Help - Brewpi suddenly heating cooling rapidly


I’m on my third brew with the BrewPi. The first two went smooth as silk, but now on my third run the BrewPi seems to have got stuck into a cycle of rapidly heating and cooling the beer continuously.

It was much more relaxed about the first two brews! But now, after four days of normal behaviour brewing a belgian double, it has got itself stuck into heating then cooling then heating then cooling rapidly.

Could anyone offer advice? Why is this happening this time when it didn’t before and what should I do?



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Hey! I don’t know if it would help in your situation, but I had something alike happening during my first fermenter test. Some possible solutions:

  • Reduce your heating source, find a lower power heater
  • Place the chamber temp sensor closer to your cooling source. I’ve put mine about 2cm from the side and 5cm from the bottom, close to the corner of my chest freezer.
  • Change the PID settings, mine : Kp 2, Ki 0.05, Kd -0.5
  • Restart your Pi…

Hope this will help.

Current run:

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Excellent advice from @PlazzmiK,

In your chart, I see that after cooling stops, the temperature still drops for a while. By placing your temp sensor closer to the cooler, you can minimize that.
What is the power of your heater? Looks like it might be a bit too much.

The next update will bring PWM for heaters, which might help with reducing heating overshoot.

If you want some more information… discussion about the problem I had…


Thanks for you help! In the end it turned out what had happened was that the probe in the thermo well had slipped out to the end of the well, so it was almost on the outside of the fermenter. I think this was causing the issue. Many thanks!