Bosch Appliances 24I RSF User Manual
Bosch Group  
24i RSF  
WALL MOUNTED COMBINATION BOILER FOR CENTRAL HEATING  
AND MAINS FED DOMESTIC HOT WATER  
INSTALLATION AND  
SERVICING INSTRUCTIONS  
GC NUMBERS  
N.G. 47 311 37 L.P.G. 47 311 38  
BOILER OUTPUT  
To Domestic Hot Water – Modulated Control  
Minimum 7.5 kW (25,600 Btu/h)  
Maximum 23.4 kW (80,000 Btu/h)  
To Central Heating – Modulated Control\  
Auto Range Rated  
Minimum 7.5 kW (25,600 Btu/h)  
Maximum 23.4 kW (80,000 Btu/h)  
THESE INSTRUCTIONS APPLY IN THE UK ONLY  
THESE INSTRUCTIONS ARE TO BE LEFT WITH THE USER OR AT THE GAS METER  
This appliance must be installed by a competent person in accordance  
with the Gas Safety (Installation and Use) Regulations 1994  
2.5 ELECTRICAL SUPPLY  
2.11 SYSTEM NOTES  
Mains supply: 230V ~, 50 Hz, 180 watts.  
IMPORTANT  
External fuse: 3A., Internal fuses: 2AT HRC(F1), and 1 AF (F2).  
2.6 GAS SUPPLY  
Check that no dirt is left in either the gas or water pipework as  
this could cause damage to the appliance. The heating system  
should be flushed and treated in accordance with the  
recommendations of BS 7593:1992. Thoroughly flush cold water  
mains supply and purge the gas supply before finally connecting  
the appliance.  
The boiler requires 2.76 m3/h (97.5 ft3/hr) of natural gas with a  
calorific value of 37.78 MJ/m3 (1014 Btu/ft3) or 1.07 m3/h (37.8  
ft3/hr) of propane with a calorific value of 95.65 MJ/m3 (2568  
Btu/ft3). The meter governor should deliver a dynamic pressure  
of 20 mbar (8in w.g.) at the appliance, equivalent to a pressure of  
about 19-19.5 mbar at the gas valve on natural gas or 37.0 mbar  
(14.8in w.g.) at the appliance for propane.  
The water pipe connections throughout a sealed system must be  
capable of sustaining a pressure of up to 3 bar.  
Radiator valves must conform to the requirements of BS  
2767:1991.  
The gas meter and supply pipes must be capable of supplying  
this quantity of gas in addition to the demand from any other  
appliances being served. The table below gives an indication of  
limiting gas pipe lengths and the allowance to be made for  
fittings. Refer to BS6891 for further information.  
The complete installation, including the gas meter, must be  
tested for soundness and purged. Refer to BS 6891.  
The relief valve discharge must be directed away from any  
electrical components or where it would cause a hazard to the  
user.  
A drain cock to BS 2879 must be fitted to the lowest point of the  
system.  
For circuit design purposes it is important that due note is taken  
of the information given in Table 3, section 3 relating to the  
available pump head.  
Total length of gas supply pipe Pipe size  
(metres)  
(Ømm)  
2.12 SHOWERS, BIDETS, TAPS AND MIXING VALVES  
Hot and cold taps and mixing valves used in the system must be  
suitable for operating at mains pressure.  
3
6
9
12  
Propane  
Gas  
Thermostatically controlled shower valves will guard against the  
flow of water at too high a temperature.  
1.5  
8.0  
15.9  
–
5.2  
8.8  
–
4.2  
8.5  
–
3.6  
7.2  
15  
22  
28  
Discharge  
Rate  
Hot and cold mains fed water can be supplied direct to an over-  
rim flushing bidet subject to local Water Company requirements.  
With all mains fed systems the flow of water from the individual  
taps will vary with the number of outlets operated  
simultaneously and the cold water mains supply pressure to the  
property. Flow balancing using “Ball-o-Fix” type valves is  
recommended to avoid an excessive reduction in flow to  
individual outlets.  
(m3/hr)  
Natural Gas  
4.6  
8.7  
5.8  
12.0  
–
–
22  
28  
18.0  
9.4  
Note: Each fitting used in the gas line from the meter is  
equivalent to a length of straight pipe which must be added to  
the straight pipe length to give the total length.  
i.e.: Bend = 0.5 metres, Tee = 0.5 metres, 90° Bend = 0.3  
metres.  
2.13 SAFETY CONSIDERATIONS  
The appliance must not be operated in a waterless condition.  
The appliance must not be operated with the boiler inner casing  
cover removed.  
2.7 PACKING  
The appliance and flue components are packaged separately.  
2.8 GENERAL INSTALLATION  
Work must not be carried out on the appliance without the gas  
and electricity supplies being switched off.  
The appliance is for connection to a sealed system only.  
The specified ventilation openings made into a wall or  
compartment door must not be obstructed.  
Checks must be made to ensure that the ventilation openings  
made into walls and partitions are unobstructed and the correct  
size.  
If the appliance is to be fitted into a compartment then the  
compartment must conform to the requirements of BS 6798:  
1987: Section 7.  
2.14 OPERATION  
Domestic Hot Water: With a demand for hot water the burner  
will light at its maximum setting and then automatically adjust  
its output to maintain the temperature of the delivered water.  
When hot water is no longer required, the burner will extinguish.  
The fan and pump may continue to run for a short period to  
dissipate the residual heat from the appliance.  
Do not place anything on top of the appliance.  
The clearances specified for servicing must be maintained.  
2.9 FLUE  
The appliance has a multi-directional fanned flue system.  
The standard telescopic flue assembly length is from 127mm to  
350mm.  
Central Heating: With a demand for heating the burner will light  
at its minimum setting and gradually increase to give a  
controlled temperature rise. When the required heating  
temperature is achieved the output of the appliance is then  
automatically adjusted to maintain the temperature of the  
system. The output can reduce down to a minimum of 7.5 kW. If  
the system no longer requires even the minimum output to  
maintain the desired room temperature the burner will  
extinguish. The fan and pump may continue to run to dissipate  
the residual heat from the appliance. The appliance will remain  
off for a fixed period before re-lighting to automatically meet the  
system requirements.  
Extension flue lengths available are from 350mm to 2500mm.  
An optional vertical flue kit to provide for flue lengths up to  
3000mm including vertical flue terminal.  
A terminal guard, Type K2, GC 393 553, is available from Tower  
Flue Components, Vale Rise, Tonbridge, TN9 1TB.  
Do not allow the flue terminal fitted to the outside wall to  
become obstructed or damaged.  
A kit for internal fixing of the flue is available separately.  
2.10 CONTROLS  
The electronic control system and gas valve modulate the heat  
input in response to the domestic hot water temperature and  
central heating setting between minimum and maximum.  
The Central Heating Temperature control knob provides for the  
selection of domestic hot water only (Turned fully anti-clockwise)  
or central heating and domestic hot water (Turned clockwise).  
A facia mounted programmer is available as an optional extra. A  
remote mounted programmer may be connected to the  
appliance.  
Domestic Hot Water and Central Heating: The appliance will  
supply heat to the central heating system as required. A demand  
for domestic hot water at a tap or shower will override the  
central heating requirement for the period of the domestic hot  
water demand. When hot water is no longer required the  
appliance will return to the central heating state and its normal  
mode of operation. The fan may continue to run to dissipate the  
residual heat from the appliance as necessary.  
There is provision for the connection of a mains voltage room  
thermostat and/or a frost thermostat.  
The electronic controls prevent rapid cycling of the appliance in  
the central heating mode.  
2.15 DOMESTIC SUPPLY  
Devices capable of preventing the flow of expansion water must  
not be fitted unless separate arrangements have been made.  
3
The data plate is fixed to the inner casing cover.  
3. Data Tables  
Table 1  
NOMINAL BOILER RATINGS  
BURNER SETTING  
PRESSURE  
OUTPUT  
INPUT (Net).  
Btu/h  
NATURAL GAS  
GAS RATE  
3
3
kW  
Btu/h  
kW  
m bar.  
in. wg.  
m /h  
ft /h  
7.5  
23.4  
(25,600)  
(80,000)  
9.60  
26.05  
(32,750)  
(88,890)  
1.0  
13.6  
0.4  
5.4  
1.01  
2.76  
35.7  
97.5  
PROPANE  
7.5  
23.4  
(25,600)  
(80,000)  
9.60  
26.05  
(32,750)  
(88,890)  
3.5  
35.0  
1.4  
14.0  
0.39  
1.07  
13.9  
37.8  
Table 2.  
FLUE DETAILS  
HORIZONTAL FLUE (Side or Rear)  
FLUE DIAMETER  
WALL HOLE DIAMETER  
WALL HOLE DIAMETER (using internal flue fitting kit)  
STANDARD FLUE – MINIMUM LENGTH  
STANDARD FLUE – MAXIMUM LENGTH  
EXTENDED FLUE – MAXIMUM LENGTH  
mm  
100  
110  
150  
127  
350  
2500  
inches  
3.9  
4.25  
5.9  
5.0  
14.0  
98.4  
Table 3  
AVAILABLE PUMP HEAD  
TEMPERATURE RISE  
BOILER OUTPUT  
HEAD  
MIN. FLOW RATE  
ACROSS HEATING  
kW  
Btu/h  
Metres  
6.0  
2.6  
Feet  
19.7  
8.5  
L/min. Gal/Min.  
FLOW AND RETURN  
7.5  
23.4  
(25,600)  
(80,000)  
9.8  
30.5  
2.2  
6.7  
11°C (20°F)  
Table 4  
SPECIFICATIONS  
CENTRAL HEATING FLOW FITTING  
CENTRAL HEATING RETURN FITTING  
COLD WATER MAINS INLET FITTING  
DOMESTIC HOT WATER OUTLET FITTING  
GAS INLET FITTING  
22mm Compression  
22mm Compression  
15mm Compression  
15mm Compression  
1
Rc ⁄2inch  
PRESSURE RELIEF VALVE DISCHARGE FITTING  
OVERALL HEIGHT (including flue turret)  
CASING HEIGHT  
CASING WIDTH  
CASING DEPTH  
15 mm Copper Tube  
960mm (37.8 inches)  
800mm (31.5 inches)  
450mm (17.7 inches)  
360mm (14.2 inches)  
44 kg  
WEIGHT(including water)  
INSTALLATION WEIGHT  
39 kg  
PACKAGED WEIGHT  
44 kg  
PRIMARY WATER CAPACITY  
MAXIMUM COLD SUPPLY PRESSURE  
3.0 litres  
10 Bar (150 psi)  
MINIMUM COLD SUPPLY PRESSURE (working) for max. hot water flow  
MINIMUM COLD SUPPLY PRESSURE (working) to operate appliance  
MAXIMUM CENTRAL HEATING FLOW TEMPERATURE  
OUTPUT TO DOMESTIC HOT WATER  
OUTPUT TO CENTRAL HEATING  
MAXIMUM DOMESTIC HOT WATER FLOW RATE (from the appliance)  
0.9 bar  
0.1 bar  
Nominally 82°C (180°F)  
Modulating 7.5 to 23.4 kW  
Modulating 7.5 to 23.4 kW  
Nominally 8.0 ± 15% litres/min  
Nominally 11.2 litres/min  
EQUIVALENT DOMESTIC HOT WATER FLOW RATE TO GIVE A TEMP RISE  
OF 30°C (SPECIFIC RATE)  
4
Fig. 2. Appliance casing dimensions and  
required clearances.  
4. Siting The Appliance  
4.1 The appliance may be installed in any room although  
particular attention is drawn to the requirements of the current  
IEE Wiring Regulations BS 7671 and, in Scotland, the electrical  
provisions of the Building Regulations applicable in Scotland,  
with respect to the installation of appliances in rooms containing  
baths or showers.  
20mm*  
180mm  
Where a room sealed appliance is installed in a room containing  
a bath or shower, any electrical switch or appliance control using  
mains electricity must not be able to be touched by a person  
using the bath or shower.  
4.2 The appliance is not suitable for external installation.  
4.3 The appliance does not require any special wall protection.  
4.4 The wall must be capable of supporting the weight of the  
appliance. See Table 4.  
4.5 The following clearances must be available for installation  
and for servicing. See Fig. 2. (note the clearances at the front are  
for a removable panel e.g. a door).  
4.6 The appliance can be installed in a cupboard used for airing  
clothes provided that the requirements of BS 6798 and BS  
5440:2 are strictly followed.  
225mm  
Front view  
Side view  
360mm  
600mm*  
450mm  
200mm* 10mm*  
10mm*  
* Space required for installation and servicing  
Above  
180mm  
0 mm  
In front  
In front to a fixed surface  
Below  
600mm  
200mm  
10 mm  
10 mm  
Right-hand side  
Left-hand side  
Notwithstanding the instructions given in BS 5440:2, this appliance  
may be fitted in a compartment with no vents as long as the  
minimum clearances stated in Section 6: Air Supply, are maintained.  
4.7 The airing space must be separated from the boiler space by  
a perforated non-combustible partition. Expanded metal or rigid  
wire mesh are acceptable provided that the major dimension is  
less than 13mm. See BS 6798:1987.  
4.8 No combustible surface must be within 75mm of the casing.  
See BS476:4.  
4.9 Always consider the possible need to disconnect the pipes  
from the appliance after installation.  
4.10 LPG Installation: The appliance shall not be installed in a  
room or internal space below ground level when it is  
intended for use with LPG. This does not preclude the  
installation into rooms which are basements with respect to  
one side of the building but open to ground level on the  
opposite side.  
5
5. Siting The Flue  
6. Air Supply  
See Fig. 3.  
6.1 The appliance does not require a separate vent for  
combustion air.  
6.2 The appliance can be fitted in a cupboard with no vents for  
cooling but the minimum clearances must be increased to those  
given below (note the clearances at the front are for a removable  
panel e.g. a door).  
5.1 The flue must be installed as specified in BS 5440:Part 1.  
5.2 The terminal must not cause an obstruction nor the  
discharge cause a nuisance.  
5.3 If the terminal is fitted within 850mm of a plastic or painted  
gutter or within 450mm of painted eaves then an aluminium  
shield at least 750mm long should be fitted to the underside of  
the gutter or painted surface.  
5.4 If a terminal is fitted less than 2 metres above a surface to  
which people have access then a guard must be fitted. See  
Section 2.9.  
5.5 The terminal guard must be evenly spaced about the flue  
terminal and fixed to the wall using plated screws.  
5.6 In certain weather conditions a terminal may steam and  
siting where this could cause a nuisance should be avoided.  
5.7 Take care to ensure that combustion products do not enter  
ventilated roof voids.  
Above the Turret  
In front  
20mm  
250mm  
200mm  
75mm  
75mm  
Below  
Right-hand side  
Left-hand side  
6.3 If the appliance is to be fitted in a cupboard or compartments  
with less clearance than those above (minimum clearances given  
in Section 4. Siting The Appliance) then permanent vents for  
cooling are required. One at high level and one at low level, either  
direct to outside air or to a room. Both vents must pass to the  
same room or be on the same wall to the outside air.  
6.4 The minimum free areas required are given below.  
POSITION OF  
AIR VENTS  
AIR FROM  
THE ROOM  
AIR DIRECT  
FROM OUTSIDE  
HIGH LEVEL  
LOW LEVEL  
270cm2  
135cm2  
270cm2  
135cm2  
6.5 Refer to BS 6798 and BS 5440:2 for additional information.  
Fig. 3. Siting of the flue terminal.  
A
L
G
B,C  
K
L
D
K
F
F
HI  
A
G
M
F
J
E
TERMINAL POSITION  
MIN. DISTANCE  
TERMINAL POSITION  
MIN. DISTANCE  
1200mm (47in.)  
A– directly below an openable window or  
I– From a terminal facing a terminal  
other opening e.g. air brick.  
300mm (12in.)  
75mm (3in.)  
25mm (1in.)  
25mm (1in.)  
25mm (1in.)  
25mm (1in.)  
300mm (12in.)  
600mm (24in.)  
J– From an opening in a car port (e.g. door  
B– Below gutters, soil pipes or drain pipes.  
C– Below eaves.  
D– Below balconies or car port roof.  
E– From vertical drain pipes and soil pipes.  
F– From internal or external corners.  
G– Above ground, roof or balcony level.  
H– From a surface facing a terminal.  
window) into dwelling.  
K– Vertically from a terminal on the same  
wall.  
L– Horizontally from a terminal on the same  
wall.  
M– From door, window or air vent (achieve  
where possible).  
1200mm (47in.)  
150mm (6in.)  
300mm (12in.)  
150mm (6in.)  
6
7.7 The filling point must be at low level. See Fig. 4.  
7.8 Water loss must be replaced. See Fig 4. The connection  
should be made in the central heating return as close to the  
appliance as possible.  
7.9 Repeated venting loses water from the system. It is essential  
that this water is replaced and the system pressure maintained.  
7.10 Connections to the mains water supply must not be made  
without the authority of the local Water Company.  
7.11 The pump is set at maximum and must not be adjusted.  
7.12 Connections in the system must sustain a pressure of up to  
3 bar.  
7.13 Radiator valves must conform to BS 2767:10.  
7.14 Other valves used should conform to the requirements of  
BS 1010.  
7.15 The appliance is fitted with a fixed internal by-pass. But it is  
advisable to keeps one radiator permanently open.  
7. Sealed System  
See Figs. 4.  
7.1 The system must comply with the requirements of BS 6798  
and BS 5449.  
7.2 The appliance must not be operated without the system  
being full of water, properly vented and pressurised.  
2
7.3 The pressure relief valve operates at 3 bar (45lb/in ). The  
discharge must be directed away from electrical components or  
where it might be a hazard to the user.  
7.4 The pressure gauge indicates the system pressure which  
must be maintained.  
7.5 The 8 litre expansion vessel is charged to 0.5 bar and is  
suitable for a static head of 5 metres (17.5ft). The pressure can be  
increased if the static head is greater than 5 metres (17.5ft).  
7.6 With an initial system pressure of 0.5 bar, a system capacity  
of up to 100 litres can be accommodated. For system capacities  
greater than this an extra expansion vessel must be fitted. Refer  
to BS 7074 Pt. 1 for more information. The charge pressure can  
be increased but with a consequent decrease in system volume.  
8. Open Vent System  
The appliance is NOT suitable for connection to an open vented  
system.  
Fig. 4. Sealed primary water system.  
Automatic  
air vent  
Mains cold  
Expansion  
vessel  
water  
Radiator  
valve  
Hot water  
out  
Lockshield  
valve  
Heating  
return  
British Standard  
stop valve.  
Fixed spindle type  
Heating  
flow  
Water main  
NOTE: A drain cock should be installed at  
the lowest point of the heating circuit and  
beneath the appliance.  
Filling Loop Detail  
Heating Return  
Non-return Non-return  
Valve Valve  
Hose union  
Stop cock  
Test cock  
Temporary Hose  
7
9.10 No anti-syphonage arrangements are necessary except for  
some loose head showers. See also Section 9.11 following.  
9.11 Thermostatically controlled or pressure equalising shower  
valves will guard against the flow of water at too high a  
temperature.  
9.12 The head of a loose head shower must not fall closer than  
25mm (1in.) above the top edge of the bath to prevent its  
immersion in bath water. Alternatively the shower must be fitted  
with an anti-syphonage device at the point of the flexible hose  
connections.  
9.13 The supply of hot and cold mains water direct to a bidet is  
permitted, (subject to local Water Company requirements),  
provided that the bidet is of the over-rim flushing type. The  
outlet(s) should be shrouded and unable to have any temporary  
hand held spray attached. No anti-syphonage arrangements are  
necessary.  
9.14 LIME SCALE. In temporary hard water areas (more than  
350mg/litre or 200ppm calcium bicarbonate) it is  
recommended that a proprietary scale reducer is fitted in the  
mains cold water connection to the appliance. Consult the  
local water company for additional advice.  
9. Hot Water Supply  
9.1 The following are general requirements and, if necessary,  
reference should be made to the local Water Company before  
fitting the appliance.  
9.2 MAINS COLD WATER INLET. Devices capable of preventing  
the flow of expansion water must not be fitted unless  
separate arrangements have been made.  
A mini expansion vessel kit is available which contains the  
necessary parts for fitting an internal expansion vessel to the  
appliance.  
See Section 19 COMPONENT PARTS LIST.  
A thread sealant compatible with potable water must be  
used. An external expansion vessel may be fitted on the  
mains cold water connection to the appliance.  
9.3 The final 600mm of the mains cold water connection to the  
appliance should be made in copper tube only.  
9.4 The appliance is suitable for a mains pressure of up to 10 bar  
2
(150 lb/in ).  
9.5 The appliance is fitted with a mains supply isolating valve.  
9.6 The maximum domestic hot water flow rate is 8.0 litres/min  
(±15%) (1.8 gallons/min).  
9.7 In winter (when the mains inlet water temperature is lower) a  
reduced flow rate at the taps may be required to achieve the  
type of hot water delivery temperature available in warmer  
weather.  
9.8 It is suggested that long pipe runs to the taps or shower  
should be insulated to prevent the rapid cooling of domestic hot  
water after a tap or shower has been turned off.  
9.9 Hot and cold taps and mixing valves used with this  
appliance must be suitable for operating at mains pressure and  
temperatures of 65°C.  
Installation of a scale inhibitor assembly should be in  
accordance with the requirements of the local Water  
Company. An isolating valve should be fitted to allow  
servicing. The water hardness can be determined by  
reference to the local Water Company.  
9.15 NOTE: HOT WATER ONLY.  
If required the appliance may be used for Hot Water only  
before the Central Heating is connected. A 22mm copper by-  
pass pipe at least 4 meters long must be connected between  
the Central Heating Flow and Return, but it is advisable to  
connect a small radiator instead.  
IT IS NOT RECOMMENDED TO USE THE BOILER IN THIS  
CONDITION FOR EXTENDED PERIODS.  
Fig. 6. 230V programmer connections.  
Fig. 5. 230V room thermostat connections.  
CN  
CI  
CL  
RN  
RI  
RL  
X2  
X2  
Remove link  
Remove link  
Motor  
8
conjunction with a programmer.  
10. Electrical  
Important: To provide external frost protection the appliance  
must have the Central Heating Temperature Control Knob set to  
supply heating (the appliance may then be left with the central  
heating turned off on the programmer).  
10.1 MAINS SUPPLY.  
230 V ~, 50 Hz, 180 watts.  
External Fuse: 3A. Internal Fuses: 2AT HRC(F1), and 1.AF (F2).  
10.2 It must be possible to completely isolate the appliance.  
10.3 The following connection alternatives must be used:  
A 3 amp fused three-pin plug and unswitched shuttered socket  
outlet (both complying with the requirements of BS 1363) or a  
double pole isolator with a contact separation of 3mm in all  
poles and supplying the appliance and controls only.  
10.4 The appliance must be earthed.  
Connection must be made at X2 terminals RI and CL. For advice  
on external frost thermostats contact Worcester Heat Systems  
Technical Helpline  
10.11 SAFETY CHECK.  
After installation or in the event of an electrical fault the  
electrical system shall be checked for short circuits, fuse failure,  
incorrect polarity of connections, earth continuity and resistance  
to earth.  
10.5 Mains Cable. 0.75mm2 (24 x 0.20mm) to BS 6500 Table 16.  
The mains cable must be connected into the terminal X1,  
marked L (Brown or Red lead), N (Blue or Black lead) and the  
earth stud and be held securely in the cable clamp. For access  
undo the three bottom screws and remove the facia access cover.  
See Fig. 7.  
Fig. 7. Mains electricity connections.  
230V  
N
L
10.6 The wiring between the appliance and the electrical supply  
shall comply with current IEE Wiring Regulations and any local  
regulations which apply.  
X1  
X2  
Blue  
10.7 If a room thermostat and/or external programmer is to be  
fitted refer to Figs 5 and 6. The devices must be suitable for use  
with mains voltage.  
10.8 A facia mounted mechanical programmer is available as an  
optional extra. Instructions are supplied with the programmer kits.  
10.9 A time switch or programmer can be fitted externally to the  
appliance.  
10.10 The boiler provides automatic frost protection, the use of  
a frost thermostat is not recommended. However if an external  
frost thermostat is considered necessary then it must be used in  
Brown  
Strain relief clamp  
Programmer and room thermostat  
strain relief clamps  
Green/yellow  
Fig. 8. Wiring diagram.  
Flame sense  
electrode  
Spark  
electrode  
Spark  
transformer  
Flow  
switch  
X5  
X4  
X3  
X1  
X2  
X6  
Link Link  
2 pink  
Mains in  
DHW  
sensor  
Air  
pressure  
switch  
Fan  
Gas  
valve  
Main  
Reg  
3 COM  
Pump  
1 NC  
2 NO  
CH  
sensor  
Safety  
limit  
stat  
9
Fig. 9. Functional flow diagram.  
Modulating  
valve  
X6 Pins 15 & 16  
Outputs  
Inputs  
FAN  
N
X4 Pin 3  
X4 Pin 1  
LOW VOLTAGE  
ELECTRONICS  
(Microcontroller)  
RL1  
RL3  
PUMP  
N
N
X3 Pin 1  
X3 Pin 2  
Mains  
indicator  
X5 Pin 3  
GAS VALVE  
F2 1.25AT  
X5 Pin 1  
X5 Pin 2  
RL4  
ROOM STAT  
6
5
4
3
2
1
FULL SEQUENCE  
CONTROLLER  
MAINS  
PROGRAMMER/CLOCK  
X2  
Flame sense  
Spark  
Optional links  
F1 2ATHRC  
X1  
3 2 1  
N
L
10  
Tchnca1H1lp.inIn. stalling The Appliance  
The appliance is only suitable for fitting to a sealed system.  
11.1 FLUE OPTIONS.  
Flue components  
1. Turret clamping ring.  
2. Flue turret assembly  
3. Flue terminal assembly  
4. Extension air duct  
5. Extension flue duct  
The standard flue length is from 127mm to 350mm measured  
from the appliance casing to the outer wall.  
Extension flue kits, a vertical take-off adapter, 45° and 90° flue  
bends are available to increase the length and redirect the flue as  
follows.  
6. In-line 90° flue bend  
7. In-line 45° flue bend  
8. Vertical flue adapter  
The flue must be installed as specified in BS 5440 Part 1.  
NOTE: READ THIS SECTION FULLY BEFORE COMMENCING  
INSTALLATION  
Horizontal balanced flue:  
a) From 127mm to 2500mm straight flue.  
b) From 127mm to 1750mm when a 90° flue bend is  
required.  
11.2 GENERAL FITTING.  
Check that the appliance carton contains:- Appliance, Installers  
Instruction Pack, Appliance Wall Plate, Users Information Pack,  
Installer Hardware Pack and an appliance template.  
Check that the position chosen for the appliance is in accordance  
with the instructions given in Sections 4 and 5.  
Hold the template to the wall. Check that the template is  
horizontal. See Fig. 10.  
c) From 127mm to 1000mm when two 90° flue bends are  
required.  
A 90° flue bend is equivalent to 750mm of straight flue. A 45°  
flue bend is equivalent to half a 90° bend.  
Refer to Figs. 21 and 22 to determine whether extension kits,  
90° flue bend, 45° flue bend, or adapters are required.  
The maximum number of 90° flue bends allowed is two.  
Mark the position of the fixing holes and the position of the flue  
hole centre line onto the wall. See Fig. 10.  
Fig. 10. Appliance mounting plate and flue position.  
Mounting wall  
Rear flue hole  
110mm dia.  
(150mm dia. for  
internal fixing)  
Rear flue hole  
110mm dia.  
(150mm dia. for  
internal fixing)  
Side wall  
166mm  
60mm  
Mounting  
plate  
Fixing holes Mounting  
(alternatives) plate  
Mounting wall  
222mm  
Appliance  
casing  
Appliance  
casing  
Side flue position  
Rear flue position  
740mm  
400mm  
Side Flue – Extend the flue hole centre line from Fig. 11 along the  
appropriate wall. Check that it remains horizontal and mark a  
horizontal line. Measure 222mm from the junction of the walls  
and mark a vertical line which will then give the position of the  
flue hole.  
Drill the two fixing holes 60mm deep for No. 12 size plugs. Cut  
the flue duct hole at 110mm diameter (150mm dia. for internal  
fitting). Ensure that the hole is horizontal through the wall. Fit  
the wall mounting bracket.  
Fig. 11. Marking out the side flue position.  
Side flue hole  
110mm dia.  
(150mm dia. for  
internal fixing)  
Drill the two fixing holes 60mm deep for No. 12 size plugs. For  
the boiler retaining screws.  
Mounting wall  
Fix the wall plate and check that it is horizontal before tightening  
the 2 screws.  
166mm  
Hang the appliance on the wall plate and screw the appliance to  
the wall using the screws provided.  
11  
Connect the gas, water and pressure relief valve connections to  
the appliance. The primary system should be flushed and  
treated in accordance with the recommendations of  
BS7593:1992.  
Measure and cut the extension ducts to length ensuring that the  
cuts are square and free from burrs. Always check the  
dimensions before cutting the ducts.  
All extension duct dimensions refer to the straight lengths. The  
socketed ends must not be removed or included in any  
measurement.  
Fig. 12. Appliance pipework connections.  
Fig. 14. Side flue.  
Make  
good  
(A)  
36.5mm  
(B)  
100mm  
(C)  
40mm  
(D)  
(E)  
Appliance side panel  
(F)  
External  
wall face  
A
B
Safety Relief  
CH Flow  
=
=
50mm  
95mm  
L
C DHW Out  
D Gas Inlet  
= 160mm  
= 225mm  
E
F
Mains Cold Water In = 290mm  
CH Return = 355mm  
If the air and flue duct assembly is to be fitted from inside the  
room then the ducts must be adjusted to length, assembled and  
inserted through the wall at this stage before fitting the flue  
turret to the appliance. Refer to Section 11.3 following for the  
assembly of the air and flue ducts.  
11.4 EXTERNAL FITTING OF THE DUCT ASSEMBLY  
Measure distance L.  
Side flue duct length = L + 184mm. See Fig. 14.  
Rear flue duct length = L + 181mm. See Fig. 13.  
Do not cut either the turret or the terminal assembly ducts  
unless L = 350 to 450mm.  
1. Should L = 350 to 450mm then cut the terminal assembly  
ducts reducing the length of the ducts to 200mm. Then cut each  
extension duct to 200mm (See Fig. 15). Assemble the flue as  
described below ensuring the correct length (L+184mm for side  
flues or L+181mm for rear flues).  
Remove the fan. See Section 14.3(e).  
11.3 AIR AND FLUE DUCT PREPARATION AND ASSEMBLY  
Check the contents of the standard flue kit against the packing  
list. Similarly check the extension kits if applicable.  
Remove all the packing from the flue and terminal assembly.  
The standard flue kit accommodates a flue assembly up to  
350mm long measured from the appliance casing to the outer  
wall face. See dimension L, Figs.13 and 14.  
When dimension L is greater than 350mm extension flue  
assemblies will be required.  
It will not be necessary to cut either the ducts attached to the  
turret or the terminal unless L = 350 to 450mm.  
Fig. 15. 350-450 Special.  
Rear flue L + 181mm  
Side flue L + 184mm  
Terminal assembly  
reduced to 200mm  
Fig. 13. Rear flue.  
Turret assembly  
with full  
standard  
duct  
lengths  
Fixing screws  
Make  
good  
Flue extension  
duct length  
200mm  
Appliance casing  
Air  
extension  
duct  
length  
200mm  
L = 350mm-450mm  
40mm  
External  
wall face  
Rear face of appliance  
and face of mounting  
wall  
L
12  
Fig. 16. Standard flue assembly.  
Fig. 18. Flue turret fixing.  
Flue turret  
Rear flue L + 181mm  
Turret  
assembly  
Side flue L + 184mm  
Fixing screw  
Terminal  
assembly  
Appliance casing  
L
Reset button  
Flue Gas  
Test Point  
Turret clamping  
ring  
2. If L is within the range 127mm to 350mm then the flue can  
be telescopically adjusted to the correct length (L+184mm for  
side flues or L+181mm for rear flues). The ducts are then fixed  
by drilling a pilot hole through the hole in the air duct and screwing  
the self tapping screw provided into the two ducts (See Fig. 16).  
3. If L is within any of the following ranges it will not be  
necessary to cut the extension ducts:  
4. In the event of L not falling within any of the above ranges  
it will be necessary to cut the FIRST extension length. The air  
and flue duct lengths should both be reduced to the same  
length: L – 240mm where one extension is used; L – 990mm with  
two extensions and L – 1,740mm with three. (See Fig. 17). The flue  
can then be assembled ensuring that the cut extension is fitted to  
the turret duct assembly first and that the flue is adjusted to the  
correct length of (L+184mm for side flues or  
0.88m to 1.10m, 1.63m to 1.85m or 2.38m to 2.50m.  
L+181mm for rear flues) (See Fig. 16).  
Each extension must be connected to the first section of flue or  
the previous extension by firstly fitting the inner flue ducts  
together and pilot drilling and fixing. (See Fig. 17). Then the outer  
air ducts can be similarly fixed using the pair of screws provided.  
The flue terminal section can then be telescopically adjusted and  
fixed as before (See Fig. 16) ensuring the correct length  
(L+184mm for side flues or L+181mm for rear flues).  
5. Finishing the flue  
Apply the plastic tape provided to the last section of flue where it  
will be sealed to the external brickwork.  
From inside, push the assembly through the wall, align the flue  
turret with the socket on the appliance, push the turret down to fully  
engage it and clamp in place with the turret clamping ring. See Fig.  
18.  
Make good the internal and external brickwork or rendering.  
Refit the fan and replace the inner casing cover.  
Fig. 17. Extensions.  
Rear flue L + 181mm  
Side flue L + 184mm  
Turret  
assembly  
Terminal  
assembly  
Fixing screws  
Fixing screw  
Extensions of equal length  
Appliance casing  
Shorten first extension fitted  
to the turret assembly  
L = 450mm-2500mm  
13  
11.5 INTERNAL FITTING OF THE DUCT ASSEMBLY  
The rubber sealing gasket and the clamping ring are available from  
Worcester Heat Systems.  
Fig. 20. Duct and terminal assembly for  
internal fitting of the flue.  
Measure and cut the ducts as previously described for external  
fitting (Section 11.4). Fix the ducts to the terminal and fit the rubber  
sealing gasket and clamp to the terminal. Centralise the gasket and  
tighten the clamping ring. See Fig. 19. Slide the flue centering ring  
onto the air duct and tighten the screw. See Fig. 20. Fix the ducts  
and terminal assembly to the flue turret as described in Section 11.4  
preceding.  
Flue centring ring  
Flue terminal  
Fig. 19. Terminal assembly for internal  
fitting of the flue.  
Rubber sealing  
gasket  
Flue duct  
Air duct  
Rubber  
sealing  
gasket  
Flue terminal  
Clamping ring  
provided into the two ducts. (See Fig. 21).  
The length Y is the distance between bends the ducts must be  
cut to Y – 162mm. The swaged ends must be removed from the  
extension tube and only the air duct needs fixing. See Fig. 21.  
Z is the final flue length from the last elbow to the outside face of  
the external wall. The first duct sections fitted to the elbow must  
have unswaged ends. The length of the air ducts should be Z –  
196mm. The inner flue duct must be 30mm longer than the air  
duct. If Z – 196mm is less than 160mm then the terminal section  
will need to be shortened to the same length as the extension flue  
section fitted to the elbow (length Z – 100). If flue extensions are  
needed to attain the required length care must be taken to ensure  
that the last section of flue is longer than 260mm.  
Apply the plastic tape provided to the last section of flue where it  
will be sealed to the external brickwork.  
Push the assembly through the wall so that the gasket flange is  
against the outside face of the wall. See Fig. 20.  
Align the flue turret with the socket on the appliance, push the  
turret down to fully engage it and clamp in place with the turret  
clamping ring. See Fig. 18.  
Each extension must be connected to the previous section of flue  
or bend by firstly fitting the inner flue ducts together and pilot  
drilling and fixing as above (See Fig. 21). Then the outer air ducts  
can be similarly fixed using the pair of screws provided. The flue  
terminal section can then be telescopically adjusted and fixed as  
before (See Fig. 21), ensuring the correct length of Z – 41.  
The silicon sealant supplied should be applied to the flue ducts  
which engage into elbows. See Fig. 21.  
Refit the fan and replace the inner casing cover.  
Seal the gap around the duct with the flexible seal provided and  
make good. See Fig. 20.  
11.6 FLUE BENDS  
See Figs 21 and 22.  
Measure distances X, Y and Z as appropriate.  
Side flue duct length = X + 63mm. See Fig. 21.  
Rear flue duct length = X + 60mm. See Fig. 21.  
Cut the flue and air ducts which are to make up the first section  
X such that both the assemblies are of equal length (either X +  
63mm or X + 60mm). Extensions will be necessary to allow X to  
be larger than 250mm.  
From inside, push the assembly through the wall  
Align the flue turret with the socket on the appliance, push the  
turret down to fully engage it and clamp in place with the turret  
clamping ring. See Fig. 18.  
Make good the internal and external brickwork or rendering.  
Refit the fan. Do not use any sealant on the joint. Replace the  
inner casing cover.  
Any extension ducts are fixed by drilling a pilot hole through the  
hole in the duct or elbow and screwing the self tapping screw  
Z
Fig. 21. Flue bends.  
56mm  
Z Ð 41mm  
Y
Y Ð 162mm  
X
56mm  
Side flue X + 63mm  
Rear flue X + 60mm  
14  
11.7 VERTICAL ADAPTER  
11.8 FINAL INSTALLATION  
Measure and fit the flue as in Section 11.6 Flue bends except the  
first section length is measured from the case top and the ducts  
are cut to X – 168mm. The minimum length for X is 190mm. See  
Fig. 22.  
Check that all the water and gas connections have been  
tightened.  
If a facia mounted programmer is to be fitted follow instructions  
with the programmer..  
Remove the facia bottom panel as described in Section 14.3(c).  
Connect the mains electrical supply to the appliance at terminal  
X1. See Fig. 23. Connect any room and/or frost thermostats. The  
electrical leads must pass through the appropriate space in the  
control panel and be fixed with the cable clamps provided. Refit  
the facia panel.  
Fig. 22. Vertical adaptor with  
horizontal flue.  
Y-162  
Test the gas supply pipework up to the appliance for soundness  
as indicated in BS 6891.  
Refer to Section 12 for a full description of the filling, venting and  
the pressurising of the system.  
90¡  
90¡  
Z-41  
If the appliance is not to be commissioned immediately, replace  
the cabinet front panel. Check that the gas supply, the electrical  
supply and the water connections are all turned off.  
If the premises are to be left unoccupied during frosty conditions,  
then drain the appliance and system. For short inoperative  
periods, leave the appliance under the control of the built in frost  
thermostat or the remote frost thermostat (if fitted) or leave  
operating continuously with the room thermostat set at 6°C.  
X-168  
Vertical flue adaptor required  
for upwards section  
Appliance  
TOTAL STRAIGHT FLUE LENGTH  
X + Y + Z or X + Z  
2500mm with one bend  
1750mm with two bends  
1000mm with three bends  
Fig. 23. Mains electricity connections.  
230V  
N
L
X1  
X2  
Blue  
Brown  
Strain relief clamp  
Programmer and room thermostat  
strain relief clamps  
Green/yellow  
15  
12. Commissioning The Appliance  
12.1 SUMMARY  
Fig. 25. Appliance components and fixings  
(upper assembly).  
The appliance is dispatched with the controls set to provide a  
maximum output for domestic hot water and central heating of  
23.4 kW (80,000 Btu/h). The appliance automatically modulates  
to satisfy lower heat loads.  
Flue Gas  
Test Point  
Flue hood  
Fan assembly  
fixing screws (4)  
Domestic Hot Water and Central Heating Systems. Check that  
both the mains water supply and central heating systems have  
been fully flushed out at installation.  
Overheat  
thermostat  
Gas Service. The complete system, including the meter, must be  
inspected and tested for soundness and purged as indicated in  
BS 6891.  
Auto air  
vent  
12.2 APPLIANCE AND CENTRAL HEATING  
SYSTEM PREPARATION  
Remove the cabinet front panel.  
Check that the electrical supply and the gas service to the  
appliance are off.  
Combustion  
chamber  
cover fixing  
clips (2)  
Check that all the water connections throughout the system are  
tight.  
Open the system valves at the appliance. Open all the radiator  
valves, fill the system and vent each radiator in turn.  
Remove the inner casing cover as described in section 14.3(b).  
See Fig 24.  
Burner fixing  
screws (2)  
Fig. 24. Appliance casing and control  
equipment fixings.  
Note: 1 bar is equivalent to 10.2 metres (33.5 ft) of water.  
Set the movable pointer on the pressure gauge to coincide with  
the indicating pointer giving a permanent record of the set  
system pressure.  
If the pressure indicated on the pressure gauge is greater than  
2.6 bar when operating at the maximum central heating  
temperature, an extra expansion vessel must be fitted to the  
system as close as possible to the appliance central heating  
return connection.  
Side casing  
Inner casing  
fixing  
cover  
screws (4)  
screws (4)  
The appliance (as dispatched) can accommodate a system  
volume of about 100 litres. Refer to BS 7074 Part 1. If the system  
volume is in excess of that accommodated by the expansion  
vessel fitted to the appliance then an extra vessel must be fitted  
as close as possible to the central heating return connection of  
the appliance.  
Any extra vessel fitted must be pressurised to the same figure as  
the integral vessel. If the expansion vessel fails then the specified  
replacement must be fitted.  
Facia panel  
fixing  
screws (2)  
Fig. 26. Pressure relief valve.  
Bottom facia  
panel fixing  
screws (3)  
The automatic air vent will vent the appliance. Check that the air  
vent cap has been removed. See Fig. 25.  
Pressure relief  
valve.  
(Turn knob  
anti-clockwise  
to test).  
Check that the pressure relief valve operates by turning the knob  
anti-clockwise until it releases. Water should be expelled from  
the discharge pipe. See Fig. 26. Lower the control box to gain  
access. Refer to Section 14.3(c).  
Set the Expansion Vessel Pressure  
The charge pressure of the expansion vessel as dispatched is 0.5 bar,  
which is equivalent to a static head of 5 metres (17ft). The charge  
pressure must not be less than the static head at the point of  
connection. A Schraider type tyre valve is fitted to the expansion  
vessel to allow the charge pressure to be increased if necessary.  
Set the System Pressure  
Fill the system until the pressure gauge shows 2.5 bar (37  
2
lb/ins ) and check for water soundness. Release water from the  
system using the relief valve test knob until the initial System  
Design Pressure is obtained, up to a maximum of 1.5 bar.  
Initial System Design Pressure (bar) = Expansion Vessel Charge  
Pressure +0.3 (bar).  
16  
12.3 PROGRAMMER  
Central Heating  
Any programmer fitted on the appliance should be set up at this  
stage following the instructions sent with the programmer.  
12.4 APPLIANCE OPERATION  
Check that all the radiator valves are open.  
Check that the system is pressurised and set to the required  
pressure as indicated on the gauge.  
Turn off the gas and electricity supplies to the appliance.  
Undo the two screws and hinge down the facia.  
Loosen the burner pressure test point screw and connect a  
pressure gauge. See Fig. 27.  
Set any Programmer to HEATING & WATER.  
Turn on the gas and electricity supplies.  
Set the room thermostat and the Central Heating Temperature  
Control to maximum.  
The burner will light.  
The appliance will modulate its output between 7.5 and 23.4 kW  
over a period of about twenty minutes.  
Fig. 27. Gas valve.  
Check the system to ensure that all the radiators are heating up  
evenly.  
Maximum pressure  
adjuster  
Minimum  
pressure  
adjuster  
Main gas valve  
connections  
(Black : blue : brown :  
green/yellow)  
Note: Clockwise to  
increase and anti-  
clockwise to  
decrease the  
pressure  
Shut down all but one of the radiators and observe the burner  
pressure fall. Open all of the radiator valves and check that the  
burner pressure rises.  
Balance the system so that the required temperature difference  
across the central heating flow and return pipes is obtained. See  
Table 3, Section 3 Data Tables.  
Burner pressure  
test point  
Set the room thermostat to minimum and check that the burner  
goes out. Reset the room thermostat to maximum and the  
burner will re-light after a short anti-cycle delay and follow the  
normal operating procedure.  
Check for proper ignition of the burner after a break in the gas  
supply. Turn off the gas service cock and wait for 60 seconds. The  
burner will go out but sparking from the electrode will continue  
for 10 seconds when the appliance will enter a “lockout” state.  
Carefully open the gas service cock, interrupt the mains power  
supply to the appliance for a few seconds to reset the controls  
and observe the burner re-light and follow the normal sequence  
of operation.  
Inlet pressure test  
point  
Turn off the gas service cock and the electrical supply to the  
appliance.  
Electrical connections Ð  
modulator (Blue : Blue)  
Drain the system while the appliance is still hot.  
Refill, vent and re-pressurise as described in Section 12.2.  
Domestic Hot Water and Central Heating  
Turn on the electricity supply to the appliance and open the gas  
supply cock at the appliance.  
Modulating  
solenoid  
Set the Central Heating temperature control knob to demand  
and any programmer to HEATING & WATER. If a programmer is  
fitted, set the domestic hot water to Continuous or 24 Hrs and  
the central heating to ON. The burner will light and heat will pass  
into the system. Turn on a hot water tap and check that after a  
short delay fully heated hot water is discharged from the tap.  
Close the tap and the burner will go off. After a short time the  
appliance will then return to the central heating mode and  
automatically balance with the system requirements.  
Set the Central Heating Temperature Control Knob to OFF and the  
burner will go out.  
Domestic Hot Water.  
Set any Programmer to HEATING & WATER.  
Turn on the gas and electricity supplies.  
Set the Central Heating temperature control knob to Off.  
A tap should be opened to create a hot water demand then a  
continuous ignition spark will occur until the burner is alight and  
sensed by the control circuit. The burner will light and remain at  
its maximum setting. The burner pressure should be between  
13.4 and 13.8 mbar on Natural gas (33.0 and 35.0 mbar on  
Propane). If the burner pressure is low, check that the supply  
pressure at the gas valve inlet is at least 19 mbar for Natural gas  
(37 mbar for Propane).  
12.5 COMPLETION OF COMMISSIONING  
Disconnect the pressure gauge and tighten the test point screw.  
Restart the appliance and check for gas soundness around the  
test point screw.  
Test for gas soundness at the joint between the burner and the  
gas valve with leak detection fluid.  
Note: The burner pressure is factory set and if (after checking  
that the supply pressure is sufficient) the correct pressure is not  
obtained then Worcester Heat Systems Service Department  
should be contacted.  
Gradually close the hot tap and check that the burner pressure  
drops. Fully open the tap and check that the burner pressure  
rises. Fully close the tap and check that the burner goes off. The  
fan may continue running until the appliance has cooled.  
Refit the cabinet front panel.  
If the appliance is being passed over to the user immediately,  
refer to Section 13 - Instructions to the User and set the controls  
to the users requirements.  
If the appliance is to be left inoperative, check that the Central  
Heating Temperature Control is set to OFF. Turn off the gas service  
cock and switch off the electricity supply.  
If there is any possibility of the appliance and system being left  
inoperative during frosty conditions, drain the appliance and  
system. If the premises are to be left unoccupied during frosty  
conditions, then drain the appliance and system. For short  
inoperative periods, leave the appliance under the control of the  
built in frost thermostat or the remote frost thermostat (if fitted)  
or leave operating continuously with the room thermostat set at  
6°C.  
17  
13. Instructions To The User  
14. Inspection And Service  
13.1 Tell the user how to operate the appliance and hand over  
the Users Instructions leaflet.  
14.1 SERVICING  
To ensure continued efficient operation of the appliance it must  
be checked and serviced as necessary at regular intervals. The  
frequency of servicing will depend upon the particular  
installation conditions and usage, but once per year should  
generally be adequate. The extent of the service required by the  
appliance is determined by the operating condition of the  
appliance when tested by fully qualified engineers.  
Any service work must be carried out by competent engineers  
such as British Gas or Corgi registered personnel.  
14.2 PRE-SERVICE INSPECTION  
13.2 Tell the user what to do if the heating system is not to be  
used in frosty weather.  
13.3 Tell the user the sealed system set pressure.  
13.4 Tell the user of the importance of regular servicing.  
Worcester Heat Systems Ltd. offer a comprehensive maintenance  
contract.  
13.5 Set the system controls to the user’s requirements.  
13.6 If an external programmer has been fitted which has a  
programmable domestic hot water facility then it is suggested  
that this be set to Continuous or the equivalent.  
Check that the flue terminal and the terminal guard, (if fitted), are  
clear.  
If the appliance is in a compartment, check that the ventilation  
openings in the compartment door or walls are clear. See Section  
6 - Air Supply.  
Fig. 28. User controls.  
Reset button  
Check the system and remake any joints or fittings which show  
signs of leakage.  
Refill, vent and re-pressurise as described in Section 12.2.  
Operate the appliance and the system taking note of any faults.  
Measurement of the Flue Gases  
For consistency of results of the flue gas measurements it is  
necessary to have a constant output and for the appliance to be  
at equilibrium.  
Turn on a tap to create a hot water demand.  
Wait until the appliance reaches thermal equilibrium (approx. 10  
minutes).  
Remove the test point sealing screw on the appliance top panel.  
See Fig. 30.  
Connect to the test point with a piece of tubing.  
Expected measurements should be between:  
For Natural Gas:  
Mains indicator  
Equivalent flue  
length (metres)  
Carbon  
Carbon  
System  
pressure  
gauge  
Dioxide (%)  
Monoxide (%)  
0.5  
1.0  
1.5  
2.0  
2.5  
6.9  
7.0  
7.1  
7.3  
7.4  
0.0008  
0.0009  
0.0010  
0.0012  
0.0013  
C.H. temperature control  
and on/off knob  
For Propane:  
Equivalent flue  
length (metres)  
Carbon  
Dioxide (%)  
Carbon  
Monoxide (%)  
0.5  
1.0  
1.5  
2.0  
2.5  
7.9  
8.0  
8.2  
8.5  
8.8  
0.0017  
0.0020  
0.0024  
0.0030  
0.0035  
When calculating the equivalent flue length a flue bend is  
equivalent to 750mm of straight flue.  
After taking the measurement replace and tighten the sealing  
screw.  
IMPORTANT  
Disconnect the electrical supply at the mains and turn off the  
gas supply at the gas service cock on the appliance before  
servicing.  
After completing the service always test for gas soundness as  
indicated in BS 6891.  
18  
14.3 DISMANTLE THE APPLIANCE  
(d) Bottom panel. Unclip and remove the appliance bottom  
panel.  
To carry out a full and comprehensive service of the appliance  
remove the following parts to gain access to the components  
which need to be checked or serviced.  
(e) Fan. Remove the inner casing cover. Carefully unplug the  
electrical connections and pull off the sensing tubes. Unscrew  
the four fixing screws and remove the fan assembly. See Fig. 30.  
(f) Combustion Chamber Front. Remove the inner casing cover.  
Undo the spring clips fixing the combustion chamber front. See  
Fig. 30.  
Fig. 29. Appliance casing and control  
equipment fixings.  
(g) Flue Hood Assembly. Remove the fan assembly. Remove the  
combustion chamber front. Lift and slide the flue hood assembly  
from the appliance. See Fig. 30. When refitting the hood ensure  
that the rear return edge passes under the lip at the rear of the  
combustion chamber.  
Side casing  
Inner casing  
fixing  
cover  
screws (4)  
screws (4)  
(h) Burner Assembly. Remove the combustion chamber front.  
Pull off the two spark electrode leads and disconnect the flame  
sense lead. Undo the burner fixing screws. Lift up and remove  
the burner assembly from the appliance. See Fig. 31.  
Fig. 31. Burner and electrode assembly.  
Facia panel  
fixing  
screws (2)  
Injector  
Bottom facia  
panel fixing  
screws (3)  
(a) Cabinet Front Panel. Remove by lifting off the supports.  
(b) Inner Casing Cover. Check that the electricity supply to the  
appliance is turned off. Remove the cabinet front panel. Unscrew  
the four screws securing the cover to the casing and lift off. See  
Fig. 29.  
(c) Facia Panel. Check that the electricity supply to the appliance  
is turned off. Remove the cabinet front panel. Unscrew the two  
upper screws as shown in Fig. 29. and hinge down the facia  
taking care not to damage the pressure gauge capillary tube or  
electrical connections.  
Spark electrode  
14.4 SERVICE OF COMPONENTS  
Clean the Fan. Any dust or fluff should be removed with a soft  
brush or by blowing. Take care not to distort the pressure  
sensing device.  
Clean the Main Burner. Brush the blade tops and mixing tube  
with a soft brush and check that all the flame ports are clear.  
Remove any blockages with a non-metallic brush. Inspect the  
injector and clean with a soft brush. Replace the injector if it  
appears damaged. Do not use a wire brush or anything likely to  
cause damage. Replace the spark and sense electrodes if they  
appear damaged.  
Fig. 30. Appliance components and fixings  
(upper assembly).  
Flue Gas  
Test Point  
Flue hood  
Fan assembly  
fixing screws (4)  
Clean the Gas to Water Heat Exchanger. Clean the heat  
exchanger using a soft brush. Remove the deposits from the  
bottom of the combustion chamber. Do not distort any of the  
blades.  
Combustion Chamber Insulation. Examine and replace any  
pads that are damaged. Remove any dust or deposits using a  
soft brush.  
Overheat  
thermostat  
Auto air  
vent  
Reassemble the appliance in the reverse order.  
Check that all components are in place and correctly fixed. Leave  
the cabinet front panel to be fitted after checking the operation  
of the appliance.  
Combustion  
chamber  
cover fixing  
clips (2)  
14.5 TEST THE APPLIANCE  
On completion of the service and reassembly of the appliance,  
check for gas soundness and the correct operation of the  
appliance as described in Section 12 - Commissioning.  
Refit the cabinet front panel and reset the controls to the users  
requirements.  
Burner fixing  
screws (2)  
19  
2. Air Pressure Switch. See Fig. 34.  
15. Replacement Of Parts  
15.1 IMPORTANT  
Check that the electricity supply to the appliance is turned off.  
Remove the cabinet front panel as described in Section 14.3 (a)  
and lower the facia. Section 14.3(c).  
Switch off the electricity and gas supplies before replacing any  
components. After the replacement of any components, check  
for gas soundness where relevant and carry out functional  
checks as described in Section 12 - Commissioning  
Carefully pull off the sensing tubes and the electrical connections  
from the switch. Remember to note their positions.  
Unscrew the two screws behind the Air Pressure Switch and  
remove the switch from the appliance.  
15.2 COMPONENT ACCESS  
Fit the replacement switch in the reverse order ensuring that the  
electrical connections have been made to the correct terminals  
on the switch. Check that the sensing tubes are fitted correctly.  
3. Fan. See Fig. 30.  
To replace components it is necessary to remove one or more  
sections of the cabinet and cover plates within the appliance as  
described in Section 14.3. The facia panel may also need to be  
hinged down as described in Section 14.3 (c).  
Check that the electricity supply to the appliance is turned off.  
Remove the fan assembly as described in Section 14.3(e).  
Fit the replacement fan in the reverse order.  
15.3 DRAINING THE APPLIANCE  
Check that the electricity supply to the appliance is turned off.  
Before removing any component holding water it is important  
that as much water as possible is removed from the appliance.  
(a) Central Heating Circuit. Turn off the central heating flow and  
return valves at the appliance. Open the pressure relief valve,  
make sure that the dust cap on the auto air vent is removed. See  
Fig. 30. Close the pressure relief valve when the flow has  
stopped. Some water will remain in the expansion vessel, pump  
and Gas to Water heat exchangers and extra care must be taken  
when removing these components.  
4. Overheat Thermostat. See Fig. 30 and 32.  
Check that the electricity supply to the appliance is turned off.  
Remove the inner casing cover as described in Section 14.3 (b).  
Carefully pull off the two wires from the thermostat head.  
Undo the retaining nut on the top of the appliance and remove  
the retaining clip from the heat exchanger. Carefully withdraw  
the thermostat from the appliance.  
Fit the replacement thermostat in the reverse order ensuring that  
some heat sink compound is between the thermostat and the  
heat exchanger.  
(b) Domestic Hot Water Circuit. Turn off the mains cold supply  
valve at the appliance and open the lowest hot water tap. A  
quantity of water will remain in the Gas to Water heat exchanger,  
extra care must be taken when removing this component.  
15.4 COMPONENT REPLACEMENT  
5. Gas to Water Heat Exchanger. See Fig. 32.  
Check that the electricity supply to the appliance is turned off.  
Drain the central heating circuit and domestic circuits as  
described in Section 15.3 (a) and (b).  
1. Automatic Air Vent. See Figs. 30. and 32.  
Remove the inner casing cover, fan, flue hood assembly,  
combustion chamber front, overheat thermostat, automatic air  
vent and combustion chamber side insulation as described in  
Sections 14.3 (b, e, f and g), 15.4 (1) and 15.4 (4).  
Remove the inner casing cover as described in Section 14.3 (b).  
Drain the central heating circuit as described in Section 15.3 (a).  
Unscrew air vent from the heat exchanger.  
Fit the replacement assembly ensuring thread sealant is applied  
and the dust cap is removed.  
Fit the replacement heat exchanger in the reverse order ensuring  
that all the fibre washers are correctly fitted and a layer of heat  
sink compound is on the thermostat.  
Open the valves and fill and re-pressurise the system as  
described in Section 12.2.  
Open the valves and fill and re-pressurise the system as  
described in Section 12.2.  
Fig. 32. Combustion chamber.  
Heat  
exchanger  
Auto air  
vent  
Overheat  
Thermostat  
Hot water heat  
exchanger  
connections  
Central heating  
heat exchanger  
connections  
Cut-outs in  
combustion  
chamber sides  
Pump bulk  
head  
connector  
20  
6. Combustion Chamber Insulation.  
Restart the appliance in central heating mode and adjust the  
minimum adjustment screw on the gas valve to give a pressure  
of 1.0 mbar on natural gas or 3.5 mbar on propane. See Fig. 33.  
After completing the adjustments, check the minimum and  
maximum pressures and re-adjust as necessary. Once this has  
been done the clear cap should be re-fitted to the adjuster and  
the retaining screw tightened. Coat the screw with paint or nail  
varnish to prevent user adjustment.  
Check that the electricity supply to the appliance is turned off.  
Drain the central heating circuit as described in Section 15.3(a).  
Remove the inner casing cover, fan, flue hood assembly, burner,  
and Gas to Water heat exchanger as described in Sections 14.3  
(b, e and f), and 15.4 (5). Remove the fibre insulation pads from  
the combustion chamber side, rear, and front sections.  
Fit the replacement pads in the reverse order taking care not to  
damage them.  
Open the valves and fill and re-pressurise the system as  
described in Section 12.2.  
Fig. 27. Gas valve.  
7. Burner. See Fig. 31.  
Maximum pressure  
adjuster  
Note: Clockwise to  
increase and anti-  
clockwise to  
Check that the electricity and gas supplies to the appliance are  
turned off.  
Main gas valve  
connections  
(Black : blue : brown :  
green/yellow)  
Minimum  
pressure  
adjuster  
Remove the burner assembly as described in Section 14.3 (h).  
Fit the replacement burner in the reverse order taking care not to  
damage the electrode leads.  
decrease the  
pressure  
Burner pressure  
test point  
8. Burner Injector. See Fig. 31.  
Remove the burner as described in Section 14.3 (h).  
Unscrew the brass injector from the manifold.  
Fit the replacement injector in the reverse order.  
9. Spark Electrode Assembly. See Fig. 31a.  
Remove the combustion chamber front as described in 14.3 (g)  
Carefully pull off the two electrode leads,  
Undo the M4 extended nut and remove the spark electrode  
assembly from the burner.  
Fit the replacement electrode in the reverse order, checking that  
the spark gap is 3.5 to 4.5mm.  
Fig. 31a. Spark electrode assembly.  
Inlet pressure test  
point  
3.5-4.5mm  
2.5-5mm  
Electrical connections Ð  
modulator (Blue : Blue)  
Modulating  
solenoid  
12. Central Heating Sensor. See Fig. 34.  
Check that the electricity supply to the appliance is turned off.  
Hinge the facia assembly in the servicing position as described in  
Section 14.3(c and d).  
Carefully pull off the two leads from the sensor.  
Pull off the sensor and spring retaining clip from the pipe.  
Fit the replacement sensor in reverse order with a layer of heat  
sink compound between the faces. Refit the leads.  
10. Flame Sensor. See Fig. 31.  
Remove the burner as described in sections 14.3(h) and 15.4(8).  
Undo the M3 screw and remove the sense electrode from the  
burner.  
Fit the replacement electrode in the reverse order, checking that  
the sense gap is 5 to 6mm.  
Fig. 34. Gas valve pump and air pressure  
switch.  
Air pressure switch  
connecting tubes  
11. Gas Valve. See Figs. 33. and 34.  
Top gas valve  
connection (4 bolts)  
Gas  
valve  
Pump  
Check that the electricity and gas supplies to the appliance are  
turned off.  
Hinge down the control box assembly in the servicing position  
as described in Section 14.3(d).  
Whilst supporting the valve unscrew the plug retaining screw  
and carefully pull off the electrical solenoid plug connection and  
the two modureg leads.  
Undo the 8 manifold screws and remove the gas valve. See Fig. 34.  
Fit the replacement gas valve in the reverse order ensuring the  
“O” rings are correctly fitted.  
Turn on the gas supply and check for soundness.  
To set the burner pressure. See Fig. 33.  
The minimum and maximum burner pressures must be set after  
a new gas control has been fitted.  
The maximum burner pressure must be set first, as any  
adjustment of the maximum pressure influences the minimum  
pressure setting.  
Red  
pipe  
Start the appliance in the domestic hot water mode as described  
in section 12.4. - Appliance Operation.  
Adjust the maximum pressure adjustment screw on the gas  
valve to give a burner pressure of 13.6 mbar on natural gas, for  
propane the maximum pressure adjustment must be increased  
to maximum clockwise, this should give 33.0 - 35.0 mbar.  
End the demand and reset the appliance by interrupting the  
mains electricity supply. (Otherwise there is a four minute anti-  
cycle delay at the end of a demand).  
Pressure gauge  
connection  
Central Heating  
Sensor  
Gas valve  
electrical  
connections  
Lower pump  
connection  
Air pressure  
switch  
21  
13. Domestic Hot Water Sensor.  
16. Pressure Relief Valve. See Fig. 35.  
Check that the electricity supply to the appliance is turned off.  
Hinge the facia assembly in the servicing position as described in  
Section 14.3(c and d).  
Drain the central heating circuit as described in Section 15.3(a).  
Hinge down the facia assembly as described in Section 14.3(c)  
Remove the Bottom panel as described in Section 14.3(d)  
Undo the discharge pipe connection and remove the valve  
retaining clip. Remove the valve taking care not to distort the  
pipework.  
Fit the replacement valve in reverse order. Reconnect the  
discharge pipe.  
Open the valves and fill and re-pressurise the system as  
described in Section 12.2  
Carefully pull off the two leads from the sensor.  
Undo and remove the clamping screw.  
Pull off the sensor and spring retaining clip from the pipe.  
Fit the replacement sensor in the reverse order ensuring a layer  
of heat sink compound is between the faces. Refit the leads.  
14. Circulating Pump. See Figs. 32 and 34.  
Check that the electricity supply to the appliance is turned off.  
Drain the central heating circuit as described in Section 15.3(a).  
Hinge the facia assembly in the servicing position as described in  
Section 14.3(c).  
Undo the two union nuts and the pipe to the expansion vessel,  
remove the pump from the pipe-work. Support the pump and  
remove the electrical cover.  
Disconnect the electrical wires taking note of their positions.  
Fit the replacement pump in the reverse order using new sealing  
washers.  
(Alternatively replace the pump head only by removing the four  
Allen screws on the pump, remove the head and support whilst  
removing the electrical connections. Refit the new head).  
Open the valves and fill and re-pressurise the system as  
described in Section 12.2  
Note: The direction of flow should be upwards. The speed should  
always be set to maximum.  
17. Water Flow Switch. See Fig. 36.  
Check that the electricity supply to the appliance is turned off.  
Drain the domestic hot water circuit as described in Section  
15.3(b).  
Remove the two upper screws and hinge down the facia panel as  
described in Section 14.3(c).  
Undo the two union nuts securing the “T” piece and remove the  
housing from the pipework.  
Disconnect the electrical connection.  
Fit the replacement water flow switch in the reverse order  
ensuring new fibre washers are fitted to the new switch body.  
Fig. 36. Water Flow Switch. (Side View)  
15. Expansion Vessel.  
Drain the central heating circuit as described in Section 15.3(a).  
Isolate the gas supply at the mains.  
Then either fit a separate expansion vessel on the central heating  
return to the appliance or replace the existing vessel as  
described below.  
Drain the domestic circuit as described in Section 15.3(b).  
Disconnect the flue system at the boiler.  
Flow Restrictor  
Disconnect the appliance pipework at the appliance entry points  
ensuring precautions are taken to cope with any water  
remaining in the appliance.  
Remove the appliance from the wall.  
Disconnect the expansion vessel from the appliance by undoing  
the fitting nut at it’s base.  
Fit the replacement vessel in the reverse order.  
Open the valves and fill and re-pressurise the system as  
described in Section 12.2  
Water Flow Switch  
ÒTÓ Piece  
Fig. 35. Pressure relief valve.  
18. Domestic Hot Water Flow Restrictor. See Fig. 36.  
Remove the water flow switch as described in Section 15.4-17.  
Undo the two union nuts securing the “T” piece and remove the  
housing from the pipework.  
Pressure relief  
valve.  
(Turn knob  
anti-clockwise  
to test).  
The plastic flow restrictor is located within the “T” piece on the  
water flow switch.  
Fit the replacement flow restrictor and reassemble in the reverse  
order ensuring the fibre washers are in place.  
19. Pressure Gauge.  
Check that the electricity supply to the appliance is turned off.  
Drain the central heating circuit as described in Section 15.3(a).  
Remove the two upper screws and hinge down the facia panel as  
described in Section 14.3(c).  
Prize back the retaining clips securing the gauge to the facia  
panel remove wire clip and unplug the gauge from the pump  
inlet pipe.  
Fit the replacement gauge in the reverse order ensuring the “O”  
ring is in place.  
Open the valves and fill and re-pressurise the system as  
described in Section 12.2  
22  
20. Control Board.  
Fit the new sensor ensuring the correct orientation and carefully  
tighten the retaining screw.  
Refit the fan assembly in reverse order.  
Check that the electricity supply to the appliance is turned off.  
Undo the 3 screws and remove the facia bottom panel.  
Remove the two upper screws and hinge down the facia  
assembly.  
Carefully pull off all the connectors. Disconnect the mains supply  
lead at terminal X1 and the earth connection at the back.  
Remove the four corner screws on the back of the facia and  
separate the metal back panel from the plastic facia.  
Remove and retain the brass nut and washer.  
Release the six pillars on the control board and pull the control  
board forward off the back panel.  
Fig. 37. Gauze Filter.  
Fit the replacement board in the reverse order ensuring it is  
pushed firmly onto the six pillars and clicks into place. Special  
care should be taken with the brass post and nut to ensure a  
good earth contact. (Check earth continuity between the  
incoming earth and the appliance chassis).  
Gauze Filter  
Isolating Valve  
Refit the facia panel and hinge the control box assembly in the  
servicing position as described in Section 14.3 (c).  
21. Gauze filter. See Fig. 37.  
Fig. 38. Flue flow sensor.  
Remove the water flow switch as described in section 15.4-17.  
Undo the lower union nut on flow switch housing.  
Undo the nut on the isolating valve and remove the mains water  
inlet pipe. Carefully extract the filter from the valve end of the  
pipe.  
Replace the filter and refit the pipe in reverse order.  
22. Flue flow sensor. See Fig. 38.  
Check that the electricity supply to the appliance is turned off.  
Remove the fan assembly as described in Section 14.3(e).  
Unscrew the single central retaining screw and withdraw the  
sensor from the fan.  
Positive  
16. Conversion Instructions  
5. Refit the end cap ensuring the bracket is in the correct  
orientation.  
6. Refit the burner to the appliance and re-assemble the  
inner casing.  
7. Follow the dismantling instructions to remove the gas  
valve and refit the new valve. See Installation Instructions:  
Section 15.4.11 Replacement of Parts, Component  
Replacement, Gas Valve.  
8. Turn on the gas and electricity supplies and following  
the commissioning procedure confirm gas soundness and  
correct boiler operation.  
These instructions should be used when converting appli-  
ances from natural gas to LPG and vice versa.  
Only components supplied by Worcester Heat Systems  
should be used.  
Only competent persons should attempt the conversion.  
Conversion from Natural Gas to LPG should not be  
carried out on appliances installed in a room or inter-  
nal space below ground level.  
1. Ensure the gas service cock is turned OFF and the elec-  
trical supply is isolated.  
9. Set the gas pressure to the required rate for the new gas  
type as specified on the data plate. When this is done refit  
the cap to the adjuster and seal its retaining screw with  
paint or nail varnish.  
2. Refer to section 14.3 Dismantle the Appliance to  
remove the boiler front panel and inner casing. Follow the  
dismantling instructions to remove the burner.  
3. Remove the injector and replace with the injector from  
the kit.  
4. Remove the nut, end cap and bracket from the end of  
the burner.  
4.1 For conversion to Natural gas remove the internal  
gauze.  
4.2 For conversion to LPG fit the gauze into the burner  
body.  
10. Turn off the boiler and when cool peel off the arrow  
from the data plate and re-stick it against the gas type for  
which the appliance is now converted.  
11.Replace the boiler front panel.  
The conversion is now complete.  
Parts List  
Item No.  
Description  
Natural Gas to LPG Kit  
LPG to Natural Gas Kit  
7 716 192 132  
7 716 192 131  
8 716 140 209  
1.  
Burner Injector  
8 716 140 224  
Stereomatic 2.78mm  
Stereomatic 4.3mm  
2.  
3.  
Burner Gauze  
Gas Valve  
8 716 142 601  
8 716 142 430  
Remove Gauze  
8 716 142 413  
23  
24  
25  
18. Fault Finding  
Modulating  
valve  
X6 Pins 15 & 16  
Outputs  
Inputs  
FAN  
N
X4 Pin 3  
X4 Pin 1  
LOW VOLTAGE  
ELECTRONICS  
(Microcontroller)  
RL1  
RL3  
PUMP  
N
N
X3 Pin 1  
X3 Pin 2  
Mains  
indicator  
X5 Pin 3  
GAS VALVE  
F2 1.25AT  
X5 Pin 1  
X5 Pin 2  
RL4  
ROOM STAT  
6
5
4
3
2
1
FULL SEQUENCE  
CONTROLLER  
MAINS  
PROGRAMMER/CLOCK  
X2  
Flame sense  
Spark  
Optional links  
F1 2ATHRC  
X1  
3 2 1  
N
L
26  
Fault in  
Central Heating  
Fault in  
Domestic Hot Water  
YES  
NO  
YES  
NO  
NO  
NO  
GO TO  
Is mains LED flashing?  
Is mains LED flashing?  
CHECK D  
NO  
NO  
Is mains LED  
iluminated?  
Is mains LED  
illuminated?  
GO TO  
CHECK C  
YES  
YES  
Turn control knob  
fully clockwise  
Is control knob  
set for demand?  
YES  
Is a room thermostat  
fitted?  
Ensure link is fitted at  
X2 pins 5 & 6  
YES  
NO  
NO  
NO  
NO  
YES  
Is room thermostat  
calling for heating?  
Set room stat to  
call for heat  
YES  
GO TO  
Ensure link is fitted at  
Is programmer fitted?  
CHECK O  
X2 pins 2 & 3  
YES  
YES  
Is programmer calling  
for heat?  
Set clock to call for heat  
YES  
GO TO  
CHECK F  
Is pump running?  
YES  
GO TO  
CHECK E  
YES  
Has overheat  
thermostat tripped?  
Has overheat  
thermostat tripped  
NO  
NO  
GO TO  
CHECK K  
GO TO  
CHECK K  
27  
No mains LED  
Is mains present at NO  
Connect mains  
supply  
X1 pins 1 & 3?  
YES  
NO  
Is F1 (2ATHRC) OK?  
Replace fuse  
Replace fuse  
YES  
NO  
Is F2 (1.25AT) OK?  
YES  
Faulty PCB  
Replace  
Flashing mains LED  
Remove X6  
Is resistance between  
NO  
NO  
Open circuit  
Short circuit  
pins 3 & 4 between  
690ohms & 33k  
YES  
YES  
Is resistance between  
Faulty  
Faulty  
Faulty  
NO  
GO TO  
GO TO  
pins 19 & 20 between  
690ohms & 33k  
Replace thermistor  
Replace harness  
CHECK H  
CHECK H  
YES  
OK  
OK  
Faulty  
GO TO  
CHECK I  
GO TO  
CHECK J  
OK  
OK  
Faulty PCB  
Replace  
28  
Overheat Thermostat Check  
The overheat thermostat can be  
reset by pressing the reset button,  
but if it trips immediately or on a  
regular basis a serious problem has  
occurred therefore contact your  
installer  
Reset thermostat  
NO  
NO  
Ensure appliance is  
cool and retest  
Is capillary broken?  
Does button hold in?  
YES  
YES  
Is capillary firmly  
NO  
Replace overheat  
thermostat  
ATTACH to heat  
exchanger  
ATTACHED  
to exchanger?  
YES  
GO TO  
CHECK I  
Pump Check  
NO  
Is pump connector  
secure on the PCB (X3)?  
Secure Connector  
YES  
Is mains present at the  
NO  
GO TO  
CHECK O  
pump connector  
(X3 pins 1 & 2)?  
YES  
Faulty pump  
Fan Check  
Is fan connector  
secure on the PCB (X4)?  
NO  
Secure Connector  
YES  
Is mains present at the  
NO  
GO TO  
CHECK L  
fan connector  
(X4 pins 1 & 2)?  
YES  
NO  
Mains at fan  
Faulty Harness  
YES  
Faulty fan  
29  
Thermistor Check  
Remove connectors  
from thermistor  
YES  
Is resistance between  
terminals of thermistor  
between 690ohms & 33k  
NO  
Faulty thermistor  
YES  
Thermistor OK  
Harness Continuity Check  
Remove appropriate  
connectors  
YES  
Is continuity observed  
between each end of  
wire in question?  
NO  
Faulty harness  
or connector  
YES  
Harness OK  
Harness Short Check  
Remove appropriate  
connectors  
YES  
Is short circuit  
observed between pair  
of wires in question?  
NO  
Faulty harness  
YES  
Harness OK  
30  
Ignition Check  
NO  
NO  
NO  
GO TO  
Is fan running?  
CHECK G  
YES  
GO TO  
CHECK E  
GO TO  
Faulty PCB  
Replace  
Does sparking occur?  
CHECK L  
YES  
Are ignition leads  
connected both  
ends securely?  
NO  
Is sparking present at  
the electrodes?  
NO  
NO  
Connect ignition leads  
securely  
Does ignition occur?  
YES  
YES  
YES  
Ignition coil faulty  
replace PCB  
GO TO  
CHECK M  
Are leads breaking  
down?  
YES  
Replace leads  
Ensure flame sense  
electrode in flame at  
minimum burner  
pressure  
NO  
Is flame sense  
NO  
NO  
Does burner continue?  
electrode in flame?  
YES  
YES  
Is lead secure  
both ends?  
Secure lead  
YES  
GO TO  
CHECK I  
HARNESS OK  
Faulty PCB  
Replace  
NO  
Does gas pressure  
modulate?  
GO TO  
CHECK N  
YES  
Ignition OK  
31  
L
Air Pressure Switch Check  
Remove BROWN and  
WHITE terminals  
from air pressure  
switch  
With no demand, is a  
short-circuit observed  
at exposed APS  
terminals?  
NO  
Air pressure switch  
faulty  
YES  
NO  
NO  
Is there mains 230V  
at fan connector X4  
pins 1 and 3?  
PCB faulty  
Reconnect the  
WHITE & BROWN  
wire and remove the  
GREEN wire. Initiate  
a demand.  
YES  
Does the fan run?  
Fan or fan cable  
faulty  
YES  
NO  
Air pressure switch  
faulty  
With fan running  
disconnect BROWN  
wire. (DO NOT touch  
chassis with it). Is a  
short circuit observed  
across exposed APS  
terminals?  
YES  
APS OK  
Gas Valve Check  
NO  
Is gas pressure present  
at input to gas valve?  
Ensure gas supply  
YES  
Is live output present at  
NO  
Faulty board  
Replace  
X5 pins 1 & 2 relative to  
neutral at pin 3?  
YES  
Is gas pressure present NO  
Faulty gas valve  
Replace  
at input to burner?  
YES  
Gas valve OK  
32  
Modulating Valve Check  
N
Is minimum pressure  
observed at burner at all  
times?  
YES  
Remove X6, measure  
resistance between  
pins 15 & 16  
NO  
NO  
Is resistance  
nominally 125ohms  
GO TO  
CHECK I  
YES  
Is pressure at burner YES  
NO  
With pressure above  
minimum, remove Modureg  
Lead. Does pressure drop to  
minimum?  
Faulty modulating valve .  
Replace gas valve  
Reconnect X6 and measure  
voltage across modulating  
valve during operation  
always the same?  
NO  
YES  
Gas valve OK  
YES  
Does voltage  
go above 6.25V  
NO  
Faulty PCB.  
Replace  
Flow Switch Check  
Remove X6  
Close all taps to set no  
domestic flow  
NO  
Is open circuit observed  
Faulty flow switch.  
Replace  
at X6 pins 1 & 2?  
YES  
Open a tap fully to set  
domestic flow  
HARNESS OK  
NO  
Faulty flow switch.  
Replace  
Is short circuit observed  
GO TO  
CHECK I  
at X6 pins 1 & 2  
YES  
Flow Switch OK  
33  
19. Component Parts List  
Key  
No.  
G.C. No.  
Part  
Manufacturer’s Reference  
Qty  
WHS  
Part No.  
1
2
3
E01-579  
E01-580  
E01-591  
E00-741  
E01-892  
E01-893  
E01-596  
375 697  
E01-612  
E01-930  
E01-598  
E01-599  
E01-600  
E01-601  
299-506  
375 699  
E01-602  
E01-603  
E01-604  
E04-582  
E01-900  
299-495  
E01-605  
324-822  
299-363  
E01-606  
E01-607  
E01-886  
299-357  
E01-610  
Burner Assembly Natural Gas  
Burner Assembly LPG  
Injector Natural Gas  
Injector LPG  
Gas Valve Natural Gas  
Gas Valve LPG  
Air Pressure Switch  
Spark Electrode Assembly  
Flame Sensor  
Flame Sensor Harness  
Ignition Harness  
Aeromatic  
Aeromatic  
Stereomatic O 4.3mm  
Stereomatic O 2.78mm  
SIT  
AC23/053586  
AC23/053587  
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
2
1
1
1
1
1
1
1
1
1
1
8 716 142 604 0  
8 716 142 611 0  
8 716 140 224 0  
8 716 140 209 0  
8 716 142 413 0  
8 716 142 430 0  
8 716 142 414 0  
8 716 142 100 0  
8 716 120 345 0  
8 716 120 126 0  
8 716 120 236 0  
8 716 142 905 0  
7 716 192 216 0  
8 716 140 504 0  
8 716 142 300 0  
8 716 142 404 0  
8 716 143 107 0  
8 716 142 502 0  
8 716 146 300 0  
8 716 142 384 0  
8 716 148 313 0  
8 716 148 303 0  
8 716 141 052 0  
8 716 148 401 0  
8 716 141 000 0  
8 716 120 993 0  
8 716 142 307 0  
8 716 120 971 0  
7 716 192 206 0  
7 716 192 218 0  
SIT  
4
5
6
Huba 605.99484  
Buccleuch  
Buccleuch  
7
8
9
10  
11  
12  
13  
14  
15  
16  
Buccleuch  
Giannonni  
WHS  
Intermes  
Gas to Water Heat Exchanger  
Insulation Pack  
Auto Air Vent  
Pressure Gauge  
Cewal  
Pressure Relief Valve  
Pump with Harness  
Expansion Vessel (8Ltr) 389mm Dia  
PCB Boiler Control  
Temperature Thermistors  
CH Thermistor Clip  
DHW Thermistor Clip  
DHW Flow Regulator  
Gauze Filter  
Flow Sensor  
Fan Assembly  
Safety Temperature Limiter  
Flow Switch Assembly  
Fuse Pack  
Caleffi 3141 3bar  
Grundfos 15 60 special  
Winkelman Panhof  
Pactrol  
Elmwood  
18  
19  
20  
21  
22  
23  
24  
25  
WHS  
WHS  
SIFAN  
Ranco LM7  
SIKA  
WHS  
WHS  
Gasket Pack  
ACCESSORIES  
299-360  
Mechanical Programmer Kit  
Gas Conversion Kit  
Gas Conversion Kit  
Deihl  
NG to LPG  
LPG to NG  
7 716 192 002 0  
7 716 192 131 0  
7 716 192 132 0  
7 716 192 188 0  
E01-940  
E01-941  
E05-341  
Mini Expansion Vessel Kit  
Including new pipe and Expansion Vessel  
FLUE OPTIONS  
E01-942  
E01-943  
E01-944  
E01-945  
E01-946  
E01-058  
E01-059  
Telescopic Horizontal Flue Kit  
Extension Flue Kit  
Vertical Flue Kit  
Vertical Flue Adaptor  
Internal Fixing Kit  
Flue Elbow Kit  
127-350 mm  
750 mm  
7 716 191 005 0  
7 716 191 006 0  
7 716 191 015 0  
7 716 191 016 0  
7 716 191 019 0  
7 716 191 013 0  
7 716 191 014 0  
Telescopic Flue  
90 deg.  
45 deg.  
Flue Elbow Kit  
34  
9
8
14  
3
21  
1
15  
22  
4
7
13  
11  
12  
10  
20  
23  
6
2
19  
16  
18  
25  
24  
35  
Bosch Group  
Worcester Heat Systems Limited, Cotswold Way, Warndon, Worcester WR4 9SW.  
Telephone: (01905) 754624. Fax: (01905) 754619.  
Technical Helpline (0990) 266241.  
This booklet is accurate at the date of printing but will be superseded and should be disregarded if specifications and/or appearances are changed in the interests  
of continued improvement.  
All goods sold are subject to our official Conditions of Sale, a copy of which may be obtained on application.  
PUBLICATION 8 716 145 028C 11/98  

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