24i, 28i RSF COMBI

G.C. NUMBERS NATURAL GAS L.P.G. 24i 28i 54
USER INSTRUCTIONS & CUSTOMER CARE GUIDE
EXCELLENCE COMES AS STANDARD
Thank you for purchasing a Worcester gas-fired combination appliance. Worcester appliances are made by Worcester Heat Systems and the strictest quality control standards are demanded throughout every stage of production. Indeed, Worcester Heat Systems have led the field in innovative appliance design and performance for more than 30 years. The result is that your new Worcester 24i or 28i appliance offers you the very best of everything quality, efficiency, economical running costs, proven reliability and value for money. Whats more, you also have the assurance of our no-nonsense 1 year parts and labour guarantee. And its backed up by Worcester Care Call a complete maintenance scheme to keep your boiler operating at peak condition and efficiency. No wonder that more and more people are agreeing that when it is gas, it has to be a Worcester 24i or 28i

CONTENTS

Page No. Operating Instructions. 3-11 Fault and Breakdowns 12 Maintenance and Extended Warranty Information. 13-14 Guarantee Details. 15-16

GENERAL INFORMATION

GAS SAFETY (INSTALLATION AND USE) REGULATIONS 1998
It is the law that all gas appliances must be installed by a competent person in accordance with the above regulations. Failure to install appliances correctly could lead to prosecution. It is in your interest and that of safety to ensure compliance with the law. The manufacturers notes must not be taken, in any way, as over-riding statutory obligations. WARNING: This appliance must be earthed and protected by a 3 amp fuse. ELECTRICITY SUPPLY: 230V ~ 50Hz IMPORTANT: To get the best from your Worcester appliance please read these instructions carefully. NOTE: In the event of a fault the appliance should not be used until the fault has been corrected by a competent person.

BENCHMARK

All CORGI Registered Installers carry a CORGI ID card and have a registration number which must be recorded in your central heating log book. You can check that your installer is CORGI registered by calling CORGI on 01256 372300.

GENERAL DESCRIPTION

(See Fig.1.) The WORCESTER 24i or 28i is a combined domestic hot water and central heating appliance. It consists of a gas fired boiler having a varying output of between 7.5 kW and 23.4 kW (24i) or 8.5 kw and 27.5 kw (28i), a combined heat-exchanger and all necessary controls to provide mains fed domestic hot water and central heating. The appliance can operate in one of two modes as required. Hot water only or hot water and central heating.

Hot Water Mode:

When a demand is made for hot water by opening a tap or shower the flow switch will energise and the burner will light at its maximum setting. When hot water is no longer required the appliance pump and fan may continue to operate to dissipate the excess heat within the boiler.
A flow restrictor is fitted within the appliance which limits the hot water delivery rate to a maximum of 8.0 (15%) litres/minute (1.8 gallons/minute) 24i or 10 (15%) litres/minute (2.2 gallons/minute) 28i.
Hot Water and Central Heating mode:
When a demand is made for heating by the system controls (i.e. a programmer or room thermostat). The pump will energise circulating primary water around the heating system and the burner will light. The heat output from the appliance in this mode has been factory set to maximum. The appliance will operate as necessary to maintain the temperature of the radiators at the level set by the adjustment of the Heating Temperature Control Knob. (See Fig. 2.) If the system no longer requires output to maintain the desired room temperature, the burner will extinguish. The pump and fan will continue to run for a short Automatic period to dissipate the air vent residual heat from the appliance and then switch off. The appliance will supply heat to the central heating system as required. A demand for hot water at a tap or shower will override the central heating function for Boiler the period of the domestic hot water demand.

Fig. 1. System Diagram.

Gas to water heat exchanger
Expansion vessel Flow switch Circulating pump

Pressure relief valve

Fixed by-pass

Safety discharge

CH flow

Domestic hot water out

Domestic cold supply

CH return

GENERAL NOTES

CENTRAL HEATING SYSTEM

During the first few hours of operation of the central heating system, check that all radiators are being heated at an even rate. Should the upper area of a radiator be at a lower temperature than the base of the radiator, it should be vented by releasing air through the venting screw at the top of each radiator. Make sure your installer shows you how to carry out the operation. Repeated venting will reduce the quantity of water in the system and this must be replenished for safe and satisfactory operation of the appliance. Should water leaks be found in the system or excessive venting be required from any radiator, a service engineer should be contacted and the system corrected.

SEALED HEATING SYSTEM

The appliance will be fitted to a sealed heating system which is pre-pressurised. Your installer will advise you on the minimum and maximum pressure that should be indicated on the pressure gauge. See Fig. 2. Check regularly that this pressure is maintained and contact your installer or maintenance engineer if there is a permanent significant drop in pressure indicated on the gauge. If the system loses pressure it should be re-pressurised as instructed by the installer (N.B. Maximum pressure 2.5 bar).

CLEARANCES

Your installer will have provided adequate space around the appliance for safety and servicing. Do not restrict this space by the addition of cupboards, shelves etc. close to the appliance. Minimum clearances in millimetres. RSF 200
Left-hand side Right-hand side In Front Above Below

ROOM THERMOSTAT

A room thermostat may be fitted for control of the central heating temperature. It will be located in one room of the home. The method of setting a room thermostat varies with the type and manufacture. Refer to the instructions supplied with the room thermostat.
THERMOSTATIC RADIATOR VALVES
If thermostatic radiator valves are to be fitted to the system then they must conform to the requirements of BS2767:1972. It is advisable to leave one valve permanently set at maximum to prevent the boiler short cycling.
SHOWERS, BIDETS, TAPS AND MIXING VALVES
Standard hot and cold taps and mixing valves used with the appliance must be suitable for operating at the available mains pressure. Thermostatically controlled or pressure equalising shower valves will guard against the flow of water at too high a temperature. Hot and cold mains fed water can be supplied direct to an overrim flushing bidet subject to local water company requirements. With all mains fed systems the flow of water from the individual taps will vary with the number of outlets operated simultaneously and the cold water mains supply pressure to the property. Flow balancing using Ball-o-Fix type valves is recommended to avoid an excessive reduction in flow to individual outlets. For further information contact Worcester Heat Systems Ltd.

HOT AND COLD FLOW

If the flow of water demanded from both hot and cold service outlets is dependent upon mains supply, it may not be possible in some installations to operate all outlets simultaneously.

WATER MAINS FAILURE

It is important to note that in the event of a mains water supply failure, no tap water will be available until the mains supply is restored.

USE IN HARD WATER AREAS

In temporary hard water areas (more than 350mg/litre or 200ppm calcium bicarbonate) it is recommended that a proprietary scale reducer is fitted in the mains cold water connection to the appliance. Consult the local water company for additional advice. Installation of a scale inhibitor assembly should be in accordance with the requirements of the local water company. An isolating valve should be fitted to allow servicing. The water hardness can be determined by reference to the local water company.

DOMESTIC HOT WATER TEMPERATURE CONTROL
By slightly reducing the flow of domestic water from the tap, the delivery temperature will be increased. This is of particular advantage in the winter, for example to increase bath water temperature and to remove heavy grease deposits on plates, etc. Also this will provide an added advantage of reducing the delay before hot water is obtained.
VENTILATION OF THE APPLIANCE
This is a room sealed appliancem, any ventilation openings in a wall or door must not be obstructed. Do not allow the flue terminal fitted on the outside wall to become obstructed or damaged. If the appliance is fitted in a compartment do not use the compartment for storage purposes unless it conforms to the requirements of BS 6798:1987: Section 6 and the requirements of Section 6. Air Supply in the Installation Instructions. It is essential that the airing space is separated from the boiler space by a perforated non-combustible partition as described in BS 6798:1987. NOTE: Do not place anything on top of the appliance.

CIRCULATING PUMP

This may be fitted with a speed adjuster. If so it will be factory set at maximum and should not be changed.

FROST PRECAUTIONS

Your British Gas Engineer, or any service engineer will advise you on suitable frost precautions. For short periods the built-in frost protection of the appliance will be adequate. If the appliance is not to be used for a long period of time and there is a likelihood of freezing, then the appliance should be drained.

SERVICE

Annual servicing is important in order to ensure continuing high efficiency and long life for your appliance. In the event of any difficulty in making suitable servicing arrangements, Worcester Heat Systems Limited, your British Gas Engineer or other competent persons will discuss regular servicing arrangements and offer a comprehensive maintenance contract. IMPORTANT: Do not touch or adjust any sealed component.

WARNING

If a gas leak exists, or is suspected, turn off the gas supply to the appliance at the service cock and consult your local British Gas Engineer or service engineer. Do not touch any electrical switches to turn them either on or off. Open all windows and doors. Do not smoke. Extinguish all naked lights.

CLEANING

Do not use abrasive cleaners on the outer casing. Use a damp cloth and a little detergent.

OPERATION OF CONTROLS

(See also label on inside of appliance front panel). The appliance is fitted with the following controls:
CENTRAL HEATING TEMPERATURE
The position of this knob will determine the temperature of the water delivered to the radiators between the I and MAX position. When the knob is turned anti-clockwise past the I position towards the (Summer Position), then the appliance will operate in the HOT WATER mode only and no heat will be delivered to the radiators.
FACIA MOUNTED PROGRAMMER (if fitted)
Your installer may have fitted a mechanical programmer into the facia of your appliance. Operating instructions are supplied with the programmer.

SYSTEM PRESSURE GAUGE

The red needle has been set to show the sealed system pressure which is required for the appliance to operate effectively. The grey needle will show the actual pressure in the system.

INDICATOR LIGHT

Mains electricity indicator: OFF : No mains electricity to the appliance ON : Mains electricity is connected to the appliance FLASHING : Sensor fault.
OVERHEAT CUT-OFF THERMOSTAT
The appliance will enter a lockout condition in the event of overheating. An overheat cut-off thermostat is fitted to the appliance which will interrupt the electricity supply to the ignition circuit. If the overheat cut-off has operated the fan and/or pump will run but the burner will not light. (No spark generation). The appliance can be reset by pressing the overheat cut-off button.
Fig. 2. 24i/28i Controls.

Overheat cut-off button

Mains indicator
Central heating temperature control and on/off knob

System pressure gauge

TO LIGHT AND STOP THE APPLIANCE

TO LIGHT THE APPLIANCE

Check that the water valves to the central heating circuit are open. Check that the grey needle on the pressure gauge is not below the required pressure. Switch on the mains electricity. The power on indicator will light. Set the room thermostat, if fitted, to maximum. Turn the central heating temperature control knob to MAX. The burner will light. Set the central heating control knob and the room thermostat, if fitted, to the desired temperature.

Fig. 3. 28i with front panel removed.

Front panel hook

DATA PLATE

Burner viewing window

Gas valve
Locating peg Circulating pump

TO STOP THE APPLIANCE

For Short Periods Turn the central heating temperature control knob fully anticlockwise to the position. Domestic Hot Water will still be available as required. For Long Periods Switch off the mains electricity. A facia mounted mechanical programmer will require resetting once the mains supply has been disconnected.
ELECTRICITY SUPPLY FAILURE
If the electricity supply fails the appliance will not operate. Once the supply is restored the appliance will return to normal operation. If a programmer is fitted, check that the settings have been maintained.

IGNITION LOCKOUT

The appliance will enter a lockout condition in the event of the burner failing to ignite. If the burner fails to light within a preset time of 10 seconds the electricity supply to the gas valve will be interrupted. The appliance can be reset by ending the present demand which in a central heating demand means turning the central heating temperature control to and back to the required setting or ending the room thermostat/programmer demand. Re-ignition will be attempted after a delay of four minutes. Domestic hot water demands do not have this delay. Check that the gas supply has not been interrupted. If this condition continues to occur, then call a service engineer.

AIR FLOW DEVICE

The appliance will enter a lockout condition in the event of an air flow fault. If the controls fail to detect the correct air flow through the appliance the electricity supply to the gas valve will be interrupted. The appliance will try to re-light once the air-flow signal is reestablished. Check that the flue terminal has not been obstructed or damaged, and that the fan and air pressure switch are in good order. If this condition continues to occur, then call a service engineer.
REMOVAL AND REPLACEMENT OF THE FRONT PANEL (See Fig. 3)
Necessary to check if burner is lit. Removal: Holding the panel at the edges, slide it upwards to disengage the clips and ease the top edge forwards and upwards to raise it clear of the two pegs on the top edge of the facia. Replacement: Locate the two holes in the bottom edge of the front panel over the two pegs on the top edge of the facia and reverse the removal procedure. WARNING: Do not touch any component within the appliance when it is running as some may be very hot.

APPLIANCE FAILS TO OPERATE
More than 30% of all calls made to Worcester Heat Systems to report appliance faults or breakdowns prove to be false alarms, as there is often a simple explanation for the apparent malfunction. So, to help you save time and money not to mention frustration and inconvenience please refer to the General Information, Notes and Lighting Instructions ensuring all controls are set correctly. If, after following the instructions the appliance still fails to operate correctly call the Worcester Heat Systems Service Centre. Arrangements will be made for an engineer to call as soon as possible.

CALL-OUT CHARGES

All of our field service engineers are factory trained. If you request a visit from an engineer and your appliance has been installed within the last 12 months, no charge will be made for parts and/or labour, providing: The appliance was commissioned correctly on installation. An appliance fault is found and the appliance has been installed within the past 12 months. A call-out charge will be made where: The appliance has been installed for over 12 months, or Our Field Service Engineer finds no fault with the appliance (see note), or The cause of breakdown is with other parts of your plumbing/heating system, or with equipment not supplied by Worcester. NOTE: Invoices for attendance and/or repair work carried out on your appliance by any third party will not be accepted.
MAINTAINING YOUR APPLIANCE
Your new Worcester gas-fired appliance represents a longterm investment in a reliable, high quality product. In order to realise its maximum working life, and to ensure it continues to operate at peak efficiency and performance, it is essential that your boiler receives regular, competent servicing and annual maintenance checks beyond the initial 12 month guarantee period.
Regular service contracts can be arranged with your installer however if you have difficulty making a satisfactory arrangement simply contact Worcester Heat Systems on for help.

SERVICE CENTRES

CONTACT NUMBERS: UK Call Centre UK Call Centre Scotland only Tel. Fax. Fax. 441 687
OPERATING HOURS: Mon - Fri Sat 8.00am to 6.00pm 8.30am to 1.00pm
Please contact our UK Call Centre number where our friendly operators will book your call with one of our team of nationwide engineers. NOTE: Sunday and Bank Holiday cover is not available
IMPORTANT Do not touch or adjust any sealed component

YOUR WORCESTER GUARANTEE

This appliance is guaranteed against faulty materials or workmanship for a period of twelve calendar months from the date of installation subject to the following conditions and exceptions.

1. That during the currency of this guarantee any components of the unit which are proved to be faulty or defective in manufacture will be exchanged or repaired free of material charges and free of labour charges by Worcester Heat Systems Limited. 2. That the householder may be asked to prove the date of installation, that the appliance was correctly commissioned and, where appropriate, the first 12 month service has been carried out to the satisfaction of Worcester Heat Systems Limited when requested. 3. That any product or part thereof returned for servicing under the guarantee must be accompanied by a claim stating the Model, Serial Number, Date of Installation. 4. That Worcester Heat Systems Limited will not accept responsibility for damage caused by faulty installation, neglect, misuse or accidental damage, the nonobservance of the instructions contained in the installation and Operating Instructions Leaflets. 5. That the appliance has been used only for normal domestic purposes for which it was designed. 6. That this guarantee applies only to equipment purchased and used in mainland Great Britain.
This guarantee is given in addition to all your normal statutory rights.

GUARANTEE REGISTRATION

You should complete and return the postpaid Guarantee Registration Card within 14 days of purchase. The card will register you as the owner of your new Worcester appliance and, while this will not affect your statutory rights in any way, it will assist us to maintain an effective and efficient customer service by establishing a reference and permanent record for your boiler. IMPORTANT: SERIAL NUMBER. Copy the number off the Guarantee Card. FOR YOUR OWN RECORD

MODEL SERIAL NUMBER

(See identity label inside appliance casing) TYPE/SIZE DATE OF INSTALLATION
Worcester Heat Systems Limited. Cotswold Way, Warndon, Worcester WR4 9SW. Telephone: (01905) 754624. Fax: (01905) 754619. Technical Service Helpline 08705 266241. www.worcester-bosch.co.uk 145 027e 11/00

28i RSF

WALL MOUNTED COMBINATION BOILER FOR CENTRAL HEATING AND MAINS FED DOMESTIC HOT WATER
INSTALLATION AND SERVICING INSTRUCTIONS
This appliance is for use with Natural Gas

Cat I2H

GC NUMBER N.G. 54

BOILER OUTPUT

To Domestic Hot Water Modulated Control Minimum 8.5 kW Maximum 27.5 kW To Central Heating Modulated Control Minimum 10.5 kW Maximum 27.5 kW
THESE INSTRUCTIONS APPLY IN THE UK ONLY AND MUST BE LEFT WITH THE USER OR AT THE GAS METER. READ THE INSTRUCTIONS BEFORE STARTING WORK - THEY HAVE BEEN WRITTEN TO MAKE THE INSTALLATION EASIER AND PREVENT HOLD-UPS. This appliance must be installed by a competent person in accordance with the Gas Safety (Installation and Use) Regulations 1998

Contents

1. Installation Regulations. Page 2. Introduction. Page 3. Technical Data. Page 4. Siting the Appliance. Page 5. Siting the Flue. Page 6. Air Supply. Page 7. Sealed System. Page 8. Open Vent System. Page 9. Domestic Hot Water. Page 10. Gas Suppy. Page 11. Electrical. Page 10 12. Installing the Appliance. Page 13 13. Commissioning the Appliance. Page 18 14. Handover. Page 20 15. Inspection and Service. Page 21 16. Replacement of Parts. Page 22 17. Operational Flow Diagrams. Page 27 18. Fault Finding. Page 29 19. Component Parts List. Page 37
1. Installation Regulations
1.1 Gas Safety (Installation and Use) Regulations, October 1998 All gas appliances must be installed by a competent person in accordance with the above regulations. Failure to install appliances correctly could lead to prosecution. 1.2 The manufacturers notes must not be taken, in any way, as overriding statutory obligations. 1.3 The compliance with a British Standard does not, of itself, confer immunity from legal obligations. In particular the installation of this appliance must be in accordance with the relevant requirements of the following; Gas Safety (Installation and Use) Regulations 1998 as amended. Current IEE Wiring Regulations BS 7671. Local Building Regulations. Building Standards (Scotland)(Consolidation). Bylaws of the local Water Company. Health and Safety Document No. 635 (Electricity at Work Regulations). The British Gas Material and Installation Specification for central heating and hot water It should be in accordance with the relevant recommendations of the following British Standards. BS6798:1987 Specification for installation of gas fired hot water boilers of rated input not exceeding 60 kW. BS5449:1990 Central Heating for Domestic Premises. BS5546:1990 Installation of gas hot water supplies for domestic purposes. BS5440:1:2000 Flues and Ventilation for gas appliances of rated input not exceeding 60 kW: Flues. BS5440:2:2000 Flues and Ventilation for gas appliances of rated input not exceeding 70kW: Air Supply. BS6891:1988 Installation of low pressure gas pipework installations up to 28mm (R1). BS7593:1993 Central Heating system cleansing and flushing. 1.4 To ensure that the installation will perform to the highest standards, the system and components should conform to any other relevant British Standards in addition to those mentioned in the instructions. 1.5 The appliance complies with the Essential Requirements of the Gas Appliance Directive and other Directives currently applicable. 1.6 This appliance contains no asbestos products. There is no potential hazard due to the appliance being electrically unsafe. There are no substances used that are a potential hazard in relation to the COSHH Regulations 1988. 1.7 The advice and instructions given in this document covers, as far as possible, the foreseeable situations which may arise. Contact Worcester Heat Systems Technical Helpline for advice on specific installations. 1.8 Product Liability regulations indicate that, in certain circumstances, the installer can be held responsible, not only for mistakes on his part but also for damage resulting from the use of faulty materials. We advise that, to avoid any risk, only quality approved branded fittings be used.

2. Introduction

The Benchmark initiative is the new code of practice to encourage the correct installation, commissioning and servicing of domestic central heating boilers and system equipment. The 'Log-book' is a vital document that must be completed by the installer at the time of installation. It confirms that the boiler has been installed and commissioned according to the manufacturers instructions. Without the completion of the Log-book, manufacturers may refuse to respond to a call-out from a householder, who will be advised that he or she must call back the installer, who has not fulfilled his obligations to record the information required by the initiative. It is important that: The services and the system are properly flushed as specified. The User is clearly instructed on the correct operation of the appliance. The benefits of regular servicing are explained - to maintain the efficiency and extend the life of the appliance. 2.1 General Information The appliance is set to give the maximum output of 27.5 kW to the domestic hot water and to the heating system. The hot water flow rate is limited to a nominal 10 l/min at a maximum temperature rise of 40C. The sanitary water section of the appliance is suitable for mains water pressure of up to 10bar. 2.2 Electrical Supply 230V - 50Hz. Load 180 watts. External fuse 3A, Internal fuses F1 - 2A, F2 - 1.0A (20mm). 2.3 Gas supply The appliance requires a maximum of 3.17 m3/h of natural gas (G20). The installation and the connection of the gas supply to the appliance must be in accordance with BS6891. The meter or regulator should deliver a dynamic pressure of 20 mbar (G20) at the appliance, which is equivalent to about 1919.5 mbar at the gas valve inlet pressure test point. 2.4 Installation The appliance is suitable for indoor installation only and for use with a sealed system only. Do not place anything on top of the appliance. It is a room sealed appliance and a separate combustion air supply is not required in any room or compartment in which the appliance is fitted. If the appliance is fitted in a cupboard or a compartment is built around it after installation, then the structure must conform to the requirements of BS6798 and BS5440 Part 2. However, because of the low casing losses, there is not a need for the cooling ventilation openings in the compartment. The spaces specified in Section 6.3 must be maintained. There is space for the service pipes to pass at the back of the appliance. 2.5 Flue The appliance has a multi-directional fanned flue system. The standard telescopic flue assembly length is from 330mm to 725mm. Extension flue kits are available for flue lengths up to 2500mm. 2

Gas Discharge Rate (m3/hr)
Note: Each fitting used in the gas line from the meter is equivalent to a length of straight pipe which must be added to the straight pipe length to give total length. i.e: Bend=0.5 metre, Tee=0.5 metre, 90 Bend=0.3 metre. Table 8 CLEARANCES (mm) INSTALLATION ABOVE APPLIANCE AND/OR FLUE ELBOW 30 IN FRONT OF APPLIANCE 600 BENEATH APPLIANCE 200 RIGHT AND LEFT HAND SIDE 10 Refer to Section 6. Table 9 SYSTEM CAPACITY TOTAL SYSTEM VOLUME litres INITIAL CHARGE PRESSURE bar 0.5 1.0 1.75 N/A 52 SERVICE 200 10
INITIAL PRESSURE bar 1.0 1.5
Fig. 3. Appliance casing dimensions and required clearances (front view).

30 170

4. Siting The Appliance
4.1 The appliance may be installed in any room but refer to the requirements of the current IEE Wiring Regulations BS 7671 and, in Scotland, the electrical provisions of the Building Regulations applicable in Scotland, with respect to the installation of appliances in rooms containing baths or showers. Where a room sealed appliance is installed in a room containing a bath or shower, any electrical switch or appliance control using mains electricity must NOT be able to be touched by a person using the bath or shower. 4.2 The appliance is NOT suitable for external installation. 4.3 NO special wall protection is required. 4.4 The wall must be capable of supporting the weight of the appliance. See Table 4. 4.5 The specified clearances must be available for installation and for servicing. See Fig. 3 and 4. (note the clearances at the front are for a removable panel e.g. a door). 4.6 The appliance can be installed in a cupboard used for airing clothes provided that the requirements of BS 6798 and BS 5440:2 are followed. Notwithstanding the instructions given in BS 5440:2, this appliance may be fitted in a compartment with no vents as long as the minimum clearances stated in Section 6: Air Supply, are maintained. 4.7 The airing space must be separated from the boiler space by a perforated non-combustible partition. Expanded metal or rigid wire mesh are acceptable provided that the major dimension is less than 13mm. See BS 6798:1987. 4.8 No combustible surface must be within 75mm of the casing. See BS476:4. 4.9 Always consider the possible need to disconnect the pipes from the appliance after installation.

All dimensions in mm

Fig.4. Appliance casing dimensions and required clearances (side view).

600 800

Fig. 6. Appliance pipework connections.
Fig. 5. Side flue opening

(A) (B) (C)

100mm 36.5mm

A B C D E F

Safety Relief CH Flow DHW Out Gas Inlet Mains Cold Water In CH Return

= = = = = =

50mm 95mm 160mm 225mm 290mm 355mm

5. Siting The Flue

5.1 The flue must be installed as specified in BS 5440:Part 1. 5.2 The terminal must not cause an obstruction nor the discharge cause a nuisance. Refer to Fig. 7. 5.3 If a terminal is fitted less than 2 metres above a surface to which people have access then a guard must be fitted. The guard must be evenly spaced around the terminal and fixed with plated screws. A type K2 guard is available from Tower Flue Components, Vale Rise, Tonbridge, TN19 1TB. 5.4 The terminal guard must be evenly spaced about the flue terminal and fixed to the wall using plated screws. 5.5 In certain weather conditions a terminal may steam and siting where this could cause a nuisance should be avoided. 5.6 Take care to ensure that combustion products do not enter ventilated roof voids. 5.7 The standard flue kit is horizontal and extends from 425 to 725mm in length. It can be shortened to 330mm (for single brick wall applications) by cutting the flue ducts if required. Extension kits are available for flue lengths up to 2500mm. A vertical flue system for heights upto 2.3m plus the terminal assembly. Refer to Table 2. 45 and 90 bends are available.

7.7 Water loss must be replaced. See Fig 4. The connection should be made in the central heating return as close to the appliance as possible. A filling loop kit is supplied. 7.8 Repeated venting loses water from the system. It is essential that this water is replaced and the system pressure maintained. 7.9 Connections to the mains water supply must not be made without the authority of the local Water Company. 7.10 The pump is set at maximum and should not be adjusted. 7.11 Connections in the system must sustain a pressure of up to 3 bar. 7.12 Radiator valves must conform to BS 2767:10. 7.13 Other valves used should conform to the requirements of BS 1010. 7.14 The appliance is fitted with a fixed internal by-pass. But it is advisable to keep one radiator permanently open.

8. Open Vent System

The appliance is NOT suitable for connection to an open vented system.
Fig. 8. Sealed primary water system.

Refer to Fig. 2.

Mains cold water

Lockshield valve

Radiator valve
Hot water out Heating return

Heating flow

NOTE: A drain cock should be installed at
British Standard stop valve. Fixed spindle type Water main
the lowest point of the heating circuit and beneath the appliance.

9. Domestic Hot Water

9.1 The following are general requirements and, if necessary, reference should be made to the local Water Company before fitting the appliance. 9.2 MAINS COLD WATER INLET. Devices capable of preventing the flow of expansion water must not be fitted unless separate arrangements have been made. A mini expansion vessel kit is available which contains the necessary parts for fitting an internal expansion vessel to the appliance. Refer to Section 19. A thread sealant compatible with potable water must be used. An external expansion vessel may be fitted on the mains cold water connection to the appliance. 9.3 The final 600mm of the mains cold water connection to the appliance should be made in copper tube only. 9.4 The appliance is suitable for a mains pressure of up to 10 bar (150 lb/in2) and is fitted with a mains supply isolating valve. 9.5 The maximum domestic hot water flow rate is 11.4 litres/min (15%). 9.6 In winter (when the mains inlet water temperature is lower) a reduced flow rate at the taps may be required to achieve the type of hot water delivery temperature available in warmer weather. 9.7 It is suggested that long pipe runs to the taps or shower should be insulated to prevent the rapid cooling of domestic hot water after a tap or shower has been turned off. 9.8 Hot and cold taps and mixing valves used with this appliance must be suitable for operating at mains pressure and temperatures of 55C. Note: The maximum domestic hot water outlet temperature is fixed at 55C and it is not adjustable. 9.9 No anti-syphonage arrangements are necessary except for some loose head showers. See also Section 9.11 following. 9.10 Thermostatically controlled or pressure equalising shower valves will guard against the flow of water at too high a temperature. 9.11 The head of a loose head shower must not fall closer than 25mm (1in.) above the top edge of the bath to prevent its immersion in bath water. Alternatively the shower must be fitted with an anti-syphonage device at the point of the flexible hose connections. 9.12 The supply of hot and cold mains water direct to a bidet is permitted, (subject to local water company requirements), provided that the bidet is of the over-rim flushing type. The outlet(s) should be shrouded and unable to have any temporary hand held spray attached. No anti-syphonage arrangements are necessary. 9.13 LIME SCALE. In temporary hard water areas (more than 350mg/litre or 200ppm calcium bicarbonate) it is recommended that a proprietary scale reducer is fitted in the mains cold water connection to the appliance. Consult the local water company for additional advice. Installation of a scale inhibitor assembly should be in accordance with the requirements of the local water company. An isolating valve should be fitted to allow servicing. The water hardness can be determined by reference to the local water company. 9.14 NOTE: HOT WATER ONLY. If required the appliance may be used for Hot Water only before the Central Heating is connected. A 22mm copper bypass pipe at least 4 metres long must be connected between the Central Heating Flow and Return, but it is advisable to connect a small radiator instead. IT IS NOT RECOMMENDED TO USE THE BOILER IN THIS CONDITION FOR EXTENDED PERIODS.

10. Gas Supply

The boiler requires 3.17m3/h (112ft3/hr) of natural gas with a calorific valueof 37.78MJ/m3. The meter govenor should deliver a dynamic pressure of 20 mbar (8in w.g.) at the appliance, equivalent to a pressure of 19-19.5 mbar at the gas valve on natural gas. The gas meter and supply pipes must be capable of supplying this quantity of gas in addition to the demand from any other appliances being served. The table below gives an indication of limiting gas pipe lengths and the allowance to be made for fittings. Refer to BS6891 for further information. The complete installation, including the gas meter, must be tested for soundness and purged. Refer to BS6891.

11. Electrical

11.1 MAINS SUPPLY. 230 V ~, 50 Hz, 180 watts. External Fuse: 3A. Internal Fuses: 2A SLOW (F1), and 1A FAST(F2). Spare fuses are supplied with the appliance and are fixed adjacent to the pressure gauge. 11.2 It must be possible to completely isolate the appliance. 11.3 The following connection alternatives must be used: A 3 amp fused three-pin plug and unswitched shuttered socket outlet (both complying with the requirements of BS 1363) or a double pole isolator with a contact separation of 3mm in all poles and supplying the appliance and controls only. 11.4 The appliance must be earthed. 11.5 Mains Cable. 0.75mm2 (24 x 0.20mm) to BS 6500 Table 16. The mains cable must be connected into the terminal X1, marked L (Brown or Red lead), N (Blue or Black lead) and the earth stud and be held securely in the cable clamp. For access undo the three bottom screws and remove the facia access cover. See Fig. 11. The earth lead must be slack when the others are taut. 11.6 The wiring between the appliance and the electrical supply shall comply with current IEE Wiring Regulations and any local regulations which apply.
11.7 If a room thermostat and/or external programmer is to be fitted refer to Figs 12 and 13. The devices must be suitable for use with mains voltage. 11.8 A facia mounted mechanical programmer is available as an optional extra. Instructions are supplied with the programmer kit. 11.9 A time switch or programmer can be fitted externally to the appliance. 11.10 The boiler provides automatic frost protection, the use of a frost thermostat is not recommended. However if an external frost thermostat is considered necessary then it must be used in conjunction with a programmer. Important: To provide external frost protection the appliance must have the Central Heating Temperature Control Knob set to supply heating (the appliance may then be left with the central heating turned off at the programmer). Connection must be made at X2 terminals RI and CL. refer to Fig. 28. For advice on external frost thermostats contact Worcester Heat Systems Technical Helpline 11.11 SAFETY CHECK. After installation or in the event of an electrical fault the electrical system shall be checked for short circuits, fuse failure, incorrect polarity of connections, earth continuity and resistance to earth.

Mark the centre-lines of the pipe connections to aid the preplumbing of the system pipework. Check the position of the fixing points and the flue opening before drilling the fixing holes 60mm deep for the No.12 size plugs and cutting the flue duct hole at 110mm diameter (150mm diameter for internally fitted flues. 12.5 Wall Mounting Plate and Manifold Fit the plugs and fix the top support to the wall. Refer to Fig. 14. Check the top support is properly aligned before tightening the screws. 12.6 Gas and Water Pipes Remove the gas cock and fix the appropriate fitting to connect the inlet pipe and re-fit. Pre-plumbing is not recommended if no movement in the pipes is available. If it is necessary for the pipes to run up the back of the appliance then they must be arranged to pass behind the expansion vessel. Pipework must not run horizontally within the limits of the casing. It is important that the pipes are not fixed near the appliance using clips that put a strain on the connections. Before the appliance is fitted to the wall thoroughly flush the system and mains water supply.
Fig. 14. Appliance mounting plate and flue position.
Mounting wall Rear flue hole 110mm dia. (150mm dia. for internal fixing) Side flue hole 110mm dia. (150mm dia. for internal fixing)
166mm 60mm Fixing holes Mounting (alternatives) plate Appliance casing 740mm Rear flue position Appliance casing Side flue position Mounting plate Mounting wall 222mm

Side wall

400mm 12.7 Install the Boiler Remove the cabinet by releasing the sides and lifting from the top location. Check that the gas and water valves are closed. Lift the appliance to the wall, engage in the top support. Fix and tighten the bottom screws. Refer to Fig. 14. Tighten the gas and water connections. Fit a discharge pipe to the relief valve leading it away from any electrics or where it might be a hazard. The pipe must not be less than 15mm in diameter and must run continuously downward outside the appliance. Refer to Fig. 6.
Fig. 15. Marking out the side flue position.
Side flue hole 110mm dia. (150mm dia. for internal fixing)

Mounting wall

222 mm

Sid ew all

Fig.16. Appliance casing and control equipment fixings.
Side casing fixing screws (4)
The standard telescopic flue assembly is suitable for flues from 425mm (without cutting) up to 725mm measured from the centre-line of the boiler flue outlet to the outer face of the wall. Refer to Fig. 18. If L is greater than 725mm then flue extension kits will be required - each kit extends the flue by 750mm up to a maximum of 2-5m. See table below. EXTENSION 3 MAXIMUM FLUE LENGTH mm 2500
Inner casing cover screws (4)
Facia panel fixing screws (2)
12.9 Measure and Cut the Ducts General: Cut the ducts as necessary, ensuring that the ducts are square and free from burrs. Always check the dimensions before cutting. Measure the distance L. Refer to Fig. 20 and 21. The standard flue can be telescopically adjusted to any length between 425mm and 725mm. Fix the flue assembly together using the self-tapping screw provided. Refer to Fig. 18. It will only be necessary to cut the standard assembly if L is less than 425mm. Cut the flue turret assembly and the terminal assembly by the same amount i.e L=350 - remove 75mm from each assembly. Minimum side flue length = 335mm (accommodating a 10mm Service clearance and a 100mm wall) Minimum rear flue length = 322mm 100mm wall) If L is between 1175 - 1475mm 1925 - 2225mm (accommodating a (1 extension) (2 extension)
Connections cover fixing screws (3)
12.8 Air and Flue Duct Preparation The method of installation of the flue system may be varied to suit the actual site conditions. The instructions for connecting and fixing the ducts must, however, be strictly followed. Remove all packing material from the flue components. Horizontal Flues up to 725mm Length Fit the flue restrictor ring by unscrewing the flue spigot from the boiler. Refer to Fig. 17.
it is not necessary to cut the ducts.
Fig.18. Standard flue assembly.
Fig.17. Flue turret fixing and automatic air vent.
1. 2. 3. 4. 5. 6. Flue spigot fixing screws Flue spigot Restrictor ring Flue spigot fixing holes Reset button Flue gas test point

Turret assembly

Fixing screw

5 Appliance casing

Telescopic adjustment

Terminal assembly

Restrictor Ring Size 75mm horizontal flue up to 725mm.

Fig. 19. Extension Duct.

Turret assembly Fixing screws Ducts of equal length Appliance casing
Terminal assembly Fixing screw
Shorten first extension fitted to the turret assembly if more than one extension is fitted
Fig. 20. Flue duct length (side flue).

Flue terminal Clamping ring

Fig. 24. Flue bends.

Air Z 81mm Flue Z 51mm

Y 162mm (plain tube)

A maximum flue assembly of 2.5m is possible with 1 X 90 bend and 2m with 2 X 90 bends. Measure the lengths X,Y and Z. Refer to Fig. 24. The maximum value of X using the turret assembly only in 506mm. Reduce the ducts to the appropriate length i.e. X = 406mm, cut 100mm from the air duct and 120mm (to cover the entry into the 45 or 90 elbow) from the flue duct. Refer to Fig.24. NOTE: The flue system ducts between the elbows, dimension Y, requires the socketed ends (of the first extension if two or more are used) to be removed and the air and flue tubes to be cut to the same length. Cut the ducts to a length Y - 162mm. Refer to Fig. 24. The final section, dimension Z, of the flue system must include a section of plain duct assembly i.e. an extension assembly with the sockets removed. Reduce the final section, including the terminal assembly, by the appropriate amount i.e. Air duct Z 81mm and the flue duct Z - 51mm. Refer to Fig. 24. If Z<425mm it will be necessary to cut the air and flue ducts of the extension to a plain length of 100mm and reduce the length 16
of the terminal assembly i.e Z=350mm - remove 75mm from the terminal assembly. If Z in 425 - 725mm it is not necessary to cut the terminal assembly or use a second extension duct as the length can be set telescopically. If Z>725mm then two extension duct assemblies will be required, the first assembly being cut to length as plain tubes. If more than two extension ducts are needed in any section to achieve the required length then the final section of the assembly must not be less than 325mm without cutting the terminal assembly. NOTE: The flue duct of the final extension must be 30mm longer than the air duct. Each section must be connected to the previous section of the flue bend by fixing the flue ducts together and then similarly fixing the air ducts which engage the elbows. Fit the assembly as described in Section 12.10, 12.11 as appropriate. Make good the internal and external brickwork or rendering.
Fig. 25 - Elbow to Flue Turret Assembly.
Fig. 27 - Facia Connections Cover.

Flue Turret

Fig. 26 Vertical Adapter.

Flue Duct

1. Control Panel Fixing Screws 2. Facia 3. Control Panel Pivot Point 4. Connection Cover 5. Connection Cover Fixing Screws

Air Duct

Adapter
12.14 Completion of the Installation Check that all the connections on the appliance have been tightened. Remove the facia bottom panel. Refer to Fig. 27. Connect the mains electricity supply lead to the appliance and secure the cable clamp. Refer to Fig. 27. and 28. Check there is sufficient loose lead to allow the release of the facia panel assembly and that the earth lead of the mains supply cable is longer than the live and neutral leads. Fit the facia mounted clock. Full instructions are sent with the programmer. Refer to Fig. 28. and 29. Connect any external controls ensuring that the leads pass through the appropriate clamps. Refer to Fig.18. Test for gas soundness as described in BS6891. If the appliance is not to be commissioned immediately, replace the cabinet and facia bottom panel. Check that the gas and electricity services have been turned off.

Fig. 30. Appliance components and fixings (upper assembly).
Reset Button Flue Gas Test Point Fan assembly fixing screws (4)

Flue hood

Overheat thermostat

Auto air vent

Combustion chamber cover fixing clips (2)

Burner fixing screw

Fig. 31. Pump venting.
1. Electrical Connections Cover 2. Pump 3. Cap
Note: 1 bar = 10.2m = 33.5ft of water. 13.3 Set the System Pressure Fill the system until the pressure gauge is at 2.5 bar and check for leaks. Release water from the system using the relief valve test knob until the required system pressure is obtained, upto a maximum of 1.5 bar. Set the pointer on the pressure gauge to record the set system pressure. If the pressure indicated on the gauge is greater than 2.65 bar when operating at the maximum central heating temperature, an extra expansion vessel must be fitted to the system as close as possible to the appliance central heating return conection. The appliance (as despatched) can accomodate a system volume of 100 litres. Refer to BS7074 Part 1, BS5449 and table 8. If the system volume is greater then an extra vessel must be fitted as close as possible to the appliance central heating return connection and pressurised to the same figure as the integral vessel.

Fig. 33. Gas valve.

Gas valve sealing cap Min 3mm Allen key

Max 2mm Allen key

Fig. 32. Pressure relief valve.
4 Burner pressure test point Electrical connections modulator (Blue : Blue) Modulating solenoid Minimum / Maximum pressure adjuster - Allen key Note: Clockwise to increase and anti-clockwise to decrease the pressure 5 Inlet pressure test point 6 Main gas valve connections
Pressure relief valve. (Turn knob anti-clockwise to test).
13.4 Clock/Programmer The controls fitted to the appliance should be set up at this stage. 13.5 Operation Check that the gas and electricity supplies are turned off. Connect a pressure gauge to the gas valve inlet and outlet pressure test points. Refer to Fig. 33. Set the temperature control to maximum and the clock/programmer to operate continuously. Turn on the gas and electricity supplies. Turn on a hot tap to give a maximum flow rate. A continuous spark will occur until the burner is alight and sensed by the control circuit. The burner will remain at its maximum domestic hot water pressure. Refer to Table 1. It should not be necessary for the gas valve to be adjusted. Refer to Section 16.4.11. Note: The burner pressure is factory set and if, after checking that the dynamic (working) supply pressure is sufficient i.e 1919.5 mb approx, at the gas valve inlet pressure test point, the correct pressure cannot be obtained then Worcester Heat Systems Service Department should be contacted. If the appliance does not light then check that it is not in the 'Lock-out' state by pressing the reset button. Refer to Fig. 34. Turn off the hot tap. The burner pressure will drop to the minimum CH setting and will ramp up to the maximum central heating pressure. 19

14. Handover

14.1 Tell the user how to operate the appliance and hand over the Users Instructions leaflet. 14.2 Tell the user what to do if the heating system is not to be used in frosty weather. 14.3 Tell the user the sealed system set pressure. 14.4 Tell the user of the importance of regular servicing. Worcester Heat Systems Ltd. offer a comprehensive maintenance contract. 14.5 Set the system controls to the users requirements. 14.6 Complete and hand over to the user the Benchmark Log-Book.

Fig. 34. User controls.

4 Reset Button Mains Indicator C.H. Temperature Control System Pressure Gauge
15. Inspection And Service
15.1 SERVICING To ensure continued efficient operation of the appliance it must be checked and serviced as necessary at regular intervals. The frequency of servicing will depend upon the particular installation conditions and usage, but once per year should generally be adequate. The extent of the service required by the appliance is determined by the operating condition of the appliance when tested by fully qualified engineers. Any service work must be carried out by competent engineers such as British Gas or Corgi registered personnel. 15.2 PRE-SERVICE INSPECTION Check that the flue terminal and the terminal guard, (if fitted), are clear. If the appliance is in a compartment, check that the ventilation openings in the compartment door or walls are clear. See Section 6 - Air Supply. Check the system and remake any joints or fittings which show signs of leakage. Refill, vent and re-pressurise as described in Section 13.2. Operate the appliance and the system taking note of any faults. Measurement of the Flue Gases For consistency of results of the flue gas measurements it is necessary to have a constant output and for the appliance to be at equilibrium. Turn on a tap to create a hot water demand. Wait until the appliance reaches thermal equilibrium (approx. 10 minutes). Remove the test point sealing screw on the appliance top panel. See Fig. 17 and 30. Connect to the test point with a piece of tubing. Expected measurements should be between: For Natural Gas: 7.0 - 7.5% 0.003 - 0.007% Carbon Dioxide Carbon Monoxide
Fig.35. Appliance casing and control equipment fixings.
Bottom facia panel fixing screws (3)
Fig. 36. Appliance components and fixings (upper assembly).
After taking the measurement replace the sealing cap. IMPORTANT Disconnect the electrical supply at the mains and turn off the gas supply at the gas service cock on the appliance before servicing. After completing the service always test for gas soundness as indicated in BS 6891. 15.3 DISMANTLE THE APPLIANCE To carry out a full and comprehensive service of the appliance remove the following parts to gain access to the components which need to be checked or serviced. (a) Cabinet Front Panel. Remove by lifting off the supports. (b) Inner Casing Cover. Check that the electricity supply to the appliance is turned off. Remove the cabinet front panel. Unscrew the four screws securing the cover to the casing and lift off. See Fig. 35. (c) Facia Panel. Check that the electricity supply to the appliance is turned off. Remove the cabinet front panel. Unscrew the two upper screws as shown in Fig. 35. and hinge down the facia taking care not to damage the pressure gauge capillary tube or electrical connections. (d) Bottom panel. Unclip and remove the appliance bottom panel. (e) Fan. Remove the inner casing cover as detailed in Section 15.3(b) above. Carefully unplug the electrical connections and pull off the sensing tubes. Unscrew the four fixing screws and remove the fan assembly. See Fig. 36. (f) Combustion Chamber Front. Remove the inner casing cover. Undo the spring clips fixing the combustion chamber front taking care not to damage the insulation on removal. See Fig. 36. (g) Flue Hood Assembly. Remove the fan assembly as described in Section 15.3(e). Remove the combustion chamber front taking care not to damage the insulation. Lift and slide the flue hood assembly from the appliance. See Fig. 36. When refitting the hood ensure that the rear return edge passes under the lip at the rear of the combustion chamber. 21

Flue hood Flue Gas Test Point Fan assembly fixing screws (4) Auto air vent Burner fixing screw Combustion chamber cover fixing clips (2) Overheat thermostat
Fig. 37. Burner and electrode assembly.
Flame sense electrode Injector

16. Replacement Of Parts

16.1 IMPORTANT Switch off the electricity and gas supplies before replacing any components. After the replacement of any components, check for gas soundness where relevant and carry out functional checks as described in Section 13 - Commissioning 16.2 COMPONENT ACCESS To replace components it is necessary to remove one or more sections of the cabinet and cover plates within the appliance as described in Section 15.3. The facia panel may also need to be hinged down as described in Section 15.3 (c). 16.3 DRAINING THE APPLIANCE Check that the electricity supply to the appliance is turned off. Before removing any component holding water it is important that as much water as possible is removed from the appliance. (a) Central Heating Circuit. Turn off the central heating flow and return valves at the appliance. Open the pressure relief valve, make sure that the dust cap on the auto air vent is removed. See Fig. 31. Close the pressure relief valve when the flow has stopped. Some water will remain in the expansion vessel, pump and Gas to Water heat exchangers and extra care must be taken when removing these components. (b) Domestic Hot Water Circuit. Turn off the mains cold supply valve at the appliance and open the lowest hot water tap. A quantity of water will remain in the Gas to Water heat exchanger, extra care must be taken when removing this component. 16.4 COMPONENT REPLACEMENT 1. Automatic Air Vent. See Fig. 36 and 38. Remove the inner casing cover as described in Section 15.3 (b). Drain the central heating circuit as described in Section 15.3 (a). Unscrew air vent from the heat exchanger. Fit the replacement assembly ensuring thread sealant is applied and the dust cap is removed. Open the valves and fill and re-pressurise the system as described in Section 13.2. 2. Air Pressure Switch. See Fig. 41. Check that the electricity supply to the appliance is turned off. Remove the cabinet front panel as described in Section 15.3 (a) and lower the facia. Section 15.3(c). Carefully pull off the sensing tubes and the electrical connections from the switch. Remember to note their positions. Unscrew the two screws behind the Air Pressure Switch and remove the switch from the appliance. Fit the replacement switch in the reverse order ensuring that the electrical connections have been made to the correct terminals on the switch. Check that the sensing tubes are fitted correctly. 3. Fan. See Fig. 36. Check that the electricity supply to the appliance is turned off. Remove the fan assembly as described in Section 15.3(e). Fit the replacement fan in the reverse order. 4. Overheat Thermostat. See Fig. 30 and 36. Check that the electricity supply to the appliance is turned off. Remove the inner casing cover as described in Section 15.3 (b). Carefully pull off the two wires from the thermostat head. Undo the retaining nut on the top of the appliance and remove the retaining clip from the heat exchanger. Carefully withdraw the thermostat from the appliance. Fit the replacement thermostat in the reverse order ensuring that some heat sink compound is between the thermostat and the heat exchanger. 5. Gas to Water Heat Exchanger. See Fig. 38. Check that the electricity supply to the appliance is turned off. Drain the central heating circuit and domestic circuits as described in Section 15.3 (a) and (b). Remove the inner casing cover, fan, flue hood assembly, combustion chamber front, overheat thermostat, automatic air vent and combustion chamber side insulation as described in Sections 15.3 (b, e, f and g), 15.4 and 16.4 (4). Fit the replacement heat exchanger in the reverse order ensuring that all the fibre washers are correctly fitted and a layer of heat sink compound is on the thermostat. 22

(h) Burner Assembly. Remove the combustion chamber front as described in Section 15.3(f). Pull off the two spark electrode leads, disconnect the flame sense lead at the connector and remove the grommet. Undo the burner fixing screw. Lift up and remove the burner assembly from the appliance. See Fig. 37 15.4 SERVICE OF COMPONENTS Clean the Fan. Any dust or fluff should be removed with a soft brush or by blowing. Take care not to distort the pressure sensing device. Clean the Main Burner. Brush the blade tops and mixing tube with a soft brush and check that all the flame ports are clear. Remove any blockages with a non-metallic brush. Inspect the injector and clean with a soft brush. Replace the injector if it appears damaged. Do not use a wire brush or anything likely to cause damage. Replace the spark and sense electrodes if they appear damaged. Clean the Gas to Water Heat Exchanger. Clean the heat exchanger using a soft brush. Remove the deposits from the bottom of the combustion chamber. Do not distort any of the blades. Combustion Chamber Insulation. Examine and replace any pads that are damaged. Remove any dust or deposits using a soft brush. Re-assemble the appliance in the reverse order. Check that all components are in place and correctly fixed. Leave the cabinet front panel to be fitted after checking the operation of the appliance. 15.5 TEST THE APPLIANCE On completion of the service and reassembly of the appliance, check for gas soundness and the correct operation of the appliance as described in Section 13 - Commissioning. Refit the cabinet front panel and reset the controls to the users requirements.
Fig. 38. Combustion chamber.
Overheat Thermostat Heat exchanger
Hot water connections Central heating connections
Cut-outs in combustion chamber sides

Pump bulk-head connector

Flame Sense Electrode

Spark Electrode Assembly

Burner
Open the valves and fill and re-pressurise the system as described in Section 13.2. 6. Combustion Chamber Insulation. Check that the electricity supply to the appliance is turned off. If replacing the rear insulation the appliance must be drained as described in Section 16.3(a) and 16.3(b) and the gas to water heat exchanger removed (see 16.4.5). If changing the front or side pieces it is not necessary to drain the appliance. Remove the inner casing cover, combustion chamber front, fan and flue hood assembly as described in Sections 15.3 (b,e,f & g). Remove the fibre insulation pads to be changed and fit the replacements taking care not to damage them. If the system has been drained, open the valves and fill and repressurise the system as described in Section 13.2. 7. Burner. See Fig. 37. Check that the electricity and gas supplies to the appliance are turned off. Remove the burner assembly as described in Section 15.3 (h). Fit the replacement burner in the reverse order taking care not to damage the electrode leads. 8. Burner Injector. See Fig. 37. Remove the burner as described in Section 15.3 (h). Unscrew the brass injector from the manifold. Fit the replacement injector in the reverse order. 9. Spark Electrode Assembly. See Fig. 39. Remove the combustion chamber front as described in 14.3 (g) Carefully pull off the two electrode leads, Undo the M4 extended nut and remove the spark electrode assembly from the burner. Fit the replacement electrode in the reverse order, checking that the spark gap is 3.5 to 4.5mm.

GO TO CHECK M

Are leads breaking down?
Ignition coil faulty replace PCB

Replace leads

Does burner continue?
Is flame sense electrode in flame?
Ensure flame sense electrode in flame at minimum burner pressure
Is lead secure both ends?

Secure lead

HARNESS OK
Does gas pressure modulate?

GO TO CHECK N

Ignition OK
Air Pressure Switch Check
Remove BROWN and WHITE terminals from air pressure switch
With no demand, is a short-circuit observed at exposed APS terminals?
Air pressure switch faulty
Reconnect the WHITE & BROWN wire and remove the GREEN wire. Initiate a demand. Does the fan run?
Is there mains 230V at fan connector X4 pins 1 and 3?

PCB faulty

Fan or fan cable faulty
With fan running disconnect BROWN wire. (DO NOT touch chassis with it). Is a short circuit observed across exposed APS terminals?

APS OK

Gas Valve Check
Is gas pressure present at input to gas valve?

Ensure gas supply

Is live output present at X5 pins 1 & 2 relative to neutral at pin 3? Note: Readings to be taken within 9 seconds of a demand.

Faulty board Replace

Is gas pressure present at input to burner?

Gas valve OK

It is not possible to seperately test the gas valve and the supply lead. Relpace the gas valve or the lead.

Modulating Valve Check

Is minimum pressure observed at burner at all times?
Remove X6, measure resistance between pins 15 & 16
Is resistance nominally 125ohms?
Is pressure at burner always the same?
With pressure above minimum, remove Modureg Lead. Does pressure drop to minimum?
Faulty modulating valve. Replace gas valve
Reconnect X6 and measure voltage across modulating valve during operation

YES YES

Does voltage go above 6.25V?

Faulty PCB. Replace

Flow turbine Check
With boiler cold, slowly open HW tap. When flow reaches 3l/min does boiler ignite? (Flow can be checked using a measuring jug and stop watch)
Does the boiler ignite at a higher flow rate?

Faulty turbine. Replace.

Disconnect the 3 way in-line connector. Check that there is 5V DC output from the PCB at the connector. Red +5V Black 0V
Re-connect the 3 way connector and open a tap to run the turbine. Check that there is between 1.5 and 4.5 V DC across the green and black wires/terminals.
Turbine OK Faulty turbine. Replace

19. Component Parts List

Key No. G.C. No. Part Burner Assembly Natural Gas Injector Natural Gas Gas valve Natural Gas Air Pressure Switch Spark Electrode Assembly Flame Sensor Flame sensor Harness Ignition Harness Gas to Water Heat Exchanger Insulation Pack Auto Air Vent Pressure Gauge Pressure Relief Valve Pump with Harness Expansion Vessel PCB Boiler Control Temperature Thermistors CH Thermistor Clip DHW Thermistor Clip DHW Flow Regulator Gauze Filter Flow Turbine Fan Assembly Overheat Thermostat Fuse Pack Gasket Pack Manufacturers Reference Aeromatic Stereomatic Dungs Huba Buccleuch Buccleuch Buccleuch Buccleuch Giannoni WHS Intermes Cewal Caleffi Grundfos Winkelman Panhof Pactrol Elmwood AC 23/053595 O 4.5mm BM771 605.99530 Qty WHS Part No. 0
E01-892 375-697 E01-612 E01-930 E01-598 E01-599 E01-600 E01-601 299-506 375-699 E01-602 E01-603 E58-079 E04-582 E01-900 299-495 E01-605 324-822
3141 3bar Special (8Ltr) 389mm Dia 423100

E01-357 E01-610

Blue WHS SIKA VTY FIME Ranco WHS WHS
ACCESSORIES 299-360 E05-341
Mechanical Programmer Kit Mini Expansion Vessel Kit
DIEHL Including new pipe and Expansion Vessel

192 188

FLUE OPTIONS E01-943 E01-944 E01-945 E01-946 E01-058 E01-059 Telescopic Horizontal Flue Kit Extension Flue Kit Vertical Flue Kit Vertical Flue Adaptor Internal Fixing Kit Flue Elbow Kit Flue Elbow Kit 425 - 725mm 750mm 191 014
Telescopic Flue 90 deg. 45 deg.
This manual is to be used in conjunction with the variant part number of the bar code below:
Worcester Heat Systems Limited (Bosch Group), Cotswold Way, Warndon, Worcester WR4 9SW. Telephone: (01905) 754624. Fax: (01905) 754619. Technical Helpline (08705) 266241. www.worcester-bosch.co.uk
This booklet is accurate at the date of printing but will be superseded and should be disregarded if specifications and/or appearances are changed in the interests of continued improvement. All goods sold are subject to our official Conditions of Sale, a copy of which may be obtained on application.
PUBLICATION 114 751a (11/07)