Application

Sequence of Operation
Occupancy
9
Siemens Industry, Inc.
Application Note, App 6751
140-1331
2015-07-07
Occupancy
The controller keeps track of the occupancy status of the room and uses that
information for the following purposes:
 To select minimum and maximum flow rates for each air terminal.
 To select whether the controller is operating in the VAV or CV mode.
 To determine whether the controller is using Supply Tracks Exhaust (STE)
or Exhaust Tracks Supply (ETS) flow tracking.
 To determine the value of VOL DIF STPT.
 To calculate the airflow level that triggers the ventilation alarm.
Occupancy status also affects the airflow level that triggers the ventilation alarm. The
occupancy status of the room is indicated by OCC.UNOCC. A digital room thermostat
can read OCC.UNOCC and display its value. This point cannot be overridden.
If the occupancy status of the room is set manually, it is necessary to work through the
following command options.
The controller works in the occupied mode whenever
one or more of the following
occupancy signals indicates occupancy:
 Commands from a field panel, NET OCC CMD
 Dry contact switch in the room, OCC SWIT DI2
 Push button on the thermostat, OCC BUTTON
If
all of these occupancy signals indicate vacancy, the controller works in the
unoccupied mode.
NET OCC CMD – The NET OCC CMD may be set from a field panel by OCC and
UNOCC commands to the LCTLR point. The commands may come from a time-of-day
schedule, a PPCL program, or operator commands. These commands work on the
LCTLR without unbundling.
NOTE:
The displayed OCC/UNOCC status of the LCTLR point does not always match the
occupancy status of the controller. To get an actual indication of occupancy status,
OCC.UNOCC must be used.
If network commands are not required and occupancy will be set by sources in the
room, set NET OCC CMD to UNOCC. If set to OCC, the controller will stay in occupied
mode.
OCC ENA is an analog point whose value determines whether or not OCC BUTN DI1,
or OCC SWIT DI2, is enabled.
The following table shows what is enabled when OCC ENA is at a particular value.
OCC ENA Values.
OCC ENA (value)
Description
0
(default)
Both OCC BUTN DI1 and OCC SWIT DI2 are disabled.
1
Only OCC BUTN DI1 is enabled.
2
Only OCC SWIT DI2 is enabled.