Worcester 24CDi Installation And Servicing Instructions Download Page 29

Page: 29 / 40

18. Oper

ational Flow Diagrams

MAIN SWITCH

Green Light

Room

thermostat

and/or mains

programmer

(or link) On

AND

Electronic

facia

programmer

(if fitted) On

AND

ST13 link in

AND

CH control

knob On

CENTRAL

HEATING

DEMAND

CH light On.

Pump On.

Fan ON High for 2

sec then Low speed -

28CDi.

Fan ON High for 2

sec then Low speed -

35CDi

Ignition Sequence.

Burner Light On.

Three minute

wait

Gas valve Off.

(CH light still

on. Pump still

On)

Over tempera-

ture shut-

down if flow
temperature

5°C above set

value

Two minute mini-

mum burner

(30 seconds -

35CDi

)

pressure then

ramp up

pressure over

next one minute

Modulate gas

to maintain

flow

temperature

set by control

knob

DEMAND

END

Pump

continue four

minutes.

Fan continue

fifteen

seconds

CENTRAL HEA

TING FUNCTION

AND

MESTIC HOT WATER FUNCTION

MAIN SWITCH

Green Light

Flow switch

(Tap open)

DOMESTIC

HOT WATER

DEMAND

(Priority over

CH demand)

HW light On.

Pump On.

Fan ON High speed -

28CDi.

Fan ON High for 2

sec then Low speed

- 35CDi

Ignition Sequence.

Burner on

Four second

ramp to max.
gas pressure.

Fan speed

changes at mid

pressure
35CDi

Modulate gas

to maintain

delivered

water

temperature

at value set by

control knob

Ten second

wait

Gas valve Off.
(HW light still

on. Pump still

On)

Over

temperature

shut-down if

water

temperature

8°C above set

value

Burner shut-

down if

primary

temperature

94°C

(until 84°C)

DEMAND

END

Fan continue

fifteen

seconds

Possible

overrun

condition

within next

four minutes

(See next

section)

Summary of Contents for 24CDi

Page 1: ...P G 47 311 31 47 311 35 47 311 59 BOILER OUTPUT Automatic Modulating Control Domestic Central Hot Water Heating 24CDi 9 24kW 9 24kW 28CDi 9 28kW 9 24kW 35CDi II 9 5 35 3kW 10 5 27 5kW 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 Installat...

Page 2: ...tallations 2 1 General Information 2 1 1 The appliance is set to provide the maximum output for domestic hot water and a central heating load of 24kW 24 28CDi or 27 5kW 35CDi II The hot water flow rate is limited to a nominal 9 l min 24CDi or 10 l min 28CDi or 12 l min 35CDi II at a maximum temperature rise of 40 C 2 1 2 The sanitary water section of the appliance is suitable for water mains press...

Page 3: ...to an over rim flushing bidet subject to local Water Company requirements With all mains fed systems the flow of water from the individual taps will vary with the number of outlets operated 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 infor...

Page 4: ...4 15 1 13 1 3 1 6 MAX OUTPUT CH kW 24 0 24 0 27 5 24 0 24 0 27 5 MAX INPUT net kW 27 0 27 0 30 1 27 0 27 0 30 1 BURNER PRESSURE mbar 14 8 10 8 8 35 3 24 3 21 3 GAS RATE m3 h 2 9 2 9 3 19 1 13 1 3 1 23 MIN OUTPUT DHW kW 9 0 9 0 9 5 9 0 9 0 9 5 MIN INPUT net kW 11 4 11 4 11 9 11 4 11 4 11 9 BURNER PRESSURE mbar 1 5 1 0 0 9 5 4 3 8 3 1 GAS RATE m3 h 1 2 1 2 1 26 0 46 0 5 0 49 Table 1 BOILER ADJUSTED ...

Page 5: ...PG PROPANE 81 D 80 7 D 80 8 D 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 6a 24CDi DOMESTIC HOT WATER TEMPERATURE RISE DISCHARGE RATE l min 7 8 9 10 TEMPERATURE RISE C 57 3 50 2 44 6 40 1 Table 6b 28CDi 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 8 7 ...

Page 6: ...bustible partition Expanded metal or rigid wire mesh are acceptable provided that the major dimension is less than 13mm See BS 6798 4 8 The distance between the inner face of a cupboard door and the cabinet front should not be less than 75mm 4 9 The pipe connection positions on the manifold are shown in Fig 3 allowing the system to be pre piped and flushed before the appliance is fitted Always con...

Page 7: ...vents for cooling are required One at high level and one at low level either direct to outside air or to a room Both vents must pass to the same room or be on the same wall to the outside air 6 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 Flue Terminal 7 POSITION OF AIR FROM AIR DIRECT AIR VENTS THE ROOM F...

Page 8: ... 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 up to 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 boilers require a gas flow in m3 h of NG G...

Page 9: ...e taps may be required to achieve the hot water delivery temperature available in warmer weather 10 8 It is suggested that long pipe runs to the taps or shower should be insulated to prevent the rapid cooling of domestic hot water after a tap or shower has been turned off 10 9 Hot and cold taps and mixing valves used with this appliance must be suitable for operating at mains pressure and temperat...

Page 10: ...the clamps provided The controls must be earthed at the connection on the control board Refer to Fig 11 and 13 11 8 A choice of programmers to fit into the facia are available to control the CH Full instructions are sent with the programmer Refer to Fig 15 11 9 On very rare occasions an external frost thermostat might be considered where parts of the system are remote from the appliance Refer to W...

Page 11: ...n Electronics Electronics Electronics Electronics Electronics Inputs Outputs Spark 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 Air pressure switch Flame sense Overheat cut off 24V programmer Reset button Gas valve mode switch CH pressure adjust pot CH Control ...

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: ...pacing frame is used then the 197mm dimension should be increased by 35mm see instructions supplied with frame Check the position and alignment of the holes before drilling the fixing holes 60mm deep for No 12 plugs and the flue holes Ø110 for external fitting and Ø150 for internal fitting Ensure that the flue hole is horizontal through the wall Refer to Fig 16 12 5 Wall mounting Plate and Manifol...

Page 14: ... Horizontal flue up to 1m 28CDi 77mm Horizontal flue up to 1m 35CDi II 85mm Horizontal flue up to 1m The standard uncut telescopic flue assembly is suitable for flues from 425mm up to 725mm measured from the centre line of the boiler flue outlet to the outer face of the wall Refer to Fig 19 20 If L 725mm then extension duct kit s will be required each kit 14 Fig 17 Fixing the appliance to the wall...

Page 15: ... not be removed Fix the flue ducts together before fixing the surrounding air duct the cut ducts fit into the flue assembly 12 10 Fitting the Flue Assembly with Access to the Terminal Prepare the flue duct assembly as described in Section 12 9 Apply the plastic tape to the air duct in contact with the external brickwork From inside push the assembly through the wall Align the flue turret and push ...

Page 16: ...ssembly If Z in 425 725mm it is not necessary to cut the terminal assembly or use a second extension duct as the length can be set telescopically If Z 725mm then two extension duct assemblies will be required the first assembly being cut to length as plain tubes If more than two extension ducts are needed in any section to achieve the required length then the final section of the assembly must not...

Page 17: ...domestic hot water and central heating load of 24 kW 24 28CDi or 27 5kW 35CDi II The appliance automatically modulates to satisfy lower heat loads Domestic Hot Water Circuit Confirm that the mains water supply has been flushed out at installation If not it will be necessary to disconnect the cold water inlet pipe from the appliance and thoroughly flush Central Heating System Confirm that the syste...

Page 18: ...pressure If the pressure indicated on the pressure gauge is greater than 2 6 bar when operating at the maximum central heating temperature an extra expansion vessel must be fitted to the system as close as possible to the appliance central heating return connection The appliance as dispatched can accommodate a system volume of about 83 litres Refer to BS 7074 Part 1 If the system volume is in exce...

Page 19: ...edure Check for proper ignition of the burner after a break in the gas supply Turn off the gas service cock and wait for 60 seconds The burner will go out but sparking from the electrode will continue for 10 seconds when the appliance will enter a lockout state Carefully open the gas service cock press the lockout reset button and observe the burner re light and follow the normal sequence of opera...

Page 20: ...nge down the facia taking care not to distort the pressure gauge capillary tube or electrical connections d Bottom panel Hinge down the facia panel Disengage the front edge of the bottom panel from the two clips and remove the bottom panel from the appliance e Fan Remove the inner casing cover Carefully unplug the electrical connections and pull off the sensing tubes Unscrew the three fixing screw...

Page 21: ...lose the drain taps when the flow has stopped Be careful not to overtighten the drain taps Some water will remain in the expansion vessel pump diverter valve water to water and Gas to Water heat exchangers and extra care must be taken when removing these components b Domestic Hot Water Circuit Turn off the mains cold supply valve at the appliance and open the lowest hot water tap A quantity of wat...

Page 22: ... heat exchanger as described in Sections 15 3 b e and f and 16 4 5 Remove the fibre insulation pads from the combustion chamber side rear and front sections To avoid the risk of fine particles dampen the pads before removal Fit the replacement pads in the reverse order taking care not to damage them Open the valves and fill and re pressurise the system as described in Section 13 2 7 Burner See Fig...

Page 23: ...or 3 1 mbar 35CDi II for natural gas or 5 4mbar 24CDi or 3 8mbar 28CDi or 3 1mbar 35CDi II for propane Turn the gas mode switch on the rear of the facia to maximum Adjust the maximum pressure screw on the gas valve to give a burner pressure of 14 8mbar 24CDi or 15 5mbar 28CDi or 13 5mbar 35CDi II for natural gas or 35 5mbar 24CDi or 35 5mbar 28CDi or 34 7mbar 35CDi II for propane Turn the gas mode...

Page 24: ...bed in Section 15 3 c Remove the bottom panel as described in Section 15 3 d Pull out the retaining clip and remove the pressure gauge connection Undo the discharge pipe connection and remove the valve taking care not to distort the pipework Fit the replacement valve in reverse order Reconnect the discharge pipe Open the valves and fill and re pressurise the system as described in Section 13 2 16 ...

Page 25: ...ge down the facia panel into the servicing position as described in Section 15 3 c Follow the proceedures as described in Section 16 4 18 and remove the water divering valve from the appliance Remove the water filter from the cold water inlet Discard or clean the filter Fit the replacement filter push fit in the reverse order Reassemble the appliance in the reverse order Open the valves and fill a...

Page 26: ... 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 termi nals from which they were removed Reassemble the f...

Page 27: ... Water Heat Exchanger Giannoni Ref PVW 12 E D2108 1 8 716 142 900 0 42 E00 711 Water to Water Heat Exchanger Giannoni Ref PVW 14 E 1 8 716 142 903 0 42 Water to Water Heat Exchanger Giannoni Ref PVW 16E 1 8 716 102 672 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...

Page 28: ...28 109 ...

Page 29: ...ure set by control knob DEMAND END Pump continue four minutes Fan continue fifteen seconds CENTRAL HEATING FUNCTION AND AND AND DOMESTIC HOT WATER FUNCTION MAIN SWITCH ON Green Light On Flow switch On Tap open DOMESTIC HOT WATER DEMAND Priority over CH demand HW light On Pump On Fan ON High speed 28CDi Fan ON High for 2 sec then Low speed 35CDi II Ignition Sequence Burner on Four second ramp to ma...

Page 30: ...primary temperature still increases above 90 C Run pump for two seconds OVERRUN FUNCTION AND Pulse pump for 2 seconds every 10 seconds 35CDi II 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 hea...

Page 31: ... 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 been operating correctly until the time of failure PRELIMINARY CHECKS Preliminary e...

Page 32: ...y to boiler Replace control board Section 16 4 23 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 23 Remove control board from facia See Section 16 4 23 and sepa rate transformer from board Measure resistance across the two pairs of adjacent pins on the transformer Is any pair above 100 ohms Rep...

Page 33: ...rogrammer Yes Yes Red diode is damaged Replace control board Section 16 4 23 Replace control board Section 16 4 23 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 Wi...

Page 34: ...INT G Primary Overheat No Re fix sensor to pipe No No Repair or replace pump Section 16 4 14 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 Remove the multiway connector from board position ST16 Is there a short circuit across contacts 5 6 Fault caused by control bo...

Page 35: ...he 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 23 If problem not solved replace gas valve Section 15 4 11 Repair or replace flame sensor Section 16 4 10 or wiring Replace gas valve...

Page 36: ...1 Remove both brown connectors from gas valve First remove pressure switch bracket Is there continuity from brown and violet wires to the multiway connector Check or replace CH sensor Section 16 4 12 Is there continuity from contacts 17 and 18 to DHW sensor Check or replace DHW sensor Section 16 4 13 Is there continuity from contacts 12 and 13 to CH sensor Repair or replace harness Repair or repla...

Page 37: ...solving the problem inspect the pressure pick up Venturi in the fan Repair or replace fan Section 16 4 3 or cable Repair or replace fan Section 16 4 3 or cable Air pressure switch is shorting Replace switch Section 16 4 2 28CDi and 35CDi II 24CDi 28CDi and 35CDi II Remove fan connector from board position ST1 and restart boiler in the fault mode After 5 seconds is there mains 230V from the left N ...

Page 38: ...or poorly fixed to pipe Repair or replace sensor Section 16 4 14 Water temperature very low low gas pressure with all knobs 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 pres...

Page 39: ...o confirm gas soundness and correct boiler operation 10 Check and adjust the setting pressures to the values in the table below and adjust if necessary Refer also to the Installation and Service Instructions Section Replacement of Parts To Set the Burner Pressure 11 Refit the plastic sealing cap to the gas valve modulating valve adjuster and seal with a dab of paint or similar 12 Turn off the boil...

Page 40: ...ject to our official Conditions of Sale a copy of which may be obtained on application PUBLICATION 8 716 102 567j 01 03 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 manual is to be used in conjunction with the variant part number of the bar code below 28CDi 24...

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