baxi 100 HE User guide

Baxi 100 HE

Wall Mounted Powered Flue Condensing Boiler

Gas Fired Central Heating Unit

Installation and
Servicing Instructions

Please leave these instructions with the user

2

Baxi UK 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 designed 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.

Everyone who works at Baxi has a commitment to

quality because we know that satisfied customers

mean continued success.

We hope you get a satisfactory service from Baxi. If

not, please let us know.

Natural Gas

Baxi 100 HE

G.C.No41 075 32

Baxi is a BS-EN ISO 9001
Accredited Company

The boiler meets the requirements of Statutory Instrument
“ The Boiler (Efficiency) Regulations 1993 N

o

3083” 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 0086.

Product/Production certified by:
Notified Body 0086.

For GB/IE only.

3

1.0 Introduction 4

2.0 General Layout 5

3.0 Appliance Operation 6

4.0 Technical Data 7

5.0 Dimensions and Fixings 8

6.0 System Details 9

7.0 Site Requirements 12

8.0 Installation 17

9.0 Electrical 23

10.0 Commissioning the Boiler 25

11.0 Fitting the Outer Case 26

12.0 Servicing the Boiler 27

13.0 Changing Components 29

14.0 Fault Finding 36

15.0 Short Parts List 44

Section Page

Contents

Baxi UK Limited declare that no substances
harmful to health are contained in the appliance
or used during appliance manufacture.

NOTE: This appliance must be installed in

accordance with the manufacturer’s instructions
and the regulations in force, and only used in a
suitably ventilated location.

All systems must be thoroughly flushed and
treated with inhibitor (see Section 6.2).

Read the instructions fully before installing or
using the appliance.

1.1 Description

1. The Baxi 100 HE is a gas fired room sealed fan
assisted condensing central heating boiler.

2. The maximum output of the boiler is preset at
75,000 Btu/hr. The boiler will automatically adjust
down to 30,000 Btu/hr according to the system
load. If required, the output can be set to 100,000
Btu/hr. Please refer to section 8.8.

3. It is designed for use on Natural Gas (G20).

4. The boiler is suitable for fully pumped open
vented central heating and domestic hot water
systems and sealed systems.

5. A label giving details of the model, serial number
and Gas Council number is situated on the rear of
the lower door panel (Fig. 1).

6. The boiler data badge is positioned on the air
box door (Fig. 2).

7. The boiler is intended to be installed in
residential / commercial / light industrial E.M.C.
environments on a governed meter supply only.

8. The boiler must be installed with one of the
purpose designed flues such as the standard
horizontal flue kit, part n

o

236921.

1.2 Important Information

This product contains Refractory Ceramic Fibres
(R.C.F.) which are man-made vitreous silicate fibres.
Excessive exposure to these materials may cause
temporary irritation to eyes, skin and respiratory tract.
Care must be taken when handling these articles to
ensure the release of dust or fibres is kept to a
minimum.
To ensure that the release of fibres from these articles
is kept to a minimum, during installation and servicing
it is recommended that a H.E.P.A. filtered vacuum is
used to remove any dust, soot or other debris
accumulated in and around the appliance. This should
be performed before and after working on the
installation.
It is recommended that any replaced item(s) are not
broken up but sealed within heavy duty polythene
bags and clearly labelled “R.C.F. waste”. This is not
classified as “hazardous waste” and may be disposed
of at a tipping site licensed for the disposal of
industrial waste.
Protective clothing is not required when handling
these articles but it is recommended that gloves are
worn and the normal hygiene rules of not smoking,
eating or drinking in the work area are followed and
always wash hands before eating or drinking.

1.0 Introduction

4

Fig. 1

H
IG

H

L
O

W

H
I

G
H

L
O

W

Data Badge

Air Box Door

Lower Door Panel

Position of Label

Fig. 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
sevice visit.

2.0 General Layout

5

2.1 Layout (Figs. 3,4 & 5)

1. Wall Plate

2. Flue Elbow

3. Heat Exchanger

4. Burner

5. Air Box

6. Fan Protection Thermostat

7. Fan Assembly

8. Condensate Trap

9. User Interface (optional timer available)

10. Gas Tap

11. Gas / Air Ratio Valve

12. Electronics Housing

13. Transformer

14. Flow Pipe Connection

15. Return Pipe Connection

16. Flow Temperature Safety Thermostat - Black

17. Flow Temperature Thermistor - Red

18. Flow Switch (dry fire protection)

H

I
G

H

L

O

W

1

2

3

4

5

6

7

9

8

10

11

12

13

17 16

14

15

18

Fig. 4

Fig. 3

Fig. 5

2.2 Optional Extras

KIT PART N

o

FLUE EXTENSION KITS (110/70)

Flue Extension 0.25M 241692

Flue Extension 0.5M 241694

Flue Extension 1M

(Use two kits for 2M etc.) 241695

Flue Bend x 2 - 45°

(Reduce overall length of flue

by 0.5m when fitting this bend)

241689

Flue Bend - 90° (

Reduce overall length of flue

by 1m when fitting each bend)

241687

VERTICAL FLUE (110/70)

Vertical Flue Terminal 242802

Vertical Boiler Connection 242886

CONTROL ACCESSORIES

Integral Electronic Twin Channel Timer Kit 242834

3.0 Appliance Operation

6

3.1

1. Switched Live On: When the switched live
switches on pump overrun occurs.

2. Pump Overrun: The pump is on while the fan,
spark generator and gas valve are off. If at any
stage during pump overrun the flow temperature
is less than the set point and the flow switch is
made then fan purge occurs. After 1 minute of
pump overrun anti-cycle occurs.

3. Fan Purge: The pump and fan are on while
the spark generator and gas valve are off. After 5
seconds ignition occurs.

4. Ignition: The pump, fan, spark generator and
gas valve are on. If a flame is detected then
burner on occurs. If a flame is not detected within
5 seconds and less than 5 ignition attempts have
been made then fan purge occurs. If a flame is
not detected within 5 seconds and 5 ignition
attempts have been made the ignition lockout
occurs.

5. Burner On: The pump, fan and gas valve are
on while the spark generator is off. Flow
temperature is controlled by varying the fan
speed (and thereby the gas rate) to achieve
optimum operation. If the flow temperature is
greater than the set point then pump overrun
occurs. If the TRVs all shut down then anti-cycle
occurs.

6. Anti-cycle: The pump, fan, spark generator
and gas valve are switched off. After 3 minutes
pump overrun occurs.

7. Ignition Lockout: The pump, fan, spark
generator and gas valve are switched off. The
boiler can only be reset by manually using the
thermostat knob.

Mains On.

Flow

temperature less

than set point and flow

switch made ?

YES

5 second

Fan Purge.

Flame Detected ?

Burner On.

Ignition

Lockout.

5 second

Ignition Period.

All TRVs

shut down ?

Flow temperature

greater than set

point ?

Ignition done and

5 attempts made ?

Ignition done

and less than 5

attempts made ?

Pump Overrun

Anti-cycle.

Pump Overrun

for 1 minute ?

YES

YES

YES

YES

YES

YES

Appliance Category CAT I

2H

4.0 Technical Data

7

Horizontal
Flue Terminal Diameter 110mm
Dimensions Projection 150mm

Outercase Dimensions

Overall Height Inc Flue Elbow - 750mm
Casing Height - 600mm
Casing Width - 390mm
Casing Depth - 320mm

Weights kg lb
Packaged Boiler Carton 40.7 89.6
Packaged Flue Kit 3.6 8.0
Weight Empty 38.2 84.1
Installation Lift Weight 31.5 69.3

Connections

Gas Supply -1/2in BSPT
Central Heating Flow - 28mm
Central Heating Return - 28mm
Condensate Drain - 1 in BSP

Recommended System
Temperature Drop

Normal 11°C20°F
Condensing 20°C36°F

Heat Input Max Min

(see note) kW 33.76 10.2

Btu/h 115,200 34,840

Heat Output

(Non Condensing 70° C Mean Water Temp)

Max Min

kW 30.18 9.14

Btu/h 102,980 31,180

Electrical Supply 230V~ 50Hz

(Appliance must be connected to an
earthed supply)

Power Consumption 80W

External Fuse Rating 3A

Internal Fuse Rating (BS 4265)

Fuse (2) 4 AT (Control Board)
Fuse (3) 2 AT (Ignition Board)

Max Gas Rate (Natural Gas)

(After 10 Mins)

Btu/hr 102,980 75,000

m3/h 2.95 2.31

ft3/h 104.2 81.6

Inlet Pressure at Gas Valve (Natural Gas)

Min 18.1 mbar

Max 22.5 mbar

(see Section 10.1)

Injector (Natural Gas)

6.3mm Diameter

Clearances

(For unventilated compartments see Section 7.5)

Both Sides 5mm Min
Above Casing 200mm Min
Below Casing 50mm Min
Front (For Servicing) 500mm Min
Front (In Operation) 5mm Min

Appliance Type C

13

C

33

Nox Class 5

Heat Output

(Condensing 40° C Mean Water Temp)

Max Min

kW 32.61 10.1

Btu/h 111,280 34,520

Water Content

litres 2.6

pints 4.6

Static Head

max 30 metres (100 ft)

min 1 metre (3.25 ft)

Low Head 0.2m (8 in) min

System Detail

fully pumped open vented & sealed systems

Gas Connection

RC1/2(1/2in BSPT)

Controls

boiler thermostat, safety thermostat,
flow switch, electronic flame sensing,
temperature protection thermostat &
condensate blockage sensor

NOTE: The maximum output of the
boiler is factory set at 22.0kW
(75,000 Btu/hr). This can be altered
to 30.18kW (102,980 Btu/hr)

- see section 8.8.

The efficiency is 90.9%

This value is used in the UK Government’s

Standard Assessment Procedure (SAP) for

energy rating of dwellings. The test data from

which it has been calculated has been

certified by 0086.

SEDBUK Declaration For 100 HE

Hydraulic Resistance Chart

220
200
180
160
140
120
100

80
60

40

Pressure Drop (mbar)

20

0 10203040

Water Flow Rate (litres/min)

9.1

8.3

7.5

6.6

5.8

5.0

4.2

3.3

2.5

1.7

0.8

Pressure Drop (in wg)

5.0 Dimensions and Fixings

8

DIMENSIONS

A 600mm

B 320mm

C 390mm

D 125mm Ø Min.

E 150mm

F 125mm

SIDE FLUE (left and right)

For every 1m of horizontal flue
length, the clearance above the
top of the flue elbow should be
55mm to incorporate the 3°
(1 in 20) fall in the flue from the
terminal to the elbow.

The 3° (1 in 20) fall provided by
the elbow is to allow condensate
to run back to the boiler, for
disposal through the condensate
discharge pipe.

Flue length (Y)

up to 1m

1m - 2m

2m - 3m

Clearance (X)

55mm

110mm

165mm

360° Orientation

Tube Ø 110mm

D

C

B

A

E

F

Y

3°

(1 in 20)

X

3°

(1 in 20)

Fig. 6

Fig. 7

6.0 System Details

9

6.1 Water Circulating Systems

1. The appliance is suitable for use with open vent
fully pumped systems and sealed systems .

The following conditions should be observed
on all systems:

• The static head must not exceed 30m (100ft)
of water.

• The boiler must not be used with a direct
cylinder.

• Drain cocks should be fitted to all system low
points.

• All gas and water pipes and electrical wiring
must be installed in a way which would not
restrict the servicing of the boiler.

• Position isolating valves as close to circulating
pump as possible.

• It is recommended that the return pipe is fitted
with an automatic air vent as close to the boiler
as is practical.

NOTE: Full TRV Systems (refer to section 6.4)
Where all the radiators are controlled by TRV’s
then pump protection will be required. This can be
done by either of the options opposite (see Fig A &
B). The option shown in Fig. A should only be

used on a full TRV system without a bypass.
Fig. B shows a system with a bypass that must
be capable of allowing a flow of at least 3 l/min.

6.2 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 upgrading existing systems that exhibit
evidence of sludging, it is advisable to clean the
system prior to treatment in order to remove any
sludge and reduce the likelihood of these
deposits damaging new components.

• 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. The recommended flushing and
cleansing agents are Betz-Dearborn Sentinel
X300 or X400 and Fernox Superfloc Universal
Cleanser which should be used following the
flushing agent manufacturer’s instructions.

• System additives - corrosion inhibitors and
flushing agents/descalers should be suitable for
aluminium and comply to BS7593 requirements.
The only system additives recommended are
Betz-Dearborn Sentinel X100 and Fernox-Copal
which should be used followng 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 the Baxi Helpline.

Boiler

No demand
for hot water

Central
heating
load

All TRV’s shut down
(boiler flow switch
causes pump to stop)

Live feed
to pump

Switch live from
programmer, etc.

S/L N

P/F

Fig. A Wiring to the pump feed connection of boiler

Fig. B Providing a 3 l/min bypass

Boiler

No demand
for hot water

Central
heating
load

All TRV’s shut down
(pump continues
around bypass)

Switch live from
programmer,
room stat, etc.

S/L
junction

S/L N

P/F

3 l/min
bypass

Boiler
Connections

Boiler
Connections

NOTE: This boiler does not require a bypass.

This boiler does not require a permanent live.
These diagrams only refer to pump protection for fully TRV’d systems.

6.0 System Details

10

6.3 Pipework

1. The sizes of flow and return pipes from the
boiler should be determined by normal methods,
according to the requirements of the system. The
connection to the boiler is 28mm (compression).

2. Due to space requirements within the boiler
outercase, pipework should comprise of solder
fittings.

3. A 20 °C (36°F) drop in temperature across the
system is recommended for condensing boilers.
Existing radiators may be oversized and so allow
this, but where radiator sizing is marginal it may be
advisable to retain a system temperature drop of
11°C (20°F).

4. In systems using non-metallic pipework it is
necessary to use copper pipe for the boiler Flow
and Return. The copper must extend at least 1
metre from the boiler and include any branches
(Fig. 7a).

6.4 System Controls

1. For optimum operating conditions, the heating
system into which the boiler is installed should
include a control system.

2. Such a system will comprise of a timer control
and separate room or cylinder thermostats as
appropriate. (An integral twin channel programmer
is available as an optional extra).

3. The boiler should be controlled so that it
operates on demand only.

4. Operation of the system under control of the
boiler thermostat & TRV’s only does not produce
the best results.

6.5 Low Head Installation

1. Using a close couple arrangement the minimum
head is as shown in the diagrams (Figs. 8 & 9)
subject to the following conditions:

a) The pump being adjusted to give an 20

o

C

drop across the boiler.
b) The pump must be fitted on the flow.
c) The pump must be fitted in accordance with

the pump manufacturer's instructions.
d) The open vent pipe must be taken up from a

tee in a horizontal section of the flow pipe.

An alternative Low Head Installation (Fig. 10)

2. For heads below 400mm then a combined vent
and feed pipe may be connected. This must be a
minimum of 22mm diameter. It is recommended
that an air separator is fitted when using a
combined feed and vent pipe.

6.6 Thermal Stores

1. When the 100 HE is fitted in conjunction with a
thermal store, jumper 2 must be removed from the
Control PCB, see Fig. 32a Section 8.8.

Typical Low Head Installation

If Conditions Require,
This System Possible

Alternative Low Head Installation

Boiler

500mm

45°

22mm
Open Vent

1000mm

Min

150mm

Max

15mm
Cold
Feed

400mm

Min Head

Return

Pump

Flow

Boiler

500mm

45°

22mm
Open Vent

400mm

Min Head

1000mm

Min

Automatic

Air Vent

15mm
Cold
Feed

150mm

Max

Return

Pump

Flow

Return

Pump

Flow

Boiler

200mm

Min

Air

Separator

22mm
Feed & Vent
Pipe

Fig. 8

Fig. 9

Fig. 10

Boiler

Flow

Return

Copper

0.5m

Copper

1m

Copper

0.5m

Fig. 7a

6.0 System Details

11

6.7 Sealed Systems

(Fig. 11)

1. SAFETY VALVE - A safety valve complying with
the requirements of BS 6750 Part 1 must be fitted
close to the boiler on the flow pipe by means of a
horizontal or vertically upward connection with no
intervening valve or restrictions and should be
positioned to facilitate testing. The valve should be
pre-set and non-adjustable to operate at a pressure
of 3 bar (45 Ibf/in

2

). It must be arranged to
discharge any water or steam through a pipe to a
safe outlet position.

2. PRESSURE GAUGE - A pressure gauge of
minimum range 0-4 bar (0-60 Ibf/in2) with a fill
pressure indicator must be fitted to the system,
preferably at the same point as the expansion
vessel in an easily visible position.

3. EXPANSION VESSEL - An expansion vessel
complying with the requirements of BS 4814 must
be fitted to the system by means of a connection
close to the inlet side of the circulating pump in
accordance with the manufacturers instructions, the
connecting pipe being unrestricted and not less
than 15mm (

1

/2in) nominal size. The volume of the
vessel should be suitable for the system water
content and the nitrogen or air charge pressure
should not be less than the system static head (See
Table. 1).

Further details of sealed system design can be
obtained from BS 5449 and the British Gas
publication entitled 'Specifications for Domestic Wet
Central Heating Systems'.

4. FILLING POINT - 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. The filling method adopted must be in
accordance with the Water Supply (Water Fittings)
regulations and the Water Bylaws (Scotland). Your
attention is drawn to: Paragraph 24 of Schedule 2
Section 8 of the publication Water Regulations
Guide which gives recommendations and guidance
on approved methods for filling sealed systems.
The sealed primary circuits may be filled or
replenished by means of a temporary connection
between the primary circuit and a supply pipe
provided the arrangement in accordance with
Diagram R24.2a of the Water Regulations Guide.
The temporary hose must be completely removed
at both ends after use.

5. MAKE UP SYSTEM - A method of replacing
water lost from the system should be provided
either by means of a make up vessel of not more
than 3 litres (5 pints) capacity, mounted above the
highest point of the system, or by re-pressurisation
of the system.

6. VENTING - A method of venting the system
during filling and commissioning must be provided
by fitting automatic air vents or by venting
manually.

7. HOT WATER STORAGE - The hot water
storage vessel must be of the indirect coil type. All
components used in the system must be suitable
for operation at 110°C (230°F) and at the pressure
allowed by the safety valve.

Safety

Valve

Pressure

Gauge

Pump

Filling

Point

Air

Vent

3 Litre
Top Up Bottle
(if required)

Radiator
Circuit

Expansion
Vessel

System Drains
at Low Point

Max Boiler Flow

Temp = 82° C

Boiler

Fig. 11

Table. 1

Vessel Charge
Pressure (Bar)

0.5

1.0

1.5

Initial System

Pressure (Bar)

0.5

1.0

1.5

2.0

1.0

1.5

2.0

1.5

2.0

Multiply Total

Water Content

Of System By

(Litres)

0.067

0.112

0.207

0.441

0.087

0.152

0.330

0.125

0.265

Method of determining minimum valve of

expansion vessel volume for sealed

systems using Baxi Boilers

System Volume = 75 litres
Vessel Charge Pressure = 1.0 bar
Initial System Pressure = 1.5 bar
75 x 0.152 = 11.4 litres
Expansion Vessel Volume

Example :-

Then :-

NOTE

Where a vessel of the calculated size is not obtainable

then the next available larger size should be used.

Stop
Valve

Double
Check
Valve

DHW
Mains
Inlet

CH
Return

Temporary
Hose

Stop
Valve

Fig. 11a

7.0 Site Requirements

12

7.1 Information

WARNING - Check the information on the data

plate is compatible with local supply conditions.

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 G

AS SAFETY (Installation

and Use) R

EGULATIONS, 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 813 “I

NSTALLATION OF

GAS APPLIANCES”. Reference should also be made
to B

RITISH GAS GUIDANCE NOTES FOR THE

INSTALLATION OF DOMESTIC GAS CONDENSING BOILERS.

7.2 B.S. Codes of Practice

Standard Scope

BS 6891 Gas Installation.
BS 5546 Installation of hot water supplies for

domestic purposes.
BS 5449 Part 1 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.

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 G

AS SAFETY

(Installation and Use) REGULATIONS.

7.3 Clearances (Figs. 12 &13)

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,
spanner access 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.

3. For unventilated compartments see Section 7.5.

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 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).

2. If the boiler is sited in an unheated enclosure
then it is recommended to incorporate in the system
controls a suitable device for frost protection.

3. If the boiler is fitted in a room containing a bath or
shower reference must be made to the current

I.E.E. W

IRING 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 Institute of Gas Engineers
document UP 7.

50mm

600mm

390mm

200mm

5mm Min

5mm Min

5mm

500mm

For Servicing

Purposes

Fig. 12

Fig. 13

In Operation

3°

(1 in 20)

320mm

7.0 Site Requirements

13

7.5 Ventilation of Compartments

1. Where the boiler is installed in a cupboard or
compartment, no air vents are required for cooling
purposes providing that the minimum dimensions
below are maintained.

Sides 15mm
Top 200mm
Bottom 50mm
Front 30mm

2. If the boiler is installed in a smaller cupboard or
compartment it must be ventilated according to
BS 5440 Part 2 and the minimum clearances given
in section 4.0 “Technical Data” maintained.

3. Any compartment should be large enough to
house the boiler only.

NOTE: The ventilation label on the front of the
outer case MUST NOT BE REMOVED when
the appliance is installed in a compartment or
cupboard.

7.6 Gas Supply

1. The gas installation should be in accordance
with BS6891.

2. The connection to the appliance is a

1

/2in BSPT
internal threaded connection located at the rear of
the gas service cock (Fig. 15).

3. Ensure that the pipework from the meter to the
appliance is of adequate size.
(22mm pipework must be connected to the
appliance gas service cock. This should extend for
at least 3 meters back towards the gas meter).

Do not use pipes of a smaller diameter than the
boiler gas connection.

7.7 Electrical Supply

1. External wiring must be correctly earthed,
polarised and in accordance with current I.E.E.

W

IRING 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 the boiler and system controls only.

7.8 Condensate Drain

NOTE: Ensure the discharge of condensate

complies with any national or local regulations
in force.

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. The pipe should run internally as much as
possible and with a 10° (1 in 6) fall to dispose of
condensate quickly to avoid freezing.

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Gas Service Cock

Fig. 15

7.0 Site Requirements

14

N

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A

A

F

H

J,K

D
E

H

Likely flue positions requiring
a flue terminal guard

C

R

A

I

J,K

I

L

S

B

7.9 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.
Recommendations for flues are given in BS 5440
Pt.1.

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. Take into consideration the effect the plume of
vapour may have on neighbours when siting the
flue.

4. Adjacent surfaces close to the flue terminal
may need protection from the effects of
condensation. Alternatively a flue deflector kit
(part no. 248167) is available.

5. For installation of the flue into an internal
corner at the 25mm dimension the flue deflector
kit (part no. 248167) must be fitted.

6. * Reduction to the boundary is possible down
to 25mm but the flue deflector kit (part no.

248167) must be fitted.

7. For fitting under low sofits and eaves it is
acceptable for the flue to project upto 500mm
from the face of the wall to the inside of the air
intake. This can be painted if required using a
suitable external paint.

8. If a terminal is less than 2 metres (78

3

/4in)
above a balcony, above ground or above a flat
roof to which people have access, then a suitable
terminal guard must be provided.

Fig. 17

Fig. 16

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

Table. 2

Terminal Position with Minimum Distance (Fig. 17) (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

(i)

or external

(ii)

corner.

(i)

25

(ii)

115
I Above ground, roof or balcony level. 300
J From a surface 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

a

In 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.

*

7.0 Site Requirements

15

7.10 Flue Dimensions

See Section 1.2. The standard horizontal flue kit
allows for flue lengths between 270mm (10

5

/8”)
and 800mm (32”) from elbow to terminal
(Fig. 18).

The maximum permissible equivalent flue
length is: 4 metres (Fig. 18a).

NOTE: Each additional 45° of flue bend will

account for an equivalent flue length of 0.5m.
eg. 45° = 0.5m, 90° = 2 x 45° = 1m etc.

7.11 Terminal Guard (Fig. 19)

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 flue terminal guard should be positioned
centrally over the terminal and fixed as
illustrated.

7.12 Vertical Flue

1. Only a flue approved with the Baxi 100 HE
can be used.

2. For information on vertical flues consult the
Baxi High Efficiency Brochure or Notes for
Guidance supplied with the vertical flue pack.

Fig. 18

Fig. 18a

Pictorial examples of flue runs where EQUIVALENT flue length equals 4m

Fig. 19

270mm

800mm

0.5m

1m

0.5m

0.5m

7.0 Site Requirement

16

Key Accessory Size Baxi Code

Number

Concentric Flue System 110mm diameter

A Straight extension kit 1000mm 241695

500mm 241694

250mm 241692
B Bend kit 93° 241687
C Bend kit (pair) 45° 241689
D Horizontal flue terminal 243013BAX

Clamp 110mm 243014BAX

Twin Flue System 80mm diameter

E Straight extension kit 1000mm 238690

500mm 238692

250mm 238694
F Bend kit 90° 246139
G Bend kit (pair) 45° 246138

Universal Vertical Flue Kits

H Twin flue adaptor kit 242757
J Vertical flue terminal 242802
K Universal roof tile 25°/50° 243015
L Roof cover plate kit 243131
M Flat roof flashing 243016BAX
N Boiler connection vertical concentric 242886

Clamp 80mm 238684

7.13 Flue options

Concentric
The maximum equivalent lengths are 4m
(horizontal) or (vertical). There lengths exclude the
standard elbow and flue/terminal assembly
(horizontal) and terminal assembly (vertical).

Twin Flue
The total maximum equivalent flue length is 150m.
NOTE: Each 1m of flue duct should be calculated
as 2m.

Any additional “in line” bends in the flue system
must be taken into consideration. Their equivalent
lengths are:

Concentric Pipes: 45° bend 0.5 m

93° bend 1.0 m

Twin Flue Pipe: 45° bend (air duct) 1.3 m

45° bend (flue duct) 2.6 m
90° bend (air duct) 4.8 m
90° bend (flue duct) 9.6 m

Detailed examples of equivalent flue length
calculation are given in the Installation Guidance
Notes for each flue system type.
(Documents 243501 and 243502 for concentric and
twin pipe respectively).

Standard Flue

C

D

A

B

J

K

C

L

H

E

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F

N

8.0 Installation

17

Check Site Requirements (section 7) before
commencing.

8.1 Initial Preparation

The gas supply, gas type and pressure must
be checked for suitability before connection
(see Section 7.6).

NOTE: If the boiler wall plate is to be pre-

hung, follow both these instructions and those
on the boiler pack.

1. Remove the fixing template (Fig. 20) from the
carton.

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. Mark the position of the centre hole for the
wall plate (Fig. 20).

4. Mark the centre of the flue hole (rear exit). For
side exit, mark as shown (Fig. 21). If required,
mark the position of the gas and water pipes.
Remove the template.

5. Cut the hole for the flue (minimum diameter
125mm, see table for wall thicknesses and flue
diameters).

6. Drill and plug the wall as previously marked.
Secure the wall plate using the centre hole.

7. Ensuring the wall plate is level both
horizontally and vertically, drill and plug at least 4
securing positions at the top and bottom through
the wall plate. Utilising the slots available ensure
the wall plate is square and secure to the wall
(Fig. 22).

8. Loosely route the condensate discharge pipe
to the lower left hand side of the wall plate.

Wall Thickness

up to 227mm

up to 750mm

up to 1200mm

Flue Hole ø

125mm core drill

150mm core drill

175mm core drill

Fig. 20

Fig. 21

Fig. 22

Horizontal

Line

Continue these lines along wall for 3° rise

Wall Plate Template

Vertical Flue
Template

Flow & Return
Pipe Positions

R/H Side Flue
Template

Rear Flue
Template

Condensate

Collector

Centre Hole

L/H Side Flue
Template

Wall Plate Template

Wall Plate

R/H Side Flue
Template

RF

Centralising

Screw

8.0 Installation

18

8.2 Preparing The Boiler

1. Remove the outer carton.

2. Remove the internal packaging.

3. Lift the outercase upwards and remove
(Fig. 23).

Baxi UK Limited declare that no substances
harmful to health are contained in the
appliance or used during appliance
manufacture.

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Lower Door Panel

Outercase

Fig. 23

8.0 Installation

19

8.3 Fitting The Boiler

(Fig. 24)

1. Remove the screw and retaining bracket from
the wall plate spring clip.

2. Offer up the boiler to the wall plate and locate
the rear bottom edge onto the self locating support
at the base of the wall plate.

3. Rotate the boiler and engage into temporary
spring retaining latch.

4. Ensure the boiler is secured with the
retaining bracket and screw previously
removed, immediately.

5. Remove thread protection caps from the FLOW
and RETURN connections.

8.4 Making the Water Connections

(Fig. 25)

1. The boiler has two side water connections, the
front connection being FLOW and the rear
connection being RETURN.

2. It is essential that Flow and Return pipes are
connected to the correct fittings. The flow
connection incorporates the boiler thermostats
and a flow switch. To avoid damage to the flow
switch when tightening the flow connection the
use of two spanners is recommended.

3. A copper elbow, compression nut and olive are
provided in the kit for the return connection.

NOTE: Drain cocks should be fitted to all
system’s low points and vents to all high points.

4. Ensure that any pipework is routed so as to
leave the boiler via the spaces at the rear of the
outer case, either at the top or at the bottom.

Pipework within the confines of the outercase
should consist of solder fittings.

NOTE: It is important that the pipework does

not interfere with the correct fitting of the outer
case and a space of 14mm clearance must be
left between any vertical pipes and the outer
edge of the wall plate.

8.5 Making the Condensate Drain

Connection

1. Connect the condensate drain using the 1”BSP
nut and seal supplied. (see section 7.8.).

NOTE: To ensure the correct operation and
integrity of the condensate drainage system

- Carefully pour approximately 1 cupful (250ml)

of water into the flue products exhaust, at the
top of the heat exchanger (Fig. 25a) to ensure
a seal is made in the trap.

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Return Pipe Connection

Flow Pipe
Connection

Boiler

Wall Plate Spring Clip

Wall Plate

Retaining Bracket

Fig. 25

Fig. 24

Flue Products Exhaust

Fig. 25a

8.0 Installation

20

8.6 Making the Gas Connection

1. Connect the gas supply to the RC1/2(1/2in BSPT
internal) gas tap located on the lower right side of
the boiler.

8.7 Fitting The Flue

Before fitting the flue, check the condensate
drain integrity (see section 8.5).

IMPORTANT: The flue should always be

installed with a 3° (1 in 20) fall from terminal to
elbow, to allow condensate to run back to the
boiler.

HORIZONTAL FLUE

1. The standard flue is suitable for lengths
270mm minimum to 800mm maximum (measured
from the edge of the flue elbow outlet).

Rear Flue: maximum wall thickness - 630mm

Side Flue: maximum wall thickness - 565mm (left or right)

2. For rear exit - measure the wall thickness
(Fig. 26) and to this dimension add 235mm. This
dimension to be known as (X).
i.e.

(X) = wall thickness + 235

3. Take the flue and mark off (X) from the
terminal end as indicated in the diagram
(Fig. 27).

Check your dimensions.

The flue tubes are fixed together. Cut through
both tubes whilst resting the flue on the semi­circular packing pieces. Deburr both tube ends.

4. For side exit - measure the distance from the
edge of the wall plate to the inner face of the wall
(Fig. 26) and to this dimension add the wall
thickness + 275mm. This dimension to be known
as (Z).
i.e.

(Z) = wall plate to wall + wall thickness + 275

5. Take the flue and mark off (Z) from the terminal
end as indicated (Fig. 27).

Check your dimensions.

The flue tubes are fixed together. Cut through
both tubes whilst resting the flue on the semi­circular packing pieces. Deburr both tube ends.

IMPORTANT: Check all measurements before
cutting.

NOTE: When cutting ensure the cut does not
interfere with the inner flue support bracket
(Fig. 27a).

360° Orientation

Inner Flue Support Bracket

Wall Thickness

(Z) Edge of Wall Plate to Wall

Wall Thickness

(Z) = Side Exit

(X) = Rear Exit

Flue

Waste

Fig. 26

Fig. 27

Fig. 27a

3°

(1 in 20)

8.0 Installation

21

8.7 Fitting the Flue (Cont)

6. Ensure the inner flue support bracket is
positioned in the flue (Fig. 28).

7. Engage the flue into the flue elbow using soap
solution to ease the engagement ensuring the
flue is assembled as shown (Fig. 29).

8. Place the gasket over the flue exit on the
boiler.

9. Slide the flue assembly through the hole in the
wall.

10. Engage the elbow on to the flue connection
on top of the boiler. Secure with the four screws
supplied in the kit.

11. Make good between the wall and air duct
outside the building ensuring the 3° drop between
the terminal and elbow.

12. The flue trim should be fitted once the
installation is complete and the flue secure
(Fig. 30). Apply a suitable mastic to the inside of
the trim and press against the wall finish, making
sure the brickwork is dust free and dry.

13. If necessary fit a terminal guard (see Section

7.11).

VERTICAL FLUEING

1. Only a flue approved with the Baxi 100 HE can
be used.

2. For information on vertical flues consult the
Baxi High Efficiency Brochure or Notes for
Guidance supplied with the vertical flue pack.

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Gasket

Flue Trim

Inner Flue Support Bracket

Flue

Flue Elbow

Fig. 28

Fig. 30

Fig. 29

8.0 Installation

22

8.8 Making The Electrical Connections

WARNING: This appliance must be earthed

1. The electrical connections are on the right hand
side of the unit inside the electrical box.

2. Undo the two screws securing the electrical box
cover and remove the cover (Fig. 31).

3. Undo the two screws securing the SL, , N, PF
cable clamp and place to one side (Fig. 32).

4. If fitting an integral programmer kit please refer
to kit instructions at this stage.

5. The boiler is factory set to give a maximum
output of 22.0 kW (75,000 Btu/hr). The Control
PCB jumper positions are as follows:

J1 In J2 In J3 In

If the installation requires a greater output to
achieve the desired room temperature, this can be
increased to 31.18 kW (103,000 Btu/hr) and the
boiler can be adjusted as follows:
a) Draw the control PCB forwards out of the

electrical box (the control PCB is the right

hand board).
b) Remove all three jumpers.
c) Replace the PCB and continue with the

installation.

If the boiler is to be used in conjunction with a
Thermal Store, the boiler can be adjusted as
follows:
a) Draw the control PCB forwards out of the

electrical box (the control PCB is the right

hand board).
b) Remove jumper N

o

2.

c) Replace the PCB and continue with the

installation.

6. Route the incoming electrical cable/s through
the grommet in the support bracket. This will
prevent damage to the cable (Fig. 31a).

7. Lay the cable through the cable clamp to gauge
the length of cable required when it is connected
to the 4-way terminal block (Fig. 32).

8. Connect the (S/L), (N) and ( ) wires to the
4-way terminal block and refit the cable clamp
(Fig. 33).

9. The pump can be wired directly to the system
controls or to the P/F connector on the boiler. For
full TRV installation refer to section 6.1.

10. The P/F connection should only be used on

a full TRV system without a bypass.

11. Check the electrical installation for;
earth continuity, short circuits, resistance to earth,
correct polarity and fuse failure.

12. Replace the electrical box cover and secure.

Fig. 31

Fig. 31a

Fig. 32

Fig. 33

S/L N

Electrical Box

Cover

Cable Clamp

Grommet

Electrical box shown

removed for clarity

P/F

Control PCB

Jumper 2

Fig. 32a

Jumper 1

Jumper 3

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9.0 Electrical

23

9.1 Schematic Wiring Diagram

Key To Wiring Colours

b - Blue

bk - Black

w - White

br - Brown

v - Violet

r - Red

g - Green

g/y- Green/Yellow

y - Yellow

o - Orange

Spark
Electrode

Ignition
PCB

Control
PCB

Condensate
Tr ap

Sensing Electrode

Gas
Valve

Mains

Input

Optional
Pump Feed

Transformer

Safety Stat

Fan Protection
Stat

Thermistor

Dry Fire
Flow Switch

DC
Fan

Interface PCB

br

r

br
w

g/y

g/y

g/y

br

b

b

b

bbk

br br

bk

bk

bk

bk

bk

r

r

r

br

g

w

w v b g y o r bk

N P/F

bk

S/L

bk

Connector

with

blue label

b

9.0 Electrical

24

Wiring Key

b - Blue
bk - Black
br - Brown
r - Red
w - White
g/y - Green/Yellow
v - Violet
y - Yellow
o - Orange

9.2 Illustrated Wiring Diagram

Ignition

PCB

Condensate
Trap

Sensing
Electrode

bk

bk

w

w

br

r

b

br

b

br

br

br bk

bk

bk

b

w b y r

v g o bk

bk

b bk

r

r

b

bk

g/y

g/y

g/y

Flow Switch

Fan

Control

PCB

Interface

PCB

Mains

Input

Transformer

Safety

Thermostat

Fan Protection

Thermostat

Flow

Temperature

Thermistor

Gas

Valve

Spark and

Earth Electrode

Earth

Earth

r

r

br

w

w

g

g

br

b

Connector

with blue label

10.0 Commissioning the Boiler

25

10.1 Commissioning the Boiler

1. Reference should be made to BS 5449
Section 5 when commissioning the boiler.

2. Flush the whole system using a suitable
flushing agent (see Section 6.2) and vent the
radiators. Check for water leaks.

3. Refill the system with inhibitor following the
inhibitor manufacturer’s instructions and BS 7593
Code of Practice for Treatment of Water in
Domestic Hot Water Central Heating Systems
(see Section 6.2).

4. Turn the gas supply on and purge the system
according to BS 6891.

5. Turn the gas service cock anticlockwise to the
ON position and check for gas soundness up to
the gas valve (Fig. 34).

6. Turn the boiler control knob fully clockwise to
‘HIGH’ (Fig. 35) and run the system and check
the boiler for correct operation.

NOTE: The boiler is self-regulating and the
gas rate will modulate between inputs of

33.76kW and 10.2kW dependent upon the
system load. The input is factory set at

24.50kW and can be altered to 33.76kW - see
section 8.8. No adjustment of the gas valve

is permissible.

7. With the system cold and all controls calling
for heat check the gas pressure at the inlet
tapping of the gas valve (Fig. 36). The pressure
must be a minimum of 18.1 mbar.

HIGH

LOW

IN OUT

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Gas Service

Cock

Control

Knob

Fig. 34

Fig. 35

Fig. 36

Open

Inlet Gas Pressure Test Point

DO NOT check gas pressure here

/ /

11.0 Fitting the Outer Case

26

11.1 Fitting The Outer Case

1. Position the outercase over the boiler
engaging the lugs in the side flanges over the
hooks on the wall plate (Fig. 37).

2. Using the two screws supplied in the kit,
secure the outercase to the combustion box
(Fig. 37).

3. Replace the lower front door panel (Fig. 38).

4. The “Important Ventilation Information” label
can be removed unless the appliance is
installed in an unventilated compartment.

5. Carefully read and complete all sections of
the “Benchmark” Installation, Commissioning
and Service Record Log Book that are relevant
to the appliance and installation. The details of
the Log Book will be required in the event of any
warranty work. The Log Book must be handed
to the user for safe keeping and each
subsequent regular service visit recorded.

6. Instruct the user in the operation of the boiler
controls. Hand over the User’s Operating,
Installation and Servicing Instructions and the
Log Book, giving advice on the necessity of
regular servicing.

7. Advise the user that they may observe a
plume of vapour from the flue terminal, and that
it is part of the normal operation of the boiler.

IMPORTANT: This boiler is fitted with an
aluminium alloy heat exchanger.
It is important that the system is thoroughly
flushed in accordance with BS 7593 and that
one of the following inhibitors is used:

BETZ DEARBORN SENTINEL X100

FERNOX COPAL

Refer to inhibitor manufacturer’s instructions
for correct use. Failure to comply with this
requirement will invalidate the appliance
warranty.
It is also important to check the inhibitor
concentration after installation, system
modification and at every service.

Date Boiler Installed

Inhibitor Used

8. This label is located on the electrical box front
cover on the boiler. Detail of system treatment
should be added for future reference.

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Outercase

Securing Screws

Lower Door Panel

Fig. 37

Fig. 38

12.0 Servicing the Boiler

27

12.1 Annual Servicing

IMPORTANT: When servicing ensure that both the

gas and electrical supplies to the boiler are isolated
before any work is started.

When the boiler control knob is switched off the
control PCB remains live. Therefore it is important to
isolate the electrical supply.

Hazardous materials are not used in the
construction of Baxi products, however reasonable
care during service is recommended.

When replacing the combustion box door after
servicing it is essential that the retaining screws are
tightened fully.

1. For reasons of safety and economy, it is
recommended that the boiler is serviced annually.
Before servicing please read Section 1.2 Important
Information.

2. After servicing, complete the relevant section of
the “Benchmark” Installation, Commissioning and
Service Record Log Book. This should be in the
possession of the user.

3. Ensure that the boiler is cool.

4. Ensure that both the gas and electrical

supplies to the boiler are isolated.

5. Remove the outercase and lower door panel
(see Fitting the Outercase, Section 11.0).

6. Release the four

1

/4turn screws securing the air

box door panel and remove the door (Fig. 40).

7. Disconnect the leads from the centre and right
hand terminals (earth and flame sensing probe).
The spark electrode lead is permanently fixed to
the electrode. Undo the re-usable cable tie and pull
down the sleeving to expose the joint in the
electrode lead. Disconnect the lead (Fig. 41a).

8. Undo the four screws securing the combustion
box door and remove the door (Fig. 41).

9. Visually check for debris/damage and clean or
replace if necessary the following:

a) Burner (Fragile - handle with care).
b) Heat exchanger fins.
c) Fan compartment

(Check also for condensate leaks).

d) Insulation.
e) Door seals-Important: Pay particular attention to

the condition of the combustion box door seals.

f) Electrodes.
g) Check condensate trap for debris. NOTE: If

necessary remove the trap drain plug and place a
vessel underneath to catch the condensate (care
should be taken as this could be hot). Clean the
trap and refit the drain plug.

h) Top of heat exchanger.

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Air Box Door Panel

Lead Terminals

Combustion Box

Door Panel

Fig. 40

Fig. 41

Fig. 41a

Cable Tie

Sensing

Earth

Spark

Sleeve

12.0 Servicing the Boiler

28

12.1 Annual Servicing (Cont)

NOTE: General cleaning can be
undertaken using a vacuum. However
debris should only be gently blown off the
burner skin due to its fragile nature.

10. To clean the heat exchanger and burner
proceed as follows:

a) Disconnect the electrical leads to the fan
component protection sensor (Fig. 42).

b) Loosen the screw retaining the gas injector
pipe at the venturi (Fig. 42).

c) Undo the two wing nuts to disconnect the fan
(Fig. 42).

d) Remove the fan and disconnect the electrical
supply to it (Fig. 42).

e) Remove the gas injector pipe from the gas
valve (push-fit) (Fig. 42).

f) Undo the condensate trap securing nut, lock
nut and the condensate drain pipe. Remove the
condensate trap and disconnect the sensor
leads (Fig. 43).

g) Remove the two screws securing the burner
and remove the burner. Visually inspect the
internal burner baffle for obstruction.

NOTE: The burner skin is fragile - handle
with care. Clean and if necessary replace the
burner (Fig. 44) (see note above).

h) Loosen the two screws retaining the heat
exchanger support bracket and slide to the left
to remove (Fig. 44).

i) Remove the four screws securing the heat
exchanger/combustion box base and withdraw
the base.

j) Lower the central insulation panel and check
condition (Fig. 44). Replace the lower insulation
pad if necessary.

k) Ensure the heat exchanger fins are clear of
any obstruction.

l) Check condition of all seals.

Important: Pay

particular attention to the condition of the

combustion box door seals.

m) Reassemble in reverse order.

11. Complete the relevant section of the
“Benchmark” Installation, Commissioning and
Service Record Log Book and hand it back to
the user.

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Combustion Box Base

Securing Screws

Burner Securing

Screws

Combustion

Box Base

Burner

Wing Nuts

Electrical Supply

Lock Nut

Condensate

Trap

Condensate
Drain Pipe

Securing Nut

Central Insulation Panel

Heat Exchanger
Support Bracket

Injector Pipe

Injector Pipe

Retaining Screw

Protection

Sensor Leads

Fan

Fig. 42

Fig. 44

Fig. 43

Sensor

Leads

13.0 Changing Components

29

13.1 Changing Components

IMPORTANT: When changing components

ensure that both the gas and electrical
supplies to the boiler are isolated before any
work is started.

When the boiler control knob is switched off
the control PCB remains live. Therefore it is
important to isolate the electrical supply.

Hazardous materials are not used in the
construction of Baxi products, however
reasonable care during service is
recommended.

When replacing the combustion box door after
changing components, it is essential that the
retaining screws are tightened fully.

1. Before changing any components please read
Section 1.2 Important Information.

2. Remove the outer case and lower door panel
(see “Fitting the Outercase” Section 11.0).

3. Isolate the water circuit and drain the system
as necessary. A drain point is located on the heat
exchanger manifold at the right hand side of the
boiler (Fig. 45) to enable the heat exchanger to be
drained.

4. Place a tube on the drain point to drain water
away from electrics. Turn anticlockwise to open
(Fig. 45).

NOTE: When reassembling always fit new ‘O’
rings, ensuring their correct location on the
spigot. Green “O” rings are used for gas joints
and Black “O” rings for water joints. Use Greasil
4000 (Approved Silicone Grease).

5. After changing a component re-commission the
boiler where appropriate and check the inhibitor
concentration (see Section 6.2 and 10.1).

The thermistor, safety thermostat, interface
PCB and the flow switch can be accessed
after removal of the outer case.

13.2 Flow Temperature Thermistor and

Safety Thermostat

(Fig. 46).

1. The procedure is the same for both the
thermistor and the safety thermostat.

2. Remove the electrical connections from the
sensor.

3. Unscrew the sensor from the pipe.

4. Fit the new thermistor or safety thermostat and
reassemble in reverse order.

H
IG

H

L
O

W

H
I

G
H

L
O

W

Drain Point

Heat Exchanger

Manifold

Tube

Electrical Connections

Flow Temperature Thermistor

Safety

Thermostat

Fig. 45

Fig. 46

13.0 Changing Components

30

13.3 Interface PCB

1. Pull the control knob off the spindle and
remove the securing nut and washer (Fig. 47).

2. Release the electrical box securing screw and
hinge the electrical box down (Fig. 48).

3. Remove the two rear cover securing screws
and remove the rear cover (Fig. 49).

4. Lift the PCB from the electrical box and
remove the electrical connections (Fig. 49).

5. Fit the new PCB and reassemble in reverse
order.

13.4 Flowswitch (Fig. 50)

1. Drain the boiler
(see Section 13.1 paragraph 2 & 3).

2. Disconnect pipework, loosen elbow locking nut
and undo screws on support bracket.

3. Remove the clip securing the flow pipe to the
flowswitch.

4. Remove the two screws securing the flow
switch to the boiler.

5. Disconnect the inline electrical connection.

6. Remove the flowswitch.

7. Fit the new flowswitch and reassemble in
reverse order.

8. Recommission the boiler and check the
inhibitor concentration (see Section 6.2 and 10.1).

H
IG

H

L
O

W

HIGH

LO

W

Electrical Box
Securing Screw

Control
Knob

Securing

Nut

Washer

Interface PCB

Electrical
Connections

Flow Switch

Clip

Flow Pipe

Electrical Box Rear
Cover Securing
Screws

Electrical Box
Rear Cover

H
I

G
H

L
O

W

Fig. 47

Fig. 48

Fig. 49

Fig. 50

Support

Bracket

13.0 Changing Components

31

The control and ignition boards can be
accessed on the removal of the main
electrical box cover.

1. Remove the two screws securing the main
electrical box cover (Fig. 51).

13.5 Control Board (Fig. 52)

1. Slide out the control board (right hand side)
and disconnect the electrical connections noting
their positions.

NOTE: Check the original board for the
presence of input jumpers - see section 8.8.
Set the new board as the original.

2. Fit the new control board and reassemble in
reverse order.

13.6 Ignition Board (Fig. 53)

1. Remove the control board, (13.5) and slide out
the ignition board (left hand side) and disconnect
the electrical connections noting their positions.

2. Fit the new ignition board and reassemble in
reverse order.

13.7 Transformer (Fig. 54)

1. After the removal of the control and ignition
boards the transformer can be accessed. Loosen
the two electrical box mounting plate securing
screws, remove the front drip tray securing screw
and lift the assembly to clear the keyhole slots.

2. The transformer is mounted on the rear of the
electrical box mounting plate.

3. Remove the two transformer mounting screws
and remove the transformer.

4. Fit the new transformer and reassemble in
reverse order.

H
I

G
H

L
O

W

Fig. 51

Fig. 52

Fig. 53

Fig. 54

Transformer

Securing Screw

Securing Screw

Control Board

Ignition Board

Electrical Box

Cover

Electrical Box

Electrical Box Mounting Plate

Drip Tray

Securing Screw

13.0 Changing Components

32

The fan and venturi, gas valve, injector pipe,
condensate trap, fan protection sensor, spark
and sensing electrodes can be accessed and
changed on the removal of the airbox door
panel.

1. Remove the airbox door panel by loosening the
four

1

/4turn screws (Fig. 55).

13.8 Spark and Sensing Electrodes

(Fig. 56)

1. Disconnect the leads from the centre and right
hand terminals (earth and flame sensing probe).
The spark electrode lead is permanently fixed to
the electrode. Undo the re-usable cable tie and
pull down the sleeving to expose the joint in the
electrode lead. Disconnect the lead.

Spark - Opaque cable
Earth - Black cable
Sensing - White cable

2. Remove the two screws securing each of the
electrodes to the combustion box door and
remove the electrodes.

3. Fit the new electrodes and reassemble in
reverse order.

NOTE: The spark electrode sleeve should
always cover the joint in the electrode lead to
prevent tracking.

13.9 Fan (Fig. 57)

1. Loosen the screw holding the injector pipe into
the venturi.

2. Remove the electrical connections to the fan
protection sensor on the fan.

3. Remove the wing nuts securing the fan to the
base of the combustion box.

4. Lower the fan and remove.

5. Disconnect the electrical supply from the right
hand rear of the fan.

6. If changing the fan remove the screws securing
the venturi and fan protection sensor bracket,
noting the positions of the injector opening and
sensor bracket, fix them to the new fan.

7. Fit the new fan and reassemble in reverse
order.

The injector pipe, condensate trap and gas
valve can be changed after the removal of
the fan.

Wing Nuts

Injector Pipe

Screw

Electrical

Connections

Electrical

Connection

Protection

Sensor

Injector

Opening

Gasket

Venturi

Fan

H

IG
H

L

O
W

Air Box Door Panel

Sensing

Earth

Spark

Combustion

Box Door

Fig. 55

Fig. 56

Fig. 57

Cable Tie

13.0 Changing Components

33

The removal of the fan is necessary to enable
the changing of the injector pipe, condensate
trap and gas valve (see section 13.9).

13.10 Injector Pipe (Fig. 58)

1. Remove the injector pipe by pulling out from
the ‘O’ ring joint in the gas valve.

2. Fit the new injector pipe and reassemble in
reverse order.

13.11 Gas Valve (Fig. 58)

1. Release user interface and pivot downward for
better access.

2. Disconnect the gas inlet union at the gas tap.

3. Undo the case pressure pipe from the gas
valve.

4. Undo the screw and disconnect the electrical
plug from the gas valve.

5. Remove the two gas valve securing screws
from inside the air box holding the gas valve.

6. Remove the gas valve from the airbox side.

7. Remove the nut union, aluminium spacer and
its gasket from the gas valve.

8. Fit the nut union, aluminium spacer and its
gasket to the new valve.

9. Fit the new gas valve and reassemble in
reverse order.

13.12 Condensate Trap (Fig. 59)

1. Disconnect the condensate trap from the base
of the heat exchanger.

2. Disconnect the condensate drain (outside the
boiler) from the condensate trap.

3. Undo the condensate trap lock nut.

4. Remove the condensate trap from the boiler.

5. Disconnect the sensor leads.

Fit the new condensate trap and reassemble in
reverse order.

H

I
G
H

L

O
W

H

I
G
H

L

O
W

Injector Pipe

Gas Tap

Case Pressure

Pipe

Boiler Side

Electrical Plug

Gas Valve

Gas Valve

Securing Screws

Nut Union

Lock Nut

Condensate

Drain Pipe

Condensate

Trap

Securing

Nut

Sensor

Leads

Fig. 58

Fig. 59

Aluminium

Spacer

‘O ring’

Gasket

13.0 Changing Components

34

The burner and heat exchanger can be
changed after removal of the combustion box
door. To change the heat exchanger, the fan
and burner must be removed first (see section

13.9).

1. Remove the combustion box door by removing
the four securing screws (Fig. 60).

IMPORTANT: On refitting the combustion box
door check the condition of the combustion
box door seals.

13.13 Burner (Fig. 61)

WARNING: The burner skin is fragile:

Handle with care

1. Remove the two screws securing the burner to
the base of the combustion box.

2. Remove the burner carefully from the
combustion box base.

3. Fit the new burner and reassemble in reverse
order.

13.14 Heat Exchanger

1. Drain the boiler (see section 13.1 paragraph
2 & 3).

2. Remove all components in the base of the
airbox.

3. Undo the screws on the support bracket.
Remove the screws securing the flow switch and
return connections and remove the connections
(Fig. 64).

4. Remove the electrical connections from the
P.C.B.s (see section 13.5 & 13.6).

5. Loosen the two screws securing the electrical
box mounting plate and remove the assembly
(Fig. 62).

6. Remove the screws securing the heat
exchanger manifold and remove the manifold
(Fig. 63).

7. Lift the heat exchanger assembly and rotate
the bottom upwards whilst pulling it forwards out
of the airbox.

8. Fit the new heat exchanger and reassemble in
reverse order.

9. Recommission the boiler and check the
inhibitor concentration (see Section 6.2 and 10.1).

H
IG

H

L
O

W

Combustion Box

Door Panel

Burner

Securing Screws

Fig. 60

Fig. 61

Fig. 62

Fig. 63

Fig. 64

Securing

Screw

Heat Exchanger

Manifold

Return

Connection

Flow

Switch

Securing

Screw

Electrical Box

Heat Exchanger

Assembly

Electrical Box

Mounting Plate

Support
Bracket

13.0 Changing Components

35

Combustion
Box Base

Central Insulation Panel

Support Bracket

Burner

13.15 Heat Exchanger Lower Insulation

Pad

(Fig. 65)

1. Remove all components in the base of the
airbox.

2. Remove the burner (see section 13.13).

3. Remove the four bolts securing the
combustion box base.

4. Remove the combustion box base.

5. Pull the central insulation panel down from the
centre of the heat exchanger and remove the
lower insulation pad.

6. Fit the new insulation pad and reassemble in
reverse order.

13.16 Heat Exchanger Upper Insulation

Pad

(Fig. 65)

1. Remove all components in the base of the
airbox.

2. Remove the burner (see section 13.13).

3. Remove the heat exchanger
(see section 13.14).

4. Remove the four bolts securing the
combustion box base.

5. Remove the combustion box base.

6. Pull the central insulation panel down from the
centre of the heat exchanger.

7. Fit the new insulation pad and reassemble in
reverse order.

Combustion Box Base

Securing Screws

Burner Securing

Screws

H
IG

H

L
O

W

Fig. 65

Upper Insulation
Pad

Lower Insulation
Pad

Go to

MAINS LED OFF

section of the fault finding

instructions.

YES

NO

Mains LED

off ?

14.0 Fault Finding

36

Mains LED

flashing ?

Lockout LED

flashing 5 times a

second ?

Lockout LED

flashing once a

second ?

Lockout LED

continuously

on ?

Fan not running

Lockout will

not reset ?

Go to

MAINS LED FLASHING

section of the fault finding

instructions.

Go to

DRY-FIRE LOCKOUT

section of the fault finding

instructions.

Go to

SAFETY LOCKOUT

section of the fault finding

instructions.

Go to

IGNITION LOCKOUT

section of the fault finding

instructions.

Go to

NO FAN

section of the fault finding

instructions.

Go to

NO LOCKOUT RESET

section of the fault finding

instructions.

YES

NO

YES

NO

YES

Lockout
LED flashing once
every 4 seconds ?

Go to THERMISTOR

OPEN CIRCUIT

section of the fault finding

instructions.

YES

NO

NO

YES

NO

YES

NO

YES

HIGH

LOW

Overheat or

Lockout (Red)

Boiler On

(Yellow)

Mains On

(Green)

Control

Knob

Please Check Following Points Before
Going Through The Fault Finding Chart.

- Check electrical system earth continuity,
short circuit, resistance to earth, fuse failure
and a minimum voltage of 195 is present at
input connections on boiler, check internal
fuse is OK, unit is not in lockout.

- There is an adequate gas supply pressure
at the inlet. A minimum pressure of 18.1 mb
is required at the inlet.

- All isolating valves are open and both the
boiler and the system are vented.

- Check installation is correct, including the
flue system.

14.0 Fault Finding

37

Is

boiler supply

fuse OK ?

Is there

230 V at mains

input terminal

block (A) ?

Is

there 230 V at

mains input connection

to control PCB

(B) ?

Is

there 230 V at

control PCB transformer

mains connection

(C) ?

Is

control PCB

fuse F2 OK ?

Is wiring

from control PCB

to interface PCB

OK (E) ?

Does

boiler produce

heat ?

Replace with 3A fuse.

No mains supply to

boiler.

Wiring from mains input
terminal block to control

PCB faulty.

Replace control PCB.

Replace transformer.

Check for short circuits

on control PCB and fan.

If OK replace fuse.

Rectify wiring

Replace control PCB.

Replace interface PCB.

YES

NO

Is there

24 V at control

PCB transformer 24V

connection

(D) ?

NO

NO

NO

NO

NO

NO

NO

YES

YES

YES

YES

YES

YES

YES

Mains LED Off

Spark
Electrode

Ignition
PCB

Control
PCB

Condensate
Tra p

Sensing Electrode

Gas
Valve

Mains

Input

Optional
Pump Feed

Transformer

Safety Stat

Fan Protection
Stat

Thermistor

Dry Fire
Flow Switch

DC
Fan

Interface PCB

br

r

br
w

g/y

g/y

br

b

b

b

b

bbk

br br

bk

bk

bk

bk

bk

r

r

r

br

g

w

w v b g y o r bk

NP/F

bk

S/L

bk

g/y

Connector

with

blue label

A

B C D

E

14.0 Fault Finding

38

Is

control knob

on ?

Switch on

Is

wiring from control

PCB to interface PCB

OK (F) ?

Does boiler

produce heat ?

Rectify wiring.

Replace control PCB.

Replace interface PCB.

NO

NO

NO

YES

YES

YES

Mains LED Flashing

Spark
Electrode

Ignition
PCB

Control
PCB

Condensate
Tra p

Sensing Electrode

Gas
Valve

Mains

Input

Optional
Pump Feed

Transformer

Safety Stat

Fan Protection
Stat

Thermistor

Dry Fire
Flow Switch

DC
Fan

Interface PCB

br

r

br
w

g/y

g/y

br

b

b

b

b

bbk

br br

bk

bk

bk

bk

bk

r

r

r

br

g

w

w v b g y o r bk

NP/F

bk

S/L

bk

g/y

Connector

with

blue label

F

14.0 Fault Finding

39

Fill system and

switch pump on.

Replace control PCB.

Replace flow switch.

Replace control PCB.

Is there

water in system

and pump on ?

Is

flow switch short

circuit (G) ?

Is

flow switch

blocked ?

Dry-fire Lockout

NO

NO

NO

YES

YES

YES

Spark
Electrode

Ignition
PCB

Control
PCB

Condensate
Tra p

Sensing Electrode

Gas
Valve

Mains

Input

Optional
Pump Feed

Transformer

Safety Stat

Fan Protection
Stat

Thermistor

Dry Fire
Flow Switch

DC
Fan

Interface PCB

br

r

br
w

g/y

g/y

br

b

b

b

b

bbk

br br

bk

bk

bk

bk

bk

r

r

r

br

g

w

w v b g y o r bk

NP/F

bk

S/L

bk

g/y

Connector

with

blue label

G

Wiring from

thermistor to logic

PCB faulty

YES

14.0 Fault Finding

40

When

fan ambient

temp < 90°C. Fan
protection stat open circuit ?
(measured at fan protection

thermostat)

Replace safety

thermostat (black)

Replace fan

protection stat.

Are

control PCB

safety thermostat

connections open

circuit ? (H)

Wiring from control PCB

to safety or fan protection

thermostats faulty.

Replace flow

temperature

thermistor (red)

Is

combustion box door

seal damaged or not

in place ?

Replace combustion

box door seal.

Replace control PCB.

When

flow temp < 60°C.

Safety thermostat
open circuit ? (measured at

safety thermostat)

NO

YES

YES

NO

NO

NO

YES

YES

NO

Safety Lockout

Open

circuit across

thermistor

connections ?

Open

circuit

across thermistor

connections on

control PCB ?

Replace thermistor

YES

NO

NO

Thermistor Open Circuit

Is

flow temperature

thermistor resistance between

0.5kΩ and 20kΩ? (measured
at flow temperature

thermistor)

Spark
Electrode

Ignition
PCB

Control
PCB

Condensate
Tra p

Sensing Electrode

Gas
Valve

Mains

Input

Optional
Pump Feed

Transformer

Safety Stat

Fan Protection
Stat

Thermistor

Dry Fire
Flow Switch

DC
Fan

Interface PCB

br

r

br
w

g/y

g/y

br

b

b

b

b

bbk

br br

bk

bk

bk

bk

bk

r

r

r

br

g

w

w v b g y o r bk

NP/F

bk

S/L

bk

g/y

Connector

with

blue label

H

Replace

control PCB

14.0 Fault Finding

41

Flow overheat

thermostat will not

reset until flow

temperature < 60° C.

Is

flow temperature

> 60° C ?

Fan protection

thermostat will not

reset until casing

temperature < 90° C.

Is

fan ambient

temperature > 90° C ?

Dry-fire lockout cannot

be reset until there is

water in the system

and the pump is on.

Is

water in system and

pump on ?

Replace interface PCB.

Control

knob switch short

circuit when on and

open circuit when

off ? (K)

Wiring from control PCB

to interface PCB faulty.

Control

PCB control knob

switch pins short circuit

when on and open

circuit when

off ? (J)

Replace control PCB.

YES

YES

YES

NO

NO

NO

NO

No Lockout Reset

No Fan

YES

YES

NO

NO

Is

flow temperature
thermistor between 0.5kΩ
and 20kΩ ? (measured at

flow temperature

thermistor)

Replace flow

temperature

thermistor (red)

Is

control PCB

sensor connections

0.5kΩ to 20kΩ ? (I)

Wiring from control

PCB to sensor faulty.

Replace control PCB.

Spark
Electrode

Ignition
PCB

Control
PCB

Condensate
Tra p

Sensing Electrode

Gas
Valve

Mains

Input

Optional
Pump Feed

Transformer

Safety Stat

Fan Protection
Stat

Thermistor

Dry Fire
Flow Switch

DC
Fan

Interface PCB

br

r

br
w

g/y

g/y

br

b

b

b

b

bbk

br br

bk

bk

bk

bk

bk

r

r

r

br

g

w

w v b g y o r bk

NP/F

bk

S/L

bk

g/y

Connector

with

blue label

I

J

K

14.0 Fault Finding

42

Is

230V S/L-N & L-E

at mains input

terminal block ?

The polarity of the
mains input to the

boiler is reversed. This

must be rectified.

Is

there at least

18.1 mb dynamic at
gas valve

inlet ?

Incorrect gas

supply to boiler.

Reset lockout.

Does fan run ?

Is

control PCB fan

connection 24 Vac

across (L) ?

Replace control PCB.

Is

there no spark

and no gas ?

(check at meter)

Is there

230V at control

PCB connection to

ignition PCB

(M) ?

Is

there gas but no

spark ?

Is

spark probe

damaged ?

Replace spark probe.

Is

there spark but no

gas ?

Is

there 230V

at ignition PCB

connection to gas

valve (O) ?

Replace ignition PCB.

Replace control PCB.

Is

the detection

probe damaged ?

Is

wiring from ignition

PCB to detection

probe OK ?

Rectify wiring.

Replace detection probe.

Ignition Lockout

NO

YES

NO

Is

condensate trap

blocked ?

Clear blockage and

dry sensors

YES

NO

NO

NO

YES

YES

YES

YESYES

NO

YES

YES

NO

NO

NO

NO

NO

YES YES

YES

YES

NO

NO

43

14.0 Fault Finding

Replace fan.

Is

fan connection

24Vac across

(L) ?

Wiring from control

PCB to fan faulty.

Is ignition PCB

fuse OK ?

Replace

ignition

PCB.

Replace

ignition

PCB.

Is there

230V at ignition

PCB connection to

control PCB

(N) ?

Wiring from control

PCB to ignition

PCB faulty.

Check for short circuits

on ignition PCB and gas

valve. If OK replace fuse.

Is

wiring from

ignition PCB to

spark probe OK ?

Is

spark gap

between 3 and 5mm ?

Set spark gap to 4mm.

Rectify wiring.

Is

sensing tube

blocked ?

Unblock

Tube.

Is

there 230Vdc at the

end of the gas valve

lead ?

Replace gas valve lead.

Replace gas valve.

Replace

control

PCB.

Is

there 230V

ignition PCB burner on

pin to control PCB

(P) ?

Replace ignition PCB.

Burner On wiring from ignition

PCB to control PCB faulty.

Is

there 230V

control PCB burner on

pin to ignition

PCB (Q) ?

NO

YES

YES

NO

NO

YES

YES

NO

NO

NO

NO

YES

YES

YES

YES

NO

NO

Spark
Electrode

Ignition
PCB

Control
PCB

Condensate
Tra p

Sensing Electrode

Gas
Valve

Mains

Input

Optional
Pump Feed

Transformer

Safety Stat

Fan Protection
Stat

Thermistor

Dry Fire
Flow Switch

DC
Fan

Interface PCB

br

r

br
w

g/y

g/y

br

b

b

b

b

bbk

br br

bk

bk

bk

bk

bk

r

r

r

br

g

w

w v b g y o r bk

NP/F

bk

S/L

bk

g/y

Connector

with

blue label

L

M

Q

N

P

O

15.0 Short Parts List

44

Short Parts List

Key G.C. Description Manufacturers
No. No. Part No.

1 E06 058 Flow Temperature

Thermistor (Red) 240670

2 E06 059 Flow Switch 242459

3 E06 060 Safety Thermostat

(Black) 242235

8 E06 064 Control PCB 5106789

9 E06 065 Ignition PCB 241838

10 E06 066 Transformer 240236

21 E06 074 Fan 242472

23 E06 075 Gas Valve 242473

28 E06 079 Interface PCB 241839

38 E06 085 Viewing Window 242484

39 E06 086 Condensate Trap 242485

44 E06 091 Electrodes Kit 242490

47 E06 093 Burner Assy 242492

52 E06 097 Heat Exchanger Assy 242497

123

89

10

21

23

28

38

39

44

47

52

16.0 Notes

45

16.0 Notes

46

47

Baxi UK Limited manufacture a comprehensive range
of products for the domestic heating market.

Gas Central Heating Boilers
(Wall, Floor and Fireside models).

Independent Gas Fires.

Renewal Firefronts.

Gas Wall Heaters.

Solid Fuel Fires.

If you require information on any of these products,
please write, telephone or fax to the Sales Department.

Baxi UK Limited

Brownedge Road

Bamber Bridge Preston

Lancashire

PR5 6SN

www.baxi.com

After Sales Service

08706 096 096

Technical Enquiries

08706 049 049

Comp No5106739 - Iss 4 - 9/02