Intake fan CFM size ???

[Dreamscape]

Hola amigos ,

I was curious as to what would be the appropriate size Intake fan in CFM for a 928 cubic foot room ??

Also if a carbon filter made to handle "4000w" of light were in this same room and there was only 2400w running, what would you suggest the CFM of the exhaust fan be ??

Many thanks as always friends ,

~ Dream

 

[MTF-Sandman]

An 8" inline oughta be plenty for the exhaust...most likely you won't need an intake fan tho...just let the negative pressure from the exhaust fan do the work.

Rating a scrubber by a wattage is a totally worthless way of measuring it's abilities. Having a slightly larger than needed scrubber is a good thing...it'll last longer and will make sure that the odor is completely removed. Depending on the exhaust fan, a CAN100 size scrubber should do the trick with that 8" exhaust fan.

 

[cadillachydro]

Can't beat that advice. A little extra is always better when it comes to scrubbing and cooling.

 

[Dreamscape]

An 8" inline oughta be plenty for the exhaust...most likely you won't need an intake fan tho...just let the negative pressure from the exhaust fan do the work.

What about CO2 and what not ?? The room would be sealed up as tight as possible.

The scrubber that would be used would be the Mountain Air 6"x40" scrubber btw ...

And as their might be a possibility of the lights going up to 3.6k from 2.4k the 4k scrubber would be beneficial in the future.

 

[MTF-Sandman]

Ahhh...didn't know you were running CO2. The way I see it, you've basically got 2 options for air quality in plants. Either suck alot of fresh air through there to keep the CO2 levels high enough or seal that bitch and control the enviro 100% via AC, dehum, and CO2 system. Trying to vent a CO2 system is a real waste as you'll be constantly trying to keep the CO2 levels up - which will go through lots of propane/bottled CO2.

You got an AC in there? If so, how many BTU's?

 

[thedarkknight]

Ahhh...didn't know you were running CO2. The way I see it, you've basically got 2 options for air quality in plants. Either suck alot of fresh air through there to keep the CO2 levels high enough or seal that bitch and control the enviro 100% via AC, dehum, and CO2 system. Trying to vent a CO2 system is a real waste as you'll be constantly trying to keep the CO2 levels up - which will go through lots of propane/bottled CO2.

yup yup

trying to do both is most likely trying to do too much... like peeing in the wind.

more details on your setup would be best. And its best to start with exhaust rating followed by intake.

 

[Dreamscape]

Ahhh...didn't know you were running CO2.

I think I worded myself wrong ...

In the first post you made - I thought you were saying that I wouldn't need an intake fan for C02 because the exhaust would suck it in with back pressure ?? I didn't understand how this would work ...

So when I said "What about CO2 and what not" I meant as in the intake fan would bring the CO2 in. Obviously the cracks of the house are going to let enough air into the house but since the plan is sealing this baby up pretty good for all general purposes and benefits (scent,security,sound,light,air flow,temp,ect) I figured having an intake into the grow room would be needed since i'm NOT running C02. Every grow room setup i've read about that was not running C02 from some mechanical source always had an intake fan breathing in fresh air from outside ...

As for the exhaust fan as well - my calculations are that I would need something around 650 cfm ?? is that close/far , where did I go wrong if so?

thanks
~ Dream

 

[MTF-Sandman]

lol...ok, I think we're on the same page now.

If you're using the fresh air to supply CO2 to your plants, then a 8" exhaust fan will take care of you. As the fan exhausts air from the room, it'll suck air in through your passive intake (basically just a hole in the wall or a door) due to the negative pressure in the room. This is also great since it keeps air from leaking out of the room but means that you'll need the exhaust fan running continuously to keep odor from leaking out the intake or any other non-sealed parts of the room. For passive intake sizing, the rule of thumb is 2-3x the sq/in of the exhaust fan - in your case an 8" inline (4x4x3.14) give you roughly 48 sq/in of exhaust - so a 10"x10" square intake (100 sq/in) should be able to provide plenty of air.

I'm running CO2 in a sealed room right now...haven't had an exhaust fan in there ever. The only aspect of "fresh" air you need is the CO2, so if you provide it from another source (ie bottle/burner), you don't need to bring in or exhaust any air from the room - but it also requires that you manage humidity and temps via AC and dehumidifier which means you're only having to control the environment in the grow area, and not the entire house. People vent CO2'd setups because they don't have complete control of the environment and are relying on the fresh air to drop the humidity/temps. Doing that, you'll be constantly fighting to keep the CO2 levels up while keeping temps/RH down and it's very inefficient.

Those CFM numbers are about right...and most 8" inlines have very similar throughput ratings that are in the range you'll be needing.

 

[thedarkknight]

so are you running a sealed room or one with in/outs?

if your going to run a sealed room you will need a dehumidifierand, a co2 source (burner/bottle) and if your going to up grade your watts then you might as well get the 12k btu model.

if your going to run in/outs then your going to need 200-300 cfm per k for your exhaust, and the highest your intake should be is 95% max of your exhaust total.

lastly, you figure your ventilation needs and then get a filter that matches accordinlgy, not vice versa.