Applications Guide Tracer Graphical Programming - Trane

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Writing the condenser water pump module
Table 8 explains how the delay timer acts based on the selected feedback
alarm relationship.
Table 8: Feedback alarm relationships
Relationship
Request XOR Status
Request AND NOT(Status)
NOT(Request) AND Status
Delay timer
The delay timer starts when the request and
status are not the same.
The delay timer starts when the request is true
and the status is false.
The delay timer starts when the request is
false and the status is true.
When the delay timer is zero, the output of the Feedback Alarm block
changes to true (on). Then when the reset input to the Feedback Alarm
block changes from off to on, the block output resets to false (off).
Add a Feedback Alarm block to the program to compare the condenser
water request to the flow status. Set the Feedback Alarm block to the
Request XOR Status relationship. Also, set the units for the delay time
interval to seconds.
Next, add a Constant block and set it to an analog value of 30. The constant
provides the delay time interval. Make the appropriate connections
to the Feedback Alarm block.
To add a Feedback Alarm block:
1. From the Blocks menu, choose Time Delay. From the Time Delay
menu, choose Feedback Alarm.
2. Click in the design space to place the Feedback Alarm block.
3. Double-click the Feedback Alarm block. The Feedback Alarm Properties
dialog box appears (Figure 98).
Figure 98: Feedback Alarm Properties dialog box
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