An EE builds a fermentation cooler...

First off I want to say that this forum, along with the helpful staff at Southern Brewing in Tampa, are the two primary reasons I am giving homebrewing a second chance. My first attempts some 10 years ago started off well enough, but each subsequent batch tasted/smelled worse and I suspect it was a combination of poor temperature control of the fermenter along with so-so sanitation practices. I have Star-San to help with the latter issue, but to deal with the former I employed a little bit of inside the box thinking, so to speak, and bought a retail display cooler off of craigslist for $100 (True model GDM-7).

As a result of doing lots of searching here, I intend to use a STC-1000 to cycle the compressor of the cooler on and off as needed to maintain my 6 gal. Better Bottle primary at whatever temperature the yeast packet says is ideal.

The Better Bottle is approximately 11" in diameter and 25" high with the 3-piece airlock installed while the interior dimensions of the GDM-7 cooler are 24" wide, 30" tall and the minimum depth just barely squeaks by at 12", so it looks like a winner.

Anyway, the first picture is the front of the cooler with the access panel for the thermostat and fluorescent light fixture removed and the second picture is of the wiring in the rear (B = Ballast [disconnected]; C = Compressor; H = Hot; N = Neutral):

I purchased a "candelabra" base socket and cord from Home Depot to use a 7W incandescent light bulb for both lighting and heating purposes. I purchased two switches from Radio Shack rather than raid my junk box so that other enterprising persons here could duplicate my work with "off-the-shelf" parts if so desired. A heavy duty rocker switch (275-0693) supplies power to the STC-1000 and circulation fan. A lighter duty push-on/push-off pushbutton switch (275-011A) is wired in parallel with the heating contact on the STC-1000 - to bypass it, in other words - which supplies power to the 7W light bulb.

The pictures show the rats nest of wiring for the STC-1000 and switches as well as the finished hack actively working to cool down 2gals. of water in a bucket for test purposes. I set the temperature to 17C - as that is the midpoint of the range that the yeast I am using now likes to work at - and the differential to 1C. I personally would not attempt to maintain a tighter temperature range than 0.5C (~1F) especially if the default compressor minimum off-time is 3 minutes (I shortened that to 2 minutes, but that was strictly a WAG on my part).

MagicSmoker said:

First off I want to say that this forum, along with the helpful staff at Southern Brewing in Tampa, are the two primary reasons I am giving homebrewing a second chance.

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A ha! I knew someone else besides me in Tampa has been scouring the craigslist ads for a fermentation chiller. I had to seriously restrain myself from buying that 60" Deerfield commercial cooler that would hold close to 50 gallons (in 6 gallon better bottles).

If you're an EE you should have no problem getting your new cooler to take your brews to the next level. Make sure you take lots of pictures! Double recommending Southern Brewing as well. Their grain selection can not be beat.

Also an EE. I built a ferm chamber from a TRUE GDM-10. I used a STC1000 initally with a heat strip mounted behind the evap fan. Added a heat / always on receptacle in place of the factory thermostat. I was able to use existing wiring between the lower and upper areas. However, I converted to a single stage/fahrenheit version of the controller during the summer and have found that I never really need the heat strip. The 9watt circulation fan provides enough heat to maintain temperature as well as raise the temperature for diacetyl rests, even with my garage in the 30's.

Build information here.

Well, I was hoping to add some more pics today because my STC-1000 was supposed to be delivered, but tracking says it is still in New Jersey. I'm thinking it ain't gonna make it here on time...

Anyway, the plan is to cut out a rectangular opening for the STC-1000 in the sheet metal cover that the fluorescent tube sockets are mounted on and have it take the place of the old school thermostat that cycled the compressor (the fan runs all the time). To spice things up I'm going to put a white LED on either side of the fan to illuminate the fermenter without hammering it with fluorescent light (which I am given to understand is bad). I'll probably tap power for the LEDs from the wiring going to the cooling fan. The LEDs need 3-4VDC each at 10-20mA which can be economically supplied by a half wave rectifier (e.g. - 1N400x diode) and a 2W 8.2k resistor (not a Radio Shack item; a 10k 1-2W resistor might be, though).

The sooner this hack is done the better: dumping ice into the bucket of water that my primary fermenter is sitting in to keep its temperature under control sucks...

MagicSmoker said:

......To spice things up I'm going to put a white LED on either side of the fan to illuminate the fermenter without hammering it with fluorescent light (which I am given to understand is bad).....

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I would recommend a switch for those LEDs and not leaving them on for extended periods.

White LEDs have a spectrum with a large spike in the blue wavelengths, which are reported to be the wavelengths, along with upper UV, that hops are most susceptible to for skunking.

raouliii said:

I would recommend a switch for those LEDs and not leaving them on for extended periods.

White LEDs have a spectrum with a large spike in the blue wavelengths, which are reported to be the wavelengths, along with upper UV, that hops are most susceptible to for skunking.

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Yikes! Okay, change of plan, then. How about a small incandescent night light bulb, then? Does double duty as a heating element, too. Not that I'll need any heating - even for the diacetyl rest - here in Florida...

Is there a reason people tend to use mini fridges for ferm chambers over full sized ones? easier to break down? cheaper? size?

All of the above in my case... I had just enough space next to the dryer in my laundry room for the size cooler I bought. Also, anything bigger wouldn't have fit into my car (a Mini Cooper!?!)

My fermentation cooler hack is done and is working right now to bring 2 gallons of water down to 17C from 25C. So far so good, but I'll withhold judgment until I see the temp stabilize and hold there, hopefully by tomorrow morning.