Delta manual DELTA MCS-1800 3U Power Shelf, Low Voltage Alarm

DELTA MCS-1800 3U Power Shelf

Installation, Operations and

Maintenance Manual

8.3.2 Troubleshooting

The HV alarm is usually caused when the equalize voltage exceeds the HV threshold setting. Another probable cause that the temperature compensation voltage exceeds the HV threshold during cold temperature operation. During this alarm condition, the system continues to operate.

8.4Low Voltage Alarm

8.4.1Description

The Low Voltage alarm (LV) is a minor alarm activated when the DC output voltage decreases below the LV threshold setting. When the system voltage decreases below the LV LED located on the ALU panel, and activates the LV alarm contact. The rectifiers remain on line during this minor alarm condition. When the system voltage increases above the threshold setting, the ALU extinguishes the LV LED and deactivates the LV alarm contact.

8.4.2 Troubleshooting

The LV alarm condition occurs during a brownout condition or prior to a complete AC Fail condition caused by commercial AC problem conditions.

Another probable cause is that the temperature compensation voltage decreases the float voltage below the LV threshold during hot temperature operation. During this alarm condition, the system continues to operate.

8.5Low Voltage Disconnect Alarm (System equipped with PDU)

8.5.1Description

During an AC Fail condition, the rectifiers are shut down and the reserve batteries begin to discharge. When the battery cells discharge below the LVD setting, the ALU lights the LVD LED on the ALU panel, activates the LVDS OPEN alarm contact, and opens the LVDS contactor. When the AC recovers, the LVBD recovers automatically. The ALU extinguishes the LVD LED and resets the normally closed set of alarm contacts.

8.5.2 Troubleshooting

If the battery disconnect switch remains open after voltage is restored to the rectifiers, one of the following is occurring:

1.The ALU may be faulty. Swap out the ALU with a spare and verify voltage settings.

2.The LVBD coil windings may be open. With a digital multimeter, check the LVBD coil windings.

8.6Fuse/Circuit Breaker Fail Alarm (System equipped with PDU)

8.6.1Description

If the DC load output fuse opens or battery switch trip off, the ALU sends the alarm condition, lights the LED on the ALU panel, and activates the Fuse Fail alarm.

8.6.2 Troubleshooting

To troubleshoot the fuse/circuit breaker fail alarm condition, perform the following steps:

1.Verify that the fuse/circuit breaker is the proper size (use 80% derating guide).

2.Verify that the external fault that might cause fuse/circuit breaker tripping is removed.

3.Replace the blown fuse with a fuse with the same rating or of the corrected value. In case of a circuit

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