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DELTA MCS-1800 3U Power Shelf
Installation, Operations and
Maintenance Manual
8-3
breaker, turn it on. If necessary replace with the correct size fuse.
If the fuse/circuit breaker continues to trip, perform the following steps:
1. Check the DC branch load to ensure tat the fuse/ circuit breaker is the correct size.
2. If the branch load exceeds the fuse/circuit breaker rating, the device must be changed to a higher rating.
3. Install a fuse/circuit breaker with a higher rating.
Warning: Ensure that the device rating does not exceed the branch load wire capacity. If the device
rating is higher than the branch load wire rating, the branch load wire must be changed to a
larger wire. Failure to protect the branch load wire may result in overheating and fire.
8.7 Alarm Unit Fail
8.7.1 Description
During an ALU fail condition, the ALU fail and status LEDs are extinguished, and all alarm contacts open.
During an ALU failure, the rectifiers status changes from equalize to float or remains in the float condition.
The LVBD does not open during an ALU failure.
8.7.2 Troubleshooting
To troubleshoot the ALU fail condition, perform the following steps:
1. Check the input fuse located on the rear of the ALU. Replace if blown.
2. Check the DC input connectors for proper connections.
3. Replace with a spare and send the faulty unit to Delta for repair.
8.8 Rectifier Fail Alarm
(1) If one rectifier fails, the MIN contacts open, and the MIN LED on the ALU lights. When two rectifiers
fail, the MAJ alarm contact is opened, and the MAJ LED lights.
Warning: Do not open the rectifier unit. There are no serviceable parts.
(2) If you want to ignore the MAJ or MIN alarm when you pull out the rectifiers from the slots, just please
press the SMR RST button on the ALU.
(3) If you insert the above rectifier back to the slot, then pull out after the “FL” LED on the SMR panel light
up. The system will alarm in the “MIN” mode.
That means if we repeat to pull out and insert in and pull out the rectifier, the condition described in item
(2) will be cleared.