IHS, a global information company, reports that more than $100 million was spent on uninterruptible power supply (UPS) in 2012 for healthcare and insurance applications in North America alone. It’s not a matter of whether or not UPS can be used in healthcare applications. Instead, we must figure out where the UPS should be applied in the electrical system.
The NEC is an advisory document for electrical system applications that sets the standard in all 50 states in North America. It outlines specific instructions for healthcare applications in Article 517 and includes a more general reference to using UPS in emergency systems in Article 700. These electrical codes are important and complex, so it’s important that we’re all on the same page. Power system designers are concerned about configuring systems that meet the requirements of the code while providing a design that will ensure critical systems are always available.
In NEC Article 517, the electrical system in a healthcare application is separated into the nonessential loads and the essential electrical system. The essential portion is divided further into the equipment branch, the life safety branch and the critical branch. To best apply the UPS system for a healthcare application, designers need to know which part of the system is being protected by the UPS, because each part has its own requirements including loads that can be located on a branch and equipment that can be used to support the branch.
Sometimes customers request guidance on supporting a life safety or critical branch with UPS. Based on our understanding of the NEC and our experience in designing power systems for healthcare customers, we do not recommend using the UPS as part of the emergency power system that supports these branches. There are several limitations in the code that may preclude applying a UPS as an alternate power source within the emergency system. Therefore, we encourage an alternative direction for supporting the emergency system without directly placing the UPS in the path between the loads and the alternate power source.
In Figure 1, the UPS is applied as part of the normal side input of the life safety or critical branch transfer switch. Adding another transfer switch ahead of the UPS allows it to receive input power from both the utility and the standby generator sets. By moving the UPS to the normal side of the life safety or critical branch transfer switches, we remove it from the emergency system, thereby avoiding areas of the code that prevent the UPS from being considered an alternate source.
The close relationships we cultivate with healthcare customers allow us to support specific requests while still providing guidance that fits within our interpretation of the NEC. It is not our practice to provide rulings on the requirements outlined in the codes. However, we’ve found that by working directly with customers and the local authority having jurisdiction, we can provide suitable solutions that meet customer needs and follow regulatory codes in a way that’s safe and effective.
We would like to learn more how you have applied UPS in healthcare applications:
Have you ever applied a UPS in an emergency system as defined by the NEC?
Do you find different interpretations of the code across the country?
What system branch typically requires medical imaging and IT loads that need UPS protection?