Applications Guide Tracer Graphical Programming - Trane

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Writing the cooling tower fan module
Implementing PID control
Modulation of fan speed to maintain the condenser water setpoint calls
for proportional, integral, derivative (PID) control. Implement PID control
in graphical programming using the PID block.
Note:
For an in-depth explanation of PID control, see the online help
for the block or the applications guide, PID Control in Tracer
Controllers (CNT-APG002-EN).
Setting up the PID block properties
1. From the Blocks menu, choose Calculation. From the Calculation
menu, choose PID.
2. ClickinthedesignspacetoplacethePIDblock.
3. Double-click the PID block. The PID Properties dialog box appears
(Figure 94).
Figure 94: PID Properties dialog box
4. In the PID name field, type:
Fan Speed
The name is used to select a PID loop for troubleshooting and plotting
purposes.
5. Under PID Action, click the Direct Acting option.
The action of a PID loop determines how it reacts to a change in the
measured variable, or the process variable. A controller using direct
action increases the output when the measured variable increases. A
controller using reverse action decreases the output when the mea-
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