Using load banks to meet emergency power generating system codes and standards

 

The NFPA is a United States trade association, albeit with some international members, that creates and maintains private, copyrighted standards and codes for usage and adoption by local governments. 

 

NFPA 99 – Healthcare Facilities Code – Healthcare facilities must exercise Emergency and Standby Power Systems under load and operating temperature conditions for at least 30 minutes at intervals of not more than 30 days. 

 

NFPA 110 – Standard for Emergency Generator Systems – This standard sets safety standards to protect commercial building occupants by making sure generator-powered backup lighting will operate as expected. Monthly testing is performed on generators whose failure could result in injury or death. If a generator fails a monthly test, it should be tested annually for two continuous hours using a load bank. Under the continuous test, the generator should be operated at 25 percent of the nameplate kilowatt rating for 30 minutes, at 50 percent of the kilowatt rating for 30 minutes and at 75 percent of the kilowatt rating for 60 minutes. 

 

 

The NEC is a regionally adoptable standard for the safe installation of electrical wiring and equipment in the United States. It is part of the National Fire Codes series published by the National Fire Protection Association (NFPA), a private trade association. 

 

NEC Article 700 – Emergency Systems – Emergency systems are required to receive an operating permit as determined by the local code enforcement authority. This requirement is a lifeline for occupants, ensuring that lighting and life safety loads take priority over other building loads. Should the main electrical power supply fail, backup emergency power for life safety systems must be available within 10 seconds. 

 

NEC Article 701 – Legally Required Standby Systems – Requires standby power to be available to legally required systems within 60 seconds of power loss. While NEC 700 is designed to ensure that people can exit a building, NEC 701 responds to the needs of firefighters and other personnel responding to an emergency. 

 

NEC Article 702 – Optional Standby Systems – Applies to situations where standby generators are optional. In these cases, the systems may be put in place to protect against economic loss or business interruptions. For instance, data centers may elect to install backup power because an outage could result in large revenue losses. 

 

NEC Article 708 – Critical Operations Power Systems – This article was developed following the 9/11 World Trade Center, Hurricane Katrina, and Hurricane Rita disasters in the United States. It requires a commissioning plan for on-site backup generation, baseline testing, and periodic witness testing, as well as a documented preventive maintenance program, written test records, and a method for testing all critical power systems for maximum anticipated load conditions. 

 

 

In international markets, ISO 8528 (BS7698) Part 6 is the standard for testing engine-driven generating sets. It details general test requirements and defines functional and acceptance load bank testing. Functional tests must always be performed, and usually occur at the manufacturer’s test cell. 

 

ISO 8528 (BS7698) Part 6 defines three performance classes – G1, G2, and G3. An additional class, G4, is reserved for performance criteria which are agreed upon between the supplier and the buyer. Each performance class has different criteria depending on the characteristics of the generator set: 

 

G1 is the least stringent and generally applies to small, simple generating sets intended to supply unsophisticated loads. 

 

G2 is broadly equivalent to commercially available power. 

 

G3 is intended for gen-sets that power strategically critical loads or those which particularly require a stable and accurate power supply such as hospitals, data centers and financial institutes.