Engineering Tomorrow Drives University Pool Pump Efficiency
Western Oregon University has been recognized as one of the top aquatic fitness programs in the United States. The recently enlarged Health and Wellness Center has also been recognized as one of the country’s best-in-class facilities in terms of design and practices — earning LEED Gold certification. Because of its dual commitment to aquatics and sustainability, the Center jumped at the chance to dramatically cut the swimming pool’s electricity consumption with two Danfoss VLT® AQUA Drives, which are specifically designed to meet the challenges of water applications.
“Being located in Monmouth, Ore., our school prides itself on teaching swimming skills for lifelong fitness and recreation,” says Jake Whisenhunt, the university electrician who supervised the drive project. “It’s important to keep pool water clean for swimmers and to meet state regulations. At the same time, we want to reduce electricity costs and the carbon emissions associated with producing electricity. That’s why we were interested to learn that Danfoss variable frequency drives could dramatically cut the pool’s pump energy usage.”
Pumps running at full speed waste energy
Whisenhunt got the energy-saving idea from Neal Hershey, director of technical services for Interlocked Filtration Systems, Tacoma, Wash. During a routine service call, Hershey suggested to Whisenhunt that equipping the pool pump motors with variable speed drives could substantially cut electricity costs.
“The Center’s pool is used more for recreational swimming than competition,” explains Hershey. “The pool measures 25 yards long, five lanes wide, and holds 100,000 gallons of water. To meet state regulations, the water is cycled through a filtration system every six hours using a 15-hp inverter-rated circulation pump. A smaller spa holds 10,000 gallons, which is cycled every 30 minutes using a 10-hp pump. Together, the pumps use about 14,200 kWh per month at an annual cost of $11,200.”
According to Hershey, the original circulation pumps were equipped with soft motor starters only, which reduced the amperage draw during motor startup and motor wear. “But because the pumps were running full speed at 60 Hz all the time, they exceeded the water turnover rate required by the state. They were wasting energy.”
Hershey calculated that the pool could still meet state requirements by running the 15-hp pump at 49 Hz and the 10-hp pump at 47.2 Hz instead of 60 Hz — an average speed reduction of 19 percent. He recommended installing a Danfoss VLT® AQUA Drive for each pump motor.