Not cooling at the start of a beer profile

#1

This is the second time that after starting a beer profile the controller sets IDLE or HEATS when the conditions, beer setpt lower 66 degf, chamber set to 55 say it should be cooling. I think the picture will explain. Yesterday the beer got up to 74 degf before it started cooling and now is controlling fine. What I’m referring to is around the 15:30 mark. Then a little after 16:00 start cooling as it should. Seems like it should have started cooling right from the start, right ??? Thanks in advance !!

Oh yea, the 90 deg spike was me holding the Fridge probe trying to get the cooling to kick in…

#2

I can’t really say without seeing the fridge setpoint, which the actuators respond to.

Probably both minimum time between heating and cooling and integrator windup in the beer PID.

#3

As I remember, the fridge temp was 55 degs at the start.

To not get into this again, what should I do, start the beer profile ahead of time ??

#4

The fridge temp was 55 degs…

#5

I think that sudden drop in beer temp caused the fridge setting to spike up through the derivative gain. You can set Kd to zero to not use the derivative. Then after heating it had to wait a while before being allowed to cool.