Vertiv™ | Liebert
®
STS2
™
100-1000A, 50/60Hz User Manual | Rev. 12 | 11/2017 62
10.1 Normal System Startup
1. Ensure that all Liebert STS2 breakers—CB1, CB2, CB3, CB3A (if supplied), CB4, and CB5—are in the OFF position.
a. Ensure that the key interlocks for CB1 and CB2 have their bolts retracted.
b. Ensure that the key interlocks for CB4 and CB5 have their bolts extended, thus preventing CB4 or CB5 from being
turned ON.
2. Source/input power should be applied to both Liebert STS2 inputs.
The touchscreen control panel should become active and operate properly when at least one of the inputs is energized is
closed.
3. Verify that nominal input voltages are applied to both inputs (Source 1 and Source 2).
The input voltages, selected preferred source, breaker and switch status, and alarms are indicated on the Mimic screen.
4. Close CB1.
5. Verify that Source 1 voltages are nominal and CB1 breaker status is correctly indicated on the Monitor/Mimic screen.
6. Close CB2.
7. Verify that Source 2 voltages are nominal and CB2 breaker status is correctly indicated on the Mimic screen.
8. Verify that boxes for the preferred source and corresponding static transfer switch are highlighted on the Mimic screen,
indicating which side of the Liebert STS2 is on.
9. Close Output Breaker CB3 (and CB3A in redundant output configurations).
10. Verify CB3, the Output box, and the Load box are highlighted, indicating that CB3 is closed and the Output and Load are
energized.
11. Press the RESET button on the touchscreen to reset any previous alarms.
12. Verify in the Event Display and the Mimic that there are no active alarms.
If any active alarms are displayed, refer to 11.0 - Alarm and Faults for a description of the alarms and possible causes. All
active alarm conditions should be corrected before proceeding.
13. Turn On the load equipment following the load equipment manufacturer’s recommendations.
10.2 Manual Transfer / Preferred Source Selection
The Source Transfer option (Source Xfers) in the touchscreen menu allows you to select a preferred source.
Transfers are only permitted when the voltage and current are within their proper operating range and the
sources are synchronized on units without Optimized Transfer. Units with the Optimized Transfer option do not
require the sources to be synchronized to make a manual transfer. The Source Transfer screen indicates the
synchronization between the two sources, while the voltage and frequency are displayed on the Mimic. See
Figure 42. Transfer is inhibited if the deviation exceeds the parameter set in the Source Set Points. See User
Settings on page 86
If your system contains the LED front panel instead of the LCD touchscreen, refer to 14.2.2 - Manual Transfer /
Preferred Source Selection for instructions on this procedure.
NOTE
If your Liebert STS2 is connected to a PDU with a Wye configuration, enable the Wye Output Transformer before
starting the system. This setting can be made from the touchscreen. Refer to Wye Output Transformer on
page 95 for instructions.
NOTE
For redundant output switch units, CB3 descriptions apply to CB3 and CB3A.
NOTE
If one source will be de-energized for an extended period (hours or days), set the unit to bypass mode for the
remaining source. Without using bypass, if a failure occurs in the switch components for remaining source, the
Liebert STS2 does not have a second source to switch to and the load would not receive power. See
Maintenance Bypass on page 64 for bypass instructions.
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