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Worcester 24ijunior, Installation And Servicing Instructions

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Worcester 24ijunior Installation And Servicing Instructions Download Page 42

42

Boiler is running in

“Autofrost stat” mode.

See Section 17.

Replace control board.

Note:

A damp board

could cause this fault.

Is the boiler in a very

cold environment (less

than 5°C)?

TEST G

No

Yes

Does the problem
occur in CH mode

only?

TEST I

No

Yes

It is not possible to

easily isolate the fault.
The most likely causes
are control board (fail),

heat exchanger

(blocked) or

gas valve (sticking).

Hot water

temperature always

too hot during a

demand (not

regulating). 

TEST H

Hot water sensor

could be off or poorly

fixed to pipe.

Repair or replace.

Problem occurs in the

HW mode only.

Check flow sensor:

with boiler cool,

slowly open a HW tap.

Does the boiler ignite

with a flow of about 

3 l/min?

(Check using a

measuring jug and

stop watch i.e 500ml

in 10 sec.

Yes

No

Turbine sticking or

seized.

Replace the turbine.

Summary of Contents for 24ijunior

Page 1: ...12 C32 24i GC NUMBER 47 311 69 N G GC NUMBER 47 311 71 L P G 28i GC NUMBER 47 311 70 N G GC NUMBER 47 311 72 L P G GB IE APPLIANCE OUTPUTS Domestic Central Hot Water Heating 24i 28i Minimum 7 5 kW 8 0 kW Maximum 23 5 kW 27 5 kW IMPORTANT THESE INSTRUCTIONS MUST BE LEFT WITH THE USER OR AT THE GAS METER Read the instructions before starting work they have been written to make the installation easie...

Page 2: ...g standards BS5482 2 LPG and EN721 ventilation 1 9 2 PARK HOMES AND RESIDENTIAL The installation must meet the following standards BS5482 1 LPG and BS3632 ventilation 1 10 These instructions cover as far as possible the foreseeable situations which may arise Contact Worcester Heat Systems Technical Department Telephone 08705 266241 for advice on specific installations In Eire call 01 494 0099 2 1 ...

Page 3: ...de 2 8 System These appliances are suitable for sealed systems only All dirt must be flushed from the system before connecting the appliance The system can be pre piped and flushed before the appliance is fitted If a system cleaner has been used then it must be completely removed before initially filling the system and adding where necessary an inhibitor The connectionsinthesystem mustwithstandano...

Page 4: ...er The appliance can provide domestic hot water whenever it is switched on electrically A demand for hot water will light the burner The pressure will immediately rise to maximum At the end of the demand the fan will continue to run for 35 seconds if there is no heating demand In winter it may be necessary to reduce the flow at the taps to maintain the delivery temperature 2 11 3 Domestic Hot Wate...

Page 5: ... MINIMUM LENGTH mm 275 425 MAXIMUM LENGTH mm 725 EXTENDED FLUE MAXIMUM LENGTH mm 3000 FLUE ASSEMBLY DIAMETER mm 100 VERTICAL FLUE VERTICAL DUCT MAXIMUM LENGTH mm 3000 TERMINAL ASSEMBLY mm 1100 Table 2 FLOW RETURN DIFFERENTIAL NOTE Minimum uncut length NOMINAL BOILER RATINGS 10 Minutes After Lighting BOILER ADJUSTED FOR G20 Natural Gas OUTPUT INPUT Net GAS RATE kW kW m bar m3 h 8 0 9 5 1 2 1 00 27 ...

Page 6: ... NUMBER LPG 80 4 82 1 SEDBUK BAND D D 6 GAS SUPPLY SYSTEM BASED ON NG G20 TOTAL LENGTH OF GAS SUPPLY PIPE COPPER metres 3 6 9 12 GASDISCHARGERATE PRESSUREDROP 1mbar m3 h PIPEDIAMETERmm 8 7 5 8 4 6 3 9 22 18 0 12 0 9 4 8 0 28 Table 7 CLEARANCES mm INSTALLATION SERVICE UNVENTILATED COMPARTMENT ABOVE FLUE ELBOW 30 30 30 BENEATH THE APPLIANCE 200 200 200 IN FRONT OF APPLIANCE 600 600 25 RIGHT LEFT HAN...

Page 7: ...nsions and required clearances for installation servicing All dimensions in mm 30 158 10 10 7 B C D E 130 24i 400 102 600 600 203 325 200 200 F All dimensions in mm 28i 440 A Fig 5 Pipework connections Unventilated Compartment for clearances refer to Table 8 Unventilated Compartment Refer to Table 8 Dimensions A B E F 18 Minimum system flow rate Please ensure that the external system flow rate ret...

Page 8: ...ion of IS813 Standard horizontal flue kit length is 265 725mm with extension kits for flues up to 3m The terminal must not cause an obstruction or the combustion products a nuisance Under some conditions the terminal might emit steam and positions where this might be a nuisance should be avoided Refer to Fig 6 If the terminal is less than 2m above a surface to which people have access then a guard...

Page 9: ...e fully vented Repeated venting loses water from the system which must be replaced The make up connection must be close to the appliance in the heating return pipe through an approved non return valve Plastic pipes must not be directly connected to the boiler A copper to plastic transition piece should be positioned a minimum of 600mm from the boiler A plastic pipe with a polymeric barrier must be...

Page 10: ... cold water connection to the appliance Installation of a scale inhibitor assembly must be in accordance with the requirements of the local Water Company The water hardness can be determined by reference to the local Water Company An isolating valve should be fitted to allow servicing The appliance requires a maximum of 2 74 m3 h 24i 3 17m3 h 28i of natural gas G20 or 1 06 m3 h 24i 1 23m3 h 28i of...

Page 11: ... 4 8mm tag Low Speed Red 2 8mm tag High Speed Flow turbine ST16 2 blue 2 orange 2 brown brown blue blue brown green 2 red 2 yellow ST2 ST15 ST1 Pump Gas valve white black Earth tabs DHW sensor Air Pressure Switch 2 green white black Regulator Valve Safety Valve red white green yellow 2 violet Safety Valve CH sensor Overheat cut off device ...

Page 12: ...uts Spark Indicators Settings Regulator valve Spark electrodes Error indicator reset Red Main valves Flow sensor CH sensor DHW sensor Air pressure switch Flame sense Overheat cut off 24V programmer if applicable Gas valve mode switch CH Control knob Convert AC to low voltage electronics Electronics microprocessor Safety Low Voltage Flame detect indicator Red ST2 centre pole Ls for other features l...

Page 13: ...es 11 6 Wall Mounting and Manifold Assembly Fit the plugs and insert the screws Check that all the service valves are closed on the manifold assembly Offer the assembly to the wall utilising the keyhole slots and fix to the wall Refer to Fig 12 and 15 Check that the assembly is properly aligned before tightening the screws 11 7 Gas and Water Pipes Fit the appropriate fitting to connect the gas coc...

Page 14: ... flexible hose Check that the O ring is in good condition Connect the hose to the system connection point HAND TIGHTEN ONLY Refer to Figs 12 17 Fit a discharge pipe to the relief valve leading it away from any electrics or where it might be a hazard The pipe must not be less than 15mm in diameter and must run continuously downward outside the appliance Refer to Fig 17 14 65 65 65 65 CH Flow DHW Fl...

Page 15: ... Flue spigot and restrictor 1 2 3 4 Fig 18 Inner case and facia fixing Fig 20 Standard flue assembly L Fixing screw Flue turret assembly Appliance casing Telescopic adjustment Terminal assembly 3 1 Inner casing cover 2 Control panel fixing screws 2 3 Inner casing cover fixing screws 2 4 Control panel 5 Controls connector cover 6 Controls connector cover fixing screws 2 7 Programmer optional 8 Faci...

Page 16: ...nsion It is necessary to shorten the assembly by cutting the first extension duct assembly eg L 1000mm remove 175mm from the air and flue ducts 1175 1000 175mm NOTE Extension duct measurements do not include the socketed end Unless specifically instructed the socketed end must not be removed Fix the flue ducts together before fixing the surrounding air duct The cut ducts fit into the terminal asse...

Page 17: ... bends Measure the lengths X Y and Z Refer to Fig 26 The maximum value of X using the turret assembly only is 506mm Reduce the ducts to the appropriate length eg X 406mm cut 100mm from the air duct and 120mm to cover the entry into the 45 or 90 elbow from the flue duct Refer to Fig 27 NOTE The flue system ducts between the elbows dimension Y requires the socketed ends of the first extension if two...

Page 18: ... Installation Check that all the gas and water connections on the manifold have been tightened Undo the two screws and remove the connections cover panel Refer to Fig 29 Connect the mains supply lead to the appliance and secure the cable clamp Refer to Fig 29 Check that there is sufficient loose lead to allow the release of the facia panel assembly Connect the earth lead The earth lead of the main...

Page 19: ...thermostat and Programmer Connections Ns Ls LR Neutral Live Neutral L i v e S w i t c h e d L i v e Motor Remove Link spare spare ST2 Remove Link Fig 30 Optional programmer connection 1 Facia gently pull forward to un clip and remove 2 Control panel boiler outer casing in place 3 Programmer cover un clip to remove 4 Programmer location in detail 5 Programmer connections 6 Programmer connector plug...

Page 20: ...eck that the pressure relief valve operates by turning the knob anti clockwise until it releases Refer to Fig 17 Water should be expelled from the discharge pipe 13 4 Set the Expansion Vessel Pressure The charge pressure of the expansion vessel as dispatched is 0 5bar which is equivalent to a static head of 5m The charge pressure must not be less than the static head at the point of connection A S...

Page 21: ... as indicated on the gauge Check that the clock programmer is set to operate continuously Set the room thermostat and the heating temperature control to maximum The burner will light and the appliance will modulate its output from minimum to maximum over a period of about two minutes Check that all the radiators are heating up evenly Shut down all but one of the radiators and observe the burner pr...

Page 22: ...d connections in the system and remake any that show signs of leakage Refill and re pressurise as described in Section 13 Commissioning Operate the appliance and take note of any irregularities Refer to Section 19 Fault Finding for rectification procedures 15 3 Combustion performance It is not normally necessary to check the combustion performance of the appliance A sampling point is however provi...

Page 23: ...ice cock on the appliance before starting any service procedures Always test for gas soundness after the service has been completed To service the appliance it may be necessary to remove some or all of the following parts to gain access to components which may need to be checked or replaced Cabinet Pull off the clip on facia cover Unscrew the two screws and release the cabinet sides Lift up and aw...

Page 24: ... to block air flow sensor Clean the burner to ensure that the blades are clear Clean the electrodes replace if there is any sign of deterioration Clean the heat exchanger Cover the burner injector Remove any deposits from the heat exchanger from the top and bottom Carefully straighten any distorted fins on the heat exchanger Check the combustion chamber insulation and replace if there is any sign ...

Page 25: ...the union connection beneath the valve and ease the valve and injector manifold from the boiler Use new gaskets when replacing the valve Do not forget to replace the burner injector and copper washer Set the Gas Valve Connect a pressure gauge to the burner and inlet pressure test points on the valve Refer to Fig 35 Switch on the gas and electricity supplies Check for gas tightness at the gas valve...

Page 26: ...rew the screw and remove the assembly Refer to Fig 48 4 Burner Remove the inner casing cover and the combustion chamber cover Carefully pull off the connections to the spark electrodes and disconnect the flame sense electrode Unscrew the single screw fixing the support bracket and withdraw the burner assembly Refer to Fig 49 26 Fig 48 Flame sense electrode rear view 1 3 2 1 Flame sense electrode 2...

Page 27: ...the appliance has been fully drained Disconnect the relief valve discharge pipe Pull down the fixing clip and pull out the relief valve Refer to Fig 17 NOTE The clip does not need to be fully removed 8 Flow Turbine Filter Restrictor Drain the DHW circuit as described at the start of Section 16 Remove the clip on facia cover cabinet unscrew the single screw and lower the facia panel onto the lower ...

Page 28: ...ransformer Refer to Fig 56 12 Clock Programmer Remove the clip on facia Remove the clock programmer assembly by releasing the clip at the top of the clock programmer and ease away from the control panel being careful not to pull on the connector lead Unplug the connector at the control board Refer to Fig 57 Comprehensive instructions are sent with the new control 13 Fan Remove the inner casing cov...

Page 29: ...rew the fitting from inside the combustion chamber Refer to Fig 41 Undo the union connection beneath the pump and carefully withdraw the pump Take care when releasing the by pass pipe Support the pump and disconnect electrically Transfer the by pass pipe expansion vessel flexible connector and the drain point and pressure gauge connector to the new pump Transfer the inlet and outlet connections Us...

Page 30: ...l for the flue hood is in good condition and secure before replacing the flue hood 22 Air pressure switch Pull off the silicone sensing tubes Unscrew the fixing bracket and remove the pressure switch See Fig 62 Unscrew and remove the fixing clip and fit to the new air pres sure switch ensuring that the orientation of the switch to the air connections is the same Refit the switch assembly Remove th...

Page 31: ...ntrol Board 1 8 748 300 484 0 21 H05 229 Silicone Sponge 24 28kW sides 1 8 716 105 766 0 22 H05 231 Silicone Sponge 24kW top bottom 1 8 716 105 767 0 23 H05 239 Silicone Sponge 28kW top bottom 1 8 716 105 768 0 24 E88 183 Transformer 1 8 747 210 294 0 25 E88 184 Flow Regulator 24kW White 1 8 716 141 255 0 26 E88 184 Flow Regulator 28kW Blue 1 8 716 141 253 0 27 H05 403 Auto Air Vent 1 8 716 106 14...

Page 32: ...32 1 2 3 4 9 10 28 12 13 14 15 16 19 20 11 18 24 8 5 27 6 7 17 25 26 21 23 ...

Page 33: ... to maintain flow temperature set by control knob 50 82 C DEMAND END Overrun function see overleaf CENTRAL HEATING FUNCTION AND AND DOMESTIC HOT WATER FUNCTION MAIN SWITCH ON Flow sensor signal Tap open DOMESTIC HOT WATER DEMAND Priority over CH demand Pump continue 4 seconds if primary temp above DHW setting Burner to MAX Modulate gas to maintain delivered water temperature 55 C Is CH interrupted...

Page 34: ...wait pump pulses for 2 seconds OVERRUN FUNCTION Run pump END DHW DEMAND END CH DEMAND Pump runs for 3 minutes AUTOFROSTAT FUNCTION Monitor central heating sensor Below 5 C 5 C to 9 C Above 9 C No demand and primary temperature below 8 C Internal Autofrostat demand Return to normal off state Fan low speed 35 seconds Fan low speed if primary temp above 85 C until below 80 C ...

Page 35: ...MMON CAUSES SEE TEST No lights and no functions with demand No CH function DHW OK No DHW function CH OK Flash once per second Ignition lockout Overheat lockout Internal error Flash 4 times per second No mains Voltage supply Fuse F1 or F2 blown Transformer or connector failed Board fault No link at ST2 Ls to Lr or failed external control input to Lr Failed programmer Board fault Flow sensor failure...

Page 36: ...eplace transformer Yes Yes No Replace control board No NOTE It is normal for there to be no facia lights if the boiler is in normal overtempera ture condition Continue this test if this fault occurs when the appliance is cold Is there a 230V AC live supply across Terminal ST2 pins Lr and N TEST B No Yes Yes Replace control board NOTE Lights will be off and pump will run if boiler is in 3min anticy...

Page 37: ...the green and black wires terminals Is there continuity in the main harness Disconnect the 3 way in line connector to the turbine Is there 5VDC between the two outer pins main harness side Take care not to damage the pins No No Yes Yes Replace control board Replace main harness TEST C Yes Replace turbine No ...

Page 38: ...n ST16 Test resistance across pins 1 and 2 brown wires also pins 8 and 9 violet Is resistance between 60Ω and 100Ω Replace gas valve Are the electrodes and gap and connections in good order Replace control board Remove brown connector from gas valve Is there continuity from brown and violet connectors to multiway connector Repair or replace harness Repair or replace spark electrode or HT leads Is ...

Page 39: ...the efficiency of the gas water heat exchanger If there is still a problem investigate flue problems or replace burner or injector or heat exchanger Check the flashing fault signal occur at the start of a demand Check flashing occurs at the end of a demand Gas valve leak is detected No Yes Check flashing occurs during a demand Pump could be partially blocked Clean pump flush system Re fix sensor t...

Page 40: ...y home on to the board Push fully home No No No No No Yes Yes Yes Check the DHW sensor Is it correctly fitted onto the pipe with heat conductive paste between the pipe and sensor Yes No Re fix sensor onto pipe TEST E Check or replace CH sensor Test resistance across contacts 14 and 15 green wire Is it open circuit Turn off electrical supply Remove fan connector from board position ST1 Test resista...

Page 41: ... fan or fan may not be running freely Inspect the flue Is it free of any restrictions Rectify flue problem Does the burner ignite burner light on and run for a short priod before the fault occurs Replace control board Repair cables or replace main harness Replace tubes If condensation has occurred also replace pressure switch and check condition of Venturi in the fan No No No No Yes Yes Yes Yes Tu...

Page 42: ...e most likely causes are control board fail heat exchanger blocked or gas valve sticking Hot water temperature always too hot during a demand not regulating TEST H Hot water sensor could be off or poorly fixed to pipe Repair or replace Problem occurs in the HW mode only Check flow sensor with boiler cool slowly open a HW tap Does the boiler ignite with a flow of about 3 l min Check using a measuri...

Page 43: ... Refit the end cap ensuring that the support bracket is in the correct orientation 7 Remove the gas valve and replace with the gas valve supplied in the kit Refer to Installation and Service Instructions Section Replacement of Parts 8 Re assemble the burner and inner casing 9 Turn on the gas and electricity supplies and follow the commissioning procedure to confirm gas soundness and correct boiler...

Page 44: ...s sold are subject to our official Conditions of Sale a copy of which may be obtained on application PUBLICATION 8 716 106 766a 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 ...

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