136
BCX-SVX002A-EN
Valves with UC400-B Controller
Table 56. 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 .
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. For modulating valves, ensure the stroke time is set correctly. Refer to Table 19, p. 40.
Table 57. 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 .
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. For modulating valves, ensure the stroke time is set correctly. Refer to Table 19, p. 40.
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.
DX Coils or Electric Heat with UC400-B Controller
Table 58. 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.
Diagnostics and Troubleshooting
To Next Page
Loading...
