How powerful of a fan and how many/how large of intake holes would I need if the cab was 24"x18"x35" (9 cubic ceet) and there was a 150w HPS light? Sorry for the noob question, just trying to get it right the first time. I tried searching around and couldn't find what I was looking for or I just suck at finding it. Thanks.
air circulation
- Thread starter BcL
- Start date
This thread should give you a basic understanding for what you need.
“Understanding Air Flow,” by Hoosierdaddy
https://www.icmag.com/ic/showthread.php?t=100823
For a more in-depth discussion, this one is as good as it gets, anywhere!
“Ventilation 101,” by redgreenry
https://www.icmag.com/ic/showthread.php?t=112862
This chart is a good rule of thumb to go by.
Try to go a bit bigger if you can. There may be variables in your particular cab that might translate into slightly higher demands than what the chart shows. The extra margin of error is just a bit of insurance.
hth
“Understanding Air Flow,” by Hoosierdaddy
https://www.icmag.com/ic/showthread.php?t=100823
For a more in-depth discussion, this one is as good as it gets, anywhere!
“Ventilation 101,” by redgreenry
https://www.icmag.com/ic/showthread.php?t=112862
This chart is a good rule of thumb to go by.
Try to go a bit bigger if you can. There may be variables in your particular cab that might translate into slightly higher demands than what the chart shows. The extra margin of error is just a bit of insurance.
hth
This thread should give you a basic understanding for what you need.
“Understanding Air Flow,” by Hoosierdaddy
https://www.icmag.com/ic/showthread.php?t=100823
For a more in-depth discussion, this one is as good as it gets, anywhere!
“Ventilation 101,” by redgreenry
https://www.icmag.com/ic/showthread.php?t=112862
This chart is a good rule of thumb to go by.
Try to go a bit bigger if you can. There may be variables in your particular cab that might translate into slightly higher demands than what the chart shows. The extra margin of error is just a bit of insurance.
hth
Thank you for those links!
I have been looking over those threads and they have helped. I have a few more questions. After reading the ventilation 101 thread, the guy said you want to recycle all the air in your cab once every 5 minutes so you don't stress your plants with one fan and use another fan system for cooling the light, but this is not an option for me and I have seen numerous grow logs on here where people have had their cabs set up with only one fan that they use to bring fresh air in with a passive intake and exhaust their hot air through a carbon scrubber. With doing this, you would need a lot higher CFM's to keep the temperatures down. I read those charts and in order to keep my temps going no higher than 7 degrees above ambient I would need 70 CFM's running. Is this correct? It seems really high for such a small cab. Would this fan work for my cab -- fan
Also, All my air is going to be pulled through a carbon scrubber and then pushed out of the cab. How much resistance does a homemade carbon scrubber normally create, if any at all? Would I need to have the fan running at 100 CFMs so when the air is pulled through the scrubber it is still running at 70 CFMs with the added drag?
I also need to have passive intakes. On the chart it said if your exhaust hole is X big, you need X amount of intake. Say my exhaust is connected to 4" diameter ducting, that means I need four 4 inch PVC pipes because according to that chart. It's four, 4 inch PVCs because that is 2 times the surface area of the exhaust surface area. Is that correct?
I'm sorry for so many questions that seem obvious to you guys, but I am really lost and want to make sure I do this right because I am in a situation where I can't have any smell leaks and I don't want my plants to get fried by too much heat in the cab!
Thanks for reading. Any help would be greatly appreciated.
A closed loop ventilation circuit for the lights and a separate one for the cab makes it easier to control temps, but, it isn't necessary. As far as that particular fan is concerned, axial fans are bad for not being able to overcome static pressure. You might get away with stacking a couple of them, but adding a scrubber will certainly complicate things. I suggest a centrifugal or even a squirrel cage fan rated for about 90-120 CFM. That may seem like overkill, but, things like a scrubber, the area of intake or exhaust, etc. can take a toll on the bare minimum you would otherwise have to work with.
A two to one ratio of intake to exhaust is a good rule of thumb to go by. Or as FreezerBoy puts it, "Three equal sized holes. One for exhaust and two for intakes."
Please, no apologies! None of us knew it before we learned it!
