Table of Contents
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24CDi/28CDi/35CDi II
WALL MOUNTED COMBINATION BOILER FOR CENTRAL HEATING
AND MAINS FED DOMESTIC HOT WATER
INSTALLATION AND
SERVICING INSTRUCTIONS
GC NUMBER (N.G)
GC NUMBER (L.P.G.)
24CDi
28CDi
35CDi II
IMPORTANT: 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
RSF
24CDi
47 311 30
47 311 31
BOILER OUTPUT
Automatic Modulating Control
Domestic
Hot Water
9 - 24kW
9 - 28kW
9.5 - 35.3kW
28CDi
35CDi II
47 311 34
47 311 58
47 311 35
47 311 59
Central
Heating
9 - 24kW
9 - 24kW
10.5 - 27.5kW
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Table of Contents
Related Manuals for Worcester 24CDi
Summary of Contents for Worcester 24CDi
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Page 1: Servicing Instructions
24CDi/28CDi/35CDi II WALL MOUNTED COMBINATION BOILER FOR CENTRAL HEATING AND MAINS FED DOMESTIC HOT WATER INSTALLATION AND SERVICING INSTRUCTIONS 24CDi 28CDi 35CDi II GC NUMBER (N.G) 47 311 30 47 311 34 47 311 58 GC NUMBER (L.P.G.) 47 311 31... -
Page 2: Table Of Contents
(24/28CDi) or 27.5kW (35CDi II). The hot water flow rate is of safety, to ensure compliance with the law. limited to a nominal 9 l/min (24CDi) or 10 l/min (28CDi) or 12 1.2 The manufacturers notes must not be taken, in any way, as l/min (35CDi II) at a maximum temperature rise of 40°C. - Page 3 Extension flue lengths available are from 726mm up to 4000mm IMPORTANT: Where back-flow prevention devices, including (24CDi) or up to 3000mm (28CDi and 35CDi II). water meters, are fitted the expansion of hot water into cold A vertical flue assembly kit is available.
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Page 4: Technical Data
Note: Gross Heat Input x 0.901 (NG) or x 0.922 (propane) = Net Heat Input. Table 1 3. Technical Data NOMINAL BOILER RATINGS BOILER ADJUSTED FOR BOILER ADJUSTED FOR (10 minutes after lighting) G31 (Propane) G20 (Natural Gas) 24CDi 28CDi 24CDi 28CDi 35CDi II 35CDi II MAX. OUTPUT (DHW) 24.0 28.0 35.3 24.0 28.0... - Page 5 *The value is used in the UK Government Standard Assesment Proceedure (SAP) for the energy rating of dwellings. The test data from which it has been calculated have been certified by the Gastec notified body. Table 6a (24CDi) DOMESTIC HOT WATER - TEMPERATURE RISE DISCHARGE RATE l/min TEMPERATURE RISE °C...
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Page 6: Siting The Appliance
4. Siting The Appliance Fig. 2. Appliance casing dimensions and required clearances. 4.1 The appliance may be installed in any room although particular attention is drawn to the requirements of the current I.E.E. Wiring Regulations BS 7671 and, in Scotland, the electrical 30mm* provisions of the Building Regulations applicable in Scotland, 159mm... -
Page 7: Siting The Flue Terminal
The standard uncut flue kit length is 425 - 725mm. Extension 6.2 The appliance can be fitted in a cupboard or compartment kits for flues up to 4m (24CDi), 3m (28CDi and 35CDi II) are with no vents for cooling but the minimum clearances must be available. -
Page 8: Sealed Primary Systems
NG (G20) LPG (G31) must be maintained. 7.5 The 10 litre expansion vessel is charged to 0.5 bar and is 24CDi 1.13 suitable for a static head of 5 metres (17.5ft). The pressure can be 28CDi increased if the static head is greater than 5 metres (17.5ft). -
Page 9: Open Vent Primary Systems
An Rc1/8” connection is 25mm (1in) above the top edge of the bath to prevent its immersion provided. A mini expansion vessel kit is available from Worcester in bath water. Alternatively the shower must be fitted with an anti- Heat Systems Ltd. -
Page 10: Electrical
11.9. On very rare occasions an external frost thermostat might 11. Electrical be considered where parts of the system are remote from the appliance. Refer to Worcester Heat Systems Technical Department for more information - Tel: 08705 266241. 11.1. Mains supply : 230V ~ 50Hz, 180watts. External fuse 3A, 11.10. - 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 24CDi Electronics Pump Electronics 28CDi 35CDi II 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.
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Page 13: Installation
a vertical line. Extend horizontally the side flue line to 12. Installation intersect the vertical line to give the position of the side flue hole. NOTE: If the optional wall spacing frame is used then the Read this section fully before starting the Installation. 197mm dimension should be increased by 35mm (see 12.1 General. - Page 14 Flue Spigot Kit. IMPORTANT Check the maximum flue length and if it is less than 1m total overall length then fit the restrictor ring as shown in Fig. 18. 40mm 24CDi 75mm Horizontal flue up to 1m...
- Page 15 750mm up to a maximum of 4m. See table below. Apply the plastic tape to the air duct in contact with the external EXTENSION MAXIMUM FLUE LENGTH mm brickwork. 35CDi II 24CDi 28CDi From inside push the assembly through the wall. Align the flue turret 1475 1475 1475 and push fully onto the spigot on the appliance.
- Page 16 12.12. Flue Bends. Fig.23 . Terminal assembly for internal 90° and 45° bends are available. A maximum of two bends may be used in addition to the first bend on the flue turret. fitting of the flue. A 90° bend is equivalent to 750mm of straight duct. A 45°...
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Page 17: Commissioning
The first, vertical, section (equivalent to dimension X) is measured from between the gas cock and the gas valve, thus enabling the leak to be the top of the boiler casing. Cut the vertical section of the extension traced to either a visible joint or to the ‘O’ ring. duct to 167mm less than the measured distance. - Page 18 should be fitted as shown in Fig. 6,6a. Set the system pressure Insert the bayonet end of the filling key into the corresponding cutouts Release water from the system using the relief valve test knob (see Fig. in the filling loop housing and twist to lock the key in place. 27), until the system design pressure is obtained, up to a maximum of Turn the grey knob anti-clockwise to allow water ingress and fill until 1.5 bar.
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Page 19: Instructions To The User
The burner pressure should be 14.8mbar Refit the cabinet front panel. (24CDi) or 15.5mbar (28CDi) or 13.5mbar (35CDi II ) for natural gas and If the appliance is being passed over to the user immediately, refer to 35.5mbar (24/28CDi) or 34.7mbar (35CDi II) for propane. -
Page 20: Inspection And Servicing
Fig. 31. Appliance components and fixings 15. Inspection And Servicing (upper assembly). 15.1 SERVICING Flue gas sample To ensure continued efficient operation of the appliance it Sensing tubes Fan assembly point (Red to +) must be checked and serviced as necessary at regular fixing screws (3) intervals. -
Page 21: Replacement Of Parts
Fig. 32. Burner and Electrode 16. Replacement Of Parts (24/28CDi shown) 16.1 SAFETY Flame sensor Switch off the electricity and gas supplies before replacing any components. After the replacement of any components, check detail for gas soundness where relevant and carry out functional checks as described in Section 13 - Commissioning 16.2 COMPONENT ACCESS To replace components it is necessary to remove one or more... - Page 22 Slacken the two screws to remove the two retaining brackets and Fig. 33. Air pressure switch. lift the heat exchanger from the casing. Take care that the rear insulation pad does not drop forwards onto the burner. Fit the replacement heat exchanger in the reverse order ensuring that both the “O”...
- Page 23 1.5mbar (24CDi) or 1.0mbar (28CDi) or 3.1 Fit the replacement electrode in the reverse order, checking that mbar (35CDi II) for natural gas or 5.4mbar (24CDi) or 3.8mbar the sense gap is 5 to 6mm. (28CDi) or 3.1mbar (35CDi II) for propane.
- Page 24 12. Central Heating Sensor. Refer to Fig. 34. Fig. 38. Expansion Vessel Remove the inner casing cover as described in Section 15.3, b. Check that the electricity supply to the appliance is turned off. Strap Carefully pull off the two leads from the sensor. Pull off the sensor and spring retaining clip from the pipe.
- Page 25 Reassemble the water diverting valve and plastic manifold Regulator size: assembly to the appliance in the reverse order. Ensure all ‘O’ ring seals and fibre washers are renewed and 24CDi 9 l/min white replaced correctly and the ‘O’ rings are lubricated.
- Page 26 22. Filling Loop. Refer to Fig. 40. Connectors are not interchangeable and will only fit the termi- Check that the electricity supply to the appliance is turned off. nals from which they were removed. Drain the central heating circuit as described in Section 16.3, a. Reassemble the facia panel and facia bottom panel in the reverse Hinge down the facia panel into the servicing position as order.
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Page 27: Short Parts List
17. Short Parts List Appliance G.C. No. Part Manufacturer’s Reference Part No. 24CDi 28CDi 35CDi E80-450 Gas Valve – Natural Gas Dungs BM 771 SL 040 8 716 102 673 0 E80-451 Gas Valve – Propane Dungs BM 771 SL 040... -
Page 29: 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 CH light On. Pump On. Two minute mini- Fan ON High for 2 mum burner Modulate gas... - Page 30 OVERRUN FUNCTION If heat Run pump demand has until primary occurred in drops to last 30 80°C minutes Within four minutes of last hot water demand primary temperature Run pump for If heat above 80°C two seconds demand has Run fan If primary until primary temperature...
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Page 31: 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 32 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 16.4.23) Replace fuse and investigate cause. Suggestions: Cable damage, connections to (or faults within) pump, fan, external 230V controls, transformer or board.
- Page 33 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 34 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 16.4.23). “Autofrost stat” mode. Note: A wet board See Section 18.
- Page 35 Is the gas supply connected and at the Rectify gas supply correct inlet and problem. outlet pressures? Remove front panel. Remove inner cover. Repair or replace Reset and restart the Reset and restart the Are the electrodes and spark electrode boiler.
- Page 36 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 resistance across Repair or replace from contacts 17 and harness. contacts 17 and 18 18 to DHW sensor? (yellow wires).
- Page 37 (L) track if DHW mode? Centre (L) track if CH mode? Repair or replace fan (Section 16.4.3) or cable. 28CDi and 35CDi II 24CDi,28CDi and 35CDi II Replace control board (Section 16.4.23). Air pressure switch Repair or replace fan is shorting (Section 16.4.3) or Replace switch cable.
- Page 38 Light indication during fault not Control board is likely covered by above to be wet or damaged details. or malfunctioning. Check for wet board or connections. Dry and re-use or replace control board. (Section 16.4.13). Hot water sensor Hot water could be off or poorly temperature always fixed to pipe.
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Page 39: Conversion Instructions
20. Conversion Instructions GAS VALVE ONLY COMPONENTS SUPPLIED BY WORCESTER HEAT Allen key SYSTEMS SHOULD BE USED. ONLY COMPETENT PERSONNEL SHOULD ATTEMPT THE CONVERSION. CONVERSION FROM NATURAL GAS TO LPG SHOULD NOT BE CARRIED OUT ON APPLIANCES INSTALLED IN A ROOM OR INTERNAL SPACE BELOW GROUND LEVEL... - Page 40 This manual is to be used in conjunction with the variant part number of the bar code below: 24CDi 28CDi 35CDi II Worcester Heat Systems Limited (Bosch Group), Cotswold Way, Warndon, Worcester WR4 9SW. Telephone: 01905 754624. Fax: 01905 754619. Technical Helpline 08705 266241. www.worcester-bosch.co.uk This booklet is accurate at the date of printing but will be superseded and should be disregarded if specifications and/or appearances are changed in the interests of continued improvement.
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Questions and answers
How do I remove the water temperature knob to see why it just spins around when I try to adjust the temp.
To remove the water temperature knob on a Worcester 24CDi, ensure you are following the servicing procedure. The document states that when replacing the control knobs, the knob with the shortest shaft should be fitted to the left-hand control position. However, it does not provide specific steps on removing the knob. Typically, knobs on such boilers can be pulled off or may have a securing screw underneath that needs to be loosened. If unsure, refer to the boiler manual or consult a qualified professional.
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