NEED WISDOM!! Need A Double Check Please ...

My new grow space i will build, will be

(Metric)
1.5m-Long
2.0m-High
0.7m-Wide

(Imperial)
5ft-Long
7ft-High
2ft-Wide

My existing 4" fan does 137m3 (cubic metres) per hour....
I have a 6" fan that does 425m3 per hour but is WAY TOO LOUD...

Iv calculated my grow space will be 2.2 cubic metres so shouldn't the 4" fan be enough @ 137 cubic metres per hour ? ?

*The manufacturer says the 4" fan is only good for 1 cubic metre ??? & that the 6" fan 425m3 is good up to 2 cubic metres WTF???

Your thoughts would be greatly appreciated). !!
Iv attached the chart showing the intake/exhaust rates..
Something isn't adding up for me??

Bloody amateur (

Will the 4" fan be enough for 3 or 4 plants in that space with 2 circulation fans ??
I will have 1000w of blurple LED's running ...
I already have 2 seedlings started (Fast n Vast) in my old cupboard...
But I need to grow extra for summer time as temperatures will exceed 36*c/. 96*farenhiet

I get 70 cubic feet for your space? That would make the 4" more than ample IMO...

The "recommended for grow volume" line I think means actual floor space, so the 4" would do a 3'x3' grow space and the 6" would do 6'x6' (sorry it's in feet, I'm a colonist )

I run an 6" fan for an 8'by 8' by 8' grow chamber with a speed controller that runs the fan at about half speed.
For noise, I built a 4' x 6" outlet muffler for the fan plus hung fan from rubber cord to lower noise.

The fan, no matter of its size, will not solve the temperature and/or a vapor pressure deficit issue you many see at those high temperature during your grow.

First off I have no experience with grow spaces that small to recommend what kind of fan to use, both in size and in power draw capacity in wattage. 18 watts for the 4" fan and 35 watts for the 6" fan tells me that the motor in those fans are incapable of achieving their advertise air flow capacity at any conditions other than zero static pressure (open free air environment with absolutely no restriction to the air flow path).

Yeah I'm gonna get a speed controller for the 6" just in case the 4" doesnt do the job... Iv already got the kit so why not another $50...
You are rite saying the chart is at a freely run fan... With ducting on the fan it seems restricted

RORSN said:

I run an 6" fan for an 8'by 8' by 8' grow chamber with a speed controller that runs the fan at about half speed.
For noise, I built a 4' x 6" outlet muffler for the fan plus hung fan from rubber cord to lower noise.

The fan, no matter of its size, will not solve the temperature and/or a vapor pressure deficit issue you many see at those high temperature during your grow.

Click to expand...

I wont grow in those temperatures... That's why I want to grow double during winter, so I'm stocked up for summer.. )

i flower in a 28x32x48 in space with a 400 watt hps, use a 4 inch fan and it keeps my flower area 78, pulling in the 72 degree air out of my house.

A small AC would be a good investment, might keep you in business in the summer. if it's hot, it's not unheard of and perfectly legal for people to use an extra AC unit, like a standard seas bought freestanding or window mounted one. For real, maybe you have skin issues and can't sweat? Maybe you recently acquired pet or antique piece of art work that can't be exposed to "extreme" conditions. People do weirder shit every day. They are not that loud next to a desk fan, and most likely the one you'll be using. Maybe a co2 controller would help it beef up under only LED's. I've only used LED's as supplementary light or vegging. No clue if you have affordable access to co2 either. Just a thought.

My main concern isn't the temperature....
Main concern is the fan size for adequate air intake..? ?
Its just starting winter here so AC is 6 months away at minimum...
I would prefer 4" kit as its more inconspicuous and iv already got it venting into the ceiling space...
). Any more opinions about the 4" fan would be great
I will have the 6" kit with speed controller ready for backup

Sounds like you have a plan, only time will tell. Or Tim if your dyslexic. That ratting bastard!... Good luck

most 4 inch fans are rated at 190 cfm. you have to take into account the route your exhaust is going to take. talking to hvac guys, i learned that they use 100 foot units as a basis, and a right angle bend can count as 25 to 30 feet of that hundred foot unit. if you have a short direct venting path a 4 inch fan may be enough, if its longer than say 15 feet, or has a lot of turns, you might be better off with a 6 inch, most of which are rated at at least 440 cfm.

https://russellking.me/2012/08/19/duct-size-vs-airflow-part-1/
this is a lot more in depth than needed, but if you look this over quick, you can get an idea of what i'm talking about

Roger A. Shrubber said:

you might be better off with a 6 inch, most of which are rated at at least 440 cfm.

Click to expand...

Yes and they are probably capable of drawing at least 130 watts @ 120 volts to achieve those kind of airflow like the Vortex or Hurricane brand name in North America. And are loud too.

Roger A. Shrubber said:

most 4 inch fans are rated at 190 cfm

Click to expand...

Yes and they are probably capable of drawing at least 90 watts @ 120 volts to achieve those kind of airflow like the Vortex or Hurricane brand name in North America. And are loud too.

i don't understand your point stevie?
thats industry standards, just go to ebay and amazon, and any grow shops website you like, most 4 inch fans are rated at 190 cfm, doesn't matter what kind of power they draw, they're all close to the same. most 6 inch fans are rated at 440, just the way it is. they make as much noise as they make. i'm currently planning a new grow box myself, where the fan will be inside the box in a smaller box lined with foam above the light, hoping it will eliminate most of the ambient noise from the fan inside the house.

It is kinda like figuring out CFM requirements for a carburetor. Book numbers aside, actual mesurements like the length of the intake runners, head material and airflow capability, cubic inch displacement/combustion chamber volume, compression ratio's, as well as exhaust restriction and other factors all play an important part in picking the carb that can supply the right amount of air and fuel for a desired application. My point being, in the end trial and error are the only way to make sure it will RUN LIKE A RAPPED APE! What I'm saying is you don't know what will and won't be effective/adequate until you use it in your application.

Roger A. Shrubber said:

i don't understand your point stevie?
thats industry standards, just go to ebay and amazon, and any grow shops website you like, most 4 inch fans are rated at 190 cfm, doesn't matter what kind of power they draw, they're all close to the same. most 6 inch fans are rated at 440, just the way it is. they make as much noise as they make. i'm currently planning a new grow box myself, where the fan will be inside the box in a smaller box lined with foam above the light, hoping it will eliminate most of the ambient noise from the fan inside the house.

Click to expand...

My 4" fan is currently inside a cardboard box that the carbon filter came in, with 1"foam sides lined inside, and blankets wrapped around it... You can just hear it purring.
Im going to have to make two - 1/2" thick walled wooden box's inside each other for 6" fan also incased inside a cardboard box & everything foam lined.. Or pillows as stuffing etc..
My 6" fan roars !!
Takes 4-5 seconds to wind up to speed

If you can afford it get the bigger fan and a speed controller.