I am a long time homebrewer and have always strived to produce the very best product that I can, given the variables inherent in any hobby that involves nature and science.
One of the most difficult to control and most important to the finished product is temperature. Keeping close control of the fermentation process yields big rewards in consistency, clarity, finish and flavor profile.
I built a version of the venerable Son of Fermentation Chiller and used it successfully for many years but was never happy with it. It was a royal pain to change ice, sometimes daily, in the hot Sacramento summers and you could never leave a batch in it and go away for even a 4 day weekend. The variability and temperature swings were troublesome from a brewing standpoint and I grew weary of bending down to the ground attempting to gently lower 6 gallons of beer in a glass carboy into and out of it.
I was convinced I could do better.
I spent hours hashing over ideas with various people including The Engineer (a licensed and skilled Mechanical Engineer and brewer) and the Asperger Kid, a brewing buddy that has read and experimented with more brew-tech and methodology than even he would care to admit.
In the end, I came up with several requirements that the new fermentation chiller must have.
I started by obtaining for free, a small “dorm fridge” from someone who was not using it. They were glad to have it gone and I was happy to have obtained one with an actual freezer compartment rather than a bar fridge, counting on its low temperature surface and higher cooling ability to assist my efforts in redesigning it for my needs. A small dorm fridge would not ordinarily be considered for a project such as this however after much consideration and consultation I decided on the following strategy: increase efficiency, improve insulation and implement potentially huge cold sinks. I think I can pull it off.
The difference in the project insulation on the left and the insulation in the standard fridge is striking.
I spent a couple of hours carefully dismantling it to its component parts being careful to not bend or kink any of the hoses and lines for the coils and once it was disassembled, I could see what I had to work with. The fridge was one of the larger of the dorm fridge styles and the compressor and motor seemed in good shape. Since I had confirmed that it worked perfectly, I moved forward with confidence.
I took my tentative plans to the local home supply store and after a few minutes of careful selection for weight and straightness, I returned home with 8 2X4’s for the frame. I knew I would need several more but I had a few old studs left over from a recent remodel that I would use to make up the difference.
I laid out my lines and assembled the frame, using either half-lap or rabbeted joints for strength and screws for durability. I covered the “floor” in the top and bottom sections with plywood, again left over from my remodel.
So far, I had 22 bucks into the project.
A Note on Scrounging
I am in inveterate scrounger. I look for situations and trade or scrounge for what I need. The insulation used in this project is a prime example. I was driving by a major construction project and saw the crew putting insulation on the roof. I drove into the loading area, looked for the construction manager and asked if I could grab some of his scraps. He was happy to keep the excess out of his trash and I got a truckload of 4X4 foot scraps that I have used on numerous projects. The moral of the story is; you get your bargains where you find them.
After considerable thought, I rebuilt the same general form that the previous fridge had, including the compressor kickout. I thought about several configurations but in the end I opted for the factory look. The extra space it gave was a bonus.
When I say that laying these pieces out was an exercise in geometry would be an understatement. The third hand I got from my neighbor Mark was a big help in laying out the pieces so that everything came out square. Well, for the most part anyway.
I spent another 18 dollars on 1X3 KD boards and the Asberger Kid gave me a hand assembling some doors. With a careful selection of boards and a few minutes with some basic joinery we had manufactured the doors.
I still had the dilemma of the uneven face frame surface to contend with however. I gave serious thought to rough sanding it and laminating some mahogany veneer I had laying around but in the end, my friend Mark suggested just belt sanding the whole thing and square it up that way.
We spent about an hour with his 18” belt sander and a straight edge and it came out nearly perfect.
I had most of the engineering details worked out so I started the rest of the fabrication. I had long ago decided to use 2 inch PVC pipe and 12 volt computer fans (also free) for the air transfer. I placed the supply and return at opposite ends of the chamber and plumbed them through the upper and lower sections.
I roughed the openings in, placed my fasteners and then disassembled it all to get ready for paint. I pulled in wire that I knew I would need to run the various fans, thermostats and other hardware and installed a separate 120 volt outlet for my stir plate. I intend to make starters at the same temperatures that the beer will ferment at and there is no place better than the same cabinet!
I was torn on paint choices but in the end, my cheap side won out and I ended up using some pure white gloss that I had laying around the house. It may not have been ideal, but the price was right!
And what a difference a coat of paint makes.
It was finally starting to look like a fridge!
After considerable thought I made the door insulation recess into the door frame and the doors face frame cover it. We hung the doors first, and then custom cut each piece of insulation to fit. Once the door frame and insulation were both ready, we secured the insulation to the door with a lot of caulk and a few screws to keep it all together while it dried.
At this point I finally ran out of caulk that I had lying around, so I had to spend money again. Chalk up another $3.20 from the orange store. Total cost so far; 43 bucks.
I spent the next few days tending to the minor but important details like fan height, sealing up some iffy caulking, completing the 12 volt wiring, installing fans and general fabrication. I am somewhat detail oriented but firmly believe in the K.I.S.S. principal. I try to build things to be as simple as needed but with attention to detail as this project reflects.
In an effort to increase efficiency I mounted a hardcore PC CPU fan and heatsink to the freezer coil. The Engineer has assured me that it will have a big payback in efficiency IF I can keep ice off it. We shall see.
The cool factor alone is worth it to me.
The Kid and I knocked out the final painting over a few beers after work and it was basically ready to go. I hacked a thermostat and moved the Thermister (the part that actually senses the temperature) to the end of a 4 foot piece of wire that can be taped to your fermentation vessel for more precise temperature measurement.
I knocked out a few more minor details, double checked my systems and fired it up to test. In testing, it took the lower chamber from 62 to 34 degrees in 3 hours. So far my plan is looking good but I will need some much warmer weather to do any actual testing.
I bought some foam insulation from the orange store and I put The Kid in charge of splitting the round foam into two pieces.
I ran a generous bead of caulk around the edge, applied the foam gaskets we manufactured and we were good to go. The door seals are exceptional and should last for years.
The fact that the door gaskets cost only 4 bucks was a bonus.
I brewed 15 gallons of beer in celebration, put it in the fermenter (no bending over, yeah !), put a few empty kegs in the bottom and called it good. It is far too cold in my shop to need the refrigerator capability for a while, in fact I had to put a keg of hot water in the bottom chamber to keep the upper chamber at 63. When spring and summer arrive I will be able to do much more thorough testing.
Out of Pocket cash - $47.00
Labor hours - Approx. 60 between The Kid, Mark and myself.
Capacity – up to 6 carboys in fermenter, up to 9 kegs in fridge section.
I postponed publishing the numbers until I had data as I knew it would be the first question anyone asked.
I decided to torture test the system by dropping the temperature as low as I could make it for the entire system empty, then again with beer in the upper half then once again with pre-cooled kegs of sanitizer in the lower half.
The results are as follows:
Test 1 – Entire system empty, Lowest air temperature achieved
Starting temp of 63, down to 42 in 36 hours
Test 2 – Lower chamber empty, Carboys in upper cooling from 63 to 52.
Cooled 13 gallons of 63 degree wort to 52 in 9 hours
Test 3 – Lower chamber with 6 kegs of sanitizer or beer at 40 degrees, upper chambers with carboys cooling from 62 to 52.
This is the test that most closely duplicates real world performance, it cooled the 62 degree wort down to 52 degrees in 6 hours.
To say I am impressed is an understatement. To take my 62 degree wort down to 52 in 6 hours in test 3 was beyond my wildest dreams. I am thrilled with my results so far and look forward to further experiments as time goes on.
Out of my original list of “must have" features I have accomplished most of them.
I strongly urge any serious brewer using ice based cooling systems to look into building one of their own. The freedom to be relieved of the tedious task of changing ice and the issues associated with it is a godsend. The added space for storage/lagering/carbonating is a bonus.
That being said, this was a serious bit of fabrication. I don’t think it is for a casual weekend warrior. It involved a lot of thought and imagination to come up with some of the ideas and a cheap and/or easy way to get around problems.