Delay Time Dominant Systems - Johnson Controls - Metasys - LIT-12011147 - Software Application - Controller Configuration Tool - 15.0

Controller Tool Help

Product name
Controller Configuration Tool
Document type
User Guide
Document number
Revision date

The PRAC+ tuning rules were designed using certain test systems, such as systems where the dead time was never greater than the time constant. Dead time dominant systems (where the dead time is greater than the time constant) are harder to control with a PID. In this case, we recommend you manually tune the system. An example of this type of system is condenser water temperature control with an abnormally long run of pipe between the chillers and the cooling towers. In this type of system, the time required to pump the water from the tower to the chiller may be longer than the time required by the cooling tower to cool the water by adjusting fan speed.