Glow-worm 23c User Manual

Instructions for Use

Installation and Servicing

To be left with the user

23c

Fanned Flue Combination Boiler

G.C. No. 47-047-18

2000225000B.02.02

10139

This is a Cat I2H Appliance

optional electro mechanical clock timer shown fitted

The instructions consist of three parts, User, Installation and Servicing Instructions, which includes the Guarantee Registration

Card. The instructions are an integral part of the appliance and must, to comply with the current issue of the Gas Safety

(Installation and Use) Regulations, be handed to the user on completion of the installation.

Guarantee Registration

Thank you for installing a new Glow-worm appliance in your home.

Glow-worm appliances' are manufactured to the very highest standard so we are pleased to offer our customers’ a

Comprehensive Guarantee.

This product is guaranteed for 24 months from the date of installation or 30 months from the date of manufacture,

whichever is the shorter, for parts. In addition this product is guaranteed for 12 months from the date of intallation or

18 months from the date of manufacture, whichever is the shorter, for labour.

The second year of the parts guarantee, from the beginning of the 13th month onwards after installation or

manufacture, is conditional upon the boiler having been serviced by a CORGI registered gas installer, in accordance

with the manufacturer's recommendations. We strongly recommend regular servicing of your gas appliance, but where

the condition is not met, any chargeable spare parts or components issued within the applicable guarantee period still

benefit from a 12 month warranty from the date of issue by the manufacturer.

We recommend you complete and return as soon as possible your guarantee registration return literature, supplied in

the document envelope.

If your guarantee registration return literature is missing you can obtain a copy or record your registration by

telephoning the Heatcall Customer Service number 01773 828100.

REGISTER YOUR GLOW-WORM APPLIANCE

CALL 0208 247 9857

One Contact Local Service

Customer Services:

Tel: [phone]

Fax: [phone]

Hepworth Heating Ltd.,

Nottingham Road, Belper, Derbyshire. DE56 1JT

General/Sales enquiries:

Tel: [phone] Fax: [phone]

Important Information

Testing and Certification

This boiler is tested and certificated for safety and performance. It is therefore important that no alteration is made to the boiler,
without permission, in writing, from Hepworth Heating Ltd.

Any alteration not approved by Hepworth Heating Ltd., could invalidate the certification, boiler warranty and may also infringe the
current issue of the Statutory Requirements. The requirements are: The installation of this boiler must be carried out by a
competent person in accordance with the current rules in force in the countries of destination at the time of installation.
Manufacture's instructions supplied. Manufacture's instructions must not be taken as overriding statutory requirements.

Note: The boiler serial number is marked on the label attached to the inside of the drop down door. Refer to the

'Introduction' section for a description of the basic functions of the boiler. The 'Users' section describes how to safely operate the
boiler.

Mandatory warning for CEE countries

Warning: This appliance is designed, approved and inspected to meet the requirements of the market. The identification plate

located on the inside of the appliance certifies the origin where the product was manufactured and the country for which it is
intended.
If you see any exception to this rule, please contact your nearest Glow-worm dealer.
Thank you in advance for your assistance.

CE Mark

This boiler meets the requirements of Statutory Instrument No. 3083 The boiler (Efficiency) Regulations, and therefore is
deemed to meet the requirements of Directive 92/42/EEC on the efficiency requirements for new hot water boilers fired with
liquid or gaseous fuels.

Type test for purposes of Regulation 5 certified by: Notified body 0063.

Product/production certified by: Notified body 0063.

The CE mark on this appliance shows compliance with:

1. Directive 90/396/EEC on the approximation of the laws of the Member States relating to appliances burning
gaseous fuels.

2. Directive 73/23/EEC on the harmonization of the Laws of the Member States relating to the electrical equipment

3. Directive 89/336/EEC on the approximation of the Laws of the Member States relating to electromagnetic
compatibility.

designed for use within certain voltage limits.

Substances Hazardous to Health

Under section 6 of the Health and Safety at Work Act 1974, we are required to provide information on substances hazardous to health.

The adhesives and sealants used in this appliance are cured and give no known hazard in this state.

INSULATION PADS/CERAMIC FIBRE, GLASSYARN, MINERAL WOOL
These can cause irritation to skin, eyes and the respiratory tract.
If you have a history of skin complaint you may be susceptible to irritation. High dust levels are usual only if the material is
broken.
Normal handling should not cause discomfort, but follow normal good hygiene and wash your hands before eating, drinking or
going to the lavatory.
If you do suffer irritation to the eyes or severe irritation to the skin seek medical attention.
The insulation is composed of non-combustible material.

Spare Parts

REMEMBER, When replacing a part on this appliance, use only spare parts that you can be assured conform to the safety and
performance specification that we require. Do not use reconditioned or copy parts that have not been clearly authorised by Hepworth
Heating Ltd.

Manual Handling Guidance

During the appliance installation it will be necessary to employ caution and assistance whilst lifting as the appliance exceeds the
recommended weight for a one man lift.

In certain situations it may be required to use a mechanical handling aid.

Take care to avoid trip hazards, slippery or wet surfaces.

22000225000B

Contents

CONTENTS DESCRIPTION SECTION PAGE No.

Important Information 2
Introduction 4

INSTRUCTION

FOR USE

INSTALLATION

INSTRUCTIONS

Controls and Lighting 4
Clock-timer (Optional) 6
Draining 6
Safety Devices 7
Servicing and Maintenance 7

Technical Data 1 8
Dimensions 2 9
Heating System Design 3 10
Domestic Hot Water System Design 4 10
Boiler Schematic 5 11
Boiler Location, flue and ventilation 6 12
Fixing jig pack 7 13
Piping System Installation 8 14
Boiler installation 8 15
Flue Installation telescopic and standard 10 16
Electrical Connection 11 19
Commissioning 12 20
Settings 14 22

SERVICING

INSTRUCTIONS

Routine Cleaning and Inspection 15 22
Fault Finding 16 27
Wiring Diagram 17 34
Replacement of Parts 18 35
Spare Parts 19 44

3

2000225000B

Introduction

The 23c boiler is a wall mounted modulating combination boiler
with electronic ignition providing central heating and
instantaneous hot water.

The boiler is of the I2H category for use with Natural Gas (G20)
as distributed in the United Kingdom.

The boiler has a fan assisted balanced flue which both discharges
the products of combustion to and draws the combustion air
from the outside of the room.

The boiler is suitable for top outlet flue connection only but can
be fitted with horizontal flue, vertical flue or twin-pipe flue. Refer
to flue options guide for further information, this is available from
your nearest stockist.

Both the central heating and domestic hot water temperature
are user adjustable from the boiler control panel.

Domestic hot water demand always has priority over heating
demand.

The pump, expansion vessel and associated safety devices are
all fitted within the boiler.

The boiler can be installed against either an external wall or on
an adjacent inside wall, that is, the flue system will pass directly
to the rear or to either side to the terminal fitted on the outside
wall face.

The installation must be carried out by a qualified registered
person in accordance with the relevant requirements of The
Building Regulations, The Water Byelaws, The Building
Standards (Scotland) Regulations and any applicable local
regulations.

These instructions should be carefully followed for the safe and
economical use of your boiler.

Electrical Supply

WARNING: This boiler must be earthed.

All system components shall be of an approved type and shall
be connected in accordance with the current issue of BS7671
and any applicable local regulations.

All external wiring between the appliance and the electrical
supply and earthing requirements shall comply with the current
IEE Regulations.

Connection of the boiler and system controls to the mains
supply must be through a common isolator and must be fused
3A, maximum. This method of connection must be by a fused
double pole isolating switch, with a minimum contact separation
of 3mm on both poles. The switch should be readily accessible

and preferably adjacent to the appliance. It should supply the
appliance only and be easily identifiable as so doing.

Alternatively, an unswitched shuttered socket outlet and 3A
fused 3 pin plug, both to the current issue of BS1363 may be
used provided that they are not used in a room containing a bath
or shower.

o

Wiring to the boiler must be PVC 85
than 0.75mm

2

(24/0.20mm).

C insulated cable, not less

Gas safety (Installation and use) Regulations

In your interests and that of gas safety, it is the law that ALL gas
appliances are installed and serviced by a qualified registered
person in accordance with the above regulations.

Gas leak or fault

If a gas leak or fault exists or is suspected, turn the boiler off and
consult the local gas supply company or your installation/
service company.

Air in the heating system

Persistent air in the heating system may indicate leaks in the
system or corrosion taking place. Call your Installation/Servicing
company.

Overheating safety

In the event of a problem, the overheating safety devices cause
safety shutdown of the boiler. If this happens, call your
Installation/Servicing company.

Boiler controls

The control panel, located at the lower front of the boiler casing,
see diagram 1, allows the boiler to be started, shut down,
controlled and monitored during use.

Flue

Do not obstruct the outside terminal of the flue.

Ancillary equipment

A range of flue accessories are available including vertical
flues, twin-pipe flues, bends etc.

For further information contact your supplier.

Controls and lighting

Your 23c boiler has been factory configured to operate at the
heart of an existing installation. However, because many
installations are specially designed, do not hesitate to contact
your installer who will be able to ensure that you get the best
performance from your installation, by adjusting the heating
circuit's maximum output or temperature.

Once these settings have been made, you can still adjust the
temperature to suit your needs.

Central heating adjustment

The selector switch enables you to vary the temperature of the
water in the central heating circuit from the minimum setting
(approx. 38˚C) up to the maximum temperature set by your
installer. Most of the time, the mid position will meet your needs
but the selector should be moved nearer to the maximum
setting in very cold weather when your home is not reaching the
required temperature.

Domestic hot water

The selector switch can be adjusted from a temperature of
(approx. 35˚C up to 60˚C or more).

The ECO setting is ideally suited for all the requirements of
normal family use (showers, washing up etc.). The maximum
setting should be reserved for occasional use when very hot
water is required.

42000225000B

Controls and Lighting

1 - On/Off switch
2 - Central heating

temperature selector
3 - Domestic hot water
temperature selector
4 - Pressure gauge (bar)
and temperature gauge (ºC)
5 - Fault display
(faults indicated by a
red flashing light)

6 - Clock-timer (Optional)

1. Lighting the boiler :

4

Make sure that:

• The boiler is connected to the electrical supply.

• The gas service cock is open.

Turn the switch ON ( I )

2

3

5

9084

1

6

Diagram 1

4. Heating temperature adjustment :

• Winter: Set the control knob between 1 and 5

• Summer: Set the control knob to

2. Stop the boiler :

• Turn the switch OFF ( 0 ) the electrical supply is
OFF.

• Turn the gas supply OFF at the gas service cock if
the boiler is to be out of use for a long time.

3. Domestic hot water adjustment :

• Position ( 0 ): Domestic hot water OFF

• Position ( I ) and ECO: Domestic hot water
between approx. 35˚C and 50˚C

• ECO: Maximum recommended for constant use

• Between ECO and maxi: Occasional use for water
above approx. 50˚C

5. If a fault occurs (indicated by red flashing
light) :

• Reset boiler: Turn the On/Off switch to ( 0 ),
wait for five seconds. Turn the On/Off switch to ( I )
the boiler is reset. If the fault continues call your
Installation/Servicing company or Heatcall.
(Glow-worm’s own service organisation) using the
telephone number on the front cover
of this literature.

6. Installation filling :

• If the boiler loses water: the pressure gauge (a)

and fault display (b) will flash. Fill the system by
the filling device (c) at the bottom of the boiler until
the pressure gauge reads 1.5 bar.

(a) (b)

(c)

➜

Diagram 2

• Warning:
pressure of 2.5 bar or above indicating over
pressure, the fault display (b) will flash. The
pressure must be reduced to 1.5 bar by bleeding a
radiator. If the fault continues call your Installation/
Servicing company or Heatcall. (Glow-worm’s own
service organisation) using the telephone number
on the front cover of this literature.

5

Take care not to overfill the boiler

. At a

2000225000B

Clock-timer instructions for use

Optional Clock-timers inclusive of installation
and user instructions:- These are available
from your nearest stockist.

Electro/Mechanical Part No. 4000122022

Digital Part No. 4000120494

Draining

Protection against freezing

The boiler has a built in frost protection programme as long as
the electricity and gas are left switched on.

If the temperature within the appliance falls to 3˚C the burner
and system pump are activated.

When the temperature inside the appliance reaches 10˚C the
burner will shut down and after a short period the pump will stop.

This device primarily protects the boiler. Any other exposed
areas of the system should be protected by a seperate frost
thermostat.

If the boiler is to be out of use for any long periods during severe
weather conditions, it is recommended that the whole system,
including the boiler, be drained to avoid the risk of freezing.

If in doubt, consult your servicing company.

Draining and filling

Caution: The boiler is installed as part of a sealed system which
must only be drained and filled by a competent person.

18

62000225000B

Safety Devices

The 23c incorporates a visual fault display that indicates certain
fault conditions, (red flashing light) should they occur.

Should the boiler fail to operate during Commissioning, the
most likely fault is that the gas supply to the boiler has not been
turned on or purged sufficiently or that there is no pressure in the
heating system.

General safety devices

Air flow rate safety device

If an obstruction, even partial, of the flue occurs, for any reason
whatsoever, the built in safety system of the boiler will turn the
boiler OFF, the red light will flash and the fan will continue to run.
The boiler will be ready to operate when the fault has been
cleared.

Heating safety valve

CAUTION: A heating safety valve with a discharge pipe is fitted

to this boiler.

The valve MUST NOT BE TOUCHED except by a qualified
registered person. If the valve discharges at any time, switch the
boiler off and isolate it from the electrical supply. Contact your
installation/service company.

If the gas supply is interrupted

The boiler switches over to safety mode, the red light will flash.
Call a qualified service engineer or Heatcall (Glow-worm’s own
service organisation) using the telephone on the front cover of
this literature.

Air in pipes

Important: A central heating system can not operate correctly

unless it is filled with water and air bled from the system. If these
conditions are not met the system may be noisy.

Bleed the air in the radiators and adjust the pressure if system
requires. If the system requires filling to often this may be due
to minor leaks or corrosion in the system. Call a qualified
service engineer or Heatcall (Glow-worm’s own service
organisation) using the telephone number on the front cover of
this literature.

Frost protection

The

23c

boiler from freezing. If the boiler is to be left and there is a risk
of frost, ensure that the gas and electrical supplies are left
connected. The frost protection device will light the boiler when
the temperature of the boiler water falls below 6°C. When the
temperature reaches 16°C, the boiler stops.

Note : This device works irrespective of any room thermostat
setting and will protect the complete heating system.

has a built in frost protection device that protects the

In case of power supply failure

The boiler no longer operates. As soon as power supply is
restored, the boiler will be automatically restarted.

Servicing and Maintenance

To ensure the continued efficient and safe operation of the
appliance it is recommended that it is checked and serviced as
necessary at regular intervals. The frequency of servicing will
depend upon the particular installation conditions and usage,
but in general once a year should be enough.

If this appliance is installed in a rented property there is a duty
of care imposed on the owner of the property by the current
issue of the Gas Safety (Installation and Use) Regulations,
Section 35.

Servicing/maintenance should be carried out by a competent
person in accordance with the rules in force in the countries of
destination.

To obtain service, please call your installer or Heatcall (Glow-
worm’s own service organisation) using the telephone number
behind the controls cover door.

Please be advised that the ‘Benchmark’ logbook should be
completed by the installation engineer on completion of
commissioning and servicing.

All CORGI Registered Installers carry a CORGI ID card, and
have a registration number. Both should be recorded in your
boiler Logbook. You can check your installer is CORGI registered
by calling CORGI direct on: 01256 372300.

Cleaning

The boiler casing can be cleaned with a damp cloth followed by
a dry cloth to polish.

Do not use abrasive or solvent cleaners.

Boiler casing

CAUTION. Do not remove or adjust the casing in any way, as

incorrect fitting may result in faulty operation. If in doubt, consult
your installation/service company.

7

2000225000B

1 Technical Data

Heating

Heat input (max) NET Q 25 kW

85,300 BTU/H

Heat input (min) NET Q 10,4 kW

35,490 BTU/H

Heat output (max) NET P 23 kW

78,480 BTU/H

Heat output (min) NET P 8,7 kW

29,670 BTU/H
Efficiency - Sedbuk D 79,90%
Maximum heating temperature 87° C
Expansion vessel effective capacity 5 l
Expansion vessel charge pressure 0,5 bar
Maximum system capacity at 75°C 110 l
Safety valve, maximum service pressure 3 bar

Hot water

Heat input (max) NET Q 25 kW

85,300 BTU/H

Heat input (min) NET Q 10,4 kW

35,490 BTU/H

Heat output (max) NET P 23 kW

78,480 BTU/H

Heat output (min) NET P 8,7 kW

29,670 BTU/H
Maximum hot water temperature 63 °C
Minimum hot water temperature 35 °C
Specific flow rate (for 30°C temp rise) 11L/min.
Threshold flow rate 1,7 L/min.
Maximum supply pressure 10 bar
Minimum supply pressure 0,5 bar

Electrical

Electrical supply 230 V ~ 50Hz
Electrical rating 122 W fused at 3A
Level of protection IPX4D
Fuse rating 125mA

Natural Gas (G20)

Ø Burner injector 1,2 mm
Inlet pressure 20 mbar
Maxi. Burner pressure 12 mbar
Mini. Burner pressure 2 mbar
Gas rate maximum 2,64 m3/h

Combustion

Products outlet diameter 60 mm
Fresh air inlet diameter 100 mm
Combustion products values CO (52 ppm)

CO2 (6,40%)

NOx (92ppm)

82000225000B

1 Technical Data

Bypass fully shut

1

2

Open 1/4 turn

3

Open 1/2 turn

Open 1 turn

4

5

Open 2 turns

The 23c is delivered in three
separate packages:

• The boiler

• The fixing jig and hanging bracket

• The flue system

heating supply and return lines

Available pressure (kPa) between

(10 kPa = 1 m WG)

50

40

30

20

10

0 500 1000

Flow rate through heating system (I/h)

1

2

3

4

5

2 Dimensions

165

10086

Diagram 1.1

9699

Net lift weight (boiler only) 36 kg

Gross lift weight (boiler and packaging) 37 kg

Optional electro mechanical
clock timer shown fitted

9

320

Diagram 2.1

2000225000B

3 Heating System Design

• The 23c is compatible with any type of installation.

• Heating surfaces may consist of radiators, convectors or fan
assisted convectors.

• Pipe sectional areas shall be determined in accordance with
normal practices, using the output/pressure curve
(diagram 1.1). The distribution system shall be calculated in
accordance with the output requirements of the actual system,
not the maximum output of the boiler. However, provision shall
be made to ensure sufficient flow so that the temperature
difference between the flow and return pipes be less than or
equal to 20°C. The minimum flow is 500 l/h.

• The piping system shall be routed so as to avoid any air
pockets and facilitate permanent venting of the installation.
Bleed fittings must be provided at every high point of the
system and on all radiators.

• The total volume of water permitted for the heating system
depends, amongst other things, on the static head in the cold
condition. The expansion vessel on the boiler is pressurised at

0.5 bar and allows a maximum system volume of 110 litres for

4 Domestic Hot Water System Design

an average temperature of 75°C and a maximum service
pressure of 3 bar. This pressure setting can be modified at
commissioning stage if the static head differs. An additional
expansion vessel can be fitted to the system if required, see

diagram 8.2.

• Provision shall be made for a drain valve at the lowest point of
the system.

• Where thermostatic radiator valves are fitted, not all radiators
must be fitted with this type of valve, and in particular, where the
room thermostat is installed.

• In the case of an existing installation, it is ESSENTIAL that the
system is thoroughly flushed prior to installing the new boiler,
using a proprietary product such as Fenox or Sentinel. Contact
the product manufacturers for specific details.

3.1 Filling the system

A filling device is fitted to the boiler to initially fill the system and
replace water lost during servicing, see the relevant parts of

diagram 2 controls and lighting and diagram 8.2.

• Copper tubing or plastic Hep
hot water system. Unnecessary pressure losses should be
avoided.

• The flow restrictor must be fitted limiting the flow through the
boiler to a maximum of 10 l/min.

• The boiler will operate with a minimum supply pressure of 0,6
bar, but under reduced flow rate.

Best operating comfort will be obtained from a supply pressure
of 1 bar.

0 may be used for the domestic

2

4.1 Hard Water Areas

In areas where the water is 'hard', more than 200mg/litre, it is
recommended that a proprietary scale reducer is fitted in the
cold water supply to the boiler.

102000225000B

5 Boiler Schematic

1 - Fan.
2 - Air pressure switch.
3 - Heat exchanger.
4 - Overheat thermostat.
5 - Combustion chamber.
6 - Expansion vessel.
7 - Ignition electrode.
8 - Burner.
9 - Flame sense electrode.
10 - Pump.
11 - Heating thermistor.

12 - Ignition module.
13 - By-pass.
14 - Gas valve.
15 - Loss of water sensor.
16 - Domestic hot water thermistor
17 - Automatic air vent
18 - Domestic water flow sensor
19 - Filter cold water inlet
20 - Filling system
21 - Discharge safety valve (3bar)
22 - Heating filter
23 - Drain valve

A - Heating flow
B - Domestic hot water outlet
C - Gas
D - Cold water inlet
E - Heating return

9720

9321

11

Diagram 5.1

2000225000B

6 Boiler Location, Flue and Ventilation

If the appliance has to be stored for any length of time before
installation it should be kept in a safe place where it will not be
a hazard to persons or obstruct any access.

6.1 Clearances

The position of the boiler must be such that there is adequate
space for servicing.

The recommended clearances are:

20 mm either side of the boiler.

600 mm at the front of the boiler.

300 mm below the boiler.

25 mm above the flue elbow.

Note: The boiler must be mounted on a flat wall which is
sufficiently robust to take its weight when full, that is, 36 kg. If
in doubt, expert advice should be obtained, in the event of the
wall being found not suitable.

Note: It is permissible to install the boiler with smaller clearances
than those quoted above PROVIDING that adequate
consideration is given for Servicing/Repairs at a later date. If
any doubt exists, contact the Glow-worm's Technical Helpline

01773 828300.

The minimum acceptable spacings from the terminal to
obstructions and ventilation openings are shown in diagram

6.1.

The boiler must be installed so that the terminal is exposed to
the external air.

Should any doubt exist as to the permissible position of the
terminal, contact the Glow-worm's Technical Helpline 01773

828300.

6.2 Terminal guard

A terminal guard is required if persons could come into contact
with the terminal or the terminal could be subject to damage.

If a terminal guard is required, it must be positioned to provide
a minimum of 50mm clearance from any part of the terminal and
to be central over the terminal.

Terminal guard type K3 supplied by:

Tower flue components Ltd.
Morley road
Tonbridge
Kent
TN9 1RA

6.3 Flue options

There are various flue systems to choose from as follows:

Telescopic horizontal flue pack, (rear only).

Standard horizontal flue pack, (left or right only).

Standard horizontal extended flue pack, for use with standard
horizontal flue pack.

Vertical flue pack.

Twin flue pack.

Extensions, 90° and 45° bends.

Flue options and accessories.

For detailed information refer to flue options guide for further
information, this is available from your nearest stockist.

6.4 Cupboard or compartment ventilation

The boiler can be fitted in a cupboard or compartment without
the need for permanent ventilation.

MINIMUM SITING DIMENSIONS FOR THE

POSITIONING OF FLUE TERMINALS MM

A DIRECTLY BELOW, ABOVE OR

HORIZONTALLY TO AN OPENING, AIR

BRICK, OPENING WINDOWS, AIR VENT, OR

ANY OTHER VENTILATION OPENING 300

B BELOW GUTTER, DRAIN/SOIL PIPE 75

C BELOW EAVES 200

D BELOW A BALCONY OR CAR PORT 300

E FROM VERTICAL DRAIN PIPES AND

SOIL PIPES 300

F FROM INTERNAL CORNERS AND

EXTERNAL CORNERS 300

G ABOVE ADJACENT GROUND OR

BALCONY LEVEL 300

H FROM SURFACE FACING THE

TERMINAL 600

I FACING TERMINALS 1200

J FROM OPENING (DOOR/WINDOW)

IN CAR PORT INTO DWELLING 1200

K VERTICAL FROM A TERMINAL 1500

L HORIZONTALLY FROM A TERMINAL 600

A

A

F

G

UNDER CAR PORT etc.

2816

C

B,C

G

A

E

G

H,I

B,C

K

F

F

G

J

K

K

L

L

K

G

D

F

Diagram 6.1

122000225000B

7 Fixing Jig Pack

The fixing jig is made up as follows:
A - Heating return fitting with isolating valve (v).
B - Cold water inlet fitting with isolating valve (m).

The cold water inlet restrictor supplied with boiler is
fitted when the boiler is installed. Refer to Section 9.

C - Heating flow fitting with isolating valve (q).
D - Domestic hot water outlet.
E - Gas fitting.

LEFT
HAND

9897

SUPPORT
BRACKET

F

H

COPPER
CONNECTIONS
AND WASHERS

D

C

(5 OFF)

ISOLATING
VALVE
PLATE

q

A

E

B

m

J

v

Other components within the fixing jig pack.

F - Hanging bracket
G - wall template
H - copper connections
J - sealing washers and screws

H

1 Heating systems connections

- Pipe diameter 22mm
2 Hot water system connections

- Pipe diameter 15mm
3 Gas connection

- Pipe diameter 15mm

RIGHT
HAND

SCREW

SUPPORT
BRACKET

9717

THE FIXING JIG
SHOWN ASSEMBLED

G

Diagram 7.1

13

2000225000B

8 Piping System Installation

8.1 Fixing jig, see diagram 7.1

• Remove the contents of the fixing jig pack.

• Secure the left and right hand support brackets to the isolating
valve plate with the securing screws (2 OFF) supplied.

• Connect the five copper connections and sealing washers to
the isolating valves.

1 Heating system connections - Pipe diam. 22mm

2 Hot water system connections - Pipe diam. 15mm

3 Gas connection - Pipe diam. 15mm

10038

165mm

8.2 Wall template

• Remove the wall template, follow the instructions given on the
wall template.

• Note: It is important the hanging bracket and service cock
bracket are fitted to a flat and true wall area for correct alignment
with the boiler. If this cannot be achieved it is acceptable to pack
out the service cock bracket to obtain the correct alignment.

• Position the wall template, see diagram 8.1.

• Mark the position of the holes for the hanging bracket and jig.

• Drill, plug and fix the hanging bracket to the wall using suitable
screws (not supplied).

• Check that the hanging bracket is level.

• Drill plug and fix the fixing jig to the wall.

• For horizontal flue system, mark the position for the flue hole
as follows:

8.3 Flue to rear of boiler

• Mark correct position of hole from template.

8.4 Flue to side of boiler

• Mark the horizontal centre line for the hole on the rear wall.
Extend the horizontal centre line to the side wall and mark the
vertical centre line of flue hole as shown in diagram 8.1.

8.5 Cutting the flue hole

• Making allowance for the slope of the flue, cut hole in external
wall, preferably using a core drill. For installations with internal
and external access use a 105 mm diameter core drill.

For installations with internal access only use a 125 mm
diameter core drill.

9898

Boiler

Filling device

20mm

MIN.

Diagram 8.1

Additional
expansion
vessel
(if required)

Domestic

water

Hot water out

Cold supply in

Important

When cutting the flue hole and when extending the flue centre
line to a side wall, remember that the flue system must have a
fall of about 35 mm per metre of flue DOWNWARD towards the
terminal. There must NEVER be a downward incline towards
the boiler.

8.6 Water connection

Connect the system pipework to the copper connections on the
fixing jig observing the correct flow and return format as shown
in diagram 8.2. Do not subject the isolating valves to heat.

8.7 Gas connection

• The supply from the governed gas meter must be of adequate
size to provide a constant inlet working pressure of 20 mbar (8
in w.g.).

Refer to

*

Section 14

Control

Drain
point

142000225000B

valve

*

Bypass

valve

Flow

Heating
circuit

Return

Diagram 8.2

8 Piping System Installation

To avoid low gas pressure problems, it is recommended that the
15 mm gas supply on the boiler is connected to using 22 mm
pipe (as close as possible to the boiler within 1 metre).

• On completion, the gas installation must be tested using the
pressure drop method and purged in accordance with the
current issue of BS6891.

9 Boiler Installation

9.1 Statutory requirements

The installation of this boiler must be carried out by a qualified
registered person in accordance with the relevant requirements
of the current issue of:

The Gas Safety (Installation and Use) Regulations

The Building Regulations

The local water company Byelaws

The Building Standards Regulations (Scotland)

The Health and Safety at Work Act

9.2 Sheet metal parts

WARNING. When installing or servicing this boiler, care should
be taken when handling the edges of sheet metal parts to avoid
the possibility of personal injury.

9.3 Installing the boiler

Prior to starting work, the system must be thoroughly flushed
using a propriety cleanser such as Sentinel X300 to eliminate
any foreign matter and contamination e.g. metal filings, solder
particles, oil, grease etc.

Note. Solvent products could cause damage to the system.

The boiler pack consists of the boiler and a document envelope
and fittings pack which contain, literature, self adhesive wiring
diagram label, magnetic user instruction label, external controls
connector, guarantee return form, sealing washers, screws,
flue restrictor, cold water inlet restrictor, filling loop extension,
discharge safety valve pipe.

• IMPORTANT: With regards to the manual handling operations,
1992 regulations, the following operation exceeds the
recommended weight for one man lift.

• Stand the boiler upright.

• Remove all packaging from around the boiler.

• Remove the transit plate from the fan outlet, on top of the
boiler, secured with two screws.

• Remove front panel, unscrew and remove the two retaining
screws from the bottom of the front panel. Remove front panel
by lifting up and forward.

• If applicable remove the self adhesive wiring diagram label
from the document envelope. Fit the self adhesive wiring
diagram label to the inside of the front panel, put front panel in
a safe place to avoid damaging it.

• Ensure the plastic plugs are removed from water and gas
pipes. NOTE: There will be some spillage of water.

• Fit water flow restrictor into cold water inlet isolating valve, see

diagram 18.4.

Lift the boiler up and engage boiler upper part onto the hanging
bracket.

• Fit the washers between the boiler pipes and the inlet and
outlet fittings on the fixing jig and connect the various couplings
between the boiler and jig.

Gas Safety (Installation and use) Regulations

In your interests and that of gas safety, it is the law that ALL gas
appliances are installed and serviced by a competent person in
accordance with the above regulations.

9.4 Discharge safety valve, refer to diagram

9.1.

WARNING. It must not discharge above an entrance or window
or any type of public access area.

A short discharge pipe is supplied in the fittings pack, when fitted
to the safety valve it will end below the boiler. The discharge
pipe must be extended using not less than 15 mm o.d. pipe, to
discharge in a visible position outside the building, facing
downward preferably over a drain.

Note: Fit a compression fitting to facilitate service of the
appliance.

The pipe must have a continuous fall and be routed to a position
so that any discharge of water, possibly boiling or steam, cannot
create any danger to persons, damage to property or external
electrical components and wiring. Tighten all pipe connection
joints.

9.5 Filling loop extension

Remove the filling loop extension knob from the fittings kit. Fit
to the filling device on/off knob this is a push fit, see diagram 9.2.

9970

DISCHARGE SAFETY
VALVE (3 bar)

FILLING
DEVICE

FILLING LOOP
EXTENSION

Diagram 9.1

Diagram 9.2

10089

15

2000225000B

10 Flue Installation Telescopic and Standard

The

Telescopic flue,

cutting) is suitable for installations that
require a flue length from 425 minimum to

659.5 maximum. There are no extensions or
bends available for this flue.

The

Standard flue, suitable for side only,

(adjustable by cutting) is suitable for
installations that require a flue length from
300 minimum to 930 maximum (without
extensions).

Note: Additional 1 metre extentions, 90° and 45° bends are

available. The maximum extended flue is 3m. The use of flue
bends requires the flue lengths to be reduced by 1m. for 90° and

0.5m. for 45°.

The boiler is only suitable for top outlet flue connection.

10.1 Top outlet flue
Telescopic kit A2004500, Standard kit 86285

10.2 Flue systems rear

Telescopic Flue

Extend to suit flue length required.

(adjustable without

10.3 Flue systems side

Telescopic Flue

Extend to suit flue length required.

Standard Flue, Refer to diagram 10.1.

10.4 Flue cutting.

Telescopic Flue

The telescopic flue cannot be cut.

Standard Flue, refer to diagram 10.2.

Important: Do not leave any burrs or sharp edges on the cut

ends of the pipes.

Max. Std flue length 930mm

Min. Std flue length 300mm

70mm

205mm

410 mm

65mm

10093

Outside

wall face

X

17mm

cutting length

Air duct cutting length

Flue

centre line

160mm

X minus 160mm

Air duct

C

L

plus 17mm =

Air duct

cutting length

Flue duct

10091

75mm
Min. Wall Thickness

SIDE FLUE

20mm
Min. Clearance

Diagram 10.1

Flue duct cutting length =
air duct cutting length + 152mm

162000225000B

95mm

check

dimension

(cut end)

Diagram 10.2

10 Flue Installation Telescopic and Standard

10.5 Installation of telescopic flue assembly

• The elbow must be removed from the air and flue duct pipes.

• Extend the telescopic flue assembly approximately 10 cm, If
the telescopic flue is pulled apart care must be taken not to
damage the ‘O’ ring on the flue duct when re-assembling.

• Remove the 2 securing screws on either side of the air elbow
end of the air duct pipe, carefully pull the air duct pipe off the air
elbow taking care not to disconnect the telescopic flue duct
pipes.

• Remove the 2 securing screws on either side of the flue elbow
to release the flue duct pipe, pull the flue duct pipe out of the flue
elbow, note the ‘O’ ring inside the flue elbow.

• Fit rubber sealing collar (B), see diagram 10.3, into groove at
the outer end of the air duct pipe (A).

• Fit air/flue duct pipe assembly (A) into wall from the outside
with rubber sealing collar to the outside.

• Pull pipe assembly inwards to bring rubber sealing collar hard
up against external wall, see diagram 10.5.

• Fit ‘O’ ring (E) into the underside of the flue elbow. Apply a
small amount of silicone grease to the ‘O’ ring when fitting.

• Remove the backing from the self adhesive gasket (C) and
carefully fit gasket to base of flue elbow.

• Leave the restrictor (a) fitted inside the fan outlet,

see diagram 10.6.

• Ensure transit plate has been removed from the fan outlet, on
top of the boiler.

• Fit elbow onto boiler and secure with the four screws (D).

• Re-fit the telescopic flue duct pipe to the flue elbow taking care
not to tear the ‘O’ ring, fit the 2 securing screws.

• Re-fit the telescopic air duct pipe to the air elbow, fit the 2
securing screws.

• For flue systems less than 1,5 m long, fit the restrictor (a) in
the fan outlet, see diagram 10.7.

• Remove the backing from the self adhesive gasket (H) and
carefully fit gasket to base of flue elbow.

• Fit elbow onto boiler and secure with the four screws (I).

A

E

C

B

10024

The flue kit A2004500 is 659.5 mm long and comprises:

-Telescopic flue assembly ..................................... A

- External rubber sealing collar ...............................B

- Gasket ..................................................................... C

- Screws ..................................................................... D

- 'O' ring ...................................................................... E

Telescopic flue kit

Diagram 10.3

D

A

B

Pho 451

10.6 Installation of standard flue assembly

• Ensure transit plate has been removed from the fan outlet, on
top of the boiler.

• Fit rubber sealing collar (F), see diagram 10.4, into groove at
the outer end of pipe (A).

• Fit air duct pipe (A) into wall with groove to the outside.

• Pull pipe inwards to bring rubber sealing collar hard up against
external wall, see diagram 10.5.

• Fit internal plastic flange (G) onto air duct pipe. Push along the
pipe until engaged against internal wall.

• From inside, insert flue duct pipe (B) into air duct pipe.

• Fit both ‘O’ rings (J) into the flue elbow (C), one at the inlet, one
at the outlet. By necessity, they are a loose fit, apply a small
amount of silicone grease to each ‘O’ ring when fitting.

• Fixing collar (D) over air duct pipe (A) and elbow (C) ensuring
it is the correct way round (Note: the fixing collar can only be
fitted one way due to the different diameters of the flue elbow
and air duct.

• Take hold of the flue duct pipe and push gently onto the elbow
outlet taking care not to tear the ‘O’ ring.

• Open fixing collar (D) and locate between elbow and air duct
pipe (A). Close fixing jig.

• Engage the two fixing clips (E) onto the collar (D) and press
down to lock into position. Secure clips with screws provided.

Important: If the flue has been cut, ensure that there are no
burrs that could damage the ‘O’ ring.

E

C

D

H

The flue kit 86285 is 1000 mm long and comprises:

- Air duct pipe .......................................................... A

- Flue duct pipe ........................................................B

- Flue elbow .............................................................. C

- Fixing collar............................................................. D

- Locking clips ............................................................ E

- External rubber sealing collar ............................... F

- Internal flange ....................................................... G

- Gasket ..................................................................... H

- Screws ....................................................................... I

- 'O' rings..................................................................... J

Standard flue kit

F

I

J

Diagram 10.4

Diagram 10.5

G

Pho 087

17

2000225000B

10 Flue Installation

Telescopic flue system (rear and side)

The maximum permissible length (L) for the telescopic flue system is 659.5mm. The restrictor (a) must be fitted to
inside the fan outlet.

FLUE
RESTRICTOR
(a)

GASKET

L

65

10094

165

Diagram 10.6

Standard flue system (side only)

The maximum permissible length (L) for the standard flue system is 3.0m. For flue systems up to 1.5m. the flue
restrictor (a) must be fitted inside the fan outlet. For longer flue systems the restrictor must be removed. For
each 90˚ flue elbow used, or (two 45˚ elbows) the maximum permissible length (L) must be reduced by 1metre.

FLUE
RESTRICTOR
(a)

GASKET

L1

65

10095

165

Diagram 10.7

182000225000B

11 Electrical Connection

Warning. This boiler must be earthed

All system components must be of an approved type.

Electrical components have been tested to meet the equivalent
requirements of the BEAB.

Connection of the whole electrical system and any heating
system controls to the electrical supply must be through a
common isolator.

Isolation should preferably be by a double pole switched fused
spur box having a minimum contact separation of 3 mm on each
pole. The fused spur box should be readily accessible and
preferably adjacent to the boiler. It should be identified as to its
use.

A fused three pin plug and shuttered socket outlet may be used
instead of a fused spur box provided that:

a) They are not used in a room containing a fixed bath or
shower.

b) Both the plug and socket comply with the current issue of
BS1363.

The mains electrical supply must be maintained at all times in
order to provide domestic hot water.

Do not interrupt the mains supply with a time switch or
programmer.

WARNING: UNDER NO CICUMSTANCES MUST ANY MAINS
VOLTAGE BE APPLIED TO ANY OF THE TERMINALS ON
THE VOLTAGE FREE HEATING CONTROLS CONNECTION
PLUG.

Warning: This appliance must be wired in accordance with

these instructions. Any fault arising from incorrect wiring cannot
be put right under the terms of the Glow-worm guarantee.

Important: If a replacement supply cable is required it must be
purchased. Part No. S1008600.

11.2 External controls - Mains Voltage

Remove the MAINS VOLTAGE HEATING CONTROLS
CONNECTION PLUG from the fittings pack and install on the
230V interface control board as shown on the instruction sheet,
also provided in the fittings pack and diagram 11.2

Gain access to the 230V interface by unclipping the control
panel and hinge forward.

The wire link (E) must be removed from the voltage free heating
controls connection plug.

External controls e.g. room thermostat, frost thermostat etc.
should be fitted in accordance with the rules in force.

Refer to the wiring diagram Section 17.

11.3 Testing - Electrical

Checks to ensure electrical safety must be carried out by a
competent person.

After installation of the system, preliminary electrical system
checks as below should be carried out.

1. Test insulation resistance to earth.

2. Test earth continuity and short circuit of all cables.

3. Test the polarity of the mains.

The installer is requested to advise and give guidance to the
user of the controls scheme used with the boiler.

Note: For further information, see the building regulations 1991

- Conservation of Fuel and Power - 1995 edition - appendix G,
Table 4b.

11.1 External controls - Voltage Free

This boiler will operate on heating as supplied, provided that the
wire link (E) fitted between the two terminals of the heating
controls conection plug is left in place, see diagram 11.1.

External controls e.g. room thermostat, frost thermostat etc.
should be fitted in accordance with the rules in force.

WARNING: UNDER NO CICUMSTANCES MUST ANY MAINS
VOLTAGE BE APPLIED TO ANY OF THE TERMINALS ON
THE VOLTAGE FREE HEATING CONTROLS CONNECTION
PLUG. If mains voltage controls are required, see section

11.2.

Refer to the wiring diagram Section 17.

➜

➜

MAINS
VOLTAGE
EXTERNAL
CONTROLS

9762

CONNECTION
PLUG

230V
CONTROLS
BOARD

9764

(E) Wire link
VOLTAGE
FREE
HEATING
CONTROLS
CONNECTION
PLUG

Diagram 11.1

10019

CONTROL PANEL

19

Diagram 11.2

2000225000B

12 Commissioning

Please ensure the “Benchmark” logbook is completed and left
with the user.

The commissioning and first firing of the boiler must only be
done by a qualified registered person.

Gas installation

It is recommended that any air is purged from the supply at the
gas inlet test point on the gas valve, see diagram 12.1.

Filling the system 1 to 8

1.

Make sure that:

• The boiler is connected to the electrical supply.

• The gas service cock is open.

Turn the switch OFF ( 0 )

9972

GAS INLET
TEST POINT

2.

• Open the three boiler isolating valves. The slot
of the screw corresponds to flow direction.
(To unscrew turn anti-clockwise).

➜

HEATING
FLOW

3.

• Undo cap on automatic air vent on top of pump
and leave undone.

9973

Fully open valves by
turning anti-clockwise.

➜

COLD
WATER IN

4.

• Turn the switch ON ( I )

• Open the tap on the
filling device and fill the
system until the pressure
indicated on the display is
2 bar. Close filling device.

Diagram 12.1

9838

➜

HEATING
RETURN

9974

➜

202000225000B

12 Commissioning

5.

• Bleed each radiator to remove air, ensure all
bleed screws are re-tightened.

• If necessary repressurise the system, refer to
procedure 4

➜

7.

• Open various hot water taps to bleed system

Ins 061a

Ins 062a

6.

• Leave cap on automatic air vent on top
of pump open.

8.

• Ensure the display indicates a system pressure
of 1.5 bar adjust if necessary.

9973

• Adjust heating temperature to maximum .

• Check that any external controls, if fitted, are calling for heat
(set room thermostat to maximum).

• Allow the temperature to rise to the maximum value, with all
radiator valves open. The temperature rise will cause release
of the gases contained in the water of the central heating
system.

• Gases driven towards the boiler will be automatically released
through the automatic air vent.

• The gases trapped at the highest point of the system must be
released by bleeding the radiators. Check the burner gas rate
required, ten minutes from lighting. Refer to Data Label on
electrical controls box. Should there be any doubt about the
gas rate it should be checked at the meter.

On reaching maximum temperature, the boiler should be
turned off and the system drained as rapidly as possible whilst
still hot.

• Refill system to a pressure of between 1 and 2 bar and vent
as before.

• Restart boiler and operate until a maximum temperature is
reached. Shut down boiler and vent heating system. If necessary,
top up heating system and make sure that a pressure of at least
1 bar is indicated when system is COLD.

Flush the domestic hot water system by opening the hot water
taps for several minutes.

Remove the magnetic lighting instructions label from the
document envelope and position it on the surface of the boiler
casing.

➜

9696

Instruct the User

Instruct and demonstrate the lighting procedure and advise the
user on the safe and efficient operation of the boiler.

Instruct on and demonstrate the operation of any heating
system controls.

Advise the user on the use and maintenance of any scale
reducer and pass on any relevant instructional documents.

Advise that to ensure the continued efficient and safe operation
of the boiler it is recommended that it is checked and serviced
at regular intervals. The frequency of servicing will depend upon
the installation conditions and usage, but in general, once a
year should be enough.

Draw attention, if applicable, to the current issue of the Gas
Safety (Installation and Use) Regulations, Section 35, which
imposes a duty of care on all persons who let out any property
containing a gas appliance.

It is the Law that any servicing is carried out by a competent
person.

Advise the user of the precautions necessary to prevent damage
to the system, boiler and the building, in the event of the heating
system being out of use during frost or freezing conditions.

Advise the user that the permanent mains electrical supply
SHOULD NOT be switched off, as the built in frost protection
and pump saver program would not be operable.

Reminder, leave these instructions and the ‘Benchmark’ logbook
with the user.

21

2000225000B

14 Settings

Bypass

The 23c boiler has a built-in bypass. This must be adjusted
according to the requirements of the system, refer to the flow
rate pressure curve (diagram 1.1). The boiler is supplied with
the built-in bypass open a half a turn. It is adjusted by turning the
bypass screw (a), see diagram 14.1. Turn the screw clockwise
to close the bypass. When using thermostatic radiator valves
(TRV’s) on all of the radiators, it is essential that a separate,
adjustable bypass of 15 mm minimum diameter is fitted between
the flow and return of the heating circuit, see diagram 8.1. Any
bypass must be fitted before system controls.

15 Routine Cleaning and Inspection

REMEMBER, when replacing a part on this appliance, use only
spare parts that you can be assured conform to the safety and
performance specification that we require. Do not use
reconditioned or copy parts that have not been clearly authorised
by Hepworth Heating.

To ensure the continued efficient and safe operation of the
boiler it is recommended that it is checked and serviced at
regular intervals. The frequency of servicing will depend upon
the particular installation conditions and usage, but in general
once a year should be enough.

It is the law that any servicing is carried out by a qualified
registered person.

A

PRODUCTS
SAMPLING
POINT

9975

Diagram 14.1

9532

Diagram 15.1

15.1 Products of combustion check

Note: To obtain a products of combustion reading, unscrew the
left hand sampling point cap on the flue elbow, located on top
of boiler, see diagram 15.1.

Connect the analyser tube onto sampling point.

Refer to the combustion product values in Section 1 Technical

Data.

Switch on the electrical supply and gas supply, then operate the
boiler.

On completion of the test switch off the electrical supply and the
gas supply, remove analyser tube and replace sampling point
cap.

15.2 Service Check and Preparation.

• Isolate boiler from the gas and electrical supplies.

• Drain the Domestic hot water circuit and the boiler, refer to
diagram 15.2.

• On completion check all gas-carrying parts for soundness with
leak detection fluid.

• Remove boiler casing as follows:

15.3 Front panel

• Unscrew and remove the two retaining screws from the bottom
of the front panel.

• Remove front panel by pulling forward and lifting up.

15.4 Control panel

• Lower forwards to gain access to lower part of boiler.

15.5 Sealed chamber cover

• Unclip the two toggle clips holding the sealed chamber cover,
see diagram. 15.3.

• Lift cover up and off pins on the top of the boiler.

222000225000B

15 Routine Cleaning and Inspection

To Drain the Domestic hot water circuit

• Close boiler isolating valve (c).• Turn on one or more hot water taps.

To Drain the boiler

• Close isolating screws on the isolating valves (b), (c) and (d) turn from vertical
to horizontal to close.

• Open the boiler drain valve (a). • Turn on one or more hot water taps.

(d)

HEATING
FLOW

Note: Isolating cocks water and gas

are shown in the: OFF position

(c)

COLD
WATER IN

BOILER DRAIN VALVE

9839

(a)

(b)

HEATING
RETURN

9836

Diagram 15.2

9976

9977

Diagram 15.3

23

Diagram 15.4

2000225000B

15 Routine Cleaning and Inspection

15.6 Side panels (for ease of access if
required), refer to diagram 15.4.

• Support the side panels as you remove them.

• Unscrew and remove the three retaining screws from front of
each side panel.

• Left hand side panel only disconnect the control panel retaining
strap at the control panel.

• Pull each panel forward from the rear retaining pins to remove.

15.7 Combustion chamber cover

• Unscrew and remove the four screws securing combustion
chamber cover to combustion chamber, see diagram 15.5.

• Remove combustion chamber cover from boiler.

• Take care not to damage the insulation.

15.8 Spark and Sense Gaps

• Check that the spark and sense gaps as shown in diagram

15.6. Note: To gain access to spark and sense electrodes for
removal, refer to Section, 18.12 and 18.13 in Replacement of
Parts.

15.9 Burner, refer to diagram 15.7.

• Unscrew and remove the two burner retaining screws.

• Remove burner from boiler by easing it forward off the two
burner guides.

• Clean burner by washing in soapy water. Dry thoroughly
before refitting.

Note: To gain access to injectors for removal and cleaning, refer
to Section, 18.8 in Replacement of Parts.

15.13 Central Heating Filter, refer to diagram

15.11.

Remove the filter retaining clip and filter clean or renew if
necessary.

Refit the filter, ensuring the correct orientation. The flat and hole
in the filter as shown. Secure with retaining clip.

15.14 Reassembly of parts removed for
servicing

All parts are replaced in reverse order to removal.

15.15 Flue system

• Check externally to make sure that flue is not blocked

• Inspect flue system to make sure that all fittings are secure.

9978

15.10 Fan, refer to diagram 15.8.

• Disconnect power supply leads and earth lead from fan.

• Remove air pressure switch sensing tube from the side of the
fan.

• Unscrew and remove the fan retaining screw.

• Ease the fan down and forwards to remove.

15.11 Heat exchanger, refer to diagram 15.9.

• Remove the two flue hood retaining screws to remove the flue
hood.

• Use a soft brush or vacuum clean the heat exchanger.

DO NOT USE ANY TOOL LIKELY TO DAMAGE PAINTED
FINISH OF HEAT EXCHANGER.

15.12 Domestic water inlet filter, refer to
diagram 15.10.

If the water flow rate through the appliance has reduced it may
be necessary to clean or replace the domestic water inlet filter.

• Pull out slotted clip securing the filter in its housing, remove the
filter to clean or renew if necessary.

Replace the filter into its housing and replace the securing clip.

• Open isolating valve (c) on cold water inlet and test the
Domestic Hot Water circuit for soundness.

Diagram 15.5

5mm

9979

8mm

SPARK GAP

9980

4mm

242000225000B

SENSE GAP

Diagram 15.6

15 Routine Cleaning and Inspection

9982

BURNER
RETAINING
SCREWS

BURNER
GUIDE

Diagram 15.7

9983

9981

FLUE HOOD

9985

9986

POWER
SUPPLY
LEADS

AIR PRESSURE
SWITCH
SENSING TUBE

FAN RETAINING
SCREW

9834

EARTH
LEAD

➜

PULL DOWN

Diagram 15.8

9984

HEAT EXCHANGER

DOMESTIC WATER
INLET FILTER
HOUSING

RETAINING CLIP

FILTER

Diagram 15.9

CLIP

Diagram 15.10

FLAT

9987

9835

FILTER

25

Diagram 15.11

2000225000B

16 Fault Finding

Before trying to operate the boiler make sure that :

• All gas supply cocks are open and that the gas supply has
been purged of air.

• The heating system pressure is at least 1 bar.

• There is a permanent mains supply to the boiler.

• The fuse on the PCB is intact.

WARNING. Always isolate the boiler from the electrical supply
before carrying out any electrical replacement work.

Always check for gas soundness after any service work.

Should there be any doubt about the voltage supply to any of
the components, it is possible to carry out a simple electrical
test to ensure all is operational in that area.

To carry out the electrical test, gain access to the main Printed
Circuit Board (PCB), as described previously, and measure
the voltages according to table 2.

IMPORTANT: On completion of the fault finding task which
has required the breaking or remaking of the electrical
connections, the continuity, polarity, short circuit and resistance
to earth checks must be repeated using a suitable multimeter.

Table 2

Voltage Measured value Measuring point

230 Volt 230V AC Between terminals H8.1 and H8.2

24 Volt maximum 33V DC Between terminals J5.3 and J15.1

minimum 20V DC

18 Volt 18V ± 1V Between terminals J2.9 and J2.10

Display 5V ± 0.5V Between terminals J13.4 and J13.1

TYPE OF FAULT CHECK

No domestic hot water or central heating • 230V supply
(No flashing warning light on control panel) • Is fuse blown

• Loose connections on control board (PCB)

• Faulty control or interface board (PCB's)

No domestic hot water or central heating • Water pressure
(A flashing warning light on control panel) • Shortage of air or gas

• Faulty temperature sensor

• Overheating

• Wrong flue length

• Connections on air pressure switch (electrical or tubes)
disconnected

No hot water but central heating ok • Loose connections at hot water flow sensor.

• Faulty hot water flow sensor.

• Faulty control board (PCB).

262000225000B

16 Fault Finding

COMPONENT NORMAL MEASURE CHECK

Gas control valve
Resistance of coil 116Ω 24V dc for 1 to 2 seconds, then is not faulty.

Adjustment valve
( step motor) Dismantle the step motor (screw not Check the connections at both

Domestic water flow

Under demand during ignition sparks: If 0 Volt:

12Vdc (constant) at the gas control
valve electrical connection.

If 24 Volts and then 12 Volts
but no gas at the burner:

Check if the gas control valve is
stuck. If not, check the
stepper valve.

the gas control valve

Close the gas inlet: If the valve does not move:

sealed in). Trigger a demand and check motor and control board (PCB).
that the valve opens during the ignition. Change the motor. Replace the

control board (PCB).

To test:

connect it electrically in place of
the faulty one . Blow through to
simulate a demand for water.

Use a new detector and

Overheat thermostat reset button.

9913

Refer to section 18.10 to locate the overheat thermostat
reset button.

Depress the button to reset.

FAULTY WATER
PRESSURE SENSOR

It is possible to replace
the sensor with two 1kΩ
resistors as shown in the
diagram.

Diagram 16.1

9988

RESET BUTTON

OVERHEAT
THERMOSTAT

Diagram 16.2

27

2000225000B

16 Fault Finding

FAULT: NO HEATING, BUT HOT WATER AT TAPS

Is the heating set high enough ?

YES

Is the room thermostat in demand ?

YES

Check by overriding the room thermostat
at the connector. Does the fault persist ?

YES

Is the system fitted with

a external sensor ?

NO

NO

The setting is too low or the boiler

is set to summer mode.

YES

Tu rn the setting up by turning the

central heating temperature

control knob clockwise.

NO

Adjust the setting.

Check the thermostat, the line,

YES

the connections both

to the room thermostat and

the control board (PCB).

Check the electrical connections

to the control board (PCB).

If the problem persists fit a

replacement control board (PCB).

YES

Unplug the sensor

and test it individually.

282000225000B

16 Fault Finding

FAULT: NO HOT WATER, BUT THE HEATING IS WORKING

Is the cold water inlet tap fully open ?

YES

Is the water pressure greater

than 0.5 bar ?

YES

Is the water flow rate greater

than 1.7l/min. (threshold figure).

YES

Is flow detector operating ?

YES

Check the connectors on the

sense electrode and the

control board (PCB).

If the fault persists, fit a relplacement

control board (PCB).

NO

NO

NO

NO

Open it.

Insufficient water pressure.

The appliance will not operate.

Find out why the pressure is so low.

Check the cold water inlet filter

for dirt. Is the cold water tap fully open ?

Check the heat exchanger for scaling.

Change or clean it.

FAULT: THE BURNER LIGHTS BUT THEN GOES OUT. THERE IS NO FLAME DETECTED.

The flame is not spreading across

the whole burner and is not reaching

the sensing electrode. Is the gas

NO

Check that the gas taps are fully open
Check the gas pressure.

pressure correct?

YES

Adjust the low flow setting of the
gas control valve.
Clean the gas filter.
Clean the burner.

29

2000225000B

16 Fault Finding

FAULT: THE BURNER LIGHTS, THEN GOES OUT.

The flame is spreading across the

whole burner, but not being detected.

CHECK THE MAINS

Check the 230V mains supply.

FAULT NOT FOUND

If the problem persists, change the
control board (PCB).
(flame detection module faulty).

CHECK

THE

PROBE

With the power turned off, check the
resistance between the spark electrode
and terminal H23 on the control board
(PCB). Check the connector on the end
of the wire.
Check that the spark electrode is
pointing towards the flame.
Check the spark electrode. Change it.

Check the earth: no power and neutral

Note: the boiler is independent of
phase and neutral; reversing phase
and neutral on the electric plug will
have no effect.

FAULT: THE BURNER DOES NOT LIGHT AT ALL, BUT THERE IS AN IGNITION SPARK.

Are the gas taps on?

YES

Is there 24Vdc at the
gas control valve?

YES

Test the gas control valve.
Check resistance of safety valve coil.

NO

NO

Tu rn on the gas taps.

Check the wiring.
If the problem persists, change the
control board (PCB).

302000225000B

16 Fault Finding

FAULT: THE RADIATORS ARE LUKE-WARM.

Is the installation fitted with a

external sensor?

NO

Is the installation fitted with a
room thermostat?

NO

Is the heating setting high enough?

YES

Is the heating power adequate?

YES

YES

NO

The temperature of the radiators
depend on the outside temperature.
If the room temperature is not sufficient,
adjust.

The radiators will only be hot if the
thermostat is demanding heat. If the
room temperature is not sufficient, turn
the setting of the room thermostat up.

Tu r n it up.

- Check the adjustment of the by-pass
(too far open).

- Check the circulation in the radiators.

- Check the thermistor.

- If problem persists, change the interface
board or the control board (PCB).

FAULT: THE WATER AT THE TAPS IS LUKE-WARM.

Is the setting high enough?

YES

Is the temperature higher if you turn the
tap down to reduce the flow rate?

NO

NO

Tu r n it up.

Check the thermistor.

YES

Check that the flow restrictor on the cold
water inlet is fitted.
Check the rate of flow.

31

2000225000B

16 Fault Finding

FAULT: THE FAN DOES NOT START.

Does the warning light flash 45 seconds

after the start of the demand?

YES

Check the fan (loose terminal
connector, windings burnt out).
Interface board or control board (PCB).

FAULT: THE FAN RUNS BUT THERE ARE NO SPARKS.

Does the warning light flash 45 seconds

after the start of the demand?

YES

NO

NO

Check the power from the room thermostat.
Replace the interface board or
control board (PCB).

Thermistor.
Control board (PCB).

The air flow switch is not operating or
is unplugged.

CONNECTIONS TO THE AIR PRESSURE SWITCH

Pr

P2

P1

LH

Air flow switch take-off.

NO

Check the pressure drop on the
flue pipe.
Is the plastic tube on the correct pressure
connection of the air pressure switch?
Are the electrical connections in place.

3

21

Electrical contacts.

322000225000B

17 Wiring Diagram

WATER
PRESSURE
SENSOR

wg

or

g/y

bbr

FAN

OVERHEAT

THERMOSTAT

THERMISTOR

CH

bgn

AIR PRESSURE
SWITCH

3

ww

gn gn

THERMISTOR

DHW

ww

bk

PLUG

g/y

3

b

PUMP

IGNITOR

UNIT

4

1

2

br

IGNITION

SENSE

ELECTRODE

1

GAS

CONTROL

VALV E

pory

w

g

gn

w

g

p

g

w

FLOW
SENSOR

w

b

r

y

gn

230V CONTROLS

br

b

BOARD

w

r

gn

by

ELECTRODES

CHASSIS

EARTH

THERMOSTAT
2 INPUT
(FROST STAT)

THERMOSTAT
1 INPUT
(ROOM STAT)

MAINS VOLTAGE
EXTERNAL
CONTROLS
CONNECTION PLUG

VOLTAGE FREE

b

*

HEATING
CONTROLS
CONNECTION
PLUG

10016

USER INTERFACE

J11

J13J15

J1

S1

J12

J4

J2

J7

REMOVE BLUE LINK IF USING

*

230V EXTERNAL CONTROLS

KEY

bk- BLACK
w- WHITE
g/y- GREEN/

YELLOW

br - BROWN
b- BLUE
p- PINK
g- GREY

r - RED
or- ORANGE
gn- GREEN
y- YELLOW

FUSE
125mAT

H2

H5

H1

H4

H3

H8

H6

H7

ON/OFF
SWITCH

g/y

br

b

br

wr

b

b
br

g/y

br

b

g/y

b

br

230V~50Hz

PERMANENT

MAINS SUPPLY

FUSED AT 3A

CHASSIS
EARTH

g/y

33

2000225000B

18 Replacement of Parts

To Drain the central heating circuit

• Open drain valve fitted at the lowest point in the system.

• Allow air into the system by opening a radiator bleed screw or the boilers drain
valve (a).

To Drain the Domestic hot water circuit

• Close boiler isolating valve (c).

• Turn on one or more hot water taps.

To Drain the boiler

• Close isolating screws on the isolating valves (b), (c) and (d) turn from vertical
to horizontal to close.

• Open the boiler drain valve (a).

• Turn on one or more hot water taps.

BOILER DRAIN VALVE

9839

(a)

9836

(d)

HEATING
FLOW

IMPORTANT INFORMATION

WARNING: Before commencing the replacement of any

component, isolate appliance from electrical supply and turn off
gas at service cock.

Replacement of parts must be carried out by a competent
person.

When replacing components it may be necessary to renew
sealing washers, gaskets and 'O' rings. If new ones are
supplied with replacement components they must be used.

All parts are replaced in reverse order to removal.

If any gas-carrying components are disturbed, removed or
replaced it will be necessary on completion to check for gas
soundness with leak detection fluid.

18.1 Central heating thermistor

Before starting refer to the front of Section 18 Important
information.

• Remove the front panel, refer to Section 15.3.

• Lower the control panel, refer to Section 15.4.

• Remove the sealed chamber cover, refer to Section 15.5.

• Locate central heating thermistor on the top left hand side of
the heat exchanger, see diagram 18.2.

Note: Isolating cocks water and gas

are shown in the: OFF position

(c)

COLD
WATER IN

CENTRAL HEATING
THERMISTOR

OVERHEAT
THERMOSTAT

• Disconnect electrical connections from thermistor.

• Remove the thermistor from the heat exchanger.

• Fit replacement thermistor.

• Refit electrical connections.

(b)

HEATING
RETURN

Diagram 18.1

Diagram 18.2

9988

342000225000B

18 Replacement of Parts

18.2 Fan, refer to ‘Section 15.10 Routine
Cleaning and Inspection’.

18.3 Air pressure switch

Before starting refer to the front of Section 18 Important
information.

• Remove the front panel, refer to Section 15.3.

• Lower the control panel, refer to Section 15.4.

• Remove the sealed chamber cover, refer to Section 15.5.

• Locate air pressure switch situated inside combustion chamber
on top left hand side, see diagram 18.3.

• Remove air pressure switch tube from sensing probe on fan.

• Disconnect air pressure switch electrical connections.

• Unclip to remove air pressure switch.

18.4 Domestic water inlet filter

Before starting refer to the front of Section 18 Important
information.

If the water flow rate through the appliance has reduced it may
be necessary to clean or replace the water inlet filter, refer to

section 15.12.

18.5 Central Heating Filter

Before starting refer to the front of Section 18 Important
information.

It may be necessary to clean or replace the central heating filter,
refer to section 15.13.

RETAINING
CLIPS

ELECTRICAL
CONNECTORS

SENSING
TUBE

10033

UNION
NUTS

9646

AIR
PRESSURE
SWITCH

Diagram 18.3

FLOW
RESTRICTOR

9777

18.6 Cold water inlet restrictor

Before starting refer to the front of Section 18 Important
information.

• Remove the front panel, refer to Section 15.3.

• Lower the control panel, refer to Section 15.4.

Drain down domestic hot water circuit of boiler only, refer to
relevant part of diagram 18.1.

• Remove the retaining wire.

• Undo union nuts from boiler cold water in isolating valve.

• Clean and inspect restrictor, replace if necessary, see diagram

18.4.

18.7 Burner, refer to Section 15.9.

Before starting refer to the front of Section 18 Important
information.

18.8 Burner injectors, refer to diagram 18.5.

Before starting refer to the front of Section 18 Important
information.

• Remove burner from boiler, refer to Section 15.9.

• Remove and replace injectors as required.

Note: The injectors may be cleaned, remove injectors inspect
and clean. Do not use a wire or sharp instrument.

Note: Make sure that injector size, marked on each injector, is
the same as that given in ‘Section 1 Technical Data’ for the
type of gas being used.

9990

COLD WATER IN
ISOLATING VALVE

BURNER
INJECTOR BAR

RETAINING
WIRE

Diagram 18.4

Diagram 18.5

35

2000225000B

18 Replacement of Parts

18.9 Burner injector assembly, refer to
diagram 18.6.

Before starting refer to the front of Section 18 Important
information.

• Remove burner from boiler, refer to Section 15.9.

• Undo the gas supply union nut from under the sealed chamber.

Note: The fibre washer between the burner injector assembly
and gas supply must be kept for use on reassembly.

• Undo and remove the sense and ignition electrode assemblies.

• Remove the burner injector assembly securing screws.

• Remove the burner injector assembly by lifting up, easing the
gas connection through the grommet in the sealing chamber.

• When refitting burner injector assembly ensure the gas
connection locates correctly through the grommet.

Note: Make sure that injector size, marked on each injector, is
the same as that given in ‘Section 1 Technical Data’ for the
type of gas being used.

18.10 Overheat thermostat

Before starting refer to the front of Section 18 Important
information.

• Remove the front panel, refer to Section 15.3.

• Lower the control panel, refer to Section 15.4.

• Remove the sealed chamber cover, refer to Section 15.5.

• Locate overheat thermostat on left hand side of heat exchanger,
see part of diagram 18.8.

• Disconnect electrical connections from thermostat

• Unclip thermostat from heat exchanger.

• When refitting electrical connections to replacement thermostat
the polarity is not important.

18.11 Domestic hot water thermistor

Before starting refer to the front of Section 18 Important
information.

• Remove the front panel, refer to Section 15.3.

• Lower the control panel, refer to Section 15.4.

• Locate domestic hot water thermistor on domestic hot water
pipe to the left of centre of the boiler, see part of diagram 18.7.

• Disconnect electrical connections from thermostat

• Unclip thermostat from flow pipe to the heat exchanger.

• When refitting electrical connections to replacement thermostat
the polarity is not important.

18.12 Ignition electrode

Before starting refer to the front of Section 18 Important
information.

• Remove burner, refer to Section 15.9.

• Remove the left hand side panel, refer to Section 15.6.

• Undo and remove screw securing electrode assembly to the
burner injector assembly, see diagram 18.6.

• Disconnect the electrical connections at the igniter unit, see

diagram 18.21. Note the routing of the cables.

18.13 Flame sense electrode

Before starting refer to the front of Section 18 Important
information.

• Remove burner, refer to Section 15.9.

• Remove the right hand side panel, refer to Section 15.6.

• Undo and remove screw securing sense assembly to the
burner injector assembly, see diagram 18.6.

• Disconnect the electrical connection from the inline connector,
Note the routing of the cable.

GROMMET

9991

GAS SUPPLY
PIPE

SENSE
ELECTRODE
ASSEMBLY

IGNITION
ELECTRODE
ASSEMBLY

9992

9993

Diagram 18.6

DOMESTIC HOT WATER
THERMISTOR

➜

➜

9996

Diagram 18.7

362000225000B

18 Replacement of Parts

18.14 Heat exchanger, refer to diagram 18.8.

Before starting refer to the front of Section 18 Important
information.

• Remove the front panel, refer to Section 15.3.

• Lower the control panel, refer to Section 15.4.

• Remove the sealed chamber cover, refer to Section 15.5.

• Remove the combustion chamber cover, refer to Section

15.7.

• Drain down central heating water circuit and domestic hot
water cuircuit of the boiler only, refer to relevant part of

diagram 18.1.

• Remove the fan, refer to Section 15.10.

• Remove the flue hood, retained by two screws lift up and off.

• Remove the electrical leads from the overheat thermostat,

refer to diagram 18.8.

• Disconnect the four union nuts.

• Lift to remove the heat exchanger taking, care not to damage
the insulation.

18.15 Combustion chamber insulation, refer to
diagram 18.9.

Before starting refer to the front of Section 18 Important
information.

• Remove the front panel, refer to Section 15.3.

• Lower the control panel, refer to Section 15.4.

• Remove the sealed chamber cover, refer to Section 15.5.

• Remove the combustion chamber cover, refer to Section

15.7.

• Remove the heat exchanger, refer to Section 18.14.

• Carefully bend back side insulation retaining tabs, pull out side
and front insulation panels from combustion chamber.

• Tilt rear insulation panel forwards slide up and out.

• Fit replacement insulation.

18.16 Printed circuit board (PCB), refer to
diagram 18.10.

Before starting refer to the front of Section 18 Important
information.

• Remove the front panel, refer to Section 15.3.

• Lower the control panel, refer to Section 15.4.

• Gain access to rear of control panel.

• Undo and remove the two cover retaining screws. This will
disconnect the metal plate heat reflector.

• Hinge up the control panel cover and ease forwards from the
rear retaining lugs to gain access to PCB. Do not strain the
cables attached to the PCB. Note the routing of the cables.

• Carefully pull off electrical connections to PCB.

• Unclip and lift out PCB.

• Fit replacement PCB in reverse order to removal. Be careful
not to trap any of the cables.

Make sure that PCB connections are fully pushed onto
replacement PCB.

ELECTRICAL
LEAD

CENTRAL
HEATING
THERMISTOR

ELECTRICAL
LEADS

9994

➜

➜

HEAT EXCHANGER

RIGHT HAND
INSULATION

RETAINING TABS
LEFT HAND SHOWN

REAR INSULATION

9988

OVERHEAT
THERMOSTAT

9995

➜

➜

Diagram 18.8

FRONT INSULATION

9997

LEFT HAND
INSULATION

9999

10031

37

Diagram 18.9

2000225000B

18 Replacement of Parts

PCB (CONTROL BOARD)

➜

CONTROL
BOARD
COVER

➜

10000

9762

➜

230V CONTROLS
INTERFACE
BOARD

➜

➜

➜

Diagram 18.10

10001

10019

CONTROL PANEL

18.17 User interface board, refer to diagram

18.11.

Before starting refer to the front of Section 18 Important
information.

• Remove the front panel, refer to Section 15.3.

• Lower the control panel, refer to Section 15.4.

• Unclip control panel user interface and hinge forward . Do not
strain the cables.

• Disconnect the electrical connections from the user inter face
board.

• Remove the two user inter face board retaining screws.

• Remove the user inter face board.

18.18 Mains switch, see diagram 18.11.

Before starting refer to the front of Section 18 Important
information.

• Remove the front panel, refer to Section 15.3.

• Lower the control panel, refer to Section 15.4.

➜

USER INTERFACE BOARD

• Unclip control panel user interface and hinge forward . Do not
strain the cables.

• Disconnect the electrical connections from the mains switch.

• Remove and replace the mains switch.

18.19 230V Controls board, refer to diagram

18.11.

Before starting refer to the front of Section 18 Important
information.

• Unclip control panel user interface and hinge forward . Do not
strain the cables.

• Disconnect the electrical connection from the 230V controls
board and the electrical connection from printed circuit board
(PCB).

• Remove the 230V controls board retaining screw.

• Remove the 230V controls board.

MAINS
SWITCH

Diagram 18.11

382000225000B

18 Replacement of Parts

18.20 Central heating pump head, refer to
diagram 18.12.

Before starting refer to the front of Section 18 Important
information.

• Remove the front panel, refer to Section 15.3.

• Lower the control panel, refer to Section 15.4.

• Drain down central heating water circuit of the boiler only, refer
to relevant part of diagram 18.1.

Note: it is not necessary to drain down the entire heating system
to carry out this work.

• For ease of access if required remove the right hand side
panel, refer to Section 15.6.

• Undo four fixing screws and remove pump head.

• Gain access to the pump electrical connection box and remove
cover.

• Disconnect pump cable from pump (avoid straining cables).

• Connect electrical connection to replacement pump head.

• Fit replacement pump head in reverse order to removal.

• Check for leaks.

18.21 Filling system tap, refer to diagram

18.13.

Before starting refer to the front of Section 18 Important
information.

• Remove the front panel, refer to Section 15.3.

• Lower the control panel, refer to Section 15.4.

• Drain down the boiler only, refer to relevant part of diagram

18.1.

• Pull out slotted metal clip securing tap into housing, remove
tap.

• Pull out slotted metal clip and remove pipe from tap.

PUMP
ELECTRICAL
CONNECTION
BOX

PUMP HEAD

HEX HEAD
SCREW
(4 OFF)

Diagram 18.12

REDUCED PRESSURE ZONE VALVE (RPZ)

➜

➜

10005

➜

➜

18.22 Reduced pressure zone valve (RPZ),
refer to diagram 18.13.

Before starting refer to the front of Section 18 Important
information.

• Remove the front panel, refer to Section 15.3.

• Lower the control panel, refer to Section 15.4.

• Drain down the boiler only, refer to relevant part of diagram

18.1.

• Pull out slotted metal clip securing pipe to RPZ.

• Pull out slotted metal clip securing RPZ into housing, remove
RPZ.

18.23 Boiler drain point, refer to diagram

18.14.

Before starting refer to the front of Section 18 Important
information.

• Remove the front panel, refer to Section 15.3.

• Lower the control panel, refer to Section 15.4.

• Drain down the boiler only, refer to relevant part of diagram

18.1.

Pull out slotted metal clip securing boiler drain valve into
housing, remove boiler drain valve.

10010

10007

FILLING TAP

Diagram 18.13

BOILER
DRAIN
VALVE

➜

Diagram 18.14

39

2000225000B

18 Replacement of Parts

18.24 Water flow sensor, refer to diagram

18.15.

Before starting refer to the front of Section 18 Important
information.

• Remove the front panel, refer to Section 15.3.

• Lower the control panel, refer to Section 15.4.

Drain down the boiler, refer to relevant part of Section 18.1.

• Undo the union on the cold water inlet isolating tap.

• Pull out slotted metal clip securing filling system tap into
housing, swing the tap forwards.

• Pull out the two slotted metal clips retaining the domestic water
inlet filter housing.

• Remove domestic water inlet filter housing.

• Remove electrical connections from water flow sensor.

• Pull off slotted metal clip and remove water flow sensor.

18.25 System water pressure sensor, refer to
diagram 18.16.

Before starting refer to the front of Section 18 Important
information.

• Remove the front panel, refer to Section 15.3.

• Lower the control panel, refer to Section 15.4.

Drain down the boiler, refer to relevant part of Section 18.1.

• Remove electrical connections from water pressure sensor.

• Pull off slotted metal clip and remove water pressure sensor.

10008

WATER
FLOW
SENSOR

9847

➜

➜

➜

➜

➜

Diagram 18.15

10006

18.26 Bypass valve, refer to diagram 18.17.

Before starting refer to the front of Section 18 Important
information.

• Remove the front panel, refer to Section 15.3.

• Lower the control panel, refer to Section 15.4.

Drain down the boiler, refer to relevant part of Section 18.1.

Pull out slotted metal clip and remove bypass valve.

SYSTEM
WATER
PRESSURE
SENSOR

BYPASS
VALVE

➜

➜

Diagram 18.16

9975

➜

10009

402000225000B

Diagram 18.17

18 Replacement of Parts

18.27 Automatic air vent, refer to diagram

18.18.

Before starting refer to the front of Section 18 Important
information.

• Remove the front panel, refer to Section 15.3.

• Lower the control panel, refer to Section 15.4.

• Drain down the boiler only, refer to relevant part of diagram

18.1.

• Unscrew to remove automatic air vent.

• After fitting replacement automatic air vent ensure the cap is
open.

AUTOMATIC
AIR VENT

9973

18.28 Gas Control valve, refer to diagram

18.19.

Before starting refer to the front of Section 18 Important
information.

• Remove the front panel, refer to Section 15.3.

• Lower the control panel, refer to Section 15.4.

• Disconnect gas supply pipe union nuts at the gas control valve.

• Disconnect injector supply pipe union nut at the gas control
valve. Slacken the union nut at the burner injector bar.

• Remove gas control valve retaining clip from the underside of
gas control valve.

• Ease gas control valve forwards and disconnect electrical
connections to gas control valve.

Note: The washers must be kept for use on reassembly.

• Withdraw gas control valve assembly.

• After fitting replacement gas control valve test for gas
soundness.

18.29 Gas control valve stepper motor

Before starting refer to the front of Section 18 Important
information.

• Remove the front panel, refer to Section 15.3.

• Lower the control panel, refer to Section 15.4.

• Disconnect the electrical connection from stepper motor, see
diagram 18.19.

• Remove the two screws securing stepper motor to the gas
control valve, see diagram 18.20.

• Fit replacement gas control valve stepper motor.

• Note: Take care not to damage the 'O' ring.

18.30 Discharge safety valve, refer to diagram

18.21.

Before starting refer to the front of Section 18 Important
information.

• Remove the front panel, refer to Section 15.3.

• Lower the control panel, refer to Section 15.4.

• Undo discharge pipe union nut.

• Pull out slotted metal clip from valve body and remove valve.

➜

GAS
CONTROL
VALVE

➜

➜

➜

10010

Diagram 18.18

➜

STEPPER
MOTOR
ELECTRICAL
CONNECTION

10011

Diagram 18.19

STEPPER
MOTOR

GAS

➜

CONTROL
VALVE

9781

➜

10029

41

Diagram 18.20

2000225000B

18 Replacement of Parts

18.31 Igniter unit, refer to diagram 18.22.

Before starting refer to the front of Section 18 Important
information.

• Remove the front panel, refer to Section 15.3.

• Lower the control panel, refer to Section 15.4.

• For ease of access remove the left hand side panel, refer to

Section 15.6.

• Disconnect electrical connections.

• Remove ignition unit securing screw.

• Pull upwards to release and remove the ignition unit from the
retaining slot.

18.32 Expansion vessel, refer to diagram

18.23.

Before starting refer to the front of Section 18 Important
information.

• IMPORTANT: With regards to the manual handling operations,
1992 regulations, the following operation exceeds the
recommended weight for one man lift.

Renewal of the expansion vessel requires the boiler to be
removed from the wall. As an alternative, a separate expansion
vessel of the same specification may be connected as close as
possible to the boiler, leaving the original in position, refer to the
installation instructions.

• Remove the front panel, refer to Section 15.3.

• Lower the control panel, refer to Section 15.4.

• Disconnect the mains cable and any external controls cables.

• Drain down the boiler only, refer to relevant parts of diagram

18.1.

• For this operation the boiler must be removed from the wall.

• Disconnect the flue system.

• Disconnect the union connections at the fixing jig.

• Disconnect the pressure relief valve discharge pipe.

• Lift up to remove the boiler from the wall.

• From the rear of the boiler. Undo pipe coupling on expansion
vessel.

• Undo and remove expansion vessel retaining nut.

• Slide expansion vessel up to remove.

Note: Check that expansion vessel pressure is correct, see

‘Section 1 Technical Data’.

IGNITER
UNIT

➜

➜

10012

➜

➜

➜

➜

Diagram 18.22

10013

EXPANSION
VESSEL

➜

➜

9970

10014

DISCHARGE
SAFETY
VALVE
(3 bar)

Diagram 18.23

Diagram 18.21

422000225000B

19 Spare Parts

When ordering spare parts, quote the part number and description, stating the appliance model number and serial number from the
data badge.

Short parts list

No. Description Part No. G.C. No.

1 Central heating thermistor 801933
2 Fan 801926
3 Air pressure switch 801928
4 Domestic water flow sensor 801910
5 Printed circuit board - Main 801915
6 Pump head 801896
8 System water pressure sensor 801911
9 Gas control valve 801911
10 Discharge safety valve 801904
11 Overheat thermostat 801927
12 Ignition electrode 801888
13 Flame sense electrode 801887
14 230V controls board
15 User interface PCB 801914
16 Stepper motor 801892
17 Ignitor unit
18 Pressure releif valve 801094
19 Heat exchanger
20 Burner

43

2000225000B

Notes

Because of our constant endeavour for improvement details may vary slightly from those in the instructions.

442000225000B