Request for help with settings (overshooting)

Hi Elco and everyone,

I just fermented my second batch with the BrewPi Spark V2 and I am loving it! Thank you for coming up with such a great product and the continuous support in the forum. I have to admit that I have very limited (almost zero) engineering/programming knowledge so just getting the BrewPi working took quite some time. The BrewPi seems to be working fine but I still have some problems with the settings which cause temperature to overshoot (by a lot). I will try to lay out the facts as much as possible in case some may be the cause of the problem.

  • The settings are default
  • I have a thermowell for my beer probe while my fridge probe is hanging about half way in the fridge.
  • I do not have a fan inside the fridge to circulate the air
  • I did not put in a heating element as I am in Thailand so the room temp is constantly around 29C
  • The fridge is an inverter type (if it makes any difference)
  • The fridge is set at 3C (mid point between selection of 1C – 7C)
  • For this particular batch, I was fiddling around with the probes a bit at the start of the session (the spikes at the beginning). Could this have caused the issue?

Below are the graphs of the brew.
Full brew

Zoom in on the first overshoot.

More zoom. In the middle part, somehow the fridge temp doesn’t seem to drop like the set temp.

I small overshoot when raising the temp for diacetyl rest. I should have gradually raised the temp but was afraid it will stall after dropping from 22C to 20C.

p.s. My first batch also overshot by setting a lot. This is a graph from the first batch.

I would greatly appreciate it if anyone could help suggest the settings (or some guidelines) to help on this or if I am doing anything wrong. Thank you very much for the great support!


I think this could be improved by increasing beer-to-fridge Kp. When the proportional part is not doing enough to correct the beer temp, the integral will slowly increase to correct this. But because this is slow to increase, it is also slow to decrease. This causes the overshoot.

When you increase Kp, the proportional part will do more work and the integral part will be less.

Thank you very much Elco. Will try adjusting these as a starting point.