What are heater control units and why will you need one?

New NOx requirements are increasing the need for aftertreatment systems to reach effective operating temperatures quickly, particularly during cold starts and low-load operation. At Cummins Inc., we're constantly innovating to meet the evolving demands of the most stringent emissions regulations. To meet ultra-low NOx standards set by state and federal regulators, Cummins developed a control technology, the heater control unit (HCU). 

What is a heater control unit?

As emissions requirements become more stringent, catalysts need to reach effective operating temperatures quickly, particularly during cold starts and low-load operation, HCUs help the aftertreatment system reach effective operating temperatures more quickly to support NOx reduction.

The HCU works alongside Cummins’ aftertreatment systems, which already filter particulate matter and reduce NOx emissions. In the past, these systems relied on engine heat to warm the catalyst that captures NOx. Today, they require additional components that operate independently of engine power to meet stricter performance demands.

How does the heater control unit work?

The HCU acts as a high‑pow er DC/DC converter, delivering up to 10 kW during startup to heat the catalyst rapidly. Once optimal temperature is reached, it intelligently adjusts output to maintain ideal conditions for NOx reduction throughout operation. This rapid heating helps support effective NOx reduction during cold starts and low-load operation while maintaining consistent aftertreatment performance. 

Cummins heater control units

At Cummins, we’re focused on making the integration of new heater control units as seamless as possible. Features such as cybersecurity, circuit protection and lightweight components are designed to support efficient, durable system integration.

Cummins heater control units have successfully completed durability testing equivalent to 22,000 hours, corresponding to 450,000 miles, and have completed field validation totaling 2.5 million miles across 49 vehicles.

Since 2024, we’ve advanced emissions reduction technology with our HCU, and we’re developing an even more advanced version for 2027 engines. Stay tuned to learn more about how Cummins aftertreatment technologies help fleets meet ultra-low NOx requirements.