# cfm's for 2 400w's



## dirtysox (Aug 17, 2009)

I have a room that is 10x12 and has 8 foot ceilings I want to use 2 400w's in that room, and use one can fan to keep the lights cool enough so that the room doesnt heat up.  

The factors involved:
The room that is mentioned has central a/c, but no return in the room. The central a/c thermostat is not in the referenced room, and the rest of that building is set for 74 degrees. Theres a 12 inch oscillating fan in the room, but the room's door will be closed, to keep out the light.  

Or do I have to do the following: 
A can fan at the top of the room pulling hot air out of the room?  In addition do I need a fresh air replacement from outside the room, or will the central a/c be enough when it comes on?


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## OGKushman (Aug 17, 2009)

Get a 250+CFM CAN FAN and a fan speed controller. Best bet for you man.

Can fan vented out will replace the old air. As long as you place the intake of the fan farthest from the fresh air intake. Central A/c should help too.


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## dirtysox (Aug 17, 2009)

so to keep a room cool with 2 400's I need 3 seperate fans, one for the reflectors, one room intake, and one room exhaust?  

But, what I wanted to do was find a big enough inline fan to cool the reflectors so no additional supply or return fans were necessary and the room door would be kept closed


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## OGKushman (Aug 17, 2009)

nonono....1 fan centrifugal style/vortex. Have it pull fresh air through hole in room filled with a particulate filter. Set vortex fan on charcoal filter, suck through filter and blow into ducted light. Duct light to other light and out of the room.


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## dirtysox (Aug 17, 2009)

ok, I think I get it,
buy the matching carbon filter for the fan, and have the fan pulling the air thru the filter (which sits in the room), then have the air forced thru the duct & reflectors, and then that hot air out will leave the room, which in this case is thru the ducting and the tight hole in the ceiling 

so, a single 6" 440 cfm can fan will do the trick for 2 400's, without having to mess with the rooms return or supply, as long as the room is not hot before the lights go on?


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## OGKushman (Aug 17, 2009)

My setup:

Just made this on MSPaint


edit: just read your post. YOU GOT IT!


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## dirtysox (Aug 17, 2009)

thanks for taking the time to draw that out, I understand, wow I love this site, the more time goes by, the more I enjoy pot


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## OGKushman (Aug 17, 2009)

No problem man. I enjoy sitting on my couch, smoking away my excess energy, and informing people of the seemingly insurmountable knowledge that seems to float around in my dome...osmisis? lol


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## dirtysox (Aug 17, 2009)

Theres one thing I just realized, the 4x4 a/c filter you have pictured, will it let light thru for when the room is to be dark, and one of the requirements was keeping the door to the room shut


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## OGKushman (Aug 17, 2009)

This is an _*idea*_ that can be used to keep the filter area light tight. http://www.1-hydroponics.co.uk/fans-and-filters/large-images/3-way-duct-spigot.jpg

imagine air flowing in but not light.


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## OGKushman (Aug 17, 2009)

better example:


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## dirtysox (Aug 17, 2009)

so Im to take down the door to the room, hang panda plastic in the door way, and then put a dryer vent into the panda plastic, and so every time I enter the room I have to move the panda plastic?

Can I just leave the door closed, use the 440 cfm fan to push air thru the sealed reflectors and then duct it into the attic and skip the a/c filter & dryer vent assembly, or will the room be to hot?  I was just thinking that the unpressurized supply of air would affect the rooms temp very little, and I like having easy access to the room thru the door


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## The Hemp Goddess (Aug 17, 2009)

Just as a side note....2 400W lights are only good for about 18-20 sq ft.   You are talking about a room that is 120 sq ft.  I would recommend that you build some kind of enclosure or the light disburses throughout the entire room.  You are going to be loosing a whole lot of the light that you could be using.


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## dirtysox (Aug 17, 2009)

thanks for the input, I understand that the light will be more effective if contained with reflective material, but right now Im just looking for someone to help me with the heat issue


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## The Hemp Goddess (Aug 17, 2009)

I understand heat issues, but IMO, you should be trying to deal with the heat in the size space that you are going to ultimately be using.....Using 2 400W in that size space is going to give you such low lumens per sq foot that you may have a hard time flowering your girls at all.


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## meds4me (Aug 17, 2009)

OGKushman said:
			
		

> My setup:
> 
> Just made this on MSPaint
> 
> ...


 

Bingo ! although i would go up in fan size to minimize run times....look at the diy section and calc out the cfm needed...


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## OGKushman (Aug 17, 2009)

Door? 


Cut a hole in the wall...


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## dirtysox (Aug 17, 2009)

The Hemp Goddess said:
			
		

> I understand heat issues, but IMO, you should be trying to deal with the heat in the size space that you are going to ultimately be using.....Using 2 400W in that size space is going to give you such low lumens per sq foot that you may have a hard time flowering your girls at all.


 
there wil be a 3x6 foot area under lights, that has reflective board standing up on all 4 sides, and its 6 ft tall (open on top, but close to the reflector), which is taller than I would want to grow.  Im still just worried about the heat in the room, and not the lumens per sq ft


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