***My cab design*** question about ventilation

[purpbythepound]

Well this will be my first grow and i've got everything figured out here besides my ventilation..i tried to do my best to give everyone here a visual so i could get some responses and be on my way to constructing my cab..so i've tried to show my cab using paint..................
sorry for the small text in the picture by the way
but anyways..this is what i was thinkin of doin as far as ventilation goes..i was thinkin about using pc fans rated at 110 cfm for my intakes and exhaust..ambient temps are 71-73F..do you guys think this will do the job and keep my cab cool?? or maybe its a little over kill?? let me hear some opinions from my fellow growers thanks all
~pbtp~

 

[green_grow]

lights in a box create a lot of heat, so i doubt that your pc fans will be even close to overkill. if anything, you may want more intake, but you can fine-tune that after you have everything plugged in and running.

 

[Cozy Amnesia]

I'd say get another fan in there to blow the plants around. The plants need air movement to displace the co2, which is excreted from under the leaves, with fresh oxygen. Another reason is that wind blows the stem around slightly which strengthens and and thickens the stems over time. You might also want more intake.

You have to remember that these plants have been growing in mother nature for thousands of years, they're not used to growing in wooden boxes with artificial lights and won't thrive if you don't replicate their natural environment well.

 

[purpbythepound]

thanks for the replies..amnesia i'll have a small circulating fan hangin around the canopy blowing down at the plants in the flower chamber..didn't really know how to illustrate that into the picture though ha..good lookin out bro

so more intake huh??what ya think maybe 1 or 2 more passive intakes in the clone chamber??or would these be better placed on the back wall of my flower chamber on the bottom left side giving me better exchange of oxygen right to the flower chamber??

 

[purpbythepound]

noone have any advice as to how i should go about adding more intake?? i was planning to start constructing this weekend so if anyoone has any suggestions as to where i should add more intake then that would set me off to work thanks alot
~pbtp~

 

[hoosierdaddy]

If you think you need about six 2" pipe 90's for intakes...mount up 12 and you will be closer to right. You cannot allow too much air in, but you can sure keep enough out by cheating yourself on intake.

Biggest first mistake made by most.
Give the thing the proper amount of air, or you will fight all sorts of other problems until you do.

Also, you are trying to separate CFL's with plexiglass. Not a good idea. The plastic will kill your light power. You need to get those CFL's in a way that you can vary the height as the plants grow. You can get CFL's within a couple inches of leaves.

 

[purpbythepound]

so hosierdaddy..you say that i need quite a bit of intake in this situation..how do you think i should place these....maybe like this??


3 passive intakes with 90 degree elbows in the mother/ clone chamber and 5 passive intakes with 90 degree elbows in the flower chamber each intake measuring 2"....also i will be raising all the plants to the lights and as they grow,lower them down graually as to always keep the tops a few inches away from the cfls...i will only have the plexishield in the flower chamber and it will stay right beneath the cfls and will serve as a split inbetween the light chamber and the flowering area..this will keep the light chamber nice and ventilated while exhausting the heat from the bulbs straight to the outside.which will lead to keeping the flowering area temps down quite a bit

 

[hoosierdaddy]

I have 12 2" intakes to my veg chamber. The air going through there is also cooling the AC unit, so I could maybe use another couple.

My flower chamber has 8 2" intakes, 5 wasn't near enough and temps would creep up. With the 3 additional the hottest place in the chamber up high is seeing 82degF tops with 86deg ambient. Before additional air, it was hitting mid 90's no matter the ambient temp.

Run as many holes as you can get across the back of the unit. If you need more, start another row.

I'd can the plexiglass. Or maybe do a search and see all the other CFL/plexiglass set-ups so you can compare. (shrug)

*EDIT:
OK, lets look at this with more depth since your thread is specifically about your air flow.
It is fairly well accepted as cab building practice to have double the size of intake as your exhaust.

Let's assume you are using a 6" fan for exhausting...
a 6" fan has about 28.3 sq in of flow area.
A 2" pipe has a total air flow area of 3.14 sq in.
28.3"/3.14"= 9.01"

So, if we accept the concept of twice the exhaust as intake, you would need 18 of the 2" pipe 90's to account for the air flow of one 6" fan (or passive orifice).
Which tells me I need more holes in my flower chamber!

Btw...I don't buy into the full double sized intake thing. It doesn't fit with physics as I know them. But it is a good practice and will not steer you wrong.
But even if you were trying to simply match orifice for orifice, you would need 9 of the pipe 90's.

(just FYI...to figure the air flow area of a pipe: radius x radius x 3.141(Pi)= sq in.)

 

[purpbythepound]

hoosier..thanks man..really informative about the air flow formula!!thanks..
as far as temps go im thinkin i should have them under control with my light chamber being exhausted and some good cirulation of air through my clone and flower chamber..so i think i'll start by having lets say 4 passive in my clone chamber and 6-8 passive in my flower chamber..i'll start with these numbers and can always add more if i see that they are needed..thanks for your help hosier..would give rep but dont have high enough post count yet