Americas Generators

EPA Tier Ratings for Generators

by 10. December 2016 15:17

In the mid-1950s, the U.S. government started controlling atmospheric pollutants. The passage of regulations governing diesel engine emissions forced manufacturers to improve engine performance and limit the amount of pollutants that they send into the atmosphere. While diesel generators were not the original targets, they are now subject to government regulations. Currently, stationary and non-road mobile diesel engines, such as those used in generator sets, are included in the stringent oversight of the U.S. Environmental Protection Agency.

(Pixabay / Hans)

Phased Emissions Tiers

The EPA implemented emissions reductions in phases to allow scientists, manufacturers, and the market to develop technologies, knowledge, and funds necessary for compliance.

  • Tier 1 – The first phase, which came in 1990, gave substantial increase in authority and responsibility to the federal government to authorize the issuance of operating permits to stationary sources. It provided the first set of emission standards covering all new non-road mobile diesel engines, regardless of horsepower categories, except those engines used in locomotives and marine vessels.
  • Tier 2 – The phase was adopted in 1998, tightening pollution regulations.  It addressed NOx (generic term for the mono-nitrogen oxides NO and NO2), carbon monoxide, unburned hydrocarbons, and particulate matter emitted. It covered all engine sizes from 2001 to 2005.
  • Tier 3 – It was implemented between 2006 and 2008, restricting exhaust emissions for engines with 50 to 750 hp.
  • Tier 4 – The final ruling was signed on May 11, 2004 with guidelines to phase it in over the period from 2008 to 2015. The new standards require a 90 percent reduction of PM and NOx emissions. The emission reductions are to be achieved through the use of new control technologies similar to the 2007 to 2010 requirements for highway engines that included advanced after-treatment of exhaust gas.

The New Source Performance Standards require most stationary diesel engines to meet the emission requirements of Tiers 2, 3, or 4, depending on the engine’s power range. Beginning in 2011, non-emergency diesel engines using less than 10 liters per cylinder and greater than 175 horsepower will fall under the Tier 4 regulations. A generator classified as an emergency generator must not run unless the primary source of electrical power is not available. It is allowed to run for testing and maintenance but not for more than 100 hours per year in non-emergency situations.



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