Emerson 250-400kVA Manuel D’Utilisation

The UPS is designed for unattended operation, but does require some common-sense maintenance.

• Keep good records—Troubleshooting is easier if you have historical background.
• Keep it clean—Maintain the UPS free of dust and any moisture.
• Keep it cool—Battery systems must be kept in the range of 72-77°F (22-26°C) in order to meet 

design specifications for capacity and longevity.
The UPS will reliably meet all performance specifications and design life at temperatures up to 

104°F (40°C) and can be slightly derated for operation at even higher temperatures or higher alti-

tudes. However, performance and longevity will be optimized when the UPS is operated at the 

same temperature as the batteries. Contact your local Liebert sales representative or call 

1-800-LIEBERT for further details.

• Keep connections tight—Tighten all connections at installation and at least annually thereaf-

ter. (See torque requirements, Table 4.)

• Keep it inspected—Periodically inspect external upstream and downstream circuit breakers to 

assure that the trip current settings are correct.
Become familiar with typical ambient conditions surrounding equipment so that abnormal condi-

tions may be more quickly recognized. Know what typical meter readings are and where adjust-

able settings should be.

Set up a maintenance log to record scheduled checks and any abnormal conditions.
The log should have space for all metered parameter indications including phase readings, alarm 

messages, UPS mode of operation, air filter replacement date and observation notes. A second log 

should be maintained for the battery module as directed by the battery manufacturer.
A periodic walk-through inspection of the UPS and battery rooms is advised to check for visible and 

audible indications of problems. Log the inspection, metered parameter indications and any discrep-

ancies.

The air filters must be inspected and serviced on a regular schedule. The period between inspections 

will depend upon environmental conditions. Under normal conditions, the air filters will require 

cleaning or replacement approximately every two months. Abnormal or dusty conditions will require 

more-frequent cleaning and replacement of air filters. Inspect installations in new buildings more 

often, then extend the inspection period as experience dictates.
All NXL models have a replaceable air filter located inside the front doors. These filters can be 

changed while the UPS is in operation.