# air exchange question



## ShOrTbUs (Mar 9, 2013)

been running my inline fan at 50% on the speedster speed controller, because temps are not an issue at all. do you think they're still getting enough air exchange when lights are on? its a 435cfm fan in a 3x3x8 space


----------



## trillions of atoms (Mar 9, 2013)

Plenty.. Even if in full flower. As long as its fresh air comming in you won't have any "air" issues.


----------



## TwoHighCrimes (Mar 9, 2013)

50% of 435=217cfm . 

3x3x8ft=72cf

72cf x 3 rotations per minute "ideally"  

72cf x 3 =216cfm  

  1cfm to spare :hubba:


----------



## BackWoodsDrifter (Mar 9, 2013)

I find as long as it be movin it be fine then gain the bigger the area the more to movin air ya need with my small grows I have bathroom exhaust runnin full time and it be all I need hope yual gets yur trail going yur ways pilgrem 

BWD


----------



## ShOrTbUs (Mar 9, 2013)

TwoHighCrimes said:
			
		

> 50% of 435=217cfm .
> 
> 3x3x8ft=72cf
> 
> ...



thanks for the equation. technically im running less then the 217 right? because of the bends in the duct + its about a 20ft run of duct from start to end. but from the look of the numbers you posted, even with all that taking into account i'm prolly still geting at least 2 rotations per min. which is still sufficient right?



			
				BackWoodsDrifter said:
			
		

> I find as long as it be movin it be fine then gain the bigger the area the more to movin air ya need with my small grows I have bathroom exhaust runnin full time and it be all I need hope yual gets yur trail going yur ways pilgrem
> 
> BWD



i run a oven range exhaust fan in the veg room. gotta use what we can get our hands on right bwd


----------



## terky (Mar 9, 2013)

TwoHighCrimes said:
			
		

> 50% of 435=217cfm .
> 
> 3x3x8ft=72cf
> 
> ...



I doubt it moves that much air. If you look at the box to your fan it states that that fan moves 435CFM with NO DUCT ATTACHED, ZERO INCHES OF WATER GAUGE STATIC PRESSURE. Water gauge is how many inches the pressure of the air would push water up (or down for negative) in a tube connected to the duct. The inside of the duct causes friction which slows air down and makes the fan less efficient.

People just do not understand how fans and duct work and should be sized. If you have that fan hooked to a 6" duct the most it will move is 300CFM, and most likely closer to 200CFM. Really 10" or 12" duct is required for that fan to move 400CFM anywhere.

Your temps and fresh air probably fine. But I guarantee you if I were to measure the airflow with industry standard tools you would not be over 250CFM at full power with 6" duct.

Union Trained HVAC Professional


----------



## BackWoodsDrifter (Mar 9, 2013)

ShOrTbUs said:
			
		

> thanks for the equation. technically im running less then the 217 right? because of the bends in the duct + its about a 20ft run of duct from start to end. but from the look of the numbers you posted, even with all that taking into account i'm prolly still geting at least 2 rotations per min. which is still sufficient right?
> 
> 
> 
> i run a oven range exhaust fan in the veg room. gotta use what we can get our hands on right bwd


 

Darn tootin ifin it works and it does what yual needs it to do then go fur it 

BWD


----------



## ShOrTbUs (Mar 9, 2013)

with all that taken into account. even if im only exchanging air 1 time a minute, i'm still getting adequate c02 into my grow room.

thank you all for your responses


----------



## ShecallshimThor (Mar 9, 2013)

Hey shortbus
I checked out your noise reducer DIY and am curious how you mounted the fan to the plywood? Was it screwed tight? 
Really like your DIY posts, nice work


----------



## ShOrTbUs (Mar 10, 2013)

ShecallshimThor said:
			
		

> Hey shortbus
> I checked out your noise reducer DIY and am curious how you mounted the fan to the plywood? Was it screwed tight?
> Really like your DIY posts, nice work



yes, the fan came with mounting brackets. i originally mounted the fan with screws, but didnt like that they stuck out of the back of the plywood. i replaced the screws with nuts and bolts. i've found though if you really want to reduce the noise. insulated duct works really well.


----------

