Glow Worm 24ci / 18si INSTRUCTION FOR USE INSTALLATION AND SERVICING (4000123942-2 07/03)

4000123942-2 07/03

Instructions for Use

Installation and Servicing

T o be left with the user

24ci

G.C. No. 47-047-19

Fanned Flue

Combination Boiler

18si

G.C. No. 41-047-61

Fanned Flue

System Boiler

18si shown

Hepworth Heating Ltd., Nottingham Road, Belper, Derbyshire. DE56 1JT

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 installation 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, 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 by telephoning

Glow-worm Service on 00 44 (0)1773 828100.

RECORD YOUR GLOW-WORM APPLIANCE DIRECT BY CALLING

0208 247 9857

Customer Service:

Glow-worm GB Great Britain:

Tel. [phone]

Fax. [phone]

Hepworth Heating Ltd.,

Nottingham Road, Belper, Derbyshire. DE56 1JT

Glow-worm IE Ireland:

Tel. 00 353 (0)16305757

Fax. 00 353 (0)16305724

C & F

Quadrant Ltd.,

Quadrant House,

Chapelizod, Dublin 20

Technical Advice Line:

Tel. [phone]

4000123942-2

General and Sales enquiries :

Tel. [phone]

Fax. [phone]

(0)

2

Contents

CONTENTS DESCRIPTION SECTION PAGE No.

Important Information 4
Draining and Filling 5

INSTRUCTION

FOR USE

INSTALLATION

INSTRUCTIONS

Appliance Introduction 5
Appliance Safety Devices 6
Maintenance and Servicing 6
User Controls and Lighting 7
Analogue Programmer 24ci only 8
Digital Programmer Kit 24ci only 8

Technical Data 1 11
General Information 2 12
Heating System Design 3 13
Domestic Hot Water System Design 24ci only 415
Boiler Schematic 24ci 516
Boiler Schematic 18si 5a 16
Boiler Location, flue and ventilation 6 17
Fixing Jig 7 18
Piping System Installation 8 19
Boiler installation 9 20
Horizontal Telescopic Top Flue Installation 10 21
Horizontal Top Flue Installation 10a 23
Electrical Connection 11 25
Commissioning 12 27
Changing Gas Type 13 29
Bypass Settings 14 29

SERVICING

INSTRUCTIONS

Routine Cleaning and Inspection 15 30
Fault Finding 16 34
Wiring Diagram 24ci 17 40
Wiring Diagram 18si 17 41
Replacement of Parts 18 42
Spare Parts 19 52

3

4000123942-2

Important Information

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 regulations.

Gas leak or fault

WARNING: 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.

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, for Ireland, install in
accordance with I.S.813 "Domestic Gas Installation".
Manufacture's instructions supplied must not be taken as
overriding statutory requirements.

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 0049.

Product/production certified by: Notified body 0049.
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
designed for use within certain voltage limits.

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

Control of 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

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.

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.

External wiring must be correctly earthed, polarised and in
accordance with the relevant standards.

In GB this is BS 6891.
In IE this is the current edition of I.S.813 "Domestic gas

installation".
Connection of the boiler and system controls to the mains

supply must be through a common isolator and must be fused
at 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

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.

Heating System Controls

The heating system must be controlled as described in the
relevant part of the current issue of :

Building Regulations, approved document L1, and the references:

1) GIL 59, 2000: Central heating system specification (CheSS)
and

2) GPG 302, 2001: Controls for domestic central heating system
and hot water. BRECSU.

3) The domestic heating and hot water guide to the building
regulations 2001.

Thermostatic radiator valves may be installed, however they
must not be fitted in a room where the room thermostat is
located.

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.

Protection Against Freezing

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

This device operates the burner and system pump when the
temperature inside the boiler falls below 6

Any other exposed areas of the system should be protected by
a separate frost thermostat.

2

(24/0.20mm).

C insulated cable, not less

0

C.

4000123942-2

4

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.

If the mains electricity and gas are to be turned off for any long
periods during severe weather, it is recommended that the
whole system, including the boiler, refer to diagram 1, should
be drained to avoid the risk of freezing. Make sure that, if fitted,
the immersion heater in the cylinder is switched off.

If in doubt, consult your servicing company.

24ci Only

• If the boiler loses water: the pressure will be indicated, see
diagram 1 (a) and the boiler ON indicator (b) will flash red
indicating a fault. Fill the system by the filling device (c) at the
bottom of the boiler until the pressure gauge reads 1.0 bar.
A mains inlet pressure of 2.0 bar is required to reach a fill
pressure of 1.0 bar.

Reset boiler: refer to diagram 2, turn the On/Off switch to (0),
wait for five seconds. Turn the On/Off switch to ( I ) to reset the
appliance.

18si Only

• If the boiler loses water: the pressure will be indicated, see

diagram 1 (a) and the running lamp (b) will flash red indicating
a fault. Fill the system with the external filling device until the
pressure gauge reads 1.0 bar.

Reset boiler: refer to diagram 2, turn the On/Off switch to (0),
wait for five seconds. Turn the On/Off switch to ( I ) to reset the
appliance.

• Warning: Take care not to overfill the boiler. At a pressure of

2.5 bar or above indicating over pressure, the boiler ON
indicator (b) will flash red indicating a fault. The pressure must
be reduced to 1.0 bar by opening the drain valve, refer to
diagram 1. If the fault continues call the relevant Servicing
organisation or Glow-worm Service using the telephone number
on the inside front cover of this literature.

(a)

9744

BOILER DRAIN
VALVE

(b)

➜

(c)

Diagram 1

Appliance Introduction

The 24ci and 18si boilers are wall mounted modulating boilers
with electronic ignition providing central heating and hot water.

The boiler is of the II
Gas (G20) as distributed in the United Kingdom, but can be
converted to use Butane (G30), Propane (G31) with the

appropriate kit.
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.

This boiler is not suitable for outdoor installation.
This boiler may be installed in any room, although particular

attention is drawn to the installation of a boiler in a room
containing a bath or shower where reference must be made to
the relevant requirements.

Any electrical switch or boiler control utilising mains electricity
should be placed so that it cannot be touched by a person using
the bath or shower.

In GB this is the current I.E.E. WIRING REGULATIONS and
BUILDING REGULATIONS.

In IE reference should be made to the current edition of I.S.813
"Domestic Gas Installations" and the current ETCI rules.

category and is for use with Natural

2H3+

The central heating and domestic hot water (24ci only)
temperatures are user adjustable.

24 ci Only. Domestic hot water demand always has priority over
heating demand.

The boiler is designed for use as part of a sealed water central
heating system with fully pumped circulation. 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.

These instructions should be carefully followed for the safe and
economical use of your boiler. The 'User Controls and Lighting'
section describes how to safely use the boiler.

Note: The boiler serial number is marked on the data label
attached to the rear of the control box.

Accessories

A range of accessories are available.
For further information contact your supplier.

5

4000123942-2

Appliance Safety Devices

Air flow rate safety device

If the flue is obstructed, the built in safety system will turn the
boiler OFF, the fan will continue to run. The boiler will be ready
to operate when the fault has been cleared.

Overheating safety

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

Electrical supply failure

The boiler will not operate without an electrical supply. Normal
operation of the boiler should resume when the electrical
supply is restored.

Reset any central heating system controls, to resume normal
operation.

If the boiler does not resume normal operation turn the mains
reset switch off and on. If the boiler does not resume normal
operation it is advisable to consult your installation / servicing
company.

Frost protection

The appliance has a built in frost protection device that
protects the boiler from freezing. With the gas and electric
supplies ON and irrespective of any room thermostat setting,
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.

Any other exposed areas of the system should be protected by
a separate frost thermostat.

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 competant
person. If the valve discharges at any time, switch the boiler off
and isolate it from the electrical supply. Contact your installation/
service company.

Maintenance and Servicing

Cleaning

WARNING: This appliance contains metal parts (components)

and care should be taken when handling and cleaning with
particular regard to edges of sheet metal parts to avoid any
possibility of personal injury.

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

Do not use abrasive or solvent cleaners.

Maintenance and Servicing

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, but in general once a year should
be enough, refer to guarantee registration on the inside front
cover of this literature.

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 the relevant service organisation
or Glow-worm Service using the telephone number on the
inside front cover of this literature.

Please be advised that the ‘Benchmark’ logbook should be
completed by the 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
benchmark Logbook. You can check your installer is CORGI
registered by calling CORGI direct on: 00 44 (0) 1256 372300.

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.

If a part or advice is required contact the relevant service
organisation or Glow-worm Service using the telephone number
on the inside front cover of this booklet.

Please quote the name of the appliance, this infomation will be
on the name badge on the front of the appliance.

4000123942-2

6

User Controls and Lighting

Central heating temperature selector

minimum setting (approx. 38˚C) up to
maximum setting (approx. 87°C).
It is supplied factory set to 38°C to 73°C

2

4

Pressure gauge (bar)
and temperature
gauge (°C)

Domestic hot water temperature selector (24ci Only)

minimum setting approx. 38°C up to maximum setting 65°C.

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.

Boiler ON/RUNNING

5

(green) indicator
(fault indicated by
light flashing red)

3

On/Off switch

1

PROGRAMMER

6

24 ci Only

11887

1. Lighting the boiler :

Make sure that:

• The boiler is connected to the electrical supply.

• The gas service cock is open.

• The room thermostat is calling for heat.

• Turn the On/Off switch to ON ( I )

• The boiler ON indicator will illuminate green.

1

5

2. Stop the boiler :

• Turn the On/Off switch to OFF ( 0 ) the
electrical supply is OFF.

1

3. Domestic hot water adjustment

(24ci Only) :

Domestic hot water between
approx. 38°C and 50°C

3

ECO Maximum

recommended for
constant use

Occasional
use for water
above
approx. 50˚C

4. Heating temperature adjustment :

Winter: Set the

control knob
anywhere
between the 5

Summer: Set
the control
knob to
(24 ci only)

segments

2

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 relevant
service organisation or Glow-worm Service using the
telephone number on the inside front cover of this
literature.

6. Pressure gauge:

• The boiler pressure gauge will show a reading

between 1.0 and 1.5 bar.
Refer to Section Draining and Filling if required.

5

4

Domestic hot
water OFF

Diagram 2

7

4000123942-2

Programmer Instructions for Use

Analogue Programmer (24 ci only)

No. A20086. Fitted as standard.

Part

Setting the time, see diagram 3

• Rotate the dial clockwise, by hand, until the indicator arrow
is pointing to the current time.

Note: The time is set in 24 hour format.

Setting the programme “on and off” times, see diagram 3

• Select the on times by pushing the black tappets to the
outside.

• Select the off times by pushing the black tappets to the
inside.

To override or advance the programmer
The clock has a manual on/off switch which operates as

follows:
Upper position I : Heating on continuously

Middle position
Lower position 0 : Heating off

To override or advance the programmer

: Heating on timed

Digital Programmer Kit. 24ci Only
Part No. A20087. Not fitted as standard.

KEYPAD DESCRIPTION

See diagram 4 for position of keypads as described below,

Time/Automatic Run Mode selection

Prog. Programme selection
Res.* Reset clears all settings

ON/OFF selector in Prog. Mode, Manual Override selector
in Run Mode

±1h* Summer/Winter time setting

h Sets the Hour (12: - - AM)
m Sets the Minute (- -: 01 AM)
Day Sets Day(s) for time and programmes

*Recessed keys; use a pen point to press

11460

OFF
TIMES

ON TIMES

BLACK TAPPETS

INDICATOR
ARROW

Diagram 4

LCD Display

The LCD incorporates a number of different elements to
display various data and information.

Diagram 3

Programmes

The Digital Programmer will accept up to 20 events

Each event consists of:

1. An ON or OFF command

2. Time of day (Hour and Minute)

3. Single day or multiple days

An event is required for each ON and OFF.

4000123942-2

8

Programmer Instructions for Use

NOTE: MULTIPLE ON OR OFF EVENTS MAY BE
PROGRAMMED, SEE EXAMPLE.

BEFORE PROCEEDING WITH SETTING THE TIME AND
PROGRAMMING THE UNIT, PRESS THE RESET KEY TO
CLEAR ALL DATA FROM THE MEMORY.

Selecting AM/PM or 24 Hour Time

After pressing reset, the display may show AM (below). The
numbered day symbols will be flashing on and off.

If the display does not show AM, it is in 24 hour time. To change
to AM/PM mode, press and hold the h key and press the
key once. AM will appear in display.

If display is in AM/PM mode and 24 hour time mode is desired,
press and hold the h key, press the

±1h key once.

±1h

Setting the Time

IF THE h AND m KEYS ARE HELD DOWN LONGER THAN 2
SECONDS, THE NUMBERS WILL ADVANCE RAPIDLY.

Press and hold the
(If British Summer Time is in effect, press ±1h first)

1. Press h to advance to the current hour
(while holding down the

2. Press m to advance to the current minute
(while holding down the

3. Press Day repeatedly to advance to current day
(while holding down the

key during the following:

key)

key)

key)

Day Key Selections

Press Day Key Display Shows Days
0 times 1 2 3 4 5 6 7 Every Day
1 time 1 2 3 4 5 6 Mon.–Sat.
2 times 1 2 3 4 5 Mon.–Fri.
3 times 6 7 Sat. & Sun.
4 times 1 Monday
5 times 2 Tuesday
6 times 3 Wed.
7 times 4 Thursday
8 times 5 Friday
9 times 6 Saturday
10 times 7 Sunday
NOTE: If the days are flashing, it indicates the day of the week

was not set when setting the time. The timer cannot be
programmed unless the day of the week is entered.

Manual GMT/BST Time Changeover

Each year, in the Spring, press ±1h to advance the time an
hour. In the Autumn, press ±1h to set back an hour.

Programming 24 Hour or 7 Day Schedules

It may be helpful to write out the programme schedules before
beginning.

THE CURRENT TIME OF DAY AND DAY OF WEEK MUST BE
SET PRIOR TO PROGRAMMING. SEE "SETTING THE TIME"

Example

Event 1: ON at 7:00AM Monday through Saturday
Event 2: OFF at 5:00PM Monday through Friday
Event 3: OFF at 7:00PM Saturday

Three events need to be entered.
Press Prog. key only once. Display shows:

Event 1 (ON at 7:00AM Monday through Saturday)
Press key once. ON symbol appears
Press h key to 07AM
Press m key once to 00
Press Day key once 1 2 3 4 5 6 is displayed
Press Prog. key to enter

Event 2 (OFF at 5:00PM Monday through Friday)
Press
Press h key to 05PM
Press m key once to 00
Press Day key two times 1 2 3 4 5 is displayed
Press Prog. key to enter

Event 3 (OFF at 7:00PM Saturday)
Press
Press h key to 07PM
Press m key once to 00
Press Day key 9 times until only 6 is displayed
Press Prog. key to enter
Press
IF AN "ON" TIME WAS PROGRAMMED THAT IS EARLIER IN

THE DAY THAN THE CURRENT TIME, PRESS ONCE TO
TURN THE TIMER "ON". (IT DOES NOT "LOOK BACK" TO
DETERMINE IF IT SHOULD BE ON OR OFF AFTER
PROGRAMMING).

IF 24 HOUR TIME CONTROL (SAME SCHEDULE EVERY DAY
OF THE WEEK) IS DESIRED, IGNORE Day KEY.

If an ON or OFF symbol is not entered, the ON symbol will flash,
and programme will not be accepted.

key twice. OFF symbol appears

key twice. OFF symbol appears

key to enter Run Mode

9

4000123942-2

Programmer Instructions for Use

Event Review

To review the programs at any time, press Prog. key. Events
will appear in the order they were entered with repeated
presses of the Prog. key. After all events have been reviewed,
the blank display will appear to allow entering another event.
Another press of the Prog. key will display the number of free
events available, such as Fr 16 if 4 events have been entered.

Manual Override

While in the Run Mode, pressing the key once will reverse
the current mode; ON to OFF or OFF to ON. The symbol
appears in the display to indicate a temporary override.
At the next scheduled switching time, automatic control
resumes, eliminating the override.

CONTINUOUS OPERATION: While in the Run Mode, press
the

Pressing the
permanently. symbol appears in display.

To terminate a continuous override, press the
appears in the display.

key twice to turn the output to permanently ON.

symbol appears in display.

key three times will turn the output OFF

key until

Changing an Event

Select the event to be changed with the Prog. key. A new set
of days may be selected with the Day key just as in initial
programming.

Hours and minutes can be changed with the h and m keys.
Press Prog. or

key to store the new programme.

Deleting an Event

To delete only one or a few events: Press Prog. key until the

desired program is displayed.
Press m key to :59 and press once more to blank out.
Press h key to 11PM and press once more to blank out.
Press

enter the Run Mode. Using the reset key will delete ALL events,
the time of day, and day of the week.

key, display will flash for several seconds and then

Troubleshooting

PROBLEM: Days are flashing, pressing any key does nothing
except key turns output ON and OFF.
SOLUTION: Time of Day and Day of Week have not been set.

See "SETTING THE TIME"
This is the condition after a reset. If the timer is found in this

condition after it has been installed, programmed and operating
for a while, it may indicate that interference has disrupted the
microprocessor causing a loss of programme information.

A second, but very unlikely cause of loss of programme is a
power failure with the backup capacitor low or dead. Check by
disconnecting power and monitoring how long the capacitor
keeps the time of day in the display. Typically, the capacitor will
maintain the time and programmes for 4 days, but not more
than 5 days.

PROBLEM: Time of day was set while holding the
down, but days are still flashing.

SOLUTION: Current day of week was not set while holding

down

PROBLEM: It is 10AM and an ON event for 8AM was entered,
but the output is not ON. Display shows the

SOLUTION: After programming, the timer does not "look back"
to determine if it should be ON. Press the

override) to turn the output ON; appears in display.
The timer will assume automatic operation at the next
programmed event.

PROBLEM: An event for 8AM Monday through Friday was
entered,

but it will not accept it and
SOLUTION: The ON

of the program. ON or OFF must be selected.

the key. See "SETTING THE TIME"

symbols.

key (temporary

is flashing.

or OFF was not entered as part

key

and

4000123942-2

10

1 Technical Data

24ci

Heating

Heat input (max) NET Q 26,94 kW

91,200 BTU/H

Heat input (min) NET Q 9,91 kW

33,820 BTU/H

Heat output (max) NET P 23,6 kW

81,550 BTU/H

Heat output (min) NET P 8,9 kW

30,370 BTU/H
Efficiency - Sedbuk D 78,3%
Maximum heating temperature 87° C
Expansion vessel effective capacity 5 litres
Expansion vessel charge pressure 0,5 bar
Maximum system capacity at 75°C 110 litres
Safety valve, maximum service pressure 3 bar

Hot water

Heat input (max) NET Q 26,94 kW

91,200 BTU/H
Heat input (min) NET Q 9,91 kW

33,820 BTU/H
Heat output (max) NET P 23,6 kW

81,550 BTU/H
Heat output (min) NET P 8,9 kW

30,370 BTU/H
Maximum hot water temperature 60 °C
Minimum hot water temperature 38 °C
Specific flow rate (for 35°C temp rise) 9,8 litres/min.
Threshold flow rate 1,7 litres/min.
Maximum supply pressure 10 bar
Minimum supply pressure 0,5 bar

Combustion

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

CO2 (6,7%)

NOx (48ppm)

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 12,2 mbar
Mini. Burner pressure 2,25 mbar
Gas rate maximum 2,74 m3/h
Gas rate minimum 1,16 m3/h

Butane Gas (G30)

Ø Burner injector 0,73 mm
Inlet pressure 29 mbar
Maxi. Burner pressure 23,2 mbar
Mini. Burner pressure 4,41 mbar
Gas rate maximum 2,01 kg/h
Gas rate minimum 0,87 kg/h

18si

Heating

Heat input (max) NET Q 20,7 kW

70,628 BTU/H

Heat input (min) NET Q 11 kW

37,532 BTU/H

Heat output (max) GROSS P 18,4 kW

62,780 BTU/H

Heat output (min) GROSS P 8,9 kW

30,366 BTU/H
Efficiency - Sedbuk D 78,3%
Maximum heating temperature 87° C
Expansion vessel effective capacity 5 litres
Expansion vessel charge pressure 0,5 bar
Maximum system capacity at 75°C 110 litres
Safety valve, maximum service pressure 3 bar

Combustion

Products outlet diameter 60 mm
Fresh air inlet diameter 100 mm
Combustion products values CO (25 ppm)

CO2 (5,5%)

NOx (48ppm)

Electrical

Electrical supply 230 V ~ 50Hz
Electrical rating 122 W fused at 3A
Level of protection IPX4D
Fuse rating 1,25mA

Natural Gas (G20)

Ø Burner injector 1,2 mm
Inlet pressure 20 mbar
Maxi. Burner pressure 8 mbar
Mini. Burner pressure 2,25 mbar
Gas rate maximum 2,2 m3/h

Butane Gas (G30)

Ø Burner injector 0,73 mm
Inlet pressure 29 mbar
Maxi. Burner pressure 14,8 mbar
Mini. Burner pressure 4,41 mbar
Gas rate maximum 1,63 kg/h
Gas rate minimum 0,87 kg/h

Propane Gas (G31)

Ø Burner injector 0,73 mm
Inlet pressure 37 mbar
Maxi. Burner pressure 19,2 mbar
Mini. Burner pressure 5,4 mbar
Gas rate maximum 1,61 kg/h
Gas rate minimum 0,83 kg/h

Propane Gas (G31)

Ø Burner injector 0,73 mm
Inlet pressure 37 mbar
Maxi. Burner pressure 29,8 mbar
Mini. Burner pressure 5,4 mbar
Gas rate maximum 2,01 kg/h
Gas rate minimum 0,83 kg/h

11

4000123942-2

The 24ci and 18si are delivered in two
separate packages:

• The boiler including fixing jig complete
with isolating valves and fittings.

• The flue system.

Net lift weight (boiler only)
24ci 34 kg
18si 32 kg

Gross lift weight
(boiler, fixing jig and packaging)
24ci 39 kg
18si 36 kg

1 T echnical Data

11658

184

740

310

2 General Information

IMPORTANT NOTICE.

Where no British Standards exists, materials and equipment
should be fit for their purpose and of suitable quality and
workmanship.

Refer to Manual Handling Operations, 1992 regulations.
The installation of this boiler must be carried out by a competent

person in accordance with the rules in force in the countries of
destination.

Manufacturer’s instructions must not be taken as overriding
statutory requirements.

2.1 Sheet Metal Parts

WARNING: When installing the appliance, care should be taken
to avoid any possibility of personal injury when handling sheet
metal parts.

2.2 Statutory Requirements

The appliance is suitable only for installation in GB and IE and
should be installed in accordance with the rules in force.

In GB the installation of the boiler MUST be carried out by a
competent person as discribed in the following regulations:

Manufacturer’s instructions, supplied.
The Gas Safety (Installation and Use) Regulations.
The appropriate Building Regulations, either The Building

Regulations, The Building Regulations (Scotland), The building
Regulations (Nothern Ireland).

410

Diagram 1.1

The Water Fittings Regulations or Water Bylaws in Scotland.
The Health and Safety at Work Act, Control of Substances
Hazardous to Health (COSHH).

The Current I.E.E. Wiring Regulations.
Where no specific instructions are given, reference should be

made to the relevant British Standard Code of Practice.
In I.E the installation must be carried out by a competent person

and installed in accordance with the current edition of I.S. 813
"Domestic Gas Installations", the current Building Regulations

and reference should be made to the current ETCI rules for
electrical installation.

In GB the following Codes of Practice apply:
BS4814, BS5440 Part 1 and 2, BS5449, BS5546 Part 1, BS6700,

BS6798, BS6891 and BS7074 Part 1 and 2, BS7478, BS7593,
BS7671.

In IE: I.S.813, BS5546, BS5449, BS7074, BS7593.
Manufacturer’s notes must not be taken as overriding statutory

requirements.

BSI Certification

This boiler certificated to the current issue of EN 483 for
performance and safety.

It is important that no alteration is made to the boiler, without
permission, in writing, from Hepworth Heating Ltd.

Any alteration that is not approved by Hepworth Heating Ltd.,
could invalidate the warranty and could also infringe the current
issue of the Statutory Requirements.

4000123942-2

12

2 General Information

2.3 Gas Supply

The gas installation must be in accordance with the relevant
standards.

In GB this is BS 6891.
In IE this is the current edition of I.S.813 "Domestic gas

installation".

The supply from the governed meter must be of adequate size
to provide a steady inlet working pressure of 20mbar (8in wg) at
the boiler.

3 Heating System Design

Bypass fully shut

1

Open 1/4 turn

2

Open 1/2 turn

3

Open 1 turn

4

50

40

30

20

Important Notice

If your boiler has been converted to use L.P.G. Propane the
following note applies:

Propane cylinders are under pressure and should never be
stored or used indoors residentially.

They should only be kept outside.
Under no circumstances should L.P.G. Propane cylinders be

fitted or stored in basement areas or boiler houses.
On completion, test the gas installation for soundness using the

pressure drop method and suitable leak detection fluid, purge in
accordance with the above standard.

9700

1

2

3

4

5

10

Open 2 turns

5

The installation of the boiler must comply with the requirements
of the current issue of BS6798, in Ireland, refer also to the
current edition of I.S.813"Domestic Gas Installations".

In GB it is necessary to comply with the Water Supply (Water
Fittings) Regulations 1999 (for Scotland, the Water Byelaws
2000, Scotland).

To comply with the Water Regulations your attention is drawn
to: The Water Regulations guide published by the Water
Regulation Advisory Service (WRAS) which gives full details of
the requirements.

In IE the requirements given in the current edition of I.S.813
"Domestic Gas Installations" and the current Building
Regulations must be followed.

• The 24ci and 18si are for use with sealed central heating
systems.

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

• The safety valve is an integral part of the boiler and it cannot
be adjusted.

• The circulation pump is integral with the boiler.

• Pipe sectional areas shall be determined in accordance with
normal practices, using the output/pressure curve
(diagram 3.1). 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 rate is shown in table 1.

Available pressure (kPa)

0 500 1000

(10 kPa = 1 m WG)

Flow rate through heating system (I/h)

Diagram 3.1

• The system can be fitted with a lockable control valve if
necessary in the main flow or return pipes shown as valve 'A'

in diagram 3.2.

• 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
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 3.2.

Guidance on vessel sizing is also given in a current issue of a
BS5449 and BS7074 Part 1, for IE refer to the current edition
of I.S.813 "Domestic Gas Installations".

• 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
a 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 from Fernox or Sentinel.

13

4000123942-2

3 Heating System Design

3.1 Bypass

• The boiler is fitted with an adjustable automatic bypass.
Ensure that under no circumstances does the flow rate drop
below the figure specified, see table 1.

• A system bypass is not required on the central heating circuit
unless the system controls will not ensure a minimum water
flow rate.

• Where a bypass has to be fitted, the bypass must be placed
at least 1.5 metres away from the appliance, see diagram 3.2.

3.2 Filling the system 24ci.

• An integral 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 1.

Additional
expansion
vessel

(if required)

Domestic

water

Boiler

Filling device

3.3 Filling the system 18si.

• Provision for filling the system must be made. The methods
are shown in diagram 3.3. There must be no permanent
connection to the mains water supply, even through a non­return valve.

NOTE: It is important that fittings used for connection to
potable water comply with the water undertakings requirements.

TABLE 1. FLOW RATE

Model Minimum flow rate

24ci 16.94 litres per minute

18si 13.21 litres per minute

This is equal to 20°C differential at maximum
heat input.

SUPPLY

PIPE

9898

BOILER

CONTROL

VALVE

11593

24ci

Hot water out

Cold supply in

Drain
point

Control

Drain
point

valve

Bypass

valve

*

'A'

Flow

Heating

circuit

Boiler

Additional
Bypass valve

*

(if required)

Return

Additional
expansion
vessel
(if required)

10157

HEATING
CIRCUIT

Method 1

BOILER

RETURNFLOW

CONTROL

VALVE

DRAIN
POINT

PREVENTION DEVICE

RETURNFLOW

DOUBLE

CHECK

VALVE

HOSE

UNION

HOSE

UNION

TYPE CA BACKFLOW

TEMPORARY
CONNECTION

Control

Drain
point

18si

4000123942-2

valve

Bypass

valve

*

'A'

Flow

Heating

circuit

Additional
Bypass valve

*

(if required)

Return

Diagram 3.2

14

HEATING
CIRCUIT

Method 2

CONTROL

VALVE

DRAIN
POINT

CONTROL

VALVE

AIR GAP

TUNDISH

SUPPLY

PIPE

Diagram 3.3

4 Domestic Hot Water System Design. 24ci Only

General - All domestic hot water circuits, connections, fittings

must be in accordance with the relevant standards and water
supply regulations.

For GB: Guidance G17 to G24 and recommendation R17 to
R24 of the Water Regulation Guide.

For IE: The current edition of I.S.813 "Domestic Gas
Installations".

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

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

0 may be used for the domestic

2

• The flow restrictor, supplied in the document envelope, must
be fitted as diagram 7.1, limiting the flow through the boiler to
a maximum of 10 litres/min.

• The boiler will operate with a minimum supply pressure of 0.5
bar, at a reduced flow rate.

Best operating performance will be obtained from a supply
pressure of 1 bar or greater.

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.

15

4000123942-2

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 unit.
13 - By-pass.
14 - Gas control valve.
15 - Loss of water sensor.
16 - Domestic heat exchanger
17 - 3 way valve
18 - Domestic water flow sensor
19 - Filter cold water inlet
20 - Filling system
21 - Discharge safety valve (3bar)
22 - Drain valve
23 - Heating filter

5 Boiler Schematic 24ci

9899

FITTED TO
REAR OF
APPLIANCE

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

5a Boiler Schematic 18si

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 unit.
13 - By-pass.
14 - Gas control valve.
15 - Loss of water sensor.
16 - Heating filter.
17 - Discharge safety valve (3bar).
18 - Drain valve

Diagram 5.1

11450

FITTED TO
REAR OF
APPLIANCE

A - Heating flow.
B - Gas.
C - Heating return.

4000123942-2

Diagram 5a.1

16

6 Boiler Location, Flue and Ventilation

6.1 Boiler Location

The recommended clearances are shown in diagram 6.1.
Note: The boiler must be mounted on a flat wall which is

sufficiently robust to take its weight when full. If in doubt, expert
advice should be obtained.

The minimum acceptable spacings from the terminal to
obstructions, other terminals and ventilation openings are
shown in diagram 6.2. For Ireland the minimum distances for
the flue terminal positionning must be those detailed in I.S.813
"Domestic Gas Installations".

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

6.2 Terminal guard, see diagram 6.3.

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.

A suitable terminal guard type K3 can be 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:
Horizontal telescopic top flue pack.
Horizontal top flue pack.
Vertical flue pack.
Twin flue pack.
Extensions, 90° and 45° bends.
For detailed information refer to flue options guide. 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.

25mm

11652

20mm

5mm

*

above
elbow

11508

MINIMUM SITING DIMENSIONS FOR THE
POSITIONING OF FLUE TERMINALS MM

HORIZONTAL FLUES

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 200
E FROM VERTICAL DRAIN PIPES AND

SOIL PIPES 150
F FROM INTERNAL/EXTERNAL CORNERS

OR TO A BOUNDARY ALONGSIDE THE
TERMINAL 300

G ABOVE ADJACENT GROUND OR

BALCONY LEVEL 300
H FROM SURFACE OR A BOUNDARY

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 300

VERTICAL FLUES

M FROM ADJACENT WALL TO FLUE 300
N FROM ANOTHER TERMINAL 600
P FROM ADJACENT OPENING WINDOW 1000
Q ABOVE ROOF LEVEL 300

Diagram 6.2

*Note: It is permissible to

install the boiler with smaller
clearances than those quoted
PROVIDING that consideration
is given for Servicing/Repairs.

600mm

450mm

*

300mm

Diagram 6.1

20mm

5mm

*

17

Diagram 6.3

4000123942-2

7 Fixing Jig

22mm

22mm

15mm

15mm

22mm

V

W

W

W

W

Z

Z

Z

Z

X

X

X

Y

Y

Y

A

B

C

D

E

The fixing jig is supplied within the boiler pack and is made up as follows :
A - Heating flow isolating valve.
B - 24ci only Domestic hot water outlet.
C - Gas service cock.
D - 24ci only Cold water inlet isolating valve.
E - Heating return isolating valve.

Documentation Pack, inclusive

- Literature (not illustrated)

- Benchmark Book (not illustrated)

- Guarantee Registration form (not illustrated)

- Rewards Club leaflet (not Illustrated)

- Wiring Diagram (not illustrated)

- Flue restrictor (not illustrated)

Bag containing :

- 1 x 15mm green fibre washer (shown as "v" in diagram)

- Cold Water Inlet Restrictor

- 5 x 22mm fibre washers (shown as "w" in diagram)

Fittings Pack, inclusive

- Wall template

- Discharge Safety valve connection incl. Knurled nut and O ring seal
15mm compression fitting

- Discharge Safety Valve Instruction sheet

- 230V External connection instruction sheet

- Filling loop extension knob

- 230V External controls connection plug

Bag containing: (24ci only)

- 3 x 22mm Installation connection pipes

- 2 x 15mm Installation connection pipes

Bag containing: (24ci only)

- 4 x 22mm boiler connection pipes

- 1 x 15mm boiler connection pipe

Bag containing : (18si only)

- 3 x 22mm Installation connection pipes

Bag containing : (18si only)

- 2 x 22mm boiler connection pipes

- 1 x 15mm boiler connection pipe

Bag containing :

- 4 x 15mm fibre washers (shown as "x" in diagram)

- 4 x 22mm fibre washers - large bore (shown as "y" in diagram)

- 5 x 22mm fibre washers - small bore (shown as "z" in diagram)

11940a

Wall template

APPLIANCE
HANGING
BRACKET

FIXING JIG
Inclusive Isolating
Valves

Sealing Washers :

24ci 18si Description

V 1 (1) 1 (1) 15 mm Gas valve Connection only*
W 4 (5) 2 (5) 22 mm - smal bore
X 3 (4) 1 (4) 15 mm
Y 3 (4) 3 (4) 22 mm - large bore
Z 4 (5) 2 (5) 22 mm - smal bore

The quantity shown in bracket ( ) denotes the number supplied
* It is essential that this green sealing washer is only fitted to the gas valve connection in the position shown in the Fixing Jig diagram

4000123942-2

18

Cold water
inlet restrictor

24ci shown

Diagram 7.1

8 Piping System Installation

20mm

MIN.

C.H. flow

Gas supply

Cold water in

C.H. return

22mm.
CENTRAL HEATING
15mm.
DOMESTIC WATER
22mm.
GAS SUPPLY

KEY

8.1 Cutting the flue hole

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

• Position the wall template, taking due regard of the minimum
clearances for the selected flue application, see diagram 8.1.

• Rear hole cutting

• Mark correct position of Top Rear flue outlet hole from
template, then remove template, before cutting, for use, later.

• Side hole cutting

• 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.

IMPORTANT NOTE: 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 35mm per metre of flue
downward towards the terminal. There MUST never be a
downward incline towards the boiler.

• 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 105mm diameter core drill.

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

80 min.

184

MINIMUM
SIDE
CLEARANCE
refer diagram

6.1

11943

8.2 Fixing jig, refer to diagram 7.1

• IMPORTANT NOTE: Ensure that the fixing jig is 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 fixing jig to
obtain the correct alignment.

Side Flue - Check the horizontal centre line and reposition the
template if necessary.

Rear Flue - Reposition the wall template over the hole in wall.

• Mark the securing position holes.

• Check that the fixing jig is level.

• Drill, plug and secure the jig to the wall, using suitable screws
(not supplied) for the wall type and capable of supporting
the total weight of the appliance.

8.3 Water connection

IMPORTANT NOTE: Do not subject the isolating valves to heat

from blowlamp, when making connection.
Connect the system pipework to the fixing jig connection pipes

and the fixing jig isolating valves, observing the correct flow
and return as shown in diagram 8.1.

8.4 Gas connection
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.

• The whole of the gas installation, including the meter, should
be inpected, tested for soundness and purged in accordance
with the current issue of BS6891 and in IE the current edition
of I.S.813 "Domestic Gas Installations".

24ci shown

Diagram 8.1

19

4000123942-2

9 Boiler Installation

9.1 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.

9.2 Installing the boiler

IMPORTANT NOTE: The system must be thoroughly flushed

using a propriety cleanser from Fernox or Sentinel to eliminate
any foreign matter and contamination e.g. metal filings, solder
particles, oil, grease etc.

Solvent products could cause damage to the system.

• 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.

• 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.

• (24ci Only) Fit the cold water inlet restrictor (supplied in the
document envelope) into cold water inlet isolating valve, see

diagram 7.1.
Important Note. With regards to the manual handling

operations, 1992 regulations, the following operation exceeds
the recommended weight for one man lift.

• Lift the boiler up and engage boiler onto the hanging bracket,
refer to diagram 7.1.

• Fit the boiler jig connection pipes and washers between the
boiler and isolating valves, see diagram 7.1.

9.3 Discharge safety valve (diagram 9.1)

The discharge safety valve pipe and sealing washer supplied
in the connections pack, when fitted to the safety valve, will
extend the valve below the boiler. The discharge pipe must be
extended using pipe not less than 15 mm o.d. to discharge in
a visible position outside the building, facing downward
preferably over a drain.

IMPORTANT NOTE: To facilitate servicing of the appliance,
the discharge pipe MUST ONLY be extended using a
compression fitting supplied.

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.

KNURLED
UNION NUT
finger tighten only

DISCHARGE
SAFETY VALVE
PIPE

9.4 Filling loop extension 24ci Only

The filling loop extension knob is supplied in the discharge

11581

safety valve pipe connection pack. Fit to the filling device on/
off knob, this is a push fit, see diagram 9.2.

9.5 Filling loop extension knob 18si

The filling loop extension is not required for this boiler, it can be
discarded.

FILLING DEVICE

10088

4000123942-2

Diagram 9.1

20

24ci Only

FILLING LOOP
EXTENSION

Diagram 9.2

10 Horizontal Telescopic Top Flue Installation

The Horizontal Telescopic Top Flue, Kit No.
A2004500

Suitable for installations that require a flue length "L" from 430
minimum to 660 maximum. If longer flueing is required extensions
and bends are available, see note below.

If the flue length, see diagram 10.2. is less than 430 'L' Do Not
cut this flue but use the horizontal top flue 86285H.

Note: Additional 1 metre extensions, 90° and 45° bends are
available. The maximum extended flue is 3.5m. The use of flue
bends requires the max extended flue lengths to be reduced by
1m. for 90° and 0.5m. for 45°.

10.1 Horizontal Telescopic Top Flue

Kit of parts, refer to diagram 10.1.

10.2 Horizontal telescopic flue system

Rear and side flue lengths and dimensions, see
diagram 10.2.

Max. Flue length 660mm

Min. Flue length 425mm

L

70mm

205mm

410 mm

11886

65mm

Note :
Top of boiler
casing not
front panel

Drill, Screw and
Tape (not supplied)

A

*

J

D

E

*

H

C

B

The flue kit A2004500 is 660 mm long and comprises:

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

- Fixing collar seal .....................................................B

- Fixing collar.............................................................C

- Elbow....................................................................... D

- External rubber sealing collar ...............................E

- *Gasket .................................................................... F

- *Screws 6 off...........................................................G

- *'O' rings .................................................................. H

- *Screws 4 off............................................................ J

* supplied in plastic bag

Diagram 10.1Telescopic Top flue kit

H

20mm
Min. Clearance

75mm

* refer to diagram 6.1

Min. Wall Thickness

SIDE FLUE

10322

*

G

*

F

*

Max. Flue length 660mm

Min. Flue length 425mm

L

70mm

184mm

65mm

Note :
Top of boiler
casing not
front panel

75mm
Min. Wall Thickness

REAR FLUE

Diagram 10.2

21

4000123942-2

10 Horizontal Telescopic Top Flue Installation

10.3 Installation of telescopic flue assembly

• For flue lengths up to 0.5m fit the restrictor (supplied in the
document envelope) inside the fan outlet, see diagram 10.3.

• Remove the elbow (D) and the telescopic flue assembly (A)
from the flue kit.

• Refer to Step 1. diagram 10.4. Fit the telescopic flue
assembly (A) into the prepared hole in the wall. Position the
elbow (D) on the boiler, do not secure. Position the telescopic
flue assembly (A) as it would be fitted.

• Refer to Step 2. diagram 10.4. Remove the telescopic flue
assembly (A) from the prepared hole in the wall, make sure the
air duct is extended to its required length. The flue duct at the
elbow end must protrude 25mm. Drill ,secure with two screws
and tape to secure the air duct, take care not to drill the inner
flue pipe. Fit the fixing collar seal (B) to the telescopic flue
assembly (A).

• Refer to Step 3. diagram 10.4. Fit the telescopic flue
assembly (A) with the fitted fixing collar seal into the prepared
hole in the wall. Remove the backing from the self adhesive
gasket (F) and carefully fit gasket to base of flue elbow. Fit the
‘O’ rings (H) into the grooves in the flue ducts within the elbow
(D). Lubricate the ‘O’ rings with silicone. Fit flue elbow (D) onto
boiler and secure with the four screws (G).

• Refer to Step 4. diagram 10.4. Fit rubber sealing collar (E),
into groove at the outer end of the air duct pipe (A). Carefully
pull flue duct pipe into the elbow (D). (If the telescopic flue has
been pulled apart care must be taken not to damage the ‘O’ ring
on the flue duct when re-assembling). Secure with two screws
(G). Pull telescopic flue assembly (A) inwards to bring rubber
sealing collar hard up against external wall.

• Refer to Step 5. diagram 10.4. Fit the fixing collar (C) using
the two screws (G).

STEP 1.

Outside

wall face

17mm

FLUE LENGTH

IMPORTANT

"BUTT FIT"

STEP 2.

Drill, screw 2 off

and tape the Air Duct

2 off

(G)

STEP 3.

(A)

(A)

(D)

90mm

centre line

BOILER

(B)

25mm

ELBOW

C

L

Flue

FIXING

COLLAR

SEAL

4 off

11879

(D)

(G)

11874

The restrictor must be fitted
to the inside of the fan outlet.

RESTRICTOR
fitted for flue lengths
less than 0.5m

Diagram 10.3

(A)

(E)

EXTERNAL RUBBER

SEALING COLLAR

STEP 4.

(A)

(E)

STEP 5.

(E)

'O' RING

(G)

(A)

FIXING

COLLAR

(H)

BOILER

(D)

2 off

(G)

(C)

Diagram 10.4

Diagram 10.4

GASKET

(F)

2 off

(D)

4000123942-2

22

10a Horizontal Top Flue Installation

10a.1 The Horizontal Top flue - kit 86285H

Is suitable for installations that require a max. flue length "L" of
740mm.

If a shorter flue length is required, the flue can be cut to a min.
length"L" of 260mm rear or 300mm side. See diagram 10a.2 for
min. flue lengths.

Note: Additional 1 metre extensions, 90° and 45° bends are
available. The maximum extended flue is 3.5m. The use of flue
bends requires the maximum extended flue lengths to be
reduced by 1m. for 90° and 0.5m. for 45°.

Max. Flue length 660mm

Min. Flue length 425mm

L

70mm

11886

65mm

10a.2 Flue systems rear and side, refer to
diagram 10a.1.

10a.3 Flue cutting, refer to diagram 10a.2.

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

ends of the pipes.

G

F

B

E

D

A

C

J

H

I

11646

205mm

410 mm

20mm
Min. Clearance

75mm

* refer to diagram 6.1

Min. Wall Thickness

SIDE FLUE

Max. Flue length 660mm

Min. Flue length 425mm

L

70mm

Note :
Top of boiler
casing not
front panel

The flue kit 86285H comprises:

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

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

- Elbow....................................................................... C

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

- Fixing collar..............................................................E

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

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

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

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

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

Horizontal Top flue kit

Diagram 10a.1

184mm

65mm

Note :
Top of boiler
casing not
front panel

75mm
Min. Wall Thickness

REAR FLUE

Diagram 10a.2

23

4000123942-2

10a Horizontal Top Flue Installation

17mm

90mm

X

cutting length

C

Air duct cutting length

X minus 90mm

plus 17mm =

Air duct

cutting length

25mm

check

dimension

(cut end)

Flue duct cutting length =
air duct cutting length + 95mm

L

Air duct

Flue duct

Outside

wall face

Flue

centre line

10a.4 Installation of horizontal top flue
assembly

Important: If the flue has been cut, ensure that there are no

burrs that could damage the ‘O’ ring.

• For flue systems less than 0,5 m long, fit the flue restrictor (a)
into the fan outlet, see diagram 10a.4.

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

• 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 suitable lubricant to each ‘O’ ring when fitting.

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

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

• Insert flue duct pipe (B) into inner end of air duct pipe (A),
rotate flue duct pipe to locate into groove inside air duct pipe.

• Fit air/flue duct pipe assembly through the wall with rubber
sealing collar to the outside.

• Fit internal plastic flange (G) onto air duct pipe (A).

• Fit the fixing collar seal (D) onto the flue duct pipe (B) ensuring
it is the correct way round (the larger diameter onto the pipe).

• Pull air/flue duct pipe assembly inwards to bring rubber
sealing collar (F) hard up against external wall, while carefully
pushing the fixing collar seal onto the elbow ensuring that the
flue duct pipe locates into the flue elbow outlet while taking
care not to tear the ‘O’ ring.

• Fit the fixing collar (E) around the fixing collar seal (D) and
secure with 2 screws provided.

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

11643

Horizontal Top flue system

The maximum permissible length (L) is 3.5 m. For flue systems up to 0.5 m length, the flue restrictor must be fitted (a) inside
the fan outlet. For longer flue systems, the restrictor must not be fitted.

For each 90° flue elbow used, (or two 45° elbows) the maximum permissible length (L) must be reduced by 1 metre.

FLUE
RESTRICTOR

a

Gasket

L

184

65

Diagram 10a.3

10092

4000123942-2

Diagram 10a.4

24

11 Electrical Connection

WARNING: This appliance must be earthed. 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.

All system components must be of an approved type.
Electrical components have been tested to meet the equivalent

requirements of the BEAB.
Do not interrupt the mains supply with a time switch or

programmer.
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 3mm 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.

11.1 Mains Cable

Important: If a replacement supply cable is required it must be

purchased. Part No. S1008600.

11.2 Voltage Free External Controls

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

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

External heating controls e.g. Room thermostat, should be
fitted in accordance with the rules in force and as shown in the
example, diagram 11.2.

RETAINING SLOTS

VOLTAGE FREE
HEATING CONTROLS
CONNECTION
TERMINAL

CONTROLS PANEL REAR
COVER

SECURING SCREW (3)

WIRE LINK(E)

11911

11994

Diagram 11.1

25

Diagram 11.2

4000123942-2

11 Electrical Connection

11.3 Mains Voltage External Controls

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

When mains voltage external controls are used, remove the
MAINS VOLTAGE HEATING CONTROLS CONNECTION PLUG
from the fittings pack and install on the control interface PCB
as follows.

Gain access to the control interface by unclipping the fascia
panel and hinging forward, see diagram 11.3.

Route the external heating controls cable (not supplied) and
connect to the plug

Insert plug onto controls interface PCB, see diagram 11.3.
Close the fascia panel and remove the screws to open the rear

cover of control panel, see diagram 11.1.
Secure the external heating control cable in the strain relief, and

thread the cable through rear of the control panel and out of the
cables exit, see diagram 11.4.

Close and secure rear cover of control panel.
IMPORTANT: Remove the wire link from the voltage free

heating controls connector terminal, see diagram 11.1.
Connect external heating controls as diagram 11.5.
External controls should be fitted in accordance with the rules

in force.

11.4 Electrical Connections - Testing

Carry out preliminary electrical system checks as below:

1. Test insulation resistance to earth of mains cables.

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

3. Test the polarity of the mains.

CONTROL PANEL USER INTERFACE

, see diagram 11.3.

RETAINING LATCHES

➜

➜

11659

OILER

CONTROLS

INTERFACE PCB

3
2


EXTERNAL

FROST

THERMOSTAT

EXTERNAL

THERMOSTAT

INTERNAL PROGRAMMER

EXTERNAL 230V AC ROOM THERMOSTAT

EXTERNAL 230V AC FROST THERMOSTAT

DO NOT

CONNECT

MAINS VOL TAE

HEATIN CONTROLS

CONNECTION PLU

ROOM

X

PRORAMMER

TO MAIN PCB

CONNECTOR J5

HEATIN CONTROLS

REMOVE LIN

HEN EXTERNAL

CONTROLS ARE SE

EXTERNAL

JUNCTION BOX

3 AMP FUSE

DOUBLE POLE

ISOLATOR

STRAIN
RELIEF

MAINS
CABLE

EXTERNAL
CONTROLS
CABLE

Diagram 11.4

VOLTAE FREE

CONNECTION

ON CONTROLS

BOX COVER

ONOFF

SITCH

LNE

230V~ 50Hz

PERMANENT

MAINS

SUPPLY

11992

The type of plug and
orientation may be
different to that
illustrated but the
wiring should always
be as wiring diagrams

PLUG

4000123942-2

EXTERNAL
CONTROLS
CABLE(MAINS
VOLTAGE)

CONTROLS
INTERFACE PCB

Diagram 11.3

11974

26

OLER

INTERFACE PCB

EXTERNAL

FROST

THERMOSTAT

EXTERNAL

ROOM

THERMOSTAT

EXTERNAL

PRORAMMER

EXTERNAL PROGRAMMER/CLOCK

EXTERNAL 230V AC ROOM THERMOSTAT

EXTERNAL 230V AC FROST THERMOSTAT

X

DO NOT

CONNECT

MAINS VOL TAE
HEATIN CONTROLS
CONNECTION PLU

CONTROLS

3
2


TO MAIN PCB

CONNECTOR J5

HEATIN CONTROLS

REMOVE LNK

HEN EXTERNAL

CONTROLS ARE SE

EXTERNAL

JUNCTION BOX

DOUBLE POLE

ISOLATOR

VOLTAE FREE

CONNECTION

ON CONTROLS

BOX COVER

ONOFF

SITCH

3 AMP FUSE

LNE

230V~ 50Hz

PERMANENT

MAINS

SUPPLY

Diagram 11.5

11993

12 Commissioning

Important: The commissioning and first firing of the boiler
must only be done by a competant person.

Gas installation

If conversion from G20 to 30 or 31 is required, refer to section

13.
It is recommended that any air is purged from the supply at the

gas purge point on the gas valve, see diagram 12.1.

Filling the system

The following steps 1 - 8, show how to fill the system.

1.

Make sure that:

• The boiler is connected to the
electrical supply.

• The gas service cock is open.
Turn the switch OFF ( 0 )

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.

BURNER
PRESSURE
POINT

GAS
PURGE
POINT

11898

24ci shown

Diagram 12.1

9796

2.

• Open the three water isolating valves.

HEATING
FLOW

24ci shown

3.

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

DOMESTIC HOT
WATER OUT

(24ci Only)

Note: Isolating valves are shown in the: OFF position

COLD
GAS SERVICE
COCK

4.

• Turn the switch ON ( I )

• 24ci Only Open the tap on the filling device

• Fill the system until the pressure indicated on
the display is 1 bar. Close filling device.

9810

WATER IN

(24ci Only)

HEATING
RETURN

11933

9792

➜

NOTE: On initial fill there may be a small discharge
of water from the Reduced Pressure Zone valve

27

➜

4000123942-2

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.

• Ensure the display indicates a system pressure
of 1.0 bar adjust if necessary.

Adjusting the Central heating output.

The central heating output is factory preset to approx. 15kW.
If a different central heating output is required, proceed as

follows:
To gain access to potentiometer P3, unclip the control box,

see diagram 11.1.

Ins 061a

10217

• Leave cap open on automatic air vent.

6.

8.

• Open various hot water taps to bleed system

The potentiometer P3, is shown in diagram 12.2,to adjust to
the required heating output, insert a small flat edge screw
driver into the arrowed slot in potentiometer P3, turn clockwise
to adjust to the desired setting. Use a manometer to monitor
the burner pressure.

9810

Ins 062a

maxi

15 kW

P.

P3

max.

mini

P3

POTENTIOMETER P3

234
1

ON DIP

POTENTIOMETER P6

P6

P7

11890

USER
INTERFACE
BOARD

Diagram 12.2

MANOMETER

SW1
DIP
SWITCH

15 kW

P.
max.

mini

ON DIP

Factory set in
"OFF" position

234
1

maxi

0

P6

+

Dip Switches

The position of the SW1Dip Switch(s), see diagram 12.2, and
the table below can be used to change the operation of the

PUMP OPERATION DIP SWITCH 1 DIP SWITCH 2 HEATING TEMP DIP SWITCH 3 DIP SWITCH 4
CONTINUOUS ON ON 53OCON ON
WITH BURNER ON OFF 87OC ON* OFF*
CONTINUOUS OFF ON 53OC OFF ON
WITH HEATING OFF* OFF* 73
DEMAND

pump and maximum heating temperature of your boiler.

O

C OFF OFF

FACTORY SETTING * GB/IE PREFFERED SETTING

4000123942-2

28

12 Commissioning

When all adjustments are completed.

• 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 air contained in the water of the central heating system.

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

• The air trapped at the highest point of the system must be
released by bleeding the radiators. Check the burner gas rate
required, ten minutes after 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, refer to technical
data.

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. If necessary, refer to section 14 to adjust the bypass.
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.

24ci Only Flush the domestic hot water system by opening the
hot water taps for several minutes.

Completion

Adjust the boiler temperature control and any system controls
to their required settings.

For IE, it is necessary to complete a "Declaration of Conformity"
to indicate compliance to I.S.813. An example of this is given
in the current edition of I.S.813.

Please ensure the “Benchmark” logbook is completed and left
with the user and the magnetic lighting instruction label is
placed on the surface of the boiler casing.

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 in the UK.

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.

13 Changing Gas Type

Should it be necessary to change the gas type, a conversion kit
with instructions will be required.

This modification must only be carried out by a competent
person.

Conversion natural gas (G20) to G30/G31 Part No. A2011900.

Setting the step pressure.

Adjusting the step pressure may be a necessary operation after
gas conversion or after changing the gas control valve when a
new replacement part is required.

Proceed as follows:

• Gain access to the gas control valve, connect a pressure
gauge.

14 Bypass Setting

Bypass

The boiler has a built-in bypass, refer to diagram 14.1.
The boiler is supplied with the bypass open half a turn. It should

not be necessary to adjust the bypass, but if required ensure
that under no circumstances does the flow rate fall below the
figures specified, refer to table 1. in section 3 (turn clockwise
'A' to close the valve ).

• Unclip the control box, see diagram 11.1.

• Run the appliance in heating mode.

• Read the burner pressure setting in heating mode, before the
boiler modulates.

• Adjust the central heating output to the minimum setting by
adjusting potentiometer P3, refer to commissioning section.

• Adjust the potentiometer P6 burner pressure to the desired
value, by inserting a small flat edge screw driver into the
arrowed slot, turn to adjust to the desired setting, see diagram

12.2.

• Return the potentiometer P3 to its initial value.

A

24ci shown

9718

29

Diagram 14.1

4000123942-2

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 competant
person.

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.

9532

PRODUCTS
SAMPLING
POINT

Diagram 15.1

15.2 Service Check and Preparation.

• Isolate boiler from the gas and electrical supplies.

• (24ci Only) Drain the Domestic hot water circuit, refer to

diagram 15.2.

• Drain the boiler, refer to diagram 15.2.

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

To Drain the Domestic hot water circuit (24ci Only)

• Close boiler isolating valve (d).

• Turn on one or more hot water taps.

To Drain the boiler

• Close isolating valves (e) and (a).

• Open the boiler drain valve (f).

(b)

(a)

HEATING
FLOW

24ci shown

DOMESTIC HOT
WATER OUTLET

(24ci Only)

Note: Isolating cocks water and gas are shown in the: OFF position

GAS SERVICE
COCK

(c)

BOILER DRAIN VALVE

(d)

COLD WATER
INLET (24ci Only)

9839

(f)

11933

(e)

HEATING
RETURN

Diagram 15.2

4000123942-2

30

15 Routine Cleaning and Inspection

15.3 Front panel

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

• Remove front panel by lifting up and forward.

15.4 Control panel

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

15.5 Sealed chamber cover

• Unscrew and remove the two retaining screws from the
sealed chamber cover, see diagram. 15.3.

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

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

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

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

• Unhook each panel from the front retaining tabs.

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

9533

15.7 Combustion chamber cover

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

• Remove combustion chamber cover from boiler.

15.8 Ignition and Flame Sensing Gaps

• Check that the ignition and flame sensing gaps as shown in
diagram 15.6. Note: To gain access to ignition and sense
electrodes for removal, refer to Section, 18.11 and 18.12 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, taking care not to damage the insulation.

• 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.

15.10 Fan, refer to diagram 15.8

• Disconnect power supply leads and earth lead from fan.

• Unscrew and remove the two fan retaining bolts.

• Ease the fan down and forwards to remove.

Diagram 15.3

9797

97999800

31

24ci shown

Diagram 15.4

4000123942-2

15 Routine Cleaning and Inspection

15.11 Heat exchanger, refer to diagram 15.9

• Remove air pressure switch sensing tube from the side of

9811

the flue hood.

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

• Unhook each panel from the front retaining tabs and ease
outwards.

• Remove the flue hood. When refitting ensure the rear of the
flue hood locates in the tabs.

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

DO NOT USE ANY TOOL LIKELY TO DAMAGE PAINTED

Diagram 15.5

FINISH OF HEAT EXCHANGER.

3.5mm

IGNITION
GAP

3.5 mm

FLAME
SENSING GAP

9812

BURNER
RETAINING
SCREWS

BURNER
GUIDE

3.5mm

Diagram 15.6

9752

9816

9818

EARTH

9741

LEAD

FAN RETAINING
SCREWS

POWER
SUPPLY
LEADS

Diagram 15.8

9742

AIR PRESSURE
SWITCH
SENSING TUBE

4000123942-2

9818

Diagram 15.7

9817

32

HEAT EXCHANGER

FLUE HOOD

9825

Diagram 15.9

15 Routine Cleaning and Inspection

15.12 (24ci Only) 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.

Push the filter fully into its housing and replace the securing
clip.

• Open isolating valve, (d) diagram 15.2, on cold water inlet and
test the Domestic Hot Water circuit for soundness.

15.13 Central Heating Filter, refer to diagram

15.11

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

Push the filter fully into its housing, ensuring the correct
orientation. The flat and hole in the filter as shown. Secure with
retaining clip.

15.14 Sealed chamber cover seal check

• Check the condition of the seal, replace as required.

• To replace remove the old seal, thoroughly clean the casing
surfaces. Fit new seal, it is supplied to the correct length, see

diagram 18.25.

DOMESTIC WATER
INLET FILTER
HOUSING

24ci only

FILTER

CLIP

9822

Diagram 15.10

11934

15.15 Combustion chamber insulation

• Check the condition of the combustion chamber insulation.
If renewing, refer to Section 18.14.

15.16 Flue system

• Check externally to make sure that flue is not blocked

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

15.17 Reassembly of parts removed for
servicing

All parts are replaced in reverse order to removal.

RETAINING
CLIP

FILTER

FLAT

11935

33

Diagram 15.1124ci shown

4000123942-2

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 and that the
polarity is correct.

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.

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.

Overheat thermostat reset button

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

Depress the button to reset.

9826

OVERHEAT
THERMOSTAT

RESET
BUTTON

Diagram 16.1

DISPLAY FAULT

'01' and 'F' and 'flashing red LED' Ignition fault (lockout) caused by no gas, no detection
'02' and 'F' and 'flashing red led' Air fault, pressure switch, no power to fan

'05' and 'F' and 'flashing red LED' Overheat fault
'06' and 'F' and 'flashing red LED' Central heating flow NTC fault
'09' and 'F' and 'flashing red LED' Water pressure sensor fault
'11' and 'F' and 'flashing red LED' No reception by the main board (MMI Lead)
'12' and 'F' and 'flashing red LED' User interface or distant control panel fault
'13' and 'F' and 'flashing red LED' Main board fault
'14' and 'flashing red LED' Over temperature on primary water circuit

'15' and 'F' and 'flashing red LED' Stepper motor fault (gas valve)
'16' and 'F' and 'flashing red LED' Gas safety value failure
'17' and 'F' and 'flashing red LED' Power supply <170V
'18' and 'F' and 'flashing red LED' Local user interface fault

'19' and 'F' and 'flashing red LED' Central heating NTC not connected to pipe
'20' and 'F' and 'flashing red LED' User interface not compatible with boiler

'0.5bar' flashing and 'F' and 'flashing red LED' Lack of water fault (<0.5b)
'2.7bar' flashing and 'F' and 'flashing red LED' Upper water pressure (>2.7b)

4000123942-2

34

16 Fault Finding

TYPE OF FAULT CHECK

No display on control panel • 230V supply

• PCB fuse

• Connection between PCBs

No domestic hot water 24ci Only) • Loose connections on control board (PCB),
No central heating • Connections on air pressure switch (electrical or tubes)
(Red flashing warning light and flashing disconnected,
fault code in display) • Faulty control or interface board (PCB's),

• Water pressure, flashing pressure

• Shortage of air or gas,

• Faulty temperature sensor,

• Overheating,

COMPONENT TESTING DATA

COMPONENT NORMAL MEASURE CHECK

Gas control valve Under demand during ignition sparks: If 0 Volt: the gas control valve
Resistance of coil 116Ω 24V dc for 1 to 2 seconds, then is not faulty.

12Vdc (constant) at the gas control If 24 Volts and then 12 Volts
valve electrical connection. but no gas at the burner:

Check if the gas control valve is

stuck. If not, check the
adjustment valve.

Adjustment valve Close the gas inlet: If the valve does not move:
(step motor) Dismantle the step motor (screw not Check the connections at both

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).

(24ci Only)

Three way valve. When heating is on: If voltages are different:
Electrical supply to motor 230V ac between 1 and 2 of the motor. Connections.
0Ω between 1 and 3. About 25V ac to 35V ac between 2 and 3. Control board (PCB).

9.6kΩ between 1 and 2. When hot water is on: Three way valve lead.

9.6kΩ between 1 and 3. 230V ac between 2 and 3 of the motor. 3 2 1
(1, 2 and 3 marked on About 25V ac to 35V ac between 1 and 2.
the motor).

Thrust action of the motor. Unfasten the clip (YES, no risk of water If electrical supply is OK.
(remove gas control valve leak), pull out the motor and leave it but the motor axle does not move
before testing) plugged in. Replace the motor, or replace

When hot water is on: the spindle should the control board (PCB).
pull in. When heating is on : the spindle
should push out.

(24ci Only)

Domestic water flow To test: Use a new detector and

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

35

4000123942-2

16 Fault Finding

FAULT: NO HEATING

Are the external heating

controls calling for heat?

YES

Is the polarity correct?

YES

Connect 1 and 2 on J10,

does boiler fire in central heating?

YES

Faulty 230V controls board.

NO

NO

NO

Rectify fault on external controls.

Rectify, check the 230V

controls board.

Faulty main PCB.

24ci ONLY

FAULT: NO HOT WATER, BUT THE HEATING IS WORKING

Is the water flow rate greater

than 1.7l/min. (threshold figure).

YES

Is flow detector operating ?

YES

Check the connectors on the

flow sensor and the control board (PCB).

If the fault persists, fit a relplacement

control board (PCB).

NO

NO

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.

11800

4000123942-2

36

16 Fault Finding

F1 FAULT DISPLAYED

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

pressure correct?

YES

NO

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

Is the boiler actually designed for the
gas being used.

YES

Clean the gas filter.
Clean the burner.

F1 or F4 FAULT DISPLAYED

FAULT: THE BURNER LIGHTS, THEN GOES OUT.

The flame is spreading across the

whole burner, but not being detected.

CHECK
THE MAINS

FAULT NOT FOUND

NO

CHECK

THE

PROBE

Change the gas type for the boiler
(gas conversion kit).

With the power turned off, check the
continuity between the flame sense
electrode and terminal H2 . 4 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.

If the problem persists, change the

control board (PCB).
(flame detection module faulty).

37

11873

4000123942-2

16 Fault Finding

F1 FAULT DISPLAYED

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?
for testing see component testing data.

YES

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

NO

NO

Turn on the gas taps.

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

FAULT: THE ROOM TEMPERATURE IS INADEQUATE AND RADIATORS ARE LUKE-WARM.

Is the room thermostat and or radiator

set high enough and calling for duty?

NO

Turn up settings

Is the heating power adequate?

YES

Is the heating temperature on the boiler
set high enough?

YES

- Check set point P3. (Refer to Commissioning)

- Check the adjustment of the by-pass internal and

external (If fitted). - 24ci Only Check the 3-way valve
is not passing into the domestic hot water heat exchanger.

4000123942-2

38

16 Fault Finding

24ci ONLY

F AUL T : THE WA TER A T THE T APS IS LUKE-W ARM.

Is the temperature higher if you reduce

the flow through the taps?

YES

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

FAULT: THE FAN DOES NOT START.

Is there 230V ac

at fan during demand?

NO

NO

Check the 3-way valve is not passing
into the radiators. (The radiators should
stay cold in Summer setting)

11875

Check continuity of fan harness.

YES

Faulty fan, replace.

Faulty PCB, replace.

YES

FAULT: THE FAN RUNS BUT THERE ARE NO SPARKS.

• CHECK CONTIUITY OF SPARK (ELECTRODES AND LEADS)

• CHECK POWER SUPPLY FROM PCB TO IGNITION UNIT

CONNECTIONS TO THE AIR PRESSURE SWITCH

Pr

P2

P1

3

2 1

LH

11876

11877

Air flow switch take-off.

Electrical contacts.

39

4000123942-2

17 Wiring Diagram 24ci

10224

4000123942-2

40

17a Wiring Diagram 18si

10298

41

4000123942-2

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 (f).

To Drain the Domestic hot water circuit (24ci Only)

• Close boiler isolating valve (d).

• Turn on one or more hot water taps.

To Drain the boiler

• Close the isolating valves (a), (d) and (e) .

• Open the boiler drain valve (f).

BOILER DRAIN VALVE

9839

(f)

11933

(b)

(a)

HEATING
FLOW

24ci shown

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 of assembly to test
for gas soundness and purge in accordance with the current
issue of BS6891 or in IE, the current edition of I.S.813 "Domestic
Gas Installations".

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.

DOMESTIC HOT
WATER OUTLET

(24ci Only)

Note: Isolating cocks water and gas are shown in the: OFF position

GAS SERVICE
COCK

(c)

CENTRAL HEATING
THERMISTOR

• Locate central heating thermistor on heating flow pipe on
centre of boiler, see diagram 18.2.

• Unclip thermistor from pipe.

• Disconnect electrical connections from thermistor.

• Fit electrical connections to replacement thermistor and fit
thermistor to pipe. The polarity is not important.

(d)

COLD WATER
INLET (24ci Only)

(e)

HEATING
RETURN

Diagram 18.1

24ci shown

Diagram 18.2

9821

4000123942-2

42

18 Replacement of Parts

18.2 Fan.

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

• Remove the front panel, refer to Section 15.3.

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

• Remove the fan, refer to Section 15.10.

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.

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

• Locate air pressure switch situated at the top right hand side,
see diagram 18.3.

• Remove air pressure switch tube from sensing probe on flue
hood.

Note: Do not fit tube until the air pressure switch is in position.

• Disconnect air pressure switch electrical connections.

• Unclip to remove air pressure switch.

RETAINING
CLIPS

ELECTRICAL
CONNECTORS

SENSING
TUBE

UNION NUT

9646

AIR PRESSURE
SWITCH

Diagram 18.3

COLD WATER INLET
RESTRICTOR

18.4 (24ci Only) Domestic water inlet filter

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.

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.

• Clean or replace the water inlet filter, refer to Section 15.12.

18.5 Central Heating Filter

It may be necessary to clean or replace the central heating filter.
Before starting refer to the front of Section 18 Important

information.

• Clean or replace the central heating filter, refer to Section

15.13.

18.6 ( 24ci Only) 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.

• 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.

• 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.

11939

11932

COLD WATER IN
ISOLATING VALVE

24ci Only

• Remove the combustion chamber cover, refer to Section

15.7.

• Remove burner from boiler, refer to Section 15.9.

Diagram 18.4

18.8 Burner injectors, refer to diagram 18.5.

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 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 implement.
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.

43

4000123942-2

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 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 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.

Note: Take care not to damage the insulation.

• 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.

9819

9820

9814

BURNER INJECTOR
BAR

SENSE
ELECTRODE
ASSEMBLY

Diagram 18.5

GROMMET
GAS SUPPLY

PIPE

IGNITION
ELECTRODE
ASSEMBLY

9813

Diagram 18.6

18.10 Overheat thermostat

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

• Remove the front panel, refer to Section 15.3.

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

• Locate overheat thermostat on heating flow pipe on right hand
side of boiler, see part of diagram 18.7.

• Disconnect electrical connections from thermostat

• Remove the thermostat and bracket assembly from heating
flow pipe by unclipping at the side of the bracket. Remove the
thermostat, fit new thermostat and replace assembly.

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

18.11 Ignition electrode

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 burner from boiler, 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 ignition unit, see
diagram 18.22. Note the routing of the cables.

OVERHEAT
THERMOSTAT

9826

CLIP

ELECTRICAL
LEADS

PIPE SECURING
CLIP 2 OFF

9825

HEAT
EXCHANGER

Diagram 18.7

18.12 Flame sense electrode

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 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.

4000123942-2

44

18 Replacement of Parts

18.13 Heat exchanger, refer to diagram 18.7.

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

• Remove the front panel, refer to Section 15.3.

• 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 of the boiler only,

refer to relevant part of diagram 18.1.

• Remove the fan, refer to Section 15.10.

• Remove air pressure switch sensing tube from the side of the
flue hood, see diagram 15.9.

• Release both side panels, refer to section 15.6.

• Remove the flue hood, lift up and off. When refitting ensure
the rear of the flue hood locates in the tabs.

• Disconnect the electrical leads from the overheat thermostat.

• Remove the two pipe securing clips.

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

18.14 Combustion chamber insulation, 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.

• 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 18.13.

• Pull out side insulation panels from combustion chamber.

• Tilt rear insulation panel forwards and out.

• Fit replacement insulation.

18.15 Printed circuit board (PCB), 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.

• Undo and remove the two front retaining screws.

• 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. Be careful not trap any of the cables.
Make sure that PCB connections are fully pushed onto

replacement PCB.

INSULATION

9824

CONTROL
BOARD
COVER

10021

24ci shown

45

PCB (CONTROL BOARD)

➜

Diagram 18.8

10001

➜

Diagram 18.9

4000123942-2

➜

18 Replacement of Parts

MAINS SWITCH230V CONTROLS BOARD

➜

➜

24ci shown

CONTROL PANEL

USER INTERFACE BOARD

18.16 User interface board, 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.

• 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.

11659

11660

➜

➜

PROGRAMMER

➜

➜

➜

Diagram 18.10

PUMP
ELECTRICAL
CONNECTION
BOX

PUMP
HEAD

9823

18.17 Mains switch, 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.

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

• Disconnect the electrical connections from mains switch.

• Remove the mains switch.

18.18 230V Controls board, 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.

• 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.

18.19 (24ci Only) Analogue programmer, 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.

HEX HEAD SCREW (4 OFF)

24ci shown

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

• Disconnect the electrical connection from the programmer.

• Undo the two securing screws and remove the programmer.

Diagram 18.11

18.20 Central heating pump head, 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.

• 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 head 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.

4000123942-2

46

18 Replacement of Parts

18.21 (24ci Only) Filling system tap, 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 the hotwater circuit, refer to relevant part of
diagram 18.1.

• Pull of the filling loop tap extension.

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

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

18.22 (24ci Only) Reduced pressure zone valve
(RPZ), 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 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

18.13.

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 boiler drain valve into

housing, remove boiler drain valve.

REDUCED PRESSURE
ZONE VALVE (RPZ)

➜

➜

➜

➜

FILLING TAP

BOILER DRAIN
VALVE

➜

11936

➜

➜

Diagram 18.1224ci Only

9841

Diagram 18.13

9846

18.24 (24ci Only) Water flow sensor, 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 hotwater circuit, refer to relevant part of

Section 18.1.

• Undo the union nut on the cold water inlet isolating valve.

• 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.

➜

➜

➜

9847

WATER
FLOW
SENSOR

24ci only Diagram 18.14

47

➜

4000123942-2

18 Replacement of Parts

18.25 System water pressure 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.

• Remove electrical connections from water pressure sensor.

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

18.26 Bypass valve, refer to diagram 14.1.

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 the ignition unit, refer to Section 18.33.
Pull out slotted metal clip, ease out bypass valve from bypass

valve housing.

18.27 Automatic air vent, 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 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.

➜

➜

24ci shown

9833

SYSTEM
WATER
PRESSURE
SENSOR

Diagram 18.15

9810

CAP

AIR VENT

Diagram 18.16

➜

11936

18.28 Gas Control 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.

• 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 the wire restraining clip from underside of gas
control valve

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

Note: Use the new washers supplied with the gas control valve.

• Withdraw gas control valve assembly.

• Fit gas restrictor to replacement gas control value.

• Fit replacement gas control valve.
If the step pressure requires adjusting, refer to Section 13

Changing Gas Type.

➜

➜

24ci shown

GAS CONTROL
VALVE

9842

➜

Diagram 18.17

4000123942-2

48

18 Replacement of Parts

18.29 Gas control valve stepper motor, 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.

• Remove the gas control valve, refer to Section 18.28.

• Disconnect the electrical connection from stepper motor.

• Remove the two screws securing stepper motor to the gas

control valve.

• Fit replacement gas control valve stepper motor.

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

18.30 Discharge safety valve, refer to diagram

18.19.

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.

• Drain down the boiler, refer to relevant part of section 18.1

• Undo discharge pipe union nut.

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

18.31 (24ci Only) Three-way valve head, refer
to diagram 18.20.

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 gas control valve, refer to Section 18.28. (It will not
be necessary to remove the gas control electrical cables).

• Remove electrical plug from valve head.

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

• Fit replacement valve head.
Note :

1) When refitting clip, ensure that letters YES are as shown.

2) It is not necessary to drain boiler to carry out this work.

10018

➜

➜

24ci shown

➜

GAS CONTROL
VALVE

STEPPER
MOTOR

➜

Diagram 18.18

PRESSURE
RELIEF
VALVE

➜

Diagram 18.19

9794

9848

49

24ci only

➜

THREE WAY
VALVE HEAD

Diagram 18.20

4000123942-2

18 Replacement of Parts

18.32 (24ci Only) Three-way valve actuator,
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.

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

18.1.

• Remove the gas control valve, refer to Section 18.28.

• Remove 3-way valve head, refer to Section 18.31.

• Remove the three way valve actuator.

18.33 Ignition 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.

24ci only

➜

➜

10017

THREE WAY
VALVE/ BYPASS
HOUSING

THREE WAY
VALVE
ACTUATOR

Diagram 18.21

IGNITION
UNIT

9785

9845

18.34 (24ci Only) Domestic hot water plate to
plate heat exchanger

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 and hotwater circuit ,refer to relevant
parts of diagram 18.1.

• Unclip the central heating thermistor.

• Unscrew the heating flow pipe union nut, swing pipe forwards.

• Remove the gas supply pipe between the gas control valve
and injector bar, see diagram 18.23.

• Disconnect the union connection from the expansion vessel.

• Supporting domestic hot water plate to plate heat exchanger,
unscrew and remove two screws securing it onto pump
mounting and 3-way valve/bypass housing.

• Remove plate to plate heat exchanger from boiler.

• Fit replacement plate to plate heat exchanger.
Note: Plate to plate heat exchanger mounting screws are offset

to ensure correct fitting.

➜

DOMESTIC HOT WATER
PLATE TO PLATE HEAT
EXCHANGER

➜

➜

Diagram 18.22

9870

➜

4000123942-2

9850

24ci only Diagram 18.23

50

18 Replacement of Parts

18.35 Expansion vessel

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.

Replacing the expansion vessel
Before starting refer to the front of Section 18 Important

information.

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

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

• 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 parts of
diagram 18.1.

• Disconnect the flue system.

• Disconnect the fixing jig connection pipes at the boiler.

• Disconnect the pressure relief valve discharge pipe.

• Disconnect the mains cable and any external controls cables.

• Lift up to remove the boiler from the wall.

• Remove sealed chamber cover, refer to Section 15.4.

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

• From the rear of the boiler, unclip wiring harness retaining wire.

• Undo pipe coupling on expansion vessel.

• Unscrew and remove expansion vessel bracket retaining screw.

• Slide expansion vessel to the left and forward to remove.
Note: Check that expansion vessel pressure is correct, see

‘Section 1 Technical Data’.

9873

24ci shown

➜

EXPANSION
VESSEL

9872

9871

Diagram 18.24

10063

18.36 Sealed chamber cover seal, refer to
diagram 18.25

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

• Remove the front panel, refer to Section 15.3.

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

• Remove the old seal, thoroughly clean the casing. Fit the new
seal, it is supplied to the correct length.

Note: Ensure the seal is fitted correctly giving an air tight seal.

SEALED
CHAMBER
COVER

SEAL

FRONT
PANEL

Diagram 18.25

51

4000123942-2

19 Spare parts

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

Short parts list

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

1 Central heating thermistor 801935 E91-959
2 Fan 801920 E92-062
3 Air pressure switch 801921 E91-953
4 24ci only Domestic water flow sensor 801910 E84-014
5 Printed circuit board - Main 801915 E91-904
6 Pump head 801896
7 System water pressure sensor 801911 E83-997
8 Gas control valve (G20) 801891 E91-945
9 Gas control valve (G30) 801978 E92-058
10 Discharge safety valve 801904 E94-000
11 Overheat thermostat 801913 E91-949
12 Ignition electrode 801888 E91-917
13 Flame sense electrode 801887 E91-922
14 230V controls board 801923 E84-018
15 User interface PCB 801922 E91-954
16 Stepper motor (G20) 801892 E91-924
17 Stepper motor (G30) 801979 E92-059
18 Ignition unit 801936 E91-960
19 24ci only Three way valve motor 801912 E88-839
20 Three way valve actuator 801903 E88-838
21 Heat exchanger 801881 E91-939
22 Burner / 14 Blades 801890 E91-944

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

4000123942-2

52