AC Boxes Made Easy (to understand and build)

[hoosierdaddy]

snowschool, the unit you may use has electronic controls, as most if not all that size do.
The only problem with an electronic control, as opposed to a manual control unit, is that when the power goes off or surges for a second, the controls will default to a shut off position. This could cause your grow to get cooked. I recommend anyone using an electronic control unit to also purchase a UPS (uninterrupted power source). The UPS will keep the unit running for a while even if the power goes off.
The RG-51C model is a 5000btu on the same page. It has manual controls. Two of those would probably do the job.

The better you have things in the room the easier to cool. If you cool the 1000's with a separate duct and fan, keeping the grow room cool is easy, and you may be able to do it with one 5000btu unit.

 

[snowschool]

Thanks Hoosier- So it looks like it would be cheaper to buy 2x 5000btu a/c s and build 2 boxes then to get a large model w/ ups? The " room " is actually a shed. Temps outside get very cold (below 0 )at night but does also get pretty hot in day. After talking to some people in this local climate we decided ( my partner and I) that condensation could be a major problem if we air-cooled the lights with our set up. We did think that an a/c box would be OK though- The shed is 8 inches off the ground so was thinking to vent through the floor. Price, stealth, and the most simple solution are our concerns. I'm just unsure if we are going the right direction-

 

[ogatec]

snowschool, the unit you may use has electronic controls, as most if not all that size do.
The only problem with an electronic control, as opposed to a manual control unit, is that when the power goes off or surges for a second, the controls will default to a shut off position. This could cause your grow to get cooked. I recommend anyone using an electronic control unit to also purchase a UPS (uninterrupted power source). The UPS will keep the unit running for a while even if the power goes off.
The RG-51C model is a 5000btu on the same page. It has manual controls. Two of those would probably do the job.
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when the electronic units 1st came out that was true, but most units that i have had experience with in the last couple of years(ge,freidrich,lg, whirlpool,frigidaire)will remember what setpoint you entered whenever the power comes back on.. it is something to check up on though.. either way it will be mentioned in the instruction manual. best to read up b4 installing the unit permanently..

 

[milehighmedical]

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[Ickis]

I have the same a/c as you hoosier. They replaced it even though I broke the other one because it cycles off and on too much in a small enclosed area. How is yours not cycling off and on constantly? I have a 3' x 8' x 8' closet that has a window and a door to the attic. The 400w heats the closet to over 90 very easily. It heats up fast in about 2 minutes in the summer. The a/c cools it very fast but it heats up before the 3 minute compressor rest period.

thoughts?

In the winter if you just use fan only and open the vent to raw in outside fresh air will the fan still freeze up when it is super cold outside or does this only happen to the compressor and coils?

 

[hoosierdaddy]

milehighmedical, The cool air of the unit is a recycling thing, so it could be feasible to duct the cool air to an from another location. But, you are talking about insulated duct and a very well thought out duct system to do this. I have never used additional Co2, and probably won't ever. It seems to me like a lot of work and trouble for very little reward.

Ickis, my unit really doesn't labor at all. The hot side gets fed plenty of fresh air, and the exhaust gets helped out with a fan to the attic. If your unit is having trouble, I would make sure you have enough intake for fresh air...and then make sure you have enough duct and fan to get rid of the hot air.
My cab's flower chamber has the cold air at the bottom at the root zone. There are fresh air intakes above where the cold air is, and an exhaust duct pulling on the top of the cab.
SO, while I am recirculating the cool air in the flower chamber, it is also exchanging fresh, warmer air, so most of the exchange is happening above the cool air zone, as cold air sinks and hot air rises.
I have seen the root zones at 68degF at the same time the canopy was at 80-85degF. We are talking about a distance of less than 2-3 feet separating these zones.
Probably worth mentioning that my lights are in a cool tube.

 

[Ickis]

So how often does your unit turn off and on the compressor. My unit doesn't labor to cool it. It just heats up as quick as it cools. I think the compressor has a 3 minute restart feature but it comes on every 3 minutes. Cools the room in maybe the same time and turns off the compressor but fan still runs because it is a manual off and on. Then in 3 minutes the compressor kicks on again.

Does your a/c have the fan running all the time and the compressor just kicks off and on when needed? I think you said you have yours set half way.

When I used one of those outlet adapters that have a temperature control, go off and on at a set temp, it is even worse because it turns off the power and when it comes on the compressor will start even if there hasn't been the mandatory delay.

Lets say I have the proper fan and duct work to exchange the air at 5 times a minute. If my ambient intake air is say 72 this should keep my room at a good temp. Correct? Then I would not need a/c.

If that wasn't enough like I assume yours wasn't and you added a/c because the box gets too hot. You still have a period where the a/c goes on and the small box is easily quickly cooled and then it would turn off the a/c then the box heats up and a/c comes on and the cycle continues. I don't understand how your compressor isn't cycling every 3 minutes or less in a small box.

I was told by the factory that to cool a small room (said it was a small playroom) that the a/c needs to be in a bigger room where it takes longer to heat back up and run the a/c. Then this cool air reserve can just be sucked in to the room that needs cooled by a fan on a temp regulated outlet to keep that room cool.

I am trying to solve this otherwise there is no a/c I am aware of made for the home that the compressor can cycle on and off with no 2-3 minute off periods. They will all break.

 

[hoosierdaddy]

DO you have any pictures or drawings of your set-up? It's a little tough to visualize what you system is like by what you described. Do you have a fan pulling air from there now?
Is the AC in a window that is in the grow area? Are you in the northern hemisphere?

Yes, the fan will always run when the unit is on. A single motor has a rod with two fans on it..one blowing on the hot coils out the back, and the other is the fan on the cool side recirc.

My unit does not cycle because it is only having to cool a very small area of ~2x2x2
It does that and shuts off (compressor) real fast. Unit isn't working hard making it cycle.
Coupled with the fact that I have my lights in cool tubes, my temps are great and the AC works fine.
I only run it in the summer when the garage is very hot. Setting the dial at about 8 keeps the root zone at 68F or so in 90degF temps.

 

[snowschool]

when the electronic units 1st came out that was true, but most units that i have had experience with in the last couple of years(ge,freidrich,lg, whirlpool,frigidaire)will remember what setpoint you entered whenever the power comes back on.. it is something to check up on though.. either way it will be mentioned in the instruction manual. best to read up b4 installing the unit permanently..

Hey thanks Ogatek! My buddy who is an electrician also said he could rig it up to suit my needs.... I ordered that A/C free ship to store-I'm sure they wanted to know why someone in rockys needs an A/C in January .... Even though I'm quite legal on state level, always hate to use anything but CASH ever!!!

On another note.... it sounds like most of you guys use the built in thermostat?....Do you think( anyone) using a separate themostat and sensor would make a big difference in accuracy? (for room is about 8x16 split in two sections)

 

[ogatec]

On another note.... it sounds like most of you guys use the built in thermostat?....Do you think( anyone) using a separate themostat and sensor would make a big difference in accuracy? (for room is about 8x16 split in two sections)

i couldnt have said it better-

Oh and as many probly find.. These things dont do to well in the winter time if they are in the window...

I dont know if it was mentioned yet but THERE IS A WAY TO FIX THIS

what you do is you just locate the thermostate its usualy just a metal wire in the front of the the ac intake.. Pul the wire out gently and pull it into your room and away from your window... If that doesnt work... Add a incandescent bulb close to the thermostat... I have the thermostat wrapped around a cfl bulb.. this keeps it from running 24 7..

hope it makes sense Im a bit sleepy.

 

[BorkBorkBork]

Picked up a window unit for the closest today. I'm not very handy, so this one's going to take me a while.

Glad I found this thread!

 

[milehighmedical]

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[hoosierdaddy]

You can see the AC unit on the lower right of the cab.
You can also see the lowest row of intake elbows on the back wall of the cab. Cold air sinks...big time, and hot air rises. The cool air stays down low around the root zone up to just below the intakes. The exhaust in the ceiling of the cab is pulling air in through the intakes, but as it is hotter air than what is just below the orifice, it mainly mingles with the air that surrounds the top of the plants.

Quite a bit more efficient than you are imagining. And the root zone is what is important to keep cool. The vegetative parts of the plants can withstand very high temps for long times, temps that would cause the plant to stall or stunt if the roots were that hot for that long. Imagine outdoor conditions in the heat of summer sun.

I have a remote temp reader that I can hang at different heights and show the dramatic difference in the zones when the door is closed. You can see it in the lower part of the shot. It stays around 65-68 degF all the time where it's at. This particular $99 walmart special has done a fine job for the last two consecutive summers.





As far as piping from the unit to the tent...it can be done.
Two separate ducts, 6 or 8 inch. You need to rig one from the cold air out to inside the floor of the tent. Another just like it coming back from the other side of the floor of the tent to the cold air in(this is the large front of the unit and often has a filter behind the grill).
The fan is not going to be real great with such ducting, so install a $30 duct booster on the end of the cold air out that is in the tent close to or on the floor (fan at the end of the duct run pulling the cool air from the unit..passive back through the other duct).

Let the original exhaust fan take care of the light heat, and the ac should keep the business end cool(er).

I always suggest folks cool tube their lights. No other way to fly.

 

[inreplyavalon]

Its working like a charm after eight hours. Will update down the road.
THANK YOU HOOSIER again for sharing the proper way of building one of these.
My wife jokingly said there is a space ship in the veg room...

well I spoke way to soon on this project. I have spent the last few days trying to find my air leaks in my room. My room is obviously sealed, and i have a tarp and panda plastic over the door along with weather stripping. Its a pretty good seal. The problem is when i turn on my A/C and 10 inch booster fan, the door seal parachutes inward. So i have been trying to find an outake air leak in the room and sure enough its my AC. two days ago i took apart the whole box and redid it in case a leak in that was causing it.

So tonight i am fiddling with my AC and i unplug it. Then when i look inside the front, the big air moving wheel is spinning fast. No power is on except my 10 inch box booster fan in the attic.

So my fan is pulling air from my room through the front of my AC and out the back.
I took apart the front of the AC as much as i could and got no where.

Anyone have a clue as to how i can get inside to fix this problem? SHould i disassemble the box again and see if i can can go in from the back?
I am having a rough few days. Lost a lot of seeds to damping off for the third time in a row, and now my whole 'sealed room' setup is backfiring.

Any assistance will be met with gratitude...

 

[hoosierdaddy]

When the exhaust fan is on, and the AC off, the fan inside the AC will turn because you are drawing air through it. Many AC units will have both the back side fan and the front side fan on a common shaft, so that any time the back fan turns, so does the front fan.
If you are feeding the air to the intake of the hot side of the unit from a separate location, as it looks like you are, there shouldn't be any air being sucked from the flower side...unless there is a fresh air vent between the hot and cold sections that is allowing this leak.

 

[inreplyavalon]

Thanks for sharing Hoosier.

There is a fresh air vent which i went in and taped closed. It is no longer a leak. Somewhere else inside is leaking and i cannot get any further inside the unit than i have. The descripton you gave is spot on for why the fan on the cold side is spinning, but the seals must be poor of something cause its pulling air out at a fast rate. Enough to keep the CO2 ppm of my room constantly above 400, with 30 big plants inside...
I can take the box off the back and try to go in there?

Anyone know if most big AC's are accessible from behind?

 

[milehighmedical]

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[hoosierdaddy]

inreply, the whole back of the unit comes off with ease (most likely it's a three sided case held by 4 or so screws). It will expose the whole schmear in the back. You will for sure be able to find a leak between the chambers. Caulk the vent if need be.

milehigh, go to HomeDePot and get a venting piece that is used leading to a house register. It will have a 6" flange on one side and will bend into a 4 sided rectangular thingy.
If you unscrewed one of your vents in your house, it would be the fist peice of galvanized duct that the vent fits around. Find one that measures the rectangle shape that your air out is. You can cut small flanges in it and screw it right to the face of the AC plastic. Caulk the thing before you screw it down. I have done it, and it works, but don't forget to have a fan in the grow helping to pull that cool air out. Try to use insulated duct too.
SHort of that, get some gorilla tape and some heavy cardboard and make it work.

 

[snowschool]

when the electronic units 1st came out that was true, but most units that i have had experience with in the last couple of years(ge,freidrich,lg, whirlpool,frigidaire)will remember what setpoint you entered whenever the power comes back on.. it is something to check up on though.. either way it will be mentioned in the instruction manual. best to read up b4 installing the unit permanently..

So I got the A/C and sure enough it did not reset when power was off......... it even turned on when I plugged it in.

For stealth in my application, this box needs to be built to exhaust through the floor . This is going in an outdoor "shed" that is about 8 inches off the ground ( no skirting so free flowing under the "shed" and will mostly only be running on cool to very cold nights. This beast of an A/C has a 12 inch exhaust fan- not sure how I should rig this up exactly. What I'm thinking is: If I can just barrier one section of the open space under the "shed" ,then have intake/ exhaust going to floor on different sides ( one on each section, barrier would be right under A/C) If that made any since I would love your advice A/C guru. (Sorry just inherited a MAC and I don't think it has paint or I would've drew it up )

 

[Medgirl]

I read your article on A/C boxes. I have a question. Building attic box. Very hot attic here in Florida. dimensions will be 32x32x48 (LxWxH in inches)
That is the dimensions of the actual grow area. I plan on adding 18" or so on top of the 48" to allow for a 5000btu a/c unit. The unit would hang out of the box somehow, not be inside.
Do you think this is feasible? I mean do you think the unit would be too much for such a small area?
Any other ideas? Which a/c box method would you recommend?

Thanks!