Fermentation Chamber

TEC-based Temperature-Controlled Fermentation Chamber Steven Keck, 07/2013

Intro They say good, consistent homebrew needs precise fermentation temperature control. That's a nice thought, but I donn't have room for an extra fridge and I didn't want to spend multiple weekends building an insulated plywood contraption. Here's my solution that fits the bill.

Parts List 1. Cooler - You need an ice chest / camping cooler that is big enough to fit a carboy and has enough interior space for a carboy cap and airlock. Getting one that is just the right size is the trickiest part of this effort. Measure your carboy with your favorite cap and airlock installed, add a few inches on top of that to be safe and then go shopping with tape measure in-hand. I found a Coleman 60 quart(?) chest at Walmart for about $35 on sale. They seem to have the best selection (my local Target sucked). There are bigger coolers, but they get pricey. You can also find this stuff on Craigslist.

2. Temperature Controller - There are many of these on the market... I chose a single-stage Ranco controller (MoreBeer #FE610, $100). It's dead-simple and works well. Best of all, the probe will fit into a matching thermowell (see below), which is key. You can buy a two-stage controller for an extra $40 if you want to cool and heat, but do really need to cool and heat at the same time?

Probably not.

3. Air-to-Air TEC - A thermoelectric cooler (TEC) will cool one side and generate heat on another.

They're not very efficient, but they are physically quite small and simple to install (no freon, cooling coils, compressors, etc). Air-to-air means that you've got a heat sink and fan on both sides of the TEC (most TECs used for PC processors have a heatink and fan just on the hot side). I bought a unit off eBay from a seller called 'oteinternational' for $45. It draws 65W, but only transfers about 32W of heat. It runs off ~12V DC @ 6-7 amps. This seller seems to perpetually sell these things. Others may work, but I wouldn't go with any less cooling capacity.

4. Heater (optional) - If you're going to brew in a garage in the winter, then you'll probably want the ability to heat your carboy. The FermWrap Heater works like a champ (MoreBeer #FE650, $30).

5. Thermowell (optional) - This is a carboy cap with a hollow metal probe (MoreBeer #FE615, $30). The probe goes into the center of the carboy liquid and lets you put your temp probe right in the middle of the fermenting beer. You don't have to have this (e.g. you could just dangle the temperature probe in the air), but the thermowell will give you the most accurate temperature control.

NOTE: You may have to sand down the Ranco temp probe coating so it can fit all the way down in the bottom of the thermowell probe. I had to do quite a bit of sanding, but apparently this varies from unit to unit.

6. Power Supply - You'll need a 12V supply beefy enough to power the TEC. It draws a lot of current (plan for 10A). An old PC power supply works great. If you find one, you'll have to hardwire the enable pin on the motherboard connector so that the supply is always-on. Once you do this, the power supply can be turned on/off via the AC input via your temperature controller.

Google 'ATX power supply for pinout' for all the info you'll need.

Build It This is pretty straight-forward assembly. The only special tools needed are a jigsaw or Sawzall to cut a hole in the cooler. Here are the steps: 1. Take an empty carboy and attach your cap and airlock. Turn the cooler on its side so that the handles are at the top & bottom. Put the carboy in the cooler and take note of the airlock location.

2. Measure the dimensions of the TEC (cold side) and mark the outline on the outside of the cooler. You want to position it so that the heatsink/fan don't interfere with your airlock or blowoff tubing as shown below.

3. With your jigsaw/Sawzall, carefully cut a hole in the cooler. When it doubt, make it slightly smaller than you think you need and then enlarge it later as necessary. If you make the hole too big you'll have an air gap.

4. Insert the TEC from the outside (top) of your cooler. Adjust the hole so it's just big enough to fit snuggly. You may need to bust out a file to get it just right. If it's snug, you probably won't need to secure it - it'll stick in there pretty tight. My TEC had a rubberized gasket already installed which was ideal.

NOTE: I cut off the handles on both sides of the cooler since they were in the way 5. Connect the +12V and GND from your power supply to the TEC. You may want to use some longer wires to give yourself some flexibility on the power supply placement vs. the cooler when in use. Make sure the wires are beefy (12 AWG or bigger) to minimize voltage drop... you're drawing a lot of current. You can also double-up multiple smaller gauge wires in parallel to accomplish the same thing.

6. Connect the AC plug from the power supply into the switched controller socket. Adjust the controller temperature setpoint to check that the TEC turns on/off as expected. In the winter you can disconnect the TEC power supply and control the ThermWrap heater instead.

7. Drill a small hole in the top of the cooler that is just big enough for your blow-off tube. It will be much easier to put your blow-off bucket outside the chamber. I used the existing drain hole for the thermal probe.

Initially, I tried putting a small bottle in the chamber with the carboy to collect blow-off liquid. It wasn't big enough to do the job and made a mess. Adding a hole in the top for an external blow-off container worked much better. It also allows you to check on the bubble rate without opening up the chamber.

Usage Here are my observations after running several batches with this chamber: • •

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Depending on your specific cooler, you may want to put rubber feet on the bottom to keep things from rocking around.

The TEC's cooling power is quite modest and 5 gallons of liquid has a big thermal mass. In my experience, it will take 1-2 hours to drop the fermenting beer by 1°F (measured via the thermowell). Don't expect it to cool things quickly like a refrigerator.

It works fantastic for holding a carboy at ale fermentation temperatures (e.g. 60's). The controller/thermowell combo will easily hold things within a degree of your target temperature.

I've been able to hold a carboy @ 50°F for several days with the external ambient air in the mid 70s. Below that is quite difficult with the TEC I've used.

Don't be surprised to see the TEC on for very long periods of time (hours or days). The lower your temp, the more likely the TEC will be running non-stop.

The warmer the ambient external air temp, the harder the TEC is going to need to work Actively fermenting beer will generate a fair amount of heat, so you're chamber will need to work harder during active primary fermentation vs. secondary or lagering.

If you want to drop the carboy temp more quickly, adding ice bags next to the carboy will help.

Once you're in your target range (>=50°F), the chamber will likely do a good job of holding it there.

Condensation will collect on the internal (cold) heatsink and fan. I don't have a creative way to prevent this.

Happy Brewing!