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17 Liebert
®
NX
™
2.4.4 Remote Emergency Power Off
The Remote Emergency Power Off control is a user-provided switch located remotely from the UPS
system. It usually is installed in the same room as the critical load equipment. This mode can also be
initiated by an automatic contact closure in the same external circuit as the manually operated
switch.
When the Remote Emergency Power Off switch is operated, the UPS will shut down and open bypass
circuit breakers. All power through the UPS is removed from the load. Typically, the REPO circuit
also opens the circuit breakers that provide power to the bypass lines and the UPS controls. Refer to
2.5.8 - Shut Down-Single Module UPS System.
Figure 18 Remote Emergency Power Off
2.5 Manual Operations—All Systems
The Liebert NX UPS is designed to function while unattended by an operator. The system control
logic automatically handles many important functions, as explained in 2.16 - Automatic Operations.
Other procedures must be performed manually.
Manual procedures available to the operator include startup, load transfers and shutdowns. These
procedures are performed by using the touchscreen and some manually operated circuit breakers and
switches.
This section lists typical step-by-step instructions.
• Startup—Including initial startup, recovering from input power failure, recovering from DC
source shutdown and recovering from shutdowns for emergencies or maintenance.
• Load Transfers-Including transfers from UPS to bypass and retransfers from bypass to the UPS
system.
• Maintenance Bypass Load Transfers—Including transfers from internal bypass to maintenance
bypass and transfers from maintenance bypass to internal bypass.
• Shutdowns—Including module shutdowns for maintenance and emergency shutdowns.
NOTE
The following procedure assumes that the UPS installation inspection and initial startup have
been performed by Emerson Network Power
®
Liebert Services. An Emerson-authorized
representative must perform the initial system startup to ensure proper system operation.
DC
Bus
BFB
UPS Module
BFB
UPS Module
To DC Supply
Module Rectifier
AC Input
Module Bypass
AC Input
UPS Output
Critical
Load
DC
Bus