Automatic Transfers To Bypass (Overload Condition); Automatic Transfers To Bypass, Ups System Faults - Emerson Liebert NXL series Operation And Maintenance Manual

Liebert NXL UPS
2.6.2

Automatic Transfers to Bypass (Overload Condition)

The UPS system will initiate an automatic load transfer to the bypass line if an overload
condition exceeds the current-versus-time curve of overload capacity or if specified UPS
system faults occur.
Load On Bypass is illustrated in Figure 29.
The Overload Transfer alarm message will initiate an automatic transfer to bypass and the
Load On Bypass message will be displayed. The active event window will display the
Automatic Transfer to Bypass message. Other UPS system faults will initiate an automatic
transfer to bypass followed immediately by the shutdown and isolation of the UPS system.
Refer to 2.6.3 Automatic Transfers to Bypass, UPS System Faults.
NOTE
A load transfer to the bypass line will be completed whenever an automatic transfer to
bypass is initiated. If the OK to Transfer condition is present, the load transfer will be
uninterrupted. If the Static Switch Unable alarm message is present for any reason, the
automatic transfer will be interrupted for 20 to 120 milliseconds. Because of the
reliability of the UPS components, an interrupted load transfer is a very unlikely
occurrence.
2.6.3

Automatic Transfers to Bypass, UPS System Faults

For specified UPS system faults, the control logic will initiate an automatic transfer to
bypass followed immediately by a shutdown and isolation of the UPS system.
The following UPS system faults will initiate an automatic transfer to bypass:
• DC Overvoltage Shutdown
• Hardware Shutdown
• Inverter Fault
• Low-Battery Shutdown
• Output Overvoltage
• Overload Shutdown
• Overtemperature Timeout
• Rectifier Fuse Blown
• Reverse Power
Refer to Table 6 for more information about these alarm messages.
NOTE
A load transfer to the bypass line will be completed whenever an automatic transfer to
bypass is initiated and the bypass line is available. If the OK to Transfer condition is
present, the load transfer will be uninterrupted. If the Static Switch Unable alarm
message is present for any reason, the automatic transfer will be interrupted for 20 to
120 milliseconds. Because of the reliability of the UPS components, an interrupted
load transfer is a very unlikely occurrence.
Some installations may include a Remote Emergency Power Off mode that can be initiated
automatically by a contact closure in the critical load equipment. Refer to 2.3.6 - Remote
Emergency Power Off.
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Operation and Maintenance Manual 250-300-400-800kVA