Emerson Liebert Static Transfer Switch - Manual (Page 114)

Operating the Liebert STS2 LED Display
106
5. Close CB2.
The green LED for CB2 turns on.
6. Verify that the preferred source LED (green) (LED_PREFx) is lit for the source that you want the
switch to be using.
7. Verify that the green LED for the corresponding SCR (Liebert STS1 or Liebert STS2) is lit,
indicating that the SCR is closed.
8. Close Output Breaker CB3 (and CB3A in a redundant output configuration).
9. Verify the CB3 LED is lit, indicating that CB3 is closed and the output and load are energized.
• In a redundant output configuration, verify the CB3A LED is lit, indicating that CB3A is
closed and the output and load are energized
10. Press the Reset and Silence buttons simultaneously to reset any previous alarms.
11. Verify that no red or yellow (amber) LEDs are lit indicating an active alarm, transfer is inhibited
or a bypass circuit breaker is closed.
If the alarm LED remains lit, check the PC terminal to identify the alarm. 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.
12. If the unit is supplied with an output distribution cabinet, close output breakers as required.
13. Turn on the load equipment following the load equipment manufacturer’s recommendations.
14.2.2 Manual Transfer / Preferred Source Selection
The preferred source buttons allow you to change the preferred source. Transfers are only permitted
when the voltage and current are within their proper operating range and the sources are synchro-
nized. Transfer is inhibited if the deviation exceeds the parameter set in the Source Set Points.
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 14.2.3 - Maintenance Bypass on page 108 for
bypass instructions.