Applications Guide Tracer Graphical Programming - Trane

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Writing the fan control program
• Use the Occupancy and the De-Enumerator blocks to interpret the
occupancy mode of the controller.
➤ Using the Occupancy block
Use the Occupancy block to provide a program with the occupancy
state of the controller. The output of the Occupancy block is the result
of arbitration among various schedule-related inputs and results in
the appropriate enumerated value for the current occupancy state.
Enumerations of the Occupancy block output are as follows:
0 = Occupied
1 = Unoccupied
2 = Occupied bypass
3 = Occupied standby
For more information about the Occupancy block, see the Tracer
MP580/581 Programmable Controller Programming guide
(CNT-SVP01A-EN).
➤ Using the De-Enumerator block
Use the De-Enumerator block to translate an analog enumeration to
one of several possible binary output values. If the analog value input
is equal to one of the enumerations for which the block tests, the
appropriate binary output is set to true. All other binary outputs are
set to false. Use the properties dialog box to select the configuration
and specify the required outputs.
• Use the binary variable, Manual Reset Alarm, to carry the alarm status
associated with manual reset alarm conditions, including low
mixed air temperature and high duct static pressure. If this alarm is
active, it prevents the fan from starting.
• Use the Feedback Alarm block to start the fan and confirm fan status.
A fan failure occurs 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.
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