402
Thermo H plus
4 Functions of the heater
4.3
D heater
The heater principle is based on a high-pressure atomizer
burner and is monitored by an integrated control unit.
The burner motor powers the fan and the fuel pump. The
fuel pump is coupled to the motor using a plastic coupling.
The fan produces the required combustion air, the com-
bustion air volume is impacted by the burner motor speed.
The speed is read and monitored by a Hall sensor.
The speed required for the CO
2
content is determined
during first calibration at Valeo and is stored in the control
unit.
In a maintenance event the workshop can adjust the CO
2
setting using the DTT diagnosis (Diagnose Thermo Test)
).
The fuel pressure is generated in the fuel pump and
reduced to the required pressure using a pressure limiting
valve.
A solenoid valve releases the fuel via the atomizer nozzle
for combustion in the combustion chamber.
As an option, the fuel pump can be equipped with a nozzle
block preheater. The nozzle block preheater heats the
nozzle holder with the atomizer nozzle at low tempera-
tures, and thus the fuel. The fuel air mixture is ignited in
the combustion chamber via a high-voltage ignition spark.
The flame is monitored by a flame detector integrated into
the control device.
Depending on the equipment, the heater is switched on
and off using a
• digital timer
• switch
• or climate control.
During heating operation the burner is automatically swit
-
ched on and off. For control a temperature sensor is
installed in the coolant outlet of the heat exchanger.
The heater is switched on, when the temperature falls
short of a lower temperature threshold, and is switched
off, if the upper temperature threshold is reached (see
).
The switching thresholds depend on the operation mode
of the heater and are programmed into the control device.
An operation indicator is available for monitoring the
operation status of the heater. A flame indication can be
optionally installed.
The operation indicator is also used to output error
messages via flash code.
CI:
Control idle
on/off :
lower/upper threshold
Aux. heating:
Heater is operating, engine is opera-
ting
Parking heating: Heater is operating, engine is off
Economy setting: Control temperature is on a lower level
NOTE:
Auxiliary heating has priority over the economy setting!
Table 401 Water Temperature Control Thresholds (standard data set)
Heater
Aux. heating
(terminal 61)
Parking heating
Econ. setting
on
off (CI)
on
off (CI)
on
off (CI)
Thermo plus 160
Thermo plus 230
Thermo plus 300
Thermo plus 350
72
82
67
77
55
70
Summary of Contents for Thermo H 160
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