I'm controlling flue levels. Are there PID reference values?

Try proportional control. Perform tuning with these reference values: P=10%, I=OFF.D=OFF, MR=0%.

Advanced Application UT75A

Temperature Controller with increased monitoring and operating capabilities
Mid-level UT55A/UT52A

Increase monitoring and operating capabilities
UP35A/UP32A

Program Controllers with 4 patterns, 40 segments, and ladder sequence functions
UP55A

Program controller with 30 patterns, simultaneous monitoring, and ladder sequence function
UT32A-D

Digital Indicating Controller with selectable 2-loop control and intuitive design
UT35A/UT32A

Increase monitoring and operating capabilities