Startup
120
UNT-SVX07J-EN
In staged electric heat applications, the simultaneous use
of electric and hydronic heat is not supported and the
controller will operate electric heat only when hot water is
not available (for example, in a changeover unit). In
addition, the controller will run the supply fan for 30
seconds after electric heat is turned
OFF
in order to
dissipate heat from the unit
Note:
This delay does not apply to steam or hydronic
heating.
Factory-configured electric heat units have built-in
mechanical protections to prevent dangerously high
discharge air temperatures.
Dehumidification Operation
The controller supports space dehumidification when:
•
Mechanical (DX or hydronic) cooling is available
•
The heating capacity is located in the reheat position
•
The space relative humidity is valid
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)
•
Frost protection on refrigerant coils
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.
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
and the preceding the Smart Reset section.
Condensate Overflow
For more information, refer to:
•
BAS-SVX48C-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
Summary of Contents for UniTrane
Page 163: ......
