Applications Guide Tracer Graphical Programming - Trane

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Chapter 6 VAV AHU example
Figure 114: Controlling outdoor air damper position
Determining the outdoor air damper position
The next piece of the puzzle involves determining the required position of
the outdoor air damper. Use the TGP module in Figure 114.
• Use a Delay on Start block to implement a 1-minute delay prior to
allowing the outdoor air damper to modulate.
• UseaPIDlooptocontroltheoutdoorairdampertomaintainthedischarge
air setpoint when economizing is permitted.
• AddasecondPIDloopasbackupprotectiontomonitorthemixedair
temperature. It determines the necessary outdoor air damper positions
to maintain the mixed air temperature at the mixed air temperature
(low limit) setpoint.
• Use a Network Configuration Input (nci) block to access low limit setpoint
for the mixed air associated with the DAC profile.
• Compare the calculated positions from the PID loops. And allow
mixed air control to overrule discharge air control when necessary to
prevent freezing of the heating or cooling coils.
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