"I'm told my new diesel generators have to meet Tier 4 requirements. What do I need? And what's the difference between certified and compliant, anyway?"
Diesel engines built since January 1, 2011 for use in stationary emergency generators operated simultaneously with normal power available exceeding 100 hours per year are required to meet T4i certifiedemission standards. EPA Tier 2 generators can be operated for unlimited time during actual normal power outages but when these generators exceed the 100 hour limit, only Tier 4i certified engines are legally acceptable according to Federal EPA law.
Many excellent manufacturers of emission control devices offer Tier 4 compliant products that can be added to existing or new Tier 2 engines, reducing some level of emissions output. However, compliant is not legally acceptable if the simultaneous use exceeds the 100 hour limit. Compliant solutions typically address only one constituent of the Tier 4i emission law and differ from certified product which is designed specifically to EPA requirements. Tier 4F regulations which will apply to engines manufactured after January 1, 2015 will further increase the emission reduction requirements.