Worcester 24CDi BF Installation And Servicing Instructions
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Worcester 24CDi BF Installation And Servicing Instructions

Wall mounted combination boiler for central heating and mains fed domestic hot water
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Bosch Group
24CDi BF
WALL MOUNTED COMBINATION BOILER FOR CENTRAL HEATING
AND MAINS FED DOMESTIC HOT WATER
INSTALLATION AND

SERVICING INSTRUCTIONS

GC NUMBER 47 311 29
BOILER OUTPUT
Automatic Modulating Control
To Domestic Hot Water and Central Heating
Minimum 9.0 kW
Maximum 24.0 kW
IMPORTANT: THIS APPLIANCE IS FOR USE WITH NATURAL GAS ONLY
THESE INSTRUCTIONS APPLY IN THE UK ONLY
THESE INSTRUCTIONS ARE TO BE LEFT WITH THE USER OR AT THE GAS METER
This appliance must be installed by a competent person in accordance
with the Gas Safety (Installation and Use) Regulations 1998

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  • Page 1: Servicing Instructions

    Bosch Group 24CDi BF WALL MOUNTED COMBINATION BOILER FOR CENTRAL HEATING AND MAINS FED DOMESTIC HOT WATER INSTALLATION AND SERVICING INSTRUCTIONS GC NUMBER 47 311 29 BOILER OUTPUT Automatic Modulating Control To Domestic Hot Water and Central Heating Minimum 9.0 kW Maximum 24.0 kW...

  • Page 2: Table Of Contents

    1.10. The advice and instructions given in this document covers, 2.6 Flue as far as possible, the foreseeable situations which may arise. The appliance has a room-sealed balanced flue system to the Contact Worcester Heat Systems Technical Department, Telephone: rear. 0990 266241, for advice on specific installations.
  • Page 3 12.Pressure relief property. Flow balancing using ‘Ball-o-Fix’ type valves is valve. recommended to avoid an excessive reduction in flow to 13.Sealed system individual outlets. For further information contact Worcester expansion Heat Systems Technical Helpline. vessel. 2.10 Safety Considerations The appliance must not be operated in a waterless condition.

  • Page 4: Technical Data

    3. Technical Data Table 1. NOMINAL BOILER RATINGS (10 Minutes After Lighting) BOILER ADJUSTED FOR G20 (Natural Gas) BURNER SETTING OUTPUT INPUT (Net) GAS RATE PRESSURE Btu/h Btu/h m bar. in. wg. 30,700 10.4 35,500 37.28 24.0 81,900 27.0 92,400 13.2 100.0 Note: Gross Heat Input x 0.901= Net Heat Input.
  • Page 5 Table 5 PERFORMANCE SPECIFICATIONS PRIMARY WATER CAPACITY 2.0 litres MAXIMUM MAINS INLET PRESSURE 10 bar MINIMUM MAINS INLET PRESSURE (working) for max. hot water flow 1.2 bar MINIMUM MAINS INLET PRESSURE (working) to operate appliance 0.7 bar MAXIMUM CENTRAL HEATING FLOW TEMPERATURE 82°C nom MAXIMUM CENTRAL HEATING SYSTEM SET PRESSURE 1.5 bar...

  • Page 6: Siting The Appliance

    4. Siting The Appliance Fig. 2. Appliance casing dimensions and required clearances. 4.1 The appliance must not be installed in any room containing a bath or shower or in a bedroom or bed-sitting room. Particular attention is drawn to the requirements of the 100mm current I.E.E.

  • Page 7: Siting The Flue Terminal

    5. Siting The Flue Terminal 6. Air Supply See Fig. 4 6.1 Installations in cupboards or compartments require permanent vents for cooling purposes, one at high level and one 5.1 The flue must be installed as specified in BS 5440:Part 1and at low level, either direct to outside air or to a room.

  • Page 8: Sealed Primary Systems

    7.10 Connections to the mains water supply must not be made 7. Sealed Primary Systems without the authority of the local Water Company. 7.11 The pump is set at maximum and must not be adjusted. 7.12 Connections in the system must resist a pressure of upto See Figs.

  • Page 9: Open Vent Primary Systems

    An Rc1/2 connection is bath water. Alternatively the shower must be fitted with an anti- provided. A mini expansion vessel kit is available from Worcester syphonage device at the point of the flexible hose connections.

  • Page 10: Electrical

    Internal fuses F1 - 2A, F2 - 1.25A (20mm). Spare internal fuses appliance. Refer to Worcester Heat Systems Technical are supplied with the appliance. Refer to Fig 14. Department for more information - Tel: 0990 266241.
  • Page 11 Fig. 10. Functional flow diagram. Outputs Inputs DHW control knob Electronics/ CH Control knob microprocessor (Safety Low Voltage) CH pressure adjust pot Gas valve mode switch Reset button Convert AC to low voltage electronics Pump Electronics...
  • Page 12 Fig 11 - Electrical Connections Fig 13 - Mains Voltage External Controls Connections Ns Ls L Ns Ls L R Spare R Spare Remove Link Motor Ns Ls L Spare 1. ST12-Mains 9. Fuse-F2 2. Fuse-F1 10. Cable Entry Clamp 3.

  • Page 13: Installation

    Separate the air and flue ducts from the terminal. 12. Installation Measure the distance from the inside edge of the mounting plate to the outside of the wall W. See Fig. 19. Fit the air ducts together and adjust the total length until it NOTE: READ THIS SECTION FULLY BEFORE COMMENCING corresponds with the W dimension.
  • Page 14 From the outside, make good the gap between the air duct and If a facia mounted programmer is to be fitted follow instructions the brickwork. Fit the flue terminal to the air duct and mark the with the programmer.. position of the four fixing holes. Drill four holes 5mm (0.19in.) Hinge down the facia as described in Section 15.3, c.

  • Page 15: Commissioning

    the indicating pointer giving a permanent record of the set system 13. Commissioning pressure. If the pressure indicated on the pressure gauge is greater than 2.6 bar when operating at the maximum central heating temperature, 13.1 SUMMARY The appliance is dispatched with the controls set to provide a an extra expansion vessel must be fitted to the system as close as maximum output for domestic hot water and central heating of possible to the appliance central heating return connection.
  • Page 16 NOTE: The burner pressure is factory set and if (after checking that the supply pressure is sufficient) the correct pressure is not Set the Programmer, if fitted, to HEATING & WATER. obtained then Worcester Heat Systems Service Department should Set the operating switch to ON. be contacted.

  • Page 17: Instructions To The User

    Close the tap and the burner will go off. The appliance will then 14.4 Tell the user of the importance of regular servicing. return to the central heating mode and automatically balance Worcester Heat Systems Ltd. offer a comprehensive maintenance with the system requirements. contract.

  • Page 18: Inspection And Servicing

    remove the two wing nuts securing the combustion chamber. 15. Inspection And Servicing Unhook the securing rods out of the locating holes in the combustion chamber sides. Ease the combustion chamber front and side assembly clear of the appliance. Refer to Fig. 26. 15.1 SERVICING (g) Burner Assembly.

  • Page 19: Replacement Of Parts

    reverse order using new gaskets/'O' rings/sealant where necessary. Always check that any electrical connections are Fig. 27. Burner and Electrode correctly made and that all screws are tight. 16.4 COMPONENT REPLACEMENT 1. Automatic Air Vent. Flame sensor Remove the inner casing cover as described in Section 15.3 (b). detail Drain the central heating circuit as described in Section 16.3 (a).
  • Page 20 Open the valves and fill and re-pressurise the system as Hinge down the facia panel into the servicing position as described in Section 13.2. described in Section 15.3, c. Remove the air pressure switch bracket as described in 4. Combustion Chamber Insulation. Refer to Fig. 29. Section 16.
  • Page 21 13. Expansion Vessel. Refer to Figs. 30,32. valve taking care not to distort the pipework. Drain the central heating circuit as described in Section 16.3, a. Fit the replacement valve in reverse order. Reconnect the Hinge the facia panel into the servicing position as described in discharge pipe.
  • Page 22 16. Water Diverting Valve. Refer to Figs. 30,33. Fig. 31. Circulating pump Check that the electricity supply to the appliance is turned off. Drain the central heating and domestic hot water circuits as described in Sections 16.3, a and b. Hinge down the facia panel into the Servicing Position as Unscrew union fittings described in Section 15.3, c.
  • Page 23 17. Inlet Water Filter. Refer to Fig. 34. 19. Domestic Hot Water Flow Restrictor. Check that the electric supply to the appliance is turned off. Remove the water to water heat exchanger assembly as Drain the central heating and domestic circuits as described in described in Section 15.4.18.
  • Page 24 223. Control Board. Refer to Fig. 35. 23. Transformer. Refer to Fig. 35. Check that the electricity supply to the appliance is turned off. Check that the electricity supply to the appliance is turned off. Remove the three screws fixing the facia bottom panel to the Remove the control board as described in Section 16.4, 23.

  • Page 25: Short Parts List

    7 716 192 205 0 299 356 ‘O’ Ring Pack 7 716 192 207 0 299 357 Fuse Pack 7 716 192 206 0 Acccessories For 24CDi BF G.C.No. Part WHS Part No. E01 064 BF Standard Terminal 225mm- 420mm 7 716 191 007...

  • Page 27: Operational Flow Diagrams

    18. Operational Flow Diagrams Room CENTRAL HEATING FUNCTION thermostat and/or mains programmer (or link) On Electronic MAIN SWITCH Green Light facia programmer (if fitted) On ST13 link in CH control knob On Two minute CH light On. minimum Modulate gas Pump On.
  • Page 28 OVERRUN FUNCTION Within four minutes of last hot water Run pump demand until primary drops to 80°C primary temperature above 80°C AUTOFROSTAT FUNCTION No demand Wait in normal and primary off state for temperature 30 minutes below 8°C Monitor Internal 5°C Return to Run pump for...

  • Page 29: Fault Finding

    19. Fault Finding Note: This fault-finding information is for guidance only. Worcester Heat Systems cannot be held responsible for costs incurred by persons not deemed to be competent. The electronic control system for this boiler incorporates four lights on the facia. These are used to show normal operating status. But as a secondary function, by flashing, they can also be used to help provide fault diagnostics.
  • Page 30 Is the facia on/off switch turned on? Turn switch on. `(Clockwise) Is there a 230V AC live supply across Check electrical Terminal ST12 pins L supply to boiler. and N Replace control board Has fuse F1 blown? (Section 16.4.22) Replace fuse and investigate cause. Suggestions: Cable damage, connections to (or faults within) pump, external 230V controls, transformer or board.
  • Page 31 With CH control knob fully clockwise, does There is no heat Is there 230V AC the boiler ignite and demand. Check room across terminal ST8 appear to run thermostat or mains pins LR and N? normally in central programmer (or link). heating mode? Red diode is Is there a link at...
  • Page 32 Drop down the facia. Is the boiler in a very Is the gas valve mode Turn to normal cold environment (less switch in the normal position. than 5°C)? position? Replace control board. Boiler is running in (Section 16.4.22). “Autofrost stat” mode. Note: A wet board See Section 18.
  • Page 33 Is the gas supply Rectify gas supply connected and at the problem. correct pressure? Remove front panel. Remove inner cover. Repair or replace Reset and restart the Reset and restart the Are the electrodes and spark electrode boiler. Can a flame be boiler.
  • Page 34 Is the multiway connector at board position ST16 pushed Push fully home. fully home on to the board? Remove multiway connector from board position ST16. Test Is there continuity Repair or replace resistance across from contacts 17 and harness. contacts 17 and 18 18 to DHW sensor? (yellow wires).
  • Page 35 Inspect the small resistor that is Replace control board. attached to the Replace control board. (Section 16.4.23). multiway connector. (Section 15.4.20). Is it missing or loose or in poor condition? Replace mains harness. Light indication during fault not Control board is likely covered by to be wet or damaged above details.
  • Page 36 Bosch Group Worcester Heat Systems Limited, Cotswold Way, Warndon, Worcester WR4 9SW. Telephone: (01905) 754624. Fax: (01905) 754619. Technical Helpline (0990) 266241. This booklet is accurate at the date of printing but will be superseded and should be disregarded if specifications and/or appearances are changed in the interests of continued improvement.

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