Viessmann VITOCROSSAL 300 Operating instructions

for use by heating contractor
Please file in Service Binder
Product may not be exactly as shown
5285 875 - 04 01/2016
Service Instructions
VITOCROSSAL 300
Vitocrossal 300
CT3 Series
Gas-fired condensing boiler
Heating input: 638 to 3361 MBH
187 to 985 kW
Read and save these instructions for
future reference.
IMPORTANT
Vitocrossal 300, CT3 boiler
with Vitotronic control

Vitocrossal 300, CT3 Series Service
5285 875 - 04
2
Safety, Installation 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).
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 in the “Service Instructions” manual.
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 section entitled “Combustion
air supply” and “Venting information”
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
Information” in this manual. All
products of combustion must be
safely vented to the outdoors.
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”.
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 section
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.
Warranty
Information contained in this and
related product documentation must
be read and followed. Failure to do
so renders the warranty null and void.

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5285 875 - 04
Vitocrossal 300, CT3 Series Service Safety
Safety, Installation and Warranty Requirements (continued)
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.
HFiberglass 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.
Suppliers of fiberglass wool products recommend the
following precautions be taken when handling these
materials:
Precautionary measures
- 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.
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.
HHazardous materials
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 water.
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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Page
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Vitocrossal 300, CT3 Series Service
Table of Contents
Safety, Installation and Warranty Requirements..............2
Product documentation...........................................2
Licensed professional heating contractor...................2
Contaminated air ...................................................2
Advice to owner ....................................................2
Warranty ..............................................................2
Carbon monoxide...................................................2
Fresh air ...............................................................2
Equipment venting .................................................2
Fiberglass wool and ceramic fiber materials...............3
Suppliers of ceramic fiber products recommend
the following first aid measures: ..............................3
Precautionary measures..........................................3
First aid measures..................................................3
Hazardous materials ...............................................3
Important Regulatory and Safety
Requirements.............................................................6
Instructing the system user .....................................6
Initial start-up........................................................6
Working on the equipment ......................................6
Technical literature ................................................6
About these Instructions .............................................7
Necessary Tools.........................................................8
Tools ...................................................................8
Cleaning supplies ...................................................8
Testing/Analysis equipment.....................................8
Technical information .............................................8
Replacement parts .................................................8
Customer Site Information...........................................9
Site......................................................................9
Boiler ...................................................................9
Burner ..................................................................9
Installing Contractor...............................................9
Product Information..................................................10
Shut Down Heating System.......................................10
Check Pressure Relief Rating......................................10
Safety
General Information

Table of Contents
5
Page
5285 875 - 03
Vitocrossal 300, CT3 Series Service
Inspection and Maintenance
Additional Information
Dispose of Condensate .............................................11
Check Flue Gas Damper ............................................11
Check Venting Connection ........................................11
Start up Heating System ...........................................12
Reduce Pulsation Noises ...........................................13
Open Combustion Chamber Door ...............................13
Clean Combustion Chamber and Heat Exchanger
Surfaces .................................................................14
Clean Observation Port in Combustion Chamber Door ...15
Check all Connections and Sensor Well for Leaks .........16
Check Proper Operation of Low Water Cut-off .............16
Check Proper Expansion Tank and System Pressures ....16
Check Flue Gas Collector for Leaks.............................17
Close Combustion Chamber Door ...............................17
Check Thermal Insulation ..........................................18
Check Viessmann Mixing Service Valve for Proper
Operation and Leaks .................................................18
Adjust Burner ..........................................................18
Check Separate Heating System Controls ...................18
Check for Proper DHW Production..............................18
Maintenance Schedule ..............................................19
Frequency...........................................................19
Performed by ......................................................19
Service...............................................................19
Danger of Freezing ...................................................21
Long Periods of Shut-down........................................21
Water Quality ..........................................................21
Technical Data.........................................................22
Parts List.................................................................24
When ordering replacement parts...........................24
Parts ..................................................................24
Maintenance Record .................................................30
Maintenance/Service ............................................30

Vitocrossal 300, CT3 Series Service
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6
Safety
Important Regulatory and Safety Requirements
Working on the equipment
The installation, adjustment, service, and maintenance
of this boiler must be performed by a licensed professional
heating contractor who is qualified and experienced in the
installation, service, and maintenance of hot water boilers.
There are no user serviceable parts on the boiler, burners,
or control.
Note: Please carefully read this manual prior to attempting
installation. 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.
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.
Note: The completeness and functionality of field supplied
electrical controls and components must be verified
by the heating contractor. This includes low water
cut-offs, flow switches (if used), staging controls,
pumps, motorized valves, air vents, thermostats, etc.
Technical literature
Literature for the Vitocrossal 300 CT3 boiler:
- Technical Data Manual
- Installation Instructions
- Service Instructions
- Operating Instructions and User’s Information Manual
Note: Leave all literature at the installation site and advise
the system operator/ultimate owner where the
literature can be found. Contact Viessmann for
additional copies.
Additional applicable literature:
- Viessmann boiler controls manuals
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 shut-
down.
Note: 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.
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.
Note: The Maintenance Record is located on page 30 of
this manual.

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Vitocrossal 300, CT3 Series Service General Information
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 loss of life, 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.

Vitocrossal 300, CT3 Series Service
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8
Necessary Tools
General Information
Tools
HAssortment of flathead and Phillips screwdrivers
HPipe wrenches
HOpen-ended wrenches
HPipe sealant
HAssortment of Allen keys
HFlashlight
HApproved leak detection fluid for natural gas and
propane gas
Cleaning supplies
HHand brush
HCleaning/service brush
HVacuum cleaner
HRags
Testing/Analysis equipment
(use only calibrated equipment)
HFlue gas analyzer to measure % CO2or O2
(i.e. Bacharach fluid samplers or a suitable electronic
analyzer)
HMultimeter to measure 0 - 120VAC, 0 - 20 amps AC,
and 0 - 20 microamps DC
HPressure gage to measure gas pressure 0 - 28 ”w.c.
(a non-electric Magnehelicrpressure gage may also be
used)
HCarbon monoxide measuring equipment (0 - 400 ppm)
HBacharach calculator or suitable tables to calculate
efficiency
HStack thermometer 0 to 250°F (0 to 121°C)
Hdin. NPT male to ¼ in. barb adaptor fitting, as well as
tubing for pressure measurement
CAUTION
Use only original Viessmann components when replacing
defective parts. Installation of incorrect replacement
parts can cause hazardous operation and will void
warranty.
Technical information
The following is a list of literature applicable to the
Vitocrossal 300, CT3 boiler:
HInstallation Instructions
HService Instructions
HOperating Instructions and User’s Information Manual
For installation of the heating system, please refer also
to the technical literature of other System Technology
devices:
HInstallation Instructions for Viessmann boiler control
HInstallation Instructions for Viessmann indirect-fired hot
water storage tank(s)
HInstallation Instructions for burner and accessories
Replacement parts
The materials listed below are recommended to be on
hand for all service calls.
For a complete listing of replacement components, please
see Parts List starting on page 24 of these instructions.
Order replacement components from your Viessmann
distributor.

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5285 875 - 04
Vitocrossal 300, CT3 Series Service
Customer Site Information
General Information
Site
Name:
Street:
City:
Tel.:
Boiler
Mfr.: Viessmann
Series:
Heating Input: MBH
Serial No.:
Burner
Mfr.:
Series:
Heating Input: MBH
Serial No.:
Installing Contractor
Firm:
Technician:
Address:
Tel.:
Installed on:
Please complete the information below.

Vitocrossal 300, CT3 Series Service
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10
Product Information
General Information
Shut Down Heating System
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, CT3 boilers are CSA certified with
Weishaupt and Riello burners which must be used in
conjunction with this boiler series.
The proper burner size must be verified and the burner
must be adjusted so that the maximum input of the
appropriate boiler size is always observed and adjusted.
The gas burner 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.
The Vitocrossal 300 boiler is suitable for a maximum
operating pressure of 30 psig and a maximum boiler water
temperature of 210°F (99°C).
The maximum hydrostatic test pressure is 45 psig.
1. Deactivate main power supply to heating system and
secure against accidental reactivation.
2. Disconnect fA plug from burner (where applicable).
3. Close main gas supply valve.
WARNING
Exposing the boiler to pressures and temperatures in
excess of those listed will result in damages, and will
render warranty null and void.
Check Pressure Relief Rating
The maximum allowable working pressure is 30 psig.
WARNING
There may be more than one electrical disconnect.
See Installation and Operating Instructions
for Vitotronic controls.
The Vitocrossal 300 boiler series is operated with
a Vitotronic control and microcomputer indoor/
outdoor control system for boiler operation without
low temperature limit. The control system must be
programmed for this type of operation.
This boiler does not require a flow switch.
This boiler is for natural gas or propane gas only.