Walls of my tent pushing out instead of sucking in

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Rollitupwarrior

Active Member
Hey, so I recently purchased 2 new 4 inch in-line fans to add to my 4x4 tent. I already had one set up for extraction but it was a bit larger and didn’t come with a wall mount so I swapped it for the littler new one with the wall mount. Even though it states they’re the same rpm the smaller one feels a bit weaker.

so the setup currently uses both of the new fans which are the exact same, one for intake and one for outtake. 2 fans on the canopy and a small fan on the floor of the tent. I noticed that when I swapped out the larger extraction fan for the small one the walls of the tent started to push out instead of sucking in.
Is it recommended to run a larger extraction fan than the intake fan so that this doesn’t happen or is it nothing to worry about?
I was thinking it could possibly be from the other 3 fans inside the tent too?
 
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Rollitupwarrior

Active Member
I grabbed a leaf and put that near the ducting and it was pulling into the fan so it’s the right way around. Should I return the old larger fan as the outtake? The walls were neither sucking in or pushing out when using that one for extraction along with one of the new ones for intake
 
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Rollitupwarrior

Active Member
I chucked the larger fan up to test it and it’s much better, slightly sucking now. The only reason I’m not running passive intake is because I’m in flower and the light is off when it’s sunny outside. Just worried about light leaks as I found 1 seed in my whole last harvest lol.
 
T macc

T macc

Well-Known Member
Sounds like you added those silver booster fans. They can't handle static pressure
 
HydroKid239

HydroKid239

Well-Known Member
Rollitupwarrior said:
I chucked the larger fan up to test it and it’s much better, slightly sucking now. The only reason I’m not running passive intake is because I’m in flower and the light is off when it’s sunny outside. Just worried about light leaks as I found 1 seed in my whole last harvest lol.
Click to expand...
Run a clean vacuum hose thru one of the small ports for passive intake without the worry of light leaks.
I set this up the other day.. I gotta find my fan controller so I can put some power to it.
 

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HydroKid239

HydroKid239

Well-Known Member
If you don't want to hook a fan up just put a women's nylon stocking over the hose and use a rubber band to hold it on as a filter, and curl the hose behind the tent. Stretch the port closures over the hose on both ends spreading out and light that may leak into the hose. Good to go. I'm doing it just to fight too much negative pressure. My girls are touching on 3 sides, and I have a heater in there. I may have to do some remodeling.
 
R

Rollitupwarrior

Active Member
HydroKid239 said:
If you don't want to hook a fan up just put a women's nylon stocking over the hose and use a rubber band to hold it on as a filter, and curl the hose behind the tent. Stretch the port closures over the hose on both ends spreading out and light that may leak into the hose. Good to go. I'm doing it just to fight too much negative pressure. My girls are touching on 3 sides, and I have a heater in there. I may have to do some remodeling.
Click to expand...
It looks very similar to my setup just without the vacuum hose. I like the idea, I’ll give it a shot, thanks!
 
K

Kdotwash

Member
When in a tent, I like using the natural negative pressure that is present with an exhaust fan, intake air passes through an acceptable filter for particulates the enters tent and is ultimately sucked out of tent by the single exhaust fan
 
Star Dog

Star Dog

Well-Known Member
If you are using a active inlet then the outlet isn't pulling enough air, active cooling is a right pain trying to match the inlet to the outlet, I added ducting then put a mesh over it to slow the inlet air flow for negative pressure.
 
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guitarguy10

Well-Known Member
HydroKid239 said:
If you don't want to hook a fan up just put a women's nylon stocking over the hose and use a rubber band to hold it on as a filter, and curl the hose behind the tent. Stretch the port closures over the hose on both ends spreading out and light that may leak into the hose. Good to go. I'm doing it just to fight too much negative pressure. My girls are touching on 3 sides, and I have a heater in there. I may have to do some remodeling.
Click to expand...
This is what i did:
http://imgur.com/a/NO9zc0X

Only difference is that there is a pair of nylons covering it to act as a sort of pre-filter (basically what you suggested). Took a pizza box, duct tape, a 6" toilet flange and a furnace filter cut up.

Anyways to add to this discussion, I don't know much about air flow mechanics but I do know that when I put a 4" inline fan in there to act as an active intake, with a 6" inline exhaust (and it's a sealed hood that has it's own dedicated fan to draw air through) the temperatures were HIGHER then when I just left intake to be passive. I don't know why but i repeated it multiple times and when there is an active fan intaking air the temp goes up, when it's passive and with one of those filters it is cooler, like upwards of 5F cooler.

Also positive air pressure isn't necessarily a bad thing. It will keep out mould and fungal particles so long as the air being intaken is clean. That's how the scientists who work with bio weapons and hazmat works, if you look at them their suits are filled with air, that way nothing can get in if its being actively pushed out.
 
Star Dog

Star Dog

Well-Known Member
That's an interesting conundrum cooler when it's passive?
I've got a few fans kicking around but don't find it necessary to install another one, I actually prefer the inlet getting split between the two sides.
 
G

guitarguy10

Well-Known Member
Star Dog said:
That's an interesting conundrum cooler when it's passive?
I've got a few fans kicking around but don't find it necessary to install another one, I actually prefer the inlet getting split between the two sides.
Click to expand...
Yeah trust me I'm still scratching my head, but I have an arduino microcontroller that actively monitors and records the temp/humitidy and plots them for me and I can watch in real time as the temps go up when I turn on the 4" intake and then go back down when I turn it off or remove it.

I have 2 small oscillating fans inside but those are just to move the air around.

I have 2 of those filter thingies, the exhaust fan pulls like 270CFM and my tent is only 2'x4'x'5' (so 30cuft) so it's sucked in hard negative pressure and I only had 2 holes left that I could open for intake.

In any event this 4" fan I had purchased is now just sitting on a shelf. That's ok though I guess cuz my room already sounds like a jetway with that 270CFM exhaust and a 6" AC Infinity (like 400CFM) connected to my sealed hood and drawing air over the bulb and then out of the tent (and outside).
 
Wastei

Wastei

Well-Known Member
Higher exhaust than intake. Problem solved? Positive pressure will not work to combat smell from flowering Cannabis plants.
 
Kalebaiden

Kalebaiden

Well-Known Member
I just did a 151 day run on positive pressure (bulging tent) and the plants were good. I really should have had negative pressure but was too lazy to turn the inline fan around.

If your pressure isn't blowing out your zippers and seams, you should be fine.

If you're seeing light leaks through the zippers, then you may want to flip your fans around.
 
HydroKid239

HydroKid239

Well-Known Member
guitarguy10 said:
This is what i did:
http://imgur.com/a/NO9zc0X

Only difference is that there is a pair of nylons covering it to act as a sort of pre-filter (basically what you suggested). Took a pizza box, duct tape, a 6" toilet flange and a furnace filter cut up.

Anyways to add to this discussion, I don't know much about air flow mechanics but I do know that when I put a 4" inline fan in there to act as an active intake, with a 6" inline exhaust (and it's a sealed hood that has it's own dedicated fan to draw air through) the temperatures were HIGHER then when I just left intake to be passive. I don't know why but i repeated it multiple times and when there is an active fan intaking air the temp goes up, when it's passive and with one of those filters it is cooler, like upwards of 5F cooler.

Also positive air pressure isn't necessarily a bad thing. It will keep out mould and fungal particles so long as the air being intaken is clean. That's how the scientists who work with bio weapons and hazmat works, if you look at them their suits are filled with air, that way nothing can get in if its being actively pushed out.
Click to expand...
That could mean it's warm outside the tent as well. Pulling in hot air won't help temps much. Only air flow.
 
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