Applications Guide Tracer Graphical Programming - Trane

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Writing the fan control program
Figure 109: Supply fan PID properties
Controlling the exhaust fan
This program also controls the exhaust fan. From the sequence of operation,
you know to:
• Turntheexhaustfanonwhenthesupplyfanisonandtheoutdoor
air damper is open beyond 30%.
• Turn the exhaust fan off when the outdoor air damper closes to below
20% open or the supply fan is turned off.
Start and stop the fan with a deadband as shown in Figure 110 on
page 118.
• Use a Deadband block to respond to the position of the outdoor air
damper.
• Use the Feedback Alarm block to start the fan and confirm fan status.
Implement a fan failure if status cannot be confirmed after a
1-minute delay.
• Connect the actual Output Status block to the Feedback Alarm block.
Use the output status to allow overrides of the fan without indicating
afanfailure.
• Use the Switch block to set the binary variable, Fan Failure Reset, to
off after it has been set to on.
CNT-APG001-EN 117