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Emergency vs Standby Generator: What’s The Difference?

Although the use of generators as a backup power source during power losses is commonly recognized, many people mistakenly interchange the terms “emergency generator” and “standby generator” when describing the equipment relied upon to safeguard critical facilities and processes. In fact, emergency generators are classified quite differently than standby systems. While both emergency and standby power systems operate on fuel to create the electricity needed to power specific loads, the two types of generators serve different purposes. However, both can play a vital role in helping an organization maintain continuous uptime ― and understanding the unique aspects of each will help you understand the option needed for your facility. It’s important to note that generators are usually paired with UPS systems, which provide alternate power to the load during the crucial seconds ― or minutes ― required for a generator to power on.

Applications Requiring Emergency Generators (Level 1)

The specification for either emergency or standby power is generally determined by a fire safety code or building code, with precise requirements varying based on factors such as occupancy type, facility use, critical function and equipment served. The National Fire Protection Association (NFPA) specifies generator types within its NFTA 110 code, requiring the use of a Level 1 emergency power system, or emergency generator, for operations that are essential for life safety. NFPA 110 also specifies that a Level 2 system, also known as a legally required standby generator, be installed where a failure of the system is less critical to human life and safety.

An emergency power generator is designed to kick in automatically in order to provide power to critical systems during an outage. The more expensive of the two classes of generators, this type of backup system starts up in about 10 seconds ― compared to about one minute needed by standby power generators ― making it significantly faster at responding when power is lost. Emergency systems are powered by fuel sources including diesel, propane or natural gas, which can either be stored onsite or delivered via tanker trucks as needed. An emergency power source is designed to operate independently with its own conduits and panels, ensuring that the system maintains a consistent supply of electricity when it’s needed most.

Emergency generators are generally installed in places where artificial illumination is required for safe exiting and for panic control in high-occupancy buildings, such as hotels, theaters, sports arenas, health care facilities and similar institutions. Common uses of emergency generators include illuminating exit signage; powering fire pumps where secondary power is required; ensuring automatic fire detection systems and fire alarm systems remain operational; providing elevator lighting; and maintaining emergency voice/alarm communications systems. Furthermore, in hospital settings, NFPA 110 requires that emergency generators support vital medical equipment such as respirators. Radio systems for firehouses, police stations and 911 operators also require the use of emergency generators to ensure that emergency services can respond in any situation. 

Applications For Legally Required Standby Generators (Level 2)

While emergency power systems are critical to life safety, standby systems are considered less essential. There are two different types of standby power supply generators: legally required and optional. Legally required standby power systems are not critical to life, but without them, hazards could arise that might hinder firefighting operations or rescue. For this reason, they are specified by NFPA codes just as emergency generators are.

While less expensive than emergency systems, standby generators are slower to respond to power losses. The biggest difference between the two generator types is that legally required standby systems have 60 seconds to automatically transfer the load, as opposed to the 10-second requirement for emergency systems. In addition, it is permissible for the wiring of a legally required standby system to share the same raceways, cables, boxes and cabinets with general wiring. Like emergency systems, standby generators are powered by diesel, propane or natural gas.

Legally required standby power systems are most often installed to serve loads such as heating and refrigeration systems, communications systems, ventilation and smoke removal systems, sewage disposal and lighting systems. They may also be used to support some medical devices, as well as industrial processes that, in the absence of an alternate power source, could create hazards during a failure in the electricity system. While some of these uses sound similar to the systems supported by an emergency system, they are not the same. The loads carried by legally required standby power systems are much less urgent than those that must continue operating long enough to evacuate the building and support critical equipment, such as fire alarm systems and fire pumps. For example, standby systems may support lighting, but not the lighting required for illumination essential to safely evacuate patrons from a building.

Applications For Optional Standby Generators 

A second type of standby power supply is referred to as an optional generator. Unlike emergency and legally required generators, optional standby power systems have no code requirements and provide backup power in environments where human life doesn’t depend on the performance of the system. Just as the name implies, an optional standby system can be deployed as a discretionary measure. The optional generator differs from the other two types in that if it failed to kick in during an emergency, human safety would not be compromised. In other words, while this type of backup source may be critical to business operations, it is not essential to life. Optional generators also differ from emergency and legally required standby systems because they have no minimum time requirement for transferring the load.

Many organizations ― including financial services, data centers and Internet/hosting companies, among others ― choose to invest in sophisticated standby backup power systems in order to avoid any disruption to their critical operations and business continuity. These systems range from extremely basic to very elaborate. In many instances, optional standby generators rely on an automatic transfer switch that is either capable of supporting the full load or includes a load management system.

Maintain Your Generator With Unified Power

Regardless of the type of generator in your facility ― emergency or standby ― routine maintenance is essential to ensuring that the system performs properly when you need it most. As a national, one-stop emergency and standby generator maintenance and repair provider, Unified Power understands how much your business relies on your backup equipment. To meet the varied needs of organizations, we offer maintenance service plans on a monthly, quarterly, semi-annual or annual basis, performed by our team of expert technicians. We also offer generator repair, with a 24/7 dispatch facility to provide mission-critical power services around the clock. All of our services are compliant with the requirements of the NFPA 110 code for generator services and testing. We also service all brands of UPS systems. No matter what type or brand of generator you have, Unified Power is prepared to handle all your service requirements.

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