Applications Guide Tracer Graphical Programming - Trane

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Chapter 5 Cooling tower with variable-speed fan example
sured variable increases. In this program, the fan speed increases
when the cooling tower supply water temperature increases.
6. In the Error Deadband field, type:
0.5
Error deadband prevents the PID from changing when the measured
value is within plus or minus this value of the setpoint.
7. Click to clear the Proportional Only check box. The Proportional Bias
field remains unavailable.
8. Under PID Frequency, verify the value is 30 seconds.
The PID Frequency defaults to the same frequency as the program.
For this program, do not change the default frequency. But note that
you may run a PID loop at the same rate as its parent program or at a
slower rate. The time interval must be an integer multiple of the program
run frequency.
9. In the Maximum field, type:
100
This field sets the maximum output of the PID loop to 100%.
10. In the Minimum field, type:
25
This field sets the minimum output of the PID loop to 25%.
11. In the Disable Position field, type:
0
When the Output Enable/Disable port of the PID block receives a
value of false, the PID loop outputs the disable-position value. Otherwise,
the PID loop outputs its calculated value.
12. In the Fail Safe Position field, type:
0
When the Fail port of the PID block receives a value of true, the PID
loop outputs the fail-safe-position value. Otherwise, the PID loop outputs
its calculated value.
13. Click OK.
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