I think I did a thing...... VENTILATION

MR.NICE.GUY.1990

MR.NICE.GUY.1990

Well-Known Member
So, I'm still pretty new to this whole perfecting you indoor grow environment, thing I'm trying to nail, and my specific problem pretains to proper ventilation. I'm on the right track, but I think I over did it with the inline fans. I have 2, 745 cfm fans in a 5×5×8. When I have them both running, i get major positive pressure and my tent balloons out like ot just cheated on its diet. Then, I remembered something about negative pressure being what you want, so I unplugged the fan pulling air in, and left the fan pulling air out plugged in. I've achieved negative pressure, but now it looks as if my tent is going to suck into itself and enter an alternative dimension. My question is this, do ineed all this or am I over doing it. Thanks a million for any help and for getting me on ze right track, in advance. rollitup
 

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macsnax

macsnax

Well-Known Member
Use one of them to suck air out the top, and use a 1-200 cfm booster for intake down low. You don't need to add that much air. Air exchange is what's important, you want to replace the air in there at least a couple times an hour. If heat is a problem try to pull air from next to a window or cold floor.
 
thumper60

thumper60

Well-Known Member
MR.NICE.GUY.1990 said:
So, I'm still pretty new to this whole perfecting you indoor grow environment, thing I'm trying to nail, and my specific problem pretains to proper ventilation. I'm on the right track, but I think I over did it with the inline fans. I have 2, 745 cfm fans in a 5×5×8. When I have them both running, i get major positive pressure and my tent balloons out like ot just cheated on its diet. Then, I remembered something about negative pressure being what you want, so I unplugged the fan pulling air in, and left the fan pulling air out plugged in. I've achieved negative pressure, but now it looks as if my tent is going to suck into itself and enter an alternative dimension. My question is this, do ineed all this or am I over doing it. Thanks a million for any help and for getting me on ze right track, in advance. rollitup
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get speed control on those fans turn down to perfect
 
Old Thcool

Old Thcool

Well-Known Member
I’m finding that a fan that will do a complete air exchange in 4 minutes or less is about the right size. 5.5.8 is 200 cf so shoot for 50 feet a minute to start. If you have an ink bird controller you can set it to run either temp or humidity, I use mine to vent when the humidity hits 60 and stop venting at 50. It takes a while to build up to 60 again and begin venting. If it takes too long I close the gap a bit until I get venting at least every 15 minutes or so. I suspect in the summer I will run a second in-line fan to vent heat in a similar fashion.
 
Roger A. Shrubber

Roger A. Shrubber

Well-Known Member
people will tell you you need an expensive variac.....i've used one of these for four years....works perfect...i leave it set to about 20%, flip it on full when the lights come on, flip it to variable when they go off, works like a charm.
this is for fans that have brush motors, you may need a variac if you have a fan with a brushless motor, but those are typically very expensive, and come with built in controllers for the most part

https://www.amazon.com/Yescom-Variable-Controller-Settings-Hydroponics/dp/B00U3LD1WA/ref=sr_1_1_sspa?ie=UTF8&qid=1548260811&sr=8-1-spons&keywords=router+speed+controller&psc=1

just open your bottom vents a little, turn your fan on, and dial it up till you start getting a little negative pressure, then leave it there. i leave mine running full for an hour or so after the lights go off, to prevent a big RH spike, then i turn it down to about 20%, kick it back up to full when the lights come back on.
 
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Juiceifer

Juiceifer

Well-Known Member
If you have a carbon filter that is resistance also the extra ducting to go from the top of the tent to the fan at the bottom is resistance that lowers your cfms on the exhaust say idk 20% (just spitballing a number) so that would give you 596 cfms on exhaust but 730ish on your intake. exhaust only needs to be slightly higher to achieve neg pressure to suck out smells and heat you could raise the fan to reduce ducting. you want as short a line as you can get but on the other side perhaps add ducting to increase resistance or maybe another carbon filter serve two fold clean your incoming air and would about equalize the pressure making it easy to go from there
 
curious2garden

curious2garden

Well-Known Mod
Staff member
MR.NICE.GUY.1990 said:
So, I'm still pretty new to this whole perfecting you indoor grow environment, thing I'm trying to nail, and my specific problem pretains to proper ventilation. I'm on the right track, but I think I over did it with the inline fans. I have 2, 745 cfm fans in a 5×5×8. When I have them both running, i get major positive pressure and my tent balloons out like ot just cheated on its diet. Then, I remembered something about negative pressure being what you want, so I unplugged the fan pulling air in, and left the fan pulling air out plugged in. I've achieved negative pressure, but now it looks as if my tent is going to suck into itself and enter an alternative dimension. My question is this, do ineed all this or am I over doing it. Thanks a million for any help and for getting me on ze right track, in advance. rollitup
Click to expand...
You're probably going to want to put a Carbon filter at the end of that run. That will slow down your exhaust some depending on the carbon filter.

This is a good article on ventilation: https://www.growweedeasy.com/exhaust
 
MR.NICE.GUY.1990

MR.NICE.GUY.1990

Well-Known Member
curious2garden said:
You're probably going to want to put a Carbon filter at the end of that run. That will slow down your exhaust some depending on the carbon filter.

This is a good article on ventilation: https://www.growweedeasy.com/exhaust
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Thanks for the article it really put concept of ventilation into an understandable perspective for me. Ill have speed dialers in by tomorrow, as well as my carbon filter. Im hoping slowing it down will help with my heat issue.
 
MR.NICE.GUY.1990

MR.NICE.GUY.1990

Well-Known Member
So the way its setup right now is a passive setup, with only one fan pulling air out. Should I add an 8" booster fan on the opposite side to create an active airflow, or is that unnecessary? I'm already having heat issues, the only light running is a t5 florescent. My humidity is hanging around at 45%, which I believe is ok especially for veg. but my temp is 68°f. I know by turning down the fan it should help with the heat, but I dont need to run them constantly correct? If I get an enviroment controller, can't I set it up to only kick on when the temp and humidity exceed a certain level. I'm in Michigan and it's cold. Were hitting low teens outside, and we dont turn the household temp past 68° degrees here.
 
curious2garden

curious2garden

Well-Known Mod
Staff member
MR.NICE.GUY.1990 said:
So the way its setup right now is a passive setup, with only one fan pulling air out. Should I add an 8" booster fan on the opposite side to create an active airflow, or is that unnecessary? I'm already having heat issues, the only light running is a t5 florescent. My humidity is hanging around at 45%, which I believe is ok especially for veg. but my temp is 68°f. I know by turning down the fan it should help with the heat, but I dont need to run them constantly correct? If I get an enviroment controller, can't I set it up to only kick on when the temp and humidity exceed a certain level. I'm in Michigan and it's cold. Were hitting low teens outside, and we dont turn the household temp past 68° degrees here.
Click to expand...
I would look at that solution. I'm in the Mojave desert so my issue is more heat than cold.
 
Renfro

Renfro

Well-Known Member
Grab a nice autopilot digital environmental controller (APCETHD) or greenhouse master controller (APCECOTH) if you currently use or intend to add CO2. Mine lets me set a day and a night temp and humidity. You can set them up so they both activate the same blower when it's too hot or too humid. It's very versatile, reliable and you won't regret the investment.
 
Old Thcool

Old Thcool

Well-Known Member
Here’s a cheap one I use. It can add heat or vent heat with either an exhaust fan or a heater on work 1 and at the same time on work 2 monitor the RH and either vent humidity or kick on a humidifier and kick it off at a set level. The instructions suck and the illuminated numbers / letters are pretty basic. The movement around the menu takes some messing with but once you figure it out it’s good. It works as advertised.
 

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Skeeter4200

Skeeter4200

Active Member
MR.NICE.GUY.1990 said:
So, I'm still pretty new to this whole perfecting you indoor grow environment, thing I'm trying to nail, and my specific problem pretains to proper ventilation. I'm on the right track, but I think I over did it with the inline fans. I have 2, 745 cfm fans in a 5×5×8. When I have them both running, i get major positive pressure and my tent balloons out like ot just cheated on its diet. Then, I remembered something about negative pressure being what you want, so I unplugged the fan pulling air in, and left the fan pulling air out plugged in. I've achieved negative pressure, but now it looks as if my tent is going to suck into itself and enter an alternative dimension. My question is this, do ineed all this or am I over doing it. Thanks a million for any help and for getting me on ze right track, in advance. rollitup
Click to expand...
I only use 1 fan of that size in a 55x55x76 & open the vents on tent with a fresh air intake
 
curious2garden

curious2garden

Well-Known Mod
Staff member
Old Thcool said:
Here’s a cheap one I use. It can add heat or vent heat with either an exhaust fan or a heater on work 1 and at the same time on work 2 monitor the RH and either vent humidity or kick on a humidifier and kick it off at a set level. The instructions suck and the illuminated numbers / letters are pretty basic. The movement around the menu takes some messing with but once you figure it out it’s good. It works as advertised.
Click to expand...
Hey, how are those drowning seedlings, on your first grow, under that advanced controller faring?
 
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