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3.2.4 Input Power Failure (Load On Battery)
If the utility AC power source fails, or is outside the acceptable range, the battery plant becomes the power
source for the UPS module inverters. The UPS system continues to supply power to the critical load, and also to
the controls of the UPS modules and the SCC.
You can use the Battery Time screen at the UPS modules to monitor the present battery voltage compared to the
shutdown value. The length of time the battery can sustain the load depends on the size of the load and the size
and condition of the battery plant. The battery plant is usually large enough to supply a 100% rated load for 15
minutes.
Alarm messages that indicate battery status are Battery Discharge, Low Battery, and Battery Shutdown. The
voltage limits for these alarms are displayed on the UPS module Alarm Limit Settings screen. These limits were
selected for your installation by Liebert Global Services during initial start-up.
The battery block in the UPS module Monitor/Mimic Display indicates Charge or Discharge and the current in
Amperes. Maximum battery discharge current ranges from 324 amps (for 150 kVA) to 1620 amps (for 750
kVA). Refer to the separate Installation Manual or drawings for specific data on your system.
Figure 51 Input Power Fail (Load on Battery)
BIB
SKRU
MIB
MBB
#2UPS
CB1
#1UPS
CB1
System
Controls
#3UPS
CB1
RIB RIB
RIB BFB
Output
SBB
SBS
I
CB2
II
CB2 CB2
R RR
SCCT
SCCT
(can accommodate up to 6 UPS modules)
To CriticalLoad
Battery
MBD
Battery
MBD
Battery
MBD