16
BAS-SVX48H-EN
AI3; Local Fan Mode Input
Local Fan Mode Input AI3 functions as the local (hard wired) fan mode switch input for
applications using the Trane space temperature sensor with a fan mode switch option. The
various fan mode switch positions (OFF, LOW, MEDIUM, HIGH, AUTO) provide different
resistances that are interpreted by the UC400 Controller.
NNoottee:: The local fan speed switch can be disabled by taking out of service the multi-state point,
supply fan speed local and setting the value for each to AUTO.
A communicated fan mode request by means of the BACnet communications link, can be used
for controllers operating on a BAS. If both hard wired and communicated fan mode values are
present and in service, the UC400 Controller uses the communicated value. However, the
controller can be configured to use the local (hard wired) input value instead of the
communicated BAS value. The supply fan speed source (local or BAS) can be selected on the
Tracer TU Setup Parameters page. If neither a hard wired nor a communicated fan mode value is
present, the controller recognizes the fan mode value as AUTO and operates according to the
default configuration. If a valid hard wired or communicated fan mode value is established, and
then is no longer present, the controller generates a Supply Fan Speed Local alarm.
AI4; Discharge Air Temperature Sensor
Discharge Air Temperature Sensor AI4 functions as the local discharge air temperature input.
NNoottee:: A valid discharge air temperature value is required for normal operation.
The UC400 Controller receives the temperature as a resistance signal from a 10 kΩ thermistor
wired to analog input AI4. The thermistor is typically located downstream from all unit heating
and cooling coils at the unit discharge area. If a discharge air temperature value is invalid, or is
not present, the controller generates a Discharge Air Temp Failure alarm. If there is a discharge
air temperature failure, the controller runs a simplified zone control algorithm and controls the
space to the unoccupied setpoints.
AI5; Entering Water Temperature
Entering Water Temperature AI5 functions as the local (hard wired) entering water temperature
input. An entering water temperature communicated by means of the BACnet communications
link, can be used for controllers operating on a BAS. If both hard wired and communicated
entering water temperature values are present, and in service, the UC400 Controller uses the
communicated value. If a valid hard wired or communicated entering water temperature value is
established, and then is no longer present, the UC400 Controller generates an Entering Water
Temperature Failure diagnostic.
For units configured as 2-pipe or 4-pipe changeover units, the entering water temperature is used
to make heating/cooling operation decisions. If neither a hard wired nor a communicated
entering water temperature value is present on changeover units, the UC400 Controller always
operates in heating mode.
NNoottee:: For units not configured as changeover units, the entering water temperature can be
manually configured and used for information and troubleshooting. It will not affect the
operation of the controller.
Universal Inputs
The UC400 Controller has two (2) universal inputs.
UI1; Relative Humidity or CO
2
Sensor
If the UC400 Controller is configured for a local hard wired RH sensor, the factory programming
assumes it is wired to UI1. The pre-configured unit requires a 4-20 mA analog input
corresponding linearly to a 0%-100% relative humidity. If the controller is configured for a local
hard wired CO
2
sensor, the factory programming also assumes it is wired to UI1. The pre-
configured unit requires a 4-20 mA analog input.
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