Emerson NX manual Detecting Trouble, Reporting a Problem, Items to check include

Maintenance

4.5Detecting Trouble

It is important that the operator check the instrument readings if abnormal equipment performance is suspected. Any metered value that differs appreciably from normal could mean an impending malfunction and should be investigated.

4.5.1Items to check include:

•If the UPS has not operated on battery power during the last 10 hours, the batteries should require little charging current. Battery mimic should indicate normal DC voltage with the battery charge current no more than 1% of maximum discharge current.

•Input current on each phase should be within 10% of the average input current.

•Alarm messages indicate malfunction or impending malfunction. A daily check of the Display Screen will help to provide an early detection of problems.

•Tracing a problem to a particular section is facilitated by alarm messages and the metered parameter indications.

NOTICE

Risk of recurring problem. Can cause degraded performance and equipment damage.

If the UPS system has an open fuse, the cause should be determined before replacing the fuse. If the cause is not corrected, it could recur. Contact Liebert Services for assistance.

4.6Reporting a Problem

If a problem occurs within the UPS, review all alarm messages along with other pertinent data. Contact Liebert Services at 1-800-LIEBERT to report a problem or to request assistance.

4.7Upstream Feeder Circuit Breaker Setting Inspections

During normal UPS operations, short-term overload current demand from the bypass source may reach 10 times the UPS output current rating. This overload current demand may be caused by the magnetizing inrush current of one or more downstream transformers (i.e., power distribution units) or faults on downstream branch circuits. The instantaneous trip point(s) of the upstream bypass feeder breaker(s) must be set to support these temporary overloads. The magnitude of short-term overload bypass current demand is typically six to eight times the UPS current rating, but must be determined by analysis on a per-site basis. This analysis, generally known as an End-to-End Fault Coordination Study, must be done by a registered professional engineer experienced in this activity and familiar with local codes and related requirements.

Liebert strongly recommends periodic inspections of the bypass feeder breaker instantaneous trip settings, as well as the module input (rectifier) feeder breaker trip settings, to ensure that they are correct. For a variety of reasons, although typically during circuit breaker maintenance procedures by others, trip settings have been known to be inadvertently left improperly set. Correct trip setting of these circuit breakers is most important to achieving high-availability from your Liebert UPS system.

For further information regarding proper trip settings for your feeder breakers, call 1-800-LIEBERT.

NOTE

The instantaneous trip setting of the breaker feeding the UPS bypass input should be high enough to accommodate short-duration overloads. The bypass static switch power path inside the UPS can draw up to 10 times the system’s rated current for up to three cycles.

NOTE

While Emerson can provide typical guidelines, the responsibility for the proper breaker trip settings outside the Emerson-manufactured UPS equipment resides with the owner. Contact Liebert Services at 1-800-LIEBERT for further information.

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