• The high and low temperature alarms are ignored for a default 20 minute period on startup to allow the system
time to settle without generating nuisance alarms.
The temperature PID control loop is operational from when the Start/Stop button is pressed and the pump has ramped up to
speed. If the secondary circuit temperature starts to rise above the setpoint, then the cooling valve starts to open to allow
more primary cooling fluid through the heat exchanger. The cooling valve modulates from 0% (full bypass) to 100% (full flow
through heat exchanger). The valve position can be monitored on the Home screen or page 2 of the Status screen. The
demand signal to the valve is compared to a position feedback signal every 15 minutes (default) to check the healthy
operation of the valve.
• If the feedback signal is more than 10% (default) of the demand signal, allowing for the drive time of the actuator
to respond to load changes, then an A26—Valve Fault event is generated. The valve will continue to operate until
fault is rectified.
The Cooling Valve is a drive open/drive close device and if the positioning signal is lost, it remains at the last known operating
position. (Assuming no signal, valve closes at 0v.)
• If the differential pressure exceeds 0.6 bar (9 psi), then an A29—Primary Filter Dirty alarm is generated.
Primary flow rate is monitored with a calorimetric flow meter at the primary inlet to the CDU. The flow can be read on the
Home screen or on page 2 of the Status screen.
IMPORTANT! The flow meter only reads the total primary flow through the CDU 600 unit. It does not monitor the flow
rate through the heat exchanger.
• An A27—Primary Low Flow alarm is generated if
• The A33—Secondary Fluid High Temperature alarm is active
• The A31—Primary Fluid High Temperature alarm is not present
• The demand to the operational cooling valve is at 100%
• An A28—Primary No Flow alarm can also be generated if
• The A33—Secondary Fluid High Temperature event is active
• There is also an A31—Primary Fluid High Temperature alarm is present
• Demand to the operational cooling valve is at 100%
IMPORTANT! Flows below 17 l/m (4.5 gpm) are outside the range of the flow sensor and will not be displayed.
4.3.2 Secondary Circuit Operation
When the ON button is pressed, the icon on the Home screen changes from red to green. If the fluid level and status pressure
are healthy, one or both pumps (depending upon configuration) start to increase in speed. Arrows are displayed on the Home
screen for both primary and secondary circuits and the pump speed is shown as a percentage of maximum will be displayed.
The inverter displays will also show the actual frequency output to the pump motors.
Fluid Level
• If both fluid level sensors located on the pump inlet header do not signal sufficient fluid, then neither main pump
P1 or P2 will run.
• If the fluid level sensors register no fluid for period of more than 1 second an A41—Level Sensor No Fluid
Detected alarm is generated.
• If the unit differential pressure or flow rate is still more than 50% of setpoint, then the unit continues to run.
4 Operation Proprietary and Confidential ©2025 Vertiv Group Corp. 43
Vertiv™ CoolChip CDU 600 Operation and Maintenance Guide
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