Years and years (Ok.. and years and years and years) ago Opto 22 had a chart that was a PID loop.
From my abused brain cells comes the faint memory that it was done by someone in Product Support.... I also recall that they left Opto some time back....
All that said, it just so happens that I used the chart inside another of my charts.
Your request jogged my memory of this and so I opened up the old archives and extracted the PID part of the chart and have attached it to this post.
Just unzip it and import it using Factory Floor.
All the variable are prefixed with 'fcu3'... I used it on Fan Coil Unit 3.. hence the name.
You can of course rename then to be anything you like, but at least all the variables used in the chart will be grouped together in your strategy tree.
I cant really offer any support on this chart... its been a long long long time since I did any work with it. To my knowledge, its still in use to this day, so its been a chart based PID loop for over 16 years now.
Lets know how you get on.