Cheaper than a Glycol setup for Fermentation Temp Control?

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Oct 21, 2021
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After checking the prices of a glycol chiller (eg: Grainfather) and as an engineer that likes to build things, I built a fermentation temp controller using a 200L 120cm tall fridge, a STC-1000, an aquarium pump and some vinyl tubing.

The temp sensor for the fermenter is inside the fermenter which also has the cooling coil inside, therefore for me it makes sense that the cooling adjusts wort temp, not ambient temp.
The fridge I bought new, and because its new I built a new door from 5cm think polystyrene foam sheets, covered with carboard to protect the foam from damage.

Fridge: $240
Foam sheets: $25
Pump: $18
Tubing: $5
STC-1000: $10
TOTAL $298

this is much cheaper than what i can buy a glycol chiller for here in Germany and the fridge can also double as a kegerator when not in use 😊.

The process works like this: the fridge runs as normal, keeping the 20L water bucket cold. The aquarium pump is submerged in the 20L bucket of water and controlled by the STC-1000, with the temp sensor inside a thermowell in the fermenter. The STC-1000 turns on the pump circulating cold water through the coils inside the fermenter when it needs to.

Why the fridge?
I used to use the same setup but without the fridge and just changing frozen water bottles morning and night to keep the 20L bucket water cold enough, as it needs to stay at least 5 degrees colder than the fermenter to work. Problem was, in the middle of the night if its not cold enough you can wake up the next day to a fermentation out of control. The fridge will always keep the 20L water bucket much colder than it needs to be. It also means the setup can go downstairs in the garage rather than 2 rooms away from the bedroom, and cheap aquarium pumps can be loud (my wife and/or daughter weren´t happy waking up at 2am when the pump turned on).

Why not just put the fermenter inside the fridge and use the STC-1000 to control the fridge compressor?
With the temp sensor inside the fermenter, this would keep the fridge compressor running until the fridge ambient temp had cooled the wort to the desired temp, you also get temp overshoot which is not a good thing.
But when its time to cold crash, the setup does most of the work to bring the temp down to 5-10degC, then its possible to disconnect the tubing and put the fermenter inside the fridge for a couple more days.

In general what I have found is that fermentation temp control has a cooling phase and a heating phase, and these phases are well separated.
The first 3-4 days the yeast is generating a lot of heat, thus you only need to cool. After this when most of the fermentation is done, you only need to heat to give the yeast a helping hand to finish and this is the time to use a thermowrap or electric blanket controlled by the STC-1000.

If someone is considering automated temperature control then this might give you some ideas, sorry my first post is a long one….

All comments welcome!