DOMUSA TEKNIK Dualtherm 25 User manual

INSTALLATION AND OPERATING INSTRUCTIONS
DUALTHERM

Thank you for choosing a DOMUSA TEKNIK heating boiler. Within the
product range offered by DOMUSA TEKNIK you have chosen DualTherm
model. With a suitable hydraulic installation and with a correct fuel, this
boilerwillprovidetheideallevelofcomfortforyourhome.
This manual forms an essential part of the product and it must be given to
the user. We recommend you read the warnings and recommendations in
the manual carefully, as they contain important information on the safety,
useand maintenance of the installation.
These boilers must be installed by qualified personnel only, in accordance
withthe legislation in force and following the manufacturer’s instructions.
Commissioning of these boilers and any maintenance operations must
only be carried out by DOMUSA TEKNIK’s Authorised Technical
AssistanceServices.
Incorrect installation of these boilers could result in damage to people,
animals or property, and the manufacturer will hold no liability in such
cases.
DOMUSA TEKNIK informs all parties concerned that, in compliance with
section 1 of the first additional provision of Law 11/1997, the
responsibility for delivering packaging waste or used packaging for its
proper environmental management will be that of the final owner of the
product (Article 18.1 Royal Decree 782/1998). At the end of its useful life,
the product must be taken to a selected collection point for electrical and
electronic equipment or must be returned to the distributor at the time of
purchasing a new equivalent appliance. For more detailed information on
the collection schemes available, contact either the collection facilities of
thelocal authority or the distributor where the purchase was made.

1
INDEX Page
1LIST OF COMPONENTS.....................................................................................................................................................4
2CONTROL COMPONENTS................................................................................................................................................5
3INSTALLATION INSTRUCTIONS.....................................................................................................................................6
3.1LOCATION.............................................................................................................................................................................................6
3.2HYDRAULIC INSTALLATION..................................................................................................................................................................6
3.3INSTALLING THE TEMPERATURE RELIEF SAFETY VALVE ......................................................................................................................7
3.4INSTALLING A SANIT HOT WATER TANK (OPTIONAL)........................................................................................................................8
3.5FEED AUGER..........................................................................................................................................................................................9
3.6ELECTRICAL CONNECTION.................................................................................................................................................................10
3.7COMBUSTION GAS EXHAUST.............................................................................................................................................................10
3.8BIOHYDRAULIC KIT INSTALLATION...................................................................................................................................................11
3.9INSTALLATION WITH A BTBUFFER TANK .........................................................................................................................................12
3.10INSTALLATION WITH A BT-DUOBUFFER TANK (OPTIONAL).......................................................................................................15
4FUEL .....................................................................................................................................................................................18
4.1WOODEN PELLET................................................................................................................................................................................18
4.2FIREWOOD..........................................................................................................................................................................................18
4.3UNSUITABLE FUEL ..............................................................................................................................................................................19
5COMMISSIONING OF THE BOILER.............................................................................................................................20
5.1PRIOR WARNINGS...............................................................................................................................................................................20
5.2ELECTRICAL CONNECTION.................................................................................................................................................................20
5.3FILLING THE INSTALLATION ...............................................................................................................................................................20
5.4INITIAL CALIBRATION OF THE FEED AUGER .......................................................................................................................................20
5.5COMMISSIONING................................................................................................................................................................................21
5.6EXPLANATION TO FINAL USER...........................................................................................................................................................21
6DIGITAL DISPLAY.............................................................................................................................................................22
7COMBUSTION MODES...................................................................................................................................................25
7.1SELECTING AND CHANGING COMBUSTIONMODES........................................................................................................................25
7.2MODE 1(PELLET ONLY).....................................................................................................................................................................25
7.3MODE 2(COMBINED MODE)............................................................................................................................................................26
7.4MODE 3(AUTOMATIC FIREWOOD)...................................................................................................................................................27
7.5MODE 4(MANUAL FIREWOOD)........................................................................................................................................................28
8OPERATION........................................................................................................................................................................29
8.1“ONLY HEATING”OPERATION ...........................................................................................................................................................29
8.2OPERATING WITH A SANIT DHWTANK (OPTION)..........................................................................................................................29
8.3BOILER TEMPERATURE SET POINT SELECTION...................................................................................................................................30
8.4DHWTEMPERATURE SET POINT SELECTION (WITH DHWTANK INSTALLED ONLY)......................................................................30
8.5SELECTING THE SET POINT TEMPERATURE OF THE BUFFER TANK (ONLY WITH BUFFER TANK)......................................................31
8.6FUNCTIONING ACCORDING TO OUTDOOR TEMPERATURE CONDITIONS OTC(OPTION).............................................................31
9OPERATING WITH BIO HYDRAULIC KITS (OPTIONAL)........................................................................................32
10 OPERATION WITH ABT BUFFER TANK..................................................................................................................33
10.1OPERATION WITH A TEMPERATURE SENSOR IN THE BTBUFFER TANK (P.08=1OR 2).............................................................33
10.2OPERATION WITH A CONTROL THERMOSTAT IN THE BTBUFFER TANK (P.08=3OR 4)............................................................34
11 OPERATION WITH A BT-DUO BUFFERTANK (OPTIONAL)..............................................................................35
12OPERATING WITH LAGO FB OT+ REMOTE CONTROL (OPTIONAL)............................................................36
13USER MENU.....................................................................................................................................................................37
14SETUP MENU...................................................................................................................................................................39
14.1TIMERS PROGRAMMING PROCESS...................................................................................................................................................40
14.2BOILER TIMER PROGRAMMING........................................................................................................................................................40
14.3CVSSUCTION SYSTEM TIMER PROGRAMMING (CVSSUCTION SYSTEM OPTION ONLY)............................................................40
14.4DHWRECIRCULATION FUNCTION TIMER PROGRAMMING (DHWTANK OPTION ONLY)............................................................41
14.5TIME SETTING ...................................................................................................................................................................................41
14.6MANUAL SETTING OF FEED AUGER CALIBRATION..........................................................................................................................41
14.7SCREEN CONTRAST SETTING............................................................................................................................................................41

DualTherm
2
15CALIBRATION MENU....................................................................................................................................................42
15.1FEED AUGER FILLING........................................................................................................................................................................43
15.2FEED AUGER CALIBRATION..............................................................................................................................................................44
15.3MANUAL SETTING OF FEED AUGER CALIBRATION..........................................................................................................................45
15.4MANUAL ASH CLEANING ACTIVATION............................................................................................................................................45
15.5MANUAL CIRCULATION PUMPS ACTIVATION.................................................................................................................................45
16TECHNICAL MENU........................................................................................................................................................45
16.1ENTRY AND SET THE ACCESS CODE ("COD",P.25)........................................................................................................................48
17BOILER'S SETUP PARAMETERS.................................................................................................................................49
17.1BOILER MODEL (P.01)....................................................................................................................................................................49
17.2BOILER HEAT OUTPUT (P.02,P.03)...............................................................................................................................................49
17.3GENERAL FAN SPEED FACTOR (P.04).............................................................................................................................................49
17.4FUEL FOR IGNITION (P.05)..............................................................................................................................................................49
17.5FUEL CONSUMPTION (P.06)...........................................................................................................................................................49
17.6MANAGING BTAND BT-DUOBUFFER TANKS (P.08,P.28)........................................................................................................50
17.7BOILER MINIMUM TEMPERATURE MODE (P.13,P.14)..................................................................................................................50
17.8FIREWOOD FIRING POWER ADJUSTMENT (P.32)...........................................................................................................................50
17.9MINIMUM FIREWOOD COMBUSTION POWER ADJUSTMENT (P.33)..............................................................................................50
17.10FAN SPEED DURING MANUAL FIREWOOD FIRING (P.34)............................................................................................................50
18HEATING CIRCUIT'S SETUP PARAMETERS............................................................................................................51
18.1HEATING PUMP POST-CIRCULATION TIME (P.15).........................................................................................................................51
18.2BOILER'S PUMP OPERATING MODE (P.18).....................................................................................................................................51
18.3MINIMUM BOILER WATER PRESSURE (P.19)..................................................................................................................................51
18.4MAXIMUM HEATING FLOW TEMPERATURE OF MIXED CIRCUITS (P.27).......................................................................................51
19DHW CIRCUIT'S SETUP PARAMETERS....................................................................................................................51
19.1DHWINSTALLATION MODE (P.09)................................................................................................................................................52
19.2DHWPUMP POST-CIRCULATION TIME (P.16)...............................................................................................................................52
19.3LEGIONELLA PROTECTION FUNCTION (P.17).................................................................................................................................52
19.4DHWRE-CIRCULATION FUNCTION (P.20=2).............................................................................................................................52
20ADDITIONAL FUNCTIONS..........................................................................................................................................52
20.1CVSSUCTION SYSTEM CYCLE TIME (P.22)....................................................................................................................................52
20.2RESET DEFAULT VALUES (P.24)......................................................................................................................................................52
20.3PUMPS ANTI-LOCK FUNCTION.........................................................................................................................................................52
20.4ANTI-FROST FUNCTION....................................................................................................................................................................53
20.5BOILER PRESSURE SENSOR FUNCTION............................................................................................................................................53
20.6CONNECTING THE LAGOFBOT+REMOTE CONTROL.................................................................................................................53
20.7ROOM THERMOSTAT CONNECTION................................................................................................................................................53
21MULTI-FUNCTIONAL RELAY (P.20).........................................................................................................................54
21.1BOILER ALARMS EXTERNAL SIGNAL (P.20=1).............................................................................................................................54
21.2DHWRE-CIRCULATION FUNCTION (P.20=2).............................................................................................................................54
21.3AUTOMATIC WATER FILLING FUNCTION (P.20=3)......................................................................................................................54
22CLEANING THE ASH DRAWER..................................................................................................................................55
22.1SAFETY WARNINGS:.........................................................................................................................................................................55
23AIR ADJUSTMENT.........................................................................................................................................................56
24SAFETY LOCK-OUTS.....................................................................................................................................................57
24.1WATER OVERHEAT SAFETY CUT-OUT (E-11).................................................................................................................................57
24.2FUEL INLET TUBE OVERHEAT SAFETY LOCK-OUT (E-05)...............................................................................................................57
24.3LOW PRESSURE LOCK-OUT..............................................................................................................................................................58
25 SHUTTING DOWN THEBOILER.................................................................................................................................58
26EMPTYING THE BOILER...............................................................................................................................................58
27BOILER MAINTENANCE...............................................................................................................................................59
27.1FREQUENCY OF MAINTENANCE OF THE BOILER AND CHIMNEY....................................................................................................59
27.2BURNER CLEANING PROCEDURE .....................................................................................................................................................60
27.3CLEANING THE VENTS AND REAR ASH DRAWER.............................................................................................................................61
27.4CLEANING OF THE FIRST STEP OF SMOKE.......................................................................................................................................62

3
27.5FUME TEMPERATURE SENSOR .........................................................................................................................................................62
27.6DRAINING THE CONDENSATE WATER .............................................................................................................................................62
27.7BOILER WATER CHARACTERISTICS...................................................................................................................................................63
28DIAGRAMS AND MEASUREMENTS.........................................................................................................................64
29CONNECTIONS DIAGRAM.......................................................................................................................................... 65
29.1BOILER ..............................................................................................................................................................................................65
29.2BURNER.............................................................................................................................................................................................66
30ELECTRICAL DIAGRAM................................................................................................................................................67
31TECHNICAL DATA.........................................................................................................................................................68
32 CIRCULATION PUMP AND PRESSUREDROP....................................................................................................... 69
32.1HIGH EFFICIENCY CIRCULATION PUMP...........................................................................................................................................69
33 SPARE PARTS LIST.........................................................................................................................................................71
34ALARM CODES...............................................................................................................................................................84

DualTherm
4
1LISTOFCOMPONENTS
1
8
7
3
4
5 6
9
2
10
1112
1.Feedauger.
2.Heatexchanger.
3.Flueoutlet
4.Fan.
5.Heatexchanger cleaning system.
6.Waterpressure sensor.
7.AutomaticAir vent.
8.Sensorsheath.
9.Fuelinlet safety thermostat.
10.Ashtray.
11.Burner.
12.Airpressure sensor.

5
2CONTROLCOMPONENTS
17 18 2019
1514 16
14. MENU touch button:
This button is used to access and browse
throughthe "User Menu".
15. Digital display:
It is the main boiler functioning display, on
which all the operating information, settings
and values appear. This display is also used to
access the appliance's user and service settings.
In standard operating mode (default display),
the actual boiler temperature is shown. If
malfunction occurs, an alarm code will appear
on the digital display instead of the
temperature.
16. RESET touch button:
This button is used to restore functioning of the
boiler after a lock-out situation. Also it is used to
exit from any of the menus or parameters of the
boiler without saving it and to return to the
previousmenu level.
17. ON touch button:
Thisbutton switches on and off the boiler.
18. Boiler temperature touch button:
This button is used to select the boiler set point
temperature. It is also used to disable the hot
waterfunction.
19. DHW temperature touch button:
This button is used to select the desired
domestic hot water set point temperature (only
if a DHW tank is connected to the boiler). It is
alsoused to disable the DHW function.
20. SET touch button:
This button is used to access and browse
through the "Setup menu". Touch this button to
accessthe settings options.

DualTherm
6
3INSTALLATIONINSTRUCTIONS
The boiler must be installed by authorised personnel in compliance with the applicable laws and
regulations.
This boiler is suitable for heating water to a temperature below boiling point at atmospheric pressure.
It must be connected to a heating installation and/or a domestic hot water distribution network,
whichmust always be compatible with its performance and power.
This appliance must only be used for the purpose for which it has been expressly designed. Any other
use is considered unsuitable and therefore hazardous. The manufacturer shall not be considered liable
under any circumstances for damagecaused by unsuitable,erroneous or irrational use.
Remove all the packaging and check the contents are complete. In case of doubt, do not use the
boiler. Contact your supplier. Keep the packaging elements out of reach of children, as they can be
dangerous.
When you no longer wish to use the boiler, disable the parts that could be a potential source of
hazard.
3.1 Location
The boiler must be installed in a sufficiently ventilated site, away from humidity. It must be located
so that the air grilles on the premises are not obstructed and normal boiler maintenance is possible
even if it is placed between items of furniture. Therefore, a free distance of at least a half metre
should be left between the reserve tank and the wall, as well as a free distance of one metre above
theboiler.
If, for transport reasons, the boiler volume must be reduced, it is possible to separate the boiler-
hopperbody assembly. To do this, release the pellet burner connectors.
3.2 Hydraulic installation
The hydraulic installation must be made by qualified personnel. The applicable installation
legislation is to be complied with, and the following recommendations should also be taken into
account:
- The inside of the installation piping should be thoroughly cleaned before switching on the
boiler.
- It is recommended inserting cut-off valves between the installation piping and the boiler to
simplifymaintenance tasks.
- Leavea free space around the boiler for carrying out any maintenanceand repair operations.
- Drain valves and suitable devices for correctly bleeding the air from the circuit during the boiler
fillingstage should be fitted.
- Install all the necessary safety elements (expansion vessel, safety valve, etc.) to comply with the
applicableregulations for the installation.
- If the boiler is installed at a lower height than the heating installation, it is recommended to
create a siphon at the boiler outlet, to prevent the installation from heating up due to natural
convectionwhen heating is not required.
- It is advisable to install an buffer. The minimum volume of the buffer tank must be calculated
basedon Standard EN 303-5.

7
• It is imperative and obligatory to install a heating water buffer when the heating system
has a mixed circuit for under-floor heating (see “Example of installation of a buffer”). The
minimumvolume of the buffer tank should be calculated based on StandardEN 303-5.
• It is obligatory and essential to install a device for raising the return temperature up to
65ºC, to prevent any water condensation in the heat exchanger. If this requirement is not
complied with, DOMUSA TEKNIK's guarantee of the appliance will automatically be null and
void.
• It is obligatory to install a thermal discharge valve tared at 95-97ºC (optionally supplied by
DOMUSA TEKNIK). To correctly install the boiler, carefully follow the instructions given in
section “Installing the temperature relief safety valve”. If this requirement is not complied with,
DOMUSA TEKNIK's guaranteeof the appliance will automatically be null and void.
3.3 Installing the temperature relief safety valve
In order to avoid the temperature inside the boiler reaching damaging levels, this valve opens and
lets the mains water supply pass through the interior coil, thereby dispelling the heat. This occurs
when, for hydraulic reasons or due to lack of electric power supply, the boiler cannot dispel the
heat it is generating. The valve is obligatory in DualTherm boiler installations.
1
2
3
2-5 bar
1
2
3
1. Thermostaticsheath
2. Mainswater inlet 3. Drain water outlet
The valve is regulated by the hot water from the boiler. If the water temperature is higher than
95ºC, the valve lets the mains water go through the interior coil. This water moving in the coil
absorbsthe boiler heat, preventing overheating and damage the boiler.
The thermal discharge valve should be connected to the tundish. The connection must not be
blocked manually. Furthermore, access must be granted to the heat protection mechanism and to
the cleaning inspection, once assembled. The minimum connection pressure for the safety heat
exchangeris 2 bars. The nominal pressure of the valve is 5bars.
The temperature relief valve is installed upstream of the coil (placed respecting the flow direction
according to the arrow on the coil). The mains water supply must be connected directly to the
temperature relief valve. The immersion sheath should be placed in the appropriate socket, as
shownin the diagram.
IMPORTANT: It should not be possible to close the supply pipe so as to avoid any accidental
blockage.
IMPORTANT: The cold water pressure should not depend on the power supply.
IMPORTANT: The pipe must be thoroughly washed before installation.

DualTherm
8
3.4 Installing a Sanit hot water tank (Optional)
For a correct electrical connection of a Sanit DHW tank with DualTherm boiler, these steps should
befollowed:
- Unplug the boiler from the mains.
- Connect a DHW temperature sensor (supplied optionally) to the sensor terminal strip J7 (Sa;
terminals18 and 19) (see " ConnectionsDiagram ").
- Insertthe temperature sensor bulb in the bulb-holder sheath provide on thehot water tank.
- Connect the 3-way DHW diverter valve or the hot water tank pump (depending on the
installation, modify parameter P.09) to the supply terminal strip J3 (BA; terminals 6and N) (see
" ConnectionsDiagram ").
The hydraulic installation for the 3-way DHW diverter valve should be made so that the heating
circuitcan flow through the valve when it is in rest position(not energised):
HEATING
BOILER
D.H.W.
NC
V3V (BA)
OPTION WITH V3V
HEATING (BC)
BOILER
OPTION WITH 2 NORMALLY OPEN PUMPS
D.H.W. (BA)
(BA)
NO
For the installation with 2 pumps, a hydraulic separator or buffer tank must be installed between
theboiler and the DHW tank.
For correct hydraulic installation of the DHW tank, carefully follow the assembly and connection
instructionsenclosed with the same.

9
3.5 Feed auger
TheDualTHerm boiler is equipped with a hopper for pellet storing.
1
2
3
4
1
23
4
NOTE: The screws to fasten the hopper with the boiler are contained in the documentation
bag.
NOTE: Position the flexible hose in such a way as to allow the feeding of the pellets with
the least possible resistance to the burner.

DualTherm
10
3.6 Electrical Connection
The boiler is suitable for a 230 V~, 50 Hz to terminals 1and 2of terminal strip J1 (see “ Electrical
ConnectionDiagram ”).The ground terminal should also be connected.
The boiler has a strip TA1(J6), prepared for connecting a room thermostat or room
chronothermostat (see Electrical Connection Diagram ) for remote control of the heating circuit. To
correctly connect the room thermostat, remove the bridge joining the terminals on the strip TA1.
Optionally, connection strip J5 can be connected to a Lago FB OT for controlling remotely the DHW
andcircuits (see “ Useof LAGO FBOT ”).
The terminal strip J2 includes terminals for connecting the feed auger, whereas the terminal strip J3
includes terminals for connecting the circulation pump of the boiler (BC) and the 3-way diverter
valve (or circulation pump) for the optional DHW circuit. The terminal strip J7 includes terminals for
connecting a sensor for the optional DHW circuit. This sensor must be supplied by DOMUSA
TEKNIK.
IMPORTANT: Before carrying out any work on the boiler's electrical installation, always ensure
it is disconnected from the mains.
3.7 Combustion gas exhaust
The DualTherm boiler is a biomass boiler and it must be connected to a flue, i.e. a smoke duct able
to create a pressure drop (which in this case should be minimum 0,15 mbar), in compliance with
theapplicable laws to this regard.
The combustion product exhaust ducts must be installed by qualified personnel and must comply
with the regulations in force. For the flue to create a pressure drop, the following recommendations
shouldbe taken into account:
- Theflue should be thermally insulated.
- Itshould be independently located, with a separate flue for each boiler.
- Itshould be vertical, avoiding any angles greater than 45º.
- It should always have the same diameter. It is recommendable for it to be circular, and never
anynarrower than the boiler outlet.
- It is obligatory to install a fume inspection plate with a condensate collector, to remove the
condensation generated in the flue. Otherwise, the condensation may reach the inside of the
boiler and cause irreparable damage, which would not be covered by DOMUSA TEKNIK’s
guarantee. The condensation pipe should lead to a drain outlet, as a large amount of water
may be generated. This connection must be made in compliance with the regulations for
draining off condensation waterto the drain network.
- It is recommended to install a draught stabiliser to prevent any pressure drop variations in
the flue due to atmospheric conditions, which could affect correct boiler combustion. This
draught stabiliser must be installed below the fume inspection plate to prevent any
leakage of combustion gases.

11
3.8 BIO hydraulic kit installation
Optionally, a BIO hydraulic kit, within the kits range offered by DOMUSA TEKNIK, could be
connected to DualTherm boiler. In that way the features of the boiler will be increased. It is
imperative and obligatory to install a buffer tank when the heating system has a mixed circuit
for under-floor heating (see“ Exampleof installation ofabuffer ” ).
Lookat the following instructions for a correct installation:
-Unplug the boiler and the hydraulic kit from the main power supply.
- Connect the communication between the boiler and BIO hydraulic kit. Use the cable of two
wires with two connectors (+A –B) supplied with the kit (documentation bag). To assure the
correct running of BIO hydraulic Kit it is essential to respect the polarity of the connection.
The same wire must be connected to the +A terminal of the boiler as well as to the +A
terminal of the hydraulic Kit. Same operation with the –B terminals as it is shown in the
picture below.
- After connecting the boiler and the hydraulic Kit, plug the BIO hydraulic Kit to the main power
supply. It is recommended to plug the Kit before the boiler to ensure the correct performance
ofthe system.
-Plug the boiler to the main power supply.
DualTherm
-B
+A
KITBIO
+A -B
Followthe instructions provided with the kit to assure a correct installation.
IMPORTANT: It is compulsory to respect the polarity of both wires of the cable to assure a
correct performance of BIO hydraulic Kit.
NOTE: It is recommended to plug the kit before the boiler to assure a correct performance.

DualTherm
12
3.9 Installation with a BT Buffer Tank
The DualTherm boiler can be installed with a BT Buffer Tank during the installation from the wide
range offered by DOMUSA TEKNIK, which may increase the benefits provided by the boiler in the
heatingservice.
For this reason, the electronic control of the boiler is equipped with an input for a temperature
sensor or a temperature thermostat (Sbt; terminals 18-19 on connection strip J7) and a circulation
pump output (Bbt; terminals N-7 on the connection strip J2) dedicated exclusively to managing the
heating of the buffer tank. Using these control elements of the boiler it is possible to manage 4
different modes of buffer tank hydraulic installation. The installation type will be selected using
parameterP.08 in the "Technician" menu on the control panel.
The boiler is supplied with this installation option disabled. To enable it, the electrical resistance
(Rbt) connected between terminals 20 and 21 of connection strip J7 (see "Connection Diagram")
must be removed and replaced with a temperature sensor (supplied as an option by DOMUSA
TEKNIK) or a control thermostat installed in the BT buffer tank. After disconnecting the P.08
parameter "Technician" menu of the control panel must be enabled, from where you can select the
installationmode desired.
3.9.1 Installation with Sanit DHW tank after BT tank and control by temperature sensor (P.08 = 1)
In this installation mode, all heating circuits, as well as the circuit for DHW production by
accumulation must be hydraulically connected to the BT buffer tank. In other words, as shown in
the following hydraulic diagram, the BT buffer tank is connected to the boiler, interposing a
circulation pump (Bbt), and all the heating circuits of the system are connected to the BT tank. The
temperature of the BT tank is controlled and managed by a temperature sensor (Sbt) immersed in
the buffer tank and electrically connected to the boiler. The temperature sensor is optionally
suppliedby DOMUSA TEKNIK.
Heating
Installation +
DHW
After the hydraulic installation of all the system components, proceed as follows to carry out the
correct electricalconnection of theBT buffer tankto the BioClass HM boiler:
- Unplug the boiler from the mains.
- Disconnect the electrical resistance (Rbt) connected between terminals 20 and 21 of
connectionstrip J7 (see"Connection Diagram") .
- Connect the BT tank temperature sensor (supplied optionally) to the sensor connection strip J7
(Sbt; terminals 20and 21) (see"Connection Diagram") .
- Insertthe temperature sensor bulb in the bulb-holder sheath provided in thebuffer tank.
- Connect the BT tank feed pump to the terminal strip J2 (Bbt; terminals Nand 7)
(see
"ConnectionDiagram")
.
- Connectthe boiler to the mains power.

13
- Using the control panel, access parameter P.08 in the "Technician" menu (see "Technician
Menu") and set the value to "1".
- If it is necessary,set the parameter P.28"BT buffer tank temperature hysteresis".
Once the hydraulic and electrical connections described above have been completed, read
carefully the section "Operation with a BT buffer tank" to adjust and configure the BT buffer tank
operation.
3.9.2 Installation with Sanit DHW tank before BT tank and control by temperature sensor
(P.08 = 2)
In this installation mode, all heating circuits must be hydraulically connected to the BT buffer tank,
and the circuit for producing DHW by accumulation should be hydraulically connected to the
boiler, upstream from the BT buffer tank. The BT buffer tank and the Sanit DHW tank, if present, are
connected in parallel to the boiler. Depending on the type of installation of the DHW tank
(installation with DHW diverter valve or with a DHW pump), the BT tank feed pump (Bbt) will be
installed as indicated in the following hydraulic diagrams. The temperature of the BT tank is
controlled and managed by a temperature sensor (Sbt) immersed in the buffer tank and electrically
connectedto the boiler. The temperature sensor is optionally supplied by DOMUSATEKNIK.
Heating
Installation
After the hydraulic installation of all the system components, proceed as follows to carry out the
correct electricalconnection of theBT buffer tankto the DualThermboiler:
- Unplug the boiler from the main.
- Disconnect the electrical resistance (Rbt) connected between terminals 20 and 21 of
connectionstrip J7 (see"Connection Diagram") .
- Connect the BT tank temperature sensor (supplied optionally) to the sensor connection strip J7
(Sbt; terminals 20and 21) (see"Connection Diagram") .
- Insertthe temperature sensor bulb in the bulb-holder sheath provided in thebuffer tank.
- Connect the BT tank feed pump to the component connection strip J2 (Bbt; terminals Nand 7)
(see"Connection Diagram") .
- Connectthe boiler to the mains.
- Using the control panel, access parameter P.08 in the "Technician" menu (see "Technician
Menu") and set the value to "2".
- After that, ifit is necessary,set also theparameter P.28 "BT buffertank temperature hysteresis".
For the correct hydraulic and electrical installation of a Sanit DHW tank with a DualTherm boiler,
carefullyfollow the directions in the section "Installinga Sanit tank" in this manual.

DualTherm
14
Once the hydraulic and electrical connection described above has been completed, to adjust and
configure the BT buffer tank operation, carefully read the section "Operation with a BT buffer tank"
inthis manual.
3.9.3 Installation with Sanit DHW tank after BT tank and control by thermostat (P.08 = 3)
In this installation mode, all heating circuits, as well as the circuit for producing DHW by
accumulation, if present, must be hydraulically connected to the BT buffer tank. In other words, as
shown in the following hydraulic diagram, the BT buffer tank is connected to the boiler, interposing
a circulation pump (Bbt), and all the heating circuits of the system are connected to the BT tank.
The temperature of the BT tank is controlled and managed by a thermostat (Tbt) installed and
immersed in the buffer tank and electrically connected to the boiler. The temperature control
thermostat is not supplied by DOMUSA TEKNIK but can be purchased at any specialist central
heatingsupplies warehouse.
Heating
Installation +
DHW
After the hydraulic installation of all the system components, proceed as follows to carry out the
correct electricalconnection of theBT buffer tankto the BioClass HM boiler:
- Unplug the boiler from the mains.
- Disconnect the electrical resistance (Rbt) connected between terminals 20 and 21 of
connectionstrip J7 (see"Connection Diagram") .
- Connect the NC contact (normally closed) on the BT tank control thermostat on the sensor
connectionstrip J7 (Sbt; terminals 20 and 21) (see"Connection Diagram") .
- Insertthe thermostat bulb into the bulb-holder sheath provided in the buffertank.
- Connect the BT tank feed pump to the component connection strip J2 (Bbt; terminals Nand 7)
(see"Connection Diagram") .
- Connectthe boiler to the mains power.
- Using the control panel, access parameter P.08 in the "Technician" menu
(see "Technician
Menu")
and set the value to "3".
Once the hydraulic and electrical connection described above has been completed, to adjust and
configure the BT buffer tank operation, carefully read the section "Operation with a BT buffer tank"
inthis manual.
3.9.4 Installation with Sanit DHW tank before BT tank and control by thermostat (P.08 = 4)
In this installation mode, all heating circuits must be hydraulically connected to the BT buffer tank,
and the circuit for producing DHW by accumulation should be hydraulically connected to the
boiler, upstream from the BT buffer tank. In other words, the BT buffer tank and the Sanit DHW tank,
if present, are connected in parallel to the boiler. Depending on the type of installation of the DHW
tank (installation with DHW diverter valve or with a DHW feed pump), the BT tank feed pump (Bbt)
will be installed as indicated in the following hydraulic diagrams. The temperature of the BT tank is

15
controlled and managed by a thermostat (Tbt) installed and immersed in the buffer tank and
electrically connected to the boiler. The temperature control thermostat is not supplied by
DOMUSATEKNIK but can be purchased at any specialist central heating supplieswarehouse.
Heating
Installation
After the hydraulic installation of all the system components, proceed as follows to carry out the
correct electricalconnection of theBT buffer tankto the DualThermboiler:
- Unplug the boiler from the mains power.
- Disconnect the electrical resistance (Rbt) connected between terminals 20 and 21 of
connectionstrip J7 (see"Connection Diagram") .
- Connect the NC contact (normally closed) on the BT tank control thermostat on the sensor
connectionstrip J7 (Sbt; terminals 20 and 21) (see"Connection Diagram") .
- Insertthe thermostat bulb into the bulb-holder sheath provided in the buffertank.
- Connect the BT tank feed pump to the component connection strip J2 (Bbt; terminals Nand 7)
(see"Connection Diagram") .
- Connectthe boiler to the mains power.
- Using the control panel, access parameter P.08 in the "Technician" menu (see "Technician
Menu") and set the value to "4".
For the correct hydraulic and electrical installation of a Sanit DHW tank with a DualTherm boiler,
carefullyfollow the directions in the section
"Installinga Sanit tank" in this manual.
Once the hydraulic and electrical connection described above has been completed, to adjust and
configure the BT buffer tank operation, carefully read the section "Operation with a BT buffer tank"
inthis manual.
3.10 Installation with a BT-DUO buffer tank (Optional)
The DualTherm boiler can be accompanied by a BT-DUO Buffer Tank during the installation from
the wide range offered by DOMUSA TEKNIK, which may increase the benefits provided by the boiler
in the heating service. This tank has a hot water storagetank inside, thereby adding the provision of
DHW in addition to the buffer tank functionality. For this reason, its connection to the boiler as well
asits operating configuration are specific.
For this reason the electronic control of the boiler is equipped with an input for connecting the
primary control thermostat Tcp of the BT-DUO tank (input Sbt; terminals 20-21 on connection strip
J7) and a circulation pump output (Bbt; terminals N-7 on the connection strip J2) dedicated
exclusively to managing the heating of the buffer tank. Also, for correctly managing the DHW
production in the tank integrated in the BT-DUO tank, a DHW temperature sensor (supplied
optionally)must be included in the installation.

DualTherm
16
The boiler is supplied with this installation option disabled. To enable it, the electrical resistance
(Rbt) connected between terminals 20 and 21 of connection strip J7 (see "Connection Diagram")
must be disconnected and replaced with a temperature sensor (supplied as an option by DOMUSA
TEKNIK) or a control thermostat installed in the BT buffer tank. After disconnecting the resistance in
the "Technician" menu of the control panel, parameter P.08 must be enabled, via which you can
selectthe installation mode and appropriate functioning for this type of buffertank.
The BT-DUO buffer tank is hydraulically connected to the boiler, interposing a circulation pump
(Bbt), and all the central heating circuits of the system are connected to the BT-DUO tank. For the
correct hydraulic installation of the BT-DUO tank and the feed pump Bbt, carefully follow the
instructionsin the following hydraulic diagram:
Heating
Installation
After the hydraulic installation of all the system components, proceed as follows to carry out the
correct electricalconnection ofthe BT-DUO buffertank tothe DualTherm boiler:
- Unplug the boiler from the mains power.
- Disconnect the electrical resistance (Rbt) connected between terminals 20 and 21 of
connectionstrip J7
(see"Connection Diagram") .
- Using a 2-wire electrical hose connect the TAcald terminals (terminals 7and 8in the wiring
diagram of the BT-DUO tank manual) of the BT-DUO tank control thermostat (Tcp) to the
sensor connection strip J7(Sbt; terminals 20 and 21)
(see"Connection Diagram") .
- Connect the DHW temperature sensor (supplied optionally) to the sensor connection strip J7
(Sa; terminals 18 and 19) (see "Connection Diagram") , previously removing the resistance Ra,
suppliedas standard with the boiler.
- Insert the DHW temperature sensor bulb into the bulb-holder sheath provided in the DHW tank
ofthe BT-DUO buffer tank.
- Connect the BT-DUO tank feed pump to the component connection strip J2 (Bbt; terminals N
and7) (see"Connection Diagram") .
- Connectthe boiler to the mains power.
- To correctly configure the type of installation you must adjust parameters P.08 y P.09 in the
"Technician" menu on the control panel. Access parameter P.08 in the "Technician" menu (see
"Technician Menu") and set the value to "4". Next, access parameter P.09 from the same menu
andset the value to "0".

17
For the correct hydraulic and electrical installation of a BT-DUO buffer tank, carefully follow the
instructionsin the manual supplied with it.
Once the hydraulic and electrical connection described above has been completed, to adjust and
configure the BT-DUO buffer tank operation, carefully read the section "Operation with a BT-DUO
buffertank" in this manual.

DualTherm
18
4FUEL
4.1 Wooden pellet
The DualTherm boiler must be fuelled with DIN PLUS-certified wood pellets. The DIN PLUS certificate
assures that the fuel's moisture levels and calorific value are ideal for optimum boiler functioning
performance. If this requirement is not complied, DOMUSA TEKNIK's guarantee will automatically be
nulland void.
Thefollowing points should be taken into account for correct fuel storage:
•Thestored pellets should be kept dry all year round.
•Theapplicable legislation in each country for correct fuel storage must becomplied.
4.2 Firewood
The quality of the firewood is very important in the performance and useful life of the DualTherm
boiler.The use of different fuels gives rise to different powers andyields.
The firewood moisture must be less than 25%. If the percentage of water in the firewood is too high,
the corrosion inside the boiler increases and the boiler performance is reduced. "Green" wood
(recently cut) may contain over 50% moisture. Its caloric power is approximately half of that of
"seasoned" wood with 15% moisture. The higher moisture of the wood, the slower the combustion
andthe lower the flame temperature. This abruptly increases the generation ofsoot and tar.
For proper operation of the DualTherm boiler, the maximum firewood length (L) should be less than
50cm and the maximum diameter (D), 15 cm, the optimal diameterbeing between 10 cm and 15 cm.
L
D
D
L
D
L