Redundant Systems - Johnson Controls - Metasys - LIT-12011147 - Software Application - Controller Configuration Tool - 15.0

Controller Tool Help

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

Data centers are often built with redundant HVAC systems so that if a single piece of equipment fails, the other equipment is able to handle the entire load. During normal operation, both systems run at less than half capacity. To PRAC+, this appears as a high-gain system, and the tuning parameters are tuned accordingly. However, if one system fails and the other has to take over the full load, the gain of the system is cut in half when full capacity is required. When this situation occurs, tuning parameters that were optimal when both systems were in operation are now sluggish, and the HVAC system may not respond quickly enough when it is most needed. In this case, it is better to turn off adaptive tuning and tune the system manually. When the system is manually tuned for optimal operation, the system is more aggressive when both systems are running (oscillates more) and still responsive if one of the systems were to fail.