Trane VUV Installation, Operation And Maintenance Manual page 88

Start-Up
The space relative humidity can be a BAS-communicated
value or come directly from a wired relative humidity sensor.
The controller begins to dehumidify the space when the space
humidity exceeds the humidity setpoint. The controller
continues to dehumidify until the sensed humidity falls below
the setpoint minus the relative humidity offset.
Peer-to-Peer Communication
Peer-to-peer communication is accomplished by means of
custom TGP2 programming in the Tracer® SC system
controller or via hard wiring only between controllers.
Unit Protection Strategies
The following unit protection strategies are initiated when
specific conditions exist in order to protect the unit or building
from damage:
• Smart reset
• Low coil temperature protection
• Condensate overflow
• Fan status
• Fan off delay
• Filter maintenance timer
• Freeze avoidance
• Freeze protection (discharge air temperature low limit)
Smart Reset
The controller will automatically restart a unit that is locked out
as a result of a Low Coil Temp Detection (BI3) diagnostic.
Referred to as smart reset, this automatic restart will occur 30
minutes after the diagnostic occurs. If the unit is successfully
restarted, the diagnostic is cleared. If the unit undergoes
another Low Coil Temp Detection diagnostic within a 24-hour
period, the unit will be locked out until it is manually reset.
Note: Freeze protection will also perform a smart reset.
Low Coil Temperature Protection
For more information, refer to:
• BAS-SVX48*-EN: Tracer® UC400/UC400-B
Programmable Controllers for Blower Coil, Fan Coil, and
Unit Ventilator Installation, Operation, and Maintenance
• BAS-SVX093*-EN: Symbio™ 400-B/500 Programmable
Controllers For Blower Coil, Fan Coil, and Unit Ventilator
Installation, Operation, and Maintenance
and the preceding section,
Condensate Overflow
For more information, refer to:
• BAS-SVX48*-EN: Tracer® UC400/UC400-B
Programmable Controllers for Blower Coil, Fan Coil, and
Unit Ventilator Installation, Operation, and Maintenance
• BAS-SVX093*-EN: Symbio™ 400-B/500 Programmable
Controllers For Blower Coil, Fan Coil, and Unit Ventilator
Installation, Operation, and Maintenance
88
"Smart Reset," p. 88.
Fan Status
In 1-, 2- and 3-speed fans, the status is based on the statuses
of the supply fan output multistate and analog points dedicated
to fan control. The fan status is reported as HIGH, MEDIUM,
LOW, and as a percentage, whenever the fan is running. The
fan status is reported as OFF whenever the fan is not running.
In addition, a fan status switch can be connected to binary input
5 (BI5) to monitor the status of the fan for belt-driven or direct-
driven units (except Trane Macon factory ECM fan motor
units). The fan status switch provides feedback to the
controller as follows:
• If the fan is not operating when the controller has the fan
controlled to ON, the controller generates a Low Airflow-
Supply Fan Failure diagnostic.
• If the controller energizes the fan output for 1 minute, and
the fan status switch indicates no fan operation, the
controller performs a unit shutdown and generates a Low
Airflow-Supply Fan Failure diagnostic.
• If the fan has been operating normally for one minute, but
the fan status switch indicates no fan operation, the same
diagnostic is generated.
This manual diagnostic discontinues unit operation until the
diagnostic has been cleared from the controller. If a diagnostic
reset is sent to the controller, and the fan condition still exists,
the controller attempts to run the fan for 1 minute before
generating another diagnostic and performing a unit
shutdown. A diagnostic reset can be sent to the controller from
the Tracer® TU Alarms page or by temporarily overriding the
Reset Diagnostic Request on the Tracer® TU Binary Status
page.
Note: In the ECM fan application, the VelociTach™ board will
monitor the status of the fan. In case of a failure, the
engine board will disable the motor immediately, and
the low airflow diagnostic is sent.
Fan Off Delay
After heating has been controlled OFF, the controller keeps the
fan energized for an additional 30 seconds in order to remove
residual heat from the heating source.
Filter Maintenance Timer
The filter maintenance timer tracks the amount of time (in
hours) that the fan is enabled. The Filter Runtime Hours
Setpoint (configurable using the Tracer® TU service tool) is
used to set the amount of time until maintenance (typically, a
filter change) is required. The timer can be enabled/disabled
from the Supply Fan group on the Setup Parameters page in
Tracer® TU.
The controller compares the fan run time to filter runtime hours
setpoint. Once the setpoint is reached, the controller
generates a Filter Change Required diagnostic. When the
diagnostic is cleared, the controller resets the filter
maintenance timer to zero, and the timer begins accumulating
fan run time again. The diagnostics can be cleared and the
filter timer reset by temporarily overriding the Filter Timer
Reset Request on the Binary Status page or by using the
reset button on the Alarms page in Tracer® TU.
UV-SVX005G-EN