1k cooling problems

[Hugh Midity]

I have a 1k in a big daddy hood in a 5'x5' tent with a can 33 and a 424 cfm 6" fan. the tent sits in an 8'x10'x8' room in a house with ch&a which runs around 72f. the tent pulls its air from the room and exhausts through the ceiling with about 5' total ducting, insulated, 2' on the scrubber side and 3' on the exhaust side. the hood is about 22" above the canopy with a circulating fan blowing between the canopy & hood. my temps stay at 84f with the ch&a blowing, opening the door or windows does not help. it gets way hot here and will be soon so I'm worried since I'm just a couple degrees away from disaster and loose nugs. basically I'm wondering if I'd see any good results from switching the fans location. the fan is attached to the scrubber blowing through the hood now(scrubber-fan-duct-hood-duct), I was always taught to pull the air instead but for some reason did it this way when I was running a 600w and it worked better to cool it seemed. I know this is a very common question and I've searched and read plenty but keep coming up with folks saying both ways are best for ____ reasons. also is there something I may be overlooking here? I'm at a loss. Thanks for any help

 

[a.k.a_Herb]

lights on at night?

 

[Hugh Midity]

nope, daytime. the house is cooled by ac and stays around 72f

 

[rives]

You say that you are exhausting "through the ceiling" so I take it that you are just dumping the air into the attic space? If your house is at all tight, you are trying to pull a vacuum on the living space - you would need a large return air path for the air to eventually get back from the attic to the fan inlet. I think that this is the most frequently over-looked part of air handling - you either have to pull air from outside and dump it outside, or pull air from inside and dump it inside. You are also working against your air-conditioning, which needs to be a closed-loop system and re-run the same air through the cooling coils time after time. A/C systems will ice up if too much outside air is introduced, and need multiple passes through the cooling coils to pull the air temperature down to the desired level.

Another point to consider is that dumping humid air into your attic will eventually cause mold problems.

 

[Hugh Midity]

hmmm, I knew I was overlooking something. as far as mold, the duct is situated right at the gable vent so I'm hoping excess humidity will end up outside. there is no where I could dump the air inside and the outside air is usually hotter than the tent. one thing I'm wondering is about the size of ducting. the hood has 8" ducts, my fan & filter are 6" and I had use reducers. any chance this is hurting me? would it do any good to take the reducer off the exhaust side and use 8" duct there or will I lose static pressure? or should I invest in an 8"fan & filter? 424 cfm seems like plenty to do the job so I have something wrong

 

[rives]

I don't think that changing duct size or other equipment is going to help until you get the air path resolved. You are trying to move 424 cubic feet of air outside without an equivalent amount of air coming inside - it's like trying to suck air out of a bottle.

 

[2 Legal Co]

The exit for your air should be ducted through the roof as well. In the attic is just begging for trouble.

Try returning your air into the house. And letting the AC do it's job as well as it can. Also...do you have 'HIGH' returns for your AC? I'm guessing that it's central air?

If you just return it to the room and back into the tent is probably best, unless you can leave doors open. .... May have to add a separate AC of some kind for that room alone.

 

[rives]

It would be pretty simple to test and see if this is your problem - if you have a cool night or early morning, open a window in the grow room or nearby. Make sure that the doors are open between wherever the open window and the grow room is, and see if your temperatures come down.

 

[Hugh Midity]

rives I've tried that with a window open in the room, no good. open the door in the room seems to help by a degree. the return is across the house and we have a den that fresh air comes in from I would think would compensate for the air I'm exhausting but idk for sure

 

[Jhhnn]

Most houses have enough air leaks for pressure differential to the attic to not be an issue. I think the problem may be the filter- a Can 33 is only rated for 200 cfm. Centrifugal fans work well against back pressure, but fare poorly with excessive inlet restriction. If your plants aren't big & stinky, try it w/o the filter to see what happens. Just for reference, when I started doing this, I got a Phat filter & they have served me well. They're a lot lighter & easier to mount overhead, too.

 

[Morcheeba*]

Strive,

I hate to suggest a window a/c unit until you can get a mini-split unit but it will help cool your lung room.

this summer ill probably vent my a/c directly into the tent and then filter and cool my lights before exhausting it back into the lung room the veg tent is in. ill see if I can stay below 80f.


peace

 

[rives]

Most houses have enough air leaks for pressure differential to the attic to not be an issue. I think the problem may be the filter- a Can 33 is only rated for 200 cfm. Centrifugal fans work well against back pressure, but fare poorly with excessive inlet restriction. If your plants aren't big & stinky, try it w/o the filter to see what happens. Just for reference, when I started doing this, I got a Phat filter & they have served me well. They're a lot lighter & easier to mount overhead, too.

Good point, Jhhnn. It's a system, and all of the components need to be balanced. I'm not sure that I agree on the air leaks keeping up with the demand - that would be a complete air exchange on a 1600 square foot house with 8' ceilings every 30 minutes. That might work in Florida, but if my house leaked like that I'd be freezing my ass off!

 

[Ez Rider]

Your exhaust fan will work better "pulling" the air than "pushing" it...simple physics.

What is the actual temp in the room the tent is in? You said the return is across the house, and typically the thermostat is near the return. It can easily be 72 at the stat, and be several degrees warmer in an outlying, south facing room.

Is there an a/c vent in the room the tent is in? Is it open/blowing air?

Like several people have mentioned, your fan is quite oversized for your filter. I'd go with a 6"max fan with that 33 if I was you.

 

[Hugh Midity]

the temp is about the same in the room, its cool from the ac vent. and you're sure pulling is best, I'm pulling through the filter and blowing on the light whiched worked much better for the 600w that was in there. for the last hour I've left the door open and turned the fan down to half speed, resulted in going from 86f to 82f. right now the door is shut and I moved the duct back in the room, waitng to see if it stays the same. if so that'll work

 

[Ez Rider]

the temp is about the same in the room, its cool from the ac vent. and you're sure pulling is best, I'm pulling through the filter and blowing on the light whiched worked much better for the 600w that was in there. for the last hour I've left the door open and turned the fan down to half speed, resulted in going from 86f to 82f. right now the door is shut and I moved the duct back in the room, waitng to see if it stays the same. if so that'll work

I'm positive "pulling" is best. It's the way centrifugal fans are designed to work.

Anything's going to work better with a 600...only 1/2 as much heat.

Turning your fan down will help. It's VERY important to correctly match your fan and filter cfm's. You're probably moving more air at 1/2 speed than you were at full. You're going to need to leave the door open, or undercut it 1/2" or so to allow for make-up air. I doubt your a/c vent is supplying >100cfm and you should be pulling ~200cfm now.

You could always duct the exhaust back into your a/c return. This would keep your a/c contained, and if your system runs often, the humidity shouldn't be a problem. I've done this for a few people, and it works well.

 

[Hugh Midity]

man that attic is low lol. the door has about an inch gap under it and terrazzo floors but its working well with the door open and the fan half speed. maybe I can cut a vent in the wall to draw in more air from another room so the door can be closed, I can't rearrange the fan til I can grab some tape & zipties though but when I can i'll move it

 

[Ez Rider]

man that attic is low lol. the door has about an inch gap under it and terrazzo floors but its working well with the door open and the fan half speed. maybe I can cut a vent in the wall to draw in more air from another room so the door can be closed, I can't rearrange the fan til I can grab some tape & zipties though but when I can i'll move it

If you don't run the exhaust back into the return, or at least back into the house, your a/c will be running constantly. Even on 1/2 speed, your fan is evacuating the entire house at least once per hour. You'd be better off ducting the exhaust into another room which is closer to the return. A 1" undercut door should be fine for 200 cfm.

FWIW, you can use a fish-tape and pull string or an extension pole to get flex duct through a tight attic. You've already got a hole to aim for.

 

[Hugh Midity]

damn, maybe I would be better off with a window unit. I can't think of a room that could stand the extra heat. I wonder if I were to duct the ac vent to the tent and dump the exhaust back into the room if it'd keep temps in line. any reason why not?

 

[2 Legal Co]

Sounds like a step in the right direction.

Don't forget to 'ventilate' your lung room as well. (Into the rest of the house), or add a Bit of CO2, and let the oxygen out. Be careful how much you add however.

I think you'll find that the change will allow your central hvac to run less, too.

A 'heat pump' would also be an avenue to explore. 'Love that 54*F core temp.'.

 

[Morcheeba*]

damn, maybe I would be better off with a window unit. I can't think of a room that could stand the extra heat. I wonder if I were to duct the ac vent to the tent and dump the exhaust back into the room if it'd keep temps in line. any reason why not?

ill let ya know very soon but I don't see why it wouldn't work.


peace