Temps still too high, what am I missing?

My grow room is a closet that is 5'x2'x6.5'. The closet is in a small room, 10x10. The closet doesn't have a door, just a 3' wide opening that is centered. I created a door with a sheet of mylar and a tarp zipper. I added a 6' inline fan rated at 400cfm and a carbon filter. The filter is hanging up in the far left corner of the closet running the depth of the closet (the 2' measurement) and is connected to duct that travels four short feet to my fan, which blows out of the top right corner of my mylar door. I have an 8" intake at the bottom right corner of the mylar door. I have a high velocity fan inside the closet hanging on the wall blowing on my plants. I normally use a 250 hps but I am early in veg so I am using about 12 23w cfls. My temps can sometimes reach 90 degrees f and are never lower than 84 with the lights on.I realized that 8" was too small of an intake because the fan was trying to rip the mylar door off the walls. I keep the lower portion of the zipper open but that hurts my natural airflow across the closet. What am I not doing that can help my temps. The small room is right off the living room which has a large, through the wall ac unit and stays at 70 degrees all day everyday. The temps in the room vary 74-79. The door to the room stays open until the lights go off. I'll post some pics of the door, the fan and the filter, and tell me if you see anything that will make a significant change to my temps. You'll notice the hard turns in the duct, I bought elbows but they didn't fit in the closet so I was unable to use them.

air conditioner. Fans don't cool air, they move it.

If its that hot.. in the summer I can't avoid it too.. A/C comes on.

Fan's help a LITTLE on temp.. meaning if no fan and stagnant maybe 90 becomes 86-87.. but the A/C is key

I'd send a pic but i never took it when I assembled last summer.. but I had basically alum duct from my A/C all the way to my grow tent like 10 ft away.. i just kept it along the ceiling. Look up DIY if you need..

mr2shim said:

air conditioner. Fans don't cool air, they move it.

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Right. So Basically I need to lower the temps in the room the closet is in. How cold do people keep their rooms to keep a nice temp inside the tent/closet/grow area? I figure the fact that I am venting in from and out in to the same room and the fact that that room is a very small room (10x10x6.5) is a problem in itself. Does anyone see any logical solutions to this? I would get a small window ac for the room but the window is a stupid crank open window instead of a normal slide up/down window and an ac wouldn't fit. Portable acs are expensive and I have read a lot of bad reviews. Summer heat should be going away soon and I guess this won't be as much of a problem then but how could I handle the summer heat? A bucket of ice water in front of my intake? Just tired of bad grows on account of heat. I know I can grow better plants than this.

Passive air intake holes do NOT work. You need to place a fan to actively draw air in. I mean right by the holes, in front, whatever. On high!

If you on a budget i suggest 2 small but pretty decent fans,yes fans only move air but they can move cool air too and that is achieved by placing it lower to the floor.1 on floor blowing up and 1 blowing over canopy/light.It won't cool it drastically but it will save the hurt of coming back to some crispy ladies.I use a closet with double sliding doors that don't lock this is how i keep my ladies cool.

hotrodharley said:

Passive air intake holes do NOT work. You need to place a fan to actively draw air in. I mean right by the holes, in front, whatever. On high!

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I have a 6" duct fan. it's rated like 160cfm and 240 cfm booster. Would replacing the 8" with a six inch hole and a booster make a huge difference. I have been considering it.

georgyboy said:

I have a 6" duct fan. it's rated like 160cfm and 240 cfm booster. Would replacing the 8" with a six inch hole and a booster make a huge difference. I have been considering it.

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Read this first. But negative pressure actually reverts warmed closet air back through passive holes before your exhaust system can handle it.

http://botanical.com/hydro/air/calculating_fan_requirements.html

I keep this bookmarked and send it to every single friend who wants to start growing. This is the most overlooked and least understood part of indoor growing for most folks.

Well I just went in my room and pulled out the duct fan. I attached it to a 6" elbow, blowing into the elbow, and set the elbow into the 8" intake. I zipped the closet back up all the way. The mylar is still being sucked in, but not nearly as drastically. The temps were at 88*F. I'm going to wait a few minutes and go see how this move affects the temps. Because the fan is on the elbow, it is sucking air from the direction of the door, which is open to the living room, which has the large ac. Should I have the fan blowing into the elbow, as I do now, or sucking through the elbow? Does it matter? I really appreciate the help from everyone.

Most general duty fans do not create enough draft to pull effectively. It is easier to push with them. Like trying to do the same yourself.

http://www.surpluscenter.com/item.asp?item=16-1393&catname=

A good inlet blower to match your 160 fan. The excess volume = increased pressure. This should help clear the charge of air through your exhaust fan and move any moist heated air right on out. Outlet is only 16" wide so not as big as it looks. 190 CFM, 120 V, simple flange mount. The pressure differential is what moves the air. Try running and breathing the whole time with your mouth as wide open as you can get it. You won't get far. Now purse your lips. The backpressure in your lungs helps keep air moving in and out with ease and effectively. Or a supercharger (blower) like a Roots-type or GMC 8-70 supercharger keeps the cylinder stuffed by keeping the intake manifold stuffed. The valve opens and fresh cool air in, hot exhaust out.

I guess I am battling basic physics here. If I can't get my ambient temps under 75* I can't expect to get my grow temps down to 75*. I just added the 250 my and shit hit the fan. 95.

O and thank you hotrod. the math suggest a 1000cfm fan haha. I just need to get the tdiff down which means I need to get my ambients down for anything to be achievable. problem is we have predicted recording breaking highs through october.

change back to hid and use a quality aircooled hood.

hotrodharley said:

Read this first. But negative pressure actually reverts warmed closet air back through passive holes before your exhaust system can handle it.

http://botanical.com/hydro/air/calculating_fan_requirements.html

I keep this bookmarked and send it to every single friend who wants to start growing. This is the most overlooked and least understood part of indoor growing for most folks.

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Yes air pressure is key to getting the cooler air at the floor to replace the heated upper air. You also need to consider how much heat is generate by 12 cfl.

I don't know what you have going but a high velocity fan blowing across a closet can cut off air flow comming in the bottom. Sounds like filter is pulling and you have high velocity sheer cutting off effective upward flow
Should have a fan drawing air in the bottom and the fan pushing air through the filter and out the top.

hotrodharley said:

Passive air intake holes do NOT work. You need to place a fan to actively draw air in. I mean right by the holes, in front, whatever. On high!

Click to expand...

untrue, I've been running this way for years. Intake fans are stupid. My tent has so much negative pressure I don't need a fan inside it to have air moving in it. I even zipped myself inside to see how it felt, nice cool breeze just from the negative pressure created by the exhaust fan. When it's all zipped up and I put my hand near the intake hole at the bottom there is a LOT of suction, almost as much as a 4" inline fan. It's created by negative pressure and works.

george xxx said:

Yes air pressure is key to getting the cooler air at the floor to replace the heated upper air. You also need to consider how much heat is generate by 12 cfl.

I don't know what you have going but a high velocity fan blowing across a closet can cut off air flow comming in the bottom. Sounds like filter is pulling and you have high velocity sheer cutting off effective upward flow
Should have a fan drawing air in the bottom and the fan pushing air through the filter and out the top.

Click to expand...

By high velocity fan I mean a 9" garage style fan i got for 15 bucks at walmart. It's hanging one the wall behind the intake hole blowing the incoming air across the plants (I think) before it is pulled up and through the filter and sucked through the ducting and pushed out the closet. I'll stop being a lazy fuck and post pictures right now.

Here is the front of the closet. As you can see I have set a 6" duct fan inside the 8" intake to try to increase the intake flow. The tarp zipper is shit but that's another story. Up in the top right you can see where the fan is blowing air out.


Here is the 6" booster fan set in the 8" intake. It is attached to an elbow to blow the cool air to the right wall of the closet.


This is the 9" fan hanging on the right wall. It is aimed down. I assumed it was pushing the incoming air across the plants.


Against the left wall, hanging from the ceiling is the carbon filter. I placed it here because I assumed this would force the air to travel across the entire closet before getting sucked up. I tried placing an elbow there but it didn't fit in the tight space, so I was forced to make this tight turn.


The duct travels 3'-4' and makes a gentle swooping turn into the inline fan. The fan is attached to this 6" flange and blows the air right out of the closet. When I took this picture I realized that air being blown out was coming right back in between the mylar and the wood so I duct taped the hole up and it stopped this. It didn't change the temps at all though haha.


Is there anything I am doing that is completely wrong here? I appreciate any insight on how I can improve this setup. Getting a cooltube is not an option here. I can spend maybe 20 more bucks if I really need to. My intake air right now is 75F and according to my thermometer it is 97F inside. Plants are starting to curl so I really need to figure this out. I run my lights at night btw. They are off from 10 am to 4 pm.

mr2shim said:

untrue, I've been running this way for years. Intake fans are stupid. My tent has so much negative pressure I don't need a fan inside it to have air moving in it. I even zipped myself inside to see how it felt, nice cool breeze just from the negative pressure created by the exhaust fan. When it's all zipped up and I put my hand near the intake hole at the bottom there is a LOT of suction, almost as much as a 4" inline fan. It's created by negative pressure and works.

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And your exhaust fan is how many CFM? Sorry to not recall.

Not everything here adds up. I went back and reread everything. You said 400cfm through carbon filter. A 160cfm fan plus a 240cfm fan does not equal 400cfm. Not possible The total CFM through a fan cannot exceed blade design and fan speed. Booster fan just means the fan does not work as hard. A 160 CFM fan through a carbon filter is probably no more than 80 CFM at the outlet you have a 65CF space with 12 cfl. 20 degree temp rise with low air flow is not good but it will not kill plants.


If your carbon filter was using the 240 CFM fan without the 160 it would actually move more air. The fan you have blowing through the intake will decrease resistence to air flow and reduce the load on the exhaust but there is no way to increase the CFM of the exhaust fan. If you stack 10 240 CFM fans together you still only get 240 CFM unless you increase fan speed and velocity.

Pics are not always as they appear. I cannot see the bottom of the pots well enough to tell what they are. Do the pots have holes at the bottom exiting the sides of the pot. You got to have air available to the roots. It looks like pots on carpeted floor with no saucers. If the pots have bottom holes that are plugged by carpet pushing plastic into them that is the same as no air hole.

97 degrees is not good but plants plants survive higher temps just fine. Given the size of the space the 88 degrees you had is not bad.

If you suck 240 CFM through a 65 CF air space yes it should be hard to keep mylar on the walls. The intake has to be able to handle more air than you exhaust or it creates a vaccum. Air flow across the space is irrelevant unless it overcomes intake or dries plants out too fast. Your plants do not know or care which way the wind blows. They just need fresh air and a slight breeze.