Ventilation HELP please

I have a 4x8" tent. In it, I have 3xair cooled hoods with 3xadjustable 600/750/1000/1150w ballasts. Currently there is a fan outside the tent pushing air through all 3 ballasts and to my chimney stack. I am growing all auto's. The first one has a 600w MH bulb, sort of for a vegging/newbie area. The 2nd light is set to 600w for a sort of flowering light right from the vegging area. The 3rd bulb is set to a 1000w as sort of the final flower area. There is also 4x54w T5HO bulbs in the 2 corners and middle beams to sort of give that 1000w area another 216w for side light during the final flowering. I have a ~400cfm inline fan hooked to a carbon filter to exhaust out and to the chimney stack. Heat was becoming an issue, so I have a portable AC hooked up outside the tent, with a 6" hose running from the front of the AC taped over the vents to inside the tent. The hot air from this is being vented out the chimney stack. See the pic here. The blue is heat being exhausted out.



And this is the problem. Air is flowing back through the WYE's from the fan's to the portable AC exhaust, which is no good. I assume maybe the height of the chimney is too high, or whatever, but I need a way to fix it, with little to no cost with what I already have. lol. Would this work instead?



Basically use 1 fan inside the tent through the filter, then the lights to a Y with the AC exhaust, and then my other inline fan#1 near the chimney stack to help pull all the air thorough the duct so there is no back pressure.

why not put the a/c in the tent? run the exhaust out of the tent and out the chimney. is that possible? put a booster fan inline if you have to.

Doesn't matter where the AC is. Besides running in the tent, one sucks up like 2 plants worth of space, and two, I can't run it in the tent since it draws air into the AC to cool, it would draw in marijuana scented air, and exhaust that out the exhaust.

My 3 exhausts are the issue. I just don't know if I should combine them to 2 exhausts and a fan to help the exhaust, booster fan, or how to get all the air out and up the chimney stack the best without it just falling back down into everything else.

gotcha. i don't care about smells. no neighbors here.

just buy a backdraft damper to put inline somewhere in all the ducting. air can only go one way then.

Not that simple, since the when say the AC is exhausting the back draft damper would be open, but hot air from Fan 1/2 is coming back down the WYE connection and back into the AC but if the damper is open, it's still going to let that air in.

I inherited this setup, so I'm working with what I have. Would it be great to go all 6" to 8" adapters then 8" WYE's and a 8" run to my chimney stack and a 8" exhaust fan then 8-6" up the stack, sure, but without spending $500+ on all that, trying to work with what I have. lol. I think I'm just trying to ram too much air down the 6" pipe, especially all at one junction since I have the two WYE's together to make 3 ports.

It's also very cramped and tight and frustrating to keep trying new things, so I'm trying to come up with a game plan before I tear everything down and try something new. Got so mad earlier trying to tighten O rings to the WYE's where I can't see, on my tippy toes....Gets to you.

put 3 backdraft dampers in then. one on a/c, one on fan1, one on fan 2. they can't be more than $10 15 bucks each.

and fan#1 in diagram 1 should be sucking thru the lights, not pushing. that would help a bit.

http://www.globalindustrial.com/p/hvac/registers-ducts/dampers/6-back-draft-damper?infoParam.campaignId=T9F&gclid=CLSM5c3PucsCFRCRaQodMnMHmQ

just rethinking and understand what you are saying about what if all dampers are open. i would think that the air would take the path of least resistance and go up the chimney.

wonder if maybe you could find a 4 way fitting? seem like if they all met in one fitting, it would have to force it up the chimney.

apparently the path of least resistance is back down. lol. I'm going to try setup #2 and see how it goes. What do I have to loose other than a few hours of time and some more of my sanity. lol.

The fan down stream of everything will work fine. You may want to put dampers in the Y branches to balance the air though. Also watch the temps going into the fan, may get pretty warm.

So far I went with with option #2, but without the 2nd fan downstream yet and it seems a lot better. I need more fast clamps if I'm going to do that but we'll see how it is. The air is hot from the AC though so I'll see if I really need to the 2nd fan to subject it to that much heat.

thanks all for the help though.

Well that didn't work, temps got over 90 to almost 100, humidity rose to the roof, but after putting the 2nd fan right as the chimney stack, temps are solid, rH is back down, everything is great. lol. Sometimes just a lot of playing around and trying every scenario till one works.

I run 3x 600w in a 4x8 during flower for example. I can keep the tent within 5 deg of the room it's in. I think you need to run an exhaust for each one directly to the chimney and keep the fans on 24/7 so no backdraft. I would not join them if you can avoid it. I have 3 tents in 1 room, each has their own exhaust port. Working well for a long time.

Yep. Fans sucking air out the lamps (and close to the outside exit hole as possible) is the way to do it. All this talk online of blowing over the lamps (positive pressure) is just silly. Ideally you would want one at the beginning and end of the vent line but for one fan....option 2 is the way bro. Ive vented every which way you can think of too. Cooled your tent by 10 degrees easily didnt it?

Now get rectangular "box ducting" from h depot and fasten it however you can to the out take (cold air) of the ac unit...have this duct transfer to round 6" duct....stick a simple booster 6" fan (or another inline if you really wanna blast) and shoot that cold air right in the tent. Shoot it opposite end of the scrubber so the cold air moves past canopy before being sucked out. I like your "y" taking ac compressor heat out the chminey with lamp heat. Your setup is not the most efficient because your basically sucking cold air back out...but at least its traveling across the plants first. Its a bitch man....trying to cool them tents. Been there done that. Good luck.

Couldnt you just use the air conditioner to cool the room that the tent is in and use an exhaust fan inside the tent to exhaust the heat through the lights and out the tent to the chimney stack? Then just have a passive intake on the tent to draw in the cool a/c controlled air from outside of the tent into the tent every time the exhaust kicks on. Have the exhaust fan plugged into a thermostat controlled outlet inside the tent.

Back drafts occur i think if the chimnie isnt higher than the tallest peak of the house... Fireplace logic may or may not apply here. Go vertical and recycle your hoods for cash. Hope that helps....

I bought a tent with a zipper on the side and wow what a difference. I can blow the AC at 70* F and keep the tent at 75 * F touching the glass on the 1k hood. I have a fan blowing the cold air from right behind the unit. I just finished this today. All the air is piped outside a vent. Before I couldn't keep it under 77-82* F with a different tent not blowing the cold air directly into the tent and before the AC it got to 88-92* F with just the fans.

pinner420 said:

Back drafts occur i think if the chimnie isnt higher than the tallest peak of the house... Fireplace logic may or may not apply here. Go vertical and recycle your hoods for cash. Hope that helps....

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Vert barebulb in a tent ? Damn that would be roasting in the summer. 3 lamps in a 4x8?

HydroRed said:

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Almost...put the inline fan near the chimney hole sucking out and hes golden.