Fermentation Temperature Control, Part III: Refrigeration

As mentioned last time, one can control fermentation temperature by using an insulated box with two chambers, one to hold ice, the other to hold the fermenter, and having a fan hooked up to a thermostat to blow air from one to the other.

Quickly, though, the limitations of this system can be reached. First, it is hard to get to lagering temps. Oh, you might be able to reach lager fermentation temperatures, say 50°F, by changing the ice more often, but you can never get to actual lagering temps, say 32°F. Another limitation is that you only control the temperature of the air inside the insulated box; you do not control the temperature of the beer inside the fermenter. All the above can be done with refrigeration, though.

This is what you will need: First, one has to acquire the refrigerator or freezer. If it is a refrigerator, it should be able to be set down the 32F, for lagering. Next, a digital temperature controller needs to be purchased. Finally, a thermowell will finish off the equipment needed.

The whole thing will be put together like this: The refrigerator will plug into the temperature controller, while the temperature probe from the temperature controller will fit into the thermowell. The thermowell will fit into a bung and be set into the fermenter. As the beer warms up, the probe will tell the temperature controller to trip, turning on the refrigerator or freezer -- visa versa as it cools down.

With this setup, one has complete control over fermentation temperature. It works with ales; it works with lagers. In fact, dropping the temperature by two degrees a day to reach lager temperatures is as simple as pushing the down button on the temperature controller.

I have a setup like this that works with my conical fermenter, which I diagrammed for a previous post. A conical is not requirement, however. In fact, it will work just as well with a carboy.

Here are pictures my setup in action:

As mentioned above, this is a diagram of my setup, showing the conical, temperature controller, and thermowell.

This is a picture of the thermowell being placed in the fermenter.

Here is a close up of the airlock and temperature probe. The probe fits into the thermowell and the airlock beside it.

This is a picture of the fermenter in the refrigerator. The fermenter barely fits. In fact, I have to pull the back leg off and lean it against the back, blocking the two front legs with a piece of wood screwed down to the refrigerator.