Generator set ratings are guidelines to help size the unit to meet the load requirements of the application. There are three common industry generator set ratings for gas generator sets: standby, prime and continuous. Each manufacturer, however, may have different engine tolerances that affect the engine and/or generator set ratings. When choosing a rating for generator sets installed within the United States, the U.S. EPA emission standards for stationary emergency and non-emergency engines must also be considered.
Standby-Rated Gas Generator Sets
Suitable for stationary emergency applications where the generator set serves as the secondary power source when the primary utility power source fails. The EPA allows for a maximum of 100 hours of operation annually on either pipeline natural gas or propane fuel sources for maintenance checks and readiness testing.
In these applications, the standby rating is typically specified at a 0.8 power factor. This rating is applicable to variable loads with an average load factor at a percentage of the standby nameplate rating.
Prime-Rated Gas Generator Sets
Suitable for stationary non-emergency applications where the generator set serves as either the primary or secondary power source when connected to an unreliable utility power source. Prime-rated gas generator sets are typically used for either peak shaving or to provide interruptible power when required by the utility. They can also serve as a secondary power source upon utility failure.
In these applications, the prime rating is typically specified at a 0.8 power factor. This rating is applicable to variable loads with an average load factor at a percentage of the prime nameplate rating for an EPA-allowable unlimited amount of total operation hours.
Continuous-Rated Gas Generator Sets
Suitable for paralleling with utility applications where the generator set serves as the primary power source. They typically cannot operate as a secondary power source upon utility failure due to their limited transient response capabilities.
In these applications, the continuous rating is typically specified at a 1.0 power factor. The load factor allows the generator set to be operated at full load for an EPA allowable unlimited amount of total operational hours.
For more information on Gas Generator sets, contact South Shore Generator.