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September 25, 2003
For hospitals, ensuring a reliable power supply is as much about strategy as it is about transformers and generators. The new surgery pavilion at the University of Washington Medical Center is an excellent example.
Of course, it helps that the new building is backed up by the campus’ emergency power system, with 4 megawatts of generating capacity that can serve the medical center during a power outage.
That much output may seem surprising, but a hospital with 11 operating rooms requires a huge amount of power — and no chance of failure.
Campus and emergency power systems ensure the surgery pavilion won’t go dark during a power outage. Design strategies have helped prepare the facility for future growth and increased operability.
The surgery pavilion’s electrical systems are designed with redundancy and the capability to operate the building during an extended outage.
What does this mean in terms of the health of its electrical systems? In essence, it’s all about substations, spot networks and power panels.
To power the pavilion, three normal feeders and one emergency feeder are distributed from UW’s main campus. These services feed into substations, each with its own transformer, to provide clean, usable power to the pavilion.
The three normal feeders are configured in a spot network, which permits switching from one substation to another without outages. The transformers are tied together to prevent interruption when substations are undergoing maintenance or are otherwise inoperable. In the unlikely event that both the normal power and emergency power feeders fail, an external generator connection is available for a portable generator.
On the pavilion’s second floor, each operating suite is fed by two isolated power panels, one from the normal system and one from the emergency system. The panels are critical to maintaining the safety of the patient and medical personnel in each operating room.
Because the specialized systems must maintain a certain tolerance to function properly, the isolated power panels monitor the ground current in the electrical systems to warn of any undesirable flow of electrical current in the system. If the normal power system fails, surgeries can still continue with emergency power.
Over and above
Strategic planning in a project’s design phase provides opportunities to exceed building requirements by recommending more extensive, flexible infrastructure.
For example, the National Electrical Code requires that three branches of emergency power serve life safety, critical loads and essential equipment. These are distributed to each floor of the pavilion. The surgery pavilion also has an additional emergency branch, optional equipment.
Distribution of this branch permits the connection of mechanical, HVAC, plumbing and hospital-related equipment to enable the building to operate during an outage. While many facilities do not have such extensive emergency equipment branches, the medical center saw an opportunity to use the additional capacity for greater benefit.
“This electrical configuration allows us the flexibility to maintain the building in operation and continue patient care service during power outages,” said Howard Schneider, director of operations and maintenance at the medical center.
Due to the building’s length — its west side is 180 feet long — two electrical risers are stacked vertically on each floor on the north and south sides of the facility.
To minimize disruptions to the pavilion during future remodels, all electrical services, including panels and large feeders, are located in the utility-oriented section of the floor outside of the potential remodel space.
Rather than relocate 4-inch feeder raceways with a lot of heavy copper cables, small conduits with branch circuit-feed receptacles can be used instead. This configuration is designed to be more flexible, cut remodel costs and reduce the overall disruption of facility operations.
Pairing powerful systems with design strategies adds value to the pavilion and sets new standards for the UW Medical Center.
Gary Batie is an associate at Sparling, an electrical engineering and technology consulting firm. He is the electrical project manager for the UW Medical Center Surgery Pavilion project.