Viessmann Vitocrossal 300 CT3 SERIES User manual

Please file in Service Binder
5285 873 - 02 12/2014
Installation Instructions
for use by heating contractor
VITOCROSSAL 300
Vitocrossal 300
CT3 Series
Gas-fired condensing boiler
Heating input: 638 to 3361 MBH
187 to 985 kW
Vitocrossal 300, CT3 boiler
with Vitotronic control
Working on the equipment
The installation, adjustment, service and
maintenance of this product must be performed
by a licensed professional heating contractor,
who is qualified and experienced in the installation,
service and maintenance of hot water heating
boilers. There are no user serviceable parts on the
boiler, burner, or control.
Ensure main power supply to equipment, the
heating system and all external controls has been
deactivated. Close main oil or gas supply valve.
Take precautions in all instances to avoid
accidental activation of power during service work.
Improper installation, service or maintenance can
cause product/property damage, severe personal
injury, and/or loss of life.
IMPORTANT
Please ensure that these instructions are read and
understood before commencing installation and
start-up. Failure to comply with these Installation
Instructions will render all warranties null and void.
Read and save these instructions
for future reference.
Product may not be exactly as shown
IMPORTANT

Vitocrossal 300, CT3 Series Installation
5285 873 - 02
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).
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.

3
5285 873 - 02
Vitocrossal 300, CT3 Series Installation 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.

4
Page
Table of Contents
5285 873 - 02
Vitocrossal 300, CT3 Series Installation
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
Codes ..................................................................7
Working on the equipment ......................................7
Mechanical room ...................................................7
Technical literature ................................................7
About these Instructions .............................................8
Product Information....................................................8
Mechanical Room .......................................................9
Minimum Clearances...................................................9
Minimum Clearances to Combustibles ......................9
Recommended Service Clearances ...........................9
Mechanical room ...................................................9
Boiler Dimensions.....................................................11
Dimensions .........................................................11
Boiler Model........................................................11
Boiler Handling, Positioning and Adjustments ...............12
Flue Gas Connections ...............................................12
Assembly When Supplied in Sections..........................13
Water Side Connections ............................................14
Hydrostatic Test Procedure........................................15
Vitocrossal 300, CT3-17 to -89.............................15
Boiler Piping in Heating/Cooling Application .................16
Initial System Fill......................................................17
Condensate Connection ............................................18
Condensate Disposal ................................................19
Safety
General Information
Set-up
Assembly
Boiler Connections
Boiler Connections/Assembly

Table of Contents
5
Page
5285 873 - 02
Vitocrossal 300, CT3 Series Installation
Assembly
Start-up
Appendix
Insulation Installation ................................................19
Preparing the Control Unit Installation .........................22
Insulation Installation ................................................24
Back panel, combustion chamber door and cable
channel installation ..............................................24
Top panel installation ...........................................25
Observation Port Installation ......................................26
Burner Installation ....................................................26
Burner Blast Tube Insulation ......................................27
Packing Materials.................................................27
Burner Settings ........................................................28
Venting Connection ..................................................28
Initial Start-Up .........................................................29
Pressure drop (primary circuit) ..............................29
Recommended Flow Rates ....................................29
Boiler model CT3 .................................................29
Technical Data.........................................................30
Boiler Model........................................................30
Input ..................................................................30
Output ...............................................................30
Combustion efficiency .........................................30
Thermal efficiency ..............................................30
Boiler output .......................................................30
Boiler standby loss...............................................30
Dimensions - boiler shell .......................................30
Overall dimensions...............................................30
Foundation..........................................................30
Weight ...............................................................30
Overall weight complete with insulation and control
(less burner) .......................................................... 30
Boiler Model........................................................31
Weight ...............................................................31
Overall weight complete with insul. and control
(w/o burner)........................................................31
Boiler water content.............................................31
Heat exchanger surface .......................................31
Max. operating temperature ..................................31
Max. operating pressure .......................................31
Flue gas resistance ..............................................31
Boiler connections................................................31
Vent pipe............................................................31
Flue gas values....................................................31
Pressure at boiler flue outlet..................................31

Vitocrossal 300, CT3 Series Installation
5285 873 - 02
6
Safety
Important Regulatory and Safety Requirements
For installations on the Commonwealth of Massachusetts, the following modifications to NFPA-54 chapter 10 apply:
Excerpt from 248 CMR 5-08:
2(a) For all side-wall horizontally vented gas fueled equipment installed in every dwelling, building or structure
used in whole or in part for residential purposes, including those owned or operated by the Commonwealth
and where the side-wall exhaust vent termination is less than (7) feet above finished grade in the area of
the venting, including but not limited to decks and porches, the following requirements shall be satisfied:
1. INSTALLATION OF CARBON MONOXIDE DETECTORS. At the time of installation of the side-wall
horizontal vented gas fueled equipment, the installing plumber or gas fitter shall observe that a hard wired
carbon monoxide detector with an alarm and battery back-up is installed on the floor level where the gas
equipment is to be installed. In addition, the installing plumber or gasfitter shall observe that a battery
operated or hard wired carbon monoxide detector with an alarm is installed on each additional level of the
dwelling, building or structure served by the side-wall horizontal vented gas fueled equipment. It shall be
the responsibility of the property owner to secure the services of qualified licensed professional for the
installation of hard-wired carbon monoxide detectors.
a. In the event that the side-wall horizontally vented gas fueled equipment is installed in a crawl space or
an attic, the hard-wired carbon monoxide detector with alarm and battery back-up may be installed on
the next adjacent floor level.
b. In the event that the requirements of this subdivision can not be met at the time of completion of
installation, the owner shall have a period of thirty (30) days to comply with the above requirements;
provided, however, that during said thirty (30) day period, a battery operated carbon monoxide detector
with an alarm shall be installed.
2. APPROVED CARBON MONOXIDE DETECTORS. Each carbon monoxide detector as required in accordance
with the above provisions shall comply with NFPA 720 and be ANSI/UL 2034 listed and IAS certified.
3. SIGNAGE. A metal or plastic identification plate shall be permanently mounted to the exterior of the
building at a minimum height of eight (8) feet above grade directly in line with the exhaust vent terminal
for the horizontally vented gas fueled heating appliance or equipment. The sign shall read, in print size no
less than one-half (b) inch in size, "GAS VENT DIRECTLY BELOW. KEEP CLEAR OF ALL OBSTRUCTIONS".
4. INSPECTION. The state or local gas inspector of the side-wall horizontally vented gas fueled equipment
shall not approve the installation unless, upon inspection, the inspector observes carbon monoxide
detectors and signage installed in accordance with the provisions of 248 CMR 5.08(2)(a) 1 through 4.
(b) EXEMPTIONS: The following equipment is exempt from 248 CMR 5.08(2)(a) 1 through 4:
1. The equipment listed in Chapter 10 entitled "Equipment Not Required To Be Vented" in the most current
edition of NFPA 54 as adopted by the Board; and
2. Product Approved side-wall horizontally vented gas fueled equipment installed in a room or structure
separate from the dwelling, building or structure used in whole or in part for residential purposes.

7
5285 873 - 02
Vitocrossal 300, CT3 Series Installation Safety
Important Regulatory and Safety Requirements (continued)
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: 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.
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.
For installation of the heating system as a whole,
please refer to the technical literature of other System
Technology devices:
- Installation Instructions for Viessmann boiler control
- Installation Instructions for Viessmann indirect-fired hot
water storage tank(s)
- Installation Instructions for burner and accessories
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
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.
We offer frequent installation and service seminars
to familiarize our partners with our products. Please
inquire.
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.
For oil-fired boiler installation, use CSA B-139 in Canada
and NFPA 31 in the U.S. 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.
Technical literature
Literature for the Vitocrossal 300, CT3 boiler:
- Technical Data Manual
- Installation Instructions
- Service Instructions
- Operating Instructions and User’s Information Manual
- Instructions of other Viessmann products utilized with
this installation
- Installation codes mentioned in this 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.
Mechanical room
Ensure the mechanical room complies with the
requirements of the System Design Guidelines and/or
Technical Data Manual. In addition, see section entitled
“Mechanical Room” on page 7 in this manual.
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).

Vitocrossal 300, CT3 Series Installation
5285 873 - 02
8
General Information
WARNING
Exposing the boiler to pressures and temperatures
in excess of those listed will result in damages,
and will render warranty null and void.
Product 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.
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).
This boiler does not require a flow switch.

9
5285 873 - 02
Vitocrossal 300, CT3 Series Installation
Mechanical Room
The Vitocrossal 300, CT3 boiler should be located in
a heated indoor space. The boiler should also be located
near a floor drain and as close as possible to the vertical
chimney or vent.
Whenever possible, install boiler near an outside wall so
that it is easy to duct fresh air directly to the boiler area.
Install boiler on flooring capable of supporting the weight
of the boiler filled with water.
Set-up
Minimum Clearances
Do not use exhaust fans without adding additional
provisions for fresh combustion air (e.g. fresh air fan) in
the boiler room and do not install the Vitocrossal 300
boiler in rooms with refrigeration equipment. This boiler
requires uncontaminated air for safe operation - do not
install where chemicals are stored.
Recommended Service Clearances
To enable convenient installation and maintenance,
observe the stated clearance dimensions. Maintain the
minimum clearances where space is tight. In the factory
set condition, the boiler door opens to the right. You can
relocate the hinge bolts so that the door can open to the
left.
Boiler model CT3- 17 22 28 37 46 57 72 89
V in. (mm) 28
(711)
28
(711)
28
(711)
35
(889)
35
(889)
39
(991)
45
(1143)
45
(1143)
W in. (mm) 62c
(1593)
65c
(1671)
69
(1752)
72
(1828)
75
(1906)
81a
(2062)
85b
(2172)
93a
(2366)
X in. (mm) 36b
(930)
39a
(1000)
43a
(1100)
59
(1500)
59
(1500)
59
(1500)
59
(1500)
59
(1500)
Y in. (mm) 40
(1012)
40
(1012)
40
(1012)
44b
(1128)
44b
(1128)
44b
(1128)
49
(1243)
49
(1243)
Z in. (mm) 41a
(1048)
41a
(1048)
41a
(1048)
45a
(1149)
45a
(1149)
45a
(1149)
48
(1219)
48
(1219)
Mechanical room
HDo not operate when air is polluted with halogenated
hydrocarbons (e.g. as in aerosols, paints, solvents and
cleaning agents)
HPrevent very dusty conditions
HPrevent high levels of humidity
HPrevent freezing and ensure good ventilation
Otherwise, the system may suffer faults and damage.
Legend
ABoiler
BBurner
Minimum Clearances to Combustibles
Boiler model
CT3- 17 22 28 37 46 57 72 89
Top 6 in. (150 mm)
Sides 6 in. (150 mm)
Flue As per vent manufacturer’s specification
Front 6 in. (150 mm)
Floor combustible
8 in.
(200mm)
Length of
burner
(500
mm) (500 mm)
x
y
z
v
B
wA
20 in. 20 in.

Vitocrossal 300, CT3 Series Installation
5285 873 - 02
10
Set-up
Minimum Clearances (continued)
Legend
V Vent pipe connection
SH Female connection R½ in. for 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 for pressure relief valve
OP Observation port (boiler from CT3-17 - 28:
offset by 90º )
IN Insulation
Note: - Boiler shell, overall and foundation dimensions
listed on page 29.
- Minimum shipping dimensions: use “o” in the
table below, and height, width 1 in the diagram
above.
*1 The minimum combustion head length of 5½ in.
(140 mm) must be maintained. When a burner with
a shorter combustion head is used, all functions
including combustion results must be verified. The
maximum combustion head length must also be
observed so that the burner on the hinged combustion
chamber door can swing into service position. Radius
of door hinge to outside combustion head: 18¾ in.
(476 mm).
Length of
boiler pad
Overall height
Length
Overall width
Width 1
Width 1
Width 2
Width 2
with IN 2
Height
Overall length
min. 5bin.
(140 mm)
with IN 1
12 in.
(160 mm)
SH
OP
BD
IO
CD
SS
BS
BR2
BR1
D
V
BTS
*1

11
5285 873 - 02
Vitocrossal 300, CT3 Series Installation Set-up
Boiler Dimensions
Di
m
e
ns
i
on
s
B
oil
e
r Mod
e
l
C
T3
-
17
22
28
37
48
57
72
89
a
i
n.
(
mm
)
2
8
c
(
715
)
2
8
c
(
715
)
2
8
c
(
715
)
2
9
c
(
751
)
2
9
c
(
751
)
2
9
c
(
751
)
2
9
c
(
751
)
2
9
c
(
751
)
b
i
n.
(
mm
)
11
c
(
2
9
8
)
11
c
(
2
9
8
)
11
c
(
2
9
8
)
1
2
c
(
325
)
1
2
c
(
325
)
1
2
c
(
325
)
14
a
(
363
)
14
a
(
363
)
c
i
n.
(
mm
)
2
0
b
(
518
)
2
0
b
(
518
)
2
0
b
(
52
9)
22
c
(
577
)
22
c
(
577
)
22
c
(
577
)
2
5
a
(
644
)
2
5
a
(
644
)
d
i
n.
(
mm
)
6
2
c
(
15
9
4
)
64
c
(
1644
)
64
c
(
1644
)
7
3
(
1854
)
7
3
(
1854
)
7
3
(
1854
)
80
b
(
2043
)
80
b
(
2043
)
e
i
n.
(
mm
)
74
(
187
9)
7
6
(
1
9
2
9)
7
6
a
(
1
9
37
)
85
b
(
2185
)
86
(
2185
)
86
(
2185
)
95
a
(
2417
)
95
a
(
2417
)
f
i
n.
(
mm
)
7
(
177
)
7
(
177
)
7
(
177
)
9
b
(
200
)
9
b
(
200
)
9
b
(
200
)
11
(
280
)
11
(
280
)
g
i
n.
(
mm
)
9
(
227
)
9
(
227
)
9
(
221
)
8
(
241
)
8
(
241
)
8
(
241
)
10
(
250
)
10
(
250
)
h
i
n.
(
mm
)
3
1
b
(
802
)
33
b
(
852
)
33
b
(
852
)
36
a
(9
21
)
36
a
(9
21
)
36
a
(9
21
)
38
(9
65
)
38
(9
65
)
k
i
n.
(
mm
)
10
(
257
)
10
(
257
)
10
(
257
)
11
a
(
284
)
11
a
(
284
)
11
a
(
284
)
14
(
360
)
14
(
360
)
l
i
n.
(
mm
)
51
a
(
12
99
)
5
3
(
134
9)
5
3
(
134
9)
5
9
(
1500
)
5
9
(
1500
)
5
9
(
1500
)
63
c
(
1621
)
63
c
(
1621
)
m
i
n.
(
mm
)
)
7
b
(
1
9
4
)
7
b
(
1
9
4
)
7
b
(
1
9
4
)
7
b
(
1
9
0
)
7
b
(
1
9
0
)
7
b
(
1
9
0
)
7
c
(
1
9
7
)
7
c
(
1
9
7
)
n
i
n.
(
mm
)
5
b
(
141
)
5
b
(
141
)
4
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121
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42
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(
107
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63
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(
1621
)

Vitocrossal 300, CT3 Series Installation
5285 873 - 02
12
Set-up
Boiler Handling, Positioning and Adjustments
Please observe the minimum clearances starting on page 8.
The boiler itself is mounted on a boiler pad.
This boiler pad should be placed on a concrete or
equivalent foundation. A recommended foundation size
for each boiler model can be found on page 29. The
minimum height should not be less than 4 in. (100 mm).
1. Remove wooden shipping blocks from boiler base.
2. Remove the 4 leveling bolts from boiler skid and
insert in the boiler skid. It is recommended to place
a flat piece of steel plate under each floor leveling
bolt for better weight distribution and adjustment,
and to compensate for an uneven floor.
3. By adjusting the floor leveling bolts and, if necessary,
adding a heavier steel plate, most of an uneven floor
can be properly corrected.
Flue Gas Connections
Internal Ø of the flue outlet at:
CT3-17 to 28 8 in. (201 mm)
CT3-37 to 57 9¾ in. (251 mm)
CT3-72 to 89 11¾ in. (301 mm)
See flue gas system installation instructions.

13
5285 873 - 02
Vitocrossal 300, CT3 Series Installation Assembly
Assembly When Supplied in Sections
1. Release the turnbuckles and screws M 12 on the
bottom of the boiler body, pull the boiler front section
out of the turnbuckles and remove it.
2. Secure supplied masking tape to all joints on the
inside of the combustion chamber to prevent sealant
adhering to these areas. Attach adhesive tape on the
rear boiler section approx. 8 to 10 mm behind the
front edge.
3. Evenly and generously apply the sealant supplied
into the annular groove on the front section of the
combustion chamber. Use supplied gasketing material
only.
4. The combustion chamber front portion must then be
aligned onto the main pressure vessel part and bolted
to the same with the two bolt clamps provided on
each vessel section together with the bolts and nuts
M16 x 150. Insert gasket on boiler connection flange
and tighten flange with nuts and bolts provided.
Attach lower section of front combustion chamber
to main vessel with nuts and bolts M12 x 25 as
provided.
5. Insert the supplied gasket in contact with the water
side between the boiler sections and connect the
proper flanges with nuts and bolts.
6. Secure the front section of the combustion chamber
at the lower end with screws M12 x 45 and nuts.
7. Using empty silicone tubes, remove all protruding
silicone sealant inside the combustion chamber.
Ensure sufficient sealant has been applied all around
to prevent any gaps appearing in the combustion
chamber. Using rubber gloves or a plastic trowel,
smooth the silicone joints.
8. Remove the adhesive tape when the sealant has
sufficiently dried (approx. four hours).
9. Position gaskets (in the pack supplied) onto both
top flanges and fit the pipework to the water side.
Connect flanges with supplied nuts and bolts.
CAUTION
Do not put any tools or any other objects into the
combustion chamber.
IMPORTANT
Do not use solvents. Use only clean towels and/or rags.

Vitocrossal 300, CT3 Series Installation
5285 873 - 02
14
Boiler Connections
Water Side Connections
1. The existing heating system must be properly flushed,
especially if the Vitocrossal 300 boiler is connected
to an existing heating system in a retrofit application.
2. Connect the boiler to the system according the
diagram. The sizes of all connections are given
in the table on page 30. The Vitocrossal 300
boiler has two boiler return connections. If the
heating system to be connected to the Vitocrossal
300 has two separate heating loops or circuits,
the heating circuit or loop with the lower return
temperature should be connected to boiler return.
1. All connections which are not being utilized for
water connections or for controls must be properly
closed.
3. The supplied air vent and pressure relief valve must
be installed on the top of the boiler - the alternate
pressure relief valve location may be in the safety
supply. The piping to the precharged expansion tank,
as well as any automatic feed water required, must
be connected to the boiler drain opening or the safety
return connection.
4. The supplied low water cut-off should be installed
in the boiler return piping above the pressure vessel
or may be installed directly on top of the boiler.
Note: - Piping diagrams for specific system layouts
are available. Please enquire with your local
Viessmann sales representative.
Legend
A High temp. heating loop
B Low temp. heating loop
C Pressure relief valve (must be installed within first
12 in. (305 mm) of piping)
D Safety supply - alternate pressure relief valve location
and additional supply
EDrain valve
F Precharged expansion tank
G Automatic fill
H Low water cut-off (install low water cut-off in boiler
supply or boiler return with min. height at boiler
supply)
I Temperature gauge. Install temperature gauge
as close as possible to the boiler supply line.
Boiler return 1 Safety return boiler return 2
Vent pipe
Flue gas damper
Boiler
supply
Condensate
drain
Air vent and
pressure
gage

15
5285 873 - 02
Vitocrossal 300, CT3 Series Installation Boiler Connections
Hydrostatic Test Procedure
All Vitocrossal boilers are factory tested (hydrostatic
testing) to ASME requirements. The following testing
procedure is to ensure that the boiler remained intact
during shipping and handling.
1. Isolate boiler from hydronic heating system using
isolating valves (i.e. expansion tank, feed water valve,
pressure relief valve etc.).
2. Remove 30 psig pressure relief valve from the boiler
and cap pipe outlet.
3. Fill boiler with city water and pressurize it to one and
a half (1½) times the maximum working pressure of
boiler. The pressure must be controlled such that it
will never be 10 psig higher than the testing pressure.
Max. allowable working pressure = 30 psig
Testing pressure = 45 psig (do not exceed 55 psig)
4. Monitor pressure over a period of approximately one
(1) hour to ensure that the pressure remains constant
and steady at 45 psig.
5. Should there be a drop in pressure, ensure that
all fittings are secure and tight. Check all flanged
connections with a flashlight.
6. Remove the condensate collection inspection cover
and observe the condensate drum for system water
or fluid.
7. With a flashlight, observe and check the lower portion
of the Inox-Crossal® wafer heat exchanger sections
for system water or fluid.
8. Open the boiler combustion chamber door and inspect
with a flashlight the top portion of the Inox-Crossal®
wafer heat exchanger sections for system water
or fluid.
9. If test is successful, reinstall all hydronic system
components and refill the boiler with water or system
fluid.
Legend
A Boiler return 1 (BR1 - low temp.)
B Drain
C Boiler return 2 (BR2 - high temp.) / safety return
D Boiler temperature sensor/AHL/FHL
E Safety supply, alternative pressure relief valve location
and additional boiler supply
F ¾ in. coupling for additional control equipment
G Boiler supply
H Coupling for air vent / pressure gage
K Condensate drain
L Condensate inspection cover
M Flue gas damper
Vitocrossal 300, CT3-17 to -89
WARNING
Never expose the boiler to any pressures higher than
55 psig during testing.

Vitocrossal 300, CT3 Series Installation
5285 873 - 02
16
Boiler Piping in Heating/Cooling Application
Boiler Connections
The boiler, when used in connection with a refrigeration
system, must be installed so that the chilled medium
is piped in parallel to the boiler with appropriate valves
to prevent the chilled medium from entering the boiler.
The boiler piping system of a hot water heating boiler
connected to heating coils located in air handling units
where they may be exposed to refrigerated air circulation
must be equipped with flow control valves or other
automatic means to prevent gravity circulation of the
boiler water during the cooling cycle.
Check installation instructions of chiller manufacturer
carefully for additional requirements.
Cooling season starts:
Close valve V1 and open valve V2.
Heating season starts:
Close valve V2 and open valve V1.
A metal tag should be attached to these valves as
to purpose.
Legend
ASystem supply
BSystem return
CValve
DFlow-check valve
ECirculation pump
FAutomatic feed valve
GPre-charged expansion tank
IMPORTANT
In the above system, the circulating pump must be
operated from a separate on/off switch - not from the
boiler control.
Cooling unit
Heating/
Cooling unit
Heating/
Cooling unit
Heating/
Water
chiller

17
5285 873 - 02
Vitocrossal 300, CT3 Series Installation Boiler Connections
Initial System Fill
The pressure relief valve must be attached to the top
tapping on the boiler shell as per diagram on page 13,
or onto the safety supply of the boiler.
No valve, shut-off device, or obstruction of any kind
and construction must be used between boiler and relief
valve or on the discharge side of the pressure relief valve.
The discharge side of the pressure relief valve must be
continued in the same size as the outlet horizontally over
the side of the boiler, and then vertically downwards
to end approximately 1 ft. (300 mm) above the floor,
and piped as close to a floor drain as possible. Do not
install this discharge pipe to the outdoors or any area
where freezing might occur or the discharge pipe could
endanger life and equipment.
Secure the discharge piping from the pressure relief valve
with the appropriate hangers or brackets.
Treatment of boiler feed water should be considered
in areas of known problems, such as high mineral content
and hardness. In areas where freezing might occur,
an antifreeze may be added to the system water to
protect the system (maximum mix ratio - 50% / 50%).
Please adhere to the specifications given by the antifreeze
manufacturer. Do not use automotive glycol!
Please observe that an antifreeze/water mixture may
require a backflow preventer within the automatic water
feed and influence components such as diaphragm
expansion tanks, radiation etc. A 40% antifreeze content
will provide freeze-up protection to -31° F (-25° C).
Do not use antifreeze other than specifically made for
hot water systems. The heating system may also contain
components which may be negatively affected by
antifreeze.
Check entire system frequently when filled with
antifreeze. Read boiler service checklist for further
information on water quality.
The Vitocrossal 300 boiler is only suitable for closed hot
water heating systems with pumps.
It is strongly recommended to install boiler isolation
valves, and above these isolation valves, drain valves
in the system supply and return. This way, in case of
maintenance work on the boiler or the heating system,
it is not required to drain the entire system.
When the boiler is utilized to supply heat to an indirectly
heated domestic hot water tank as well, it is necessary
that the heating loops without a mixing valve are
equipped with flow check valves on the discharge side
of the pumps to avoid reverse flow.
IMPORTANT
All system pumps must be installed from boiler supply
to the system.
IMPORTANT
Ensure that there is no leak on any of the connections
which are covered by the insulation.
IMPORTANT
Cold water fill pressure must equal expansion tank
pressure.
CAUTION
Before the heating boiler is installed and piped into
an existing system, the heating system itself must
be properly flushed to remove dirt and system sludge.
Accumulations in old heating systems will tend to settle
in the boiler and can lead to deposits which can cause
hot spots, noise and water-side corrosion.
For damages resulting from those kinds of impurities,
the warranty will be null and void.
The boiler should be filled and properly bled of air,
and the cold water fill pressure should not exceed
18 - 20 psig. All openings, as well as pipe connections
on the boiler, should be observed for possible leaks. Once
all connections are tight, the insulation can be mounted.

Vitocrossal 300, CT3 Series Installation
5285 873 - 02
18
Condensate Connection
Boiler Connections
1. Locate the neutralization unit either behind or next
to the boiler.
2. Trim the plastic hose supplied to the required
dimension, and connect it as a P-trap (or with a
siphon) to the condensate drain and the neutralization
unit.
If the condensate outlet of the Vitocrossal 300 boiler
is lower than the drain, a condensate pump must be
installed. Select a pump which is approved for condensing
boiler applications. To avoid condensate spillage, select a
pump with an overflow switch. The drain connection must
terminate into an open or vented drain as close to the
boiler as possible to prevent siphoning of the boiler drain.
Note: The “amount of condensate” and the “flue gas
temperature gross” graphs are independent of each
other.
IMPORTANT
Pipe ventilation must take place between the siphon trap
and the neutralization unit (if applicable).
IMPORTANT
Always connect the drain with a P-trap or siphon to
prevent flue gas from escaping into the space.
3. Connect the neutralization unit to the dewatering
system.
The amount of condensate to be expected during the
operation of the boiler can be read from the diagram
on the left.
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

19
5285 873 - 02
Vitocrossal 300, CT3 Series Installation Boiler Connections/Assembly
Condensate Disposal
All condensate disposal piping from boiler and from vent
pipe system can be made from stainless steel, CPVC,
or the appropriate rubber hose material as long as there
is a P-trap installed in the disposal lines to avoid flue gas
spillage through the condensate lines.
The condensate occurring will show a reading of 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.
The condensate drain to the sewer connection must
be accessible to inspection.
Route it with a gradient and equip the pipe with a P-trap;
also provide suitable facilities for taking samples.
The bottom drain should be located below the anti-
flooding level of the flue gas collector box.
Condensate drains must only be made from corrosion
resistant materials (e.g. fiber reinforced hoses). Never
use any galvanized materials or those containing copper
or black iron for pipes, connectors, etc.
Install a P-trap in the condensate drain to prevent flue
gases from escaping.
Ensure that the domestic drainage systems are made from
materials which are resistant to acidic condensate, e.g.:
HStoneware pipes
HHard PVC pipes
HPVC pipes
HPE-HD pipes
HPP pipes
HABS/ASA pipes
HStainless steel pipes
HBorosilicate pipes

Vitocrossal 300, CT3 Series Installation
5285 873 - 02
20
Insulation Installation
Assembly
1. Remove combustion chamber door. Remove all
hexagon bolts and the two hinge pins.
2. Mount the three distance bolts to the threaded
openings provided on the top of the boiler shell.
3. Mount the three mounting brackets (long) complete
with bolts and washers to the boiler front.
4. Mount the three mounting brackets (short) complete
with bolts and washers to boiler rear.
5. Mount large rear insulation blanket (black nylon
backing facing out) on top of main vessel, sliding
it through the boiler supply header.
6. Insert four spacer bolts M8 x 105 into the threaded
holes in the front and back of the boiler.
7. Mount small front insulation blanket (black nylon
backing facing out) on top of front combustion
chamber.
Ensure that all pipe connections and distance bolts
are properly pushed through, and secure with supplied
spring hooks.
8. Mount lower front and lower rear insulation blankets
over the distance brackets and secure in place with
supplied spring hooks.
9. Install top rear and top front insulation blankets.
Ensure that all brackets and openings for the
attachment of bolts, brackets and pipe connections
are properly pushed through.
All necessary parts are packed and shipped inside the
insulation cartons.
The installation of the insulation should only be performed
once all the piping has been attached to the boiler shell
and all access openings are properly closed.
See following pages for installation steps.
CAUTION
Do not put any tools or any other objects into the
combustion chamber.