Emerson 10-30kVA Manuel D’Utilisation

The Load Bus Synchronizer (LBS) keeps the output of two independent UPS systems or parallel UPS 

systems in synchronization even when the systems are operating in different modes and even when 

either or both systems are operating on batteries. When the LBS is used, one UPS system is desig-

nated as master, the other as slave.
The LBS option is typically used with dual-corded equipment or with either the Liebert SmartSwitch 

or Static Transfer Switch (STS) for single-corded equipment.

The DBS operates under the following conditions:

• Both master and slave are on inverter

(either system may be on inverter through the rectifier or on inverter through the batteries)

• Master on inverter, and slave on bypass
• Master on bypass, and slave on inverter
• Master and slave on bypass IF the bypass source is the same for both systems

For NX-to-NX dual bus configuration, only one optional LBS cable is required, the built-in LBS will 

operate normally without extra LBS control box or interface box. The LBS port is X4 on the parallel 

board (M3). The parallel board is on the interior of the NX, above and left of the power electronics; see 

Figure 30.
An optional, 9-pin LBS cable is used to connect two UPS systems through each system’s DB9 port on 

its parallel board. For two parallel systems, the LBS cable can be mounted between any two units 

belonging to different parallel systems. For information about the LBS kit or to order the optional 

equipment, see your local Liebert representative.
The LBS cable is connected as illustrated in Figure 21.

The LBS function is activated with configuration software; when the LBS takes effect, the graphic 

LCD will display “LBS active.”

The parallel board is on the 
interior of the NX, above and 
left of the power electronics; 
see Figure 30