I’m a beginner who’s assembled a small indoor tent system. The temperature inside the tent hits 100° F with the lights on full and the inline fan and an oscillating circulatory fan running at max RPM. Ambient varies from 84 - 86°, so the tent’s lights, etc. add roughly 15° to a temperature that’s already at the upper acceptable limit.
The 3 lights are 200-W LEDs (600 W total). The ballasts aren’t removable.
The room is open to the rest of the house, so cooling it to 70 degrees with the house HVAC system isn’t practical. I may be able to drop it a few degrees that way.
I estimate that I’m getting 137 CFM from my 4" inline fan with its filter attached. The tent measures 2’ x 4’ x 6’11’ (76 cubic feet), which yields 1.8 air exchanges per minute. The screened inlet port at the bottom measures 6" x 12".
The filter is connected to the fan with a short rubber hose and the fan exhausts directly out a port in the tent. That configuration is the most efficient I can imagine. (See photo below.) The exhaust presumably increases the ambient temperature, but venting out a window isn’t practical.
Is it feasible to keep the tent temperature = ambient with a fan alone without making my tent suitable for use as a wind tunnel? I could swap my 4" for a larger one or add another at the top that exhausts in the opposite direction.
A bigger in-line fan such as AC infinity 8” with 69 controller left on at all times. You can control the speed I have a bigger tent (4x8) and don’t have some of the restrictions you do but I leave mine on about 50%. You need air conditioning or more fans pulling fresh air into your room. Not being able to vent exhaust outside and no AC presents a slight problem. More so in flower stage because you need temps in 70 or below to prevent bud mold. Lights can be at 60-70% in veg stage and full power during flower
I put a window unit in the room I have my tent in. I just keep that room cool and if it gets hot exhaust fan kicks on in tent for a minute and cools it right down.
Helps with humidity too but you might want to consider a humidifier for flowering. You will most likely need it depending on where you live of course.
If I can keep the room cool and dry then the tent will be fine.
Infinity makes a great all in one unit that does all this for you. Of course it cost quite a bit.
There’s no way fans alone can give me that unless the ambient is 70 or below.
And they’re sold out. Do you recall what they sold for? They may be pricey, but they may be the best solution for me.
I don’t believe they have a place to insert a carbon filter, which surprises me. Of course, one can be placed at the end of the exhaust duct, inside the tent.
The size of the fan probably won’t help much. You’ll have to get more cool air in the tent.
I had to use a window unit in a small 8x12 room, and built a “shade tree” duct to direct the house AC into the room with no return to the house AC.
I’ve made the decision to grow in the winter. Cheaper and easier to raise temps compared to lowering.
If you decide to get an AC of some kind, get it double the size you calculate for the room size. You have heat sources which have to be overcome.
I’ve looked hard at the ACI a/c, if I decide I need more than my current set up that’s the way I’ll go. Even if I have to wait.
Some basic questions.
You said the room is open to the rest of the house. Is there a door and / or window?
Does the tent exhaust fan exhaust back into the room?
What other electronics or possible heat sources are in the room?
In the pic, it’s hard to tell orientation of the filter, is this the very top of the tent?
Answers to the questions will lead to additional questions or suggestions. For example, if there is a window, is it in the sun, facing public view… etc.
Most cases I see there’s not one thing which solves the challenge, but multiple little things that add up.
Since we only have a couple more months of summer and I’m uncertain of your humidity in the tent just buy a cool mist humidifier. It dropped my temperatures from 82 down to 78, this is still pretty high but honestly I’ve seen multiple people state to just have more humidity if hotter(VPD chart). So even in flower even though it’s not ideal than you just raise the humidity and increase airflow and there shouldn’t be a difference. Once summer is over you probably won’t struggle with heat so much. I’m in Florida btw and our days are around 90-92 right now
Can you run a 6” inline fan booster and hose to a lower tent port using the cooler house air. I do this in my lung room to help the tent temps and where are you exhausting the air to🤟
Wow. There are so many helpful people here – thanks to all of you!
AC Infinity has confirmed to me that their Terraform 7 doesn’t incorporate a carbon filter. Price will be $699 + shipping, when they’re back in stock.
I think you’re right. Maybe I just wanted to hear some experienced people say “No, fans won’t provide the temperatures you need when the ambient temperature is too high to begin with.”
I’m in Ohio, so that solution would work for me, although I might need a heater. I’m keen to get started growing, though, so I’d rather not wait.
As for your questions:
No door – just an archway. There is a north-facing window nearby. It’s on the side of the house, facing a neighbor’s home.
Yes, the exhaust fan blows the air back into the room, which is counterproductive.
The tent, etc. are the only heat sources in the room.
Yes, the photo shows the top of the tent. It’s meant to show that the inline fan setup is maximally efficient – no ductwork with bends, etc.
Humidity in the tent is 27% at 100° with the ambient at 85° and 43%. A humidifier would help (and may be needed, even if I can get the temperature down), but a 4° reduction in temperature won’t be enough.
Yes, but wouldn’t that be equivalent to boosting the exhaust CFM by adding a 2nd inline fan or substituting a larger one?
The AC Infinity Terraform 7 pumps cool air into a lower port. That makes sense for obvious reasons, but I wonder about the effect of blowing cool air directly on plants, especially when they’re small.
The humidity being raised is a must for that high of temperatures. Google Vpd charts to get an idea of what moisture needs to be in the air in relation to the temperature for each stage of life
Looking at the unit, I see no way to cram a filter in there without 90° turns that would reduce efficiency. A 6" filter can be attached to the end of the exhaust (i.e., return to the Terraform) hose, at the top of the tent. The provided hoses are 5.9" in diameter.
@Bigcbud: You’re right, of course. But I figure the harder nut to crack for me is temperature, so I’ll tackle humidity after I address the temperature. The Terraform may fix both problems for me.
I actually read earlier today that LED light temperatures effects on leaves are a lower temperature than the ambient air. Not sure if you have an infrared laser but try to take that temperature. Good luck with those temps growmie
The inline booster fan is feeding your tent with cooler air that’s outside the tent , the exhaust fan inside the tent up high is exhausting the hot stale air
I temp gun my leaves and then any non-reflective material surface in the tent at about the same level, then split the difference for my leaf temp offset because of this.
I’m happy running my 300-watt Mars Hydro TSL-2000 light in a roughly 2x4 tent dimmed to 80% in mid-flower. Your use of 600-watts of led light in a 2x4 tent exceeds the frequently cited rules of thumb for watts/SF.
That’s a good point. Plants can cool themselves evaporatively by opening stomata. They need more water to do this, but the difference between leaf temperature and ambient can be substantial (10° F or more).
But I have no leaves to measure yet. I’m trying to get my gear right first – it makes no sense to put plants in a tent that’s much too hot.
The exhaust fan also sucks cooler air in through the 6" x 12"inlet at the bottom. What effect would an inline booster have when the only way for air to escape (given that the 6x12 inlet is closed) is through a 195-CFM inline exhaust fan with a filter? I’m unsure.
I set my lights to a height of 36" from the floor, turned them on full, and then measured the light at various locations on the floor with a Phantom Photobio meter. The PPFD readings ranged from roughly 600 - 1000 umol/m^2/s. I believe the max recommended value during flowering is 950. If CO2 is used, the limit increases to 1800. (My source is here.)
I’m going to try adjusting their heights to get a more uniform light distribution. But your point is well taken: I can lower the lights and reduce power to them, which will reduce the heat. For example, the inverse square law says that 600 umol/m^2/s at 36" becomes ((36/24)^2 x 600 =) 1350 at 24". At the 16" recommended here for flowering, it would increase to 3000 (!)
So I have more than enough light to benefit from CO2 if/when I want to try it. When I was choosing my lighting, I wanted to avoid the common beginner’s error of having too little. The three lights cost me $467, so I’m happy to have the problem of needing to turn them down.
I should repeat my temperature measurements with the lights at a lower height and dimmed to produce 850 umol/m^2/s. That will reduce my heat problem.
I give up, sorry Growmie but at best the fresh air coming in is passive. The inline booster fan piped into your tent through a lower port would be pulling in more cooler air at a constant higher volume , hot air rises and is being exhausted by your exhaust fan
You seem to be thinking that a booster fan would increase the CFM exiting the exhaust fan at the top of the tent. For example, adding a 100-CFM booster to a 100-CFM exhaust fan would yield 200 CFM total. Is that correct?
I’m keen to get started growing, though, so I’d rather not wait.