Question on PID settings MLT

Hi all,
I hope it is not a too general or theoretical question, but I’m curious about whether an MLT’s temperature can be controlled using a PID in general (with one setting for all the variables).

My setup at home uses an Auber PID for a 10L volume and no matter how many times I set the autocalibrate function, it will hit the 62C mark perfectly but will overshoot a subsequent increase to 72 by at least 2C. The setup that I brew with at work is 500L and uses a Chinese PID, but there the settings behave in a similar way. Strike temperature is easily reached (water only) but with malt in the mashing liquid it doesn’t hit the marks anymore and ‘surfing’ by hand is the solution.

I tried to solve it but couln’t find a single solution, which made me think about the physics of brewing. Would one set of settings (of variables, eg P, I, D, etc) be sufficient for different brews, where volume in the MLT differs, but also the recipe (and therefor properties of the liquid, maybe heat capacity)? I called with Coenco, which was the first company I thought of that could help me with solving this theoretically, and they say their settings vary per recipe.

But have others also experienced this? Is there a solution to my home issue or the one at the brewery?

If this is not the right place to post this, please let me know. Please also let me know where better to ask this, as I hope this community is the right mix of brewing, physics and settings of controller software!

Best wishes, and thanks,

PID settings are partially determined by the heat capacity of your brew, so you can’t get a universally perfect set of settings if the variables include volume. If you want to have variable volume, your best bet is to have some sort of calibration table.

The starting point for the PID should be irrelevant (20-68 vs 68-72), but without detailed stats and internal PID settings we can’t pinpoint why exactly your other PIDs are malfunctioning.