can you have too much exhaust power?

so my future box will be 96 ft^3, 4x4x6. i know you want to circulate air 3-4 time a min. this would make a 400 cfm fan a no brainer. my question is if i upgraded to around a 760 cfm fan would it have any ill consequences or only help that much more?

Well noise would be a lot more. Power use would go up, but probably nothing you would ever notice in your bill. I would just buy what you need and spend the extra money on some other aspect of your grow where it would be put to better use. My 2 JR

If you decide you might want a bigger grow room down the line; get the bigger fan and a fan controller. THat way you can turn down the power of the fan to find the best setting (noise will decrease as well). Then when you build your new room later on, you already have a fan. Less $$ in the long run.

Plants need air as long as you are letting new air in itll be ok

thanks for the input all! would it be a drastic noise difference? that was my main concern. energy bill issue is ok by me. here are the two fans i am looking at, the 435 and 745 fans are the ones in interest. anyone used these or have any input? a 745 fan wouldnt make air move too fast, right? thanks a ton.

http://www.plantlightinghydroponics.com/valueline-centrifugal-fans-c-76_629.html

Hold up a second...you dont need to exchange the air 3-4x/min, this is serious oery verkill...unless you want to burn a couple 1kw in that box?? Once every 5 min or 12 exchanges per hour is the recommended minimum. I think a 100cfm fan would be more than enough...that would give you 60 exchanges/hour....plenty

redi jedi said:

Hold up a second...you dont need to exchange the air 3-4x/min, this is serious oery verkill...unless you want to burn a couple 1kw in that box?? Once every 5 min or 12 exchanges per hour is the recommended minimum. I think a 100cfm fan would be more than enough...that would give you 60 exchanges/hour....plenty

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i understand this is fine for fresh air for the plants, but for heat control? i will have 900-950 watts of lighting in there. gotta get the hot air out and replace it with cooler stuff. this is correct right? please tell me if otherwise, thanks!

Well thats a different story. You didn't say anything about heat from your lights in your first post. Anyways...you could use a single 400cfm to ventilate and cool your light(s).

cool thanks my bad for not being specific

Hi jact55.

I notice you havnt mentioned anything about odour control, or are you in a lucky situation where u might not need it?

The one thing id say, if your planning on a carbon filter make sure you get one with higher or on par cfm as your extraction fan, or else you'l suck up the air through your carbon too fast and have a smell issue to deal with. Ofc sumone mentioed a fan speed controller which will help that kind of situation too i think.

Iv just learned this the hard way, im off out to buy a rhino filter which is 350cfm to work with my rvk 100 whcih is only 175cfm. Hope it does the job and will be suitable, i asked on here but havnt had much input back on my post, was only looking for a simple yes or no.
Im having smell issues i need to get sorted as im venting into another room in my house.

Hope that helps you in some way. Good luck with it.

** just seen your on your 712 post and you 6th grow so you porb already knew this m8, i thought this was you planning your first grow. My bad.

View attachment 979819

Goin by that pic^^, yeah... you def know what your doin lol. Damn nice lardass bud mate.

Hi monty, I am gonna make a diy carbon scrubber. thanks

as far as you issue, are you saying that the filter needs a 350 cfm fan to work? if so, i think that you are gonna have problems forcing air out of your filter and therefore out of your room. i had that issue with a small fan and a filter before. might have to get a bigger fan. please let me know if i misinterpreted your question though.

Hi mate, yeah, im goin to upgrade my filter to a rhino, but hoping my rvk 100 will still have enough pull in it to pull through the 350cfm filter and also give me adequate air exchange for my dr60. I think it should, as i see a few hydro shops selling these two together as a kit.
I hope it does because if not, i simply do not have any more money to buy another fan any time soon. I never thought id be getting problems like this with a dr60.

Thanks man.

i just bought a 200cfm fan for my closet that is 3 x5 space. and let me tell you its plenty!! its kinda loud so i would keep it to 200. it definitely does the job though.
when should i turn it on though? every 30 minutes? im confused about that.

also, i only have a cfm fan for exhaust yet no intake. unless i open my closet door flap thats my intake. but ive noticed when i seal up my closet and turn on the exhaust its AIR TIGHT like a mother! and if i open a little flap at the corner of the opening it automatically starts pulling in a bunch of fresh air from outside like a natural backdraft intake. would this be sufficient enough if i left my closet closed up for hours on end except for the natural intake?
i hope i explained that well enough i just took a huge dab

thanks roll it up!

It's difficult to move air too fast, but it's easy to waste money on useless excess. 2-400CFM is plenty per kw. Your box size isn't terribly relevant. How many watts ya tossing into that little box?

graab187 said:

i just bought a 200cfm fan for my closet that is 3 x5 space. and let me tell you its plenty!! its kinda loud so i would keep it to 200. it definitely does the job though.
when should i turn it on though? every 30 minutes? im confused about that.

also, i only have a cfm fan for exhaust yet no intake. unless i open my closet door flap thats my intake. but ive noticed when i seal up my closet and turn on the exhaust its AIR TIGHT like a mother! and if i open a little flap at the corner of the opening it automatically starts pulling in a bunch of fresh air from outside like a natural backdraft intake. would this be sufficient enough if i left my closet closed up for hours on end except for the natural intake?
i hope i explained that well enough i just took a huge dab

thanks roll it up!

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1. NEVER run a light without the exhaust running. (with the caveat of super-advanced and way-monitored systems using CO2 enrichment)

2. Input vents should be DOUBLE the size of exhaust vents.

There ya go. At least 20% of everything you need to know about vents...

graab187 said:

i just bought a 200cfm fan for my closet that is 3 x5 space. and let me tell you its plenty!! its kinda loud so i would keep it to 200.

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Air resistance is to the cube or so of speed. Thus, buying a 400cfm fan and a fan controller that drops it down to 200 cfm is INFINITELY better from a loudness and efficiency standpoint. Like filters, it is almost impossible to go wrong by buying the biggest fan you possibly can and downgrading it through a controller.

ManyAndVaried said:

2. Input vents should be DOUBLE the size of exhaust vents.

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im pretty sure its the other way around dood.