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.

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.

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

Originally Posted by 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.

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

Originally Posted by 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

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

[ezgo1]

Wow good info

Ezgo