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70 Operation
Table 1 Alarm Messages - Meaning and Corrective Action
Alarm
Message
Cabinet
Location
Special
Functions
Meaning and
Corrective Action in Brackets [ ]
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.
DC BUS
DC Ground Fault MMU L, S Either the positive (+) or negative (-) DC bus is grounded. Notransfer
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 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 breakerso the rectifier can
charge the battery.]
Battery
Discharging
MMU 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 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 Over-Voltage
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, E, F 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 1 Abbreviations
D = auto-dial; L = latches
E = reports 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