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Chapter 4 Input/output functions and wiring for typical applications
18 CNT-SVX07C-EN
For units not configured as changeover units, the entering water temper-
ature value is used for information and troubleshooting only and does not
affect the operation of the controller.
AI2: Discharge air temperature
The AI2 analog input functions as the local discharge air temperature
input.
IMPORTANT
The Tracer ZN521 cannot operate without a valid discharge air tempera-
ture value.
The controller receives the temperature as a resistance signal from a
10 kΩ thermistor wired to analog input AI2. The thermistor is typically
located downstream from all unit heating and cooling coils at the unit dis-
charge area.
If a discharge air temperature value is invalid or is not present, the con-
troller generates a Discharge Air Temp Failure diagnostic and shuts
down the equipment. When the thermistor returns to a valid tempera-
ture, the controller automatically allows the equipment to resume normal
operation.
AI3: Outdoor air temperature or generic temperature
The AI3 analog input can function as either:
• An outdoor air temperature input
• A generic temperature input
If AI3 is configured as the local (hard-wired) outdoor air temperature
input, the controller receives the temperature as a resistance signal from
a 10 kΩ thermistor wired to analog input AI3. An outdoor air tempera-
ture value communicated by means of a LonTalk link can also be used for
controllers operating on a BAS. If both hard-wired and communicated
outdoor air temperature values are present, the controller uses the com-
municated value. If a valid hard-wired or communicated outdoor air tem-
perature value is established and then is no longer present, the controller
generates an Outdoor Air Temp Failure diagnostic.
Note:
AI1 is not polarity sensitive; you can connect either terminal to
either sensor lead.
Note:
AI2 is not polarity sensitive; you can connect either terminal to
either sensor lead.