Liebert XD Systems

The Liebert XD system offers a flexible, energy-efficient solution to your extreme density cooling needs. By eliminating the extreme heat densities associated with increased computing capacities, the Liebert XD system enables IT and data center managers to take advantage of the newest, most advanced computing technologies available – which means your computing and cooling can keep pace with your business.

What is the Liebert XD system?

Liebert XD is a high heat density cooling solution that offers solutions utilizing Open or Closed Architecture, Water based or Pumped Refrigerant based technology, and a wide range of equipment configurations. Open architecture systems utilize cooling coils near the heat load, either inside or outside the open server rack, and utilize the room air volume as a thermal storage to ride through short power outages. Closed architecture systems fully enclose the rack with the cooling coils inside. Other provisions are required for power-loss ride-through. Pumped Refrigerant technology eliminates the presence of water in a data center. It operates at low pressure in the piping system and becomes a gas at room temperatures, if a leak would occur. It utilizes micro-channel coil efficiency and low pressure drop.

Water based systems offer a cooling alternative where electrical hazards are minimal or the use of water is not a concern. They are also designed to work in any size space from a small computer room to a large data center.

How can I design a Liebert XD high heat density cooling solution with built in redundancy?

Redundancy can be designed into a solution utilizing the open architecture version of Liebert XD by combining CRAC units and interlaced pipe connection between the cooling modules and the supporting XDP/XDC. The interlaced connection means that cooling modules next to each other are connected to different XDP/XDC units. For the XDH, which has dual piping circuits, this interlacing can even be done within each module.

How much time do I have until the servers start to shut down in case of a cooling system failure?

For a closed architecture cooling solution, how fast this situation might occur depends in general on the load in the rack, the thermal mass in the rack and the heat exchange with the surroundings (leaks). In extreme situations, an over temperature situation can occur within seconds. For an open architecture solution, similar factors have an impact on how fast this situation would occur. However, since the room works as a heat sink, it will typically take minutes until an over temperature is reached. Full scale tests that Liebert have done together with Hewlett Packard showed that 104ºF entering air temperature to the server (which is the temperature when most servers start to shut down) was reached after 23 minutes at 3.5kW per rack heat load in the room. At 7kW per rack heat load, it was reached after 7 minutes; and at 11kW per rack, 104ºF was reached after 2 minutes.

What is the difference between Open and Closed architecture and which architecture is recommended?

Each architecture has its advantages. In general, an Open architecture allows the room to be a heat sink (for ride through during failures or power loss), does not limit the rack selection, has a less complex emergency mode and allows the racks to “borrow” cold air from each other. A Closed architecture solution has low audible noise, is deployable as a single rack, minimizes the air circulation in the room and does not require hot/cold aisle arrangement.

Why is Liebert XD called Supplemental High Heat Density Cooling?

The Liebert XD system is doing sensible cooling (the temperature of the cooling fluid supplied to the cooling modules is always above the actual dew point in the room so no condensation can occur on the coils in the modules or on the piping) to match the high heat density load. It supplements the precision cooling equipment which typically still is required for humidity control and air filtration.

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