Emerson Liebert NXr, User Manual

Chapter 5  Operator Control And Display Panel      39 

NXr UPS Module And Parallel System 30kVA ~ 200kVA    User Manual 

Alarm Explanation 

tolerance through the service configuration software 

Inverter Asynchronous 

This alarm is triggered by an inverter software routine when the inverter and bypass waveforms are 
misaligned by more than six degrees in phase. The amplitude threshold is fixed for ±10% rating. This 
alarm resets automatically once the condition is no longer true. 
1. First check if the alarm Bypass unable to trace or Bypass abnormal occurs. If so, solve it first. 
2. Verify the waveform of the bypass voltage 

Inverter fault 

Inverter output voltage outside specifications. Load transfers to bypass. The faulty power module will 
shut down and open output relay, and the remaining power

modules will remain online 

Fan fault 

At least one of the cooling fans failed 

Bypass STS Fail   

At least one of the STSs at the bypass side is open or shorted. This fault is locked until power-off 

Output Fuse Fail 

At least one of the inverter output fuses is blown. The inverter shuts down, and the load transfers to 
bypass if the remaining power modules are insufficient to support the load 

Control power 1 fail 

The UPS is operating but the redundant control power is abnormal or not available 

Unit Over load 

This alarm appears when the load arises above 105% of the nominal rating. The alarm automatically 
resets once the overload condition is removed. 
1. Find out if this alarm is true by checking which phase has overload through the load (%) displayed 
on the LCD. 
2. If this alarm is true, measure the actual output current to confirm if the displayed value is correct.   
3. If yes, disconnect the non-critical load.   
In a parallel system, this alarm will be triggered if the load is severely unbalanced 

System Over load 

This alarm appears when the total load rises above 105% of the nominal rating of the parallel 
system.The alarm automatically resets once the overload condition is removed.   
1. Find out if this alarm is true by checking which phase of which unit has overload through the load (%) 
displayed on the LCD. 
2. If this alarm is true, measure the actual output current to confirm if the displayed value is correct. 
3. If yes, disconnect the non-critical load. 
This alarm will be triggered if the load is severely unbalanced 

Unit Over load Timeout

The UPS overload status continues and the overload times out. 
Note that: 
1. T

he highest loaded phase will indicate overload time-out first.

2. When the timer is active, then the alarm Unit Over load should also be active as the load is above 
the nominal rating. 
3. When the time has expired, the load transfers to static bypass. The inverter shuts down and will 
restart after 10 seconds. 
4. If the load decreases to lower than 95%, after five minutes, the system will transfer back to the 
inverter.Check the load (%) displayed on the LCD to confirm if this alarm is true. If the LCD tells that 
overload happens, then check the actual load and confirm if the UPS has overload before the alarm 
happens 

Byp. Abnormal Shutdown  Both the bypass and inverter voltages are abnormal, and the output is off 
Inverter Over Current 

The inverter has overcurrent fault 

Bypass Phase Reversed 

The phase rotation of the bypass voltage is reverwed. Normally, phase B lags 120 degrees behind 
phase A, and phase C lags 120 degrees behind phase B. 
Check that the phase rotation of the UPS bypass supply is correct 

Load Impact Transfer 

A transfer to bypass occurred due to a large step load. The UPS can recover automatically. Turn on the 
load equipment in stages to reduce the load impact on the inverter 

Transfer Time-out 

The load remains on bypass power owing to excessive number of transfers that occurred within the last 
hour. The UPS can recover automatically and will transfer the load back to inverter power within an 
hour 

Load Sharing Fault 

The UPSs in a parallel system are not sharing the load current correctly 

DC Bus Abnormal 

The DC bus voltage is abnormal and results in inverter shutdown. The load transfers to bypass 

System Transfer 

All UPSs in the parallel system transfer to bypass at the same time when one of them needs to transfer 
to bypass. This message appears on the LCD of the UPS with passive transfer to bypass 

DC Bus Over Voltage 

The rectifier, inverter and battery converter shut down because the DC bus voltage is too high.. Check 
if the rectifier has any fault. If no, check if an overload has occurred. Restart the inverter after the fault 
is cleared 

Bypass Over Current 

The bypass current is above 135% of the rated current. The UPS alarms but has no action 

LBS Active 

The LBS setting is active. The UPS is acting as an LBS master or slave in a dual bus configuration 

Mains Neutral Lost 

The neutral line of the AC input mains is not detected 

Battery ground fault 

The battery ground fault option has detected a battery ground fault. Contact the local customer service 
center of Emerson to inspect the battery installation