Disabling PRAC+ Loop Tuning - Johnson Controls - Metasys - LIT-12011147 - Software Application - Controller Configuration Tool - 13.1

Controller Tool Help
Product
Controls > Control Tools > Controller Configuration Tool
Document type
User Guide
Document number
LIT-12011147
Version
13.1
Revision date
2019-12-04

About this task

If your system is not suited for PRAC+ adaptive tuning (see Systems Not Suited for PRAC+), you may need to turn off adaptive tuning.

The following are two scenarios for disabling PRAC+ tuning:
  • Use PRAC+ Adaptive Tuning until you achieve stable control, then disable it. This scenario may be necessary when you experience large load disturbances or when the system is not always delivering a repeatable response.
  • Use Manual Tuning and set your own values. In this scenario, keep in mind that if you leave the connections to the PID Pre-Processor, you must change the parameters in the PID Pre-Processor. This scenario may also require you to set the Standard Tuning parameter to False. You can also break the connections from the PID Pre-Processor to the PID and set the desired parameters in the PID.
Note: PRAC+ adaptive control cannot correct for mechanical system problems or systems that cannot deliver predictable, repeatable responses.

To disable PRAC+ loop tuning:

Procedure

  1. In the CCT/PCT UI, right-click the output controller and select Logic View. The Logic View appears.
  2. Select Control Mode. This view shows the flow of the PID.
  3. Right-click the PID and select View > Details. The Details window appears.
  4. In the Inputs column, select Adaptive Tuning and change the value from True to False. Adaptive Tuning is now turned off. For information on manual tuning, see Disabling PRAC+ Loop Tuning.

Results

When manually tuning a controller, the key attributes of the PID Pre-Processor are Proportional Band and Integral Time. See Table 13.

Table 1. Manual Tuning Using Proportional Band and Integral Time
Current Loop Behavior Proportional Band Integral Time
Slow/Sluggish Decrease Decrease. Note that this value must be at least two times the Interval setting in the PID Pre-Processor.
Excessive Cycling Increase Increase. Note that this value must be at least two times the Interval setting in the PID Pre-Processor.
Important: Make sure to manually transfer tuned controllers to the computer to preserve the tuning parameters. Doing so prevents the loss of optimum tuning parameters and eliminates the need to perform the entire manual tuning process on a controller again.