This article is taken form a thread on www.homebrewtalk.com by John Beere http://www.homebrewtalk.com/showthread.php?t=11440
 Project Goal
I am also considering creating a fermentation cooler that is external to the cooler but is fed cold air on demand from a hole in the side of the cooler. It will have its own temperature controller which will power two fans (one push, one pull) and baffles to exchange cold air as necessary to maintain whatever my target fermentation temperature is.
I will update this post as I make progress but it will be a little slow going as I am pretty busy with work right now. I also plan on detailing the entire process on my website www.johnbeere.com when I get it set up as there is very limited information on this type project on the net - but from the info I've found (mainly on this forum), I am confident in the results.
 The Walk-in Cooler
Update on the AC: I test wired a new Ranco controller into the AC this evening. This was the step I was most worried about and, now that its done, I can't believe how easy it was... I was able to completely bypass the built-in controls on the first try. I will officially re-wire it tomorrow. The diagram at http://franklinbrew.org/members/sj/walkin.html is correct, even for my brand new AC.
Lowes didn't have but about 10 sheets of that Dow board so I bought a pallet of another called R-Max. Its 3/4" thick with an R value of R5. I plan on lining the walls 3 sheets thick.
Made some progress today... I totally re-wired the AC to completely remove the built-in controls as well as got it working off of only one plug. The diagram I linked to last night shows the need for a second plug and is what I tried last night. The only reason the ground is clipped is I cut it last night during my test. After that, I framed out and installed the AC in the window, plugged up all the holes with great stuff, and lined it with Reflectix like the rest of the walls. I then wired up a new breaker in my breaker box, ran it under the house (absolutely horrible place), out the back of the house through 1" conduit, into the garage, and wired up four new plugs in the garage (only one in the cooler itself - been needing better power out there for some time). And finally, I put a couple of pieces of the foam board on the walls just to see how it was going to work. Turns out there is just no way I can compress the insulation behind the foam board all the way down to the 2x2 extensions I added. So I pushed the board as square as I could and nailed into place leaving about another 1.5" gap. The insulation is pretty much taking up all that room but the back of the foam board is lined in foil and it says dead spaces is OK.
Made some progress today but also took a step back. I hadn't put the front of the AC back on and something fell into the fan while testing - shattering it into a million pieces. Damn it. I have no idea what it was as there is no way I was putting stuff in there. I'll find out when I take it all back apart... I framed out the final wall and installed the door. The perspective in this first photo is a little hard to follow. It was taken from outside the utility room looking through the door. The wall for the cooler is on about a 30 degree angle.
And finally, the ceiling after insulation. Once the walls are fully lined with foam board, I will line the ceiling from the inside with it as well.
I haven't had much time to work on the cooler this week but have made some progress. I was hoping by this point to be able to cool the area while I worked but no such luck since I shattered the AC's fan blade. Hopefully the replacement will be here this weekend. Anyhow, I have all the framing done as well as the wall insulation wrapped up. Now its down to installing all the foam board. Here is a photo of the cooler looking into the utility room. We'll put some trim around it to finish it off once everything else is complete. I'm hoping to make serious progress by this weekend and be ready to finish it up as soon as the replacement fan arrives.
Got all the walls finished today. Now it is down to the ceiling, floor, and the door... should go pretty quick over the next few evenings. Still debating what wall board to use to finish off the inside but will have that settled in the next few days. What I really want is $30 a sheet... and I need eight sheets - whew. Regardless of the wall board, I am in hopes to start testing later this week.
Got the ceiling finished. Its lined with three layers of foam insulation. On top of the ceiling was exactly enough room to pack the R30 insulation on its side - six pieces across. No photos as its really more the same at this point. Plan on doing the floor tomorrow night... I tested it down to 60 degrees for about 30 minutes. I didn't pay that close of attention but the temperature dropped from 84 to 60 within 10~15 minutes and the AC never came back on until after I opened the door. Can't wait to test it once the floor and door are fully insulated.
Got the floor finished up tonight... ended up laying six layers of the foam insulation. Pretty much came out flush with the bottom of the doorway. Scroll back to post #75 for the before shot of the floor and doorjam to get a feel for how thick it turned out to be. Here is a photo of the floor now:
After a few days away from the project, I'm back on it. I put 1/2" MDF on the floor and started placing the wall board. The plastic wall board I chose is EXPENSIVE at $30 a sheet (I needed 7 sheets) but it is going to look really good once finished. Here is a photo of the floor. A layer of the plastic wall board will go on top of this to finish it off.
For the corners I went with the only thing I could find wide enough to cover the gaps. It is really made for outside corners but worked pretty well on inside corners. I haven't caulked around it yet so I am holding final judgement until I get that done. Either way, it is what it is... Here is a picture of the back corner as it stand now. Should get a chance to caulk it all in the next few days. Notice the one piece is discolored... didn't notice that until it was glued on tight. O well...
Got the door insulated today... still needs to be sanded a bit and then caulked. Its six layers of 3/4" foam board thick. The side of the door away from the hinges is on a 15 degree angle for clearance. I tried several different angles just to make sure it couldn't be less - 15 degrees is the answer.
I also bought a "Kill A Watt" from Amazon ( http://www.amazon.com/gp/product/B00...148944?ie=UTF8 ) which will measure how much electricity the AC is using over the course a week / month / etc. Very interested to see the results... Did some more testing today... slowly dropped the temperature down to 35 degrees and held it with no problems. I had a thermometer in the AC's vent to measure air temperature - it was holding steady at 19 degrees but rose to 21 degrees before I could take a photo. The other thing I did that is still experimental is I took a white labs yeast jar, filled it with the goop from an ice pack, drilled a hole in the top, placed the temperature controller's probe through the hole and into the goop. I then placed the container in the very top of the back of the cooler. I know I don't want to measure the air temperature, so I'm thinking this will work well. Time will tell...Dismiss the 106 on the LCD... that was some alarm setting.
The cooler is rocking along at 33 degrees without any problems so far. I did a longer test with the "kill-a-watt" after filling the cooler with as much stuff as I could find and it averages out to .17 KWPH - which translates into about $12.50 in electricity per month...
The cooler is holding steady at 36 degrees at an average .14 KWPH (roughly $.014 an hour based on a cost of $.10 KWPH).
I noticed the first real problem about two weeks ago. The weather stripping around the door had several small gaps where the 2x4s weren't exactly straight and the seal wasn't air tight. I knew the door was leaking as there was condensation build-up all around it as well as considerable ice build up on the AC coils - although it technically wasn't "froze up" and was still running just fine.
I decided to remove all the existing weather stripping and start over with a 2" wide insulated foam tape. Its 1/8" thick and needed two layers installed where the weather stripping originally was. I then ran a ring of duct tape (looks better than it sounds) on the inside of the door in the exact pattern of the insulated tape. Had to experiment some with this as there were places that needed several layers of duct tape to properly seal the imperfections of the 2x4s. It only took about an hour to get it as air tight as I could make it and still close and lock the door. After doing this, there have been no signs of condensation build up around the door but there was still ice build up on the AC. The ice build up is somewhat coming from moisture in the cooler (cardboard, condensation, etc) but mainly is coming in through the AC itself and there isn't much that can be done about it at this point as that is the nature of a window AC. To combat the ice build up and hopefully improve efficiency, I've placed a small desk fan inside the cooler that runs 24/7 to stir the air. I'm still experimenting with efficiency but it has kept all signs of ice from forming on the AC coils. I'm trying to determine now if the fan needs to be pointed directly on the AC coils or just stir the air to combat the moisture - will report back on this once I better understand. Overall, good and bad, I really couldn't be happier with how it turned out...
I modified the AC to include seven small (40mm) 12v fans in the front grill which constantly draw "warmer than freezing" air over the AC coils. Right now I have the fans running 24x7 but will probably start experimenting with different cycles soon.
The fans have completely solved all moisture problems by keeping ice from building up on the coils. Notice in the second picture the ice build up on the AC coils. This ice is now completely gone.
Here is my best guess at the materials used. Remember that I built it with quaility in mind rather than a fixed budget... although I had guessed it would cost around $1,000 total.
- $250.00 (1) 12k BTU AC
- $50.00 (1) Ranco Controller
- $300.00 (30) R5 insulated board
- $160.00 (4) R30 Insulation
- $70.00 (14) 2x4x10
- $20.00 (1) 5/8" MDF
- $30.00 (1) 24" Door
- $240.00 (8) 4'x8' wall board
- $180.00 (60) Tube adhesive