Filter
Top Products
Operation
Liebert
®
NX
™
16
2.4.2 Input Power Failure—Load on DC Source
If the utility AC power source fails or is outside the acceptable range, the DC source becomes the
power source for the UPS module inverters. The UPS continues to supply power to the critical load
and also to the UPS controls.
Use the Battery Time screen at the UPS modules to monitor the present DC source voltage compared
to the shutdown value. The time the DC source can sustain the load depends on the size of the load
and the size and condition of the DC source.
The battery block in the UPS module Monitor/Mimic Display indicates Charge or Discharge and the
current in amperes.
Figure 16 Input power fail, load on DC source
2.4.3 Off DC Source
The DC source can be disconnected from the UPS, if required for maintenance, by opening the module
battery disconnect (MBD) circuit breaker. In this situation, the UPS module will continue to supply
conditioned power to the critical load, but if input power fails, the UPS system cannot supply power to
the load.
NOTICE
Risk of unexpected power loss to the connected load. Can cause equipment damage.
When the UPS is operating with the module battery disconnect (MBD) circuit breaker(s)
open, the critical load is not protected from loss of the utility source power.
Figure 17 Load on UPS, DC source not available
DC
Bus
BFB
UPS Module
To DC Supply
Module Rectifier
AC Input
Module Bypass
AC Input
UPS Output
Critical
Load
BFB
UPS Module
To DC Supply
Module Rectifier
AC Input
Module Bypass
AC Input
UPS Output
Critical
Load
DC
Bus