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Is Your Backup Power System Ready? Prove It.

Regardless of how carefully a backup power system is designed, it won’t matter if the system doesn’t provide power when its needed most. How can facilities know whether their backup power system will be ready and available? By implementing an adequate program of maintenance and testing.

An Overview of NFPA 110

The National Fire Protection Agency publishes NFPA 110 - Standard for Emergency and Standby Power Systems. It provides minimum guidance on the design, installation, maintenance, and testing of backup power systems, guidance that is referenced by other industry standards such as NFPA 70 – National Electrical Code, NFPA 99 – The Healthcare Facilities Code, and The Joint Commission Hospital Accreditation Standards. Furthermore, reliable backup power is not just an issue for healthcare … The Uptime Institute reports that 36% of data center outages are power-related.

Key Provisions

NFPA 110 categorizes Emergency Power Supply Systems (EPSS), then prescribes requirements for installation, system maintenance, and periodic operational testing as follows.

EPSS Categories

NFPA identifies backup power systems by Class, Type, and Level.


The code classifies EPSS into classes according to the amount of time that they must be able to provide power without refueling or recharging. Five time classes range from 5 minutes to 48 hours, and a sixth class allows the runtime to be defined by application, code, or the user.


NFPA 110 classifies EPSS by how quickly backup power must become available. The maximum amount of time that the load terminals of a transfer switch can be without power are defined by four Types that range from “basically uninterruptible” to 120 seconds, plus a fifth type for manual switches, which has no time limit, as shown in the table above.


NFPA Level 1 systems are required where a failure of backup power could result in loss of human life or serious injuries. Level 2 systems can be used where backup power is less critical to human life and safety.

        Common Application

The Class, Type, and Level assigned to backup power systems vary by the missions of the facilities they serve. Many hospitals and healthcare facilities require Class 48, Type 10, Level 1 EPSS. In other applications such as data centers, the class and level may depend on the maximum time that an Uninterruptible Power Supply can keep the facility running as well as the nature of the operations or services supported by the facility.

Environmental Requirements

The standard requires facilities to protect EPSS from exposure to environmental conditions. For outdoor locations, an EPS must be installed in an enclosure that can resist rain and snow pursuant to local building codes and minimize damage from flooding. For indoor applications, Level 1 EPS equipment must be installed in a dedicated room that is constructed to a two-hour fire resistance rating.

NFPA 110 also addresses heating, ventilation, and air conditioning requirements for the EPSS spaces. Temperatures cannot exceed those specified by a system’s emergency power equipment manufacturers. Level 1 systems require heating to maintain ambient temperatures above 4.5°C (40°F).

Installation Testing

Once installed, EPSS must be tested to prove they can deliver backup power as required. The testing is completed without and with load for the durations shown in the following table.
Maintenance Requirements

After an EPSS is installed, accepted, and placed in service, equipment maintenance and testing are necessary to demonstrate that backup systems can provide power when needed. NFPA 110 requires a written maintenance and testing program that complies with:
  1. manufacturers’ recommendations
  2. instruction manuals
  3. minimum requirements of the Standard
  4. the requirements of the Authority Having Jurisdiction
The standard prescribes a scope of maintenance activities. For transfer switches and paralleling gear, this includes checking connections, inspecting or testing for overheating and corrosion, cleaning components, and replacing contacts when required. For paralleling gear, the proper function of controls must also be verified. Maintenance and testing of batteries and fuel is specified, and all actions must be performed by qualified personnel. Testing must also be completed after equipment repairs; specific requirements can be found in the standard. The following table summarizes periodic requirements.
Notably, NFPA 110 Article 8.1.2 states, “Consideration shall be given to temporarily providing a portable or alternate source whenever the emergency generator is out of service...” and cannot meet the performance requirements for supplying power to loads. A quick connect panel and a permanent switching means can meet this requirement.


Omitting or delaying the maintenance and testing of Emergency Power Supply Systems leaves facilities and their customers and patients without assurance that vital backup power will be available when its needed most. A program that records and documents how maintenance and testing activities met or exceeded the minimum requirements of NFPA 110 is the first step to demonstrating readiness.

Readers should note that this article provides a cursory review of NFPA 110. For additional detail, consult the information sources below. Any evaluation of a compliance strategy should be made only after reviewing NFPA 110 directly and/or consulting a qualified professional.


For related reading, see:

        National Fire Protection Agency
                • NFPA 110 - Standard for Emergency and Standby Power Systems
        ASCO Power Technologies, Inc.
                • White Paper - NFPA 110 – Standard for Emergency and Standby Power Systems, 2022 Edition.
                • White Paper - NFPA 110 Overview Part 2: Installation, Environment, and Testing
                • Infographic - Understanding NFPA 110 Standards
                • Technical Brief - NEC Requirement for Permanent Manual Switching Means

For additional information, contact ASCO Customer Care.