Fondital Nias Dual Line Tech BTN 24 Quick start guide

INSTALLATION
USE AND MAINTENANCE
NIAS DUAL
GB
High quality Italian product
IST 03 C 294 - 02

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Dear Customer,
Thank you for choosing and buying one of our boilers. Please read these instructions carefully in order to install,
operate and service the boiler properly.
The Manufacturer recommends that Customers contact authorized qualified personnel only for maintenance
and repair operations.

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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 fitter 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 is designed for connection to a central heating system and to a hot domestic water system.
Any other use is considered incorrect and therefore dangerous.
The boiler must be installed in compliance with the applicable laws and standards and according to the manufacturer’s instructions given in
this manual. Incorrect installation may cause injury to people or animals and damage to property. The manufacturer shall not be held liable
for any such injury or damage.
Damage or injury caused by incorrect installation or use, or by failure to follow the manufacturer’s instructions will relieve manufacturer of 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 has not been damaged during transport and handling. Do not install equipment which is damaged or
faulty.
Do not obstruct the air intake or heat dissipation openings.
Only Manufacturer-approved accessories or optional kits must be installed.
All the packaging materials can be recycled and must be disposed of correctly. They must be sent to a specific waste management site. Keep
the packaging out of the reach of children as it may represent a hazard.
In the event of failure or faulty operation, switch off the boiler. Do not attempt to make any repairs and contact a qualified technician.
Manufacturer-approved parts must be used for all repairs to the boiler.
Failures to comply with the above requirements may affect the safety of the boiler and endanger people, animals and property.
Routine boiler maintenance should be performed according to the schedule in the relevant section of this manual.
Appropriate boiler maintenance ensures efficient operation, preservation of the environment, and safety for people,
animals and property. Incorrect and irregular maintenance can be a source of danger for people, animals and property.
The Manufacturer recommends that Customers contact an authorized Service Centre for maintenance and repairs.
If the boiler is to remain inactive for a long time, disconnect it from the power mains and close the gas tap.
Warning! If the boiler is disconnected from the mains, the electronic anti-freeze function will not operate.
Should there be a risk of freezing, add anti-freeze to the heating system. It is not advisable to empty the system as this may result in damage.
Use specific anti-freeze products suitable for multi-metal heating systems.
If you smell gas:
 •donottouchanyelectricalswitchesanddonotturnonelectricalappliances;
 •donotigniteflamesandextinguishanycigarettes;
 •closethemaingastap;
 •opendoorsandwindows;
 •contactaServiceCentre,aqualifiedfitterorthegassupplycompany.
Never use a flame to detect a gas leak.
WARNING
This boiler has been built for installation in the country indicated on packaging and the rating plate.
Installation in a country other than the specified one may be a source of danger for people, animals and property.
The Manufacturer cannot be held contractually or extra-contractually liable in the event of failure to comply with the above.

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RAPID OPERATING INSTRUCTIONS
The following instructions will help you to switch the boiler on quickly and regulate it for immediate use.
It is presumed that the boiler has been installed by a qualified fitter, it has been used before and is ready
to operate correctly.
If any accessories have been fitted on the boiler, these instructions will not cover them. You will therefore have
to refer to the full boiler instructions as well as to the specific instructions for the accessories.
This manual contains full details of how the boiler works, and full operating and safety instructions.
1. Open the gas cock.
2. Turn the master switch to ON: the display comes on and shows the function set via the boiler selector (2, fig. 1).
3. If you do not wish to activate the heating function, turn the boiler selector (2, fig. 1) to SUMMER. This will activate domestic hot water
(DHW) only, and the display will show the flow water temperature.
4. If you wish to activate the heating function, turn the boiler selector (2, fig. 1) to WINTER. This will activate both DHW and heating, and
the display will show the flow water temperature.
5. If you wish to activate the Aqua Premium system, proceed as follows to regulate the hot water temperature.
Turn the regulator (3, fig. 1) anticlockwise as far as it will go. The storage symbol , is displayed, showing that the Aqua Premium system
is active (if it was already active, this operation deactivates it). Then turn the selector (3) until the desired hot water temperature is
displayed (at least 40°C).
While the DHW temperature is being regulated, the display shows the temperature setting and the tap symbol flashes.
6. To regulate the CH water temperature, first set the regulator (4, fig. 1) to 3 o’clock (about 70°C), then regulate it as required. While the
DHW temperature is being regulated, the LCD displays the temperature setting and the tap symbol flashes.
7. Set the desired temperature on the (optional) room thermostat in the building.
The boiler is now ready to operate.
If the boiler shuts down, turn the boiler selector (2in fig. 1) to reset for a few seconds, then back to the desired position. If the boiler does not
restart, contact an Authorised Service Centre.
Boiler selector on SUMMER
Boiler selector on WINTER
DHW temperature regulator
CH water temperature regulator
Boiler selector on RESET
Liquid crystal display (LCD)
Liquid crystal display (LCD)

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TABLE OF CONTENTS
General information for the fitters, maintenance technicians and users page 3
Rapid operating instructions page 4
1. User instructions page 7
1.1. Control Panel page 7
1.2. LCD page 8
1.3. BOILER STATUS – LCD ACTIVATION CORRESPONDENCE page 9
1.3.1. Normal operation page 9
1.3.2. Malfunction page 9
1.4. Operating the boiler page 10
1.4.1. Switching on page 10
1.4.2. CH function page 10
1.4.3. DHW function page 10
1.4.3.1. AQUA PREMIUM system page 10
1.4.3.2. Instantaneous production of DHW page 11
1.4.4. Anti-freeze function page 11
1.4.5. Pump and valve anti-shutdown function page 12
1.4.6. Operation with (optional) remote control page 12
1.4.7. Operation with an (optional) external probe page 12
1.5. Boiler shutdown page 13
1.5.1. Burner shutdown page 13
1.5.2. Shutdown due to overheating page 13
1.5.3. Shutdown due to air/flue gas system malfunction page 13
1.5.4. Shutdown due to insufficient water pressure page 13
1.5.5. Alarm due to temperature probe malfunction page 14
1.5.6. Alarm due to external probe malfunction (optional) page 14
1.5.7. Alarm due to gas valve modulator malfunction page 14
1.5.8. Alarm due to (optional) remote control connection malfunction page 14
1.6. Maintenance page 14
1.7. Notes for the user page 14
2. Technical features and dimensions page 15
2.1. Technical features page 15
2.2. Dimensions page 16
2.3. Boiler layout page 18
2.4. Operating data page 19
2.5. Technical specifications page 20
3. Instructions for the fitter page 21
3.1. Installation standards page 21
3.2. Installation page 21
3.2.1. Packaging page 21
3.2.2. Deciding where to install the boiler page 21
3.2.3. Positioning the boiler page 21
3.2.4. Installing the boiler page 23
3.2.5. Boiler room ventilation page 23
3.2.6. Air/flue gas system for natural draught boilers (BTN) page 23
3.2.7. Air/flue gas system for forced draught boilers (BTFS) page 24
3.2.7.1. Air/flue gas pipe configuration: B22, C12, C32, C42, C52, C82 page 25
3.2.7.2. Air/flue gas system with 100/60 mm diameter coaxial pipes page 26
3.2.7.3. Air/flue gas system with 80 mm diameter split pipes page 27
3.2.7.4. Direct air intake and flue gas discharge with 80 mm diameter duct page 28
3.2.8. Measuring combustion efficiency page 29
3.2.8.1. Chimney-sweep function page 29
3.2.8.2. Measurement procedure page 29
3.2.9. Gas mains connection page 30
3.2.10. Plumbing connection page 30
3.2.11. Adjustable by-pass page 31
3.2.12. Power mains connection page 31
3.2.13. Room thermostat installation (optional) page 31
3.2.14. Installation of the OpenTherm remote control (optional) page 31
3.2.15. Installation of the (optional) external probe and sliding temperature operation page 32
3.3. Filling the system page 33
3.4. Starting the boiler page 33
3.4.1. Preliminary checks page 33
3.4.2. Switching on and off page 33
3.5. Wiring diagram page 34
3.6. Adapting to other gases and regulating the burner page 35
4. Testing the boiler page 36
4.1. Preliminary checks page 36
4.2. Switching on and off page 36
5. Maintenance page 36
5.1. Maintenance schedule page 36
5.2. Combustion analysis page 37
6. Troubleshooting page 38

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LIST OF FIGURES
fig. 1 - Control panel page 7
fig. 2 - Liquid crystal display page 8
fig. 3 - Fictitious room temperature page 12
fig. 4 - Thermoregulation curves page 12
fig. 5 - Filling tap page 13
fig. 6 - Dimensions for model BTN page 16
fig. 7 - Dimensions for model BTFS page 17
fig. 8 - Plumbing system diagram page 18
fig. 9 - Installation template page 22
fig. 10 - Dimensions for connection to a flue gas pipe – model BTN page 24
fig. 11 - Connection to the stack – model BTN page 24
fig. 12 - Coaxial air/flue gas discharge pipes - models BTFS page 26
fig. 13 - Dimensions for connecting the coaxial air/flue gas system – models BTFS page 26
fig. 14 - 0SDOPPIA06 split kit (for models BTFS) page 27
fig. 15 - Dimensions for connecting split air/flue gas system – models BTFS page 28
fig. 16 - Opening the casing page 29
fig. 17 - Chimney-sweep function page 29
fig. 18 - Examples of points for measuring combustion efficiency page 29
fig. 19 - Gas mains connection page 30
fig. 20 - By-pass adjustment page 31
fig. 21 - Thermoregulation curve adjustment page 32
fig. 22 - Thermoregulation curves page 32
fig. 23 - Wiring diagram page 34
fig. 24 - Gas conversion – gas selection jumper page 35
fig. 25 - Gas conversion – gas valve modulation coil page 35
fig. 26 - Gas conversion – pressure intake page 35
fig. 27 - Gas conversion – control panel settings page 35
fig. 28 - Gas conversion – gas valve regulation page 35
LIST OF TABLES
Table 1 - Liquid crystal display during normal operation page 9
Table 2 - Liquid crystal display in the event of a malfunction page 9
Table 3 - Operating data - model BTN 24 page 19
Table 4 - Operating data - model BTFS 24 page 19
Table 5 - Operating data - model BTFS 28 page 19
Table 6 - Operating data - model BTFS 32 page 19
Table 7 - Overall data page 20
Table 8 - Combustion data - model BTN 24 page 20
Table 9 - Combustion data - model BTFS 24 page 20
Table 10 - Combustion data - model BTFS 28 page 20
Table 11 - Combustion data - model BTFS 32 page 20
Table 12 - Relation between the temperature and nominal resistance of probes page 34

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1. USER INSTRUCTIONS
1.1. Control panel
1. Liquid crystal display (LCD)
The LCD displays the boiler status and operating data (see fig. 2).
2. Boiler mode selector
With the selector on RESET , the boiler restarts after activation of the burner shutdown device.
With the selector on OFF, the boiler is in stand-by mode, with the heating and hot water functions disabled.
With the selector on SUMMER , the boiler is ready to produce domestic hot water only.
With the selector on WINTER , the boiler is ready to heat and produce hot water.
With the selector on ANTI-FREEZE , only the anti-freeze function is enabled.
3. DHW temperature regulator
This is used to enable/disable water storage and to set the DHW temperature in the range 35-57°C.
4. CH water temperature regulator
This is used to select the temperature of the water in the heating system in the range 35-78°C.
5. Water pressure gauge
This shows the pressure of the water in the heating system.
fig. 1
1
2345

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1.2. LCD
a. DHW indicator (tap symbol)
This comes on when the boiler is in DHW mode.
It flashes when the DHW temperature is being regulated via regulator 3(fig. 1).
b. Water heater on indicator
This indicator comes on when Aqua Premium system is activated via regulator 3(fig. 1). Refer to subsection 1.4.3.
c. Alphanumeric indicator
This shows the following:
- boiler status
- CH temperature
- CH temperature setting
- DHW temperature setting
- boiler diagnostics
d. Central heating indicator
This comes on when the boiler is in CH mode.
It flashes when the CH temperature is being regulated via regulator 4(fig. 1).
e. Boiler shutdown indicator
This comes on when there is a malfunction that cannot be reset via the boiler funtion selector (2, fig. 1).
The problem must be solved before the boiler can be restarted (see 1.5. and following).
f. Ignition power indicator (for fitter only)
Refer to subsection 3.6., for the fitter only.
g. Burner shutdown indicator
This comes on when the burner shutdown device activates due to a malfunction.
To restart the boiler, turn the boiler selector (2, fig. 1) to the RESET position for a few seconds and then back to the desired position (see
1.5. and following).
h. Flame indicator
This comes on when the burner flame is present.
i. Chimney-sweep function indicator (for fitter only)
This comes on when the chimney-sweep function is activated (see 3.2.8.1, for the fitter only).
l. Thermoregulation indicator (for fitter only)
This comes on when the thermoregulation curve is set (see 1.4.7. and 3.2.15., for the fitter only).
m. Fictitious ambient temperature indicator
When an external probe is installed, this indicator flashes when the fictitious ambient temperature is set via regulator 4(see 1.4.7).
fig. 2
a b c d
e
f g h i l m

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1.3. BOILER STATUS – LCD ACTIVATION CORRESPONDENCE
1.3.1. Normal operation
Boiler selector on OFF
Boiler selector on ANTI-FREEZE
Boiler selector on SUMMER or WINTER
Aqua Premium system disabled, no function active
The water flow temperature is displayed
Boiler selector on SUMMER or WINTER
Aqua Premium system enabled, no function active
The water flow temperature is displayed
Boiler selector on SUMMER or WINTER
DWH function active (with Aqua Premium system disabled)
The water flow temperature is displayed
Boiler selector on WINTER
CH function active
The water flow temperature is displayed
Table 1
1.3.2. Malfunction
Boiler not powered on
Boiler shutdown due to flame absence
Boiler shutdown due to safety thermostat activation
Boiler shutdown due to flue gas thermostat activation (BTN)
Boiler shutdown due to air pressure switch activation (BTFS)
Low system pressure alarm
CH probe failure
DHW probe failure
Storage probe fault
Gas valve modulator malfunction alarm
Remote control connection failure
External probe failure
Table 2

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1.4. Operating the boiler
1.4.1. Switching on
It is presumed that the boiler has been installed by a qualified fitter, it has been used before and is ready
to operate correctly.
• Open the gas cock;
• Turn the master switch to ON – the LCD (g. 1) light up and shows the active function (see table 1)
OFF/SUMMER/WINTER/ANTI-FREEZE;
• choose the boiler mode via selector 2 (g. 1): OFF/SUMMER/WINTER/ANTI-FREEZE;
• Set the temperature for the heating system on regulator 4 (g. 1);
• Set the DHW temperature on regulator 3 (g. 1);
• Set the ambient temperature on the (optional) thermostat.
IMPORTANT
If the boiler is not used for a long time, particularly when it runs on propane gas, ignition may be difficult. So, before starting
the boiler, switch on a different gas-fired device (e.g. a cooker).
Note that the boiler may still shut down a couple of times. If this happens, turn selector 2 (fig. 1) to the RESET position for a
few seconds, then back to the desired position.
1.4.2. CH function
The heating function is only active when the boiler selector (2, fig. 1) is on WINTER .
The water temperature can be set on regulator 4(fig. 1).
The temperature range is 35-78°C (from the fully anticlockwise to the fully clockwise position).
During temperature setting, the CH symbol on the LCD flashes and the CH setting is displayed.
When the CH system demands heat, the LCD shows the (fixed) CH symbol and the instant temperature of the
CH water.
The burner symbol only shows while the burner is operating.
In order to avoid frequent switching on and off of the heating function, the boiler has a 4-minute waiting time between subsequent
ignitions. If, however, the temperature in the system drops below 40°C, this waiting time is cancelled and the boiler reignites.
1.4.3. DHW function
The domestic hot water function is active with the boiler selector 2 (fig. 1) on SUMMER or WINTER .
The boiler always gives priority to DHW demand over the CH function.
The boiler is equipped with the AQUA PREMIUM system, which combines the instantaneous production of domestic hot water with a
storage function.
1.4.3.1. AQUA PREMIUM system
The boiler comes with a 25-litre stratification storage tank and a secondary plate heat exchanger.
The boiler can either function as a standard instantaneous boiler, when the storage tank is deactivated, or
with the innovative Aqua Premium system, when the storage tank is switched on.
The storage tank function is controlled via regulator 3(fig. 1).
When regulator 3is turned fully anticlockwise, the storage tank symbol is displayed. Then turn regulator 3clockwise until a setting
of at least 40°C is reached.
To deactivate the storage function, turn regulator 3 fully anticlockwise until the symbol disappears, then back to a setting of at least
40°C.
The temperature range is 35-57°C (from the fully anticlockwise to the fully clockwise position of regulator 3).
During temperature setting, the DHW symbol on the LCD flashes and the water temperature is displayed.
In Aqua Premium mode, when a hot water tap is turned on, the flow switch cuts off the supply of water. The boiler switches on, the
cutoff valve opens and the DHW pump activates (the flow rate is fixed).
When DHW demand is less than the pump’s flow rate, water to the tap is only supplied by the secondary plate heat exchanger and
excess DHW is deviated to the storage tank.
When the DHW demand exceeds the flow rate, water produced by the secondary heat exchanger is added to that from the storage
tank. This gives a higher hot water flow than produced by instantaneous boilers with an identical thermal output and traditional ones
with a storage tank of the same capacity.

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When there is a demand for hot water, the tap symbol (fixed) and the instantaneous water temperature are
displayed.
The burner symbol shows while the burner is in operation.
The boiler can also operate as a standard instantaneous boiler, with the storage tank disabled.
1.4.3.2. Instantaneous production of DHW
When the storage tank is disabled, the boiler operates as a standard instantaneous boiler: the cutoff valve is closed and the DHW
pump is off. In this case, DHW demand is met by the secondary heat exchanger only.
The temperature can be selected on regulator 3in the range 35-57°C (from the fully anticlockwise to the fully clockwise position).
During temperature setting, the DHW symbol on the LCD flashes and the DHW temperature is displayed.
The DHW flow rate in litres per minute at the set temperature depends on the boiler’s thermal output and
the water supply temperature. It can be calculated from the following formula:
K
l = litres of hot water per minute = ---
ΔT
where:
K is
- 334 for model BTN 24
- 341 for model BTFS 24
- 407 for model BTFS 28
- 449 for model BTFS 32
ΔT = DHW temperature – cold water supply temperature
For instance, with model BTFS 24, if the water supplied is 8°C and you want shower water at 38°C, the value of ΔT is:
ΔT = 38°C – 8°C = 30°C
and the number of DHW litres per minute available at 38°C is:
I = 341 / 30 = 11.4 [litres per minute ]
When there is a demand for hot water, the tap symbol (fixed) and the instantaneous flow water temperature
are displayed.
The burner symbol shows while the burner is in operation.
1.4.4. Anti-freeze function
The boiler comes with an anti-freeze function which is active in SUMMER, WINTER and ANTI-FREEZE modes.
The anti-freeze function protects the boiler only, not the whole heating system.
The heating system must be protected by a room thermostat, which is disabled when selector 1 is on ANTI-FREEZE
or OFF. So, if you wish to protect the heating system as well, turn selector 2 to WINTER .
The heating system can also be protected effectively from frost by using specific anti-freeze products suitable for multi-metal
systems.
Do not use vehicle anti-freeze products. Periodically check the effectiveness of the additive.
When the heating water temperature sensor reads a temperature of 5°C, the boiler switches on at minimum thermal output until the
temperature rises to 30°C or 15 minutes have elapsed.
If the boiler shuts down, the pump continues to operate.
When the DHW temperature sensor reads a temperature of 5°C, the boiler switches on at minimum thermal output until the
temperature rises to 10°C or 15 minutes have elapsed (the switching valve switches to the DHW position).
If the boiler shuts down, the pump continues to operate.
When the storage tank temperature sensor reads a temperature of 5°C, the boiler switches on at minimum thermal output until the
temperature rises to 10°C or 15 minutes have elapsed (the switching valve switches to the DHW position).
If the boiler shuts down, the pump continues to operate.

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1.4.5. Pump and valve anti-shutdown function
If the boiler remains inactive and:
- selector 2is not in the OFF position,
- the boiler is still connected to the mains supply,
the pump, the switching valve and the two-way valve activate briefly every 24 hours to keep them efficient.
1.4.6. Operation with (optional) remote control
The boiler can be linked to an (optional, can be supplied by the Producer) remote control, which can be used for setting numerous
parameters, including::
• boiler status;
• ambient temperature;
• CH system water temperature;
• DHW system water temperature;
• CH system activation times and storage activation times;
• boiler diagnostics display;
• boiler reset,
and other parameters.
For instructions on how to connect the remote control, refer to subsection 3.2.14.
Only original remote controls supplied by the manufacturer must be used.
If non-original remote controls are used, correct operation of the boiler, or of the remote control, cannot be
guaranteed.
1.4.7. Operationwithan(optional)externalprobe
The boiler can be connected to an (optional, can be supplied by the Producer) external temperature probe.
When the external temperature has been measured, the boiler automatically regulates the heating water temperature, increasing
it when the outside temperature drops and decreasing it when it rises, which improves comfort and saves fuel (this is referred to as
sliding temperature operation).
The heating water temperature varies according to a program in the boiler’s
microprocessor.
When an external probe is installed, regulator 4(fig. 1) looses its heating
water temperature function and becomes a fictitious ambient temperature
regulator (fig. 3) for the temperature desired in the areas to be heated.
During temperature setting, the fictitious ambient temperature symbol flashes and the
temperature setting is displayed.
Regulator 4in the fully anticlockwise position corresponds to a fictitious ambient temperature
of 15°C, 9 o’clock corresponds to 18°C, 12 o’clock to 25°C, 3 o’clock to 32°C and the fully clockwise
position to 35°C. To get an optimal curve, a setting of approximately 20°C is recommended.
 Onlyoriginalexternalprobessuppliedbythemanufacturermustbeused.
 Ifnon-originalexternalprobesareused,correctoperationoftheboiler,oroftheprobe,cannotbeguaranteed.
fig. 4
25
18 32
15 35
fig. 3
Figure 4 shows the curves for a fictitious
ambient temperature of 20°C.
When this value is increased or decreased
via regulator 4, the curves move up or
down, respectively, by the same amount.
With a temperature setting of 20°C,
for example, if you select the curve
corresponding to parameter 1 and the
external temperature is -4°C, the flow
temperature will be 50°C.
Flow temperature (°C)
External temperature (°C)
Thermoregulation
coefficient

13
Filling tap
fig. 5
1.5. Boiler shutdown
The boiler shuts down automatically if a malfunction occurs.
Refer to Tables 1 and 2 to identify the boiler operating mode.
Refer to Table 2 and section 6 to identify possible causes of the shutdown. The troubleshooting section is at the end of this manual.
Below is a list of kinds of shutdown and the procedure to follow in each.
1.5.1. Burner shutdown
If the burner shuts down as there is no flame, the burner shutdown symbol is displayed and code E01
flashes.
If this happens, proceed as follows:
• check that the gas cock is open and light a gas ring for example to check the gas supply;
• if the gas supply is normal, turn selector 2to the reset position for a few seconds, then back to the desired position. If after three
attempts the burner still fails to ignite, contact an Authorised Service Centre or a qualified service engineer.
If the burner shuts down frequently, there is a recurring malfunction, so contact an Authorised Service Centre or a qualified service
engineer.
1.5.2. Shutdown due to overheating
If the water temperature is too high, the boiler will shut down. The burner shutdown symbol is displayed
and code E02 flashes. Contact an Authorised Service Centre or a qualified service engineer.
1.5.3. Shutdown due to air/flue gas system malfunction
If the air/flue gas system malfunctions, the boiler shuts down. The burner shutdown symbol is displayed
and code E03 (for model BTN) or code E20 (for model BTFS) flashes.
Contact an Authorised Service Centre or a qualified service engineer.
1.5.4. Shutdown due to insufficient water pressure
If the water pressure in the heating system is too low, the water pressure switch activates and the boiler shuts down. The boiler
shutdown symbol is displayed and code E04 flashes.
Open the filling tap to fill the system (fig. 5). The pressure with the boiler cold must be 1-1.3 bar.
Proceed as follows to restore the correct water pressure:
• Turn the lling tap (g. 5) anticlockwise to allow water to aenter the boiler.
• Keep the tap open until the pressure gauge shows a value of 1-1.3 bar.
• Turn the tap clockwise to close it.
• If the boiler still does not work, turn selector 2to the RESET position for a few seconds, then back to the desired position.
If the boiler still fails to operate, contact an Authorised Service Centre or a qualified service engineer.
Make sure you close the tap carefully after filling.
If you do not, when the pressure increases, the safety valve may activate and discharge water.

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1.5.5. Alarm due to temperature probe malfunction
If the burner shuts down due to malfunction of the temperature probes, the boiler shutdown symbol is displayed and the
following codes may flash:
• E05, CH probe: the boiler does not work;
• E06, DHW probe: the boiler only operates in CH mode, not DHW mode;
• E12, storage probe; the boiler operates in CH and instantaneous DHW mode, not Aqua Premium mode.
Contact an Authorised Service Centre or a qualified service engineer.
1.5.6. Alarmduetoexternalprobemalfunction(optional)
If the (optional) external temperature probe malfunctions, the boiler shutdown symbol is displayed and
code E23 flashes.
The boiler will continue to operate, but the sliding temperature function is deactivated. The temperature of
the CH water is regulated according to the position of regulator 4(fig. 1), which in this case loses its function
as a fictitious ambient temperature regulator (see 1.4.7.).
Contact an Authorised Service Centre or a qualified service engineer.
1.5.7. Alarm due to gas valve modulator malfunction
If the gas valve modulator malfunctions, the boiler shutdown symbol is displayed and code E16 flashes.
The boiler will continue to operate, but at the minimum power available.
Contact an Authorised Service Centre or a qualified service engineer.
1.5.8. Alarm due to (optional) remote control connection malfunction
The boiler recognises whether or not there is a remote control (optional). If the remote control is connected
but the boiler does not receive instructions, the boiler shutdown symbol is displayed and code E22
flashes.
The boiler will continue to operate according to the settings on the control panel (fig. 1) and ignore the
remote control settings.
Contact an Authorised Service Centre or a qualified service engineer.
1.6. Maintenance
The boiler must be serviced periodically as indicated in the relevant section of this manual.
Correct maintenance of the boiler will allow it to work efficiently, without harming the environment, and in complete safety.
Maintenance and repairs must be performed by qualified personnel.
The user is strongly advised to have the boiler serviced and repaired by one of the Manufacturer’s fully qualified and authorised
Service Centres.
Refer to Section 5 – Maintenance for detailed instructions.
Theusermayonlycleantheexternalcasingoftheboiler,usingordinaryfurniturecleaningproducts.
Do not use water.
1.7. Notes for the user
The user may only access parts of the boiler that can reached without using special equipment or tools. The user is not
authorised to remove the boiler casing or to operate on any internal parts.
No one, including qualified personnel, is authorised to modify the boiler.
The manufacturer cannot be held liable for damage or injury due to tampering of the boiler or improper intervention.
If the boiler remains inactive and the power supply is switched off for a long time, it may be necessary to reset the pump.
This involves removing the casing and accessing internal parts, so it must only be done by suitably qualified personnel.
Pump failure can be avoided by adding to the water filming additives suitable for multi-metal systems.

15
2. TECHNICAL FEATURES AND DIMENSIONS
2.1. Technical features
This boiler has a built-in multi-gas atmospheric burner.
All versions come with electronic ignition, an ionization flame and an AQUA PREMIUM system for the production of DHW, with a 25-
litre stratification storage tank and a secondary plate heat exchanger.
The following versions are available:
BTN 24 a natural-draught open-flue boiler for CH and DHW, heat output 23.31 kW
BTFS 24 a forced-draught balanced-flue boiler for CH and DHW, heat output 23.8 kW
BTFS 28 a forced-draught balanced-flue boiler for CH and DHW, heat output 28.4 kW)
BTFS 32 a forced-draught balanced-flue boiler for CH and DHW, heat output 31.3 kW
These boilers meet all the requirements in the country of destination indicated on the rating plate.
Installation in a different country may cause a hazard for people, animals and property.
The main technical features of the boiler are given below.
Construction characteristics
• IPX4D electrically protected control panel
• Electronic safety board and integrated modulation
• Electronic ignition with separate igniter and ionization flame
detector
• Stainless steel multi-gas atmospheric burner
• Modulating double-shutter gas valve
• High output monothermal copper heat exchanger
• DHW stainless steel plate heat exchanger
• 25-litre vertical stratification storage tank with magnesium
anode
• Motorized switching valve
• 3-speed CH pump with built-in deaerator
• DHW pump
• 8-litre CH expansion vessel (models BTN 24 and BTFS 24) and
10-litre expansion vessel (models BTFS 28 and BTFS 32)
• 2-litre DHW expansion vessel
• Combustion fan (BTFS)
• Low-water pressure switch
• DHW priority ow switch
• DHW lter
• Adjustable bypass
• Boiler lling and drain cocks
• DHW, CH and storage tank temperature probes
• Safety limit thermostat
• Flue gas thermostat (BTN)
• Dierential pressure switch (BTFS)
• 3-bar CH safety valve
• 6-bar DHW safety valve
User interface
• Liquid crystal display showing the boiler operating status
• Mode selector: RESET, OFF, WINTER, SUMMER and ANTI-FREEZE
• CH water temperature regulator: 35-78°C
• DHW water temperature regulator: 35-57°C (also used to
(de)activate the AQUA PREMIUM system)
• Water pressure gauge
Operating features •
•CH electronic flame modulation with timer-controlled rising
ramp (50 seconds)
• DHW electronic flame modulation
• DHW priority function
• CH anti-freeze function (ON 5°C; OFF 30°C or after 15 minutes
of operation)
• DHW anti-freeze function (ON 5°C; OFF 10°C or after 15 minutes
of operation)
• Storage tank anti-freeze function (ON 5°C; OFF 10°C or after 15
minutes of operation)
• Anti-legionella function
• Timer-controlled chimney-sweep function (15 minutes)
• Ignition flame propagation function
• CH maximum heat input adjusting trimmer
• Ignition heat input adjusting trimmer
• Timer-controlled room thermostat (240 seconds with CH flow
temperature >40°C)
• Heating pump post-circulation function in CH, ANTI-FREEZE
and CHIMNEY-SWEEP mode (180 seconds)
• Heating pump post-circulation function in DHW mode (6
seconds, only with selector 2 on WINTER)
• Post-circulation function for heating temperature >85°C (30
seconds).
• Post-ventilation safety function (ON 95°C; OFF 90°C).
• Anti-blocking function for CH pump, DHW pump, switching
valve and 2-way valve (6-second operation every 24 hours of
boiler inactivity)
• Ready for connection to a room thermostat (optional)
• Ready for operation with an external probe (optional, supplied
by the manufacturer)
• Ready for operation with an OpenTherm remote control
(optional, supplied by the manufacturer)

16
2.2. Dimensions
GMCF
RRC
SV6 RSR
SV3
43 56 98 75 98 80
350
389
RSS
372
221
450
750
534
GGas inlet
MCH flow
CDHW outlet
FCold water inlet
RCH return
RC Filling tap
RSR CH drain tap
RSS Storage/DHW drain tap
SV3 3-bar safety valve (CH)
SV6 6-bar safety valve (DHW)
Mod. BTN
View from
below
fig. 6
View from
above

17
GMCF
RRC
SV6 RSR
SV3
30670
7196120
43 56 98 75 98 80
350
389
RSS
450
750
534
Mod. BTFS
View from
below
View from
above
fig. 7
GGas inlet
MCH flow
CDHW outlet
FCold water inlet
RCH return
RC Filling tap
RSR CH drain tap
RSS Storage/DHW drain tap
SV3 3-bar safety valve (CH)
SV6 6-bar safety valve (DHW)

18
2.3. Boiler layout
BOLLITORE
acqua fredda
acqua calda
SCAMBIATORE
Bruciatore
TS
PS
V3V
RUBINETTO
DI SCARICO
VASO ESP. RISCALDAMENTO
VALVOLA DI SICUREZZA
3bar
VALVOLA DI SICUREZZ
A
6 bar
VASO ESP.
SANITARIO
RITORNO RISCALDAMENTO
MANDATA RISCALDAMENTO
SONDA A PIASTRE
SONDA BOLLITORE
RUBINETTO
DI SCARICO
VM (2 vie)
PRESSOSTATO
ACQUA
M
M
F
RUBINETTO DI
RIEMPIMENTO
PR
SCAMBIATORE
SECONDARIO
A PIASTRE
SONDA RISCALDAMENTO
fig. 8
TS LIMIT THERMOSTAT
V3V MOTORIZED 3-WAY VALVE
VM MOTORIZED 2-WAY VALVE
PR CH PUMP WITH DEAERATOR
PS DHW PUMP
F PRIORITY FLOW SWITCH
CH probe
Heat exchanger
Burner
Filling tap
Drain tap
CH expansion vessel
3-bar safety valve
Water pressure
switch
CH return
CH flow
Plate heat exchanger
probe
Water storage tank
Water storage
tank probe
Hot water
Watern tank drain tap
6-bar safety valve
Cold water
DHW expansion vessel
Secondary plate
heat exchanger

19
2.4. Operating data
BTFS 24
Fuel Max.heatinput
(kW)
Min. heat
output
(kW)
Max.heat
output
(kW)
Gas mains
pressure (mbar)
Nozzle
diameter
(mm)
Burner pressure
(mbar)
min max
Methane gas G20 25.5 9.5 23.8 20 1.25 2.5 13.5
Butane gas G30 25.5 9.5 23.8 29 0.77 4.2 27.0
Propane gas G31 25.5 9.5 23.8 37 0.77 5.5 35.7
Table 4
Instantaneous DHW supply ΔT 45 K = 7.6 l/min
Instantaneous DHW supply ΔT 40 K = 8.5 l/min
Instantaneous DHW supply ΔT 35 K = 9.7 l/min
Instantaneous DHW supply ΔT 30 K = 11.4 l/min
Instantaneous DHW supply ΔT 25 K = 13.6 l/miin
BTFS 28
Fuel Max.heatinput
(kW)
Min. heat
output
(kW)
Max.heat
output
(kW)
Gas mains
pressure (mbar)
Nozzle
diameter
(mm)
Burner pressure
(mbar)
min max
Methane gas G20 30.5 10.0 28.4 20 1.35 1.3 11.5
Butane gas G30 30.5 10.0 28.4 29 0.80 3.5 28.5
Propane gas G31 30.5 10.0 28.4 37 0.80 4.5 33.0
Table 5
Instantaneous DHW supply ΔT 45 K = 9.0 l/min
Instantaneous DHW supply ΔT 40 K = 10.2 l/min
Instantaneous DHW supply ΔT 35 K = 11.6 l/min
Instantaneous DHW supply ΔT 30 K = 13.6 l/min
Instantaneous DHW supply ΔT 25 K = 16.3 l/min
BTFS 32
Fuel Max.heatinput
(kW)
Min. heat
output
(kW)
Max.heat
output
(kW)
Gas mains
pressure (mbar)
Nozzle
diameter
(mm)
Burner pressure
(mbar)
min max
Methane gas G20 33.6 12.2 31.3 20 1.40 1.7 9.2
Butane gas G30 33.6 12.2 31.3 29 0.78 4.1 28.2
Propane gas G31 33.6 12.2 31.3 37 0.78 5.5 34.8
Table 6
Instantaneous DHW supply ΔT 45 K = 10.0 l/min
Instantaneous DHW supply ΔT 40 K = 11.2 l/min
Instantaneous DHW supply ΔT 35 K = 12.8 l/min
Instantaneous DHW supply ΔT 30 K = 15.0 l/min
Instantaneous DHW supply ΔT 25 K = 17.9 l/min
Burner pressures must be checked after 3 minutes of boiler operation.
BTN 24
Fuel Max.heatinput
(kW)
Min. heat
output
(kW)
Max.heat
output
(kW)
Gas mains
pressure (mbar)
Nozzle
diameter
(mm)
Burner pressure
(mbar)
min max
Methane gas G20 25.7 9.85 23.31 20 1.25 2.5 13.0
Butane gas G30 25.7 9.85 23.31 29 0.77 5.3 27.0
Propane gas G31 25.7 9.85 23.31 37 0.77 6.6 35.5
Table 3
Instantaneous DHW supply ΔT 45 K = 7.4 l/min
Instantaneous DHW supply ΔT 40 K = 8.4 l/min
Instantaneous DHW supply ΔT 35 K = 9.5 l/min
Instantaneous DHW supply ΔT 30 K = 11.1 l/min
Instantaneous DHW supply ΔT 25 K = 13.4 l/min
Note: DHW supply refers to instantaneous production.

20
BTN 24 BTFS 24 BTFS 28 BTFS 32
Boiler category - II2H3+ II2H3+ II2H3+ II2H3+
Number of burner nozzles - 12 12 13 15
Minimum CH pressure bar 0.5 0.5 0.5 0.5
Maximum CH pressure bar 3 3 3 3
Minimum DHW pressure bar 0.5 0.5 0.5 0.5
Maximum DHW pressure bar 8 8 8 8
DHW specific flow rate (ΔT 30K) l/10’ 155 160 180 200
Power supply – voltage/frequency V ~ Hz 230 ~ 50 230 ~ 50 230 ~ 50 230 ~ 50
Power mains fuse A 2 2 2 2
Maximum power consumption W 140 180 200 230
Index of protection IP X4D X4D X4D X4D
Methane gas consumption at maximum flow (*) m3/h 2.72 2.70 3.23 3.46
Butane gas consumption at maximum flow kg/h 2.02 2.01 2.40 2.62
Propane gas consumption at maximum flow kg/h 1.99 1.98 2.37 2.51
Maximum CH operating temperature °C 83 83 83 83
Maximum DHW operating temperature °C 62 62 62 62
Total capacity of expansion vessel l 8 8 10 10
Maximum recommended CH system capacity (**) l 160 160 200 200
Table 7
(*) Value refers to 15°C - 1013 mbar.
(**) Maximum water temperature = 83°C. Expansion vessel pressure pre-charge = 1 bar.
BTN 24 Maxoutput Min output 30% output
Outer casing heat loss % 0.8 0.8 -
Flue system heat loss with burner on % 8.5 9.7 -
Flue system mass capacity g/s 16.2 13.7 -
Flue temp. - Air temp. °C 85 50 -
CO2% 6.2 3.0 -
Boiler efficiency rate % 90.7 89.5 88.7
Efficiency class (acc. to 92/42/CE) - * *
NOx emissions class - 2
Table 8
BTFS 24 Maxoutput Min output 30% output
Outer casing heat loss % 0.23 0.23 -
Flue system heat loss with burner on % 6.57 9.67 -
Flue system mass capacity g/s 14.0 14.4 -
Flue temp. - Air temp. °C 75 67 -
CO2% 7.2 2.8 -
Boiler efficiency rate % 93.2 90.1 90.2
Efficiency class (acc. to 92/42/CE) - * * *
NOx emissions class - 2
Table 9
BTFS 28 Maxoutput Min output 30% output
Outer casing heat loss % 0.23 0.23 -
Flue system heat loss with burner on % 6.67 8.87 -
Flue system mass capacity g/s 18.2 18.7 -
Flue temp. - Air temp. °C 75 45 -
CO2% 6.6 2.1 -
Boiler efficiency rate % 93.1 90.9 90.4
Efficiency class (acc. to 92/42/CE) - * * *
NOx emissions class - 2
Table 10
BTFS 32 Maxoutput Min output 30% output
Outer casing heat loss % 0.23 0.23 -
Flue system heat loss with burner on % 6.67 9.77 -
Flue system mass capacity g/s 18.9 19.2 -
Flue temp. - Air temp. °C 92 45 -
CO2% 6.9 2.5 -
Boiler efficiency rate % 93.1 90.0 90.3
Efficiency class (acc. to 92/42/CE) - * * *
NOx emissions class - 2
Table 11
2.5. Technical specifications