Viessmann VITOCROSSAL 300 Operating instructions

Service Instructions
VITOCROSSAL 300
5838 946 - 13 01/2022
for use by heating contractor
Vitocrossal 300 with Graphical User Interface HI932
CA3B Series 2.5, 3.0, 3.5, 4.0, 5.0 and 6.0
Gas condensing boiler with cylinder burners
Read and save these instructions
for future reference.
Please file in Service Binder
Product may not be exactly as shown
IMPORTANT
H
Heating input: 2500 to 6000 MBH
(733 to 1758 kW)

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5838 946 - 13
Vitocrossal 300 CA3B Series 2.5 to 6.0 Service
Safety, Service and Warranty Requirements
Safety
Please ensure that these instructions are read and understood before commencing installation. Failure to comply with
the instructions listed below and details printed in this manual can cause product/property damage, severe personal
injury, and/or loss of life. Ensure all requirements below are understood and fulfilled (including detailed information
found in manual subsections).
WARNING
Installers must follow local regulations with respect to
installation of carbon monoxide detectors. Follow the
Viessmann maintenance schedule of the boiler contained
in this manual.
Product documentation
Read all applicable documentation before commencing
installation. Store documentation near boiler in a
readily accessible location for reference in the future
by service personnel.
For a listing of applicable literature,
please see section entitled “Important
Regulatory and Safety Requirements”.
Warranty
Information contained in this and
related product documentation must
be read and followed. Failure to do
so renders the warranty null and void.
Licensed professional heating contractor
The installation, adjustment, service and maintenance
of this equipment must be performed by a licensed
professional heating contractor.
Please see section entitled
“Important Regulatory and Installation
Requirements”.
Contaminated air
Air contaminated by chemicals can cause by-products
in the combustion process, which are poisonous to
inhabitants and destructive to
Viessmann equipment.
For a listing of chemicals which
cannot be stored in or near the
boiler room, please see subsection
entitled “Mechanical room” in this
manual.
Advice to owner
Once the installation work is complete, the heating
contractor must familiarize the system operator/
ultimate owner with all equipment, as well as safety
precautions/requirements, shutdown procedure, and
the need for professional service annually before the
heating season begins.
Carbon monoxide
Improper installation, adjustment, service and/or
maintenance can cause flue products to flow into
living space. Flue products contain poisonous carbon
monoxide gas.
For information pertaining to the
proper installation, adjustment, service
and maintenance of this equipment to
avoid formation of carbon monoxide,
please see subsection entitled
“Mechanical room” and “Venting
requirements” in this manual.
Fresh air
This equipment requires fresh air for
safe operation and must be installed
ensuring provisions for adequate
combustion and ventilation air exist.
For information pertaining to the
fresh air requirements of this product,
please see subsection entitled
“Mechanical room” in this manual.
Equipment venting
Never operate boiler without an installed venting
system. An improper venting system can cause
carbon monoxide poisoning.
For information pertaining to
venting and chimney requirements,
please see section entitled “Venting
Connection”. All products of
combustion must be safely vented
to the outdoors.

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5838 946 - 13
Vitocrossal 300 CA3B Series 2.5 to 6.0 Service
Safety, Service and Warranty Requirements (continued)
Safety
WARNING
Inhaling of fiberglass wool and/or ceramic fiber
materials is a possible cancer hazard. These materials
can also cause respiratory, skin and eye irritation.
Fiberglass wool and ceramic fiber materials
WARNING
Appliance materials of construction, products of
combustion and the fuel contain alumina, silica, heavy
metals, carbon monoxide, nitrogen oxides, aldehydes
and/or other toxic or harmful substances which can
cause serious injury or loss of life and which are
known to the State of California to cause cancer,
birth defects and other reproductive harm. Always
use proper safety clothing, respirators and equipment
when servicing or working nearby the appliance.
The state of California has listed the airborne fibers of
these materials as a possible cancer hazard through
inhalation. When handling these materials, special care
must be applied.
First aid measures
- If eye contact occurs, flush eyes with water to remove
dust. If symptoms persist, seek medical attention.
- If skin contact occurs, wash affected areas gently
with soap and warm water after handling.
Suppliers of fiberglass wool products recommend the
following precautions be taken when handling these
materials:
- Avoid breathing fiberglass dust and contact with
skin and eyes.
- Use NIOSH approved dust/mist respirator.
- Wear long-sleeved, loose fitting clothing, gloves
and eye protection.
- Wash work clothes separately from other clothing.
Rinse washer thoroughly.
- Operations such as sawing, blowing, tear-out and
spraying may generate airborne fiber concentration
requiring additional protection.
Codes
The installation of this unit shall be in accordance with
local codes. In the absence of local codes, use:
CAN/CSA-B149.1 or .2 Installation Codes for Gas Burning
Appliances for Canada. For U.S. installations, use the
National Fuel Gas Code ANSI Z223.1. Always use latest
editions of codes.
In Canada all electrical wiring is to be done in accordance
with the latest edition of CSA C22.1 Part 1 and/or local
codes. In the U.S., use the National Electrical Code ANSI/
NFPA 70.
The heating contractor must also comply with the Standard
for Controls and Safety Devices for Automatically Fired
Boilers, ANSI/ASME CSD-1 where required by the authority
having jurisdiction.
Mechanical room
Viessmann recommends installation of an additional
electrical disconnect switch and a fuel shut-off valve (if
possible) outside the mechanical room or enclosed area
of installation.
The maximum room temperature of the mechanical room
where the boiler is located must not exceed 104°F (40°C).
Suppliers of ceramic fiber products recommend the
following first aid measures:
- Respiratory tract (nose and throat) irritation:
If respiratory tract irritation develops, move the
person to a dust free location.
- Eye irritation: If eyes become irritated, flush immediately
with large amounts of lukewarm water for at least 15
minutes. Eyelids should be held away from the eyeball
to ensure thorough rinsing. Do not rub eyes.
- Skin irritation: If skin becomes irritated, remove soiled
clothing. Do not rub or scratch exposed skin.
Wash area of contact thoroughly with soap and cold
water (as warm or hot water may worsen the irritation).
Using a skin cream or lotion after washing may be
helpful.
- Gastrointestinal irritation: If gastrointestinal tract
irritation develops, move the person to a dust free
environment.

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Vitocrossal 300 CA3B - 3.5, 4.0, 5.0 and 6.0 Service
Table of Contents
Safety
General Information
General Service Information
Commissioning
Operating
Service
Page
Safety, Service and Warranty Requirements ................. 2
About these Instructions .............................................6
Product Information ....................................................6
Service Equipment......................................................7
Important Regulatory Requirements ..............................8
Safety Instructions.................................................. 9
Commissioning the System..................................... 11
Removing the Boiler Panels ..................................... 11
Filling Condensate Trap with Water .......................... 11
Filling the Heating System with Water and Ventilating.. 12
Checking the Water Conditions ..................................13
Checking Static and Connection Pressure ....................15
Checking Heating Water Connections for Leakage ....... 16
Checking for Flue Gas Leakage ..................................16
Checking On-site Gas Connections for Leakage ............17
Instructing the Operator of the System .......................17
Operating and Service Documents ..............................17
Operating the Burner Control Unit...............................18
Burner Control Unit.................................................. 20
Resetting Operating Parameters to Factory Settings......24
Manual Mode and Service Display ..............................24
Burner Control Unit Flow Diagram ..............................25
Burner Control Unit Faults .........................................27
Burner Control Unit Fault Codes .................................28
Burner Control Unit Faults Without Fault Display ..........31
Operating the System ...............................................32
Integrating the Control Unit into the LON.....................34
Adjusting the Heating Curve ......................................36
Boiler Water Temperature Control...............................38
Heating Circuit Control ............................................39
DHW Tank Temperature Control.................................43
Setting the Boiler Sequence (burner sequence) .............45
Cascade Control Unit ...............................................45
Installing the Boiler Panels ........................................49
Turning the System Off.............................................49
Preparing for Service Work ........................................50
Burner Parts ........................................................... 52
Burner Interface Panel...............................................53
Display and Programming Unit of Burner Control Unit ... 54
Coding Card on Burner Control Unit ...........................54
Burner Control Unit.................................................. 55
Fuel Conversion NG to LPG....................................... 55
Boiler Water Temperature Sensor ...............................56
3A and 3B Boiler Temperature Sensor Description ....... 57
Boiler Secondary Temperature Sensor .........................58
Manual Reset Limits.................................................59
Gas Valve ...............................................................60
Air Pressure Switches ............................................ 61
Ignition Unit ............................................................63
Ignition Cables.........................................................63
Rotary Damper and Servomotor .................................64
Replacing the Solenoid Valve .....................................65
Fan.........................................................................65
Checking the Rotary Damper Setting ..........................66
Measuring CO2Content ............................................67
Displaying Ionization Current.................................... 69
Dismantling the Burner........................................ 70
Checking and Cleaning the Burner Tube ......................72

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Vitocrossal 300 CA3B Series 2.5 to 6.0 Service
Service (continued)
Coding Levels
Coding Level 1
Coding Level 2
Service Scans
Troubleshooting
Connection and Wiring Diagrams
Parts
Specifications
Inspection and Maintenance
Table of Contents
Checking the Ignition Electrodes and Ionization Electrode ...73
Cleaning the Burners .............................................. 73
Cleaning the Combustion Chamber and Heating Surfaces ...74
Burner Reassembly .................................................. 75
Automatic Leakage Test for Valves of the Combined
Gas Valve ...............................................................75
Taking Final Measurement Reading ............................75
Checking Expansion Tank and System Pressure .......... 76
Mixing Valve Movement and Leak Check.....................76
Checking Air Intake in the Installation Room (visual check) .76
Sensors................................................................ 77
Cleaning of Condensate Drainage System .................. 78
Replacing the Supply Air Filter (for room air dependant
operation) ............................................................. 79
Calling up Coding Levels ....................................... 80
Resetting Coding to their Factory Set Condition ...........80
“General” Group.......................................................81
“Combustion Controller” Group ..................................83
“Boiler” Group .........................................................83
“Cascade” Group ................................................... 84
“DHW” Group..........................................................86
“Solar” Group.................................................... 87
“Heating Circuit...” Group.........................................88
“General” Group.......................................................92
“Combustion Controller” Group ................................100
“Boiler” Group ....................................................... 101
“Cascade” Group ..................................................101
“DHW” Group........................................................ 104
“Solar” Group.................................................. 106
“Heating Circuit...” Group....................................... 110
Calling up the Service Menu ...................................116
Leaving the Service Menu .......................................117
Change Passwords ................................................. 117
Resetting all Passwords to Factory Settings .............117
Scanning Operating Data ........................................117
Resetting Operating Data.......................................117
Brief Scan ............................................................. 118
Carrying Out an Actuator Test ................................119
Checking Sensors...................................................120
Maintenance Display...............................................120
Fault Display.......................................................... 121
Boiler System Fault Codes ........................................122
Burner Fault Codes................................................128
Burner Control unit Connection Diagram....................131
Boiler Connections.................................................. 132
Overview .............................................................. 134
PCB Extention for Heating Circuits 2 and 3 with
Mixing Valve ......................................................... 135
PCB, Low Voltage ..................................................135
PCB 120V~.......................................................... 136
Parts Lists ...........................................................137
Technical Data ....................................................... 159
Requirements for Water Conditions...........................161
Maintenance Record............................................ 162
Maintenance Schedule ............................................ 162
Page

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5838 946 - 13
Vitocrossal 300 CA3B Series 2.5 to 6.0 Service
Product Information
High efficiency gas-fired hot water condensing boiler.
For operation with modulating boiler water temperatures
in closed loop, forced circulation hot water heating
systems.
The Vitocrossal 300, CA3B boilers are CSA certified with
Viessmann burners which must be used in conjunction
with this boiler series.
The proper burner size must be verified and the burners
are factory adjusted so that the maximum input of the
appropriate boiler size is always observed. The gas burners
must always be installed according to the instructions
provided by the burner manufacturer.
The boiler model selected should be based on an accurate
heat loss calculation of the building. The boiler selected
must be compatible with the connected radiation.
WARNING
Exposing the boiler to pressures and temperatures in
excess of those listed will result in damages, and will
render warranty null and void.
The Vitocrossal 300, CA3B boiler is suitable for a
maximum operating pressure of 160 psig and a maximum
boiler water temperature of 210°F (99°C).
This boiler does not require a flow switch.
About these Instructions
Take note of all symbols and notations intended to draw attention to potential hazards or important product
information. These include “WARNING”, “CAUTION”, and “IMPORTANT”. See below.

IMPORTANT
Warnings draw your attention to the presence of
potential hazards or important product information.
Cautions draw your attention to the presence of
potential hazards or important product information.
Helpful hints for installation, operation or maintenance
which pertain to the product.
This symbol indicates that additional, pertinent
information is to be found.
This symbol indicates that other instructions must
be referenced.
WARNING
Indicates an imminently hazardous situation which,
if not avoided, could result in death, serious injury
or substantial product/property damage.
CAUTION
Indicates an imminently hazardous situation which,
if not avoided, may result in minor injury or product/
property damage.
General Information

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5838 946 - 13
Vitocrossal 300 CA3B Series 2.5 to 6.0 Service General Service Information
Service Equipment
Tools
Assortment of flathead and Phillips screwdrivers
Pipe wrenches
Open-ended wrenches
Pipe sealant
Assortment of Hex keys
Flashlight
Approved leak detection fluid for natural gas and
propane gas
Cleaning supplies
Plastic hand brush
Cleaning/service brush
Vacuum cleaner
Clean rags
Testing/analysis equipment
(use only calibrated equipment)
Flue gas analyzer to measure % CO2or O2
(e.g. Bacharach fluid samplers or a suitable electronic
analyzer).
Multimeter to measure 0-120VAC, 0-25 amps AC
and 0-100 microamps DC.
Pressure gage to measure gas pressure 0 - 28 "w.c.
A non-electric Magnehelic pressure gage (0 - 10 psig)
may also be used.
Carbon monoxide measuring equipment (0 - 400 ppm).
Bacharach calculator or suitable tables to calculate
efficiency.
Stack thermometer dial settings range 0ºF to 250ºF
(0ºC to 121ºC).
din. NPT male to ¼ in. barb adaptor fitting, as well
as tubing for pressure measurement.
Technical information
The following is a list of literature applicable to the
Vitocrossal 300, CA3B boiler:
Installation Instructions
Service Instructions
Operating Instructions
Technical Data Manual
Wiring diagrams
For installation of the heating system, please refer also
to the technical literature of other Viessmann System
Technology devices:
Installation Instructions for accessories
Installation Instructions for Viessmann indirect-fired
hot water storage tank(s)
Replacement parts
For a complete listing of replacement components, please
see Parts List starting on page 137 of these instructions.
Order replacement components from your Viessmann
distributor.
CAUTION
Use only original Viessmann recommended components
when replacing defective parts. Installation of incorrect
replacement parts can cause hazardous operation and
will void warranty.

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5838 946 - 13
Vitocrossal 300 CA3B Series 2.5 to 6.0 Service
Important Regulatory Requirements
Instructing the system user
The installer of the system is responsible to ensure the
system operator/ultimate owner is made familiar with
the functioning of the system, its activation, and its
shutdown.
Initial start-up
Initial start-up must be performed by a qualified heating
contractor. Completion of the Maintenance Record by
the heating contractor is also required.
Working on the equipment
The installation, adjustment, service, and maintenance of
this equipment must be done by a licensed professional
heating contractor who is qualified and experienced in
the installation, service, and maintenance of hot water
heating systems. There are no user serviceable parts on
this equipment.
Ensure main power supply to equipment, the heating
system, and all external controls has been deactivated.
Close main gas supply valve. Take precautions in all
instances to avoid accidental activation of power during
service work.
The following topics must be covered:
Proper system operation sequence. Explain the
equipment as well as the need for combustion air.
Demonstrate an emergency shut-down, what to
do and what not.
Explain that there is no substitute for proper
maintenance to help ensure safe operation.
The Maintenance Record is located on page 162 of
this manual.
Please carefully read this manual prior to attempting
start-up, maintenance or service. Any warranty is
null and void if these instructions are not followed.
For information regarding other Viessmann System
Technology componentry, please reference
documentation of the respective product.
Viessmann offers frequent installation and service
seminars to familiarize our partners with our products.
Please inquire.
The completeness and functionality of field supplied
electrical controls and components must be verified
by the heating contractor. These include low water
cut-offs, flow switches (if used), staging controls,
pumps, motorized valves, air vents, thermostats, etc.
General Service Information

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5838 946 - 13
Vitocrossal 300 CA3B Series 2.5 to 6.0 Service General Service Information
■ Shut down the heating system.
■ Ventilate boiler room.
■ Close all doors in the living space
Target group
These instructions are intended exclusively for qualified
contractors.
■ Work on gas installations must only be carried out
by a licensed professional heating contractor.
■ Work on electrical equipment must only be carried
out by a qualified electrician.
■ The system must be commissioned by the system
installer or a qualified person authorised by the installer.
■ This appliance has not been designed to be operated
by individuals other than those qualified and trained.
Regulations
Observe the following when working on this system:
■ Statutory regulations regarding the prevention of accidents
■ Statutory regulations regarding environmental protection
■ Codes of practice of the relevant trade associations.
Safety Instructions
■ Do not smoke. Prevent naked flames and sparks. Do
not press any switches for lights or electrical appliances.
■ Close the gas shut-off valve.
■ Open windows and doors.
■ Remove all people from the danger zone.
■ Notify your gas or electricity supply utility from outside
the building.
■ Shut off the electricity supply to the building from a
safe place (outside the building).
If you smell flue gas
WARNING
Escaping gas can lead to explosions which may result
in serious injury.
WARNING
Flue gas can lead to life threatening poisoning.
Auxiliary components, spare and wearing parts
Note: Spare and wearing parts that have not been tested
together with the system can compromise its function.
Installing non-authorized components and making
non-approved modifications or conversions can
compromise safety and may invalidate our warranty.
For replacements, use only original spare parts
supplied or approved by Viessmann.
Note: Electronic assemblies can be damaged by
electrostatic discharges. Before beginning work,
touch grounded objects, such as heating or water
pipes, to discharge static loads.
Repair work
Note: Repairing components that fulfil a safety function
can compromise the safe operation of your system.
Replace faulty components only with original
Viessmann spare parts.
Working on the system
■ Where gas is used as the fuel, close the main gas
shut-off valve and safeguard it against unintentional
reopening.
■ Isolate the system from the power supply (e.g. at the
separate fuse or a main switch) and check that it is
de-energized.
■ Safeguard the system against reconnection.
If you smell gas

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5838 946 - 13
Vitocrossal 300 CA3B Series 2.5 to 6.0 Service
Fixed High Limit test procedure:
1. Use the emission test switch on each boiler section
to generate call for heat.
2. As described in the table on page 23, adjust item #4
“Max. boiler water temperature” under menu 6 of each
burner control (GC310) to a max. setting of 243°F
(117°C), as an example, higher than fixed high limit
temperature setting [factory default setting is 203°F
(95°C)].
For testing of the adjustable limit ‘Max. boiler
temperature’ for a reduced temp. value as required
[e.g. 122°F (50°C)].
3. Press/activate emission test switch of the applicable
boiler section, the burner will start.
4. Gradually and slowly throttle the water flow to the
boiler.
5. Observe temperature on the relative GW6C service
display.
6. Once the temperature reached the fixed high limit
setting, burner control will have a hard lock out with
F F2 fault displayed. Burner fan stays on for 10 min.
The fault can only be manually reset once the water
temperature in the boiler drops.
7. Reset to original settings as needed (item #4 under
submenu 6).
General Service Information
Safety Instructions (continued)
Menu item “6“ is used to change the following operating parameters: (refer to page 23 for more detail)
Sub-menu
Item
Parameter Units/Scale Factory set
condition
1 Maximum operational input % of rated input 100%
2 Gas type 0=NG (natural gas)
1=LPG (liquid propane gas)
0
3 Not assigned -- --
4 Maximum boiler water temperature from 41°F to 260°F (5°C to 127°C) 203°F (95°C)
5 Integral threshold value of controller In Kmin from 1 to 255 30 Kmin
6 Runtime optimization 0=minimum pause
1=integral method
1
0 Reset all operating parameters to their
factory set condition. -- --
Note: Each boiler section is equipped with its own fixed
high limit. Each fixed high limit must be tested
individually.
Refer to Vitocrossal 300 CA3B Operating
Instructions.
CSD-1 Field Testing of High Limit Switches for Vitocrossal
300, CA3B boilers – where required by law.
As per ASME Boiler and Pressure Vessel Code, section IV,
subsection HG-613 TEMPERATURE CONTROL
requirements, Vitocrossal 300, CA3B hot water boilers
are protected from over-temperature by two temperature-
operated controls. These temperature control devices
conform to Standards for Limit Controls, and are accepted
by CSA, a nationally recognized testing agency.
Each boiler is equipped with a manual reset high
temperature limit control and a temperature control that
will cut off fuel supply when the system water
temperature reaches a preset operating temperature.
VIESSMANN IS NOT RESPONSIBLE FOR ANY DAMAGES
THAT THE FOLLOWING TEST PROCEDURE MAY RESULT
IN BY OVERHEATING THE SYSTEM.
The Vitocrossal 300, CA3B boilers are equipped with 2
RTD temperature sensors (per boiler section) that when
activated on temperature rise (high fixed limit of 210°F
(99°C) disable the burners to operate.
The fixed high limit, when tripped, produces a fault that
will require manual reset of the boiler control.
Checking the high limit safety cut-out setting
The high limit safety cut-out is preset to 210°F (99°C).
If this temperature needs to be changed, this can only
be done by changing the coding card.
Refer to the control section of the Installation
Instructions.

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5838 946 - 13
Vitocrossal 300 CA3B Series 2.5 to 6.0 Service Commissioning
Commissioning the System
2. For room air dependant operation:
Check that the ventilation facility in the installation
room is open.
3. Check the gas supply pressure (for set value refer to
page 15).
4. Open the gas line shut-off valves.
5. Check the function of the neutralising system (if
installed), including the hydraulic seal in the trap.
6.
Check all gaskets and plugs, and retighten if necessary.
7. Switch ON the mains isolator (outside the installation
room).
8. Start the control unit.
WARNING
CO build-up as a result of incorrect burner adjustment can
have serious health implications. Always carry out a CO
test before and after work on gas appliances.
Note: The burner adjustment has to be checked with the
boiler heated to operating temperature (min. 40°C).
Perform checks in the partial load range as well.
Refer to the control Instructions and
Neutralizing system Operating Instructions.
Note: Check all connections on the heating water side
for leaks approx. every 500 operating hours.
Filling Condensate Trap with Water
1. Remove the siphon cup Aand fill with water
(otherwise flue gas may escape).
2. Check that the condensate can drain freely.
3. Refit the siphon cup A.
Note: The hose connection to the on-site condensate
system or to the neutralizing system must not
be permitted to sag; support hose where required.
Leak test
Gaskets on the burner plate and components routing flue gas
can be checked during operation with an inspection mirror.
If required, remove the thermal insulation components.
Condensate traces on the outside of the flue gas collector
or on thermal insulation components also indicate leaks.
1. Check the heating system pressure.
Maximum operating pressure: .............. 160 psi (11 bar)
Minimum operating pressure: ..................8 psi (0.6 bar)
1. Remove the screws from the right side of the top panels.
2. Lift and remove the top right side panels.
3. Slide the top panels toward the right side and remove.
4. Lift and remove the top left side panels.
5. Lift and remove the bottom left side panels.
6. Tilt forward, lift and remove lower front panel.
7. Remove the screws from the lower front cover plate
and remove plate.
8. Lift and remove the top front panel (for CA3B 5.0 and
6.0 only).
9. Remove the screws from the top front cover plate and
remove plate (for CA3B 5.0 and 6.0 only).
Removing the Boiler Panels

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Vitocrossal 300 CA3B Series 2.5 to 6.0 Service
Commissioning
Filling the Heating System with Water and Ventilating
1. Fill Vitocrossal 300, CA3B with fully softened water.
2. Enter the fill quantity, water softness and pH-value in
the chart provided on page 161.
3. Before filling push the actuator release button and open
each isolation valve (located near the return header of
each boiler section).
4. When fill is complete push the actuator release button
and close each isolation valve (located near the return
header of each boiler section).
IMPORTANT
See page 13 for water quality requirements.
Valve closed
To open valve
To close valve
Valve open
Installing the isolation valve handle
Remove the isolation valve handle Afrom the accessory
pack and insert it into the receiver handle Bof the
isolation valve until it locks into place. Repeat for all valves.
Note: The handle is only used for initial installation and
for service. The handle must be removed prior to
putting the boiler into operation.
Note: Store the handle in a safe place for future use.

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Vitocrossal 300 CA3B Series 2.5 to 6.0 Service Commissioning
Checking the Water Conditions
Water quality requirements
Note: Observing the following requirements is necessary
to safeguard your warranty rights. The warranty
excludes damage due to corrosion and scaling.
The standard values assume the following:
The total volume of fill and top-up water during its
service life will not exceed three times the water content
of the heating system.
IMPORTANT
Total output (MBH) Total Hardness (ppm of CaCO3)
> 2050 <150
Water Quality
The lifetime of the entire heating system is influenced by
the water quality. A water treatment system will protect
against damages caused by corrosion and lime formation.
Hard water conditions (i.e. calcium carbonate) must be
avoided as it will cause deposits to accumulate on the
heat exchanger surfaces.
If in any doubt about the water quality, please have a
proper water analysis done. Check with regional chemical
suppliers for boiler water treatment or with Viessmann
Manufacturing Company Inc. directly.
The pH value of the heating water should be between 8.2
and 9.5
Only fill the boiler with water that conforms with water
quality guidelines of VDI 2035-1.
Soften the fill and top-up water in heating systems operating
under the following conditions:
The total of alkaline earths in the fill and top-up water
exceeds the standard value.
Higher fill and top-up water volumes are expected.
In systems > 170 MBH (50 kW), install a water
meter to capture the amount of fill and top-up water.
Enter the volume of fill water and the water hardness
into the boiler maintenance checklists.
Operating information:
During expansion or repair work, only drain the
pipework sections which are crucial.
Check, clean and activate filters, dirt traps and other
blow-down or separating facilities in the heating
water circuit frequently after commissioning and in
new installations. Thereafter check and maintain as
required, depending on the type of water treatment
applied (e.g. water softening).
If the heating system is filled with fully softened
water, no other measures for start-up are required.
If the heating system is not filled with fully softened
water but with water which fulfils the requirements
given in the table above, the following should also
be considered for commissioning:
Start the system step by step with a high heating
water flow rate, starting with the lowest boiler
output. This prevents localized concentration of lime
scale deposits on the boiler heating surfaces.
In multiple boiler systems, start all boilers simultaneously
to prevent the entire lime scale deposit settling in the
heat exchanger of just one boiler.
Where water treatment is required, treat the first fill
of the heating system prior to start-up. This also
applies to any subsequent filling, e.g. when adding
top-up water or after a repair, or for any system
expansion.
The build-up of lime scale deposits on the heating
surfaces will be minimised if these instructions are
followed.
Fill Vitocrossal 300 CA3B with fully softened water only!

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Vitocrossal 300 CA3B Series 2.5 to 6.0 Service
Checking the Water Conditions (continued)
Commissioning
Avoiding damage caused by water corrosion
The corrosion-resistance on the heating-water side of
ferrous materials used in heating systems and heat
generators depends on the absence of oxygen in the
heating water. The oxygen that enters the heating
system upon initial and subsequent filling reacts with
the system materials without causing damage.
The characteristic blackening of the water after a certain
operating time is a sign that there is no longer any free
oxygen.
During operation, oxygen can enter due to:
Open vented expansion vessels due to flow through
Negative pressure in the system
Through permeable components
Correctly sized sealed unvented systems operating at the
correct pressure, e.g. systems with expansion vessel,
offer good protection against the ingress of airborne
oxygen. The pressure must be above the pressure of the
ambient atmosphere at all times during operation and at
every point in the heating system, including the suction
side of the pump. Check the precharge pressure of the
expansion vessel at least during the annual service.
Avoid the use of components permeable to gas, e.g.
permeable plastic pipes in underfloor heating systems.
If they are used, system separation should be provided.
This system separation must separate the water flowing
through the plastic pipes from other heating circuits,e.g.
from the boiler, by the provision of a corrosion resistant
heat exchanger. No other protective measures against
corrosion are necessary in corrosion-resistant closed hot
water heating systems in which the previous points
have been taken into account. However, take additional
precautions where there is a risk of oxygen ingress,
for example by adding oxygen binder sodium sulphite
5 to 10 ppm (5 to 10 mg/L) into the excess. The pH
value of the heating water should be 8.2–9.5.
Different conditions apply to systems that contain
aluminium components.
Where chemicals are used as part of the corrosion
protection, we recommend that the manufacturer of the
chemicals issues a certificate of suitability of the additives
with regard to the boiler materials and the materials
of other components. Please refer questions regarding
water treatment to an appropriate contractor.
Further details can be found in the VDI guideline
2035-2 and EN 14868.
Prevention of damage due to scaling
Prevent excessive scale build-up (calcium carbonate) on
the heating surfaces. For heating systems with operating
temperatures up to 212°F (100°C), VDI Guideline
2035 Part 1 “Prevention of damage in water heating
installations – Scale formation in domestic hot water
supply installations and water heating installations”
applies together with the following standard values.
See the explanations in the original text of the Guideline.

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Vitocrossal 300 CA3B Series 2.5 to 6.0 Service
Checking Static and Connection Pressure
Commissioning
Static Pressure
1. Close gas shut-off valve.
2. Loosen screw in the measuring connector Ado not
remove.
3. Connect pressure measuring device at measuring
connector A.
4. Open gas shut-off valve.
5. Measure static pressure max. 14 “w.c.
6. Record measurement reading in the maintenance record
(on page 162).
WARNING
Ensure that there is no open flame in the room.
WARNING
Never purge a gas line into a combustion chamber. Never
use matches, candles, flame, or other sources of ignition
for purpose of checking leakage. Use a soap-and-water
solution to check for leakage. Failure to follow this warning
could result in fire, explosion, personal injury, or death.
IMPORTANT
The burner is automatically ignited and starts operation
after a safety time has elapsed.
During initial start-up, the unit may indicate a fault because
of air in the gas supply pipe.
After approximately 5 seconds, press the reset button R
to reset the burner. The ignition procedure is repeated.
This boiler employs a direct spark ignition system.
A CO2measurement (see page 67) must be taken before
and after working on gas appliances to eliminate risks to
health and to guarantee the satisfactory condition of the
system.
IMPORTANT
Supply pressure for NG/LPG
1. Start the burner.
Note: Switch the burner to maximum heating output.
For this, activate the emissions test switch at the
boiler control unit.
2. Measure the supply pressure (running pressure).
Use suitable measuring instruments calibrated with
a minimum resolution of 0.04 “w.c. Value must be as
per the chart below:
Note: The supply pressure should be between 4 “w.c.
and 14 ”w.c. for NG and 10” w.c. to 14” w.c.
for LPG. The gas pressure switch for the inlet
pressure test/check is factory set to 4 ”w.c.
Never alter this setting.
3. Record the actual value in the maintenance record
(on page 162).
4. Close the gas shut-off valve.
5. Remove the pressure tester and close test nipple A.
Supply pressure with: Corrective action
Natural gas Liquid propane gas
under 4 ”w.c. under 10 ”w.c. Do not attempt adjustment. Call local gas utility
4 to 14 “w.c. 10 to 14 ”w.c. Start up boiler.
over 14 ”w.c over 14 ”w.c. Do not attempt adjustment. Call local gas utility to decrease pressure.
Boiler valve must not be exposed to pressure over 14 ”w.c.

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Vitocrossal 300 CA3B Series 2.5 to 6.0 Service
WARNING
Working on pressure loaded parts can be dangerous.
Connections around the heating water should only be
opened if the boiler is unpressurized.
CAUTION
Under-pressure in the boiler can lead to material
damages. Only empty boiler with open ventilation
with a suction pump.
IMPORTANT
Checking Heating Water Connections for Leakage
Ensure that connections for control equipment and
minimum pressure monitor (low-water indicator) are also
leakage-free.
Commissioning
Checking for Flue Gas Leakage
IMPORTANT
Gaskets can be checked with a dew point hygrometer
at full load operation. Detach thermal insulation parts if
necessary. Traces of condensed water on the exterior of
the glue gas collector or on the thermal insulation parts
also indicate leakages.
Check flue gas collector and boiler body for leakage.
CAUTION
Failure to ensure that all flue gases have been safely
vented to the outdoors can cause property damage,
severe personal injury or loss of life. Flue gases may
contain deadly carbon monoxide.
Commissioning

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Vitocrossal 300 CA3B Series 2.5 to 6.0 Service
1. Insert and tighten new gaskets at all detached
on-site connections.
2. Open gas shut-off valve.
3. Check sealing points at input side of the combination
gas valve for leakage.
4. Put boiler into operation (refer to page 18).
5. Check output-side sealing points of combination gas
valve, sealing points between fan and burner plate
and sealing points between fan and Venturi-tube for
leakage.
Checking On-site Gas Connections for Leakage
WARNING
Risk of explosion due to gas leakage. Check for gas
leakage at the gauge connections.
CAUTION
Use of leak detection spray can lead to operational
malfunctioning. Leak detection spray must not come
into contact with electrical contacts.
Commissioning
The system manufacturer must hand over the operating
instructions to the system operator and instruct him in
its operation.
1. Complete customer information file and separate:
Hand over segment for system operator to system
operator.
Retain segment for heating contractor in files.
2. Assemble all parts lists, operating and service
instructions in a file and deliver to the system operator.
After installation, the installation instructions will no
longer be required and do not need to be retained.
This includes all accessories that have been installed
as components, such as remote controls. The system
manufacturer must also provide instruction regarding
maintenance work.
Instructing the Operator of the System
Operating and Service Documents

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Vitocrossal 300 CA3B Series 2.5 to 6.0 Service
7. Switch ON the individual section control power
switches (the control display will show system
activation).
8. Match the coding card at the burner control unit,
refer to page 55.
9. Check the function of the neutralizing system.
Note: Neutralizing system operating instructions.
10.Check all gaskets and plugs, and retighten if
necessary.
Note: We recommend you check all connections on
the heating water side for leaks after approximately
500 hours initial run (refer to page 16).
See the neutralizing system instructions.
1. Check the heating system pressure.
Max. permissible boiler operating pressure: .... 160 psi.
Min. permissible boiler operating pressure: .........8 psi.
2. Check the gas supply pressure. Permissible gas
pressure 4-14 “w.c. (NG) and 10-14 “w.c. (LPG).
3. Open the gas line shut-off valves.
4. Switch ON the internal power disconnect switch.
5. Switch ON the main power (breakers).
6. Switch ON system ON/OFF switch at the control unit.
If fault indicator on the control unit illuminates and
burner control unit display A flashes, first press
reset button R B on the burner control unit.
WARNING
Failure to ensure that all flue gases have been safely
vented to the outdoors can cause property damage,
severe personal injury, or loss of life. Flue gases may
contain deadly carbon monoxide.
Note: The system can enter a fault state during
commissioning if there is insufficient gas in the
supply line (the fault indicator on the control unit
illuminates). Purge the gas supply line again and
reset the burner control unit.
Remove air from the gas line with an approved
gas purge burner or vent outdoors.
See the control section of the Installation
Instructions and neutralizing system
Operating Instructions.
Operating the Burner Control Unit
Gas type characteristics
The Vitocrossal 300 CA3B boiler is for use with gases
whose characteristics fall within the following ranges.
Natural Gas Liquid Propane Gas
Heating value
(gross) Btu/ft3970 to 1100 2466 to 2542
Specific gravity 0.57 to 0.70 1.522 to 1.574
Ultimate carbon
dioxide (CO2) % 11.7 to 12.2 13.73 to 13.82
1. The burners are factory set for operation with
natural gas.
2. Record gas type in the maintenance record on page 162.
Note: To change gas type refer to page 55.
Operating

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Vitocrossal 300 CA3B Series 2.5 to 6.0 Service
Operating the Burner Control Unit (continued)
Operating
The burners heating output can be reduced via the
individual burner control unit.
As an alternative, the adjustment can be made via the
burner control unit.
If required, the maximum heating output of the burners
can be set at 70% to 100% of the rated heating output.
1. Press button S Efor longer than 2 sec. will blink.
2. Press button Funtil “6” appears in the display C
under Service.
3. Press button S E, “6” appears in the display C
under Status.
4. Press button S E, “1” appears in the display C
under Status and the actual value for the maximum
heating output will be indicated in % under Service.
5. Press button For Dfor the desired maximum
heating output.
6. Press button S Eto confirm. If successfully
completed, “1” appears in the display Cunder
Service, a failed attempt results in a “0”.
7. Press button S Eto make a change in operating
status indicator.
8. Press button R G. A system reboot will be initiated.
Reducing Operational Output (if required)

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Vitocrossal 300 CA3B Series 2.5 to 6.0 Service
Operating
Burner Control Unit
Display and programming unit
A display and programming unit is integrated into each
burner control unit. The display indicates the relevant
operating conditions, the service and parameter conditions
as well as all fault and error messages, relative to that
boiler section.
The display comprises four elements of seven segments
each. Four buttons enable adjustments to be made at the
different operating levels.
A Status display
B Service display
C Reset button
D LEDs, from left: heat demand, flame,
maintenance and fault.
F Selection button
E/G Cursor button
Operating display
In standard mode, the status display shows the current
operating conditions. The same applies in a fault state
after pressing reset button R C.
The following displays are scrolled through automatically.
In case of faults, see the fault codes starting at page 28.
You can exit at any time by pressing and holding the
reset button R C for 0.5 to 10 seconds.
Idle state check
System tests
Fan ramp-up
Pre-purge
Standby
Section start-up
after power supply
is switched ON.
Gas valve and/or
relay test