Recently we’ve been talking about the innovations and trends within the data center world. One of the great innovations that isn’t necessarily ‘new’, but is becoming more and more prevalent in the construction and infrastructure of state-of-the-art data centers is utilizing air-handlers as opposed to air conditioners. The acronyms CRAH (pronounced “kraw”) and CRAC (pronounced “krak”) stand for Computer Room Air Handler and Computer Room Air Conditioner respectively.
As is common knowledge, most facilities utilize a pressurized air-system under the floor (typically raised 36 inches from the concrete slab). Once a cabinet is placed, a perforated floor tile is positioned to allow the pressurized air to flow up into the front of the equipment. The air is then pulled through the equipment to cool it via fans and released through the back of the equipment (we will talk about hot/cold aisle containment another day).
Now that we understand how air circulates in the data center, we must understand the difference between air handling and air conditioning. Anyone who pays their power-bill at home knows that the cost of cooling/heating a home is one of the highest costs associated with power. The same holds true for data centers. Cooling a data center, which houses equipment that generates substantial heat, is very expensive. Because of this, data centers have turned to what is call air-side economization. What that means is that when the ambient outside temperature is within a certain threshold, the air is then ‘handled’ and pulled into the facility and pushed down in the pressurized sub-floor. The handled air flows through the data center as traditional air conditioned air would. However, in this scenario, the facilities with CRAH units are actually using ‘free’ air and the cost to cool the facility significantly drops.
The efficiency of this method obviously depends on climate, but in the Ashburn, VA market we can use this technology about 60% of the year. This saves immense power cost, which in turn lowers PUE and drives the cost per kilowatt down for you.
Overall, the utilization of air-handling and air-side economization rather than traditional air-conditioning is an all-around innovation win for the industry and its clients.