Trane Tracer ZN.520

Analog inputs
CNT-SVX04A-EN
33
Table 28 identifies the fan speed to select with various fan modes and unit
configurations.
Table 28 Fan modes supported by the Tracer™ ZN.520 zone controller
Entering water temperature
The Tracer™ ZN.520 zone controller uses analog input 1 (AI 1) as the entering
water temperature input for use with a 10 kΩ thermistor only. This analog input
is factory-configured as an entering water temperature input, as required.
When a valid entering water temperature input exists (either hardwired to AI 1
or communicated), the controller automatically uses this value for heat/cool
changeover decisions when entering water input is required. Refer to “Entering
water temperature sampling function” on page 59.
Once a valid entering water temperature is established through the hardwired
input and that the entering water temperature input is no longer valid, the
controller generates an Entering Water Temperature Failure diagnostic.
Discharge air temperature
The Tracer ZN.520 zone controller cannot
operate without a valid discharge air
temperature input. When the sensor
returns to a valid value, the controller
automatically allows the unit to resume
operation.
The Tracer ZN.520 zone controller uses analog input 2 (AI 2) as the discharge air
temperature input with a 10 kΩ thermistor only. This sensor is hardwired and
typically located downstream from all unit heating/cooling capacity at the unit
discharge area. The discharge air temperature is used as a control input to the
controller for discharge air temperature tempering.
Once a valid discharge air temperature signal has been established by a
thermistor and the value is no longer present, the controller generates a
Discharge Air Temp Failure diagnostic and performs a unit shutdown. When the
sensor returns to a valid input, the controller automatically allows the unit to
resume operation.
Fan mode Single fan speed unit Two fan speed unit Three fan speed unit
Off Off Off Off
Auto High Auto Auto
Low — Low Low
Medium ——Medium
High High High High