My BrewPi is now starting to cold crash my brew and the Fridge Set temp is -7 Celcius, is this ok or should i change a setting? My fermentation chamber is a larder fridge with fan, image below:
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That’s fine. As the beer temp approaches setpoint, the fridge setting will change.
Thanks Elco, it did do exactly as you said. In all the cold crash took about 18 hours to get down to set temp and another 6 hours to stabilize there which i thought was pretty impressive. It does seem to overshoot when cooling by a degree or so which i know is not the end of the world but are there any changes that i should make in the advanced settings from the default and if so to what? At the moment the PWM value is 1200. I’ve attached zoomed in screenshots of the initial overshoot when bringing the wort down to primary temp and then the cold crash.
The overshoot is due to integrator windup in the beer-to-fridge PID.
If you increase the beer-to-fridge Kp, the proportional part will be bigger and the integrator will not be needed as much.
Your integrator time constant should also be set to about 4 hours.
I assume that’s the ‘Beer to Fridge’ Kp and 'integral time constant? The Kp value is at 2 what should i increase that to? The Beer to Fridge Ti was 7200 so i have upped that to 14400.
Kp at 2 is very low. That means that with the beer 1 degree to warm, the fridge setpoint will be 2 degreees under the beer setpoint. This is not enough, and the integrator has to make up for it.
Increasing Kp to 5 or 10 will probably work a lot better.