Tutorial Ventilation 101

[GrüneErd]

hey red, why is it do you think that i can't even cool 300w of CFL's in a 2.5'Lx4'Wx8'H closet with the door open and a 340cfm panasonic whisper for exhaust (and sometimes a stanley blower for intake as well as the door open)?
i know ventilation and cooling lights are different, but man, i've tried everything. i have a 400w with a hood and everything, that just gets WAY too hot to the point that it's ridiculous, so i've NEVER used it.
i've never understood how to cool these lights and as a result can't get big buds, though i've had many harvests, they're just small.
i see people using MORE than my 400w's in the same size with no problems. i just would like to do that as well.
any help from ANYONE would be great.
peace

 

[moses224]

man running cfls all you need is a 8" floor fan from hd or lowes...it will kewl the closet for sure. I kewl 3000w with one bringing ac air from living room

 

[Blizztech420]

hmm to sound like a nub...would you by any chance know how to rig a computer fan to run off a computer power supply..i remember a while ago i found a thread that told ya how i just cant find it , so i though i would ask in this thread, stonerpride

 

[guest 77721]

hey red, why is it do you think that i can't even cool 300w of CFL's in a 2.5'Lx4'Wx8'H closet with the door open and a 340cfm panasonic whisper for exhaust (and sometimes a stanley blower for intake as well as the door open)?
i know ventilation and cooling lights are different, but man, i've tried everything. i have a 400w with a hood and everything, that just gets WAY too hot to the point that it's ridiculous, so i've NEVER used it.
i've never understood how to cool these lights and as a result can't get big buds, though i've had many harvests, they're just small.
i see people using MORE than my 400w's in the same size with no problems. i just would like to do that as well.
any help from ANYONE would be great.
peace

Using the chart, you need 100-110 CFM to cool either the 300W of CFL or the 400 W HPS. There must be something really blocking your airflow from the fans closet. Are you running the air into a scrubber?

Some pics of your closet would help.

 

[moses224]

just use power supply from old computer it has plug and everything for both wall and fans.....been years since i used anything that small but know it works

 

[guest 77721]

hmm to sound like a nub...would you by any chance know how to rig a computer fan to run off a computer power supply..i remember a while ago i found a thread that told ya how i just cant find it , so i though i would ask in this thread, stonerpride

Connect the fan to Yellow +12V and one of the Blacks which is Ground. If the fan doesn't run or runs reverse, then swap the leads.

The red wire is +5V and can be used for running the fan at a lower speed.

 

[Old MacDonald]

Lovin the info on here! Makes the mad scientist go cuckoo for co-co nugs!

 

[808kahumai]

Redgreenry: I am dreaming of a set up that can be connected through the normal a/c unit with all the extra ducting in the atic and to have the outflow out the vent through the roof as well. 12x12 room 9' tall with two 600watt lamps. A proper room with a gardening table, bench, and shelves. Any ideas? I didn't see anything posted about this kind of a set up, perhaps I missed it. Can this be done? Thanks!

 

[hoosierdaddy]

Very nice job, red. Well done.

 

[GrüneErd]

red, thanks for the info. i have a thread about this i just started.
basically, i'm scrapping the cfl's and would like to know how YOU (or any reader) would set up a grow room with the items i have listed on there.
i've given up on my ideas and am opening my mind to all of yours here, because there's definitely some pro's out there that can help i'm sure.
and ALL i wanna do is grow big buds, which at this point is only lacking decent cooled light.
the thread is here:
http://www.icmag.com/ic/showthread.php?p=2198957&posted=1#post2198957
thanks red, your info is helpin me get a feel that what i have is adequate, i'm just not using it correctly apparently.
peace

 

[guest 77721]

My Growbox Design

My Growbox Design

Ok lads, here's my grow cabinet. It's designed to take 4 x 42W CFL or a 150 HPS with 2 x 42W CFL. Currently I'm vegging seedlings so I put 4 x 13W CFL and move up to 4 x 26W CFL for early veg. The CFL lightbar makes this box very flexible.

The ventilation design uses a single 65CFM AC 80mm fan from RadioShack in the top section. The lights are separated from the grow chamber similar to a ventilated hood or a cooltube. The fan runs at rated flow because I don't block it up too much and have the intakes opened up to twice the exhaust duct size.

The grow chamber has a small scrubber that runs around 10 CFM. It doesn't need a high flowrate, just enough to change the air every few minutes otherwise a wind in the growbox just stresses the plants.


I picked this cabinet up a Crappy Tire for $50. It's 2' wide x 1' deep and 60" tall. There is 40" of growspace inside.



The top section contains the lights which are sealed off from the grow chamber with a sheet of glass. The scrubber is built into the duct grill. There is a passive intake in the floor of the box.




A sheet of glass separates the light section from the grow section.



This is the light section cooling fan. I've lined the fan chamber with this furnace filter material which works good to muffle the fan noise as well as providing a light trap.



The fan behind the furnace filter material.



This is the intake to the light chamber. It's 5" x 5" to match up with the 4" exhaust fan.


Here's a view of the intake 5"x5" and the 4" exhaust fan.



My scrubber is a cold air return filter for a furnace. I take the filter, spray it with rubber adhesive and shake on aquarium carbon. There is a 65CFM 4" AC computer fan mounted on the back of the cabinet.

 

[Blizztech420]

thanks for the quick reply got it to work, stoner pride

 

[GrüneErd]

hey red, thanks for stoppin by my thread. i'm gettin it all figerrred out!
so according to this:

Intake Calculator

Exhaust------ Intake------ Square------- # of------- # of------ #of
Inches------- Area-------- Hole--------- 1" PVC----- 2" PVC--- 4" PVC
4 ------------25.2-------- 5"x5"--------- 32--------- 8-------- 2
6 ------------56.6-------- 8"x8"--------- 70 --------18-------- 5

ANY 6" exhaust in ANY size grow space using the proper amount of CFM's to successfully exhaust will require only an 8"x8" hole (or equivalent thereof in smaller holes) for passive intake?

thanks.
peace.

 

[hoosierdaddy]

That chart equates to doubling the size of your exhaust. This is usually a good rule of thumb to follow for grow boxes and rooms. However, the 6 inch opening and fan can only handle so much CFM, and usually 10% over size on the intake opening is sufficient to supply enough air to the satisfy a well designed system. But if there is any question at all in the restrictions of your air flow, then using that chart and doubling the intake size is fine to do. More will not hurt, while less most certainly can.

 

[guest 77721]

R2D2 Design

R2D2 Design

This is my R2D2 Rubbermaid design. It looks really ghetto but this is an engineered ventilation solution using a 2 stage ventilation design.

The top tub contains 252W of CFL's and a single 38CFM computer fan. The intake is 5"x5" exhausting into a 4" duct.

On top of the R2D2 is a easy to build carbon scrubber that has a single computer fan.

Both the light section and scrubber exhaust into 4" flexible ducting that blow out the crack in closet door when closed.

I really wanted to keep the losses down with the scrubber so there are 2 x 4" ducts from the scrubber to the grow chamber and 2 x 4"x4" intakes in the bottom tub.

The scrubber passes about 10-15 CFM. I measured this by filling a large garbage bag with a known volume and measuring the time to fill.





Here is a peek at the light section. The light section is sealed off from the grow tub with plexiglass. This works the same as a sealed ventilated hood or a cooltube. To the left is the 5"x5" intake and the right is the 38CFM computer fan.

Temperatures in the growbox run 2*F above ambient.




Here is the R2D2 with a 150HPS installed using the same ventilation design. It too runs 2*F above ambient in the growbox and actually cooler in the light section than the CFL's.

I'm going to plug the Rubbermaid tubs here for a bit. I used the tub design as an entry into this hobby. The cost to build is $100 or less if you are able to scrounge and all the parts are transferrable to a wood cabinet if you so desire. I prototyped my design with these tubs because they are easy to cut and work with and are only $6 to replace them.

Both the 252WCFL and 150HPS model can produce 4 oz of primo bud with 2 plants using SCROG methods which is plenty for the average personal conniseur.

 

[moses224]

i must say for a micro thats pretty impressive...pretty work my man

 

[guest 77721]

That chart equates to doubling the size of your exhaust. This is usually a good rule of thumb to follow for grow boxes and rooms. However, the 6 inch opening and fan can only handle so much CFM, and usually 10% over size on the intake opening is sufficient to supply enough air to the satisfy a well designed system. But if there is any question at all in the restrictions of your air flow, then using that chart and doubling the intake size is fine to do. More will not hurt, while less most certainly can.

Yup, the purpose of the chart is to provide 2x intake sizes for common exhaust duct sizes. A common problem with many growbox designs is that the intakes are not even sized to the exhaust to begin with. A very common mistake is to cut four 1" inch holes for a 4" intake.

The maximum airflow from any fan is when there is nothing connected to it. When you add ductwork or pull air through a growbox or a scrubber, the airflow will drop because of the static pressure losses. Losses at the intake are significant so any size larger than the exhaust duct size is effective because it drops the static pressure and air velocity at the intakes.

I can't tell you at what point 10% to 100% oversize is best but the benefits are marginal beyond 100% or 2x duct size.

Oversizing intake and duct sizes are beneficial in reducing duct noise by dropping the velocity of the air by increasing the area of the chamber or ducting it passes through. Anytime you can reduce noise and turbulence, it will improve airflow.

 

[GrüneErd]

thanks hoosier and red, big help.
got my closet up and running now, which would NOT have happened without red.
i appreciate it more than you could ever know man
peace

 

[guest 77721]

thanks hoosier and red, big help.
got my closet up and running now, which would NOT have happened without red.
i appreciate it more than you could ever know man
peace

Woohoo!!! That's awesome news. What are your temps like now?

 

[ezgo1]

Wow good info

Ezgo