Portable AC and grow tent venting

I have a 4'x4'x8' tent, 400cfm exhaust fan/filter at the top of the tent with 1000w induction light. I am having a problem with controlling temperature. I added a portable AC unit and cannot for the life of me get the right vent combo to control the temps.

- If I vent from the bottom, blow cold from above the exhaust seems to suck out the cold and pull in the heat from outside

- I have kind of controlled it by blowing the cold on the lights from below, assuming the cold air will sink to the plants.

Right now I got the vents on the bottom shut with the exhaust turned off, it's working but will not be work down the road. I've googled advice and find conflicting comments. Can anyone give me any suggestions for the best configuration?

Thanks!

Venting should be running constant. Try to control the air temps in the room the tent is in and that will intern help the tent temps. Exhaust heat out of the tent and the room directly from tent to outside the room. If you can afford induction lighting, you can afford some expandable ducting line I would guess. Remember to "pull" the heat out with the ducting, not push it.

Dr. Who said:

Venting should be running constant. Try to control the air temps in the room the tent is in and that will intern help the tent temps. Exhaust heat out of the tent and the room directly from tent to outside the room. If you can afford induction lighting, you can afford some expandable ducting line I would guess. Remember to "pull" the heat out with the ducting, not push it.

Click to expand...

Thanks for your reply - the exhaust fan is already at the end of the duct line I have a lot of negative pressure, when I turned off the exhaust fan, things got cooler. What I'm wondering is where to put the fans - do I put the AC duct at the top of the tent where the exhaust fan/filter is located and chance the airflow coming from the bottom to suck it out the exhaust vent. Right now the AC is used to cool the light - maybe I should I install the AC duct at the top of the tent and use a fan to blow air down and open the bottom vents?

I would put the AC outside of the tent, bring in cool air. Then i would get some sort of normal fas blowing along the top of the lights. I used to do this when running a cfl hood.

Growing dad hit the nail on the head.
You want another fan like your exhaust but with lower cfm rating, use that as your intake to draw new air into the tent, it can come from the same room outside the tent where the AC should be.
The exhaust has to be exhausted out of the room the tent is in, preferably out of a window.
Have a rotating or clip fan in the tent and your temps should stabilize.

Tents are sometimes the only way,but im old school they was not around when i started i bought one kept it for one grow then got shut.The tents are just to hard to get everthing bang on temp wise, unless you have one of the bigger bloom tents.

I would opt for a room within a room any day of the week,stud work plasterboard and just polly the inside,and mylar the bottom mtr.
Get the biggest filer and same size fan.I have a 10 ince fan out let,but i step down 2 ince for in let with duct work that runs along the floor of the grow room with holes punched in the side of it.

If you are wanting to continue with the tent thing then get a cool hood's not tube,tubes lose lumens i not saying hoods don't lose any but not has much i vent into a loft hatch but in summer temps get to around 29/30 winter 28 all the time with a heater in room.

A friend of mine got a small chest freeezer 4 ft x 4ft square we cut a hole in the door sealed the door of the freezer then run duct from
that to the room and he had a sep,inlet bringing in air from out side cheap ac if ya can get old small freezer.
The one he used was out of a caravan perfect,but make sure if ya try this to have it on a timer

That is one great thing growin LED. Temps in my tent are barely higher than the outer room. Passive intake actually. If I want to warm it a bit, I slow my exhaust fan down a bit. Central AC and heat for the room. The biggest challenge I face environmentally is RH as the lights do not lower it. But I have a dehumidifier in the room that controls it.

But a dedicated $10 box or round fan set to blow on the light helps to cool. And yes, a fan on the plants. i like a tower fan for that. they hit more of the plant vertically and don't seem as rough. Though the fucking things break too often!

GrowinDad said:

That is one great thing growin LED. Temps in my tent are barely higher than the outer room. Passive intake actually. If I want to warm it a bit, I slow my exhaust fan down a bit. Central AC and heat for the room. The biggest challenge I face environmentally is RH as the lights do not lower it. But I have a dehumidifier in the room that controls it.

But a dedicated $10 box or round fan set to blow on the light helps to cool. And yes, a fan on the plants. i like a tower fan for that. they hit more of the plant vertically and don't seem as rough. Though the fucking things break too often!

Click to expand...

But it is also good to have low floor fans faceing up that way the hot air is vented faster,why i love growing useing cool hoods been tempted with l-e-d but seen plenty of so called cold grows and im not impressed they look pretty but that it hps all the way.

cflGROWERanon said:

Growing dad hit the nail on the head.
You want another fan like your exhaust but with lower cfm rating, use that as your intake to draw new air into the tent, it can come from the same room outside the tent where the AC should be.
The exhaust has to be exhausted out of the room the tent is in, preferably out of a window.
Have a rotating or clip fan in the tent and your temps should stabilize.

Click to expand...

???? Why another fan to "help" intake? The exhaust fan IS creating the intake (and it should be coming in from the bottom)! Another fan for intake, just wastes electricity and ups the bill! A fan moving air around the lamp ,,,, yeah I understand that ok.

Control the temp in the room the tent is IN. That in tern will help out the tent.
I agree with tyke. Tents are a pain.

Dr. Who said:

???? Why another fan to "help" intake? The exhaust fan IS creating the intake (and it should be coming in from the bottom)! Another fan for intake, just wastes electricity and ups the bill! A fan moving air around the lamp ,,,, yeah I understand that ok.

Control the temp in the room the tent is IN. That in tern will help out the tent.
I agree with tyke. Tents are a pain.

Click to expand...

This is exactly what I've been working on the last 2 days and have found to be the problem. I found the key IS controlling the temp the room is sitting in. I built the room in the garage and installed the tent inside the room. The AC is being pulled from the central house air with the idea of providing coolness to the "shell room" , and the portable unit sits outside the tent but inside the shell room. When I built the room, I did insulate the walls but neglected to insulate the ceiling. I installed R30 up there and the temps in the shell room have dropped 7 degrees and the AC is currently only taking 5 mins to cool to 74 and takes an 20 mins till the sensor kicks it on at 77. I'm going to keep adding insulation to the walls until I can get the shell room to cool to where the AC doesn't come on at all at lights off.

As for the air flow, I have the tent closed off except for one vent at the bottom for the tent intake, I have run the AC duct from the portable to the top of the tent blowing downwards. I have tried pointing a fan across the lights but that seemed to actually raise the temps - I'm thinking it's blowing the cold descending air up and out the exhaust vent, so right now I'm running a small oscillating fan at floor level and that seems to work.

Thanks for everyone's input!

Dr. Who said:

???? Why another fan to "help" intake? The exhaust fan IS creating the intake (and it should be coming in from the bottom)! Another fan for intake, just wastes electricity and ups the bill! A fan moving air around the lamp ,,,, yeah I understand that ok.

Control the temp in the room the tent is IN. That in tern will help out the tent.
I agree with tyke. Tents are a pain.

Click to expand...

the other fan acts has a poor mans ac