AC Boxes Made Easy (to understand and build)

[BorkBorkBork]

Thanks for the inspirational tutorial hoosier! It was a ton of work, but I've got a veeeeeeeeeeeeery shitty version of your a/c box kicking in the closet with a 6500btu unit.

The intake is just a vent into the room outside the closet, cut on the right side of the pic (though obscured by the wall and box), rather than a duct run.

The exhaust is only 4", and is curved, and is longer than it should be, but it is just about the best I could do. As you may or may not be able to see, I'm working in a very cramped environment. The only pluses are that I insulated the duct (make that a necessity), and it is powered (also a necessity) by an s&p inline ~100cfm fan (.....with plastic blades...).

My major flaws are: most likely insufficient intake. undersized, underpowered, long distance curved exhaust. and finally, neglected to account for access to the rear of the unit to check for water buildup.

Even with all those negatives, it is keeping my closet nice and cool, and doesn't seem to be struggling.

With these flaws built into my system, would you predict an early death on the a/c? Or...worse?

edit: end of exhaust duct run (~6 foot) with inline fan.

 

[Gsizzle]

Hoosierdaddy whats up hope all is well. I was curious about the A/C box. Will it possible to build a box with a 24,000 btu A/C? Probally take large ducting and large fans to make a A/C unit with that amount of btu's effective.

 

[hoosierdaddy]

Gsizzle,
Yes, anything is possible! that is what makes this so much fun.
I have covered most of what you need to know about all of this in the tutorial. Not to put you off or anything, but going back and reading the basic first stuff has about all I can give you. Any more would simply be repeating, which I don't mind...but it would be better if you have all the basic stuff down, and if you have a specific question concerning the setup, I will help you all I can.

Sizing of this ductwork is of the utmost importance. The internal AC unit fan is blowing air at X amount of CFM through a fixed port size. Any time we restrict the size of the originally intended air flow, we jeopardize the integrity of the unit.
The vents in the side and top of the AC cover have provided adequate opening for the proper amount of ambient air to enter the unit. And as long as you do not choke down the air flow path downstream from the fan, then the unit will function properly.

The vents in to the back of the unit dictate how much air the unit needs to function. It is a pain, but all you need to do is measure one of the little slit openings. You will need the proper formula to figure what the sq in of air flow through that one oriface is, and then take that times how many of the slits there are. That is all the sq in of air flow needed at the exhaust end, as it can only push out from what came in. (hope that makes sense)'

 

[Lone Wolf]

thanks alot everyone who posted here, and most importantly hoosierdaddy for starting this thread.... click my grow thread in my sig if you would like to see the AC box I built around my 22000 BTU AC unit, inside of my 4kw attic box...

it involved a days worth of trial and error, but on my second shot, i got it figured out to a T !

knock on wood tho, cuz anything can go wrong in my life!

can't forget to show you guys that box fan I installed for that added push!

 

[InducedSerenity]

Lone Wolf, holy crap! Talk about taking it to another level... that's awesome. I'm in the middle of building the box for my 10500 BTU unit now.. I'm putting it in a closet with a narrow door so I'm having to build the box outside and assemble it in the little closet.. not fun!

 

[hoosierdaddy]

Very nice, Lone Wolf! Only thing I could add is to make sure there is plenty of exhaust area in the attic vent out. And it is probably a good idea to have the box fan as far downstream as possible.
WTG!

 

[InducedSerenity]

My AC is done, and works like a charm without any additional fans thanks to those in this thread who have stressed large ducting again and again.

Thank you.

 

[Lone Wolf]

My AC is done, and works like a charm without any additional fans thanks to those in this thread who have stressed large ducting again and again.

Thank you.

lets see

 

[SumDumGuy]

Amazing writeup Hoosierdaddy. Thank you!!!

 

[blazeoneup]

Nice thread, Only thing is I dont see any mention of the condensation water produced by the window units, It can cause a problem over time if it's not taken into consideration.

I am building a ac box currently, I am doing it a bit different from this thread, I am building a single box to sink the ac unit into, and then adding a reservoir below the unit to catch the condensation water. I also built a styrofoam box around the intake which I will run ducting into and also added another duct on the box to suck the heated air out.

Plan is to pull ambient air from outside the growspace in through the condenser and then directly out of the house using a dryer vent. I am going to add a drain line to the res to easily remove the build up condensation water...

It's not completed but here is what I have so far! I'll post the final pics once it's completed, This is a test unit and will be removed and replaced as soon as I verify the box works properly, I see no reason why it wont but only testing can verify that...

I'll finish it tommorow and get the rest of the pictures up!

 

[Lone Wolf]

its been about 4 days since Ive had my box all together, and its working PHENOMENALLY! well, the other problem I had was the 2nd day, I had used some SHITTY duct tape on a section of my box and it came apart, and caused the hot air to escape into the attic... i sealed it with some foil tape, and instantly the temps dropped...

boy am I glad that I never went ahead and purchased one of them portable AC units off of ebay! thank god for the internet- specifically craigslist, and icmag... I cannot imagine where I would be without them....

 

[hoosierdaddy]

I am so glad folks are having success with their AC's.
Thanks for all the kind words.

blazeoneup,
The original tutorial mentions condensation drains in detail, and it can be found mentioned multiple times after that. I don't have pictures of drains, as mine is evaporative style with no drain.
Just at first glance, I can tell you that a 4" duct is not enough for either the intake or the exhaust. You should always feed as much air in as the unit can take, and then the flow will be dictated by the exhaust port and fan(s). To be precise in how much opening to have for intake, you can measure one of the vents in the side of your unit...figure out what the area of the vent opening is in square inches, and then multiply that one vent space times as many vents as is in the top and sides. This will show you exactly how much area the unit provides for intake volume, and you should provide that much area of fresh air duct.

 

[Danks2005]

Hoosier, I am about to install a 5000btu unit. It has to be completely contained in the grow space. I was planning on exhausing heat from back of unit into the attic. Then boxing then intake and drawing air from under my house (no lung room available). My outside ambient temps are in the 90's with fairly high RH. Do you think this will be ok. Should work as long as outside air is cooler than the condensed refrigerant right? I will be doing this in the next day or so, so any input would be greatly appreciated.

 

[hoosierdaddy]

Danks,
Considering that a window AC normally works by drawing in hot summer air, you should be fine drawing in ambient outside air from anywhere you can get it. Just make sure you feed the unit plenty of it.

 

[blazeoneup]

I am so glad folks are having success with their AC's.
Thanks for all the kind words.

blazeoneup,
The original tutorial mentions condensation drains in detail, and it can be found mentioned multiple times after that. I don't have pictures of drains, as mine is evaporative style with no drain.
Just at first glance, I can tell you that a 4" duct is not enough for either the intake or the exhaust. You should always feed as much air in as the unit can take, and then the flow will be dictated by the exhaust port and fan(s). To be precise in how much opening to have for intake, you can measure one of the vents in the side of your unit...figure out what the area of the vent opening is in square inches, and then multiply that one vent space times as many vents as is in the top and sides. This will show you exactly how much area the unit provides for intake volume, and you should provide that much area of fresh air duct.

You may be correct, That's what testing is all about once I test whether or not the unit works correctly or not I will know what needs done, If I cannot make it work I'll toss it and buy a split unit to install.

I got a 4" vortex fan I was gonna use for an active exhaust, The unit is 5200btu the vortex is 170 cfm and the box is 48cf which means with the vortex I can vent the box around 3 & 1/2 times per minute.

No garuntee it will work, But my math says it should. If I were trying to use strictly passive intake and the fan in the ac unit to move the air I know for sure this wouldnt work. However I am using active exhaust passive intake. According to my math it should work. Only way to find out is to test it

I dont disagree with your method and math, I just know that portables can and do work well as long as you get the right model. You get a dual duct portable and it will work well, with 2 4" vents in it. One for intake and one for exhaust. I used a 12k btu portable some years back and neverhad any trouble with it, and all it had was 2 4" vents one for exhaust and one for intake, it worked well so I am going out on a limb and trying this box, Either it works or it dont I'll be sure to post up whether it does or doesnt work....

 

[Danks2005]

Danks,
Considering that a window AC normally works by drawing in hot summer air, you should be fine drawing in ambient outside air from anywhere you can get it. Just make sure you feed the unit plenty of it.

Thanks, thats what I figured. I got a 6" Hurricane inline, should be more than enough I think.

I ran the active exhaust with 6" insulated duct powered by the 620cfm inline fan. Then I cut out the grills on the side intakes to make one large rectangular hole, boxed them and ran a 4" duct on each side. So I got a 6" going up and out, and two 4" ducts feeding it. Hopefully it works well enough. One thing I can tell you, is that it is way quieter than I had anticipated.

One thing I don't like is all the hot air running through my $200 fan, shortening its life. But, its a give and take I guess, I sure cant have an a/c hanging outside

 

[hoosierdaddy]

Well, I have to disagree with a little of your logic, blazeoneup. Testing is not needed. The laws of physics are what they are and you can prepare things properly ahead of time, instead of using a hit and miss, try and try again sort of method.

If you have a passive intake with a 4" hole, and a exhaust with a 4" fan, then I don't know what "math" you say is working out for you. Common practice for design of air flow applications is to have at least 10% more passive intake than you have exhaust. Much better to have double the passive intake as you have exhaust.

A 5200btu unit, which is what I am using, needs to have at least a 6" duct exhausting with a fan helping the internal AC fan. The fan should also be at the end of the run to let the air cool a bit before it gets to it. And with a 6" exhaust, it requires more than a 6" hole as a passive intake, best to be double that.

There is no testing of this method, it works and will work if you do things properly. Trying to rig things your own way, with total disregard for what physics says has to happen, and what others try to tell you has to happen, will end up in you buying a mini-split and dissing window AC's, and probably warning people off of the window AC.
Hell, you are damn near doing that now!

You are at a position now that you can make the unit a top shelf thing...but cheaping out with dryer vents because that is all you have isn't going to get you there.
Visit HomeDepot and get some proper duct pieces for cheap and do it right.

Post up what you find...if it doesn't work, I can assure you I can tell you why, and what you need to do to make it work. There is no "it don't work".
I am not trying to be a hard ass, but look...I have spent HOURS AND HOURS of my time with this tutorial...and I will help each and every person that wants it.
I did the thing in the first place because tutorials were out there put together by Bozo the Clown and his pals that I know for a fact don't work. I wanted people to have something to depend on that works, and I can assure you it works and works well.
And it was obvious that you didn't read the thing anyway. Had you actually read it you would have known about drains being mentioned, and you would not be trying to go against the grain of what has already be gone over and over and over again.

OK, Rant over.

 

[blazeoneup]

Well, I have to disagree with a little of your logic, blazeoneup. Testing is not needed. The laws of physics are what they are and you can prepare things properly ahead of time, instead of using a hit and miss, try and try again sort of method.

If you have a passive intake with a 4" hole, and a exhaust with a 4" fan, then I don't know what "math" you say is working out for you. Common practice for design of air flow applications is to have at least 10% more passive intake than you have exhaust. Much better to have double the passive intake as you have exhaust.

A 5200btu unit, which is what I am using, needs to have at least a 6" duct exhausting with a fan helping the internal AC fan. The fan should also be at the end of the run to let the air cool a bit before it gets to it. And with a 6" exhaust, it requires more than a 6" hole as a passive intake, best to be double that.

There is no testing of this method, it works and will work if you do things properly. Trying to rig things your own way, with total disregard for what physics says has to happen, and what others try to tell you has to happen, will end up in you buying a mini-split and dissing window AC's, and probably warning people off of the window AC.
Hell, you are damn near doing that now!

You are at a position now that you can make the unit a top shelf thing...but cheaping out with dryer vents because that is all you have isn't going to get you there.
Visit HomeDepot and get some proper duct pieces for cheap and do it right.

Post up what you find...if it doesn't work, I can assure you I can tell you why, and what you need to do to make it work. There is no "it don't work".
I am not trying to be a hard ass, but look...I have spent HOURS AND HOURS of my time with this tutorial...and I will help each and every person that wants it.
I did the thing in the first place because tutorials were out there put together by Bozo the Clown and his pals that I know for a fact don't work. I wanted people to have something to depend on that works, and I can assure you it works and works well.
And it was obvious that you didn't read the thing anyway. Had you actually read it you would have known about drains being mentioned, and you would not be trying to go against the grain of what has already be gone over and over and over again.

OK, Rant over.

You are at a position now that you can make the unit a top shelf thing...but cheaping out with dryer vents because that is all you have isn't going to get you there.
Visit HomeDepot and get some proper duct pieces for cheap and do it right.

That ^^^^ cheap dryer vent is all I have line was a wee bit overboard...

If you look at the material I am using and how its put together it should be obvious that I am not going the cheap route. I guess I am kinda, cheap route building a ac box and not just buying a split or portable but thats where cheap ended. I guess I could have used insulation board and duct tape...

Actually the intake is 2 3" ducts which is 50% more intake then exhaust. Who said anything about using a 4" exhaust and 4" intake? I said I am using a 4" active exhaust with passive intake, I never stated what I was doing for intake.

I did mention I have used portable ac units in the past that had 2 4" vents one for intake one for exhaust, Maybe thats what caused some confusion.

I never planned to put the fan directly above the box either was putting it outside the room probably 15ft from the actual unit, I know your trying do a nice thread here and I never intended to get into a debate, I'm posting what I am doing no need to get all touchy....

Not finished yet but here is the incomplete intakes....

2 3" intakes for the box...


2 3" intakes from outside the room...


You have not got the full picture or idea of what I am doing obviously. Either way I will post whether or not it works when its complete and if it doesnt, I'll be sure to let ya know....

Also you are right I didnt read the thread and was browsing Icmag wen I noticed this thread and seeing I was currently building one I figured why not post it up, I am not bozo the clown and I have a pretty good general knowledge about ventilation.

I skimmed through the thread a little bit to see what others were doing and also checked out the diagrams, I never seen any mention of the condensation so I posted that I hadnt wasnt like I said it wasnt mentioned. Either way your thread is useful and good for the community...

 

[Danks2005]

Sometimes I feel like I need to lay off the pipe. I completely forgot to add my condensate line. LOL Now I got a puddle, and some more work to do.

 

[Crispyone]

Hey guys
First a big thank you for the thread


I'd like to throw my set up out there for review. I start with an over sized carbon phresh filter on top of that is a 6" ho can fan blowing thru my 1000 watt air cooled hood then straight into the intake on my 5000 btu zenith ac then exhausted out of my all concrete 12x7 room. All 6" ducting is isolated which is a must.

Exhaust from the light really didn't feel that hot to me so I said fuck it and fed to ac..

Lights on ac is blowing 66 degree air. Lights off it's at 54 degrees. This is with the temp probe right in the ac grill. I'm running a dehuey full time with 1400 watt of lights. Lights on rooms is solid at 82-83. Lights off 73. 61 humidity. 25 monsters in e+ f , 4 weeks into flower and 50 30 day old clones in a tent.

Ac has been running full time now for about a week now and all is solid. I have it tilted forward with run off in the front left corner. It will pull 5 gallons of water a day and I still need a dehuey heating up the place full time.

After this round I'm opening up exhaust to 8 inch.

That's about it. Thanks again for the great thread.

Crispy