Alpha Alpha CD25X Installation And Servicing Instructions

Instructions Alpha CD25X/28X Range of Wall Mounted, Fan Assisted, Room Sealed, Gas Fired, High Efficiency Condensing Combination Boilers Alpha CD25X G.C. No. 47 532 39 Alpha CD28X G.C. No. 47 532 37 British Gas Service Listed For use with Natural Gas only Leave these instructions with the User Nepicar House, London Road, Wrotham Heath, Sevenoaks, Kent TN15 7RS For Technical help or for Service call ... ALPHA HELPLINE Tel: 0870 3001964 0051

CONTENTS 1 Introduction ....................................... 2 2 Technical data................................... 3 3 General boiler information.................. 7 4 Installation ......................................... 13 5 Commissioning ................................. 19 6 Boiler operation ................................. 22 7 Routine servicing ............................... 23 8 Component replacement ................... 25 9 Wiring diagrams ................................ 31 10 Fault finding ...................................... 33 11 Short parts list ................................... 37 12 Benchmark Checklist ........................ 38 13 Service record ................................... 39 The Alpha CD range of high efficiency condensing boilers are wall mounted, fan assisted room-sealed combination boilers. The burner is lit electronically and the heat output is controlled by a modulating fan and gas valve. These are combination boilers providing both central heating and domestic hot water at mains pressure. The boilers are supplied with a pump, pressure relief valve, expansion vessel and pressure gauge fully assembled and tested. They are designed for use with a fully pumped, sealed and pressurised central heating system using only Natural gas. The CD25X boiler is suitable for central heating loads of between 5.6 and 19.5kW (19 100 and 66 530 Btu/h). The CD28X boiler is suitable for central heating loads of between 4.9 and 25.8 kw (16 720 and 88 030 Btu/h). The maximum output available for domestic hot water is 24.0 kW (81 900 Btu/h), capable of providing 9.6 litres/min for the Alpha CD25X boiler, 28.7 kW (97 900 Btu/h), providing 11.4 itres/min and for the Alpha CD28X boiler, all with a temperature rise of 35°C. IMPORTANT It is the law that all gas appliances are installed by a competent person, ie CORGI registered personnel, in accordance with the following recommendations:- Current Gas Safety (Installation and Use) Regulations All current Building Regulations issued by the Department of the Environment, i.e. Approved Document L1. Building Standards (Scotland) (Consolidation) Regulations issued by the Scottish Development Department UK Water Regulations/Byelaws (Scotland) Health & Safety Document No. 635 (The Electricity At Work Regulations 1989) The installation should also be in accordance with the following British Standard Codes of Practice:- BS 5440:1:2000 Flues BS 5449:1990 Forced circulation hot water systems BS 5546:2000 Installation of hot water supplies for domestic purposes BS 6700:1997 Design, installation, testing and maintenance of services supplying water BS 6798:2000 Installation of gas fired hot water boilers BS 6891:1998 Gas installation BS 7593:1992 Code of Practice for treatment of water in heating systems BS 7671:2001 Requirements for electrical installations, IEE Wiring Regulations Reference should be made to DEFRA document 'Guide to condensing boiler installation assessment procedures for dwellings'. If installation is in a timber framed building, refer to the Institute of Gas Engineers document IGE/UP/7. This appliance meets the requirements of IPX4D, ie degree of protection against moisture. This appliance contains no asbestos and no substances have been used in the construction process that contravene the COSHH Regulations (Control of Substances Hazardous to Health). Failure to install this appliance correctly could lead to prosecution. It is in your own interest and that of safety to ensure that the law is complied with. Manufacturer's instructions must NOT be taken in anyway as over-riding statutory obligations. Notes: 1. Ensure that the Benchmark Checklist has been completed after the boiler has been installed and commissioned. 2. It is the law that all boiler installations are registered by the installer through the CORGI Gas Work Notification Scheme. 3. The boiler must only be used with Alpha CD condensing flue components. 1 INTRODUCTION

2 TECHNICAL DATA Alpha CD25X/28X - Technical Data Alpha CD25X MAX. 20.4 69 600 18.4 62 780 19.5 66 530 18.0 61 420 3.32 1.33 1.95 68.8 MIN. 5.2 17 740 4.7 16 040 4.8 16 400 4.5 15 350 0.4 0.16 0.6 21.2 Room sealed chamber panel fitted Central Heating Heat Input (Hs) kW (Gross) Btu/h Heat Input (Hi) kW (Net) Btu/h Heat Output (Hs condensing) kW (50°C/30°C) Btu/h Heat Output (Hi non-condensing) kW (80°C/60°C) Btu/h Differential Burner mbar Pressure in wg Gas Rate m³/h ft³/h 9.6 2.2 11.2 2.5 MAX. 26.6 90 760 24.0 81 900 24.0 81 900 5.20 2.08 2.54 89.7 MIN. 5.2 17 740 4.7 16 040 4.5 15 350 0.4 0.16 0.6 21.2 Domestic Hot Water Heat Input (Hs) kW (Gross) Btu/h Heat Input (Hi) kW (Net) Btu/h Output to Water (Hs) kW (modulating) Btu/h Differential Burner mbar Pressure in wg Gas Rate m³/h ft³/h Flow Rate at 35°C Rise L/min gal/min Specific Flow Rate (D) at 30°C Rise L/min (Flow rate @ 30K to EN625) gal/min Room sealed chamber panel fitted Alpha CD25X MAX. 27.3 93 150 24.6 83 930 25.8 88 030 24.0 81 900 6.6 2.64 2.61 92.1 MIN. 5.5 18 760 5.0 17 060 5.1 17 400 4.9 16 720 0.24 0.10 0.53 18.7 Room sealed chamber panel fitted Central Heating Heat Input (Hs) kW (Gross) Btu/h Heat Input (Hi) kW (Net) Btu/h Heat Output (Hs condensing) kW (50°C/30°C) Btu/h Heat Output (Hi non-condensing) kW (80°C/60°C) Btu/h Differential Burner mbar Pressure in wg Gas Rate m³/h ft³/h Alpha CD28X 11.4 2.5 13.3 2.9 Domestic Hot Water Heat Input (Hs) kW (Gross) Btu/h Heat Input (Hi) kW (Net) Btu/h Output to Water (Hs) kW (modulating) Btu/h Differential Burner mbar Pressure in wg Gas Rate m³/h ft³/h Flow Rate at 35°C Rise L/min gal/min Specific Flow Rate (D) at 30°C Rise L/min (Flow rate @ 30K to EN625) gal/min Room sealed chamber panel fitted Alpha CD28X MIN. 5.5 18 760 5.0 17 060 4.9 16 720 0.24 0.10 0.53 18.7 MAX. 31.8 108 500 28.7 97 900 28.7 97 900 8.83 3.53 3.03 106.9 Note: The above appliances are fully modulating and are not range rated.

Gas Connection Primary Water Content CD25X CD28X Air Duct Diameter Flue Duct Diameter 2.6 GENERAL Min. Clearances for Servicing Top (from casing) Bottom Sides Front Flue Terminal Size Flue Terminal Protruding Hole Size Required For Flue Assy. Lift Weight CD25X CD28X 2.5 INSTALLATION 235 mm 250 mm 5 mm 450 mm 100 mm Dia. 100 mm 110 mm Dia. 41 kg 42 kg Central Heating (Sealed System) Max. Working System Pressure Min. System Pressure Max. System temperature Pressure Relief Valve Setting Expansion Vessel Size (pre-charge press.) Flow Connection Return Connection Relief Valve Connection Recommended System Pressure (cold) CH Water Temp. (Approx. max.) 2.5 bar 0.5 bar 82°C 3 bar (44 PSI) 8 L at 0.8 bar 22 mm 22 mm 15 mm 1.0 bar 82°C (180°F) Domestic Hot Water Max. Mains Inlet Water Pressure Min. Mains Water Pressure Min. DHW Flow Rate Mains Inlet Connection DHW Outlet Connection DHW Water Content CD25X CD28X Outlet Water Temp. (Approx. max.) Flow Regulator Fitted CD25X CD28X 8 bar 0.2 bar 2.5 l/min 15 mm 15 mm 0.2 L 0.26 L 62°C (144°F) 10 l/min 12 l/min 2.2 SYSTEM Burner Main Heat exchanger DHW Heat Exchanger Main Burner Injector CD25X CD28X Flue - Outer Duct Flue - Inner Duct Stainless steel Stainless steel Stainless Steel 5.2 mm 5.4 mm White Plastic 2.3 COMPONENTS 2.4 ELECTRICAL Alpha CD25X/28X - Technical Data 2.7 PERFORMANCE DATA %CO2 content (± 0.2%) Sedbuk rating Natural Gas Efficiency band A A SAP efficiency (%) 90.1 90.0 Min 9.0 8.9 DHW max 9.4 9.4 NOx class 5 5 Boiler model CD25X CD28X Supply External Fuse Power Consumption Internal Fuse - Main Terminal PCB Fuse F1 PCB Fuse F2 and F3 Electrode Spark Gap Electrical Enclosure Degree of Moisture Protection 230/240 V ~ 50 Hz 3 A 120 W F2 A 315 mAT 2.5 AF 3 - 4 mm IPX4D

Fig. 1 2.8 FLUE LENGTHS CD Easy-Flue 500 mm with terminal and 90° bend. A CD Easy-Flue 1000 mm with terminal and 90° bend is also available. CD 750 mm and 1000 mm flue extensions are available. Length of Flue Required:- Rear Flue = wall thickness + 140 mm (includes terminal). This is without back frame, add 40 mm if the wall jig is used. Side Flue = wall thickness + distance between wall and side of boiler + 225 mm (includes terminal) Vertical Flue = distance from top of boiler side panel to required roof position minus 1000 mm for vertical terminal assembly Maximum horizontal flue length = 12 m. Maximum vertical flue length including terminal is 15 m. Each additional CD 90° Bend is equivalent to 1.3 m of flue length. Each CD 45° Bend is equivalent to 0.9 m of flue length. The CD Vertical Flue terminal assembly is equivalent to 1 m of flue length. 2.9 AVAILABLE PUMP HEAD FOR CENTRAL HEATING gal/min 3.7 2.8 2.3 1.8 0.7 Btu/h 86 700 64 000 53 000 42 200 18 100 kW 25.40 18.70 15.60 12.35 5.30 Output (50/30°C) Available pump head metres 2.3 3.5 3.8 4.0 4.6 feet 7.6 11.6 12.6 13.2 15.2 litre/min 16.6 12.6 10.5 8.3 3.2 20°C 20°C Flow rate This information is based on 20°C system design temperature difference. Note: For outputs upto 28 kW refer to Section 3.7. 2.10 ELECTRICAL CONNECTIONS Note: This Appliance Must Be Earthed An optional integral single channel Clock kit is available if required. Note: Only use the Alpha single channel clock. Do not fit any two channel clocks. Boiler terminal block Clock connections 1. Ensure wires are connected correctly 2. Only fit the Alpha recommended single channel clock. Other clocks could cause damage. WARNING Blue Wire Brown Wire Red Wire 1 2 3 4 5 Internal Clock Terminals Red Wire Not Used

2 - DHW flow switch, filter and flow regulator 3 - Diverter valve 4 - Gas valve 5 - Primary temperature sensor 6 - DHW heat exchanger 7 - Main burner 8 - Primary/condensing heat exchanger 9 - Room sealed chamber 10 - Fan 11 - Pressure differential test points 12 - Flue hood Fig. 2 13 - Overheat thermostat 14 - Expansion vessel 15 - Automatic air vent 16 - Pump 17 - Drain point 18 - Pressure relief valve 19 - Primary pressure switch 20 - Ignition electrodes 21 - Flame sensing electrode 22 - DHW temperature sensor 23 - Flue sampling point 24 - Gas service cock 25 - Mains inlet on/off valve 26 - On/off valve (2 off) 27 - Automatic by-pass 28 - Cyclone separator (if applicable) 29 - Condensate trap 30 - Injector 31 - Venturi 32 - Venturi negative point 33 - Venturi positive point 34 - Flue temperature sensor 35 - Diverter valve motor Alpha CD25X/28X - Technical Data Gas Condensate discharge Primary Heating return Primary Heating flow 24 4 23 - - + + 9 1 10 29 35 11 34 5 13 20 14 32 33 15 16 17 18 27 28 26 Domestic hot water outlet Cold mains water inlet 2 3 6 19 22 25 12 8 7 21 31 30

The Alpha CD28X boiler requires a gas rate of 3.03 m³/h (106.9 ft³/h). The meter and supply pipes must be capable of delivering this quantity of gas in addition to the demand from any other appliances in the house. The boiler requires at least a 22 mm gas supply pipe. The complete installation, including the meter, must be tested for gas tightness and purged as described in BS 6891. 3.2 ELECTRICAL SUPPLY The boiler requires a 230/240 V ~ 50 Hz mains supply, fused at 3 A The boiler must be earthed. There must only be one common isolator, providing complete electrical isolation, for the boiler and any external controls. This boiler has been fitted with a supply cable, however, if it is necessary to fit a cable use PVC insulated cable not less than 0.75 mm² (24 x 0.2 mm) to BS 6500 Table 16. The boiler should be connected to a fused three pin plug and unswitched shuttered socket outlet (both complying with BS 1363), or a fused double pole switch with a contact separation of at least 3 mm in both poles. Wiring external to the boiler must be in accordance with the current IEE Wiring Regulations (BS 7671). Note: If a room thermostat is fitted, it must be suitable for 230/240 V switching. 3.3 AIR SUPPLY The boiler does not require any air vents for cooling in the room in which it is installed or when installed in a cupboard or compartment. The minimum clearances for servicing must always be maintained. Note: A cupboard or compartment used to enclose the boiler must be designed and constructed specifically for the purpose, i.e. comply with the Building Regulations. 3.4 FLUE SYSTEM - Fig. 3 The flue system must be installed in accordance with BS 5440:1. For horizontal flues ensure the Easy Flue assembly is horizontal and the inner duct is sloping downwards towards the boiler. When additional flue extensions are used, ensure the flue slopes downwards towards the boiler by a minimum of 25 - 30 mm per metre of flue. It is recommended that horizontal flue assemblies should be supported approximately every 1.5 m with access provided to the joints. Flue components are available as follows:- CD Easy-Flue 500 mm (includes 90° bend and terminal) - Part No. 6.2000510 (this inludes plume management facility). CD Easy-Flue 1000 mm (includes 90° bend and terminal) - Part No. 6.2001010 (this inludes plume management facility). CD 750 mm flue extension - Part No. 6.2000750. CD 1000 mm flue extension - Part No. 6.2001050. CD 90° bend - Part No. 6.2000590. CD 45° bend - Part No. 6.2000545. CD Vertical flue terminal assembly. Refer to the separate installation instructions supplied with the assembly. CD Ridge flue terminal assembly. Refer to the separate installation instructions supplied with the assembly. The following methods determine the correct length of flue required. For rear exit flue (including terminal) L = B + 140 mm (180 mm if wall jig is used) For side exit flue (including terminal) L = B + C + 225 mm (min. side clearance required is 5 mm) For vertical flue L = H - 1000 mm for vertical terminal assembly Where L = Required flue length B = Finished wall thickness C = Distance from the inside wall to the side of the boiler H = Distance from top of boiler side panel to roof position Note: 1. If an extra 90° bend is used, this reduces the maximum flue length by 1.3 m. Each 45° bend used reduces the maximum flue length by 0.9 m. 2. Under no circumstances must the flue length (including allowances for extra bends) exceed 12 metres horizontally and 15 metres vertically. 3. Failure to use Alpha CD flue components with the boiler will invalidate the boilers CE approval, guarantee and may be unsafe. 4. Further plume management flue accessories are available - refer to the Easy-Flue installation instructions. 3 GENERAL BOILER INFORMATION Alpha CD25X/28X - General Boiler Information

L = B + C + E + 225 mm Alpha CD25X/28X - General Boiler Information L = B + C + 225 mm C B E C B E B F B C L = B + E + F + 225 mm + (90° bend = 1.3 metre) (add 40 mm to 'F' if a jig is used) L = B + C + 225 mm + (2 x 45° bends = 1.8 metre) Fig. 3 VERTICAL FLUE OPTIONS Not less than 300 mm Not less than 300 mm H Hmax = 15 m Not less than 300 mm Not less than 300 mm H Hmax = 13.2 m

Note: In certain weather conditions the terminal will emit a plume of steam. If possible avoid positioning the terminal where this may cause a nuisance, i.e. positions A, D, G, H, J or M. The flue terminal must be exposed to the external air and the position must allow the free passage of air across it at all times. A terminal must not be sited below 2.1 m where people have access to, such as public footpaths, access routes, patios etc. However, If the terminal is fitted less than 2.1 m above a surface where there is no public access, the terminal must be protected by a terminal guard. A suitable guard is available from Alpha Therm Ltd. 3.6 BOILER LOCATION The boiler is not suitable for external installation unless it is installed within a purpose designed weatherproof building. The boiler must be installed on a flat vertical wall which is capable of supporting the weight of the boiler. The boiler can be fitted to or adjacent to a wall comprising of a combustible material without the need for a special thermal insulation barrier. If the boiler is to be fitted in a timber framed building, it should be fitted in accordance with the Institute of Gas Engineers 'Guide for Gas Installations in Timber Frame Housing', reference IGE/UP/7. The boiler may be installed in any room or internal space, although particular attention is drawn to the requirements of the current IEE Wiring (BS7671) Regulations, and in Scotland, the electrical provisions of the Building Regulations applicable in Scotland, with respect to the installation of the boiler in a room or internal space containing a bath or shower. Where a room- sealed boiler is installed in a room containing a bath or shower, it must not be possible for a person using the bath or shower to touch any electrical switch or boiler control utilising mains electricity. The boiler may be installed in a cupboard or compartment, provided it is correctly designed for that purpose, i.e. complies with the Building Regulations and the requirements of BS 6798. Alpha CD25X/28X - General Boiler Information Notes: 1. In addition, the terminal should not be nearer than 150 mm to the framework of an opening into the buiding, i.e. a window surround or door surround. 2. This clearance may be reduced to 25 mm without effecting the performance of the boiler. However, to ensure the condensate plume does not affect adjacent surfaces a clearance of 300 mm is preferable. 3. These clearances may be reduced to 25 mm without effecting the performance of the boiler. However, to ensure the condensate plume does not affect adjacent surfaces the terminal can be extended beyond gutters, pipes, eaves, balconies etc. by upto 500 mm. If the flue is extended more than 500 mm outside, it should be boxed and insulated. 4. To reduce the possibility of nuisance to neighbouring buildings etc. it is recommended the terminal shouild not be less than 2500 mm from car parking spaces, building boundary walls, fences etc. Note: A terminal must not be sited under a car port roof A Directly below an opening, air brick, windows, etc. B Below gutters, soil pipes or drain pipes C Below eaves D Below balconies E From a vertical drain pipe or soil pipe F From an internal or external corner G Above ground, roof or balcony level H From a surface or boundary facing the terminal I From a terminal facing the terminal J Above an opening, air brick, window etc. K Vertically from a terminal on the same wall L Horizontally from a terminal on the same wall M Horizontally from an opening, air brick, window etc. N Minimum protrusion through a roof O From a vertical obstruction P From an openable window Q From an adjacent vertical terminal Min. distance (mm) Terminal position 300 (See Note 1) 75 (See Note 3) 200 (See Note 3) 200 (See Note 3) 150 (See Note 3) 300 (See Note 2) 300 600 (See Note 4) 1200 mm 300 (See Note 1) 1500 mm 300 mm 300 mm (See Note 1) 300 mm 300 mm 600 mm 600 mm J D G H I Q Boundary O P N Fig. 4

The boiler is designed for use in a sealed central heating system in accordance with the requirements of BS 5449 and BS 6798. The system should be designed to operate with flow temperatures of up to 82°C. When designing the system, the pump head, expansion vessel size, mean radiator temperature, etc. must all be taken into account. Refer to the pump performance table for guidelines. System volume - The expansion vessel incorporated into the boiler is suitable for a sealed heating system with a maximum water content of 80 litres (18 gal). Above 80 litres, consideration should be given to fitting an additional expansion vessel fitted in the position shown in Fig. 5. To check correct operation of the expansion vessel(s) the system pressure should not be more than 2.5 bar when the system is at maximum operating temperature (for further guidance refer to BS 7074:1). The boiler is supplied with the following components built in:- Pressure relief valve - complying with BS 6759 and set to operate at 3 bar. The discharge pipe must be routed clear of the boiler and terminated in such a manner that it can be seen, but cannot cause injury to persons or property. Pressure gauge - To indicate the system pressure to be maintained. Expansion vessel - Conforming to BS 4814 with a capacity of 8 litres and pre-charged to a pressure of 0.8 bar. By-pass - The boiler incorporates an automatic by-pass, therefore an automatic by-pass is not required for the system. Cyclone - This is a device fitted in the heating return within the optional Premier Pack wall jig to remove any foreign or solid matter etc. from the system. Alpha CD25X/28X - General Boiler Information 3.8 FILLING THE CENTRAL HEATING SYSTEM - Figs. 6, 7 The system design pressure (cold) should be set to 1.0 bar. This pressure is equivalent to a static head (see Fig. 5) of 10.2 metres of water. Provision should be made to replace water lost from the system. This can be by manual or automatic means, as shown in Figs. 6 and 7. The position for connecting an automatic make-up vessel is indicated in Fig. 5. A double check valve assembly must be used, as shown in Fig. 7. Filling of the system must be carried out in a manner approved by the local Water Undertaking. Where allowed, the system may be filled via a temporary connection as shown in Fig. 6. After filling, always disconnect the flexible hose of the filling loop. All fittings used in the system must be able to withstand pressures up to 3 bar. Drain taps (to BS 2879) must be used to allow the system to be completely drained. Note: A drain tap should be installed at the lowest point of the heating circuit and beneath the appliance. System drain tap Note: If the mains is fitted with water meter, check valves or loose jumper stop cock, then a DHW expansion device must be fitted. Static head of system Make up vessel DHW outlet Mains water inlet Additional expansion vessel (if required) Automatic air vent Boiler casing Heating flow Heating return Filling point Double check valve assy. Fig. 5 Fig. 6 Fig. 7 Filling loop temporarily connected Heating circuit return Mains water supply Stop valve Hose unions Stop valve Double check valve assembly Test cock Feed cistern to be located above highest point in the system Mains water supply Stop valve Test cock Double check valve assembly Overflow Heating circuit return

3.9 FLUSHING THE HEATING SYSTEM It is essential that the central heating system is thoroughly cleaned and flushed when fitting an Alpha CD boiler. Failure to do so will invalidate the warranty. The primary condensing heat exchanger is constructed in stainless steel and therefore is compatible with most materials used in a heating system. If a cleaning agent and inhibitor are used, they must be applied in accordance with their manufacturers instructions. Only products from Fernox and Sentinel are acceptable for use with the Alpha CD boilers. Further information can be obtained from Fernox (Tel: 0179 9521133) or Sentinel (Tel: 0151 4209563). If the Cyclone is fitted in the heating return on the jig, the heating system should still be thoroughly flushed as detailed below. The Cyclone collection point should be emptied via the drain point (see Fig. 13b) after flushing has been completed. The system should be flushed in accordance with BS 7593 and BS 5449. The following procedures are recommended: 1. Installing onto a new system:- a.Fill the system, vent at high points, at pump and radiators. b.Check for leaks. c. Rapidly drain the system. d.If required, chemically clean the system as instructed by the recommended cleaner manufacturer. Note: Ensure that the system is flushed to remove any remains of the cleaner. e.If chemical cleaner is not used to clean the system:- i) Refill the system. ii) Switch on the boiler and allow the system to heat up to the normal operating temperature. iii) Rapidly drain the system while the water is still hot. iv) Refill the system. f. As required, add the recommended inhibitor to the system as instructed by the inhibitor manufacturer. g.Recheck for leaks. 2. Installing onto an existing system, clean the system before fitting the new boiler:- a.If the old boiler is still working:- i) Switch on the boiler and allow the system to heat up to the normal operating temperature. ii) Rapidly drain the system while the water is still hot. iii) Refill and chemically clean the system as instructed by the recommended cleaner manufacturer. iv) Ensure the system is flushed to remove any remains of the cleaner. v) Fit the new boiler. b.If the old boiler is not working:- i) Rapidly drain the system. ii) Remove the old boiler. iii) Flush the system through. iv) Fit the new boiler. v) Refill and chemically clean the system as instructed by the recommended cleaner manufacturer. vi) Ensure the system is flushed to remove any remains of the cleaner. c. As required, add the recommended inhibitor to the system as instructed by the inhibitor manufacturer. d.Check for leaks. 3.10 DISPOSAL OF CONDENSATE Provision must be made for the safe disposal of condensate produced by the flue gases of the Alpha CD boilers and reference should be made to BS 6798: 2000 for the requirements on the disposal of condensate. The boilers incorporate a condensate trap which has a seal of 75 mm, therefore no additional trap is required. The condensate should ideally be discharged internally into an internal waste pipe (washing machine/sink waste) or soil pipe to avoid the possible risk of freezing. The pipework must be in 22 mm pipe. External pipe runs should be avoided, but if it is necessary, the pipework should be at least 32 mm and protected from the risk of freezing with a waterproof insulation and the length should be kept to a maximum of 3 m. Termination should be into an external gulley or soakaway as shown in Figs. 8 and 9. Note: All pipework must have a continuous fall (see Figs. 8 and 9) from the boiler and must be of an acid resistant material such as plastic waste pipe. (copper or steel is not suitable). It should be noted that the connection of a condensate pipe to a drain may be subject to local building control requirements.

Fig. 9 - External soakaway 3.11 DOMESTIC HOT WATER SYSTEM The minimum flow rate needed for the flow switch and burner to operate is 2.5 litres/min. The incoming mains water pressure should be between 0.2 and 8 bar to ensure efficient operation. If the pressure is above 7 bar a pressure reducing valve must be fitted. To ensure economic use, the pipe runs between the boiler and taps should be in 15 mm copper pipe and be as short as possible. Where possible the pipework should be insulated to reduce heat loss. All taps and mixing valves used with the hot water system must be suitable for operating at a mains pressure of up to 8 bar. Showers - A shower may be used with the boiler if required. If a loose or flexible head type shower is used it may require the fitting of a double check valve, to comply with Water Bye Law 17. Bidets - No anti-syphonage arrangements are necessary, provided the outlets are shrouded and it is not possible to attach a temporary hand held spray. A supply of direct mains fed hot and cold water is permitted provided the appliance is of the over- rim flushing type. Before the mains water supply pipe is connected to the boiler, it should be thoroughly flushed out to avoid the danger of dirt or foreign matter entering the boiler. Ground level (either/or) 22mm termination from boiler 2½ fall O 25mm 300mm Two rows of 3 x 12mm holes at 25mm centres, 50mm from the bottom of the tube. Holes to face away from house. Cement mortar sealing 100mm plastic tube Bottom of tube sealed Soakaway depth 400mm filled with limestone chippings 500 mm min. Fig. 8 - External gully

4 INSTALLATION 4.1 UNPACKING 1. The boxes required when the boiler is installed with a horizontal flue are as follows:- Box 1 ............................. Cased boiler fitted with water and gas valves, union bends and washers Mounting bracket plus screws and wall plugs Condensate discharge pipe Literature pack and Wall template Box 2 ............................. CD Easy-Flue 500 mm or CD Easy-Flue 1000 mm. Both include 90° bend and horizontal flue terminal Note: NOT required for vertical flue Notes: a. All flues must be suitable for CD condensing boilers. b. CD 750 mm and 1000 mm flue extensions are available, if required. Box 3 (if applicable) ....... Premier Pack includes: wall mounting jig with template, cyclone, bottom tray,earth bonding plate, spacers, pressure relief pipe terminal, split flow and return union bends, screw pack and fitting instructions. 2. Unpack boiler and remove the loose items packs and mounting bracket. Note: The boiler can be stood in an upright position, (to allow this, the union bends have been turned upwards so that they do not protrude beneath the bottom - check this before standing the boiler upright). 4.2 CLEARANCES REQUIRED - Fig. 10 Fig. 10 4.3 PREPARE THE WALL - Figs. 11 If the optional wall jig is used refer to the instructions supplied with the kit. 1. Decide upon the position of the boiler taking into account the clearances required for servicing and the flue terminal position. 2. Tape the template to the wall (ensure it is level and the right way up) and mark the position of the holes for the boiler mounting bracket or, if applicable the wall jig fixings. If rear exit flue is used, mark the position of the hole for the flue. The wall jig is supplied with a pressure relief valve discharge pipe for use when the boiler is mounted on an external wall where the outside is inaccessible, if you wish to use this pipe - mark it's position. 3. Side exit flue - Continue the horizontal centre line of the flue across the wall to the side wall, then along the side wall 140 mm, 180 mm if the wall jig is used (ensure the lines are horizontal). This will give the position of the centre of the hole for the flue. Fig. 11 720 mm 300 mm Minimum clearance of 450 mm from front of boiler 440 mm 235 mm 250 mm 5 mm 5 mm Boiler Minimum clearances (340 mm if wall jig fitted) Template Outline of boiler Wall mounting bracket fixing holes Wall jig fixing holes 140 mm (180 mm if wall jig used) Ensure line is level Rear exit hole 110 mm dia. Position of 110 mm hole to be cut for side exit flue 145 mm = =

Notes: 1. Ensure the hole is horizontal. 2. For internal fitting of the flue, using the flue sealing collar supplied, cut a 130 mm dia. flue hole using a 127 mm core drill. 5. Drill the fixing holes (10 mm dia.) to accept the No.10 plugs supplied. Using the screws supplied, fit the mounting bracket or wall jig if used. If applicable drill a 22 mm dia. hole for the pressure relief valve discharge pipe terminal supplied with the jig. IMPORTANT: If the wall jig is used, follow the instructions supplied with the Premier Pack to fit the jig, mount the boiler and connect the pipework. 4.4 FIT THE BOILER - Refer to Fig. 11, 12 Lift the boiler and locate it on the mounting bracket. Note: When handling or lifting always use safe techniques - keep your back straight, bend your knees, don't twist - move your feet, avoid bending forwards and sideways and keep the load as close to your body as possible. Where possible transport the boiler using a sack truck or other suitable trolley. Always grip the boiler firmly, and before lifting feel where the weight is concentrated to establish the centre of gravity, repositioning yourself as necessary. 4.5 CONNECT THE PIPEWORK - Fig. 13 1. Thoroughly flush out all the water pipework. Refer to Section 3.9. 2. The valves/fittings have been factory fitted, however, check that all the connections underneath the boiler have been tightened, especially the union bends. Note: If applicable the heating union bends supplied with the wall jig have been designed to enable the heating pipes to be routed from above and/ or below using the same fitting. Note: When soldering to the boiler union bends, ensure the bends are not connected to the valves, otherwise the internal seals may be damaged. 3. Connect the system pipework to the boiler. Note: Do not forget that the pressure relief valve discharge pipe must be routed clear of the boiler to a drain in such a manner that it may be seen, but cannot cause injury to persons or property. 4. Connect the 22 mm condensate trap drain pipe to the condensate discharge pipe using the clip supplied. Ensure that the condensate discharge pipe is as required in Section 3.10. Pour at least 0.5 litre of water into the flue duct, as shown in Fig. 12, and check the condensate discharge pipe for soundness. 5. Ensure that all the valves are closed (spindle flats at right angles to valve) and do not turn on the water or gas supplies at this stage. Alpha CD25X/28X - Installation Fig. 12 - rear of boiler Location for wall mounting bracket on rear of boiler Pour water into flue duct Fig. 13a - Without wall jig A - Heating flow (22 mm) B - Hot water outlet (15 mm) C - Gas inlet (22 mm) D - Cold water mains inlet (15 mm) E - Heating return (22 mm) F - Pressure relief valve (15 mm) 23 20 Heating drain point Condensate trap Heating return valve Cold water inlet filter Heating flow valve C B F D E A 65 70 45 70 58 95 37 Condensate discharge pipe

Rear flue L = wall thickness (B) + 60 mm Side flue L = wall thickness (B) + distance between boiler and wall (C) + 120 mm Fig. 16 3. Adjust the telescopic section of the flue to the distance 'L', ensuring that the two labels marked 'TOP' are aligned, then seal and secure the joint between the ducts with the sealing tape supplied. 4. Pass the flue assembly through the wall (from inside or outside). Note: Internal fitting - If there is no access to make good the outside wall, locate the flue sealing collar onto the outer duct of the flue immediately before the terminal grille onto the location provided. Push the flue assembly through the 130 mm flue hole, so that the collar completely passes through the wall. Then pull the flue assembly back into the correct position. Visually check that the collar is sealing the outside wall and that it is not restricting any of the openings of the flue terminal. 4.6 FIT THE FLUE - Figs. 14, 15 The following procedure applies to fitting an Alpha CD Easy-Flue to both rear or side exit flue - horizontally only. 1. The CD Easy-Flues are suitable for use in the flue length ranges shown in the tables below. Note: Where the length is less than the minimum or more than the maximum, refer to Section 4.7. Alpha CD25X/28X - Installation Fig. 14 Fig. 15 CD Easy-Flue 500 mm 1000 mm B (mm) Max 550 945 Min 310 705 CD Easy-Flue 500 mm 1000 mm Max 465 860 Min 225 620 B + C (mm) Note: Add 40 mm to dimension B if the wall jig is used. Fig. 13b - With wall jig A - Heating flow (22 mm) B - Hot water outlet (15 mm) C - Gas inlet (22 mm) D - Cold water mains inlet (15 mm) E - Heating return (22 mm) F - Pressure relief valve (15 mm) 23 20 Heating drain point Cyclone drain point Wall jig Condensate trap Heating return valves Cold water inlet filter Heating flow valve C B F D E A 65 70 45 70 58 95 37 Condensate discharge pipe

Secure in position using the seal and clamp, ensuring the seal is located centrally over both the bend and boiler adaptor. 6. Fit the inside flue sealing collar over the Easy-Flue. Fit the outside flue sealing collar onto the flue immediately before the terminal grille onto the location provided. 7. Slide the clamp (three screws) over the outer duct and pull the flue assembly towards the bend, locating the inner duct into the seal joint on the bend. Ensure the labels marked 'TOP' are positioned at the top before securing the flue assembly to the bend with the clamp (three screws) located centrally over the joint. Note: Check the flue terminal protrudes 90 mm out of the wall and the inner duct of the terminal is positioned correctly (see Fig. 18). 8. Make good the inside wall by pushing the inside flue sealing collar upto the wall. Alpha CD25X/28X - Installation Fig. 18 - Rear flue Flue Length Up to maximum:- Between:- Between:- Between:- Less than:- Rear Flue (B) 11.86 m 705 mm and 945 mm 550 mm and 705 mm 310 mm and 550 mm 310 mm Side Flue (B + C) 11.775 m 620 mm and 860 mm 465 mm and 620 mm 225 mm and 465 mm 225 mm Comments Alpha CD 750 mm or 1000 mm flue extension (Part No. 6.2000750 or 6.2001050) is required to extend the range of telescopic flue. Refer to Section 4.7 paragraph 2 for instructions on how to extend the flue. Note: A 130 mm flue hole (127 mm core drill) is required in the wall. Within the standard Easy-Flue 1000 mm (Part No. 6.20001000) telescopic range. Use an Easy-Flue 1000 mm (Part No. 6.20001000) and the terminal may protrude somewhat from the outside wall. Within standard Easy-Flue 500 mm (Part No. 6.2000500) telescopic range. Terminal may protrude somewhat from the outside wall. Note: Subtract 40 mm to dimension B if the wall jig is used. 40 (80 if wall jig used) 140 (180 if wall jig used) 90 Outer duct clamp Inner duct seal joint Inner duct seal joint 90° bend Terminal Flue sealing collar Note: Ensure the outer flue duct is horizontal Boiler side CD Easy-Flue Ensure the inner duct within the terminal is at the top. The inner duct must be positioned to slope towards the boiler Note: 4.7 EXTENDING THE FLUE - Fig. 19 Note: The maximum horizontal flue assembly length must not exceed a length of 12 metres. 1. When the flue length required is more than the maximum or less than the minimum stated in Section 4.6, paragraph 1, refer to the table below. Fig. 17 - Fitting the flue from inside

2. Use the template (supplied with the boiler) to mark the required flue position and cut a 130 mm diameter hole for the flue (use a 127 mm core drill). The size of the hole provides sufficient clearance for the clamps on the flue extension to pass through the hole. 3. Determine the overall flue length as described in Section 4.6, paragraph 2 to determine the number of Alpha CD 750/1000 mm flue extensions required. 4. Assemble the flue extensions together by locating the inner duct into the seal joint and secure each extension together with the clamps supplied (three screws). Ensure that the clamps are positioned centrally over the joints. Note: If it is required to cut an extension, DO NOT cut the end of the inner duct that incorporates the seal joint. Ensure the inner duct end without the seal joint is cut so that it is 15 mm longer than the outer duct. 5. Adjust the telescopic section of the Easy-Flue to the required length and secure the Easy-Flue with the sealing tape supplied. Fit the Easy-Flue to the extensions by locating the inner duct into the seal joint and secure with the clamp (three screws), ensuring it is located centrally over the joint. 6. Mark the end of the flue assembly 'TOP' where it is connected to the boiler,so that the 'TOP' of the flue terminal is aligned with the 'TOP' at the boiler end of the flue assembly. 7. Pass the complete flue assembly through the wall. 8. Position the seal and clamp (two screws) supplied, over the bend. Fit the bend to the boiler and rotate to the correct position and secure in position using the seal and clamp, ensuring that the seal is positioned centrally over both the bend and adaptor. 9. Slide the clamp (three screws) over the outer duct and pull the flue assembly towards the bend, locating the inner duct into the seal joint on the bend. 10. Secure the flue assembly to the bend with the clamp (three screws) ensuring it is positioned centrally over the joint, ensuring the 'TOP' marked on the outer duct is positioned at the top. Note: Check the flue terminal protrudes 90 mm out of the wall and that the inner duct of the terminal is positioned correctly, i.e. the inner duct within the terminal is at the top. See Fig. 19. 11. Make good the outside wall by fitting a flue sealing collar onto the location provided immediately behind the flue terminal grille. Make good the inside wall as required. Note: If flue sealing collars are being used to make good the inside wall, then they will need to be fitted before assembling the flue. Fig. 19 - Side flue 90 25 220 220 125 Note: Ensure the flue extension slopes downwards towards the boiler by a minimum of 25 - 30 mm per metre Boiler front Outer duct clamp Inner seal joint Inner seal joint Flue length (L) Clamp and seal 90° bend Seal joint CD Easy-Flue CD Flue extension Flue sealing collar Flue terminal Ensure the inner duct within the terminal is at the top. The inner duct must be positioned to slope towards the boiler Note:

4.8 CONNECT THE MAINS SUPPLY - Fig. 20 1. Gain access to the boiler terminal block by releasing the two fixing screws (one each side) securing the control panel and lowering the panel. Refer to Technical Data, Section 2.10 for connection details. 2. Note: This boiler has been fitted with a mains supply cable. However, if it is necessary to fit an alternative supply cable, ensure the cable clamp that has been fitted is removed and connect as follows:- Remove the two screws securing the terminal block cover from the back of the control box (see Fig. 20). Pass the mains supply cable through the cable clamp and connect as follows:- Brown to L, Blue to N and Green/Yellow to . Ensure correct polarity. Note: Ensure that the length of the earth wire is such that if the supply cable is pulled out of its clamp the live and neutral wires become taut before the earth wire. The main terminal block can be removed by pulling it off the pins to give easy access to the terminals. Do not switch on the electrical supply at this stage. 3. If an external control, i.e. room thermostat or external clock is to be fitted, remove the terminal block cover and remove the link between terminals 1 and 2. Pass the cable through the cable clamp and connect it to terminals 1 and 2. Replace the terminal block cover. (Refer to Section 2.10). 4. Replace the terminal block, ensuring it is located correctly on the plastic pins and replace the cover. 5. Ensure that there is sufficient free cable to allow the control panel to be raised and lowered then tighten the cable clamp screws. 6. Leave the control panel open until commissioning procedures have been completed. 7. Carry out electrical system checks - Short circuit, Polarity, Earth continuity and Resistance to earth with a suitable multimeter. 4.9 FIT THE CLOCK KIT - Fig. 21 Ensure the electrical supply to the boiler is isolated. Important: Only use an Alpha single channel clock. Do not fit a two channel clock. 1. Remove the two screws securing the clock cover at the rear of the control panel. 2. Remove and discard the clock blanking panel. 3. Insert the clock into the opening and secure in place with the screws supplied. 4. Disconnect the clock wiring from the terminal block and connect it to the clock as follows:- Blue wire to terminal 1, Brown wire to terminal 2 and Red wires to terminals 3 and 4, (or as per the instructions supplied with the clock). Ensure wiring is correct. 5. Replace the clock cover. Do not overtighten the fixing screws. 6. Leave the control panel open until commissioning procedures have been completed. Fig. 20 Fig. 21 Fuse Cover Grommets Cable clamps Rear of control panel Remove link to connect external controls Fuse Clock cover Grommets Clock fixing pillars Rear of control panel

5 COMMISSIONING When commissioning the boiler, ensure the Benchmark Checklist is completed. 5.1 FILL THE SYSTEM 1. The boiler is fitted with an automatic air vent positioned on the pump (see Fig. 2), ensure that the vent is always open. 2. Open the central heating flow and return valves (vertical slot in-line with valve) (see Fig. 13). 3. Open the fill point valve on the filling loop until water is heard to flow. To aid venting, the boiler drain point (see Fig. 13) may be opened until water flows out. Close the drain point as soon as water appears. 4. To remove the air - Vent each radiator in turn, starting with the lowest in the system. 5. It is important that the pump is properly vented to avoid it running dry and damaging its bearings. Unscrew and remove the cap from the centre of the pump. Using a suitable screwdriver rotate the exposed spindle about half a turn, then replace the cap. 6. Check the operation of the pressure relief valve (see Fig. 2) by turning the head anti-clockwise until it clicks. The click is the valve lifting off its seat allowing water to escape from the system - check that this is actually happening. 7. Continue to fill the system until the pressure gauge indicates 1.0 bar. Close the fill point valve and check the system for water soundness, rectifying where necessary. Disconnect the filling loop from the mains supply. Water may be released from the system by manually operating the drain point (see Fig. 2) until the system design pressure is obtained. The system design pressure (cold) should be between 0.75 and 1.25 bar. Refer to Sections 3.8 and 3.9. Filling and Flushing the system. 8. Open the mains water inlet valve (see Fig. 2). Turn on all hot water taps and allow water to flow until no air is present. Turn off taps. 9. Ensure that the condensate trap has been filled with water. Refer to Section 4.5, paragraph 4. 5.2 BOILER CONTROLS - Fig. 22 Fig. 22 5.3 TEST FOR GAS TIGHTNESS AND PURGE THE SUPPLY 1. With the boiler gas service cock closed (slot at right angles to valve). Pressure test the gas supply and inlet pipework connection to the boiler gas service cock for tightness in accordance with BS 6891. 2. Loosen the gas inlet pressure test point screw on the gas valve (see Fig. 23). Ensure the gas supply is on and open the boiler service cock to purge in accordance with BS 6891. 3. Retighten the test point screw and test for gas tightness. Close the boiler gas service cock. 0 1 2 3 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 bar 0 4 3 2 1 RESET A D B C SELECTOR THERMOSTAT THERMOSTAT OFF Clock (if fitted) Indicator Neons Selector Switch Domestic Hot Water Thermostat Central Heating Thermostat System Pressure Gauge

1. Ensure that the gas and electrical supplies to the boiler are off and that the mains water inlet valve and the central heating flow and return valves are open. 2. Turn on the gas and electrical supplies to the boiler. 3. Ensure all external controls are calling for heat. If the optional Clock is fitted, refer to the User's instructions, set the time and ensure the Clock is in an 'on' mode. 4. Set the hot water and central heating thermostats to maximum. 5. Set the selector switch to (DHW only). Open a hot water tap, the main burner will light and the boiler will provide hot water. Close the tap and the burner will go out. 6. Set the selector switch to (CH and DHW). The boiler will now run in the central heating mode. The pump will start, the fan will start and the main gas valve solenoid will open allowing the main burner to light. 5.5 CHECK THE BURNER PRESSURES - Figs. 23, 24 Turn the boiler off. Remove the two pressure test point screws at the top of the boiler and connect a differential pressure gauge to P1 and P2 as shown in Fig 24. Allow the boiler to run for 10 minutes and check the differential burner pressures. Hot water mode 1. Set the selector switch to (DHW only) and fully open a hot water tap. 2. The burner will light at the ignition rate and the burner pressure will increase to maximum. 3. Gradually close the hot tap and check that the burner pressure decreases to its minimum. Fully open the tap and check that the burner pressure increases. Close the tap and check that the burner goes off. Note: The burner pressure settings have been factory set and do not require adjusting. If incorrect, check that the inlet gas pressure is 20 mbar. If the inlet gas pressure is not 20 mbar, either the pipework is too small or the gas supply to the house is insufficient, in which case contact your gas supplier. Central heating mode 1. Set the selector switch to (DHW and CH). 2. The burner will light at the ignition rate and will increase to the factory pre-set maximum output after 1 minute. 3. Turn off the boiler. Disconnect the pressure gauge and tighten the test point screws. Test for gas tightness using suitable leak detection fluid. Note: Refer to Technical Data, Section 2.1 for the required differential burner pressures. 5.6 FINAL COMMISSIONING 1. Allow the heating system to heat up, then balance the system to achieve the necessary temperature difference across the heating flow and return pipes at the boiler and check the system volume and pressure. (Refer to Technical Data, Sections 2.1 and 2.2). 2. Turn off the boiler. 3. Thoroughly flush out the water pipework (refer to Section 3.9) and with no pressure in the boiler heating circuit, empty the cyclone (if applicable) at it's drain point (see Fig. 13) of any debris. Clean the mains water inlet filter (see Fig. 13). 4. Re-pressurise the system as described in Section 5.1. Alpha CD25X/28X - Commissioning Fig. 23 Do not connect here Do not connect here Inlet gas pressure test point Fig. 24 + + - - P1 P2 Flue sample point (marked 'F') - +

5.7 FINAL ASSEMBLY 1. Raise the control panel and secure in position with the screws provided. Note: If the wall jig is used, fit the bottom tray over the base of the boiler. 2. If the boiler is to be left in service with the User, set the controls, clock (if fitted, see User's Operating manual) and room thermostat (if fitted) to the User's requirements. 3. If the boiler is not to be handed over immediately, close the boiler gas service cock and switch off the electrical supply. 4. If there is any possibility of the boiler being left during frost conditions, then the boiler and system should be drained (refer to Section 8.2). It is recommended that a label is attached to the boiler drawing attention to the fact that the system has been drained. 5. Complete the details of the installation in the Benchmark Checklist on page 38. 5.8 USER INFORMATION The User must be advised (and demonstrated if necessary) of the following important points:- 1. How to light and turn off the boiler and how to operate the system controls. 2. The importance of annual servicing of the boiler to ensure safe and efficient operation. 3. That any servicing or replacement of parts must only be carried out by CORGI registered personnel. 4. Ensure that the boiler controls and room thermostat (if fitted) are set to the User's requirements. 5. Tell the User about the sealed system pressure. 6. Tell the User that if the electrical supply is on and the boiler has not operated for 24 hours for heating or hot water, the pump will automatically operate for 30 seconds. 7. Explain to the User that an internal frost thermostat is fitted in the boiler, and that the electrical supply to the boiler must be left on for the thermostat to operate, i.e. the selector switch must be set at (DHW only) or (CH and DHW). 8. Explain to the User that in certain weather conditions the terminal will emit a plume of steam, i.e. water vapour. This is safe and quite normal. 9. Show the User the position of the pressure relief valve and condensate discharge pipes. 10. Hand the User's instructions to the User. 11. Ensure the Benchmark Checklist in Section 12 on page 38 has been completed after the boiler has been installed and commissioned. Note: It is a requirement that the installation is registered by the installer through the CORGI Gas Work Notification Scheme. 12. Leave these Installation and Servicing instructions with the User for use on future calls.

When set to , the boiler will only operate in the Domestic Hot Water mode. When set to , it will operate in the Domestic Hot Water and Central Heating mode. Note: The clock (if fitted) only controls the operating times of the central heating, not domestic hot water - DHW is available continuously. Domestic hot water supply always takes priority over central heating. If a demand for hot water is required during a central heating period, the boiler will automatically switch to the hot water mode until the demand is satisfied. This interruption in the central heating is only when the demand for hot water is present and should not be noticed by the User. 6.1 CENTRAL HEATING MODE If there is a call for heat, the pump will start to circulate the central heating water. The fan will run and the pre-mix burner will light. The burner output then automatically adjusts to suit the system demand; as the temperature of the water in the boiler approaches that set by the adjustable temperature thermostat, the burner output is reduced. When the set temperature is reached, the burner is turned off. The fan continues to run for 50 seconds and the pump continues to run for three minutes, after which the burner can relight if required. If the primary sensor has not registered the pre-set temperature but the room thermostat is satisfied the burner is turned off. The fan continues to run for 50 seconds and the pump continues to run for 60 seconds. In this instance there is no delay before the burner will relight. If there is a demand for DHW during the burner delay, the boiler will operate to provide DHW until the tap is closed; the boiler will then immediately revert to provide CH if there is a demand. Note: If the system pressure is very low, the primary pressure switch will prevent the boiler from operating. 6.2 DOMESTIC HOT WATER MODE When a demand for hot water (by opening a hot tap, etc.) is sensed by the flow switch, the pump starts and the burner lights, increasing immediately to its maximum output. Water in the boiler is then diverted from the central heating system to the domestic hot water heat exchanger, heating the incoming mains water. The burner output is varied to maintain the temperature of the hot water as that set by the adjustable temperature selector. When the flow switch senses that hot water is no longer required the burner is turned off and the boiler immediately returns to the central heating mode. If the selector is set for hot water only - The burner is turned off, the fan will continue to run for 50 seconds and the pump will stop immediately. In both modes the fan modulates according to the output required. 6.3 FROST THERMOSTAT The boiler incorporates a built in frost thermostat which automatically turns on the boiler and pump if the water in the boiler falls below 4°C, providing the electrical supply is on and the selector switch is set to position 1 ( ) or position 2 ( ). The boiler will operate until the water temperature in the system reaches approximately 30°C. 6.4 PUMP If the electrical supply is on and the boiler has not operated for 24 hours for heating or hot water, the pump will operate automatically for thirty seconds every 24 hours. 6.5 INDICATOR NEONS When neons A (red), B (red), C (yellow), D (green) are illuminated, the following conditions apply:- Neon D Illuminated continuously - Electricity supply to the boiler is on. C Illuminated continuously - Burner is alight. A Flashing on and off - Temperature sensor fault. B Flashing on and off - Overheat thermostat has operated. Rotate selector switch to the reset position (3) to reset. B Illuminated continuously - Burner has failed to light. Rotate selector switch to the reset position (3) and the ignition sequence will restart after a delay of about 30 seconds. A and B Flashing on and off at the same time - Blocked flue or fan fault. A and B Flashing on and off alternatively - System pressure is very low and re-pressurisation is required. A Flashing and B Illuminated continuously - Pump fault or restricted flow. Note: Do not hold the selector switch in the reset position (3) for more than 2 to 3 seconds. Alpha CD25X/28X - Boiler Operation 6 BOILER OPERATION

The frequency of servicing will depend upon the particular installation conditions and usage, but in general once per year should be adequate. It is the law that any service work must be carried out by a competent person, i.e. CORGI registered personnel. Warning: Before servicing the boiler, isolate the electrical supply and close the boiler gas service cock. Allow the boiler to cool. The data label is positioned on the inside of the left hand side panel. Always test for gas tightness after servicing any gas carrying components. Always carry out electrical system checks i.e. Earth Continuity, Resistance to Earth, Short Circuit and Polarity with a suitable meter after servicing. Notes: 1. Prior to servicing, it is recommended that a flue gas analyser is used to measure the performance of the boiler (refer to Fig. 2 for the position of the flue sampling point). If the CO/CO2 ratio measured is greater than 0.003 or when other checks and comments from the customer have indicated that there may be problems, cleaning of the heat exchanger will be necessary. All Sections 7.1, 7.2, 7.3 and 7.4 must be carried out. Repeat the flue gas analyser test after reassembling the boiler and check that the CO/CO2 ratio is less than 0.003. 2. If the CO/CO2 ratio measured is less than 0.003 and other checks and comments from the customer suggest there are no problems then only Section 7.1 and Section 7.2 paragraphs 1, 2 and 3 need to be carried out to allow a visual check of the components within the room sealed chamber. 3. If a flue gas analyser is not available, then all Sections 7.1, 7.2, 7.3 and 7.4 must be carried out. 7.1 IMPORTANT NOTES PRIOR TO SERVICING 1. Check the flue terminal outside and ensure it is not blocked. 2. Run the boiler and check the operation of its controls. 3. Refer to Fig. 2 for location of flue sampling point. 4. Ensure that all system connections and fittings are sound. Remake any joints and check the tightness of any fittings that may be leaking. 5. Refill, vent and re-pressurise the system as necessary. (Refer to Commissioning, Section 5.1). If the system pressure exceeds 2.5 bar when operating at maximum temperature, the heating expansion vessel should be checked and re-pressurised, if necessary. Notes: 1. Check the expansion vessel charge only when the system pressure is zero. 2. The expansion vessel pressure test point is accessible from inside the boiler at the top. 6. Check that the condensate trap drain pipe is connected and all joints are sound. 7. Record details of the service in the Service Record Section on page 39. Alpha CD25X/28X - Routine Servicing 7 ROUTINE SERVICING Fig. 26 Front case locating pins Front case fixing screws Combustion chamber front assembly Gas pipe union Fan assembly fixing screws Fan assembly Pressure tube connections Ignition generator Viewing window Four nuts and washers securing combustion chamber front assembly

1. Ensure the electrical supply is isolated and the gas supply is off. 2. Unscrew the two screws securing the control panel and lower the panel. 3. Remove the four screws securing the front case. Lift the case up and forwards to remove. 4. Disconnect the gas supply pipe union from the manifold. 5. Remove the two screws securing the fan assembly to the combustion chamber front. 6. Remove the two pressure tubes, noting their positions. 7. Disconnect the electrode lead from the ignition generator and the in-line connector to the flame sensing electrode. 8. Remove the four nuts and washers and four screws securing the combustion chamber front assembly and remove the assembly. 7.3 CLEANING THE BOILER 1. Remove any deposits from heat exchanger using a suitable soft brush. Do not use a brush with metallic bristles. 2. Check the condition of the combustion chamber insulation panels. Any damaged panels must be replaced. (Refer to Component Replacement, Section 8.19). 3. Check the condition of the burner injector on the combustion chamber front assembly, carefully clean them with a soft brush if necessary. Do not use a brush with metallic bristles as this might damage the injector. 4. Remove any deposits from the heat exchanger coils. This can be done by suction or water sprayed onto the coils. Ensure all electrical components are protected from water. Any water used to clean the heat exchanger will drain to the condensate trap. 5. Unscrew and replace the injector should it appear damaged. 6. Remove the four screws securing the burner (see Fig. 27) and remove the burner. Clean the burner with a soft brush and check that the flame ports are clear. Blockages may be removed with a stiffer brush. Tap the burner, open end down, to remove any deposits from inside. 7. Check the condition of the electrodes. 9. Check the spark gap, positioning and height of the electrodes. See Fig. 27. 10. Unscrew the condensate trap drain cap to remove any deposits. Note: Before removing the cap, ensure that the water released from the trap can be contained to avoid spillage. The trap will contain no more than 200 cc of condensate water. Replace the drain cap. 7.4 RE-ASSEMBLE THE BOILER 1. Replace the burner, ensuring it is located correctly and secure it in position using the four screws previously removed. Important: Before replacing the combustion chamber front assembly, pour at least 200 cc of water into the coils of the heat exchanger. This is to ensure the condensate trap is full of water before operating the boiler. 2. Replace the combustion chamber front assembly, ensuring it is correctly located. 3. Ensure the electrode lead is connected and the grommet is in position in the bottom of the room sealed chamber. 4. Test the connections for gas tightness and re-commission, Sections 5.4 and 5.5. 5. Place the front case panel in position and secure in position with the four screws previously removed, see Fig. 26. 6. Raise the control panel and secure in position with the two screws provided. 7. Check the operation of the boiler. (Refer to Boiler Operation, Section 6). 8. Return all controls to their original settings. Alpha CD25X/28X - Routine Servicing Fig. 27 Electrode gap 3 - 4 mm Burner Burner to electrode gap 16 mm Flame sensing electrode Front panel insulation Ignition electrodes Combustion chamber front assembly

It is the law that any service work must be carried out by a competent person, i.e. CORGI registered personnel. Warning: Before replacing any boiler components, isolate the electrical supply and close the boiler gas service cock. Allow the boiler to cool. Always test for gas tightness after replacing any gas carrying components or disturbing any gas connections. Always carry out electrical system checks i.e. Earth Continuity, Resistance to Earth, Short Circuit and Polarity with a suitable meter after servicing. Check the operation of the boiler. (Refer to Boiler Operation, Section 6). Ensure that all the controls are returned to their original settings. The replacement of components in Sections 8.3 to 8.15 does not require draining of the boiler. 8.1 GENERAL ACCESS - Fig. 26 Ensure the electrical supply is isolated and the gas supply is off. 1. If access is required behind the control panel - Lower the control cover flap and remove the two control panel fixing screws (one each side) and lower the panel. 2. To gain access behind the casing - When the control panel is lowered, it exposes four fixing screws that secure the front cover. Remove these screws and lift the front cover off its locating pins at the top of the boiler. 3. To gain access to the control panel components/PCB - Remove the five screws securing the rear cover and carefully raise the cover. When replacing the cover, ensure no wires are trapped and all wiring is secured. Secure with five screws - do not overtighten. 8.2 DRAINING THE BOILER - Refer to Figs. 2, 13 Isolate the electricity supply and close the boiler gas service cock (see Fig. 13). Allow the boiler to cool. 1. Heating circuit Close the central heating flow and return valves (see Fig. 13). Connect a suitable pipe to the drain point (see Fig.13) and route it to a suitable container. Open the drain point. 2. Hot water circuit Close the mains water inlet valve (see Fig. 13). Open any hot tap below the level of the boiler to allow as much draining as possible. Note: Some water will remain in the components and care must be taken when removing them. 8.3 ELECTRODES - See Fig. 27 Gain access behind the room sealed chamber panel as in Section 8.1. 1. Ignition electrode and lead Disconnect the lead from the ignition generator, noting its position. Remove the two screws securing the electrode to the front of the combustion chamber and carefully withdraw the electrode. 2. Flame sensing electrode and lead Disconnect the flame sensing electrode in-line connector. Remove the two screws securing the electrode to the front of the combustion chamber and carefully withdraw the electrode. Re-assemble in reverse order 8.4 MAIN BURNER - Fig. 27 1. Remove the burner assembly as described in Routine Servicing, Section 7.2. 2. Remove the four screws securing the burner to the combustion chamber front assembly. 3. Re-assemble with a new burner as described in Routine Servicing, Section 7.4. 8.5 BURNER INJECTOR - Fig. 26 1. Gain access to the room sealed chamber as described in Section 8.1. 2. Undo the gas inlet union to the combustion chamber front to gain access. 3. Unscrew the damaged injector and screw in a replacement. 4. Re-assemble in reverse order.

1. Gain access behind the room sealed chamber as described in Section 8.1. 2. Remove the combustion chamber front as described in Section 7.2. 3. Withdraw the fan. 4. Remove the air inlet pipe from the fan. Fit it to the new fan and re-assemble in reverse order. Ensure that the pressure tubes are connected correctly. 5. Re-assemble and test the boiler as described in Routine Servicing, Section 7.4 paragraphs 5 to 9. 8.7 IGNITION GENERATOR - Fig. 28 1. Gain access behind the front panel as described in Section 8.1. 2. Disconnect all the wiring from the ignition generator. 3. Remove the two screws securing the generator and remove. 4. Secure the new generator in position and re- connect the wiring. 5. Re-assemble in reverse order. 8.8 TRANSFORMER - Fig. 28 1. Gain access behind the front panel as described in Section 8.1. 2. Remove the two screws securing the transformer and remove the transformer. 3. Disconnect all of the wiring noting their position. 4. Fit the new transformer and re-assemble in reverse order. 8.9 OVERHEAT THERMOSTAT - Fig. 28 1. Gain access behind the front panel as described in Section 8.1. 2. Disconnect the wiring from the overheat thermostat. 3. Remove the two screws securing the overheat thermostat and remove it from the flow pipe. 4. Fit the new overheat thermostat and re-assemble in reverse order. 8.10 FLUE TEMPERATURE SENSOR - Fig. 28 1. Gain access behind the front panel as described in Section 8.1. 2. Disconnect the wiring. 3. Using a 13 mm spanner, turn the sensor 90° anti-clockwise and withdraw it from the heat exchanger. 4. Fit the new sensor and re-assemble in reverse order. 8.11 GAS VALVE - Fig. 28 1. Gain access behind the front casing as in Section 8.1. 2. Disconnect the positive pressure tube from the gas valve. 3. Loosen the one screw securing the electrical plug and disconnect the plug. 4. Disconnect the burner manifold pipe union and the gas inlet pipe union. 5. Remove the two manifold screws from beneath the boiler and lift out the valve assembly. 6. Lift out the gas valve. 7. Fit the new assembly and re-assemble in reverse order and test for gas tightness. 8. Light the boiler. (Refer to Commissioning, Section 5.4) and adjust the gas valve as described in the instructions supplied with the replacement valve. 9. Complete re-assembly as described in Routine Servicing, Section 7.4 paragraphs 5 to 9. Alpha CD25X/28X - Component Replacement Fig. 28 Flue temperature sensor Expansion vessel Heat exchanger thermal fuse Ignition electrodes Overheat thermostat Ignition generator Fan assembly Primary temperature sensor Transformer Gas valve

The fuse is located in the boiler terminal block. 1. Gain access as described in Installation, Section 4.8. 2. Lift out the fuse holder and remove the fuse. Fit a fast blow 2 A fuse as a replacement, ensuring that the holder snaps into position. Note: A spare fuse is supplied in the terminal compartment. 3. Re-assemble in reverse order, ensuring the terminal block is located correctly on the plastic pins. 8.13 PCB - Fig. 29 1. Gain access behind the control panel as described in Section 8.1. 2. Disconnect all the wiring connectors from the PCB. 3. Remove the four fixing screws and carefully withdraw the board from the switch spindles. 4. Re-assemble in reverse order. Refer to the wiring diagram in Section 9.1 for connections. 5. Light the boiler and adjust the PCB as described in the instructions supplied with the replacement PCB. Alpha CD25X/28X - Component Replacement 8.14 DIVERTER VALVE MOTOR - Fig. 30 1. Gain access behind the front casing as described in Section 8.1. 2. Remove the diverter valve motor head by unplugging its electrical connection and removing the retaining clip from the back of the motor. 3. Withdraw the motor forwards from the valve body. 4. Re-assemble in reverse order with a new motor. 8.15 CLOCK (if fitted) - Refer to Fig. 21 Note: For replacement only use an Alpha single channel clock. Do not fit a two channel clock. 1. Gain access behind the control panel as described in Section 8.1. 2. Remove the two screws securing the clock cover at the rear of the control panel. 3. Disconnect the wiring from the clock. 4. Remove the clock retaining screws and withdraw the clock from the control panel. 5. Fit the new clock, and connect the wires as follows:- Blue to terminal 1, Brown to terminal 2 and Red wires to terminals 3 and 4, (or as per the instructions supplied with the clock). 6. Re-assemble in reverse order. Refer to the User's instructions and the boiler's control cover to set the clock. 8.16 HEAT EXCHANGER THERMAL FUSE Note: If the thermal fuse has failed or operated, the heat exchanger must be replaced. Do not attempt to remove the thermal fuse. Disturbing the sealant securing the thermal fuse will invalidate the warranty. 1. Gain access behind the front casing as described in Section 8.1. 2. Disconnect the wire from the thermal fuse and remove the heat exchanger as described in Section 8.18. 3. Fit a new heat exchanger and re-assemble in reverse order. Fig. 29 Fig. 30 Terminal block fuse PCB fuses PCB DHW Flow switch Diverter valve motor and assembly Retaining nut

1. Gain access behind the front casing as described in Section 8.1. 2. Isolate the mains water supply and open all hot taps to drain any water from the boiler. 3. Disconnect the wires from the switch. 4. Undo the nuts at the inlet and outlet of the switch and undo the retaining nut at the bottom. Lift out the switch. 5. Fit the new switch and re-assemble in reverse order. 8.18 PRIMARY HEAT EXCHANGER - See Fig. 31 and 28 1. Gain access behind the room sealed chamber panel as described in Section 8.1 and drain the boiler heating circuit as described in Section 8.2. 2. Remove the burner as described in Section 7.2 (Routine Servicing). 3. Unplug the connections from the flue temperature sensor and thermal fuse. See Fig. 28. 4. Disconnect the condensate drain pipe by pulling its rubber connector from the heat exchanger. 5. Remove the screws securing the ignition generator, disconnect the earth lead and remove the ignition generator. 6. Unplug the fan and remove it from the boiler. 7. Remove the heating flow and return pipe-retaining clips from the primary heat exchanger and pull the pipes downwards from the heat exchanger connections. 8. Slide the heat exchanger downwards and forwards to disconnect from the flue connection and withdraw it from the boiler. 9. Re-assemble in reverse order, ensuring that new seals are used. Lubricating the seals with the grease supplied will aid assembly. 10. Refill and pressurise the system. (Refer to Commissioning, Section 5.1). 8.19 COMBUSTION CHAMBER INSULATION Gain access to the combustion chamber as described in Section 8.1. Front panel insulation - see Fig. 27 1. Remove the electrodes from the combustion chamber front as described in Section 8.3. 2. Remove the four screws securing the burner. 3. Carefully remove the insulation. Back panel insulation - see Fig. 31 1. Remove the combustion chamber front/burner assembly. 2. Remove the centre screw retaining the insulation. 3. Carefully remove the insulation, suction applied to the centre of the insulation will aid this. Fit a new panel and re-assemble in reverse order. 8.20 PRESSURE GAUGE - Fig. 32 1. Gain access behind the casing and drain the boiler heating circuit as described in Sections 8.1 and 8.2. 2. Remove the circlip securing the pressure gauge sensor and withdraw the sensor. 3. Remove the main cable grommet in the bottom panel and remove the sensor tube. 4. Depress the two lugs on the pressure gauge and push it out of the control panel. 5. Fit the new gauge using a new 'O' ring on the connection if necessary. 6. Refill and pressurise the system. (Refer to Commissioning, Section 5.1). Fig. 32 Alpha CD25X/28X - Component Replacement Fig. 31 Thermal fuse Back panel insulation Primary pressure switch Primary temperature sensor Automatic air vent Pump Pressure relief valve Pressure gauge Cable grommet DHW sensor

Note that both sensors are the same. 1. Gain access as described in Section 8.1 and drain (heating circuit for primary sensor or hot water circuit for DHW sensor) as described in Section 8.2. 2. Primary Sensor - The primary sensor is positioned on the bottom left hand side in the primary flow pipe, see Fig. 28. Disconnect the wiring and unscrew the sensor. Re-assemble in reverse order with a new sensor and sealing washer. 2a. DHW Sensor - The DHW sensor is positioned in the hot water outlet pipe, see Fig. 32. Close the mains cold water inlet valve and open the lowest hot water tap to drain the DHW system. Disconnect the wiring and unscrew the sensor from the hot water outlet pipe. Re-assemble in reverse order with a new sensor, replacing the sealing washer if necessary. 8.22 AUTOMATIC AIR VENT - Fig. 32 1. Gain access behind the front casing and drain the boiler heating circuit as described in Sections 8.1 and 8.2. 2. Remove the retaining clip from the manifold and lift out the automatic air vent. Fit a new one using a new 'O' ring. 3. Refill and pressurise the system. (Refer to Commissioning, Section 5.1). 8.23 PUMP - Refer to Fig. 32 Gain access behind the front casing and drain the boiler heating circuit as described in Sections 8.1 and 8.2. Pump head 1. Using a 5 mm Allen key remove the four socket head screws securing the pump head to the body. Withdraw the head, remove the wiring cover and disconnect the plug. 2. Connect the plug to the new head. Ensure the pump is set to maximum (3) and re-assemble in reverse order. 3. Refill and pressurise the system. (Refer to Commissioning, Section 5.1). 8.24 PRIMARY PRESSURE SWITCH - Fig. 32 1. Gain access behind the front casing and drain the boiler heating circuit as described in Sections 8.1 and 8.2. 2. Disconnect the wiring from the pressure switch. 3. Unscrew the switch from the primary flow pipe. 4. Using the new washer supplied, re-assemble in reverse order. When connecting the wiring to the new switch the polarity of the wires is not important. 8.25 PRESSURE RELIEF VALVE - Fig. 32 1. Gain access behind the front casing and drain the boiler heating circuit as described in Sections 8.1 and 8.2. 2. Disconnect the pressure relief valve outlet fitting. 3. Remove the four screws at the bottom of the boiler, either side of the flow and return connections, the two screws securing the expansion relief valve and the left hand DHW manifold securing screw. 4. Lift the pump assembly and pull the pressure relief valve to disconnect it from the pump housing. 5. Re-assemble in reverse order. 6. Refill and pressurise the system. (Refer to Commissioning, Section 5.1). 8.26 DHW HEAT EXCHANGER 1. Gain access behind the front casing and drain the boiler heating and hot water circuits as described in Sections 8.1 and 8.2. 2. Release the nut securing the condensate pipe and remove the flexible condensate pipe from the condensate trap. Rotate the pipe to clear. 3. To create more space to withdraw the heat exchanger - Remove the screw securing the fan air inlet pipe and remove the pipe, remove the screws securing the fan and move it to the right hand side of the chamber. 4. Remove the diverter valve motor as described in Section 8.14. 5. Using a 4 mm Allen key unscrew the two socket head capscrews securing the DHW heat exchanger. Withdraw the heat exchanger from the boiler by moving it to the left and rotating it to remove. Note: Be careful not to allow water to drip onto any electrical components. 6. Re-assemble in reverse order making sure that the printing on the heat exchanger is at the top when fitted and that the seals are in position in the manifold. 7. Refill and pressurise the system. (Refer to Commissioning, Section 5.1). Alpha CD25X/28X - Component Replacement

1. The mains water inlet filter is located in the body of the DHW flow switch. Refer to Section 8.17 to remove the flow switch. 2. The filter can be removed using a small screwdriver. 3. Clean the filter and re-assemble in reverse order. 8.28 DIVERTER VALVE ASSEMBLY - Fig. 30 1. Gain access behind the front casing and drain the boiler heating circuit as described in Sections 8.1 and 8.2. 2. Remove the three screws securing the right hand side panel and slide the panel forwards to remove. 3. Remove the diverter valve motor as described in Section 8.14. 4. Remove the screw securing the fan inlet pipe and remove the pipe from the fan. 5. Remove the heating flow and return pipe-retaining clips from the primary heat exchanger and pull the pipes downwards from the heat exchanger connections. 6. Remove the heating flow and return pipe-retaining clips from the diverter valve and withdraw from the diverter valve. Leave the pipes in the back of the boiler. 7. Remove the DHW outlet pipe-retaining clip from the diverter valve and undo the nut connecting the other end to the DHW temperature sensor housing. Withdraw the pipe from the diverter valve and leave inside the boiler. 8. Using a 4 mm Allen key undo the two cap head screws securing the DHW heat exchanger and push the heat exchanger to the back of the boiler away from the diverter valve assembly. 9. Undo the heating flow valve and return valve from their boiler connections. 10. Completely remove the drain valve nipple from the boiler and undo the expansion relief pipe from the manifold. 11. Remove the four screws at the bottom of the boiler, either side of the flow and return connections, the two screws securing the expansion relief valve and the left hand DHW manifold securing screw. 12. Lift the diverter valve and pump assembly and pull the diverter valve to the right to disconnect it from the pump housing. 13. Re-assemble in reverse order using new seals and washers. 14. Refill and pressurise the system. (Refer to Commissioning, Section 5.1). 8.29 EXPANSION VESSEL - Fig. 28 Note: Check that the pressure of the new vessel is 1 bar before it is installer. 1. Gain access behind the front casing and drain the boiler heating circuit as described in Sections 8.1 and 8.2. 2. Disconnect the pipe from the expansion vessel. 3. Remove the screw securing the top support bracket. 4. Remove the three screws securing the side panel and remove the panel. 5. Lift the expansion vessel out of the boiler. 6. When replacing the vessel, ensure that the connection is towards the left of the boiler and re-assemble in reverse order using new seals as necessary. 7. Refill and pressurise the system. (Refer to Commissioning, Section 5.1). 8.30 CYCLONE (if wall jig is fitted) - Fig. 13 1. Remove the bottom tray and close the isolating valves either side of the cyclone. 2. Disconnect the unions from the cyclone. Remove the two screws securing the support bracket and remove the cyclone. Re-assemble with a new cyclone. 3. Pressurise the system. (Refer to Commissioning, Section 5.1). 8.31 CONDENSATE TRAP - Fig. 13 1. Gain access behind the front casing as described in Section 8.1. 2. Disconnect the top and drain connection of the condensate trap. 3. Place a container under the boiler and unscrew the bowl at the bottom of the trap, see Fig. 13. Some water will spill from the trap. 4. Remove the screw securing the trap to the bottom of the boiler casing and lift out the trap. 5. Fit the new trap in reverse order. Note: Fill the new trap with water once installed. Alpha CD25X/28X - Component Replacement

Alpha CD25X/28X - Wiring Diagrams Clock (Optional) 1 2 3 4 Pump Fan Gas Valve Primary Temperature Sensor DHW Switch Primary Pressure Switch NO COM Spark Generator Overheat Thermostat Heat Exchanger Thermal Fuse Fuse F2A 2 1 230/240V ~ 50Hz Fuse 3A Remove link to connect external control N N Note: Main Terminal Block N L L DHW Temperature Sensor Flue Temperature Sensor Transformer N L N TO CONNECT EXTERNAL CONTROL REMOVE LINK FROM TERMINALS 1 AND 2 AND CONNECT 240 V SWITCHED LIVE TO TERMINAL 1. 240 Vac 24 Vac Diverter Valve Motor S3 S1 S2 Main PCB CH CAP MAX CAP X7 X3 1 2 X8 3 2 1 X4 1 2 3 4 X13 4 5 3 2 1 X6 4 3 2 1 X12 4 5 3 2 1 X15 4 6 5 2 3 1 X9 4 6 9 5 8 2 3 7 10 1 X11 4 6 5 8 2 3 7 1 CH SET DHW SET Green LED Yellow LED Red LED Red LED Fuse F1 315 mAT max 250 V Fuse F2 and F3 2.5 AF 250 V F1 F2 F3

10.1 CARRY OUT INITIAL FAULT FINDING CHECKS 1. Check that gas, water and electrical supplies are available at the boiler. i.e. Inlet gas pressure = 20 mbar Electrical supply = 230/240 V ~ 50 Hz CH water system pressurised to between 0.75 and 1.25 bar DHW flow rate is more than 2.5 litre/min 2. Carry out electrical system checks, i.e. Earth Continuity, Resistance to Earth, Short Circuit and Polarity with a suitable meter. Note: These checks must be repeated after any servicing or fault finding. 3. Ensure all external controls are calling for heat and check all external and internal fuses. 4. Check that the gas and water pipework has been connected to the correct connections on the boiler and all valves are open. However, before any servicing or replacement of parts ensure the gas and electrical supplies are isolated. 10.2 CENTRAL HEATING - Follow operational sequence Alpha CD25X/28X - Fault Finding Turn thermostat to max. External controls not calling for heat If fitted, internal clock calling for heat 240 V across main terminal block, terminals 1 and N YES YES NO Turn selector to Go to section ' ', page 35 A YES YES (BUT) Pump runs and fan runs Go to section ' ', page 36 I YES Go to section ' ', page 35 D Burner output modulates until set temperature is reached Burner goes out NO YES Operation sequence successful Pump continues to run until temperature reduces to set temperature YES Go to section ' ', page 35 D Fan stops after 50 seconds Check gas valve adjustment CH system pressure too low. Re-pressurise to 1.0 bar Primary/DHW temperature sensor faulty NO NO Go to section ' ', page 36 J Neon A and B flashing alternately Neon B illuminated cont. Neon A flashing Neon A and B flashing at the same time Neon A flashing Go to section ' ', page 35 C YES YES YES YES YES Fan or flue fault Neon B illuminated continuously YES (BUT) Go to section ' ', page 36 G Burner does not stay alight after 10 seconds Spark at ignition electrodes for upto 10 seconds YES Burner lights Neon C illuminated YES YES NO Reset by rotating selector switch Reset by rotating selector switch Overheat thermostat or thermal fuse has operated Neon B illuminated continuously YES Reset by rotating selector switch Neon B illuminated continuously Neon B flashing NO YES If still no spark Go to section ' ', page 36 F Go to section ' ', page 36 E If still illuminated, Go to section ' ', page 36 H Neon D illuminated continuously Pump fault or primary flow restricted Go to section ' ', page 35 B

Alpha CD25X/28X - Fault Finding Turn thermostat to max. Open DHW tap fully DHW flow rate more than 2.5 L/min. DHW switch/diverter valve fault YES YES Turn selector to Primary water is diverted from CH system to DHW heat exchanger. DHW switch operated Pump runs and fan runs Is mains filter clean YES NO NO NO YES YES Go to section ' ', page 35 A Neons A and B flashing at the same time Go to section ' ', page 35 D Burner output modulates to maintain temperature set at thermostat NO YES DHW temp. sensor and DHW heat exchanger are clean Reduce DHW flow rate from 10 to 5 L/min. Burner modulates NO YES Close DHW tap YES DHW flow valve senses no flow. Primary water diverted to CH system. DHW flow switch released (off) Diverter valve/DHW switch fault NO YES YES Burner goes out Fan stops after 50 seconds YES Operation sequence successful Pump stops YES Go to section ' ', page 35 D YES CH system pressure too low. Re-pressurise to 1.0 bar Flue or faulty fan Primary/DHW temperature sensor fault NO Pump fault or primary flow restricted Go to section ' ', page 35 B Go to section ' ', page 36 K Go to section ' ', page 36 J Neon A and B flashing alternately Neon A flashing Go to section ' ', page 35 C YES YES YES Check gas valve adjustment Neon D illuminated continuously Neon B illuminated cont. Neon A flashing Spark at ignition electrodes for upto 10 seconds YES Burner lights Neon C illuminated YES YES NO Reset by rotating selector switch Reset by rotating selector switch Overheat thermostat or thermal fuse has operated Neon B illuminated continuously YES Reset by rotating selector switch Neon B illuminated continuously Neon B flashing NO YES If still no spark Go to section ' ', page 36 F Go to section ' ', page 36 E If still illuminated, Go to section ' ', page 36 H Neon B illuminated continuously YES (BUT) Go to section ' ', page 36 G Burner does not stay alight after 10 seconds YES (BUT)

10.4 FAULT FINDING SOLUTIONS A to D NO YES Pump If pump jammed, release Replace PCB NO PCB - X3 connector, terminals 2, 3 B Replace pump 1. 2. 240 V ac at:- Replace PCB Replace PCB Replace PCB Replace transformer NO NO NO NO YES NO NO NO Main terminals L and N Check electrical supply Replace fuse Check wiring Main terminal fuse PCB - X12 connector, terminals 5, N Neon D illuminated continuously A 240 V ac at:- 1. 2. 3. NO YES Replace fuse Neon D illuminated contiuously Is 240 V ac across PCB X6 connector terminals 1, 2 Is 26 V ac across PCB X4 connector terminals 1, 2 PCB fuse 4. C DHW/Primary temp. sensor faulty. Cold resistance approx. 12-14 k ohms (resistance reduces with increase in temp. i.e. when hot, resistance is approximately 3 k ohms) Check and correct connections/wiring at sensor and PCB 2. 1. YES YES Check resistance throughout the range from cold to hot DHW temperature sensor faulty i.e. heating OK. Hot water operates but does not modulate Primary temperature sensor faulty i.e. no heating or hot water Replace sensor Boiler cycles on and off Remove the motor from the diverter valve. Does the piston move in and out when operating the boiler between CH and DHW In CH mode. PCB - X15 connector, is 240 V across terminals 4, 6 In DHW mode. PCB - X15 connector, is 240 V across terminals 4, 5 YES YES NO Replace lead Check continuity of plug and lead NO NO NO YES YES Is diverter valve spindle sticking D Check and correct:- 1. Electrical connections 2. Restriction in flue Neon A and B flashing at the same time YES YES (BUT) 1. Replace PCB Ensure by-pass slot is in horizontal position and that the valve is not stuck open Replace diverter valve Replace PCB Replace PCB Replace motor YES NO NO 2. 3. 3. Fan connections correct at fan and PCB connector X13 Fan runs at maximum speed PCB connector, is 36 V dc across terminals 5 and 3 or 4 Fan jammed or faulty winding Is dc volts at PCB, X13 connector:- across terminals 5 and 4 - 34 V dc across terminals 2 and 4 - 4 V dc YES YES YES Replace fan Replace fan

10.5 FAULT FINDING SOLUTIONS E to K NO Check and correct:- 1. Ignition electrode and lead 2. Electrode connections 3. Spark gap and position 4. Connections at ignition generator and PCB connector X8 5. Blocked flue F Is spark generator (T2) making a clicking noise Disconnect the plug from the spark generator. PCB, X8 connector is 240V ac across terminals 2, 3 during ignition Replace PCB Replace ignition generator YES NO YES NO YES 240V at internal clock terminals 1 and 2 I 240V at PCB - X12 connector, terminals 5 and 1 240V at PCB - X12 connector, terminals 5 and 1 Wiring between clock and PCB is correct YES YES NO YES Continuity across clock terminals 3 and 4 Internal clock calling for heat Wiring between clock and PCB is correct Replace clock Check external controls are calling for heat YES YES NO J Replace primary pressure switch Replace PCB Continuity across primary pressure switch terminals Unplug leads from primary pressure switch 5 V DC at PCB across X9 connector terminal 1 and 3 YES NO NO YES YES YES YES YES YES Replace PCB Replace PCB Replace lead Replace motor Replace valve Replace DHW flow switch Continuity across DHW flow switch (hot tap on) Diverter valve spindle operating Check DHW heat exchanger for blockage Check by-pass valve is not stuck open 36 V DC at PCB across X4 connector terminal 3 and X13 connector terminal 3 240 V AC at PCB across X15 connector terminals 4, 5 Remove the diverter valve motor, is the brass piston fully extended (flush with plastic housing) Flow rate above 2.5l/min Check mains supply. Clean mains inlet filter Check continuity of motor plug and lead NO NO YES NO NO NO NO NO NO K G Check and correct:- 1. Pressure tubes are connected and not blocked 2. If explosive ignition, check wiring to ignition generator is correct 3. Polarity 4. Flame sensing electrode and lead connections 5. Electrode position E Check pressure tubes are connected PCB - X3 connector, is 240 V across terminals 1, 2 YES NO Gas at burner Replace gas valve Adjust gas valve NO NO Ensure gas is on and purged Replace PCB H NO NO Allow to cool. Continuity across thermostat terminals NO YES YES Air in main heat exchanger. Blocked heat exchanger/pipework or pump not circulating water Vent air, clear blockage Replace pump Continuity across thermal fuse Replace overheat thermostat Replace heat exchanger - t remove the thermal fuse. It is important to find the exact cause of the overheat and rectify it before operating the boiler with the new heat exchanger Do no Note:

Reference Burner - CD25X Burner - CD28X Main injector 5.2 mm - CD25X Main injector 5.25 mm - CD28X Primary heat exchanger - CD25X Primary heat exchanger - CD28X DHW heat exchanger - CD25X DHW heat exchanger - CD28X Gas valve Pump Fan assembly Primary pressure switch DHW flow switch PCB Flue temperature sensor Ignition generator Transformer Temperature sensor Fuse F2A - Main terminal block PCB fuse F1 - 315mA PCB fuse F2, F3 - 2.5 AF Overheat thermostat 100°C Expansion vessel 8 Litre Pressure relief valve 3 bar Automatic air vent Pressure gauge Ignition electrode and lead Flame sensing electrodes and lead Diverter valve motor Diverter valve assembly By-pass assembly Combustion chamber insulation panel front Condensate trap Flow regulator 10 l/min (blue) - CD25X Flow regulator 12 l/min (red) - CD28X Description British Gas GC No. Alpha Pt. No. 1.023999 1.019622 1.024374 1.022709 1.021750 1.023016 1.022220 1.022221 1.023673 1.024097 1.021206 1.021715 1.020831 1.024826 1.024296 1.022297 1.019189 1.021762 1.6098 1.013931 1.2379 1.012067 1.023560 1.023565 1.022102 1.023551 3.017477 1.019293 1.018064 3.015562 3.017174 1.024543 3.017281 1.020428 1.020412 Qty. 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 1 1 2 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Fig. 27 Fig. 27 Fig. 2, item 30 Fig. 2, item 30 Fig. 31 Fig. 31 Fig. 2, item 6 Fig. 2, item 6 Fig. 28 Fig. 32 Fig. 28 Fig. 32 Fig. 30 Fig. 29 Fig. 28 Fig. 28 Fig. 28 Figs. 28 and 32 Figs. 20 and 29 Fig. 29 Fig. 29 Fig. 28 Fig. 2, item 14 Fig. 32 Fig. 32 Fig. 22 Fig. 27 Fig. 27 Fig. 30 Fig. 30 Fig. 2, item 27 Fig. 27 Fig. 2, item 29 Fig. 2 Fig. 2 Alpha CD25X/28X - Short Parts List H50-442 H50-443 H50-444 H50-451 H50-452 H50-454 H50-455 H28-396 H50-456 H50-457 H50-460 798-413 E76-378 E96-571 E94-413 H50-462 H50-463 H50-464 H50-465 E96-572 H50-469 H50-472 H50-474 H50-476

12 CHECKLIST Ensure the following is completed after the boiler has been installed and commissioned:- 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 Time & temperature control to hot water Heating zone valves Hot water zone valves Thermostatic radiator valves Automatic by-pass to system FOR ALL BOILERS CONFIRM THE FOLLOWING: The system has been flushed in accordance with the boiler manufacturer's instructions? Yes No The system cleaner used .................................................................................................................... The inhibitor used ................................................................................................................................ FOR CENTRAL HEATING MODE, MEASURE AND RECORD THE FOLLOWING: Gas rate m³/hr ft³/hr Burner operating differential pressure (if applicable) N/A mbar Central heating flow temperature °C Central heating return temperature °C FOR COMBINATION BOILERS ONLY Has a water scale reducer been fitted? Yes No What type of scale reducer has been fitted? ...................................................................................... FOR DOMESTIC HOT WATER MODE, MEASURE AND RECORD THE FOLLOWING: Gas rate m³/hr ft³/hr Maximum burner operating differential pressure (if applicable) N/A mbar Cold water inlet temperature °C Hot water outlet temperature °C Water flow rate lts/min FOR CONDENSING BOILERS ONLY CONFIRM THE FOLLOWING: The condensate drain has been installed in accordance with the manufacturer's instructions? Yes FOR ALL INSTALLATIONS CONFIRM THE FOLLOWING: The heating and hot water system complies with current Building Regulations Yes The appliance and associated equipment has been installed and commissioned in accordance with the manufacturer's instructions Yes 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 Yes The manufacturer's literature has been left with the customer Yes COMMISSIONING ENG'S NAME: Print ...................................................................... CORGI ID No. .................................................. Sign ...................................................................... Date ................................................................. room t/stat & programmer/timer cylinder t/stat & programmer/timer Fitted Fitted Fitted Fitted Programmable roomstat Combi boiler Not required Not required Not required

It is recommended that your heating system is serviced regularly and that you complete the appropriate Service Interval Record below. Service Provider: Before cpmpleting the appropriate Service Interval Record below, please ensure you have carried out the service as described in this instruction manual. Always use the manufacturer's specified spare parts when replacing all controls. SERVICE 1: Date ....................................................................... Engineers Name ......................................................................... Company Name .......................................................................... Telephone No. ............................................................................. CORGI ID card serial No. ........................................................... Comments ................................................................................... ..................................................................................................... Signature ..................................................................................... SERVICE 2: Date ....................................................................... Engineers Name ......................................................................... Company Name .......................................................................... Telephone No. ............................................................................. CORGI ID card serial No. ........................................................... Comments ................................................................................... ..................................................................................................... Signature ..................................................................................... SERVICE 3: Date ....................................................................... Engineers Name ......................................................................... Company Name .......................................................................... Telephone No. ............................................................................. CORGI ID card serial No. ........................................................... Comments ................................................................................... ..................................................................................................... Signature ..................................................................................... SERVICE 4: Date ....................................................................... Engineers Name ......................................................................... Company Name .......................................................................... Telephone No. ............................................................................. CORGI ID card serial No. ........................................................... Comments ................................................................................... ..................................................................................................... Signature ..................................................................................... SERVICE 5: Date ....................................................................... Engineers Name ......................................................................... Company Name .......................................................................... Telephone No. ............................................................................. CORGI ID card serial No. ........................................................... Comments ................................................................................... ..................................................................................................... Signature ..................................................................................... SERVICE 6: Date ....................................................................... Engineers Name ......................................................................... Company Name .......................................................................... Telephone No. ............................................................................. CORGI ID card serial No. ........................................................... Comments ................................................................................... ..................................................................................................... Signature ..................................................................................... SERVICE 7: Date ....................................................................... Engineers Name ......................................................................... Company Name .......................................................................... Telephone No. ............................................................................. CORGI ID card serial No. ........................................................... Comments ................................................................................... ..................................................................................................... Signature ..................................................................................... SERVICE 8: Date ....................................................................... Engineers Name ......................................................................... Company Name .......................................................................... Telephone No. ............................................................................. CORGI ID card serial No. ........................................................... Comments ................................................................................... ..................................................................................................... Signature ..................................................................................... SERVICE 9: Date ....................................................................... Engineers Name ......................................................................... Company Name .......................................................................... Telephone No. ............................................................................. CORGI ID card serial No. ........................................................... Comments ................................................................................... ..................................................................................................... Signature ..................................................................................... SERVICE 10: Date ..................................................................... Engineers Name ......................................................................... Company Name .......................................................................... Telephone No. ............................................................................. CORGI ID card serial No. ........................................................... Comments ................................................................................... ..................................................................................................... Signature ..................................................................................... Alpha CD25X/28X - Service Record

05/07/D208 Part No. 1.024831 These instructions have been carefully prepared but we reserve the right to alter the specification at any time in the interest of product improvement. © Alpha Therm Limited 2007. Alpha Therm Limited. Nepicar House, London Road, Wrotham Heath, Sevenoaks, Kent TN15 7RS Tel: 0870 3001964 email: [email protected] website: www.alpha-boilers.com