Fondital NIAS series Quick start guide

NIAS
INSTALLATION, USE AND
MAINTENANCE
GB
IST 03 C 167 - 01

2
Thank you for choosing our boiler. Please read these installation and maintenance instructions with
care.
Please note that the boiler must only be installed, repaired and serviced by qualified personnel.

3
General information for fitters, maintenance technicians and users
This INSTRUCTION MANUAL,
which is an integral and
indispensable part of the
product, must be handed over
to the user by the installer and
must be kept in a safe place for
future reference. The manual
must accompany the boiler
should it be sold or its
possession transferred.
This boiler must be used for
the purposes for which it has
been intended. Any other use
shall be considered incorrect
and therefore dangerous.
The boiler must be installed in
compliance with applicable laws
and standards and according to
the manufacturer’s instructions
given in this manual. Incorrect
installation may cause injury to
persons and/or animals and
damage to property. The
manufacturer shall not be held
liable for any such injury and/or
damage.
Damage and/or injury caused
by incorrect installation or use
and/or damage and/or injury
due to non-observance of the
manufacturer’s instructions
shall relieve FONDITAL from
any and all contractual and
extra-contractual liability.
Before installing the boiler,
check that the technical data
correspond to the requirements
for its correct use in the system.
Check that the boiler is intact
and it has not been damaged
during transport and handling.
Do not install equipment which
is damaged and/or faulty.
Do not obstruct the air suction
and/or heat dissipation
openings.
Only FONDITAL-approved
accessories or optional kits
must be installed.
Properly dispose of the
packaging as all the materials
can be recycled. The packaging
must therefore be sent to
specific waste management
sites.
Keep the packaging out of the
reach of children as it may
represent a choking and
suffocation hazard.
In the event of failure and/or
faulty functioning, switch off the
boiler. Do not attempt to make
repairs: contact qualified
technicians.
FONDITAL approved parts
must be used for all repairs to
the boiler.
Non-observance of the above
requirements may jeopardize
the safety of the boilers and
expose people, animals and
property to danger.
To guarantee efficiency and
correct functioning of the
equipment it is legally
binding to service the boilers
once a year according to the
schedule indicated in the
relative section of this
manual.
In the event of long periods of
inactivity of the boiler,
disconnect it from the power
mains and close the gas tap
(Warning!
In this case the boiler’s
electronic anti-freeze function
will not be operative).
Should there be a risk of
freezing, add antifreeze: it is not
advisable to empty the system
as this may result in damage;
use specific anti-freeze
products suitable for multimetal
heating systems.
IMPORTANT
If you smell gas:
- do not turn on or off electrical
switches and do not turn on
electrical appliances;
- do not ignite flames and do
not smoke;
- close the main gas tap;
- open doors and windows;
- contact a Service Centre, a
qualified installer or the gas
supply company.
Never use flames to detect
gas leaks.
WARNING
This boiler has been built for
installation in the country
indicated on the technical data
plate: installation in any other
country may be a source of
danger for people, animals
and property.

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Contents
Warning ............page 2
General information for fitters, maintenance technicians and users ............page 3
1 Instruction for the user ............page 5
1.1 Control panel ............page 5
1.2 Operating the boiler ............page 6
1.2.1 Switching on ............page 6
1.2.2 Boiler shutdown ............page 6
1.3 Maintenance ............page 6
1.4 Information for the user ............page 6
2 Technical characteristics and dimensions ............page 8
2.1 Technical characteristics ............page 8
2.2 Dimensions ............page 9
2.3 Hydraulic connections ............page 9
2.4 Technical data ............page 10
2.5 General specifications ............page 11
3 Instructions for the fitter ............page 13
3.1 Installation regulations ............page 13
3.2 Installation ............page 13
3.2.1 Packaging ............page 13
3.2.2 Choosing where to install the boiler ............page 13
3.2.3 Positioning the boiler ............page 13
3.2.4 Installing the boiler ............page 14
3.2.5 Boiler room ventilation ............page 15
3.2.6 Flue system ............page 15
3.2.7 Flue system configuration ............page 17
3.2.8 Flue system with coaxial pipes 100/60 mm diameter ............page 18
3.2.9 Flue system with split pipes 80 mm diameter ............page 19
3.2.10 Measuring combustion efficiency ............page 21
3.2.11 Connection to the gas mains ............page 22
3.2.12 Connection to the power mains ............page 22
3.2.13 Hydraulic connection ............page 22
3.3 Filling the system ............page 23
3.4 Starting the boiler ............page 24
3.4.1 Preliminary checks ............page 24
3.4.2 Switching on/off ............page 24
3.5 Wiring diagram ............page 25
3.5.1 Connection diagram ............page 25
3.6 Switching to different gas ............page 27
3.7 Burner adjustment ............page 28
3.8 Adjusting boiler output to the system ............page 29
4 Testing the boiler ............page 30
4.1 Preliminary checks ............page 30
4.2 Turning the boiler on or off ............page 30
5 Maintenance ............page 30

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1 Instruction for the user
1.1 Control panel
A = Summer/OFF/Winter/Anti-
freeze selector
B = Power light
C = CH temperature regulator
D = DHW temperature regulator
E = Shutdown light
F = Reset button
G = Water pressure gauge
H = Thermometer
Summer/OFF/Winter/Anti-
freeze selector (A)
This selector allows choosing
the boiler mode.
When the selector is on the
Summer position, the boiler is
ready to work only for DHW
production.
When the selector is on the
OFF position, the boiler is
switched off.
When the selector is on the
Winter position, the boiler is
ready to work both for heating
and for DHW production.
When the selector is on the
Anti-freeze position, the boiler
is switched off but the function
protecting the heating system
and the water storage tank from
freezing is active.
Power light (B)
The light indicates that power is
being supplied to the boiler.
Central Heating temperature
regulator (C)
The knob sets the heating
system water temperature from
a minimum value of 35°C to a
maximum of 85°C.
Domestic Hot Water
temperature control (D)
The knob sets the temperature
of DHW stored in the tank, from
a minimum value of 40°C to a
maximum of 60°C.
Shutdown light (E)
The light indicates that the
burner shutdown function has
been activated due to a
malfunction.
Reset button (F)
Use this button to reactivate the
boiler after the burner shutdown
function has been activated.
Water pressure gauge (G)
The gauge shows pressure of
the heating system water; the
value of such pressure must not
be less than 0.8/1 bar (while the
boiler is cold).
Thermometer (H)
The thermometer shows
temperature of the heating
system water set by means of
the appropriate regulator.
pic. 1

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1.2 Operating the boiler
1.2.1 Switching on
* open the gas tap;
* set the power mains switch to
ON;
* set the desired boiler
operating mode through switch
A Summer/OFF/Winter/Anti-
freeze; power light Bcomes on.
Sselecting the Summer mode
the boiler supplies DHW only;
selecting the Winter mode the
boiler supplies both central
heating and DHW; with the
Anti-freeze mode central
heating and DHW functions are
not active and the boilers is
protected against freezing;
* set the temperature value
desired for the central heating
through the CH regulator C;
* set DHW temperature through
knob D; if the water
temperature in the storage tank
is lower than the one set on the
boiler, the boiler automatically
heats it to the set value. The
boiler prioritizes DHW and
water tank temperature
holding functions to central
heating function. Control
knob allows setting of
temperature in a 40 °C to 60 °C
range: when the knob is in
middle position DHW is set to
approximately 50 °C;
* set room temperature through
the ambient thermostat if
available;
Warning: when starting the
boiler after a long period of
inactivity, particularly boilers
powered by LPG, air bubbles
may be present in the supply
line.
Before switching on the boiler
switch on another gas powered
device (e.g. Light a kitchen gas
appliance).
The boiler may still shut down
once or twice.
If boiler shuts down use the
reset button F to resume
operation (see below).
1.2.2 Boiler shutdown
In case of malfunction the boiler
automatically turns off: the
shutdown light Eon the control
panel comes on. Then follow
the below instructions:
* check that the gas tap is open
and that gas is flowing, for
example by lighting a kitchen
gas appliance;
* if there is gas supply wait for a
minute before restarting the
boiler using reset button Fif the
boiler does not restart, try to
reset the boiler three additional
times. Should the boiler still not
resume operation, call an
authorised Service Centre or
qualified maintenance
personnel.
If the boiler shuts down
frequently, this indicates that
there is a recurring
malfunction. In this case
contact qualified personnel or
an authorised Service Centre
for maintenance.
WARNING
In order to prevent flue gas
leaks, natural draught boilers
are fitted with a safety device
with automatic reset. When
the safety device detects a
leak, the boiler holds standby
mode for 15 minutes.
Should the above mentioned
boiler status frequently
occur, the flue system is not
properly functioning. In this
case contact a qualified
technician to check the flue
system. A persistent
malfunction in the flue
system might put people and
animals at risk.
1.3 Maintenance
The boiler must be serviced
once a year.
Correct servicing ensures boiler
performance, prevents
environment pollution and
potential danger for people,
animals and property.
The boiler must be serviced by
qualified personnel. FONDITAL
strongly recommends
customers to refer exclusively
to qualified personnel.
The user may only clean the
exterior boiler housing using
domestic products .
Do not use water!
1.4 Information for the user
The user can access only the
parts of the boiler which can
be reached without using
tools: it is therefore forbidden
to disassemble the exterior
cover of the boiler and
tamper with the interior parts.
NO-ONE, INCLUDING
QUALIFIED PERSONNEL,
MAY MAKE MODIFICATIONS
TO THE BOILER.
FONDITAL cannot be held
liable in the event of injury to
persons and animals and
damage to property resulting
from tampering or improper
operations on the boiler.
If the boiler is inactive and
disconnected from the power
supply for long periods the
pump might be blocked and it
may be necessary to manually
turn the pump rotor to resume
its operation.
The above mentioned
operation, which requires
disassembling the boiler
housing and accessing internal
parts of the boiler, must be
performed by qualified service
personnel.
It is possible to prevent the
pump from blocking by adding
special filming products suitable
for multi-metal systems to the
water.
If the boiler is not disconnected
from the mains power supply,

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the pump will not block because
the boiler’s electronic system
has an automatic anti-block
function: the pump is operated
for a few seconds every day.
The boiler electronic has a
boiler anti-freeze function which
can be chosen by means of
selector A.
This function starts
automatically as below
described:
- heating system:
should the temperature of the
heating system water drop
below 7 °C the pump is
automatically switched on; if the
temperature drops below 5 °C
the burner lights up for a
maximum time of 15 minutes or
until the temperature of the
water in the system reaches 15
°C.
- DHW system:
when the probe inside the water
storage tank detects a
temperature lower than 6 °C
the burner switches on for a
maximum time of 15 minutes or
until the temperature of the
water in the system reaches 15
°C.
WARNING
This function is not active if
the boiler is disconnected
from the power and gas
supply and the gas tap is
closed.
The heating system can also be
effectively protected against
freezing by using specific anti-
freeze products suitable for
multi-metal systems. Do not
use car engine anti-freeze
products and check the
effectiveness of the product
over time.
The boiler has a temperature
and pressure gauge which
allows you to check the
temperature and pressure of
the water in the heating system.
When the boiler is switched off
the pressure of the water must
be 0.8/1 bar.
If this value drops then use the
pressure control tap to adjust to
the correct value.
WARNING
After adjusting the pressure,
close the tap without over-
tightening it. If the tap is not
closed properly the pressure
could rise, resulting in the
safety valve intervention and
water outflow.

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2 Technical characteristics
and dimensions
2.1 Technical characteristics
NIAS is a gas boiler with
atmospheric gas burner and water
storage tank; it is available in the
following versions:
24 24 kW heat output;
28 28 kW heat output;
TN natural draught open
combustion chamber;
TFS forced draught, sealed
combustion chamber;
All versions have electronic ignition.
Models in the NIAS series:
NIAS BTN 24 open combustion
chamber, natural draught,
electronic ignition;
NIAS BTFS 24 sealed combustion
chamber, forced draught, electronic
ignition;
NIAS BTN 28 open combustion
chamber, natural draught,
electronic ignition;
NIAS BTFS 28 sealed combustion
chamber, forced draught, electronic
ignition;
NIAS boilers comply with the
following EEC directives:
Gas directive 90/396/EEC dated 29
June1990;
Yield Directive 92/42 EEC dated 21
May 1992;
EMC Directive 89/336/EEC dated 3
May 1989 amended by Directive
92/31/EEC dated 28 April 1992;
European Community’s Low
Voltage Directive 73/23/EEC dated
19 February 1973 amended by
Directive 93/68/EEC dated 22 July
1993;
NIAS boilers are equipped with
safety features, according to
applicable laws.
The main technical features of
NIAS boilers are below
summarized.
* High performance copper heat
exchanger;
* Vertical enamelled water storage
tank, 60 l capacity with helicoidal
steel coil heat exchanger;
* Sacrificial magnesium anode;
* Electronic ignition;
* Electronic flame modulation;
* Adjustable heat output control
(CH only)
* Adjustable minimum heat output
control;
* Ignition train electronic
adjustment;
* Night temperature reduction
function;
* Anti-freeze function;
* Priority switch for DHW;
* Pump anti-locking function;
* Pump post-circulation function
both in CH and DHW systems;
* Safety limit thermostat (105 °C);
* Motorized three way valve;
* Three-speed circulating pump
with deareator;
* Manual air purging valve for
system filling;
* 7.5 liter expansion vessel;
* Water inlet tap;
* Low water pressure safety switch;
* IPX4D protection class control
panel;
* Thermometer;
* Pressure gauge;
* Power supply and emergency
shutdown lights;
* DHW temperature regulator
(40/60 °C);
* CH temperature regulator (35/85
°C).
* Reset button;
* Summer/OFF/Winter/Anti-freeze
boiler selector;
* Boiler installation template.

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2.2 Dimensions
2.3 Hydraulic connections
pic. 2
pic. 3
1 Three-way valve
2 Low water pressure sensor
3 Circulating pump with built-in deareator
4 Ignition board
5 Gas valve
6 Ignition electrode
7 Burner
8 Detection electrode
9 Heat exchanger
10 Manual air purging valve
11 Temperature probe
12 Expansion vessel (heating system)
13 Optional expansion vessel (DHW system)
14 Water storage tank anode
15 Water storage tank
16 Water storage tank thermostat
17 Overheating shutdown sensor
18 Safety valve 3 bar
19 Safety valve 7 bar
20 Water storage tank drain cock
21 Flue gas safety thermostat
22 Filling tap
23 Adjustable by-pass
24 No-return valve
C DHW outlet
F Cold water inlet
G Gas supply
M Central heating flow
R Central heating return

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2.4 Technical data
Burner pressures indicated in the following table must be checked after the boiler has been operating for 3
minutes.
BURNER PRESSURE
(mbar)
BOILER
MODEL HEAT OUPUT (kW) HEAT INPUT (kW) Natural gas Butane Propane
NIAS 24 BTN 23.8 12.5 – 26.5 2.9 – 12.3 5.3 – 23.5 7.1 – 30.3
NIAS 24 BTFS 24.0 12.5 – 26.5 3.2 – 13.2 5.8 – 25.1 7.6 – 32.2
DHW production by 45 °C ∆t = 7,6 lts/min. DHW production by 35 °C ∆t = 9,8lts/min.
DHW production by 40 °C ∆t = 8,6 lts/min. DHW production by 30 °C ∆t = 11,4 lts/min.
45 °C DHW supply during the first 10 minutes (storage tank water 60 °C – cold water 10 °C) = 116 l
BURNER PRESSURE
(mbar)
BOILER
MODEL HEAT OUPUT (kW) HEAT INPUT (kW) Natural gas Butane Propane
NIAS 28 BTN 28.2 13.5 – 31.0 3.0 – 13.7 4.9 – 26.8 6.9 – 34.6
NIAS 28 BTFS 28.3 13.5 – 31.0 2.8 – 13.3 5.1 – 27.3 6.8 – 35.2
DHW production by 45 °C ∆t = 8.9 lts/min. DHW production by 35 °C ∆t = 11.5 lts/min.
DHW production by 40 °C ∆t = 10 lts/min. DHW production by 30 °C ∆t = 13.4 lts/min.
45 °C DHW supply during the first 10 minutes (storage tank water 60 °C – cold water 10 °C) = 135 l
pic. 4
1 Three-way thermostatic valve
2 Low water pressure sensor
3 Circulating pump with built-in deareator
4 Ignition board
5 Gas valve
6 Ignition electrode
7 Burner
8 Detection electrode
9 Heat exchanger
10 Manual air purging valve
11 Temperature probe
12 Expansion vessel (heating system)
13 Optional expansion vessel (DHW system)
14 Water storage tank anode
15 Water storage tank
16 Water storage tank thermostat
17 Overheating shutdown sensor
18 Safety valve 3 bar
19 Safety valve 7 bar
20 Water storage tank drain cock
21 Flue gas safety thermostat
22 Filling tap
23 Adjustable by-pass
24 No-return valve
25 Flue fan
C DHW flow
F Cold water inlet
G Gas supply
M Central heating flow
R Central heating return
NIAS BTFS 24
–
NIAS BTFS 28

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2.5 General specifications
Equipment category II2H3+
Burner nozzles (BTN 24 \ BTFS 24) n° 13
Burner nozzles (BTN 28 \ BTFS 28) n° 15
Minimum central heating circuit flow l/min 7.5
Minimum central heating working pressure bar 0.5
Maximum central heating working pressure bar 3
Minimum DHW working pressure bar 0.5
Maximum DHW working pressure bar 7
Water storage tank capacity l 60
Power supply - Voltage / Frequency V-Hz 230 – 50
Fuse on the power mains A (F) 4
Maximum absorbed power BTN 24 \ BTN 28 W 110
Maximum absorbed power BTFS 24 \ BTFS 28 W 165
Net weight BTN 24 \ BTN 28 kg 72.5
Net weight BTFS 24 \ BTFS 28 kg 78
Natural gas consumption BTN 24 \ BTFS 24 (*) m³/h min 1.32 – max 2.80
Butane consumption BTN 24 \ BTFS 24 kg/h min 0.98 – max 2.09
Propane consumption BTN 24 \ BTFS 24 kg/h min 0.97 – max 2.05
Natural gas consumption BTN 28 \ BTFS 28 (*) m³/h min 1.43 – max 3.28
Butane consumption BTN 28 \ BTFS 28 kg/h min 1.06 – max 2.44
Propane consumption BTN 28 \ BTFS 28 kg/h min 1.04 – max 2.41
Maximum CH working temperature °C 89
Maximum DHW working temperature °C 64
Expansion vessel capacity l 7.5
Maximum system capacity (**) l 138
(*) At 15 °C – 1013 mbar (**) Calculated for maximum temperature of 90 °C

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NIAS BTN 24
Heat dispersion from the boiler casing max input min. input 30% red. load
Boiler installed indoor % 1.9 3.5
Boiler installed outdoor % 3.0 4.54
Boiler installed in a boiler room % 2.2 3.9
Chimney loss with burner in function % 7.2 9.5
Flue gas mass g/s 19.8 18.1
Flue - air temperature °C 86.9
CO2% 4.9
Boiler efficiency % 89.81 88.78
NIAS BTFS 24
Heat dispersion from the boiler casing max input min. input 30% red. load
Boiler installed indoor % 1.45 0.8
Boiler installed outdoor % 1.85 1.09
Boiler installed in a boiler room % 1.6 0.85
Chimney loss with burner in function % 7.7 11.1
Flue gas mass g/s 16.5 17.7
Flue – air temperature °C 108.8
CO2% 5.9
Boiler efficiency % 90.45 88.36
NIAS BTN 28
Heat dispersion from the boiler casing max input min. input 30% red. load
Boiler installed indoor % 1.0 0.78
Boiler installed outdoor % 1.59 0.97
Boiler installed in a boiler room % 1.3 0.82
Chimney loss with burner in function % 7.2 10.2
Flue gas mass flow g/s 22.2 19.4
Flue - air temperature °C 92.1
CO2% 5.3
Boiler efficiency % 91.21 90.11
NIAS BTFS 28
Heat dispersion from the boiler casing max input min. input 30% red. load
Boiler installed indoor % 1.04 1.42
Boiler installed outdoor % 1.53 1.80
Boiler installed in a boiler room % 1.23 1.6
Chimney loss with burner in function % 7.0 12.1
Flue gas mass g/s 17.6 17.4
Flue – air temperature °C 114.1
CO2% 6.9
Boiler efficiency % 91.47 89.58

13
3 Instructions for the
fitter
3.1 Installation regulations
NIAS is an II2H3+ class boiler
which must be installed in
compliance with applicable
country standards, laws and
regulations.
3.2 Installation
3.2.1 Packaging
NIAS is packaged and
delivered in a strong cardboard
box on wooden pallet. Once the
boiler has been unpacked
check the boiler is undamaged.
The packaging material can be
recycled and it must be
disposed of accordingly.
Keep the packaging out of the
reach of children as it may
represent a choking and
suffocation hazard.
FONDITAL cannot be held
liable for injury to persons
and animals or damage to
property resulting from non-
observance of the above.
The packaging contains:
- copper pipe kit for hydraulic
connection of the boiler to
heating system, water system
and gas mains,
- metal template for boiler wall-
hanging and system
connecting,
- installation, use and
maintenance handbook,
- 4 screws with dowels for boiler
wall-hanging,
- for BTFS models only: flue
diaphragm.
3.2.2 Choosing where to
install the boiler
When choosing the position of
the boiler:
- refer to instructions given in
the “Flue system“ section,
- remember that it is advisable
to leave a space of 50 mm on
each side of the boiler to
facilitate maintenance
operations,
- check wall sturdiness,
- avoid fixing the boiler to thin
partitions,
- avoid installing the boiler
above appliances which might
affect boiler operation (E.G.
kitchen appliances emitting
greasy steam, washing
machines etc.),
- avoid installing natural draught
boilers in corrosive vapor or
dusty air areas like
hairdressers’, laundrettes etc.
as boiler components life span
might be considerably shorter
than average,
- leave a 350 mm space
between the upper part of the
boiler and the ceiling in order to
facilitate replacement of the
water tank magnesium anode:
this condition is respected when
between the axe of the fixing
holes of the bracket supporting
the boiler and the ceiling the
distance is 436 mm.
3.2.3 Positioning the boiler
Each boiler package includes a
metal template. It allows for CH,
DHW and gas mains
connection locating when
hydraulic system piping is being
laid out before boiler is yet to be
physically installed.
Use the lower part of the
template to mark the exact
location of gas supply, cold
water inlet pipe, DHW flow, CH
flow and return.
Since temperature of wall on
which the boiler is installed and
temperature of coaxial flue
system are lower than 60°C, it
is not necessary to keep a
minimum safe distance
between boiler and temperature
sensible surface wall.
Boilers with split duct flue
system: place insulating
material between temperature
sensible surface wall and flue
system.

14
3.2.4 Installing the boiler
Before connecting the boiler to
DHW and CH system pipes,
clean the pipes removing any
trace of metal from processing
and welding as well as any oil
and grease which could
damage the boiler or interfere
with its good operation.
NB: Do not use solvents
which could damage the
components.
FONDITAL shall be waived
from all liabilities for injury to
persons and animals or
damage to property resulting
from non-observance of the
above.
To install the boiler:
- fix the template to the wall by
means of four Ø 10 mm screws
and dowels.
IMPORTANT: ceiling and
screws clearance must be 436
mm.
- position connections of gas
supply pipe, cold water supply
pipe, DHW flow, CH flow and
return according to template
marks (lower part);
- hang the boiler onto the
support hooks of metal
template;
- connect boiler and supply
pipes using the pipe kit
supplied;
- connect the boiler to air intake
and flue systems;
- connect the boiler to the
power mains.
R = CH return ¾”
G = Gas supply ¾”
M = CH flow ¾”
C = DHW flow ½"
F = Cold water mains ½"
S = Safety valve drain pic. 5
TEMPLATE FOR BOILER CONNECTION
Ø 100 (BTFS 24-28 models only)

15
3.2.5 Boiler room ventilation
BTN 24 and BTN 28 models
have an open combustion
chamber and have been built
for flue exhaust connection to a
chimney while combustion air is
taken directly from the room
in which the boiler is
installed.
The boiler must be installed in
an appropriate room according
to applicable standards and
laws which shall be
considered as having been
transcribed in full in this
manual.
BTFS 28 and BTFS 28 models
have a sealed combustion
chamber with reference to the
environment in which they are
installed, so no special
measures need be taken as
regards ventilation for the
combustion air.
This is also valid for the room
the boiler will be installed in.
The boiler must be installed in a
suitable room pursuant to
applicable standards and laws
which shall be considered as
having been incorporated in
full in this manual.
3.2.6 Flue system
The boiler must be installed
exclusively by Qualified
personnel in compliance with all
local standards and laws
applicable in the country of
installation which shall be
considered as having been
transcribed in full in this
manual.
NATURAL DRAUGHT BOILER
Connection to the chimney
The chimney is indispensable
for the correct functioning of the
boiler; it must therefore conform
to the following requirements:
- it must be made by waterproof
material and be resistant to the
temperature of flue gas and
relative condensate;
- it must have appropriate
mechanical strength and low
thermal conductivity;
- it must be perfectly sealed to
prevent cooling due to parasite
air inlets;
- it must be as vertical as
possible and the end section
must have a roof top which
ensures efficient and constant
removal of the combustion
products;
- the chimney section must be
large at least as the boiler’s
anti-wind gust device; for
chimneys with a square or
rectangular section, the internal
section must be 10% larger
than the section of the
connecting duct to the boiler’s
anti-wind gust device;
- starting from the anti-wind
gust device, the duct fitting
must have a vertical section of
more than twice the diameter
before joining the chimney.
Direct emission into the
atmosphere
Natural draught boilers can
discharge combustion products
directly into the atmosphere
using a duct which goes
through the outside walls of the
building connected to a flue
outlet terminal.
The outlet duct must also
comply with the following
requirements:
- the sub-horizontal part inside
the building must be as short as
possible (no more than 1.000
mm);
- for boilers with vertical outlets,
such as BTN 24 and BTN 24
models, there must be no more
than 2 direction changes;
- it must receive the discharge
from a single boiler;
- the part going through the wall
must be protected by a sheath
duct; the part of the sheath duct
facing the inside of the building
must be closed and the part
facing outwards must be open;
- the final section, on which the
draught outlet will be fixed,
must protrude from the wall of
the building for a length of a
least twice the diameter of the
duct;
- the draught outlet must
overlap the connection to the
boiler exhaust duct connection
by at least 1.5 metres (see pic.
6).

16
pic. 6
Incline
Incline
pic. 7
pic. 8
WARNING:
The boiler is fitted with an automatic safety
reset device as protection against leakage of
combustion products inside the building.
The device includes an automatic bi-metallic
reset thermostat (pic. 8) mounted on the anti
wind gust cover. After 15 minutes the boiler
will automatically restart.
It is absolutel
y
forbidden to tamper with
and/or exclude the safety device.
If the boiler shuts down frequently, check the
flue outlet duct. This duct may be obstructed
or may be unsuitable for the discharge of flue
gas into the atmosphere.
FONDITAL shall not be held responsible
for dama
g
e resultin
g
in incorrect
installation, use, modification of the
boilers or for non-observance of the
instructions provided b
y
the manufacturer
or applicable installation standards for
the product.
FORCED DRAUGHT BOILER
The distances of boiler vent terminals on
walls must comply with standards and laws
applicable in the country of installation which
shall be considered as having been
transcribed in full in this manual.
DIMENSIONS FOR CONNECTING THE FLUE SYSTEM DUCTS

17
3.2.7 Flue system configuration
C12 Boiler connected to horizontal
air intake and outlet ducts directly into
the atmosphere using coaxial or split
ducts.
The distance between the air intake
duct and the flue gas outlet duct must
be at least 250 mm (see pic. 15) and
both end sections must be located
within a 500 by 500 mm surface area.
C32 Boiler connected to vertical
air intake and outlet ducts directly into
the atmosphere using coaxial or split
ducts.
The distance between the air intake
duct and the flue gas outlet duct must
be at least 250 mm (see pic. 15) and
both end sections must be located
within a 500 by 500 mm surface area.
C42 Boiler connected to collective
chimneys including two ducts, one for
the air intake for combustion and the
other for the discharge of the
combustion products, through coaxial
or split ducts.
The chimney must comply with
applicable law provisions.
C52 Boiler connected to separate
combustion air intake and outlet
ducts.
These ducts can discharge into
areas at different pressure values.
Split ducts external terminals must
not be located on two directly
facing walls.
C82 Boiler connected to a duct for
conveying combustion air and an
individual or collective chimney for
discharging the flue gas.
The chimney must comply with
applicable law provisions.
Type
C12
Type
C32
Type
C42
Type
C52
Type
C82

18
3.2.8 Flue system with coaxial pipes
100/60 mm diameter (Type A accessories)
Type C12
Minimum length of horizontal coaxial ducts is
0.5 meters. Maximum allowable length of
horizontal coaxial ducts is 3meters; for each
elbow after the first, the maximum allowable
length must be reduced by 1 meter.
Moreover, the duct must have a downward
dip of 1% towards the outlet point to prevent
rain water from getting into the duct.
Type C32
Minimum length of vertical coaxial ducts is 0.5
meters. Maximum allowable length of vertical
coaxial ducts is 4meters including the
chimney; for each additional elbow after the
first, the maximum allowable length must be
reduced by 1 meter.
In installations using coaxial pipes of 0.5
m to 1.5 m install the 46 mm diaphragm as
shown in picture 9.
Diaphragm
Ø 46
Neoprene
seal Diaphragm
Max length 1.5 mt
COAXIAL DUCTS
SAMPLE INSTALLATION
COAXIAL FLUE SYSTEM DISTANCES
pic. 9
pic. 10

19
3.2.9 Flue system with split pipes 80 mm
diameter (type B accessories)
NB: Maximum flue system load loss,
according to installation, must
correspond to values indicated below.
For flue system with a load loss value
not exceeding 40 Pa, the 44mm
diaphragm in BTFS 28 model and the 46
mm diaphragm in BTFS 24 model must
be installed as shown in pic. 11
(diaphragms are supplied with boiler).
IMPORTANT
Should flue system cross walls and/or
infrastructure or if it easily accessible, it
is mandatory to install an appropriate
thermal insulation.
During the boiler functioning the duct
can reach very high temperatures (more
than 120 °C).
pic. 11
Diaphragm
Diaphragm
Neoprene
seal
∆P max = 40 Pa
SPLIT DUCTS FLUE SYSTEM INSTALLATION SAMPLE
pic. 12
DIMENSIONS FOR CONNECTION OF THE FLUE
GAS OUTLET WITH SPLIT DUCTS

20
Configurations relative to Ø 80 split pipe
flue system
Sample No. 1 (pic. 13)
Air intake and flue gas outlet from two outside
facing perimeter walls.
Maximum allowable load loss: 80 Pa
Sample No. 2 (pic. 14)
Air intake from perimeter wall and flue gas
roof outlet.
Maximum allowable load loss: 80 Pa
Sample No. 3 (pic. 15)
Air intake from perimeter wall and flue gas
outlet from the same outside perimeter wall.
Maximum allowable load loss: 80 Pa
pic. 13
pic. 14