An important facet of preventative maintenance is generator load bank testing. A load bank test ensures that your generator will run at proper rating so you can have peace of mind when power goes out. This is particularly important for standby and emergency generator sets that do not run often and may not be operated at full rated capacity during regular exercising. If a load bank test is not performed, your generator may not function properly when needed during your next power outage. This paper will detail purpose, process, results and frequency proper load bank testing.
Load bank testing simulates the designed usage of the generator at the advertised rating located on the nameplate of the unit. It verifies that all primary components of the generator set are functioning properly under loaded conditions. The equipment used to perform a load bank test produces an artificial load on the generator by bringing the engine to an appropriate operating temperature. The key to a proper test is that your generator must be tested at its full output rating. When a generator operates during the weekly or monthly exercise, it runs at a lower load than the unit’s full-rated output ability. Load banking tests the generator’s ability to execute and deliver the required kW during an emergency. Many generator owners exercise their standby generators weekly un-loaded, but rarely test them with building loads, relying on the occasional utility loss to completely exercise the entire back-up power system. Manufacturers do not recommend this practice.
Load bank testing is mandatory for several applications. A number of regulatory oversight conditions and code requirements are mandatory for emergency power generation systems where failure of equipment could lead to loss of human life, according to NFPA 110 Level 1. Both the National Fire Protection Agency (NFPA) and the National Electric Code (NEC) have mandates pertaining to load bank testing of emergency generators.
Load banks can be defined as a self-contained, unitized, systematic device that includes load elements or steps. The following types of load testing are available: