Froling FHG Operation manual

Froling GmbH, Industriestraße 12, 4710 Grieskirchen, AUSTRIA
www.froling.com
A French language manual may be
obtained from Tarm Biomass by
calling 800-782-9927 or by email
request to: in[email protected].
Operation and Service Manual
Wood-Fired Central Heating Boiler
FHG
Read and follow the operating instructions and safety information! Subject to technical change!

Update Date: May 2014
Reprint date: Nov 2014

Introduction
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Dear customer!
Congratulations on choosing a quality product from FROLING.
The Froling FHG Boiler features a state-of-the-art design.
Please read and observe the operating instructions and always keep
them close to the boiler for reference. They contain safety information
and all the operation and maintenance specifications needed to operate
the boiler safely, properly and economically.
The constant further development of our products means that there may
be minor differences from the pictures and content. If you discover any
errors, please let us know.
Subject to technical change.
The FHG boiler is produced using the highest quality materials and a
modern production system. The use of high technology laser cutting and
robotic welding system, accompanied by time honored European design,
craftsmanship and attention to detail, results in a long lasting boiler with
unmatched fit and finish.
With proper installation, operation and maintenance your FHG log wood
boiler will provide years of safe, dependable, economic and earth friend-
ly heating.
This manual contains paragraphs that require your special attention.
These paragraphs are marked with the safety information according to
ANSI Z535 described in chapter 2.
Units of Measurement
Most hardware and fittings on the boiler are metric (some plumbing fit-
tings are British Straight Thread). In this manual the convention used
for dimensions is that values are presented in English units, followed by
metric units in parenthesis, for example: 6” (152 mm).
In this manual temperatures are presented as degrees Centigrade.
Note: A conversion table between Centigrade and Fahrenheit is provided
in chapter 4.3 Setting parameters.
Installation and Warranty Requirements
This product is provided with a limited warranty which is described in
chapter 7.1 Warranty conditions within this manual. The warranty is
contingent upon the successful and legal installation of the boiler. At a
minimum, the installation, adjustment, start up, service, and mainte-
nance of this product must be performed by a licensed professional
heating system installer. Where applicable, the installation must be in-
spected and accepted by the legally responsible entity. Conditions de-
scribed in the text of the warranty for keeping it in force must be fol-
lowed by the owner/ system operator.
If the boiler has been purchased through a dealer, the warranty claim
must be made to the dealer. Otherwise, claims may be made directly to
Tarm Biomass.
Please read the literature enclosed by the manufacturer regarding the
various accessory devices. These devices are warranted by the manufac-
turer, NOT BY Tarm Biomass. These accessory devices must be installed
and used according to the recommendations of the manufacturer.

Introduction
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Failure to follow these instructions could result in property damage, bod-
ily injury, or death. All boilers must be installed in accordance with na-
tional, state, and local plumbing, heating, and electrical codes and the
regulations of the serving electric, water, and gas utilities. Contact local
building or fire officials before installation about restrictions and installa-
tion inspection requirements in your area. This boiler is safety tested
and listed. The FHG boiler does not carry an ASME stamp.
The instructions in this manual and in supporting documentation (addi-
tional instructions, diagrams, and component information provided by
Tarm Biomass) must be followed. If the instructions are in conflict with
local code requirements, the local code requirements will prevail. When
in doubt, contact your dealer or Tarm Biomass. The manual and sup-
porting documentation must be retained by the owner/ system operator
for reference and future use.
The installer is responsible for familiarizing the owner/ system operator
with all aspects of boiler operations, safety procedures, monitoring and
cleaning requirements, shut down procedures, and annual maintenance
requirements.

Contents
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1 Product overview 8
1.1 Boiler Fabrication and Testing 10
1.2 Models and Applications 10
2 Safety 11
2.1 Safety information 12
2.1.1 Installation Hazards.......................................................................................... 13
2.1.2 Operation Hazards............................................................................................ 14
2.2 Permitted Uses 16
2.2.1 Permitted fuel .................................................................................................. 16
2.2.2 Non-permitted fuels.......................................................................................... 17
2.2.3 Who may operate the boiler .............................................................................. 17
2.3 Design information 18
2.3.1 Approvals and reporting obligations.................................................................... 18
2.3.2 Requirements for initial filling and re-filling of heating system................................ 18
2.3.3 Ventilation of boiler room .................................................................................. 19
2.3.4 Installing the heating system............................................................................. 19
Minimum Return water temperature .................................................................. 19
Combination with Thermal Storage System ........................................................ 19
2.4 Safety devices 20
2.4.1 Devices for Preventing the Boiler from overheating .............................................. 20
Pressure Relief Valve ....................................................................................... 20
Overheat Thermostat (Safety Temperature Limit Switch –STL) ............................ 21
Gravity Over-heat Dump Loop .......................................................................... 21
Overheat loop: with electricity .......................................................................... 21
2.5 Emergency procedure 21
2.5.1 In the event of loss of electrical power................................................................ 21
2.5.2 Overheating of the system ................................................................................ 22
2.5.3 In the event of runaway fire .............................................................................. 22
2.5.4 Strong Smell of flue gas.................................................................................... 22
3 Operating the system 23
3.1 General information 23
3.1.1 Preparing fire wood .......................................................................................... 23
3.1.2 Main Switch at Boiler Control System.................................................................. 23
3.1.3 Error status of Boiler Control System .................................................................. 23
3.1.4 Operation status of Boiler Control System ........................................................... 24
3.1.5 Starting the boiler for the first time .................................................................... 24
3.1.6 Ignition........................................................................................................... 25
3.2 When do you need to heat up or refuel your boiler 26
3.2.1 Inspect the burning flame ................................................................................. 26
3.3 Heat up the boiler 27
3.3.1 Prepare for Fueling ........................................................................................... 27
3.3.2 Fueling the boiler ............................................................................................. 28
3.3.3 Ignition........................................................................................................... 28

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3.4 Refueling the boiler 30
3.4.1 Prepare for Fueling............................................................................................30
3.4.2 Fueling the boiler ..............................................................................................30
4 Boiler Control System Lambdatronic S 3200 31
4.1 Overview of the Basic Functions 31
4.1.1 Control keys and Display....................................................................................31
Navigation Keys...............................................................................................31
Status LED ......................................................................................................32
Function Keys..................................................................................................32
Info Key .........................................................................................................32
4.1.2 Graphical Display ..............................................................................................34
Thermal Storage System loading status ..............................................................34
4.1.3 Operating modes ..............................................................................................35
4.2 Initial start-up 36
4.2.1 Changing the User Level ....................................................................................36
4.3 Setting parameters 37
4.4 Menu Overview 38
4.5 Menu - Storage tank 38
4.5.1 Status display of the Thermal Storage System ......................................................38
4.5.2 Temperature settings for Thermal Storage System ................................................39
4.6 Menu - Boiler 39
4.6.1 Status Displays for the Boiler..............................................................................39
4.6.2 Temperature settings for the Boiler .....................................................................39
4.7 Menu - System 40
4.7.1 Current values ..................................................................................................40
4.7.2 Error ...............................................................................................................40
4.7.3 Basic Display parameters ...................................................................................40
4.7.4 Time settings....................................................................................................41
4.7.5 Current User Level ............................................................................................41
5 Boiler Maintenance 42
5.1 General 42
5.2 Inspection, cleaning and maintenance 43
5.2.1 Daily Maintenance / Before every firing................................................................43
Cleaning of Heat Exchanger pipes ......................................................................43
5.2.2 Weekly Maintenance..........................................................................................43
Removing the ash ............................................................................................43
Cleaning the flue channels both sides of the Combustion Chamber .........................44
5.2.3 Monthly Maintenance.........................................................................................44
Cleaning the grate ...........................................................................................44
5.2.4 Annual Maintenance ..........................................................................................44
Cleaning flue gas pipe and flue gas sensor ..........................................................44
Checking the primary air openings .....................................................................45
Cleaning the Smoke Extraction Duct...................................................................45
Checking the tightness of door gaskets ...............................................................45
Checking the Draft Regulator and blowback flap ..................................................45

Contents
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6 Troubleshooting 46
6.1 General faults in power supply 46
6.2 Excessive temperature 46
6.3 Error messages at Boiler Control System 47
6.3.1 Acknowledging a error message ......................................................................... 48
6.3.2 List of possible error message............................................................................ 48
6.4 Misoperation of Door Switch 50
7 Appendix 51
7.1 Warranty Fröling FHG Wood Boiler 51
7.2 Temperature conversion table 53
7.3 Manufacturer 54
7.4 Importer 54
7.5 Local Dealer 54

Product overview
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1Product overview
Pos.
Component
1
FHG Wood-Fired Central Heating Boiler
2
Boiler Control System Lambdatronic S3200
3
Ash-Pit Cover
4
Lever for Heat Exchanger Cleaning System
5
Main Switch (Located on side box)
6
Overheat Thermostat (Safety Temperature Limit Switch - STL)
7
Control Panel of Boiler Control System Lambdatronic S 3200
7.1
Large graphical display to show operating modes, states of components and parameters
7.2
Status LED (operating status): - green light flashing slowly: boiler activated
- green light flashing quickly: boiler deactivated
- red light flashing: error
Navigation keys for navigation within the menus and to set parameter values:
7.3
UP arrow
7.4
DOWN arrow
7.5
Enter key
7.6
Back key
7.7
Function keys for selection of individual boiler functions or heating modes directly
1
2
7
4
3
5
6
7.1
7.2
7.6
7.5
7.4
7.3
7.7

Product overview
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Pos.
Component
8
Insulation Door
9
Fuel Loading Chamber Door
10
Ignition Door
11
Combustion Chamber Door
12
Ash-Pit Door
13
Heat Exchanger Insulation Cover
14
Heat Exchanger Cover
15
Fuel Loading Chamber
16
Combustion Chamber
17
Flame Slot
18
Smoke Extraction Duct
19
Primary Air Damper Actuator
20
Secondary Air Damper Actuator
21
Heat Exchanger
22
Induced Draft Fan (ID Fan)
23
Flue Gas Connector
24
Lambda Probe
25
Boiler Sensor and Sensor of Overheat Thermostat (position 6)
26
Overheat aquastat well
8
9
10
11
15
16
17
12
14
13
20
19
21
22
23
24
25
18
26

Product overview
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1.1 Boiler Fabrication and Testing
Your boiler was manufactured by Froling, a world leader in hot water
(hydronic) heating for over 40 years. The FHG Series boiler conforms to
traditional high standards for quality and reliability. It offers modern
wood gasification technology with high operating efficiencies at over
90%. If treated properly and operated according to the guidelines in this
manual it will provide years of safe, dependable, and economical heat-
ing.
FHG boilers are designed and built in accordance with European Stand-
ard EN 303-5. Safety and performance testing and listing for North
American markets have been performed by OMNI Test Laboratories,
Inc., Portland, Oregon. The boiler is tested and listed to applicable UL,
CAN and other standards. The boiler is not ASME stamped. The installer
should follow local or state installation requirements.
The FHG wood gasification boiler is a log wood fired boiler designed and
constructed for highly efficient combustion of log wood.
Do not burn other fuels in the FHG boiler. The FHG is not a self con-
tained weather-tight boiler. It should be installed within the heated
building. FHG log wood boilers must be installed with a thermal storage
system capable of absorbing the complete output of the boiler during
periods when the building is not calling for heat.
1.2 Models and Applications
Four FHG models are available (20, 30, 40 and 50) covering an output
range between 68,000Btu/hr and 170,000Btu/hr. Specification data for
each FHG is provided in the Installation Manual.
The boilers can be utilized as a single heat source, or in parallel with an-
other boiler.

Safety
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2Safety
This manual contains paragraphs that require your special attention.
These paragraphs are marked with the symbols described below:
This is the safety alert symbol. It is used to alert you to potential per-
sonal injury hazards. Obey all safety messages that follow this symbol to
avoid possible injury or death.
DANGER indicates a hazardous situation which, if not avoided, will
result in death or serious injury.
WARNING indicates a hazardous situation which, if not avoided, could
result in death or serious injury.
CAUTION, used with the safety alert symbol, indicates a hazardous
situation which, if not avoided, could result in minor or moderate injury.
NOTICE is used to address practices not related to personal injury.

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2.1 Safety information
Inappropriate use will cause faulty operation of the boiler. The
instructions and information provided in this manual shall be ob-
served.
Detailed information is given in individual instructions for
operation, maintenance and cleaning, as well as troubleshooting. Any
further work shall be carried out by authorized dealer.
Faulty operation conditions (e.g. insufficient combustion air,
non-permitted fuels) will cause serious faults in combustion
(e.g. spontaneous combustion of carbonization gases or
flash fires)!
Instructions and guidelines for system configuration and
minimum operation data values, as well as regulations, standards and
codes for safe and lawful operation together with other
heating components as given in the manuals must be observed!
Inadequate design, installation and maintenance of the flue gas
system will cause insufficient chimney draft and serious faults in
combustion (e.g. spontaneous combustion of wood gases or
flash fires)!
Keep flue system tight and cleaned according to the owner's manual

Safety
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2.1.1 Installation Hazards
Install, modify and use only in accordance with manufacturer’s manuals.
Refer to authorities having jurisdiction for proper installation. Contact
local building and fire officials about restrictions and installation inspec-
tion in your area. If there are no applicable local codes, follow
ANSI/NFPA 211 and CAN/CSA B365. Special precautions are required
for passing the Chimney through a combustible wall or ceiling.
Inspect and clean exhaust system, Fuel Loading Chamber, Combustion
Chamber, Ash-Pits, and Heat Exchanger frequently in accordance with
owner’s manual.
DANGER!
Working on electrical components may cause severe injuries from electric
shocks!
WARNING!
The electrical system of the boiler shall be supplied from a double 115 V 60
Hz (nominal 230 V AC) 15 amp branch circuit including neutral and ground
connection. For wiring instructions please refer to Installation Manual!
Chimney must be 6’’ (150 mm) diameter listed UL-103 HT or ULC-S629
residential all-fuel type or tile-lined masonry. Flue connector pipe must be
6’’ (150 mm) diameter made of a minimum 24 MSG black steel.
Inadequate design, installation and maintenance of the flue gas system will
lead to insufficient chimney draft and could result in Danger of Life or Se-
vere Injury caused by serious faults in combustion, e.g. explosively com-
bustion of wood gases and flash fires!
This boiler requires fresh air for safe operation and must be installed so
there are provision for adequate combustion and ventilation air!
CAUTION!
Do not connect this unit to a Chimney flue serving another appliance!
Flooring must be a minimum 3/8’’ (10 mm) non-combustible material cov-
ering the installation clearance area! The floor must be level and reinforced
if required. For construction of the floor beneath the boiler please pay at-
tention to weight of boiler, water content and wood fuel according to the
Installation Manual!
This boiler is not for use with an automatic stoker
Connect to an existing boiler system in combination with heat storage only!
Use original spare parts only. Installation of non-licensed replacement parts
will void the warranty!

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2.1.2 Operation Hazards
NOTICE!
Burn Wood only, max. length 20'' (50cm)!
Load fuel carefully or damage will result!
Build the wood fire directly on the boiler Fuel Loading Chamber refractory
floor!
Do not use small pieces or wood waste that could fall through the Flame Slot
in the refractory.
DANGER!
Risk of Fire or Explosion!
Do not burn coal, fuel coke, garbage and other residual material, painted or
treated wood, gasoline, diesel, fuel oil, naphtha, engine oil, drain oil or
other flammable liquids or any other organic materials or other inappropri-
ate materials!
Do not use chemicals, gasoline, oil or any other combustible fluids to start
the fire!
Use of inappropriate fuels can result in Danger of Life or Severe Injury
caused by explosive combustion and flash fires!
Burn fuels other than those designated in the manual will void warranty
DANGER!
Explosive Gases!
Never open Combustion Chamber Door, Ash-Pit Door, Ash-Pit Cover or
Heat Exchanger Cover during operation or refueling!
Faulty operation of boiler system will cause Danger of Life or Severe Injury
and Property damage!
Flue gases can cause fatal poisoning! In case of strong smell of flue gas:
1. For safety keep all Boiler Doors and Ash-Pit Doors tightly closed!
2. Ventilate the room where boiler is installed!
3. Close the door of the boiler room and doors to living areas!

Safety
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WARNING!
Risk of Fire!
For safety keep all Boiler Doors and Ash-Pit Doors and all Covers tightly
closed during operation!
Do not operate with flue draft exceeding 0.10 inches in water column (25
Pa), if no Draft Regulator is installed!
Do not store fuel, clothing, furniture or other combustible material within
marked installation clearances within boiler is installed!
Faulty operating conditions not complying with Owner’s Manual, such as
insufficient combustion air, incorrect or insufficient cleaning and mainte-
nance or non-permitted fuel could result in Danger of Life or Severe Injury
caused by serious faults in combustion (e.g. spontaneous combustion of
wood gases or flash fires)!
Inspect and clean Boiler, Flue Gas Pipe and Chimney regularly!
The Heat Exchanger, Induced Draft Fan, Flue Gas Pipe, and Chimney must
be cleaned regularly to remove accumulated creosote and ash. Ensure that
the Heat Exchanger, Flue Gas Pipe, and Chimney are cleaned at the end of
heating season to minimize corrosion during the summer months.
First firing during start-up of boiler system shall be carried out in accord-
ance to Instruction Label at Fuel Loading Chamber Door and in attendance
of an authorized installer or manufacturer’s representative only! Disregard-
ing of warning may cause damage or explosion of Combustion Chamber
and severe injuries unfavorably!
Gas created during solid-fuel combustion may cause a small flash when the
boiler is refueled if not properly vented!
CAUTION!
Hot Surfaces!
Hot parts and the Flue Gas Pipe can cause serious burns!
Unauthorized access to the boiler room could result in personal injury and
damage to property!
Keep children away!
Always use protective gloves while loading boiler or carry out other work on
boiler!
Always use Control Handles when opening Boiler Doors!
Do not touch Flue Gas Pipe during operation!
Do not carry out maintenance when the boiler is hot!
Do not touch hot surfaces behind Insulation Door!

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2.2 Permitted Uses
The boiler should only be operated when it is in full working order. It
should be operated in accordance with the instructions, observing safety
precautions, and you should ensure you are aware of the potential haz-
ards. Ensure that any faults, which might impair safety, are rectified
immediately.
The FHG is intended exclusively for heating up hydronic heating
systems or hydro-air systems. Use only the fuels specified below.
The manufacturer or supplier is not liable for any property dam-
ages resulting from non-permitted uses.
2.2.1 Permitted fuel
Burn Wood only, max. length 20’’ (50 cm)
Chemically treated or painted wood is unsuitable as fuel. The FHG boiler
is designed for burning of cord wood only. Wood briquettes or manufac-
tured pure wood logs can also be used as fuel provided they have a min-
imum cross section of 2.5 sq in (16 cm²). Manufactured logs should be
at least 12” (0.25 m) in length. The Fuel Loading Chamber can be filled
to the top. Excessively small and compact pieces of wood or wood pel-
lets are not suitable. Coal cannot be used as it destroys the combustion
chamber!
The FHG is made to burn natural forest wood. Both hardwood and soft-
wood are suitable, but oak should not be burned as the only source of
wood for long periods because of its high acid content.
For effective gasification, the wood must be dry, i.e. moisture content
15-25%. In addition to increasing the likelihood of generating creosote
in the boiler, burning wet wood uses a substantial amount of the wood
energy to evaporate the water present in the wood, reducing the availa-
ble energy for heat (Fig 2.2).

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The wood will dry out most quickly if it is cut into the appropriate length
and split into pieces 4”-5” (10-12cm) thick. The best length is 20” (0.5
m) for the FHG. The wood is best stored in the open air under cover.
Wood will dry most quickly if it is carefully stacked alternatively length-
wise and crosswise so that air can penetrate into the stack. Ideally the
wood should be stored for at least one and a half years (two summer
seasons). Do not burn small pieces of wood or wood chips in the boiler
as they can block the combustion slot. Also, it can be difficult to control
the combustion process effectively with small wood pieces and chips.
2.2.2 Non-permitted fuels
Using non-permitted fuels will cause serious faults in combustion
(e.g. spontaneous combustion of wood gases or flash fires).
Do not burn: coal, fuel coke, garbage or other residual material, gas-
oline, diesel, fuel oil, naphtha, engine oil or other organic materials
and any other inappropriate materials!
Do not use chemicals or fluids to start the fire!
2.2.3 Who may operate the boiler
Non-permitted use of the boiler by unauthorized persons can cause
faults in combustion. The operator is responsible to explain all cautions
before allowing any person’s access to boiler room.
Unauthorized persons, especially children, are to be kept away from the
boiler.
Only trained operators are permitted to operate the boiler!
Successful operation of this boiler will require daily involvement by the
owner/system operator.
Biomass boilers operate differently from fossil fuel boilers, requiring
more oversight and a diligent cleaning regimen.
• The owner/system operator is responsible for correct operation of the
boiler per guidelines in this manual.
• Incorrect operation can reduce the boiler life.
Throughout this manual, safety considerations are noted and discussed.
A few general safety considerations to be considered are:
• Safety faults or deficiencies with the boiler or installation must be rec-
tified as quickly as possible. Either by the owner/system operator or the
installer.
• Outlet pipes, ventilation channels, fresh air openings, etc. must not be
closed or blocked.

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2.3 Design information
It is unlawful to carry out modifications to the boiler or to change or
deactivate safety equipment.
In addition to the operating instructions and the applicable national and
local codes and regulations for installation and operation of the boiler
system, all fire, police, and electrical regulations must be observed.
2.3.1 Approvals and reporting obligations
IMPORTANT: Install, modify and use only in accordance with manu-
facturer’s installation & operation manuals. Refer to authorities hav-
ing jurisdiction for proper installation. Contact local building and fire
officials about restrictions and installation inspection in your area. If
there are no applicable local codes, follow ANSI/NFPA 211 and
CAN/CSA B365. Special precautions are required for passing the
Chimney through a combustible wall or ceiling.
Inspect and clean exhaust system frequently in accordance with
Owner’s Manual.
2.3.2 Requirements for initial filling and re-filling of heating system
Water quality conditions for initial filling the heating system:
For first filling of heating system water must be clean, pure or purified,
odorless and without suspended matter.
For re-filling of small amounts water shall be clean at least.
For swimming pools or spas do not use heating water directly. Proper
sized heat exchangers are required! Boiler water is not potable!
Use of a suitable antifreeze mix is allowed, but will cause a loss in heat
transfer efficiency.

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2.3.3 Ventilation of boiler room
During the installation of your boiler provision was made by the installer
to provide a source of combustion air for the boiler. Maintaining this
combustion air source is critical for proper operation of your boiler, do
not close off, block or otherwise obstruct the combustion air source for
your boiler. If you have questions regarding the combustion air source
please contact your installer.
In addition to local codes and regulations a minimum cross section of
combustion air and exhaust air shall be 28 sq.in. (180 cm²) each. Mind
open cross section if gratings or fins are used!
IMPORTANT for Canada: In accordance to ANSI/NFPA outside air
requirements of 1 sq. inch per 1,000Btu/hr.
2.3.4 Installing the heating system
The entire heating system has to be designed according relevant nation-
al and local codes. The nominal power of the Central Heating Boiler shall
be corresponding to the calculated heat demand for all heating applianc-
es connected to the heating system both in summer and winter time.
The heating system must be able to carry all heat produced by the Cen-
tral Heating Boiler and additional heat source, if applicable. The whole
heating system as well as all heating zones has to be hydraulically bal-
anced.
Special arrangements have to be provided for initial filling or re-filling
and bleeding of all heating zones. Flow-check valves and zone-valves
have to be installed for proper adjustment of water flow rates. All piping
must be water and air tight and insulated safely.
If there is a risk of freezing for parts of the heating system all water
within these heating zones has to be frost-proof!
Minimum Return water temperature
If the return water temperature is below the minimum, a part of the
heated water output flow shall be mixed in.
Installing the boiler without a proper valve or loading unit providing a
minimum return water temperature (e.g. Termovar loading valve) can
cause condensation water and fuel residue to combine to form an ag-
gressive condensate, leading to damage to the boiler!
Minimum return water temperature is 142°F (61°C)
Combination with Thermal Storage System
Your FHG boiler has been installed with a Thermal Storage System, this
system may require periodic maintenance. Please review the periodic
maintenance requirements of your thermal storage system with your in-
staller.

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2.4 Safety devices
5
Main switch
For shutting down the entire system
All components are switched off and
powered down
6
Overheat Thermostat
(Safety Temperature
Limit Switch –STL)
See below
2.4.1 Devices for Preventing the Boiler from overheating
The FHG comes with safety systems to prevent the
following:
• Pressure in the boiler exceeding 30 psi (over pressure)
• Boiler water temperature exceeding 212ºF (100º C)
Pressure Relief Valve
Protection against over-heating/ excessive pressure:
When the system pressure reaches a maximum of 30 psi (2 bar), the
Pressure Relief Valve opens and the heating water is released in the form
of steam.
5
6