Worcester 24 SI II LPG User guide

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24Si II / 28Si II

WALL MOUNTED COMBINATION BOILERS FOR CENTRAL HEATING

AND MAINS FED DOMESTIC HOT WATER

INSTALLATION AND

SERVICING INSTRUCTIONS

This appliance is for use with Natural Gas or LPG (Cat II 2H3P TYPE C12 & C32) 24SiII GC NUMBER 47 311 65 (N.G.) GC NUMBER 47 311 66 (L.P.G.) 28SiII GC NUMBER 47 311 67 (N.G.) GC NUMBER 47 311 68 (L.P.G.)

GB/IE

APPLIANCE OUTPUTS

Domestic Central Heating

Hot Water

24Si II 28Si II 24Si II 28Si II Minimum 6.9 kW 8.1 kW 6.9 kW 8.1 kW Maximum 24 kW 28 kW 24 kW 28 kW

IMPORTANT: THESE INSTRUCTIONS APPLY IN THE GB/IE ONLY

AND MUST BE LEFT WITH THE USER OR AT THE GAS METER

It is IMPORTANT to read the instructions before starting work - they have been

written to make the installation easier and prevent hold-ups.

Worcester supports the

Benchmark code of practice

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1.1 Gas Safety (Installation & Use) Regulations 1998:

The appliance is suitable for installation in GB/IE only and should be installed in accordance with the rules in force. It is the law in GB that a competent person in accordance with the above regulations installs all gas appliances. Failure to install appliances correctly could lead to prosecution. It is in your interest, and that of safety, to ensure compliance with the law.

1.2 The manufacturers notes must not be taken, in any way, as overriding statutory obligations.

1.3 The compliance with a British Standard or European Norm does not, in itself, confer immunity from legal obligations.

1.4.1 The installation of the appliance must be in accordance with the relevant requirements of the Gas Safety Regulations, current IEE Regulations, Building Regulations, Building Standards (Scotland) and local water by-laws.

1.4.2 In Eire the installation must be carried out by a competent person and installed in accordance with IS 813, Domestic Gas Installations (Edition 2), the current building regulations and the electrical installation must follow the ETCI rules.

1.5 The installation should follow the recommendations of the following British Standards unless otherwise indicated. BS5440:1 - Flues and ventilation for gas appliances: Flues BS5440:2 - Flues and ventilation for gas appliances: Air supply. BS5449 - Central heating for domestic premises. BS5482 - Domestic propane gas burning installations. BS5546:1 - Installation of gas hot water supplies. BS6700 - Domestic water supply in buildings. BS6798 - Installation of gas fired hot water boilers. BS6891- Low pressure gas pipework installations upto 28mm (R1). BS7593 - Water treatment. BS7671 - Requirements for electrical installations.

1.6 The appliance does not contain any substances which are harmful to health.

1.7 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 are used.

1.8 LPG Installation:

The appliance shall not be installed in a room or internal space below ground level when it is intended for use with LPG. This does not preclude the installation into rooms, which are basements with respect to one side of the building but open to the ground on the opposite side.

1.9 These instructions cover, as far as possible, the foreseeable situations, which may arise. Contact The Worcester Technical Department, Telephone: 08705 266241, for advice on specific installations.

2.1 The initiative is the new code of practice to encourage the correct installation, commissioning and servicing of domestic central heating boilers and system equipment.

The 'checklist' 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.

A declaration of conformity (Refer to IS 813 Annex D1) must be completed by the installer and a copy supplied to the appliance operator for boilers installed in Eire. Without the completion of the checklist and/or declaration, 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.

Service:

To ensure continued efficient operation of the appliance it must be checked 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 registered engineers (CORGI in GB).

2.2 General Information

The appliance is set to give the maximum output of 28 kW [28Si II] or 24kW [24Si II] to the domestic hot water and to the heating system. The hot water flow rate is limited to a nominal 10 l/min [28Si II] or 8 l/min [24Si II] at a maximum temperature rise of 40°C. The sanitary water section of the appliance is suitable for mains water pressure of upto 10bar. Kits are available to convert the appliance from Natural Gas to Propane operation and vice versa.

2.3 Electrical Supply

230V - 50Hz. Load 180 watts. External fuse 3A (to BS1362), Internal fuses F1 - 2A, F2 - 1.25A (20mm).

2.4 Gas Supply

The appliances require a maximum of 3.25 m

/h of natural gas

(G20) or 1.25 m

/h of propane (G31) [28Si II] or 2.8 m3/h of

natural gas (G20) or 1.08 m

/h of propane (G31) [24Si II]. 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) or 37mbar (G31) at the appliance, which is equivalent to about 19 mbar or 36 mbar at the gas valve inlet pressure test point.

2.5 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. This 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 no need for cooling ventilation openings in

2. Introduction1. Installation Regulations

1. Installation Regulations . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 2 10. Electrical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 9

2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 2 11. Installing the Appliance . . . . . . . . . . . . . . . . . . . . . . . . . . Page 12

3. Technical Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 4 12. Commissioning the Appliance . . . . . . . . . . . . . . . . . . . . Page 19

4. Siting the Appliance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 7 13. Handover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 21

5. Flue Terminal Positions . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 7 14. Inspection and Service . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 21

6. Air Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 8 15. Replacement of Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 24

7. Sealed System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 8 16. Short Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 30

Open Vent System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 8 17. Operational Flow Diagram . . . . . . . . . . . . . . . . . . . . . . . Page 32

8. Domestic Hot Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 9 18. Fault Finding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 34

9. Gas Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 9 19. Conversion Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . Page 42

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Contents

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the compartment provided the increased clearances are used. See Fig. 5. The spaces specified for servicing must be maintained.(See Table 8). There is space for the service pipes to pass at the back of the appliance.

2.6 Flue

Multi-Directional Horizontal Flue Kit.

Standard Flue Kit can be adjusted from 425mm to

725mm without cutting. The minimum length is 265 mm with cutting. Extended flue lengths are available upto a maximum of 4m for natural gas appliances and 2.5m for LPG. Optional 45° and 90° flue bend kits are available NOTE: When using flue bends the maximum flue length is reduced (see Section 11.12). If access to the flue terminal will be a problem then a kit is available to enable the horizontal flue to be fitted from inside the house. Do not allow the flue terminal to the outside wall to become obstructed or damaged. A Tower guard type K2 CG 393553 is available from Tower Flue Components, Vale Rise, Tonbridge TN9 1TB. A vertical flue system is available.

2.7 Controls

The appliance has controls for switching the appliance On or Off, [this does not electrically isolate the appliance] for adjusting the CH and DHW temperatures. The CH control knob also switches the CH off and on. A programmable 'wire free' room thermostat or a facia mounted programmer or clock is available. A room thermostat and/or an externally mounted programmer for mains voltage operation may be connected to the appliance.

2.8 System

All dirt must be flushed from the system before connecting the appliance. The system can be pre-piped and flushed before the appliance is fitted. The connections in the system must withstand an operating pressure of upto 3 bar. Radiator valves must conform to BS2767: 10:1977. Table 3 gives the pump head available for the system and the required temperature differential. A drain cock must be fitted to the lowest point and an air vent to the highest point of the system.

2.9 Showers, Bidets, Taps and Mixing Valves

All taps and mixing valves must be suitable for the available mains pressure and temperatures upto 65

C. It may be necessary to fit a pressure reducing valve. Hot and cold mains fed water can be supplied to overrim bidets but is subject to local water company requirements. The flow of water from individual outlets varies on all mains fed systems that are not fitted with flow balancing valves. Thermostatically controlled or pressure equalising shower valves give extra comfort and protection. If a pressure equalising valve is fitted then the domestic hot water temperature should be set to maximum.

2.10 Safety The appliance must not be operated with the inner casing cover removed or without being full of water and pressurised. The gas and electricity supplies must be turned off before working on the appliance.

Temperature monitoring controls are fitted to prevent overheating. Automatic frost protection is provided together with automatic pump seizure protection. The gas valve solenoids are automatically checked for gas soundness.

IMPORTANT: Where back-flow prevention devices, including water meters, are fitted the expansion of hot water into cold water main can be prevented. This can result in a pressure build-up that may cause damage to the boiler and household devices such as showers, washing machines etc.

In these cases we recommend that a mini-expansion vessel be fitted adjacent to the boiler in the cold water supply pipe.

2.11.1 Operation Central Heating:

A demand for heat will ignite the burner. It will operate at minimum pressure for 15 seconds before increasing to the maximum pressure over a period of 1 minute and then automatically match the system requirements. At the end of the demand the burner will go out, the pump will continue to run for upto 4 minutes or the fan for 15 seconds. There is an anti-cycle time of 3 minutes.

2.11.2 Domestic Hot Water:

A demand for hot water will light the burner. The pressure will immediately rise to maximum. At the end of the demand the fan will continue to run for 15 seconds if there is no heating demand. There is an anti-cycle time of 10 seconds.

2.11.3 Domestic Hot Water and Central Heating Mode.

The demand for hot water will override the CH function when the appliance is in the heating and hot water mode of operation. In winter it may be necessary to reduce the flow at the taps to maintain the delivery temperature.

Fig. 1. Facia controls

Fig. 2. Water flow diagram.

2 3

7 6

1. Mains On/Off control 5. Optional programmer

2. CH temperature control 6. Lockout indicator light and

3. DHW temperature control reset button

4. System pressure gauge 7. Burner indicator light

2 3 4

1. CH flow 7. Circulating pump

2. Domestic hot water flow 8. Expansion vessel

3. Domestic hot water supply 9. Primary heat exchanger

4. CH return 10. Automatic air vent

5. Pressure relife valve discharge 11. By pass

6. Domestic water flow turbine

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3. Technical Data

MAXIMUM AVAILABLE PUMP HEAD

BOILER OUTPUT HEAD MIN. FLOW RATE

kW Metres L/min. °C

6.9 5.2 9 11

24 1.8 22 15.5

28 1.8 22 18

Table 3

MECHANICAL SPECIFICATIONS 24Si II 28Si II

CENTRAL HEATING FLOW - COMPRESSION 22mm 22mm

RETURN - COMPRESSION 22mm 22mm

COLD WATER INLET - COMPRESSION 15mm 15mm

DOMESTIC WATER FLOW - COMPRESSION 15mm 15mm

GAS INLET Rp

⁄4 Rp 3⁄4

RELIEF VALVE DISCHARGE (PUSH-IN) 15mm 15mm

CASING HEIGHT 740mm 740mm

CASING WIDTH 400mm 440mm

CASING DEPTH 360mm 360mm

WEIGHT - LIFT 36kg 36kg

WEIGHT - PACKAGED 48kg 50kg

WEIGHT - DRY 39kg 40kg

Table 4

FLUE DETAILS

HORIZONTAL FLUE G20 LPG

WALL HOLE DIAMETER EXTERNAL FIX mm 110 110

INTERNAL FIX mm 130 130

STANDARD FLUE MINIMUM LENGTH mm 275/*425 275/*425

MAXIMUM LENGTH mm 725 725

EXTENDED FLUE MAXIMUM LENGTH mm 4000 2500

FLUE ASSEMBLY DIAMETER mm 100 100

Table 2.

FLOW/RETURN

DIFFERENTIAL

* NOTE : Minimum uncut length

NOMINAL BOILER RATINGS (10 Minutes After Lighting)

BOILER ADJUSTED FOR G20 (Natural Gas)

OUTPUT INPUT (Net) GAS RATE

kW kW m bar. m

8.1 9.2 0.7 0.97

28 30.7 13.1 3.25

BOILER ADJUSTED FOR G31 (Propane)

8.1 9.2 2.8 0.38

28 30.7 34.5 1.25

Table 1. 28Si II

BURNER

PRESSURE

NOMINAL BOILER RATINGS (10 Minutes After Lighting)

BOILER ADJUSTED FOR G20 (Natural Gas)

OUTPUT INPUT (Net) GAS RATE

kW kW m bar. m

6.9 7.9 0.9 0.84

24 26.4 12.1 2.8

BOILER ADJUSTED FOR G31 (Propane)

6.9 7.9 3.1 0.32

24 26.4 35.0 1.08

Table 1. 24Si II

BURNER

PRESSURE

Natural Gas: Net Input = Gross Input x 0.901 LPG (Propane): Net Input = Gross Input x 0.922

NOTE: With longer flue lengths, not using a restrictor, the minimum burner pressure will rise, naturally due to the flue, to 1.1mbar on G20 appliances only.

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PERFORMANCE SPECIFICATIONS 24Si II 28Si II

PRIMARY WATER CAPACITY litres 2.0

IP RATING (WHOLE OF BOILER) IP 20

MAXIMUM MAINS INLET PRESSURE bar 10

MINIMUM MAINS INLET PRESSURE (WORKING) FOR MAXIMUM FLOW bar 1.0

MINIMUM MAINS INLET PRESSURE (WORKING) FOR OPERATION bar 0.25

DOMESTIC HOT WATER TEMPERATURE RANGE °C 40 - 60

MAXIMUM CENTRAL HEATING FLOW TEMPERATURE °C 82 (nom)

MAXIMUM CENTRAL HEATING SYSTEM SET PRESSURE bar 2.65

MINIMUM CENTRAL HEATING SYSTEM PRESSURE bar 0.5

OUTPUT TO CENTRAL HEATING & DHW kw NATURAL GAS (G20) 24 28

LPG - PROPANE (G31) 24 28

DOMESTIC HOT WATER SPECIFIC RATE - 30°C RISE l/min 11.5 13.5

MAXIMUM DOMESTIC HOT WATER FLOW RATE - 40°C RISE l/min 8.5 10

FLUE GAS MASS FLOW RATE 14.9 17.4

FLUE GAS TEMPERATURE °C 146.0

NOx CLASSIFICATION FOR BOTH 24 & 28Si II Class 3

SEDBUK NUMBER 78.0 78.2

SEDBUK NUMBER LPG 80.5 80

SEDBUK BAND* D D

GAS SUPPLY SYSTEM - BASED ON NG (G20)

TOTAL LENGTH OF GAS SUPPLY PIPE (COPPER) metres

3 6 9 12

GAS DISCHARGE RATE - PRESSURE DROP mbar. m

/h PIPE DIAMETER mm

8.7 5.8 4.6 3.9 22

18.0 12.0 9.4 8.0 28

Table 7

CLEARANCES (mm)

INSTALLATION SERVICE UNVENTILATED COMPARTMENT

ABOVE FLUE ELBOW 30 3 0 15 0 IN FRONT OF APPLIANCE 600 600 *240 BENEATH APPLIANCE 200 200 200 RIGHT AND LEFT HAND SIDE 10 10 80

Table 8

SYSTEM CAPACITY

TOTAL SYSTEM VOLUME litres

INITIAL INITIAL CHARGE PRESSURE bar PRESSURE bar 0.5 1.0 1.5

1.0 57 75 N/A

1.5 31 42 52

Table 9

Refer to Section 6. * Front clearance is to a removable panel (eg. door)

DOMESTIC HOT WATER TEMPERATURE RISE

DISCHARGE RATE l/min 7 8 9 10 TEMPERATURE RISE °C 24kw 49 43 38 34 TEMPERATURE RISE °C 28kw 57 50 45 40

Table 6

Table 5

* The value is used in the UK Government Standard Assessment Procedure [SAP] for the energy rating of dwellings. The test data from which it has been calculated have been certified by the GASTEC notified body.

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Fig. 4. Appliance casing dimensions and

required clearances (side view).

All dimensions in mm

Fig. 6. Side flue opening

24Si II 28Si II A CH Flow = 55 75 B DHW Flow = 120 140 C Gas = 185 205 D Cold Water Inlet = 250 270 E CH Return = 315 335 F Relief Valve Discharge = 375 395

Fig. 3. Appliance casing dimensions and required clearances for installation/servicing

All dimensions in mm

150

190

(A, B, C, D,)

A B C D E

View of underside of appliance showing

connections

Valves shown closed.

Fig. 7. Pipework connections

All dimensions in mm

24Si II = 400

11 4

600

740

230

360

200

All dimensions in mm

11 4

28Si II = 440

Fig. 5. Unventilated compartment clearances

230

200mm

150mm from the top of the flue elbow

80mm

240mm

From a removable panel eg. door

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The appliance may be installed in any room but refer to the requirements of the current IEE Regulations and, in Scotland, the relevant electrical provisions of the Building Regulations with respect to the installation of appliances in rooms containing baths or showers. In Eire refer to the ETCI rules for electrical installations. Where a room sealed appliance is installed in a room containing a bath or shower, any switch or appliance control using mains electricity must NOT be able to be touched by a person using the bath or shower. The IP rating of the appliance may only allow it to be located in specific 'zones'. Refer to, in GB, Electrical Regulations 16th Edition. The appliance is NOT suitable for external installation No special wall protection is required. The wall must be able to support the weight of the appliance. Refer to Table 4. The specified clearances must be available for installation and servicing. Refer to Table 8 and Fig.3, 4. The appliance can be installed in a cupboard/compartment to be used for airing clothes providing that the requirements of BS6798 and BS5440 Part 2 are followed. Refer to Section 2.5. The airing space must be separated from the boiler space by a perforated non-combustible partition. Expanded metal or rigid wire mesh is acceptable provided that the major dimension is less than 13mm. The clearance between the front of the appliance and the cupboard or compartment door should be not less than 75mm. LPG Installation. Refer to Section 1.8.

The flue system must be installed following the requirements of BS5440: 1. In Eire the flue termination must be sited as described in Table 5 of the current edition of IS 813. Standard horizontal flue kit length is 275 – 725mm with extension kits for flues upto 4m for natural gas and 2.5m for LPG. The terminal must not cause an obstruction or the combustion products a nuisance. Under some conditions the terminal might steam and positions where this might be a nuisance should be avoided. Refer to Fig 8. If the terminal is less than 2m above a surface to which people have access then a guard must be fitted. The guard must be evenly spaced about the terminal and fixed with plated screws. A Type K2 guard is available from Tower Flue Components, Vale Rise, Tonbridge, TN9 1TB.

5. Flue terminal positions4. Siting The Appliance

D,E.

Fig. 8. Siting of the flue terminal.

TERMINAL POSITION MIN. DISTANCE

Aa– Directly below an opening, air brick,

opening windows etc. 300 mm

B– Above an opening, air brick,

opening windows etc. 300mm

C– Horizontally to an opening, air brick,

opening windows etc. 300mm D– Below gutters, soil pipes or drain pipes. 75mm E– Below eaves. 200 mm F– Below balconies or car port roof. (Lowest point) 200 mm G– From a vertical drain pipe or soil pipe. 150 mm H– From an internal or external corner. 300 mm I– Above ground, roof or balcony level. 300 mm J– From a surface facing the terminal. 600 mm K– From a terminal facing the terminal 1200 mm L– From an opening in a car port (e.g. door

window) into dwelling. 1200 mm M– Vertically from a terminal on the same

wall. 1500 mm N– Horizontally from a terminal on the same

wall. 300 mm O– From the wall on which the terminal

is mounted N/A

P– From a vertical structure on the roof N/A

Q– Above intersection with roof N/A

NOTE N/A = Not applicable

In addition, the terminal should be not nearer than 150mm (fanned draught) to an opening in the building fabric formed for the purpose of accommodating a built-in element such as a window frame.

Advice should be taken if the terminal is in close proximity to surfaces which may be of plastic materials ie. car-ports, gutters etc.

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6.1 A separate vent for combustion air is not required. Refer to BS5440:2. If the appliance is in a cupboard or compartment then, because of the low casing losses, it is not necessary to have any cooling ventilation for the boiler. Refer to Section 2.5. There must be increased clearance around the appliance to allow the free movement of the air. Refer to Table 8 and Fig 3, 4 and 5.

6.2 If the appliance is to be fitted in a cupboard or compartments with less clearance than the minimum clearances given in Section

4. (Siting The Appliance) then permanent vents for cooling are required. One at high level and one at low level, either direct to outside air or to a room. Both vents must pass to the same room or be on the same wall to the outside air.

6.4 The minimum free areas required are:

The system must comply with requirements of BS6798 and BS5449 and must not be operated without being full of water and correctly pressurised. Refer to Fig 8. The pressure relief valve will operate at 3 bar. The discharge pipe, of 15mm diameter, must be directed as such that the discharge of water or steam is visible, will not discharge onto the occupants of the premises or cause any damage to the premises, in particular any electrical components or wiring. The expansion vessel, to BS4814, has a capacity of 8 litres charged to 0.5 bar, which is suitable for a static head of 5 metres. A schraeder type valve allows the pressure to be increased if the static head is greater than 5 metres. If the expansion vessel fails then it must be replaced with the designated spare part. Refer to BS 7074:1, BS5449 and Table 9 for a guide to the available system capacity. The maximum system design pressure is 1.5 bar. If the pressure is above 2.65 bar when the appliance is at maximum temperature then an additional expansion vessel must be fitted as near to the appliance as possible in the return pipe. The pressure gauge shows the system pressure. Fill and pressurise the system through a WRAS approved filling kit. Refer to Fig. 10 and 11. An optional kit is available. Refer to Section 16. The system and the appliance must be fully vented. Repeated venting loses water from the system, which must be replaced. The make-up connection must be close to the appliance in the heating return pipe through an approved non-return valve. Refer to current building regulations or Good Practice Guide 302 which lists the requirements.

Plastic Pipes

Plastic pipes must not be directly connected to the boiler. A copper to plastic transition piece should be positioned a minimum of 600mm from the boiler. A plastic pipe with a polymeric barrier should be used. The connection to the mains water supply must have the approval of the local Water Company. The pump is set at maximum and should not be adjusted. All connections in the system must withstand a working pressure of up to 3 bar. The radiator valves must conform to BS 2767:10 and other valves to BS1010.

Open Vent System

This appliance is NOT suitable for connection to an open vent system.

7. Sealed System6. Air Supply

Fig. 9. Sealed primary water system.

Lockshield valve

Radiator valve

Heating return

Hot water out

Water main

British Standard stop valve. Fixed spindle type

NOTE: A drain cock should be installed at the lowest point of the heating circuit and below the level of the appliance.

Mains cold

water

Heating flow

APPLIANCE

Refer to

'Water Flow

Diagram'

Fig.2.

Cold water inlet

POSITION OF AIR FROM AIR DIRECT

AIR VENTS THE ROOM FROM OUTSIDE

HIGH LEVEL 307cm

154cm

LOW LEVEL 307cm

154cm

POSITION OF AIR FROM AIR DIRECT

AIR VENTS THE ROOM FROM OUTSIDE

HIGH LEVEL 264cm

132cm

LOW LEVEL 264cm

132cm

24 kW

28 kW

Page 9

It may be necessary to contact the local Water Company before connecting the appliance.

Where back-flow prevention devices, including water meters, are fitted the expansion of hot water into cold water main can be prevented. This can result in a pressure build-up that may cause damage to the boiler and household devices such as showers, washing machines etc. In these cases we recommend that a mini-expansion vessel be fitted adjacent to the boiler in the cold water pipe.

The last 600mm of mains water pipe before the appliance must be in copper. The domestic hot water circuit of the appliance is suitable for a mains pressure of upto 10bar. A pressure reducing valve must be fitted if necessary. A mains water supply isolating valve is fitted. The maximum hot water flow rate is set at the factory to 8 l/min [24Si II] and 10 l/min [28Si II] giving a nominal temperature rise of 40

C with the temperature control at maximum. This rate is equivalent to a Specific Rate of 11.5 l/min [24Si II] and 12.9 l/min [28Si II] at a rise of 30

C. Refer to Table 6. The temperature rise, upto the maximum set by the user, is maintained by the automatic modulation of the heat input. In winter, when the water temperature is lower it may be necessary to reduce the water flow at the tap or shower to maintain the maximum delivery temperature. It is recommended that long pipe runs to taps or showers are insulated to prevent the rapid cooling of the water. Hot and cold taps and mixing valves must be suitable for the available mains pressure. No anti-syphonage arrangements are necessary for fixed head showers. The hose of a loose-head shower must be fixed so that the shower head cannot get closer than 25mm to the top edge of the bath to prevent its immersion in the water. Alternatively the shower can be fitted with an anti-syphonage device at the flexible hose connection. Thermostatically controlled or pressure balancing shower valves will give extra comfort and guard against extreme temperature. Hot and cold mains water direct to a bidet is, subject to the approval of the local water company, permissible provided that the bidet is of the overrim flushing type. The outlets must be shrouded and unable to be fitted with a hand-held spray. No antisyphon arrangements are needed. LIME SCALE: In areas of temporary hardness [>200ppm of calcium carbonate] it is suggested that a proprietary scale reducer is fitted in the mains cold water connection to the appliance. Installation of a scale inhibitor assembly must be in accordance with the requirements of the local Water Company. The water hardness can be determined by reference to the local Water Company. An isolating valve should be fitted to allow servicing.

The appliance requires a maximum of 2.8 m

/h [24Si II],

3.25m

/h [28Si II] of natural gas (G20) or 1.08 m3/h [24Si II],

1.25m

/h [28Si II] of propane (G31). Refer to Table 7. A natural gas appliance must be connected to a governed meter. The installation and connection of the gas supply to the appliance must be in accordance with BS6891. The meter (NG) or regulator (LPG) and the pipework to the appliance must be checked, preferably by the gas supplier, to ensure that a dynamic pressure of 20mbar for natural gas or 37mbar for propane is available at the appliance (contact gas supplier if in doubt) equivalent to about 19mbar [NG] or 36mbar [LPG] respectively at the gas valve inlet pressure connection and that the gas flow is adequate for all the installed gas appliances operating together.

Mains supply: 230V ~ 50 Hz 180watts. External fuse 3A to BS1362. Internal fuses F1-T2A, F2-TI.25A (20mm). Spare internal fuses are supplied with the appliance. The mains cable must be 0.75mm

(24x0.20 mm) to BS6500 Table 16 and must be connected to the terminal ST2 marked L (red or brown lead), N (black or blue lead) and the Earth stud (green or green/yellow lead) and secured with the cable clamp. The Earth lead must still be slack when the other leads are taut. Refer to Fig 14 and 15.

The appliance must be earthed.

The wiring between the appliance and the electrical supply shall comply with current IEE wiring regulations (and any local regulations which apply) for fixed wiring to a stationary appliance. NB. It must be possible to completely isolate the appliance with at least 3mm contact separation in both poles. A room thermostat or externally mounted programmer must be suitable for mains voltage operation. The leads must be securely fixed in the cable clamps (see Fig. 35) A facia mounted digital programmer or mechanical timer or receiver for wireless programmable room thermostat is available as an optional extra. Instructions are supplied with the product. On very rare occasions it may be necessary to fit an external frost thermostat to protect remote parts of the system. In this case refer to the WHS Technical Department for information, Tel: 08705 266241.

10. Electrical

8. Domestic Hot Water

9. Gas Supply

Fig 10 - System Fill

Fig 11 - System make up

1.Central Heating Return

2.Auto Air vent

3.Non-return Valve

4.Make-up Vessel

5.Stop Cock

6.Fill Point

300mm Above

the highest point

of the system

Heating

return

Stop cock

Hose union

Temporary hose

Non return

valve

Non return

valve

Test cock

Mains water

supply

Page 10

Control Board

Fig. 12. Wiring diagram.

Fan

Flame sense electrode

Spark electrode

Spark Generator

Mains in

Link

CH sensor (front of heat exchanger)

Flow turbine

ST16

2 blue

green

2 green

brown

blue

brown

white

red

yellow

ST2

ST15

ST1

Pump

Gas valve

2 green

white

black

Overheat cut-off device

DHW sensor

Air

Pressure

Switch

black

green

Safety

valve

red

green/yellow

2 brown

Safety

valve

Regulator

valve

Earth tabs

small tab=L high speed (red) medium tab = L low speed (white) large tab=N (black)

ST5

Code Plug

black

red

black

blue

black

blue

Page 11

Fig. 13. Functional flow diagram.

On/Off

switch

ST2

(LS)

ST2

ST1

centre

ST15

right

Pump

Fan

ST2 Pin N

Optional link

Room

thermostat

Transformer

Fuse F2

(1.25A Slow)

Fuse F1

(2A Slow)

ST2 Pin L

LIVE

Electronics

Inputs

Outputs

Spark Indicators

Settings

Regulator valve

Spark

electrodes

Error

indicator/reset

Red

Main valve

Flow sensor

CH sensor

DHW sensor

Air pressure switch

Flame sense

Overheat cut-off

24V programmer (if applicable)

Gas valve mode switch

CH Control knob

DHW control knob

Convert AC to low

voltage electronics

Electronics/

microprocessor

(Safety Low Voltage)

Flame detect

indicator

Red

ST2

centre pole

(Ls)

(for other features)

low

high

Electronics

ST1

right

Reset button

white

red

Page 12

NOTE: READ THIS SECTION FULLY BEFORE COMMENCING THE INSTALLATION.

11.1 General

The appliance is only suitable for fitting to a sealed system. The flue must be installed as specified in BS5440:1 and the current Building Regulations.

11.2 Unpacking

Remove the appliance from its packaging and check the contents against the packing list. Unscrew the service connections and remove the wall mounting assembly. NOTE: The wall mounting assembly can be removed from the carton without having to remove the boiler.

11.3 Site Preparation

Check that the correct position for the appliance has been chosen. Refer to Section 4 and Table 8. Check that the wall is flat and will support the weight of the appliance. Refer to Table 4.

11.4 Fixing Holes and Flue Opening

Hold the wall mounting assembly or template against the wall. Check that the assembly or template is level. Mark the position of the fixing holes and the flue opening. Refer to Fig 16. The diamond cut-out indicates the centreline of the appliance. Mark the centrelines of the pipe connections to aid the preplumbing of the system pipework. Pre-plumbing is not recommended if no movement in the pipes is available. Check the position of the fixing points and 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].

11.5 Wall Mounting and Manifold Assembly

Fit the plugs and insert the bottom screws. Check that all service valves are closed. Offer the assembly to the wall utilising the keyhole slots on the manifold assembly and fix to the wall. Refer to Fig 16 and 17. Check that the assembly is properly aligned before tightening the screws.

11.6 Gas and Water Pipes

Remove the gas cock and fix the appropriate fitting to connect the inlet pipe and refit. Refer Fig 17. If it is necessary for any of the pipes to run up the back of the appliance then they must be arranged to pass behind the expansion vessel. Refer to Fig 3. 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.

11. Installing The Appliance

Fig. 16. Wall mounting assembly



218



480



338

740

367

All dimensions in mm

Fig. 14. Access to internal fuses and

electrical connections.

Fig. 15 . Mains electricity connections.

1. Connection cover fixing screws

2. Connection cover

3. Control panel

4. Connections

230V

MAINS

230V

Page 13

11.7 Install the Boiler

Pull off the clip on facia cover and remove the cabinet by unscrewing the two fixing screws, releasing the sides and lifting from the top location. Check that the gas and water valves are closed. Refer to Fig 17. Fit the new seals, in the hardware pack, to the service valves on the manifold.

Lift the appliance to the wall, engage in the top support and lower onto the manifold assembly. 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. Lower the facia to gain access. The pipe must not be less than 15mm in diameter and must run continuously downward outside the appliance. Refer to Fig 20.

Wall

Frame

Wall

Frame

Flow

DHW

Flow

Gas

DHW

Cold Inlet

Return

Fibre

Washer

Fig. 17 . Manifold assembly

All dimensions in mm

Fig. 20 . Relief valve drain connection

Fig. 18 . Facia cover

1. Appliance

2. Controls

3. Facia cover

4. Facia cover clips (4)

Fig. 19 . Wall mounting frame

1. Wall mounting frame

2. Hanging bracket

3. Appliance

4. Support hook

1. Pump

2. Boiler drain

3. Pressure gauge capillary

4. Relief valve

5. Relief valve drain connection (push fit)

Page 14

11.8 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.

Fit the flue restrictor ring by unscrewing the flue spigot from the boiler. Refer to Fig. 22. The standard telescopic flue assembly is suitable (without cutting) for flues from 425mm up to 725mm measured from the centre-line of the boiler flue outlet to the outer face of the wall. Refer to Fig.23. The minimum length of the standard flue, after cutting is 275mm. If L is greater than 725mm then extension duct kit/s will be required

- each kit extends the flue by 750mm up to a maximum of 4000 mm for natural gas boilers and 2500mm for LPG. See table below.

EXTENSION MAXIMUM FLUE LENGTH mm

1 1475 2 2225 3 2975 4 3725 5 4000

11.9 Measure and Cut the Ducts. General: Cut the ducts as necessary, ensuring that the cuts are

square and free from burrs. Always check the dimensions before cutting. Measure the distance L. Refer to Fig. 23, 24, 25 and 26.

The standard flue can be telescopically adjusted to any length between 425mm and 725mm measured from the centre of the turret without the need to cut the ducts. Fix the flue assembly together using the self-tapping screws provided. Refer to Fig. 23.

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 eg. if L=350 – remove 75mm (425-350) from each

assembly.

Fig. 22. Flue spigot and restrictor

Fig. 21. Inner case and facia fixing

Fig.23. Standard flue assembly

Fixing screw

Flue turret assembly

Appliance casing

Telescopic adjustment

Terminal assembly

1. Inner casing cover

2. Cabinet fixing screws (4)

3. Inner casing cover fixing screws (2)

4. Inner casing cover fixing screws (2)

5. Facia control panel

6. Controls connector cover

7. Controls connector cover fixing screws (2)

8. Programmer (optional)

9. Facia control panel fixing screw

10. Top support lug (2)

11. Bottom support lug (2)

RESTRICTOR RINGS

Flue length 24Si II 28Si II

Horizontal up to 725mm 76mm 78mm Horizontal above 725mm None None LPG Horizontal up to 725mm 76mm 77mm Vertical terminal length only 1200mm 78mm 82mm Vertical flue greater than 1200mm None None

1. Flue spigot fixing screws

2. Flue spigot

3. Restrictor ring

4. Flue spigot fixing holes

Page 15

It is not necessary to cut the ducts

If L is between 1175 - 1475mm (1 extension)

1925 - 2225mm (2 extension)

*2675 - 2975mm (3 extension)

3425 - 3725mm (4 extension)

(* Maximum length 2500mm for LPG boilers)

It will be necessary to cut the ducts

If L is between 725 - 1175mm (1 extension)

1475 - 1925mm (2 extension)

*2225 - 2675mm (3 extension)

2975 - 3425mm (4 extension) 3725 - 4000mm (5 extension)

(* Maximum length 2500mm for LPG boilers)

It is necessary to shorten the assembly by cutting the first extension duct assembly eg. L = 1000mm - remove 175mm from the air and flue ducts (1175 – 1000 = 175mm).

NOTE: Extension duct measurements do not include the socketed end. Unless specifically instructed the socketed end must not be removed.

Fix the flue ducts together before fixing the surrounding air duct, the cut ducts fit into the terminal assembly.

11.10 Fitting the Flue Assembly with Access to the Terminal.

Prepare the flue duct assembly as described in Section 11.8. Apply the plastic tape to the air duct to be in contact with the external brickwork. From inside push the assembly through the wall. Align the flue turret and push fully onto the spigot on the appliance. Tighten the clamping ring. Refer to Fig.27.

Make good the internal wall face and the external brickwork or rendering.

11.11 Fitting of the Flue Assembly without access to the Terminal.

The rubber gasket kit is available as a spare part. NOTE: A larger diameter opening in the wall is required. Refer to Table 2.

Fig. 24. Extension duct

Fixing screw

Flue turret assembly

Appliance casing

Terminal assembly

Fixing screw

Ducts of equal length

Fig. 25. Flue duct length - side

Flue turret assembly

Terminal assembly

Flue turret assembly

Terminal assembly

Fig. 26. Flue duct length - rear

Page 16

Prepare the flue assembly as described in Section 11.8.

Fit the rubber sealing gasket centrally onto the terminal assembly and tighten the clamp. Refer to Fig. 28.

Apply the plastic tape to the air duct to be in contact with the external brickwork.

From inside push the assembly through the wall so that the gasket flange is against the outer face. Refer to Fig. 28. It may be necessary to adjust the legs of the flue centering ring. Align the flue turret and push fully onto the socket on the appliance. Tighten the clamping ring. Refer to Fig 27. Seal the gap around the duct at the inner wall face with the flexible seal provided and make good.

11.12 Flue Bends.

90° and 45° bends are available. A maximum of two bends may be used in addition to the first bend on the flue turret. A 90° bend is equivalent to 750mm of straight duct. A 45° bend is equivalent to 375mm of straight duct.

A maximum flue assembly of 3250mm for natural gas and 1750mm for LPG is possible with 1 X 90° bend and 2500mm natural gas and 1000mm for LPG with 2 X 90° bends. Measure the lengths X,Y and Z. Refer to Fig.29. The maximum value of X using the turret assembly only is 506mm. Reduce the ducts to the appropriate length eg. 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.30.

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.29. The final section, dimension Z, of the flue system must include a section of plain duct assembly eg. an extension assembly with the sockets removed. Reduce the final section, including the terminal assembly, by the appropriate amount eg: Air duct Z - 81mm and the flue duct Z – 51mm. Refer to Fig.29.

If Z is less than 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 of the terminal assembly eg. Z=350mm - remove 75mm from the terminal assembly.

If Z is between 425 - 725mm it is not necessary to cut the terminal assembly or use a second extension duct as the length can be set telescopically.

Fig. 27 . Flue Turret Fixing

1. Flue turret assembly

2. Clamp

3. Appliance

Fig. 28 . Terminal assembly for internal

fitting of the flue.

Flue centering ring

Flue Terminal

Rubber sealing gasket

Clamping ring

Flue terminal

Air duct

Flue duct

Rubber sealing gasket

Fixing clamp

Fig. 29. Flue bends

Y-162

Plain tube

Page 17

If Z is greater than 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 275mm 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 11.9, 11.10 as appropriate. Make good the internal and external brickwork or rendering.

11.13 Vertical Adapter for Horizontal Flues

An adapter is available for an initial short section of vertical flue. Refer to Fig. 31. Measure and cut the flue as described in Section 11.11. The first, vertical, section (equivalent to dimension X) is measured from the top of the boiler casing. Cut the vertical section of the extension duct to 167mm less than the measured distance. Do not remove the socketed ends. The minimum measured distance is 167mm. Seal the air duct to the spigot using silicone sealant.

11.14 Completion of the Installation

Check that all the gas and water connections on the manifold have been tightened. Undo the two screws and remove the connections cover panel. Refer to Fig 32.

Connect the mains supply lead to the appliance and secure in the cable clamp. Make sure that the lead is isolated before connection. Refer to Section 10. Check that there is sufficient loose lead to allow the release of the facia panel assembly and that the earth lead of the mains supply is longer than the live and neutral leads. Fit the facia-mounted clock or programmer. Full instructions are sent with the control. Refer to Fig 33 and 34. Connect any external controls ensuring that the leads pass through the appropriate cable clamp. Refer to Section 10 and Fig 35 and 36. Test for gas soundness as described in BS6891. If the appliance is not to be commissioned immediately, replace the connection cover panel and the cabinet. Check that the gas and electricity services have been turned off.

120mm

100mm

Fig. 30 - Elbow to Flue Turret

Assembly.

Fig. 31 Vertical Adapter.

Flue Duct

Air Duct

Adapter

Flue Spigot

Flue Turret

Bend

Fig. 32. Facia connections cover

Fig. 33. Programmer connection

1. Facia (gently pull forward to un-clip and remove)

2. Control panel (boiler outer casing in place)

3. Programmer cover (un-clip to remove. See Fig. 34)

4. Programmer location in detail

5. Programmer connections (See Fig. 34)

6. Programmer connector plug

7. Programmer

1. Controls connector cover

2. Controls connector cover fixing screws (2)

*5mm

*When connecting to an elbow the flue duct must be

5mm longer than the air duct.

Page 18

Fig. 34. Programmer cover

Fig. 35. Facia connections

Fig 36 - Mains Voltage External Controls

Connections

230 V room thermostat and Programmer Connections

Neutral

Live

Neutral

Live

Switched Live

Motor

1. Programmer connections

2. Boiler outer casing

3. Cover panel

ST2

Series

connection

point

1. Controls connector cover

2. Controls connector cover fixing screws (2)

3. Facia control panel

4. Earth connection (tags)

5. Earth connection (screws)

6. Cable clamp

7. Fuse F1 2A (slow)

8. Cable clamp

9. ST15 Pump

10. ST1 Fan

11. Fuse F2 1.25A (slow)

12. Code plug

13. Commissioning switch

(gas valve mode switch)

14. Internal controls connectors

15. Mains and external controls connectors

(230 Volt)

ST2

Remove Link

230 V Room Thermostat Connections

Ns Ls LR

ST2

Neutral

Live

Switched Live

Remove Link

spare

Neutral

ST2

Remove Link

Live

Switched Live

Motor

230 V Programmer Connections

Ns LsNLNsLsL

spare

Ns LsNL

Ns Ls L

spare

Ns LsNL

Page 19

Water Treatment: For optimum performance after installation, this boiler and its associated central heating system should be flushed in accordance with the guidelines given in BS7593: 1992 – Treatment of water in domestic hot water heating systems. Full instructions are supplied with proprietary cleansers sold for this purpose. If an inhibitor is to be used after flushing, it should be used in accordance with the manufacturers instructions. Remove all system cleanser before adding any inhibitor. Suitable flushing agents and inhibitors are available from Betz Dearborn on 0151 4209563 or Fernox on 01799 550811.

12.1 System Set up

Remove the cabinet by pulling off the clip-on facia cover. Unscrew the two fixing screws, release the sides and lift from the top location. Check that the electrical supply and the gas supply to the appliance are turned off and that all the water connections throughout the system are tight. Open the system valves at the appliance. Refer to Fig 17. Open all the radiator valves. Remove the automatic air vent cap. Refer to Fig 37.

Fill the system through an external WRAS approved filling loop or Worcester Filling Link and Key optional extra, Part N

: 7 716 192 281. Refer to Section 7, Sealed System. Vent each radiator in turn. The automatic air vent, cap removed, will vent the appliance. Refer to Fig 37. It is very imortant that the appliance and system are fully vented and that all air pockets are removed. Remove the cap from the pump and turn the shaft about half a turn. Replace the cap. Refer to Fig 38.

Check that the pressure relief valve operates by turning the knob anti-clockwise until it releases. Lower the facia to gain access to the relief valve. Refer to Fig 20. Water should be expelled from the discharge pipe. Refer also to Fig 54.

The appliance [as despatched] can accommodate 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.

12.2 Set the Expansion Vessel Pressure

The charge pressure of the expansion vessel as dispatched is

0.5bar, which is equivalent to a static head of 5m. The charge pressure must not be less than the static head at the point of connection. A Schraeder type valve is fitted to the

expansion vessel to allow the charge pressure to be increased if necessary. Refer to Fig 37. The expansion vessel must be charged to 0.35bar less than the initial system design pressure.

Note: 1bar = 10.2m of water.

12.3 Set the System Pressure

Fill the system until the pressure gauge is at 2.5bar 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 1.5bar. Set the pointer on the pressure gauge to record the set system pressure. If the pressure indicated on the gauge is greater than 2.65bar when operating at the maximum central heating temperature then an extra expansion vessel must be fitted to the system as close as possible to the appliance central heating return connection.

12.4 Clock/Programmer

The controls fitted to the appliance should be set up at this stage. Refer to the instructions sent with the control.

12.5 Checking the Burner Pressure

Check that the gas and electricity supplies are turned off. Connect pressure gauges to the gas valve to measure the inlet and burner pressures. Refer to Fig 39. The appliance is fully set up in the factory and no adjustment should be necessary.

12. Commissioning The Appliance

Fig. 37. Automatic air vent and combustion

test point

Fig. 38. Pump venting.

Pump

Pump cap

Electrical connections cover

Fig. 39. Gas valve.

Automatic air vent

Flue connections

Expansion vessel charging point

Expansion vessel

Wall mounting frame

Combustion products test point (front cap)

Max

2mm

Allen key

Min

3mm

Allen key

Gas valve sealing cap

Burner pressure test point

Electrical connections modulator (Blue:Blue)

Minimum / Maximum pressure adjuster Allen key* (see Note)

Inlet pressure test point

Main gas valve connections

*Note: Clockwise to increase and anti-clockwise to decrease the pressure.

Page 20

Unscrew and remove the control connector cover to display the mode switch. Refer to Fig 32. Check that all the radiator valves are open. Check that the system is fully vented, pressurised and set to the required pressure as indicated on the gauge. Set the temperature control knobs to maximum and the clock/programmer to operate continuously. Fully open a hot tap.

Set the mode switch to MAX. Refer to Fig 40. Turn on the gas and electricity supplies. 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 for 1 minute. Refer to Table 1. It should not be necessary for the gas valve to be adjusted. Note: The burner pressure is factory set and if, after checking that the dynamic (working) supply pressure is sufficient i.e. 19.0mb approx. [NG] or 36mbar approx. [LPG] at the gas valve inlet pressure test point, the correct pressure cannot be obtained then The Worcester Service Department should be contacted. If the appliance does not light then check that it is not in the ‘lock-out’ state by gently pressing the reset button for 5 seconds. Refer to Fig 41. Set the mode switch to Normal. Turn off the hot tap. The burner pressure will drop to the minimum setting and will ramp up to the maximum central heating pressure appropriate to the appliance and the gas. Refer to Table 1. Set the mode switch to MIN. The burner pressure will drop to the minimum burner pressure appropriate to the appliance and the gas for both the central heating and domestic hot water modes. Refer to Table 1. Test for gas soundness at the joint between the burner and the gas valve with leak detection fluid. Set the mode switch back to Normal. Turn the electricity supply off and then back on to reset the controls. Replace the controls connector panel.

12.6 Operation of the appliance

Domestic Hot Water Turn the central heating temperature control knob fully anticlockwise. Open a hot tap near the appliance. The burner will light and go to the maximum burner pressure appropriate to the appliance and the gas. Refer to Table 1. Gradually close the tap and check that the burner pressure falls. Fully open the tap and check that the pressure rises. Close the tap and check that the burner goes out. The fan and pump may continue running until the appliance has cooled to a pre-set temperature.

12.7 Central Heating

Check that all the radiator valves are open. Check that the system is fully vented, pressurised and set to the required pressure as indicated on the gauge. Check that the clock/programmer is set to operate continuously. Set the room thermostat and the central heating temperature control to maximum. The burner will light and the appliance will modulate its output from minimum to maximum over a period of about two minutes. Check that all the radiators are heating up evenly. Shut down all but one of the radiators and observe the burner pressure fall. Open all the radiators and check that the burner pressure rises.

Balance the system to give the required temperature differential. Refer to Table 3.

Set the room thermostat to minimum and check that the burner goes out. Reset the room thermostat to maximum and the burner will relight and follow the normal operating procedure.

12.8 Check flame failure device

Turn off the gas service cock. The burner will go out but sparking from the electrode will continue for 10 seconds when the appliance will ‘lock-out’. After 60 seconds carefully open the gas service cock, press the reset button and observe the burner relight and follow the normal sequence of operation. Refer to Fig 17 and 41. Turn off the gas service cock and the electricity supply to the appliance.

Drain the system while the appliance is hot.

Refill, vent and re-pressurise the system as described in Section

12.1 preceding, adding, if necessary, a suitable proprietary inhibitor. Further information is available from Betz Dearborn on 0151 4209563 or Fernox on 01799 550811.

12.9 Domestic Hot Water and Central Heating

Set all controls to maximum. Turn on the electricity supply to the appliance and open the gas service cock at the appliance. The burner will light and heat will pass into the system. Turn on a hot tap and check that hot water is soon discharged from the tap. Close the tap and the burner will go off. The appliance will then return to the central heating mode and automatically balance with the system requirements.

12.10 Completion of Commissioning

Turn off the appliance and disconnect the pressure gauge and tighten the test point screw. Restart the appliance and check for gas soundness around the test point screw. Refit the cabinet. If the appliance is to be passed over to the user immediately then set the controls to the users requirements. If the appliance is to be left inoperative in frosty conditions then set the programmer, if fitted, to off. Do not turn the electricity or gas supplies off. The appliance will operate under the control of the integral frost protection facility. If there is any possibility of the appliance being left totally unused in freezing conditions then switch off the gas and electricity and drain the appliance and the system. The appliance must be fully re-commissioned when it is returned to service. The venting of the appliance is very important.

Fig.40. Mode adjustment

Betrieb

Max

Min

Page 21

Hand over the User Booklet and the completed Benchmark Checklist. Explain how to operate the appliance safely and efficiently. Tell the user what to do if the appliance is not to be used in very cold conditions. Tell the user what to do if the system pressure falls. Explain that regular servicing will maintain the safe and efficient operation and extend the life of the appliance. WHS or their agent can offer a comprehensive maintenance contract. Tell the user that any work on the appliance must only be carried-out by a competent, registered, person (CORGI in GB).

14.1

14.2 Inspection

Check that the terminal and the terminal guard, if fitted, are clear and undamaged. If the appliance is in a compartment or cupboard check that the specified service space around the appliance is clear. Refer to Table 8. Check all the joints and connections in the system and remake any that show signs of leakage. Refill and re-pressurise as described in Section 12-Commissioning. Operate the appliance and take note of any irregularities. Refer to Section 18-Fault Finding for rectification procedures. If the combustion performance is to be checked: Remove the cap from the sample point on the top of the appliance. Refer to Fig 37. Connect an approved sampling meter. With the appliance at maximum rate and stable in the DHW mode expect readings of:

24kW NG CO

2 5.3—6.2% CO 0.002—0.010%

LPG CO

2 6.4—7.4% CO 0.004—0.010%

28kW NG CO

2 5.6—6.4% CO 0.006—0.010%

LPG CO

2 6.3—7.3% CO 0.003—0.010%

NB For flues greater than 725mm without a restrictor the CO

may be up to 0.5% lower.

These figures cover all flue conditions. Refit the cap after the test. Disconnect the electrical supply at the mains and turn off the

gas supply at the gas service cock on the appliance before starting any service procedures. Always test for gas soundness after the service has been completed.

14.3 Component Access

To service the appliance it may be necessary to remove some or all of the following parts to gain access to components which may need to be checked or replaced. Cabinet Pull off the clip-on facia cover. Unscrew the two

screws and release the sides. Lift up and away from the top locating pegs.

Facia Panel Unscrew the single screw, lift off and lower onto the

lower support lugs. Refer to Fig 42 & 43.

14. Inspection And Service

13. Handover

Fig. 42. Inner case and facia fixing

1. Inner casing cover

2. Cabinet fixing screws (4)

3. Inner casing cover fixing screws (2)

4. Inner casing cover fixing screws (2)

5. Facia control panel

6. Controls connector cover

7. Controls connector cover fixing screws (2)

8. Programmer (optional)

9. Facia control panel fixing screw

10. Top support lug (2)

11. Bottom support lug (2)

12. Sight glass

7 2

9 8

Fig. 41. Facia controls

1. Mains On/Off control 5. Optional programmer

2. CH temperature control 6. Lockout indicator lamp and

3. DHW temperature control reset button

4. System pressure gauge 7. Burner indicator lamp

Fig. 43. Facia in service position

Page 22

Fig. 44. Inner case components

1. Flue hood

2. Primary sensor

3. Heat exchanger

4. Combustion chamber assembly

5. Spark electrode assembly

6. Inner case cover fixing (bottom)

7. Burner assembly

8. Combustion chamber fixing screw

9. Inner case

10. Fan assembly

11. Inner case cover fixing (top)

12. Air pressure switch

13. Combustion sensing point

14. Fan harness

15. Main wiring harness

Page 23

Inner Case Cover Unscrew the four screws and remove. Refer to Fig 42. Combustion Chamber Unscrew the two screws at the top and

the two wing nut extended screws at the sides, pull forward and remove. Refer to Fig 44.

Fan Carefully pull off the electrical connections and the

tubes from the airflow-sensing device. Unscrew the four screws and remove the fan assembly. Refer to Fig 45.

Flue Hood Remove the fan. Unscrew the four screws and slide

out the hood. Refer to Fig 47.

Burner Remove the combustion chamber. Carefully pull-off

the connections to the spark electrodes. Pull off the connection to the flame sense electrode. Unscrew the support bracket. Release the union nut beneath the burner and carefully remove the burner. Refer to Fig 46.

14.4 Component Cleaning

Only use a non-metallic brush to clean components. Do not use a metal probe to clean the injectors. Clean the fan taking care not to block air flow detector. Clean the burner to ensure that the blades and injectors are clear. Clean the electrodes, replace if there is any sign of deterioration. Clean the heat exchanger. Cover the gas inlet tube and remove any deposits from the heat exchanger from the top and bottom. Carefully straighten any distorted fins on the heat exchanger. Check the combustion chamber insulation and replace if there is any sign of damage or deterioration. Refer to Section 15.5. Clean the controls in-situ using a non-metallic brush. Carefully refit any components removed in the reverse order. Check that all screws are tight and the connections properly remade with the appropriate gaskets/O-rings. Re-commission, as necessary, for correct operation to the users requirements. Refer to Section 12 Commissioning.

Fig. 45. Fan assembly

Fig. 47. Flue hood

Fig. 46. Burner assembly

1. Flue hood fixing screws (4)

2. Flue hood

3. Flue hood/Heat exchanger guide

1. Fan assembly

2. Fan assembly fixing screws (4)

3. Flue hood

4. Flue hood fixing screws (4)

5. Air flow detector

1. Burner assembly

2. Spark electrode assembly

3. Spark electrode assembly fixing screw

4. Flame sense elctrode

5. Flame sense elctrode fixing screw

Page 24

IMPORTANT: Turn off the gas supply and electrically isolate the appliance before replacing any components.

After the replacement of any components always check for gas soundness where relevant and carry out functional checks as described in Section 12-Commissioning. Any O-ring or gasket that appears damaged must be replaced. Complete gasket and O-ring packs are available for gas and water connections on the appliance.

Component Access

Refer to Section 14, Inspection and Servicing for access to components.

Draining the Appliance

Primary System: Turn off the heating flow and return valves at the appliance. Refer to Fig 17.

Open the drain tap a short tube is already connected to the drain point. Refer to Fig. 20. Close the drain tap when the flow from the appliance has stopped.

DHW Circuit: Turn off the mains cold water supply at the appliance. Refer to Fig 16. Open a hot tap below the level of the appliance to drain the domestic hot water from the appliance.

Important: A small quantity of water will remain in some components even after the appliance has been drained. Protect any electrical components when removing items from the water circuits.

Component Replacement

Refer to Fig 42 and 44 for an indication of the location of the various components. Replace any components removed from the appliance in the reverse order using new gaskets/O-rings/sealant/heat transfer paste where necessary. Always check that any electrical connections are correctly made and that all screws are tight. Remove casing and cover panels and lower the facia onto lower lugs, as necessary, to gain access to the components. Refer to Section 14, Inspection and Servicing.

15.1 Gas Valve

Unscrew the union connections above and below the gas valve and remove the assembly. Disconnect/unplug the electrical connections from the valve. Use new gaskets when replacing the valve. Refer to Fig 48. Set the Gas Valve: Connect a pressure gauge to the burner and inlet pressure test points on the valve. Refer to Fig 39. Switch on the gas and electricity supplies. Check for gas tightness at the gas valve inlet. Refer to Section 12.5 Commissioning for the method of checking/setting the pressures. Check for gas soundness at the gas valve outlet. Adjust the maximum and start pressure [minimum], as necessary, to obtain the required pressures. Switch off the appliance and disconnect the pressure gauge. and tighten the screw. Refer to Section 12.5 and Fig 39 for setting instructions. Check for gas soundness at the test point.

15. Replacement Of Parts

Fig. 48 . Lower casing - gas and water

controls.

1. Gas valve

2. Pump

3. Pressure guage

4. Relief valve

5. Manifold assembly

6. Control panel in lowered position

7. DHW sensor

8. DHW flow turbine

9. Control panel top support

10. Drain tap

11. Drain tube

Fig. 49. Spark electrode assembly

1. Spark electrode assembly

2. Fixing screw

3. Burner blade assembly (LH)

Page 25

15.2 Spark Electrode

Remove the inner casing cover and the combustion chamber. Carefully pull off the lead from the electrode. Unscrew the screw and remove the assembly. Refer to Fig 49. Ensure that the electrode is at the correct height above the burner blade. 6.5mm ±1mm.

15.3 Flame Sense Electrode

Remove the inner casing cover and the combustion chamber. Remove burner as in 15.4. Carefully pull off the leads from the electrode assembly. Unscrew the screw and remove the assembly. Refer to Fig 50. Ensure that the sense electrode is at the correct height above burner blade. 6.5mm ±1mm.

15.4 Burner

Remove the inner casing cover and the combustion chamber. Remove the spark electrode connections. Unscrew the two burner bracket fixing screws. Release the union connection beneath the burner and remove the burner from the appliance. Refer to Fig. 46. and 51. Do not omit the gasket when fitting the new burner.

Fig. 50. Flame sense electrode

1. Flame sense electrode

2. Fixing screw

3. Burner blade assembly (RH)

Fig. 51. Burner

1. Flame sense elctrode

2. Spark electrode assembly

3. Burner blade assembly (LH)

4. Burner manifold

5. Burner blade assembly location points

6. Burner blade assembly (RH)

7. Cross- lighting strip fixing screws (2)

8. Cross-lighting strip

9. Cross-lighting strip fixing holes (2)

10. Burner assembly

11. Burner support bracket

12. Burner fixing screw

13. Bracket fixing screws (2)

Page 26

15.5 Combustion Chamber Insulation, Front &Sides

Remove inner casing door and combustion chamber. Remove damaged insulation, replacement is the reverse of removal. See Fig 52.

Combustion Chamber Insulation, Rear

Remove heat exchanger as described in 15.21. Remove side panels first. Pull insulation forward and up to remove. Replacement is the reverse of removal. Refer to Fig 52.

15.6 Pressure Gauge

Remove the clip-on facia cover, cabinet and lower the facia panel onto the lower support lugs. Refer to Fig 43. Check that the appliance has been fully drained. Withdraw the clip and remove the pressure-sensing head. Refer to Fig 53. Unclip the gauge head from its mounting bracket and remove. Refer to Fig 53. Do not omit the washer from the pressure capillary when fitting the replacement gauge.

15.7 Relief Valve

Remove the clip-on facia cover, cabinet and lower the facia onto the lower support lugs. Check that the appliance has been fully drained. Unclip and pull-out the valve body. Refer to Fig 54

15.8 Flow Turbine

Drain the DHW circuit as described at the start of Section 15 preceding. Remove the clip on facia cover, cabinet and lower the facia panel onto the lower support lugs. Separate the in-line connector. Remove the two fixing clips and withdraw the turbine. Refer to Fig 48 and 55. Do not omit the gaskets when fitting the replacement turbine.



Fig. 53. Pressure Gauge head

Fig. 54. Relief valve boiler drain connection

Fig. 52. Combustion Chamber Insulation

Front and Sides.

1. Insulation panel-side

2. Insulation panel-front 3. Combustion chamber assembly

1. Pump

2. Pressure gauge capillary

3. Pressure gauge head

4. Mounting bracket

1. Pump

2. Boiler drain

3. Pressure gauge capillary

4. Boiler Drain ON/OFF

5. Relief valve

6. Relief valve drain connection (push fit)

Fig. 55. Water flow turbine.

1. Flow turbine

2. Flow turbine clips

3. Inlet

3. Outlet

Page 27

15.9 Inlet Water Filter

Remove the flow turbine as described in 15.8 preceding. Taking care, remove flow restrictor assembly from the flow turbine inlet. Refer to Fig 55 Carefully clean wire mesh by back flushing with water or replace assembly if necessary. Refer to Fig 56.

15.10 Control Board

Remove the clip-on facia cover, cabinet and the connections cover. Carefully disconnect all the electrical connections. Refer to Fig 35 and 43. Remove the facia panel and unscrew the four screws and remove the cover from the rear of the facia. Refer to Fig 57. Lift out the control board. Refer to Fig 57 Pull out and transfer the transformer to the new board. Re-commission the appliance to check and set the burner pressures. Refer to Section 12, Commissioning.

15.11 Transformer

Unscrew the four screws and remove the cover from the rear of the facia as described in 15.10 preceding. Refer to Fig 57. Pull out and transfer the transformer to the new board. Refer to Fig 57.

15.12 Clock/Programmer

Remove the facia by gently pulling it away from the boiler to release the clips. Remove the clock/programmer assembly by releasing the clip at the top of the clock/programmer and ease away from the control panel being careful not to pull on the connector lead. Unplug the connector at the control board. Refer to Fig 58. Comprehensive instructions are sent with the new control.

15.13 Fan

Remove the inner casing cover. Remove the fan as described in Section 14.3, Inspection and Servicing. Ensure that all the connections are correctly made to the new fan.

15.14 Air Flow Detector

Remove the fan as described in 15.13 preceding. Unscrew and withdraw, through the fan outlet, the airflow detector. Refer to Fig 45.

Fig. 57. Control board

Fig. 56.Inlet water filter and flow restrictor

1. Control panel 4. Transformer

2. Rear cover 5. Control board

3. Rear cover fixing screws (4)

Fig. 58. Programmer connection

1. Facia (gently pull forward to un-clip and remove)

2. Control panel (boiler outer casing in place)

3. Programmer cover (un-clip to remove. See Fig. 34)

4. Programmer location in detail

5. Programmer connections (See Fig. 34)

6. Programmer connector plug

7. Programmer

1. Flow restrictor

2. Inlet water filter

Page 28

15.15 Primary [ch] Sensor

Remove the clip-on facia cover, cabinet and inner casing cover. Carefully pull-off the connections. Release the clip and lift out the sensor. Refer to Fig 59 and 62. Do not omit the heat transfer paste when fitting the replacement sensor.

15.16 Overheat Thermostat

Remove the clip-on facia cover, cabinet and the inner casing cover. For the position of the overheat thermostat refer to Fig 62. Carefully pull-off the connections. Unscrew the two screws and remove the thermostat and fixing bracket. Refer to Fig 60. Apply a small quantity of heat transfer paste to the face of the replacement thermostat. Carefully position the thermostat so that the connections are away from the flue hood.

15.17 DHW Sensor

Remove the clip-on facia cover, cabinet and lower the facia onto the lower support lugs. Carefully pull off the connections. Unscrew the clip and remove the sensor. Apply a small quantity of heat transfer paste to the face of the replacement sensor. Refer to Fig 61.

15.18 Pump

Check that the primary circuit has been fully drained. Use a 4mm Allen key to release the four pump head fixing screws and remove the pump head. Refer to Fig 48. Disconnect and transfer the electrical connections to the new pump head. Take care not to scratch the mating surfaces.

15.19 Expansion Vessel

It will be necessary to remove the appliance from the wall to replace the expansion vessel. Refer to Fig 37. Alternatively the specified replacement can be fitted into the heating system return as close to the appliance as possible. Re-fill and pressurise the system as described in Section 13 Commissioning.

15.20 Auto Air Vent

Drain the primary circuit. Unscrew and remove the auto air vent. Do not omit the sealing washer when fitting the replacement air vent. Remove the cap. Refer to Fig 37.

15.21 Primary Heat Exchanger

Check that the appliance has been fully drained. Remove the temperature sensors as described in 15.15, 16 and 17 preceding. Remove the combustion chamber, fan and flue hood as described in Section 14.3, Inspection and Servicing and burner as described in 15.4. NOTE: The heat exchanger is unsupported when both the combustion chamber and flue hood are removed. Undo the four union connections and remove the heat exchanger. Do not omit the sealing washers when fitting the replacement heat exchanger. Refer to Fig 62.

Fig. 59. Primary (CH) sensor.

1. CH Sensor

2. Clip

Fig. 60. Overheat thermostat

1. Overheat thermostat

2. Fixing bracket

3. Overheat thermostat fixing screw

Fig. 61. DHW sensor

1. DHW sensor

2. DHW sensor fixing bracket and screw

3. DHW outlet pipe

Page 29

15.22 Air pressure Switch

The air pressure switch is held in position by a fixing bracket. In order to remove the switch: Gently move outwards the securing clips holding the switch to the bracket. Remove the air pressure tubes and wires from the switch. Push the replacement switch, with the tube connectors pointing forwards, into the bracket and then replace the wires and pressure tubes. If the fixing bracket needs replacing, remove the switch as described above then remove the two screws holding the bracket to the top of the appliance. Refer to Fig 63 and 64.

15.23 Sight Glass

Remove and replace the inner casing cover complete. Refer to Section 14.3, Inspection and Servicing. Refer to Fig 42.

Fig. 62. Primary heat exchanger

1. Heat exchanger

2. CH flow/return pipes

3. DHW inlet/outlet pipes

4. Seal

5. Overheat thermostat

6. Primary sensor

Fig. 64. Air flow pressure switch

1. Electrical connections

2. Air pressure switch

3. Screws

4. Air pressure switch fixing clip

5. Securing clip

6. Tube connectors

Fig. 63. Air flow pressure switch location

1. Air pressure switch

2. Fixing bracket

3. Air pressure switch fixing clip

4. Combustion sensing point location

5. Negative pressure tube (–)

6. Positive pressure tube (+)

+Ve

—Ve

Page 30

1 E88-141 Burner 24Si II NG RSF 1 8 716 101 900 0 2 E88-142 Burner 24Si II LPG RSF 1 8 716 102 396 0 3 E88-143 Burner 28Si II NG RSF 1 8 716 105 008 0 4 E88-144 Burner 28Si II LPG RSF 1 8 716 105 009 0 5 E88:450 Gas Valve NG Dungs BN771SL040 - 239675 1 8 716 102 673 0 6 E88:451 Gas Valve LPG Dungs BN771SL040 - 239676 1 8 716 102 868 0 7 E88-146 Air Pressure Switch 1 8 716 104 896 0 8 E88-169 E lectrode Set (Flame and Ignition) 1 8 716 101 901 0

9 E88-170 Overheat Stat 1 8 717 206 200 0 10 375-696 NTC/Thermistor DHW 1 8 716 142 302 0 11 E88-171 NTC/Thermistor CH 1 8 714 500 029 0 12 378-809 Air Vent Manual

/4BSP 1 8 716 140 516 0 13 299-363 Air Flow Sensor 1 8 716 141 000 0 14 E88-172 Heat Exchanger 24Si II 1 8 715 406 670 0 15 E88-173 Heat Exchanger 28Si II 1 8 715 406 814 0 16 E88-174 Insulation Pack 24Si II 1 8 716 101 877 0 17 E88-175 Insulation Pack 28Si II 1 8 761 105 010 0 18 E88-176 Pressure Gauge 1 8 716 142 398 0 19 E27-580 Pressure Relief Valve 1 8 716 156 764 0 20 E88-177 Pump 1 8 716 143 116 0 21 E27-587 Expansion Vessel 1 8 715 407 154 0 22 H02-152 Control Board 1 8 748 300 488 0 23 E88-179 Fan Assembly - 24Si II 1 8 716 104 814 0 24 E88-180 Fan Assembly - 28Si II 1 8 716 104 815 0 25 E88-181 Flow Sensor 1 8 716 146 164 0 26 E88-182 Seal-Door Extrusion 1 8 716 104 609 0 27 E88-183 Transformer 1 8 747 210 294 0 28 E88-184 Flow Regulator 24Si II 1 8 716 141 255 0 29 E88-185 Flow Regulator 28Si II 1 8 716 141 253 0 30 H02-155 Code Plug 24Si II RSF 1 8 714 421 166 0 31 H02-157 Code Plug 28Si II RSF 1 8 714 421 167 0

A001 Charging Link Assembly 1 7 716 192 281 A002 Installer Pre-Filling Kit 1 7 716 192 282 A004 Gas Conversion Kit NG to LPG 24Si II 1 7 716 192 288 A005 Gas Conversion Kit NG to LPG 28Si II 1 7 716 192 289 A006 Simplefit Telescopic Flue Kit - F105H500 1 7 716 191 068 A007 Vertical Flue Kit 1 7 716 191 079 A008 90° Flue Elbow - F106E90 1 7 716 191 013 A009 45° Flue Elbow (Pair) - F 106E45 2 7 716 191 014

A010 Vertical Flue Adaptor Kit 1 7 716 191 016 A011 Security Kit 1 7 716 192 246

A012 Mechanical Programmer 1 7 716 192 027 A013 Digital Programmer 1 7 716 192 028

Key G.C. No. Part Qty WHS No. Part No.

16. Short Parts List

Accessories and Kits

Page 31

1 - 4

5/6

14 -15

16 -17

23 - 24

28 - 29

30 - 31

Page 32

Room

thermostat

and/or mains

programmer

(or link) On

facia

programmer

(if fitted) On

CH control

knob On

17. Operational Flow Diagrams

MAIN SWITCH

CENTRAL

HEATING

DEMAND

Pump on.

Fan ON/

ignition

sequence.

Burner Light

On.

Three minute

wait

Gas valve Off.

Burner light

off. (Pump still

On)

Over tempera-

ture shutdown if flow temperature

5°C above set

value

Fifteen second

minimum

burner

pressure then

ramp up

pressure over

next one

minute

Modulate gas

to maintain

flow

temperature

set by control

knob

(50-82°C)

DEMAND

END

Overrun function

(see overleaf)

CENTRAL HEATING FUNCTION

AND

DOMESTIC HOT WATER FUNCTION

MAIN SWITCH

Flow sensor

signal

(Tap open)

DOMESTIC

HOT WATER

DEMAND

(Priority over

CH demand)

Pump continue

4 seconds if

primary temp

above DHW

setting. Burner

to MAX.

Modulate gas

to maintain

delivered

water

temperature

set by control

knob

(40-60°C)

Is CH

interrupted?

DHW temp

drops to user

set point

Over

temperature

shut-down if

water

temperature

above 80°C

Primary

temperature

94°C

DEMAND

END

Overrun

function

(see overleaf)

YES

Ignition

sequence and

burner to MAX

Gas valve off.

Primary

78°C

Gas valve off.

Pump on

Page 33

Commence normal

central heating mode

until temperature

reaches 20°C

Pump overrun

function active

for 3 minutes

OVERRUN FUNCTION

Run pump

END DHW

DEMAND

END CH

DEMAND

Pump runs

for

3 minutes

Pump on if

primary temp

above 80°

until temp

below 75°C

AUTOFROSTAT FUNCTION

Monitor

central

heating

sensor

Below

5°C

9°C

Above

9°C

No demand and primary temperature

below 8°C

Internal

"Autofrostat"

demand

Return to

normal off

state

Fan low speed

35 seconds

Fan low speed if

primary temp

above 80°C until

below 75°C.

Page 34

Note: This fault-finding information is for guidance only. Worcester, Bosch Group cannot be held responsible for costs incurred by persons

not deemed to be competent.

By flashing at various rates, the oval shaped facia light will indicate specific fault conditions. If this is used with other observations during a fault, then every normal fault can be identified.

To use the fault finding system, use the table below to select the failure condition during your fault. The most common causes are listed, then refer to the test in the following section. This fault finding system assumes that the appliance has been operating normally until the time of failure (ie not a first installation fault).

PRELIMINARY CHECKS

Preliminary electrical system checks are the first electrical checks to be carried out during a fault-finding procedure. On completion of the Service/Fault-Finding task which has required the breaking and remaking of electrical connections, check (a) EARTH CONTINUITY, (b) SHORT CIRCUIT CHECK, (c) POLARITY and (d) RESISTANCE TO EARTH.

18. Fault Finding

(reset lockout by gently pressing reset button for 5 seconds)

FAULT LIST

OBSERVED FAULT COMMON CAUSES SEE TEST

No lights and no functions (with demand)

No CH function (DHW OK)

No mains Voltage supply. Fuse F1 or F2 blown. Transformer or connector failed. Board fault.

No link at ST2 Ls to Lr, or failed external control input to Lr.

Failed programmer. Board fault.

No DHW function (CH OK)

Flash once per second

Ignition lockout Overheat lockout Internal error

Flash 4 times per second

Flow sensor failure. DHW sensor (LED 4 flash/second). Board fault.

No gas or low gas pressure. Weak spark or spark not across elecrodes. Gas valve leaking or failed. Low water pressure or boiler dry. Pump fail. Primary sensor position. Flame sensor fail or connector. Overheat stat tripped or disconnected or faulty. Blocked burner. Blocked heat exchanger. Faulty harness. Board fault.

Code plug missing or failed. CH or DHW Sensor fault or out of position. Air pressure switch fault or condense in tubes. Fan fail or stiff. Blocked flue. Faulty harness. Board fault.

Flash 8 times per second

GV mode switch

Burner on with no demand

Water temperature too hot

Water temperature too cool

Gas Valve mode switch on min or max.

Autofroststat. Board fault.

Sensor off pipe.

Low gas pressure. Pot P1 not turned up. Stiff/sticking gas valve. Stiff/sticking flow sensor. Board fault.

G H

Page 35

Is there a 230V AC live

supply across

Terminal ST2 pins L

and N?

Switch off electrical

power.

Has fuse F1 blown?

Caused by mains 230V

parts external to the

control board ie (wiring

to or faults within)

pump, fan, transformer

or other external

controls connected to

ST2. Check all these

parts for malfunction.

Repair/replace part, replace fuse and run

boiler.

Note: tracks on board

may also be damaged.

Replace board if

necessary

Check electrical

supply to boiler.

Has fuse F2 blown?

TEST A

Yes

Likely to be caused by control board internal

fault or low voltage wiring (eg shorts to

chassis). Replace fuse

F2 and check wiring

or replace control

board.

Remove control board from facia

and separate transformer from

board. Measure resistance across

the two pairs of adjacent pins on

the transformer. Is any coil above

120 ohms?

Replace transformer.

Yes

Replace

control

board.

NOTE: It is normal for

there to be no facia

lights if the boiler is in

normal overtempera-

ture condition.

Continue this test if

this fault occurs when

the appliance is cold.

Is there a 230V AC live

supply across

Terminal ST2 pins Lr

and N?

TEST B

Yes

Replace

control

board.

NOTE: Lights will be

off and pump will run

if boiler is in 3min

anticycle condition.

With CH control knob

fully clockwise, if

there is still no CH

function, continue:

There is no heat

demand. Check room

thermostat or external

programmer (or link).

Is there a facia

mounted programmer

at connection ST5 at

right-hand end of

board?

Remove programmer

connector from edge

of board. Does the

boiler now ignite?

Correctly set or

replace programmer.

Yes

Page 36

Re-connect the 3-way connector and open a tap to run the turbine.

Is there between 1.5

and 4.5VDC across

the green and black

wires/terminals?

Is there continuity in

the main harness?

Disconnect the 3 way

in-line connector to

the turbine.

Is there 5VDC between

the two outer pins

(main harness side)?

Take care not to

damage the pins.

No No

Yes

Replace control

board.

Replace main

harness.

TEST C

Yes

Replace turbine.

Page 37

Is the boiler fully

water pressurised and

is all air vented?

Rectify fault.

Reset and restart the

boiler in CH mode.

Does the pump run?

Yes

Remove front panel.

Reset and restart the boiler. Can a flame be seen through the spy

glass?

Remove inner cover.

Reset and restart the

boiler. Does a spark

occur across the

electrodes?

Turn off boiler. Remove

the multiway

connector from board

position ST16.

Test resistance across

connector contact

pins 1 and 2 (green wires)

and 8 and 9

(brown wires).

Are both reading

below 100 ohms?

Replace gas valve.

Are the electrodes and

gap and connections

in good order?

Replace

control board.

Remove both

connectors from gas

valve.

Is there continuity

from these

to multiway

connector?

Repair or replace

harness.

Repair or replace

spark electrode

or HT leads

Is the gas supply

connected and at the

correct pressure?

Rectify gas supply

problem.

No No

Yes

Replace control board.

If problem not solved

replace gas valve.

Yes

Replace or repair

pump.

Yes

TEST D

Test resistance of each

ignition cable.

Is it 2000-3000 ohms?

Yes

Replace (both) ignition

cables

Is there continuity

between pins 6 and 7?

(green wires to HL

stat)

Replace overheat stat

or wiring to it.

Page 38

Remove combustion

chamber cover.

Is the sense electrode

and lead in good

condition and is gap

correct?

Replace flame sensor

or wiring.

Remove multiway

connector from board

position ST16.

Is there continuity from pin 10 (green

wire) to flame sensor?

Yes

Relace control board.

NOTE: It is not

possible to reliably

check the cross-light

performance of the

burner, or the

efficiency of the

gas/water heat

exchanger.

If there is still a

problem, investigate

flue problems or

replace burner or

injector or heat

exchanger.

Does the flashing fault

signal occur at the

start of a demand?

If flashing occurs at

the end of a demand.

Gas valve leak is

detected.

Replace gas valve.

Yes

If flashing occurs during a

demand.

Pump could be partially

blocked.

Clean pump & flush system.

Re-fix sensor to pipe.

Turn off boiler. Remove inner casing cover and

inspect the primary

sensor (on heat

exchanger in front of

overheat thermostat).

Is it correctly fixed to

pipe?

Yes

Page 39

Remove multiway

connector from board

position ST16. Test

resistance across

contacts 15 and 16

(black & yellow wires).

Is it between 1 kOhm

and 30 kOhm?

Test resistance across

contacts 12 and 13

( red & black wires). Is

it between 1 kOhm

and 30 kOhm?

Is there continuity

from individual

contacts 15 and 16 to

DHW sensor?

Check or replace

DHW sensor.

Is there continuity

from individual

contacts 12 and 13 to

CH sensor?

Repair or replace

harness.

Repair or replace

harness.

Is the multiway

connector at board

position ST16 pushed

fully home on to the

board?

Push fully home

Yes

Check the DHW

sensor. Is it correctly

fitted onto the pipe

with heat conductive

paste between the

pipe and sensor?

Yes

Re-fix sensor onto pipe

Is the Code plug fitted

and

fully home?

Fit/push fully home

Yes

TEST E

Check or replace

CH sensor.

Test resistance across

contacts 13 and 14

(black & blue wires).

Is it open circuit?

Turn off electrical

supply.

Remove fan connector

from board position

ST1.

Test resistance across

contacts to black &

white cables.

Is it between 75 and

175 ohms?

Check/repair fan

harness or repalce fan.

Air pressure switch

is shorting.

Check tubes for

blockage or replace

switch.

Yes

Test resistance across

contacts to black &

red cables. Is it

between 20 and 60

ohms?

Yes

Page 40

Replace control board.

In the unlikely event of this not solving the problem replace code

plug.

Pressure switch has

opened during

operation.

Check flue for

blockage.

Also investigate sense

tubes and pressure

switch.

Replace fan connector

ST1.

Remove electrical

connectors from air

pressure switch and

reset/restart boiler.

Is there continuity

between C and NO

terminals (where wires

were fitted) when the

fan runs?

(Test within 30

seconds).

Pressure switch has

not closed. Are the silicon tubes in good condition and free of

condensation.

Replace air pressure

switch.

Note: In the unlikely

event of this not solving the problem inspect the pressure

pick-up (Venturi) in the

fan or fan may not be

running freely.

Inspect the flue. Is it

free of any

restrictions?

Rectify flue problem.

Does the burner ignite

(burner light on) and run for a short priod

before the fault

occurs?

Replace control board.

Repair cables or

replace main harness.

Replace tubes. If

condensation has

occurred, also replace

pressure switch and

check condition of

Venturi in the fan.

Yes

Turn to 'NORM'

position

The gas valve mode

switch (concealed by

the facia side panel)

is not set correctly

TEST F

Replace multiway

connector to position

ST16 (but not fan

connector at ST1) and

reset/restart the

boiler.

Is there mains 230V

across the right (L)

and left (N) tracks at

board position ST1?

NOTE: Take care not to

short L to N.

Yes

Remove multiway

connector from board

position ST16.

Is there continuity of

black & blue cables to

the air pressure

switch?

Yes

Page 41

Boiler is running in

“Autofrost stat” mode.

See Section 17.

Replace control board.

Note: A damp board

could cause this fault.

Is the boiler in a very

cold environment (less

than 5°C)?

TEST G

Yes

Is the CH limit potentiometer

(concealed behind

facia bottom panel)

set to maximum?

Does the problem occur in CH mode

only?

Water flow

temperature very low

(with all knobs set at

maximum).

TEST I

Yes

It is not possible to easily isolate the fault. The most likely causes are control board (fail),

heat exchanger

(blocked) or

gas valve (sticking).

Hot water

temperature always

too hot during a

demand (not

regulating).

TEST H

Hot water sensor

could be off or poorly

fixed to pipe.

Repair or replace.

Yes

Turbine sticking or

seized.

Replace the turbine.

Increase

potentiometer to

allow more gas in CH

mode.

Check flow sensor:

with boiler cool,

slowly open a HW tap.

Does the boiler ignite

with a flow of about

3 l/min?

(Check using a

measuring jug and

stop watch i.e 500ml

in 10 sec.

Replace gas valve or

check wiring.

Remove multiway

connector from board

position ST16. Is the

resistance across

contacts 4 and 5 (blue

wires) below 60

ohms?

Yes

Could be

domestic hot

and cold pipes

crossed.

Page 42

ONLY COMPONENTS SUPPLIED BY WORCESTER SHOULD BE USED. ONLY COMPETENT PERSONNEL SHOULD ATTEMPT THE CONVERSION. CONVERSION FROM NATURAL GAS TO LPG SHOULD NOT BE CARRIED OUT ON APPLIANCES INSTALLED IN A ROOM OR INTERNAL SPACE BELOW GROUND LEVEL

24kW 28kW

Conversion Kit NG to LPG 7 716 192 288 7 716 192 289

1. Ensure the gas service cock is turned OFF and the electrical supply is ISOLATED.

2. Refer to the Installation and Service Instructions Section14: Inspection and Servicing to remove the cabinet front panel and outer casing.

3. Follow the dismantling instructions to remove the burner. Refer to Section: 14.3 Inspection and Servicing.

4. Remove the burner blades as shown in 15.4.

5. Replace the burner manifold with a new one supplied in the kit.

6. Refit burner blades taking care to assure that the cross

lighting strip and blades are correctly fitted and aligned.

7. Remove the gas valve and replace with the gas valve supplied in the kit. Refer to the Installation and Servicing Instructions Section 15- Replacement of Parts. NOTE: Replace the fibre washer with one of those supplied in the kit.

8. Refit the burner assembly to the gas valve using the other fibre washer supplied in the kit.

9. Ensure that the sealing grommet around the burner manifold is correctly sealed to the boiler casing.

9. Remove plastic anti-tamper seal and plastic cap from the gas valve.

10. Turn on the gas and electricity supplies and follow the commissioning procedure to confirm gas soundness and correct boiler operation.

11. Check and adjust the setting pressures to the values in Table 1 and adjust if necessary. Refer to the Installation and Service Instructions Section 12.5 for the setting of the gas valve and refer to Fig 1.

Ensure that the joints on the gas valve to the burner and inlet are both checked for gas soundness.

12. Refit the plastic sealing cap to the gas valve modulating valve

and seal with a dab of paint or similar.

13. Turn off the boiler and when cool peel off the arrow from the

data plate on the combustion box front panel and re-stick against the gas type for which the boiler has been converted and adjusted.

13. Replace the boiler front panel.

The conversion is now complete.

19. Conversion Instructions

NOMINAL BOILER RATINGS (10 Minutes After Lighting)

BOILER ADJUSTED FOR G20 (Natural Gas)

OUTPUT INPUT (Net) GAS RATE

kW kW m bar. m

8.1 9.2 0.7 0.97

28 30.7 13.1 3.25

BOILER ADJUSTED FOR G31 (Propane)

8.1 9.2 2.8 0.38

28 30.7 34.5 1.25

Table 1. 28Si II

BURNER

PRESSURE

NOMINAL BOILER RATINGS (10 Minutes After Lighting)

BOILER ADJUSTED FOR G20 (Natural Gas)

OUTPUT INPUT (Net) GAS RATE

kW kW m bar. m

6.9 7.9 0.9 0.84

24 26.4 12.1 2..8

BOILER ADJUSTED FOR G31 (Propane)

6.9 7.9 3.1 0.32

24 26.4 35.0 1.08

Table 1. 24Si II

BURNER

PRESSURE

Natural Gas: Net Input = Gross Input x 0.901 LPG (Propane): Net Input = Gross Input x 0.922

NOTE: With longer flue lengths, not using a restrictor, the minimum burner pressure will rise, naturally due to the flue, to 1.1mbar on G20 appliances only.

Injector sizes and markings

G20 Natural gas G31LPG

24kW 1.07 mm 0.65 mm

(marked 107) (marked 65)

28kW 1.12 mm 0.69 mm

(marked 113) (marked 69)

Max

2mm

Allen key

Min

3mm

Allen key

Gas valve sealing cap

Burner pressure test point

Electrical connections modulator (Blue:Blue)

Minimum / Maximum pressure adjuster Allen key* (see Note)

Inlet pressure test point

Main gas valve connections

*Note: Clockwise to increase and anti-clockwise to decrease the pressure.

Gas valve bracket

Fig 1. Gas Valve

Page 43

BENCHMARK No.

COLLECTIVE MARK

GAS BOILER COMMISSIONING CHECKLIST

BOILER SERIAL No. NOTIFICATION No.

CONTROLS To comply with the Building Regulations, each section must have a tick in one or other of the boxes

TIME & TEMPERATURE CONTROL TO HEATING ROOM T/ST AT & PROGRAMMER/TIMER PROGRAMMABLE ROOMSTAT

TIME & TEMPERATURE CONTROL TO HOT W ATER CYLINDER T/STAT & PROGRAMMER/TIMER

HEA TING ZONE VAL VES FITTED NO T REQUIRED

HOT W ATER ZONE V ALVES FITTED NO T REQUIRED

THERMOSTATIC RADIA TOR VALV E S FITTED

AUT O M ATIC BYPASS TO SYSTEM FITTED NOT REQUIRED

COMBI BOILER

FOR ALL BOILERS CONFIRM THE FOLLOWING

THE SYSTEM HAS BEEN FLUSHED IN ACCORDANCE WITH THE BOILER MANUFACTURERS INSTRUCTIONS?

THE SYSTEM CLEANER USED

THE INHIBIT O R USED

FOR THE CENTRAL HEATING MODE, MEASURE & RECORD

GAS RATE ft3/hr

BURNER OPERATING PRESSURE (IF APPLICABLE) mbar

CENTRAL HEATING FLOW TE MPERATURE ¡C

CENTRAL HEATING RETURN T E MPERATURE ¡C

m3/hr

N/A

FOR COMBINATION BOILERS ONLY

HAS A W A TER SCALE REDUCER BEEN FITTED?

W H AT TYPE OF SCALE REDUCER HAS BEEN FITTED?

YES NO

FOR THE DOMESTIC HOT WATER MODE, MEASURE & RECORD

GAS RATE ft3/hr

MAXIMUM BURNER OPERATING PRESSURE (IF APPLICABLE) mbar

COLD WATER INLET T E MPERATURE ¡C

HO T W ATER OUTLET TEMPERATURE ¡C

W ATER FLOW RATE

N/A

/hr

FOR CONDENSING BOILERS ONLY CONFIRM THE FOLLOWING

THE CONDENSATE DRAIN HAS BEEN INST ALLED IN ACCORDANCE WITH THE MANUFACTURERS INSTRUCTIONS? YES

FOR ALL INST ALLATIONS CONFIRM THE FOLLOWING

THE HEATING AND HOT W ATER SYSTEM COMPLIES WITH CURRENT BUILDING REGULATIONS

THE APPLIANCE AND ASSOCIATED EQUIPMENT HAS BEEN INSTALLED AND COMMISSIONED IN ACCORDANCE WITH THE MANUFACTURERS INSTRUCTIONS

IF REQUIRED BY THE MANUFACTURER, HAVE YOU RECORDED A CO/CO2 RATIO READING? N/A YES CO/CO2 RATIO

THE OPERATION OF THE APPLIANCE AND SYSTEM CONTROLS HAVE BEEN DEMONSTRATED TO THE CUSTOMER

THE MANUFACTURERS LITERATURE HAS BEEN LEFT WITH THE CUSTOMER

lts/min

COMMISSIONING ENGS NAME PRINT CORGI ID No.

SIGN DATE

Page 44

SERVICE INTERVAL RECORD

It is recommended that your heating system is serviced regularly

and that you complete the appropriate Service Interval Record Below .

Service Provider. Before completing the appropriate Service Interval Record below , please ensure you have carried out the service

as described in the boiler manufacturer s instructions. Always use the manufacturer s specified spare part when replacing all controls

SERVICE 1

ENGINEER NAME

COMPANY NAME

TEL No.

CORGI ID CARD SERIAL No.

COMMENTS

SIGNATURE

SERVICE 3

ENGINEER NAME

COMPANY NAME

TEL No.

CORGI ID CARD SERIAL No.

COMMENTS

SIGNATURE

SERVICE 5

ENGINEER NAME

COMPANY NAME

TEL No.

CORGI ID CARD SERIAL No.

COMMENTS

DATE

SERVICE 2

ENGINEER NAME

COMPANY NAME

TEL No.

CORGI ID CARD SERIAL No.

COMMENTS

SIGNATURE

SERVICE 4

ENGINEER NAME

COMPANY NAME

TEL No.

CORGI ID CARD SERIAL No.

COMMENTS

SIGNATURE

SERVICE 6

ENGINEER NAME

COMPANY NAME

TEL No.

CORGI ID CARD SERIAL No.

COMMENTS

DATE

SIGNATURE

SERVICE 7

ENGINEER NAME

COMPANY NAME

TEL No.

CORGI ID CARD SERIAL No.

COMMENTS

SIGNATURE

SERVICE 9

ENGINEER NAME

COMPANY NAME

TEL No.

CORGI ID CARD SERIAL No.

COMMENTS

SIGNATURE

DATE

SIGNATURE

SERVICE 8

ENGINEER NAME

COMPANY NAME

TEL No.

CORGI ID CARD SERIAL No.

COMMENTS

SIGNATURE

SERVICE 10

ENGINEER NAME

COMPANY NAME

TEL No.

CORGI ID CARD SERIAL No.

COMMENTS

SIGNATURE

DATE

Page 45

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 8 716 114 750a (11/07)

This manual is to be used in conjunction with the variant part number of the bar code below:

Worcester, Bosch Group, Cotswold Way, Warndon, Worcester WR4 9SW.

Telephone: 01905 754624. Fax: 01905 753130.

Technical Helpline 08705 266241.

Worcester, Bosch Group is a trading name of BBT Thermotechnology UK Limited.

www.worcester-bosch.co.uk

Bosch Group

Worcester 24 SI II LPG User guide

Specifications and Main Features

Frequently Asked Questions

User Manual