Please help- Exhaust fan 4” or 6”

[RobC]

Just realized the one I bought might not be enough (AC Infinity Cloudline T4). My tent is 3x3x6’ with a HLG 300L 270w LED. My place is always cool 64-73 F and low humidity, no summer/heat waves which might help.
According to growweedeasy’s calculations I need 270 CFM w the carbon filter and this fan does 205, the 6” jumps to 402. I’m assuming at max setting.
Smell would be the other concern, will it scrub the space properly enough.
So should I go through a lot of trouble and $ (I’m not in the US so can’t just return them) upgrading fan+duct+filter or will it be fine with 1-2 circulation fans in my conditions?
Thanks

[crunchyfrog]

I would say it is okay, what I would really worry about would be how high temperature you get with the light on. For that size light, from GWE (below), looks to me like you would be okay. I would suggest giving it a go. There will be plenty of C02 available for the plant with 200 cfm pull through. Yes, air circulation is very,very important, and you may need two (or more) recirc fans, depending on the size.

2’ x 2’ x 5’	120W	60-100 CFM
2’ x 4’ x 5’	250W	120-200 CFM
3’ x 3’ x 6’	400W	162 – 270 CFM
3.5’ x 3.5’ x 6.5’	600W	238 – 398 CFM
4′ x 4′ x 7′	1,000W	336 – 560 CFM

[RobC]

Sounds good, only worry then is if it will be stealthy smell wise

[Hammer53]

Hi RobC and welcome aboard. I did the same thing, ordered wrong set up
I have 3x3x6 tent with 4" fan and filter, and oscillating fan. Am going to get 6" fan and filter, but so far no issues, and it's been 9 months.
But then I'm stuck with 4" fan ( might use it in closet that I dry my harvest in)

[RobC]

Thanks! If you have no issues why are you getting a 6”? What light are you using?

[Tersky]

Depending on light setup and ambient temps (which you indicate are not high) you probably will be fine. Since i live in the south, temps an humidity require a little more airflow but as long as temps and humidity are ok it should be fine to be just under the recommended CFM.

That said, I recommend getting a fan that is more than you need as fans on high tend to be loud. Having a higher cfm fan allows you to run at lower speeds decreasing sound made by fans, if that is a thing you care about.

[RobC]

You are right, I’m worried I might have to run it at max but don’t know how loud it will be from inside the tent

[Tersky]

For reference, i have a 400ish cfm fan on low and it can drown out a knock at the front door if i am in the same room as the tent. It isnt unmanageable on low, but on max, they reeeeaaaaal loud. The tent wont block the sound that much but may muffle it a tad. It all depends on whether you want to be more stealthy and be able to hear decently in the same room or if that is not an issue.

[RobC]

I see, thanks for the reference. These AC Infinity are supposed to be the quietest ones which is why I chose it, I need stealth as in the sound can’t get out of that small bathroom tent is in. Guess ill put it in and test it

[grouchyoldman]

Do any of you know if there is CFM loss if a 6" fan is exhausted through a 4" duct? I have a framing issue that makes 6" difficult.

[Poppa]

grouchyoldman Could you use oval ducting like this https://www.homedepot.com/p/Speedi-P...O-06/202907169 or is it a joists to close issue over height of joist issue?

[grouchyoldman]

Oval ducting is a good idea Poppa. Thanks. I have experience in most of the trades, but I'm an HVAC novice.

[Hammer53]

Hi RobC and welcome aboard. I did the same thing, ordered wrong set up
I have 3x3x6 tent with 4" fan and filter, and oscillating fan. Am going to get 6" fan and filter, but so far no issues, and it's been 9 months.
But then I'm stuck with 4" fan ( might use it in closet that I dry my harvest in)

I wanted.a 6" fan all along. I'd rather have more if needed, and wouldn't have to run on high. Although I've seldom run this one high.

[Hammer53]

I've upgraded from a blurple to a QB

[RobC]

Nice. Are you using a carbon filter? If so is effectively scrubbing the smell?

[Hammer53]

RobC Yes am using carbon scrubber, but I have a situation that enables me to vent.into the attic. So nobody.knows but me lol. And very little scent.in lung room. (Until I open the tent) and still not much smell

[Hammer53]

Robc if you are growing in small bathroom I believe it will be noisy, I'm in a spare bedroom. Good luck to yah I think you can do this just might have to experiment a little