6 Parallel System and LBS System
This chapter gives details on the installation of parallel system and LBS system.
6.1 General
The UPS parallel system consists of up to two single UPS of the same model. The parallel system does not require a
centralized bypass. Instead, each UPS bypass shares the load when the system is transferred to the mains bypass supply.
From a power viewpoint, each module is internally identical to the single module configuration. A parallel system requires inter
module control signals to manage the load sharing, synchronizing and bypass switching. The control signals are connected
through the parallel cables, which are multi way ribbon cables connected between the units of the system to form a ring.
When two modules are to be connected in parallel, it is recommended that inductor should be inserted in the bypass line. This
can be installed internal to the UPS as an option.
6.2 Requirements
A UPS system comprising of multiple parallel connected UPSs is equivalent to a large UPS system. Nevertheless, it provides
increased system reliability. To ensure equal utilization of all UPSs and compliance with relevant wiring regulations, the
following requirements must be met:
• All single UPSs must have the same capacity.
• The bypass input power and the rectifier input power must be connected to the same neutral line input terminal.
• If a residual current detector (RCD) is required, it must be set correctly and installed before the same neutral line
input terminal, or it must monitor the protective earth current of the system. Refer to 'Warning: high leakage
current of Safety Precautions before Contents.
• The outputs of all single UPSs must be connected to the same output bus.
6.3 System Installation Procedures
The basic installation procedure of a parallel system comprising two or more UPS modules is the same as that of single
module system. This section only introduces the installation procedures specific to the parallel system. The installation of a
parallel UPS should follow the installation procedure for a single UPS module with the additional requirements detailed in this
section.
WARNING! To achieve normal operation of the parallel system, Vertiv service personnel must execute the
CAN resistance operation. Failure to do so could result in system fault.
6.3.1 Preliminary checks
Ensure that correct parallel cable option has been selected, and that the module ratings, model, and software and hardware
releases are consistent.
WARNING! To achieve coordinated operation of the modules in the parallel system, it is required to configure
each module separately using Vertiv setting software. This must be done by Vertiv service personnel.
6 Parallel System and LBS System Proprietary and Confidential ©2023 Vertiv Group Corp. 47
Vertiv™ Liebert® EXS Installer/User Guide
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