Installation and Maintenance Manual

Startup
98 UNT-SVX07D-EN
controller ignores the hard-wired space temperature input
and uses the communicated value.
External Setpoint Adjustment (Tracer ZN520)
Zone sensors with an external setpoint adjustment (1kΩ)
provide the Tracer ZN520 controller with a local setpoint
(50°F to 85°F or 10°C to 29.4°C). The external setpoint is
exposed on the zone sensor’s front cover.
When the hard-wired setpoint adjustment is used to
determine the setpoints, all unit setpoints are calculated
based on the hard-wired setpoint value, the configured
setpoints, and the active mode of the controller. The hard-
wired 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.
When a building automation system or other controller
communicates a setpoint to the controller, the controller
ignores the hard-wired 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
These setpoint limits only apply to the
occupied and
occupied standby heating and cooling setpoints. These
setpoint limits do not apply to the unoccupied heating and
cooling setpoints stored in the controller’s configuration.
When the controller is in unoccupied mode, it always uses
the stored unoccupied heating and cooling setpoints.The
unit can also be configured to enable or disable the local
(hard-wired) setpoint. This parameter provides additional
flexibility to allow you to apply communicated, hard-
wired, or default setpoints without making physical
changes to the unit.
Similar to hard-wired setpoints, the effective setpoint
value for a communicated setpoint is determined based
on the stored default setpoints (which determines the
occupied and occupied standby temperature deadbands)
and the controller’s occupancy mode.
Fan Switch (Tracer ZN520)
The zone sensor fan switch provides the controller with an
occupied (and occupied standby) fan request signal (Off,
Low, Medium, High, Auto). If the fan control request is
communicated to the controller, the controller ignores the
hard-wired fan switch input and uses the communicated
value. The zone sensor fan switch input can be enabled or
disabled through configuration using the Rover service
tool. If the zone sensor switch is disabled, the controller
resorts to its stored configuration default fan speeds for
heating and cooling, unless the controller receives a
communicated fan input.
When the fan switch is in the off position, the controller
does not control any unit capacity. The unit remains
powered and all outputs drive to the closed position. Upon
a loss of signal on the fan speed input, the controller
reports a diagnostic and reverts to using the default fan
speed.
On/Cancel Buttons (Tracer ZN520)
Momentarily pressing the on button during unoccupied
mode places the controller in occupied bypass mode for
120 minutes. You can adjust the number of minutes in the
unit controller configuration using Rover service tool. The
controller remains in occupied bypass mode until the
override time expires or until you press the Cancel button.
Communication Jack (Tracer ZN520)
Use the RJ-11 communication as the connection point
from Rover service tool to the communication link—when
the communication jack is wired to the communication
link at the controller. By accessing the communication jack
via Rover, you can access any controller on the link.
Communications (Tracer ZN520)
Tracer ZN520 controller communicates via Trane’s LonTalk
protocol. Typically, a communication link is applied
between unit controllers and a building automation
system. Communication also is possible via Rover, Trane’s
service tool. Peer-to-peer communication across
controllers is possible even when a building automation
system is not present. You do not need to observe polarity
for LonTalk communication links.
The controller provides six 0.25-inch quick-connect
terminals for the LonTalk communication link connections,
as follows:
• Two terminals for communication to the board
• Two terminals for communication from the board to
the nex
t unit (daisy chain)
• Two terminals for a connectio
n from the zone sensor
back to the controller
Table 33. Zone sensor wiring connections (Tracer ZN520)
TB1 Description
1 Space temperature / timed override detection
2Common
3Setpoint
4Fan mode
5 Communications
6 Communications
UNT-SVX07_-EN.book Page 98 Friday, April 27, 2012 9:40 AM