CDU Operating & Maintenance Guide Page 34
Neptune DWC RM100 in-rack Coolant Distribution Unit
Will only activate when Valve Demand is at 100%, A32 - Secondary Water High Temp and A30 - Primary
High Temp alarms are active (default 5 minute delay applies).
Check that the chiller or facility water supply is operational and fault free
Level Sensor – No Water Detected
While Unit is Running only – if level sensor is open circuit for more than 1 sec. then this alarm will be
raised, providing flow or DP (depending on control function set) is >50% of flow/DP setpoint. If
flow/DP is below this threshold, then 'A16 - Leak Shutdown/Insufficient Water’ alarm (refer to A16 for
detail) will be raised & unit will shut down after a 1 sec. delay.
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.
Illegal Water Sensor Condition
On Initial Start-up – if fill pressure has been achieved, but level sensor is not made.
Group Control Network Fault
Comms failure between CDUs on network
Check wiring & terminations
Group Control Insufficient Units
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
Check status of redundant unit, check wiring & terminations
Differential pressure across Secondary filter is greater than 0.2Bar (3PSI), indicating that the filter
should be cleaned (default 60 second delay applies).
Clean filter screen as described in the Maintenance Section
Power Meter Communications Fault
(not currently supported)
Secondary Temp T2a Diff Fault
Difference between Secondary temp. sensor T2a is more than default 1°C (2°F) adrift from T2b & T2c,
for a period of 30 seconds (default) or more. Controller will read the average of T2b & T2c only.
Check T2a sensors against temperature sensor resistance chart in Section 2.7 and replace if faulty.
Secondary Temp T2b Diff Fault
Difference between Secondary temp. sensor T2b is more than default 1°C (2°F) adrift from T2a & T2c,
for a period of 30 seconds (default) or more. Controller will read the average of T2a & T2c only.
Check T2b sensors against temperature sensor resistance chart in Section 2.7 and replace if faulty.
Secondary Temp T2c Diff Fault
Difference between Secondary temp. sensor T2c is more than default 1°C (2°F) adrift from T2a & T2b,
for a period of 30 seconds (default) or more. Controller will read the average of T2a & T2b only.
Check T2c sensors against temperature sensor resistance chart in Section 2.7 and replace if faulty.
Pump 1 Communications Fault
Controller unable to communicate with Pump 1 speed controller. Pump 1 will stop and Pump 2 will
then run
Check all cables & connections. Replace pump
Pump 2 Communications Fault
Controller unable to communicate with Pump 2 speed controller. Pump 2 will stop and Pump 1 will
then run
Check all cables & connections. Replace pump
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