Liebert NXC 40kVA - Maintenance Bypass Procedures

58 Chapter 7 Parallel System And LBS System
Liebert NXC 30kVA And 40kVA UPS User Manual
1. These procedures result in mains voltage being applied to the UPS output terminals.
2. If any load equipment is connected to the UPS output terminals, check with the user that it is safe to apply power. If the load is
not ready to receive power, disconnect the downstream load switch, and stick a warning label on the connection point of the load.
Use the following procedures to turn on the UPS from a fully powered down condition.
1. Confirm that the total external maintenance bypass switches are disconnected. Open the front door of each UPS in
turn, ensure that the internal maintenance bypass switch Q3 is disconnected and switch Q6 is closed, while the input
cables and copper bars are reliably connected, and the parallel cables are firmly connected.
Warning
All operations relating to disconnect or close the switch of maintenance bypass switch shall be finished within three seconds, in
case of misreporting as faults.
2. Close the total bypass input switches.
3. Close the bypass input switch Q2, rectifier input switch Q1, output switch Q5 and all external output isolating
switches (if any) of each UPS in turn.
At the moment, the system is power on, and the startup screen pops up. Refer to 4.2.1 Start Screen.
About 25 seconds later, confirm that the LCD shows the rectifier power supply and the bypass power supply are
normal; if not, check whether the switches Q1 and Q2 are closed and the parallel cables of each UPS are connected
reliably. Then the rectifier starts up and the alarm indicator (red) is on, at the same time, the bypass static switch is
closed. About 30 seconds later, the alarm indicator (red) is flashing, then the rectifier startup is finished. After all the
rectifiers startup of the UPSs is finished, the alarm indicators (red) are flashing.
4. For each UPS, press the ON key for two seconds. The inverter starts up, and the inverter indicator (green) of each
UPS is flashing. After all the UPS inverter indicators turn solid green, the whole UPS system will power the load.
7.3.2 Maintenance Bypass Procedures
Warning
If the UPS system is composed of more than 2 parallel UPS modules, and the load capacity exceeds the single module capacity,
do not use the internal maintenance bypass switch.
This operation will make the load transfer from UPS power supply protection state to direct connection with AC input
bypass state.
Caution: power supply interruption danger of the load
Before performing this procedure, you should check the LED information first, and make sure the bypass is normal and inverter
synchronized. Otherwise, it may result in the load power interruption for a while.
1. Press the OFF key of each UPS in turn for two seconds. The inverter indicators are off and the buzzer alarms. The
load transfers to the static bypass, and the inverter shuts down. At last, all UPSs are transferred to load supply mode.
Note
Press the ALARM CLEAR button can silence the alarm, but the alarm message of the the LCD does not disappear until the alarm
status is cleared.
2. Close the UPS external total maintenance bypass switches, and do not close the internal maintenance bypass
switch Q3 of each UPS.
3. At this moment, the external total maintenance bypass should be parallel connected with each UPS’s static switch.
4. At this moment, the LCD of each UPS displays ‘Maint. sw. closed’.
5. Disconnect the output switch Q5 and neutral line switch Q6 of each UPS in turn, and the maintenance bypass can
supply power to the load.
Caution