Caution Issuance for Eaton 9390: Check Power Supply Alarm
We have learned the Check Power Supply alarm in an Eaton 9390 needs special attention. The UPS has multiple (4 in the specific case we learned of this problem or risk) power supplies that are to provide redundancy in case of failure. Redundancy is provided only if the unit is already running. If the unit input power is interrupted and the unit shuts down for any reason (battery time exceeded, purposeful shutdown or if on bypass when shut off) the UPS will not come back on EVEN IN BYPASS MODE! This means the load is dead in the water until the UPS is repaired. If an external maintenance bypass is not part of the system configuration, the load cannot be powered even if utility power is present. In short if there is a Check Power Supply alarm or Power Supply Failure do not shut off an Eaton 9390.