Applications Guide Tracer Graphical Programming - Trane

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Chapter 5 Cooling tower with variable-speed fan example
4. Under Request/Status Relationship, click the Request XOR Status
option.
5. In the Units list, click Seconds.
6. Click OK.
7. Place a Constant block in the design space and assign the value 30.0
to it.
8. Connect the Pump Start/Stop output status block to the Request port
of the Feedback Alarm block.
9. Connect the FlowStatus wireless read block to the Status port of the
Feedback Alarm block.
10. Connect the AlarmReset wireless read block to the Reset port of the
Feedback Alarm block.
11. Connect the 30.0 constant block to the Delay port of the Feedback
Alarm block (Figure 99).
Figure 99: Feedback Alarm block
Checking conditions to start and stop the pump
Because control of the pump is dependent on two conditions, both the condenser
water request and the flow status, add an And block just before
the Pump Start/Stop output block.
To check conditions to start and stop the pump:
1. Place an And block in the design space and connect it so that it checks
the state of both the Condenser Water Request input block and the
Feedback Alarm block.
2. Connect the And block to the Pump Start/Stop output block.
3. Connect the Feedback Alarm block to the Pump Fail variable block
(Figure 100 on page 99).
98 CNT-APG001-EN