Data Center Fan/Motor Upgrades Provide Large Energy Savings

Many conventional data center spaces are cooled with computer room air conditioner (CRAC) and computer room air handler (CRAH) units with constant-speed, belt-driven, forward curved fans. Replacement of these fans/motors with plug fan/motor assemblies is becoming a common retrofit in SVP territory. One manufacturer of EC fan/motor upgrade kits, STULZ Air Technology Systems, Inc., claims that a 20% motor horsepower reduction is typical while maintaining airflow rates.

In practice, SVP customers are achieving greater reductions in fan hp. Two projects recently realized fan horsepower reductions of 33% and 40%. This was made possible by the existing
large excess capacity (redundancy) typical in data center spaces and by combining these fan upgrades with airflow management improvements such as cold or hot aisle containment and the addition of more precise controls, e.g., those possible with the addition of inlet temperature and plenum pressure sensor networks. These additional measures reduced the data center cfm requirement.

NVIDIA implemented a fan upgrade in one of their Santa Clara data centers, replacing the fans/motors in twenty-one CRAH units with EC plug fan/motor assemblies. They also added a network of temperature sensors and plenum pressure sensors and controls to modulate fan speeds and chilled water valves. At project completion, the EC fans were operating at approximately 63% of full speed. The annual fan energy savings is projected to exceed 1.2 million kWh. The project payback after the rebate is approximately 2.4 years.

Savvis, a large data center colocation facility, recently implemented a similar upgrade to fifty-six CRAH units in one of their Santa Clara facilities. Each unit originally utilized two 10 hp fans. These were replaced with an upgrade kit containing three EC plug fans totaling 12 hp. Cold aisle containment and the addition of a wireless sensor network resulted in the fans operating between 30% and 68% of full speed. The annual fan energy savings is projected to be nearly 3.8 million kWh. The project cost of $1.28 million is expected to be recouped in 2.85 years after an SVP rebate of over $300,000.