Trane UniTrane Installation, Operation And Maintenance Manual page 148

Diagnostics and Troubleshooting
Table 89. Valves remain open
Probable Cause
Unit wiring
Failed end device
Normal operation
Diagnostic present
Unit configuration
Entering water temperature
sampling logic
Valve configuration
Freeze avoidance
DX Coils or Electric Heat with UC400-B Controller
Table 90. DX or electric heat does not energize
Probable Cause
Unit wiring
Failed end device
No power to the controller
Diagnostic present
Normal operation
Unit configuration
Requested mode off
Freeze avoidance
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Explanation
The wiring between the controller outputs and the valve(s) must be present and correct for normal valve operation.
Refer to applicable wiring diagram.
The valves must be checked to ensure proper operations.
The controller opens and closes the valves to meet the unit capacity requirements.
Several diagnostics affect valve operation. For detailed information about these diagnostics, refer to
p. 145.
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.
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.
Ensure the valves are correctly configured, using the Tracer
closed (NC) as dictated by the application. For modulating valves, ensure the stroke time is set correctly. Refer
to Table 23, p. 58.
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.
Explanation
The wiring between the controller outputs and the end devices must be present and correct for normal operation.
Refer to applicable wiring diagram.
Check the control contactors or the electric heat element, including any auxiliary safety interlocks, to ensure proper
operation.
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.
Several diagnostics affect DX and electric heat operation. For detailed information about these diagnostics, refer
to Table 86, p. 145.
The controller controls compressor or electric heat outputs as needed to meet the unit capacity requirements.
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.
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.
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.
®
TU service tool, as normally open (NO) or normally
Table 86,
UNT-SVX07J-EN