AC Boxes Made Easy (to understand and build)

[mrdizzle]

i wonder all this because im having a hard time figuring out how to build a wooden box, that covers the intake and the outtake but keeps them separate. the ac is going to be inside the room so i cant just seal up the back and leave it in a ambient air room

 

[hoosierdaddy]

Man, if you go back through the thread, you will see how easy it is to construct a box that does exactly as you described. Using aluminized foam board and aluminum tape makes it a snap.

And yes, what you are describing will work just fine. Suck the exhaust out...and the units fan will help to blow on it's end.
You cannot pull too much air over the back of the unit...worry more about the other way around.

 

[mrdizzle]

I like the insulation idea, but I want more soundproofing.



so i think im going to pull the back metal shell off the A/C, then build a nice big wooden box around it, passive intake and a strong outtake. thanks for the help

 

[terminalc]

Ok I like this FAS296R2A 28,500btu Frigidaire a/c.
With an anemometer i read between 550-650 fpm off the back exhaust.
The vent dimentions are 24.5" x 17.6"

431/144 = 2.99 sq/ft

2.99*550= 1646 cfm
2.99*650= 1943 cfm

Am i doing this right?
Would this mean i need a 1900 cfm fan to run this a/c efficiently? What about if you wanted to use two of them you would have to double that? 3800 cfm? The ducting size/airflow speed seem like they make that unfeasible. I imagine an 18" pair of holes out the side of the building is more obvious than a central a/c unit that runs all the time. I really like the window units because you can just take them in for repair and have extra in case one fails another one just turns on.

Has anyone done 5 tons of window a/c in a box?

 

[hoosierdaddy]

No matter the size of unit, it will run efficiently all on it's own...IF you are providing all the intake air it needs to satisfy itself, AND you are evacuating the heated air that the unit's fan pushes over the hot coils.

Provide enough passive to equal the sq inches of vent opening in the box. It can't take in more than what the total area of vent openings equal, but less goes against it's design and will starve it for air.

I'm not sure I am absorbing the fpm and how that relates to the mass of heated air you need to get rid of....I have a suspicion that if we dig deeper we would find that the formula tells us we need a duct the size that the back is now. (shrug)
But, in any event, if you are choking the exhaust down to a duct, obviously the bigger the better. You will need to determine what your opening is going to be, and size the fan from there. If you could manage to just vent the back of the unit with ducting the size of the back, even if it were 50 feet away, you wouldn't need an additional fan at all.
It all stems on how big you can make it.

 

[BigGreen]

Killer thread Ive been beating my head off the wall all day I moved the a/c from the window to my inside grow room wall and the other room is like 120f. Explained very well and I am very thankful we'll see how she works tomorrow.

 

[BigGreen]

Well she worked out good the only problem I have now is its spraying water out the side vent. Do you think that is just from built up water from when it was hot or is it gonna be a permanent problem.
Thanks in advance much appreciated

 

[hoosierdaddy]

First thing is to run a piece of wire down the condensation drain, as they get clogged up.

A unit that size will probably need the condensation drain tube run into a bucket or outside.
Small units rely on evaporation and many have no drains, but one your size will.
Sounds like it is blocked and your fan is throwing the water around under the cover.

 

[BigGreen]

Thanks hoosier it got me to read the instruction manual to find out it has what is called a slinger fan that spits the water out in extra humid or rainy weather. Im pretty sure my 90 day return policy isnt up yet. Looks like Im going a/c shopping again.

 

[ItsAllOver]

Cooooool, man. Valuable info!

 

[mrdizzle]

that slinger actually cools down your coils

 

[Norrath]

i see in your own cabinet, hoosierdaddy, you have separated the cool air out, from the intake vents and the exhaust air out, is it more efficient that way than simply separating hot exhaust from ambient AND cool air out?

actually i should edit this, i realise it is obviously more efficient, however this whole procedure will not be thwarted by merely overlooking the boxing of intake vents and forcing spent air into them would it?

then i wouldnt have to worry about satisfying the intake vents, they would be natural. it's a small bedroom too, fairly easy to cool. 90sq feet maybe

 

[hoosierdaddy]

If you are talking about using the cool air to also feed the hot side intake...it will work, and you seem to understand that it will be less efficient. (depending on your unit and situation, it could be to the point of eventual failure)
You need three separations using such a AC.

 

[Norrath]

i was wondering, ive never actually used it in the window properly, are the hot side intakes SUPPOSED to be outside or inside under normal window circumstances?

the hot side intakes are mainly for taking hot air in? wouldnt this be more inefficient trying to sap the energy from the hot air coming in to make it cold? i figured by sucking in cooled air, mixing in the room providing a cooler atmosphere would be become more efficient over the course of cooling the room, since it's easier to cool already cool air, and thus the machine would start from a better point than ALWAYS putting hot air into those...as you call them, hot side intakes.

clarification on this would certainly put my eager mind to rest.

thanks very much for the DIY, should be a sticky!

 

[raphaelwilliams]

That's a great idea. Thanks for the detailed tutorial...

 

[hoosierdaddy]

Norrath, I think all your questions are answered in the tutorial. Maybe the graphics will help you understand it a bit more.

Thanks, raph.
Hope it helped.

 

[Norrath]

heh, well a few blue lines may help someone else out, but what really set my question in motion was this statement of yours:

One is to simply cut a hole in the grow room wall and only allow the cold side in the grow. The hot side can be in another room, and it can draw the ambient air needed to cool the hot side coils from that room.Although you must make certain that the room itself can draw in fresh air for the unit to use.

that ambient air in my case, comes from a tent sucking 80 degree air through a carbon scrubber through a cooltube(HOT) and then into the side of the air conditioner, or hot side intakes as we are calling them.

see where the paradox in my question is starting to form? for starters it's not set up in the grow tent itself, but it is situated where i need it to be to supplement the rest of my vegging plants in closet/cabinets. If that ambient air that i put into the side of the air conditioner is hotter than one might like, asking the air conditioner to sap the energy from that air, expelling it out the back, could be construed as inefficient??

it's all fine and dandy to segregate the intakes and the cold air coming out to keep convection out of the picture, but when im STILL ADDING hot air to it, where's efficiency go? downwards? i fink so!

here is my set up so far.

it's my mother cabinet, with an ac stuck in the vacuous area where i used to have a microwave stuck. im going to block it off into sections like your diagram, but i can only bring in fresh air from the window next to the whole cabinet/unit, i cant actually extend an intake ducting/diaphragm to the outside. so the unit would be bringing in hot air and a bit of ambient bedroom air(perhaps negative pressure bringing air in from outside since im venting out into the attic, less air in the room, will get replenished via outside air..thus negative pr.)

ill become bold and presume im correct in saying since it cant draw in fresh air, it would be inefficient the way it's set up, do you think simply adding louvers on the exact opposite side(LEFT SIDE) from my hot side intake that ive drawn upon the right side, would add sufficient..."fresh air" for a bit more efficiency gain?

thx for letting us use your thread to pick your brain hoosierdaddy, im just following by example. hopefully someone else will find my trouble/query useful in their endeavor. in fact ive read this whole thread twice fully, and then some; and i thought i was good at inventing and troubleshooting i think im just burnt out, but more importantly i dont want to MAKE IT without it being right, eh? anyway, ill let you reply before i keep on yappin.

 

[inreplyavalon]

This is a diagram of what i am considering doing. Hoping ya'll can chime in on whether it sounds plausible. My main question is that i will have the back end of the AC in my 8 ft X 8 ft veg room. I will duct the hot air into the large attic above, but am wondering where i should bring the intake air from? I can use air from outside, except i am concerned this will be too cold for the plants in veg as this is a COLD climate i am growing in.
Could i use the air in the attic as the attic has an ambient vent to the outside? I am also going to be depositing my exhaust from air cooling lights up there.

 

[sirripalot]

hey hoosier, i want to thank you for calling me out on my slightly inefficient setup. i didn't even really think about how much performance increase i could receive. i'm going to redesign my box AS MUCH as i don't want to .

i have a VERY important topic, that i haven't seen discussed (unless i missed it): VIBRATION.

from my current box, vibration is a big factor. in fact, when i'm standing on the floor above the grow, you can feel a slight vibration, in turn it generates some noise.

does anybody have any ideas to eliminate this? i've tried remounting my box with peices of foam between it and the wall, and it made no difference. any good vibration insulating ideas?

the best idea i've come up with so far is to HANG the unit from wire on each corner so the unit itself isnt attached to anything to "conduct" vibration....any ideas before my redesign?

thanks.

 

[Che]

You've got the right idea, but use bungee or rubber to hang the box.