Trane LO - Manual (Page 76)

Tracer ® ZN.520
76 UNT-IOM-6
The Tracer ® ZN.520 controller accepts the following zone sensor
module inputs:
• Space temperature measurement (10kW thermistor)
• Local setpoint (either internal or external on the zone sensor
module)
• Fan switch
• Timed override (On) and Cancel timed override
• Communication jack
Trane zone sensors use a 10kW thermistor to measure the space
temperature. Typically, zone sensors are wall-mounted in the room
and include a space temperature thermistor. As an option, the zone
sensor can be unit-mounted with a separate space temperature
thermistor located in the unit’s return air stream. If both a hardwired
and communicated space temperature value exist, the controller
ignores the hardwired space temperature input and uses the commu-
nicated value.
Zone sensors with an external setpoint adjustment (1kW) provide the
Tracer ® ZN.520 controller with a local setpoint (50 to 85 F or 10 to
29.4 C). The external setpoint 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. The hardwired setpoint is used with the controller’s occu-
pancy 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 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 occu-
pancy 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
Zone Sensor
Space Temperature
Measurement
External Setpoint Adjustment