Delta MCS-600 Power Shelf
Installation, Operations and
Maintenance Manual
REV.: 03
8-1
Customer Specification Confidential
8 System Alarms and Troubleshooting
8.1 AC Fail Voltage Alarm Description
8.1.1 Description
If the ALU detects an input AC voltage below 50 VAC, the ALU sends an AC Fail alarm signal and activates
the dry contact. The AC Fail LED on the ALU panel lights up. When AC voltage is restored to the
nominal input voltage, the ALU extinguishes the AC Fail LED, and returns the contact to the normally closed
position.
8.1.2 Troubleshooting
The AC Fail alarm is normally caused by a commercial AC interruption due to a storm or maintenance. If
commercial AC is detected at the AC panel, check the rectifier input breakers in the AC panel for a tripped or
failed breaker.
Warning: The ALU senses the AC line through the AC Input terminal. If this connection is missing,
the system generates an AC Fail alarm.
8.2 High Voltage Shutdown Alarm
8.2.1 Description
When the ALU detects the output DC voltage exceeding the HVSD threshold setting, the ALU sends an
HVSD alarm signal and activates the dry contact. The ALU lights the HVSD LED located on the ALU
panel and shuts down each rectifier. At this point, the system is running on reserve batteries. When the
DC voltage falls below the HVSD threshold voltage, and push the HVSD RST Button, then the system
recovers. The ALU extinguishes the HVSD LED, returns the rectifiers to service, and closes the normally
closed set of contacts.
8.2.2 Troubleshooting
High voltage shutdown occurs when the output voltage exceeds the HVSD threshold. This can be caused by
a rectifier failure, the system equalize voltage exceeding the HVSD threshold, or temperature compensation
exceeding the HVSD threshold setting.
1.
Restart the rectifiers by resetting the HVSD RST button located on the ALU.
2.
Verify the output voltage of each rectifier in both float and equalize.
3.
Verify that the equalize voltage setting does not exceed the HVSD threshold setting.
4.
Verify the temperature compensation voltage setting. Ensure that Temp Comp does not exceed the
HVSD threshold setting when operating in cold temperatures.
8.3 High Voltage Alarm Description
8.3.1 Description
The High Voltage alarm (HV) is a minor alarm activated when the DC output voltage exceeds the HV
threshold setting. When the system voltage exceeds the HV setting value, the ALU sends the HV alarm
signal, lights the HV LED located on the ALU panel, and activates the HV alarm contact. The rectifiers
remain on line during this minor alarm condition. When the system voltage decreases below the threshold
setting, the ALU extinguishes the HV LED and deactivates the HV alarm contact.
