Worcester 240 Combi BF Installation And Servicing Instructions

WALL MOUNTED COMBINATION BOILER FOR CENTRAL HEATING AND MAINS FED DOMESTIC HOT WATER INSTALLATION AND SERVICING INSTRUCTIONS GCNUMBER47 31110 BOILER OUTPUT Automatic Modulating Control To Domestic Hot Water and Central Heating Minimum 9.2 kW (31 ,400 Btu/h) Maximum 24.0 kW (82,000 Btu/h) IMPORTANT: THIS APPLIANCE IS FOR USE WITH NATURAL GAS ONLY THESE INSTRUCTIONS APPLY IN THE UK ONLY . ' ' THESE INSTRUCTIONS ARE TO BE LEFT WITH THE USER OR AT THE GAS METER

2. General Information ...................................................... Page 2 3. Data Technical ................................................................ Page 4 4. Siting the Appliance ...................................................... Page 5 5. Siting the Flue Terminal ................................................ Page 6 6. Air Supply ....................................................................... Page 7 7. Sealed System ................................................................ Page 7 8. Open Vent Primary Water System ............................... Page 8 9. Domestic Hot Water ...................................................... Page 9 ·1 . Installation R1egulations 1.1 Gas Safety (Installation and Use) ~egulations 1984 All gas appliances must be installed: by a competent person in accordance with the above regulations. Failure to install appli· ances correctly could lead to prosecution. 1.2 The manufacturers notes must not be taken,in any way,as overriding statutory obligations. 1.3 The compliance with a Briti<>h Stnnrl;ml rlnAs nnt, nf itsAlf, r.nn· fer immunity from legal obligations. In particular the installation of this appliance must be in accordance with the relevant require· ments of the Gas Safety (Installation and Use) Regulations 1 984 as amended, current lEE Wiring Regulations, local Building Regula· tions, Building Standards (Scotland)(Consolidation) and byelaws of the local Water Company. Health and Safety Document No. 635 (Electricity at Work Regulations). It should be in accordance with the relevant recommendations of the following British Standards. BS 6798:1987 Specification for installation of gas fired hot water boilers of rated input not exceeding 60 kW. BS 5449:1990 Central Heating for Domestic Premises. BS 5546:1990 Installation of gas hot water supplies for domes· tic purposes. BS 5440:1:1990 Flues and Ventilation for gas appliances of rated input not exceeding 60 kW: Flues. BS 5440:2:1989 Flues and Ventilation for gas appliances of rated input not exceeding 60kW: Air Supply. BS 6891 :1988 Installation of low pressure gas pipework installa· tions up to 28 mm (R 1 ). 1.4 To ensure that the installation will perform to the highest standards, the system and components should conform to any other relevant British Standards in addition tci those mentioned in the instructions. 2. General Information 2.1 This appliance is not suitable for external installation. 2.2 The appliance controls are set to provide a maximum output of 24 kW for the domestic hot water and a central heating load of up to 16.1 kW. 2.3 The appliance has a permanent pilot. 2.4 PRINCIPLE APPLIANCE COMPONENTS See Fig. 1. A low thermal capacity Gas to Water heat exchanger. A Water to Water heat exchanger to provide domestic hot water. Ft,dly modulating controls in the central heating and domestic hot water modes of operation. An expansion vessel, pressure gauge and pressure relief valve. A by-pass for the central heating system. Temperature safety cut·out controls. 2 10. Electrical ...... , .................................................................. Page 10 11. Installation ..................................................................... Page 1 4 12. Commissioning .............................................................. Page 17 13. Instructions to the User ................................................ Page 18 14. Inspection and Servicing .............................................. Page 19 15. Replacement of Parts .................................................... Pc;~ge 21 16. Short Parts List .............................................................. Page 28 17. Operational Flow Diagram ............................................ Page 29 18. Fault Finding ................................................................... Page 31 A water flow regulator. A standard horizontal flue assembly giving flue lengths from 229 mm to 420 mm. An optional extra extension flue kit to provide for flue lengths up to 559 mm long. An optional facia mounted programmer instead of the standard Operating Switch. 2.5 ELECTRICAL SUPPLY Main5 5upply: 2-1 OV ··, 50 I Iz, 150 wiltts. External fuse 3A. Internal fuses: T2A (F1) and T315mA (F2). 2.6 GAS SUPPLY The boiler requires 2.81 m' /h (99.3 ft' /hr) of gas. The gas meter and supply pipes must be capable of supplying this quantity of gas in addition to the demand from any other appliances being served. The table below gives an indication of limiting gas pipe lengths and the allowance to be made for fittings. Refer to BS6891 for further information. The meter governor should deliver a dynamic pressure of 20 mbar (Sin wg.) at the appliance. The complete installation, including the gas meter, must be test- ed for soundness and purged. Refer to BS 6891 . TOTAL LENGTH OF GAS SUPPLY PIPE (metres) Pipe Diameter 3 6 9 (mm) Gas Discharge Rate (m3/h) 2.9 - - 15 8.7 5.8 4.6 22 18.0 12.0 9.4 28 Note: Each fitting used in the gas line from the meter is equivalent to a length of straight pipe which must be added to the straight pipe length to give the total length. ie: Elbow = 0.5 metres, Tee = 0.5 metres, 90° Bend = 0.3 metres. 2.7 PACKING The appliance and flue components are packed in separate car- tons. 2.8 GENERAL INSTALLATION The appliance is supplied for connection to a sealed system but is suitable for use with an open vent system. The connections are supplied as an optional kit. The specified ventilation openings made into a wall or compart- ment door must not be obstructed. If the appliance is to be fitted into a compartment then the com- partment must conform to the requirements of BS 6798: 1987: Section 6. Do not place anything on top of the appliance. The clearances specified for servicing must be maintained.

Waterflow manifold [._ Central heating by-pass adjuster L__ Automatic air vent Gas to Water I h t h ea exc anger ~-. ------ Boiler I Sealed system l expansion vessel ~ Circulating pump Water to Water heat exchanger tl-r-A#11 ~ -c ----- Waterdiverter r- valve 14•---~ - -l ~ I I I I . ~~ ( ~ Pressure relief val ve - Domestic hot water o ut -- Mains cold water in - Central heating return ' -- Central heating flow 2.9 FLUE The appliance has a room-sealed balanced flue system to the rear. The standard flue assembly length is from 240 mm to 420 mm. An extention flue length from 420 mm to 559 mm is available. A terminal guard, Type GC 393 545, is available from Tower Flue Components, Vale Rise, Tonbridge, TN9 1 TB. Do not allow the flue terminal fitted to the outside wall to become obstructed or damaged. 2.1 0 CONTROLS The electronic control system and gas valve modulate the heat input in response to the central heating and domestic hot water temperature settings between minimum and maximum. The Operating Switch provides for the selection of domestic hot water only (WATER) or central heating and domestic hot water (HEATING & WATER) or OFF. A facia mounted programmer is available as an optional extra. A remote mounted programmer may be connected to the appli· ance. The integral facia displays indicate the status of the appliance. There is provision for the connection of a mains voltage room thermostat and/ or a frost thermostat. The electronic controls prevent rapid cycling of the appliance in the central heating mode. 3 2.11 SYSTEM NOTES WARNING Check that no dirt is left in either the gas and water pipework as this could cause damage to the appliance. Thoroughly flush the heating system and the cold water mains supply. Purge the gas supply before finally connecting the appliance .. The water pipe connections throughout a sealed system must be capable of sustaining a pressure of upto 3 bar. Radiator valves must conform to the requirements of BS2767 (10): 1972. The relief valve discharge must be directed away from any elec· trical components or where it would cause a hazard to the user. A drain cock to BS 2879 must be fitted to the lowest point of the system. For circuit design purposes it is important that due note is taken of the information given in Table 3 relating to the available pump head. 2.12 SHOWERS, BIDETS, TAPS AND MIXING VALVES Hot and cold taps and mixing valves used in the system must be suitable for operating at a mains pressure of up to 1 0 bar. Thermostatically controlled or pressure equalising shower valves will guard against the flow of water at too high a temper· ature. Hot and cold mains fed water can be supplied direct to an over· rim flushing bidet subject to local Water Company requirements. With all mains fed systems the flow of water from the individual taps will vary with the number of outlets operated simultane· ously and the cold water mains supply pressure to the property. Flow balancing using 'Ball·o·Fix' type valves is recommended to avoid an excessive reduction in flow or even starvation to indi· vidual outlets. For further information contact Worcester Heat Systems Ltd. 2.13 SAFETY CONSIDERATIONS The appliance must not be operated with the boiler inner casing cover removed. Work must not be carried out on the appliance without the gas and electricity supplies being switched off. Checks must be made to ensure that the ventilation openings made into walls and partitions are of the correct size and are not obstructed. 2.14 OPERATION Domestic Hot Water: With a demand for hot water the burner will light at its maximum setting and then automatically adjust its output to maintain the temperature rise of the delivered water. When hot water is no longer required, the burner will extinguish. The pump will continue to run for a short period to dissipate the residual heat from the appliance. Central Heating: With a demand for heating the burner will light at its minimum setting and gradually increase to give the maximum output. The output of the appliance is then automatically adjusted to maintain the temperature of the system. The output can reduce down to a minimum of 9.2 kW. If the system no longer requires even the minimum output to maintain the desired room temperature the burner will extinguish. The pump will continue to run to dissipate the residual heat from the appliance. The appliance will remain off for a fixed period of two minutes before re-lighting to automatically meet the system requirements. Domestic Hot Water and Central Heating: The appliance will supply heat to the central heating system as required. A demand for domestic hot water at a tap or shower will override the central heating requirement for the period of the domestic hot water demand. When hot water is no longer required the burner will extinguish and the appliance will return to the cen- tral heating state and its normal mode of operation. The pump will continue to run to dissipate the residual heat from the appli· ance as necessary.

The Data Plate is fixed to the control box casing. TABLE 1 TABLE 2 - Flue Details NOMINAL BOILER RATINGS mm inches Output Input Burner Setting Gas Rate Pressure Wall Hole Size Width 365 14.4 kW Btu/h kW Btu/h mbar. in.wg. m3!h tt3!h 9.2 31,400 12.6 43,000 3.0 1.2 1.22 43.0 24.0 82,000 30.0 102,400 14.7 5.9 2.81 99.3 Height 265 10.5 Standard Flue - Minimum Length 240 9.5 Standard Flue - Maximum Length 420 16.5 Extended Flue - Maximum Length 559 22 TABLE3 AVAILABLE PUMP HEAD Boiler Output Head Min. Flow Rate Temp. rise across Btu/h feet litres/min gal/min heating flow kW metres and return 9.2 31,400 4.9 15.9 12.0 2.64 11 °( (20°F) 24.0 82,000 2.0 6.5 22.0 4.81 15"C (28°F) TABLE4 SPECIFICATIONS CENTRAL HEATING FLOW FITTING 22 mm Compression CENTRAL HEATING RETURN FITTING 22 mm Compression COLD WATER MAINS INLET FITTING 1 5 mm Compression DOMESTIC HOT WATER OUTLET FITTING . 15 mm Compression 4VA1i.;A!ibi t~UMI~ i-l£1it) l -~"*''!1""m~ ....... -"'....-.:., ... w·~. ""'""'/,.,.;...,.;.w.1f ....... r· """""Mi·vf'o.·.""1-W'r-~;.,....,!'-."~: Mt ....... tfi'""'~'l"''l-}~~ · · 1..~1 ~r 1ju · ·ut . :m~· . i ltl: Fitiw ~t~ . 1HfiJf:ji~ ~.~ i,(;(~si! PKt:SSU~E Kt:d£YVALVt. u:l:J\RGEtrl'l~J.\11 """"''"d:,,, 1 !:l mm LompressiOn CASING HEIGHT 900 mm (35.4 in.) CASING WIDTH 450 mm (17.7 in.) CASING DEPTH 360 mm (14.2 in.) WEIGHT (including water) 48.7 kg (107lb.) INSTALLATION WEIGHT ~ 46.5 kg (1 02 lb.) " PACKAGED WEIGHT 49.6 kg (1 09lb.) TABLE 5 SPECIFICATIONS PRIMARY WATER CAPACITY 2.7litres (0.6 galls.) MAXIMUM COLD SUPPLY PRESSURE 10 Bar (150 psi) MINIMUM COLD SUPPLY PRESSURE (WORKING) FOR MAXIMUM HOT WATER FLOW 1.6 Bar (23.5 psi) MINIMUM COLD SUPPLY PRESSURE (WORKING) TO OPERATE THE APPLIANCE 0.6 Bar (9 psi) MAXIMUM CENTRAL HEATING FLOW TEMPERATURE Nominally 82°C (180°F) MAXIMUM STATIC HEAD (PRIMARY) 25 metres (81 ft) MIMIMUM STATIC HEAD (PRIMARY) 0.3 metres (1 ft) OUTPUT TO DOMESTIC HOT WATER Modulating 9.2-24 kW (31 ,400-82,000 Btu/h) OUTPUT TO CENTRAL HEATING Modulating 9.2-24 kW (31 ,400-82,000 Btu/h) MAXIMUM DOMESTIC HOT WATER FLOW RATE FROM THE APPLIANCE Nominally 8.5 litres/min ( ± 15%) (1 .87 gallons/min) EQUIVALENT DOMESTIC HOT WATER FLOW RATE TO GIVE A TEMPERATURE RISE OF 35°C Nominally 9.8litres/min (2.16 gallons/min) 4

4.1 The appliance may be installed in any room although par· ticular attention is drawn to the requirements of the current I.E.E. Wiring Regulations and, in Scotland, the electrical provi· sions of the Building Regulations applicable in Scotland, with respect to the installation of appliances in rooms containing baths or showers. Where a room sealed appliance is installed in a room contain· ing a bath or shower, any electrical switch or appliance control using mains electricity must not be able to be touched by a person using the bath or shower. 4.2 The appliance is not suitable for external installation. 4.3 The appliance does not require any special wall protection. 4.4 The wall must be capable of supporting the weight of the appliance. See Table 4. 4.5 If the appliance is to be fitted in a timber framed building, refer to the British Gas publication "Guide for Gas Installations in Timber Framed Housing". 4.6 The following clearances must be available for installation and for servicing. See Fig. 2. Installation Servicing Above 100mm 100mm In front 600mm 600mm Below 230mm 230mm Right hand side 5mm 5mm Left hand side 5mm Smm 4. 7 The appliance can be installed in a cupboard used for airing clothes provided that the requirements of BS 6798 and BS 5440:2 are strictly followed. 4.8 The airing space must be separated from the boiler space by a perforated non-combustible partition. Expanded metal or rigid wire mesh are acceptable provided that the major dimension is less than 13 mm. See BS 6798:1987. 4.9 No combustible surface must be within 75 mm of the cas- ing. See BS476:4. 4.1 0 The distance between the inner face of a cupboard door and the cabinet front should not be less than 75 mm. 4.11 Always consider the possible need to disconnect the pipes from the appliance after installation. Fig. 2. Appliance casing dimensions and required clearances. 600mm Space required in front SIDE VIEW for installation and servicing. I I 360 mm 1 I I I I I I I I I I I I I I I I I I I I I I I I -------------- I I I I I I I I FRONT VIEW 450mm Fixing holes 1 r-- 413 mm CRS. _, 1 I ~-~0~:--f _________ _j I II li I ! ,-fl .a_Lf,: 900m ~ 1 Space required below 5 mm i 1 I /). 1 for installation and servicing. Space required at left hand side -+t ~-+- . -.r ~ /) ________ ._j t for installation and servicing. ! L ______________ _j l Smm m Space required at right hand side for installation and servicing. 5

,_ ... -·ao· :e-···. ii ::,..:;;.r - -· Central heating flow -+--""' Central heating return Mains cold water in --It+--- Pressure relief valve discharge .......j.---------- 306 mm --~ • I \' . . _, TIW!M.T\1111- l_l ~ mm All~"""" Gas cock ---------405mm --------1~ 5. Siting the Flue Terminal See Fig. 4 5.1 The flue must be installed as specified in BS 5440:Part 1. 5.2 The terminal must not cause an obstruction nor the dis- charge cause a nuisance. 5.3 If the terminal is fitted within 850 mm of a plastic or painted gutter or within 450 mm of painted eaves then an aluminium shield at least 750 mm long should be fitted to the underside of the gutter or painted surface. 5.4 If a terminal is fitted less than 2 metres above a surface to which people have access then a guard must be fitted. See Sec- tion 2.9. Fig. 4. Siting of the flue terminal. MINIMUM SITING DIMENSIONS FOR POSITIONING THE BALANCED FLUE TERMINAL. A 6 5.5 The terminal guard must be evenly spaced about the flue terminal and fixed to the wall using plated screws 5.6 In certain weather conditions a terminal may steam and sit- ing where this could cause a nuisance should be avoided. 5.7 Take care to ensure that combustion product:; do not enter ventilated roof voids. TERMINAL POSffiON MIN. DISTANCE A-Directly below an openable window or other opening e.g. air brtck 300 mm (12in.) B-Below gutters, soil pipes or drain pipes 300 mm (12in.) c- Below eaves 300 mm (12in.) D-Below balconies or car port roof 600 mm (24in.) E- From vertical drain pipes and soil pipes 75mm(3in.) F- From internal or external corners 600 mm (24in.) G--Above ground, roof or balcony level 300 mm (12in.) H-From a surface facing a terminal 600 mm (24ln.) I- From a terminal facing a terminal 600 mm (24ln.) J- From an opening in a car port (e.g. door window) Into dwelling 1200 mm (47in.) K- Vertically from a terminal on the same wall 1500 mm (59in.) L- Horizontally from a terminal on the same wall 300 mm (12ln.) M-From door, windoworairvent(achieve where possible) 300 mm (12in.)

6.1 The appliance does not require a separate vent for combus- tion air. 6.2 Installations in cupboards or compartments require perma· nent vents for cooling purposes, 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. 6.3 There must be sufficient clearance around the appliance to allow proper circulation of ventilation air. The clearances required 7. Sealed System See Figs. 5 and 6 7.1 The system must comply with the requirements of BS 6798 and BS 5449:1. 7.2 The appliance must not be operated without the system being full of water, properly vented and pressurised. 7.3 Tht:! pressure relief valve operates at 3 bar (45lb/in2). The dis- charge must be directed away from electrical components or where it might be a hazard to the user. 7.4 The pressure gauge indicates the system pressure which must be maintained. 7.5 The 10 litre expansion vessel is charged to 0.5 bar and is suitable for a static head of 5 metres (17 .Sft). The pressure can be increased if the static head is greater than 5 metres (17.5ft). 7.6 With an initial system pressure of 0.5 bar, a system capacity of about 104 litres can be accommodated. Refer to BS 707 4 Pt. 1 for more information. The charge pressure can be increased but with a decrease in system volume. Fig. 5. Sealed primary water system. lockshield valve. Radiator valve. lllllllll J 11111111 Note. A drain cock should be installed at the lowest point of the heating circuk and beneath the appliance. 7 for Installation and Servicing will normally be adequate for venti· lation. See Section 4.6. 6.4 The minimum free areas required are given below. Position of Air from Air direct air vents the room from outside High Level 270 cm2• 135 cm2• (42in2.) (21 in2) Low Level 270cm2• 135 cm 2 • (42in2.) (21 in2.) 6.5 Refer to BS 6798 and BS 5440:2 for additional information. 7.7 The filling point must be at low level. See Figs. 5 and 6. 7.8 Water loss must be replaced, See Fig 6. The connection should be made in the central heating return as close to the appliance as possible. See Figs. 5 af)d 6 7.9 The make-up vessel must be fitted with a non-return valve. 7.1 0 Repeated venting loses water from the system. It is essen- tial that this water is replaced and the system pressure main· tained. 7.11 Connections to the mains water supply must not be made without the authority of the local Water Company. 7. 12 The pump is set at maximum and must not be adjusted. 7.1 3 Connections in the system must resist a pressure of up to 3 bar. 7.14 Radiator valves must conform to BS 2767(10):1972. 7.15 Other valves used should conform to the requirements of BS 1010. 7.16 To make use of the extra heating available from the appli· ance at the end of any demand, it is recommended that a single small radiator be left permanently open. Sealed system --expansion vessel -· Water to Water heat exchanger Central heating by-pass adjuster- '+t--T"H--' Fill point-----' Heating return Heating flow. Domestic hot water out t I l Note. The mains cold inlet connection to the appliance must come before any other connection from the cold supply. Domestic coldwater. _.. British Standard stop valve. Fixed spindle type. +- Water main.

Heating Return Non return valve +- Worcester Combi-Fill System Non return va-4!- ~ Hose union 1 1-----t..•--.f .... lll-..;...===:u ~=· •• ~ +- !! !! Stop cock u ,. Test cock \l,m,;~ Temporary hose 8. Open Vent Primary Water System See Fig. 7 8.1 The size of the flow and return pipework is given in Section 3 - Table 4. The components required to connect the appliance to an open vent system are available as an optional extra kit. 8.2 The feed and expansion cistern should be arranged so that there is a minimum static head of 0.3 metres (12in.) above the top of the appliance or above the highest point in the heating circuit, whichever is the higher. See Fig. 7. 8.3 The feed and vent pipe should be 22 mm diameter and rise continuously from the appliance to the feed and expansion cis- tern. Fig. 7. Open vent water system. S.H.-Minimum static head 300 mm 112 in. I measured from the top surface of the appliance or highest point in the heating system to the water level in the feed and expansion tank. Feed and expansion tank lockshield valve. Radiator valve. lllllllll J 11111111 Note. A drain cock should be installed at the lowest point of the heating circuit and beneath the appliance. 8 Heating Return Auto air vent 1-.... 1-- Fill Point ' Heating Return 300mm (12inl min. above the highest point of the system. 8.4 A pressure relief Viilve is not required on an open vented sys· tem. If the pressure relief valve is left in position then a discharge pipe must be fitted which terminates in a position such that any water or steam discharge does not cause a hazard to the occu- pants or damage electrical components. 8.5 Air within the appliance will be expelled via the feed and vent connection or dissipated into the rest of the system which must be fitted with manual air vents at any high point. 8.6 The pump is set to maximum and must not be reset. 8.7 To make use of the extra heating available from the appli· ance at the end of any demand, it is recommended that a single small radiator be left permanently open. Central heating Sealed system --expansion vessel --Water to Water heat exchanger by-pass adjuster -'"l'f+---!-+--1---l Fill point ---- .J Heating return Heating flow. Domestic hot water out I Note. The mains cold inlet connection to the appliance must come before any other connection from the cold supply. Domestic cold water. ,.. British Standard stop valve. Fixed spindle type. -Water main.

9.1 The following are general requirements and, if necessary, reference should be made to the local Water Company before fitting the appliance. 9.2 MAINS COLD WATER INLET. Devices capable of preventing the flow of expansion water must not be fitted unless separate arrangements have been made. An expansion vessel connection point (Rc'h) is provided adjacent to the flow switch within the appliance. A Zilmet Z160 expansion vessel is the preferred type. A thread sealant compatible with potable water must be used. 9.3 The final 600 mm of the mains cold water connection to the appliance should be made in copper tube only. 9.4 The appliance is suitable for a mains pressure of up to 1 0 bar (150 lb/in'). 9.5 The appliance is fitted with a mains supply isolating valve. 9.6 The maximum domestic hot water flow rate is 8.5 litres/min. ( ± 15%) (1.87 gallons/min.). 9.7 In winter (when the mains inlet water temperature is lower) a reduced flow rate at the taps will be required to achieve the maximum hot water delivery temperature available in warmer weather. 9.8 It is a requirement that long pipe runs to the taps or shower should be insulated to prevent the rapid cooling of domestic hot water after a tap or shower has been turned off. Refer to BS5546: 1990. 9 9.9 Hot and cold taps and mixing valves used with this appli· ance must be suitable for operating at a pressure of up to 1 0 bar (1 SO lb/in'). 9.10 No anti·syphonage arrangements are necessary except for some loose head showers. See also Section 9.11 following. 9.11 Thermostatically controlled or pressure equalising shower valves will guard against the flow of water at too high a temper· ature. 9.12 The head of a loose head shower must not fall closer than 25 mm (1 in.) above the top edge of the bath to prevent its immersion in bath water. Alternatively the shower must be fit· ted with an anti·syphonage device at the point of the flexible hose connections. 9.13 The supply of hot and cold mains water direct to a bidet is permitted, (subject to local Water Company requirements), pro· vided that the bidet is of the over·rim flushing type. The outlet(s) should be shrouded and unable to have any temporary hand held spray attached. No anti·syphonage arrangements are nee· essary. 9.14 AS the maximum temperature of the Water to Water heat exchanger is limited by the control circuit, there is normally no need for water treatment to prevent scale accumulation. In exceptional circumstances a device to prevent scale formation can be fitted. Installation of a scale inhibitor assembly should be in accor· dance with the requirements of the local Water Company. An isolating valve should be fitted to allow servicing. The water hardness can be determined using a standard test paper or by reference to the local Water Company.

See Figs. 8, 9,10,11 and 12. 1 0. 1 MAINS SUPPLY. 240 V - , SO Hz, 1 SO watts. External Fuse 3A. Internal Fuses: T2A (F1) and T31 SmA (F2). 1 0.2 It must be possible to completely isolate the appliance. 1 0.3 Connection to the mains supply should be via a double pole isolator with a contact separation of 3mm in aU poles and supplying the appliance and controls only. 1 0.4 The appliance must be earthed. 1 0.5 Mains Cable. 0. 7S mm• (24 x 0.20 mm) to BS 6SOO Thble 16. If a new cable is needed it must be connected into the terminals marked L (Brown or Red lead), N (Blue or Black lead) and ;!<- (Green/Yellow or Green) and be held securely in the cable clamp. For access refer to Section 14. NOTE: Ensure the earth lead is longer than the live and neutral leads. 10.6 The wiring between the appliance and the electrical supply shall comply with current lEE Wiring Regulations and any local regulations which apply. 10.7 If a room and/or frost thermostat is to be fitted refer to Figs. 11 and 12. The thermostats must be suitable for use on mains voltage. 1 0.8 A facia mounted programmer is available as an extra. Instructions are supplied with the programmer kit. 10.9 A time switch or programmer can be fitted externally to the appliance. 10.10 SAFETY CHECK. After installation or in the event of an electrical fault the electrical system shall be checked for short circuits, fuse failure, incorrect polarity of connections, earth continuity and resistance to earth. Fig. 8. Wiring Diagram - Control panel and facia. (All components shown viewed from front of appliance) A TO GAS VALVE MAIN ~Fr:w~ fj-m~------------1 br e3X OX11 ~ 1 • • 410 3 F2 FUSE I br1]1 4 I bl 0 2X8 MAIN DRIVER BOARD I r----;C;y 3 fiFt I br : 1L tj FUSE 1~: bl I 2NX7 X1 v • 3E 2 pk I 4E X5 X4 X3 X2 3 I v 112 31 2312345123 4581234 5 81 gvt~rn!9J11~!tr1Jr~!ttr.r~r.r~ ~ 'i~tVV%-J ~~~ ~ ~ in I ;_ .:.: ~~ .. :.. ---' OVERRUN ~ Iii DIVERTER H£ATING HOT WAml MODUREG THERMOSTAT i j! VALVE SENSOR msOR REGULATOR 12 12 MICRO·SWITCH MAINS COLOUR CODE br-brown bl-blue gy-green and yellow bk-black or-orange r-red w-white y-yellow g-grey v-violet pk-pink 10

(All components shown viewed from front of appliance) ~-- /~~-~--~__:-_-_-:.==== = = = =-= ~~~==:--i I // "" I 1 r i : I I I I I I I I I I I I I COLOUR CODE I ~ br-brown bl-blue gy-green and yellow bk-black or-orange I ~ r-red w-white y-yellow g-grey v-v1olet pk-p1nk l I ------:~ ...L . ...--· ---· --·----·-- ~ L.__..- . --·-- ·---·--· L-.---- T·-·- I I I I I I I I I ~ I I Pump Overrun Thermostat or ----~ _____ _j I ---·-·==--~: ------·- I i : I I I I I I I I I /) I -----~/ I I I I ---------------------------1 Diverter Valve Micro-Switch br gy-4--- bl 11 l~bl ~llt=1 y .If "L-- ~~~~~~ Gas Valve ~~ Domestic Hot ~UW Water Sensor r r C F Main Valve Modureg Regulator I I I I I I I I I I I - ....L

l I .X11!PIN2t -------------- FROST THERMOSTAT IIF FITTED I black DEMAND INDICATOR :,:,:- ---------- -;,;INDRi~R-;,.u;;; l I FUSE F1 T2A 1---------_r::::::]_ lr--1 X4 !PIN 41 u X41PIN 51 RELAYRY1 I XBIPIN 11 brown XIO !PIN 31 white XIO !PIN 21 OPERATING SWITCH lOR PROGRAMMER! X4 !PIN 3! MICRO SWITCH w I c DHW . I I grey X3 !PIN 31 L_ _______ _ XSIPIN 1) brown PUMP OVERRUN THERMOSTAT I I I I I I I I I I I I I I I I I I L ~~z _ ----------- X6!PIN3i ------------ Fig. 1 0. Functional flow diagram Fig. 11 . Room thermostat connections. Remove link. 1 2 3 4 5 PUMP Terminal X4 on main driver board. Honeywell room thermostat T60608 (or similar.) orange brown TRANSFORMER violet FUSE F2 T315 rnA X31PIN 41 WATER DIVERTER VALVE MICRO SWITCH • _______ _j red XlWIN 51 CENTRAL HEATING SENSOR DOMESTIC HOT WATER SENSOR ELECTRONICS ELECTRONICS TEMPERATURE CONTROL POTENTIOMETER _____ __J brown I •N ~----------------------------------------~N ~----------------------------------------------~~N Fig. 12. Frost thermostat connections. 1 2 3 4 5 Terminal X4 on main driver board. Honeywell frost thermostat T 4160A (or similar.)

9mm ~el 1: I 2i.E COL<'> ~~ 5: w Wal mounting plate Inside plaster I E E ~ I I 450mm 365 mm Wall aperture 348mm --t=j---o-- 410mmCRS U'J a: u E E ... CD "' "'- E E = 0.0 <0 Drill four holes in wall to suit No. 12 wall plugs .., .-

1. Unpack the appliance and check the contents against the enclosed packing list. . 2. Remove the cabinet:- (a) Remove the cabinet front cover by lifting and pulling for- ward. (b) Remove the inner casing by unscrewing the four retaining screws. 3. From the carton containing the flue kit, remove the flue terminal, flue duct, air duct and the package containing: 4- No. 8 wall plugs. 1 - Roll ducting tape. 4 - No. 8 wood screws 1 - Tube of silicone sealant. Separate the air and flue ducts from the terminal. 4. Unscrew the two M6 nuts from inside the boiler casing holding the wall mounting plate onto the back of the boiler and remove the plate. Retain the nuts for future use. 5. From the dimensions given in Fig. 13 and, using the wall mounting plate as a guide, carefully mark the four mounting holes and the position of the balanced flue duct. Make sure the marking is accurate as the eventual squareness of the appliance will depend on this. 6. Drill the four retaining holes 70mm (2.75 in.) deep. fit the wall plugs supplied with the appliance. 7. Cut the 36.5 mm (14.4 in.) x 265 mm (10.5 in.) hole through the wall for the balanced flue air duct. Make good any plas- ter or brickwork. 8. Screw the wall mounting plate into position using the four No. 12 x 60 mm (2.5 in.) long screws provided with the appli- ance. 9. Measure the distance from the inside edge of the mounting plate to the outside of the wall W. See Fig. 13. 10. Fit the air ducts together and adjust the total length until it corresponds with the W dimension. Using the ducting tape provided firmly tape the joint. See fig. 14. 11 . From the inside, push the assembled air ducts through the aperture with the flanged end of the duct on the inside. 12. Remove the two screws holding the flue hood in position and remove the flue hood. 1 3. Apply the silicone sealant in a bead approximately 10 mm (0.38 in.) diameter around the balanced flue locating spigot on the back face of the appliance. See Fig. 1 5. 14. Lift the appliance onto the mounting plate and locate the two M6 studs on the back plate into the twci holes in the back of the casing. Locate the balanced flue spigot into the balanced flue air ducts. fasten the appliance with the two M6 nuts retained from instruction 4. 15. From the outside, make good the gap between the air duct and the brickwork. Fit the flue terminal to the air duct and mark the position of the four fixing holes. Drill four holes 5 mm (0.19 in.) diameter x 30 mm (1.25 in.) deep in the wall and fit the wall plugs provided. 16. Fix the flue terminal to the wall using the four No. 8 wood screws. NOTE: The flue terminal is not symmetrical and the narrow air inlet gap is at the top. The top flange is marked TOP. 17. From inside the appliance enter the exhaust duct, plain end first. Engage the exhaust duct over the front half of the exhaust duct attached to the flue terminal. Slide in the exhaust duct and secure the flange with the screws but do not tighten. 18. Engage the spigot on the flue hood into the exhaust duct and slide into position on the heat exchanger. Fix into position with the two screws at the front. 14 19. Tighten the screws from instruction 17. Seal telescopic joint with tape provided. Fig. 15. Arrangement of balanced flue and terminal. 10 mm 10.4 in.) diameter continuous seam of silicone sealant all around. !See below.) Telescopic flue duct. Drill and plug wall. Secure mounting plate '...-----------..... with four screws. 1 0 mm (0. 4 in.) diameter continuous seam of silicone sealant all around.

Open Vent System: Undo the three screws securing the casing sealing plate. Discard the plate and retain the gasket. See Fig. 17. Remove and discard the automatic air vent. Fit the preformed pipe (optional extra) using the three screws, washers and gasket. See Fig 18. Connect the feed and expansion tank. Remove the knock-out section in the top panel with a pair of pliers. Fig. 16. Automatic air vent. Unscrew and discard the cap Automatic air vent (Sealed systems only! 1111111111 mmm Feed and vent connection _:::_l~~r !Open vent water system only) Gas to Water heat exchanger 15 Fig. 17. Cover plate (Sealed Systems). Appliance casing top panel Cover plate fixing screws 131 Fig. 18. Pipe connection for open vent systems. Appliance casing top panel Pre-formed feed and vent pipe To Gas to Water heat exchanger

Check that all the water connections and the gas connection have been tightened. If a facia mounted programmer is to be fitted, unscrew the upper two screws holding the facia panel in place and carefully lower the facia. See Fig. 19. Unplug the Operating Switch from the terminal X1 0 on the main driver board. See fig. 8. Unscrew the four screws holding the switch plate and remove the complete Operating Switch assem· bly. Fit the programmer and tighten the four screws. Plug the programmer into terminal X10 on the main driver board. Lower the control box as described in Section 14.3(d). Connect the mains electrical supply to the appliance and con· nect any room and/or frost thermostats. The electrical leads to the room and frost thermostats must pass through the appropri· ate holes in the control panel and be fixed with the cable clamps provided. See Fig. 20. Refit the facia panel. Test the gas supply pipework up to the appliance for soundness as indicated in BS 6891. Refer to Section 12 for a full description of the filling, venting and, with a sealed system, the pressurising of the system. If the appliance is not to be commissioned immediately, replace the cabinet front panel and control box. Check that the gas supply, the electrical supply and the water connections are all turned off. If the premises are to be left unoccupied during frosty condi· tions, then commission the appliance as described in Section 1 2 and leave it under the control of the frost thermostat or leave operating continuously with the room thermostat set at 6°C. 16 Fig. 1 9. Appliance casing and control equipment fixings. -;L Top panel fixing screws 121 ,. Inner casing cover fixing screws 14) • • p c Control box fixing screws 12) Upper facia panel fixing screws 12) l I I -·· ····~c m·e -· -: __ ; ~,: ..... .._ .... " ... - Lower facia panel fixing screws 12)

ro GAS VALVE Earth MAINS ro ro TO WATER DIVfRTER VALVE MICRO-SWITCH ro ro ro 12. Commissioning 12.1 The appliance is despatched with the controls set to provide a maximum output for domestic hot water of 24 kW (82,000 Btu/h) and satisfy a central heating load of 16.1 kW (54,900 Btu/h). The controls can be reset to increase the heat load capability to 24 kW (82,000 Btu/h). Refer to Section 12.4- Central Heating. It is not necessary to set the output below 16.1 kW (54, 900 Btu/h) as it is automatically modulated to satisfy lower heat loads. Domestic Hot Water System. Check that the mains water sup· ply has been fully flushed out at installation. Central Heating System. Check that the central heating system has been fully flushed out at installation. Gas Service . The complete system, including the meter, must be inspected and tested for soundness and purged as indicated in BS 6891. 12.2 APPLIANCE AND CENTRAL HEATING SYSTEM PREPARATION Remove the cabinet front panel. Check that the electrical supply and the gas service to the appli· ance are off. See Fig 3. Check that all the water connections throughout the system are tight. Open the system valves at the appliance. See Fig 3. Open all the radiator valves, fill the system and vent each radiator in turn. On sealed systems the automatic air vent, (fixed to the flow manifold) will vent the appliance. Remove the boiler inner casing cover to check that the air vent cap has been removed. See Figs 16 and 19. Replace the cover immediately. Check that the pressure relief valve operates by turning the knob anti-clockwise until it releases. Water sho1,.tld be expelled from the discharge pipe. See Fig. 21. Lower the control box to gain access. Refer to Section 14.3(d). SEALED SYSTEMS ONLY Set the Expansion Vessel Pressure The charge pressure of the expansion vessel as despatched is 0.5 bar, which is equivalent to a static head of 5 metres (17 ft). The charge pressure must not be less than the static head at the point of connection. See Fig. 5. A Schraider type tyre valve is fit· ted to the expansion vessel to allow the charge pressure to be 17 PUMP PUMP ~-ll\JN TltERMOSTAT TO ROOM THERMOSTAT I OPTIONAL I CENTl\AL DOMESTlC GAS VALVE HEATING HOT WATER MOOUREG SENSOR SENSOR REGULATOR TO FIIOST TltEAMOSTAT IOPTlONALI increased if necessary. Set the System Pressure Fill the system until the pressure gauge shows 2.5 bar (37 lb/ins') and check for water soundness. Release water from the system using the relief valve test knob until the System Design Pressure is obtained, up to a maximum of 1 .5 bar. System Design Pressure in bar = Static Head of the System in bar+ 0.3 Note: 1 bar is equivalent to 10,2 metres (33.5 ft) of water. Set the movable pointer on the pressure gauge to coincide with the indicating pointer giving a permanent record of the set sys· tern pressure. If the pressure indicated on the pressure gauge is greater than 2.5 bar when operating at the maximum central heating tern· perature, an extra expansion vessel must be fitted to the system as close as possible to the appliance central heating return con· nection. The appliance (as despatched) can accommodate a system vol· ume of about 104 litres. Refer to BS 7074 Part 1. If the system volume is in excess of that accommodated by the expansion vessel fitted to the appliance then an extra vessel must be fitted as close as possible to the central heating return connection of the appliance. Any extra vessel fitted must be pressurised to the same figure as the integral vessel. If the expansion vessel fails then the speci· fied replacement must be fitted . Fig. 21 . Pressure relief valve. r Pressure gauge capillary connection Pressure relief valve discharge pipe

Any programmer fitted on the appliance should be set up at this stage following the instructions sent with the programmer. The plug-in programmer will retain the setting for up to four weeks following an interruption in the electricity supply. 12.4 APPLIANCE OPERATION Check that the electrical supply to the appliance is off. Set the Operating Switch (or Programmer) to OFF. Remove the inner casing cover. Refer to Section 14.3(b). Disconnect the electrical connections from the Modureg actua- tor. Do not leave them unprotected. See Fig. 22. Turn on the gas supply and reconnect the electricity supply. Push hard on the gas valve button and keep it pressed in. At the same time push the red igniter button. When it clicks the pilot (see through the inspection window) should light. If the pilot does not light immediately, press the igniter button repeatedly until it does. When the pilot has lit continue to hold the gas valve button in for a further 20 seconds, then release it slowly. CAUTION: If the pilot does not stay alight, twist the gas valve button in the direction of the arrow. Wait for three minutes and repeat the operation until the pilot is lit Continue to hold the gas valve button for thirty seconds. then release it slowly. Test for gas soundness at the joint between the pilot pipe and the burner with leak detection fluid. Observe the pilot flame. It should be about 20 mm long and envelope the spark electrode tip. It not, reler to Section 14.4. See Fig. 25. If the pilot still does not light, contact Worcester Heat Systems Service Department. Replace the inner casing cover. Reconnect the electrical connections to the gas valve. Loosen the hurnRr prRssurR t.P.st point sr.rP.w and mnnP.r.t a pmssurR gau~;P. See Fig 22. Domestic Hot Water. Switch on the electncity supply. Set the Operating Switch (or Programmer) to WATER and fully open a hot water tap. The boiler should light at a burner pressure of between 1 4 and 15mbar (5.6 and 6.0 in. wg.). If the burner pressure is low, check that the supply pressure at the gas valve inlet is at least 19 mbar (7.6 in. wg). Note: The burner pressure is factory set and if (after checking that the supply pressure is sufficient) the correct pressure is not obtained then Worcester Heat Systems Service Department should be contacted. Gradually close the hot tap and check that the burner pressure drops. Fully open the tap and check that the burner pressure ris- es. Fully close the tap and check that the burner goes off. The pump will continue running until the appliance has cooled to a preset temperature. Set the Operating Switch (or Programmer) to OFF. Central Heating Check that all the radiator valves are open. Set the room thermo- stat and the Central Heating Temperature Control to maximum. On sealed systems check that the system is pressurised and set to the required pressure as indicated on the gauge. Set the Operating Switch (or Programmer) to HEATING & WATER. The burner will light. The appliance will modulate its output from 9.2 kW (31 ,400 Btu/h) to the set output of 24 kW (82,000 Btu/h) over a period of about two minutes. Check the system to ensure that all the radiators are heating up evenly. Shut down all but one of the radiators and observe the burner pressure fall. Open all of the radiator valves and check that the burner pressure rises. 18 Balance the system so that the required temperature difference across the central heating flow and return pipes is obtained. See Table 3. Adjust the central heating by-pass valve until the same tempera- ture difference is obtained. See Fig 23. This should be carried out with only a single radiator operating. If thermostatic radiator valves are fitted then one radiator should be left uncontrolled. The bypass valve should never be fully closed. If the heat load is in excess of 16.1 kW (54,900 Btu/h) then reset the controls to the maximum of 24 kW (82,000 Btu/h) by carefully rotating the adjustment potentiometer to its maximum position. Access is gained to the adjustment point by lowering the electrical control box. Indicate the new setting pressure on the data plate. Set the room thermostat to minimum and check that the burner goes out. Reset the room thermostat to maximum and the burn- er will relight and follow the nqrmal operating procedure. Set the Operating Switch( or Prograr.1mer) to OFF. Turn off the gas service cock and the electrical supply to the appliance. Drain the system while the appliance is still hot. Refill, vent and, with a sealed system, re-pressurise as described in Section 12.2. Domestic Hot Water and Central Heating Turn on the electricity supply to the appliance and open the gas supply cor.k at the appliance. Light the appliance as described in the preceding notes. Set the Operating Switch (cr Programmer) to HEATING & WATER. If a programmer Is fitted, set the domestic hol water Lo Continuous or 24Hrs and the central heating to ON. The burner will light and heat will pass into the system. Turn on a hot water tap and check that fully heated hot water is 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. Set the Operating Switch (or Programmer) to OFF and the burner will go out. 12. 5 COMPLETION OF COMMISSIONING 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 front panel. If the appliance is being passed over to the user immediately, refer to Section 13 - Instructions to the User and set the controls to the user's requirements. If the appliance is to be left inoperative, check that the Operating Switch is set to OFF. Turn off the gas service cock and switch off the electricity supply. If there is any possibility of the appliance and system being left inoperative during frosty conditions, drain the appliance and system. For short inoperative periods leave the boiler under the control of a frost thermostat or operating continuously under the control of a room thermostat set at 6°C. 13. Instructions To The User 13.1 Tell the user how to operate the appliance and hand over the Users Instructions leaflet. 1 3.2 Tell the user what to do if the the heating system is not to be used in frosty weather. 13.3 Tell the user the sealed system set pressure if applicable. 13.4 Tell the user of the importance of regular servicing. Worces- ter Heat Systems Ltd offer a comprehensive maintenance con· tract.

Electrical connections - Main valve ----"'""'- {brown • blue • green/yellow) Maximum pressure adjuster -----.._ Minimum pressure adjuster Note. Turn the nuts clockwise to increase and anti-clockwise to""""'"

Section 14.3(a). Unscrew the two screws as shown in Fig. 19, Support the assembly and allow it to hinge down into the servic· ing position. Make sure no damage is done to the pressure gauge capillary tube or electrical wires. (e) Flue Hood. Unscrew the two screws fixing the flue hood and slide the flue hood assembly from the appliance. See Fig 24. When refitting the hood ensure that the rear return passes under the lip at the rear of the combustion chamber. (~ Combustion Chamber Cover. Remove the the inner casing cover. Unscrew the six screws securing the cover and remove the cover. See Fig 24. (g) Main Burner Assembly. Remove the combustion chamber cover. Unscrew the pilot fixing screws. Pull off the electrode lead and pull out the electrode. Undo the pilot pipe and remove the pilot burner. See Fig 25. Unscrew the two screws and remove the burner assembly by lifting the front of the burner and pulling forward. See Fig 26. 14. 4 SERVICE OF COMPONENTS Clean the Main Burner. Brush the blade tops and mixing tube with a soft brush and check that all the flame ports are clear. Remove any blockages with a non-metallic brush. Inspect the injector and clean with a soft brush. Replace the injector if it appears damaged. Do not use a wire brush or anything likely to cause damage. Clean the Pilot Burner Assembly. Brush with a soft brush. Remove the pilot injector and clean by rinsing it in warm water. Replace the spark electrode if it appears damaged. Fit the elec· trade lead before replacing the electrode. When reassembling see Fig. 25 for correct positioning of the spark electrode. Clean the Gas to Water Heat Exchanger. Cover the main burner manifold with a cloth. Clean the heat exchanger using a soft brush. Remove the deposits from the bottom of the combustion chamber. Do not distort any of the blades. Combustion Chamber Insulation. Examine and replace any pads that are damaged. See Section 15.6. Controls. Remove any dust or deposits using a soft non-metallic brush. Take care not to mishandle any component connections. Reassemble the appliance in the reverse order. Check that all components are in place and correctly fixed. Leave the cabinet front panel to be fitted after checking the oper· ation of the appliance. 14. 5 TEST THE APPLIANCE On completion of the service and reassembly of the appliance, check for gas soundness and the correct operation of the appli· ance as described in Section 12 - Commissioning. Refit the cabinet front panel and reset the controls to the users requirements. Fig. 24. Appliance components and fixings (upper assembly). L Combustion chamber cover and flue hood fixing screws 12). 0 Combustion chamber cover fixing screws 14) Combustion chamber cover 0 0 20 1 ~ Pump overrun thermostat ~Overheat thermostat 0 0 0

Thermocouple 0 2 mm PILOT SHIELD REMOVED FOR CLARITY Fig. 26. Main burner fixings. Fig. 27, Pilot burner settings. Main burner fixing screws 121 15. Replacement of Parts · 15.1 WARNING. Switch off the electricity and gas supplies before replacing any components. After the replacement of any components, check for gas soundness where relevant and carry out functional checks as described in Section 1 2 - Commissioning 15.2 COMPONENT ACCESS To replace components it is necessary to remove one or more sections of the cabinet and cover plates within the appliance as described in Section 14.3. The facia panel and control box may also need to be lowered as described in Section 14.3 21 PILOT SHIELD REMOVED FOR CLARITY 15.3 DRAINING THE APPLIANCE Check that the eLectricity supply to the appliance is turned off. Before removing any component holding water it is important that as much water as possible is removed from the appliance. (a) Central Heating Circuit. Turn off the central heating flow and return valves at the appliance. See Fig 3. Fit a tube to the drain tap on the Water to Water heat exchanger and open the tap about one turn. See Fig 30. Close the drain tap when the flow has stopped. Some water will remain in the expansion vessel, pump, diverter valve and Gas to Water heat exchanger and extra care must be taken when removing these components. (b) Domestic Hot Water Circuit. 1l.irn off the mains cold supply valve at the appliance and open the lowest hot water tap. See Fig 3. A quantity of water will remain in the Water to Water heat exchanger and the diverter valve and extra care must be taken when removing these components.

See Fig 16. Remove the inner casing cover and flue hood assembly as described in Section 14.3(b) and (e). Drain the central heating circuit as described in Section 15.3(a). Unscrew the assembly. Fit the replacement assembly. Open the valves and fill and re-pressurise the system as described in Section 12.2. 2. Overheat Thermostat. See Fig. 24 Check that the electricity supply to the appliance is turned off. Remove the inner casing cover as described in Section 14.3(b). Lower the facia as described in Section 14.3(c). Remove the two M3 screws holding the overheat thermostat to the heat exchanger. Unscrew the overheat leads from the gas valve. Push the grommet through the hole in the casing and thread the lead assembly through the hole. Fit the replacement overheat thermostat in reverse order ensuring a layer of heat sink compound is under the thermostat head. 3. Gas to Water Heat Exchanger. See Figs 16, 28 and 29. Check that the electricity supply to the appliance is turned off. Drain the central heating circuit as described in Section 15.3(a). Remove the flue hood assembly, pump overrun thermostat, overheat thermostat and main burner as described in Sections 14.3(e, f, and g), 15.4(4) and 15.4(6). Unscrew the flow connectors at the heat exchanger and at the bottom left of the inner casing and move the heat exchanger to one side. Unscrew the return connection at the bottom left of the inner casing and manoeuvre the heat exchanger from the casing. Carefully remove the left hand insulation pad and left hand com· bustion chamber side panel. Transfer the return pipe to the new heat exchanger leaving the connector nut loose. Fit the replacement heat exchanger in the reverse order ensuring all the fibre washers are in place and a layer of heat sink com· pound is on both the thermostats. Align the return pipe and tighten the connection. Refit the side panel and the insulation pad. Open the valves and fill and re-pressurise the system as described in Section 12.2. 4. Pump Overrun Thermostat. See Figs 9 and 24 Check that the electricity supply to the appliance is turned off. Remove the inner casing cover and flue hood assembly as described in Section 14.3(b) and (e). Carefully remove the three wires from their connections and make note of their positions. Loosen the rear M4 screw securing 22 the thermostat to its mounting plate on the Gas to Water heat exchanger. Remove the front screw and thermostat. Fit the replacement thermostat ensuring a layer of heat sink compound is between the faces. 5. Combustion Chamber Insulation. See Fig 29 Check that the electricity supply to the appliance is turned off. Drain the central heating circuit as described in Section 15.3(a). Remove the inner casing cover, flue hood assembly, and Gas to Water heat exchanger as described in Sections 14.3(b, and e), and 15.4.(3), Remove the fibre insulation pads from the combus· tion chamber side, rear, and front sections. Fit the replacement pads in the reverse order taking care not to damage them. Open the valves, fill and re-pressurise the system as described in Section 12.2. 6. Main Burner. See Fig. 26 Check that the electricity supply to the appliance is turned off. Remove the burner assembly as described in Section 14.3(g). Fit the replacement burner in the reverse order taking care not to bend the pilot bracket on the main burner. 7. Pilot Burner. See Figs. 25 and 27 Unscrew the two screws and remove the pilot burner and pilot shield from the main burner. Remove the spark electrode cable and pull out the electrode. Undo the pilot pipe, unscrew and remove the thermocouple. Fit the replacement burner in the reverse order. Fit the electrode lead before replacing the electrode. Check the pilot burner set- tings as shown in Fig. 27. Make sure the pilot shield is in place. Fig. 28. Gas to Water heat exchanger connections. Boiler return i Boiler flow connector screws

Gas to Water heat exchanger " r I I. @"': I I I lo:•• .·~·"· I ,~:~~--~:: I I I .... ~ Side insulation pad Rear insulation pad ' I I • I I I I I I I IJJI'I. ~ ~I Main burner Fig. 30. Appliance components (lower assembly). WATER DIVERTER VALVE EXPANSION VESSEL DOMESTIC HOT WATER FLOW RESTRICTOR HOUSING 23 WATER TO WATER HEAT EXCHANGER DOMESTIC HOT WATER SENSOR ('5I "I I .I I~ I I I ;}i~ I I : . ~:: ,«. Side insulation pad { ,· ~-· -~ .. I I I I I I I I I I .I :~ ~ [l;. -~~~ PILOT GAS PIPE THERMOCOUPLE ELECTRODE LEAD SPARK GENERATOR (REO KNOB) OVERHEAT THERMOSTAT LEADS DRAIN COCK GAS INLET

Remove the main burner as described in Section 15.4(6). Unscrew the brass injector at the back of the combustion cham· ber. Fit the replacement injector in the reverse order. 9. Spark Electrode. See Figs. 25 and 27 Check that the electricity supply to the appliance is turned off. Remove the pilot burner assembly as described in Sections 14.3(b) and 15.7. Pull the spark electrode out of the clip. Fit the replacement electrode in the reverse order, checking that the spark gap is 4 to 5 mm. Fit the electrode lead before replac- ing the electrode. 1 0. Pilot Burner Injector. See Fig 25 Check that the electricity supply to the appliance is turned off. Remove the inner casing cover and pilot burner assembly as described in Sections 14.3(b) and 15.7. Remove the injector (a push fit inside the pilot assembly). Fit the replacement injector in the reverse order. 11. Thermocouple. See Figs 25 and 27. Check that the electricity supply to the appliance is turned off. Remove the inner casing cover and pilot burner assembly as described in Sections 14.3(b) and 15.7. Unscrew the thermocouple at the gas valve. Remove the pilot pipe cover plate and thread the thermocouple through the hole in the casing. Fit replacement thermocouple in reverse order. 12. Spark Electrode Lead. See Fig. 25 Check that the electricity supply to the appliance is turned off. Remove the inner casing cover as described in Section 14.3(b). Carefully pull the lead from the spark electrode and withdraw from the inner casing. Fit the replacement lead in the reverse order. Loosen the pilot assembly to refit the lead to the electrode. 13. Gas Valve. See Fig. 22. Check that the electricity and gas supplies to the appliance are turned off. Fig. 31 . Circulating pump. 24 Hang the control box assembly in the servicing position as described in Section 14.3(d). Disconnect the pilot pipe. Unscrew and remove the black plastic plug. Carefully pull off the two yellow wires from their termi· nals. Remove the thermocouple connection and the white leads from the gas valve. Remove the eight screws securing the valve to the pipework and remove the valve from the appliance. Fit the replacement gas valve in the reverse order ensuring the sealing washers are correctly fitted. '!Urn on the gas supply and check for soundness. To replace the Modureg head only. Pull off the electrical connections. Unscrew the two screws securing the Modureg head to the main body and remove. Fit the new Modureg head (Honeywell 3061) in the reverse order ensuring that the gasket is in the correct position. To set the burner pressure. See Fig. 22. The minimum and maximum burner pressures must be set after a new gas control has been fitted. Follow the procedure desc,ribed in Section 12.4 - Appliance Operation. The maximum burner pressure must be set first, as any adjust· ment of the maximum pressure influences the minimum pres· sure setting. Remove the the fixing scrl?w and rP.mnvP. the the Modureg cover. The Modureg cap must be replaced immediately the adjust· ments have been made to ensure the proper operation of the gas control. Start the appliance in the domestic hot water mode as described in Section 12.4- Appliance Operation. Adjust the maximum pressure adjustment nut to give a burner pressure of 14.7 mbar. See Fig 22. Switch off the appliance and turn off the electricity supply. Remove a lead to the Modureg head. Switch on the electricity supply to the appliance and re-light in the domestic hot water mode. The burner pressure will remain at the minimum setting. '!Urn the minimum pressure adjustment screw until the burner pressure is 2.8 mbar. See Fig.22. Switch off the appliance and turn off the electricity supply. Refit the lead to the Modureg head. It should not be necessary to alter the central heating paten· tiometer setting when the gas control is replaced and the mini· mum and maximum burner pressures are set. Fig. 32. Expansion vessel and pump assembly.

Check that the electricity supply to the appliance is turned off. Carefully pull off the two leads from the sensor. Loosen the two M3 screws securing the sensor to the fitting and remove the sen· sor Fit the replacement sensor with a layer of heat sink compound between the faces. Refit the leads. 15. Domestic Hot Water Sensor. See Fig. 30 Check that the electricity supply to the appliance is turned off. Hang the control box assembly in the servicing position as described in Section 14.3(d). Carefully pull off the two leads from the sensor. Loosen the two M3 screws holding the sensor to the fitting and remove the sen· sor. Fit the replacement sensor in the reverse order ensuring a layer of heat sink compound is between the faces. Refit the leads. 16. Circulating Pump. See Fig 31 Check that the electricity supply to the appliance is turned off. Drain the central heating circuit as described in Section 15.3(a). Hang the control box assembly in the servicing position as described in Section 14.3(d). Undo the two union nuts and remove the pump from the pipework. Support the pump and remove the electrical cover. Dis· connect the electrical wires taking note of their positions. Fit the replacement pump in the reverse order using new sealing washers. Ease back the sleeved connector to allow the fitting of the bottom washer. Altematively replace the pump head only by removing Lhe four Allen screws. Open the valves and fill and re-pressurise the system as described in Section 12.2 Note. The direction of flow should be downwards. The speed should always be set to maximum. 1 7. Expansion Vessel. See Fig 3 2 Drain the central heating circuit as described in Section 15.3(a). Hang the control box assembly in the servicing position as described in Section 14.3(d). Remove the gas valve as described in Section 15.13. Undo the expansion vessel connection at the boiler flow connec- tion and remove the vessel. Fit the replacement vessel in the reverse order. Open the valves and fill and re-pressurise the system as described in Section 12.2 18. Pressure Relief Valve. See Fig 21 Drain the central heating circuit as described in Section 15.3(a). Lower the control box assembly as described in Section 14.3(d) Undo the discharge pipe connection and unscrew the valve tak- ing care not to distort the pipework. Fit the replacement valve using a suitable thread sealing com- pound. Reconnect the discharge pipe. Open the valves and fill and re-pressurise the system as described in Section 12.2 Fig. 33. Water diverter valve. Water diverter valve micro-switch assembly Fig. 34. Water to Water heat exchanger connections. Boiler return pipe .._ Boiler flow pipe Water to Water heat exchanger Mains cold water in Drain point 25

Check that the electricity supply to the appliance is turned off. Lower the control box assembly as described in Section 14.3(d). Using a pair of fine nosed pliers, pull the circlip off and remove the micro switch assembly from the valve. Lower the facia as described in Section 14.3(c). Carefully pull off the Molex connec· tion from terminal X3 on the driver board. Remove the strain relief bush to withdraw the switch and lead assembly from the appliance. Fit the replacement micro switch assembly in the reverse order. 20. Water Diverting Valve. See Fig 33 Check that the electricity supply to the appliance is turned off. Drain the central heating and domestic hot water circuits as described in Sections 15.3(a and b). Hang the control box assem· bly in the servicing position as described in Section 14.3.(d). Remove the micro switch assembly as described in Section 15. 4. 19. Undo all the water connections to the valve and remove from the appliance. Fit the replacement valve in the reverse order ensuring that the filter and all fibre washers are in place. Open the valves and fill and re·pressurise the system as described in Section 12.2 Fig. 35. Facia (rear view in lowered position). 0 F====::::;;;;f 22. Domestic Hot Water Flow Restrictor. See Fig 30 Check that the electricity supply to the appliance is turned off. Drain the domestic hot water circuit as described in Section 15.3(b). Hang the control box assembly in the servicing position as described in Section 14.3(d). Undo the water connection A and remove the fitting. The plastic flow restrictor is located within the brass housing. Fit the replacement flow restrictor and reassemble in the reverse order ensuring the fibre washers are in place. 23. Pressure Gauge. See Fig 35 Check that the electricity supply to the appliance is turned off. Drain the central heating circuit as described in Section 15.3(a). Lower the facia panel as described in Section 14.3(c). Remove the two screws securing the gauge to the facia panel. Hang the control box assembly in the servicing position as described in Section 14.3(d). Disconnect the capillary at the pressure relief valve. Fit the replacement gauge in the reverse order ensuring the fibre washer is in place. Open the valves and fill and re·pressurise the system as described in Section ·12.2 Temperature control potentiometer /0" 0 l:==v== \ Operating Switch p~ Indicator lights~ [] w ~------------~~~~----~ ~~----------------0~x 1----~ -, Pressure gauge fixing screws (2) Operating Switch plate (or programmer) fixing screws (4) 21. Water to Water Heat Exchanger. See Figs. 3, 30, 33 & 34. Check that the electricity supply to the appliance is turned off. Drain the central heating and domestic hot water circuits as described in Sections 15.3(a and b). Loosen the mains cold water inlet connection and locknut at the appliance. See Fig.3. Hang the control box assembly in the servicing position as described in Section 14.3(d). Undo connection A and remove the coupling. Undo connection B and move the pipe to one side. Undo con- nections C, D and E. Loosen the two screws at the right hand fix· ing bracket. Protect the control box and carefully remove the heat ex- changer as some water remains. Transfer the boiler flow pipe (removed with the old heat ex· changer) to the new heat exchanger using a new fibre washer.. Fit the replacement heat exchanger in the reverse order ensuring all the fibre washers are in place. Open the valves and fill and re·pressurise the system as described in Section 12.2 26 or 24. Operating Switch. See Fig. 35 Check that the electricity supply to the appliance is turned off. Lower the facia panel as described in Section 14.3(c). Remove the. leads from the rear of the switch making note of their positions. Squeeze together the two plastic retaining lugs to remove the switch from the facia. Snap in the replacement switch and reconnect the leads. Refer to the wiring diagram, Fig. 8 25. Temperature Control Potentiometer. See Fig 35 Check that the electricity supply to the appliance is turned off. Lower the facia as described in Section 14.3(c). Pull the knob off the spindle. Unscrew the locknut and remove the potentiometer from the facia panel. Remove the Molex plug from terminal X1 on the driver board. Fit the replacement potentiometer in the reverse order.

Check that the electricity supply to the appliance is turned off. Lower the facia panel as described in Section 14.3(c) Carefully pull off all the Molex connectors. Disconnect the room and frost thermostat connections (if fitted) from terminal X4. Remove the Operating Switch (or programmer) plug from termi· nal X10. Disconnect the mains supply leads at terminal X7. Release the plastic catch in each corner of the driver board and pull forward off the control panel. Fit the replacement board in the reverse order ensuring it is pushed firmly onto the four posts and clicks into place. 27 Refit the facia panel and hang the control box assembly in the servicing position as described in Section .14.3 (d). Set the central heating operating pressure to maximum by turn· ing the central heating potentiometer anti-clockwise as accessed through an opening in the rear of the control box. The adjustment is made using a thin flat-bladed screwpriver .. 27. Piezo Spark Generator Remove the cabinet front panel as described in Section 14.3(a). Pull the spark electrode lead from the connection on the spark generator. Unscrew the two MS screws and remove the spark generator from the appliance. Fit replacement spark generator in reverse order.

Key GCNo. Part No. Manufacturer's Reference No. WHSPartNo. 41 378 581 Gas Valve Honeywell· V 4600N3061 1 ZAGAS181 114 378 585 Modureg Head (Gas Valve) Honeywell·V7335A3008 1 ZAGAS185 33 378 025 Main Burner Aeromatic·AC 23/053576 1 ZAGAS154 34 379 040 Main Burner Injector Stereomatic 4.4mm Dia. '!ype 7 1 ZAGAS163 35 379 673 Pilot Burner Honeywell·Q385A 2010 1 ZBGAS092 36 382 850 Pilot Burner Injector Honeywell-45.004, 108·001 38/36A 1 ZBGAS016 37 386 575 Spark Electrode Honeywell-45900413-004 1 ZBGAS093 38 324 887 Spark Electrode Lead Vernitron 0. 7 PTFE 1 ZBGAS025 21 299 150 Gas to Water Heat Exchanger Giannoni·PR 20/321 1 ZAGAS165 24 379 419 Automatic Air Vent Intermes-02, 50, 010 1 ZMMIS055 53 299 199 Sensor and paste Elmwood-6655·9428·4 2 SPK0039 94 299 202 System Pressure Gauge (with Washer) Cewal 1 SPK0040 74 386 789 Pressure Relief Valve Caleffi·3141, 3bar 1 ZCVLV018 50 378 034 Circulating Pump Grundfos·UPS 15·60, 120CL, NOCL 50526613 1 ZAMAJ198 70 378 027 Expansion Vessel (Sealed System) Inter Albion·MIS082/240 1 ZMMIS082 79 371 537 Water to Water Heat Exchanger 1 SSA6161/1 57 379 216 Diverter Valve Giannoni·D2040 1 ZAGAS166 97 I 379 730 Driver Board HoneywellW411 SB, 1226 1 ZAGAS228 90 386 227 CH Temperature Control Potentiometer Omeg-OW20BU 1 SSAHAR002 93 386 778 Operating Switch Arrow· 200400£83 9AA 1 ZDELE237 10 299151 Combustion Chamber Insulation (Complete) 1 SPK0033 122 371 539 Programmer Kit (Optional) WHS Single Channel Grey 490 488 1 ZAMAJ164 42 371 540 Gasket Pack - Gas 1 SPK0022 61 371 541 Gasket Pack - Water 1 SPK0023 60 379 215 DHW Flow Restrictor '!ype E, White 8litres/min. (± 10%) 1 ZBUNC138 91 371 524 Indicator Light - DEMAND Neon (Green)- complete with plug IMO Ref. N19L R/S-Green 1 SSAHAR081 92 371 525 Indicator Light - POWER ON Neon (Amber)- complete with plug IMO Ref. N19L R/S·Amber 1 SSAHAR082 22 299 277 Pump Overrun Thermostat plus paste Thermodisc 60T1 3·.5001 03 1 SPK0088 59 378 416 Filter MPMV 3326 Stainless Steel 1 ZBUNC229 115 299 032 Fuse Pack 1 SPK0024 40 390 210 Thermocouple Honeywell Q309A2747 1 ZBGAS035 48 393 652 Spark Generator Vernitron 0207 1 ZBGAS010 4 299 152 Limit Thermostat Elmwood 2455RC, c/w lead 1 SSAHAR013 28

room thermostat on. Frost thermoStat on. EITHER ~·, Cmrtr.dbeatiO! ~ ~. Demand. End of domestic hot water Demand. Main Gas valve opens m Pump on, or continue from pump overrun mode. I Da:::!~r I I Mains gas available Primary water temperature. monitored by central heating sensor Primary water temperature monitored by central heating senSOt Depress gas valve button J 17. Operational Flow Diagrams Note. The alpha references in these charts are to be used for cross- referencing when fault finding. See Section 18. Main gas valve off. II .II minutes. m m Central heating temperature above set level Heat input modulated to maintain Dow ternperatl!re set by Temperature Control Potentiometer. 1. Central Heating Mode. II II - .:. Repeatedly press red After 20 seconds slowly igniter button release gas valve button Pilot Dame until pilot (30 seconds if Dame has FLAME established flame is previously extinguished} CONTINUES observed f FLAME EXTINGUISHED Twist gas valve Wait for 3 minutes? I+- button in the direction of the arrow Operating SWitch off. EITHER OU1 DEMAND indicator off. Main gas valve off. Pump off, or continue if pump overrun is required.

and tap on. Hot water Demand. (Overrides central heating mode and pump overrun funct1on.) Pilot lit Pump on, or continue from pump overrun mode. Signal from flow switch. Wait for domestic hot water temperature to fall below set level (Pump remains on). VALVE ON Automatic start up sequence Domestic hot water I • I temperature monitored by domestic hot water senSOJ: m Domestic hot water temperature rises above pre·set leveL II water temperature at factory pre-set level. IJ DEMAND indicator iUuminated SEE DETAILED SEQUENCE ABOVE. No Demand and primary water temperature above 6o•c. II Pump on until primary l 1'!1 water temperature 1!1 falls below 6o•c. 3. Pump Overrun Function. Iii 2. Domestic Hot Water Mode. Gas to Water heat exchanger excess temperature causes boiler overheat thermostat to trip. Gas valve shuts down but pump and indicator lights remain on (If Demand still exists) 4. Overheat Protection. .m r--.... - Operating Switch OFF. Tap off. I r+ DEMAND indicator off. Monitor primary water via central heating sensor and continue into central heating Main gas valve and mode. ..... pilot valve off. EITHER YES Hot water ..... Is there a central NO - Demand heating Demand? ~ satisfied. ! ~ Pump off, or continue into overrun mode.

, This Fault Finding Chart is tope used in conjunction with the Operational Flow Diagrams in Section 17. To find the fault, locate the point on the flow diagram at which the appliance has failed, eg, letter B. Then read the corresponding section in the fault finding chart, eg. Failure at point B. Note: Each section assumes that the appliance operates correctly up to that point. Notes. 1. All voltage measurements are with respect to neutral unless otherwise stated. 2. Before changing any component indicated in the chart, it is essential that the associated wiring is checked for continuity, condition and correct routing. 3. 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. NO Switch on the mains electrical supply. Is the STANDBY indicator illummated? Is there a 240V supply to terminal X7pin 1? Cherk the mains electrical supply and external wirtng YES Cherk connections at the gas valve Repair or replace as required. Start of pilot lighting test Sat operator SWitch or programmer n (If fitted) to off. Tum the room thermostat (II ntted) to lsthereagas·="'· NU Tum on gas supply J mm. Rlllow the manual operanon of the lighting Supplytotheboiler and check pressure sequence to point A Ciln a pilot flame be observed? ~ YES Check that the p~ot adjustment screw is NO Cherk condition of correctly set by screwing it m fully clockwise 1---- Igniter leads and and tllen unscrewmg two revolutions. Does connections Does the the lngmter produce a spark? igniterproduceaspark? J NO YES ~ YES ~r Re~acelgniter l Jsthep1lotinjector 0 free from any blockage? I Replace Injector + YES l Ensure gas has bled through the system Has the Is the pilot FollowthemanualprocedurelopointBDoesthepilot r NO NO Check the p1lot i7ector for fiameremamestablished' overheat -- flame -- blockage.Replace necessary thennostat height 18 and ensure the pilot tnppW? 20mm? adjustment serew is correctly set by screwing ' YES m fully and then unscrewing YES two revolutions is the primary water temperature lessthan95'C? NO ~ YES Wait for the temperature to fall below 95'Cto reset the thermostat c...,. D1scon~ect the overheat thermostat and A Replacethe I ched: for cononuity across the devce. overheat Does continurty occu~ thennostat t YES Check the soundness of the ECOconnectionsatthe thermocouple and gas valve -=-1 Replace the I {improve if necessary). Rlllow procedure 5 m the thermocouple mult1meter handbock. Does theclosedCJJtUitvoltage exceedBmV' t YES I END OF PILOT I I Replace the I ' UGHTINGTEST gas valve 31

Set the Operating Switch (or programmer) to HEATING & WATER and set the temperature control potentiometer and room thermostat (if fitted) to maximum. Does the DEMAND indicator illuminate? YES YES YES Is the STANDBY indicator still illuminated? YES Is there a 240V supply at pin 2 on terminal X5? YES Refer to section STANDBY indicator light does not illuminate. Replace the Operating Switch (or programmer). Replace the room thermostat. Replace the flowswitch. Replace the pump overrun thermostat. ,....f----------1 Remove the plated screw in the Replace the pump. burner Ignite? centre of the pump and turn the shaft with a flat bladed screwdriver. Does the pump now run? Refer to failure at point A andB Is there a 240v supply at NO Is there approx 24V ac pin 1 on terminal X8 across the test pins on the driver board? YES YES Check connections to gas valve or replace gas valve Remove the C.H. molex plug from terminal X2. Is the sensor resistance between 1.5 and 25 kohms across the white leads? 32 NO Transformer is faulty. Replace the driver board NO Check the connections at 1---+1 the central heating sensor or replace the sensor

mbar for approximately two minutes and then increase to the set level over the next one minute? Note. The system load must be greater than 9kW and in a cool state for this to be possible. YES Does the gas pressure settle to maintain a constant flow temperature set by the temperature control potentiometer? (If the burner pressure is correctly balanced to the system load). YES Gradually tum off the radiators one by one so that the burner shuts down as the system temperature rises above the set levei.Does the output drive at pin 1 on terminal XS drop from 240V to OV during the shutdown? YES Does the DC voltage across the gas valve Modureg terminals remain at a constant low voltage for approximately two minutes and then gradually increase over the next one minute? Note. The voltage values are not important. YES Remove the Molex plug from terminal X1. Measure the resistance as follows: Between purple and yellow pins ·10 kohms between purple and pink pins · between zero and 10kohms depending on the setung of the temperature control potentiometer. Is this correct? YES Remove the left hand Molex plug from terminal X2.ls there a resistance of between 1.5 and 25 kohms across the two white pins? · Nb j Replace the main driver board: · . · 1 The overheat thermostat has activated. Has the voltage across the modureg terminals dropped below 5Vdc? Wait for the temperature to fall below we to reset the thermostat. Relight the pilot Replace the main driver board. 33 NO Replace the main driver board. Replace the temperature control potentiometer on the facta paneL Replace the central heating sensor.

Set the Operating Switch (or programmer) to WATER. Turn a domestic hot water tap on fully. Does the DEMAND indicator illuminate? YES YES Is the STANDBY indicator still illuminated? YES ..,.1----------1 Remove the plated screw in the centre of the pump and turn the shaft with a flat bladed screwdriver. Does the pump now run? j Refer to failure at point E. 34 Refer to section STANDBY Indicator light does not illuminate. Replace the Operating Switch (or programmer). Replace the pump overrun thermostat. Replace the pump. Investigate and rectify low flow rate.

water flow rate so that the gas pressure reduces and settles. Does the domestic hot water temperature stabilise at 55·60°C? YES Further reduce the domestic hot water flow rate so that the appliance shuts down as the domestic hot water temperature rises above the set level. Does the burner re·ignite if the flow is increased again? YES YES Does the DC voltage across the Modureg terminals decrease as the flow rate reduces? The overheat thermostat has activated. Atlow the overheat thermostat and repeat this test. Does the DEMAND indicator light go out immediately? YES START OF PUMP OVERRUN TEST With no central heating or domestic hot water demand and with primary water above 60°C (approx.), does the pump operate? YES When the primary temperature drops below 60°C (approx.), does the pump stop? YES Is the STANDBY indicator light illuminated? YES , Replace the pump overrun ·thermostat. OVERHEAT PROTECTION TEST [ Does the burner shut down if the Gas·to.Water heat exchanger water exceeds 100°C Replace the system overheat thermostat. 35 Remove the domestic hot water Molex plug from terminal X2. Is there a resistance of 1.5 to 25 kohms across the red pins? YES Replace the flow switch. Refer to section STANDBY Indicator does not illuminate. Replace the pump overrun thermostat. Replace the domestic hot water sensor. Replace the main driver board.

Telephone: (0190$) 754624 Fax:.(01905) 754619 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. 8 716 115 057a