Viessmann Vitocrossal 300 CT3 SERIES Guide

Please file in Service Binder
for use by heating contractor
Read and save these instructions for
future reference.
IMPORTANT
Product may not be exactly as shown
5285 874 - 01 03/2015
Operating Instructions and
User’s Information Manual
VITOCROSSAL 300
Vitocrossal 300
CT3 Series
Gas-fired condensing boiler
Heating input: 638 to 3361 MBH
187 to 985 kW
Do not store or use gasoline or other flammable
liquids in the vicinity of this or any other appliance.
WHAT TO DO IF YOU SMELL GAS
HDo not try to light any appliances.
HDo not touch any electrical switches, do not use
any phone in your building.
HImmediately call your gas supplier from
a neighbor’s phone. Follow the gas supplier’s
instructions.
HIf you cannot reach your gas supplier, call the
fire department.
Installation and service must be performed by a
qualified installer, service agency or the gas supplier.
WARNING
Improper installation, adjustment, and/or
operation could cause carbon monoxide poisoning
resulting in injury or loss of life.
This product must be installed and serviced
by a professional service technician who
is experienced and qualified in hot water boiler
installation and gas/oil combustion.
WARNING
If the information in this manual is not followed
exactly, a fire or explosion may result causing
property damage, personal injury or loss of life.

Vitocrossal 300, CT3 Series Operating
5285 874 - 01
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).
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.
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 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.
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.

Table of Contents
3
Page
5285 874 - 01
Safety
General Information
Operation
Inspection and Maintainance
Vitocrossal 300, CT3 Series Operating
Safety, Installation and Warranty Requirements..............2
Product documentation...........................................2
Warranty ..............................................................2
Licensed professional heating contractor...................2
Contaminated air ...................................................2
Advice to owner ....................................................2
Carbon monoxide...................................................2
Fresh air ...............................................................2
Equipment venting .................................................2
About These Instructions ............................................4
Important Regulatory and Safety Requirements ..............5
Operation .............................................................5
Working on the equipment ......................................5
Dangerous conditions .............................................5
Gas smell..............................................................5
Flue gas smell .......................................................5
Combustion air and ventilation air openings...............5
Carbon monoxide...................................................5
Frozen water pipe hazard ........................................5
Regular maintenance and service .............................6
Technical information .............................................6
Product Information....................................................7
Fuel(s) ......................................................................7
Boiler Control.............................................................7
Boiler Location ...........................................................8
Condensate Disposal ..................................................8
Venting Connection ....................................................8
For Optimum Operation...............................................9
Operation ..................................................................9
System shut-down.................................................9
Separate Heating System Controls................................9
Domestic Hot Water Production ...................................9
Maintenance Schedule ..............................................10
Frequency...........................................................11
Performed by ......................................................11
Service...............................................................11
Additional Maintenance Information............................12
Danger of freezing ...............................................12
Long Periods of Shut-down........................................12
Water Quality ..........................................................12

Vitocrossal 300, CT3 Series Operating
5285 874 - 01
4
Safety
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.

5
5285 874 - 01
Vitocrossal 300, CT3 Series Operating Safety
Important Regulatory and Safety Requirements
HCombustion air and ventilation air openings
Ensure that combustion air openings and ventilation air
openings in the mechanical room are open.
CAUTION
Incomplete combustion and poisonous gases result if
the fresh air intakes in the mechanical room are closed.
Never close these openings.
HOperation
Before operating the boiler, make sure you fully
understand its method of operation. Your heating
contractor should always perform the initial start-up and
explain the system.
Any warranty is null and void if these instructions are not
followed.
HWorking on the equipment
All personnel working on the equipment or the heating
system must have the proper qualifications and hold all
necessary licenses.
Ensure main power to equipment, heating system, and
all external controls has been deactivated. Close main oil
or gas shut-off valve. Take precautions in all instances to
avoid accidental activation of power during service work.
HDangerous conditions
– Deactivate main power immediately.
– Close main gas or oil shut-off valve.
HGas smell
Follow the instructions on the front page of this manual.
HFlue gas smell
– Deactivate heating equipment.
– Open windows and doors.
– Inform your heating contractor.
HCarbon monoxide
The U.S. Consumer Product Safety Commission strongly
recommends the installation of carbon monoxide
detectors in buildings in which gas-burning equipment
is installed.
Carbon monoxide (CO) is a colorless, odorless gas, which
may be produced during incomplete combustion of fuel
and/or when the flame does not receive an adequate
supply of combustion air.
Carbon monoxide can cause severe personal injury or loss
of life.
Therefore, carbon monoxide detectors that are in
compliance with a nationally recognized standard (e.g.
ANSI/UL 2034-2002, CSA 6.19-01) should be installed
and maintained in buildings that contain gas-burning
equipment.
Note: Viessmann does not test any detectors and makes
no representation regarding any brand or type of
detector.
Your heating boiler is designed to provide a warm and
comfortable living environment. It is NOT designed to
ensure against freezing of water pipes.
The boiler is equipped with several safety devices that are
designed to shut down the boiler and to prevent it from
restarting in the event of various unsafe conditions.
If your boiler remains off for an extended period of time
during cold weather, water pipes may freeze and burst,
resulting in extensive water damage and conditions in
which mold could grow. Certain molds are known to
cause respiratory problems, as well as to pose other
serious health risks. In case of water damage, immediate
measures should be taken to dry out affected areas as
quickly as possible to prevent mold from developing.
If your home will be unattended for an extended period
of time during cold weather, you should...
Shut off the water supply to the building, drain the water
pipes and add an antifreeze for potable water to drain
traps and toilet tanks. Open faucets where appropriate.
Or..
Have someone check the building frequently during cold
weather and call a qualified service agency if required.
Or...
Install a reliable remote temperature sensor that will notify
somebody of freezing conditions within the home.
WARNING
Failure to protect against frozen pipes could result in
burst water pipes, serious property damage and/or
personal injury. Boiler may shut down.
Do not leave your home unattended for long periods
of time during freezing weather conditions without
turning off the water supply and draining water pipes
or otherwise protecting against the risk of frozen pipes.
Frozen water pipe hazard

Vitocrossal 300, CT3 Series Operating
5285 874 - 01
6
Safety
Important Regulatory and Safety Requirements (continued)
HRegular maintenance and service
The entire heating system must be cleaned and serviced
on a regular basis by a qualified heating contractor or
service agency to ensure reliable, energy-efficient, and
environmentally friendly operation.
The build-up of soot on the heat exchanger raises the flue
gas temperature and reduces efficiency.
Indirect-fired domestic hot water storage tanks (if
installed) must be serviced within two years (at most) of
the installation date, and regularly thereafter (see Service
Schedule starting on page 10).
For an overview of scheduled service procedures, please
see section entitled “Service Schedule” on page 10 of this
manual.
The owner or dedicated personnel should perform the
checks outlined in the Service Schedule to ensure proper
operation of the heating system.
WARNING
Improper installation, adjustment, service, or
maintenance can cause flue products to flow into
living space. Flue products contain poisonous carbon
monoxide gas which can cause nausea or asphyxiation
resulting in severe personal injury or loss of life.
WARNING
As there are no user-serviceable parts on the boiler,
burners or control, the end-user must not perform
service activities of any kind on system components.
Failure to heed this warning can cause property
damage, severe personal injury, or loss of life.
WARNING
The boiler must not be located in areas or rooms
where chemicals are stored, or aggressive vapors
from (i.e. bleach, hair spray, methyl chloride, carbon
tetrachloride or perchloroethylene) or high dust
levels or humidity levels are present. Heat exchanger
corrosion might occur and reduce the lifetime of the
boiler significantly. If above criteria are not properly
observed and boiler damage results, any warranty
on the complete boiler and related components will
be null and void.
IMPORTANT
Keep boiler and boiler room clear and free from combustible
materials, gasoline and other flammable vapors and liquids.
Do not obstruct the flow of combustion and ventilation air.
All inspection, maintenance and service must be performed
by a qualified heating contractor.
IMPORTANT
Keep all literature in a safe place at the installation site.
Contact Viessmann for additional copies.
CAUTION
Do not use this boiler if any part has been under water.
Immediately call a qualified heating contractor to inspect
the boiler and to replace any part of the control system
and any gas control which has been under water.
HTechnical information
Literature applicable to the Vitocrossal 300, CT3 boiler:
- Installation Instructions
- Service Instructions
- Operating Instructions and User’s Information Manual
- Installation codes mentioned in this manual

7
5285 874 - 01
Vitocrossal 300, CT3 Series Operating
Product Information
General Information
The Viessmann Vitocrossal 300, CT3 boiler series is CSA
certified for Canada, is constructed in compliance with
CSA B51 Standard and carries Canadian Registration
Numbers.
The boiler is suitable for a maximum operating pressure
of 30 psig and a maximum boiler water temperature
of 210° F (99° C).
The Vitocrossal 300 boiler must only be installed in
closed loop hot water heating systems using a precharged
membrane expansion tank.
The Vitocrossal 300 boiler series is CSA certified together
with Weishaupt and Riello burners which must be used
in conjunction with this boiler.
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 be installed according to the
instructions supplied by the burner manufacturer.
Legend
V Vent pipe connection
SH Female connection R ½ in. for safety header (air vent
and pressure gage)
D Drain
CD Condensate drain
BR 1 Boiler return 1
BR 2 Boiler return 2
BTS Boiler temperature sensor
BD Boiler door with burner connecting flange
BS Boiler supply
IO Inspection opening
SS Safety supply (pressure relief valve)
OP Observation port (boiler from CT3-17 - 28:
offset by 90º)
Fuel(s)
Natural gas (NG) or liquid propane gas (LPG).
Control instructions supplied
with boiler control.
Boiler Control
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 by the installer.

Vitocrossal 300, CT3 Series Operating
5285 874 - 01
8
Condensate Disposal
General Information
CAUTION
The boiler room must be safe from frost and be
properly ventilated.
Boiler Location
The boiler must not be installed in rooms or areas where
halogenated hydrocarbons are present in the combustion
air, such as barber shops and beauty salons, printing
shops, chemical cleaners, laboratories etc.
Vitocrossal 300 boiler efficiency dependent on system
heating water return temperatures and load conditions
The values given are approximate amounts occurring
under practical conditions. Not included in the chart
is the amount of condensate occurring in the vent pipe
and chimney system. The condensate from the chimney
system can be collected together with the condensate
from the heating boiler and be disposed of into a floor
drain.
The condensate occurring will have between 3 and 4
on the pH scale. If local building requirements demand
neutralizing the condensate before disposal, contact
Viessmann Manufacturing Company Inc. for a correctly
sized neutralization tank. The treated condensate will
show pH values of between 6.5 and 9 and can then be
disposed of into the waste water system.
During the operation of the Vitocrossal 300 boiler,
the amount of condensate as per the diagram can be
expected.
A large amount of water vapor contained in the flue gases
of condensing boilers condenses. The condensate pH
value is between 3 and 5.5. The flue gas temperatures
depending on the boiler water temperature may be
between 77° F (25° C) and 257° F (125° C).
Venting Connection
The manufacturer of the chimney system or venting
system has to properly design the venting system as well
as select proper materials.
If there are any questions in regards to the neutralization
of the condensate and/or to the venting of this boiler
series, contact your local Viessmann Sales Representative.
Flue gas temperature gross
Boiler water return temperature
Amount of condensate
Flue gas temp
at full input
Flue gas temp
at partial load
Amount of
condensate

9
5285 874 - 01
Vitocrossal 300, CT3 Series Operating Operation
The boiler controls monitor the operation of your heating
system in conjunction with installed system controls
(if applicable) based upon indoor/outdoor control, setback
programming and other settings. Please refer to the
respective documentation of the boiler controls, or other
system controls, to make adjustments.
Deactivate main power switch and all additional switches
controlling additional pumps or controls, including main
switch for burner. Close all valves in the system.
IMPORTANT
Read the operating instructions supplied with the Vitotronic
control, as well as Operating Instructions of the gas burner
before deactivating or activating the heating system.
Operation
The Vitocrossal 300 boiler may be used to supply
domestic hot water heating by means of an indirect-fired
hot water storage tank. The appropriate connections
to the boiler must be made, as well as the correct size
circulating pump must be used. The control circuit to
provide domestic hot water is already provided within the
Vitotronic control.
In case additional controls are installed in the boiler room,
e.g. control aquastats, mixing valves, controls etc., please
observe their respective operating instructions.
Separate Heating System Controls
Domestic Hot Water Production
To ensure optimum operation of your heating system
do the following:
HKeep the boiler and the boiler room clean and free
of dust and dirt.
HEnsure proper and adequate system pressure
by occasionally checking the pressure gage.
HHave a qualified heating contractor service and maintain
your heating system on a regular basis. See Service
Schedule starting on page 10 for details.
For Optimum Operation

Vitocrossal 300, CT3 Series Operating
5285 874 - 01
10
Starting the Heating System
Ask your heating contractor about the following:
HBoiler and relevant control unit type
HLevel of the required system pressure
HPosition of the pressure gauge, shutoff valve,
gas shut-off valve, ventilation apertures
1. Check the heating system pressure at the pressure
gauge. If the heating system pressure is too low, top
up the water or notify your local heating contractor.
2. Open the shut-off valves in the oil lines (at the tank
and filter) or open the gas shut-off valve.
3. Switch ON the power supply, e.g. at a separate MCB/
fuse or a mains isolator.
4. Switch the ON/OFF switch ON. After a short time,
the standard menu is displayed and the green ON
indicator illuminates. Your heating system and, if
installed, your remote control unit are now ready for
use.
Operation / Inspection and Maintenance
Maintenance Schedule
IMPORTANT
Keep boiler and boiler room clear and free from combustible
materials, gasoline and other flammable vapors and liquids.
Do not obstruct the flow of combustion and ventilation air.
All inspection, maintenance and service must be performed
by a qualified heating contractor.
IMPORTANT
The boiler should be cleaned at least once a year by a
qualified heating contractor or service agency.

11
5285 874 - 01
Vitocrossal 300, CT3 Series Operating
Maintenance Schedule (continued)
Inspection and Maintenance
The following is an overview of scheduled service steps. Regular service work ensures reliable, energy-efficient,
and environmentally friendly operation.
Frequency Performed by Service
Monthly Owner /
Operator
Check the system pressure frequently
Ensure proper operation of the boiler control.
Inspect all seals; retighten or replace as necessary.
Ensure an adequate supply of combustion air and ventilation air into and out of the
mechanical room is being maintained.
Ensure that nothing is obstructing the flow of combustion - ventilation air, and no
chemicals, garbage, gasoline, combustible materials, flammable vapors, or liquids are
stored, not even temporarily, in the vicinity of the boiler.
Check for water on the floor from the discharge pipe of pressure
relief valve or any other pipe, pipe joint, valve, or air vent.
Test pressure relief valve and check for proper operation.
Check all operational high limits for proper operation.
Check for proper operation of the condensate neutralization system (if used).
Test pressure relief valve and check function.
Check the condition and fill status of the neutralization media.
Check the pH value of the flue gas condensate.
Check for moisture water on vent pipe joints and appearance of ice on the vent pipe
or chimney outlet in the winter time.
Annually Owner /
Operator
Ensure service work/test is conducted at least annually by qualified personnel,
and that any deficiencies are corrected immediately.
Heating
Contractor
Test functionality of safety high limits.
Test burner with burner accessories according to their corresponding maintenance
checklist.
Test and establish proper chemical makeup of system water.
Check flue pipe condition, chimney connection and chimney itself.
Check pressure relief valve and system pressure, and verify proper operation
Check heating pipe joints, valves, air vents, etc. System leaks must be corrected
immediately to avoid further defects.
The cause of defect must also be determined in order to avoid further problems.
Check for proper combustion air supply and ventilation to boiler / mechanical room.
Check for combustible materials or chemicals stored too close to the boiler.
Test high limits by dialing lower settings, switching burner on/off to verify
functioning of same. Test low water cut-off, check and verify proper function
according to manufacturer’s instructions.
When circulating pump is field-installed or existing, check requirements
for maintenance or lubrication according to manufacturer’s specifications.
Check for oil-tight fuel lines; clean or exchange fuel oil filters annually.
Check and inspect oil tank.
Check for gas-tight connection of gas piping, unions, gas valve and manifold.
Check proper ignition on oil or gas burner operation.
Combustion test must be performed by a qualified heating contractor.
Ensure proper operation of door safety switch.
Periodically Heating
Contractor
Ensure functionality of low water cut-offs, including flushing of float types (if used)
during operation, based on supplier’s instructions.
Inspect low- and/or high pressure gas switch (if used).
Inspect main burner flame and follow burner manufacturer’s instruction manual
for detailed service and maintenance guidelines. Manual shipped with burner.
All boilers and the boiler room must be kept free of high dust levels, high humidity,
aggressive vapors and/or chemicals containing chlorine.
Ensure proper boiler room ventilation and combustion air is maintained.
Valves, fittings and pipes not pressure tight must be repaired.
Combustion chamber door, clean-out opening covers, glass fiber rope seals and
flanges may need to be retightened and resealed.

Technical information subject to change without notice. Printed on environmentally friendly
(recycled and recyclable) paper.
Inspection and Maintenance
In case the heating boiler is shut down for an extended
period of time, i.e. after the heating season, the
combustion chamber, the flue gas collector and the vent
pipe should be properly cleaned to avoid corrosion.
Danger of freezing
If the system is subject to freezing temperatures and
is not filled with antifreeze for protection, the system
including the boiler must be drained of water.
Long Periods of Shut-down
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 heating system can stay filled and under pressure.
The remaining condensate should be removed from the
flue gas collector by means of the front inspection service
opening.
Additional Maintenance Information
The valve before automatic feed valve (if installed) must
be closed. All other valves, air vents and drain valves
must remain open.
5285 874 - 01
Vitocrossal 300 CT3 Series Operating
12