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Taking A/C boxes to the next level: multi-ton split systems

M

micro gro

I was first introduced to "A/C boxes" for window-mount A/C's back when I needed air conditioning for the first time in a sealed room (thanks ICMag). I'm taking that concept to the next level: concealing multi-ton compressors, indoors.

A little history: The reason for the need for a vent box was because of size and location limitations on the window, as well as airflow near it. The reason for the need for a window-mount A/C (instead of a fancy mini-split) was budget, but that's another story and probably an not a major issue for most people interested in this thread.

Whatever your reasons are for housing the (normally outdoor) compressor unit indoors, whether it be physical limitations (simply no space) or landlord / neighbor issues (new large A/C unit would draw attention), I'm here to discuss and show you how I implemented this concept on a 3.5 ton (42,000 BTU) split A/C system.

The concept is pretty simple: build a device or enclosure to house the compressor unit that can draw in fresh, cool air and exhaust the hot air out.

Here's the compressor room being built. Bottom 4' is left open and covered by a simple fiber air filter. Passive intake from windows, although active intake through a smaller hole may have been quieter. Wasn't a concern in this case, though.

Preferably framed to allow for R-19 or better insulation, and double drywalled to stop sound transmission.



12" vent hole cut, inline fan mounted.



Tired now. More tomorrow.
 
M

micro gro

Philosophelon said:
Nice. I now have three threads of interest to which to subscribe. K+
Click to expand...
Philosophelon, what are the other two? :chin:

BTW I forgot to take more pics of the A/C setup today. In the mean time, if anyone has any questions / comments I'll be glad to address them.
 
wizberry

wizberry

Member
micro gro,

I know it's not directly related, but how do u have your electricity panels arranged, and how is your AC unit hooked up to the panel? Do u do it yourself, or do u need an electrician?
 
M

micro gro

wizberry said:
micro gro,

I know it's not directly related, but how do u have your electricity panels arranged, and how is your AC unit hooked up to the panel? Do u do it yourself, or do u need an electrician?
Click to expand...



Goes something like:

main -> 40A for A/C
main -> 100A for subpanel
sub -> 50A for lights
sub -> multiple 15/20A for misc 120v

(Main panel not pictured.) The two metal boxes on the lower right corner are service disconnect switches.

Did it myself.
 
M

micro gro

I suppose until I get around to taking more pictures of the installation, we can briefly discuss the installation process. Generally means finding a suitable location for the compressor unit, as well as a location (and orientation) for the air handler unit.

Typically with non-mini split units installation involves connecting the outdoor (compressor) and indoor (air handler) units using a copper line set by the method of sweating copper fittings. I've seen some with flared compression fittings, but most seemed to involve sweat fittings.

If you've got the money, you can get the Excel Air split systems which requires no lineset vacuuming on installation (unique resealable quick connect fittings). Refrigerant recovery or refills aren't necessary as the lineset itself is somehow sealable (with refrigerant trapped inside, it sounds like), so you can move this unit or take it with you without the need for a HVAC tech or refrigerant / special tools. I have no actual experience with the Excel Air systems but have heard nice things about them.

The insulated lineset will need a roughly 3" diameter hole to pass. The compressor room has double lining of drywall (to reduce noise transmission), and the compressor unit itself was left on its original wooden shipping pallet. If vibration became an issue, the plan was to mount industrial rubber feet on it. The room was double-framed on relevant sides to allow for two layers of R-13 (totaling ~R-26) insulation. I had considered surfacing the room with some other material, perhaps rigid, foil-covered insulation board or other more heat-resistant material (I think FC Sheetrock safe enough for 95-98F, but just in case.)

In the ceiling is a 12" hole with a start collar for an inline fan. At the present time (due to time / schedule restrictions during build) the fan is mounted directly on the collar, but the plan is to install an inline muffler first at the intake to reduce the noise from the fan. The exhaust fan is ducted directly to the roof.

Hope that's clear. Pictures to follow, soon.
 
M

micro gro

Here's the compressor hooked up, and you can see the 12" fan running there.



Air handler hookup.

 
Philosophelon

Philosophelon

Member
micro gro said:
Philosophelon, what are the other two? :chin:
Click to expand...

H3ad goes coco & Ceramic Metal Halide (CMH)

I like H3ad's coco thread because I switched (earlier this year) from organic nutes in soilless to refined mineral nutes in coco/perlite, and his thread has the most technical detail of any that I've found. His modified coco-specific lucas formula and background on the unique properties of coco saved me a TON of time and money getting used to a totally new kind of medium and nutes, and I'm still reading through it at my leisure in order to familiarize myself with any and all potential problems.

I'm also reading through the CMH thread because I recently installed a few for early veg phase, and I like to know as much as possible about my equipment.
 
hazy

hazy

Active member
Veteran
Is that box to the right in that pic the air handler? I'd like to see it. I know the air handler in a mini split is basically like the front half of a window unit. Coils and a fan. How's the whole air disribution thing work with yours? Do you have to run ducting from the air handler?
 
G

Guest 18340

Looking good so far dude, :yes::yes: for the thinking outside the box (inside the box in this case).
I dont think I've ever seen a hook up like that here on icmag, though I could be wrong. Alot of people could glean something from this thread.
Can you give us info 'bout the growroom its gonna cool? With a unit that size I'm assuming this is gonna be a decent size grow?:lurk:
 
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M

micro gro

hazy said:
Is that box to the right in that pic the air handler? I'd like to see it. I know the air handler in a mini split is basically like the front half of a window unit. Coils and a fan. How's the whole air disribution thing work with yours? Do you have to run ducting from the air handler?
Click to expand...
Yes, the large dark gray box is the AH. It's just a large, ductable version of a mini-split's AH. Metal box with motor, contacts, coils, and drain pan... fairly simple device.

No duct, just sitting openly in the room. Ducts & dampers will be run when room #2 goes live.

Pics of air handler.

Dark gray box, left half:



Dark gray box, right side:

 
G

Guest 18340

Holy shit! How did I miss that build thread:bashhead:
I love it man, your room fuckin rocks!
 
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caljim

caljim

I'm on the edge. Of what I'm not sure.
Veteran
Great build Micro, Thanks for sharing.

In the compressor room will you be venting the whole room or ducting off the top of the compressor through the silencer and then the 12inch fan.


If you ran duct off the of the unit and out the roof the condensor fan would likely be enough by itself to move the hot air and quieter than the vortex...:2cents:
 
M

micro gro

Thanks.

caljim, the fan in the compressor unit will not push much air through ducting.

I'm venting the whole room. I guess the key is to size & shape the room so that effective / efficient air exchange is done. I'm still not sure that the hole at the "other end" of the room (opposite intake) was the right choice. Perhaps centered right above the compressor fan would be best? I'll experiment later.

The room size is almost 8' x 8', which leaves a solid 2' of space around all sides of the unit.
 
wizberry

wizberry

Member
micro gro,

I've been checking out your gro room thread and you have quite a few lites. How did u decide on 3 1/2 tons as being the best size for your needs? On a smaller scale what would you recommend for a sealed room w/ 4K? I'd like to run lites w/ no glass if possible.

BTW, that's gotta be the biggest AC box on ICG. :laughing:
 
M

micro gro

wizberry said:
How did u decide on 3 1/2 tons as being the best size for your needs?
Click to expand...
Combination of an educated guess based on previous experience and the 4-5000 BTU-per-light rule-of-thumb. Turns out (in this particular scenario) that a 3 ton system would have done OK as well, but feel better with the 3.5.

wizberry said:
On a smaller scale what would you recommend for a sealed room w/ 4K? I'd like to run lites w/ no glass if possible.
Click to expand...
For 4000w non-air-cooled I'd say something in the neighborhood of a 1.5 ton (18000 BTU) unit will do. In the past I ran a 4000w (air-cooled, non-sealed) grow in a basement without any air conditioning. I've also done 6000w (air-cooled, sealed) grows with a boxed 14500 BTU window-mount A/C that barely cycled. I'm guessing an 8000 BTU unit would have kept up. Your mileage may vary, however, largely depending on your environment (elevation, ambient temperatures, insulation, etc).

On that 6000w sealed setup I had a 6" Vortex (440cfm) that exhausted the hot air from:

  • 14500 BTU window-mount A/C, boxed
  • 1000w HID air-cooled reflector
  • Small room containing 7 x 1000w magnetic ballasts

I have a feeling a 6" inline fan would work for up to a 2 ton unit if properly ducted / vented. (I'd feel much better with an 8", though.)

I've also since learned that a mini-split would have easily paid for itself in many more ways than one, compared to the much cheaper window-mount's or portables. If anyone wants to talk about total cost of ownership...

wizberry said:
BTW, that's gotta be the biggest AC box on ICG. :laughing:
Click to expand...
Thanks, taken as a compliment.
 
wizberry

wizberry

Member
So why are mini splits better than window-mounts/portables? Is it related to the efficiency ratings?

Also I was wondering, what's more efficient, 2 smaller AC units with a higher EER, or 1 larger unit with a slightly less EER rating? For example, would 2 9000 btu units work better or worse than 1 18000 btu unit?
 
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