Frequently Asked Questions

Below are frequently asked questions about Asetek liquid cooling. If you have a question not answered here, email us at

Why Water?

  • What are the key benefits of Asetek’s RackCDU?

    • Improves TCO by dramatically decreasing power consumption on data center cooling, increasing data center compute density and enabling server waste heat  reuse.
    • Ongoing OpEx impact:
      • Decreases data center cooling energy costs by more than 50%
      • Reduces IT power consumption by 5 to 10% (fan energy savings)
      • Offsets heating fuel consumption (and reduce GHG emissions)
    • Increases data center compute density: 2.5-5x impact
    • Reduces data center water usage dramatically
    • Cost effectively enables high-density data centers, Hyper Scale, Scale Out and HPC
    • Lowers cost of adding cooling infrastructure and mitigates need for data center build-outs
    • Implements as a non-intrusive upgrade to existing data centers during server refresh cycles
    • Reduces PUE, WUE, and ERE
  • What are the dimensions of Vertical-RackCDU?

    Vertical-Rack is delivered in a 26.7cm (10.5”) deep rack extension with the RackCDU on one side and room for 3 additional PDUs on the other. The extension width matches the mating rack and the height adds 11.5cm (4.5”) to the height of the rack resulting in a professional and integrated look.  

  • What is the impact on the Date Center [hot] aisle width?

    Each Vertical RackCDU typically consumes 26.7cm (10.5”) of  aisle width. In a data center with hot aisle / cold aisle arrangement (back-to-back rows) using RackCDU extensions reduces aisle width by 53.4cm (21”). With the use of shallower racks, this can be reduced.

  • Where do the tubes exit the server to interface with the Vertical-RackCDU?

    Tubes can exit through an unused PCI shield or through a custom opening, typically at the back of the server.

  • What racks is RackCDU compatible with?

    Any rack can be supported and the number of already supported racks is growing constantly. RackCDU extensions mount in place of the rear or front doors, and the  doors mount on the outside of the RackCDU extension.

  • What CPUs and GPGPUs types are currently supported?

    • Cooling solutions are available for x86 servers equipped with:
      • All current Intel CPU mounting schemes  
      • All current AMD CPU mounting schemes
      • nVidia Tesla K10 and K20 SXM
      • Intel Xeon Phi
    • Additional processor support is enabled as chips are released.
  • Are there any sensor/control interfaces to the pumps, CDU, etc.

    Yes, RackCDU comes with a full monitoring system. This system monitors temperatures, facilities flow, pressures, liquid level, and detects leaks. It is capable of sending alarms and alerts when user definable points for these parameters are crossed. Each RackCDU monitor is addressable via its own IP address and communicates all these values via SNMP or via the included web browser interface.

  • Are cable management arms supported?

    Vertical-RackCDU can operate with or without cable management arms. Operating without cable management arms allows shorter connecting tubes.

    Any cable management system that supports these tube characteristics is supported

    • Outer diameter of tubes: 10.8mm
    • Minimum bend radius of tubes: 22mm
  • What size dry cooler or chiller is sufficient to support RackCDU?

    The choice and sizing of adiabatic fluid coolers, dry coolers or cooling towers is site specific. Contact Asetek with site details and Asetek can provide guidance on choice and sizing. 

  • Can RackCDU be used with existing chilled water systems?

    Yes, in-fact the study of RackCDU conducted by Lawrence Berkeley National Laboratory found that significant energy savings are possible with just this approach.

  • What if it leaks?

    RackCDU is designed and built to prevent leaks. The stator and pump rotor are magnetically coupled, eliminating a shaft seal that could leak. Every joint is double sealed and every cooler is helium leak tested at the factory. Lastly, the server coolers operate at very low pressure (less than 0.5 PSI) so in the unlikely event that a leak does occur, it will drip, not spray. Server liquid and facilities liquid are separated at the RackCDU. As a result, the amount of liquid that could ever leak in the rack is limited to about 8.5 liters.

    Leak detection is provided at the bottom of the RackCDU extension. The monitoring system is capable of notifying staff via e-mail or SNMP alerts.

  • What liquid is used inside RackCDU?

    The liquid is mainly deionized water mixed with environmentally friendly additives providing antifreeze, anti-corrosion and bio inhibitor protection. The additives are commonly used for airplane deicing and are approved for use in food processing equipment. 

  • How is RackCDU serviced?

    • RackCDU systems are designed to be maintenance free for the life of the liquid cooled servers.
    • RackCDU systems have nominal training requirements and existing IT staff is more than capable of providing service. Handling an Asetek-liquid cooled server is no different from handling an air cooled server.
    • Although probably never applicable in real life, RackCDU includes a refillable reservoir that replenishes liquid that slowly permeates (evaporates) through the non-metal parts of the system. The MTTS for refilling the reservoir is 5-7 years and a low liquid level alarm is provided as part of the RackCDU monitoring system.
    • RackCDU is connected to servers via dripless self-sealing quick connectors. Twist lock quick connectors are used for rack servers. These are as easy to connect / disconnect as network cables. Blind mate connectors are often used in blade applications. These connectors work automatically as the blade is installed or removed from its chassis.
    • Servicing liquid cooled servers is much like servicing air-cooled servers. CPU (Central Processing Unit) and GPGPU (General-Purpose Computing on Graphics Processing Units) coolers are drop in replacements for their air-cooled counter parts. DIMM modules can be removed with memory coolers in place. Full access to hot-swap parts is maintained.
    • Pumps have a rated life of over 100,000 hours (MTTF). The pump’s moving parts are fully immersed in cooling liquid, vastly reducing wear as compared to server fans. Pump motor electronics are hot swappable without removing the cooling system from the server. Simply pinch the pump cap and remove three screws. In addition, each pump provides redundancy for the other as in a dual CPU server only one pump is actually needed to efficiently cool 2 CPUs. 
  • What quick connectors are used in RackCDU?

    Asetek has developed its own purpose built dripless quick connectors that are double sealed in every position. They are rated for over 1,000 connect / disconnect cycles, although in normal use they will see less than 1 dozen connects in a lifetime. 

  • What pump and cold plates are used in RackCDU?

    Asetek server coolers use the same Asetek manufactured pump /cold plates as our line of desktop PC liquid coolers.