Attributes (Cooling Tower PID Control v61) - Johnson Controls - Metasys - LIT-12011147 - Software Application - Controller Configuration Tool - 13.1

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Johnson Controls
Product name
Controller Configuration Tool
Document type
User Guide
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The following table describes the attributes used by the Cooling Tower PID Control v61 modules:

Table 1. Cooling Tower PID Control Attributes


Type 1


Default Value

Control Status


This output indicates the current status of the cooling tower PID.

Set Name: Control Status



This is the value used to prevent the PID from overreacting when the process variable is near the setpoint.

1 °C, 2 °F

Fan Type


This input indicates the type of fans controlled by the central cooling plant. This module supports variable speed fans, 1-speed fans, 2-speed fans, 3-speed fans, and vernier control.

Set Name: Tower Fan Type

Integral Time


This input is the Integral Time used by the cooling tower PID controller.

600 Seconds

Display Precision: 1s

Limited Max Value


Defines the proportional output 0% when the module is in Limited Max mode.


Display Precision: 10ths

Min Speed


This value is the minimum output for the Percent Cmd when VFD Fan is true. This value is the minimum speed at which the fan runs.




This input indicates the desired operating mode for the cooling tower PID.

Set Name: Off/Max/Control/Limited Max

Number Available


This input indicates the number of cooling towers that are enabled.

Display Precision: 1s

Number Of Towers


This input indicates the number of cooling towers in the central plant.

Display Precision: 1s



This input is the value for Percent Cmd when the error is zero. The output can vary from this value if the cooling tower PID had to integrate for some time to drive the Process Variable to the Setpoint.


Percent Cmd


This modulating signal is used to drive variable speed fan drives.


Process Variable


This input is the value that is controlled by modulating the Percent Cmd output.

25 °C, 78 °F

Proportional Band


This input is the Proportional Band used by the cooling tower PID controller.

10 °C, 20 °F



This is the setpoint that the cooling tower PID attempts to control the Process Variable to.

25 °C, 78 °F



This output is the current state of the cooling tower control module.

Set Name: Off/Max/Control

1 B - BACnet Exposed Parameter, C - Configuration Mode Only, G - Default Element (Generated State, if applicable), SC - Simulation and Commissioning Modes Only, V - Calculated Value (Outputs)