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UPS Alarm and Status Messages
49
Controls
Comm Fail
The Controls Communication Failure event
indicates a loss of communications between the
Controls and Human Machine Interface (HMI).
The Controls Communication Failure event is
displayed when the HMI detects a loss of
communication with Controls on the Controller
Area Network (CAN).
An infrequent occurrence that resets immediately
is probably not serious.
If the alarm does not clear, or if the alarm condition
returns, contact your factory-authorized service
provider.
Controls Reset
Required
This alarm means one or more critical settings
have been changed by user during UPS
operation.
The change(s) will not take effect until after a UPS
Controls reset. This operation should only be
performed by an authorized service personnel.
This alarm is cleared after UPS Controls reset.
Press “SILENCE” to silence the audible alarm.
DC Link
Gnd Fault -
The negative DC Bus has a ground fault.
The UPS controls monitor the DC Bus negative
half for a voltage imbalance caused by current
flow to ground. This fault means excessive
ground current is detected.
In normal operation, with the batteries connected,
the most likely cause of a current path to ground
is a leaking battery.
If your system includes an optional Battery
Ground Fault Monitor, check if the Battery Ground
Fault message is present also.
Press “SILENCE” to silence the audible alarm.
Press “RESET” to clear the fault.
Perform a visual inspection of the batteries. Look for
signs of leaking battery acid or excessively
corroded battery terminals.
If there are no visible signs of defective batteries,
open one Battery Breaker. Press “RESET” and see
if the condition clears. If the condition clears, you
have isolated the problem to that battery string.
If the condition will not clear, repeat the test with
each connected battery string.
Once the location is identified, or if the battery string
tests are inconclusive, contact your factory-
authorized service provider.
DC Link
Gnd Fault +
The positive DC Bus has a ground fault.
The UPS controls monitor the DC Bus positive
half for a voltage imbalance caused by current
flow to ground. This fault means excessive
ground current is detected.
In normal operation, with the batteries connected,
the most likely cause of a current path to ground
is a leaking battery.
If your system includes an optional Battery
Ground Fault Monitor, check if the Battery Ground
Fault message is present also.
Press “SILENCE” to silence the audible alarm.
Press “RESET” to clear the fault.
Perform a visual inspection of the batteries. Look for
signs of leaking battery acid or excessively
corroded battery terminals.
If there are no visible signs of defective batteries,
open one Battery Breaker. Press “RESET” and see
if the condition clears. If the condition clears, you
have isolated the problem to that battery string.
If the condition will not clear, repeat the test with
each connected battery string.
Once the location is identified, or if the battery string
tests are inconclusive, contact your factory-
authorized service provider.
EMO Shutdown
An Emergency Module Off (EMO) command has
been detected.
The EMO signal means the front panel EMO
button was pressed. A Remote EMO would
display the “REMO Shutdown” alarm.
In response to an EMO, the UPS transfers to
Bypass and shuts off.
Press “SILENCE” to silence the audible alarm.
Resolve the issue that precipitated the EMO.
For safety, the UPS latches an EPO event. To clear
the latch, press the EMO Reset pushbutton on the
External Interface Board (EIB).
Verify the EMO is cleared by pressing “RESET” and
observing that the EPO alarm in the Active Event
Window is gone.
Restart the UPS by pressing “Startup,” “Manual
Start,” and follow the prompts.
Table 7 Liebert NXL alarm and status messages (continued)
Event Message Event Definition Recommended Action