Baxi Combi 105 HE Release note

© Baxi Heating UK Ltd 2007
Baxi Combi 105 HE
Gas Fired Wall Mounted
Condensing Combination Boiler
These instructions include the Benchmark Commissioning Checklist
and should be left with the user for safe keeping.
Installation & Servicing Instructions

2© Baxi Heating UK Ltd 2007
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.
CORGI operate 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Benchmark Logbook is being withdrawn.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 2007 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, Pentagon House,
Sir Frank Whittle Road, Derby, DE21 4XA.
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.
Baxi Heating UK Ltd is a
BS-EN ISO 9001 Accredited Company
The code of practice for the installation,
commissioning & servicing of central
heating systems.
“Baxi” supports

Installer Notification Guidelines
3
© Baxi Heating UK Ltd 2007
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
CORGI will record the data and
will send a certificate of
compliance to the property
You must ensure that the
notification number issued by
CORGI is written onto the
Benchmark Checklist
Scheme Members only
Call CORGI on: 0870 88 88 777
or log onto:
www.corgi-notify.com
within 10 days
If you notify via CORGI Scheme,
CORGI will then notify the
relevant Local Authority
Building Control Scheme
on member's 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 2007
Codes of Practice, most recent version should be used
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 CORGI registered company and
holding current certificates in the relevant ACS modules, is deemed competent.
All CORGI registered installers carry a CORGI identification card and have a
registration number. You can check your installer is registered by telephoning
0870 4012300 or writing to:-
1 Elmwood,
Chineham Business Park,
Crockford Lane,
Basingstoke. RG24 8WG
or check online at www.corgi-gas-safety.com
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 CORGI
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 5449 Forced circulation hot water 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 BS standards give valuable additional information;
BS 5546 Installation of hot water supplies for
domestic purposes.
BS 5449 Forced circulation hot water 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 0051.
Product/Production certified by:
Notified Body 0086.
For GB/IE only.

Safe Manual Handling
5
© Baxi Heating UK Ltd 2007
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 2007
Data Badge
Fig. 1
Control Box
Case Front Panel

2.0 General Layout
7
© Baxi Heating UK Ltd 2007
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
30o40o50o60o70o80o
24 25 26 27 28 29
30 31 32 33
20

3.0 Appliance Operation
8© Baxi Heating UK Ltd 2007
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
5 Gas Valve
6 Pump
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 2007
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)
35°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 2007
Dimensions
A780mm
B345mm
C450mm
D116mm Ø Min.
E185mm
F190mm
G131mm
360° Orientation
Tube 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
1.5o
28mm
Condensate
Drain

6.0 System Details
11
© Baxi Heating UK Ltd 2007
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 Betz-Dearborn Sentinel X300 or X400 or
Fernox Superfloc Universal Cleanser. 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.
Betz-Dearborn Sentinel X100 and Fernox-Copal which should
be used following the inhibitor manufacturer’s instructions.
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 2007
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.
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 2007
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. A single check valve must be fitted as shown in Fig. 7
to prevent backflow to the supply pipe and to ensure the
efficient operation of the expansion vessel which is
required to accommodate the thermal expansion of the
water.
4. When the domestic water system includes any device
which prevents water expanding back towards the supply
(check valve, loose jumpered stopcock, water meter,
water treatment device) then an expansion vessel must
be fitted (eg. Zilmet 160ml, R1/215bar).
5. If the hot water expansion is not provided for, then
high pressures can develop which may result in damage
to fittings and devices on the system.
6. 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

7.0 Site Requirements
14 © Baxi Heating UK Ltd 2007
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 2007
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 2007
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 6798:2000 & 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 2007
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.
IMPORTANT:
• Only ONE 25mm clearance is allowed per installation.
• 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
Terminal Position with Minimum Distance (Fig. 11) (mm)
AaDirectly below an opening, air brick, opening
windows, etc. 300
BaAbove an opening, air brick, opening window etc. 300
CaHorizontally to an opening, air brick, opening window etc. 300
D Below gutters, soil pipes or drain pipes. 25
E Below eaves. 25
F Below balconies or car port roof. 25
G From a vertical drain pipe or soil pipe. 25
H From 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
aIn 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. See BS 5440 Pt. 1.
*
Opening Window
or Door
100mm
MIN.
IMPORTANT: If fitting a Plume
Displacement Flue Kit, the air inlet
must be a minimum of 100mm from
any opening windows or doors (see
Section 9.0).
Plume
Displacement Kit
Air Inlet
Fig. 12a

8.0 Flue Options
18 © Baxi Heating UK Ltd 2007
8.1 Horizontal Flue Systems
1. The Baxi Combi 105 HE can be fitted with either
horizontal, vertical or twin flue systems as illustrated.
2. The standard flue is suitable only for horizontal
applications.
3. Maximum permissible equivalent flue lengths are:-
Horizontal Concentric 3m
Vertical Concentric 3m
Vertical Twin Pipe 12m
4. 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.
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 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 (upto 3m) =
A+B+C+2x90°Bends
B
AC
This bend is equivalent to
1 metre

8.0 Flue Options
19
© Baxi Heating UK Ltd 2007
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.
4. 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.

8.0 Flue Options
20 © Baxi Heating UK Ltd 2007
Key Accessory Size Baxi 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°/45° 246141
Lead tile 35°/55° 246142
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