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Using a portable a/c inside a grow tent...venting in room ok?

Discussion in 'Grow Room Design & Setup' started by (Butters), Jun 10, 2010.


    (Butters) Well-Known Member

    Hey All,

    I grow in a smallish tent (3'x3'x5') in my basement that has absolutely no windows. Heat is a constant issue in the summer with my 400w HPS (with air cooled head). Problem is, I have no cool air to supply. So, here's my question: :confused:

    Can I use a small portable air conditioner, put it INSIDE the grow tent, and run the venting hose OUTSIDE of the tent area instead of putting the venting hose outside of a window (which I do not have access to)?

    Will this work? I realize that this won't air cool the hood whatsoever but I would imagine that it would significantly cool the area inside the tent which is just as good.

    Thanks for the help.:mrgreen:

    - Butters :bigjoint:

    researchkitty Well-Known Member

    You can do that, they make a/c units specifically for this that are around $250.

    If you really have to have an air conditioner for a 3x3 space..................well, good luck with that. :)

    Still better off probably putting an in-line fan in front of the A/C's cool air and venting that to the room instead, but the whole notion of a/c in a 3x3 space still makes me frown a little. Consider flowering at night instead of daytime too. Night temps usually much lower than day temps.
    714steadyeddie and (Butters) like this.

    (Butters) Well-Known Member

    Already flowering at night. Temps in 90's inside the tent! :fire: Just from a single 400watter too. :cuss:

    Getting an AC for a 3' by 3' by 5' space is absolutely f***ing crazy I know. Just no other options that I can think of. :dunce:

    Unfortunately, while I do have plenty of ACs in my house, the closest one to my grow tent is probably a good 20 to 30 feet away. No way to discreetly run ducting and an inline fan that kind of distance...discreetly that is. :blsmoke:

    I hear what you're sayin about keeping the portable AC outside of the tent and just fanning/ducting it's cool air inside of the tent. Makes sense to me and doesn't crowd my grow tent space as much. I just want to make sure that it's ok to VENT the portable AC into the room that the grow tent is in.

    Thanks for the advice boss. ;-)

    Anyone else want to weigh in?

    -Butters :bigjoint:

    desertrat Well-Known Member

    an a/c puts out more heat in its exhaust than the amount of cool air it puts out. whether or not your plan works depends completely on the ability of your home a/c to cool the room with the extra heat added. you have no chance if there is not a thermostat in the room.
    (Butters) likes this.
    OMG LS6

    OMG LS6 Member

    I was in a similar situation as yours. I just bought 25' of 4" dryer duct and hooked it up to the exhaust of my AC and ran it to a window so it exhaust outside...The heat from that exhaust will heat up your basement quick and will be countering the cooling of your AC. If there are no windows and you own the house you can drill a 4" hole and put a Vent cover on the outside so it looks clean.
    (Butters) likes this.

    (Butters) Well-Known Member

    Thanks for all of the replies fellas, :mrgreen:

    Desertrat hit on my concern about trying this right on the head. Sure, the tent would be cooler for some period of time, but the tent would be pulling in cool air from the portable a/c which would need to use the even-warmer air from the very space that it was venting it's own hot air. Given that the portable a/c would be creating more hot air than it would cold air, the system would eventually crumble and the hot air would win out. :fire:...:cry:

    I may have a couple of other venting options that I failed to mention. In that same room as my tent, I have a washer and dryer...meaning that I have a dryer exhaust that I could connect to in the very same room. I've read up on this a bit and it seems like the primary limitation to this is that most portable a/c's venting ducts are 5" while dryer venting ducts are 4". So, I figure a simple 5" to 4" connector (i.e. reducer) will probably work fine. :grin:

    That's option number 1. Option number 2 is that I could vent the hot air from the a/c into the stairs in the basement that lead upstairs to my living room. Heat rising will take care of the rest. Option number 3 would be to vent the hot air from the ac into a well insulated tank of water, effectively heating the water instead of the air. That'd mean I'd have to dump alot of water once a day but it's doable. :blsmoke:

    Probably the craziest part of all of this is that I don't even REALLY need to cool the 9 sq ft tent...just that f'n air cooled hood that houses the 400w HPS. That's probably like a 1 sq ft area + ducting length that I need to actually cool to get the temps reasonable. A whole lotta work for such a small space to cool. :roll:

    Thanks for weighing in everyone.

    -Butters :bigjoint:

    asszilla Member

    I have almost the same exact problem, I was thinking of putting the AC exhaust to my cold air return, would that work???

    mrboots Active Member

    An air conditioner seems like a lot of trouble, you cant use one with out venting the air exhaust somewhere. you should be able to comtrol the heat with just fans, not ac. How hot is the basement? with good air flow your tent shouldn't be much hotter. If its too hot why dont you just vent the hot air from your air cooled hood out the dryer vent?
    (Butters) likes this.

    (Butters) Well-Known Member

    The basement probably runs an even 75f at night when she is flowering and it's 90 degrees outside. Don't quote me on that but it should be pretty close. So, pulling 75f air through the air cooled hood would definitely lower temps in there. No doubt. But I'm really not sure how much. Definitely worth a shot though before going to get a portable ac. I could probably live with temps of 84f at canopy level in the summer if need be. Would definitely prefer 75f even though.

    Good advice boots. Ty.


    mrboots Active Member

    i live in the middle of the desert, its been over 100 degrees (i just spent way long looking for a "degrees" symbol on my keyboard, I dont have one) but i keep my air at 80 and I can keep my flowerbox below 90 with just a 4" inline duct fan blowing out in to the room. An ac is too much work for a 400 watt light, if you make your whole basement a growroon you should look at some ac units.

    (Butters) Well-Known Member

    :lol:...:eyesmoke: I searched endlessly for a degrees sign too. How is there not a degrees sign on keyboards these days :cuss:. I have a british pound symbol on my keyboard for f's sakes (I'm in US) but no freaking degrees sign! :shock:

    My guess is that I'll have to try running ducting from outside the tent, directly connected to the air cooled hood, running outside the tent again (warmer air this time), attached to an inline duct fan to move the air and see if the tent maintains a reasonable temp from that. My only concern is that I'm still essentially dumping that warmer air (from cooling the hood) into the air in the immediate room. But, it is a good size room and I would imagine that it may only bump up the temp in the room by a couple of degrees. :clap:

    The only question that I have left is in the event that the above plan continues to run the room too hot (anything above 85f is a no-no for me as it damages my yield too much). The next step would then be to try and vent into that dryer duct so it's removed from the room completely. But that's about 8' worth of ducting there and I have NO idea how many inline fans it would take to move that length of ducting. 2?...maybe 3? :?

    -Butters :bigjoint:

    mmd604 Member

    Never use a portable ac they always draw from the run even dual hose all brands. U have a fresh air intake right hook up to that with aircooled hood exhuast out the tent into the void space. A 400 should not bad.

    rockinlespaul Well-Known Member

    Is the tent closed up when the lights are on? If so, open it up a little. Its certainly not going to hurt anything. I keep mine open about the size of a door. Definetely helps the temps and heats the room...bonus!

    ms.erge Member

    I am having the same problem. But just to let you know when you vent the a/c exhaust it's going to reek. I have a 4' scrubber with inline 190cfm fan in a 4x4 area with a 400 hps running and its freaking BAKING in there... And even with my scrubber filtering the air when the a/c exhausts it still smells STRONGLY (because its warm also) Therefore I think I am going to have to make a diy scrubber for the end of my a/c exhaust house as well... blah. if i knew the a/c exhaust was going to be such a dillema I would have put more money into exhaust fans to cool the room...

    mashroom777777 Active Member

    hi there, u need also Co2 that means fresh air to grow.without any windows in the basement ,do u have fresh air ?

    Nottabot420 Member

    i suggest running a single hose from a/c to inside the tent, that way its doing the job of just cooling inside temp

    sheeeesh_batter_haze New Member


    zem Well-Known Member

    just make sure you exchange the air somehow, it is not only the heat, you also want plants to breathe and not get moldy

    texasjack Well-Known Member

    Soooooo olddddd

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