need a lil carbon scubber help

[richirich_99]

Im in process of getting everything together to build a diy carbon scrubber. I plan on using 2 6in net pots from the hydro store, and some active carbon from walmart or the pet store. My question is how think of a layer of carbon will i need to effectively scrub the air from my grow room? I have a 150 w hps cooltube that is exhausted into my utility area with a small 80 cfm duct booster fan, and have my s&p 125 exhausting the entire cab, both the mother veg area and flower/utilty. My fan is running on high at 197 cfms, so any help with the filter would be great. I need to filter to be very efficient for airflow to help keep temps down during these summer months. Thanks again.

 

[FreezerBoy]

I built a DIY. Killed smell completely but, the 1" core of carbon seriously reduces airflow of my TD100x set at 100 CFM. So much so, I've rebuilt it to a 1/2 inch core. Can't report on effectiveness as I'm still in veg.

Because you've double my CFMs, I'd suggest starting at 1". My girls were stinking to high heaven and the 1" core wiped out the smell completely.

 

[richirich_99]

Thanks for the help freezerBoy, always glad to have you around for your help. as i know you also like those s&p fans. I still have to get a 5" to 6" adapter to connet my fan to a 6
net pot.

 

[FreezerBoy]

My home Depot had reducers for both 4 to 5, and 5 to 6. But, not a 5" cap to be found anywhere. I made my own from a plastic "jar" of baby wipes from the supermarket.

 

[Haps]

FB you were right with a half inch or 1cm for that size fan, more would be less effective.
H

 

[richirich_99]

i'll start with that 1/2 inch of carbon and see how it works out. Love the ingenutity freezerboy.

 

[FreezerBoy]

Oh, by the way, no WallyWorld or fishstores. They'll hit you for $4-$5 a lb. Ebay runs closer to $2. Check out a guy called thirdmilleneum I think it was $2.35 delivered ($1.99+shipping)

 

[JackTheGrower]

I worked it out once long ago when I build my DIY filter box.. I posted some photos in a thread here a week ago?


Let me say that I know there is a better figure for the weight of a cubic foot of 4mm pellets but I can't find it atm..


I once posted..

Activated carbon has incredible porosity and a large and a highly active surface area. One pound of activated carbon has the surface area equal to 125 acres and a bulk density: 30-32 lbs/ft3 (480-512 kg/m3).

one cubic foot is 1728 cubic inches so If a filter is 12 inches by 24 inches for example that's 288 inches square.
a 600 CFM fan needs 18 pounds of carbon pellets ( 600 *0.03 )
18 lbs of carbon is 0.5625 * 32 lbs for one cubic foot of pellets. 0.5625 times 1728 cubic inches is 972.
Divide that by the square inches of filter surface and I get a thickness of 3.375 inches.
I guess I would round that up to 4 inches.

The idea is to match CFM to volume of carbon.. How much that walmart carbon weighs per cubic foot I don't know so I'll assume it's a bonus on odor scrubbing that it packs in tighter.

With the box design I use 14x20 air filters in the intake and exhaust sides to clean the incoming and catch carbon dust on the exit



Lets see if I can work the math.

I researched how much carbon commercial scrubber units used as well as a metal can I won on ebay to get an idea on volume for the carbon in relationship to the CFM of the fan.

What is the surface area of the container that holds the carbon in square inches..

Let me just use as an example this Seaworld pail with crayons in it sitting on the desk . The Kids were here..

The pail has a diameter of 6 inches at the top and tapers down to 5 inches.. I'll just assume a 6 inch cylinder.

To find the square inches or the area of a circle I found this formula on WikiAnswers

Area of a circle = Pi x diameter^2/4 = 3.142 x 36/4 = 28.28 sq ins

So if I have a can or tube that has a diameter of 6 inches I would multiply PI or 3.142 * (6 inches )^2 divided by 4

This gives me a surface area and I can calculate the depth of the carbon which is the question asked here..

So 80 CFM fan * .03 = 2.4

2.4 / 32 = 0.075 1728 * 0.075 = 129.6 129.6 / 28.28 = 4.58 inches thick.


So I would put about 4 and 1/2 inches of carbon in a can that has a diameter of 6 inches. That would be 4mm pellets.

LOL.. It works just fine and making it a little thicker isn't a bad thing..

Square area round area rectangle area it's all the same.. Just find the surface area.. Know the CFM of the fan (((CFM * 0.03)/ 32 ) * 1728)/Surface_Area_SQ_INCHES = depth of carbon

The number for weight of the carbon is close to the actual weight for 4 mm pellets. I do not know the weight of a cubic foot of the type of carbon you will buy. But 32 lbs sounds okay to me..


What I do suggest is a proper fan tho.. That duct booster isn't my choice for a good scrubber. Maybe a nice 4 inch fan?
I hope I got that right..

Anyone got a better formula?

Jack

---

I found this long ago if .. Handy for designing the kind of "Can" filter where the air is drawn through carbon into the center of a cylinder.http://www.abe.msstate.edu/~fto/tools/vol/cylinder.html

 

[FreezerBoy]

So 80 CFM fan * .03 = 2.4

2.4 / 32 = 0.075 1728 * 0.075 = 129.6 129.6 / 28.28 = 4.58 inches thick.

I'm having a hard time believing this. One inch was choking my 100 CFM fan to near uselessness.

Maybe it's because you're using pellets with their lower surface area and looser packing than the granules I've got?

 

[richirich_99]

by the way im not using the 4in duct booster for my filter, its just an addition to help cool my grow room. I have my S&P 125 hooked up to exhaust both the mother cab and the flower cab. I'll have to re-read over that post with all the math as im way too high to make sense of it right now.

 

[Haps]

Bad formula Jack, it was way off. It must be for a diffrent style of function, 32 pounds for a small fan should be a clue that something is off. If you make it too thick, you loose flow and function. I got no formula, I build em, they flipping work, eh?
H

 

[JackTheGrower]

I'm having a hard time believing this. One inch was choking my 100 CFM fan to near uselessness.

Maybe it's because you're using pellets with their lower surface area and looser packing than the granules I've got?

My bad.. 4mm Pellets..

I was just at walmart and saw that 9 oz jar.. Is that what you guys are using? man that's fine.. No wonder it clogs..

Then again you aren't ordering 55 lbs sacks

650cfm 8 inch here.

 

[JackTheGrower]

Bad formula Jack, it was way off. It must be for a different style of function, 32 pounds for a small fan should be a clue that something is off. If you make it too thick, you loose flow and function. I got no formula, I build em, they flipping work, eh?
H

yeah I saw that fine aquarium carbon this morning at Walmart..

9 oz in a jar.. I take it it gets changed more often then 6 to 12 months. NP


32 lbs is the approximate weight of a cubic foot of 4 mm pellet AFAIK..

I did some detective work on how to figure pounds of carbon per CFM with those pellets.. i came up with 0.03 as a multiplier.

Like you and others with common sense i fudge on the side of function.. 600 cfm for a 8 inch hurricane rated at 650 cfm and a little extra pellet room by rounding up.

Then find the weight of that amount of pellet such as 600 x 0.03 = 18 lbs

Then what is that in terms of cubic foot weight 18/32 = 0.5625
Then in terms of cubic foot volume 1728 sq in * 0.5625 = 972 cubic inches..

In my case I was building a filter box so the surface area of the 14" x 20" air filter is a bit under 280 sq in.. Since cubic inches are sq in x sq in I divide 972 by 280 and that turned out to be about 3.47 and I rounded up to 4 inches..

http://www.icmag.com/ic/showthread.php?t=125750

In this case the air pull is alright.. Enough to blow two cool tubes with 250 watt MH bulbs while being the main scrubber for my box.. ( see bird and bull go back to work in organic soil )

So I feel comfortable to suggest the formula.. Common sense not to get too thick applies I'm sure.

Now I am wondering if i can fill a length of 6 inch duct with pellets and put one of these 85 cfm muffin fans on it and see if that will work to scrub the air.. I need to pick up some Nag Chompa incense for the odor test.

If anyone is wondering I can try it.. If not

Tell me a bit more about the granular carbon.. How long does it last? I'm wondering if granular is more effective at low flows..
I am considering options on a clone/mother box..

Jack

 

[Haps]

I use the one liter jars from wallyworld, my scrubber takes three liters of carbon, and works for a bit over a year on a 750cfm fan. The 750 will pull through an inch and a half, not much more, but I do not need more, this works. If you want to see an efficient design, my scrubber is in the diy link. It is small, but it cleans the air for two bloom rooms.
H

 

[richirich_99]

i will be taking a look at that haps. I shouldnt need much to kill the smell of my small grow box, and currently its not too bad and i have to leave it open during day until i swap my light timing around to being on at night.