Emerson Liebert NX 50 and 60 Hz - Manual (Page 112)

Operator Control Panel and Display
100
System Over load
The UPS parallel system is confirmed to overload when the total load arises above
105% nominal rating for the set basic number of UPSs. The alarm automatically
resets once the overload condition is removed.
1. Confirm that the alarm is true by checking the system load percent indicated on
the LCD panel to determine which phase is being overloaded.
2. If the alarm is true, measure the actual output current to verify that the indications
are valid.
Disconnect unnecessary load and ensure the safety. In a parallel system, a severe
load sharing error can also leads to the alarm.
Unit Over load Timeout
The UPS is confirmed to overload and the overload times out.
Note 1: the highest loaded phase will indicate overload timing-out first.
Note 2: When the timer is active then alarm “unit overload” should also be active as
the load is above nominal.
Note 3: When the timer has expired, the inverter Static Switch is opened and the
load transferred to bypass. The inverter shutdown and will restart after 10 seconds.
Note 4: If the load decreases lower than 95% after 5 minutes, the system will
transfer back to inverter mode.
Confirm that the alarm is genuine by checking the load percent indicated on the
LCD. If an overload is indicated then check the load, and investigate any additional
load connected prior to the alarm (if applicable).
Byp. Abnormal Shutdown Both bypass and inverter voltages unavailable. Load interruption
Inverter Over Current Inverter Pulse Width Modulation module overloaded.
Bypass Phase Reversed
The phase sequence direction of bypass voltage is reversed.
Normally, the phase of phase B lags 120 degrees behind phase A, and the phase of
phase C lags 120 degrees behind phase B.
Verify that the phase rotation of the bypass supply presented to the UPS is correct,
and rectify it if it is found to be in error
Load Impact Transfer
A transfer to bypass occurred due to a large step load. The UPS should recover
automatically. Turn on connected equipment in sequential order to reduce the step
loading of the inverter.
Transfer Time-out
The load is on bypass power due to excessive number of transfers that occurred
within the last hour.
The UPS will recover automatically and will transfer the load back to inverter power
within an hour.
Load Sharing Fault UPS modules within a parallel system are not sharing the load current equally.
DC Bus Abnormal
DC input voltage to inverter beyond limits. Inverter shuts down. Load transfers to
bypass.
System Transfer
The whole paralleled UPS system transferred to bypass at the same time. This
message will appear on the UPS which passive transfer to bypass
Parallel Board Fault
Malfunction of the paralleling control circuits of this UPS module. Can cause
“System Transfer” to bypass.
DC Bus Over Voltage
Rectifier, inverter and battery converter were shutdown because DC bus voltage is
too high. Check whether there is a fault in rectifier side. If no, then check whether
overload occurs. Restart the inverter after resetting the fault
Parallel Connect Fault
The parallel cables are not connected correctly in a parallel system.
Reset the fault by pressing the “fault clear” button, then restart the inverter by
pressing the “inverter on” button.
Bypass Over Current
Bypass current is over limit above 135% rating. The UPS just alarms and does
nothing.
LBS Active
Load Bus Synchronisation is active. The UPS is acting as an LBS master or slave in
a dual bus configuration.
Setting Save Error History records not saved. (Reserved)
Mains Neutral Lost AC Input mains reference neutral not detected.
Protocol version clash
Firmware incompatibility between Monitor Board and Digital Signal Processor
Board.
Battery ground fault Battery leakage to ground detected (option)
Inv. turned On Manually Manual Turn On via front panel
Table 23 UPS messages
Message Description / Suggested Action (if any)