Question about ventilation

vitalsine

vitalsine

Well-Known Member
I had a quick question about ventilation.

First I'll break down my calculations.

Tent is 5x5x7 = 175cf
4 SF 2000 = +20% or 35 CFM
Carbon Filter = +50% or 87.5 CFM
Ducting = +25% or 43.75 CFM
Total minimum CFM = 307 CFM

Exhaust fan: AC Infinity T8 (807 CFM) 10-speed settings so 80 CFM per. I set it to 4, which gives me a total of 320 CFM.

Other fans/airflow -
Active intake: AC Infinity T6 (402 CFM) this runs at the same speed as exhaust, 4, which would make it 160 CFM.
2x Honeywell 10" circulation fans (not oscillating) mounted in 2 corners, up top, opposite each other (front right, back left) pointing down at lights (185 CFM each)
2x Genesis 6" clip fans (not oscillating) mounted in 2 corners, down low opposite each other (front left, back right) pointing towards plants. (unsure of CFM)

Now I present the problem.

I think my temps are too low. RH is good. Currently, I am sitting at 78F and 65% RH. I keep hearing that because I am running LED, my temps should be closer to 82F.

How big of a deal is this? Should I turn the fans down that are pointing at the lights? Should I remove the circulation fans all together? Can I turn the exhaust fan down, or would that be bad? What's more important, adhering to the minimum CFM needed, or paying more attention to temp/RH?

Also, should I be adding the intake and circulation fans to my calculations anywhere? or do I just use the CFM of the exhaust fan?

On a side note, I know the T8 is super overkill for a 5x5x7, but when I get my other tents setup, I plan to use the T8 to exhaust multiple tents. I'd be running it to the 5x5, a 4x3x6 and a 2x2x4. I'd need an additional 200 CFM (roughly) for the other tents, possibly more with the additional ducting, but I'd still be way under the total CFM of the exhaust fan. These other tents will have a passive intake, just drawing from the ACed room. Or I am considering removing the T6 as an active intake on the 5x5 and repurposing it as an exhaust for the other tents, as I'd have to run an additional 10ft or so of ducting to provide exhaust for them if I use the T8. Ultimately that doesn't really matter though because I still won't be anywhere near needing 800CFM, even if I had to add 100% for the other tents. The T8 is mounted right next to the 5x5 and maybe about 6 ft of ducting runs directly out the window. The only real plus to repurposing the T6 would be that I could take maybe a 1 amp load off the panel by not having to run the T8 at full speed.

If you guys need any further clarification, let me know. I appreciate any help or comments!
 
vitalsine said:
I had a quick question about ventilation.

First I'll break down my calculations.

Tent is 5x5x7 = 175cf
4 SF 2000 = +20% or 35 CFM
Carbon Filter = +50% or 87.5 CFM
Ducting = +25% or 43.75 CFM
Total minimum CFM = 307 CFM

Exhaust fan: AC Infinity T8 (807 CFM) 10-speed settings so 80 CFM per. I set it to 4, which gives me a total of 320 CFM.

Other fans/airflow -
Active intake: AC Infinity T6 (402 CFM) this runs at the same speed as exhaust, 4, which would make it 160 CFM.
2x Honeywell 10" circulation fans (not oscillating) mounted in 2 corners, up top, opposite each other (front right, back left) pointing down at lights (185 CFM each)
2x Genesis 6" clip fans (not oscillating) mounted in 2 corners, down low opposite each other (front left, back right) pointing towards plants. (unsure of CFM)

Now I present the problem.

I think my temps are too low. RH is good. Currently, I am sitting at 78F and 65% RH. I keep hearing that because I am running LED, my temps should be closer to 82F.

How big of a deal is this? Should I turn the fans down that are pointing at the lights? Should I remove the circulation fans all together? Can I turn the exhaust fan down, or would that be bad? What's more important, adhering to the minimum CFM needed, or paying more attention to temp/RH?

Also, should I be adding the intake and circulation fans to my calculations anywhere? or do I just use the CFM of the exhaust fan?

On a side note, I know the T8 is super overkill for a 5x5x7, but when I get my other tents setup, I plan to use the T8 to exhaust multiple tents. I'd be running it to the 5x5, a 4x3x6 and a 2x2x4. I'd need an additional 200 CFM (roughly) for the other tents, possibly more with the additional ducting, but I'd still be way under the total CFM of the exhaust fan. These other tents will have a passive intake, just drawing from the ACed room. Or I am considering removing the T6 as an active intake on the 5x5 and repurposing it as an exhaust for the other tents, as I'd have to run an additional 10ft or so of ducting to provide exhaust for them if I use the T8. Ultimately that doesn't really matter though because I still won't be anywhere near needing 800CFM, even if I had to add 100% for the other tents. The T8 is mounted right next to the 5x5 and maybe about 6 ft of ducting runs directly out the window. The only real plus to repurposing the T6 would be that I could take maybe a 1 amp load off the panel by not having to run the T8 at full speed.

If you guys need any further clarification, let me know. I appreciate any help or comments!
Click to expand...
Just turn the exhaust fan down. T8 is temperature controlled..... set up the temperature controller.... As for intake.... you dont need an intake fan. The exhaust fan will pull air into the tent through the vent flaps (open them) all by itself.
 
JoeBlow5823 said:
Just turn the exhaust fan down. T8 is temperature controlled..... set up the temperature controller.... As for intake.... you dont need an intake fan. The exhaust fan will pull air into the tent through the vent flaps (open them) all by itself.
Click to expand...

Alright, so I will probably run the T6 as exhaust for the other side of the room. It's a 30x10 room that I am going to keep filling up with tents as I go. Plan to run a res in the center of the back wall, so tents will basically have about 10x10 on either side, leaving 10x10 in the center of the room for res, tools, etc etc.
 
Like set the fan at 2 when temp is under 82 and 6 when its over 82. Thats the whole point of paying more for the temp controlled unit. Temp gets to 83, fan ramps up to 6 until temp drops to 81 then goes back to 2. Air flow recommendations are for temp and humidity control. Estimates and real world experiences vary greatly. You always want some airflow but if temp and humidity are under control, you dont need a ton of airflow. I run HPS and I actually need 80% of the power of a 8'' for my 5x5 during summer.

vitalsine said:
Alright, so I will probably run the T6 as exhaust for the other side of the room. It's a 30x10 room that I am going to keep filling up with tents as I go. Plan to run a res in the center of the back wall, so tents will basically have about 10x10 on either side, leaving 10x10 in the center of the room for res, tools, etc etc.
Click to expand...
That sounds like a great setup. Just remember, whatever air you push out of the room has to be replaced; be mindful of where the replacement air is coming in from. (like if its 90 degrees outside, you could potentially be pulling 90 degree air into the room)
 
JoeBlow5823 said:
That sounds like a great setup. Just remember, whatever air you push out of the room has to be replaced; be mindful of where the replacement air is coming in from. (like if its 90 degrees outside, you could potentially be pulling 90 degree air into the room)
Click to expand...

I am not pulling any air in from outside at all. The entire floor is sealed and air-conditioned/heated to stay at 75F year-round. The only thing I need to play with is humidity. I may let some fresh air in during cooler months and drop the AC, but for the time being I have to run them, although they arent on very long since I sealed the whole floor up here. Keeping that hot muggy air out!
 
vitalsine said:
I am not pulling any air in from outside at all. The entire floor is sealed and air-conditioned/heated to stay at 75F year-round. The only thing I need to play with is humidity. I may let some fresh air in during cooler months and drop the AC, but for the time being I have to run them, although they arent on very long since I sealed the whole floor up here. Keeping that hot muggy air out!
Click to expand...
Thats what im saying.... If you set a fan up to push air out of the room, new air has to come in from somewhere.... You cant just push air out and it not be replaced.
 
JoeBlow5823 said:
Thats what im saying.... If you set a fan up to push air out of the room, new air has to come in from somewhere.... You cant just push air out and it not be replaced.
Click to expand...

Of course, I mean obviously it is coming from outside, but not directly. It's more or less being sucked up from downstairs, or through the next room where the window AC is in, but all gaps are sealed tight. Not really 100% sure where the air is coming from but it's there haha.
 
vitalsine said:
Of course, I mean obviously it is coming from outside, but not directly. It's more or less being sucked up from downstairs, or through the next room where the window AC is in, but all gaps are sealed tight. Not really 100% sure where the air is coming from but it's there haha.
Click to expand...
Yeah thats my point. Air will come in around every window/door/little crack you cant even see. Some people think they can just blast their 800cfm fan at full tilt outside and everything will be fine and then wonder why their house cant get below 80 degrees with the ac running nonstop. And then the electric bill comes and they shit themselves.
 
JoeBlow5823 said:
Yeah thats my point. Air will come in around every window/door/little crack you cant even see. Some people think they can just blast their 800cfm fan at full tilt outside and everything will be fine and then wonder why their house cant get below 80 degrees with the ac running nonstop. And then the electric bill comes and they shit themselves.
Click to expand...

hahaha. I'm hoping that I won't have that issue. My AC's in this room and the room next door are almost never on. Or at least I tell myself that. LOL
 
Using a lesser active intake flow rate than what is used for the exhaust flow rate makes no sense at all! Why, because the exhaust fan is pulling more air in than what the intake fan is pushing in, which completely voids the intake fans flow rate.
 
piratebug said:
Using a lesser active intake flow rate than what is used for the exhaust flow rate makes no sense at all! Why, because the exhaust fan is pulling more air in than what the intake fan is pushing in, which completely voids the intake fans flow rate.
Click to expand...

That's how you create negative pressure... lol
 
Another note on negative pressure, from what I gather as long as the tent isn't caving in, your good. Before installing my SCROG the sides of the tent did suck in a bit, but it's fine now. No visual difference on the tent poles, so it isn't too much negative pressure. With both fans I have control over it. If your intake was putting as much in as the exhaust was putting out, you'd have no negative pressure.
 
vitalsine said:
Another note on negative pressure, from what I gather as long as the tent isn't caving in, your good. Before installing my SCROG the sides of the tent did suck in a bit, but it's fine now. No visual difference on the tent poles, so it isn't too much negative pressure. With both fans I have control over it. If your intake was putting as much in as the exhaust was putting out, you'd have no negative pressure.
Click to expand...
Depends so much on the tent, but with correct negative pressure you will see the tent walls cave in slightly. If you are collapsing poles, it’s too high, but in general I look to see the fabric of the tent concave slightly.

Your active intakes need to be a lot less than you think, I’d imagine.
 
Mine runs at exactly 50% of the exhaust, which from what I was able to research is pretty much what you want, Could probably even go a little lower.
 
Cinco said:
Depends so much on the tent, but with correct negative pressure you will see the tent walls cave in slightly. If you are collapsing poles, it’s too high, but in general I look to see the fabric of the tent concave slightly.

Your active intakes need to be a lot less than you think, I’d imagine.
Click to expand...
If you are collapsing poles, return the engine to the 747 you stole it from and buy a normal inline fan.
 
NO that
vitalsine said:
That's how you create negative pressure... lol
Click to expand...

No, that doesn't create a real negative pressure zone, and besides what i already told you, you are also creating a hindrance on the exhaust fan because it simply doesn't have free access to all the air you have asked it to remove. So your setting of 305CFM(s) won't ever be met, not even close! Anyhow, a negative pressure zone means that the entire zones air circulation system is controlled at the exhaust port, where that port will draw air from all freely open intake ports that are attached to that negative pressure zone!
 
piratebug said:
No, that doesn't create a real negative pressure zone, and besides what i already told you, you are also creating a hindrance on the exhaust fan because it simply doesn't have free access to all the air you have asked it to remove. So your setting of 305CFM(s) won't ever be met, not even close! Anyhow, a negative pressure zone means that the entire zones air circulation system is controlled at the exhaust port, where that port will draw air from all freely open intake ports that are attached to that negative pressure zone!
Click to expand...

To each his own I guess lol. I'm going to leave it on til I set up the other tents, then I'll be opening the vents and putting some sort of filter over them. Your the only person I've talked to that has a difference of opinion, but I'll take it haha. Thanks dude.
 
vitalsine said:
To each his own I guess lol. I'm going to leave it on til I set up the other tents, then I'll be opening the vents and putting some sort of filter over them. Your the only person I've talked to that has a difference of opinion, but I'll take it haha. Thanks dude.
Click to expand...
I recently installed these top of the line, state of the art filters on my intakes. They dont catch everything but its a hell of a lot better than nothing.
IMG_5127.JPG
 
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