Tracer UC 400 Controller
UNT-SVX07E-EN
147
Valves
DX Coils or Electric Heat
Table 89. Valves remain closed
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 87,
page 145
.
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 90. Valves remain open
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 87,
page 145
.
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 91.
DX or electric heat does not energize
Probable Cause
Explanation
Unit wiring
The wiring between the controller outputs and the end devices must be present and correct for normal operation.
Refer to applicable wiring diagram.
Failed end device
Check the control contactors or the electric heat element, including any auxiliary safety interlocks, to ensure proper
operation.
No power to the controller
If the controller does not have power, heat outputs do 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 DX and electric heat operation. For detailed information about these diagnostics, refer
to
Table 87, page 145
.
Normal operation
The controller controls compressor or electric heat outputs as needed 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, DX or electric heat may not operate correctly.
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 shuts off the compressor or electric heat.
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 disables compressors and electric heat outputs (100%) to prevent coil freezing.
This includes unoccupied mode when there is no call for capacity or any other time the fan is
OFF
.
