Webasto Air Top 3500 ST, Air Top 5000 ST Workshop Manual
Air heaters
03/2003
Workshop manual
Air Top 3500 ST
Air Top 5000 ST
Air Top 3500/5000 ST B (petrol)
Air Top 3500/5000 ST D (diesel)
Air Top 3500 ST D Volume Plus (diesel)
Air Top 3500/5000 ST Table of contents
I
Table of contents
1 Introduction
1.1 Contents and purpose ........................................................................................................................... 101
1.1.1 Using the air heaters ................................................................................................................... 101
1.2 Meaning of signal words........................................................................................................................ 101
1.3 Additional documentation to be used................................. ... ... .... ... ... ... ... .... ... ... ... .... ... ... ... ... .... . ............ 101
1.4 Statutory regulations and safety instructions.................................. .......................................... ............. 101
1.4.1 Regulations for installation in the vehicle .................................................................................... 101
1.4.2 General safety information .......................................................................................................... 102
1.5 Suggestions for improvements and modifications ................................................................................. 104
2 General description
2.1 Drive unit........................... .... ... ... ... .... ... .......................................... ... ... ... .... ... ....................................... 202
2.2 Heat exchanger ..................................................................................................................................... 202
2.3 Burner insert with burner pipe................................................................................................................ 202
2.4 Control unit ............................................................................................................................................ 203
2.5 Glow plug/Flame sensor.......................................... ... .... ... .......................................... ... ... .................... 203
2.6 Overheating sensor .............................................. ... ... .... ... ... ... .... ... ....................................................... 203
2.7 Metering pump....................................................................................................................................... 203
3 Function description
3.1 Control element ..................................................................................................................................... 301
3.2 Switch on............. .... .......................................... ... ... ... .......................................... .... ............................. 301
3.3 Heating mode ........................................................................................................................................ 301
3.4 Control mode......................................................................................................................................... 301
3.5 Control pause ........................................................................................................................................ 302
3.6 Switch off.................................................... ... .... ... .......................................... ... ... ................................. 302
3.7 Heater functions when installed in ADR vehicles .................................................................................. 302
3.8 Fault lock-out......................................................................................................................................... 302
3.8.1 Error monitor............................ ... ... ... ... .... ... .......................................... ... ... .... ... .......................... 303
3.8.2 Reset a fault lock-out............................... ... ... ... .... ... ... ... .......................................... ... ................. 303
4 Technical data................................................................................................................................................ 401
Table of contents Air Top 3500/5000 ST
II
5 Troubleshooting
5.1 General................................................................................................................................................. 501
5.2 General error symptoms....................................................................................................................... 501
5.3 Error symptoms during function............................................................................................................ 502
5.4 Fault code output............................ ... ... .... ... .......................................... ... ... ... .... ... ... ... ......................... 503
6 Function tests
6.1 General................................................................................................................................................. 601
6.2 Settings................................................................................................................................................. 601
6.2.1 Setting the CO
2
content.............................................................................................................. 601
6.3 Testing individual components..................................... ... ............................................. .... ... .................. 601
6.3.1 Resistance test on the glow plug/flame sensor .......................................................................... 601
6.3.2 Resistance test on the overheating sensor................................................................................. 601
7 Circuit diagrams
7.1 General................................................................................................................................................. 701
8 Servicing work
8.1 General................................................................................................................................................. 801
8.2 Work on the heater ............................................................................................................................... 801
8.3 Work on the vehicle .............................................................................................................................. 801
8.4 Heater trial ............................................................................................................................................ 801
8.5 Servicing work....................................................................................................................................... 801
8.6 Visual inspections and installation instructions..................................................................................... 801
8.6.1 Hot air system.............................................................................................................................. 801
8.6.2 Fuel supply ................................................................................................................................. 802
8.6.3 Metering pump............................................................................................................................ 804
8.6.4 Fuel filter..................................................................................................................................... 804
8.6.5 Combustion air supply............................. ... .... ... ... ... .... ... ... ... .... ... ... ... ......................................... 805
8.6.6 Exhaust pipe...................... .......................................... ... ... ... .... ... ... ... ... ...................................... 805
8.6.7 Combustion air intake and exhaust pipes............. ... .............................................. ... ... ... ... .... ... .. 805
8.6.8 Electrical connections........ ... ... ... .... ... ... .......................................... ... ... .... ... ... ... .... ... .................. 806
8.7 Removal and installation
8.7.1 Heater, removal and installation................................................................................................. 808
8.8 Start-up.................................................................................................................................................. 808
Air Top 3500/5000 ST Table of contents
III
9Repair
9.1 General.................................................................................................................................................. 901
9.1.1 Working on components after they have been dismantled.......................................................... 901
9.1.2 Carrying out modifications........................................................................................................... 901
9.2 Dismantling and assembling.................................................................................................................. 902
9.2.1 Remove the casing parts............................................................................................................. 902
9.2.2 Fit the casing parts ............................................... ... ... ... .... ... ... .................................................... 902
9.2.3 Change the control unit ............................................................................................................... 904
9.2.4 Change the overheating sensor .................................................................................................. 904
9.2.5 Change the combustion and hot air blower (drive unit)............................................................... 904
9.2.6 Change the burner and the glow plug/flame sensor.................................................................... 906
9.2.7 Change the combustion pipe and the heat exchanger................................................................ 906
10 Packaging, storage and shipping
10.1 General................................................................................................................................................ 1001
Table of illustrations Air Top 3500/5000 ST
IV
List of illustrations
501 General error symptoms ...................................................... ... .... ... ... ... .... ... ... ... ... .... ... ... ............................ 501
502 Error symptoms during function................................................................................................................. 502
503 Troubleshooting......................................................................................................................................... 503
701 Plug assignment ........................................................................................................................................ 701
702 System circuit diagram 12V/24V with control element and vehicle blower................................................ 702
703 System circuit diagram 12V/24V with combination timer and vehicle blower ............................................ 703
704 System circuit diagram 12V/24V with combination timer and electrical battery isolation switch................ 704
705 System circuit diagram 24V (diesel) ADR operation with control element................................................. 705
706 System circuit diagram 24V (diesel) ADR operation with control element without auxiliary drive unit....... 706
707 Schematic connection of the combination timer ........................................................................................ 707
801 Fuel supply................................................................................................................................................. 802
802 Webasto fuel extractor............................................................................................................................... 803
803 Fuel extraction from the plastic tank (extraction through tank drain screw)............................................... 803
804 Fuel extraction from the plastic tank (extraction through tank fittings)....................................................... 803
805 Pipe/Hose connections .............................................................................................................................. 804
806 Metering pump, installation position........................................................................................................... 804
807 Fuel filter.................................................................................................................................................... 804
808 Exhaust silencer......................................................................................................................................... 805
809 Exhaust pipe mouth, installation position................................................................................................... 805
810 Remove the fastening plate on the fuse holder ......................................................................................... 806
811 Fuse holder, installation position................................................................................................................ 806
812 Control element.......................................................................................................................................... 806
813 Disconnect the plug ................................................................................................................................... 806
814 Specimen installation for heater in air circulation mode.................................... ... .... ... ... ... ......................... 807
901 Remove / Fit the casing parts .................................................................................................................... 903
902 Change the control unit, overheating sensor and the combustion and hot air blower (drive unit) .............. 905
903 Change the burner, glow plug/flame sensor, the combustion tube and the heat exchanger..................... 907
Air Top 3500/5000 ST 1Introduction
101
1Introduction
1.1 Contents and purpose
This workshop manual is designed to assist trained
personnel with repairing both the petrol and the diesel
versions of the Air Top 3500/5000 ST air heaters.
1.1.1 Use of the air heaters
The Webasto Air Top 3500 ST and Air Top 5000 ST air
heaters are designed
– to heat cabins, boats, trucks, minibuses, vans,
ambulances and motorhomes.
– to defrost vehicle windows.
– to heat cargo.
They are not designed for heating cargo areas used to
carry hazardous substances.
The heaters operate independently of the engine and are
connected to the fuel tank and the electrical system of the
vehicle.
They not designed for installation in vehicles with water or
air-cooled engines.
1.2 Meaning of signal words
Throughout this manual, the signal words WARNING,
CAUTION and NOTE have the following meanings:
WARNING
This heading is used to highlight operating instructions or
procedures which, if not or not correctly followed, may
result in personal injury or fatal accidents.
IMPORTANT
This heading is used to highlight operating instructions or
procedures which, if not or not correctly followed, may
result in damage to the equipment or its components.
NOTE
This heading is used to direct your attention to a special
feature deemed essential to highlight.
1.3 Additional documentation to be used
This workshop manual contains all the information and
instructions required for repairing the Air Top 3500 ST
and Air Top 5000 ST air heaters.
Normally, there is no need to use additional
documentation. If necessary the operating / installation
instructions and the installation suggestion for the specific
vehicle may also be used.
1.4 Statutory regulations and safety
instructions
In principle, the general accident prevention regulations
and current works safety instructions are applicable.
The "General safety regulations" that go beyond the
scope of the above regulations are stated below.
Any special safety regulations relevant to this instruction
manual will be highlighted in the relevant sections or text
passages of the procedures.
1.4.1 Statutory regulations governing
installation
The Air Top 3500 ST / Air Top 5000 ST he aters have been
type-tested and approved in accordance with EC
Directives 72/245/EEC (EMC) and 2001/56/EC (heater)
with the following EC permit numbers:
e1*72/245*95/54*1221*00
e1*2001/56*0021*00
e1*2001/56*0020*00
Installation is governed above all by the provisions in
Annex VII of Directive 2001/56/EC.
NOTE
The provisions of these Directives are binding within the
territory governed by EU Directive 70/156/EEC and
should similarly be observed in countries without specific
regulations.
(Extract from Directive 2001/56/EC Annex VII)
1.7.1. A clearly visible indicator within the user's field of
vision must show whether the heater is switched on or off.
2. Regulations for installation in the vehicle
2.1. Scope
2.1.1. Subject to the provisions of paragraph 2.1.2,
internal combustion heaters must be installed in
accordance with the requirements contained in
this Annex.
2.1.2. In the case of class O vehicles (trailers) with
heaters for liquid fuel, it is presumed that these
vehicles comply with the requirements in this
Annex.
2.2. Position of the heater
2.2.1. Parts of the vehicle body and other components in
the immediate vicinity of the heater must be
protected against excessive heat and the danger
of contamination by fuel or oil.
1Introduction Air Top 3500/5000 ST
102
2.2.2. The internal combustion heater must not pose a fire
hazard even when overheated. This requirement is
deemed to have been met if care is taken during
installation to ensure an adequate distance from all
parts, as well as adequate ventilation and if fireresistant materials or heat shields are used.
2.2.3. In class M2 and M3 vehicles the heater must not be
installed in the passenger cabin. A device in a
sealed cover, which also meets the requirements
set out in paragraph 2.2.2, may be used, however.
2.2.4. The plate mentioned in paragraph 1.4 (model plate)
or a duplicate thereof (duplicate model plate) must
be fitted in such a way that it is still clearly legible
when the heater has been installed in the vehicle.
2.2.5. When positioning the heater, all reasonable
precautions must be taken to minimise the risk of
personal injury or damage to items in the vehicle.
2.3. Fuel supply
2.3.1. The fuel filler neck must not be located in the
passenger compartment and must have a tightly
fitting cap to prevent any fuel leaks.
2.3.2. The type of fuel and the fuel filler neck must be
clearly identified on heaters for liquid fuel, for which
the fuel supply is separate from the fuel supply for
the vehicle.
2.3.3. A sign must be affixed to the fuel filler neck warning
that the heater must be switched off before
refuelling. An identical warning must also be
included in the manufacturer's operating
instructions.
2.4. Exhaust system
2.4.1. The exhaust outlet must be positioned in such a
way that exhaust fumes cannot get into the interior
of the vehicle through ventilation devices, hot-air
inlets or open windows.
2.5. Combustion air inlet
2.5.1. The air for the combustion chamber of the heater
must not be extracted from the passenger cabin of
the vehicle.
2.5.2. The air inlet must be positioned in such a way that
it cannot be obstructed by other objects.
2.6. Hot air inlet
2.6.1. The supply of heating air must consist of either
fresh air or recirculated air and must be taken from
a clean area which cannot be contaminated by
exhaust fumes from the engine, the internal
combustion heater or any other source in the
vehicle.
2.6.2. The inlet line must be protected by a grating or other
suitable means.
2.7. Hot air outlet
2.7.1. Hot air lines within the vehicle must be positioned or
protected in such a way as to exclude all risk of
injury or damage caused by direct contact.
2.7.2. The air outlet must be positioned or protected so
that it cannot be obstructed by other objects.
2.8. Automatic control of the heating system
When the engine stops, the heating system must
cut out automatically and the fuel supply must be
stopped within 5 seconds.
The heating system may remain in operation if a
manual unit has already been activated.
1.4.2 General safety information
The mouth of the exhaust pipe should be installed
upwards, to the side or, if the exhaust pipe passes under
the floor of the vehicle, to the side or rear limit of the
driver’s cab or the vehicle.
The function of important parts of the vehicle must not be
adversely affected. It must not be possible for condensate
or water to collect in the exhaust pipe. Drain holes may b e
used.
The electric cables and controls for the air-conditioning
system must be arranged in the vehicle so that their
proper functioning cannot be adversely affected in norma l
operating conditions.
Air Top 3500/5000 ST 1Introduction
103
Compliance with §§ 45 and 46 of the Road Vehicle
Licensing Act must be ensured for the installation of fuel
lines and the installation of additional fuel tanks.
The main points from this law:
– Fuel pipes must be designed in such a way that
torsion in the vehicle, movements by the engine and
the like do not have a negative effect on their
durability. They must be protected from mechanical
damage.
– Parts that carry fuel must be protected from heat that
will adversely affect their function and positioned so
that dripping or evaporating fuel cannot collect or
ignite on hot parts or on electrical equipment.
The air heater’s heat exchanger can be used for a
maximum of 10 years and must then be replaced by the
manufacturer or one of its authorised workshops using a
genuine spare part. A label must then be affixed to the
heater showing the date of sale and the wording “Genuine
spare part”.
When you change the heat exchanger it is essential that
you also replace the overheating protection element
(temperature sensor) to prevent po ssib le func tio n fau l ts
caused by using the old temperature sensor.
The Air Top 3500 ST and Air Top 5000 ST air heaters are
prepared for interior installation and sealing direct on the
cabin floor or a cabin wall. Non-release connections must
be used in the interior for combustion air and exhaust
pipes with the accessories available from Webasto.
The seal between the heater mounting and the vehicle
floor must always be installed, otherwise harmful
emissions may get into the interior of the vehicle.
The hot and combustion air intake openings must be
positioned in such a way that no water can ingress into
them if the vehicle drives through a water hazard for which
it has been approved.
The heater must not be installed in the driver’s or
passenger cabin of buses (vehicle classes M
2
and M3). If
the heater is nevertheless installed in such a place, the
installation box must be tightly sealed against the vehicle
interior. The installation box must have sufficient external
ventilation to ensure that a maximum temperature of
40 °C is not exceeded in the box. Fault faults may occur if
the temperature exceeds this level.
The heater must be switched off at filling stations and fuel
tank farms because of the risk of explosion.
Wherever inflammable vapours or dust may form (for
example near fuel, coal, wood dust or cereal stores or the
like), the heater must be switched off because of the risk
of explosion.
The neater must not be operated in enclosed areas, such
as garages or workshops without an exhaust emissions
extraction system, not even using the timer, because of
the risk of asphyxiation and poisoning.
In the event of lengthy heavy smoke development,
unusual combustion noise or a smell of fuel, the heater
must be put out of action by removing the fuse and must
not be started again until it has been examined by
Webasto-trained personnel. Liability claims can only be
lodged if the claimant can prove that it has complied with
the servicing and safety instructions.
Installation regulations for Webasto fuel tanks for
supplying fuel to heaters in vehicles:
• The tank must not be installed in the passenger or
driver’s cabin of buses.
• The fuel filler neck must not be inside the passenger
or driver’s cabin in any vehicle.
• Fuel tanks for normal and super grades of petrol must
not be immediately behind the front trim of the vehicle.
They must be separated from the engine in such a
way that in the event of an accident the fuel will not be
expected to ignite. This does not apply to tractor units
with an open driver’s seat.
The fuel lines (Mecanyl hose) must not be immediately
next to the exhaust pipe and must be thermally insulated
if necessary, otherwise they will pose a fire risk.
All pipes that come into contact with fuel must have sealed
connections, they must not be damaged in any way and
the must be checked at regular intervals (at least the
same intervals as an inspection of the vehicle as a whole).
NOTE
If any damage or leaks are found on the fuel line, the
heater must not be used until the damage has been
rectified by an authorised Webasto workshop.
Put the heater out of action by removing the fuse.
1Introduction Air Top 3500/5000 ST
104
Overheating
Keep hot air inlet and hot air outlet free of dirt and other
items. Dirty, blocked air lines can cause the heater to shut
down due to overheating.
After an overheating lock-out, check that the air system is
clear, remove any materials that may block the air current
and have any damage to the air lines repaired by an
authorised Webasto workshop. After this the heater lockout can be cancelled by switching it off and then on again.
If this action does not produce the required success (if the
heater overheats again) take it to an Webasto-autho rised
workshop.
The air outlet jets or air vents with adjustable flaps must
always be opened to some extent so that the air current
through the heater is not completely blocked. It must be
impossible to close at least one air vent.
If the heater is installed in a storage area, you must
ensure that no inflammable substances are kept in this
area and that other material does not restrict the air supply
to the heater.
Air lines must be securely fixed to the heater (using pipe
clips, for example) and all other connection points (for
example vents).
IMPORTANT
The errors described below are to be avoided at all costs:
• Do not stand on the heater or place or throw any
heavy objects on the heater.
• Do not place any items of clothing, textiles or similar
materials over the heater or in front of the hot air inlet
and hot air outlet.
• The current of hot air from the heater must not be
restricted or blocked by highly inflammable
substances or materials such as rags, cleaning wool,
etc.
• Inflammable or explosive substances and gases must
not be placed near or in contact with the heater, the
hot air line, the current of hot air or the exhaust pipe.
• The heater must not be cleaned with a high pressure
cleaner.
• Do not switch the heater off at the main battery switch
or battery isolation switch since otherwise it is
possible that it may suffer long term damage if it is
switched off frequently using the battery isolation
switch and this can cause damage and negative
influences on the function of the heater.
NOTE
Failure to follow the installation instructions and the notes
contained therein will lead to all liability being refused by
Webasto The same applies if repairs are carried out
incorrectly or with the use of parts other than genuine
spare parts. This invalidates the type approval for the
heater and its homologation / EC type permit.
You must read the operating manual before starting the
heater for the first time.
1.5 Suggestions for improvements and
changes
Complaints, improvement suggestions or corrections
relating to this workshop manual should be addressed to:
Webasto AG
BU SPM / Dept ATT-I
Kraillinger Strasse 5
D-82131 Stockdorf
Phone: +49 (89) 85794 - 634
PC-Fax: +49 (89) 899 214 - 397
Air Top 3500/5000 ST 2 General description
201
2 General description
The Air Top 3500 ST and Air Top 5000 ST air heaters are
based on the evaporator principle and essentially consist
of the following
– The drive unit with a combustion and hot air blower
– The heat exchanger
– The burner insert with combustion pipe
– The control unit.
To control and monitor it, the heater has
– a control unit with temperature sensor
– a glow plug / flame monitor
– an overheating sensor
inside it.
Air Top 3500/5000 ST air heater
The fuel supply is provided from an external source using
a metering pump.
If a fault occurs, an error code will be output in the display
of the combination or standard timer. If the heater has a
control element, the ON control light will flash. In addition
the heater can be checked using a personal computer
(see PC heater diagnostic operating manual).
The heater may be controlled using an external
temperature sensor instead of the internal temperature
sensor.
Air Top 3500/5000 ST air heater without casing
2 General description Air Top 3500/5000 ST
202
2.1 Drive unit
The drive unit consists of the drive motor, the combustion
air blower, the heat air blower and the intake casing.
The combustion air blower supplies the air required for the
combustion process from the combustion air inlet to the
burner insert.
The hot air blower transports the hot air from the hot air
inlet via the heat exchanger to the hot air outlet.
Drive unit
2.2 Heat exchanger
The heat generated by the combustio n pr oc ess is
transferred to the air transported by the combustion and
hot air blowers in the heat exchanger.
Heat exchanger
2.3 Burner insert with combustion pipe
The fuel is distributed over the burner cross-section in the
combustion pipe in the burner insert. The mixture of fuel
and air burns in the combustion pipe, thus causing the
heat exchanger to become hot.
Burner insert (diesel) and combustion pipe
Burner insert (petrol) and combustion pipe
Air Top 3500/5000 ST 2 General description
203
2.4 Control unit
The control unit is the central component for e nsuring the
function is maintained and for monitoring the heater’s
operation. A temperature sensor in the control unit is
designed to control the room temperature. An external
temperature may also be connected to all the heat er s.
If a fault occurs, an error code will be output in the display
of the combination timer. If the heater has a control
element, the ON control light will flash. In addition the
heater can be checked using a personal computer (see
PC heater diagnostic operating manual).
Control module
2.5 Glow plug/Flame monitor
The glow plug also acts as a flame monitor.
The mixture of fuel and air is ignited by the glow plug when
the heater is started. The glow plug takes the form of an
electrical resistor and is positioned in the burner on the
side facing the flame.
As a flame sensor the glow plug reacts in the same way
as a low ohm PTC resistor, which changes its resistance
depending on the heat emitted by the flame. The signals
are fed to the control unit where they are processed.
The flame status is monitored by the flame sensor
whenever the heater is operating.
Glow plug / Flame monitor
2.6 Overheating sensor
The overheating sensor measures the temperatures in
the rib area of the heat exchanger whenever the heater is
operating.
The control unit evaluates the signal and protects the
heater from hot air outlet temperatu res above 150 °C and
surface temperatures above 80 °C by shutting down the
combustion process and blowing cold air over th e heater.
The heater then suffers a fault lock-out and can by
restarted by being switched off and on again (see 3.2).
Overheating sensor
2.7 Metering pump
The metering pump is a combined transport, metering an d
shut-off system for supplying fuel from the vehicle’s tank
to the heater.
Metering pump DP 30.2/3
2 General description Air Top 3500/5000 ST
204
Page for notes
Air Top 3500/5000 ST 3 Function description
301
3 Function description
3.1 Control element
The control element is designed to switch the heater on
and off, adjust the required room temperature (intake
temperature between 5 °C and 35 °C) and to reset the
heater after a fault.
The integral green LED is designed to act
• as an ON signal (LED permanently lit)
• as a fault signal (LED flashes).
NOTE
ADR operation:
After an operating voltage has been applied by switching
the battery isolation switch and control element to “ON”
the control unit will be set to the “Fault lock-out” position.
Before it can be restarted the control element must be set
to “OFF”.
3.2 Switch on
Set the control element to the required temperature.
If the hot air temperature is lower than the nominal
temperature the heater will start
NOTE
If the temperature of the hot air intake is above the set
nominal temperature, only the motor for the hot and
combustion air blower will start (control pause). Special
feature: The control pause speed is 0 rpm if boat heaters
are used.
The function of the flame sensor is checked. If the flame
sensor now reports “light”, the system will attempt to cool
the flame sensor for 60 seconds. If the flame sensor still
reports “light” the control unit will suffer a fault lock-out. If
another monitored component has suffered a fault, the
fault lock-out will take effect without any slow down time.
Start
When the heater is switched on the ON signal light will be
lit and the glow plug will be switched on (cycled). The
motor for the hot and combustion air blower will be set to
approx. 50% of its maximum speed.
After approx. 40 seconds the fuel metering pump will start
and the flame formation will begin. To improve the starting
quality the metering pump and combustion air blower are
started with different frequencies and speeds.
After a further 90 seconds the glow plus will be switched
off and the existence of the flame established.
2. Automatic restart
If the flame sensor does not find a flame, the starting
procedure will be repeated. The glow plug will be switched
on again (cycled). The motor for the hot and combustion
air blower will be set to approx. 50% of its maximum
speed.
After approx. 40 seconds the fuel metering pump will start
and the flame formation will begin.
After a further 50 seconds the glow plus will be switched
off and the existence of the flame established.
If the heater has again failed to ignite properly, the it will
be shut down using a fault slow down procedure at
maximum speed after 180 seconds and will suffer a fault
lock-out.
NOTE
After a restart the heater will suffer a fault lock-out. To
reset the fault switch the heater off briefly (at least
2 seconds) and then on again.
3.3 Heating mode
Whilst the heater is operating the combustion gases pass
through the heat exchanger. During this process the
combustion heat is given off to the walls of the heat
exchanger, absorbed by the hot air transported by the hot
air blower and fed into the interior of the vehicle.
The temperature of the hot air intake is measured by a
temperature sensor in the control unit or an external
temperature sensor. If the measured temperature is lower
than the value set on the control element, the output of the
heater is increased to maximum heat output.
To increase the burner service life when it is used
continuously the transport capacity of the metering pump
is reduced for 10 seconds every 10 minutes.
In addition, heating mode is interrupted every 8 hours in
the same way as for a control pause.
3.4 Control mode
In control mode the blower speed and the metering pump
delivery rate are dependent on the heat output. The glow
plus is switched off.
3 Function description Air Top 3500/5000 ST
302
3.5 Control pause
After the temperature set on the control element has been
reached the heat output is reduced. The speed of the
heating and combustion air blower and the delivery rate of
the metering pump are reduced.
If, at minimum heat output, the intake temperature set on
the control element is exceeded, the metering pump is
shut down and the combustion process ended. To burn off
the flame properly the blower speed falls after 2 0 seconds
to low-fire rate speed and then returns to the initial speed
after 15 seconds, after which it falls to the control pause
speed in 3 minutes, where it remains for the entire control
pause.
The control pause speed on boat heaters is 0.
If the temperature set on the control element is exceeded
at the temperature sensor, the heater will restart.
NOTE
Changes to the setting on the control element are
implemented by the control unit and heater after a delay.
3.6 Switch off
When the heater is switched off the ON control LED on the
control element goes out. If no fuel has been transported
or if the heater is in the control pause, the heater is
switched off immediately without a slow down time.
If the fuel transport has been started it is ended when the
heater is switched off. The heater is switched off using the
same method as the transition from control mode to
control pause. The heater is then switched off
automatically.
NOTE
The heater may be switched on again during the slow
down time. In this case the slow down time is completed
and the heater is then restarted.
3.7 Heater functions
when installed in ADR vehicles
NOTE
Only for Air Top 3500/5000 ST D heaters that are
installed in vehicles for transporting hazardous
substances (ADR).
If the heater is switched off using the control element the
slow down time remains unchanged.
A brief slow down time (max. 40 seconds) is started
automatically if
• the vehicle’s engine is switched off
• a transport device is started.
After an ADR shut down process the control unit is in the
“Fault lock-out” position. Before it can be restarted the
control element must be set to “OFF”.
3.8 Fault lock-out
Errors on the various heater components and faults in the
starting process and in heating mode are identified in the
control unit. The heater is switched off and goes into fault
lock-out if the following conditions occur:
• No or incorrect start
• Temperature sensor defective
• Overheating sensor interrupt or short circuit
• Overheating sensor installed incorrectly
• Glow plug/Flame monitor interrupt or short circuit
• Blower motor overload or blocked or short circuit or
break
• Error in metering pump circuit
• Undervoltage below 10.5 V / 21 V for longer than
20 seconds
• Overvoltage above 16 V / 32 V for longer than 6
seconds
• Control unit defective
• Overheating
The fuel supply is stopped if the heater overheats.
The heater continues to run in the same way as if it is
switched off manually.
After it stops the control unit will be set to fault lock-out.
The overheating is indicated by the indicator flashing
10 times.
Rectify the cause of the fault.
To reset the fault, switch the heater off briefly (at least
22 seconds) and then on again.
3.8.1 Error monitor
The overheat, incorrect start and flame failure errors are
counted and cause the heater to suffer a fault lock-out
after an error has occurred the maximum number of times.
The incorrect start counter FSZ is incremented by 1 each
time the heater fails to start and decremented by 1 each
time it starts correctly, but does not fall below 0. If the
incorrect start counter reaches its maximum value of 9 the
heater will go into the heater lock-out status HGV.
Air Top 3500/5000 ST 3 Function description
303
The error counter SZ is incremented by 1 each error for
which there is no separate counter. The error counter is
reset to 0 at the start of control mode. If the error counter
reaches its maximum value of 9 the heater will go into the
heater lock-out status HGV.
The overheating counter ÜHZ is incremented by 1 each
time the heater overheats. If the overheating counter
reaches its maximum value of 3 the heater will go into the
heater lock-out status HGV.
The flame failure counter FAZ is increased by 1 each time
the flame fails during heating mode.
The counter is decremented by 1 each time the heater is
in control mode.
If the FAZ reaches a value of 3 the heater will go into fault
lock-out mode and the permanent flame failure counter
FAZP will be incremented by 1. In control mode the
permanent flame failure counter FAZP will be
decremented by 1. When the heater is burning properly
again, the FAZP will return to 0 after a few control cycles.
If the permanent flame failure counter exceeds its
maximum value of 3, however, the heater will go to
permanent heater lock-out status (error code F13).
3.8.2 Reset a fault lock-out
The various fault statuses can be reset as follows.
Fault lock-out: Switch heater off using the
control element and then on
again after more than 2 seconds
Heater fault lock-out: Remove the fuse and
reinsert it
Permanent heater fault Delete the error using the
lock-out: PC diagnostic
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