Baxi Maxflow Combi WM User guide

Baxi Maxflow Combi WM Please leave these instructions with
the user
Gas fired Wall Mounted Combination Boiler
with Unvented Hot Water storage
Comp No247308 - Iss 3 – 6/00
Installation and
Servicing Instructions

2
Page 2
Baxi Maxflow Combi WM
G.C. No47 075 03
Baxi Limited is one of the leading
manufacturers of domestic heating products in
the UK.
Our first priority is to give a high quality service
to our customers. Quality is built into every
Baxi product -products which fulfil the
demands and needs of customers, offering
choice, efficiency and reliability.
To keep ahead of changing trends, we have
made a commitment to develop new ideas
using the latest technology - with the aim of
continuing to make the products that
customers want to buy.
Baxi is also the largest manufacturing
partnership in the country. Everyone who
works at the company has a commitment to
quality because, as shareholders, we know
that satisfied customers mean continued
success.
We hope you get a satisfactory service from
Baxi. If not, please let us know.
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 0051.
For GB/IE only.
Baxi is a BS-EN ISO 9001
Accredited Company

3
Contents - Page 3
Section
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
10.0
11.0
12.0
13.0
14.0
Introduction
General Layout
Appliance Operation
Technical Data
Dimensions and Fixings
System Details
Site Requirements
Installation
Commissioning the Boiler
Servicing the Boiler
Changing Components
Illustrated Wiring Diagram
Fault Finding
Short Parts List
Page
4
5
6
7
8
9
13
18
23
25
27
36
38
42

4
1.0 Introduction – Page 4
NOTE: 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.
Baxi UK Limited declare that no substances harmful to
health are contained in the appliance or used during
appliance manufacture.
1.1 Description
1. The Baxi Maxflow Combi WM is a fully automatic gas
fired wall mounted combination boiler incorporating a 54
litre unvented hot water storage cylinder. It is room sealed
and fan assisted.
2. The boiler is designed for use with a fully pumped,
sealed and pressurised system and provides central
heating and hot water at mains pressure. It incorporates a
pump, diverter valve, pressure relief valve, expansion
vessel and pressure gauge.
3. As supplied the boiler will automatically modulate to
provide a central heating output between 10.4kW and 28.0
kW. The maximum output to central heating can be
adjusted between 10.4 kW and 28.0 kW (see Section 9.2).
The maximum output available for domestic hot water is
28.0 kW.
4. The boiler has been approved to the Building
Regulations for unvented hot water storage systems and
the Local Authority must be informed of the intention to
install.
IMPORTANT: The installation of unvented hot water
storage systems and their components must only be
carried out by suitably qualified personnel.
Consideration should be given to Building Regulations
document G3.
5. The components supplied in the box marked ‘Unvented
Kit” MUST be fitted to the mains water supply in
accordance with the instructions included.
6. It is designed for use on Natural Gas (G20) and can be
converted to use Propane or Butane.
7. A label giving details of the model, serial number and
Gas Council number is situated on the rear of the facia
panel (Fig. 1).
8. The boiler data badge is positioned inside the left hand
outercase panel (Fig. 2).
9. The boiler is intended to be installed in residential /
commercial / light industrial E.M.C. environments on a
governed meter supply only.
10. The boiler must be installed with one of the purpose
designed flues such as the standard horizontal flue kit.
11. All systems must be thoroughly flushed and
treated with Inhibitor (see section 6.2).
“Benchmark” Log Book
As part of the industry-wide “Benchmark” initiative all Baxi
boilers now include an Installation, Commissioning and
Service Record Log Book. Please read the Log Book
carefully and complete all sections relevant to the appliance
and installation. These include sections on the type of
controls employed, flushing the system, burner operating
pressure etc. The details of the Log Book will be required in
the event of any warranty work. Also, there is a section to
be completed at each subsequent regular service visit.
1.2 Installation
1. The appliance is suitable for installation only in G.B.
and I.E. and should be installed in accordance with the
rules in force. For Ireland install in accordance with l.S.813
“Installation of Gas Appliances”. The installation must be
carried out by a CORGI Registered Installer or other
competent person and be in accordance with the relevant
requirements of current Gas Safety (Installation and Use)
Regulations, the Building Regulations (Scotland)
(Consolidation), the Local Building Regulations, the
Current I.E.E. Wiring Regulations and the bye laws of the
Local Water Undertaking. Where no specific instructions
are given, reference should be made to the relevant
BRITISH STANDARD CODES OF PRACTICE.

5
2.0 General Layout – Page 5
2.1 Layout
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Fan Assembly
Sensing Electrode
Pressure Relief Valve
Automatic Air Vent
Circulation Pump
Gas Valve Assembly
Facia and Control Panel
Optional Integral Timer
Pressure Gauge
Electrical Box
Motorised Valve
Burner
Spark Electrodes
Heat Exchanger
Expansion Vessel
Air Pressure Switch
Cylinder Safety Valve
Hot Water Storage Cylinder
Central Heating Temperature Control
Domestic Hot Water Temperature Control
ON/OFF Selector Switch
Indicator Neons
Reset Button
Flame Failure Reset Button
Pressure Gauge
2.2 Optional Extras
KIT PART No
HORIZONTAL FLUE KITS
1M Flue Extension (use two kits for 2M etc.) 247723
0.5 M Flue Extension 247724
Flue Bend - 45º (Reduce overall length of flue 247725
by 0 5m when fitting this bend)
Flue Bend . 90º(Reduce overall length of flue 247726
by 1 m when fitting this bend)
Wall Liner/Internal Fixing 236441
VERTICAL FLUE KITS
See the Boiler Installers Guide
CONTROL ACCESSORIES
Programmable Room Thermostat (24 hour) 236254
Programmable Room Thermostat (7 day) 238326
Integral Electronic Timer Kit (7 day) 247207
Integral Electro-Mechanical Timer Kit 247206
(12 hour am/pm)
FUEL KIT
LPG Conversion. Propane / Butane 247372

6
3.0 Appliance Operation – Page 6
Main Heat Exchanger 14 Heating Flow
Automatic Air Vent 15 Heating Return
Burner 16 Cold Water Inlet
Ignition Electrodes 17 Domestic Hot Water Outlet
Flame Sensing Electrode 18 Flow Restrictor
Differential Pressure Switch 19 Hot Water Storage Temperature
Sensor
Gas Valve 20 Temperature/Pressure Relief Valve
Primary Flow Temperature Sensor 21 Storage Cylinder
3-Way Diverter Valve 22 Secondary Heat Exchanger
0 Pump 23 Central Heating Expansion Vessel
1 By-Pass 24 Safety Unit Thermostat
2 Pressure Gauge 25 Central Heating Pressure Relief Valve
3 Gas Inlet
1.3 Boiler Operation
1. The boiler operating mode is controlled by the selector
switch on the control panel. When set to it will operate
in the Domestic Hot Water and Central Heating modes.
For Domestic Hot Water only the selector switch should be
set to .
2. Domestic hot water supply always takes priority over
central heating. If a demand for hot water is required
during a central heating period, the boiler will automatically
switch to hot water mode until the demand is satisfied i.e.
storage water has reached the set temperature.
Interruption to the central heating only occurs when there
is a demand for hot water and should not be apparent to
the User.
3. Central Heating Mode (Fig. 4)
If there is a call for central heating the diverter valve
operates and the pump circulates the primary heating
water, operating the differential pressure switch. The fan
will run at full speed; once the air pressure switch has
been proved the burner will light. The burner output then
automatically adjusts to suit the system demand; as the
temperature of the heating water in the boiler approaches
that set by the adjustable central heating control knob the
burner output is reduced. When this set temperature is
reached, the burner extinguishes and the fan stops. The
pump continues to run for 3 minutes to prevent residual
heat build up in the boiler. The burner will not re-light for 3
minutes unless there is a demand for domestic hot water
during this period.
4. Domestic Hot Water Mode (Fig. 5)
When there is a demand for hot water (temperature of
stored hot water is below that set by the thermostat), the
pump will start to circulate the primary heating water,
operating the differential pressure switch. The fan will run
at full speed; once the air pressure switch has been proved
the burner will light. The burner output then automatically
adjusts to suit the demand required to raise the
temperature of the domestic hot water within the store to
the temperature set by the adjustable domestic hot water
control knob. When this temperature is reached the burner
extinguishes and the fan stops. The pump continues to run
for 3 minutes to prevent residual heat build up in the boiler.
When the hot water demand has been satisfied, the 3-way
diverter valve operates to divert the primary heating water
to the central heating, if the selector is set to and
there is a C.H. demand.
3.2 Frost Protection Mode
1. The frost protection feature will operate when the
selector switch is in the central heating and domestic hot
water mode.
The gas and electrical supplies to the boiler must be on
and the system pressure between 0.5 and 2.5 bar.
2. If the system temperature falls below 5º C, then the
boiler will fire until the water temperature has been raised.
3. Further frost protection can be incorporated by using a
frost thermostat to protect the whole system.
3.3 Pump Protection
1. With the selector switch in either operating position the
pump will automatically operate for 1 minute in every 24
hours to prevent sticking.

7
4.0 Technical Data – Page 7

8
5.0 Dimensions and Fixings – Page 8

9
6.0 System Details – Page 9
6.1 Information
1. The Baxi Maxflow Combi WM Combination Boiler is a
‘Water Byelaws Scheme - Approved Product’.
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 116 - Byelaw 90 and 91.
c) 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.
•For optimum performance after installation this boiler
and its associated central heating system must be
flushed in accordance with the guidelines given in BS
7593 “Treatment of water in domestic hot water central
heating systems”.
•This must involve the use of a proprietary cleanser,
such as BetzDearborn Sentinel X300 or X400, or
Fernox Superfloc. Full instructions are supplied with
the products, but for immediate information please
contact BetzDearborn (0151 420 9563) or Fernox
(01799 550 811) directly.
•For long term protection against corrosion and scale,
after flushing it is recommended that an inhibitor such
as BetzDearborn Sentinel X100, or Fernox MB-1 or
Copal is dosed in accordance with the guidelines
given in BS 7593.
Failure to flush and add inhibitor to the system
may 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 the Baxi Helpline.

10
6.0 System Details – Page 10
6.3 Bypass
1. The boiler has an integral bypass and in most cases
this should suffice. However in certain circumstances, e.g.
on systems where there is a high resistance and TRV’s are
fitted to all the radiators it may be necessary to fit an
external by-pass. For example, a 15mm pipe between the
flow and return controlled by a valve, or an uncontrolled
radiator.
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 thermostat, such as
one of the Baxi Maxflow Combi WM Controllers, is
recommended.

11
6.0 System Details – Page 11
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. The filling method adopted must be in accordance with
all relevant water supply bye-laws and use approved
equipment.
3. Your attention is drawn to: IRN 302 and Byelaw 14.
4. 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 (Fig. 6).
6.6 Expansion Vessel (Fig. 7) (Central Heating only)
1. The appliance expansion vessel is pre-charged to 0.8
bar. Therefore, the cold fill pressure is 0.8 bar. The vessel
is suitable for correct operation for system capacities up to
125 litres (27.5gal). For greater system capacities an
additional expansion vessel must be fitted - refer to BS
7074 Pt 1.
6.7 Pressure Relief Valve (Fig. 8)
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 (Fig. 9).
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.

12
6.0 System Details – Page 12
6.8 Domestic Hot Water Circuit
1. All DHW circuits, connections, fittings, etc. should be
fully in accordance with relevant standards and water
supply bye-laws.
2. Your attention is drawn to:
IRN 116 and Byelaw 90 and 91.
Sealed primary circuits and/or secondary hot water
systems shall incorporate a means for accommodating the
thermal expansion of water to prevent any discharge from
the circuit and/or system, except in an emergency
situation.
3. When the 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 (e.g.
Zilmet 160ml, R ½ 15bar)
To comply with Byelaw 91, a check valve must also be
fitted on the supply as shown, to ensure efficient operation
and also to prevent the reverse flow of hot water into the
supply pipe.
4. 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. The pressure
reducing valve supplied in the ‘Unvented Kit’ must be
fitted. 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.

13
7.0 Site Requirements – Page 13
7.1 Information
1. The installation must be carried out by a CORGI
Registered Installer or other registered competent person
and be in accordance with the relevant requirements of the
current Gas Safety (Installation and Use) Regulations, the
Building Regulations (Scotland) (Consolidation), the Local
Building Regulations, the current I.E.E. Wiring Regulations
and the bye laws of the Local Water Undertaking. Where
no specific instruction is given reference should be made
to the relevant British Standard Codes of Practice. For
Ireland install in accordance with IS 814 “Installation of
Gas Appliances”.
STANDARD SCOPE
B S 6891 Gas Installation
B S. 5440: Pt 1 Flues
B S. 5440: Pt 2 Air Supply.
B S. 5546 Installation of hot water supplies for
domestic purposes.
B S. 7074 Expansion vessels and ancillary
equipment for sealed water systems.
B S. 5449: Pt 1 Forced circulation hot water systems.
B S. 6798 Installation of gas fired hot water boilers.
WARNING - The addition of anything that may interfere
with the normal operation of the appliance without the
express written permission of Baxi UK Limited could
invalidate the appliance warranty and infringe the Gas
Safety (Installation and Use) Regulations.
7.3 Clearances (Fig. 11 & 12)
1. A flat vertical area is required for the installation of the
boiler.
2. The clearances around the outer case are for the flue
elbow, pipework etc. The clearance in front of the
appliance is for servicing purposes when installed in a
cupboard or compartment.
3. Additional clearances at the side must be left to
accommodate any rising pipework. It is not possible to
route any pipework within the outercase.

14
7.0 Site Requirements – Page 14
7.4 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 wall must be
capable of supporting the weight of the appliance.
2. 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 7.5).
3. 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.
4. If the boiler is fitted in a room containing a bath or
shower reference must be made to the current I.E.E.
Wiring Regulations and Building Regulations. 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).
Free area of air vent (cm2)7.5 Ventilation of Compartment
Position of vent
High Level
Low Level
Air from room
310.5
310.5
Air from outside
155.25
155.25
1. The boiler does not require any air vents in the room
in which it is installed. If it is installed in a cupboard or
compartment permanent air vents are required at high
and low levels (see Table 1). The vents must
communicate with the same room or be direct to outside
on the same wall.
Table 1 2. When installed in a cupboard or compartment a
75mm clearance for air movement must be left in front of
the boiler when any door or panel is closed
7.6 Gas Supply
1. The gas installation should be in accordance with
BS6891.
2. The connection to the appliance is a 22mm copper
tail. This is connected to the gas service cock (Fig. 14).
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).
7.7 Electrical Supply
1. External wiring must be correctly earthed, polarised
and in accordance with current l.E.E. Wiring Regulations.
2. The mains supply is 230V ~ 50Hz fused 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 site boiler and system controls only.

15
7.0 Site Requirements – Page 15
7.8 Flue
1. An internal fitting kit is available for installations where
the flue terminal is inaccessible from the outside. This is
available direct from Baxi UK Limited. Quote Part No
236441 when ordering.
2. The following guidelines indicate the general
requirements for siting balanced flue terminals.
Recommendations for flues are given in BS 5440 Pt.1.
3. If the terminal is fitted within 850mm of a plastic gutter,
within 450mm of a painted eave or a painted gutter, an
aluminium shield of at least 1 metre long should be fitted to
the underside of the gutter or painted surface. An air space
of 5mm should be left between shield and gutter (Fig. 15).
4. 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.
5. 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.
Terminal Position with Minimum Distance (Fig .10) mm
A
B
C
D
E
F
G
H
I
J
K
L
A Directly below an openable window or
Other opening. e.g. an air brick.
Below eaves.
Below gutters, soil pipes or drain pipes.
Below balconies or car port roof.
From vertical drain pipes and soil pipes.
From internal or external corners.
Above ground. roof or balcony level.
From a surface facing a terminal.
From a terminal facing a terminal.
Vertically from a terminal on the same wall.
Horizontally from a terminal on the same waIl.
For an opening in a car port (e.g. door,
window) into a dwelling.
300
25
75
25
25
25
300
600
1200
1500
300
1200

16
7.0 Site Requirements – Page 16
7.9 Flue Dimensions
The standard horizontal flue kit allows for flue lengths
between 100mm and 1m from elbow to terminal (Fig. 17).
The maximum permissible equivalent flue length is: 4
metres.
NOTE: Each additional 45º of flue bend will account
for an equivalent flue length of 0.5m. eg. 45º = 0.5m,
90º = 2 x 45º = 1m etc.
7.10 Flue Terminal Trim
1. Once the flue is secure the trim can be fitted if required.
2. Remove the protective backing from the adhesive seal.
Apply the seal to the rear of the trim flange (Fig. 18).
3. Locate the trim over the flue terminal and push it back
to the wall to compress the seal (Fig. 19).
7.11 Terminal Guard (Fig. 20)
1. When codes of practice dictate the use of terminal
guards, they can be obtained from most Plumbers’ and
Builders’ Merchants.
2. When ordering a terminal guard, quote the appliance
model number.
3. The guard manufacturers listed below can be contacted
for terminal sizes and guard model numbers.
Tower Flue Components Ltd.,
Tower House,
Vale Rise,
Tonbridge,
Kent.
Tel: [phone].
Quinnell, Barrett & Quinnell,
884 Old Kent Road,
London,
Sel15 1NL.
Tel: [phone].
4. The flue terminal guard should be positioned centrally
over the terminal and fixed as illustrated.

17
7.0 Site Requirements – Page 17
7.12 Flue Options
1. The Baxi Maxflow Combi WM can be fitted with flue
systems as illustrated.
2. The standard flue is suitable only for horizontal
applications.
3. Maximum permissible equivalent flue lengths are:
Horizontal 4.0 metres
Vertical 4.0 metres
Vertical (Twin Pipe) 15.0 metres
4. Any additional “in line” bends in the flue system must be
taken into consideration.
Their equivalent lengths are:-
Concentric Pipes:
45º bend 0.5 metres
90ºbend 1.0 metres
Twin Flue Pipe
45ºbend 0.25 metres
90ºbend 0.50 metres
The elbow supplied with the standard horizontal flue is not
included in any equivalent length calculations. This elbow
is of the same type as the optional concentric 90º bend.
Bends can be used to route the flue pipe around obstacles
within the dwelling and to enable the flue terminal to be
positioned according to requirements.
By combining two 45ºbends and a straight piece, a wide
90ºbend can be achieved.
As it is possible to rotate the bends through 360º, various
‘”S” bends can be produced.
5. The illustrations opposite show examples of maximum
equivalent lengths.
6. Full details of part numbers and descriptions of all
optional flue components and kits can be found in the Baxi
Gas Central Heating Boilers Installers’ Guide.
7. Instructions for guidance and fitting are included in each
kit.

18
8.0 Installation – Page 18
8.1 Initial Preparation & Fitting the Boiler
The gas supply, gas type and pressure must be
checked for suitability before connection
(see Section 7.6).
1. Locate the wall template (Fig. 21) in the appliance
packaging.
2. After considering the site requirements (see Section 7.0
) position the template on the wall ensuring it is level both
horizontally and vertically.
3. Select the six most suitable fixing holes and mark their
position.
4. Mark the centre of the flue hole (rear exit). For side exit,
mark as shown. If required, mark the position of the gas
and water pipes. Remove the template.
5. Cut the hole for the flue (minimum diameter 107mm).
6. Drill and plug the mounting bracket fixing holes.
7. Using the screws and washers provided, secure the
mounting bracket to the wall.
8. Lift the boiler and locate the slots in the upper chassis
over the hooks on the mounting bracket (Fig. 22).
THIS OPERATION WILL REQUIRE ASSISTANCE!
9. Remove the sealing plugs from the gas and water
connections.
10. Connect the gas and water valves together with the
appropriate copper tail ensuring that the sealing washers
are correctly fitted.
NOTE: The rubber gas sealing washers are an integral
part of the gas valve.
8.2 Flushing
1. Thoroughly flush the system - see Section 6.2.

19
8.0 Installation – Page 19
8.3 Fitting the Pressure Relief Discharge Pipe (Fig.
24)
1. Remove the discharge pipe from the kit.
2. Determine the routing of the discharge pipe in the
vicinity of the boiler. Make up as much of the pipework as
is practical, including the discharge pipe supplied.
3. The pipework must be at least 15mm diameter and run
continuously downwards to a discharge point outside the
building. See section 6.7 for further details.
4. Utilising one of the sealing washers, connect the
discharge pipe to the adaptor and tighten the nut.
5. Complete the discharge pipework and route it to the
outside discharge point.
8.4 Unvented Hot Water Storage
NOTE: The installation is subject to Building
Regulations approval and the Local Authority must be
informed of the intent to install.
Consideration must be given to Building Regulations
document G3.
1. The components supplied in the box marked ‘Unvented
Kit” MUST be fitted to the mains water supply.
2. No isolating valves must be fitted between these
components and the boiler.
3. The combined filter and pressure reducing valve must
ideally be fitted before the mains water supply divides to
feed the boiler and the rest of the dwelling.
4. The discharge pipes from the expansion relief valve
supplied in the kit and the temperature/pressure relief
valve on the boiler storage cylinder must be routed to the
tundish supplied.
5. These discharge pipes must be 15mm, and the pipe
downstream of the tundish at least 22mm.
6. See the instructions supplied in the unvented kit for full
details.

20
8.0 Installation – Page 20
8.5 Fitting The Flue
HORIZONTAL FLUE
1. The standard flue is suitable for lengths 100mm
minimum to 1m maximum (measured from the edge of the
flue elbow outlet).
Rear Flue: maximum wall thickness - 900mm
Right Side Flue: maximum wall thickness - 875mm
Left Side Flue: maximum wall thickness - 615mm
2. If using the optional internal fitting kit, flue extension kit
or elbows, refer to the instructions provided with the kits.
3. Locate the flue elbow on the adaptor at the top of the
boiler. Set the elbow to the required orientation (rear, right
or left).
4. Measure the distance from the outside wall face to the
elbow (Figs. 25 & 26). This dimension will be known as ‘X’.
5. Taking the air duct, mark dimension ‘X’ as shown (Fig.
27). Measure the length of waste material, and transfer the
dimension to the flue duct (Fig. 27).
6. Remove the waste from both ducts. Ensure that the cut
ends are square and free from burrs.
7. Remove the flue elbow from the adaptor.
IMPORTANT: Check all measurements before cutting