Tent Walls Squashing Crop Under Negative Pressure

slinkysaurus

slinkysaurus

Well-Known Member
I posted this in another thread under another question, but I thought it might be handy to have a post about this question only, as after a search I couldn't come up with anything.

Title says it all. My tent walls are squashing my plants under negative pressure. Not just a wee bit either. I'm losing about .25m+ of space either side when the the tent's in negative state. That's more than a 1m area lost in my 1.5mx1.5mx2.0m space. That's less yield right there....
Who else had this problem?
 
Flaming Pie

Flaming Pie

Well-Known Member
I have this problem as well. I added extra circulation fans and usually trim back growth that is pressed against the sides.

I wish there was a simple and cheap solution to this problem.

Reducing fan speed is NOT the solution. This deprives a full tent of its appropriate fresh air exchange and can allow temps/humidity to sky raise.
 
GrowinDad

GrowinDad

Well-Known Member
Increase intake should be the simple fix... If you have a huge fan for a small spae, then decreasing outake as well. Yeah, like deadgro said!
 
Flaming Pie

Flaming Pie

Well-Known Member
old shol4evr said:
try taking 1x2 wood ,cut to length of walls ,drill hole in the ends and take a zip tie,zip tie to corner post in the middle of walls.this is what i do i also hang my clip on lights on them,they keep walls from coming in .hope this helps
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Yeah I was just reading a similar solution, but with pvc pipe, drilled holes in end and ziptie right above tent middle. It could easily work. Maybe a spring clip rigged to a pvc pipe would be good.
 
Mr.Goodtimes

Mr.Goodtimes

Well-Known Member
I added an active intake fan to solve this, with a speed controller so I could turn it to the point where the tent barely starts to suck in. Helped my temps a great deal too.
 
WattSaver

WattSaver

Well-Known Member
Increase your intake size, more square inches. Then you'll be able to decrease your fan speed, and have better overall environmental control.
 
WeedFreak78

WeedFreak78

Well-Known Member
slinkysaurus said:
Then my temps and humidity go awry.....
Click to expand...
Flaming Pie said:
I wish there was a simple and cheap solution to this problem.
Reducing fan speed is NOT the solution. This deprives a full tent of its appropriate fresh air exchange and can allow temps/humidity to sky raise.
Click to expand...
If you have extreme negative pressure in your tent that means your fan is overpowering your intake..slowing down the fan to a speed that matches, or just slightly exceeds, your intake volume will still give you the same amount of air exchange. If that isn't enough air to control your temps and humidity, you will need to increase the intake size. There are charts out there showing how much CFM a certain size square or round hole will flow, I know a 12"x12" open square flows appx. 200cfm as a passive intake. Match your intake size to your ventilation needs and the neg. pressure issues will disappear, along with gaining better control of temps/humidity.
 
Southerner

Southerner

Well-Known Member
Flaming Pie said:
I have this problem as well. I added extra circulation fans and usually trim back growth that is pressed against the sides.

I wish there was a simple and cheap solution to this problem.

Reducing fan speed is NOT the solution. This deprives a full tent of its appropriate fresh air exchange and can allow temps/humidity to sky raise.
Click to expand...

If your fan is running high enough to literally cause the tent to crush in on it self then there's no question that it is running too high. As long as there's negative pressure it should be plenty of "air exchange".

Yes, it as simple as slowing said fan down and/or increasing the passive intake.
 
slinkysaurus

slinkysaurus

Well-Known Member
Thanks for your replies! All duly noted and added to my never ending learning curve!
Easiest and most fun fix ever... got a bigger tent and a 6'' powered inline, dehumidifier etc etc..feels like christmas! =]

P.s my fan was over engineered from the start as I didn't want to have to get a new one when i went bigger! It's the biggest 6'' Rhino would do
 
Doer

Doer

Well-Known Member
slinkysaurus said:
Then my temps and humidity go awry.....
Click to expand...
I had this and I simply created 1/4" x 2" wide braces that went behind the up-right tubes at each end of the tent wall you need to hold back. 4 walls, 4 horizontal braces at 1/2 way up the wall.
 
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Doer

Doer

Well-Known Member
Southerner said:
If your fan is running high enough to literally cause the tent to crush in on it self then there's no question that it is running too high. As long as there's negative pressure it should be plenty of "air exchange".

Yes, it as simple as slowing said fan down and/or increasing the passive intake.
Click to expand...
Not in every case. In a small tent, 32x32x60 I had a 177 cfm exhaust, full blast to keep the temperature correct. I had to pull in cold fog at that rate to keep the humidity up for Veg.
 
Doer

Doer

Well-Known Member
Flaming Pie said:
I have this problem as well. I added extra circulation fans and usually trim back growth that is pressed against the sides.

I wish there was a simple and cheap solution to this problem.

Reducing fan speed is NOT the solution. This deprives a full tent of its appropriate fresh air exchange and can allow temps/humidity to sky raise.
Click to expand...
There is. Add wood slat braces to hold the wall back.
 
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