Attributes (Fan Return or Exhaust Volume Match Control) - Johnson Controls - Metasys - LIT-12011147 - Software Application - Controller Configuration Tool - 15.0

Controller Tool Help

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Controller Configuration Tool
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User Guide
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The following table describes the attributes used by the Fan Return or Exhaust Volume Match Control modules.

Table 1. Fan Return or Exhaust Volume Match Control Attributes


Type 1


Default Value

Fan Return or Exhaust Volume Match Common Attributes


V, G

Indicates the current operational mode of the output controller. This output is the current state of the activity.


Set Name: AHU RF VOL State



Contains the desired mode of operation.


Set Name: AHU RF VOL Mode

Process Units


Allows the user to define the units for the process.

l/s, cfm

Set Name: Unit

Return Fan Control Status


Displays the PID Status. The possible values are normal, overridden, disabled, low, timing low, high, and timing high.


Set Name: Control Status

Return Fan OnOff


On/off signal for the return fan.


Set Name: Off/On

Return Fan Percent Cmd


Contains the analog signal for the return fan used to command a fan speed. This output can range from 0% to 100%.


Return Flow


Use to connect the return airflow or the exhaust airflow to this input.

10000 l/s, 22000 cfm

Supply Fan Percent Cmd


Contains the analog signal from the supply fan used in the Failsoft mode.


Supply Flow


Discharge airflow.

10000 l/s, 22000 cfm

Vol Process Range


Specifies that the magnitude of the range that the PID Process Variable traverses as the PID Present Value varies between its minimum and maximum values. For example, the process range should be configured to be the design flow of the return fan.

10000 l/s, 22000 cfm

Volume Diff Setpoint


Contains the volume differential (Supply Flow - Return Flow or Supply Flow - Exhaust Flow) setpoint.

0 l/s, 0 cfm

Variable Capacity Return Fan Volume Match Control Specific Attributes

Low Limit Process Variable


Low limit temperature process variable. This temperature is usually the mixed air temperature or the preheat air temperature.

7 °C, 45 °F

Low Limit Proportional Band


Defines the temperature range where the flow differential setpoint is reset to control the low limit process variable to the low limit temperature setpoint.

5 °C, 9 °F

Low Limit Setpoint


Contains the upper threshold for the low limit process function. When the low limit process variable is above this temperature, the return fan may be modulated to maintain the desired flow differential between the supply duct and the return duct. Below this setpoint, outdoor air levels may be limited by resetting the differential flow setpoint.

7 °C, 45 °F

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