Trane LO Zone Sensor, Tracer ZN.520, Space Temperature Measurement, External Setpoint Adjustment

Tracer® ZN.520

Zone Sensor

Space Temperature Measurement

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.

External Setpoint Adjustment	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

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