Emerson NX User Manual

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.

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 

®

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