Understanding air flow

[hoosierdaddy]

Thanks for the kind words.

OM, I have never used a dr louver before, but I hear they restrict the air flow quite a bit. Not sure of the actual air flow ratings on them, but I would suspect you would need about double your intake if using them.
I'll dig around and see what I can find about louvers.
For one thing, I know they are too expensive for my tightness.

 

[Owl Mirror]

Thanks for the kind words.

OM, I have never used a dr louver before, but I hear they restrict the air flow quite a bit. Not sure of the actual air flow ratings on them, but I would suspect you would need about double your intake if using them.
I'll dig around and see what I can find about louvers.
For one thing, I know they are too expensive for my tightness.

LOL, mine too !
They just look like the best solution.
McGyver moved out and, took my duct tape :>}

 

[hoosierdaddy]

Damn his hide anyway!

As long as you provide plenty of openings, PVC 90's work very well and are cheap.

 

[Owl Mirror]

Damn his hide anyway!

As long as you provide plenty of openings, PVC 90's work very well and are cheap.

Could you explain? Is this PVC 90's used for airflow as well as blocking the light ?

 

[hoosierdaddy]

If you paint the inside of a 90 flat black, it blocks light well. You can also put 2 90's together and not have to paint.

 

[Owl Mirror]

If you paint the inside of a 90 flat black, it blocks light well. You can also put 2 90's together and not have to paint.

I'm still a bit confused. Are you calling a 90, what I would call an elbow?

 

[hoosierdaddy]

That would be the unit.

 

[Jamerican63]

Great Info, thanks, and may I use your disclaimer

 

[hoosierdaddy]

Thanks for the kind words, Jamerican63
No, write your own. (lol..I don't care if you copy my disclaimer)

 

[Jamerican63]

I'm a lazy bastard, Sometimes... Thanks again Bro

 

[Rouxdy]

Wow.. what a great read! And very timely too!

I think this has helped me figure this all out, but a second much more knowledgeable opinion would really go a long way.



This is my cab work in progress. The bottom will be the flowering room and I will divide the top chamber in half... left side for veg, right side for venting and storage. All holes and louvers you currently see will be sealed and a door will be added for the top.

Using the formula at the beginning of the thread I came up with needing 19.38"s of intake for my fan. All intake holes will be in the bottom shelf as it'is raised above the floor.

Size of flower room is 16.5" w x 27 .5" t x 11" d. Upper is 16.5 x 16 x 11.

My first question was about moving air in the veg room. I was just going to cut an intake hole through the shelf which would be into the flower room and then cut an exhaust hole in the upper back corner of the soon to be installed divider into my ventilation room. Would that work, and as always, does size matter? I was thinking two one inch holes at each location....

Second question. After reading this thread, I'm thinking what I'm looking for in regards to air passage between the flower room and the vent room is an area at least a little larger than my cabinet intake so as to create minimal resistance??

The fan and scrubber will be mounted on the back wall in the vent room.

Does that make sense... am I on the right track?

Thanks in advance!!

 

[hoosierdaddy]

lol...you gotta realize you are dealing with stoners here...
Can you do up a diagram of what you are trying to accomplish so we don't have to try and visualize? Makes my brain hurt.

 

[furley]

Could someone help me with a dilemma.. I have a 3x6x9 room that is currently vented through the light through 4" ducting. My question is, will another 4" hole with (or without) an intake fan be enough intake? I also have a 471cfm intake fan but it is 8", a hole size I can't put in the wall. Could the intake fan be restricted into the 4", or is that a complete waste?

 

[hoosierdaddy]

You have 8" out, you need at least 8" + at least 10% more of intake opening.
So, two 4 inch intakes is still starving the system for air flow.
I think I have provided all the formulas and sizes for your convenience.

Forget the intake fan, it doesn't help anything, and can hurt.

If there are things you can't do, you may not be able to get to optimum performance.
But it is hard for me to envision being able to add a 4" hole, but not an 8"?

When I say you need to increase intake...it would only be to accommodate the exhaust you have. There are many factors involved, but you need to figure on how fast you need to run CFM wise to exchange the air in the room properly.

 

[fish83]

this is a damn good, very informative threead that all should read....

 

[qbert]

This info is most excellent, thank you

One question, is this product useful for this application or would it cause to much of a restriction ?

Darkroom Light Tight Louvers, 8"X8"

I'm currently designing a new room, two separate chambers inside a 6 ft L x 2.5 ft D x 7 ft H space.
I was thinking of installing one on each (2) door and, one in the separation wall.

I've read at least one report that they are more restrictive than the purchaser expected leading to ventilation and heat problems. I would definitely not consider it to flow as much as a 8"x8" open hole, possibly less than 50% as much.

Also, check out the DIY method of darkroom louvers: https://www.icmag.com/ic/showthread.php?t=135524

 

[k1net1k]

Its awesome that people discuss this in such detail

Thanks for the trouble of compiling this info

 

[hoosierdaddy]

No trouble, friend.

 

[J23]

venting my first built cab

venting my first built cab

First things first: great thread. Thanks to all of you putting your effort in educating everybody.
Now, I'm working on my first DIY cab. It's 30W x 19D x 34H (in.) so it's 10 cu ft. I have 250w hps with a cool tube (PYREX bake a round, 14" long x 3.75" wide). I plan on mounting ballast remotely to lower inside temps. I like the idea of installing inline fan and scrubber @ cooltube intake so fan pulls the air through scrubber and push it through the bulb out (scrubber with a 1" layer of carbon, 10" long). Assuming that I will have 2 x 3" passive intakes and FAN, is this a go or do I need another solution. Note, that box is intended for one plant SCRoG so not too much smell to beat.
I greatly appreciate any suggestions!

 

[hoosierdaddy]

Thanks for the kind words.
The determining factor will the size of the fan and the exit port. If you have a 4 inch duct leading to a 4 inch exhaust fan, then you should probably have two 4inch holes for your passive intake. The restriction of the scrubber would allow you to get by with slightly less intake, but it should be easy to just cut two 4" holes for intake, and another 4inch for exhaust.
Two 3" intakes will not feed the requirements of a 4" exhaust fan.
4 inch duct has 12.56 sq inches of free flow area, and a 3inch duct has 2.25 sq inches of free flow area. Doubling the size of the exhaust, you would need about 12 of them.