Installation and Maintenance Manual

Diagnostics
124 UNT-SVX07D-EN
Troubleshooting (UC400)
Tab l e 5 5 through Table 60, p. 125 provide troubleshooting
information if encountering operational problems with the
UC400 controller.
Table 55. Fan does not energize (UC400)
Probable
Cause Explanation
Unit wiring The wiring between the controller outputs and the fan
relays and contacts must be present and correct for normal
fan operation. Refer to applicable wiring diagram.
Failed end
device
The fan motor and relay must be checked to ensure proper
operation.
Normal
operation
The fan will turn OFF when:
• The controller receives a communicated off signal
• The fan-speed switch is set to OFF if no communicated
value is present
• Specific diagnostics are generated
• The default fan speed is set to OFF and the fan is
operating in the Auto mode.
If the controller is in unoccupied mode, the fan cycles
between OFF and the highest fan speed.
No power to
the controller
If the controller does not have power, the unit fan does not
operate. For the controller to operate normally, it must
have an input voltage of 24 Vac. If the Marquee/Power LED
is OFF continuously, the controller does not have sufficient
power or has failed.
Diagnostic
present
Several diagnostics affect fan operation. For detailed
information about these diagnostics, refer to Table 44,
p. 116.
Unit
configuration
The controller must be properly configured based on the
actual installed end devices and application. If the unit
configuration does not match the actual end device, the
fans may not work correctly.
Random start
observed
After power-up, the controller always observes a random
start from 5 to 30 seconds. The controller remains OFF
until the random start time expires.
Cycling fan
operation/
continuous
The controller continuously operates the fan when in the
occupied, occupied standby, or occupied bypass mode.
When the controller is in the unoccupied mode, the fan is
cycled between high speed and OFF with capacity.
Unoccupied
operation
Even if the controller is configured for continuous fan
operation, the fan normally cycles with capacity during
unoccupied mode. While unoccupied, the fan cycles ON or
OFF with heating/cooling to provide varying amounts of
heating or cooling to the space.
Fan mode off If a local fan mode switch determines the fan operation, the
OFF position controls the fan to off.
Requested
mode off
The user can communicate a desired operating mode (such
as OFF, heat, and cool) to the controller. If OFF is
communicated to the controller, the unit controls the fan to
off. There is no heating or cooling.
Table 56. Valves remain closed (UC400)
Probable
Cause Explanation
Unit wiring The wiring between the controller outputs and the valve(s)
must be present and correct for normal valve operation.
Refer to applicable wiring diagram.
Failed end
device
The valves must be checked to ensure proper operation.
No power to
the controller
If the controller does not have power, the unit valve(s) will
not operate. For the controller to operate normally, apply
an input voltage of 24 Vac. If the Marquee/Power LED is
OFF continuously, the controller does not have sufficient
power or has failed.
Diagnostic
present
Several diagnostics affect valve operation. For detailed
information about these diagnostics, refer to Table 44,
p. 116.
Normal
operation
The controller opens and closes the valves to meet the unit
capacity requirements.
Unit
configuration
The controller must be properly configured based on the
actual installed end devices and application. If the unit
configuration does not match the actual end device, the
valves may not work correctly.
Random start
observed
After power-up, the controller always observes a random
start from 5 to 30 seconds. The controller remains OFF
until the random start time expires.
Requested
mode off
The user can communicate a desired operating mode (such
as OFF, heat, and cool) to the controller. If OFF is
communicated to the controller, the unit controls the fan to
off. There is no heating or cooling.
Entering water
temperature
sampling logic
The controller includes entering water temperature
sampling logic, which is automatically initiated during
2-pipe and 4-pipe changeover, if the entering water
temperature is either too cool or too hot for the desired
heating or cooling.
Valve
configuration
Ensure the valves are correctly configured, using the Tracer
TU service tool, as normally open or normally closed as
dictated by the application.
Table 57. Valves remain open (UC400)
Probable
Cause Explanation
Unit wiring The wiring between the controller outputs and the valve(s)
must be present and correct for normal valve operation.
Refer to applicable wiring diagram.
Failed end
device
The valves must be checked to ensure proper operations.
Normal
operation
The controller opens and closes the valves to meet the unit
capacity requirements.
Diagnostic
present
Several diagnostics affect valve operation. For detailed
information about these diagnostics, refer to Table 44,
p. 116.
Unit
configuration
The controller must be properly configured based on the
actual installed end devices and application. If the unit
configuration does not match the actual end device, the
valves may not work correctly.
Entering water
temperature
sampling logic
The controller includes entering water temperature
sampling logic, which is automatically initiated during 2-
pipe and 4-pipe changeover, if the entering water
temperature is either too cool or too hot for the desired
heating or cooling.
Valve
configuration
Ensure the valves are correctly configured, using the Tracer
TU service tool, as normally open (NO) or normally closed
(NC) as dictated by the application.
Freeze
avoidance
When the fan is OFF with no demand for capacity (0%),
and the outdoor air temperature is below the freeze
avoidance setpoint, the controller opens the water valves
(100%) to prevent coil freezing. This includes unoccupied
mode when there is no call for capacity or any other time
the fan is OFF.
Table 56. Valves remain closed (UC400) (continued)
Probable
Cause Explanation
UNT-SVX07_-EN.book Page 124 Friday, April 27, 2012 9:40 AM