Tier 4F Inducement

Tier 4F Background
Emissions standards for non-road (off-road) engines, including stationary, compression-ignition (diesel) engines are established by the United States Environmental Protection Agency (USEPA). The initial federal standards included a Tier 1 standard and later expanded to include more stringent Tier 2 and Tier 3 standards. Tier 4 standards were introduced in 2004, which required significant reductions in nitrogen oxides (NOx), hydrocarbons (HC), and particulate matter (PM). To comply with Tier 4F standards, emissions reductions are achieved through the addition of exhaust after treatment, such as diesel oxidation catalysts (DOCs), selective catalytic reduction (SCR) and diesel particulate filters (DPFs).

The California Air Resources Board (CARB) established the California state emissions standards in the 2011 Airborne Toxic Control Measure for Compression-Ignition Engines (ATCM), requiring Tier 2 or Tier 3 compliance for stationary diesel engines, based on horsepower rating. The ATCM requires end users to obtain an air operating permit for stationary diesel engines rated 50 horsepower (hp) or more from the local air district. California’s 35 independent air districts have the authority to require more stringent emissions standards in order to comply with federal and state ambient air quality standards.

With the increasing prevalence of stationary diesel engines throughout California, some air districts have taken measures to reduce emissions and comply with ambient air quality standards through the implementation of Tier 4F emissions standards for stationary, emergency and standby diesel engines.

Tier 4F Certified vs. Tier 4F Compliant/Retrofitted Engines
Air districts that have established Tier 4F emissions limits will allow Tier 4F EPA certified engines, or Tier 4F compliant/ retrofitted engines that demonstrate compliance with Tier 4F standards, to be permitted.

A Tier 4F Certified Engine is a new engine with integral emissions reductions technologies that is certified by USEPA to comply with Tier 4F emissions standards. Tier 4F certified engines include inducement features, and do not require emissions testing.

A Tier 4F Compliant or Retrofitted Engine is a new or existing EPA-certified engine retrofitted with OEM (Compliant) or third-party (Retrofitted) after treatment to achieve Tier 4F emissions standards. Inducement features on non-certified Tier 4F engines are disabled. Non-certified Tier 4F engines require initial performance testing and ongoing emissions testing to demonstrate compliance with Tier 4F emissions standards.

Inducement
EPA and CARB Tier 4 Final regulations mandate inducement strategies for certified engines to ensure proper emissions control. These strategies involve the engine's ECU providing visual and audible alarms to alert operators to required maintenance or repairs. Additionally, the ECU progressively derates engine speed and power at specific inducement levels to protect the emission control system and prevent permanent damage.

To address emergency situations, the EPA allows a temporary 120-hour "Operator Inducement Emergency Override." This restores full engine power during qualified emergencies, defined as significant direct or indirect risks to human life.

Direct risks include situations where the engine is used in life-saving rescues. Indirect risks encompass powering critical infrastructure like emergency communication centers that support emergency response.

Using the override outside of these defined emergency criteria is prohibited. If proper actions are not taken to correct faults, the engine will derate and eventually shut down. End users are required to report all uses of the emergency override to the EPA. An authorized technician must arm the override feature, although the end user can activate it.

Federal regulations strictly prohibit improper use of the override, failure to deactivate it after an emergency, and failure to report its use. Violations are subject to severe civil penalties, assessed per day of operation.

For critical operations where uninterrupted power is essential, especially during emergencies, non-certified Tier 4F engines, which do not incorporate inducement features, may be a preferred option to avoid potential shutdowns.

Conclusion
In conclusion, the evolution of emissions standards, driven by both federal EPA and state CARB regulations, has significantly impacted the deployment and operation of stationary diesel engines, particularly in California. The transition to Tier 4F standards, with its emphasis on advanced after treatment technologies, presents a critical choice between certified engines with integrated inducement features and compliant/ retrofitted engines that bypass these safeguards. While certified engines ensure stringent emissions control through automated systems and emergency overrides, they also introduce potential operational limitations during critical situations. Conversely, retrofitted engines offer the advantage of uninterrupted power, albeit with the necessity for rigorous and ongoing emissions testing. Ultimately, the selection of engine type hinges on

a careful evaluation of operational priorities, regulatory compliance, the critical nature of the application, and balancing environmental responsibility with the imperative need for reliable power. For help making the right selection, contact Generac Industrial Energy at https://www.generac.com/ industrial/ or toll free at 1-844-ASK-GNRC.

About the Authors

Jesus Chavira currently works as a Power Solutions Manager and is responsible for the California and the Pacific Northwest territory. With a degree in mechanical engineering, he has spent more than 9 years in the power generation industry. His career started in new product design for FT4 mobile power generation equipment, focusing on wire harness design and controller programming. For the last four years, he has worked as part of the field applications team at Generac. His specialties include codes and standards, diesel emissions, and generator set packaging.

Kathleen Beresh is Energy Systems’ Environmental Permitting Manager and has nearly 20 years of experience in environmental compliance and permitting consulting, specializing in air quality. For the last 5 years she has overseen Energy Systems’ air permitting services and provides compliance and permitting support in California and the Pacific Northwest. With extensive experience in federal, state and local engine regulatory requirements, she supports customers in navigating the complexities and challenges of air permitting and identifying cost- effective and compliant solutions.