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68 UNT-SVX041D-EN
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
• Condensate overflow
• Fan status
• Fan off delay
• Filter maintenance timer
• Freeze avoidance
Smart Reset
The controller will automatically restart a unit that is
locked out as a result of a Low Coil Temp Detection
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.
Condensate Overflow
For more information, refer to:
• BAS-SVX48*-EN Tracer® UC400-B Programmable
Controller for Blower Coil, Fan Coil, and Unit Ventilator
Installation, Operation, and Programming Guide
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.
• 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.
Freeze Avoidance
Freeze avoidance is used for low ambient temperature
protection. It is initiated only when the fan is OFF. The
controller enters the freeze avoidance mode when the
outdoor air temperature is below the freeze avoidance
setpoint (configurable using the Tracer® TU service tool).
The controller disables freeze avoidance when the outdoor
air temperature rises 3°F (1.7°C) above the freeze
avoidance setpoint.
The following occurs when the controller is in freeze
avoidance mode:
• Valves are driven open to allow water to flow through
the coil
• Fan is OFF
• Economizing is disabled
• The outdoor/return air damper is closed
• Electric heat stages are OFF
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