run 6" fans in my 4x4s, and have enough vents open to provide fresh air to pull in. I make baffles out of ducting or cardboard so light doesn't leak into my intake vents.
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So your 6” fan is your exhaust?
 
#4
I leave at least 1 bottom vent open for air flow but don’t worry about pressure to much. You can easily make extra support poles to hold the sides of the tent out if they are crowding your plants. I use emt electrical conduit but anything will work. The main reason I replied was to suggest you get a longer extension cord. Having it hanging like that it's likely to come unplugged.
 
#6
orggrwr said:
I leave at least 1 bottom vent open for air flow but don’t worry about pressure to much. You can easily make extra support poles to hold the sides of the tent out if they are crowding your plants. I use emt electrical conduit but anything will work. The main reason I replied was to suggest you get a longer extension cord. Having it hanging like that it's likely to come unplugged.
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Thanks for the advice. And yes. I really need longer cords and more plugs with grounds. It’s just a pain in the butt having so many things plugged in at once. Hard to route everything where I want/need without adding more extensions or plugs.
 
#7
ArtfulCodger said:
Yes. Smaller fans inside the tent to create airflow, but the main exhaust in both of my 4x4s is an ACI 6" fan.
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Thank u.! Do u exhaust outside. I just kinda went over board on this set up and can’t really move exhaust very easily. Hoping it’ll stay warm enough In winter!
 
#8
danielbmk97 said:
hey guys. I have two 4x4 grow tents with one 6” inline fans exhausting outside thru window. Each tent also has a fan on the inside of tent to move air around but there is no real “intake as rest of tent is sealed up. Exhaust comes on when temp hits 75f. Issues is the tent is sucking in hard. And I have seen mixed reviews about weather this is good or bad. Just trying to get some expert advice. (I understand it has negative pressure and why but not sure if this is ok. Every other forum I read says it should be positive pressure the other half say it should be .PLEASE HELP!
Click to expand...
Passive intake on the bottom, active exhaust fan on top. The rest sealed well and there you go, negative pressure
 
#9
There are no pro's or con's to negative or positive air pressure in your grow environment as far as the plants are concerned. I keep the back vent panel open and one lower power cord port open. Set my exhaust fan controller to 80f. When the inside tent temp hits 80f exhaust fan turns on and turns off at 79f. Have max speed setting at 6 right now. With three 6" fans circing air in the tent. Just need enough fresh air in the tent to control temps and keep standard levels of CO2 in the tent environment for the plants. If the fans running it's sucking humidity out. I use Gorilla tents and they have what they call a Hi CFM Kit which are side bars that snap on to the vertical tent poles. I always get the Hi CFM Kit when I buy a tent. Not for High CFM but net mounting. I run ACI 6" exhaust fans with my 2 x 4 and 3 x 3. Will be getting a new Gorilla 4 x 4 this winter and will use a ACI 8" with that tent as I retire the bastard sized 3 x 3.
Setup
 
#10
Blastfact said:
There are no pro's or con's to negative or positive air pressure in your grow environment as far as the plants are concerned. I keep the back vent panel open and one lower power cord port open. Set my exhaust fan controller to 80f. When the inside tent temp hits 80f exhaust fan turns on and turns off at 79f. Have max speed setting at 6 right now. With three 6" fans circing air in the tent. Just need enough fresh air in the tent to control temps and keep standard levels of CO2 in the tent environment for the plants. If the fans running it's sucking humidity out. I use Gorilla tents and they have what they call a Hi CFM Kit which are side bars that snap on to the vertical tent poles. I always get the Hi CFM Kit when I buy a tent. Not for High CFM but net mounting. I run ACI 6" exhaust fans with my 2 x 4 and 3 x 3. Will be getting a new Gorilla 4 x 4 this winter and will use a ACI 8" with that tent as I retire the bastard sized 3 x 3.
View attachment 2272180
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sounds good man! I’ll keep this in mind for sure. I am a little concerned setting my fan to come on at that temp just because I live in Maine and it’s pretty cold here. If I set it to come on at 80 some days it may never come on so I stuck with 75. With that being said. I will try opening a vent or two and keep exhaust where it is. Just hoping to give plants every possible route for succes
 
#11
danielbmk97 said:
sounds good man! I’ll keep this in mind for sure. I am a little concerned setting my fan to come on at that temp just because I live in Maine and it’s pretty cold here. If I set it to come on at 80 some days it may never come on so I stuck with 75. With that being said. I will try opening a vent or two and keep exhaust where it is. Just hoping to give plants every possible route for succes
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It's rare I run into your problem here in Okiehoma with temps too cool for the grow come winter. And I don't vent outside. Don't even use carbon filters anymore. What I do in the winter is block off the heat/ac register in my office and use the lights in the tents to heat with. Having powerful lights I can turn them down in the summer and lower them close to the plants. Come winter I raise the lights high in the tents and crank them up. So the lights are a active part of my environment control and can still do as I wish concerning PAR / lighting levels.
 
#12
danielbmk97 said:
hey guys. I have two 4x4 grow tents with one 6” inline fans exhausting outside thru window. Each tent also has a fan on the inside of tent to move air around but there is no real “intake as rest of tent is sealed up. Exhaust comes on when temp hits 75f. Issues is the tent is sucking in hard. And I have seen mixed reviews about weather this is good or bad. Just trying to get some expert advice. (I understand it has negative pressure and why but not sure if this is ok. Every other forum I read says it should be positive pressure the other half say it should be .PLEASE HELP!
Click to expand...
Two fans two seperate ducts out. It’s the only way to make it work correctly.
 
#14
I just changed my setup, so I have one 6” exhaust fan blowing air outside of window when temps hit 75 in tent. Than I have two small fans inside tent to bow air around and also suck air inside tent as I opened on bottom vent. I am in a spare bedroom with window all sealed from light so not really worried about light leaks
 
#15
I stopped venting outside and worrying about light leaks decades ago.

IMG 7304
 
#16
danielbmk97 said:
Thank u.! Do u exhaust outside. I just kinda went over board on this set up and can’t really move exhaust very easily. Hoping it’ll stay warm enough In winter!
Click to expand...
I don't exhaust to the outdoors.
 
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