I recently built a HERMS system and am using an Auber SYL-2362 to keep the mash temperature stable.
My RTD is mounted in the wort stream a few inches before it re-enters the mash tun. I am using a 2KW 120V element in a small 2 gallon cooler and the wort runs through what is basically an immersion coil chiller that is immersed in the cooler. I'm also using a small pump to circulate the water in the small cooler (HEX).
I have two different PID controllers that I have tried. A cheapo e-bay MYPIN controller and the Auber 2362. They are very similar in form and function.
In my testing with water (rather than wort), I auto-tuned both controllers under the same environment... same starting temp for the water, same valve opening position on my march pump, etc.
After auto tuning, the MYPIN behaved as I would have expected. It will operate the element at 100% until the SV nears the PV, then it will scale the output of the element down to account for the momentum of the temp change increase and will then maintain the temperature within about half a degree F.
With the Auber, it doesn't seem to matter if the PV is within the proportional band or way below it. It won't take the element to 100%. It seems to want to take an hour to creep up on the temperature set point. If I kick it into manual mode and set the output to 100%, then dial it back to 25% or so when it nears the SV, it will then do a good job of maintaining the temperature.
Does anyone have any ideas on what the issue might be? Or is that just how the Aubers work?
I can post my settings tonight. I have tried setting the P, I, & D to the same values, but the two controllers have several other settings that are not common to each other. For example, the MYPIN doesn't have a SouF (damp constant for the auto tune).
I have tried higher and lower settings for SouF (and re-tuned) on the Auber and it doesn't seem to have changed much.
I've done one brew with the Auber. My target mash temp was 152 and I mashed in a little low at 149. It was obvious that the Auber was going to take way too long to get the temp up to the SV, so I kicked it to 100% for a short period and then let it take back over and it worked great from there.
Do I need to set my proportional band much narrower? Right now I think it works out to about a 10 degree F band (P=0.9).
I can always switch back to the MYPIN, but I wouldn't mind figuring out the Auber.