Viessmann VITODENS 200-W B2HA 150 Operating instructions

Please file in Service Binder
Service Instructions
5683 710 - 23 04/2018
for use by heating contractors
Vitodens 200-W, B2HA
Models 112, 150, 399, 530
Wall-mounted, gas-fired condensing boiler
Natural gas and LPG version
For operation with Natural Gas and Liquid Propane Gas
Heating input 113 to 530 MBH
33 to 150 kW
Read and save these instructions
for future reference.
Product may not be exactly as shown
VITODENS
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200-W
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IMPORTANT

Vitodens 200-W B2HA 112, 150, 399, 530 Service
5683 710 - 23
2
Safety
Safety, Installation and Warranty Requirements
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
0 equipment.
For a listing of chemicals which
cannot be stored in or near the
boiler room, please see subsection
entitled “Mechanical room” in the
“Installation Instructions”.
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 the “Installation Instructions”.
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 the “Installation
Instructions”.
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.
Operating and Service Documentation
It is recommended that all product documentation such as
parts lists, operating and service instructions be handed
over to the system user for storage. Documentation is to
be stored near boiler in a readily accessible location for
reference by service personnel.
WARNING
This boiler requires fresh air for safe operation and must
be installed with provisions for adequate combustion
and ventilation air (in accordance with local codes and
regulations of authorities having jurisdiction).
Do not operate this boiler in areas with contaminated
combustion air. High levels of contaminants such as
dust, lint or chemicals can be found at construction
sites, home renovations, in garages, workshops, in dry
cleaning/laundry facilities, near swimming pools and in
manufacturing facilities.
Contaminated combustion air will damage the boiler
and may lead to substantial property damage, severe
personal injury and/or loss of life. Ensure boiler/burner is
inspected and serviced by a qualified heating contractor
at least once a year in accordance with the Service
Instructions of the boiler.

Vitodens 200-W B2HA 112, 150, 399, 530 Service
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5683 710 - 23
Safety
Safety, Installation and Warranty Requirements
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.
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.

Vitodens 200-W B2HA 112, 150, 399, 530 Service
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Table of Contents
Safety, Installation and Warranty Instructions................2
About these Installation Instructions.............................6
Necessary Tools.........................................................6
Important Regulatory and Installation Requirements........7
For installations on the Commonwealth of
Massachusetts.......................................................8
CSD-1 Field Testing of High Limit Switches..................8
Applicability..............................................................9
Product Information....................................................9
Mechanical Room.....................................................10
Accessing the User Interface Programming Unit...........11
Select Language.......................................................11
Set Time and Date....................................................11
Removing Front Enclosure Panel.................................12
Fill Condensate Trap with Water.................................12
Fill Heating System with Water...................................13
Bleed (Vent) Air from Boiler Heat Exchanger................14
Check Power Supply Connection................................15
Designating Heating Circuits......................................15
Select Gas Type.......................................................15
Convert Fuel Type to Liquid Propane Gas.....................16
Setting High Altitude.................................................16
Measure Static Pressure and Running Pressure.............17
Pressure Switches.....................................................18
Sequence of Operation and Potential Faults
During Each Start-up Cycle........................................19
Set Maximum Input...................................................20
Check all Primary and Secondary Circuit
Connections for Leaks...............................................20
Perform Combustion Analysis.....................................20
Check Coaxial Venting System for Leaks.....................21
Remove Burner Assembly..........................................21
Checking the Flue Gas Flapper....................................22
Check Burner Refractory............................................22
Check and Adjust Ignition and Ionization Electrodes......23
Clean Combustion Chamber/Heat Exchanger Surface....23
Check Condensate Drain.........................................24
Check Neutralization Unit (if applicable)......................25
Check Diaphragm Expansion Tank and System Pressure...25
Check Functioning of Safety Valves............................26
Check Electrical Connections......................................26
Check Pipes and Fittings for Leaks..............................26
Clock Natural Gas Meter............................................27
Check CO2Setting....................................................28
Start-up and Shutdown..............................................29
Menu......................................................................29
Functional Description...............................................31
Combustion Management Systems.............................31
Installation Examples.................................................32
Heating Curve Adjustments........................................36
Connecting the Boiler Control to a LON System............38
Safety
General Information
Start-up and Service
Outdoor Reset Programming Unit
Page

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Table of Contents
Coding 1
Coding 2
Diagnosis and Service Scans
Troubleshooting
Function Description
Additional Information
General...................................................................40
Boiler......................................................................42
DHW.......................................................................42
Solar.......................................................................43
Heating Circuit 1, 2 and 3..........................................44
General...................................................................48
Boiler......................................................................55
DHW.......................................................................56
Solar.......................................................................58
Heating Circuit 1, 2 and 3..........................................62
Calling up the Service Level........................................68
Diagnosis.................................................................69
Checking Outputs (Relay Test)...................................71
Fault Display............................................................72
Fault Codes..............................................................72
Corrective Action......................................................80
Continuous boiler pump operation............................80
Checking the outside temperature sensor..................80
Check fuse...........................................................80
Check fuses in the external accessories
connection box......................................................80
Checking the boiler temperature sensor and
fixed high limit, DHW tank temperature sensor or
flow temperature sensor for the low loss header........81
Replacing the flow rate sensor.................................82
Extension kit for heating circuit with mixing valve......83
Changing the rotational direction of the
mixing valve motor (if required)................................83
Checking the Vitotronic 200-H (accessories)..............83
External Extensions AM1 (accessory)..........................84
Internal Extensions EA1.............................................85
Control Functions......................................................87
Wiring Diagram.........................................................90
Burner Program Sequence of Operation........................92
Parts List.................................................................93
Technical Data.........................................................98
Maintenance Record................................................100
Lighting and Operating Instructions............................101
Page

Vitodens 200-W B2HA 112, 150, 399, 530 Service
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General Information
About these Service 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.
Necessary Tools
Testing/analysis equipment (Use only calibrated equipment)
HMultimeter to measure 0 - 120V, 0 - 12A AC and
0-100 mA DC
HFlue gas analyzer to measure % CO2or O2(i.e.
Bacharach fluid samplers or suitable electronic analyzer)
HManometer to measure gas pressure 0 to 11 "w.c.
(accurately) and up to 28 "w.c. gas pressure (or a non-
electric Magnehelic® manometer may also be utilized)
HStack thermometer 0 to 500°F (0 to 260°C)
HBacharach calculator or suitable tables to calculate
efficiency
HCarbon monoxide measuring equipment 0 to 400 ppm
Cleaning supplies
HPlastic hand brush
HRags
Special items
HApproved leak detection fluid for natural gas and
liquid propane gas
HPipe joint sealant

Vitodens 200-W B2HA 112, 150, 399, 530 Service
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General Information
Important Regulatory and Installation Requirements
Codes
The installation of this unit shall be in accordance with
local codes or, 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
both the Standard for Controls and Safety Devices for
Automatically Fired Boilers, ANSI/ASME CSD-1, and
the Installation Code for Hydronic Heating Systems,
CSA B214-01, where required by the authority having
jurisdiction.
Instructing the system user
The installer of the system is responsible to ensure the
system operator/ultimate owner is made familiar with the
system functioning, its activation, and its shut-down.
Initial start-up
Initial start-up must be performed by a qualified heating
contractor. Proper completion of the Maintenance Record
by the heating contractor is also required.
Working on the equipment
The installation, adjustment, service, and maintenance
of this boiler must be done 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.
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 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.
The following topics must be covered:
Proper system operation sequence.
Explain the equipment.
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 in the Service
Instructions
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.
We offer frequent installation and service seminars to
familiarize our partners with our products. Please inquire.
Technical literature
Literature for the Vitodens boiler:
- Technical Data Manual
- Installation Instructions
- Service Instructions
- Operating Instructions and User’s Information Manual
- Instructions of other Viessmann products utilized and
installed
- Installation codes mentioned in this manual
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.
This product comes with several safety instruction labels
attached.
Do not remove!
Contact Viessmann immediately if replacement labels are
required.

Vitodens 200-W B2HA 112, 150, 399, 530 Service
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8
Important Regulatory and Installation Requirements (continued)
General Information
Flow Switch /Sensor Test:
The Vitodens 200 B2HA models 112 and 150 boilers are equipped with two flow sensing devices. Upon detection of an
inadequate flow rate, the switches will shut down the burner and will prevent restarting until an adequate flow rate is restored. To
test the sensors, throttle down the flow of water to or from the boiler. The boiler will shut down once the flow has dropped below
it’s safe operating set point.
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 inwhole or in
part for residential purposes, including those owned or operated by the Commonwealth and where the sidewall 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 gasfitter 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 (1/2) 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.
CSD-1 Field Testing of High Limit Switches for Vitodens boilers – where required by law.
As per ASME Boiler and Pressure Vessel Code, section IV, subsection HG-613 TEMPERATURE CONTROL requirements, Vitodens
200-W 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 Vitodens 200 boilers are equipped with flow switches or sensors that when activated enable the burner to operate.
The fixed high limit, when tripped, produces a fault that will require manual reset of the boiler control.
Fixed High Limit fault simulation #1:
- Ensure that the boiler and boiler pump are in normal operating condition (pump output sÖ is the boiler pump).
- Remove the cover from the back of the boiler control allowing access to the boiler control plugs.
- Under the extended menu (in the Operating manual), select ‘Test mode’ then ‘flue gas test ON’ and press ‘OK’.
- The boiler/burner will start a firing cycle and will gradually go into high fire mode.
- Once the burner ignites, disconnect the boiler pump plug sÖ from the boiler control board (gently with pliers).
Note: For boiler models equipped with flow switches (only boiler sizes 19 to 100), it may be required that flow switches be
jumpered during testing.
- Observe the boiler temperature on the control display.
- The temperature will gradually rise as more heat is put into the boiler heat exchanger. The burner will then shut off.
- The boiler temperature should continue to rise and once it reaches 210ºF (99ºC) the manual reset high limit safety switch
will trip electronically generating an F2 fault.
- Should the limit temperature not be reached during the test, repeat the test with the following additional step;
- two minutes after the burner shuts off, energize the boiler pump for a maximum of 1 second (by plugging in boiler pump plug sÖ).
Fixed High Limit fault simulation #2:
- Close the boiler valve and jumper across the flow switch.
- Run the boiler at high fire and it will shut down by the coding card (in B2TB models, set coding address 06 to maximum) but
should continue to steady increase the boiler temperature until the fixed high limit is tripped.
- Once the fixed high limit is tripped, slowly open the boiler valve to safely cool the boiler down.

Vitodens 200-W B2HA 112, 150, 399, 530 Service
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Applicability
General Information
Natural gas-fired wall-mounted condensing heating boiler
for weather-responsive operation in closed loop, forced
circulation hot water heating systems for space heating
and domestic hot water (DHW) production.
Models B2HA series boilers are for operation with natural
gas. For a fuel conversion to liquid propane gas (see page
16).
Boiler model must be selected based on an accurate heat
loss calculation of the building. Ensure boiler model is
compatible with connected radiation.
Vitodens 200-W, B2HA series boilers are factory-tested
and calibrated. Further gas valve adjustments are not
typically required during field start-up.
Product Information
CAUTION
The boiler serial number must be provided when
ordering replacement parts. Some replacement parts are
not reverse compatible with previous versions of the
Vitodens 200-W B2HA boiler.
When ordering replacement parts, provide either the
16-digit boiler serial number (on the bar code label) or
the 12-digit ASME/NB serial number, located as shown
underneath boiler front enclosure panel. Refer to page 12
for instructions on how to remove front enclosure panel.
Model No. B2HA 112, 399
Serial No. 7510835 jjjjjjjjj
Model No. B2HA 150, 530
Serial No. 7510836 jjjjjjjjj
IMPORTANT
AInox-Radial heat exchanger made from stainless steel
– for high operational reliability and a long service life.
Large heating output in the smallest of spaces
B Modulating MatriX cylinder burner for extremely
clean combustion and quiet operation
CVariable speed combustion fan for quiet and
economical operation
DGas and water connections
EDigital boiler control unit
Multi boiler system
In connection with the installation of a multi boiler system
observe the installation instructions of the multi boiler
system accessories.
Product may not be exactly as shown
Follow the Vitodens Venting System
Installation Instructions to vent this boiler.

Vitodens 200-W B2HA 112, 150, 399, 530 Service
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10
Mechanical Room
General Information
During the early stages of designing a new home, we recommend that proper consideration be given to constructing a
separate mechanical room dedicated to the gas- or oil-fired heating equipment and domestic hot water storage tank(s).
The boiler must be located in a heated indoor area, near a floor drain, and as close as possible to a wall. Whenever
possible, install the boiler near an outside wall so that it is easy to duct the venting system to the boiler.
Locate the boiler on a wall capable of supporting the weight of the boiler filled with water (see section entitled
“Technical Data” on page 98 for information required for total boiler weight calculation). Ensure that the boiler location
does not interfere with the proper circulation of combustion and ventilation air of other fuel burning equipment within
the mechanical room (if applicable).
The maximum room temperature of the mechanical room where the boiler is located must not exceed 104ºF (40ºC).
HEnsure ambient temperatures are higher than 32°F
(0°C) and lower than 104°F (40°C).
HPrevent the air from becoming contaminated by
halogenated hydrocarbons (e.g. as contained in paint
solvents or cleaning fluids) and excessive dust (e.g.
through grinding or polishing work). Combustion air
for the heating process, and ventilation of the boiler
room must be free of corrosive contaminants. To that
end, any boiler must be installed in an area that has no
chemical exposure. The list to the right indicates the
main, currently known sources.
HAvoid continuously high levels of humidity (e.g. through
frequent drying of laundry).
HNever close existing ventilation openings.
Sources of combustion and ventilation air contaminants
Areas likely to contain contaminants:
HNew building construction
HSwimming pools
HRemodelling areas, hobby rooms
HGarages with workshops
HFurniture refinishing areas
HDry cleaning/laundry areas and establishments
HAuto body shops
HRefrigeration repair shops
HMetal fabrication plants
HPlastic manufacturing plants
HPhoto processing plants
HBeauty salons
Products containing contaminants:
HChlorine-type bleaches, detergents and cleaning
solvents found in household laundry rooms
HPaint and varnish removers
HHydrochloric acid, muriatic acid
HChlorine-based swimming pool chemicals
HSpray cans containing chlorofluorocarbons
HChlorinated waxes and cleaners
HCements and glues
HRefrigerant leaks
HCalcium chloride used for thawing
HSodium chloride used for water softening salt
HPermanent wave solutions
HAdhesives used to fasten building products and other
similar items
HAntistatic fabric softeners used in clothes dryers
Boiler operation in marine environments (damp, salty
coastal areas)
WARNING
If you notice fire coming from the appliance, call the fire
department immediately! Do not attempt to extinguish
the fire unless qualified to do so.
WARNING
Fire causes a risk of burns and explosion!
HShut down the boiler
HClose fuel shut-off valves
HUse a tested fire extinguisher, class ABC.
IMPORTANT
The service life of the boiler’s exposed metallic surfaces,
such as the casing and fan housing, is directly influenced
by proximity to damp and salty marine environments. In
such areas, higher concentration levels of chlorides from
sea spray, coupled with relative humidity, can lead to
degradation of the exposed metallic surfaces mentioned
above. Therefore, it is imperative that boilers installed
in such environments not be installed using direct vent
systems which draw outdoor air for combustion. Such
boilers must be installed using room air dependent vent
systems; i.e. using room air for combustion. The indoor
air will have a much lower relative humidity and, hence,
potential corrosion will be minimized.
Installation area conditions
WARNING
Incorrect ambient conditions can lead to damage to the
heating system and put safe operation at risk.