I had an idea for cycling chilled water through something like a small copper wort chiller during fermentation to keep the temperature down. I have no problem setting up the peltier, pump, and thermostat - but I'm uncertain if it's ok to leave the copper in the fermenter with the beer the whole fermentation, or what tubing to use. Thinking about using some soft copper tubing like this: refrigerator copper tubing off ebay

Would using copper tubing like this in the fermentation be likely to affect the beer? Here is a rough sketch of what I'm thinking of trying:

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3 Answers 3


Based on what John Palmer says about cleaning copper with various acids, I wouldn't use copper in the acidic environment of fermenting beer.

If you can get your hands on a stainless coil though, the idea will work. SS Brewtech has a Fermentation Temp Stabilization System along these lines.


Rather than circulate a coolant, you could also mount the peltier on top of a long heatsink (SS304) that extends into the beer. Use a H-bridge to change the direction of the peltier so you can switch it from heating or cooling.

  • That's a clever idea, more straight forward too. Guessing I would need to mount it through the fermenter wall though, and I'm not sure I'll be able to seal it well enough. Do you know where I might order/look for that type of heatsink?
    – Tim
    Dec 27, 2016 at 11:51

I use a Peltier cooling/heating system to control the temperature of a water bath around the carboy. That is much simpler and avoids any problems with sanitation of the cooling coil, etc. The carboy contains only pure beer. I have measured the temperature difference between the center of the beer and the outside at the peak of fermentation and it is only about 0.5 F, so that is much better than a carboy being cooled by air. By the way, I didn't see a temperature sensor in your setup. In my case the bath is in an insulated cooler so the heat gain from the environment is small. The only downside of doing it this way is that there is increased thermal mass and the system response is slower.

Happy experimenting!!

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