DPF System Overview
How the Diesel Particulate Filter works and regenerates
The Diesel Particulate Filter (DPF) system traps soot and ash from the APU exhaust. It consists of a filter element, an electrical heater, a controller, and sensors for exhaust temperature and backpressure.
The DPF uses a flow-through design where channel ends are alternately plugged, forcing exhaust gas through porous ceramic walls that act as filters. Soot is trapped in the filter and later burned off during regeneration.
• Filter Element — Ceramic honeycomb structure that traps exhaust ash and soot. • Electrical Heater — Heats the filter element to oxidize collected soot. • Insulated Exhaust Tubing — Maintains optimal exhaust gas temperatures and efficiency. • Back Pressure Sensor — Measures exhaust backpressure and signals when regeneration should begin. • Exhaust Temperature Sensor — Measures temperature inside the DPF housing to determine regeneration status. • DPF Controller — Connects to the Climate Control Module (CCM) via CANBUS, processes sensor data, and powers the heater using 120 VAC from the generator. Alarms are displayed on the Aspen Interface (AI).
Ash accumulates in the filter channels as part of normal regeneration. The impact on backpressure is only noticeable toward end of system life, depending on duty cycle.
Normal Operation
During normal operation, backpressure will not exceed 130 mbar. The APU is designed to operate 8 to 10 hours before regeneration is needed.
Automatic Regeneration
When a regeneration cycle starts, the system disables climate control functions and applies APU power to the exhaust heater. The system monitors backpressure and exhaust temperature to verify the heater is working correctly.
Regeneration ends when backpressure falls below 30 mbar or after a timeout of 30 minutes, whichever comes first. Regeneration typically takes less than 20 minutes.
If three consecutive regeneration timeout events occur, the filter needs cleaning. A message will be displayed to inform you.
You can also start a manual DPF regeneration. Refer to the Run Mode page for manual DPF regen instructions.
Backpressure Zones
• Below 5 mbar (APU running) — Backpressure Sensor Failure. • Below 30 mbar — Filter is clean. • Below 100 mbar — Normal operating range. • 100–130 mbar — Filter will regenerate as soon as you shut the APU down. Engine continues to run through the regeneration process. Manual regeneration is allowed. • 130–190 mbar — All convenience features are immediately turned off on APU start. Regeneration starts immediately. Main Engine Interlock is disabled (you can operate the main truck engine without shutting down the APU). • 190–230 mbar — Excessive backpressure detected; immediate engine shutdown. System needs service, including DPF cleaning. • Above 230 mbar — Backpressure Sensor Failure. System requires immediate service (APU engine is disabled).
If backpressure reaches 190–230 mbar, the APU engine shuts down immediately. The system must be serviced and the DPF cleaned before further operation.