booster fan needed? CLOSED AIR SYSTEM USING C02!! HELP! - GreenPassion.org - Dedicated to Medicinal Cannabis Cultivation and Education

GreenPunter · #1 (**permalink**) 07-17-2009, 08:04 PM

the attached drawing is a diagram of my ventilation system. i have a standard home register for my inlet vent. It then divides to supply my hood and the room itself with fresh air. i have a 6" fan without any filter (using ozone) that draws air out when the thermostat kicks it on. My question is whether or not i would need a booster fan for the room inlet. with the light on, air would be moving rapidly through the ducting so i would be relying on a change in air pressure in the room to overcome the airflow to the hood and draw air into the room itself. would this work as drawn or would a booster fan be necessary. thanks.

gP

jangel · #2 (**permalink**) 07-18-2009, 12:13 PM

Hi there GreenPunter. I think you must increase your cool air intake in order to get a good draw on this. I do not know about a closed system as you are using. Is this already built or in the thinking stage?

Please read this post to understand the principles of air exchange and exhaust:

The Knowledge Project~Air Exchange

First off, for a good draw for your hood you will need to have 3 times the cool air coming into the space. So your vent pipe out of the grow is 6 inches. You will need 3 X 6 inches of cool air coming into the space to create the correct draw for you air exchange system. It works like this: Air will not allow a vacuum, so as your system pumps out the air through the exhaust system it will draw or suck the air in through the cool air vents low in the grow at the same rate. Now, yours is a closed system so this might indeed work totally differently. Either way, a fan at the cool air intake will not at all increase the rate the air comes in, it is pulled out by the exhaust fan so that is the rate it will come in as well. Putting a fan where the air comes into the space could in theory slow down the flow of air and it will not work as fast as just a passive cool air intake. It is pure physics. If the draw and air pressure is not equal, then you will see a vacuum in the space and your exhaust will not work as efficiantly as it could.

I am not sure about using C02 in a grow so hold tight I am sure others will comment.

I have also added to your title so other wiser heads than mine can contribute.

Feezle · #3 (**permalink**) 07-22-2009, 05:26 AM

I think ya' need to consider looking at your plan again ... and without going into the physics and math here, what you have planned will pull intake directly thru lamp tube and out. Good for removing heat, but not for supplying fresh air to plants.

jangel · #4 (**permalink**) 07-22-2009, 09:57 AM

Quote:

Originally Posted by Feezle

I think ya' need to consider looking at your plan again ... and without going into the physics and math here, what you have planned will pull intake directly thru lamp tube and out. Good for removing heat, but not for supplying fresh air to plants.

That is awesome the level of help you have offered this member. Thank you for paying it all foreward.

Pullo · #5 (**permalink**) 07-22-2009, 10:20 AM

Proper ventilation and cooling can be tricky when using Co2, eventually you will have to get out the calculator and do the math.
Feezle has got you on the right track though, and look over the ventilation link that Jangel posted for you.
If you have any questions regarding the math and physics, feel free to PM me and I'm sure we can get it figured out.
I am an indoor cabinet grower that uses Co2 also, maybe I can help you avoid some of the headaches that I ran into.

Best of luck to you!

Pullo

GreenPunter · #6 (**permalink**) 07-23-2009, 04:11 AM

thanks guys. i hope the air going through my hood isn't getting into my room because that would cause CO2 leakage. i have a dedicated inlet that branches off of the 1ftx6" vent at a Y, that's why i'm wondering if just static air pressure will defeat the air current being sucked through the hood and allow air to be drawn into the other arm of the Y and then into the room. if you think of the air as water, it's rushing through one side of the Y and then i'm expecting a change in air pressure to suck a chunk of water off the large fast moving stream, splitting this stream and drawing water (air) into the other side of the Y. that all seems dubious to me but i'm not a physicist.

i've attached some pics. if you look at the last pic, my question is whether or not i need to add a 4" fan after the Y joint and after the 6" to 4" reducer to get air to flow into my grow room when the 6" fan above turns on and starts sucking air out of my grow room. that's it. thanks.

gP

Feezle · #7 (**permalink**) 07-23-2009, 11:23 AM

GreenPunter,

Assuming that 6” CAP and 6” ECO Plus are your inline fans, and assuming you have no other exhaust fan, it’s clear that you would run these two fans in cycles independent of one another. In looking at your ‘air out” ‘Y’ , keep in mind that you will likely introduce efficiency losses by placing those fans anywhere but at the very closest point to end of exhaust run. Not always possible. I get that.

1) Lights On (6” CAP ON – 6” ECO Plus OFF): 6” CAP pulls thru hood and removes heat – good. But I’m not seeing any air being removed from the room. The system as setup is essentially a closed system. You may in fact find that your 4” vent allows some room air to be pulled back (reverse your air flow arrows) from the room and into the 6” duct to your hood and 6” CAP and out. The problem at that point is that your system being “Closed” does not provide an air inlet into the room to supply make up air for any drawn out thru your 4” should it do so. And I could be wrong. And no, your 6” ECO Plus, as installed, will not provide inlet air to your room during either cycle.

2) Lights Off (6” CAP OFF – 6” ECO Plus ON): 6” ECO Plus pulls from room with make-up air being drawn thru 4”, and looks like it would work. Pretty simple. And I could be wrong.

Any 4” fan you might place in your 4” duct will only be over powered by your 6”. If you add a 4” anything, add a 4” or 6” ( or 2) INLET VENT directly to the room and as near the bottom as possible.

I am once again assuming that you are at a flowering stage, only because you mention CO2. I’m not a resident expert, but have been doing HVAC for roughly 40 yrs, and have moved a little air in that time. It would seem to me that your system could be somewhat simpler. That being said, I think you should keep on keeping on. But TEST what you have drawn before you start adding additional fans at additional cost. The main idea is to get your plants good cool fresh air to respirate (much more important than the addition of CO2) and to concurrently remove the excess heat created by your lamp.

These are opinions only. Keep on.

GreenPunter · #8 (**permalink**) 07-23-2009, 01:04 PM

feezle, thank you so much for taking the time to answer my question in such detail. my pictures aren't very good so i'll try to elaborate a little better in text and i've added to my pictures. first, the dimension of my inlet is wrong. it's actually 18" by 10". from there there is a "y" pipe that splits the air. one side feeds the hood, the other side feeds the air INLET into my room. if you look at the side drawing (the first pic) you can see the split where half the air goes to the hood and half goes to the 4" inlet to the room itself.

when the light is on, air is flowing through the left hand side of the "Y", through the hood, and out of the room. if the room gets too hot, the 6" Eco Plus fan turns on and draws air straight out of the room. this is where the right side of the "Y" comes in. The right side of the "Y" feeds the 6" to 4" inlet into my grow room. so my question(s) relate(s) to whether or not air moving through the left side of the "Y" can be split so air can also be pulled through the right side of the "Y" and into the grow room without using a booster fan, rather relying on the change of air pressure due to the removal of air from the room by the 6" eco plus exhaust fan. i have a one way damper that is between the right side of the "Y" and the 6" to 4" reducer so air cannot leak from the room back out the 4" vent.

thanks again for the help.

gP

Feezle · #9 (**permalink**) 09-28-2009, 06:39 AM

Hey Green,

It's two (2) months later ....... Gonna' give us an update ?? Is that system working well ??? Hope all is well.

Feez