Liebert 100-1000A user manual Maintenance Bypass, Bypass Procedures for Source

Operating the Liebert STS2 LED Display

14.2.3Maintenance Bypass

The Liebert STS2 is equipped with two key-interlocked, bypass breakers, CB4 and CB5, to allow manual bypass of the switch electronics for either input source in the event of switch failure or for maintenance 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.

In the event of source or switch failure, the unit should be bypassed only to the current input source.

The LED display is used to verify the status of the unit during the bypass procedures. In the unlikely event that the LED 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.

Bypass Procedures for Source 1

To bypass the switch for Source 1:

NOTE

To bypass the Source 1 static transfer switch when Source 2 is presently active, you must first transfer to Source 1. See Manual Transfer / Preferred Source Selection on page 66.

1.Verify that Source 1 is supplying power via the LED display.

•If the LED Display is not available, check the gate driver board LEDs through the slots in the control panel. See Figure 47.

2.Remove the interlock key from CB5 and place it in the CB4 interlock.

3.Open the alternate source input breaker CB2. Verify that CB2 LED is off.

4.Rotate and remove the CB2 interlock key.

5.Insert the key in the CB4 bypass breaker interlock.

6.Rotate the interlock keys in the CB4 bypass breaker interlock to retract the interlock.

7.Close bypass breaker CB4. Verify that CB4 LED is on.

8.Open source input breaker CB1. Verify that CB1 LED is off.

9.Rotate the CB1 interlock key and remove it to lock out the breaker.

10.Secure the key according to your site’s lockout/tagout procedure.

11.Open output breakers CB3 and CB3A (if supplied) to remove power and isolate the static switch from the load.

Verify that CB3 and CB3A LEDs (if supplied) are off.

12.Verify that the output LED is on.

Power is now flowing directly from the source to the load, without passing through the static transfer switch.

To return to normal mode:

1.Verify that the LED for Source 1 is on, indicating that the source is supplying power and is operating within acceptable tolerances.

2.Insert the key in the CB1 breaker interlock.

3.Rotate the key to retract the interlock.

4.Close source input breaker CB1. Verify that CB1 LED is on.

5.Select the SOURCE 1 button in the SOURCE XFERS menu.

6.Close output breakers CB3 and CB3A (if supplied). Verify that CB3 and CB3A LEDs are on.

7.Verify that STS SOURCE 1 and OUTPUT LEDs are on.

8.Open bypass breaker CB4. Verify that CB4 LED is off.

9.Rotate the keys in the CB4 interlock to extend the interlock.

10.Remove the proper key from the CB4 interlock and insert it in the CB2 breaker interlock.

11.Rotate the key to retract the CB2 breaker interlock.

12.Close source input breaker CB2. Verify that CB2 LED is on.

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