question about fans
- Thread starter ryan1918
- Start date
ficklejester
Well-Known Member
It should be closest to the source of heat or smell you're trying to alleviate. It both pushes and pulls- pulls hot air in and pushes it out of the roon.
If there a carbon filter involved, the fan should pull air through the filter and push it out of the room.
If there a carbon filter involved, the fan should pull air through the filter and push it out of the room.
Fan's are usually more efficient pulling. I use passive intakes. I size my fans so I can exchange my enitre room every 2 minutes and plan intake on that as well.
BongboyMMA
Active Member
Sorry to hijack the thread but does this mean you only have the fans running every 2 mins?
You have to know how much air your fan moves. Then determine how often the grow space's air should be replaced. Common recommendation is 5 cfm per minute, but other factors like humidity and heat could influence the frequency of exchange.
Whatever the frequency, some people put the fan on a switch. For example, on 5 minutes, off 5. I use a variac ($50) to control the speed. It's very quiet unlike the cheap $20 dimmer-like controllers. (There are also heat-controlled devices to increase the speed if the temperature get too high.).
BROBIE
Well-Known Member
No, CFM (Cubic feet/min) is the rating your fan has which is the cubic feet a minute it is capable of pushing(or pulling) air through the fan and filter if used. So if you have an 8x8x8 room, you have an 8*8*8 or 512 cubic feet room. So if you have a 512cfm fan, it would take 1 munute to scrub the entire room. So when the poster says "every 2 minutes" it is always on but all the air is cleansed ever 2 minutes. In this example he would be using a 256 cfm fan running constantly.
edit: Like the poster above stated. You want a bigger fan that you can turn down for noise abatement.
BongboyMMA
Active Member
Cool again sorry for the hijack you guys cleared up a lot. Is there any specific way to figure out how big the intake should be so the room is always just a little negative and not to much?4x2x6.5ft so roughly 52cft I'd be straight with a really low end fan?i feel like the lowest I see is 256cfm except for a booster but I've read boosters can't scrub
^^^^^^^^^^^^^^
This thanks
I spent the day offline trimming the skirts LOLLOL Sorry it means I exchange all the air in my room every 2 minutes. I don't turn it off. If you oversize buy a variac
The cheap dimmers are hard on the fans too.
Rifleman420
Member
spot on.
ficklejester
Well-Known Member
How is pulling more efficient?
Rifleman420
Member
it creates what's called "negative pressure", which aids as well from natural pressure from the outer atmosphere. they work together.
pushing air creates "positive pressure", which works against the outer atmosphere.
or something like that.
ficklejester
Well-Known Member
How does that make the fan more efficient? A fan is always pushing and pulling in separate directions.
Rifleman420
Member
Also, negative pressure in your tent is definitely better for not allowing grow room smells to leak.
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Rifleman420
Member
thank you.
ficklejester
Well-Known Member
The op didn't ask about carbon filters. "Spot on" was clearly just to boost your comments.
I have no clue why you are making this a personal argument. As for Carbon filters the OP merely asked about fans. He never asked anything about the reason for deploying them. So YOU went off topic first assuming heat and odour control. Now if you are really interested in fans you can either ask politely or simply go read on fan efficiency curves and how they are calculated as I had to do when I actually took Physics, sigh.
Rifleman420
Member
Complete speculation on your part. You obviously didn't read the thread.
So, why not reply to this post and give me another great opportunity to "boost my comments".
Or, do what you should have done in the first place, and STFU.