Applications Guide Tracer Graphical Programming - Trane

®
Chapter 7 Constant-volume AHU example
Determining a programming approach
As in the previous chapter, the programming instructions in this chapter
are in a modular form. Remember that this sequence of operation could
result in a large number of variations in program content and programming
technique.
From the sequence of operation, determine the basic control functions
required. The required control functions are very similar to those for the
Chapter 6, “VAV AHU example.” Address the following control functions:
• Effective space setpoint calculation
• Mode determination, including night heat/cool
• Supply fan control
• Exhaust fan control
• Mixed air and outdoor air damper control
• Discharge air setpoint calculation
• Cooling valve control, including dehumidification
• Heating valve control, including dehumidification
• Alarm management
Not every control function fits into one program. Determine the number
of programs required by grouping control functions together that require
the same information, and/or the same run frequency as shown in
Table 22.
Table 22: Control functions within each program
Program name
FanControl
MixedAirControl
DischargeAirControl
Alarms
ModeAndSetpoints
Control functions
Supply fan control
Exhaust fan control
Mixed air/outdoor air damper control
Discharge air setpoint calculation
Cooling valve control
Heating valve control
Dehumidification
Humidification
Alarm management
Effective space setpoint calculation
Setpoint source determination
Mode determination
The functionality of many components of the constant-volume air handler
is similar to that of the VAV air handler. Keep in mind that you can modify
those programs and re-use them for the constant-volume air handler.
154 CNT-APG001-EN