AC Boxes Made Easy (to understand and build)

[sirripalot]

man, hoosier. i want to call you out and see what your response is.

the first thing: your comments on how inefficient it is to use your house air for intake instead of a "lung room". i don't want to pull high RH, cold air from outside, when i have low RH, still pretty cool air inside. or what about when it's hot as hell outside, why would i want to pull hot ass air over my condensors? also, i dont have the capabilities to do so (exhaust OR intake air from outside).

i want to make a point that generally saying using your house air is inefficient is inaccurate because it's not 100% the case. for example, i'm actually HEATING my house with the heat output from the a/c unit in my grow. so obviously using the air from within my house is NOT inefficient, or am i wrong?

obviously if i were running my A/C inside, it would be wasteful to use that cold air for the grow room A/C, but my question is..is it that serious? what type of electricity usage are you talking across a month, 10-20 bucks?

my point is, i think you need to make it more clear when you're saying not to do things that it's totally feasible to do so in certain situations, it's a little misleading.

the same for having two separate chambers (one for ambient, one for exhaust) vs having ONE chamber, with both an exhaust/intake to keep constant flow to the A/C. do you actually have any data to backup what you're saying is, or is "ask an hvac man" you're only backup?

i'm very tempted to build two small chambers, same A/C one with one chamber box, another with two chamber box, to prove you wrong.

i think i'm going to stick with my one chamber as it's much more practical, and has been running smooth as a mother fucker for weeks now.

now if my A/C breaks in a month i'll be holding my tongue!

convince me otherwise, please.

I WANT TO BE CLEAR, I AM NOT ARGUING THE POINT THAT TWO CHAMBERS IS MORE EFFICIENT AS THAT IS FAIRLY OBVIOUS. I JUST WANT TO DECIDE THE EASE OF BUILDING vs EFFICIENCY, which one outweights the other.

 

[Mr-B]

Sir: I don't have the answers to all of your questions but I* can tell you that all AC pumps and window style units are designed to run with the hot air from outside cooling the coils.

Every window unit made uses the hot outside air to cool them. If you put your hand up against the hot exhaust you will notice that it's much hotter than the surrounding ambient air.


I recently made an AC box using Hoosier daddy's method and it works perfectly in my grow. Right now my rooms temps never get warm enough to turn on the ac as I run my lights at night, through a vented cool tube which pulls it's air from under the house.
My 600W lamp doesn't make enough heat to get the room over 80 degrees.

I'm sure this summer will be a different story.

Peace.

B

 

[sirripalot]

Sir: I don't have the answers to all of your questions but I* can tell you that all AC pumps and window style units are designed to run with the hot air from outside cooling the coils.

Every window unit made uses the hot outside air to cool them. If you put your hand up against the hot exhaust you will notice that it's much hotter than the surrounding ambient air.


I recently made an AC box using Hoosier daddy's method and it works perfectly in my grow. Right now my rooms temps never get warm enough to turn on the ac as I run my lights at night, through a vented cool tube which pulls it's air from under the house.
My 600W lamp doesn't make enough heat to get the room over 80 degrees.

I'm sure this summer will be a different story.

Peace.

B

yeah scratch that one point about the hot air, the main point was i would rather use the air within my house as the ambient air BECAUSE i am blowing the hot air right back into my house, it's working as a heating unit during the winter. so basically my house acts as the outside would in relation to the a/c unit if it were mounted in a window. get me? yes, the summer will be a different story. basically i'll be cranking my house a/c.

 

[hoosierdaddy]

I think the information is only misleading if your goal is to go outside the box of what normal set-ups require.
When we try to rig things...like running your whole grow system from inside the house without any additional air movement considerations made, we are not going to have an efficient system.
The same as not boxing up the AC unit like it needs to be...it aint gonn awork like it could by doing so. Sure, you can put wrinklewall slicks on the front of a drag car, and put the skinny tires on the back...and try to drag it...and even make excuses for why you need to run them that way...but, it aint kosher. And it really isn't getting much done trying to pick apart my work, when it may not be my work that needs to be looked at here.
Dig?

 

[sirripalot]

I think the information is only misleading if your goal is to go outside the box of what normal set-ups require.
When we try to rig things...like running your whole grow system from inside the house without any additional air movement considerations made, we are not going to have an efficient system.
The same as not boxing up the AC unit like it needs to be...it aint gonn awork like it could by doing so. Sure, you can put wrinklewall slicks on the front of a drag car, and put the skinny tires on the back...and try to drag it...and even make excuses for why you need to run them that way...but, it aint kosher. And it really isn't getting much done trying to pick apart my work, when it may not be my work that needs to be looked at here.
Dig?

No doubt bro. I debate with people, that's my thing. Sometimes i'm wrong, sometimes i'm right, that's how it goes. One thing i've learned in my short life is to ALWAYS question things. I'm simply debating, not picking anything a part.

Just to give credit where it's due your DIY is VERY good, and VERY accurate information. Thanks.

 

[chytil151]

running A/C in winter time

running A/C in winter time

I am using a window mounted A/C unit to cool my room but now that it is getting colder out side my a/c is freezing up what are my options here? Can i pull the unit into the room more, then build a intake box around the cooling part of the compresser fan? or would it hurt to just use the ambient room temp to keep it cooled? I just got my room fairly dialed in now this problem has happened. there is no way for me to cool my lights and I am using 2- 600w hps along w/ 2- 400w hps so an A/C is a must for my situation. Any tips or comments are welcome TY for any advice in advance.

 

[whatissixbynine]

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[inreplyavalon]

Hoosier this is a sweet tutorial and i am understanding it pretty well i think. I do have a couple questions. I am trying to put this idea into practice using a 24,000 btu AC.

Questions if you will...

1. How should i size my fans for either the incoming air or the exhaust?

2. If i were to only use one fan would it be more productive to just have a bigger fan pulling from after the hot exhaust?

I see that there is a big fan inside the AC, looks like a twelve incher or so, but does it spin like an can inline or like a duct booster? Not sure of the power i should be using?

Thanks for your help. I understand a lot of the determining factor will be turns in the duct, but i should be able to keep those to a minimum.

 

[hoosierdaddy]

I am using a window mounted A/C unit to cool my room but now that it is getting colder out side my a/c is freezing up what are my options here? Can i pull the unit into the room more, then build a intake box around the cooling part of the compresser fan? or would it hurt to just use the ambient room temp to keep it cooled? I just got my room fairly dialed in now this problem has happened. there is no way for me to cool my lights and I am using 2- 600w hps along w/ 2- 400w hps so an A/C is a must for my situation. Any tips or comments are welcome TY for any advice in advance.

You could pull the unit inboard enough to bring the intake vents inside. However, that will cause it to use grow air and will not be very efficient...but probably better than it is now.

The best bet would be to pull the unit in, and then enclose the intake vents with a box, and feed the box air via a duct to your attic or some other non-grow room air. Just remember that when you do this, it creates a need for more air to enter wherever you get it from. What I'm saying is...if you box up the intake vents and dcut to it from the room next door, be sure the room next door has an intake of fresh air somehow.

 

[hoosierdaddy]

Hoosier this is a sweet tutorial and i am understanding it pretty well i think. I do have a couple questions. I am trying to put this idea into practice using a 24,000 btu AC.

Questions if you will...

1. How should i size my fans for either the incoming air or the exhaust?

2. If i were to only use one fan would it be more productive to just have a bigger fan pulling from after the hot exhaust?

I see that there is a big fan inside the AC, looks like a twelve incher or so, but does it spin like an can inline or like a duct booster? Not sure of the power i should be using?

Thanks for your help. I understand a lot of the determining factor will be turns in the duct, but i should be able to keep those to a minimum.

The size of your exhaust will dictate how big the fans should be.
And the size of the AC unit should somewhat dictate the size of the ducting.
If you want to know the exact size that the intake duct should be, measure one of the vents both length and width. Then multiply length times width and that will tell you what the area in sq inches is of one vent. Multiply that time how many vent holes are in the top and sides, and that will give you your total intake vent area of the AC unit. Your intake duct should be at least that big.

If you have one fan, then by all means make the intake as large as you can so it can supply the big fan inside the unit, then put your fan at the end of the hot air exhaust to help the AC fan.

The fan inside is more akin to a duct booster than an inline fan.
However, it is a big one and can move lots of air. So it needs lots of air. Don't choke the intake down.

 

[inreplyavalon]

Thanks for the quick response Hoosier. The total sq. inches of my three intakes on the AC are 361. So, if i understand this correctly, you are saying I would need an intake duct with a 361 sq inch surface area? Or do I need a fan that somehow equals that?
I know fans are measured in cubic feet per minute but don't know how that translates.
Thanks again for helping out.

 

[inreplyavalon]

a few more thoughts...
this AC cost a pretty penny and I'm not about to be cheap on the fans that will be supplying it air. I'd prefer overkill for this element. Do you think that a 10 in CanFan Max with a cfm of 1023 hooked up at the end of the outtake would be pulling enough air to keep AC happy? In this set up, I would have a 10 in duct running from outside passively attached to my intake vent box. What do you suggest?

Also was wondering if ducting in freezing or below freezing air will negatively effect the unit. I've heard of some AC units turning off once air reaches a certain temperature.

 

[chytil151]

thats what I was figuring. I plan on pulling it in far enough to run an intake to the one side w/ fresh air that come's in from the next room over. The length would only be maybe a foot at best to run the intake for it. This is just a "for now" fix till I can get all my hoods enclosed and ran w/ fresh air from the attic. thanks for the reply hoosier have a great holiday and be safe in everything you do.

 

[hoosierdaddy]

inreply,
Yeah, freezing temp is not a good thing for the AC.
I would not include a scrubber of any sort in the AC air train. A 10" passive intake should be plenty of path in. Just be sure you have at least 10" duct from the back of the unit out. Place a fan at the end of that exhaust run (last or near last thing the air sees).

When a fan is rated for CFM, it means that when it is at it's fullest potential of turning, and there is zero restriction in the duct path, it can create the listed CFM.
Anything that hinders the air path at all will lessen the amount of CFM that fan can create.
Having any duct that is smaller than the diameter of the fan will create resistance. A scrubber also creates resistance.
If you keep your fan at the end of any run, and keep the duct run larger than what the fan diameter is, the fan can work to it's fullest potential.
Placing fans at the intake side and pushing the air can be a bad thing. It takes a professional set-up to overcome the obstacles it can create...keep the fan at the exhaust.
And simply turning up a fan that is too small will indeed make mor eair pass through, but it also makes the motors wear fast and creates big noise. A well balanced system will have little noise and will move air well.
So you understand the CFM better...if I have a 6" inline fan that is rated at 250CFM, and I hook a 6" flexible duct to the intake side of the fan, it will cause the fan to labor some and it cannot create a full 250CFM. This is due to the duct itself is not smooth and creates restriction when the air makes friction with the very non-smooth sides of the duct.
Hooking up a smooth pipe duct will let the fan create more CFM than it did with the flex duct, BUT if you take that smooth duct out for a long distance the fan will also labor. The longer the duct, the more surface area the air rubs against and creates friction...that friction translates to the fan having to work harder and harder.
IF I would run an 8" duct with few restrictions to my 6" fan, I can feel more confident that I am pulling the maximum CFM the fan can pull. You can judge how well the fan works by the noise it creates. The noise effect is exactly the same principle as placing your hand over the hose of a vacuum cleaner...and the more you cover, the louder the fan motor gets, until you completely block the end and a full on vacuum is created within the duct path (inside the hose and canister).
Your duct and grow room are the hose and canister of the cleaner.

 

[inreplyavalon]

Thanks for your help Hoosier. I understand things much better now. I'll be documenting this grow and especially the build and when my box is complete i'll post a pick or two in this thread.
Have a nice weekend

 

[hoosierdaddy]

Glad I could help some. Best of luck!

 

[inreplyavalon]

Well construction has begun and I gor yet another question for you Hoosier. I think this will work.

The exhaust and intake side of my AC is in my Veg room. I am feeding it air from the attic above and exhausting the air through the wall in the veg room to the outside.
My question is that since this is in my veg space i was thinking of using Just one of the intake side vents on the AC and having it also act as an exhaust for the veg space. So it would go
Veg space air>intake cooling port of AC>into box joining the other air on intake vents of box>then all being pulled by my can fan 10 inch max out the side of the house.

The reason i think this will work is because the ten inch fan is pretty strong and as its pulling air down from the attic through the two boxed in vents on the AC, the other unboxed vent i think will also be sucking out towards the fan.

the issue i see could be a problem is that when the AC box is not being used(when the flower room is sleeping) no outake will be happening in the veg, hence no real air flow.

Is this understanable? Thanks

 

[hoosierdaddy]

Where is the air in the veg room coming from? Make sure you have plenty of intake for it too.
And yes, I think what you described will effectively pull air through the veg area. My AC unit pulls air through the veg of my cab then into the ac intakes. The fan in the attic runs even when the AC doesn't.

 

[bostrom155]

Hello Hoosierdaddy, the time has arise for me to ask you another question, currently im using my central air to cool my room. with winter coming that's coming to a stop, so i dont freeze the ol lady out. anyway, i have a 10k that i want to exhaust into the attic, i just got a dresser to set it on. Im going to cut a square hole in the ceiling I guess the size of the back of the ac, and use foam board out the back of the ac and straight up to the attic, what would my max distance be without a fan, i cant get it all the way to the ceiling but fairly close

 

[BorkBorkBork]

Hrrrrmm, now here's an interesting thread. I don't think I can keep the house cool enough to grow next summer, wonder if I can find an ac unit small enough for my closet?

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