Trane Tracer ZN.520 Manual page 47

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
Sequence of operation
The external setpoint (when present) is exposed on the zone sensor's front
cover.
When the hardwired setpoint adjustment is used to determine the setpoints, all
unit setpoints are calculated based on the hardwired setpoint value, the
configured setpoints, and the active mode of the controller.
Example: Assume the controller is configured with the following default
setpoints:
Unoccupied cooling setpoint
Occupied standby cooling setpoint
Occupied cooling setpoint
Occupied heating setpoint
Occupied standby heating setpoint
Unoccupied heating setpoint
Absolute setpoint offset = setpoint input – mean setpoint
From the default setpoints in this example, the mean of the occupied cooling
and heating setpoints is 72ºF (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 73ºF , 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. 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 ZN.520 controller determines the effective setpoint based on the following:
I Hardwired setpoint input
I Communicated setpoint input
I Communicated setpoint offset
I Default setpoints
85ºF
76ºF
74ºF
70ºF
66ºF
60ºF
85ºF (same as default)
77ºF (default + 1 = 77)
75ºF (default + 1 = 75)
71ºF (default + 1 = 71)
67ºF (default + 1 = 67)
60ºF
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