Emerson Liebert Static Transfer Switch - Manual (Page 75)

Operating Instructions for the Touch Screen Interface
67
To manually select the preferred source:
1. Verify that the input breakers CB1 and CB2 are closed.
2. Select SOURCE XFERS from the menu bar.
The Select Preferred Source screen is displayed in the Event Display.
3. Check the Mimic to verify that Source 1 and Source 2 input voltages are correct.
4. Select SOURCE 1 or SOURCE 2 as your preferred source.
When conditions are correct, the switch transfers the load to the alternate source by selecting the
alternate source as the preferred source.
This source is now monitored as the preferred source throughout the various configurations set up
through the touch screen.
5. Verify that the correct source is designated as the preferred source and that the input source
changes to the desired source.
The Mimic is updated to indicate the new preferred source. The source is now highlighted with blue
and that source is labeled as the preferred source.
If the Transfer Inhibit message is displayed, check for alarm messages on the Active Status window.
Correct alarm conditions before attempting a source transfer.
10.3 Enabling Remote Source Selection
If your system is equipped with the optional Remote Source Selection option, it must be enabled.
If you your system includes the Color Graphical Display:
1. Select CONFIG from the menu bar.
2. Select SYSTEM SETTINGS from the Configuration menu.
3. Select SYSTEM OPTIONS from the System Settings menu.
4. Select YES for the REMOTE SOURCE SELECT choice.
If your system contains the LED display or you are configuring the system from the RS-232 port, see
12.1 - Using the RS-232 Port on page 76 for instructions on using the that interface.
10.4 Maintenance Bypass
The Liebert STS2 is equipped with two key-interlocked, bypass breakers, CB4 and CB5, to allow man-
ual bypass of the switch electronics for either input source in the event of switch failure or for mainte-
nance of the switch. Refer to the static transfer switch one-line diagram (Figure 3). While operating
on maintenance bypass, all voltages are removed from the Liebert STS2 electronics to facilitate safe
repair, without de-energizing the load using a make-before-break switching sequence.
However, the unit can be bypassed using a make-before-break switching sequence only to the same
source to which that the switch is connected, as indicated by the highlighted static transfer switch box
on the Mimic screen.
In the event of source or switch failure, the unit should be bypassed only to the current input source.
For convenience, instructions for the bypass procedure can be displayed on the touch screen by select-
ing the BYP. PROC option from the menu bar.
The Mimic is used to verify the status of the unit during the bypass procedures. In the unlikely event
that the Color Graphical Display is not available, open the front door and look through the slots in the
control door. If you can see green LEDs on the gate driver board through that slot, then the unit is
connected to the source referenced on the label below that slot. See Figure 47.
NOTE
The preferred source may also be changed via the optional Remote Source Selection option,
thereby initiating a transfer remotely.