Fermentation Cabinet

How can I make my homebrew better? That was and still is the #1 question for most homebrewers. Temperature control during the fermentation is very important but it was difficult for me to control. Cooling was my problem, so I came up with this fermentation conditioner idea. I decided to take an old dehumidifier and donate it to a better cause. The only tricky challenge was reworking the Freon coil without damaging it. After that I could insert the coil into an insulated box with a gasketed door. I also needed a fan to blow air over the coil to keep the coil from icing and improve the air circulation in the chamber. The controls consisted of an external temperature controller with a capillary tube inside the box. A good dial thermometer and a vent to let the “yeast exhaust” escape completed the project. Also, safety is #1 when I build anything, especially when it comes to working with electricity.

With this build, I can hold my temperatures right on the money. The best part is that I built it all for free! I used all recycled materials from home and construction jobsites (one of the perks from being a construction electrician.) A year later I remodeled my kitchen, which left me with a nice countertop for the top of the chamber. Even if you have to buy some material, you can build this project for a reasonable cost. I recommend a helper for this project.

Safety note: Make sure there are no live un-insulated electrical components exposed while you build this chamber. Also, protect yourself by plugging the dehumidifier into a ground fault interrupter receptacle (GFI). Stay clear of all electrical connections and the compressor fan when you have the cover removed.

Tools and Materials
Tubing bender
Circular saw with wood blade
Sawzall w/wood and metal blades
Drill w/bits and driver tips
Razor knife
Wire strippers/crimpers
Plywood/OSB (Oriented strand board)
1-inch Dowfoam insulation board
1 pair of hinges
1 hasp or latch
1⁄4-in. x 3⁄4-in. self-stick gasket material
Framing lumber 2 x 4’s etc. (not treated)
3 Conductor 14-gauge SJO cord
Wire nuts and ring terminals
Rubber cord connectors
Unistrut and angle clips
Misc. nuts and bolts, screws
Duct seal/caulking
Computer fan with guard
Temperature controller w/remote sensor
Dial thermometer and bracket
Misc. closed cell insulation
Drip pan
Construction adhesive/glue
Ground fault receptacle (GFI)
Kitchen countertop (optional)
Paint or stain (optional)
Misc. 3⁄4-in. PVC fittings (optional)

1. Harvest the cold coil
Start the dehumidifier and make sure the Freon coil gets cold and the compressor cooling fan works. Unplug the power and remove the cover. See if you think it is possible to rework the coil so as to bend the tubing out away from the main appliance body. I reworked mine out 180 degrees, but 90 degrees might work too. Do this work outdoors and go slow. If you break the coil’s tubing, Freon will be released, which is toxic to inhale and can displace oxygen in enclosed areas. You will also have to start over with another dehumidifier. Do not kink the tubing. Use a tubing bender to help you. Remove the coil support clips and save them for later. Now rework your coil. Remember to keep a temporary support on the coil all times until you add the permanent support back in step 3. Test the operation of the modified dehumidifier. Make sure the coil still gets good and cold.

2. Build your insulated box
My box started out with a piece of galvanized ductwork 24 inches (61 cm) wide x 26 inches (66 cm) high x 24 inches (61 cm) deep (open on both ends). Next, I insulated it with a layer of 1-inch (2.5 cm) thick Dowfoam board insulation, followed by an exterior layer of plywood and OSB board. You could make your box any size, just make sure your fermenter and airlock will fit inside comfortably. My box can hold two fermenters.

Next add an insulated door with a pair of hinges and a hasp or latch. I also used 1⁄4-in. x 3⁄4-in. wide self-stick gasket material to give the door a good seal.

Finally, cut a window in the lower back corner for your Freon coil. Take a little time to figure out exactly where you think it would work best for you. Make it big enough so as not to damage your coil while inserting it later. You will end up insulating this opening anyway.

3. Assemble and support
I mounted my insulated box and dehumidifier on a common piece of 1⁄4-in. thick plywood. Mine was 26 inches deep x 42 inches wide. First I mounted the box, then carefully inserted the coil into the previously created window in the box. I then fastened the dehumidifier to the base plywood.

Next I made a stand. Mine is 16 inches (41 cm) high. Note that this stand MUST be strong and sturdy as it will have a lot of weight on it when you have full carboys in it. Make sure you fasten this base plywood to the stand securely. Wood screws worked well for me.
Now it is time to support the Freon coil. I used a short 11-inch (28-cm) piece of Unistrut with a 2 x 2 Unistrut angle bracket fastened to the bottom of the box. I then used the coil clips I saved from the original support in the dehumidifier. Be careful not to pinch or clamp the coil too tight so as to cause a leak.

Finish this step by insulating the window at the coil. Soft closed cell packing foam worked well for me.

4. Electrical controls and fan
SAFETY NOTE: Electrical work should only be done by a qualified person. All electrical components and all metal parts must be properly grounded. Also, proper use of ground fault interrupter receptacles (GFIs) should always be used to prevent electrical shock.

The temperature controller is mounted in a convenient spot outside the box, with clear vision of the set point temperature dial. I drilled a hole into the box near the ceiling and mounted the sensor on the ceiling with a little plastic one-hole strap. Be careful not to kink the capillary tube. Seal the hole with a little duct seal. I used 3-conductor 14-gauge SJO cord from the controller to the compressor junction box. It is wired to have the contacts close on temperature rise. Follow this by mounting a computer fan in front of the Freon coil. I used a little piece of predrilled angle iron and a few nuts and bolts. This fan is also wired with 3-conductor 14-gauge SJO cord. It is wired to run full time, even when the compressor is not running. Make sure your fan has a guard or screen.

5. Install vent, thermometer and cover
To vent the “yeast exhaust,” I drilled a 11⁄8 inch hole with a holesaw near the top of the box (on the sidewall). I dressed it up with 3⁄4-in. PVC fittings. Location is not critical, so long as it is at the top. I also added a drip pan under the Freon coil to catch any condensate. This pan could be anything lying around the house.

Next I added a dial thermometer. This item, although convenient, is not necessary. A crystal thermometer on your fermenter will work just fine.

Finally, reinstall the original cover for your dehumidifier. I had to modify mine by cutting a section of the side panel off with a Sawzall. Reinstalling this cover will keep your hands away from the compressor fan and the electrical parts. Also, make sure you seal all openings (except the vent) with duct seal, insulation or caulking. This will add to the efficiency of your unit.

6. Finishing touches
As mentioned earlier, I added a formica kitchen countertop. It was 25 inches (64 cm) deep x 37 inches (94 cm) long with a backsplash. That worked really well for scales and test equipment. My countertop ended up at 52 inches (132 cm) above the floor. Take time to smooth all edges with a wood or metal file. Paint and stain are optional. Decorations and data sheets are easy and practical.

Finally, test it out. Make any necessary adjustments — there are always a few. If you are like me, you will start making better beers with your next batch! This will also allow you to brew your favorite flagship brews over and over with wonderful results and consistency.

Issue: March-April 2013