# Passive or Active Intake; Which Is Best For This Space?



## IllusionalFate (Oct 8, 2008)

The dimensions of my upcoming grow room will be 4'4"x4'4"x6'7", so a total of 142 cubic feet. I will be using an 8" Can Max fan to cool the reflector, but I don't know what would be the best option for exchanging the air in the room; Two 667cfm 8" Can Max fans (1 intake+1 exhaust) or one 10" 1019cfm Can Max fan for exhaust with a passive intake?


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## ugmjfarmer (Oct 9, 2008)

Two 8" will give you better air flow.

Split the intake fan so that the air is distributed in multiuple spots within the room, such as all 4 corners, 2 corners, ect.


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## NorCalHal (Oct 9, 2008)

Wow Illusion.
The 8"maxfan will cool your light no problem, as a matter of fact, you might glue your bulb in so it don't get sucked out! That 8 " max fan will cool 4-6 1000w lights with no issues, so cooling one light will be no issue.

I use a 10' max fan for exhaust (hooked to a carbon filter), with a passive intake (about 7"). And this is a 1000 cubic foot room. I can BARELY close the door as it is. I ended up getting a speed controller to slow the 10" down.

I think if you have 2 8" for intake/exhaust, it is WAY overkill and it will be like Katrina in your grow room.


Really, for the size of the room you have, you can take that one 8"maxfan and have it PULL thru your lights and be used for room exhaust.
Have the fan pulling from one end of the light, and the other end of the light, duct it to your carbon filter. So it pulls air out of your room, thru the lights, and exhaust out of the room.

I pretty much have allways used Can Fans.4-12" Then I bought thier Can Max Fans. BIG difference. I will allways buy the Max Fans from now on.


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## ugmjfarmer (Oct 9, 2008)

Yeah for a 3' x 1' x 8' box, im using a 6" fan pulling from a carbon filter, through the cool tube and up into the attic. Managing 1 degree over ambient 1' away from the light.


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## IllusionalFate (Oct 10, 2008)

NorCalHal said:
			
		

> Wow Illusion.
> The 8"maxfan will cool your light no problem, as a matter of fact, you might glue your bulb in so it don't get sucked out! That 8 " max fan will cool 4-6 1000w lights with no issues, so cooling one light will be no issue.
> 
> I use a 10' max fan for exhaust (hooked to a carbon filter), with a passive intake (about 7"). And this is a 1000 cubic foot room. I can BARELY close the door as it is. I ended up getting a speed controller to slow the 10" down.
> ...


 That's an interesting idea you have there. So you're saying use the AC as the room exhaust and have one 8" intake? I would install the intake at the bottom of the room, and use a rack placed above the intake for the pots to ensure the plants don't get blown over. Would this be a sensible idea or still too reckless?

I was wondering if I should go with Max Fans or the original Can fans, good to see I made the right choice. Their electrical efficiency is impressive.


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## NorCalHal (Oct 10, 2008)

You can use 1 8"canmax fan to cool your light and exhaust your room.

Sorry, If you still have questions, I will be back sunday. It is Fleet week in SF and the Blue Angles are doing a show. Nothing like watching fighter jets go under the Golden Gate Bridge stoned on Kush!


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## JBonez (Oct 13, 2008)

Im going to use 1 8" can fan to exhaust two 112 cubic foot grow rooms, and one 6" can fan to force cool air into the rooms, about a 100 cfm difference between the two fans, the 1000w lights will have their own ventilation. and there own 300 cfm fans, ill let you guys know how it works when i build it next week.


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## IllusionalFate (Oct 30, 2008)

Alright, I have a plan that I think should work well. How does having one 6" fan for intake, then using the 8" to exhaust air through the AC sound? I would leave one end of the reflector open, then attach flexible ducting on the other end which leads to the 8" max fan which either pushes air through or pulls it through a carbon filter.


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