IS THE PLANT GETTING ENOUGH AIR AND CO2 USING JUST PASSIVE EXHAUST?

Mcoocoo

Mcoocoo

Well-Known Member
I USE A 3X3 TENT WITH A 6 INCH CAN-FAN EXHAUST FAN AND CARBON FILTER. THE TENT HAS 3 PASSIVE INTAKE VENTS AT THE BOTTOM AND WHEN THE LIGHTS ARE ON THE EXHAUST FAN COOLS THE TENT ENOUGH WHERE IT KEEPS THE TEMPS AT A STEADY 75-78 DEGREES. THE PROBLEM OR SHOULD I SAY QUESTION THAT I HAVE IS THIS: WHEN I PLACE A STATIONARY/CLIP ON FAN BLOWING OVER THE PLANT CANOPY, IT RAISES TEMPS TO ABOUT 82-84 SOMETIMES 85 DEGREES. IS IT REALLY NECESSARY TO HAVE A FAN BLOWING OVER THE CANOPY IF THE TEMPERATURES ARE IN CHECK? IS THE PLANT GETTING ENOUGH AIR AND CO2 WITH JUST THE PASSIVE EXHAUST MOVING OVER THEM?
 
jondamon

jondamon

Well-Known Member
Mcoocoo said:
I USE A 3X3 TENT WITH A 6 INCH CAN-FAN EXHAUST FAN AND CARBON FILTER. THE TENT HAS 3 PASSIVE INTAKE VENTS AT THE BOTTOM AND WHEN THE LIGHTS ARE ON THE EXHAUST FAN COOLS THE TENT ENOUGH WHERE IT KEEPS THE TEMPS AT A STEADY 75-78 DEGREES. THE PROBLEM OR SHOULD I SAY QUESTION THAT I HAVE IS THIS: WHEN I PLACE A STATIONARY/CLIP ON FAN BLOWING OVER THE PLANT CANOPY, IT RAISES TEMPS TO ABOUT 82-84 SOMETIMES 85 DEGREES. IS IT REALLY NECESSARY TO HAVE A FAN BLOWING OVER THE CANOPY IF THE TEMPERATURES ARE IN CHECK? IS THE PLANT GETTING ENOUGH AIR AND CO2 WITH JUST THE PASSIVE EXHAUST MOVING OVER THEM?
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The reason we use fans inside a tent or area is to keep the air from stagnating in and amongst the plants.

Between touching leaf surfaces we get micro climates forming and this can have a negative impact on our plants.

Such as 2 touching leaves create moisture between them and thus create a micro climate where Relative Humidity could be as high as 80-100% causing the growth of spores that we don’t particularly want.

So in short always make sure your plants are “dancing” in the breeze from the oscillating fans inside your grow area.
 
A

Apalchen

Well-Known Member
I have run a 3x3 with no clip fan as mine broke right at the beginning of run, I though that since the exhaust fan pulled so hard that the plants seemed to be bouncing and it would be enough. The problem came late on flower as the buds got heavy. Even with a trellis plants just started laying all over. That movement from the clip also strengthens your stems to hold your bud up.
 
Hydro4life

Hydro4life

Well-Known Member
Also helps encourage bud development as cannabis is a wind pollinated plant. Those bitches are trying to catch any pollen in the air. Buds will swell more and produce more trichs from my understanding. Cannabis has a very short annual life and its main focus is reproduction ;) you dont want a hurricane in there but as jondamon said make them dance!
 
Mcoocoo

Mcoocoo

Well-Known Member
jondamon said:
The reason we use fans inside a tent or area is to keep the air from stagnating in and amongst the plants.

Between touching leaf surfaces we get micro climates forming and this can have a negative impact on our plants.

Such as 2 touching leaves create moisture between them and thus create a micro climate where Relative Humidity could be as high as 80-100% causing the growth of spores that we don’t particularly want.

So in short always make sure your plants are “dancing” in the breeze from the oscillating fans inside your grow area.
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that is very interesting, that is exactly what I am concerned about, hot spots and humidity. I have tried putting an oscillating fan on the floor in there and it is just too much wind, the entire plant sways from it, not to mention that it also raises the temps just as much. A 3x3 is just too tight of an area for floor fans, without causing wind burn on the leaves. I have been trying to come up with an idea about how to hang one from the top bars and having it oscillate directly at the top of the canopy or I may try placing a few small fans at the bottom of the tent, directly in front of the inlets, in hopes that it will force the cooler air upwards over the canopy. I am about out of ideas, but I do know that I do need a fan in there.
 
Renfro

Renfro

Well-Known Member
I hear ya on the fan location issue. I recently setup my first tent, a 2x4. I don't have a fan in the tent, all I have is my inline exhaust fan. It pulls air from the top and the passive intakes are low on both sides and the back. I have a 10 inch vortex on it and it's turned way down on a variac, I know the 10 incher is overkill but it was $114, cheaper than a 4 incher. It pulls a strong negative pressure and you can feel the airflow from bottom to top. This has done me well and I haven't had any issues without a fan in the tent. It vents all the time.
 
Mcoocoo

Mcoocoo

Well-Known Member
Renfro said:
I hear ya on the fan location issue. I recently setup my first tent, a 2x4. I don't have a fan in the tent, all I have is my inline exhaust fan. It pulls air from the top and the passive intakes are low on both sides and the back. I have a 10 inch vortex on it and it's turned way down on a variac, I know the 10 incher is overkill but it was $114, cheaper than a 4 incher. It pulls a strong negative pressure and you can feel the airflow from bottom to top. This has done me well and I haven't had any issues without a fan in the tent. It vents all the time.
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I used to use a 2x2 tent and the passive exhaust was amazing, it used to rock the plant back and forth. I think with your setup in the 2x4 with the 10 inch is more than enough to stave off any mold or mildew issues. I should probably just up-size my tent to 4x4 and use a larger fan for exhaust.
 
SPLFreak808

SPLFreak808

Well-Known Member
My cab used to have a 5 - 15f difference from top to bottom, using a strong enough oscilating fan can actually mix the upper hot air with the cool air down low.

Personally, I really enjoyed the results of just using an exhaust at a high enough speed to lightly dance the foliage, fresh/dense air moving from the bottom up worked very well for me.
 
coreywebster

coreywebster

Well-Known Member
A 7 degree temp rise by adding a small fan ?
Weird.

Sounds to me like all your heat is building up at the top of the tent and adding the fan and mixing that air is raising your temps.
But I would like to see a picture of the set up.
I assume your venting heat out the house?

My entire set up raises 7 degree from ambient and that's with two fans and my 260w light. Im not even running my extraction near full either.

If your fans too powerful get some usb air movers that stand on floor and point up and gently move air or get a couple of pc fans.

When I had bigger tents I used to run 16" wall fans mounted to the ceiling facing directly down.
You could look into secret jardin monkey fans, they are small, low wattage and oscillate without taking up valuable room since they clip to the tent bars.
Mcoocoo said:
that is very interesting, that is exactly what I am concerned about, hot spots and humidity. I have tried putting an oscillating fan on the floor in there and it is just too much wind, the entire plant sways from it, not to mention that it also raises the temps just as much. A 3x3 is just too tight of an area for floor fans, without causing wind burn on the leaves. I have been trying to come up with an idea about how to hang one from the top bars and having it oscillate directly at the top of the canopy or I may try placing a few small fans at the bottom of the tent, directly in front of the inlets, in hopes that it will force the cooler air upwards over the canopy. I am about out of ideas, but I do know that I do need a fan in there.
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Mcoocoo

Mcoocoo

Well-Known Member
yeah, I think that is what's going on, it is mixing the hot with the cold air. I say this because it is approx 10 degrees cooler at the floor level. I have some 4 inch stationary fans that I have used in the past to blow the cooler air upwards before but they caused wind burn on some of the bottom leaves. I may just buy one of those monkey fans, I have seen them online before, but they got some real negative reviews.
 
coreywebster

coreywebster

Well-Known Member
Mcoocoo said:
yeah, I think that is what's going on, it is mixing the hot with the cold air. I say this because it is approx 10 degrees cooler at the floor level. I have some 4 inch stationary fans that I have used in the past to blow the cooler air upwards before but they caused wind burn on some of the bottom leaves. I may just buy one of those monkey fans, I have seen them online before, but they got some real negative reviews.
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I have had a few clip on style fans in the past and they had various problems ranging from hardly moving air to sliding down the pole you clip to. But I bought a monkey fan a few months back and was that impressed I bought 3 more.
They come with 3 sizes clips so they attach to any tent pole and don't move from where you place them, they also come in 2 or 3 sizes , oscillating and non oscillating and in 3 different wattages with a two speed switch on each.
They really are ideal for folks that don't want to lose floor space and cant have large fans on ceilings.

Right now because I have multiple smaller tents I have monkey fans blowing across tops and PC fans actually inside the plants blowing up, those are tie wrapped to the branches.

In all my years Iv never seen windburn, I was starting to think it was a myth because I have had almost gale like winds on plants in bigger tents, so its interesting to hear you say you've had first hand experience with it.
 
JonathanT

JonathanT

Well-Known Member
My solution to the heat issue, not having an inline fan yet, was to put my tent in upside down. Left a ton of ventilation up top. I do have a big oscillating fan with no base attached to one of the tent poles with hose clamps to save floor space. The fan is blowing upward over the lights. It gets pretty humid at times tho. Stupid budget.
 
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