Installation manual

Pumped Refrigerant System Operation and Maintenance8
Operation
The Pumped Refrigerant System
System Operation
The primary function of the Pumped Refrigerant System is to capture the heat generated by IT
equipment and neutralize it before it mixes with the room air. The pumped refrigerant system uses two
circuits to remove heat. In the first circuit, water or a water/glycol mixture is pumped from the chiller
into a brazed plate heat exchanger located inside the RDU.
In the second circuit, R134a refrigerant circulates from the RDU to Cooling Modules located either over
the hot aisle or in the row. Cooling Module fans draw in hot air across their micro channel coil
completely evaporating the liquid refrigerant. The refrigerant vapor then returns to the RDU. There the
vapor is condensed back into a liquid in the brazed plate heat exchanger which rejects the heat to the
chilled water.
The system does only sensible cooling. No energy is wasted in latent energy removal. Less energy is
used to satisfy the IT load. A thermal containment system will further increase efficiency. A
conventional computer room air conditioner is used in conjunction with the pumped refrigerant system
to provide humidity control.
The pumped refrigerant system is flexible. Each system is configured to the user’s specific requirements.
As cooling needs increase, the system can be expanded. A system may have multiple RDUs. One RDU
can supply OA Cooling Modules and RA Cooling Modules.
Note: Only APC certified technicians should service the pumped refrigerant system.
Refrigerant Circulation
Each cooling module is connected to the RDU by overhead or under floor refrigerant distribution piping.
Note: Under floor refrigerant piping is not recommended.
Multiple electronic valves in each CM automatically regulate the refrigerant flow and coil temperature to
met the IT load at the desired supply air set point.
See the “OA Piping Diagram” on page 1 for the locations of the valves and sensors on the OA
Cooling Modules. See “RA Piping Diagram” on page 1 for the locations of the valves and
sensors on the RA Cooling Module
Refrigerant is circulated through the system by two fully redundant refrigerant pumps. The RDU display
interface allows you to program the number of run hours a pump will operate before switching to the
second pump. Pump redundancy ensures that the cooling modules continue to run uninterrupted.
The RDU is equipped with a subcooler to further cool the refrigerant leaving the brazed plate heat
exchanger. This additional subcooling allows the refrigerant pumps to operate correctly and efficiently
while responding to varying IT loads.