Trane Tracer ZN.520 Manual page 39

The hardwired setpoint is used with the
controller's occupancy mode (occupied,
occupied standby, or unoccupied), the
heating or cooling mode, the temperature
deadband values, and the heating and
cooling setpoints (high and low limits) to
determine the controller's active setpoint.
CNT-SVX04A-EN
Zone sensor
Absolute setpoint offset = setpoint input – mean setpoint
From the default setpoints in this example, the mean of the occupied cooling
and heating setpoints is 72°F [(74+70) / 2]. The absolute setpoint offset is the
difference between the setpoint input and the mean setpoint. For this example,
assume a setpoint input of 73°F , resulting in an absolute setpoint offset of one
degree (73 –72=1).
The controller adds the absolute setpoint offset to occupied and occupied
standby default setpoints to derive the effective setpoints as follows:
Unoccupied cooling setpoint
Occupied standby cooling setpoint
Occupied cooling setpoint
Occupied heating setpoint
Occupied standby heating setpoint
Unoccupied heating setpoint:
The Tracer ZN.520 zone controller determines the effective setpoint based on
the following:
I Communicated setpoint input
I Communicated setpoint offset
I Hardwired setpoint input
I Default setpoints
I Occupancy mode
I Heating or cooling mode
I Setpoint high and low limits
When a building automation system or other controller communicates a
setpoint to the controller, the controller ignores the hardwired setpoint input
and uses the communicated value. The exception is the unoccupied mode,
when the controller always uses the stored default unoccupied setpoints.
After the controller completes all setpoint calculations, based on the requested
setpoint, the occupancy mode, the heating and cooling mode, and other
factors, the calculated setpoint is validated against the following setpoint limits:
I Heating setpoint high limit
I Heating setpoint low limit
I Cooling setpoint high limit
I Cooling setpoint low limit
85°F (same as default)
77°F (default+1=77)
75°F (default+1=75)
71°F (default+1=71)
67°F (default+1=67)
60°F (same as default)
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