Baxi COMBI 424 Manual

54United
Kingdom
en
424 Combi 2 - 430 Combi 2
424 Combi LPG 2 - 430 Combi LPG 2
These instructions include the Benchmark Commissioning Checklist and should be left with the
user for safe keeping.They must be read in conjunction with the Flue Installation Guide.
Installation and Service Manual
High-efficiency wall-hung condensing gas boiler

Dear Customer,
Thank you very much for buying this appliance.
Please read through the manual carefully before using the product, and keep it in a safe place for later reference. In order to
ensure continued safe and efficient operation we recommend that the product is serviced regularly. Our service and customer
service organisation can assist with this.
We hope you enjoy years of problem-free operation with the product.

Contents
Contents
1 Safety........................................................................................................................................................................................................ 6
1.1 Benchmark...................................................................................................................................................................................... 6
1.1.1 Building regulations and the benchmark commissioning checklist. ....................................................................... 6
1.1.2 The benchmark scheme............................................................................................................................................... 6
1.1.3 Installer notification guidelines..................................................................................................................................... 7
1.2 General safety instructions............................................................................................................................................................8
1.3 Recommendations......................................................................................................................................................................... 8
1.4 Specific safety instructions ...........................................................................................................................................................9
1.4.1 Handling .........................................................................................................................................................................9
1.5 Liabilities......................................................................................................................................................................................... 10
1.5.1 Manufacturer's liability.................................................................................................................................................10
1.5.2 Installer's liability........................................................................................................................................................... 10
1.5.3 User's liability................................................................................................................................................................10
2 About this manual................................................................................................................................................................................ 11
2.1 General...........................................................................................................................................................................................11
2.2 Additional documentation............................................................................................................................................................ 11
2.3 Symbols used................................................................................................................................................................................11
2.3.1 Symbols used in the manual.......................................................................................................................................11
2.4 Abbreviations/glossary................................................................................................................................................................. 11
3 Technical specifications.......................................................................................................................................................................... 12
3.1 Homologations............................................................................................................................................................................... 12
3.1.1 Safety, performance & quality .................................................................................................................................. 12
3.1.2 Certifications................................................................................................................................................................ 12
3.1.3 Gas category.................................................................................................................................................................12
3.1.4 Standards......................................................................................................................................................................12
3.2 Technical data.............................................................................................................................................................................. 13
3.2.1 Technical information...................................................................................................................................................13
3.2.2 Features of the temperature sensors ........................................................................................................................16
3.3 Dimensions and connections .....................................................................................................................................................16
3.4 Electrical diagram..........................................................................................................................................................................18
4 Description of the product......................................................................................................................................................................19
4.1 General description...................................................................................................................................................................... 19
4.2 Operating principle....................................................................................................................................................................... 19
4.2.1 Air-gas adjustment...................................................................................................................................................... 19
4.2.2 Combustion...................................................................................................................................................................19
4.2.3 Heating and domestic hot water production............................................................................................................19
4.2.4 Schematic diagram ..................................................................................................................................................... 20
4.3 MAIN COMPONENTS.................................................................................................................................................................20
4.4 Control panel description............................................................................................................................................................21
4.4.1 Description of the control panel..................................................................................................................................21
4.5 Contents of the package.............................................................................................................................................................. 21
4.6 Accessories & options................................................................................................................................................................. 21
5 Before installation................................................................................................................................................................................ 22
5.1 Installation standards and rules ................................................................................................................................................. 22
5.2 Installation requirements..............................................................................................................................................................22
5.2.1 Gas supply. .................................................................................................................................................................. 22
5.2.2 Electrical supply............................................................................................................................................................ 22
5.2.3 Hard water area............................................................................................................................................................ 23
5.2.4 Bypass........................................................................................................................................................................... 23
5.2.5 System control.............................................................................................................................................................. 23
5.2.6 Treatment of water circulating systems.....................................................................................................................23
5.2.7 Showers......................................................................................................................................................................... 24
5.2.8 Expansion vessel (CH only).........................................................................................................................................24
5.2.9 Safety pressure relief valve.........................................................................................................................................24
5.3 Flow rate/head at the plate characteristics ................................................................................................................................25
Combi 2 3

Contents
5.4 Choice of the location. ..................................................................................................................................................................... 26
5.4.1 Location of the boiler ...................................................................................................................................................26
5.4.2 Bath and shower rooms ............................................................................................................................................. 26
5.4.3 Ventilation..................................................................................................................................................................... 27
5.4.4 Condensate drain........................................................................................................................................................27
5.4.5 Clearances.................................................................................................................................................................. 29
5.4.6 Flue/chimney location................................................................................................................................................. 29
5.4.7 Horizontal flue/chimney systems. .............................................................................................................................31
5.4.8 Flue/chimney trim........................................................................................................................................................32
5.4.9 Terminal guard............................................................................................................................................................ 32
5.4.10 Flue/chimney deflector .............................................................................................................................................. 32
5.4.11 Flue/chimney accessories..........................................................................................................................................32
5.4.12 Data plate and boiler service level........................................................................................................................... 33
5.5 Transport...................................................................................................................................................................................... 33
5.6 Unpacking and initial preparation. ............................................................................................................................................ 34
5.6.1 Unpacking................................................................................................................................................................. 34
5.6.2 Initial preparation.......................................................................................................................................................35
5.7 Connecting diagrams......................................................................................................................................................................35
5.7.1 Filling information..................................................................................................................................................... 35
5.7.2 Domestic hot water circuit....................................................................................................................................... 36
6 Installation. .............................................................................................................................................................................................37
6.1 General.......................................................................................................................................................................................... 37
6.2 Assembly........................................................................................................................................................................................37
6.2.1 Fitting the pressure relief discharge pipe................................................................................................................. 37
6.2.2 Connecting the condensate drain............................................................................................................................. 38
6.3 Air supply/flue gas connection ................................................................................................................................................... 38
6.3.1 Connecting the flue/chimney......................................................................................................................................38
6.4 Electrical connections...................................................................................................................................................................39
6.4.1 Accessing the electrical connections........................................................................................................................ 40
6.4.2 Connecting the room thermostat...............................................................................................................................40
6.4.3 Service connection (SERVICE).................................................................................................................................41
6.4.4 Connecting on wall outdoor sensor. .........................................................................................................................41
6.4.5 Connecting the outside sensor..................................................................................................................................41
6.4.6 Identifying label............................................................................................................................................................41
6.5 Filling the installation ................................................................................................................................................................... 42
6.5.1 Flushing the system.................................................................................................................................................... 42
6.5.2 Fill the installation........................................................................................................................................................42
6.5.3 Filling the condensate trap..........................................................................................................................................42
6.6 Draining the installation............................................................................................................................................................... 42
7 Commissioning...................................................................................................................................................................................... 43
7.1 General...........................................................................................................................................................................................43
7.2 Checklist before commissioning .................................................................................................................................................43
7.3 Commissioning procedure...........................................................................................................................................................43
7.4 Gas settings................................................................................................................................................................................... 44
7.4.1 Check the operational (working gas inlet pressure and gas rate) ........................................................................ 44
7.4.2 Combustion parameters..............................................................................................................................................44
7.4.3 Service settings............................................................................................................................................................46
7.4.4 Calibrating the gas valve.............................................................................................................................................47
7.5 Final instructions.......................................................................................................................................................................... 49
7.5.1 Handover.......................................................................................................................................................................49
8 Operation.....................................................................................................................................................................................................50
8.1 Use of the control panel....................................................................................................................................................................50
8.1.1 Browsing the menus ....................................................................................................................................................50
8.1.2 Running the automatic detection function.................................................................................................................50
8.1.3 Information menu display............................................................................................................................................50
8.1.4 Counter menu display................................................................................................................................................. 50
4 Combi 2

Contents
Combi 2 5
8.2 Start-up ...............................................................................................................................................................................................51
8.2.1 Procedure for first start-up.......................................................................................................................................... 51
8.2.2 Changing the heating flow temperature.................................................................................................................... 51
8.2.3 Changing the domestic hot water (DHW) temperature........................................................................................... 51
8.3 Shutdown....................................................................................................................................................................................... 52
8.3.1 Switching off the heating and domestic hot water (DHW)......................................................................................52
8.4 Degassing function .......................................................................................................................................................................52
8.5 Frost protection ............................................................................................................................................................................. 52
9 Settings........................................................................................................................................................................................................53
9.1 Accessing the settings. ................................................................................................................................................................53
9.2 List of parameters.........................................................................................................................................................................53
9.2.1 Resetting factory settings.................................................................................................................................................. 57
9.3 Setting the parameters................................................................................................................................................................ 57
9.3.1 Setting the heating curve ..................................................................................................................................................57
9.4 Reading out measured values ...................................................................................................................................................58
9.4.1 Statuses and sub-statuses. .............................................................................................................................................. 59
9.5 Reading meters........................................................................................................................................................................... 61
10 Maintenance .............................................................................................................................................................................................62
10.1 General...........................................................................................................................................................................................62
10.2 Maintenance message.................................................................................................................................................................63
10.2.1 Service notification..................................................................................................................................................... 63
10.2.2 Resetting the displayed maintenance message .....................................................................................................63
10.2.3 Resetting the upcoming maintenance message..................................................................................................... 64
10.3 Standard inspection and maintenance operations................................................................................................................... 65
10.3.1 Checking the water pressure..................................................................................................................................... 64
10.3.3Checking the expansion vessel..................................................................................................................................64
10.3.4Checking the flue gas discharge and the air supply...............................................................................................65
10.3.5Checking the combustion...........................................................................................................................................65
10.3.6Checking the automatic air vent................................................................................................................................65
10.3.7Cleaning the siphon.................................................................................................................................................... 65
10.3.9Checking the burner and cleaning the heat exchanger ..........................................................................................67
10.3.8 Electrode distances......................................................................................................................................................65
10.3.10 Water unit......................................................................................................................................................................67
10.3.12 Removing limescale.................................................................................................................................................... 67
10.4 Specific maintenance operations .. ...............................................................................................................................................68
10.4.1 Detection/ignition electrode replacement..................................................................................................................68
10.4.2 Dismantling the water-water exchanger ...................................................................................................................68
10.4.5Replacing the 3-way valve......................................................................................................................................... 69
10.4.10 Replacing the pump....................................................................................................................................................71
10.4.11 Replacing the expansion vessel.................................................................................................................................71
10.4.12 Replacing the PCB.......................................................................................................................................................71
11 Troubleshooting.....................................................................................................................................................................................72
11.1 Temporary and permanent faults ...............................................................................................................................................72
11.2 Error codes.................................................................................................................................................................................... 72
12 Decommissioning.................................................................................................................................................................................77
12.1 Disassembly..................................................................................................................................................................................77
12.2 Recommissioning...........................................................................................................................................................................77
13 Disposal.................................................................................................................................................................................................78
13.1 Disposal and recycling.................................................................................................................................................................78
10.3.2Annual servicing.......................................................................................................................................................... 66
10.3.11 Cleaning/replacing the DHW filter..............................................................................................................................65
10.4.3Replacing the flow and return sensors.....................................................................................................................68
10.4.4Replacing the return valve .........................................................................................................................................69
10.4.6Replacing the pressure sensor.................................................................................................................................. 69
10.4.7Replacing the hall effect sensor.................................................................................................................................70
10.4.8Replacing the safety pressure relief valve............................................................................................................... 70
10.4.9Replacing the diverter valve motor.............................................................................................................................70
Annual servicing.......................................................................................................................................................... 66

1 Safety
6 Combi 2
1 Safety
1.1 Benchmark
1.1.1 Building Regulations and the Benchmark
Commissioning Checklist
Building Regulations (England & Wales) require notification of the installa-
tion of a heating appliance to the relevant Local Authority Building Control
Department. This can be achieved via a Competent Persons Self
Certifica-tion Scheme as an option to notifying the Local Authority directly.
The Health & Safety Executive operates the ’Gas Safe Register’, a selfcer-
tification scheme for gas heating appliances.
This company is a member of the Benchmark initiative and fully supports
the aims of the programme. Its aim is to improve the standards of installa-
tion and commissioning of central heating systems in the UK and to en-
courage the regular servicing of all central heating systems to ensure
safe-ty and efficiency.
Building Regulations require that installations should comply with manu-
facturer’s instructions. It is therefore important that the commissioning
checklist is completed by the installer. The relevant section of Building
Regulations only relates to dwellings. Therefore the checklist only applies
if the appliance is being installed in a dwelling or some related structure.
The flowchart opposite gives guidance for installers on the process neces-
sary to ensure compliance with Building Regulations.
1.1.2 The Benchmark Scheme
Fig.1 Benchmark
AD-3000725-01
Benchmark places responsibilities on both manufacturers and installers.
The purpose is to ensure that customers are provided with the correct
equipment for their needs, that it is installed, commissioned and serviced
in accordance with the manufacturer’s instructions by competent persons
and that it meets the requirements of the appropriate Building Regulations.
The Benchmark Checklist can be used to demonstrate compliance with
Building Regulations and should be provided to the customer for future ref-
erence.
Installers are required to carry out installation, commissioning and servic-
ing work in accordance with the Benchmark Code of Practice which is
available from the Heating and Hotwater Industry Council who manage
and promote the Scheme. Visit www.centralheating.co.uk for more
infor-mation.

1 Safety
Combi 2 7
Choose Building
Regulations
Notification
Route
Competent Person's
Self Certification Scheme
Building Control
Install and Commission this
appliance to manufacturer's
instructions
1.1.3 Installer Notification Guidelines
Fig.2 Installer Notification Guidelines
Contact your relevant Local
Authority Building Control
(LABC) who will arrange
an inspection or contact
a governmentapproved
inspector
Install and Commission this
appliance to manufacturer's
instructions
AD-3000696-01
If you notify via the ‘Gas Safe
Register’, the register will issue
the Building Regulations
certificate on members’ behalf
Scheme Members only
Call ‘Gas Safe Register’ on:
0800 408 5577
or log onto:
www.gassaferegister.co.uk
within 10 days
Complete the
BenchmarkChecklist
‘Gas Safe Register’ will issue a
Building Regulations Compliance
Certificate to the property owner
and inform the relevant LABC
You must ensure that the
certificate number issued by
the ‘Gas Safe Register’ is written
onto the Benchmark Checklist
LABC will record the data
and will issue a
certificate of compliance
Complete the
BenchmarkChecklist

1 Safety
8 Combi 2
Warning Installation and maintenance of the boiler must be
carried out by a competent person in accordance with local
and national regulations.
Warning If the mains lead is damaged, it must be replaced by the
original manufacturer, the manufacturer's dealer or another
suitably skilled person to prevent hazardous situations from
arising.
Warning Always disconnect the mains supply and close the
main gas tap when working on the boiler.
1.2 General safety instructions
Danger This boiler can be used by children aged 8 years and
above and by persons with reduced physical, sensory or mental
capabilities or lack of experience and knowledge when they have
been given supervision or instruction concerning the safe use of
the device and understand the resulting risks. Children must not
be allowed to play with the appliance. Cleaning and user
maintenance must not be carried out by children without
supervision.
Danger If you
smell gas:
1. Do not use a naked flame, do not smoke, do not operate elec-
trical contacts or switches (doorbell, light, motor, lift, etc.).
2. Shut off gas supply.
3. Open the windows.
4. Trace possible leaks and seal them immediately.
5. If the gas leak is before the gas meter, contact the supplier 6.
Telephone the National Gas Emergency Service on:- 0800
111 999.
Danger If you smell
flue gases:
1. Switch off the boiler.
2. Open the windows.
3. Trace possible leaks and seal them immediately.
Warning Do not touch the flue gas pipes. Depending on the
boiler settings, the temperature of the flue gas pipes may exceed
60oC.
Warning Do not touch the radiators for long periods. Depending
on the boil-er settings, the temperature of the radiators may
exceed 60oC.
Warning Take precautions with the domestic hot water.
Depending on the boiler settings, the domestic hot water
temperature may exceed 65oC.
Danger Before any work, switch off the mains supply to
the boiler.
Caution After maintenance or repair work, check the entire
heating installation to ensure that there are no leaks.
1.3 Recommendations

1 Safety
Combi 2 9
Important
Keep this document near to the boiler.
Important Casing panels may only be removed for maintenance
and servic-ing purposes. Refit all panels when maintenance work
and servic-ing are complete.
Note Instruction and warning labels must never be removed or
covered and must be clearly legible throughout the entire service
life of the boiler. Replace damaged or illegible instruction and
warning labels immediately.
Note
The boiler must not be modified in any way.
1.4 Specific safety instructions
1.4.1 Handling
General
The following advice should be adhered to, from when first handling the
boiler to the final stages of installation, and also during maintenance.
Most injuries as a result of inappropriate handling and lifting are to the
back, but all other parts of the body are vulnerable, particularly should-
ers, arms and hands. Health & Safety is the responsibility of EVERY-
ONE.
There is no "safe" limit for one man - each person has different capabili-
ties. The boiler should be handled and lifted by TWO PEOPLE. Do not
handle or lift unless you feel physically able. Wear appropriate Personal
Protection Equipment e.g. protective gloves, safety footwear etc.
Preparation
Co-ordinate movements - know where, and when, you are both going.
Minimise the number of times needed to move the boiler - plan ahead.
Always ensure when handling or lifting the route is clear and unobstruc-
ted. If possible avoid steps, wet or slippery surfaces, unlit areas etc. and
take special care on ladders/into lofts.
Technique
When handling or lifting always use safe techniques - keep your back
straight, bend your knees. Don’t twist - move your feet, avoid bending
forwards and sideways and keep the load as close to your body as
possible.
Where possible transport the boiler using a sack truck or other suitable
trolley.
Caution
Make sure the boiler can be reached at all times. The boiler
must be installed in a frost-free area. In the case of a fixed
connection to the power cord, you must al-ways install a main
double pole switch with an opening gap of at least 3 mm (EN
60335-1). Drain the boiler and central heating system if you are
not going to use your home for a long time and there is a chance
of frost. The frost protection does not work if the boiler is out of
opera-tion. The boiler protection only protects the boiler, not the
system. Check the water pressure in the system regularly. If the
water pressure is lower than 0.8 bar, the system must be topped
up (recommended water pressure between 1 and 2 bar).

1 Safety
10
Combi 2
Always grip the boiler firmly, and before lifting feel where the weight is
concentrated to establish the centre of gravity, repositioning yourself as
necessary. See the "Installation" section of these instructions for recom-
mended lift points.
Remember
The circumstances of each installation are different. Always assess the
risks associated with handling and lifting according to the individual
con-ditions.
If at any time when installing the boiler you feel that you may have in-
jured yourself STOP !! DO NOT "work through" the pain - you may
cause further injury.
IF IN ANY DOUBT DO NO HANDLE OR LIFT THE BOILER —
OBTAIN ADVICE OR ASSISTANCE BEFORE PROCEEDING !
1.5 Liabilities
1.5.1 Manufacturer's liability
Our products are manufactured in compliance with the requirements of the
various Directives applicable. They are therefore delivered with the
marking and any documents necessary. In the interests of the quality of
our products, we strive constantly to improve them. We therefore reserve
the right to modify the specifications given in this document.
Our liability as manufacturer may not be invoked in the following cases:
Failure to abide by the instructions on installing the appliance.
Failure to abide by the instructions on using the appliance.
Faulty or insufficient maintenance of the appliance.
1.5.2 Installer's liability
The installer is responsible for the installation and initial commissioning of
the appliance. The installer must observe the following instructions:
Read and follow the instructions given in the manuals provided with the
appliance. Install the appliance in compliance with prevailing legislation
and standards.
Carry out initial commissioning and any checks necessary. Explain the
installation to the user. Ifmaintenance is necessary, warn the user of the
obligation to check the appliance and keep it in good working order. Give
all the instruction manuals to the user.
1.5.3 User's liability
To guarantee optimum operation of the system, you must abide by the
following instructions:
Read and follow the instructions given in the manuals provided with the
appliance. Call on a competent person to carry out installation and
initial commissioning.
Get your installer to explain your installation to you. Have the required
inspections and maintenance carried out by a qualified installer. Keep
the instruction manuals in good condition close to the appliance.

2 About this manual
2 About this manual
2.1 General
This manual is intended for installers of Baxi Combi 2 boilers
2.2 Additional documentation
These Installation & Service Instructions must be read in conjunction with
the Flue Accessories Fitting Guide supplied in the Literature Pack.
Various timers, external controls, etc. are available as optional extras. Full
details are contained in the relevant sales literature.
2.3 Symbols used
2.3.1 Symbols used in the manual
This manual uses various danger levels to draw attention to special
instructions. We do this to improve user safety, to prevent problems and to
guarantee correct operation of the appliance.
Danger Risk of dangerous situations that may result in serious
personal injury.
Danger ofelectric shock Risk ofelectric shock.
Warning Risk of dangerous situations that may result in minor
personal injury.
Caution Risk of material damage.
Important
Please note: important information.
See Reference to other manuals or pages in this
manual.
2.4 Abbreviations/Glossary
BS
CH
DHW
GB
British Standard
Central heating
Domestic hot water
Great Britain
HHIC Heating and Hotwater Industry Council
Hi
Hs
IE
PCU
Pn
Pnc
SU
Lower heating value (LHV)
Higher heating value (HHV)
Ireland
PCB for managing burner operation
Nominal output
Condensing output
Safety PCB
Combi 2 11

3 Technical specifications
12 Combi 2
Practice apply:
3 Technical specifications
3.1 Homologations
3.1.1 Safety, Performance &Quality
This boiler has been assessed by an appropriate Notified Body and shown
to meet the requirements of all Directives and Regulations as applicable.
These Directives and Regulations lay down requirements for the safety
and efficiency of the appliance, together with its design, construction and
use of materials. They also require the production process to be covered
by an approved and monitored system of quality assurance.
Tab.1 Certifications 3.1.2 Certifications
CE certificate number
0085CU0338
NOx class
6
Boiler type
C
13
, C
33
Tab.2 Gas category, type and supply pressure 3.1.3 Gas category
Gas category
Gas type
Supply pressure (mbar)
I
2H
G20 (H natural gas)
20
II
2H3P
G31 (Propane)
37
Important This appliance is suitable for G20 gas
containing up to 20% hydrogen (H2). Due to variations
in the percentage of H2, the percentage of O2may vary
over time. (For example: 20% of H2in the gas may lead
to a 1.5% increase of O2in the flue gases) The gas
valve may need to be adjusted more accurately. This
must be adjusted using standard O2values for the gas
used.
3.1.4 Standards
Codes of Practice — refer to the most recent
version Tab.3 In GB the following Codes of
Standard Scope
BS 6891 Gas Installation.
BS 5546 Installation of hot water supplies for domestic purposes.
BS EN
12828 Heating systems in buildings.
BS EN
12831
Heating systems in buildings — Calculation of load.
BS EN
14336 Installation & commissioning of water based heating systems.
BS 6798 Installation of gas fired hot water boilers.
BS 5440
Part 1 Flues.
BS 5440
Part 2 Ventilation.

3 Technical specifications
Combi 2 13
Standard Scope
BS 7074 Expansion vessels and ancillary equipment for sealed
water systems.
BS 7593 Treatment of water in domestic hot water central heating
systems.
BS 4814 Specification for Expansion Vessels using an internal
diaphragm, for sealed hot water systems.
IGE/UP/
7/1998 Guide for gas installations in timber framed housing.
3.2 Technical data
Tab.4 In IE the following Code of Practice apply:
Standard Scope
IS 813 Domestic Gas Installations.
The following standards give valuable additional information:
BS 5546 Installation of hot water supplies for domestic purposes.
BS EN
12828 Heating systems in buildings.
BS EN
12831 Heating systems in buildings — Calculation of load.
BS EN
14336 Installation & commissioning of water-based heating
systems.
BS 7074 Expansion vessels and ancillary equipment for sealed
water systems.
BS 7593 Treatment of water in domestic hot water central heating
systems.
3.2.1 Technical information
Important
All data in these sections are nominal and subject tonormal
production tolerances.
Tab.5 Technical settings for combination heaters with boilers
Baxi Combi 2
424
430
Condensing boiler
Yes
Yes
Low-temperature boiler(1)
No
No
B1 boiler
No
No
Cogeneration space heater
No
No
Combination heater
Yes
Yes
Rated heat output
Prated
kW
20
20
Useful heat output at rated heat output and
high temperature setting (2) P4 kW 20 20
Useful heat output at 30% of rated heat
out-put and low temperature setting(1) P1 kW 6.7 6.7

3 Technical specifications
14 Combi 2
Baxi Combi 2
424
430
Seasonal space heating energy efficiency
ƞs
%
93
93
Useful efficiency at rated heat output and high
temperature setting(2) ƞ4%88.2 88.0
Useful efficiency at 30% of rated heat output
and low temperature setting(1) ƞ1%97.9 97.8
Auxiliary electricity consumption
Full load
elmax
kW
0.037 0.026
Partial load
elmin
kW
0.014
0.014
Standby mode
PSB
kW
0.004
0.004
Other items
Heat loss on standby
Pstby
kW
0.04
0.04
Ignition burner power consumption
Pign
kW
-
-
Annual energy consumption
QHE
GJ
62
62
Sound power level, indoors
LWA
dB
50
49
Nitrogen oxide emissions
NOx
mg/kWh
21
21
Domestic hot water parameters
Declared load profile
XL XL
Daily electricity consumption
Qelec
kWh
0.176
0.189
Annual electricity consumption
AEC
kWh
39
42
Water heating energy efficiency
ƞwh
%
88
89
Daily fuel consumption
Qfuel
kWh
22.03
21.66
Annual fuel consumption
AFC
GJ
17
17
(1) Low temperature means for condensing boilers 30°C, for low temperature boilers 37°C and for other heaters 50°C return temperature
(at heater inlet).
(2) High temperature setting means 60 °C return temperature at boiler inlet and 80 °C flow temperature at boiler outlet
Tab.6 General
424
430
Rated heat input (Qn) for domestic hot water
kW
24.7
30
Rated heat input (Qn) with domestic hot water tank
kW
–
-
Rated heat input (Qn) for heating
kW
20.6
20.6
Reduced heat input (Qn) 80/60 °C
kW
4.9
6.0
Rated heat output (Pn) for domestic hot water
kW
24
29.1
Rated heat output (Pn) with domestic hot water tank
kW
–
-
Rated heat output (Pn) 80/60 °C for heating
kW
20
20
Rated heat output (Pn) 50/30 °C for heating
kW
21.8
21.8
Reduced heat output (Pn) 80/60 °C
kW
4.8
5.8
Reduced heat output (Pn) 50/30 °C
kW
5.2
6.3
Rated efficiency 50/30 °C (Hi)
%
105.8
105.8

3 Technical specifications
Combi 2 15
Tab.7 Characteristics of the heating circuit
424
430
Maximum pressure
bar
2.5
2.5
Minimum pressure
bar
0.5
0.5
Temperature range for heating circuit
°C
25 - 80
25 - 80
Water capacity of expansion vessel
l
7
7
Tab.8 Characteristics of the domestic water circuit
424
430
Minimum pressure
bar
0.8
0.8
Maximum pressure
bar
8.0
8.0
Minimum dynamic pressure
bar
0.15
0.15
Minimum water flow
l/min
2.0
2.0
Specific flow (D)
l/min
11.5
14
Temperature range for domestic water circuit
°C
35 - 60
35 - 60
Domestic water production with ΔT = 25 °C
l/min
13.8
16.7
Domestic water production with ΔT = 35 °C
l/min
9.8
11.9
Tab.9 Combustion characteristics Dynamic (nominal) inlet pressure (Natural gas — G20) 20mbar with a CV of 37.78 MJ/m3
424
430
G20 gas consumption (Qmax)
m
3
/h
2.61
3.17
G20 gas consumption (Qmax) with domestic hot water tank
m3/h
–
-
G20 gas consumption (Qmin)
m3/h 0.52 0.63
G31 propane gas consumption (Qmax)
kg/h
1.92
2.33
G31 propane gas consumption (Qmin)
kg/h
0.38
0.47
Diameter of separate discharge pipes
mm
80/80
80/80
Diameter of coaxial discharge pipes
mm
60/100
60/100
Flue gas mass flow rate (max)
kg/sec
0.011
0.014
Flue gas mass flow rate (max) with domestic hot water tank
kg/sec
–
-
Flue gas mass flow rate (min)
kg/sec
0.002
0.003
Tab.10 Electrical characteristics
424
430
Power supply voltage
V
230
230
Power supply frequency
Hz
50
50
Rated electric power
W
90
90
Rated electrical output with domestic hot water tank
W
–
-
Tab.11 Other characteristics
424
430
Humidity protection rating (EN 60529)
IP
X5D
X5D
Net weight when empty/filled with water
kg
28/30
29/31
Dimensions (height/width/depth)
mm
700/395/285
700/395/285

3 Technical specifications
16 Combi 2
3.2.2 Features of the temperature sensors
Tab.12 Temperature sensor outdoor sensor (NTC1000 Beta 3419 1 kOhm @ 25 °C)
Temperature [°C]
-20
-15
-10
-5
0
5
10
15
20
25
30
Resistance [Ω]
7578
5861
4574
3600
2857
2284
1840
1492
1218
1000
827
Tab.13 Temperature flow/heating circuit return sensor (NTC10K Beta 3977 10KOhm@25°C)
Temperature [°C]
0
10
20
25
30
40
50
60
70
80
90
Resistance [Ω]
32505
19854
12483
9999
8060
5332
3608
2492
1754
1257
915
Tab.14 Flue gas temperature sensor (NTC20K Beta 3970 20kOhm@25°C)
Temperature [°C]
0
10
20
25
30
40
50
60
70
80
90
100
Resistance [Ω]
66050
40030
25030
20000
16090
10610
7166
4943
3478
2492
1816
1344
— — — — —>
110
120
130
140
150
160
170
180
190
-
-
-
— — — — —>
1009
768
592
461
364
290
233
189
155
-
-
-
3.3 Dimensions and connections
Fig.3 Dimensions and connections
BO-0000199-1
1
2
3
Safety valve
Heating circuit flow fitting (G3/4”)
Fitting for condensate discharge
DHW (Domestic Hot Water) outlet fitting (G1/2”)
Gas inlet fitting (G3/4”)
Domestic cold water inlet fitting (G1/2”)
Heating circuit return fitting (G34")
4
5
6
7
1
2
4
5
3
6
7
700 mm

3 Technical specifications
Combi 2 17
Fig.4 Paper template

3 Technical specifications
18 Combi 2
Electrical diagram
Fig.5 Boiler electrical wiring diagram
Tab.15 Electrical connections
X1
Power supply: L: Live
230V – 50 Hz N:
Neutral
: Earthing connector
X9 CAN connection
X2
Fan supply (FAN)
X10
Service interface
X3
Gas valve (GV)
X17
Open Therm room unit (OT)
X4
Pump power supply
X17
Outside sensor (T/OUT)
X5
3-way valve motor power supply
X17
External tank sensor - accessory (T/DHW)
X6
Earth connections
X15
Boiler stoppage (with open contact)
X7
Sensors:
Limit thermostat (ST) Installation
return temperature (SRT) Installation
flow temperature (SFL) Flue gas
temperature (FS)
RT Room thermostat contact (230 V)
X8
Sensors:
DHW flowmeter (HS) Heating circuit
pressure switch (SP) Pump PWM
signal (PWM PUMP)
Tab.16 Cable colour key
BK
Black
GY
Grey
BN
Brown
RD
Red
BU
Blue (and light blue)
WH
White
GNYE
Green/Yellow
YE
Yellow
3.4

4 Description of the product
Combi 2
19
4 Description of the product
4.1 General description
The purpose of this gas-fueled condensing boiler is to heat water to a
temperature that is lower than boiling point at atmospheric pressure. It
must be connected to a heating installation and to a domestic hot water
distribution system that is compatible with its power and performance
ratings. Features of this boiler:
Low pollutant emissions,
High-efficiency heating, Combustion products discharged through
a concentric connector, Front control panel with display,
Lightweight and compact.
4.2 Operating principle
4.2.1 Air-gas adjustment
The air is drawn in by the fan and gas injected directly at the height of the
venturi. The fan revolution speed is regulated automatically by the
electronic board based on the adjustment settings. The gas and air are
mixed in the manifold. The gas/air ratio ensures that the quantity of gas
and air are adjusted correctly to always obtain optimal combustion. The
gas/air mixture is fed into the burner at the front of the exchanger.
Here, the electric igniter triggers the mixture with a series of sparks that
burn, producing thermal energy.
4.2.2 Combustion
The burner heats the heating water circulating in the heat exchanger.
When the temperature of the combustion gas is lower than the dew point
(around 55 °C), the water vapour contained in the combustion gas
condenses in the flue gas side of the heat exchanger. The heat recovered
during this condensation process (the latent heat or condensing heat) is
also transferred to the heating water. Once cooled, the combustion gases
are discharged through the exhaust pipe. The condensed water is
discharged through a siphon.
4.2.3 Heating and domestic hot water production
In boilers used for heating and for producing domestic hot water, an
integrated plate heat exchanger heats the domestic water. The heated
water is then channeled to the heating installation or to the plate heat
exchanger via a three-way valve. A flow sensor detects that a hot water
tap has been turned on and communicates this to the PCB, which
switches the three-way valve to the hot water position and activates the
pump. The three-way valve is spring-loaded and only consumes electricity
when switching from one position to another. Precedence is given to a
heat request in domestic water mode.

4 Description of the product
20 Combi 2
Fig.6 Schematic diagram
4.3 MAIN COMPONENTS
Fig.7 Functional diagram
4.2.4 Schematic diagram
1
Heat exchanger (heating)
2
Water unit
3
Plate heat exchanger (DHW)
4
Safety valve
5
Heating flow
6
DHW outlet (G1/2")
7
DHW inlet (G1/2")
8
Heating return
9
Pump (heating circuit)
10
Motorised three-way valve
1. Construction
2. Hooks for fastening the bracket to the wall
3. Flue gas tower
4. Expansion vessel air control/filling valve
5. Expansion vessel
6. Hydraulic circuit-expansion vessel connection pipe
7. Air-gas collector
8. Fan (air-gas assembly: Control board and mixer valve)
9. Heating return sensor
10. Gas valve
11. Heating system and pump venting valve
12. Pump
13. Cable gland
14. Control panel with boiler PCB and display
15. Domestic hot water plate heat exchanger fastening screws
16. Domestic hot water priority sensor
17. Domestic hot water plate heat exchanger
18. Siphon
19. Hydraulic safety valve (3 bar)
20. Hydraulic pressure gauge
21. 3-way valve
22. Air-gas silencer assembly
23. Heating circuit water flow sensor (°C)
24. Safety thermostat (limit)
25. Condensate drain pipe connection towards discharge
26. Detection/ignition electrode
27. Burner flange
28. Flue gas temperature sensor
29. Boiler earthing socket
BO-7746442
2
3
4
1
29
5
28
27
6
26
7
25
8
24
9
23
22
10
11
21
20
12
19
13
18
14
17 16
15