I have room for 2 5-gallon fermenters (ale pails) in my fermentation chest, and would like to conduct two fermentations at once. Typically, I insulate my temp controller's probe against a fermenter, so it is regulating fermenter temp and not ambient.

If I want to regulate temp on two separate fermenters, I would think that the best way to do this with my chest freezer/temp control set up is to suspend the probe inside the fermenter so it regulates the ambient temperature and have it set 5-6 degrees below my desired fermentation temp (in this case 65 degrees, so I would have the controller set to 60 degrees).

3 Answers 3


I have had fine luck by simply wedging the probe between the two carboys. Then I tape some insulation (rags) against it across the two carboys and over the probe body.

Its not perfect but it does seem to work pretty well. Unfortunately there is no really good way to do it once you go to two in there at once.


I would tape the probe to whichever fermentation started most recently. Temperature control is most important in the first couple days of fermentation, when the yeast are growing. After that, it's not super important, as long as you're in the right ballpark.

You could also get a couple of thermometers and try to figure out whether one side of your chamber is colder than the other, which might help keep two different batches at slightly different temps, if desired.


Controlling 2 fermentations at once will require at least 2 controllers, and 2 temp inputs (as in heating and refrig). If you can't guarantee which fermentation will be the most active, you will need 3 controllers.

Keeping things simple and assuming you only need to cool things down, a common solution for staggered ferms is to use a controller and fermwrap (DIY versions are cheap) for the less active ferm, and another controller, with the sensor on the active vessel, to control the refrigeration.

If you need heating and/or cooling, you would need at least a 2 stage controller (STC-1000, or Love), and a heat source, for the chamber.

  • Basically your description requires two fermentation chambers/units. You can't control both in one freezer/fridge even with multiple controller.
    – brewchez
    Sep 18, 2012 at 22:46
  • I realize that ideally, I would have a separate chamber, heating/cooling element, and controller for each ferment, but my question was, with the setup I have, what is the best way to get a controlled fermentation. I'm thinking two pieces of styrofoam to make a channel between the two, taped to each fermenter.
    – Pietro
    Sep 24, 2012 at 18:55

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