Installation manual

9Pumped Refrigerant System Operation and Maintenance
In the absence of an IT load or when all the CMs are turned off, the RDU refrigerant pumps continue to
operate by bypassing the refrigerant through a pump head pressure control valve. This head pressure
control valve allows continuous operation of the pumps regardless of the load. While in bypass, the
refrigerant pumps reduce to a minimum speed allowing minimal power consumption and avoid the wear
of frequent starts and stops.
See the “Pumped Refrigerant System Piping Diagram” on page 1 for the locations of the RDU
components discussed above.
The RDU monitors room conditions to control the refrigerant condensing temperature relative to the
room dew point.
See the RDU Installation Manual, OA Installation Manual, and RA Installation Manual for
more information.
System Architecture
The pumped refrigerant system can be configured based on the customer requirements.
Examples below illustrate group usage with a single RDU.
RDU
ID: 1
CM
Unit: 1
RDU: 1
Group: 1
CM
Unit: 2
RDU: 1
Group: 1
CM
Unit: 3
RDU: 1
Group: 1
CAN Bus
Liquid Supply
Vapor Return
RDU
ID: 1
CM
Unit: 1
RDU: 1
Group: 1
CM
Unit: 2
RDU: 1
Group: 1
CM
Unit: 3
RDU: 1
Group: 1
One RDU, One Group
CM
Unit: 1
RDU: 1
Group: 2
CM
Unit: 2
RDU: 1
Group: 2
CM
Unit: 3
RDU: 1
Group: 2
One RDU, Two Groups
Group 1
Group 2
Group 1