Applications Guide Tracer Graphical Programming - Trane

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Chapter 7 Constant-volume AHU example
Figure 147: Operate the cooling valve?
Think of the cooling valve control in two parts.
• Use a combination of logic blocks to determine if the cooling valve
operates.
• Apply the output of the economizer decision here.
• Use a Deadband block to consider the position of the outdoor air
damperasshowninFigure147.
When the cooling valve is enabled, use a PID loop to perform discharge
air temperature control. However, if dehumidification is also active, you
need a second PID loop to calculate the cooling valve position based on
the space relative humidity. Control the valve to the greater of the two
calculated valve positions (Figure 148 on page 171).
170 CNT-APG001-EN