Fans size / CFS size for grow box

Discussion in 'Growing Marijuana Indoors' started by dimyself, Feb 16, 2009.

  1. #1 dimyself, Feb 16, 2009
    Last edited by a moderator: Feb 16, 2009
    I need to know what kind/size fans I need to get and what size carbon scrubber to build for my box/room size and the fans I'm using. I'm a little confused about the different kind of fans I need (inline, or whatever...)

    My box will be 5-6' tall, 3.5' x 3.5 and in my closet. The light is a 400w with digital ballast. I was going to have 1 intake fan (what size do I need??) and 1 out (exhaust) fan (what size??). Once I know what fans to get, then I also need to know how long/big of a carbon scrubber I need to build.

    I will of course test this setup before using it. If it doesn't cool adequately, I will modify my setup or an a cool tube, something to get it down... I will also have a fan running inside my box.

    Also I will add, that I want the power to cool it off, but at the same time want a cheaper setup. I don't need the best/most expensive equipment...
  2. Anybody? Or if anyone can refer me to a fan guide on here
  3. What kind of lighting do you have? What size can filter 33 do you have?

    SO, in my grow box of 5-6' x 3.5' x 3.5', a 4" inline fan that is 150cfm and exhaust fan of 200cfm will be good enough to ventilate it? How big should my exhaust fan be? How big in diameter and length should my carbon filter scrubber be??

    Could I just use a fan like this??? This is 200cfm and inline:

    or like this:|66:2|65:12|39:1|240:1318|301:0|293:1|294:50

  4. #5 Mr.Bubb-es, Feb 17, 2009
    Last edited by a moderator: Feb 17, 2009

    CFM ratings are joke do not shop fans by this alone. The fans you posted a link to are GARBAGE IMO. Both of those fans were designed to work in conjunction with your homes or alternate central system. These fans entrusted to stand on their own will do little to cool even a CFL grow. I posted this once before and its true, if you can stick your finger in the fan, stop the blade, and still be smiling don't waste your money.

    I made the fatal mistake of stage building with ventilation however I have all but given up giving out advice since few rarely listen. BUT if you want a decent fan get a CAN-FAN or VORTEX, do it ONCE, do it RIGHT...

    FYI I have owned roughly 8 of the second link produced by SunCourt commonly found in HD and Lowes. GARBAGE :)
  5. #6 dimyself, Feb 17, 2009
    Last edited by a moderator: Feb 17, 2009
    Thanks for the tips! Can you tell what kind of fans I DO NEED? I know I need an inline fan for my incoming air going into the box, correct?? I guess what I really need is a guide that gives a general overview of what kind of fans I need, sizes for my box/lights, etc... Because I see all these setups (different fan sizes, different types of fans, different types of carbon filters) and I don't know what kind I need or what to pick!

    1. What are the fan TYPES I need?
    2. WHat size fans (in cfm's and inches) do I need for 400w and 6x3.5x3.5 box?
    3. What brands or types of fan work well but are economical as well?
    4. I just need 3 fans correct? 1 blowing in air from outside my box and the 2nd one blowing air from inside the box through a carbon filter/scrubber and 3rd inside box for general ventilation??
    5. What diameter AND length carbon filter/scrubber do I need?

    What does this mean?? You made the mistake of stage building? What is stage buiiding? What was the fatal mistake? Are you talking about the material I'm using to build my box or what?? Sorry, not trying to be rude...I just don't understand what that means... :)
  6. #7 ricard0, Feb 17, 2009
    Last edited by a moderator: Feb 17, 2009
    Mr.Bubb|es is a bit of a regular here so don't let his technical jargon scare you off. I think what he's trying to say, is to get a good fan like this one --->|66:2|65:12|39:1|240:1318|301:1|293:1|294:50
    and a carbon filter to match (ie.) --->|66:2|65:12|39:1|240:1318|301:0|293:1|294:50.

    I could be wrong but the "stage building" he referred to is often times associated with having several stages of smaller fans working in groups to get the job done instead of using a real centrifugal inline fan to get it done right the first time.

    EDIT: You may want to check out the "Absolute Beginners Section" for all the basics on grow setup.
    Here's one of the GC classics --->

    You may want to grab yourself some literature as well. Jorge Cervantes and Ed Rosenthal are two noteworthy MJ horticulture authors.
  7. #8 Mr.Bubb-es, Feb 17, 2009
    Last edited by a moderator: Feb 17, 2009
    Before I put on a thinking cap;

    1) Is the 400w enclosed ready to be setup on a circuit ?
    2) Let me get this straight this is a box with the demsions above inside a closet ?
    3) What are your outside of the box temps
    4) What is above your closest ? Can you cut holes in the walls / door ?
    5) Magnetic ballast, maybe digital ? going outside the BOX or in the BOX ?

    Those should get others and myself started on some good suggestions.

    Stage building is spending $900.00 on All Terrain tires knowing you needed a Mud Terrain that is $1100.00. Next you hit the world and get stuck. And before you know it you are forced to upgraded to the Mud Terrain total spent $2000.00.

    EDIT; You could always look at my space for some ideas, I run a 400w in about the same space...
  8. Thanks again for the help!

    1. I'm still waiting on the light. It is a 400w digital HPS from htg. I haven't seen it yet, but was planning on running the power of the light into power strip inside the box
    2. Correct, I'm working on the box now. Those are about the dimensions I will use and it will be in my closet of my room.
    3. My closet temp is currently not as hot as my room so it's probably about 70-73F in my closet currently.
    4. I want to avoid cutting holes in my closet/door. What I can do is leave the door open or build a fake door to cut a hole into.
    5. It is a digital ballast, but I'm not sure if it should go inside or outside. I was going to put inside, but it doesnt really matter I guess.

    Yea, I check out the carbon scrubber you made a tutorial for and that's what I was going to use for mine. I just don't know the length/diameter I need to use when making it!

  9. Thanks for the links! On the carbon scrubber I was going to build the one out of Mr. Bubbles...I just don't know the size I need. Anythoughts on what size filter I need so I can go get the parts??

    Is the 4" fan of only 170cfm's enough? Any other recommendations? It seems I've seen cheaper fans that have more output than that vortex? Like the HO fan mentioned below...

    Now this fan would be my IN fan going into the tent? What fan would I use for exhaust thats attached to my carbon scrubber??
  10. Sorry to use your thread but I have a question, and it may even help you. Im using about the same dimensions for my grow room as you. My question is can I use a 4" fan for the intake and a 4" fan for the exhaust? I read you need a bigger exhaust than intake to create a negative pressure inside the box. Will that work or do I have to do somehthing like a 4" intake and 6" exhaust?
  11. Here is what I would do with that fan ... :) Some might say not to split with the Y Duct and run a second circuit with another fan.


    I have run a similar to the above image and it works great. The intake can go either way. Your best bet is trying it passive to save $$$$$. Worst case address the issue later if you need more clean air being pushed in. I am betting it will work.

    The big question is how the temp outside the box is going to hold up. The less space in your closet the harder it is going to keep cool. If your closest is the same or smaller than any in my house your going to have to consider other ways of getting the heat out. You should also have something to clean the air in your closet like ONA or similar.
  12. That is to control the fan speed?

    When you say 'enclosed reflector' are you referring to something like a cool tube? I was thinking about it because I found a tutorial for building one...Would it be to hard to implement or any more expensive?

    If I did do a cool tube, how would I have to change the fans / holes in my box?
  13. Sorry for my ignorance, but can you please explain the drawing a bit?

    It looks like there is a:
    "6 inch in" fan bringing in fresh air (what kind of fan should I use here???) --> goes through a carbon filter --> then gets split using Y duct from my light and the other duct on the filter --> then my vortex would suck the air coming from my Y and out a 6" hole??

    I have a few questions about that:

    1.) What kind of fan should I use on step #1 (for fresh air coming in the 6")? Would it need to be another fan just like the vortex I got? Same power? more? less?
    2.) On the drawing it shows the carbon filter split at the light with the Y. Shouldn't the carbon filter be connected directly to my OUT fan (vortex) so it gets ALL the air leaving the box? I mean if I suck air from my light after it comes from my filter then that air won't pass through the filter?
    3.) You draw a line for duct coming out of the light....I'm not sure if my light hood even has a hole for duct? If it doesn't, would I need to make a hole on the hood or something so the vortex can suck air from the light?
    4.) What is the 8" passive? Is that for another 8" fan bringing in more air? If so, what kind of fan should I use?
    5.) Can you tell me if the carbon filter in your tutorial is the right size for my setup or is it overkill? What size filter should I build?

    THANK YOU VERY MUCH!!! I'm sorry for all the questions! I just can't really proceed until I have the right equipment and understanding!

  14. There is no 6" in because the vortex at the end of the circuit will be pulling air through the Y and through both the light and carbon filter. This drawing is for an enclosed reflector. (like a cool tube)

    1) no fan in that 6" in, that is duct to the reflector than duct to the Y splitter to Vortex.

    2) the filter is being draw by the Vortex, the air coming through the light is being drawn from OUTSIDE the grow so it does not need to be cleaned.

    3) you will need an enclosed reflector aka cool tube or such. I run an easy cool 6.

    4) 8" in passive is just a HOLE no fan, we are counting on the suction from the vortex from the carbon filter to draw air in.

    5) my size or even a 4-6 inches bigger will work for you. Check out the one in my setup thread hanging from the ceiling area its like 24 inches
  15. Ahh, I got you! Makes sense now :)

    1.) Wow, so you're saying I only need that 1 Vortex fan, that should be enough? I guess it would be since all the heat from the lamp won't be in the box...

    2.) If I build a cool tube myself such as this one: will it work just as well? I suppose that will depend on what kind it is...I will see it when it gets here.

    3.) 8" hole with no fan? The smell will not come out of the hole? What if I threw a cheap passive fan from home depot or something in there?

    I will start building the carbon fiber scrubber!
  16. Just thought Id add my 2 cents...When determining the proper fan CFM, Id start with the math (height x length x width), once you know how many cubic feet of air you have in the box (something like 73.5), then you decide how many times a minute you want that air volume replaced.. If your going with a cool tube, and vent the heat it generates and not let it heat the box, you wont have to replace the air as often in the grow box (which helps when using co2). Im going to convert my box over to a cool tube set up this week, if the hydro store gets their order in. just to cut a few degrees and give me more height for plants...
  17. #20 dimyself, Feb 17, 2009
    Last edited by a moderator: Feb 17, 2009
    Ok, I'm trying to get my supply list of things for the hardware store. If someone can let me know what else I'm missing so I dont have to make several trips...

    - box material
    - nails
    - sealant
    - 6" duct?? Since I'm using 6" fan, I assume I need 6" duct.
    - Y duct adapter for 6"
    - clips for duct??
    - tape/clips for fan?
    - chain for my light (although if I use a reflector, I can't raise lower my lights with chains can I??
    - material from Mr. Bubbles for carbon scrubber
    - thermometer
    - plastic wrapping for in my closet
    - door hinges
    - door handle
    - maybe weather stripping
    - light adapter that plugs into my closet light socket

    What else am I missing?

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