Bosch Appliances GREENSTAR 28i junior User Manual
THE APPLIANCE IS FOR USE WITH  
NATURAL GAS OR L.P.G. (Cat II 2H3P TYPE C13 & C33)  
NATURAL GAS:  
WORCESTER GREENSTAR 24i junior GC NUMBER 47-311-86  
WORCESTER GREENSTAR 28i junior GC NUMBER 47-311-87  
LIQUID PETROLEUM GAS:  
WORCESTER GREENSTAR 24i junior GC NUMBER 47-311-90  
WORCESTER GREENSTAR 28i junior GC NUMBER 47-311-91  
GB/IE  
CHECKLIST & service  
interval record, printed within this  
manual  
CONTENTS  
SAFETY & REGULATIONS  
SAFETY PRECAUTIONS & SYMBOLS  
INSTALLATION REGULATIONS  
3
3
APPLIANCE INFORMATION  
GENERAL INFORMATION  
TECHNICAL DATA  
4
5
LAYOUT & COMPONENTS  
6-7  
PRE-INSTALLATION  
CLEANING PRIMARY SYSTEMS  
MAINS SUPPLY  
8
9
WATER SYSTEMS & PIPEWORK  
CONDENSATE PIPEWORK  
PRESSURE RELIEF PIPEWORK  
BOILER LOCATION & CLEARANCES  
PLUMBING MANIFOLD  
10  
11  
12  
13-14  
15  
FLUE TERMINAL POSITIONS  
FLUE OPTIONS  
16  
17  
INSTALLATION  
UNPACKING THE WALL FRAME  
WALL MOUNTING TEMPLATE / FLUE OPENING  
UNPACKING THE APPLIANCE  
BOILER CONNECTIONS  
18  
19  
20  
21-22  
23-25  
26  
FLUE INSTALLATION  
CONDENSATE CONNECTIONS  
ELECTRICS  
27  
POSITION OF WIRED COMPONENTS  
28  
COMMISSIONING  
PRE-COMMISSIONING CHECKS  
FILLING THE SYSTEM  
29  
30  
31  
32  
33  
34  
STARTING THE APPLIANCE  
WATER TREATMENT  
COMMISSIONING  
FINISHING COMMISSIONING  
SERVICING & SPARES  
INSPECTION AND SERVICE  
REPLACEMENT OF PARTS  
SETTING THE GAS/AIR RATIO  
SHORT PARTS LIST  
35-40  
41-50  
51  
52  
CONVERSION KITS  
L.P.G. CONVERSION  
53  
FAULT FINDING & DIAGNOSIS  
FAULT FINDING  
54  
55  
CH FUNCTION  
DHW FUNCTION  
56  
PROTECTION FUNCTION  
57-58  
BENCHMARK CHECKLIST  
SERVICE INTERVAL RECORD SHEET  
2
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
CONTENTS  
SAFETY PRECAUTIONS  
INSTALLATION REGULATIONS  
IF YOU SMELL GAS:  
Gas Safety (Installation & Use) Regulations 1998:  
All gas appliances must be installed by a  
competent person in accordance with the above  
regulations. Failure to install appliances correctly  
could lead to prosecution.  
✗ DON’T SMOKE OR STRIKE MATCHES  
✗ DON’T TURN ELECTRICAL SWITCHES ON OR OFF  
The appliance must be installed in accordance  
with, and comply to, the current: Gas Safety  
Regulations, IEE Regulations, Building  
Regulations, Building Standards (Scotland)  
(Consolidation), Building Regulations (Northern  
Ireland), local water by-laws, Health & Safety  
Document 635 (The Electricity at Work  
Regulations 1989) and any other local  
requirements.  
✗DO PUT OUT NAKED FLAMES  
✗DO OPEN DOORS AND WINDOWS  
✗DO KEEP PEOPLE AWAY FROM THE AREA AFFECTED  
✗DO TURN OFF THE CONTROL VALVE AT THE METER  
✗DO CALL YOUR GAS COMPANY  
British Standards:  
The relevant British Standards should be followed,  
including:  
BS7074:1 : Code of practice for domestic and hot  
water supply  
BS6891 : Installation of low pressure gas  
pipework up to 28mm (R1)  
BS5546 : Installation of gas hot water supplies for  
domestic purposes  
EN:12828 : Central heating for domestic premises  
BS5440:1 : Flues and ventilation for gas appli-  
ances of rated heating not exceeding 70kW (net) :  
Flues  
BS5440:2 : Flues and ventilation for gas appli-  
ances of rated heating not exceeding 70kW (net) :  
Air Supply  
A Benchmark Checklist is provided by the manufacturer for the installer to complete  
including their CORGI registration number to confirm that the boiler has been installed,  
commissioned and serviced according to the manufacturer’s instructions.  
IMPORTANT: The completed Benchmark Checklist will be required in the event of any  
warranty work and may be required by the local Building Control Inspector.  
BS7593 : Treatment of water in domestic hot  
water central heating systems  
BS 6798 : Installation of gas fired boilers of rated  
input up to 70kW (net)  
Where no specific instruction is given, reference  
should be made to the relevant British Standard  
codes of Practice.  
HEALTH & SAFETY  
The appliance contains no asbestos and no substances have been used in the  
construction process that contravene the COSHH Regulations (Control of Substances  
Hazardous to Health Regulations 1988).  
COMBUSTIBLE AND CORROSIVE MATERIALS  
L.P.G. Installation:  
Do not store or use any combustible materials (paper, thinners, paints etc.) inside or  
within the vicinity of the appliance.  
An appliance using L.P.G. must not be installed in  
a room or internal space below ground level unless  
one side of the building is open to the ground.  
Chemically aggressive substances, such as halogenated hydrocarbons containing  
chlorine or fluorine compounds can corrode the appliance and invalidate any warranty.  
Timber framed buildings:  
Where the boiler is to be fitted to a timber framed  
building the guidelines laid down in BS5440: Part  
1 and IGE "Gas Installations in Timber Frame  
Buildings” should be adhered to.  
FITTING & MODIFICATIONS  
Fitting the appliance and any controls to the appliance may only be carried out by a  
competent engineer in accordance with the current Gas Safety (Installation and Use)  
Regulations.  
Flue systems must not be modified in any way other than as described in the fitting  
instructions. Any misuse or unauthorised modifications to the appliance, flue or  
associated components and systems could invalidate the warranty. The manufacturer  
accepts no liability arising from any such actions, excluding statutory rights.  
Potable water:  
All seals, joints and compounds (including flux and  
solder) and components used as part of the  
secondary domestic water system must be  
approved by WRAS.  
SERVICING  
CH water:  
Advise the user to have the system serviced annually by a competent, qualified  
engineer (such as British Gas or CORGI registered personnel) using approved spares,  
to help maintain the economy, safety and reliability of the appliance.  
IMPORTANT - The service engineer must complete the Service Record on the  
Benchmark Checklist after each service.  
Artificially softened water must not be used to fill  
the central heating system.  
3
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
SAFETY PRECAUTIONS  
8 716 107 336b (11/05)  
& INSTALLATION REGULATIONS  
GENERAL INFORMATION  
STANDARD PACKAGE:  
A - Wall hung gas fired condensing combi boiler for  
central heating and domestic hot water  
B - Boiler support frame  
C -Hardware literature pack  
D -Bottom Panel  
B
(When fitted to wall frame)  
Depth to wall  
A
330mm  
700mm  
D
C
SPECIFICATIONS:  
400mm  
Pre-wired and pre-plumbed  
Galvanised steel inner frame  
Digital control system  
Automatic ignition  
Direct burner ignition electrodes  
Built-in frost thermostat  
D
Built-in fault finding diagnostics  
Modulating automatic gas valve  
Combustion air fan with speed regulator  
CH temperature sensor & control  
Pump anti-seizure protection  
Flue gas temperature limiter  
Condensate trap & syphon  
DHW flow sensor  
Plate type DHW heat exchanger  
4
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
GENERAL INFORMATION  
TECHNICAL DATA  
DESCRIPTION  
NATURAL GAS  
L.P.G.  
24i junior  
UNITS  
24i junior  
28i junior  
28i junior  
Domestic Hot Water  
Min. heat input  
KW  
KW  
KW  
7.38  
24  
7.38  
28  
9.64  
24  
9.64  
28  
Max. rated heat output  
Max. rated heat input  
24.49  
28.57  
24.49  
28.57  
Gas flow rate - Max. 10 minutes from lighting  
Natural Gas G20  
m3/h  
kg/h  
bar  
2.59  
-
3.02  
-
-
-
Propane Gas (LPG)  
1.9  
10  
2.22  
10  
Max. mains inlet pressure  
10  
10  
Min. mains inlet pressure (working) for max flow  
Min. mains inlet pressure (working) for operation  
Domestic Hot Water temperature setting  
Domestic Hot Water specific rate - 30°C rise  
Max. Domestic Hot Water flow rate - 40°C rise +/— 15%  
Central Heating  
bar  
1.3  
0.2  
55  
1.3  
0.2  
55  
13.4  
10  
1.3  
0.2  
55  
1.3  
0.2  
55  
bar  
°C  
l/min  
l/min  
11.5  
8.6  
11.5  
8.6  
13.4  
10  
Max. rated heat input  
KW  
KW  
KW  
KW  
°C  
24.62  
25.67  
25.45  
24  
24.62  
25.67  
25.45  
24  
24.62  
25.67  
25.45  
24  
24.62  
25.67  
25.45  
24  
Max. rated heat output 40/30°C  
Max. rated heat output 50/30°C  
Max. rated heat output 80/60°C  
Max. flow temperature  
82  
82  
82  
82  
Max. permissible operating pressure  
Available pump head at 21°C system temperature rise  
Flue  
bar  
m
2.5  
2.5  
2.5  
2.5  
2.0  
2.0  
2.0  
2.0  
Flue Gas Temp. 80/60°C, rated/min. load  
Flue Gas Temp. 40/30°C, rated min. load  
°C  
°C  
%
78/63  
54/35  
9.8  
78/64  
54/36  
9.8  
79/64  
55/38  
11.0  
10.5  
5
79/65  
55/39  
11.0  
10.5  
5
CO level at max. rated heat output  
2
CO level at min. rated heat output  
2
%
9.2  
9.2  
NOx - class  
5
5
Condensate  
Max. condensation rate  
pH value, approx.  
Electrical  
l/h  
2.0  
4.8  
2.0  
4.8  
2.0  
4.8  
2.0  
4.8  
Electrical power supply voltage  
Frequency  
AC...V  
Hz  
230  
50  
230  
50  
230  
50  
230  
50  
Max. power consumption  
General Data  
W
140  
140  
140  
140  
SEDBUK  
band  
IP  
A
A
A
A
Appliance protection rating  
X4D  
20  
X4D  
20  
X4D  
20  
X4D  
20  
Appliance protection rating with mechanical or RF mechanical timer fitted IP  
Permissible ambient temperatures  
Nominal capacity of appliance  
Noise output level (Max central heating)  
Packaged boiler weight  
Total boiler weight  
°C  
Itr  
0-50  
3.9  
0-50  
3.9  
0-50  
3.9  
0-50  
3.9  
dB(A)  
kg  
42  
42  
42  
42  
44.4  
39.5  
27.1  
90.1  
44.4  
39.5  
27.1  
90.1  
44.4  
39.5  
27.1  
91.8  
44.4  
39.5  
27.1  
91.8  
kg  
Lift weight  
kg  
SEDBUK  
%
5
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
TECHNICAL DATA  
LAYOUT & COMPONENTS  
The diagram opposite shows the controls in the  
servicing position and excludes the outer case.  
1
2
3
4
5
6
7
8
AIR / GAS MANIFOLD  
FAN  
AIR / GAS ADJUSTMENT SCREW  
GAS VALVE  
INLET PRESSURE TEST POINT  
EXPANSION VESSEL  
WALL MOUNTING FRAME  
COVER FOR EXTERNAL WIRING  
CONNECTIONS  
9
CONDENSATE CONNECTION FROM  
HEAT EXCHANGER  
10 PLATE TO PLATE  
DHW HEAT EXCHANGER  
11 FLUE PRESSURE SWITCH  
12 FAN PRESSURE TEST POINT  
13 MANUAL VENT POINT  
14 IGNITION AND FLAME SENSE ELECTRODES  
15 OVERHEAT THERMOSTAT  
16 FLAME VIEWING MIRROR  
17 SECURING NUT, AIR /  
GAS MANIFOLD CLAMP  
18 SENSOR - BOILER FLOW  
19 FLUE AIR PRESSURE SWITCH  
CONNECTION  
20 FLUE OVERHEAT THERMOSTAT  
21 ACCESS POINT FOR CLEANING HEAT  
EXCHANGER/SUMP  
22 REMOVABLE TOP CASE PANEL FOR  
SERVICING  
23 GAS INLET CONNECTION 22mm  
COMPRESSION  
24 TRAP / SYPHON  
25 TRAP / SYPHON OUTLET  
CONNECTION ( 22mm PLASTIC PIPE)  
26 MAINS COLD WATER IN  
27 CH FLOW  
28 DHW OUT  
29 CH RETURN  
30 DRAIN POINT  
31 SILICONE TUBE (USE TO VENT AIR  
FROM HEAT EXCHANGER)  
32 PUMP  
33 SYSTEM PRESSURE GAUGE  
34 CONTROL PANEL IN SERVICE  
POSITION  
35 HEAT EXCHANGER  
36 ACCESS COVER FOR TRANSFORMER &  
PCB  
6
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
LAYOUT & COMPONENTS  
LAYOUT & COMPONENTS  
10 PLATE TO PLATE DHW  
HEAT EXCHANGER  
32 SYSTEM PUMP  
36 FLOW TURBINE  
37 UNUSED PORT  
38 AUTO AIR VENT  
39 FLOW CONNECTION FROM BOILER  
HEAT EXCHANGER  
40 DHW SENSOR  
41 CH FLOW CONNECTION TO  
SERVICE VALVE  
42 DHW OUT CONNECTION  
43 COLD WATER IN CONNECTION  
44 CH RETURN CONNECTION TO  
SERVICE VALVE  
45 DIVERTER VALVE  
46 PRESSURE RELIEF VALVE  
47 COMPACT HYDRAULIC MOUNTING  
SCREW (2) TO BOILER  
48 CH TEMPERATURE CONTROL  
49 MAINS ON/OFF INDICATOR/  
DIAGNOSTIC LIGHT (BLUE)  
50 SERVICE MODE BUTTON  
51 BURNER ON INDICATOR LIGHT (GREEN)  
52 MASTER SWITCH ON/OFF  
53 ECO BUTTON  
54 FAULT RESET BUTTON  
55 SYSTEM PRESSURE GAUGE  
56 POSITION FOR OPTIONAL  
PROGRAMMER  
57 INTERNAL BY-PASS WITHIN  
PLASTIC MOULDING  
7
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
LAYOUT & COMPONENTS  
CLEANING PRIMARY SYSTEMS  
IMPORTANT: All the following Pre-Installation sections must be read and  
requirements met before starting boiler or flue installation.  
IMPORTANT: Debris from the system can  
damage the boiler and reduce efficiency.  
Failure to comply with the guidelines for  
the use of water treatment with the  
appliance will invalidate the appliance  
warranty.  
CAUTION: ISOLATE THE MAINS SUPPLIES BEFORE STARTING ANY WORK AND  
OBSERVE ALL RELEVANT SAFETY PRECAUTIONS.  
BEFORE CLEANING THE SYSTEM:  
ENSURE THE SYSTEM AND PIPEWORK IS  
IN GOOD WORKING ORDER  
KEEP THE EXISTING BOILER/  
CIRCULATING PUMP WHERE POSSIBLE  
OR USE A POWER FLUSHING MACHINE  
TO AID THE CLEANSING PROCEDURE  
BEFORE INSTALLING A NEW BOILER.  
CLEANING THE PRIMARY SYSTEM:  
1
2
3
Fill the system with cold water and  
check for leaks.  
Open all drain cocks and drain the  
system.  
Close drain cocks and add a suitable  
flushing agent compatible with  
aluminium at the correct strength for  
the system condition in accordance with  
the manufacturer's instructions.  
The PH value of the system water  
must be less than 8 or the appliance  
guarantee will be invalidated.  
ꢀ Circulate the flushing agent before the  
boiler is fired up.  
4
5
Run the boiler/system at normal operating  
temperature as directed by the manufacturer  
of the flushing agent.  
Drain and thoroughly flush the system to  
remove the flushing agent and debris.  
8
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
CLEANING PRIMARY SYSTEMS  
MAINS SUPPLY  
ELECTRIC SUPPLY:  
• Supply: 230V - 50Hz, 140 watts  
• Cable: PVC insulated 0.75mm2 (24 x 0.2mm)  
temperature rated to 90°C.  
• External 3A fuse to BS1362.  
• The appliance must be earthed.  
• IPX4D. NOTE: this is reduced to IP20 if the  
following mechanical timers are fitted:  
7 716 192 036 or 7 716 192 037.  
• All pipes to the boiler must be cross-bonded.  
• Wiring must comply with IEE wiring regulations.  
GAS SUPPLY:  
• Boilers using NG must be connected to a  
governed meter.  
• LPG boilers must be connected to a  
regulator.  
• Installation and connection of the gas supply  
to the boiler must be in accordance with  
BS6891.  
• Under no circumstances should the size of  
the gas supply pipe be less than that of the  
appliance inlet connection.  
• The meter or regulator and pipework to the  
meter must be checked, preferably by the gas  
supplier, to ensure it is in good working order  
and can meet the gas flow and pressure  
requirements in addition to the demand from  
any other appliance being served.  
WATER SUPPLY:  
Water mains pressure:  
• Minimum mains water pressure 1.3 bar for  
maximum performance.  
• Maximum mains fed water pressure 10 bar.  
If necessary, fit a pressure reducing valve.  
MAINS WATER EXPANSION VESSEL:  
A - Mini expansion vessel, part No. 7 716 102 105  
B - Mains water inlet  
C - Non-return valve  
D - Boiler  
D
IMPORTANT: Non-return, back flow pre-  
vention devices (including those associ-  
ated with water meters) fitted to the  
mains water supply can cause a pres-  
sure build up which could damage the  
boiler and other household appliances.  
A
C
B
• Where the mains water supply has a non-  
return, back flow prevention valve fitted, a  
mini expansion vessel (A) should be connect-  
ed to the mains water inlet pipe (B) between  
the non-return valve (C) and the boiler (D) as  
shown opposite.  
Use in hard water areas:  
Normally there is no need for water treatment to  
prevent scale formation as the maximum tem-  
perature of the DHW heat exchanger is limited  
in the electronic circuit.  
In areas where temporary water hardness  
exceeds 200ppm, consideration may need to  
be given to the fitting of a scale prevention  
device. In such circumstances, the advice of  
the local water authority should be sought.  
9
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
MAINS SUPPLY  
WATER SYSTEMS & PIPEWORK  
PLASTIC PIPEWORK:  
• Any plastic pipework must have a polymeric  
barrier with 600mm (minimum) length of  
copper or steel pipe connected to the boiler.  
• Plastic pipework used for underfloor heating  
must be correctly controlled with a  
thermostatic blending valve limiting the  
temperature of the circuits to approx. 50°C.  
The pipework from the boiler to the blending  
valve must be in copper or steel (protected  
from corrosion).  
PRIMARY SYSTEMS CONNECTIONS/VALVES:  
• All system connections, taps and mixing  
valves must be capable of sustaining a  
pressure up to 3 bar.  
• Radiator valves should conform to  
BS2767:10.  
• All other valves should conform to BS1010.  
• Thermostatic radiator valves (TRV’s) must be  
used on all radiators within the sleeping  
accommodation but not the radiator where  
the room thermostat is sited. This must be  
fitted with lockshield valves and left open.  
• A drain cock is required at the lowest point  
in the system.  
• An air vent is required at all the high points in  
the system.  
NOTE: The boiler is equipped with an automatic  
internal by-pass.  
SYSTEM FILL  
SHOWERS/BIDETS:  
• If a shower head can be immersed in water or  
comes closer than 25mm from the top edge  
of a bath or shower tray spill over level then  
an anti-siphon device must be fitted to the  
shower hose.  
• Bidets with direct hot and cold mains water  
can be used (with the approval of the local  
water authority) and must be the over rim  
flushing type with shrouded outlets to prevent  
the fitting of hand held sprays.  
TYPICAL SEALED SYSTEM  
A - Appliance expansion vessel -  
central heating  
B - Extra expansion vessel -  
central heating return  
C - Drain cock  
SEALED PRIMARY SYSTEM:  
• The CH sealed system must be filled using a  
WRAS approved filling loop or comply with  
the diagram opposite for system fill.  
• Where the system volume is more than 100  
litres or exceeds 2.65 bar at maximum  
heating temperature, an extra expansion  
vessel (B) must be fitted as close as possible  
to the appliance in the central heating return.  
• Pressurise the extra expansion vessel (B) to  
the same figure as the expansion vessel built  
into the appliance.  
R
R
P - Pressure relief discharge  
R - Radiators  
A
• Do not use galvanised pipes or radiators.  
R
R
B
C
P
C
10  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
WATER SYSTEMS & PIPEWORK  
CONDENSATE PIPEWORK  
CONDENSATE PIPEWORK:  
• The condensate pipe must be a minimum of  
22mmØ plastic pipe.  
• The condensate pipework must fall at  
least 50mm per metre towards the outlet  
and should take the shortest practicable  
route.  
• The pipework must follow one of the options  
shown opposite into an internal serviceable  
trap (min. 75mm) such as a sink/washing  
machine) or discharge direct into a vent  
stack (E) 450mm min. above pipe invert or  
into a gulley (D) below ground but above the  
water level.  
• Use waterproof pipe insulation in exposed  
positions and for external pipework.  
IMPORTANT: Ensure there are no  
blockages in the pipe run.  
1 Internal sink/washing machine drain  
2 Internal waste drainage system  
3 Soil/vent stack  
4 External drainage system  
5 External condensate absorption point  
A - Condensate from boiler  
B - Sink  
C - 22mmØ plastic condensate pipe  
D - Gulley  
E - Internal soil and vent stack  
F - Serviceable waste trap (75mm min)  
G - 300mm x 100mmØ sealed plastic tube  
H - Ground level  
J - Drainage holes 50mm from base of tube  
(12mmØ at 25mm centres) facing away from  
building  
K - Limestone chippings  
11  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
CONDENSATE PIPEWORK  
PRESSURE RELIEF PIPEWORK  
PRESSURE RELIEF PIPEWORK:  
IMPORTANT: The pressure relief valve  
is a safety device for the boiler and if  
activated may discharge boiling water  
steam through the relief valve drain  
pipe.  
Care should be taken when siting the  
outlet pipe so that it does not cause an  
obstruction or discharge above a  
window, entrance or other public access  
where it could cause a hazard.  
• The pressure relief drain pipe (M) from the  
boiler should be at least 15mm diameter  
copper pipe and run downwards away from  
any electrics or other hazard, preferably to an  
external drain or soakaway.  
• Pipe (M) should be finished with a partial  
bend, near the outlet to face the external wall  
(as shown) to help prevent freezing.  
M
L - Outside wall  
O,M - Drain pipe  
N - External drain  
L
O
N
12  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
PRESSURE RELIEF PIPEWORK  
SERVICING CLEARANCES  
VENTED COMPARTMENT  
BOILER LOCATION &  
CLEARANCES  
This boiler is only suitable for installing internally  
within a property at a suitable location onto a  
fixed, rigid non-combustible surface at least the  
same size as the boiler and capable of support-  
ing the boiler weight.  
COMPARTMENTS:  
Follow the requirements of BS6798 and  
BS5440 Part 2 and note:  
• Minimum clearances must be maintained  
• An access door is required to install, service  
and maintain the boiler and any ancilliary  
equipment.  
Using 100mm flue kit  
1080mm  
Using 125mm flue kit  
- 1110mm  
• If fitting the boiler into an airing cupboard  
use a non-combustible perforated material  
(maximum hole sizes of 13mm) to separate  
the boiler from the airing space.  
BOILER CLEARANCES:  
The diagram opposite shows the minimum  
space required to install and service the boiler.  
If a boiler is installed in a compartment with  
clearances less than shown in the tables oppo-  
site, ventilation is required. Refer to tables  
below for ventilation requirements.  
VENTILATION FREE COMPARTMENTS  
INSTALLATION CLEARANCES  
24 & 28 kW  
Vent  
position  
To room or  
internal space  
Direct to  
outside  
Ventilation Free Compartments Installation Clearances  
The suggested total unventilated compartment minimum clearances are:  
High  
level  
Minimum free  
area 122 cm2  
Minimum  
free area  
61 cm2  
Side  
Above  
Below  
Front (to removable door)  
Low  
level  
Minimum free  
area 122 cm2  
Minimum  
free area  
61cm2  
400mm  
170mm approx.  
(30mm above  
the elbow)  
200mm  
100mm  
(Note: Top and bottom clearances must not be reduced below these values as they are the  
minimum required for servicing).  
BOILER CLEARANCES - UNVENTILATED  
COMPARTMENTS:  
The tables opposite show the options for the  
minimum space required to install and service  
the boiler inside an unventilated compartment.  
If Side Clearances are Reduced  
Front clearance (to removable  
door) must be increased to:  
If total side clearance is Then overall height clearances  
OR  
reduced to:  
must be increased to (approx):  
350mm  
441mm  
523mm  
617mm  
727mm  
856mm  
1012mm  
1202mm  
129mm  
161mm  
200mm  
243mm  
295mm  
358mm  
434mm  
300mm  
250mm  
200mm  
150mm  
100mm  
50mm  
If Front Clearance is Reduced  
Total side clearance must be  
increased to:  
If front clearance (to  
removable door) is  
reduced to:  
Then overall height clearances  
must be increased to (approx):  
OR  
50mm  
25mm  
511mm  
596mm  
505mm  
569mm  
13  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
BOILER LOCATION & CLEARANCES  
BOILER LOCATION &  
CLEARANCES  
BATHROOMS:  
If the appliance is fitted in conjunction with a  
mechanical or RF mechanical timer, the  
appliance can only be fitted in zone 3 .  
1
1
2
Otherwise the appliance can be fitted in both  
zones 2 and 3 .  
2
3
3
See IEE wiring regulations.  
IMPORTANT: any switch or appliance  
control using mains electricity must not be  
able to be touched by a person using the  
bath or shower.  
Electrical switches, fused spur and socket  
outlets must not be situated in the  
bathroom.  
1
1
2
3
14  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
BOILER LOCATION & CLEARANCES  
PLUMBING MANIFOLD  
Gas Supply (alternative from above appliance) 22mm  
DHW OUT 15mm  
CH Flow 22mm  
CONNECTIONS:  
Heating System: 22mm compression fittings  
DHW IN (alternative from  
above appliance)  
15mm  
CH Return 22mm  
DHW:  
Gas:  
15mm compression fittings  
22mm compression fittings  
Use the fittings supplied in the Lit/Hardware  
pack.  
• If the boiler pipes are to be run behind the  
appliance ensure that the pipes pass through  
the slot in the yellow plastic guide (A). This is  
fitted to the boiler frame.  
Further guidance on pipe routing can be  
found printed on the boiler template  
(supplied with the boiler).  
*
A
Mains Gas Supply 22mm  
Mains Water (DHW IN) 15mm  
15  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
PLUMBING MANIFOLD  
FLUE TERMINAL POSITIONS  
• The flue must be fitted and terminated in  
accordance with the recommendations of  
BS5440 : Part 1.  
Minimum dimensions of flue terminal positions for balanced room sealed flues with  
fanned draught:  
• The flue must not cause an obstruction.  
• Discharge and any noise from the flue outlet  
must not cause a nuisance.  
• Flue gases have a tendency to plume and in  
certain weather conditions a white plume of  
condensation will be discharged from the flue  
outlet. This could be a nuisance, for example,  
near security lighting.  
• The air inlet/outlet duct and the terminal of  
the boiler must not be closer than 25mm to  
any combustible material.  
Detailed recommendations on protection of  
combustible materials are given in  
BS 5440:1.  
• A protective terminal guard must be fitted if  
the terminal is 2m or less above a surface  
to which people have access.  
The guard must be spaced equally (minimum  
50mm) around the flue and fixed to the wall  
with plated screws.  
DRWG. TERMINAL POSITION  
REF:  
DISTANCE  
A1  
B1  
C1  
D
E
Directly below an opening, air brick, opening windows, etc.  
300mm  
300 mm  
300 mm  
75mm  
Above an opening, air brick, opening window, etc.  
Horizontally to an opening, air brick, opening window, etc.  
Below gutters, soil pipes or drain pipes  
Below eaves  
200mm  
200mm  
150mm  
F2  
G
H
I
Below balconies or car port roof (lowest point)  
From a vertical drain pipe or soil pipe  
From internal or external corner or to a boundary alongside the terminal 300mm  
**  
Above ground, roof or balcony  
300mm  
J
From a surface or boundary facing the terminal  
From a terminal facing the terminal  
600mm  
**  
K
1200mm  
L2  
M
N
O
P
From an opening in the car port (e.g. door, window) into the dwelling 1200mm  
See Contact Information (inside front cover).  
Vertically from a terminal on the same wall  
Horizontally from a terminal on the same wall  
From a non combustible vertical structure on the roof  
Above intersection with the roof  
1500mm  
300mm  
*
*
1
In addition, the terminal should not be nearer than 150mm (fanned draught)  
to an opening in the building fabric formed for the purpose of accommodating  
Terminals adjacent to windows or openings on pitched  
and flat roofs.  
a built-in element such as a window frame.  
2
Not recommended.  
See instructions supplied with vertical flue kits.  
Care should be taken to ensure terminal siting  
The flue should not penetrate  
the shaded area.  
*
**  
does not cause a nuisance to adjacent properties.  
600mm  
600mm  
2000mm  
16  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
FLUE TERMINAL POSITIONS  
FLUE OPTIONS  
MAXIMUM FLUE VERTICAL  
START + 2 BENDS  
STANDARD FLUE HORIZONTAL  
A
• The diagrams (opposite) show the  
components used and the maximum flue  
length for each configuration of 100mm and  
125mm flues.  
• Shaded flue components indicate the  
standard 100mm horizontal flue.  
• Only straight flue sections can be reduced in  
length and cut.  
A
F
B
C
Ø100  
MAX 686 A x 1  
MIN 250 A x 1*  
Ø100 - 2600mm  
A x 1 + C x 2 + B x 4 +  
F x 1  
Ø125  
• The flue terminal end can be fitted from the  
inside or outside of the building.  
• Fixing kits are supplied with the flue extension  
kits.  
MAX 1070 A x 1  
MIN 250 A x 1*  
* Requires cutting  
Ø125 - 11000mm  
A x 1 + C x 2 + B x 13 +  
F x 1  
• Horizontal 125mm and Vertical 100mm and  
125mm flue kits are available with separate  
instructions. Contact your supplier or  
Worcester.  
MAXIMUM FLUE VERTICAL  
START + 3 BENDS  
MAXIMUM FLUE HORIZONTAL  
A
A
B
F
B
C
Ø100 - N/A  
Ø100 - 4600mm  
A x 1 + B x 5  
Ø125 - 9000mm  
A x 1 + C x 3 + B x 11 +  
F x 1  
Ø125 - 13000mm  
A x 1 + B x 13  
A - Standard horizontal flue (100mm diameter  
shown)  
B - Straight flue extension  
C - Flue bend 90°  
D - Flue bend 45°  
MAXIMUM FLUE VERTICAL  
WITH 2 x 45° BENDS  
MAXIMUM FLUE VERTICAL START + 1 BEND  
E - Vertical terminal (vertical adaptor supplied  
with terminal)  
F - Vertical adaptor (used with horizontal  
terminal)  
A
B
F
E
B
D
C
Calculating the flue length:  
Measure the total flue length required, noting  
that the maximum straight flue length including  
the terminal is:  
Horizontal 60/100mm: 4600mm  
Horizontal 80/125mm: 13000mm  
Vertical 60/100mm: 6400mm  
Ø100 - 4600mm  
Ø100 - 4400mm  
A x 1 + C x 1 + B x 5 +  
F x 1  
(including terminal)  
B x 5 + D x 2 + E x 1  
Ø125 - 13000mm  
A x 1 + C x 1 + B x 13 +  
F x 1  
Ø125 - 13000mm  
(including terminal)  
B x 13 + D X 2 + E x 1  
Vertical 80/125mm: 15000mm  
Then reduce the total straight flue length for  
each extra flue bend (excluding the flue elbow)  
by:  
MAXIMUM FLUE HORIZONTAL + 1 BEND  
2000mm for 90°  
1000mm for 45°  
VERTICAL FLUE WITH  
2 x 90° BENDS  
A
B
Flue Extension lengths:  
Horizontal & Vertical 60/100mm: 960mm  
Horizontal & Vertical 80/125mm: 1000mm  
E
C
B
C
Flue Terminal lengths:  
Ø100 - 2600mm  
Horizontal 60/100mm: 800mm including terminal  
Horizontal 80/125mm: 1200mm including terminal  
Vertical 60/100mm: 1140mm to top of terminal  
Vertical 80/125mm: 1365mm to top of terminal  
A x 1 + B x 3 + C x 1  
Ø100 - 2400mm  
(including terminal)  
B x 4 + C x 2 + E x 1  
Ø125 - 11000mm  
A x 1 + B x 11 + C x 1  
Ø125 - 11000mm  
(including terminal)  
B x 13 + C x 2 + E x 1  
17  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
FLUE OPTIONS  
UNPACKING WALL FRAME AND  
ANCILLARY ITEMS  
IIMPORTANT: All the previous Pre-Installation sections must be read  
and requirements met before starting boiler or flue installation.  
LIFTING AND CARRYING PRECAUTIONS:  
•
Lift only a manageable weight, or ask for  
help.  
•
When lifting or putting things down, bend  
the knees, and keep the back straight  
and feet apart.  
1
•
•
Do not lift and twist at the same time.  
Lift and carry objects close to the body  
A - Straps  
A
B
B - Outer carton  
C - Installer pack  
D - Bottom panel  
E - Wall mounting frame  
F - Wall template  
G - Inner packaging  
2
E
IMPORTANT HANDLING INSTRUCTIONS  
• It is advised that two people are used to carry  
the carton from the van to the point of delivery.  
• Once the carton has been delivered, the outer  
carton is removed first. Care should be taken  
when releasing the straps. If a sharp implement  
is used make sure the outer carton is not  
pierced and that the implement is used in such  
a way so that it may not cause personal injury.  
All sharp objects must be covered or the blade  
retracted after use and put away in a safe  
place. The wall mounting frame, Installer  
pack, template and bottom panel are now  
removed. Care should be taken when lifting the  
boiler from the base and the proper technique  
for safe lifting of any heavy object should be  
strictly observed.  
3
C
G
C
D
Additional requirements for roof space  
installation:  
F
• The boiler should be first unpacked before  
ascending ladder to loft space.  
• Two sets of steps should be used.  
• Two people should share the lifting of the  
boiler up to the loft hatch, where the boiler is  
entered into the loft space tilted and slid on its  
back into the loft.  
Once the appliance is removed from its  
packaging check the contents against the  
packing list.  
Before installing appliance ensure system has  
been cleaned as explained on page 8.  
ꢀ 1. Remove straps (A) and open the top of the  
boiler packaging.  
ꢀ 2. Remove template (F) and wall mounting  
frame (E) from the packaging.  
ꢀ 3. Remove boiler bottom panel (D) and  
installer pack (C).  
18  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
UNPACKING WALL FRAME AND  
ANCILLARY ITEMS  
WALL MOUNTING TEMPLATE  
FLUE OPENING  
A
X 4  
X 4  
CAUTION: Ensure there are no pipes,  
electric cables, damp proof courses or  
other hazards before drilling.  
SAFETY:  
All relevant safety precautions must be undertaken.  
Protective clothing, footwear, gloves and safety  
goggles must be worn as appropriate.  
USE APPROPRIATE  
FIXINGS FOR  
WEIGHT AND  
WALL TYPE  
FIXING THE MOUNTING FRAME:  
•
The boiler template shows the relative  
positions of the flue and the top and bottom  
fixing of the mounting frame.  
ꢀ Fix the template to the wall in the desired  
position (A).  
ꢀ Drill 4 holes for the wall mounting frame  
through the template (2).  
NOTE: The template has been sized to allow for  
minimum clearances of 5mm sides, 200mm  
base and 30mm above a Ø100mm flue elbow.  
REAR FLUE OUTLET  
•
The drawing (B) opposite shows the boiler  
template with the flue centre lines of both the  
100mm and 125mm flue systems.  
B
ꢀ Mark centreline of flue to be used (1); the  
external diameter of the hole can also be  
marked if required.  
189mm  
•
If a Ø100mm diameter flue is to be used,  
a125mm diameter hole is required. However, if  
using the weather sealing collar by pushing it  
through from inside the property, then a  
150mm diameter hole is required to  
accommodate this.  
• The terminal section of the 100mm flue has an  
inbuilt 3° angle.  
If extensions are to be added then the complete  
flue must rise at an angle of 3°.  
• The 125mm Ø flue system will require the flue  
to rise at an angle of 3°.  
ꢀ Drill hole using a core drill or similar.  
SIDE OUTLET:  
ꢀ Mark from the centre line of the wall template  
to the wall which the flue will pass through (3).  
ꢀ Allow for a rise of 52mm per metre length of  
flue, to give a 3° angle.  
ꢀ Clear any debris from the site.  
• A pre-filling kit 7 716 192 282 is available for  
installations where the boiler will not be fitted  
immediately to the heating system. This allows  
the heating system and mains water connec-  
tions to be filled and checked prior to boiler  
installation.  
2
This kit can be used in conjunction with the  
optional filling loop 7 716 192 281(not sup-  
plied with the boiler).  
19  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
WALL MOUNTING PLATE FLUE OPENING  
UNPACKING THE APPLIANCE  
UNPACKING THE APPLIANCE  
4
A - Outer carton  
B - Inner sleeve (unwraps from front)  
C - Packaging base  
5
D - Protective wrapping  
A
E - Appliance outer case  
F - Protective inner packaging  
F
ꢀ 4. Remove outer carton (A) and place  
safely away from the working area.  
ꢀ 5. With the outer packaging removed and  
the inner sleeve (B) still in place gently  
lay the boiler on its back.  
B
B
C
F
ꢀ 6. The boiler will lie at an angle to the  
floor to allow the boiler outer casing (E)  
to be removed. The inner sleeve (B)  
opens as shown. Remove the protective  
wrapping (D) and undo the four screws,  
two at the bottom of the boiler (H) and  
two at the top (H) (see diagrams 6.1 and  
6.2). Remove any packaging within the  
boiler and the packaging base (C).  
ꢀ 7. Stand boiler upright and remove the  
protective inner packaging (F) at the rear  
of the boiler.  
C
6.1  
E
6
6.2  
H
H
C
B
CAUTION: Caps fitted to pipes must be  
removed before hanging the boiler.  
F
D
7
F
20  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
UNPACKING THE APPLIANCE  
Do not lift by the  
air gas manifold.  
3
BOILER CONNECTIONS  
CAUTION: ISOLATE THE MAINS GAS  
SUPPLY BEFORE STARTING ANY WORK  
AND OBSERVE ALL RELEVANT SAFETY  
PRECAUTIONS.  
GAS AND WATER CONNECTIONS:  
ꢀ Remove template and secure the wall  
mounting frame to the wall with the fixings  
supplied.  
ꢀ System pipes may be run vertically upwards  
behind the boiler or below it. See  
Plumbing Manifold Section on page 15.  
A
E
A - CH flow (22mm), B - CH return (22mm),  
C - Gas inlet (22mm), D - Mains water inlet  
(15mm), E - DHW outlet (15mm)  
B
ꢀ 1. If using the optional filling loop 7 716 192  
281 (not supplied with the boiler) fit it  
before hanging the boiler on the wall frame.  
ꢀ 1A. Fit sealing washers to service valves  
before hanging boiler.  
NOTE: The bonded washer supplied is for the  
Gas connection only.  
IMPORTANT:  
Before hanging the boiler onto the wall  
mounting frame ensure that the pressure relief  
valve connection is in the DOWN position. This  
is located on the right hand side of the wall  
frame at the rear.  
ꢀ 2. Pull the extended tab/lever forward and  
H
down until there is no further travel.  
2
2 & 4  
ꢀ 3. Hang the boiler on to the wall mounting  
frame by the two brackets positioned left  
and right at the top rear of the appliance.  
Do not lift the appliance by the air gas  
manifold. There are two handling holes  
incorporated into the inner casing left and  
right in the lower section of the appliance.  
Handling  
Hole  
22mm 15m22mm  
1A  
IMPORTANT:  
The pressure relief connector must be  
repositioned after the boiler has been correctly  
mounted to the wall mounting frame.  
ꢀ 4. Push the lever on the pressure relief  
connector UP until the stop on the inside of  
the handle is over the shoulder of the metal  
bracket to secure in place.  
C
D
1
4
Stop in  
locked  
position  
21  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
BOILER CONNECTIONS  
BOILER CONNECTIONS  
F
5
CAUTION: ISOLATE THE MAINS GAS  
SUPPLY BEFORE STARTING ANY WORK  
AND OBSERVE ALL RELEVANT SAFETY  
PRECAUTIONS.  
GAS AND WATER CONNECTIONS:  
A - CH flow (22mm), B - CH return (22mm),  
C - Gas inlet (22mm), D - Mains water inlet  
(15mm), E - DHW outlet (15mm)  
ꢀ 5. Lower the control panel into the service  
position by removing the screw (F) from the  
retaining bracket.  
A
E
B
ꢀ 6. Make connections to the heating system.  
ꢀ Connect the gas supply to the boiler gas  
cock 22mm compression.  
ꢀ Connect mains water in and DHW out.  
ꢀ 7. Connect the expansion vessel flexible  
pipe to the hydraulic manifold situated left of  
the pump. It is necessary to remove and  
discard the gray plastic blanking plug (G)  
from the pressure vessel connection at the  
hydraulic manifold before securing the  
expansion vessel flexible pipe (H) in place  
with the wire retaining clip ( I ) .  
ꢀ 8. Connect the pressure relief drain pipe to  
15mm compression joint (J) using the  
compression nut and olive supplied in the  
hardware literature pack.  
H
7
G
I
J
6
C
D
H
I
H
A
E
C
D
B
22mm 15mm 22mm 15mm 22mm  
22  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
BOILER CONNECTIONS  
FLUE INSTALLATION  
WALL  
HORIZONTAL FLUE  
(60/100mm diameter)  
For vertical flues and 80/125mm horizontal flues,  
please refer to separate instructions supplied with  
the flue kit.  
189mm  
NOTE: to ease the assembly of flue components,  
apply silicone lubricant to sealing surfaces.  
The instructions for the 60/100mm diameter flue  
are shown below.  
93mm  
MEASURING THE FLUE (Standard Flue):  
ꢀ Measure from the outside wall to the centre  
line of the flue turret.  
ꢀ Subtract 93mm from the length L to give  
the correct dimension to the flue elbow  
connection.  
ꢀ The terminal section should be cut to this  
dimension, however it must not be cut  
shorter than 250mm.  
Edge of  
case  
200mm  
ꢀ After cutting, the end must be square and  
free from burrs to prevent damage to the  
flue seals.  
(250mm min)  
Turret  
Clamp  
Flue  
23  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
FLUE INSTALLATION  
FLUE INSTALLATION  
MEASURING THE FLUE (Extension Flue Kits):  
ONLY CUT EXTENDED FLUE LENGTHS  
ꢀ As with the Standard Flue measure from the  
outside wall to the centre line of the flue  
turret.  
ꢀ Subtract the length of the Standard Flue  
and turret (725mm) from length L .  
ꢀ Subtract the full length 1m extension(s)  
from the figure.  
Clamp  
Clamp  
ꢀ Cut one of the 1m extensions to the remainder.  
ꢀ Cut both tubes square taking care not to distort  
the tubes.  
ꢀ Remove any burrs.  
EXAMPLE:  
Length L  
Subtract Standard Flue+Turret  
Subtract Full Extension  
Cut Length  
=
2380mm  
— 686mm  
— 960mm  
734mm  
2380mm  
=
NOTE: The minimum length a flue extension  
can be cut to is 100mm  
734mm  
Cut Length  
Standard Flue  
Extension  
Required Length  
NOTE: Where extensions are reduced, cut  
length which DOES NOT contain the seal.  
Seal  
94mm  
94mm  
ADDITION OF FLUE BENDS:  
When flue bends are being used an allowance  
of 98mm per bend must be allowed from the  
centre line of the bend. In the example shown  
using a flue extension with 2 bends will  
achieve a total length of 1148mm.  
24  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
FLUE INSTALLATION  
FLUE INSTALLATION  
A - Standard Flue  
B - Internal Wall Seal  
C - External Wall Seal  
D - Clamp  
ASSEMBLING THE FLUE  
1
2
Slide inner collar (B) onto terminal (A)  
Additional extensions or bends:  
E - Extension Duct  
Push fit all extensions/bends/terminal  
together and secure connections with  
clamps (D). The slope of the terminal outlet  
must face downwards.  
C
FITTING THE FLUE  
A
B
3
4
Fit the terminal (A) through the flue opening  
in the wall, exposing the plastic outlet  
section to the outside and fit the outer  
flue collar ( C ) over the notches to secure.  
D
E
Assemble elbow to boiler using the three  
screws (see below).  
Note: Screws are in boiler not in flue kit.  
FITTING THE ELBOW:  
•
Flue elbow should push directly down and  
not be twisted into correct position.  
Apply silicone  
grease to seal  
This screw should  
be fitted last for  
easier installation  
ꢀ Remove the 3 inner flue tube retaining  
screws. The inner tube will be held in place  
in the appliance.  
ꢀ Fit turret onto appliance and retain with the  
three removed screws.  
NOTE: The clamping plate flat should be at  
the rear of the appliance.  
ADDITIONAL NOTES AND REMINDERS:  
• Ensure that all cut lengths are square and  
free from burrs.  
• The flue, when assembled, is fully sealed and  
components are pushed home.  
• The flue is set at an angle of 3° or 52mm per  
1m length.  
Flat at back  
This screw should  
be fitted last for  
rear exit  
25  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
FLUE INSTALLATION  
CONDENSATE CONNECTION  
CONDENSATE CONNECTION:  
Never terminate or discharge into any open  
source, including; sink, bath, shower, bidet,  
toilet etc.  
Note: any external condensate pipework  
should be protected with weather resistant  
insulation to help prevent freezing.  
• Ensure that the condensate drain is 22mm  
diameter plastic pipe. It must fall at least  
50mm per metre towards the outlet.  
• An adapter in 22mm pipe is contained in the  
fitting pack (A) along with sealing washer (B).  
B
A
26  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
CONDENSATE CONNECTION  
ELECTRICS  
1
2
A
CAUTION: ISOLATE THE MAINS  
B
ELECTRICITY SUPPLY BEFORE STARTING  
ANY WORK AND OBSERVE ALL  
RELEVANT SAFETY PRECAUTIONS  
Mains supply to the boiler must be through a  
fused double pole isolator situated adjacent  
to the appliance. The isolator must have a  
contact separation of 3mm minimum in all  
poles. External fuse rating 3A.  
3
4
C
ROOMSTAT  
ONLY  
When stripping wires always ensure copper  
strands do not fall into the control box.  
7
Access to electrical connections:  
Remove boiler casing to access control panel.  
D
1
Unscrew screw (A) and lower the control  
box into the horizontal position.  
ROOMSTAT  
2
Unscrew the three screws (B) in the control  
panel and pull off the connections cover.  
Unclip cable clamp (C).  
Cut off the tapered cable entry to fit cable  
diameter required.  
5
ROOMSTAT  
AND  
3
4
PROGRAMMER  
PROGRAMMER  
5
Turn cable retaining screw (D) anti-clockwise.  
ꢀ Run cable over the main crossbar and  
through the cable clamp (C), ensuring there  
is ample cable to reach the connectors.  
ꢀ Turn cable clamping screw (D) clockwise to  
secure cable.  
230V  
ꢀ After wiring to connectors is complete, snap  
cable clamp (C) into control box.  
MAINS  
SUPPLY  
6
8
6
Mains power 230v connection (ST10):  
FROSTSTAT  
ꢀ Separate wires from cable end and  
strip to 6mm  
ꢀ Connect LIVE wire to terminal (L)  
ꢀ Connect NEUTRAL wire to the terminal (N)  
ꢀ Connect EARTH wire to the bracket  
NOTE: Earth cable to be longer so that it pulls  
out last if mains cable is snagged.  
7
230V room stat/clock (ST10):  
The diagram shows the option of roomstat with  
programmer or roomstat only.  
ꢀ Remove link.  
ST10  
ST6  
ꢀ Connect LIVE supply to terminal (LS).  
ꢀ Connect SWITCHED LIVE to terminal (LR),  
NOTE: This is sometimes refered to as ‘call for  
heat’ or ‘heating load’.  
ꢀ Connect NEUTRAL to terminal (NS).  
NOTE: Some devices do not require this.  
8
Optional external frost stat connection (ST6):  
F1  
ꢀ Connect froststat cables to terminals (FS) and  
(FR). These are not polarity sensitive.  
9
Refit panels.  
F3  
F2  
27  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
ELECTRICS  
POSITION OF WIRED  
COMPONENTS  
28  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
POSITION OF WIRED COMPONENTS  
PRE-COMMISSIONING  
CHECKS  
1
A
D
B
CAUTION: ISOLATE THE MAINS  
SUPPLIES BEFORE STARTING ANY  
WORK AND OBSERVE ALL  
RELEVANT SAFETY PRECAUTIONS  
1
Check that the service and water pipes are  
connected to the correct position on the  
manifold.  
A - CH Flow (22mm)  
B - CH Return (22mm)  
C - Gas inlet (22mm)  
D - DHW (15mm)  
E - Water in (15mm)  
2
Check the gas type specified on the  
identification plate (F) matches that of the  
gas supply. Turn on the main gas supply,  
check the gas pipework, connections and  
rectify any leaks.  
3
4
Check that the condensate pipe has been  
connected to the syphon.  
J
Check pressure relief drain pipe (J) is  
correctly fitted and securely tightened.  
IMPORTANT: If the boiler is not to be  
commissioned immediately then:  
after successfully completing all of the  
checks and any rectification work,  
close the gas and water valves, shut off  
the gas supply and electrically isolate  
the boiler and label appropriately.  
C
E
A
D
C
E
B
22mm 15mm 22mm 15mm 22mm  
3
2
F
29  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
PRE-COMMISSIONING CHECKS  
FILLING THE SYSTEM  
1
Turn on the water main and open the  
system valves.  
2
3
Open all radiator valves.  
Fill the system via a WRAS approved filling  
loop to 1 bar then turn the valve anti-clock-  
wise to close.  
4
Vent (A) any air from the boiler heat  
exchanger using a suitable container to  
collect any water. Ensure tube outlet (B) is  
directed away from the fan or any other  
electrical component to prevent any water  
damage. Also place a suitable cover over  
the fan to prevent any spillage of water  
on to electrical connections. Ensure the  
cover is removed after venting.  
E
C
D
5
•
Vent all radiators, retighten when completed  
and check the system and correct any leaks.  
The boiler integral expansion vessel is pre-  
charged to 0.75 bar (equal to a static head  
of 7.5m (22ft). A Schraeder type valve is  
fitted to the expansion vessel to allow for  
pressure adjustment if required.  
A
•
If an extra expansion vessel is fitted to the  
central heating return, adjust this to the  
same pressure as the appliance internal  
expansion vessel, refer to separate instruc-  
tions with the extra expansion vessel.  
6
7
8
Briefly open the pressure relief valve to test  
its operation.  
If required increase system pressure back to  
1 bar.  
Rotate the adjustable pointer on the  
pressure gauge to record the set system  
pressure.  
B
9
Isolate and remove filling loop connection to  
system or if using the optional integral filling  
connection (C) (not supplied with the  
boiler) remove key (D) and place in  
its storage position (E) on the bottom cover  
of the boiler.  
• A pre-filling kit 7 716 192 282 is available for  
installations where the boiler will not be fitted  
immediately to the heating system. This  
allows the heating system and mains water  
connections to be filled and checked prior to  
boiler installation.  
This kit can be used in conjunction with the  
optional filling loop 7 716 192 281(not sup-  
plied with the boiler).  
30  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
FILLING THE SYSTEM  
STARTING THE APPLIANCE  
IMPORTANT: Never run the appliance  
when the appliance/system is empty or  
partially filled.  
Switching the appliance on/off:  
1 ꢀ Turn on mains power supply  
ꢀ Turn on any external controls  
Set the thermostatic radiator controls to  
maximum temperature  
Set the clock/programmer to continuously  
ON and the room thermostat to maximum  
temperature  
2
A - On/off button  
B - On/off and fault indicator (BLUE)  
C - Central heating temperature control  
D - Burner indicator (GREEN)  
E - Reset button  
F - Service button  
G - ECO button  
H - System pressure gauge  
I - Cover or optional programmer  
ꢀ
Press power button (A) and the power  
on indicator (B) illuminates BLUE.  
3 ꢀTurn the boiler thermostat control (C) to  
maximum. The burner on indicator (D)  
illuminates GREEN when the burner  
has lit.  
4 ꢀ If the boiler fails to light the BLUE power  
indicator (B) and reset button (E) will  
flash alternately.  
To reset press and hold the reset button  
(E) for 2 seconds. The boiler will be  
reset.  
I
CAUTION: DO NOT PRESS POWER  
INDICATOR (B) TO RESET BOILER.  
A
H
E
D
F
G
C
B
31  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
STARTING THE APPLIANCE  
WATER TREATMENT  
5
A
1
IMPORTANT: Debris from the system  
can damage the boiler and reduce  
efficiency. Failure to comply with the  
guidelines for the use of water  
treatment with the appliance will  
invalidate the appliance warranty.  
J
B
K
ENSURE THAT THE SYSTEM HAS BEEN  
CLEANED AS ON PAGE 8 OF THESE  
INSTRUCTIONS.  
C
FLUSHING (Central Heating):  
1
Switch off the boiler (A).  
2
3
4
ꢀ Open all drain cocks (B) and drain the  
D
system (C) while the appliance is hot.  
L
2
Close drain cocks (D) and add a suitable  
flushing agent (E) at the correct strength for  
the system condition in accordance with the  
manufacturer's instructions.  
E
3
4
Run the boiler/system at normal operating  
temperature (F) for the time stated by the  
manufacturer of the flushing agent (G).  
Drain (H) and thoroughly flush the system to  
remove the flushing agent and debris ( I ).  
INHIBITOR (Central Heating):  
7
5
Check drain cocks are closed ( J ) and all  
radiator valves are open (K) before adding a  
suitable*inhibitor (or combined inhibitor/anti-  
freeze if the system is exposed to freezing  
conditions) to the heating system water (L) in  
accordance with the manufacturers instructions.  
Fill system via a WRAS approved filling loop  
to between 1 and 2 bar.  
Vent all radiators; retighten vents when  
complete (M). Vent any air from the boiler  
heat exchanger using a suitable container to  
collect any water (N).  
M
F
G
6
7
N
ꢀ Ensure tube outlet (O) is directed away  
from the fan or any other electrical  
component to prevent damage. Also  
place a suitable cover over the fan to  
prevent any spillage of water onto  
electrical connections. Ensure the cover  
is removed after venting.  
O
H
8
Vent all radiators (P).  
I
ꢀ Re-pressurise if necessary to 1bar (Q).  
P
ꢀ Set all controls to maximum (R).  
8
ꢀ Record the date when the inhibitor was  
added to the system on the guarantee card.  
NOTE: The concentration level of inhibitor in  
the system should be checked every 12  
months, or sooner if system content is lost.  
J
The addition of sealing agents to the system  
water is not recommended as this can cause  
problems with deposits left in the heat exchang-  
er.  
KEY  
Q
Valve  
R
Flushing  
Agent  
* compatible with aluminium. The pH  
value of the system water must be  
less than 8 or the appliance guarantee  
will be invalidated.  
Inhibitor  
32  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
WATER TREATMENT  
COMMISSIONING  
NOTE: When running in the service  
mode, the boiler will operate both  
the central heating and the domestic  
hot water circuits. This is to allow  
sufficient time for this part of the  
commissioning procedure. It will be  
necessary to run water through the  
domestic hot water circuit to ensure  
that the boiler will not cycle on low  
heating demands.  
THE COMBUSTION FOR THE APPLIANCE  
IS FACTORY SET.  
NO ADJUSTMENT IS REQUIRED IF THE  
GAS INLET PRESSURE IS CORRECT.  
CHECKING GAS INLET PRESSURE:  
The inlet pressure to the appliance must be  
checked using the following procedure:  
SETTING THE BOILER TO MAXIMUM:  
1
Press service button (F) for 10 seconds and  
set Central Heating temperature to maximum.  
The service button will illuminate continually  
and the blue power indicator will flash quickly.  
•
MEASURING THE INLET PRESSURE:  
2
Slacken the screw in the inlet pressure test  
point and connect a manometer.  
ꢀ Measure the pressure with the boiler  
running at maximum.  
ꢀ Check the gas supply working pressure at  
the gas valve inlet point is not less than:  
N.G. 18.5 mbar  
L.P.G. 37 mbar  
ꢀ The gas rate should be measured at the  
gas meter after 10 minutes operation at  
maximum. See technical data section at the  
front of this manual.  
I
ꢀ Ensure inlet pressure is satisfactory with all  
other gas appliances working.  
ꢀ Replace controls cover. NOTE: This boiler is  
designed with a differential of 20°C across  
the heating system.  
A
H
E
D
F
ꢀ If pressure is satisfactory press the  
G
IMPORTANT: Do not continue  
commissioning until the correct  
gas pressure is achieved.  
service button (F) again and the boiler  
will return to normal operation.  
If left in the service mode the control will  
return to normal operation after 15 minutes.  
C
•
ꢀ Re-seal the screw in the gas inlet pressure  
test point.  
DOMESTIC HOT WATER:  
Controlling the hot water temperature  
The hot water temperature is fixed at 55°C.  
B
DOMESTIC HOT WATER PRE-HEAT:  
Pre-heat reduces the time taken to produce hot  
water at the tap and is controlled by the ECO  
button (H).  
A - On/off button  
B - On/off and fault indicator (BLUE)  
C - Central heating temperature control  
D - Burner indicator (GREEN)  
E - Reset button  
ꢀ Press the ECO button to select either:  
When the ECO button is not illuminated the  
boiler will be in pre-heat mode (which will  
reduce the time taken to produce hot water at  
the tap).  
F - Service button  
G - ECO button  
Inlet Test Nipple  
OR  
H - System pressure gauge  
I - Cover or optional programmer  
When the ECO button is illuminated the boiler  
will be in economy mode with pre-heat no  
longer active.  
33  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
COMMISSIONING  
FINISHING COMMISSIONING  
The boiler has been factory set, so there  
should be no need to adjust any controls.  
REPLACE OUTER CASING:  
1
Replace outer casing making sure that the  
securing points are properly located.  
ꢀ Replace top two screws (A).  
ꢀ Retighten bottom two screws (B).  
A
INSTALLING BOTTOM PANEL:  
A
2
The bottom panel slides onto two ledges  
(C) either side of the boiler frame.  
ꢀ Hold the panel up against the underside of  
the boiler and slide towards the rear until it  
is fully engaged.  
HANDOVER:  
ꢀ Complete the Benchmark checklist.  
NOTE: The Benchmark Checklist can be  
found at the rear of these instructions.  
ꢀ Open the facia cover by gently pressing the  
centre top of the cover (D).  
ꢀ Set up the controls and show the user how  
to operate all the controls shown in the User  
Guide.  
B
B
ꢀPlace the user guide into the tray (E) on the  
inside of the facia cover.  
ꢀ If the appliance is unused and exposed to  
freezing conditions, shut off all the mains  
supplies and drain the system and boiler.  
C
D
A
C
C
C
E
34  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
FINISHING COMMISSIONING  
INSPECTION AND SERVICE  
CAUTION: TURN OFF THE GAS SUPPLY AND ISOLATE THE MAINS  
SUPPLIES BEFORE STARTING ANY WORK AND OBSERVE ALL  
RELEVANT SAFETY PRECAUTIONS.  
IMPORTANT: Any service work  
must be carried out by competent  
registered engineers such as  
British Gas or Corgi registered  
personnel.  
IMPORTANT: AFTER REPLACEMENT OF ANY COMPONENTS ALWAYS  
CHECK FOR GAS SOUNDNESS WHERE RELEVANT AND CARRY OUT  
FUNCTIONAL CHECKS AS DESCRIBED IN COMMISSIONING.  
ANY O-RING OR GASKET THAT APPEARS DAMAGED MUST BE  
REPLACED.  
ꢁ
To ensure the continued efficient operation  
of the appliance it must be checked at  
regular intervals.  
1
ꢁ
The frequency of servicing will depend upon  
the particular installation conditions and  
usage. However, an annual service is  
recommended .  
ꢁ
ꢁ
The extent of the service required by the  
appliance is determined by the operating  
condition of the appliance when tested by  
fully qualified engineers.  
The service interval record sheet at the rear  
of these instructions must be completed  
after each service.  
2
Inspection  
1
Check that the terminal and the terminal  
guard, if fitted, are clear and undamaged.  
If the appliance is in a compartment or  
cupboard check that the specified service  
space around the appliance is clear.  
Check all the joints and connections in the  
system and remake any that show signs of  
leakage. Refill and re-pressurise if  
applicable as described in Commissioning.  
Operate the appliance and take note of any  
irregularities.  
2
3
ꢀ
Refer to Fault Finding for rectification  
procedures.  
3
35  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
INSPECTION AND SERVICE  
INSPECTION AND SERVICE  
1.  
1.1  
1.2  
Component Access  
1. Removing outer case  
A
1. Remove bottom panel by pulling it forward  
and off.  
B
1.1 Undo and remove 2 screws (A) securing  
boiler casing at the top of the appliance.  
1.2 Undo but do not remove the 2 screws  
(B) securing boiler casing at the bottom of  
the appliance.  
1.3  
1.3 Pull case forward and remove.  
2. Adjusting boiler control to  
service position  
2.1 Remove screw (C) securing control.  
2.2 Gently pull forward until it comes to  
rest in service position.  
2.1  
C
2.2  
Primary Heat Exchanger  
There is a special accessory kit available  
specifically designed for cleaning the  
heat exchanger. If required order  
7 716 192 312.  
3
Check fan pressure at the test point next to  
the fan using an electronic manometer.  
The boiler must be run at maximum output.  
Pressure will read negative and be greater  
than:  
ꢀ
Natural gas  
LPG  
24i junior - 3.1 mbar 24i junior - 3.6 mbar  
28i junior - 3.9 mbar 28i junior - 4.6 mbar  
ꢀ
Pressures measured below these figures  
will indicate that the heat exchanger will  
require cleaning.  
36  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
INSPECTION AND SERVICE  
3
INSPECTION AND SERVICE  
Setting Boiler to Maximum.  
NOTE: When running in the service mode, the  
boiler will operate both the Central Heating and  
DHW circuits. This is to allow sufficient time for  
the setting procedure.  
It will be necessary to run water through the  
DHW circuit to ensure that the boiler will not  
cycle on low heating demands.  
A - On/off button  
B - On/off and fault indicator (BLUE)  
C - Central heating temperature control  
D - Burner indicator (GREEN)  
E - Reset button  
F - Service button  
G - ECO button  
H - System pressure gauge  
I - Cover or optional programmer  
1
Press and HOLD service button (F) for 10  
seconds and set Central Heating temperature  
to maximum.  
•
•
The service button will illuminate continually  
and the blue power indicator will flash quickly.  
The boiler will stay in this mode for 15  
minutes unless the service button is pressed  
again.  
1
2
Pull the cover off and connect a manometer  
to the fan pressure test point.  
I
ꢀ After measurement replace test point cover.  
Pressure will read negative and be greater than:  
Natural gas  
LPG  
24i junior - 3.1 mbar  
28i junior - 3.9 mbar  
24i junior - 3.6 mbar  
28i junior - 4.6mbar  
A
H
•
Pressures measured below these figures  
will indicate that the heat exchanger will  
require cleaning.  
E
D
F
G
There is a special accessory kit available  
specifically designed for cleaning the  
heat exchanger. If required order  
7 716 192 312.  
C
2
B
37  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
INSPECTION AND SERVICE  
INSPECTION AND SERVICE  
COMBUSTION TESTING MUST BE CARRIED  
OUT BY A COMPETENT PERSON. IT MUST  
NOT BE ATTEMPTED UNLESS THE PERSON  
CARRYING OUT THE COMBUSTION CHECK  
IS EQU I PPE D WITH  
A
COM B USTION  
ANALYSER CONFORMING TO BS 7927 AND  
IS COMPETENT IN IT’S USE.  
IMPORTANT: IF THE JOINT  
BETWEEN THE AIR/GAS MANIFOLD  
AND THE HEAT EXCHANGER IS  
DISTURBED THE SEALING GASKET  
MUST BE REPLACED.  
1
B
To Clean the Heat Exchanger  
1
With outer case and base panel removed and  
the power isolated from the appliance,  
remove the cover panel (A) by removing the  
retaining screw (B).  
A
2
ꢀ
Remove clip (C) from gas valve outlet.  
Pull gas adjustment assembly (D) free from  
the plastic connection on the gas valve.  
Pull gas adjustment assembly (D) forward to  
clear case.  
ꢀ
Removing Siphon  
3.1 Undo plastic nut (E) on the siphon outlet.  
Drop condensate tube away from siphon.  
3.2 Remove hose (F).  
3.3 Remove siphon  
Siphon  
ꢁ The siphon body is transparent so contents  
can be examined for any blockage.  
ꢀ
If necessary flush with clean water.  
3.1  
3.3  
3.2  
E
F
2
D
C
38  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
INSPECTION AND SERVICE  
INSPECTION AND SERVICE  
5
E
4
5
Remove electrical connector from fan.  
Undo and remove securing nut (E) from the  
top of the heat exchanger.  
6
7
Remove stainless steel viewing mirror (F).  
Rotate fan and air/gas manifold assembly (G)  
around the top of the heat exchanger until it  
stops at the lug.  
ꢀ
Lift up assembly and remove from boiler.  
Disconnect spark electrode and flame sensor  
connections (J).  
8
6
ꢀ
ꢀ
Remove clamping plate (K).  
Remove spark/flame electrode assembly  
from boiler.  
F
ꢀ
Remove seal from the top of the heat  
exchanger  
8
K
4
J
7
G
39  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
INSPECTION AND SERVICE  
Q
INSPECTION AND SERVICE  
9
Remove burner (L).  
Remove top baffle (M).  
Remove baffle (N).  
9
ꢀ
ꢀ
ꢀ
Remove the two hexagon headed screws (O)  
retaining the access cover (P) on the sump.  
Access the heat exchanger flue ways by  
inserting the cleaning brush (7 716 192 312)  
through the top access hole in the casing (Q).  
Clean heat exchanger flue ways (R) using the  
cleaning brush (7 716 192 312) removing  
any debris from the access point in the sump.  
ꢀ
ꢀ
Small  
tab  
M
N
R
Clean around sealing surface on sump and  
replace access cover (P). Using a suitable  
container to collect water from syphon  
connection at the base of the boiler flush  
heat exchanger with water.  
ꢀ
ꢀ
Re-assemble ensuring that the lower baffle  
(N) and the top baffle (M) are refitted  
correctly.  
When re-fitting the burner ensure that it fits  
centrally within the heat exchanger and  
location tabs are situated in location holes.  
Ensure seal is replaced with new seal  
and is correctly fitted.  
ꢀ
ꢀ
ꢀ
Check the syphon unit for blockage before  
refitting to boiler.  
Reassemble and check combustion as  
stated in the gas conversion section.  
NOTE: To show the heat exchanger more  
clearly it has been shown external to the  
appliance  
P
THE BAFFLES (N) AND (M) MUST  
BE REFITTED INTO THE HEAT  
EXCHANGER AS SHOWN IN 9.  
FAILURE TO DO SO MAY RESULT  
IN DAMAGE TO THE BOILER  
0
IMPORTANT: IF THE JOINT  
BETWEEN THE AIR/GAS MANIFOLD  
AND THE HEAT EXCHANGER IS  
DISTURBED THE SEALING GASKET  
MUST BE REPLACED.  
40  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
INSPECTION AND SERVICE  
REPLACEMENT OF PARTS  
CAUTION: TURN OFF THE GAS SUPPLY AND ISOLATE THE MAINS  
SUPPLIES BEFORE STARTING ANY WORK AND OBSERVE ALL  
RELEVANT SAFETY PRECAUTIONS.  
1. Removing outer case  
1.1 Undo 4 screws (A) securing boiler casing.  
1.2 Pull case forward and remove.  
IMPORTANT: AFTER REPLACEMENT OF ANY COMPONENTS ALWAYS  
CHECK FOR GAS SOUNDNESS WHERE RELEVANT AND CARRY OUT  
FUNCTIONAL CHECKS AS DESCRIBED IN COMMISSIONING.  
ANY O-RING OR GASKET THAT APPEARS DAMAGED MUST BE  
REPLACED.  
ꢀ
To remove bottom tray, pull forward on the  
tag on the underside of the tray.  
The following components can be  
replaced with the outer case  
removed:  
Primary sensor  
Overheat thermostat  
1.1  
1.2  
Flue limit thermostat  
A
2. Primary sensor  
ꢀ
Remove electrical connection (B) by pulling  
upwards. Squeeze retaining clip on plastic  
moulding (C) and pull sensor (D) upwards  
until clear of pocket in heat exchanger.  
Coat new sensor with heat conductive  
paste and replace.  
A
ꢀ
3. Overheat thermostat  
ꢀ
ꢀ
ꢀ
Remove two electrical connectors from  
thermostat.  
Slacken and remove fixing screw and  
thermostat.  
When replacing ensure thermostat sits  
correctly on surface of the casting with the  
left hand side of thermostat siting up  
against the shoulder.  
2
3
4
B
C
D
NOTE: It is essential that the mating surface of  
the thermostat is coated with heat conductive paste.  
4. Flue overheat thermostat  
ꢀ
Remove electrical connections.  
Unscrew thermostat from flue.  
ꢀ
41  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
REPLACEMENT OF PARTS  
REPLACEMENT OF PARTS  
5.1  
5.2  
The following components require  
the control to be moved in to the  
service position:  
Gas valve  
Siphon  
PCB fuse  
A
Transformer  
5. Moving boiler control to service  
position  
5.1 Remove screw (A) securing control.  
5.2 Gently pull forward.  
6. Gas valve  
7
6.1  
ꢀ
Isolate gas supply at boiler gas cock.  
6.1 Remove wire clip from gas valve outlet then  
pull gas adjustment assembly free from  
plastic connector and pull forward clear of  
case.  
6.2 Undo bottom gas connection to gas valve.  
6.3 Undo two securing screws (C) on the  
underside of casing.  
ꢀ
ꢀ
ꢀ
Pull valve up and forward out of boiler.  
Disconnect electrical connections.  
Replace valve with new seals and check for  
gas soundness.  
D
Note: The valve will require setting; follow  
procedure “Setting the gas/air ratio” in the gas  
conversion section.  
6.2  
7. Gas adjuster  
ꢀ
ꢀ
ꢀ
Isolate gas supply at boiler gas cock.  
Repeat step 6.1 above.  
Twist retaining clip (D) to release then  
remove clip and tube.  
ꢀ
Refit new adjuster and secure with clip.  
8. Siphon  
8.1 Undo plastic nut (E) on the siphon outlet.  
Drop condensate tube away from siphon.  
8.2 Remove hose (F).  
8.3 Remove siphon.  
6.3  
C
8.1  
8.3  
8.2  
E
F
42  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
REPLACEMENT OF PARTS  
REPLACEMENT OF PARTS  
9
9. Access to boiler control components  
ꢀ
Remove 3 screws (A) and remove cover  
from control.  
A
10. PCB fuse  
ꢀ
Remove fuse F1(B) from the PCB and  
replace.  
ꢀ
There is a spare fuse clipped into the  
underside of the electrical cover.  
11.Transformer / PCB  
ꢀ
Disconnect all electrical connections from  
the control.  
ꢀ
Remove 5 screws (C) retaining the rear  
panel of the control and remove panel.  
10  
B
Spare Fuse order  
T1.6L 250V F2  
T2.5H 250V F1  
T500L 250V F3  
11  
C
C
43  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
REPLACEMENT OF PARTS  
REPLACEMENT OF PARTS  
12  
A
12. Replacing control  
The control is supplied within its plastic  
housing. The complete unit must be replaced.  
ꢀ
Remove ALL electrical connections from  
the control PCB including where cables run  
through restraints. These can be unclipped  
from the plastic moulding noting their  
position.  
ꢀ
Remove the code plug (B). The code plug  
should be left attached to the frame of the  
boiler by its plastic safety thread.  
B
12.1 Remove the 3 screws (C) retaining the  
front facia making sure to support the facia  
when removing the last screw.  
12.2 Using a suitable tool (D), press the button  
(E) upwards and slide the control support  
bracket (F) to the left.  
12.1  
C
C
12.3 Support the control and unclip control  
support cable (G) from the boiler frame.  
ꢀ
Remove the support cable and fit to the  
new control.  
C
ꢀ
Remove appropriate cable restraints from  
the new control box.  
ꢀ
ꢀ
Fit control to the boiler.  
Re-connect support cable to the boiler and  
all electrical connections to the new control.  
IMPORTANT: ENSURE CODE PLUG  
IS RE-FITTED TO THE NEW  
CONTROL. IF THIS IS NOT DONE  
THE BOILER WLL INDICATE  
ERROR AND WILL NOT FUNCTION.  
12.2  
F
E
F
D
E
12.3  
G
44  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 12i System/24i System  
8 716 107 375b (07/05)  
REPLACEMENT OF PARTS  
REPLACEMENT OF PARTS  
13.1  
A
The following components require  
the air / gas manifold and fan  
assembly to be removed:  
Pressure switch  
Fan  
Electrode assembly  
Burner  
Heat exchanger  
IMPORTANT: IF THE JOINT  
BETWEEN THE AIR/GAS MANIFOLD  
AND THE HEAT EXCHANGER IS  
DISTURBED THE SEALING GASKET  
MUST BE REPLACED.  
13.2  
B
IMPORTANT: AFTER REASSEMBLY  
THE COMBUSTION MUST BE  
CHECKED USING THE PROCE-  
DURE IN THE SECTION “SETTING  
THE GAS AIR RATIO”. MEASURE-  
MENT AND SETTING (IF NECES-  
SARY) OF THE GAS RATIO MUST  
NOT BE ATTEMPTED UNLESS THE  
PERSON IS EQUIPPED WITH A  
COMBUSTION ANALYSER CON-  
FORMING TO BS 7927 AND IS COM-  
PETENT IN ITS USE.  
13.3  
13. Air / gas manifold and fan  
assembly  
ꢀ
Remove electrical connector from fan.  
Remove wire clip from gas valve outlet then  
pull gas adjustment assembly free from  
plastic connector and pull clear of case  
(see 6.1).  
ꢀ
13.1 Undo and remove securing nut (A) from the  
top of the heat exchanger.  
13.2 Remove stainless steel viewing mirror (B).  
13.3 Rotate fan and air/gas manifold assembly  
(shaded) around the top of the heat  
exchanger until the lug on the air/gas  
manifold is visible.  
14.4  
ꢀ
Lift up assembly and remove from boiler.  
14. Pressure switch  
14.1 Remove electrical connections (C).  
14.2 Slacken top retaining screw and remove  
bottom screw. (D).  
F
14.3 Remove tube (E).  
14.4 Remove 2 screws (F) retaining pressure  
switch to bracket.  
ꢀ
Refit new pressure switch to bracket.  
IMPORTANT: ENSURE TUBE IS  
REFITTED TO PRESSURE SWITCH  
14.1  
14.2  
14.3  
E
D
C
45  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
REPLACEMENT OF PARTS  
REPLACEMENT OF PARTS  
15.1  
15.2  
15. Fan  
15.1 Remove 3 screws (A) retaining mixing  
chamber.  
B
15.2 Remove 2 screws (B) retaining the fan to  
the air/gas manifold.  
15.3 Remove screw (C) retaining plate and  
remove.  
A
ꢀ
Re-assemble with new fan ensuring seals  
are correctly fitted.  
16. Electrode assembly  
ꢀ
Disconnect spark electrodes and flame  
sensor connection.  
15.3  
ꢀ
ꢀ
Remove clamping plate (D).  
Remove spark/flame electrode assembly (E)  
from heat exchanger.  
16  
C
17. Burner  
ꢀ
Remove seal (F) from the top of the heat  
exchanger.  
Remove burner (G).  
Replace new burner in correct position.  
Ensure that burner tab fits correctly into hole.  
Ensure that the seal is replaced with a new one.  
D
ꢀ
ꢀ
ꢀ
ꢀ
E
18. Heat Exchanger  
ꢀ
Isolate flow and return valves then drain the  
boiler.  
Remove siphon.  
17  
ꢀ
18.1 Remove clip from plastic elbow on the flow  
pipe and pull flow pipe away from heat  
exchanger.  
18.2 Remove plastic nut from the bottom of  
the boiler.  
F
18.3 Rotate lever to release return pipe.  
18.4 Undo flue connection from sump.  
G
ꢀ
Pull heat exchanger assembly up to clear.  
Reassemble and check combustion as  
stated in the gas conversion section.  
ꢀ
IMPORTANT: IF THE JOINT  
BETWEEN THE AIR/GAS MANIFOLD  
AND THE HEAT EXCHANGER IS  
DISTURBED THE SEALING GASKET  
MUST BE REPLACED.  
18.4  
18.2  
18.3  
18.1  
H
46  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
REPLACEMENT OF PARTS  
REPLACEMENT OF PARTS  
19. Diverter valve motor  
19.1  
ꢀ
Insure the appliance is in service mode  
(there is no need to drain the appliance).  
Disconnect the electrical connector from the  
diverter valve motor.  
A
ꢀ
18.1 Pull the motor assembly (A) towards you. The  
assembly will slide free from the valve.  
ꢀ
To refit, follow the above in reverse.  
20. Diverter valve  
ꢀ
Ensure the appliance has been fully drained.  
Disconnect the electrical connector from the  
diverter valve motor.  
ꢀ
ꢀ
Undo the two screws holding the valve to the  
plastic housing.  
20.1 Withdraw the valve (B) and clean the valve  
chamber if necessary.  
20.1  
ꢀ
To refit, follow the above in reverse. Ensure  
any seals that have been disturbed are  
renewed.  
21. Auto air vent  
B
ꢀ
Ensure the appliance has been fully drained.  
21.1 Use a screwdriver or similar to rotate the air  
vent anticlockwise.  
21.2 Lift the air vent (C) out of the housing and  
remove.  
ꢀ
To refit, follow the above in reverse.  
22. DHW temperature sensor  
ꢀ
Ensure the domestic hot water circuit is fully  
drained (see draining the domestic hot water).  
Disconnect the electrical connection from  
the sensor.  
ꢀ
22.1 Withdraw the spring clip.  
22.2 Withdraw the sensor (D) from the housing.  
21.1  
21.2  
ꢀ
To refit, follow the above in reverse.  
C
22.1  
22.2  
D
47  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
REPLACEMENT OF PARTS  
23.1  
REPLACEMENT OF PARTS  
23.2  
A
A
23. Pump head  
ꢀ
Ensure the boiler is fully drained (see  
draining the appliance).  
ꢀ
Disconnect the electrical connection from  
the bottom of the pump.  
23.1 Remove the four Allen bolts (A) securing the  
pump at each corner.  
23.2 Gently pull the pump towards you and  
remove.  
ꢀ
To refit, follow the above in reverse.  
Pressure gauge  
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
Ensure the appliance has been fully drained  
(see draining the appliance).  
Withdraw the spring clip from the pressure  
sensing head housing.  
Undo the nut on the rear of the pressure  
gauge.  
Remove the pressure sensing head and  
pressure gauge capillary from the housing.  
To refit, follow the above in reverse. DO NOT  
omit the washer from the capillary when  
fitting a replacement gauge.  
24.1  
24. Flow sensor, flow restrictor  
housing and filter  
ꢀ
ꢀ
ꢀ
Ensure the domestic hot water circuit is fully  
drained (see draining the domestic hot water).  
Disconnect the electrical connection to the  
turbine.  
Remove the spring clip from the housing and  
move the brass pipe to one side.  
24.1 Withdraw the flow sensor and filter from the  
25.1  
housing.  
ꢀ
Using the cartridge tag, withdraw the flow  
restrictor housing. If the regulator housing  
has become stuck, a pair of long nosed pliers  
may be used to grip the housing.  
ꢀ
To refit, follow the above in reverse. Ensure  
any seals that have been disturbed are  
renewed.  
25. Flow regulator  
ꢀ
Remove the flow restrictor housing (See  
Removing the flow sensor, flow restrictor  
housing and filter).  
25.1 Using a small Allen key or similar, push the  
flow restrictor cartridge out of it’s housing.  
ꢀ
To refit, follow the above in reverse. Ensure  
any seals that have been disturbed are  
renewed.  
26.1  
26.2  
26. Drain tap  
ꢀ
Ensure the appliance has been fully drained.  
26.1 Rotate the drain tap fully anticlockwise.  
26.2 Withdraw the drain tap from its housing  
ꢀ
To refit, follow the above in reverse. Ensure  
any seals that have been disturbed are  
renewed.  
48  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
REPLACEMENT OF PARTS  
REPLACEMENT OF PARTS  
27.1  
27. Hydraulic Block  
ꢀ
ꢀ
ꢀ
Ensure the appliance has been fully drained  
(see draining the appliance).  
Disconnect the electrical connections to the  
NTC, Turbine and pump.  
Undo the nuts securing the copper water  
pipes to the manifold (there is no need to  
remove the gas pipe)  
ꢀ
ꢀ
Release the spring clips securing these  
water pipes to the plastic housing and  
remove the pipes.  
Release the spring clip securing the  
expansion vessel pipe to the plastic housing  
and remove the pipe.  
ꢀ
ꢀ
Undo the nut securing the pressure gauge to  
its bracket and remove the gauge.  
Release the locking devices that secure the  
two copper water pipes leading to the  
combustion chamber by squeezing the two  
tabs together and rotating anticlockwise  
(viewed from above).  
27.2  
ꢀ
Remove the rubber pipe connecting the  
sump and remove the syphon. NOTE: this is  
not essential but makes the removal of the  
block easier.  
27.1 Undo the two screws securing the hydraulic  
block to the chassis (located top left / top  
right of the housing)  
27.2 Lift the left hand side of the block slightly,  
then manoeuvre the block out, starting with  
the right hand side.  
ꢀ
Take care not to snag the harness or  
pressure gauge bracket.  
NOTE: the block will still contain a small amount  
of water, which will spill if the block is tilted.  
ꢀ
To refit, follow the above in reverse. Ensure  
any seals that have been disturbed are  
renewed.  
28. CH pressure relief valve  
ꢀ
Remove the hydraulic block from the boiler  
(See Removing the Hydraulic Block).  
28.1 Remove the spring clip from the Pressure  
relief valve housing.  
28.2 Withdraw the pressure release valve (A) from  
its housing.  
ꢀ
To refit, follow the above in reverse. Ensure  
any seals that have been disturbed are  
renewed.  
28.1  
28.2  
A
49  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
REPLACEMENT OF PARTS  
REPLACEMENT OF PARTS  
29.1  
29. Plastic protection device  
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
Ensure the system is fully drained (see  
draining the appliance).  
Disconnect all pipes connected to the pump  
housing.  
Remove the electrical connection to the  
pump.  
Withdraw the metal clip to the right of the  
pump head to release the pump housing.  
Slide the device to the left and then withdraw  
it from the appliance.  
29.2  
A
29.1 Remove the spring clip from the pressure  
relief valve housing.  
29.2 Withdraw the pressure relief valve (A).  
ꢀ
To refit, follow the above in reverse. Ensure  
any seals that have been disturbed are  
renewed.  
30. DHW Heat exchanger  
ꢀ
Remove the Hydraulic block from the boiler  
(See Removing the Hydraulic Block).  
30.1 Undo the two screws (B) securing the plastic  
housings to the heat exchanger.  
30.2 Remove the heat exchanger  
ꢀ
To refit, follow the above in reverse. Ensure  
any seals that have been disturbed are  
renewed.  
30.1  
B
30.2  
50  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
REPLACEMENT OF PARTS  
REPLACEMENT OF PARTS  
31.1  
31. Bypass valve  
ꢀ
Remove the Hydraulic block from the boiler  
(See Removing the Hydraulic Block).  
31.1 Remove the two spring clips at either end of  
the copper bypass pipe.  
ꢀ
ꢀ
ꢀ
Undo the screw securing the left hand  
plastic housing to the heat exchanger  
Move the housing to the left to free up the  
one end of the pipe.  
Remove the pipe from the right hand housing  
to reveal the bypass valve  
31.2  
31.2 Using a pair of pliers, pull out the bypass  
valve (A) from the housing  
ꢀ
To refit, follow the above in reverse. Ensure  
any seals that have been disturbed are  
renewed.  
32. Expansion vessel  
The expansion vessel can be replaced with the  
boiler in position if there is a side exit flue fitted  
and there is a minimum clearance of 340mm  
above the boiler casing. If vertical flue is fitted  
then a similar clearance to one side and the flue  
is required.  
A
If clearance is not available, the boiler will need to  
be removed from the mounting frame to gain  
access to the expansion vessel.  
32.1  
32.2  
Alternatively a second vessel of at least the  
capacity of 7lts can be fitted to the return from  
the heating system as close as possible to the  
boiler.  
Expansion vessel replacement  
(Boiler in place)  
ꢀ
ꢀ
ꢀ
Isolate mains power from the boiler.  
Place the controls in service position.  
Isolate the boiler from the heating system  
(and cylinder return if internal diverter valve is  
fitted) using service valves.  
32.3  
ꢀ
Drain boiler.  
32.1 Remove clip from expansion vessel  
connection.  
32.2 Remove screw retaining the vessel to the top  
of the boiler casing.  
32.3 Pull the vessel up and out over the flue  
system or to one side if fitted with a vertical  
flue.  
ꢀ
Remove the flexible hose from the expansion  
vessel and fit to the replacement vessel  
using a new seal. Ensure that the connection  
to the boiler will be pointing to the right hand  
side of the appliance when fitted.  
ꢀ
Reassemble expansion vessel into boiler and  
connect flexible pipe to boiler.  
Removing boiler  
ꢀ
Isolate electrical supply.  
ꢀ
Isolate system and gas connections at the  
service valves.  
ꢀ
ꢀ
Drain boiler.  
Disconnect electrical supply and any external  
controls.  
ꢀ
ꢀ
ꢀ
Disconnect flue connection from the boiler.  
Undo connection to boiler at the service valves.  
Remove clip from expansion vessel  
connection to the boiler.  
ꢀ
ꢀ
Gently raise the boiler off the mounting frame.  
Replace expansion vessel and refit the boiler  
to the mounting frame.  
ꢀ
Follow the commissioning procedure in this  
manual.  
51  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
REPLACEMENT OF PARTS  
SETTING THE GAS / AIR RATIO  
THE SETTING OF THE GAS RATIO MUST BE  
CARRIED OUT BY A COMPETENT PERSON.  
SETTING OF THE GAS RATIO MUST NOT BE  
ATTE M PTE D U N LESS TH E PE R SON  
CAR RYI NG OUT TH E CONVE R SION IS  
EQUIPPED WITH A COMBUSTION ANALYSER  
CON FOR M I NG TO B S 7927 AN D IS  
COMPETENT IN ITS USE.  
33.1  
C
33. Setting the CO2  
Note: When running in the service mode, the  
boiler will operate both the central heating &  
DHW circuits. This is to allow sufficient time for  
the setting procedure. It will be necessary to run  
water through the DHW circuit to ensure that  
Inlet Test Nipple  
the boiler will not cycle on low heating demands.  
33.2  
5.1 Connect manometer to inlet pressure point  
on the gas valve.  
ꢀ
ꢀ
To adjust the CO2 it will be necessary to first  
operate the boiler at maximum output.  
Press and hold down the service button (A) for  
10 seconds until illuminated. The blue power  
indicator will flash.  
5.2 Turn central heating control to maximum; the  
boiler will then go to maximum output.  
Note: The control will resume normal operation  
after 15 minutes or if the service button is pressed  
for over a second.  
33.3  
5.3 Using a flat blade screwdriver set the CO2  
via adjuster (B) using table below.  
CO settings  
2
+
–
Note. CO2 should be measured after 10 minutes  
Gas type  
CO setting  
2
CO setting  
2
maximum  
minimum  
A
Natural gas  
LPG  
9.8% 0.2  
9.2% 0.2  
B
11.0% 0.2  
10.5% 0.2  
ꢀ
ꢀ
Check CO is less than 200ppm.  
Measure the inlet pressure; it should be no  
less than 18.5mb for natural gas and 37mb  
for LPG.  
33.4  
5.4 Set the central heating control to minimum.  
This will make the boiler go to minimum power.  
5.5 Measure the CO2; it should now be at the  
figure for minimum output. If not adjust (C)  
on the gas valve until correct.  
ꢀ
Return to maximum and re-check the CO2. If  
correct press and hold down the service  
button for 2 seconds; the button will cease to  
be illuminated and the blue power indicator will  
be permanently illuminated.  
5.5  
ꢀ
ꢀ
ꢀ
ꢀ
Remove manometer and re-seal inlet pressure  
point on gas valve.  
Fit new plastic sealing cover on to outlet  
adjuster (B).  
Fit white cover over valve adjuster (C) and  
secure with black security tag.  
Remove red arrow from data plate and fit new  
one in correct position for gas type.  
Re-assemble and refit boiler case.  
Re-connect mains electrical supply and  
check boiler operation as stated in the  
commissioning section.  
–
+
Please note: The flue gas test point can be  
accessed on the appliance flue elbow by  
removing cap D  
C
D
ꢀ
ꢀ
ꢀ
Fit new label from kit over existing label on the  
appliance bottom panel.  
52  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
REPLACEMENT OF PARTS  
SHORT PARTS LIST  
1
4
7
2
5
8
3
6
9
1
2
3
Fan  
WORCESTER Part No.  
GC No.  
8 717 204 453 0  
H26 536  
Burner  
WORCESTER Part No.  
GC No.  
8 718 120 609 0  
H26 538  
Gas valve  
NG WORCESTER Part No.  
NG GC No.  
8 716 107 052 0  
H26 540  
LPG WORCESTER Part No.  
LPG GC No.  
8 716 107 053 0  
H26 539  
4
5
6
7
8
9
Control board  
WORCESTER Part No.  
GC No.  
8 716 109 539 0  
H28 966  
Air pressure switch  
WORCESTER Part No.  
GC No.  
8 716 106 633 0  
H26 543  
Temperature limit sensor  
WORCESTER Part No.  
GC No.  
8 722 963 858 0  
H08 291  
Electrodes  
WORCESTER Part No.  
GC No.  
8 718 107 087 0  
H26 544  
Gasket - burner/electrodes  
WORCESTER Part No.  
GC No.  
Seal - inner case/mantel  
WORCESTER Part No.  
GC No.  
8 716 106 506 0  
H26 545  
8 716 106 635 0  
H26 546  
10  
13  
11  
14  
12  
15  
10 Flow reg. Type E 8 litre  
WORCESTER Part No.  
GC No.  
8 716 141 143 0  
379 215  
11 Flow reg. Type E 10 litre  
WORCESTER Part No.  
GC No.  
8 716 107 044 0  
394 291  
12 Pressure relief valve DHW  
WORCESTER Part No.  
GC No.  
8 717 401 029 0  
H02 526  
13 Pump assembly 3 speed  
WORCESTER Part No.  
GC No.  
8 716 106 355 0  
H02 527  
14 Pressure gauge  
WORCESTER Part No.  
GC No.  
8 717 208 107 0  
H02 528  
15 Flow sensor  
WORCESTER Part No.  
GC No.  
8 716 107 223 0  
H02 529  
18  
21  
16  
19  
22  
17  
20  
16 Heat exchanger 12 plate  
WORCESTER Part No.  
GC No.  
8 716 106 686 0  
H02 538  
17 Heat exchanger 16 plate  
WORCESTER Part No.  
GC No.  
8 716 106 685 0  
H02 531  
18 By-pass valve  
WORCESTER Part No.  
GC No.  
8 716 106 434 0  
H02 532  
19 Diverter valve assembly  
WORCESTER Part No.  
GC No.  
8 716 106 845 0  
H02 533  
20 Diverter valve motor  
WORCESTER Part No.  
GC No.  
8 716 106 847 0  
H02 534  
21 Control sensor - primary  
WORCESTER Part No.  
GC No.  
8 716 106 688 0  
H26 542  
22 High limit stat  
WORCESTER Part No.  
GC No.  
23 DHW temperature sensor  
WORCESTER Part No.  
GC No.  
8 707 206 196 0  
H26 584  
23  
24  
8 714 500 081 0  
H02 538  
24 Expansion vessel  
WORCESTER Part No.  
GC No.  
8 716 105 545 0  
H05 206  
25 Pressure relief valve  
WORCESTER Part No.  
GC No.  
8 716 106 431 0  
H09 750  
25  
53  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
REPLACEMENT OF PARTS  
L. P. G. CONVERSION  
1.1  
1.2  
ISOLATE MAINS ELECTRICAL  
SUPPLY AND REMOVE OUTER CASE  
AS SHOWN IN THE INSTALLATION,  
COMMISSIONING & SERVICING  
INSTRUCTIONS  
A
THE CONVERSION MUST BE CARRIED OUT  
BY A COMPETENT PERSON. IT MUST NOT  
B E ATTE M PTE D U N LESS TH E PE R SON  
CAR RYI NG OUT TH E CONVE R SION IS  
EQUIPPED WITH A COMBUSTION ANALYSER  
CON FOR M I NG TO B S 7927 AN D IS  
COMPETENT IN IT’S USE.  
2.1  
2.2  
Important: The appliance shall not be installed  
into a room or internal space below ground  
level when it is intended for use with LPG  
(propane - G31). This does not preclude the  
installation into a room or space which is a  
basement on one side of the building but open  
to ground on the opposite side.  
Installation Regulations  
In addition to those specified in the main  
booklet the following standard applies when  
converting to an LPG appliance: BS 5842  
2.3  
Domestic  
Propane  
Gas  
Burning  
Installations.  
All conversions will require the air gas ratio to  
be set correctly for the gas used. The  
procedure for setting the air gas ratio is at  
the rear of these instructions.  
1. Moving boiler control to service  
position  
B
ꢀ
Remove boiler case, as described on page  
36.  
1.1 Remove screw (A) from retaining bracket.  
1.2 Lower control panel into service position.  
3
2. Gas valve  
ꢀ
Isolate gas supply at boiler gas cock.  
2.1 Remove wire clip from gas valve outlet then  
pull gas adjustment assembly free from  
plastic connector and pull forward clear of  
case.  
C
2.2 Undo bottom gas connection to gas valve.  
2.3 Undo two securing screws (B) on the  
underside of casing.  
ꢀ
ꢀ
ꢀ
Pull valve up and forward out of boiler.  
Disconnect electrical connections.  
Fit plastic retaining nut to the outlet of the  
gas valve from the kit and hand tighten.  
Replace valve with new seals.  
4.1  
4.2  
ꢀ
ꢀ
Check for gas soundness.  
3. Gas adjuster  
A
ꢀ
Twist retaining clip (C) to release then  
remove clip and tube.  
ꢀ
Refit new adjuster and secure with clip.  
Coloured red for LPG or black for NG.  
4. Code plug  
4.1 Remove 3 screws (D) retaining plastic  
cover at rear of control box and remove.  
4.2 Replace code plug (E) with new one  
supplied with conversion kit.  
E
D
ꢀ
Replace plastic cover.  
ꢀ
Place control in normal position and secure  
with screw.  
Code plugs  
THE GAS / AIR RATIO MUST BE  
RESET AFTER CONVERSION. THE  
PROCEDURE CAN BE FOUND IN  
THE REPLACEMENT PARTS SECTION  
OF THIS MANUAL.  
24kW NG  
-
100  
101  
24kW LPG  
-
28kW NG  
28kW LPG  
-
-
102  
103  
54  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
L.P.G. CONVERSION  
FAULT FINDING  
NOTE : This fault finding information is for guidance only. Worcester cannot be held responsible for costs incurred by persons not deemed  
to be competent.  
The electronic control system for this boiler incorporates a blue central indicator. This normally confirms the permanent mains supply but, by  
flashing at different rates during a fault, provides a guide to the cause as listed.  
This fault finding system assumes that the appliance has been operating normally until the time of failure (i.e. not a first installation error).  
PRELIMINARY CHECKS : Preliminary electrical system checks are the first electrical checks to be carried out during a fault-finding  
procedure. On completion of the Service/Fault-Finding task which has required the breaking and remaking of electrical connections, check  
(a) EARTH CONTINUITY, (b) SHORT CIRCUIT CHECK, (c) POLARITY and (d) RESISTANCE TO EARTH.  
Blue light Lockout reset  
indication button  
Fault  
Possible solution/check  
Permanent mains supply to boiler.  
Boiler mains switch.  
Off  
No power at control board  
Off  
Fuse F1, 2.5A or Fuse F3, 0.5A  
Transformer (both coils below 100Ω).  
Otherwise replace control board.  
On  
Live demand at ST10-LR (from external roomstat/timer).  
Facia mounted timer (if fitted).  
CH knob in winter position.  
Diverter valve.  
Off  
Boiler not operating during  
central heating demand  
(HW ok)  
Control board.  
Boiler operating  
Some older thermostats (containing capacitors) may give a low  
voltage return at ST10-LR when the thermostat contacts are open.  
Check that there is not a permanent live at ST10-LR from another  
source.  
without live demand at  
ST10-LR (from external  
roomstat timer).  
Boiler not operating during  
hot water demand (CH ok).  
See Flow Sensor Test below.  
or  
Diverter valve.  
Control board.  
Boiler not operating during  
any demand.  
Fan.  
Control board.  
Slow flash  
Gas present and at correct pressure.  
Flashing (reset required)  
Flashing (reset required)  
Ignition lockout  
Combustion CO level.  
(normally off,  
flashes on)  
2
Flue condition.  
Ignition electrodes / harness / connections.  
Gas valve (coils 140-190Ω) / low voltage harness connection.  
Otherwise replace control board.  
Slow flash  
(normally on,  
flashes off)  
Heat exchanger blocked.  
Heat exchanger baffles removed and not refitted.  
Flue overheat  
Heat exchanger overheat  
Water pressure.  
All air vented.  
Pump / harness / connections.  
Water leaks / blockages.  
Safety thermostats / low voltage wiring harness / connections.  
Otherwise replace control board.  
Flue blockage  
Volatile lockout  
Blockage in flue system.  
Fast flash  
Temperature sensor (8000-20,000Ω).  
Low voltage wiring harness / connections to sensor.  
Fan / fan harness / connections to fan.  
Code plug fitted.  
Off  
Replace control board  
Internal fault  
Fast flash  
2 pulses  
5 pulses  
Flashing  
No light  
No light  
Not a fault code  
Not a fault code  
Service mode selected to min, press service button to return to normal.  
Service mode selected to max, press service button to return to normal.  
Flow Sensor Test  
:Replace control board if: 5V is not across the red and black cables.  
:1.5V-3.5V is across the yellow and black cables (with water flowing).  
Otherwise replace flow sensor.  
55  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
FAULT FINDING  
8 716 107 336b (11/05)  
CENTRAL HEATING FUNCTION  
56  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
CENTRAL HEATING FUNCTION  
PREHEAT AND DHW FUNCTION  
57  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
PREHEAT AND DHW FUNCTION  
PROTECTION FUNCTION  
Boiler temperature  
below 8°C  
Run autofroststat  
function  
Pump run 5 seconds  
every 24hrs  
Pump antiseize  
58  
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR 24 i junior/28 i junior  
8 716 107 336b (11/05)  
PROTECTION FUNCTION  
BENCHMARK No.  
GAS BOILER COMMISSIONING CHECKLIST  
NOTIFICATION No.  
C O L L E C T I V E M A R K  
BOILER SERIAL No.  
CONTROLS To comply with the Building Regulations, each section must have a tick in one or other of the boxes  
TIME & TEMPERATURE CONTROL TO HEATING  
TIME & TEMPERATURE CONTROL TO HOT WATER  
HEATING ZONE VALVES  
ROOM T/STAT & PROGRAMMER/TIMER  
PROGRAMMABLE ROOMSTAT  
COMBI BOILER  
CYLINDER T/STAT & PROGRAMMER/TIMER  
FITTED  
FITTED  
FITTED  
FITTED  
NOT REQUIRED  
HOT WATER ZONE VALVES  
NOT REQUIRED  
THERMOSTATIC RADIATOR VALVES  
AUTOMATIC BYPASS TO SYSTEM  
NOT REQUIRED  
FOR ALL BOILERS CONFIRM THE FOLLOWING  
THE SYSTEM HAS BEEN FLUSHED IN ACCORDANCE WITH THE BOILER MANUFACTURER’S INSTRUCTIONS?  
THE SYSTEM CLEANER USED  
THE INHIBITOR USED  
FOR THE CENTRAL HEATING MODE, MEASURE & RECORD  
m3/hr  
N/A  
GAS RATE  
ft3/hr  
mbar  
°C  
BURNER OPERATING PRESSURE (IF APPLICABLE)  
CENTRAL HEATING FLOW TEMPERATURE  
CENTRAL HEATING RETURN TEMPERATURE  
°C  
FOR COMBINATION BOILERS ONLY  
HAS A WATER SCALE REDUCER BEEN FITTED?  
YES  
NO  
WHAT TYPE OF SCALE REDUCER HAS BEEN FITTED?  
FOR THE DOMESTIC HOT WATER MODE, MEASURE & RECORD  
m3/hr  
N/A  
GAS RATE  
ft3/hr  
mbar  
°C  
MAXIMUM BURNER OPERATING PRESSURE (IF APPLICABLE)  
COLD WATER INLET TEMPERATURE  
HOT WATER OUTLET TEMPERATURE  
WATER FLOW RATE  
°C  
lts/min  
FOR CONDENSING BOILERS ONLY CONFIRM THE FOLLOWING  
THE CONDENSATE DRAIN HAS BEEN INSTALLED IN ACCORDANCE WITH  
THE MANUFACTURER’S INSTRUCTIONS?  
YES  
FOR ALL INSTALLATIONS CONFIRM THE FOLLOWING  
THE HEATING AND HOT WATER SYSTEM COMPLIES  
WITH CURRENT BUILDING REGULATIONS  
THE APPLIANCE AND ASSOCIATED EQUIPMENT HAS BEEN INSTALLED AND COMMISSIONED  
IN ACCORDANCE WITH THE MANUFACTURER’S INSTRUCTIONS  
IF REQUIRED BY THE MANUFACTURER, HAVE YOU RECORDED A CO/CO2 RATIO READING? N/A  
YES  
CO/CO2 RATIO  
THE OPERATION OF THE APPLIANCE AND SYSTEM  
CONTROLS HAVE BEEN DEMONSTRATED TO THE CUSTOMER  
THE MANUFACTURER’S LITERATURE HAS BEEN LEFT WITH THE CUSTOMER  
COMMISSIONING ENG’S NAME PRINT  
CORGI ID No.  
SIGN  
DATE  
SERVICE INTERVAL RECORD  
It is recommended that your heating system is serviced regularly  
and that you complete the appropriate Service Interval Record Below.  
Service Provider. Before completing the appropriate Service Interval Record below, please ensure you have carried out the service  
as described in the boiler manufacturer’s instructions. Always use the manufacturer’s specified spare part when replacing all controls  
SERVICE 1 DATE  
ENGINEER NAME  
COMPANY NAME  
TEL No.  
SERVICE 2 DATE  
ENGINEER NAME  
COMPANY NAME  
TEL No.  
CORGI ID CARD SERIAL No.  
COMMENTS  
CORGI ID CARD SERIAL No.  
COMMENTS  
SIGNATURE  
SIGNATURE  
SERVICE 3 DATE  
ENGINEER NAME  
COMPANY NAME  
TEL No.  
SERVICE 4 DATE  
ENGINEER NAME  
COMPANY NAME  
TEL No.  
CORGI ID CARD SERIAL No.  
COMMENTS  
CORGI ID CARD SERIAL No.  
COMMENTS  
SIGNATURE  
SIGNATURE  
SERVICE 5 DATE  
ENGINEER NAME  
COMPANY NAME  
TEL No.  
SERVICE 6 DATE  
ENGINEER NAME  
COMPANY NAME  
TEL No.  
CORGI ID CARD SERIAL No.  
COMMENTS  
CORGI ID CARD SERIAL No.  
COMMENTS  
SIGNATURE  
SIGNATURE  
SERVICE 7 DATE  
ENGINEER NAME  
COMPANY NAME  
TEL No.  
SERVICE 8 DATE  
ENGINEER NAME  
COMPANY NAME  
TEL No.  
CORGI ID CARD SERIAL No.  
COMMENTS  
CORGI ID CARD SERIAL No.  
COMMENTS  
SIGNATURE  
SIGNATURE  
SERVICE 9 DATE  
ENGINEER NAME  
COMPANY NAME  
TEL No.  
SERVICE 10 DATE  
ENGINEER NAME  
COMPANY NAME  
TEL No.  
CORGI ID CARD SERIAL No.  
COMMENTS  
CORGI ID CARD SERIAL No.  
COMMENTS  
SIGNATURE  
SIGNATURE  
Pack Number  
Check List  
Greenstar 24i Junior/28i Junior  
Hardware/Literature Pack  
Item  
Qty  
Greenstar 24i Junior/28i Junior Installation/Servicing Instructions.....1  
Users Instructions ..........................................................................................1  
Consumer Guarantee Card .........................................................................1  
Sealing Pack...................................................................................................1  
Compression Nut 22mm .......................................................................3  
Compression Ring 22mm .....................................................................3  
Compression Nut 15mm ....................................................................... 3  
Compression Ring 15mm ..................................................................... 3  
Fibre Washer 18.6 x 13.5 x 1.5 ............................................................ 2  
Fibre Washer 23.9 x 17.2 x 1.5............................................................. 2  
Bonded Washer 3/4 ...............................................................................1  
Elbow Assembly Pack  
(may already be fitted to the appliance - if so, be sure to remove  
sealing cap before connecting condensate drain pipe) .................1  
Elbow Assembly .......................................................................................1  
Fibre Washer .............................................................................................1  
Irish Guidelines Leaflet ..................................................................................1  
Warranty Return Envelope ...........................................................................1  
INSTRUCTION MANUAL  
INSTALLATION, COMMISSIONING  
& SERVICING  
EXCELLENCE COMES AS STANDARD  
Worcester, Bosch Group  
Cotswold Way, Warndon, Worcester WR4 9SW.  
Tel. 01905 754624 Fax. 01905 754619  
Worcester, Bosch Group is a trading name of BBT Thermotechnology UK Ltd.  
www.worcester-bosch.co.uk  
8 716 107 336b (11.05)  

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