Understanding air flow

[hoosierdaddy]

Hey, maxx. Thanks for making this your first post. Hope you have many more.

A 3" duct is 7 sq in of flow area. A 1" duct is .785 sq in of flow area.
.785 will go into 7 = 9 times. So as a minimum, you will need 9 of the 1" holes for intake, better to have 15.
That fan will be a bit noisy and will not really pull a true 50cfm. Your cab size will support a much larger grow, but with the minimal air flow, I would only plan on flouros, cfls, or a 150hps as a maximum light.
If you do complete your cab, and get one grow out of it, I guarantee you will be looking to increase the size of your light...and that means increasing air flow capability.
WHat you have planned is fine...but if you think you may consider upgrading, I would plan on it now. No better time to plan than during the plan. And patience is a virtue that is required in this sport.
Best of luck!

 

[maxx8246]

Haha yeaa thanks for the warm welcome. You know what I should probably just get the 80cfm which I think has a 4" duct.
http://www.rewci.com/panfv08.html
Yeaa I'm definitely still in the planning stage. Getting the materials and numbers in order.
I'm most likely going to be using flouros.. hopefully I dont have too many heat issues but I dont think it will be a problem. I'm trying to go for extreme stealth although the fan is pretty big...well I got the idea from another thread:
http://www.icmag.com/ic/showthread.php?t=45196
I'm probably going to go with the same route but not sure bout the carbon filter because i dont have enough room to put the fan in the box. yupp thanks for all your help, cuz i have a long way to go.

 

[touchofgrey]

Thanks for the thread, just got here and am pretty impressed with the quality of the discussions I've seen. Built a cabinet a few years back and spent a lot of time with the ventilation design. I used a 6" fan rated at 230 cfm with 2-3" and 2-4" inlets. I double checked the areas with your numbers at the beginnng and it comes up at 138%. I've got 3 chambers and sized the vents to draw based on the volume of each chamber. I've smoke tested at the first transfer pipe and it's sucking. Here's a drawing of the box

 

[hoosierdaddy]

A couple of thoughts...
If you can manage to simply have a hole between the chambers instead of using the pipes, it will give you more grow room inside. Pipes and things take up precious space.
The 90's will work to block light on the initial openings, but it may be best to try and have the bends outside the cab (in the back out of sight). If that is a Closet Made or similar 2 door cab, you can take in air from the floor too with just holes.

And also consider that air will travel down the least resistive path. And as you have a single fan pulling all of your air, your veg chambers may get robbed a little of flow. The larger dia holes in the flower chamber are going to feed the fan with the most air, and if it can pull any more, it will get it from the other chambers up stream. If the 2 4" holes are providing as much as the fan can pull, then the other chambers will not see much air movement.

Final note...the Suncourt inline that you have may well push/pull 250 cfm if it is sitting on a table, but it will probably not pull near that with any sort of restriction, say like hooked up to ducting. They are very weak fans that create very little back pressure. They work OK for cooling a single light, but they need to be in a very efficient system to work. Now, they are cheap, and easy to stack together. Two of them together won't increase the CFM, but it will nearly double the pressure it can pull.

 

[touchofgrey]

Good points. I was tring to remember the design process involved but it's been a few years and I seem to have misplaced some brain cells. I sorta recall adding up the static pressure drops from the piping and elblows and trying to keep a balance between the 3 chambers. I remember getting some formula from OG and setting up a spreadsheet but that hard drive died and all was lost. I've tested by closing the door on the flowering chamber and holding a smoking pipe next to the inlet from the mother room to the clone room. I can see it pulling smoke so I know I have airflow but I'm sure you're correct that it is limited. I always figured that I could damper down or put a restriction on the 4" inlets if I wanted to draw more from the bottom but I just haven't messed with it yet. BTW, the fan I'm using is rated at 200 cfm at .15" sp and that was my target.

I know the pipes take up some space but I wanted to keep them inside to be a bit more inconspicious. That's also why the 90 elbows are added - to prevent light getting out of the box and trap light between chambers. The box is big enough to satisfy my little subsistance farm and I located the 4" pipes just above the SWC tubs and below the plant canopy so they could bush out above.

Thanks again and be safe

 

[dixbutler]

Hoosier I got my airflow design from this thread, and couldn't find the thread again. I posted this question in another thread, and copied it here because this thread inspired the airflow design. What do you think?




I got a new box. Downstairs: 60"X33"X48" perpetual grow. Upstairs: 42"X33"X33" 5 plant scrog and 2 single scrogs. 16"X17"X33" mom/pop room. 16"X16"X16" utility room. Atic: 16"X16"X17" ventilation room.
I'm going to put the 400 watt HPS in the downstairs part with a few CFLs for the perpetual grow, and put the T12s upstairs in a scrog with 2 bucket scrogs. I'm going to remote ballast the T12s as well as the HPS.

I'm going to suck air into the downstairs through vents to the upstairs. Then into a mom/pop room. and finally to scruber.

I'm going to get a 4" can fan or the like. Do you think that's enough? I was going to put my dayton blower on the HPS, but I'm not sure what to do with it. Should I let it go in the one of the upstairs apartments, or vent it and scrub it by itself?

I had in mind that the 4" can would suck through a scruber in the mom and pop room, which would suck through two 4" light trapped holes from the upstairs compartment, which would suck through 4 4" vents(one of which would be the dayton blower) from the downstairs apartment which would suck intake through a 33"X31" light proofed vent.

do you think it will work?

 

[hoosierdaddy]

I actually read your post in the other thread, and I really don't follow. A picture, or a hand sketch would help.
If there is ever a question of if there is enough fan/airflow, then that usually means that you have an option of going to the next size up. It is always better to get a bit more than you need to have a bit less. A 4" system is bare bones minimum for a grow, and I really wouldn't use a 4" system for anything but 250watts or less.
So, without really having a grasp of your set-up, my first advise is to use your 4" stuff to cool your light, and increase anything to be scrubbed to 6".

Hard to visualize things when you are talking attics and stuff...(scratchin head) and I so hate to think hard....

 

[uncle louie]

good info= thanks for working up numbers =

 

[uncle louie]

hey hoosierdaddy sounds like you could help me design the hvac system for my house

 

[dixbutler]

Sorry, I guess my pet names for different areas of my box are only amusing to me.

I try to show whats going on here.

 

[dixbutler]

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I'll try again

 

[dixbutler]

So you think I need a 6" or 8" can fan and vent my hps by itself?

 

[hoosierdaddy]

I would vent the hps light through a tube and fan.
The system you have should accommodate a 6" or 8" fan without much work on the intakes.
However, what you have now will only flow what that 4" at the end of the run can flow. Which aint much.

After adding a larger exhaust fan/port, then add two more 4" holes where you have only two. No reason to choke down as you go, it only restricts everything downstream.

Again...the two 4" holes will be the bottleneck once you have a larger exhaust, and the hps box will only have air flowing through it that is equal to what can flow through the two 4" holes.

 

[dixbutler]

thanks

 

[Smiler]

Just read through the thread changed my setup and dropped 5 degrees nearer ambient. Many thanks for the brill thread Hossierdaddy. globel should have read this and the your AC info before opening his immature mouth.

Cheers

 

[bdomina]

jumping the gun shooting a reply without reading the whole thread but i wanted this in my posts for retrevial in case this falls off the first few pages.

I have PC fans on the elbows i use for intakes. how does this effect the pressure and intake. can i get by with less intake space with boosters like this on the few elbows i have? BTW i am running a cab w multi compartments ie. flower veg clone and mother boxes all within 1 wardrobe.

 

[hoosierdaddy]

IMO use the fans for exhausting and turbulence within the grow. No need for them in the intakes, and they will not help if you do not have at the very least the same size intake opening plus 10% as you do exit.
The elbows are good for the inside diameter of the hole. They will not hinder the airflow past that.

If your exhaust is not getting rid of the air that you push in with fans fast enough, the fans will push air out of every nook and cranny it can find, and the smell will escape the grow. Best to never use fans on your intakes.
Search for a thread by Freezerboy for a nice tutorial on this topic.

 

[jugdishe]

another excellent thread HD, thanks a million

my question is very simple and I think I know what to do but...
I am in the process of adapting a a8k btu window unit to work indoors
i have read you post on building a box and I will be using your instructions for the exhaust box and going with a 6" vortex to suck. I am going to leave both side of the ac open to passively intake ambient air
I have to make a 90 turn to properly vent the hot exhaust air

should I put the fan before or after the turn
before would be closer to the ac unit,
after would be pulling air through the turn, which I know is better

thanks again for all of your help
j~

 

[hoosierdaddy]

Put it after the turn at the exit, then it can help the AC fan at the entrance.

 

[Owl Mirror]

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.