Operating Instructions

10.4Maintenance Bypass

The STS2/PDU 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 Figure 3. While operating on maintenance bypass, all voltages are removed from the static transfer switch 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 61.

Figure 61 Gate board viewing slot locations

Touch Screen

Viewing Slot for the Source 2 Gate Drive Board

Viewing Slot for the Source 1 Gate Drive Board

Green LEDS on the Gate Driver Board are viewable through this slot indicate that the STS is on

Source 1

GREEN LEDS ON THE GATE DRIVER BOARD ARE VIEW-

ABLE THROUGH THIS SLOT INDI- CATE THAT THE STS IS ON SOURCE 2

GREEN LEDS ON THE GATE DRIVER BOARD ARE VIEW-

ABLE THROUGH THIS SLOT INDICATE THAT THE STS IS ON SOURCE 1

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Liebert PDUTM, STS2 manual Maintenance Bypass, Gate board viewing slot locations