Ventilation Questions

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infdjedi

Well-Known Member
Hi All,

I have a couple questions about my grow room if some of you could help out that would be awesome.


My grow room is 4H X 4L X 2W = 32 Cubic Feet. I have a 400W HPS in a 6'' cool tube. I sorta cheated.. and have my cool tube acting as my exhaust system.. pulling air from inside the box over the light, then out of the box into my room. The box is mostly air tight but I do not have an intake system.. just using passive. I am thinking of changing this and hooking up the other end of the cool tube to a window to get cooler air over the light so I can get it closer to the plants. THe only problem is that this will require me to buy an additional fan to act as an exhaust. I also might as well get another one for intake as well. So, my questions:

1. Is a 4'', 80 CFM duct fan sufficient for my grow box? That will be circulating air over twice per minute.

2. Can I get away with using passive exhaust? I dont really want to get ANOTHER fan to bring cool air in as I am kinda broke and trying to reduce excessive noise.

Thanks for any help you can provide.
 
keico

keico

Well-Known Member
infdjedi said:
Hi All,

I have a couple questions about my grow room if some of you could help out that would be awesome.


My grow room is 4H X 4L X 2W = 32 Cubic Feet. I have a 400W HPS in a 6'' cool tube. I sorta cheated.. and have my cool tube acting as my exhaust system.. pulling air from inside the box over the light, then out of the box into my room. The box is mostly air tight but I do not have an intake system.. just using passive. I am thinking of changing this and hooking up the other end of the cool tube to a window to get cooler air over the light so I can get it closer to the plants. THe only problem is that this will require me to buy an additional fan to act as an exhaust. I also might as well get another one for intake as well. So, my questions:

1. Is a 4'', 80 CFM duct fan sufficient for my grow box? That will be circulating air over twice per minute.

2. Can I get away with using passive exhaust? I don't really want to get ANOTHER fan to bring cool air in as I am kinda broke and trying to reduce excessive noise.

Thanks for any help you can provide.
Click to expand...
As long as the room that the cool air is coming from through your passive intake is very cool, then you should be ok

I have an ac in my room and make sure my temps never get over 80 degree Fahrenheit
 
doitinthewoods

doitinthewoods

Well-Known Member
I'd use the fan for the exaust and have a passive intake. It's not really cheating pulling the air through a filter, through the light and out of the exaust. That's actually one of the better ways to do it, and it's kinda pointless to do it any other way unless you have a substantial op and have the need to have an independent air filtration system. As long as your exaust is pulling more than your intake is taking in, you'll create a vacume and the air exchange should be fine (assuming that your box is tight. If not, seal it a little better). Leave the passive intake, and use that fan, or a bigger fan to exaust. More fan on the exaust will draw more air through the passive intake.
 
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infdjedi

Well-Known Member
Hmm, interesting. So you are saying hook up the carbon filter INSIDE the box and pull air through the filter, over the light, and then out of the box? I always thought that the best way was to have the filter at the other end of the exhaust where the air is being pushed OUT of the filter. Does it make a difference?

Thank you for helping me out.
 
ow.douglas

ow.douglas

Well-Known Member
At 80 CFM (pretty low) I suspect that you are using a booster fan without a filter. You don't say what the conditions in box are. If your temps are good and you are only looking to cool the light I agree with the others that passive intake is fine. If the room temp is lower than the box temp, pull room air over the light and exhaust back to the room. Flowing more air would also help a 4" centrifugal would double the air, around 170 CFM for about $100. You could also use a small filter with a 170 if you wanted to go that way in the future. Just an opinion and an option, take it for what it's worth.
 
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infdjedi

Well-Known Member
Temps range from 80 ON to 65-70 OFF. Not sure what you mean by a duct booster. I have a 6'' duct fan pulling air from inside the box out through a duct muffler. Going to buy a carbon filter soon (which is why I am reworking my ventilation system). Do you think a 4'' Carbon Filter or a 6'' carbon filter would suffice for my area?

thank you for the advice and options.
 
keico

keico

Well-Known Member
infdjedi said:
Temps range from 80 ON to 65-70 OFF. Not sure what you mean by a duct booster. I have a 6'' duct fan pulling air from inside the box out through a duct muffler. Going to buy a carbon filter soon (which is why I am reworking my ventilation system). Do you think a 4'' Carbon Filter or a 6'' carbon filter would suffice for my area?

thank you for the advice and options.
Click to expand...
Look before you spend the money to buy, a carbon filter just DIY your own.

I always here people talk about these carbon filters they buy and then need a strong fan to either push or pull through them

I built my own and it does not require a strong fan at all

http://forum.grasscity.com/general-indoor-growing/273604-small-carbon-filter-diy.html

This comes another website. Sorry, but it easy to construct.
 
ow.douglas

ow.douglas

Well-Known Member
In the first note you say 4" the last said 6". If it's 6" and 80 CFM That's really low. 4" should be fine for the small box but, get a better fan.
 
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infdjedi

Well-Known Member
Sorry, I meant to say that I currently have a 6'' fan for the light but was curious if the 4'' would be enough for the new exhaust. I think I have it figured out right now, thank you so much for your help guys. That carbon filter looks great.
 
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