CNT-SVX05A-EN
17
Analog inputs
Local setpoint
The local setpoint input is a hardwired setpoint connected on analog input IN 2.
The local setpoint is a resistive input for use with Trane zone sensors. If neither
a hardwired nor communicated setpoint is present, the controller uses the stored
default configured heating and cooling setpoints:
• Occupied setpoints
• Occupied standby setpoints
• Unoccupied setpoints
Once a valid setpoint is established through the hardwired input IN 2 or through
communication, and when neither a local setpoint nor communicated setpoint
is present, the controller generates a
setpoint Failure
diagnostic.
Rover
™
, Trane's service tool communication software package, allows you to
monitor, configure, and test Tracer
™
AH.540 unit controllers via a connection to
the communication link.
When a
setpoint Failure
diagnostic occurs, the controller operates using the
default heating and cooling setpoints. These setpoints are factory-configured,
but you can change them using the Rover service tool.
The Tracer AH.540 controller uses the following steps to determine the space
temperature setpoint:
1. Check for a communicated setpoint. If present, validate this setpoint.
2. Check for a hardwired setpoint and validate the setpoint.
3. Use the default setpoints if neither the hardwired setpoint nor the
communicated setpoint is available.
Note 1
: Communicated inputs to the Tracer AH.540 controller have precedence over locally wired inputs.
Fan mode switch
The fan mode analog input IN 3 responds to specific resistances corresponding
to a fan mode switch provided with certain Trane zone sensors. The fan mode
switch on a Trane zone sensor generates the fan mode signal.
The Tracer AH.540 controller detects the unique resistance corresponding to
each position of the fan mode switch. By measuring this resistance, the
controller determines the requested fan mode.
If the Tracer AH.540 controller does not receive a hardwired or communicated
request for fan mode, the unit recognizes the fan input as Auto.
Table 17 — Tracer AH.540 fan modes
Tracer AH.540
status
Communicated setpoint
input - nviSetpoint (Note 1)
Local, wired setpoint
input - IN 2
Result
Standalone
N/A
Not present
Configured default
setpoints are used
Standalone
N/A
Present - local zone
sensor thumb wheel
Local setpoint input
Communicating
Communicated
setpoint input
Not present
Communicated setpoint
Communicating
Communicated
setpoint input
Present - local zone
sensor thumb wheel
Communicated setpoint
Fan modes
Tracer AH.540 operation
Off
Fan off (4870 ohms +/-1%)
Auto
In occupied mode, the fan runs. In unoccupied mode, the fan cycles Off
when no heating or cooling is required. (2320 ohms +/-5%)