Trane Tracer ZN.520

Zone sensor
CNT-SVX04A-EN
37
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 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.
The controller adds the absolute setpoint offset to occupied and occupied
standby default setpoints to derive the effective setpoints as follows:
The Tracer ZN.520 zone controller determines the effective setpoint based on
the following:
■ Communicated setpoint input
■ Communicated setpoint offset
■ Hardwired setpoint input
■ Default setpoints
■ Occupancy mode
■ Heating or cooling mode
■ 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:
■ Heating setpoint high limit
■ Heating setpoint low limit
■ Cooling setpoint high limit
■ Cooling setpoint low limit
Unoccupied cooling setpoint 85°F (same as default)
Occupied standby cooling setpoint 77°F (default+1=77)
Occupied cooling setpoint 75°F (default+1=75)
Occupied heating setpoint 71°F (default+1=71)
Occupied standby heating setpoint 67°F (default+1=67)
Unoccupied heating setpoint: 60°F (same as default)