Applications Guide Tracer Graphical Programming - Trane

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Chapter 5 Cooling tower with variable-speed fan example
Figure 92: Checking a setpoint against limits using the Min and Max blocks
Implement the simpler module using the Limit block in your program.
The Limit block compares a value with high and/or low limit values,
depending on how you set the properties for the block. If the value is
higher than the high limit, the high-limit value is passed out of the block.
If the value is lower than the low limit, the low-limit value is passed. If
the value is within the limits, the value itself is passed.
To impose limits:
Figure 93: Checking a setpoint against limits using the Limit block
1. Delete the connection between the Supply Temp Setpoint variable
block and the Deadband block.
2. From the Blocks menu, choose Function. From the Function menu,
choose Limit.
3. Click in the design space to place the Limit block.
4. Place two constant blocks in the design space and assign 95.0 to one
for the high limit and 65.0 to the other for the low limit.
5. Connect the Limit block so that it compares the Supply Temp Setpoint
to the low and high limit and passes the correct value to the
Deadband block (Figure 93).
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