Negative static pressure

[HAZEOHOLIC]

Hello everyone have a question on negative pressure.
I have currently a closet that is 2'W x 2'D x 7.5'H I went to the local hydro store pick up a 6" axial fan made a hole behind the closet almost at the bottom. place the 6" fan there as an intake now I already had a 150CFM 4" centrifugal exhaust fan plus 4" carbon filter rated for 200CFM will I achieve the negative pressure that i want for smell?
Thanks for the advice people.

 

[GrowTech]

You need a higher exhaust speed than inlet speed.

170CFM exhaust.
70CFM inlet.

^Would work

 

[Seamaiden]

Why do you need to push air as well as pull it, GT? Negative pressure, if intake is sufficient, will allow the air in just fine.

If my math is right, total volume is approximately 30'cu. If he were to turn over about 3x total volume/minute, then he'd have LOTS of negative pressure going on, no need to push that with another fan (more electricity + waste heat, too). Just be sure that intake is sufficient or you'll get noise. 170cfm is easily 3x turnover.

 

[HAZEOHOLIC]

You need a higher exhaust speed than inlet speed.

170CFM exhaust.
70CFM inlet.

^Would work

I really don't know what CFM the 6" axial fan is it doesn't say but i think it has to be a little more then 200CFM that sucker blows. Also I notice that the carbon filter when on the exhaust fan it slows ithe fan down quict abit. I have the filter so that the exhuast fan suck out of the filter throught the ducts and out on top of the closet clean.

Why do you need to push air as well as pull it, GT? Negative pressure, if intake is sufficient, will allow the air in just fine.

If my math is right, total volume is approximately 30'cu. If he were to turn over about 3x total volume/minute, then he'd have LOTS of negative pressure going on, no need to push that with another fan (more electricity + waste heat, too). Just be sure that intake is sufficient or you'll get noise. 170cfm is easily 3x turnover.

I know that passive intakes just takes for a opening or open door for air to come in but if I made a hole in the bottom of the closet with no fan blowing into it won't smell come out that hole if left exposed?

 

[Seamaiden]

No, not if the fan is moving air out of the room in sufficient volume, otherwise there wouldn't be negative pressure. Try pushing the air through the filter instead of pulling it through.

 

[HAZEOHOLIC]

No, not if the fan is moving air out of the room in sufficient volume, otherwise there wouldn't be negative pressure. Try pushing the air through the filter instead of pulling it through.

you mean having the exhaust fan sucking up all the air in the closet., and into the filter? If that's the case then once the air travels into the filter where does the filter air goes if the carbon filter is in the closet.?
cause the carbon filter is caped on one end one way is locating the filter outside the closet. but the reason it's inside is to hide it from being seen

 

[Seamaiden]

What? Um... yeah.. I think. What I mean is like this.. Grow box/room --> exhaust fan --> filter.

Just put the filter in line with the fan, but have the fan push the air through the filter, don't try to have it pull the air through the filter and then the fan itself. If no air goes through the filter, then how does it work? Where does the exhaust ultimately end up? Every set-up I've seen has duct work in which a filter could easily be placed, so I guess I'm not quite understanding what you've got going on there.

 

[JordanTheGreat]

it really depends on the type of fan that you are operating...axial fans dont have a lot of back pressure so having them pull air through a scrubber would be pointless. an inline fan would pull the air better through the scrubber and in this case the clean exhaust would be ducted outside of the tent/closet/cab. if sufficient negative pressure is attained within your grow enclosure than no air would ever be able to escape the passive intakes because they are always drawing air into the tent to be cleaned.

 

[JordanTheGreat]

there is also a filter design i saw somewhere on RIU that might work well with an axial fan. its some scotchbrite cloth sewn together like a pillow case, filled with activated carbon and fastened over the exhaust. people said it worked very well, i think its called my $3 carbon scrubber...

 

[Seamaiden]

That was panhead's thread. I need to learn more about fans. Especially if I want to keep my title here at home as Queen of Fans.
(I create a wind tunnel effect so we don't have to turn on the central A/C.)

 

[HAZEOHOLIC]

So hot stinky air goes in the carbon filter caused by the suction of the exhaust fan and exhaust fan sucks it out through flex duct and out the top hole in the grow room.

Or air being drawn into the flex ducting and into the exhaust fan and into the carbon filter and out the filter if this method is right then after it leaves the filter where does the clean air goes if the filter is still in the grow room.


sorry if this is stupid but that's 2 blunts of sour dress to the face will do to you. lol

 

[JordanTheGreat]

clean air can get exhausted via ducting... or something else i have seen is a small multi pass carbon scrubber that is not even on the exhaust line at all...dude was usin CO2 and no filter on his exhaust for prompt temp/humidity adjustment... all in all, if the filter is on your exhaust line, the clean air goes wherever the air from your vent fan blows

 

[HAZEOHOLIC]

clean air can get exhausted via ducting... or something else i have seen is a small multi pass carbon scrubber that is not even on the exhaust line at all...dude was usin CO2 and no filter on his exhaust for prompt temp/humidity adjustment... all in all, if the filter is on your exhaust line, the clean air goes wherever the air from your vent fan blows

Thanks Jordan I finially got to take a pic of the closet as you can see I put a 4" duct in the top part of the closet and my 6" axial fan close to the bottom how would one set this up nice and neat.Also I,m not trying to show any kind of duct or filter on the outside thanks everyone for the advise.

 

[JordanTheGreat]

secure the filter directly to the fan, and if it wont fit between the wall and the hole up top, then face it so that the duct would have to make a 'U' to get out, keep everything as close to the roof as possible. as long as you dont run any ducting past the wall of the cab you should be alright. i had to get insulated ducting to quiet down my vortex though, damned thing sounds like a leer jet...

 

[HAZEOHOLIC]

Hello everyone well i think I finally got it down pack I put up my inline fan and filter I posted up pic to see if I installed it right please feel free to comment don't worry about the wires I clean it all up once it's suppose to go that why. I'm try to get a negative pressure effect, I have a 6" passive intake towards the bottom. You really can see the passive intake hole cause of the lamp covering it

Also wanted to comment once i turn off the fans at lights off smell will escape through the passive intake hole? if so what can I do to prevent that from happening. Thanks again everyone for all the help once I figure out the vent system I'll have no problems setting up the flower room which is next.

 

[HAZEOHOLIC]

Anyone has no comment I really need to know if this is the way it goes. the last thing I need is for the neighbors to smell it and I really need to bring my mothers from the other place there starting to stink over there. Thanks for listening.

 

[smoke and coke]

i usually run exhaust fan all the time.

 

[HAZEOHOLIC]

i usually run exhaust fan all the time.

Thanks smokeNcoke that's what i thought have to run exhaust all the time to prevent the smell from coming out the passive intake hole. Now what are people doing about the lights off temps at night if the exhaust is running will temps drop drasticly?

 

[Seamaiden]

They should not go any lower than the surrounding ambient air temperature. And, even if they do drop, as long as we're not talking about a hard frost, they'll be ok. A bit of slowing on the growth, but won't kill them. Do you let your house get colder than 55F? (Yes, I know what the books say, I'm talking about what I've experienced.)

 

[HAZEOHOLIC]

They should not go any lower than the surrounding ambient air temperature. And, even if they do drop, as long as we're not talking about a hard frost, they'll be ok. A bit of slowing on the growth, but won't kill them. Do you let your house get colder than 55F? (Yes, I know what the books say, I'm talking about what I've experienced.)

Thanks for the reply seamaiden no I don't keep my apartment colder then 55F have thermostat at 75F so ambient temps in the room will keep closet around room temp? ok I get.
Also seamaiden what do you think about my exhaust filter setup need your input is that the right why to achieve odor control? take a look at my pics a couple of posts up.thanks for the check in