A Peek “Under the Hood” of the New High Precision Computer Room Air Conditioners

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To a visitor who walks into a data center only once every 5 years, the computer room air conditioner (CRAC) units that line the perimeter may look remarkably the same as they did 5 or even 10 years ago.  It’s like an imaginary alien who comes to visit earth in 1957 and sees a Mercedes-Benz automobile. When he comes back in 2017, he still sees metal vehicles with four rubber tires, a hood, a trunk, doors, seats and a steering wheel.  He might come to the conclusion that nothing much has changed.

However, as all car owners know, what is hidden underneath the hood is what makes the car so different in terms of performance.  The same holds true for the new CRAC units.  For data center owners, the technology changes inside the box radically alter data center energy costs and how that data center operates.

A case in point is the new Schneider Electric’s family of Uniflair LE 50Hz CW (chilled water) CRAC units. As data centers consolidate and continue their rapid migration to colocation and cloud facilities, the demand for such chilled water units continues to grow.

At one Schneider Electric colocation customer, the cooling experts onsite had the luxury of accessing two CRAC units of different vintages side by side.  One was 15 years old and the other was a brand new Uniflair LE unit. Both were operated under similar conditions and were tasked with the same workload. Although roughly the same physical size, the new Uniflair LE unit consumed 50% less power at the same capacity.  Studies have shown that in data centers, 41% of the energy coming in feeds the cooling systems.[1]  Therefore, adding high efficiency cooling units to the data center means that significant operational savings will result.

Why is there such a stark performance contrast between the old and new units?  The answer lies “under the hood”:

  • New materials that streamline the fan design – The fan technology inside the box has moved on from metal blades to a moldable composite based design. More flexibility in molding the blades allows for engineers to design around a more aerodynamically efficient shape. Such designs are now crafted in 3D as opposed to the old 2D.  This alone added 20% in efficiency and results in lower power consumption and less noise.
  • New motors – The old asynchronous motors (motors with brushes) have been removed and been replaced by electronically commutated motors integrated with an impeller (brushless motors). Such a change avoids the friction of brushes and allows the motor to run more efficiently. In addition, these motors are controlled by variable speed drives (as opposed to fixed speed drives) which means that motors only spin at the speed needed to accomplish the task at hand.
  • New ability to handle a broader range of data center temperatures – Increases in the ASHRAE recommended data center operation temperature ranges present technological challenges for older CRAC units. The “chilled” water that the units traditionally utilize has now turned “lukewarm” and with larger temperature differentials; this impacts how the thermodynamics are managed. To accommodate this wider temperature range, the coils inside the box are optimized differently than before. The recommended operating conditions also modify how humidity control should be managed (humidification targets are no longer based on relative humidity but on actual moisture content in the air).
  • A system that facilitates high efficiencies for system-wide cooling, beyond just the CRAC – The Green Grid survey of data center operators showed that use of economizers will result in saving an average of 20% of the money, energy, and carbon for cooling when compared to data center designs without economizers.[2] The new CRAC units utilize an Optimized Management Interface (OMI) that is designed to maximize chiller/economizer efficiencies by responding to the cooling load in real time.

Data center professionals can leverage best practices related to cooling that supports an increase of operational efficiency, sustainability and reduce energy consumption by up to 20-30%. To explore the latest generation of cooling solutions at Schneider Electric, including the Uniflair LE if it is offered in your location, visit Cooling Solutions.  


[1] Rasmussen, Neil, Schneider Electric, “Allocating Data Center Energy Costs and Carbon to IT Users”, 2011

[2] The Green Grid. WP #41 – Survey Results: Data Center Economizer Use. 2011. Available from: https://www.thegreengrid.org.

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