FUCK!! Frustrated w/heat OR positive pressure. Fan type question

Z

zat

Active Member
Would a 4" inline Vortex rated at 172 cfm actually be better than my 6" inline duct booster fan from Lowes which is rated at 240cfm? I've read a few places that a duct booster fan has no pressure so even though it's rated higher it's effectiveness is cut up to 75% when you get the carbon filter/ducting hooked up. I have 484 watts of cfls, so heat builds up pretty quickly. I had been trying passive intake and thought that was the problem, so I added a 100cfm intake fan and now I have positive pressure in my tent. So far my temps are hovering at 82 degrees w/lights on, which I'm fine with, but positive pressure = smells, so what the hell is it going to take?

Here are my calculations:

I have a DR60 grow tent 2' x 2' x 4.6' so that's only 18.4 cubic feet. I need to exchange air once every 3 minutes, so that would mean I'd need a fan rated at a mere 55 cfm.

Add 20% for a carbon filter so now I'm at 66 cfm


There are a few bends in my duct work (unavoidable) but I can feel a good amount of airflow being exhausted by my Lowes fan which is pulling air through the carbon filter. I'm shocked this is not working honestly.

So should I get the vortex rated at the lower 172 cfm? Will this give me negative pressure w/my intake fan AND keep air exchanged enough to keep temps down?
 
P

puffdatchronic

Well-Known Member
get a heat resistant strain..mandala seeds claim to have all heat resistant strains ,lemon skunk was very heat resistant for me
 
Z

zat

Active Member
richinweed said:
yes...the bigger fan, yes
Click to expand...

Well technically the Lowes' fan is bigger (6" 240 cfm) so do you mean to get a vortex (or vortex type) fan even if it's rated at lower cfms and is 4"? I'm choosing that fan btw b/c it fits my carbon filter and is rated at what my carbon filter fits too. thanks.
 
S

stusghost

Member
Zat, I'm into my 2nd cfl grow running alittle over 450w in the flower tent. My temps avg 79-82 w/lights on. I made the mistake of buying the exact same duct boosters when i started so here's what i did. I combined the 2 boosters with a 260cfm oscillater (blow 2x harder than the boosters): https://www.globalindustrial.com/p/hvac/fans/office/holmes-oscillating-table-3-speed

I then added a 6" 560cfm inline ($66.00 amazon) for exhaust. My carbon filter is rated for 460cfm so i bought a reducer for the inline fan. Hope this helps....Burn One.
 

Attachments

TechnoMage

TechnoMage

Well-Known Member
You're talking about Axial vs Centrifugal. Duct booster fans are Axial similar to what you would have in a box or pc fan. They can move a lot of air but their ability falls off drastically under load. Centifugal fans like a Vortex maintain a much more level cfm under load. Personally I run larger fans but use a speed dial to run them at a lower speed to keep the noise down From my own observations (no measurements, just personal experience) a 6" fan at 75% moves about as much air as a 4" fan at 100% at 1/2 the noise.
 
Z

zat

Active Member
TechnoMage said:
You're talking about Axial vs Centrifugal. Duct booster fans are Axial similar to what you would have in a box or pc fan. They can move a lot of air but their ability falls off drastically under load. Centifugal fans like a Vortex maintain a much more level cfm under load. Personally I run larger fans but use a speed dial to run them at a lower speed to keep the noise down From my own observations (no measurements, just personal experience) a 6" fan at 75% moves about as much air as a 4" fan at 100% at 1/2 the noise.
Click to expand...
Thanks for the explanation....it makes total sense and now that I've got good inflow, my temps are great. I just found a new 4" Hurricane centrifugal fan for $65.00 shipped, so I think this will work. Also, I'm going to mount it in my attic (where it exhausts) and this will probably take care of any sound issues. If not...then I'll either go w/a speed controller or acoustic ducting, but I think this will work.
 
zem

zem

Well-Known Member
zat said:
Would a 4" inline Vortex rated at 172 cfm actually be better than my 6" inline duct booster fan from Lowes which is rated at 240cfm? I've read a few places that a duct booster fan has no pressure so even though it's rated higher it's effectiveness is cut up to 75% when you get the carbon filter/ducting hooked up. I have 484 watts of cfls, so heat builds up pretty quickly. I had been trying passive intake and thought that was the problem, so I added a 100cfm intake fan and now I have positive pressure in my tent. So far my temps are hovering at 82 degrees w/lights on, which I'm fine with, but positive pressure = smells, so what the hell is it going to take?

Here are my calculations:

I have a DR60 grow tent 2' x 2' x 4.6' so that's only 18.4 cubic feet. I need to exchange air once every 3 minutes, so that would mean I'd need a fan rated at a mere 55 cfm.

Add 20% for a carbon filter so now I'm at 66 cfm


There are a few bends in my duct work (unavoidable) but I can feel a good amount of airflow being exhausted by my Lowes fan which is pulling air through the carbon filter. I'm shocked this is not working honestly.

So should I get the vortex rated at the lower 172 cfm? Will this give me negative pressure w/my intake fan AND keep air exchanged enough to keep temps down?
Click to expand...
a few things you are doing wrong there... 1st, you'll get more light and less electric use and less heat if you used 400w HPS instead of those cfls. actually if your area is only 2x2 then 250w HPS is more than enough. one problem is that you are stuffing this small room with 484w of cfl light, overlkill! 2nd you'll be better exchanging the air if you have both fans as exhaust instead of using 1 intake and 1 exhaust. the curves in the ducts diminish venting. try making 45degree bends instead of 90 degrees...
 
Canibitual

Canibitual

Well-Known Member
zem said:
a few things you are doing wrong there... 1st, you'll get more light and less electric use and less heat if you used 400w HPS instead of those cfls. actually if your area is only 2x2 then 250w HPS is more than enough. one problem is that you are stuffing this small room with 484w of cfl light, overlkill! 2nd you'll be better exchanging the air if you have both fans as exhaust instead of using 1 intake and 1 exhaust. the curves in the ducts diminish venting. try making 45degree bends instead of 90 degrees...
Click to expand...
+2
Positively correct...
 
  • Like
Reactions: zem
TechnoMage

TechnoMage

Well-Known Member
zem said:
a few things you are doing wrong there... 1st, you'll get more light and less electric use and less heat if you used 400w HPS instead of those cfls. actually if your area is only 2x2 then 250w HPS is more than enough. one problem is that you are stuffing this small room with 484w of cfl light, overlkill! 2nd you'll be better exchanging the air if you have both fans as exhaust instead of using 1 intake and 1 exhaust. the curves in the ducts diminish venting. try making 45degree bends instead of 90 degrees...
Click to expand...
I must have been baked to have missed that part. That almost directly mirrors my first grows. Here's exactly what I had from my logs

Flower Cabinet: Flower
TypeQuantityWattsLumensKelvinT/WattsT/Lumens
Side63228003,000K19216,800
Side23228006,500K645,600
Canopy35548003,000K16014,400
Total 42136,800


Same problem, too much heat. I switched to and air cooled 250w HPS and saw both temps drop and yield increase.
 
Z

zat

Active Member
Ok, I just installed my 4" Hurricane 171 cfm centrifugal fan...and WHAT A DIFFERENCE!! Instantly negative pressure, sides of my tent are getting sucked in. I'm doing tests right now to see if it's enough to keep temps down w/passive intake, but if not, I've got that intake fan 100 cfm but will need a speed controller for it, as even w/the Hurricane, that little intake fan can still overpower it and cause positive pressure. No worries though...I'm about $20 away (or not) from finally having my set up working properly. Also I could put the Hurricane in my attic, so you can't even hear it. After I confirm everything is good to go....it's time to switch to 12/12! :clap:
 
TechnoMage

TechnoMage

Well-Known Member
Glad to hear things are working better. Not surprised about the difference, Axial fans fall off real quick under ANY type of load/restriction.
 
guevera

guevera

Member
Those duct booster fans from Lowe's/Home Depot are next to worthless... any real fan will do much better. CFM on a fan is sort of like watts on an amplifier: it's not exactly meaningless, it just doesn't mean nearly as much as many people think (and it can be endlessly manipulated for use in catalog or advertisements).

Funny thing, couple of weeks ago I was in HD when these two kids, maybe 18-19 years old, asked me a question about how they'd hook up one of those duct boosters. I took one look at them, and it was clear these two stoners were lost. So I quickly explained how to hook up the fan, then said "but this really won't do much for you. You've got the get a real centrifugal fan or even a squirrel cage blower if you're trying to cool down your lights," before explaining that even a bathroom fart fan would be a better choice than a duct booster. They were very much not expecting grow room tips from the random straight-looking dude at the home depot, and the look on this kids face as he realized how obvious he was was truly priceless.
 
TechnoMage

TechnoMage

Well-Known Member
guevera said:
Those duct booster fans from Lowe's/Home Depot are next to worthless... any real fan will do much better. CFM on a fan is sort of like watts on an amplifier: it's not exactly meaningless, it just doesn't mean nearly as much as many people think (and it can be endlessly manipulated for use in catalog or advertisements).
Click to expand...
They can work, you're line just has to be very unrestricted. No carbon filter and very little bending which makes it hard to light proof.
 
You must log in or register to reply here.
Top