Baxi BAXI COMBI INSTANT 105 HE User guide

© Baxi Heating UK Ltd 2011
Baxi Combi 105 HE
Gas Fired Wall Mounted
Condensing 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 2011
Natural Gas
Baxi Combi 105 HE
G.C.No47 075 18
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Logbook is being withdrawn.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.
Legislation 4
1.0 Introduction 6
2.0 General Layout 7
3.0 Appliance Operation 8
4.0 Technical Data 9
5.0 Dimensions and Fixings 10
6.0 System Details 11
7.0 Site Requirements 14
8.0 Flue Options 18
9.0 Plume Displacement 23
10.0 Installation 27
11.0 Commissioning the Boiler 32
12.0 Completion 34
13.0 Servicing the Boiler 35
14.0 Changing Components 37
15.0 Illustrated Wiring Diagram 47
16.0 Fault Finding 48
17.0 Short Parts List 53
Benchmark Checklist 54
Section Page
Contents
© Baxi Heating UK Ltd 2011 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 Limited,
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.
0086
ISO 9001
FM 00866
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.

Installer Notification Guidelines
3
© Baxi Heating UK Ltd 2011
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

Legislation
4© Baxi Heating UK Ltd 2011
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).
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 0051.
Product/Production certified by:
Notified Bodies 0051 & 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
Codes of Practice - refer to the most recent version
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.

Safe Manual Handling
5
© Baxi Heating UK Ltd 2011
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 !!

1.1 Description
1. The Baxi Combi 105 HE is 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
31.0 kW (condensing).
3. It is designed for use on Natural Gas (G20) and can be
converted to use Propane.
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
control box. It is visible when the case front panel is
removed (Fig. 1).
6. The boiler is intended to be installed in residential /
commercial / light industrial E.M.C. environments on a
governed meter supply only.
7. The boiler must be installed with one of the purpose
designed flues such as the standard horizontal flue kit,
part no. 5118489.
8. All systems must be thoroughly flushed and treated
with inhibitor (see section 6.2).
1.0 Introduction
6© Baxi Heating UK Ltd 2011
Data Badge
Fig. 1
Control Box
Case Front Panel

2.0 General Layout
7
© Baxi Heating UK Ltd 2011
2.1 Layout
1. Air Pressure Switch
2. Expansion Vessel
3. Burner Manifold
4. Automatic Air Vent
5. DHW Plate Heat Exchanger
6. Circulation Pump
7. Drain Off Point
8. Pressure Relief Valve
9. Optional Integral Timer
10. Central Heating System Pressure Gauge
11. PCB
12. Control Box
13. 3-Way Valve Assembly
14. Condensate Trap
15. Flame Sensing Electrode
16. Spark Electrode
17. Burner
18. Primary Heat Exchanger
19. Fan Assembly
20. Secondary Heat Exchanger
21. On/Off/Reset Selector Switch
22. Central Heating Temperature Control
23. Hot Water Temperature Control
24. Flame Failure or Blocked Condensate Drain
25. Safety Thermostat Activated (Boiler or Flue)
26. Fault on Fan or Flue
27. Fault on Pump or Low System Pressure
28. Fault on Hot Water Sensor
29. Fault on Central Heating Sensor
30. Power On
31. Domestic Hot Water Mode
32. Central Heating Mode
33. Burner On
When neons 24 to 29 are constantly illuminated, they
indicate the temperature of the central heating water.
19
18
17
14
15
16
13
12 11
10 9
21 22 23 10 9
7
6
3
4
5
8
2
1
30o40o50o60o70o80o
Reset
bar
0
1
2
3
4
30o40o50o60o70o80o
24 25 26 27 28 29
30 31 32 33
20

3.0 Appliance Operation
8© Baxi Heating UK Ltd 2011
NOTE: All delay timers mentioned in 3.1 and 3.2 are
overridden by domestic hot water demand.
3.1 Central Heating Mode (Fig. 2)
1. With a demand for heating, the pump circulates water
through the primary circuit. At a pre-determined flow
rate the central heating flow switch operates, initiating
the ignition sequence.
2. The main burner ignites at low rate, then the gas valve
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 DHW flow switch
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 (if fitted) 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.
1
2
4
5 6
7
8
9
10
11
1213141516
17
18
19
20
21
22
23
24
25
26
3
1 Primary Heat Exchanger
2 Burner
3 Ignition Electrode
4 Flame Sensing Electrode
5GasValve
6Pump
7 Automatic Air Vent
8 Plate Heat Exchanger
9 Flow Sensor with Filter
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 Hydraulic Differential Pressure Sensor Microswitch
19 Automatic By-Pass
20 Hydraulic Differential Pressure Sensor
21 Diverter Valve Assembly
22 Domestic Hot Water Flow Priority Assembly
23 Domestic Hot Water Flow Priority Microswitch
24 Safety Thermostat
25 Central Heating Temperature Sensor
26 Expansion Vessel
27 Domestic Hot Water Temperature Sensor
28 Secondary Heat Exchanger
Key
Central Heating Circuit
Domestic Hot Water Circuit
Fig. 3
1
2
4
5 6
7
8
9
10
11
1213141516
17
18
19
20
21
22
23
24
25
26
3
Fig. 2
27
27
28
28

4.0 Technical Data
9
© Baxi Heating UK Ltd 2011
4.1 Combi 105 HE
Flue Terminal Diameter 100mm
Dimensions Projection 125mm
Outercase Dimensions
Casing Height - 780mm
Overall Height Inc Flue
Elbow - 965mm
Casing Width - 450mm
Casing Depth - 345mm
Clearances
Above Casing 200 mm Min
Below Casing 200 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)
20mm Min (See Note*)
*NOTE: The boiler can be operated with a
clearance of 5mm at the right. This is also
sufficient for routine maintenance. However a
clearance of 20mm is required if it is necessary to
remove the secondary heat exchanger. This
should be considered when siting the appliance
and in the event of any subsequent alterations in
the area of installation
Weights kg
Packaged Boiler Carton 54
Installation Lift Weight 44
Central Heating Primary Circuit
Pressures
bar
Safety Discharge 3
Max Operating 2.5
Min Operating 0.5
Recommend Operating 1-2
DHW Circuit bar
Pressures
Max Operating 8
Min Operating 0.2
Min Operating Pressure
at 13.2 l/min 0.96
Flow Rates l/min
DHW Flow Rate
@ 30°C Rise 14.1
DHW Flow Rate
@ 35°C Rise 12.1
Min Working
DHW Flow Rate 2.5
Pump
Available Head See graph below
Expansion Vessel - (For Central Heating
only. Integral with appliance)
bar
Min Pre-charge Pressure 0.5
litre
Max Capacity of
CH System 125
Primary Water Content 1.2
of Boiler (unpressurised)
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)
30°C to 85°C max (± 5°C)
D.H.W. Flow Temp (adjustable)
35°C to 65°C max (± 5°C)
dependent upon flow rate
Heat Input CH
Max Min
kW 30.5 11.9
Heat Output CH (Non-Condensing)
Max Min
kW 29.6 11
Electrical Supply 230V~ 50Hz
(Appliance must be connected to an
earthed supply)
Power Consumption 180W
External Fuse Rating 3A
Internal Fuse Rating
Fuse 2A Fast Blow to BS 4265
Appliance Category CAT II 2H 3P
Inlet Pressure (Natural Gas - G20)
mbar 20
Burner Injector (Natural Gas - G20)
15 x 1.25mm Diameter
Burner Pressure (Natural Gas - G20)
Max Rate Min Rate
mbar 12.1 ± 0.5 2.1 ± 0.2
Appliance Type C12 C32 C52
NOxClass 3
Electrical Protection IPX5D
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 have been certified by 0051.
SEDBUK Declaration For Combi 105 HE
The seasonal efficiency (SEDBUK) is 87.3% (89.4% LPG)
Band B
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
4.5
LPG Propane - G31
Burner Injector 15 x 0.77mm diameter
Burner Pressure
Propane mbar
Inlet Pressures
mbar
Max Rate
32.3 ± 0.5
Min Rate
5.2 ± 0.2
37
Heat Output CH (Condensing)
Max Min
kW 31 11.3
Heat Input DHW
Max
kW 30.5
Heat Output DHW
Max
kW 29.6
Condensate Drain 1” BSP
Max Gas Rate (Natural Gas - G20)
(After 10 mins)
m3/h 3.22

5.0 Dimensions and Fixings
10 © Baxi Heating UK Ltd 2011
Dimensions
A780mm
B345mm
C450mm
D116mm Ø Min.
E185mm
F190mm
G131mm
360° Orientation
Flue Ø 100mm
DC
B
A
E
G
F
Domestic Hot
Water Outlet
(15mm)
Cold Water
Inlet
(15mm)
Heating
Return
(22mm)
Heating
Flow
(22mm)
Pressure Relief
Valve
(15mm)
Gas
Inlet
(22mm)
65 mm 65 mm 65 mm 65 mm 65 mm
Tap Rail
At least 1.5o
28mm
Condensate
Drain

6.0 System Details
11
© Baxi Heating UK Ltd 2011
6.1 Information
1. The Baxi Combi 105 HE Condensing Combination Boiler is
‘Water Byelaws Scheme - Approved Products’.
To comply with the Water Byelaws your attention is drawn to
the following installation requirements and notes (IRN).
a) IRN 001 - See text of entry for installation
requirements and notes.
b) IRN 302 - Byelaw 14.
2. Reference to the WRc publications, ‘Water fittings and
materials directory’ and ‘Water supply byelaws guide’ give full
details of byelaws and the IRNs.
6.2 Central Heating Circuit
1. The appliance is suitable for fully pumped SEALED
SYSTEMS ONLY.
Treatment of Water Circulating Systems
• All recirculatory water systems will be subject to
corrosion unless an appropriate water treatment is
applied. This means that the efficiency of the system will
deteriorate as corrosion sludge accumulates within the
system, risking damage to pump and valves, boiler noise
and circulation problems.
• When fitting new systems flux will be evident within the
system, which can lead to damage of system components.
• All systems must be thoroughly drained and flushed out
using, for example, Sentinel X300 or X400 or Fernox F3.
They should be used following the flushing agent
manufacturer’s instructions.
• System additives - corrosion inhibitors and flushing
agents/descalers should comply to BS7593 requirements,
e.g. Sentinel X100 and Fernox MB-1 which should be used
following the inhibitor manufacturer’s instructions.
• Full instructions are supplied with the products, for
further information contact Sentinel (0800 389 4670) or
Fernox (0870 870 0362)
Failure to flush and add inhibitor to the system will
invalidate the appliance warranty.
• It is important to check the inhibitor concentration after
installation, system modification and at every service in
accordance with the manufacturer’s instructions. (Test kits
are available from inhibitor stockists.)
• For information or advice regarding any of the above
contact Technical Enquiries.
6.3 Bypass
1. The boiler is fitted with an automatic integral bypass.
6.4 System Control
1. The boiler is designed for use in a heating system that
incorporates external controls, i.e. a minimum of a timer
device.
2. Suitable timer kits are available as optional extras.
3. For optimum operating conditions and maximum
economy the fitting of a programmable room thermostat,
is recommended.

6.0 System Details
12 © Baxi Heating UK Ltd 2011
6.5 System Filling and Pressurising
1. A filling point connection on the central heating return
pipework must be provided to facilitate initial filling and
pressurising and also any subsequent water loss
replacement/refilling.
2. There are connection points on the mains cold water
inlet and central heating return isolating taps (Fig. 5) to
which the optional filling loop kit (Part No. 248221) can
be assembled.
3. The filling method adopted must be in accordance with
all relevant water supply regulations and use approved
equipment.
4. Your attention is drawn to,
for GB: guidance G24.2 and recommendation R24.2 of
the Water Regulations Guide.
for IE: the current edition of I.S. 813. “Domestic Gas
Installations”.
5. The sealed primary circuits may be filled or replenished
by means of a temporary connection between the circuit
and a supply pipe provided a ‘Listed’ double check valve
or some other no less effective backflow prevention
device is permanently connected at the inlet to the circuit
and the temporary connection is removed after use.
6.6 Expansion Vessel
(Central Heating only)
1. The appliance expansion vessel is pre-charged to 0.5
bar. Therefore, the minimum cold fill pressure is 0.5 bar.
The vessel is suitable for correct operation for system
capacities up to 125 litres. For greater system capacities an
additional expansion vessel must be fitted. For GB refer to
BS 7074 Pt 1. For IE, the current edition of
I.S. 813 “Domestic Gas Installations”.
6.7 Pressure Relief Valve (Fig. 6)
1. The pressure relief valve is set at 3 bar, therefore all
pipework, fittings, etc. should be suitable for pressures in
excess of 3 bar.
2. The pressure relief discharge pipe should be not less
than 15mm dia, run continuously downward, and
discharge outside the building, preferably over a drain. It
should be routed in such a manner that no hazard occurs
to occupants or causes damage to wiring or electrical
components. The end of the pipe should terminate facing
down and towards the wall.
3. The discharge must not be above a window, entrance
or other public access. Consideration must be given to the
possibility that boiling water/steam could discharge from
the pipe.
4. A remote relief valve kit is available to enable the boiler
to be installed in cellars or similar locations below outside
ground level (kit no. 5121379).
Fig. 4
Fig. 6
Stop
Valve
Double
Check
Valve
DHW
Mains
Inlet
CH
Return
Temporary
Hose
Pressure Relief Valve Discharge Pipe
Filling Loop
Fig. 5
Stop
Valve

6.0 System Details
13
© Baxi Heating UK Ltd 2011
6.8 Domestic Hot Water Circuit (Fig. 7)
1. All DHW circuits, connections, fittings, etc. should be
fully in accordance with relevant standards and water
supply regulations.
2. Your attention is drawn to:
for GB: Guidance G17 to G24 and recommendation R17
to R24 of the Water Regulations Guide.
for IE: the current edition of I.S. 813. “domestic Gas
Installations”.
3. The Water Regulations recommendations for England
and Wales prohibits backflow from appliances into the
wholesome water supply due to thermal expansion.
However this type of instantaneous combination boiler,
with less than 15 litres of stored capacity, does not
require any backflow prevention device as any thermal
expansion is accommodated within the appliance.
It is possible in certain circumstances that other cold
water demands (e.g. washing machines, flushing of W.C.s)
may affect the DHW function of the boiler. In these
instances the fitting of a backflow prevention device and
expansion vessel is recommended.
4. Also if there is an existing check valve, loose jumpered
stop cock, water meter or water treatment device
already fitted to the wholesome water supply connected
to the boiler domestic hot water (DHW) inlet supply
then a suitable expansion device may be required.
5. The boiler’s maximum working mains pressure is 8 bar,
therefore all pipework, connections, fittings, etc. should
be suitable for pressures in excess of 8 bar. A pressure
reducing valve must be fitted for pressures in excess of 8
bar. The manufacturer of any outlet fittings, such as a
shower valve, may require a lower maximum pressure.
The pressure reduction must take account of all fittings
connected to the DHW system.
6.9 Showers
1. If a shower control is supplied from the appliance it
should be of the thermostatic or pressure balanced type.
Thermostatic type shower valves provide the best
comfort and guard against water at too high a
temperature. Existing controls may not be suitable - refer
to the shower valve manufacturer.
6.10 Hard Water Areas
1. If the area of the installation is recognised as a HARD
WATER AREA then a suitable device should be fitted to
treat the mains water supply to the boiler. Contact your
Water Distribution Company for advice on suitable
devices.
Boiler
Other Tap
Outlets
Expansion
Vessel*
To Hot
Taps
Check
Valve*
Pressure Reducer
Valve*
Stop Tap
Fig. 7
*See 6.8 for instances when
these items may be required

7.0 Site Requirements
14 © Baxi Heating UK Ltd 2011
7.1 Location
1. The boiler may be fitted to any suitable wall with the
flue passing through an outside wall or roof and discharging
to atmosphere in a position permitting satisfactory removal
of combustion products and providing an adequate air
supply. The boiler should be fitted within the building
unless otherwise protected by a suitable enclosure i.e.
garage or outhouse. (The boiler may be fitted inside a
cupboard-see Section 7.3).
2. If the boiler is sited in an unheated enclosure then it is
recommended to leave the ON/OFF Selector Switch in
the domestic hot water and central heating position to
give frost protection.
3. If the boiler is fitted in a room containing a bath or
shower reference must be made to the relevant
requirements.
In GB this is the current I.E.E. Wiring Regulations and
Building Regulations.
In IE reference should be made to the current edition of
I.S. 813 “Domestic Gas Installations” and the current ETCI
rules.
4. If the boiler is to be fitted into a building of timber frame
construction then reference must be made to the current
edition of Institute of Gas Engineers Publication IGE/UP/7
(Gas Installations in Timber Framed Housing).
7.2 Clearances (Figs. 8 & 9)
1. A flat vertical area is required for the installation of the
boiler.
2. These dimensions include the necessary clearances
around the boiler for case removal, access during routine
maintenance and air movement. Additional clearances may
be required for the passage of pipes around local
obstructions such as joists running parallel to the front face
of the boiler.
* NOTE: The boiler can be operated with a clearance
of 5mm at the right. This is also sufficient for routine
maintenance. However a clearance of 20mm is
required if it is necessary to remove the secondary
heat exchanger. This should be considered when
siting the appliance and in the event of any
subsequent alteration in the area of installation.
200mm Min
780mm
450mm
200mm Min
20mm/5mm Min
See * NOTE:
5mm Min
5mm Min
450mm Min
For Servicing
Purposes
Fig. 8
Fig. 9
In Operation

7.0 Site Requirements
15
© Baxi Heating UK Ltd 2011
7.3 Ventilation of Compartments
1. Where the appliance is installed in a cupboard or
compartment, no air vents are required.
2. BS 5440: Part 2 Clause 4.2 refers to room sealed
appliances installed in compartments. The appliance will
run sufficiently cool without ventilation.
7.4 Gas Supply
1. The gas installation should be in accordance with the
relevant standards. In GB this is BS 6891. In IE this is the
current edition of I.S. 813 “Domestic Gas Installations”.
2. The connection to the appliance is a 22mm copper
tail located at the rear of the gas service cock (Fig. 10).
3. Ensure that the pipework from the meter to the
appliance is of adequate size. Do not use pipes of a
smaller diameter than the boiler gas connection
(22mm).
7.5 Electrical Supply
1. External wiring must be correctly earthed, polarised
and in accordance with relevant regulations/rules. In GB
this is the current I.E.e. Wiring Regulations. In IE
reference should be made to the current edition of
ETCI rules.
2. The mains supply is 230V ~ 50Hzfused at 3A.
NOTE: The method of connection to the
electricity supply must facilitate complete electrical
isolation of the appliance.
Connection may be via a fused double-pole
isolator with a contact separation of at least 3mm
in all poles and servicing the boiler and system
controls only.
Fig. 10
Gas Service Cock

7.0 Site Requirements
16 © Baxi Heating UK Ltd 2011
7.6 Condensate Drain
FAILURE TO INSTALL THE CONDENSATE
DISCHARGE PIPEWORK CORRECTLY WILL AFFECT
THE RELIABLE OPERATION OF THE BOILER
The condensate discharge pipe MUST NOT RISE at any
point along its length. There MUST be a fall of AT LEAST
2.5° (50mm per metre) along the entire run.
1. The condensate outlet terminates in a 1” BSP nut and seal
for the connection of 21.5mm (3/4in) plastic overflow pipe
which should generally discharge internally into the household
drainage system. If this is not possible, discharge into an
outside drain is acceptable.
2. Ensure the discharge of condensate complies with any
national or local regulations in force.
BS 6798 & Part H1 of the Building Regulations give further
guidance.
3. The discharge pipe should be run in a proprietary drain pipe
material e.g. PVC, PVC-U, ABS, PVC-C or PP.
4. Metal pipework is NOT suitable for use in condensate
discharge systems.
5. The pipe should be a minimum of 21.5mm diameter and
must be supported using suitably spaced clips to prevent
sagging.
6. It is advisable to keep the condensate pipe internal.
7. External runs greater than 3 metres or runs in cold areas
should use 32mm waste pipe.
8. If the boiler is fitted in an unheated location the entire
condensate discharge pipe should be treated as an external
run.
9. In all cases discharge pipe must be installed to aid disposal
of the condensate. To reduce the risk of condensate being
trapped, as few bends and fittings as possible should be used.
10. When discharging condensate into a soil stack or waste
pipe the effects of existing plumbing must be considered. If soil
pipes or waste pipes are subjected to internal pressure
fluctuations when WC's are flushed or sinks emptied then
back-pressure may force water out of the boiler trap and
cause appliance lockout.
Examples are shown of the following methods of termination:-
i) to an internal soil & vent pipe
ii) via an internal discharge branch (e.g. sink waste)
iii) to a drain or gully
iv) to a purpose made soakaway
Boiler
2.5° Minimum fall
Termination to an internal soil and vent pipe
450mm min
Boiler
2.5° Minimum fall
External termination via internal
discharge branch
e.g sink waste - downstream
Sink
Pipe must terminate
above water level but
below surrounding
surface
Boiler Pipe must terminate above
water level but below
surrounding surface
2.5° Minimum fall
External termination to a drain or gully
Boiler
500mm min
2.5° Minimum fall
External termination to a purpose made soak-away
Holes in the soak-away must
face away from the building
50mm per metre of pipe run
50mm per metre of pipe run
50mm per metre of pipe run
50mm per metre of pipe run

7.0 Site Requirements
17
© Baxi Heating UK Ltd 2011
7.7 Flue
NOTE: Due to the nature of the boiler a plume of water
vapour will be discharged from the flue. This should be
taken into account when siting the flue terminal.
1. The following guidelines indicate the general requirements
for siting balanced flue terminals. For GB recommendations
are given in BS 5440 Pt 1. For IE recommendations are given
in the current edition of I.S. 813 “Domestic Gas
Installations”.
2. If the terminal discharges onto a pathway or passageway,
check that combustion products will not cause a nuisance
and that the terminal will not obstruct the passageway.
3. If a terminal is less than 2 metres above a balcony, above
ground or above a flat roof to which people have access,
then a suitable terminal guard must be provided.
4. * Reduction to the boundary is possible down to 25mm
but the flue deflector kit (part no. 5111068) must be fitted.
IMPORTANT:
• Under car ports we recommend the use of the plume
displacement kit.
• The terminal position must ensure the safe and
nuisance - free dispersal of combustion products.
N
I
I
G
F
M
I
AAF
H
J,K
D
E
H
Likely flue positions requiring
a flue terminal guard
C
RA
I
J,K
I
L
S
B
T
U
Fig. 11
Fig. 12
300 min
Terminal
Assembly
Top View Rear Flue
Property Boundary Line
NOTE: The distance from a fanned draught appliance terminal
installed parallel to a boundary may not be less than 300mm in
accordance with the diagram below
*
Opening Window
or Door
150mm
MIN.
IMPORTANT: If fitting a Plume
Displacement Flue Kit, the air inlet
must be a minimum of 150mm from
any opening windows or doors (see
Section 9.0).
Plume
Displacement Kit
Air Inlet
Fig. 12a
Terminal Position with Minimum Distance (Fig. 11) (mm)
A1Directly below an opening, air brick, opening
windows, etc. 300
B1Above an opening, air brick, opening window etc. 300
C1Horizontally to an opening, air brick, opening window etc. 300
D2Below gutters, soil pipes or drain pipes. 25
E2Below eaves. 25
F2Below balconies or car port roof. 25
G2From a vertical drain pipe or soil pipe. 25
H2From an internal or external corner. 25
I Above ground, roof or balcony level. 300
J From a surface or boundary line facing a terminal. 600
K From a terminal facing a terminal (Horizontal flue). 1200
From a terminal facing a terminal (Vertical flue). 600
L From an opening in carport (e.g. door, window)
into the dwelling. 1200
M Vertically from a terminal on the same wall. 1500
N Horizontally from a terminal on the same wall. 300
R From adjacent wall to flue (vertical only). 300
S From an adjacent opening window (vertical only). 1000
T Adjacent to windows or openings on pitched and flat roofs 600
U Below windows or openings on pitched roofs 2000
1In addition, the terminal should be no nearer than 150 mm to an opening in the
building fabric formed for the purpose of accommodating a built-in element such as
a window frame.
2Only ONE 25mm clearance is allowed per installation. If one of the dimensions
D, E, F, G or H is 25mm then the remainder MUST be as B.S.5440-1.

8.0 Flue Options
18 © Baxi Heating UK Ltd 2011
8.1 Horizontal Flue Systems
1. The standard flue is suitable only for horizontal
applications.
2. Maximum permissible equivalent flue lengths are:-
Horizontal Concentric 3m
3. Any additional “in line” bends in the flue system must
be taken into consideration. Their equivalent lengths
are:-
Concentric Pipes:
135° bend 0.5 metres
93° bend 1.0 metres
Twin Flue Pipe
135° bend 0.25 metres
91.5° bend 0.50 metres
The elbow supplied with the standard horizontal flue is
not included in any equivalent length calculations.
NOTE: Flue length is measured from point X to Y
as shown.
IMPORTANT: All flue systems must be securely
supported at least once every metre. Suitable pipe
supports are available as accessories.
Horizontal
Flues
Y
X
Plume Displacement Kit 60 /100 Ø
1M Extensions, 45° & 93° elbows
are also available - see Section 9.0
NOTE: Horizontal flue pipes should always be installed with at least a 1.5° fall
from the terminal to allow condensate to run back to the boiler.
Y
X
This bend is equivalent to
1 metre
Total equivalent length =
A+B+C+2x90°Bends
B
AC
This bend is equivalent to
1 metre

8.0 Flue Options
19
© Baxi Heating UK Ltd 2011
Vertical
Flues
(Twin Pipe)
Y
X
Vertical
Flues
Y
X
The total equivalent length for this example is
= 6.5 metres.
1m extension
135°bend
91.5°bend
1m
0.25m
0.5m
5
2
2
5.0m
0.5m
1.0m
AIR DUCT
Noof
fittings/pipes Sub total
Equivalent
Length Value
Equivalent Length Air Duct = 6.5m
1m extension
135°bend
91.5°bend
1m
0.25m
0.5m
5
2
2
5.0m
0.5m
1.0m
FLUE DUCT
Noof
fittings/pipes Sub total
Equivalent
Length Value
Equivalent Length Flue Duct = 6.5m
Y
X
C
Roof
Terminal
A
B
This bend is equivalent to
1 metre
Total Equivalent Length =
A+B+C+1x90°Bend
All vertical and angled runs must be included,
measured from the boiler adaptor (point X) to the
joint with the flue terminal (point Y). One 91.5°
bend or two 135° bends can be included without
reduction of the flue length.
If further elbows are required the flue length must
be reduced by the following amounts:-
1 metre for each 91.5° bend
0.5 metre for each 135° bend
8.2 Twin & Vertical Flue Systems
1. Maximum permissible equivalent flue lengths are:-
Vertical Concentric 3m
Vertical Twin Pipe 12m*
* Both the air and flue duct can be up to 12 metres
long each.
2. Any additional “in line” bends in the flue system must
be taken into consideration. Their equivalent lengths
are:-
Concentric Pipes:
135° bend 0.5 metres
93° bend 1.0 metres
Twin Flue Pipe
135° bend 0.25 metres
91.5° bend 0.50 metres
The elbow supplied with the standard horizontal flue is
not included in any equivalent length calculations
NOTE: Flue length is measured from point X to Y
as shown.
IMPORTANT: All flue systems must be securely
supported at least once every metre. Suitable pipe
supports are available as accessories.

8.0 Flue Options
20 © Baxi Heating UK Ltd 2011
Key Accessory Size Code No
FLUE GROUP A
Concentric Flue System 100mm diameter
A3 Telescopic Internal Flue Kit 315-500mm 5119654
A2 Telescopic Flue (incl elbow) 5118069
A Horizontal flue Terminal (incl elbow) 5118489
B Flue extension 1000mm 5111074
C Flue Bend 93° 5111075
D Flue Bend (pair) 135° 5111085
U Pipe support (painted) 100mm 5111080
R Vertical flue adaptor (use with 5111078) 5111070
P Wall Liner 5111067
S Flue Terminal Deflector 5111068
FLUE GROUP N
Twin Flue System 80mm diameter
E Flue extension (pair) 1000mm 5111087
F Flue Bend (pair) 90° 5111072
G Flue Bend (2 pair) 135° 5111086
J Vertical flue boiler adaptor kit 5111079
H Vertical flue adaptor 5111084
W Pipe support (pair) 80mm 5111081
FLUE GROUP A, N,
Vertical Flue Kits
K Vertical flue terminal (use with 5111070) 5111078
K1 Vertical flue terminal 5118576
L Lead tile 25°/50° 5122151
M Roof cover plate 246143
N Flat roof flashing 246144
A
B
K, K1
R
D
C
N
U,W
S
L
H
J
M
E
GF
P
8.3 Flue Accessories
A2
A3