Applications Guide Tracer Graphical Programming - Trane

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Writing the mode and setpoints program
Figure 175: Space temperature setpoint source determination
Writing the mode and setpoints
program
The mode and setpoints program in Chapter 7 provides a solid base for
the program required by the more complex air handler in this chapter.
The following considerations require additions or changes to the program:
• Consider a third source of the space temperature setpoint—the building
automation system.
• Implement the pre-cool and warm-up mode decisions.
Modifying the effective setpoint calculation
The first module in the program, which calculates the setpoint offset, is
unaffected by the modifications. See “Implementing effective space setpoint
calculation” on page 181 for more information.
Use additional programming in the space temperature setpoint source
determination to include a setpoint from the building automation system.
According to the sequence of operation:
The space temperature setpoint source may be the building automation
system, the operator display, or a wired thumbwheel setpoint
adjustment knob, with the building automation system setpoint given
first consideration.
Use the nviSetpoint network variable input block, associated with the
SCC profile, to communicate the building automation setpoint. If a valid
setpoint is communicated, apply limits to it and accept the result as the
space temperature setpoint. Use a Fail block to switch to the operator display
setpoint or the wired setpoint if the communicated setpoint becomes
invalid (Figure 175).
The remaining portions of the program regarding effective setpoint calculations
are the same as those in Chapter 7.
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