• If the differential pressure or flow drops below 50% of setpoint, then the unit will stop and an A40—
Insufficient Fluid alarm is generated. This is a latched alarm and it will be impossible to restart the unit until
the event has been manually cleared.
The system pressure at the CDU inlet (PS1) is continuously monitored to ensure that the system is always pressurized. See
Status Screen on page17
Static Pressure
• Once the unit is running, a low system pressure below the default 0.8 bar at PS1 will not stop t he main pump from
running, but will initialize the P3 fill pump. After a 10 second default delay, the PS1 pressure is raised to a default
of 1.0 bar (15 psi) and the fill pump stops. If the reservoir tank very low level sensor is activated while fill pump P3
is running, an A51—Reservoir Tank Empty alarm is generated and fill pump P3 stops. This is a latched alarm and
will need to be manually cleared, but will not stop the unit from running.
• If inlet pressure drops to 0.2 bar (3 psi) below fill pump activation threshold for more than 1 minute, an A39
System Low Pressure event is generated. The inlet pressure drop value is set at 0.2 bar (3 psi) and is non-
adjustable. Time value for the below pump activation threshold is set at 1 minute and is non-adjustable.
The flow charts in DP Control below show the unit pressure/level monitoring and fill pump control during initial startup of the
unit after commissioning (from a unit offline condition) and also during normal running (unit online).
Pump Control Logic
Pump flow/pressure performance (pump speed) is controlled through a differential pressure control loop.
If pumps are set up for run/standby operation, they operate on a duty sharing cycles during normal healthy running. By
default, every 7 days, the operational pump ramps down to a stop and the standby pump starts and continues to operate for
the next 7 days. Default changeover time is 10:00 a.m. on Monday and the complete changeover sequence takes
approximately 0.25 seconds (default).
IMPORTANT! Each time that the unit is stopped and restarted, it selects the initial operating pump that has the lowest
accrued run time hours.
DP Control
DP Control monitors the secondary differential pressure with sensors on the supply and return connections of the CDU. Upon
startup, the control loop increases the pump speed in stages until the DP matches the DP setpoint.
The pump control loop has a default scan time of 10 seconds to avoid control oscillation.
• If Pump 1 fails to reach 90% (default)of the DP demand in 100 seconds (default time period), it is assumed there
is a pump flow/pressure fault. Pump 1 ramps down to a stop and Pump 2 is initialized. At the same time, an A22-P1
Inverter Low Flow alarm is generated.
• If Pump 2 fails to reach 90% of the set DP demand within the time limit, an A25-P2 Inverter Low Flow alarm is
generated.
• The above assumes that Pump 1 is the initial operating pump. The reverse would apply if Pump 2 was the
operating pump.
44 Proprietary and Confidential ©2025 Vertiv Group Corp. 4 Operation
Vertiv™ CoolChip CDU 600 Operation and Maintenance Guide
To Next Page
Loading...
