Analog inputs for 4-cool applications
CNT-SVX12C-EN 35
AI2: Outdoor air temperature or generic temperature
The AI2 analog input can function as either:
• An outdoor air temperature input
• A generic temperature input
If AI2 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 AI2. 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 you set DIP switch 3 to
ON for economizing (see “DIP switch settings”
on page 30), you automatically configure AI2 as an outdoor air tempera-
ture input. Economizing (free cooling) is a function whereby outdoor air is
used as a source of cooling before hydronic or DX cooling is used. The
Tracer ZN517 uses the outdoor air temperature value to determine
whether economizing is feasible. Economizing is not possible without a
valid outdoor air temperature. (For more information, see “Economizing”
on page 41.)
If AI2 is configured as a generic temperature input, it can be monitored
by a BAS. The controller receives the temperature as a resistance signal
from a 10 kΩ thermistor wired to analog input AI2. The generic tempera-
ture input can be used with any Trane 10 kΩ thermistor. The thermistor
can be placed in any location and has no effect on the operation of the con-
troller. If you set DIP switch 3 to
OFF (see “DIP switch settings” on
page 30), you automatically configure AI2 as a generic temperature input.
DAT: Discharge air temperature
The DAT analog input functions as the local discharge air temperature
input. The controller receives the temperature as a resistance signal from
a 10 kΩ thermistor wired to analog input DAT. The thermistor is typically
located downstream from all unit heating and cooling coils at the unit dis-
charge area.
Trane recommends the use of a discharge air temperature sensor to uti-
lize the cascade control function (see “Cascade zone control” on page 38).
Cascade control is a more accurate method of temperature control. If no
discharge air temperature sensor is used, the controller will default to
control based solely on the zone temperature (see “Simplified zone con-
trol” on page 38).
Note:
AI2 is not polarity sensitive; you can connect either terminal to
either sensor lead.
Note:
DAT is not polarity sensitive; you can connect either terminal
to either sensor lead.
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