One Module Off-Line; Figure 57 One Module Off-Line, Load On Ups - Liebert 1000kVA Operation & Maintenance Manual

3.3.5

One Module Off-Line

A multi-module UPS system can be supplied with a back-up (redundant) UPS module, which is the
typical configuration. A redundant system includes one more module than the number required to
supply the critical load. A redundant system operates in the redundant mode if all modules are ON
LINE. Note that the UPS system can also operate in the redundant mode with one module OFF
LINE if the critical load is reduced so that not all ON LINE modules are required. The UPS modules
share the load and the critical load will remain on the UPS system if any one of the modules is discon-
nected (goes OFF LINE) for maintenance or because of an internal fault.
The system control logic monitors the connected critical load and the number of UPS modules ON
LINE. If the UPS system is operating in the redundant mode, the REDUNDANT status message
will be displayed at the System Control Cabinet (SCC). If the UPS system is operating in the non-
redundant mode (redundant module is OFF LINE or was not included in the system configuration),
the NON-REDUNDANT status message is displayed at the SCC. In the Non-Redundant mode, the
critical load will be transferred to bypass if any UPS module goes OFF LINE and you must transfer
the load to bypass in order to perform maintenance on any UPS module.

Figure 57 One module off-line, load on UPS

UPS
CB1
CB2
MBD
Battery
RIB RIB RIB RIB
#3 UPS #2
CB1
R R
I I
CB2
MBD
Battery Battery
RIB RIB
UPS #1
CB1
SBS
R
SBB
I
System
CB2
Controls
Output
SCCT
MBD
(can accommodate up to 6 UPS modules)
78
Operation
BFB BFB
BIB
MBB
SKRU
MIB
To Critical Load
SCCT