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CFM for 4x4x6 tent?

R

rydin4life

New member
My 4x4 tent in my basement has been between 82 and 86 the past two weeks with one viparspectta 450 and two Mars hydro 300s. When my plants get bigger I have two more Mars 300s so Ithose temp will incrrase even more. I have a 190 cfm 4" fan with catbon filter for exhaust along with an 8" circulating fan. If I bump up to a 350+ cfm fan for exhaust with new filter, is that too much for my space? I just want to get those temps down.
 
That temp is perfect . 74-86 86 is the sweet spot imo . That’s my goal temp everyday. If your just worried about the increase just try decreasing but ambient temperature of the room this is what I do I never change the temperature of my tent I just change the temperature of the room that it sits and intern my tent adjusts itself
 
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Proper air circulation is a full renewal of the air inside your room/tent every minute. CFM stands for CUBIC FEET PER MINUTE. The calculation to see whether or not your fan is big enough is simple. You first find your grow spaces cubic feet.

LxWxH=cubic feet.

4x4x6=96 cubic feet.

A 190 CFM fan, unrestricted at full power, would recirculate all the air in your tent 2 times per minute.

Now it’s important to remember if you’re putting any kind of load on the fan the fan’s CFM’s will be reduced. You explained you have a carbon filter attached which a general rule for carbon filtration is that it will reduce your fan’s CFM rating by ONE THIRD.

190x0.33=62.7 (63 for ease of speaking)

190-63=127CFM

this is technically just enough fan for your grow space. It is recirculating air plenty good if you’re running it full power. I personally have a 4x4x7 flower tent. I have opted for a 6inch fan and filter because the extra CFMs help lengthen my fans lifespan. Not only can I open all my vents and crank 3 times the air needed through my tent, but I can run it on half speed to achieve the same level of air circulation a 4 inch does at full speed. This GREATLY reduces stress and wear on your fan, lengthening it’s lifespan, and also running a bit quieter.

If you’re tight on cash a new fan isn’t a must. You’ve got the circulation you require. The best way to lower tent temps is

air cooled tube hoods (should be separate from circulation/air filtration ducts)
insulated ducting
A/C in tent’s room (reduces tent temp by making the air drawn into the tent cooler than inside air)
lots of airflow (yours is sufficient)
 
Hey rydin, like IslandColas said, maybe just enough. But a 6inch would work alot better.
My tent is 3x3x6 and mine is 6inch, 460cfm, on a timer, every few minutes it comes on, an sucks out the heat an humidity.
 
Yeah mine works so well I struggle to keep the humidity up sometimes . Got it for 20$ at Home Depot it’s a 6in in-line 240ish . Doesn’t have an on off switch or a hi low setting but it does the trick
 
Right now I have 4 seedlings and one plant in flower. I have 4 Mars hydro 300w and one viparspectra 450 and temp is at 92. Could it be that my carbon filter is in need of a change..maybe that's restricting airflow causing the heat buildup? Ambient temperature outside the tent is at 74.

I was thinking of going to a 6" exhaust and using the 4" for intake.
 
rydin4life said:
Right now I have 4 seedlings and one plant in flower. I have 4 Mars hydro 300w and one viparspectra 450 and temp is at 92. Could it be that my carbon filter is in need of a change..maybe that's restricting airflow causing the heat buildup? Ambient temperature outside the tent is at 74.

I was thinking of going to a 6" exhaust and using the 4" for intake.
Click to expand...

6 inch will most definitely increase airflow and if you use your 4 inch as an intake it will drastically reduce strain on your exhaust while providing maximum air circulation. Is your tent holding negative pressure? Meaning are the walls slightly sucked in and taught? Are you drawing air in from the room in which the tent sits or from the exterior air? That many LEDS create quite a bit of heat in their sinks and since you’re growing in a tent there’s no direct airflow over those sinks (other than the built in computer fans). Are you drawing air in from the room in which the tent sits or from the exterior air?

I personally think you should ditch the cheap LEDs, they’re ineffective. If you bought an air cooled tube reflector 50-60$ on Amazon and put a 600w bulb and balast (another 120$) in there you would get much better lighting and be able to directly cool your lamp while sucking all that hot air right off the lamp (keeping it separate) and out of the ROOM (not tent).

If your stuck on your LEDs then I would add a small clamp fan that blows directly over them to try and circulate the air around those sinks.

Unless your carbon filter is 6+ months old or you’re filtering high particulate air, your carbon filter doesn’t need to be replaced.
 
No negative pressure. Right now I have 3 vents open at bottom of tent and an 8" fan circulating air on bottom of tent. I'm stuck on the leds for now, but I can add a clamp fan to move air around them. I'm venting air into my basement where the tent is. My filter is probably close to a year old actually..so time for a new one u auppose
 
Yeah I would change yearly or you can even push them till you start smelling what they’re supposed to be scrubbing if you’re on a budget, but better safe than sorry, and the older they get the lower the air flow through them.

If you’re looking to make the carbon filter work properly for you, you must be creating slight negative pressure in the tent. This assures all air is entering from the bottom and exiting through the top of the tent And all smells are being contained and forced through your carbon filter. You’re filter should always be positioned at the top, Where I sure hope you’re you filter resides.

When it comes to circulation, you want cool fresh air in from the bottom and hot stale air out from the top.

Why that intake would be awesome is the fact that you can maintain that negative pressure while pumping way more air a minute than the cubic feet in your tent. Then you can increase circulation rates to once every 30 seconds or so (possibly more). That would really help.

Add the clamp fan and increase circulation as much as possible. If you’re growing in a soil medium your air temp can be slightly above 80 degrees Fahrenheit before you start seeing any kind of drawbacks from the heat. If you’re hydro make sure your water is 65-70 degrees, and don’t worry about air temps until they get above 80ish like soil. You’re going to be great. I can tell you care about your crop and as long as you keep it up everything will be cherry at harvest time:)

Aloha!
 
Hey Rydin, if your scrubber, is like mine, or alot of different kinds, you can change ends, and they are good for another 6months.
Mine only had 4screws to take out. Pull the cover off, an put it on the other end, just like new, almost, it will get the job, done though.
IslandColas, you know any old heads-hippies,in Hawaii, that's still in possession on some original MauiWowi, or Kona Gold seeds.
I've still got lots of old Oaxacan sativa landrace, seeds that we still grow every year outdoors. Some of the seeds are over 40years old. And younger, But some of the old ones still germinate, I'd love to get my hands on some of those Hawaiian island seeds though.
One of my best friends, was the boss at Airborne Freight, years ago, and one of his jet pilots, used to bring all kinds of good stuff, back from Hawaii.
I know you can get them from the seed banks, but I'd rather get mine from an old freak, that knows his business.
Have a great day.
 
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