Trane UniTrane Installation, Operation And Maintenance Instructions page 90

Start-Up
Occupied Standby Mode
The controller can be placed into the occupied standby mode when a communicated occupancy
request is combined with the local (hardwired) occupancy binary input signal. When the
communicated occupancy request is unoccupied, the occupancy binary input (if present) does not
affect the controller's occupancy. When the communicated occupancy request is occupied, the
controller uses the local occupancy binary input to switch between the occupied and occupied
standby modes.
During occupied standby mode, the controller's economizer damper position goes to the
economizer standby minimum position. The economizer standby minimum position can be
changed using Rover service tool.
In the occupied standby mode, the controller uses the occupied standby cooling and heating
setpoints. Because the occupied standby setpoints typically cover a wider range than the occupied
setpoints, the Tracer ZN520 controller reduces the demand for heating and cooling the space. Also,
the outdoor air economizer damper uses the economizer standby minimum position to reduce the
heating and cooling demands.
When no occupancy request is communicated, the occupancy binary input switches the
controller's operating mode between occupied and unoccupied. When no communicated
occupancy request exists, the unit cannot switch to occupied standby mode.
Occupied Bypass Mode
The controller can be placed in occupied bypass mode by either communicating an occupancy
request of Bypass to the controller or by using the timed override On button on the Trane zone
sensor.
When the controller is in unoccupied mode, you can press the On button on the zone sensor to
place the controller into occupied bypass mode for the duration of the bypass time (typically
120 minutes).
Occupancy Sources
There are four ways to control the controller's occupancy:
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A communicated request from a building automation system or another peer controller can change
the controller's occupancy. However, if communication is lost, the controller reverts to the default
operating mode (occupied) after 15 minutes (configurable, specified by the "receive heartbeat
time"), if no local hardwired occupancy signal exists.
A communicated request can be provided to control the occupancy of the controller. Typically, the
occupancy of the controller is determined by using time-of-day scheduling of the building
automation system. The result of the time-of-day schedule can then be communicated to the unit
controller.
Tracer Summit with Supply Fan Control
If the unit is communicating with Tracer Summit and the supply fan control programming point is
configured for Tracer (the factory configures as local), Tracer Summit will control the fan regardless
of the fan mode switch position.
When the fan mode switch is set to Off or when power is restored to the unit, all Tracer ZN520
lockouts (latching diagnostics) are manually reset. The last diagnostic to occur is retained until the
unit power is disconnected. Refer to Trane publication, CNT-SVX04A-EN (Tracer ZN.520 Unit
Controller: Installation, Operation and Programming Guide) for specific instructions regarding the
procedure for running the Tracer ZN520.
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Communicated request (usually provided by the building automation system or peer device)
By pressing the zone sensor's timed override On button
Occupancy binary input
Default operation of the controller (occupied mode)
UNT-SVX07B-EN