Worcester 24CDi BF Installation And Servicing Instructions Download Page 32

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Boiler is running in

“Autofrost stat” mode.

See Section 18.

Replace control board.

(Section 16.4.22).

Note:

A wet board

could cause this fault.

Is the boiler in a very

cold environment (less

than 5°C)?

Drop down the facia.

Is the gas valve mode

switch in the normal

position?

Turn to normal

position.

FAIL POINT F

Yes

Is the boiler fully

water pressurised and

is all air vented?

Rectify fault.

FAIL POINT G “Primary Ov

erhea

t”

Re-fix sensor to pipe.

Repair or replace

pump.

(Section 16.4.12).

Reset the controls and

restart the boiler.

Does the pump run?

Yes

Remove inner casing

cover and inspect the

primary sensor (left of

heat exchanger).

Is it correctly fixed to

pipe?

Yes

Fault caused by control

board or primary heat

exchanger.

Yes

Remove the multiway
connector from board

position ST16.

Is there a short circuit
across contacts 5& 6?

Yes

Replace overheat

thermostat or check

wiring to it.

Summary of Contents for 24CDi BF

Page 1: ...ng 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 Bosch Group ...

Page 2: ... Worcester Heat Systems Technical Department Telephone 0990 266241 for advice on specific installations 2 1 General Information 2 1 1 The appliance is set to give a maximum output of 24kW to the domestic hot water and to the heating system The hot water flow rate is limited to a nominal 9 l min at a maximum temperature rise of 40 C 2 1 2 The sanitary water section of the appliance is suitable for ...

Page 3: ... an over rim flushing bidet subject to local Water Company requirements With all mains fed systems the flow of water from the individual taps will vary with the number of outlets operated simultaneously and the cold water mains supply pressure to the property Flow balancing using Ball o Fix type valves is recommended to avoid an excessive reduction in flow to individual outlets For further informa...

Page 4: ...60 22 Table 2 PUMP HEAD BOILER OUTPUT HEAD MIN FLOW RATE FLOW RETURN DIFFERENTIAL kW Btu h Metres Feet L min Gal Min C F 9 0 30 700 4 8 15 7 11 7 2 57 11 C 20 F 24 0 81 900 2 0 6 6 20 5 4 5 12 5 C 22 F Table 3 MECHANICAL SPECIFICATIONS CENTRAL HEATING FLOW COMPRESSION 22mm CENTRAL HEATING RETURN COMPRESSION 22mm COLD WATER INLET COMPRESSION 15mm DOMESTIC HOT WATER FLOW COMPRESSION 15mm GAS INLET R...

Page 5: ...T 30 RISE 12 4 l min MAXIMUM DOMESTIC HOT WATER FLOW RATE FROM APPLIANCE AT 40 RISE 9 0 l min NOx CLASSIFICATION Class 3 Table 5 DOMESTIC HOT WATER TEMPERATURE RISE DISCHARGE RATE l min 7 8 9 10 TEMPERATURE RISE C 49 42 9 38 1 34 3 Table 6 GAS SUPPLY SYSTEM BASED ON NG G20 TOTAL LENGTH OF GAS SUPPLY PIPE meters 3 6 9 GAS DISCHARGE RATE m3 h PIPE DIAMETER mm 2 9 15 8 7 5 8 4 6 22 18 0 12 0 9 4 28 T...

Page 6: ...rforated non combustible partition Expanded metal or rigid wire mesh are acceptable provided that the major dimension is less than 13mm See BS 6798 1987 4 9 The distance between the inner face of a cupboard door and the cabinet front should not be less than 75mm 4 10 The pipe connection positions on the manifold are shown in Fig 3 allowing the system to be pre piped and flushed before the applianc...

Page 7: ...fer to BS 6798 and BS 5440 2 for additional information 6 3 There must be sufficient clearance around the appliance to allow proper circulation of ventilation air The clearances required for Installation and Servicing will normally be adequate for ventilation 6 4 The minimum free areas required are given below 6 5 Refer to BS 6798 and BS 5440 2 for additional information 6 Air Supply 5 Siting The ...

Page 8: ... 7 10 Connections to the mains water supply must not be made 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 3bar 7 13 Radiator valves must conform to BS2767 10 7 14 Other valves used should conform to the requirements of BS1010 7 15 No special system inhibitor is needed 8 1 The ...

Page 9: ...essel kit is available from Worcester Heat Systems Ltd A thread sealant compatible with potable water must be used 10 3 The final 600mm of the mains cold water connection to the appliance should be made in copper tube only 10 4 The appliance is suitable for a mains pressure of up to 10 bar 150 lb in2 10 5 The appliance is fitted with a mains supply isolating valve 10 6 The maximum domestic hot wat...

Page 10: ...r mains voltage operation and the leads securely fixed in the clamps provided The controls must be earthed at the connection on the control board Refer to Fig 13 11 8 A programmer to fit into the facia is available to control the CH Full instructions are sent with the programmer Refer to Fig 15 11 9 A clock to fit into the facia is available to control the operation of the central heating 11 10 On...

Page 11: ...ark Indicators Settings Regulator valve CH demand indicator Red Spark electrodes DHW demand indicator Red Flame detect indicator Red Main valve Main valve Flow switch CH sensor DHW sensor Flame sense Overheat cut off 24V programmer Reset button Gas valve mode switch CH pressure adjust pot CH Control knob DHW control knob Convert AC to low voltage electronics Electronics microprocessor Safety Low V...

Page 12: ...Cover Fixing Screws Fig 13 Mains Voltage External Controls Connections 230 V Room Thermostat Connections Ns Ls LR Spare ST8 Ns Ls LR Spare ST8 Remove Link Neutral Live Switched Live Neutral Live Switched Live Motor 230 V Programmer Connections 230 V room thermostat and Programmer Connections Ns Ls LR Spare ST8 Neutral Live S w it c h e d L iv e Neutral L i v e S w i t c h e d L i v e Motor Fig 14 ...

Page 13: ...ng screws Remove the flue hood by releasing the clip at the front and pulling forwards 12 3 AIR AND FLUE DUCT PREPARATION AND ASSEMBLY From the carton containing the flue kit remove the flue terminal flue duct and the package containing 4 No 8 wall plugs 1 roll ducting tape 4 No 8 wood screws 1 tube of silicone sealant Separate the air and flue ducts from the terminal Measure the distance from the...

Page 14: ...T 12 See Fig 8 Connect any room and or frost thermostats The electrical leads must pass through the appropriate space in the control panel and be fixed with the cable clamps provided See Figs 11 and 12 Refit the facia panel Test the gas supply pipework up to the appliance for soundness as indicated in BS 6891 Refer to Section 13 2 for a full description of the filling venting and the pressurising ...

Page 15: ...he facia panel to gain access Refer to Section 15 3 c Set the Expansion Vessel Pressure The charge pressure of the expansion vessel as dispatched is 0 5 bar which is equivalent to a static head of 5 metres 17 ft The charge pressure must not be less than the static head at the point of connection Refer to Fig 18 A Schraeder type tyre valve is fitted to the expansion vessel to allow the charge press...

Page 16: ...oom thermostat and the Central Heating Temperature Control to maximum Set the DHW temperature control to MIN On sealed systems check that the system is pressurised and set to the required pressure as indicated on the gauge Set the Programmer if fitted to HEATING WATER Set the operating switch to ON The burner will light The appliance will modulate its output from 9 0 to 24 0 kW over a period of ab...

Page 17: ...and automatically balance with the system requirements Set the Operating Switch to OFF and the burner will go out 13 5 COMPLETION OF COMMISSIONING Disconnect the pressure gauge from the gas valve and tighten the test point screw Restart the appliance and check for gas soundness around the test point screw Refit the cabinet front panel If the appliance is being passed over to the user immediately r...

Page 18: ...Undo the two screws securing the flue hood Lift and slide the flue hood assembly from the appliance See Fig 26 When refitting the hood ensure that the rear return edge passes under the lip at the rear of the combustion chamber f Combustion Chamber Front and Sides Remove the inner casing cover Slacken off to the end of the thread but do not remove the two wing nuts securing the combustion chamber U...

Page 19: ...r casing cover as described in Section 15 3 b Drain the central heating circuit as described in Section 16 3 a Remove the circlip and lift the assembly from the appliance Unscrew air vent from the pipe Check the condition of the fibre washer Fit the replacement assembly making sure the O ring is in good condition Ensure that the circlip is correctly fitted and the dust cap is loosened Open the val...

Page 20: ...nces the minimum pressure setting Start the appliance in the domestic hot water mode as described in Section 13 4 Appliance Operation Turn the gas valve mode switch on the rear of the facia to maximum Adjust the maximum pressure adjustment screw on the gas valve to give a burner pressure of 13 2 mbar for natural gas Turn the gas valve mode switch on the rear of the facia to minimum Adjust the star...

Page 21: ...pipe Open the valves and fill and re pressurise the system as described in Section 13 2 15 Water Diverting Valve Micro Switch Assembly Refer to Figs 30 33 Check that the electricity supply to the appliance is turned off Hinge down the facia panel as described in Section 15 3 c Remove the bottom panel as described in Section 15 3 d Using a pair of fine nosed pliers pull the circlip off and remove t...

Page 22: ... Remove the securing bracket from the valve and the water filter from the valve cold water inlet Retain the plastic manifold fixing screws support bracket and water filter Discard the water diverting valve Reassemble the original support bracket water filter and new O ring seals to the replacement valve Lubricate the O ring seal and push the plastic flow manifold onto the valve Reassemble the wate...

Page 23: ...emble in the reverse order ensuring the fibre washers and O rings are in place 20 Pressure Gauge Refer to Figs 30 34 Check that the electricity supply to the appliance is turned off Drain the central heating circuit as described in Section 16 3 a Hinge down the facia panel into the servicing position as described in section 15 3 c Remove circlip and pull out the capillary sensing bulb in the retur...

Page 24: ... one direction only Locate the replacement control board over the four mounting posts and push back squarely until the plastic catch on the end of each post clicks into place Reassemble in the reverse order and ensure i the spark electrode leads are re connected Polarity is not important ii the connectors are fitted to the correct terminals Connectors are not interchangeable and will only fit the ...

Page 25: ...42 800 0 68 E00 716 Automatic Air Vent Intermes ref 02 05 010 1 8 716 140 500 0 85 299 506 System Pressure Gauge Cewal spec D2111 1 8 716 142 300 0 40 375 699 Pressure Relief Valve Caleffi ref 312439 1 8 716 142 404 0 29 173 006 Circulating Pump Grundfoss ref 50 50 6601 1 8 716 143 100 0 25 173 001 Expansion Vessel Zilmet ref 301010 1 8 716 142 500 0 42 299 353 Water to Water Heat Exchanger Gianno...

Page 26: ...26 ...

Page 27: ...e gas to maintain flow temperature set by control knob DEMAND END Pump continue four minutes CENTRAL HEATING FUNCTION AND AND AND DOMESTIC HOT WATER FUNCTION MAIN SWITCH ON Green Light On Flow switch On Top open DOMESTIC HOT WATER DEMAND Priority over CH demand HW light On Pump On Ignition Sequence Burner on Four second ramp to max gas pressure Modulate gas to maintain delivered water temperature ...

Page 28: ... FUNCTION AND Above 9 C Commence normal central heating mode until temperature reaches 30 C 5 C to 9 C Below 5 C No demand and primary temperature below 8 C Internal Autofrostat demand Wait in normal off state for 30 minutes Run pump for four minutes Monitor central heating sensor Return to normal off state AUTOFROSTAT FUNCTION ...

Page 29: ...y flashing they can also be used to help provide fault diagnostics Therefore with individual or groups of lights being permanently off on or flashing every normal fault can be identified To use the fault finding system select a box below which represents the light situation during your fault Then refer to the appropriate following section This fault finding system assumes that the appliance has be...

Page 30: ...to boiler Replace control board Section 16 4 22 FAIL POINT A No No Yes Yes Yes No Replace fuse This will be caused by fuse fatigue or by the board Has fuse F2 blown Replace control board Section 16 4 22 Remove control board from facia See Section 16 4 22 and sepa rate transformer from board Measure resistance across the two pairs of adjacent pins on the transformer Is any pair above 100 ohms Repla...

Page 31: ...mmer Yes Yes Red diode is damaged Replace control board Section 16 4 22 Replace control board Section 16 4 22 With a hot water tap fully open does the boiler ignite and appear to run normally in hot water mode Remove multiway connector from board position ST16 With tap still open is there continuity across contacts 19 and 20 2 pink wires Remove the black cover from the microswitch assembly With ta...

Page 32: ...pressurised and is all air vented Rectify fault FAIL POINT G Primary Overheat No Re fix sensor to pipe No Repair or replace pump Section 16 4 12 No Reset the controls and restart the boiler Does the pump run Yes Remove inner casing cover and inspect the primary sensor left of heat exchanger Is it correctly fixed to pipe Yes Fault caused by control board or primary heat exchanger Yes Remove the mul...

Page 33: ...ve Section 16 4 9 Remove inner cover Reset and restart the boiler Does a spark occur across the electrodes Turn off boiler Remove the multiway connector from board position ST16 Test resistance across contacts 7 and 8 brown wires and 9 and 10 violet wires Are both reading below 100 ohms Replace control board Section 16 4 22 Repair or replace flame sensor Section 16 4 8 or wiring Replace gas valve ...

Page 34: ...alve Section 16 4 9 Remove both brown connectors from gas valve Is there continuity from brown and violet wires to the multiway connector Check or replace CH sensor Section 16 4 10 Is there continuity from contacts 17 and 18 to DHW sensor Check or replace DHW sensor Section 16 4 11 Is there continuity from contacts 12 and 13 to CH sensor Repair or replace harness Repair or replace harness Repair o...

Page 35: ... set to maximum Remove multiway connector from board position ST16 Is the resistance across contacts 1 and 2 blue wires below 60 ohms Remove blue top connector from gas valve Is there continuity along blue wires to multiway connector Is the gas set to correct pressure Set pressure No No Repair wires or replace harness No Yes Yes Replace gas valve Section 16 4 9 Replace control board Section 16 4 2...

Page 36: ...anged in the interests of continued improvement All goods sold are subject to our official Conditions of Sale a copy of which may be obtained on application PUBLICATION 8 716 145 063g 10 99 Bosch Group Worcester Heat Systems Limited Cotswold Way Warndon Worcester WR4 9SW Telephone 01905 754624 Fax 01905 754619 Technical Helpline 0990 266241 ...

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