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  1.     
    #11
    Senior Member

    Fans - Not just blowing hot air!

    I know this thread is cold but a lot of people view it so if you have the answers please post!

    1. Tokudai mentions that the calculation parameters are more relaxed for a "complete room." His cabinet size for the example was 2x2x6. At what size do the parameters shift? 4x4x6? 8x8x7?

    2. Does anyone know the multiplier for adding a reduction in this scheme? What does stepping down from a 6" to a 4" duct do? Obviously this creates additional load on the fan but how can that be calculated?

    One additional thought - you could add a duct iris to the passive intake. Coupled with a speed controller for the fan you should be able to micro adjust air pressure to an optimal point. They are a little pricey though...

    Also, the Noob's guide to grow room setup also has some good examples of how to calculate fan needs. Find it here: http://boards.cannabis.com/indoor-gr...-progress.html

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  3.     
    #12
    Senior Member

    Fans - Not just blowing hot air!

    More fan thoughts related to a reduction in the duct diameter.

    How would these two scenarios play out?

    1. 6" duct with 6" inline fan. The duct reduces to 4" half way through the run. Assuming the run is 10' with no bends.

    2. 6" duct reduced to 4" duct with 4" inline fan.

    How does a reduction impact the venting capacity?

    Silly questions to some I'm sure but it is worth adding to the knowledge base here. Further, I have venting issues. I can probably get a 4" duct through but want to be sure that my venting strategy will be adequate to vent my 4x4x6 space.

  4.     
    #13
    Senior Member

    Fans - Not just blowing hot air!

    Well here is my :twocents:

    Just spend the extra $$$$ the fist time round to get a kick ass fan/w speed controller and no worries who cares.

    And it will add some stress ya fan with the reducers how much all depends on number things. I was told awhile back but don't remember the cfm count tho. I would say just add 30-40 more cfm if you plan on using 1 reducer Imo.

    But get a good fan and controller is the way to go. You can always adjust your fan speed and upgrade your lighting while not having to worry about it later. And ventilation is a key thing Imo with growing, It will either make your grow or break it, you decide.

    Why would you wanna use reducers anyway, As this will reduce airflow.

    Lets say your fan can more 60 cubic feet/min air moving with a 6in line, but you only allow 40 cubic feet/min to move as the 4in line is 1/3 the size smaller than the 6 so the fan is only moving 2/3 of the air the fan is capable of moving.... Makes sense, Sorry if it don't in :S5: the middle of my cigar.

    Only thing that makes sense to reduce is a line off you Ac hood which would be stupid.

    ~One~:rastasmoke:
    ~budG~:rastasmoke::rastasmoke:

  5.     
    #14
    Senior Member

    Fans - Not just blowing hot air!

    My ducting options are SEVERELY limited. I have a 2" opening that I may be able to widen to 4" but that is the most I can do.

  6.     
    #15
    Junior Member

    Fans - Not just blowing hot air!

    It looked like some people knew what they were talking about here so I thought I'd throw this out there to see what info I could gather :jointsmile::jointsmile:
    I have a 7x9x10 room. So that 630 cubic feet

    I plan on having two(2) home-made grow tanks

    3x3x6 54 cubic feet x 2 = 108 cubic feet

    3x3x8 72 cubic feet x 2 = 144 cubic feet

    ( Have not decided on the height yet so both figures are given )

    From what I have gathered I need to cycle the air 1 to 2 times a min. for best results ? I want to connect both hoods together and run through one carbon filter before it goes up in the attic where I plan to have it vented towards my bathroom air drain having it pass through one smaller carbon filter in the attic before attaching it to the bathroom air vent (stink pipe?)

    With this information can anyone give me a little insight on what size of can fan or vortex power fan I should be aiming for ? Or better yet what kind of CFM's I need to be pumping out!

    I appreciate the input and advice! If you have a better idea or tips I will keep them all in mind.

  7.     
    #16
    Senior Member

    Fans - Not just blowing hot air!

    Quote Originally Posted by the image reaper
    if venting directly from the lamp, do not use your fan on the exhaust-side, unless it is made for hot-air transfer ... like a furnace duct fan, for instance ... heat and electrical motors aren't a good idea, unless the fan is specifically designed for it ... :smokin:

    You are soooo right! Take a Hydrofarm 465 or a 265 cfm fan,for instance.. Both these type fans are what they refer to as active air blowers. They are meant to be used inside the grow area and blown out of the room.A furnace duct fan keeps itself cool by being inside the cabinet. If you use an active air blower then it is advised that you not use it as an exhaust fan. You have 3 ways that air can be used to serve your needs.

    Passive air
    Exhaust air
    Active air

    Each one has it's own application.Passive air will occur when used with an exhaust or an active air blower/fan. Exhaust is where the fan is placed on the outside of the grow area.

    Ga Grown!

  8.     
    #17
    Senior Member

    Fans - Not just blowing hot air!

    Quote Originally Posted by DeeMar10
    It looked like some people knew what they were talking about here so I thought I'd throw this out there to see what info I could gather :jointsmile::jointsmile:
    I have a 7x9x10 room. So that 630 cubic feet

    I plan on having two(2) home-made grow tanks

    3x3x6 54 cubic feet x 2 = 108 cubic feet

    3x3x8 72 cubic feet x 2 = 144 cubic feet

    ( Have not decided on the height yet so both figures are given )

    From what I have gathered I need to cycle the air 1 to 2 times a min. for best results ? I want to connect both hoods together and run through one carbon filter before it goes up in the attic where I plan to have it vented towards my bathroom air drain having it pass through one smaller carbon filter in the attic before attaching it to the bathroom air vent (stink pipe?)

    With this information can anyone give me a little insight on what size of can fan or vortex power fan I should be aiming for ? Or better yet what kind of CFM's I need to be pumping out!

    I appreciate the input and advice! If you have a better idea or tips I will keep them all in mind.
    I would just leave it vented into the attic at the soffit vent. You'll get a sewage smell in your grow as gas from the pipe your planning to use as a vent. A backdraft damper won't even help you in this situation. Hope this helped ya!

    Ga Grown!

  9.     
    #18
    Senior Member

    Fans - Not just blowing hot air!

    Quote Originally Posted by GaGrown
    You are soooo right! Take a Hydrofarm 465 or a 265 cfm fan,for instance.. Both these type fans are what they refer to as active air blowers. They are meant to be used inside the grow area and blown out of the room.A furnace duct fan keeps itself cool by being inside the cabinet. If you use an active air blower then it is advised that you not use it as an exhaust fan. You have 3 ways that air can be used to serve your needs.

    Passive air
    Exhaust air
    Active air

    Each one has it's own application.Passive air will occur when used with an exhaust or an active air blower/fan. Exhaust is where the fan is placed on the outside of the grow area.

    Ga Grown!

    I should mention this since this thread is about ventilation... If an active air blower is used other than by instructions,you could risk a fire.

    If you pull exhaust air through an active air blower your heating the motor and damaging the bearings.If you hook it up right and use it the way it is designed to be used it will serve you well.If not? They get wobbly and noisey.A 1000 watter is an active air blowers worst enemy!! Be safe not sorry!

    Ga Grown!

  10.     
    #19
    Senior Member

    Fans - Not just blowing hot air!

    Ach, what a bunch of wind....

  11.     
    #20
    Member

    Fans - Not just blowing hot air!

    I am currently using a 440cfm inline fan to pull air through my 1000w hps and out the roof of my garage. I have 6" from the hood of light to the fan then 4" from the fan out the roof. This system has been running for about 9mths now 24hrs 7 days a week with no problems. Noise level is very low and air really moves well.

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