Nate42 wrote:It might perhaps be a meaningful and useful thing to begin the tuning process immediately AFTER pulling a shot or series of shots, but I wouldn't mess with anything during the actual tuning.

Makes a lot of sense, based on the publicly available code for Arduino that I've seen. This one, Arduino PID Autotune Library, comes with a pretty clear explanation. It doesn't do any tuning until it gets an oscillation cycle, and stops when it sees three cycles in good agreement (with max of 10 cycles.) In the documentation, the purpose of the 3 cycles in agreement is: "... trying to ensure that we've reached a stable oscillation and there's no external strangeness happening." Trying to brew, or even an autofill would be "strangeness happening."

just if there was a way to run 2 PID programs so one would override the initial PID algorythm . So when you hit button to start hot, the secondary PID algorithm would kick in to adjust for faster temp fluctuations as cold water enters boiler . then after temp is stabilized it would switch back to initial PID parameters for idle heating...

hugz wrote:I run a 3gp Linea as my home machine, so power usage is a concern to me. I want to insulate the boilers. It's easier to insulate the brew boiler because it's not as hot as the steam boiler, so there's a bigger range of non-fiberglass products.

I've been told that you shouldn't insulate the brew boiler because it lessens the temp control because the machine can't shed temperate as easily when needed.

Does this apply if the boiler has a PID? I'm hoping that a PID will intelligently control the temperate so well that it won't need the ability to shed large amounts of heat through the boiler wall... the temp will always be exact

Insulating a small brew boiler e.g. 800ml or less, is not a problem if the PID is retuned. However, it will ALWAYS have the effect of reducing recovery time for any given small boiler machine you insulate (and assuming you keep using the same PID). This is purely physics.

With a large boiler 1 litre +, insulation with retuning of the PID, doesn't really affect recovery time (especially in the home environment, because it has a larger thermal mass. The only time recovery time might be affected is if it's pulling a lot of shots in a commercial environment. Even then the effect will be smaller and the system won't be as stable.

When working on the Duetto (initial production machines), I advised no insulation of the brew boiler, because it was only 800 ml and the PID used on the early models was quite basic, with limited parameter setting. in addition the width of the proportional band could not be controlled at all. The very up to date offerings from Gicar allow for this control. In addition, on the early Duetto (and probably current ones), the steam boiler shared the brew boiler PID parameters, so insulation would have required less aggressive settings and thus worse steam performance.

So what I have said above is a generalisation and should be read in context of the capabilities of the PID and whether the steam boiler shares the same PID loop as the brew boiler. There other factors which should get consideration such as heating element size, minimum pulse time etc..but usually these effects can be ignored.