where to intake cold air??

[dontstepongrass]

let's say i have an a/c and i would like to know where i should have this cold air coming into my cab. should i keep my intake at the bottom where it was before a/c (exhaust is in top right corner) or should i have the cold a/c air come into the top blowing the cold air down past the light? OR should i just have it come in at light level and blow directly under light going across cab?

thanks

 

[GirthDogg]

I would vote for cold air intake on the floor on one end of the cab and hot air exhaust on the top at the other side. This way the cold air comes in and helps force the hot air up towards the exhaust and out.

 

[Mr Celsius]

Always have you exhaust at the top of the room/cab (heat rises) and always have your intake half the size, on the opposite side of the room/cab and on the floor (cold falls).

You now have a wind tunnel threw your cab/room that show create an equal temp throughout the room. The intake half the size of the outtake is for negative pressure and odor control.

 

[dontstepongrass]

ok so you're saying that if my exhaust were 4" circle then my intake should be a 3" circle so that i would have roughly a 1:2 intake area to exhaust area ratio.

 

[green_tea]

yeah hes talking overall area i believe.

Or you could go a different route and make the hole bigger, but cover it with a carbon filter.

(i dont mean a canister scrubber, just like a furnace filter kinda deal.)

thats if you want to be super paranoid about smell.

 

[Guest]

yeah hes talking overall area i believe.

Or you could go a different route and make the hole bigger, but cover it with a carbon filter.

(i dont mean a canister scrubber, just like a furnace filter kinda deal.)

thats if you want to be super paranoid about smell.

WTF are you talking about? Do YOU know WTF you are talking about?, I don't know WTF your talking about. Most other folks in here don't know WTF you're talking about either. Enough already Kid. An absolutely freaking BRILLIANT answer on your part.

 

[GirthDogg]

I think he is saying that if your exhaust is 4 inches then your intake should be 2 inches.
The negative pressure Mr. C is talking about is crucial, both for maintaining heat control and ensuring that no air has a chance to "leak" out of your controlled area.



...and I also have no idea what green tea is talking about.

 

[Guest]

I think he is saying that if your exhaust is 4 inches then your intake should be 2 inches.
The negative pressure Mr. C is talking about is crucial, both for maintaining heat control and ensuring that no air has a chance to "leak" out of your controlled area.



...and I also have no idea what green tea is talking about.

Absolutely amazing GirthDogg, that and ten cents won't buy you a cup of coffee.

 

[GirthDogg]

ok...? what exactly does that mean?

Man, is this another thread where I am the only one talking about the topic?

 

[dontstepongrass]

i'm assuming maybe he's referring to the fact that 3" circle, not a 2" circle, has roughly half the area of a 4" circle. he could have been a bit more polite tho...

 

[FirstTracks]

My experience may differ from that of others....

I've only worked with 150, 250, and 400 watt setups, but i've had best results in each setup with an intake that's twice the size of my exhaust and i've always had plenty of negative pressure.

 

[dontstepongrass]

i appreciate all feedback. i've been tweakin the setup and in a short time i will again know what im still up against.

 

[PharmaCan]

ok so you're saying that if my exhaust were 4" circle then my intake should be a 3" circle so that i would have roughly a 1:2 intake area to exhaust area ratio.

I'll be damned, someone who understands simple math. LOL - I wish I could pin a gold star on your post.

Two points here - some things to consider. First of all, air can form thermoclines and putting the cold air into the bottom of the cabinet would be more conducive to this kind of effect. Circulating fans in the grow room can mitigate this problem, but I have my cold air intake in the middle of the wall - vertical orientation.

Additionally, while the 2:1 intake:exhaust ratio is commonly accepted, it really is applicable ONLY when both intake and exhaust vents are powered. With a powered exhaust and a passive intake, the exhaust port is, for mathematical purposes, "bigger" than its actual size because air is being forced through it at an artificial rate. My intakes are bigger than my exhausts on all my cabs and there is negative air pressure in all of them.

Just my $.02

PC

 

[GirthDogg]

Any info as to the power of the exhaust fan?
That seems to be the missing piece of data in this equation.

As for the original question in the title of the thread, I believe the consensus seems to be "the Bottom of the cab."

 

[dontstepongrass]

my intake is now at the bottom, but then it goes through a stanley blower pushing the cold air straight at the lights. so far this is proving to work. we shall see. more testing to be done!

 

[Mr Celsius]

Glad you got it figured out dontstepongrass, don't let anybody muddle such a simple process up. I've never used an active intake... never needed to, so I can't really bring any real experience, but I've always had my intake half the size of my outtake.

All that needs to be known is that negative pressure is a good thing, so make your intake smaller.

 

[brainlab]

i agree with PharmaCan , a passive intake should be about dubble in size of the power exhaust.