passive intake on 6'x7'x7' room ?

[hbstoner]

Currently running active intakes on this room, but wondering if switching to passive intake would make a big difference. Exhaust fan is a stanley blower (mod'd) and so is the intake. The intake right now is only running at the "1" speed setting and the exhaust is running at "3" which from what i have read is about 235CFM. Both are going through 6" ducting . would just removing the intake fan and making a large passive intake be a better idea and keep the room cooler? Or is this size room a little to big to only have passive intakes..

 

[Whatever]

would just removing the intake fan and making a large passive intake be a better idea and keep the room cooler?

An active intake system is the most efficient and especially important as the grow space gets larger. You only need a touch more exhaust cfm than intake cfm to maintain negative pressure.

 

[hbstoner]

thanks for the input, is there any way to calculate if you have negative pressure.. i know there is the "door closes on its own" way but that way is not possible in my space. Anyone know of any other ways to test and see if you have neg pressure?

 

[Whatever]

thanks for the input, is there any way to calculate if you have negative pressure.. i know there is the "door closes on its own" way but that way is not possible in my space. Anyone know of any other ways to test and see if you have neg pressure?

No way to really calculate except you can get close by knowing the ratings of your intake/exhaust fans and make sure they're matched properly. Use a lit stick of incense held right near any cracks or just before you close whatever it is that seals your space and make sure the smoke goes into the room. Best thing to use for fine tuning the intake/exhaust balance is a speed controller dialing down the stronger fan...whichever it is intake or exhaust.

 

[hbstoner]

No way to really calculate except you can get close by knowing the ratings of your intake/exhaust fans and make sure they're matched properly. Use a lit stick of incense held right near any cracks or just before you close whatever it is that seals your space and make sure the smoke goes into the room. Best thing to use for fine tuning the intake/exhaust balance is a speed controller dialing down the stronger fan...whichever it is intake or exhaust.

ah incense , great idea. thanks much!

 

[hbstoner]

just tested with incense and it didn't suck in with the intake fan on low and the exhaust on high.. so do you think my only next options are to get a bigger exhaust fan or to do a passive?

 

[FreezerBoy]

You can't exhaust more than you intake but, you can intake more than you exhaust. That's what you're doing here and it's why you have positive pressure. On another note a 256 CFM fan in a 294 CF room seems grossly underpowered.

 

[hbstoner]

ya it seems that is the case, that could be why my temps are a tad high as well. out to get a new exhaust fan

 

[Whatever]

You can't exhaust more than you intake but, you can intake more than you exhaust. That's what you're doing here and it's why you have positive pressure. On another note a 256 CFM fan in a 294 CF room seems grossly underpowered.

Sentence 1: You can do either with an active system if your space is leaky enough.
2: With the intake set on low and the exhaust set on high and no negative pressure something is wrong somewhere. Sounds like some type of bottleneck on the exhaust side and not the intake/exhaust fan setup itself or maybe a very leaky setup.

 

[FreezerBoy]

You can't pump air out faster than it comes in. You can't pump out what isn't there.

Pull the fan off the intake and see what happens.

 

[starrider]

Do what Freezer Boy says just use a passive intake and if anything add to your exhaust .peace