Webasto Air Top 2000 Service And Repair Manual - page 13
3.1.5 Control Operation
During control operation fan speed and dosing pump
rate of delivery are subject to heating performance.
The glow plug is deactivated.
3.1.6 Control Idle
In case the air intake temperature set with the control ele-
ment is exceeded and the minimum heating perfor-
mance had been achieved for longer than 5 seconds,
the fuel supply is cut off to terminate combustion.
The motor of the combustion and heating air fan con-
tinues operation for another 155 seconds at 2/3 of maxi-
mum speed to cool down the air heater (run-down). In
control idle the combustion and heating air fan runs at
minimum speed. The operation indication remains lit.
After reaching the air intake temperature set with the
control element a new start procedure is launched (with-
out break-away).
3.1.7 Switch-Off
Switching the heater off extinguishes the operation indi-
cation of the control element.
If no fuel has been delivered (within 20 seconds for Die-
sel operated heaters or within 15 seconds for fuel oper-
ated heaters after switch-on) or if the air heater is in
control idle, the air heater is deactivated immediately
without run-down.
If fuel supply has commenced it will be immediately
stopped at switch-off. The fan speed decreases within
35
seconds to 2/3 of maximum.
Subsequently or if the flame sensor detects “no flame”
the fan speed is increased to maximum for 60 seconds
and run-down is initiated to last 120 seconds. Run-down
is automatically halted.
NOTE
Re-activation of the heater during run-down is permitted.
Run-down will be completed first with a subsequent re-
start.
3.1.8 Functions of the Air Heater in
TRS Vehicles
NOTE
Applicable only for Air Top 2000 D Air Heaters installed
in vehicles for the transportation of dangerous goods
(TRS).
If the heater is deactivated using the control element,
run-down will not change.
A short run-down (max. 40 seconds) is automatically
activated if:
l
the vehicle engine is turned off
l
a conveyor facility is put into operation
The short run-down time depends on the operational
condition at which TRS switch-off occurs.
A 40 second run-down with maximum speed is initiated
(TRS switch-off) when:
l
air heater is still in the start phase; stabilization
not yet achieved
l
air heater is in normal run-down
l
air heater is in control idle.
A 20 second run-down is switched on in normal combus-
tion operation with the fuel delivery immediately halted
maintaining the fan speed for 5 seconds. Then the
speed is increased for 30 seconds within another 5 sec-
onds.
For all heaters after July 1995 the short run-down
out of all operating conditions is a max. of 20 sec-
onds.
After a TRS switch-off the control unit is in the “error
lockout” condition.
Prior to resuming operation the control element has to
be set to “OFF”.
3.1.9 Switch-off upon Failure
The control unit recognises failures of individual air
heater components and malfunctions in the start se-
quence and in normal operation.
The air heater is deactivated and enters the error lockout
mode under the following conditions:
l
flame sensor resistance out of tolerance
l
temperature sensor resistance out of tolerance
l
glow plug/glow plug trigger defective
l
fan speed too low, short circuit or open circuit
l
error in dosing pump electrical circuit or of
overheat protection (in start phase only)
l
low voltage below 10 Volt and in excess of 20
seconds for 12 Volt heaters
l
low voltage below 20 Volt and in excess of 20
seconds for 24 Volt heaters
l
control unit defective
In case of overheating there will be no fuel supply. A run-
down like after manual switch-off will be performed.
After run-down the control unit is in the error lockout
mode. Overheating is indicated by the operation indica-
tion flashing. For error unlock the air heater has to be
switched off momentarily to be switched on again.
302
3 Functional Description
Air Top 2000