Everyone talks about the high cost of hospital care, but for medical centers across the country, the cost to operate the building on a daily basis also continues to climb. As the largest regional medical center in San Joaquin County, St. Joseph’s Medical Center in Stockton, Calif., knows this well. The 359-bed facility employs over 400 physicians and more than 2,400 employees providing medical, surgical and diagnostic services. Operating the HVAC mechanical equipment for a facility this large is a huge energy-conservation challenge. That's why in the 1980s, St. Joseph’s made the decision to use variable frequency drives (VFDs) on HVAC pump and fan motors —a decision that continues to pay off today, thanks to an innovative upgrade plan using Danfoss VLT® Drives.
“Starting in the 1980s, St. Joseph’s began applying VFDs on pumps and air handlers to save energy,” says Bruce Kreiss, chief engineer for plant maintenance and operations. “Over the years, that investment has paid off by minimizing electricity costs —which is especially important given recent electric rate increases in California. But after 20 years of operation, we were looking for an affordable upgrade path.”
Thinking outside the box to control costs
Rather than opt for short-sighted short-term first-cost savings of single- or two-speed motors, St Joseph’s Medical Center elected to go with the long-term energy savings obtained with VFDs. VFDs offer substantial energy savings when applied to centrifugal fan and pump motors. In fact, due to the physics of Affinity Laws, reducing fan or pump speed by 20 percent provides a potential energy savings of 50 percent.
Hospitals operate 24 hours a day, seven days a week, so most HVAC fans and pumps run well below 100 percent load, making variable speed drive technology an ideal solution to generate energy savings.
In the 1980s and early 1990s, St. Joseph purchased VFDs from Graham Company in Milwaukee. Danfoss acquired Graham in 1995. In 1998 and 1999, the hospital purchased 30 Danfoss VLT® 6000 drives. After enjoying nearly two decades of VFD energy savings, it was clear that St. Joseph’s needed a strategy to replace these older drives.
“Danfoss drives are designed and manufactured to provide the longest service life available in the industry. Like all electronic devices, electrical component life span is determined by duty cycle, load characteristics, ambient temperatures, and other environmental factors,” says Tim Smith, Danfoss DrivePro service sales manager. “In this case, the Danfoss VLT® Drives were in operation over 10 years. That’s good value. But now we had to put on our thinking hats to create an affordable way to stage the replacement of the installed base.”
Due to budget constraints and the quantity and age of the drives, St. Joseph’s was looking for a flexible, long-term solution for managing its VFD assets. In 2003, Danfoss proposed a program to replace 15 old Graham drives with new Danfoss drives over a multi-year period as part of its SmartStep program.
SmartStep provides a proactive upgrade path
“The beauty of the SmartStep program is that St. Joseph’s can lock in the price of the drive and service at current costs while replacing equipment over a multi-year period,” says Smith. “In this case, the drives were legacy products from Graham, so we have a unique specific understanding of each drive. However, the program can provide service support and an equipment migration strategy regardless of the original drive’s manufacturer.”
Smith explains that SmartStep is a customizable program that can meet a wide range of customer’s long-term needs. The plan allows drive replacements to be scheduled to fit into the maintenance budget and minimizes unpredictable service expenditures. Replacing drives over a multi-year period also eliminates the huge upfront capital expense of replacing all the drives at once.
Based on the success of the 2003 SmartStep program, in 2011 St. Joseph’s purchased a program covering 47 drives —practically its entire installed base of VFDs —with 50 percent used for fans and the other 50 percent used for pumps. Sizes ranged from 100 hp for cooling tower fan motors to 1.5 hp for small pump motors. The first four drives installed under the plan were VLT® HVAC Drives.
VLT® HVAC Drives were developed by Danfoss to be dedicated for HVAC applications with features specifically for controlling pumps and fans —from auto-tuning, energy optimization, and monitoring. For hospital applications involving sensitive high-tech equipment, the drive incorporates protection to minimize harmonic and electromagnetic interference (EMI)/radio frequency interference (RFI) noise. These features make it easier to comply with local harmonic limitations and reduce the risk of needing to retrofit harmonic mitigation measures in the future.
The SmartStep plan includes removal of the existing drives, installation of the new drives, commissioning service, and customer training. Additionally all 47 drives are covered under the Danfoss DrivePro-tection program for the length of the contract. DrivePro-tection is a premium coverage program that not only covers defects and normal wear but also covers accidental drive damage such as lightning strikes or exposure to water.
“Our goal was to create a plan that would provide for a replacement and service path so the entire drive infrastructure could be managed as a maintenance expense,” Kreiss explains. “So I was glad Danfoss had the flexibility to customize SmartStep and DrivePro-tection to accommodate our budget and timetable.”