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Table 9 Alarm messages - meaning and corrective action
Alarm
Message
Cabinet
Location
Special
Functions Meaning and Corrective Action
AC INPUT
Input Fail MMU —
The rectifier input line voltage is outside of specified limits or the input
circuit breaker is opened while the battery circuit breaker remains closed.
The battery supplies power to the critical load through the UPS inverter.
Provide an alternate source of AC power or prepare to initiate critical load
procedures when battery reserve time is low.
DC BUS
DC Ground Fault MMU D, L, S
Either the positive (+) or negative (-) DC bus is grounded. No transfer or
shutdown occurs.
Contact Liebert Global Services at once. Do not attempt to locate or repair
the fault.
DC Capacitor
Fuse Blown
MMU D, F, S
At least one DC capacitor fuse has opened. The UPS module is taken off-
line and the input and battery circuit breakers trip open.
Contact Liebert Global Services at once. Do not attempt to reset the
circuit breakers.
Battery CB Open MMU D, R, S
The module battery circuit breaker (MBD) is open. This circuit breaker can
be opened either manually or automatically in a UPS shutdown
procedure. If the UPS is operating with this breaker open, the critical
load is not protected from loss of the utility source power.
After AC power is restored and the DC bus is at 100% operating voltage,
manually close the battery circuit breaker so the rectifier can charge the
battery.
Battery
Discharging
MMU D, R, S
The battery is discharging. This occurs whenever the battery supplies
power to the load for more than 5 seconds because of input power failure,
a rectifier problem or an overload condition. If the input power or a source
of auxiliary power is restored to the UPS module, the UPS automatically
returns to normal operation.
Watch the battery voltage carefully. Reduce the load (begin controlled
shutdown) to extend the battery back-up time. Reset the UPS alarms after
the input power is restored. The message clears after 30 seconds.
Low Battery
Warning
MMU D, R, S
The battery voltage is approaching the minimum discharge voltage
(approximately 5 minutes remaining).
Complete the controlled shutdown of the critical load. Reset the alarms if
the input power is restored before shutdown.
Low Battery
Shutdown
MMU D, F, L, S
The battery voltage has decreased to the minimum discharge value. The
UPS module is taken off-line (no power to the critical load) and the
battery and input circuit breakers trip open.
Perform a UPS system start-up procedure when AC power becomes
available.
DC Overvoltage
Shutdown
MMU D, F, L, S
The maximum preset value of the DC Bus voltage has been exceeded.
The UPS module is taken off-line and the input and battery circuit
breakers trip open.
Contact Liebert Global Services at once. A fault may have occurred within
the UPS. Do not attempt to reset the circuit breaker.
BYPASS
Load On Bypass SCC D
The critical load is being supplied power from the bypass line and is
therefore exposed to utility power disturbances.
Clear all of the alarms before attempting to retransfer the load from the
bypass line to the UPS.
Table 9 Abbreviations
D = auto-dial; L = latches
E = logs only; R = remote
F = freezes; S = summary
D* = auto-dial initiated by Auto Transfer to Bypass if load is on UPS when alarm occurs
D# = auto-dial initiated through Module N (1-6) off-line