PC grow case - Negative pressure question - Growroom Designs & Equipment - International Cannagraphic Magazine Forums

Seshwan · 10-30-2017, 12:43 PM

Hi all,

Looking for some advice on negative pressure with regards to a carbon filter.

I am aware that there needs to be negative pressure inside the case in order for the carbon filter to work. It is my understanding that you create this negative pressure by having more exhaust than intake.

My plan was to have 1 intake fan and 2 exhausts however I don't think I can do that due to the proximity of both exhausts not leaving enough space for me to add carbon filters to BOTH of them..

My question is would I still be able to create negative pressure if rather than having 2 separate exhausts in 2 separate spots could I just make my carbon filter and have both the exhausts stacked ontop of each other both pulling air though the same carbon filter?

I do have a fan controller just FYI.

Thanks in advance!

Fuel · 10-30-2017, 12:57 PM

The need of negative pressure in an indoor grow space (no matter the dimensions) is now generally bad understandood. Initially it mean to don't have any air leak FROM the space. Nothing else.

If you push it to the extrem (in thinking that the more negative, the better), your airflow will be too fast and you will create loops of hot air that are never renewed (because less dense that fresh air). The only way to keep an insane negative pressure and to have a decent climate is to split your intake in "airsocks-like" that cover entirely the ground of your space ^^

If you have doubts in what i say, as usual with next gens, just spend time on aerodynamic basis rules. No need to be engineer, and you will learn by the way that the diameter of your intake/outake have to be set together with rules and simple calculations. More that theyr number or anything else.

btw a PC grow case is perfect to learn that, tests cost near nothing and the effects of each ones are very obvious by the little volume of air in the equation.

stay curious and green

Seshwan · 10-30-2017, 01:56 PM

Quote:

Originally Posted by Fuel

The need of negative pressure in an indoor grow space (no matter the dimensions) is now generally bad understandood. Initially it mean to don't have any air leak FROM the space. Nothing else.

If you push it to the extrem (in thinking that the more negative, the better), your airflow will be too fast and you will create loops of hot air that are never renewed (because less dense that fresh air). The only way to keep an insane negative pressure and to have a decent climate is to split your intake in "airsocks-like" that cover entirely the ground of your space ^^

If you have doubts in what i say, as usual with next gens, just spend time on aerodynamic basis rules. No need to be engineer, and you will learn by the way that the diameter of your intake/outake have to be set together with rules and simple calculations. More that theyr number or anything else.

btw a PC grow case is perfect to learn that, tests cost near nothing and the effects of each ones are very obvious by the little volume of air in the equation.

stay curious and green

Appreciate your response and not just giving me the answer so I actually understand it by learning it myself!

I have done some reading and it seems that I will not actually need any intake at all. Passive intake should do the trick. I think I will use two exhaust fans and leave intake passive with a dust filter to stop anything getting sucked in.

Fuel · 10-30-2017, 04:16 PM

Start to calculate first the total volume of the space and the area of your intake and outake to get the maximum "static" air flow rate that will never change. Then regulate it with basic thermodynamic rules. I swear, it's just basic maths that anyone can handle.

Make your fail/win experiences on something rationnal and that you can improve with time. It will make you ready for the day that you can enjoy a bigger space with more power. These rules are universal, your pc case will be dominated by exactly the same laws that the ones of an entire room dedicated.

have fun!

MrBungle · 10-30-2017, 04:36 PM

passive intakes, and good exhaust will do the trick..

You may want to filter or at least screen your intakes to prevent critters or dust... That is only optional of course

also look for light leaks

AvidLerner · 10-30-2017, 04:54 PM

Air pressure is additive. So if you place two fans behind each other you will increase flow by 50% or more. You do not need a fan for intake let air flow passive as was noted and you should be fine with one filter.

Seshwan · 10-30-2017, 05:13 PM

Thanks guys, passive intake with one exhaust fan/filter it is!

I do have 3 or 4 decent PC fans to use and a fan controller so can add more if needed. Also I am building my own LED light using Bridgelux strips so they will be cool as is but im also only running them at 350mA so they will be even more so.

I am so close to getting this built that the suspense killing me! Just need to wait for delivery of a few more bits and then get it all built, I am the type of person that likes to get everything done at once so haven't done anything other than order parts and strip the case so far

10-30-2017, 12:43 PM	#1
Seshwan Newbie Join Date: Sep 2017 Posts: 34	PC grow case - Negative pressure question Hi all, Looking for some advice on negative pressure with regards to a carbon filter. I am aware that there needs to be negative pressure inside the case in order for the carbon filter to work. It is my understanding that you create this negative pressure by having more exhaust than intake. My plan was to have 1 intake fan and 2 exhausts however I don't think I can do that due to the proximity of both exhausts not leaving enough space for me to add carbon filters to BOTH of them.. My question is would I still be able to create negative pressure if rather than having 2 separate exhausts in 2 separate spots could I just make my carbon filter and have both the exhausts stacked ontop of each other both pulling air though the same carbon filter? I do have a fan controller just FYI. Thanks in advance!
	Quote

10-30-2017, 12:57 PM	#2
Fuel Member Join Date: Jul 2009 Location: Moving around Posts: 185	The need of negative pressure in an indoor grow space (no matter the dimensions) is now generally bad understandood. Initially it mean to don't have any air leak FROM the space. Nothing else. If you push it to the extrem (in thinking that the more negative, the better), your airflow will be too fast and you will create loops of hot air that are never renewed (because less dense that fresh air). The only way to keep an insane negative pressure and to have a decent climate is to split your intake in "airsocks-like" that cover entirely the ground of your space ^^ If you have doubts in what i say, as usual with next gens, just spend time on aerodynamic basis rules. No need to be engineer, and you will learn by the way that the diameter of your intake/outake have to be set together with rules and simple calculations. More that theyr number or anything else. btw a PC grow case is perfect to learn that, tests cost near nothing and the effects of each ones are very obvious by the little volume of air in the equation. stay curious and green
	Quote 2 members found this post helpful.

10-30-2017, 04:16 PM	#4
Fuel Member Join Date: Jul 2009 Location: Moving around Posts: 185	Start to calculate first the total volume of the space and the area of your intake and outake to get the maximum "static" air flow rate that will never change. Then regulate it with basic thermodynamic rules. I swear, it's just basic maths that anyone can handle. Make your fail/win experiences on something rationnal and that you can improve with time. It will make you ready for the day that you can enjoy a bigger space with more power. These rules are universal, your pc case will be dominated by exactly the same laws that the ones of an entire room dedicated. have fun!
	Quote 2 members found this post helpful.

10-30-2017, 04:36 PM	#5
MrBungle Senior Member Join Date: Aug 2015 Posts: 1,112	passive intakes, and good exhaust will do the trick.. You may want to filter or at least screen your intakes to prevent critters or dust... That is only optional of course also look for light leaks
	Quote 1 members found this post helpful.

10-30-2017, 04:54 PM	#6
AvidLerner Member Join Date: Apr 2008 Location: Universe Posts: 447	Air pressure is additive. So if you place two fans behind each other you will increase flow by 50% or more. You do not need a fan for intake let air flow passive as was noted and you should be fine with one filter. __________________ I'm just a poor boy, I need no sympathy Because I'm easy come, easy go A little high, little low Anyway the wind blows, doesn't really matter to me, to me.
	Quote 2 members found this post helpful.

10-30-2017, 05:13 PM	#7
Seshwan Newbie Join Date: Sep 2017 Posts: 34	Thanks guys, passive intake with one exhaust fan/filter it is! I do have 3 or 4 decent PC fans to use and a fan controller so can add more if needed. Also I am building my own LED light using Bridgelux strips so they will be cool as is but im also only running them at 350mA so they will be even more so. I am so close to getting this built that the suspense killing me! Just need to wait for delivery of a few more bits and then get it all built, I am the type of person that likes to get everything done at once so haven't done anything other than order parts and strip the case so far
	Quote