G
gazcat
My exhaust is twice the CFM as my intake, what are the benefits? What are the disadvantages as opposed to the other way around. Thanks!
You most likely have extreme negative pressure and are putting unnecessary strain on the exhaust fan. Instead of going with a passive intake I'd recommend using a speed controller to slow down your exhaust fan a bit. An active, as opposed to passive, intake is always better. You want negative pressure for odor control but you only need a little bit of negative pressure...I mean like your exhaust fan trying to pull out just a bit more than your intake fan can feed in. That's all you need. Passive intakes are OK for very small grow spaces IMO.gazcat said:My exhaust is twice the CFM as my intake, what are the benefits? What are the disadvantages as opposed to the other way around. Thanks!
If you have a 400cfm fan on the exhaust side and a 200cfm fan on the intake side what is that? I think that's what he's talking about. Also it does not matter how many exhaust or intake fans you have just the total volume trying to be exhausted and the total volume that can actively be fed to the space.FreezerBoy said:Your exhaust is not twice the CFM as your intake.
In any passive intake setup I've seen negative pressure has never been a problem and always present...unless someone builds a very leaky room I guess.One powered exhaust with dual passive intakes allows you to pull air rather than push while retaining negative pressure.
That's overstressing your fans and increasing noise while restricting exhaust to the amount of air coming in.Whatever said:If you have a 400cfm fan on the exhaust side and a 200cfm fan on the intake side what is that?
Which is why it's a benefit.Whatever said:In any passive intake setup I've seen negative pressure has never been a problem and always present
Most passive intake setups I've seen are undersized restricting airflow too much.FreezerBoy said:Which is why it's a benefit.
That's called bad carpentry.Whatever said:Most passive intake setups I've seen are undersized restricting airflow too much.
2X Exhaust=IntakeChaghatai said:Anyone know of a rule of thumb chart or som ething for passive intake size. Like a desired cfm to inches^2 kinda thing?
You got it backwards. 1/2 intake=exhaust. Example 8" intake=4" exhaust.gazcat said:Ok so would it be best to go 2X intake = exhaust?
I could get a 8" 500cfm can fan for an intake and a 6" 250cfm for exhaust
gazcat said:No I am saying the most efficient way to vent is with a active intake? rather than passive?
im simply asking if a 500cfm intake and a 250cfm exhaust would be a good thing
JohnnyToke said:blowing air into the intake causes positive pressure and can lead to smell leaks among other things. you dont want that.
make the intakes down low and the exhaust up high.
For a small grow like a closet one exhaust without an intake fan, relying on a passive intake, is fine. How many watts are you planning on running and in what size space? So are you saying if odor leaks from the closet into the living space no problem?My grow is in my closet and smell really isnt a big deal... whast the best way?
Farmer John has 19 cows. All have balloons attached to their butts. After a fine meal of bean and hay burrittos and several kegs of Shlitz Malt Liquor, the cows begin to fart. The balloons swell and eventually burst, permeating the barn with the foul smell of concentrated methane. Why? Positive pressure. Gas enters the enclosure faster than it can exit causing the balloon to explode. Explosions bad. Positive pressure=explosions=bad. Positive pressure bad.gazcat said:whast the best way?
Damn, and I thought this was just a friendly conversation about ventilation concerns. Thanks for the info about the negative/positive pressure though.FreezerBoy said:The best way to get arrested is to put up a neon sign and scream from your front yard that you're growing pot while blowing smoke into the face of local gendarmes and passing out samples and clones. But pumping positive pressure into your cab is a close second. Make sure your affairs are in order and your lawyer well paid. Then kiss your freedom goodbye. Have fun in jail.
An active system only causes UNDUE stress if not balanced properly. Having negative pressure, even minor, with a passive intake is putting stress on the fan cause it's trying to exhaust more air than it can take in. Too small a passive intake and UNDUE stress.JohnnyToke said:my .02 is pumping air in with a fan and pulling air out with another cause the fans to stress. A central a/c unit on a home or apt has a passive intake for a reason, it is the most efficient way to create airflow.
Positive/negative pressure regulation is soooooo simple in an active system.But pumping positive pressure into your cab is a close second.