Passive intake size
- Thread starter Amalthea
- Start date
jondamon
Well-Known Member
You should make 2-3 5inch holes for passive intakes.
Each hole needs to be the same size of your extraction fan.
Depending on the temps of the room where you are pulling the passive air from you may have more benefit running ducting to a window but if that is the case then you will need to power the intake and not have them as passive.
If you can get your hands on a copy of July/August edition of URBAN GARDEN MAGAZINE as there is a grow room design and setup section detailing all of your needs.
J
Each hole needs to be the same size of your extraction fan.
Depending on the temps of the room where you are pulling the passive air from you may have more benefit running ducting to a window but if that is the case then you will need to power the intake and not have them as passive.
If you can get your hands on a copy of July/August edition of URBAN GARDEN MAGAZINE as there is a grow room design and setup section detailing all of your needs.
J
mistaphuck
Well-Known Member
my passive intake is the gap under the door, but its a pretty big gap...
kingofqueen
Well-Known Member
Mine is 4in in and 4in out it pulls air in just fine . 4" can fan and 10' long 4 in intake . I know its not right but it works .
kingofqueen
Well-Known Member
That rule of thumb is beyond my mathmatical skills .
Amalthea
Active Member
So I need more passive intake holes compared to extract ? So I need 3 holes 5 inches in Diameter ?
I'm planning to intake from the window by running ducting in which case can I just have the one hole ? I was planning on using a 4 inch inline fan for the intake ?
Sorry I'm a bit confused!
I'm planning to intake from the window by running ducting in which case can I just have the one hole ? I was planning on using a 4 inch inline fan for the intake ?
Sorry I'm a bit confused!
mistaphuck
Well-Known Member
<<<< I think that would be a better rule of thumb, just add an "about" in there and bam, you just made a rule of thumb up!
Oldgrowth
Well-Known Member
One more thought to confuse you more, if you intake is as large as 3x your output you will lose the negitive presure effect. I use smaller intakes than that so no smell will escape my grow room. Negitve presure, get it? just adjust your fan size as needed. This way i can use a spare bedroom and rest of house does not smell!
Amalthea
Active Member
Yes I need to maintain negative preassure so if I only do one hole nd keep it small would that be fine ? I can use an intake fan ? Will enough air get in or will the room implode from too much negative preassure?
jondamon
Well-Known Member
If you are using passive intakes then you have to make sure the exhaust fan can pull enough clean air through the holes. This is why you have to have more holes when its passive.
If you are using a powered intake fan then aslong as you fan is roughly 25% less powerfull than that of your exhaust you will not get any odour leaks.
You also will not get any odour leaks using 3 5inch holes in your door. Just make sure they are vented to reduce the light leakage.
If you are using the 5inch as exhaust then aslong as the 4inch is 25% less powerfull than your 5inch then you DO NOT NEED passive intake vents as the negative pressure will be enough to keep odour leakage at bay if you opt for a powered intake.
However if you are running a Carbon filter attached to the 5inch you have to allow a 20% reduction in the power of the exhaust. Thus you have to allow this into your intake fan too.
so for instance if you are running a 5inch 690m3/h fan with carbon filter your extraction is only going to be pulling around 550m3/h with the filter attached. So as long as your intake fan is 440m3/h or less then you will be fine.
Did that make sense?
J
If you are using a powered intake fan then aslong as you fan is roughly 25% less powerfull than that of your exhaust you will not get any odour leaks.
You also will not get any odour leaks using 3 5inch holes in your door. Just make sure they are vented to reduce the light leakage.
If you are using the 5inch as exhaust then aslong as the 4inch is 25% less powerfull than your 5inch then you DO NOT NEED passive intake vents as the negative pressure will be enough to keep odour leakage at bay if you opt for a powered intake.
However if you are running a Carbon filter attached to the 5inch you have to allow a 20% reduction in the power of the exhaust. Thus you have to allow this into your intake fan too.
so for instance if you are running a 5inch 690m3/h fan with carbon filter your extraction is only going to be pulling around 550m3/h with the filter attached. So as long as your intake fan is 440m3/h or less then you will be fine.
Did that make sense?
J
Amalthea
Active Member
That is the clearest most coherent response I've had to this problem in the last few weeks of searching. Thank you so much. It makes sense now!!!
Thanks,
Amalthea
Thanks,
Amalthea
janiking
Well-Known Member
I lold
