A Peek “Under the Hood” of the new High Precision CRAC

To a visitor who walks into a data centre only once every five years, the computer room air conditioner (CRAC) units that line the perimeter may look remarkably the same as they did five 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 centre owners, the technology changes inside the box radically alter data centre energy costs and how that data centre operates.

A case in point is the new Schneider Electric’s family of Uniflair LE 50Hz CW (chilled water) CRAC units. As data centres 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 per cent less power at the same capacity. Studies have shown that in data centres, 41 per cent of the energy coming in feeds the cooling systems. Therefore, adding high-efficiency cooling units to the data centre 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 mouldable composite-based design. More flexibility in moulding 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 per cent 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• New motors – The old asynchronous motors (motors with brushes) have been removed and been replaced by electronically commutated motors integrated with an impeller (brushless motors).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 centre temperatures – Increases in the ASHRAE recommended data centre operation temperature ranges present technological challenges for older CRAC units. The “chilled” water that the units traditionally utilise 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 optimised 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 centre operators showed that use of economisers will result in saving an average of 20 per cent of the money, energy, and carbon for cooling when compared to data centre designs without economisers. The new CRAC units utilise an Optimised Management Interface (OMI) that is designed to maximise chiller/economiser efficiencies by responding to the cooling load in real time.

Find out more about how you can be more efficient with perimeter cooling for medium and large data centre environments.

This sponsored content was provided by Schneider Electric.