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How To Use A Digital Thermostat Controller To Keep Your Beer Cool

When we put up a video about how to change the jumpers in a Johnson Controls thermostat controller, there was a comment on YouTube that asked if we could show how this piece of equipment works for keeping your fermentating beer cool in the fridge.

Thinking that was a valid question for someone who may not understand the concept of a thermostat override and how it works, I put together this video to show the different features of the controller.

The thermostat controller itself has a few main features. It has a few cords coming out of it. One is an electrical plug with three prongs that you plug into the wall a socket of your choice.

The other large cord has a female plug on it and this is where you plug your fridge or chest freezer plugs into so that the unit can controls when to turn on or shut off the motor on your fridge/chest freezer.

The last thin cord coming out of the controller is a temperature probe and it looks similar to one you would find on a digital thermometer. At least it does to me – we had a big weather tracking device when I was growing up that reporting on the temperature, atmospheric pressure, and humidity but it had a probe that looked just like the one on the thermostat control to measure the outside temperature.

The settings on the unit takes some reading to understand what they are and how you can modify them. There are a few settings that I do not really use but the two that are important are the set point and the differential.

Set Point – This setting is for the temperature you would like the unit to control your fridge/chest freezer to maintain.

Differential – This setting controls an acceptable range plus or minus around the temperature you selected for your set point.

For instance, if you inputted a set point to 50° F and a differential of 1, the control would turn on your fridge if the internal temperature rose to 51° F or above and would shut off if 49° F was detected.

I like keeping my differential tight since a degree is a big deal to a small yeast cell.

If you are thinking about buying a thermostat control, go for it. They are easy to use and will come in handy from brewing lagers.


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  1. You guys are SO cool for posting things like this, big thanks to all involved! #MyVoteForMostUsefulBeerBlog


  2. Nitch – you are too kind. Thanks!

  3. Wil

    Thanks for posting this. Do you just drill a hole somewhere in the freezer/fridge in order to insert the probe? Where is the ideal location for that hole? My guess is somewhere at the bottom where the temperature would be the lowest.

  4. Sorry about that.

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