Baxi Duo-tec Combi HE a Range User guide

© Baxi Heating UK Ltd 2012
Duo-tecCombiHEARange
Gas Fired Wall Mounted Condensing
Combination Boiler
Installation & Servicing Instructions
These instructions include the Benchmark Commissioning Checklist
and should be left with the user for safe keeping.

2© Baxi Heating UK Ltd 2012
Natural Gas
Baxi Duo-tec Combi 24 HE A
G.C.No47 075 35
Baxi Duo-tec Combi 28 HE A
G.C.No47 075 36
Baxi Duo-tec Combi 33 HE A
G.C.No47 075 37
Baxi Duo-tec Combi 40 HE A
G.C.No47 075 38
Building Regulations and the Benchmark Commissioning
Checklist
Building Regulations (England & Wales) require notification of
the installation of a heating appliance to the relevant Local
Authority Building Control Department. From 1 April 2005 this
can be achieved via a Competent Persons Self Certification
Scheme as an option to notifying the Local Authority directly.
Similar arrangements will follow for Scotland and will apply in
Northern Ireland from 1 January 2006.
The Health & Safety Executive operates the ‘Gas Safe Register’,
a self-certification scheme for gas heating appliances.
These arrangements represent a change from the situation
whereby compliance with Building Regulations was accepted as
being demonstrated by completion of the Benchmark Logbook
(which was then left on site with the customer).
With the introduction of Self Certification Schemes, the
Benchmark Logbook is being withdrawn. However, a similar
document in the form of a commissioning checklist and service
interval record is incorporated at the back of these instructions.
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 installation and commissioning of central heating
systems in the UK and to encourage the regular servicing of all
central heating systems to ensure safety and efficiency.
Building Regulations require that installations should comply
with manufacturer'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 necessary to ensure compliance with Building
Regulations.
© Baxi Heating UK Ltd 2012 All rights reserved. No part of this publication may
be reproduced or transmitted in any form or by any means, or stored in any
retrieval system of any nature (including in any database), in each case whether
electronic, mechanical, recording or otherwise, without the prior written
permission of the copyright owner, except for permitted fair dealing under
Copyrights, Designs and Patents Act 1988.
Applications for the copyright owner’s permission to reproduce or make other
use of any part of this publication should be made, giving details of the proposed
use, to the following address:
The Company Secretary, Baxi Heating UK Ltd,
Brooks House, Coventry Road, Warwick. CV34 4LL
Full acknowledgement of author and source must be given.
WARNING: Any person who does any unauthorised act in relation to a
copyright work may be liable to criminal prosecution and civil claims for damages.
The Benchmark Scheme
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 reference.
Installers are required to carry out installation, commissioning and servicing 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 information.
0086
ISO 9001
FM 00866

3
Installer Notification Guidelines
© Baxi Heating UK Ltd 2012
Choose Building
Regulations Notification
Route
Contact your relevant Local
Authority Building Control
(LABC) who will arrange
an inspection or contact
a government approved
inspector
LABC will record the data
and will issue a
certificate of compliance
‘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
Scheme Members only
Call ‘Gas Safe Register’ on:
0800 408 5577
or log onto:
www.GasSafeRegister.co.uk
within 10 days
If you notify via the ‘Gas Safe
Register’, the register will issue
the Building Regulations
certificate on members’ behalf
Complete the
Benchmark Checklist
Install and Commission this
appliance to manufacturer's
instructions
Competent Person's
Self Certification Scheme
Building Control
Complete the
Benchmark Checklist
Install and Commission this
appliance to manufacturer's
instructions

4
Legislation
© Baxi Heating UK Ltd 2012
Codes of Practice - refer to the most recent version
IMPORTANT - Installation, Commissioning, Service & Repair
This appliance must be installed in accordance with the manufacturer’s instructions and
the regulations in force. Read the instructions fully before installing or using the
appliance.
In GB, this must be carried out by a competent person as stated in the Gas Safety
(Installation & Use) Regulations.
Definition of competence: A person who works for a Gas Safe registered company
and holding current certificates in the relevant ACS modules, is deemed competent.
In IE, this must be carried out by a competent person as stated in I.S. 813 “Domestic
Gas Installations”.
The addition of anything that may interfere with the normal operation of the appliance
without express written permission from the manufacturer or his agent could invalidate
the appliance warranty. In GB this could also infringe the Gas Safety (Installation and
Use) Regulations.
Warning - Check the information on the data plate is compatible with local supply
conditions.
This company declare that no substances harmful to health
are contained in the appliance or used during appliance
manufacture.
The appliance is suitable only for installation in GB and IE and
should be installed in accordance with the rules in force, and
only used in a suitably ventilated location.
In GB, the installation must be carried out by a Gas Safe
Registered Installer. It must be carried out in accordance with
the relevant requirements of the:
• Gas Safety (Installation & Use) Regulations.
• The appropriate Building Regulations either The Building
Regulations, The Building Regulations (Scotland), Building
Regulations (Northern Ireland).
• The Water Fittings Regulations or Water Byelaws in
Scotland.
• The Current I.E.E. Wiring Regulations.
Where no specific instructions are given, reference should be
made to the relevant British Standard Code of Practice.
In IE, the installation must be carried out by a competent
Person and installed in accordance with the current edition of
I.S. 813 ‘Domestic Gas Installations’, the current Building
Regulations and reference should be made to the current ETCI
rules for electrical installation.
All systems must be thoroughly flushed and treated with
inhibitor (see section 6.2).
In GB the following Codes of Practice apply:
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 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.
BS 7074 Expansion vessels and ancillary equipment for
sealed water systems.
BS 7593 Treatment of water in domestic hot water
central heating systems.
In IE the following Codes of Practice apply:
Standard Scope
I.S. 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 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.
The boiler meets the requirements of Statutory Instrument “ The Boiler (Efficiency)
Regulations 1993 No3083” and is deemed to meet the requirements of Directive
92/42/EEC on the energy efficiency requirements for new hot water boilers fired with
liquid or gaseous fuels:-
Type test for purpose of Regulation 5 certified by:
Notified Body 0085.
Product/Production certified by:
Notified Bodies 0085 & 0086.
For GB/IE only.
All Gas Safe registered engineers carry an ID card with their licence number and a
photograph. You can check your engineer is registered by telephoning
0800 408 5500 or online at www.GasSafeRegister.co.uk

5
Safe Manual Handling
© Baxi Heating UK Ltd 2012
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 shoulders, arms and hands.
Health & Safety is the responsibility of EVERYONE.
There is no ‘safe’ limit for one man - each person has different capabilities. 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 unobstructed. 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.
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 recommended lift points.
Remember
The circumstances of each installation are different. Always asses the risks associated with handling and lifting according to the individual conditions.
If at any time when installing the boiler you feel that you may have injured yourself STOP !!
DO NOT ‘work through’ the pain - you may cause further injury.
IF IN ANY DOUBT DO NOT HANDLE OR LIFT THE BOILER - OBTAIN ADVICE OR ASSISTANCE BEFORE PROCEEDING !!

6© Baxi Heating UK Ltd 2012
CONTENTS
1.0 Introduction 7
2.0 General Layout 8
3.0 Appliance Operation 9
4.0 Technical Data 10
5.0 Dimensions and Fixings 11
6.0 System Details 12
7.0 Site Requirements 15
8.0 Flue Options 21
9.0 Plume Displacement 26
10.0 Installation 30
11.0 Commissioning 35
12.0 Completion 37
13.0 Servicing 38
14.0 Changing Components 40
15.0 Setting the Gas Valve 49
16.0 Electrical 50
17.0 Short Parts List 51
18.0 Fault Finding 52
Benchmark Checklist 58
Section Page

7
1.0 Introduction
© Baxi Heating UK Ltd 2012
1.1 Description
1. The Baxi Duo-tec Combi HE Ais a fully automatic gas fired
wall mounted condensing combination boiler. It is room sealed
and fan assisted, and will serve central heating and mains fed
domestic hot water.
2. The boiler is set to give a maximum output of :-
24 models - 24 kW DHW
21 kW CH (Condensing)
28 models - 28 kW DHW
25.9 kW CH (Condensing)
33 models - 33 kW DHW
30.3 kW CH (Condensing)
40 models - 40 kW DHW
34.4 kW CH (Condensing)
3. It is designed for use on Natural Gas (G20).
4. The boiler is suitable for use only on fully pumped sealed
heating systems. Priority is given to domestic hot water.
5. The boiler data badge gives details of the model, serial
number and Gas Council number and is situated on the inner
door panel. It is visible when the case front panel is removed
(Fig. 1).
6. The boiler model name and serial number are also shown
on the information label on the underside of the facia. This is
for user reference.
7. The boiler is intended to be installed in residential /
commercial / light industrial E.M.C. environments on a
governed meter supply only.
8. The boiler must be installed with one of the purpose
designed flues such as the standard horizontal telescopic flue
kit, part no. 5118069.
9. All systems must be thoroughly flushed and treated with
inhibitor (see section 6.2).
1.2 Optional Extras
Integral timers, RF room thermostats etc. are available as
optional extras.
1.3 Contents of Pack
The pack contains:-
• Boiler
• Wall Plate (including taps)
• Set of Pipe Connections
• Template & ‘Quick Fit’ Guide
• Literature Pack
• Filling Loop
Fig. 1
Control Box
Case Front Panel
Data Badge
Information Label

8
2.0 General Layout
© Baxi Heating UK Ltd 2012
2.1 Layout
1. Expansion Vessel
2. Automatic Air Vent
3. DHW Plate Heat Exchanger
4. Circulation Pump
5. Drain Off Point
6. Pressure Relief Valve
7. Selector Switch
8. Central Heating System Pressure Gauge
9. PCB
10. Control Box
11. 3-Way Valve Assembly
12. Condensate Trap
13. Flame Sensing Electrode
14. Spark Electrode
15. Primary Heat Exchanger
16. Fan Assembly
17. On/Off/Reset Selector Switch
18. Central Heating Temperature Control
19. Hot Water Temperature Control
20. Venturi
21. Air/Gas Collector
22. Combustion Box Cover & Burner
23. Igniter
24. Burner On Light
25. Central Heating Mode Light
26. Domestic Hot Water Mode Light
27. Display
28. Position of Optional Integral Timer
1
17 18 19 8
bar
0
1
2
3
4
22
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
20
21
23
24
25 26
27 28

9
3.0 Appliance Operation
© Baxi Heating UK Ltd 2012
3.1 Central Heating Mode (Fig. 2)
1. With a demand for heating, the pump circulates water
through the primary circuit.
2. Once main burner ignites the fan speed controls the gas
rate to maintain the heating temperature measured by the
temperature sensor.
3. When the flow temperature exceeds the setting
temperature, a 3 minute delay occurs before the burner
relights automatically (anti-cycling). The pump continues to
run during this period.
4. When the demand is satisfied the burner is extinguished
and the pump continues to run for a period of 3 minutes
(Pump Overrun).
3.2 Domestic Hot Water Mode (Fig. 3)
1. Priority is given to the domestic hot water supply. A
demand at a tap or shower will override any central heating
requirement.
2. The flow of water will operate the Hall Effect Sensor
which requests the 3 way valve to change position. This will
allow the pump to circulate the primary water through the
DHW plate heat exchanger.
3. The burner will light automatically and the temperature of
the domestic hot water is controlled by the temperature
sensor.
4. When the domestic hot water demand ceases the burner
will extinguish and the diverter valve will remain in the
domestic hot water mode, unless there is a demand for
central heating.
IMPORTANT: When the selector switch is in the ‘0’
(Off) position the electrical supply to the boiler is isolated.
The boiler will not operate and the integral timer will
require resetting once the selector switch is set to either
Position (i) or Position (ii).
3.3 Frost Protection Mode
1. The frost protection mode is integral to the appliance and
functions only with the selector switch (see Section 2.1) in
the domestic hot water and central heating position. If the
system temperature falls below 5° C then the boiler will fire
on its minimum setting until a flow temperature of 30° C is
reached. Further protection can be incorporated by using a
system frost thermostat.
3.4 Pump Protection
1. With the selector switch (see Section 2.1) in either the
central heating or central heating and domestic hot water
position, the pump will automatically operate for 1 minute in
every 24 hours to prevent sticking.
Fig. 3
1
2
4
5 6
7
8
9
10
11
1213141516
17
18
21
22
24
25
26
3
1 Primary Heat Exchanger
2 Burner
3 Ignition Electrodes
4 Flame Sensing Electrode
5 Gas Valve
6Pump
7 Automatic Air Vent
8 Plate Heat Exchanger/Automatic By-pass
9 Flow Sensor with Filter & Regulator
10 Pressure Relief Valve
11 Boiler Drain Point
12 Heating Return
13 Cold Water Inlet On/Off Valve and Filter
14 Gas Inlet
15 Domestic Hot Water Outlet
16 Heating Flow
17 Pressure Gauge
18 Water Pressure Sensor
20 Fan
21 Diverter Valve Assembly
22 Diverter Valve Motor
23 Domestic Hot Water Flow Temperature Sensor
24 Safety Thermostat
25 Central Heating Temperature Sensor
26 Expansion Vessel
27 Heat Exchanger Air Vent
Key
Central Heating Circuit
Domestic Hot Water Circuit
1
2
4
5 6
7
8
9
10
11
1213141516
17
18
21
22
24
25
26
3
Fig. 2
23
23
20
20
27
27

10
4.0 Technical Data
© Baxi Heating UK Ltd 2012
0
200 400 600 800 1000 1200
0.5
1
1.5
2
2.5
3
3.5
4
Metre (wg)
Flow Rate (l/h)
Pump - Available Head
0
5
5.5
4.5
4.1 Duo-tec Combi 24, 28, 33 & 40 HE A
Flue Terminal Diameter 100mm
Dimensions Projection 125mm
Outercase Dimensions
Casing Height - 780mm
Overall Height Inc Flue Elbow - 965mm
Casing Width - 450mm
Casing Depth - 345mm
Weights
(24 model)
Packaged Boiler Carton 48.6 kg
Installation Lift Weight 43.6 kg
(28 model)
Packaged Boiler Carton 49.2 kg
Installation Lift Weight 44.2 kg
(33 & 40 model)
Packaged Boiler Carton 51kg
Installation Lift Weight 46kg
Central Heating Primary Circuit
Pressures
bar
Safety Discharge 3
Max Operating 2.5
Min Operating 0.5
Recommended Operating Range 1-2
DHW Circuit bar
Pressures
Max Operating 8
Min Operating 0.15
Flow Rates (24) (28) (33) (40)
l/min l/min l/min l/min
DHW Flow Rate
@ 30o C Rise 11.43 13.3 15.7 19.1
DHW Flow Rate
@ 35o C Rise 9.8 11.5 13.5 16.4
Min Working
DHW Flow Rate 2 2 2 2
Pump
Available Head See graph below
Expansion Vessel - (For Central Heating only.
Integral with appliance)
bar
Min Pre-charge Pressure 0.5
(24 & 28) (33 & 40)
litre litre
Max Capacity of
CH System 125 155
Primary Water Content
of Boiler (unpressurised) 2.5 2.8
Connections copper tails
Gas Supply - 22mm
Central Heating Flow - 22mm
Central Heating Return - 22mm
Cold Water Mains Inlet - 15mm
DHW Flow - 15mm
Pressure Relief Discharge - 15mm
Temperatures
C.H. Flow Temp (adjustable)
25°C to 80°C max (± 5°C)
D.H.W. Flow Temp (adjustable)
35°C to 60°C max (± 5°C)
dependent upon flow rate
NOxClass 5
Heat Input CH (Net) Max Min
24 model kW 20.5 7
28 model kW 24.7 9
33 model kW 28.9 9.7
40 model kW 32.8 9.9
Heat Output CH (Non-Condensing)
Max Min
24 model kW 20 6.8
28 model kW 24 8.7
33 model kW 28 9.4
40 model kW 32 9.6
Electrical Supply 230V~ 50Hz
(Appliance must be connected to an
earthed supply)
Power Consumption
155W (24, 28) 160W (33 & 40)
Electrical Protection
IPX0D (with timer)
IPX5D (without timer)
Internal Fuse Rating F2L
Appliance Category CAT I 2H
Inlet Pressure (Natural Gas - G20)
mbar 20
Injector (Natural Gas - G20)
7.5mm (24 & 28) 12mm (33 & 40)
Appliance Type C13 C33 C53
Heat Output CH (Condensing)
Max Min
24 model kW 21 7.4
28 model kW 25.9 9.5
33 model kW 30.3 10.2
40 model kW 34.4 12.1
Heat Input DHW (Net) Max
24 model kW 24.7
28 model kW 28.9
33 model kW 34
40 model kW 41.2
Heat Output DHW Max
24 model kW 24
28 model kW 28
33 model kW 33
40 model kW 40
Max Gas Rate (Natural Gas - G20)
(After 10 mins)
24 model m3/h 2.61
28 model m3/h 3.1
33 model m3/h 3.6
40 model m3/h 4.36
Condensate Drain
To accept 21.5mm (3/4in) plastic waste pipe
Heat Input CH (Gross) Max Min
24 model kW 22.7 7.8
28 model kW 27.4 10
33 model kW 32.1 10.8
40 model kW 36.4 11
Heat Input DHW (Gross) Max
24 model kW 27.4
28 model kW 32.1
33 model kW 37.7
40 model kW 45.7
External Fuse Rating 3A
The efficiency for all models is 91.1%
This value is used in the UK Government’s Standard
Assessment Procedure (SAP) for energy rating of
dwellings. The test data from which it has been calculated
has been certified by 0087.
SEDBUK Declaration
Clearances
Above Casing 200 mm Min
Below Casing 150 mm Min*
Front 450 mm Min (For Servicing)
Front 5 mm Min (In Operation)
L.H. Side 5 mm Min
R.H. Side 5 mm Min (In Operation)
*This is MINIMUM recommended dimension. Greater
clearance will aid installation and maintenance.
IMPORTANT: Where Low Flow Taps or Fittings are
intended to be used in the DHW system connected it is
strongly recommended that the DHW flow rate DOES
NOT fall below 2.5l/min. This will ensure reliable
operation of the DHW function.
NOTE: All data in this section are nominal values
and subject to normal production tolerances.