BrewProf: How to build your own dual stage temperature controller

CINCINNATI -- This weekend it is time for you to take control of your fermentation temperature with a DIY dual stage temperature controller.

The inexpensive, tried and true, STC-1000 temperature controller  is the key to managing your fermentation within half a degree of accuracy.  Regulation of your fermentation temperature can have a significant impact on the homebrew you produce.

One of the things I love most about home brewing is the extremely intelligent and talented people that have figured out very simple ways to manage seemingly complex processes.

For under $50 in supplies you can turn an old fridge, mini-fridge, or chest freezer into an extremely accurate fermentation chamber. I’ve had mine rigged up for more than six months and it has worked perfectly.

The Parts

A quick shopping trip on Amazon or eBay, plus your garage or local hardware store, can yield all the items you need.

  • STC-1000 Temperature Controller with Probe  (about $20; this only reads Celsius but I have a great Fahrenheit conversion chart below)
  • Electrical Outlet (about $1, any residential grade receptacle from Walmart or Home Depot will do)
  • Power Cable  (an old computer plug or grounded extension cord will work too)
  • Junction/Project Box (something from a home improvement store or electronics store will do, make sure you have at least 3 inches depth to clear the wires coming out of the back of the controller)
  • Extra Wires (cannibalize an old power or electrical cable, or buy something like this)
  • Wire Nuts  (just some small and medium size ones, you can get them almost anywhere)

The Tools

A few common tools are all you need to get this done.  Some will make the project go faster.

  • Screwdriver (a standard size Phillips and perhaps a #0 for screwing in the wires to the controller)
  • Needle Nose Pliers  (any old pair will do)
  • Wire Stripper  (you could always carefully use a pocket knife too)
  • Coping Saw (you could also probably use a small hack saw or reciprocating saw)
  • File (not necessary but you can smooth out rough cuts for a nicer finish)
  • Drill and small drill bits (to allow power cord and probe to exit the box)


There are two excellent videos put together by some kind souls on YouTube to walk you through the process of wiring an outlet to the controller.  Watch these and then also reference the wiring chart below.  It’s pretty simple if you keep your wires organized and pay attention to where the wires are going.

Programming the STC-1000

It can be a little tricky to set-up the heating and cooling temperatures at first, but with a little practice you will get the hang of it.  I also taped a printed and laminated instruction sheet to my fridge right next to the controller so I never forget.  This video will walk you through the process to make you more familiar the first time around.

You might also need the original instructions and a Celsius to Fahrenheit Conversion chart .

Regulating Temperature

You rigged up a dual-stage temperature controller so you could both heat and cool.  The cooling part is relatively simple but what is the best way to heat and also measure temperature?

I picked up the cheapest, lowest powered hair dryer I could find at Walmart that is very similar to this one . I basically (carefully) screwed an S-hook into the top of the fridge to hang it from so that it can gently blow warm air around until temperature is reached.

I wanted something low-watt from a safety perspective yet could get the entire chamber up to temperature relatively quickly.  So it is suspended away from the carboy and isn’t near any of the plastic walls.

You may also wonder where to place the temperature probe.  I’ve had good luck taping it to the side of the carboy with a small layer of bubble wrap on top so it is less sensitive to fluctuations in the air temperature.

You should also expect the internal carboy fermentation temperature to be a degree or two higher than what the probe registers.  You can also consider investing in a thermowell that allows you to insert your probe into the fermenting wort for a more accurate reading.

I also set my temperature sensitivity to 1.0°C and set my compressor delay to 10 minutes to avoid burning out my old garage fridge.  So far, this has worked pretty well for me but you may want to monitor it closely if you experience extreme temperature swings (like I do in my garage).

Happy Fermenting

Best of luck and don’t be intimidated by this project. It’s actually pretty easy if you take the time to watch the videos and ensure you have all the necessary parts.

For more on homebrewing projects and parts, go to: