AC Boxes Made Easy (to understand and build)

[Gold123]

I am having a problem with the fact that even with the box the air is still being pulled from the room. Then exhausted out the back. i must be missing something. I have a sealed room and have my central ac routed to it but dont want it running all night. So i bought a 15000 btu window ac thinking i could fabricate a duct that would just fit over the outlet of the ac. I could then have the whole unit outside of my room to supplement my cooling, Would this work? any help would be appreciated.

Did you seal the fresh air vent in the unit?

 

[slaveinc]

no. i haven't done anything yet. I am still brain storming.

 

[hoosierdaddy]

slaveinc,
The cold air section of the AC has both an intake an an exhaust. These recirculate the cold air. Usually the cold air comes from vents on top of the unit, and the intake will be behind the front grill of the unit and usually covered with some foam for a filter.

The hot air side has it's own intake and exhaust that are separate from the cold air.
If you read the tutorial you will see that I only show the cold air side in the grow and nothing about ducting the cold air to the grow. I don't show that because it is not very efficient at all to do it that way. You need a cold duct to the grow, and another cold duct leading back. The units just aren't built to deal like that. But, keeping the cold in the grow and ducting the hot side works fine. You can have the whole thing in the flower room, as long as you have the hot side ducted in and out sufficiently.

If you haven't went through the whole tutorial yet, I highly suggest reading it, or going back through it. I think I have answered just about all the questions there could be about setting the units up.

 

[slaveinc]

ok so on my unit the part of the ac that intakes cold air from the room is not properly sealed from the ambient air section. So the air in the room would be pulled out into the ambient air section and out the exhaust, right? Oh and I have defenetly read the tutorrial even all the back and forth posts about cfm and what size duct to use. hahahahahh I really appreciate the help and knowledge. Also my grow room is built in another room so is the box necessary for me because I use a scrubber in the outside room anyway?

 

[hoosierdaddy]

Yes, if the cold air section is not sealed from the ambient air section in the back of the unit, it can indeed suck funky air from the grow and exhaust it out the back of the AC.
15k unit most likely has a fresh air vent that separates the two areas. Make it so it no longer functions and seal it up.

 

[Danks2005]

The dripping is driving me crazy, can't seem to get it sealed up properly. Everytime I get it plumbed through my runoff tube and out of the grow space, a week or two goes by, and it's back on my floor. Can you suggest an Evaporative system in the 10,000-12,000BTU capacity (looking for good make/model window units). Thanks

 

[hoosierdaddy]

I'm not sure such a model in that size exists, Danks.
AC drains are notorious for getting clogged up. As long as you keep it cleared out on a regular basis, I can't see there being a problem. Unless your plumbing job needs to be addressed. Is the tube clogging up or coming lose?
Also, make sure you have the unit tipped slightly towards the drain.

 

[sparkjumper]

Dank I use an LG 12,500 in my flowerroom remote control just open the door and you dont have to walk through plants.Mine works great

 

[ZENARCADE]

Hey guys! great thread hoosierdaddy!
I had a question, and sorry if this has already been answered and I missed it.

So once you build the box/fan to exhaust the hot air out of the back of the unit, where are you guys sending that hot 100 degree air?

I have a 10x12 finished room for flowering in a 25x35 basement. I'm going to be switching from aircooled horizontal to 4-5k bare bulb so I will be installing a 24500btu ac. If I'm using a 10-12" fan to suck from the box I can't see cutting a hole that big in an exterior wall and pumping the hot air outside all winter; a 12" hole blasting warm air in January might look funny. Should I suck from the back of the box and let the ducting just dump out in the other unused 3/4's of the basement or will this make the basement hotter than hell? I would like to just do a mini split but those plug-n-play units are like 5k and I def can't get an HVAC guy over here.......
Any thoughts......
Thanks!

 

[Gold123]

Hey guys! great thread hoosierdaddy!
I had a question, and sorry if this has already been answered and I missed it.

So once you build the box/fan to exhaust the hot air out of the back of the unit, where are you guys sending that hot 100 degree air?

I have a 10x12 finished room for flowering in a 25x35 basement. I'm going to be switching from aircooled horizontal to 4-5k bare bulb so I will be installing a 24500btu ac. If I'm using a 10-12" fan to suck from the box I can't see cutting a hole that big in an exterior wall and pumping the hot air outside all winter; a 12" hole blasting warm air in January might look funny. Should I suck from the back of the box and let the ducting just dump out in the other unused 3/4's of the basement or will this make the basement hotter than hell? I would like to just do a mini split but those plug-n-play units are like 5k and I def can't get an HVAC guy over here.......
Any thoughts......
Thanks!

I knew a guy in Chicago that removed a toilet and ducted out the sewer. If your in a cold winter place why not just duct in some nice cold outside air.

 

[ZENARCADE]

Thanks for the input, unfortunately the ducting fresh air in won't work for a number of logistical issues. Also, where I live 6-7 months out of the year fall right into that climate category where a window a/c would look funny to anyone normal but the grow room still needs it.

 

[hoosierdaddy]

That unit is going to need lots of air coming in, so you need to make sure your basement has enough intake, or you provide intake directly to the AC unit with a duct. The hot air leaving is the same deal, you need to have a place for it to escape. Exhausting the hot air into the room is not an option, as it will continue to heat up further and further, and unless you have a separate air in duct to the AC, it will keep drawing in the hot air and eventually not be able to cool to a point of failure.

A window with an old AC in it that has a winter cover over it is not an attention getter. You can put just the box of an old AC in the widow and disguise it as a working AC that is just covered for the winter. Those covers only cover 3 sides of the thing, and you can duct right to the back of the false AC.

However you do it, you need sufficient air in, and a way for the hot air to get out.

 

[ZENARCADE]

^ So there is a cover I can by for a/c's that stay in the window year 'round? A winter cover? I never new these existed, this opens up a whole new world of stealth possibilities!
Thanks!

 

[hoosierdaddy]

I'm talking about buying/finding an old junk AC and gutting it out, only hanging the box it all came in. From the outside, it is probably not going to be known that there is no AC works in the thing unless someone would actually look through the vents. But, you can cover even these vents with a common AC cover for winter. They can be found at Walmart or hardware stores, and are usually nothing more than nylon tarpaulin with string or elastic ties that fits the AC.

Be aware that if anyone is close to the thing, they will probably hear air working through it.
And if you cover the vents it has, you need to cut new in the bottom of the box.

 

[Gold123]

I'm talking about buying/finding an old junk AC and gutting it out, only hanging the box it all came in. From the outside, it is probably not going to be known that there is no AC works in the thing unless someone would actually look through the vents. But, you can cover even these vents with a common AC cover for winter. They can be found at Walmart or hardware stores, and are usually nothing more than nylon tarpaulin with string or elastic ties that fits the AC.

Be aware that if anyone is close to the thing, they will probably hear air working through it.
And if you cover the vents it has, you need to cut new in the bottom of the box.

They look like BBQ covers.

 

[blazeoneup]

Well after 30+ days running the ac unit in the box I put together, I noticed the high temp got up to 127f which is much to high, Even though the unit still seemed to function fine, I decided I needed to just do it up right, Minimal just wasnt cutting it, So I cut a 6x12" intake and added a 6" 440 cfm to the intake side of the ac and a 8" exhaust for the box....

End result works great, I guess minimal just doesnt cut it for these ac boxes.

 

[Gsizzle]

Well we live and learn. Good of you to come back with the info and update.

 

[hoosierdaddy]

I'm glad you got your system squared away to your satisfaction, bou.
Minimal works, but not as well as optimal. The very thing that inspired me to do this tutorial was seeing other tutorials that were bad set-ups, and I knew for a fact that they may well work, but not efficiently. And there is no way a unit can last long when combining the intake and exhaust.

Same with starving the flow in or out...the unit may well function fine, but when it has unrestricted air flows and things done right, the compressor will last longer than one set up in dubious fashion. The unit will also use less energy getting the task done if it has plenty of air flow.

The box and everything looks real nice, blaze!

 

[Rasta311]

what do you think the max intake temp can be for a window AC?

 

[hoosierdaddy]

I wouldn't go above 110degF, as that is just about as hot as it gets in summer most places.
I am certain an AC unit is engineered with the normal highest ambient outdoor temps in mind.