Critical Data Points - Johnson Controls - Metasys - LIT-12011147 - Software Application - Controller Configuration Tool - 13.1

Controller Tool Help

Brand
Johnson Controls
Metasys
Product name
Controller Configuration Tool
Document type
User Guide
Document number
LIT-12011147
Version
13.1
Revision date
2019-12-04
Language
English

In addition to understanding how the PID module and PRAC+ function, other parameter settings within the CCT/PCT application can affect how well a mechanical system controls. Certain parameters, if not set correctly, could create situations where a mechanical system behaves poorly, resulting in a control loop that cannot tune itself correctly, or system performance that is worse. See Table x for a list of critical data points to keep in mind when you use adaptive tuning.

Table 1. Critical Data Points

Issue

Application

Variables

Notes

Slow control loop response to a setpoint change

VAV Occupied Zone Sequencing (See Figure 1.)

Fast Sequence Enabled

Setpoint Threshold

Ensure that Fast Sequence Enabled is set to True. This setting allows the user to enable or disable the transition to satisfied when the setpoint changes by more than the Setpoint Threshold.

Ensure that the Setpoint Threshold is less than 0.5 degrees if Fast Switch Enabled is set to True to ensure a fast response on zone temperature changes.

Figure 1. VAV Occupied Zone Sequencing

Zone recovers slowly or responds poorly to large setpoint changes

Box Heating/Discharge Air Reset by Zone (See Figure 2.)

Discharge Air Setpoint Cooling Min

Discharge Air Setpoint Heating Max

Discharge Air Setpoint Zone Satisfied

Set the minimum and maximum discharge air temperatures of the VAV Box so that these match the minimum and maximum discharge air temperatures of the fan system.

To limit heat in the zone, lower the maximum discharge air setpoint to prevent overheating.

Figure 2. Box Heating/Discharge Air Reset by Zone