I live and brew in Brooklyn, NY - it goes without saying space for anything is at a premium in NYC. The only place I can keep my carboys is in my windowless office in the middle of the apartment. The only problem? It's always 80ºF in here regardless of season or the temperature of the other rooms in the house. I needed a solution that: 1 doesn't take up a lot of space; 2 doesn't use a lot of electricity; 3 doesn't cost an arm and a leg; 4 requires very little work to maintain a consistent temperature; 5 lets me easily check the progress of fermentation. This ruled out a modified mini-fridge, a brew box with ice and fans (my last solution, too big), a swamp bucket (my first solution, too much work and it started to smell), a dedicated AC unit in the room, etc. I think I came up with an ideal solution that solves most of my problems. Here's what I did:
I made a circulating cold water carboy wrap out of a copper sheet, some copper coil, a small fountain pump, a small cooler, a couple of freezer gel packs, a Johnson Controls regulator, and a couple of other miscellaneous items. The wrap comes off by loosening three pipe clamps I riveted across the seam of the copper sheet.
(This was my first time soldering anything larger than a breadboard - I know it ain't pretty.)
The small cooler holds the fountain pump, two or more medium frozen gel packs, and about a half gallon of water. I added some alcohol to the water to keep it from getting rancid - vodka smells better than bleach and it does the trick.
The pump is plugged into a Johnson Controls A419, the probe is inserted into a thermowell in the stopper. The controller was by far the most expensive component of the system, but necessary to regulate the temperature. I use a cheap indoor/outdoor thermometer with a wired probe to check the difference between the outside temperature of the carboy vs the inside temp of the probe, as well as check the ambient temperature of the room (81.3ºF in the photo).
For insulation I wrap the whole thing in vinyl cloth (from another project) and two Mexican wool blankets. The pump only runs a few times a day and I change the gel packs once in the morning and once at night. I'm brewing a Belgian Blond right now and holding it at 69ºF but with more gel packs I could get it down another 10 degrees at least. Not exactly lager temps, but that might come in version 2.0.
Here's my parts list:
1 20x40" copper sheet - 20oz ($40)
1 20' 3/8" copper coil ($21)
1 Coleman 9 Qt Excursion cooler ($15)
1 Johnson Controls A419 ($76)
1 Stopper thermowell ($25)
1 pound solid core solder and flux ($18)
4' automotive silicone hose ($10)
6 pipe clamps ($5)
4 gel packs ($8)
66 GPH Mini submersible pump ($10)
While I'm pretty happy with the results, I have a few complaints. It's not quite as compact as I had hoped. The wrap can be a little challenging to remove easily. This only works with my Mexican 6 gallon carboy with smooth sides, the Italian carboy I have for secondary has ridges on the outside and won't hold the same temps. This solution was more expensive than buying a used mini-fridge, but I'm hoping I will save the difference in electricity. It's also much quieter than a fridge compressor would be.