Code Description Severity Self-Clear Latching Shutdown Shutdown
(refer to A43 for detail) will be raised and unit will shutdown after a 1 second delay.
Action:
Check that water make-up container is properly connected (or filling wand is fully immersed, if used). Check system for leaks. Check there
is no trapped air in fill pump hoses and system is fully vented. Check auto air vents are open.
A42 Illegal Fluid Sensor Condition 2
ü
— — —
Detail: On Initial Start-up – if fill pressure has been achieved, but level sensors are not made.
Action: Likely cause is trapped air. Vent air from Secondary circuit.
A43* Group Control Network Fault 2
ü
— — —
Detail: Comms failure between CDUs on network
Action: Check wiring and terminations
A44*
Group Control Insufficient Units
Available
2
ü
— — —
Detail:
Group control cannot bring a redundant unit on-line because it’s either in a fault condition, has locally been put into standby mode, or has a
comms. failure.
Action: Check status of redundant unit, check wiring and terminations
A45* Secondary Filter 1 Dirty 3
ü
— — —
Detail:
Differential pressure across Secondary filter 1 (if fitted) is greater than 0.2 bar (3PSI), indicating that the filter should be cleaned (default 60
second delay applies).
Action: Clean filter screen as described in the Maintenance Section.
A46* Secondary Filter 2 Dirty 3
ü
— — —
Detail:
Differential pressure across Secondary filter 2 (if fitted) is greater than 0.2 bar (3PSI), indicating that the filter should be cleaned (default 60
second delay applies).
Action: Clean filter screen as described in Secondary Filter Service (if Fitted) on page73
A47* Secondary Temp T2a Diff Fault 2
ü
— — —
Detail:
Difference between Secondary temp. sensor T2a is more than default 1°C (2°F) adrift from T2b and T2c, for a period of 30 seconds (default)
or more. Controller will read the average of T2b and T2c only.
Action: Check T2a sensors against temperature sensor resistance chart in Section 2.5 and replace if faulty.
A48* Secondary Temp T2b Diff Fault 3
ü
— — —
Detail:
Difference between Secondary temp. sensor T2b is more than default 1°C (2°F) adrift from T2a and T2c, for a period of 30 seconds (default)
or more. Controller will read the average of T2a and T2c only.
Action: Check T2b sensors against temperature sensor resistance chart in Section 2.5 and replace if faulty.
A49 Secondary Temp T2c Diff Fault 3
ü
— — —
Detail:
Difference between Secondary temp. sensor T2c is more than default 1°C (2°F) adrift from T2a and T2b, for a period of 30 seconds (default)
or more. Controller will read the average of T2a and T2c only.
Action: Check T2c sensors against temperature sensor resistance chart in Section 2.5 and replace if faulty.
A50 Reservoir Tank Fluid Required 3
ü
— — —
Detail: Fluid level in the reservoir tank has dropped to the low level sensor.
Table 4.41 Alarm Identification and Severity Level (continued)
4 Operation Proprietary and Confidential ©2025 Vertiv Group Corp. 57
Vertiv™ CoolChip CDU 600 Operation and Maintenance Guide
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