Maximum difference between fridge and beer set point

Hi All, Elco,

I received my BrewPi Spark 3 last week, and hacked my freezer this weekend. Very exciting, was a lot easier than i thought it was going to be.

I got my hands on a 430 litre upright feezer where all the shelves come out, so i can fit my large 60 litre fermenter in easily.
Having a freezer will be quite handy as i really want to try brewing a Eisbock.

I am however having a couple of issues.

  1. I can’t work out how to change the minimum fridge set point. It seems that there is a setting in the advanced settings called Maximum difference between fridge and beer set point (= output of PID). The default value was 10. I am doing a trial now with just water, and i have the beer set to 14 c. I notice that the fridge set point is hovering around 4… presumably because of this setting not allowing a difference bigger than 10 degrees.
    I changed it to 20 and clicked ‘Send to controller’ but it didn’t change the fridge set point…
    Given i have a freezer, it would work much better at cooling the currently 17degree beer down if the fridge set point was -6 or even lower.
    Is there a process that you need to follow when changing the setting so it gets used?

  2. When in hardware test mode, the touch button for actuator 1 doesn’t work. All the others work, but actuator 1, the button just flashes on then off again in a split second - like it barely has enough time to change the text in the button to say ON. you just see a tiny flicker of red on the button then back to OFF with black background. I can see it flicking the SSR on and off too because of the LED.
    The actuator works fine when in profile mode. I am actually using that actuator for the cooling cycle and am not seeing any issues. It looks like an issue with the touch screen perhaps.


Hi @MikeT,

About your first problem, 10°C of difference should be enough to cool/heat your fermenter at the correct temperature.
So, if you beer setpoint is at 14°C and your fridge is targeting 4°C, then you will reach 14°C in a few hours if, let’s say, your ambient temperature is around 25°C. It’s a good practice to slowly cool so you don’t choke your yeasts.

About the second issue, most of time, when the button blinks and goes back to the original state, it means that you already have a PID attached to this output. What you can do is go back to normal mode, then set it to OFF. Then, go back to hardware testing mode, you should be able to toggle this output. If not, then detach this output totally from the configuration panel.

Good luck :slight_smile:


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