4.3.4.8 RA heating system
A Heating zone, SCR system 1
B Heating zone, SCR system 2
C Heating zone, PFM
D Heating zone, RA tank
1 Reducing agent lines
2 Electrical cabling
3 RA suction filter
4 RA main filter
5 Temperature sensor
6 Pressure sensor
7 Pump speed sensor
8 Filling level sensor
9 RA quality sensor
10 Heating element (24 V)
11 Main heater for RA tank (not
controlled by ECU)
12 Engine
An electrically heated version of the RA system is available which features an integrated electrical heater for
the PFM, SU/DU systems and the RA lines.
The RA system is separated into three heating zones:
RA tank heating zone:
Including the tank connections and the RA lines between the RA tank and PFM. This heating zone is trig-
gered by the temperature of the RA in the RA tank and the heating demand from the PFM heating zone.
RA tank main heating control is not included in this heating zone.
PFM heating zone:
Including the PFM and the RA lines between the PFM and the SCR system. This heating zone is triggered
by the temperature of the RA in the PFM and the heating demands from the RA tank and SCR system
heating zones.
SCR system heating zone:
Including the SUs and all RA lines installed on the SCR system. This heating zone is triggered by the
internal heating demand of the SU/DU systems.
Two heating levels are used depending on the heating zone triggers measured:
• Full heating power in response to a frozen RA dosing system
• Reduced heating power to prevent the RA dosing system freezing up again.
At an ambient temperature of ≥-20 °C, the RA dosing system is thawed out and ready for dosing within
40 min of engine starting when the heating elements are supplied with a voltage of ≥16.8 V. Lower tempera-
tures (down to ≥-40 °C) require a voltage supply in the generator voltage range (≥27.5 V)
88 | RA Dosing System | MS15065/01E 2019-01
TIM-ID: 0000072460 - 001
