HL 90
3 Functional Description
301
3 Functional Description
(Fig. 301)
3.1 Controls
The heaters may be equipped with the following controls:
– room thermostat (mechanical)
–switch
–timer
Activation and deactivation is by means of the switch,
timer or room thermostat with on/off switch.
An operating indicator light (in timer, switch or room
thermostat) indicates the heater on condition.
3.2 Switch On
Upon switch on the operating indicator light goes on and
the glow plug is powered. After approximately 35 seconds
the fuel dosing pump is put into operation. After another
5 seconds the motor of the heating and combustion air fan
is activated. Combustion commences. After flame-up the
glow plug is switched off.
If no proper combustion is achieved within 100 seconds,
an automatic restart is performed. If the no combustion
condition persists, an error lockout will occur within
another 80 seconds with a subsequent run-down of
150 seconds.
The operating indicator light remains on in case of an
error lockout condition.
3.3 Heating Operation
During operation combustion gasses flow through the
heat exchanger to dissipate heat onto the heat exchanger
casing from where it is picked up by the heating air flow to
the vehicle interior maintained by the heating air fan.
3.3.1 Operation with Room Thermostat
(mechanical)
The room thermostat (mechanical) allows selection of
full load / part load or part load / off.
• Full load / part load operation
After reaching the temperature set with the room
thermostat (upper switching point of the room thermostat)
part load operation will be initiated. When the temperature
drops below the lower switching point, the heater resumes
full load operation. In part load operation motor speed and
dosing pump fuel delivery is reduced.
• Part load / off operation
After reaching the temperature set with the room
thermostat (upper switching point) the heater is switched
off. The operating indicator light remains on to indicate a
run-down with full speed operation of the heating and
combustion air fan motor.
When the temperature reaches the lower switching
threshold of the room thermostat, a new start procedure
commences. The heater operates in full load.
After a short time of full load combustion operation there
will be transition to part load operation.
3.3.2 Operation with Switch
During heating operation with a switch manual selection
between full load and part load is possible.
3.3.3 Operation with Timer
The timer is used for switch on with a switch (instant heat)
or for time preset operation. A control in the operating
modes full load / part load may be provided by integration
of the room thermostat (mechanical).
3.4 Switch Off
Switching the heater off extinguishes the operating
indicator light of the room thermostat, the switch or the
timer. Fuel supply is cut off stopping combustion.
The motor of the heating and combustion air fan continues
operation to cool the heater down (run-down).
Run-down time: 150 to 190 seconds
Run-down operation is controlled automatically.
NOTE
The motor of the heating and combustion air fan always
operates in full load during run-down.
Re-activation of the heater during run-down is permitted.
Run-down is then completed with a subsequent new start.
3.5 Ventilation Operation
When equipped with a room thermostat ventilation
operation is only possible with a separate switch
(order no. 109 995 (24V), 109 999 (12V)).
(96 pages)
(83 pages)
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