Worcester Greenstar 25Si Installation And Servicing Instructions

25Si / 28Si
WALL MOUNTED COMBINATION BOILERS FOR CENTRAL HEATING
AND MAINS FED DOMESTIC HOT WATER
INSTALLATION AND
SERVICING INSTRUCTIONS
0
I
This appliance is for use with Natural Gas or LPG (Cat II 2H3P).
25Si GC NUMBER 47 311 49 (N.G.)
CG NUMBER 47 311 50 (L.P.G.)
28Si GC NUMBER 47 311 51 (N.G.)
CG NUMBER 47 311 52 (L.P.G.)
APPLIANCE OUTPUTS
Minimum
Maximum
Domestic
Hot Water
25
28
8.5 kW
8.5kw
25.0kW
28.0kw
Central Heating
25
8.5 kW
25.0kW
28
8.5kw
28.0kw
IMPORTANT: THESE INSTRUCTIONS APPLY IN THE UK ONLY
AND MUST BE LEFT WITH THE USER OR AT THE GAS METER
Read the instructions before starting work - they have been written to make
the installation easier and prevent hold-ups.
Contents
1. Installation Regulations . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 2
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 2
3. Technical Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 4
4. Siting the Appliance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 6
5. Flue Terminal Positions . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 7
6. Air Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 7
7. Sealed System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 8
Open Vent System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 8
8. Domestic Hot Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 9
.........................................................
9. Gas Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 9
10. Electrical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 9
11. Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 12
12. Commissioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 18
13. Handover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 20
14. Inspection and Servicing . . . . . . . . . . . . . . . . . . . . . . . . . Page 20
15. Replacement of Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 22
16. Short Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 28
17. Operational Flow Diagram . . . . . . . . . . . . . . . . . . . . . . . Page 30
18. Fault Finding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 32
1. Installation Regulations
2. Introduction
1.1 Gas Safety (Installation & Use) Regulations 1998.
It is the law that all gas appliances are installed by a competent
person in accordance with the above regulations. Failure to
install appliances correctly could lead to prosecution. It is in
your interest, and that of safety, to ensure compliance with the
law.
1.2 The manufacturers notes must not be taken, in any way, as
overriding statutory obligations.
1.3 The compliance with a British Standard or European Norm
does not, in itself, confer immunity from legal obligations.
1.4 The installation of the appliance must be in accordance with
the relevant requirements of the Gas Safety Regulations, current
IEE Regulations, Building Regulations, Building Standards
(Scotland) and local water bye-laws.
1.5 The installation should follow the recommendations of the
following British Standards unless otherwise indicated and to
any other relevant standards.
BS5440:1 - Flues and ventilation for gas appliances: Flues
BS5440:2 - Flues and ventilation for gas appliances: Air supply.
BS5449 - Central heating for domestic premises.
BS5482 - Domestic propane gas burning installations.
BS5546:1 - Installation of gas hot water supplies.
BS6700 - Domestic water supply (when relevant).
BS6798 - Installation of gas fired hot water boilers.
BS6891 - Low pressure gas pipework installations up to 28mm
(R1).
BS7593 - Water treatment.
1.6 The appliance and/or components must conform, where
applicable, to all relevant Directives.
1.7 In accordance with COSSH the appliance does not contain
any substances which are harmful to health.
1.8 Product Liability regulations indicate that, in certain
circumstances, the installer can be held responsible, not only for
mistakes on his part but also for damage resulting from the use
of faulty materials. We advise that to avoid any risk, only
quality approved branded fittings are used.
1.9 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 the ground on the opposite side.
1.10 These instructions cover, as far as possible, the foreseeable
situations which may arise. Contact Worcester Heat Systems
Technical Department, Telephone: 0990 266241, for advice on
specific installations.
The Benchmark initiative is the new code of practice to
encourage the correct installation, commissioning and servicing
of domestic central heating boilers and system equipment.
The 'Log-book' is a vital document that must be completed
by the installer at the time of installation. It confirms that the
boiler has been installed and commissioned according to the
manufacturers instructions.
Without the completion of the Log-book, manufacturers may refuse
to respond to a call-out from a householder, who will be advised
that he or she must call back the installer, who has not fulfilled his
obligations to record the information required by the initiative.
It is important that:
The services and the system are properly flushed as specified.
The User is clearly instructed on the correct operation of the appliance.
The benefits of regular servicing are explained - to maintain the
efficiency and extend the life of the appliance.
2.1 General Information
The appliance is set to give the maximum output of 28 kW [28Si]
or 25kW [25Si] to the domestic hot water and to the heating
system. The hot water flow rate is limited to a nominal 10 l/min
[28Si] or 9 l/min [25Si] at a maximum temperature rise of 40°C.
The sanitary water section of the appliance is suitable for mains
water pressure of upto 10bar.
Kits are available to convert the appliance from Natural Gas to
Propane operation and vice versa.
2.2 Electrical Supply
230V - 50Hz. Load 180 watts. External fuse 3A, Internal fuses F1
- 2A, F2 - 1.6A (20mm).
2.3 Gas Supply
The appliances require a maximum of 3.38 m3/h of natural gas
(G20) or 1.25 m 3/h of propane (G31) [28Si] or 2.98 m 3/h of
natural gas (G20) or 1.12 m3/h of propane (G31) [25Si].
The installation and the connection of the gas supply to the
appliance must be in accordance with BS6891.
The meter or regulator should deliver a dynamic pressure of 20 mbar
(G20) or 37mbar (G31) at the appliance, which is equivalent to about
18.5 mbar or 36 mbar at the gas valve inlet pressure test point.
2.4 Installation
The appliance is suitable for indoor installation only and for use
with a sealed system only.
Do not place anything on top of the appliance.
It is a room sealed appliance and a separate combustion air
supply is not required in any room or compartment in which the
appliance is fitted.
If the appliance is fitted in a cupboard or a compartment is built
around it after installation, then the structure must conform to
the requirements of BS6798 and BS5440 Part 2. However,
because of the low casing losses, there is not a need for the
cooling ventilation openings in the compartment. The spaces
specified in Section 6. Air Supply must be provided.
There is space for the service pipes to pass at the back of the appliance.
2.5 Flue
The flue can be to the right, left or rear. A vertical flue system is available.
The flue terminal, on the outside wall, must not be obstructed or damaged.
An internal flue fitting kit is available. Fitting instructions are
given in Section 11.9.
2
Fig. 2. Water flow diagram.
Fig. 1. Facia controls
Central Heating
Indicator
Reset
Light
Button
Power ON
Indicator
11
Domestic Hot
Burner
Water Indicator Operation Light
Light
10
!
0
I
9
Mains
ON/OFF
Switch
Central Heating
Operation and
Temperature
Control Knob
Domestic
Hot Water
Temperature Control
Knob
System
Pressure
Gauge
2.6 Controls
Controls for switching the appliance On or Off and for adjusting
the CH and DHW temperatures. The CH control knob also
switches the CH off and on.
A programmable room thermostat or a facia mounted
programmer or clock is available.
A room thermostat and/or an externally mounted programmer
for mains voltage operation may be connected to the appliance.
Only double insulated mains voltage controls not requiring
an earth can be used.
2.7 System
All dirt must be flushed from the system before
connecting the appliance.
The system can be pre-piped and flushed before the appliance is fitted.
The connections in the system must withstand a pressure of
upto 3 bar.
Radiator valves must conform to BS2767: 10:1977.
Table 3 gives the pump head available for the system and the
required temperature differential.
A drain cock must be fitted to the lowest point and an air vent to
the highest point of the system.
2.8 Showers, Bidets, Taps and Mixing Valves
All taps and mixing valves must be suitable for the available
mains pressure and temperatures up to 65°C. It may be
necessary to fit a pressure reducing valve.
Hot and cold mains fed water can be supplied to overrim bidets
but is subject to local water company requirements.
The flow of water from individual outlets varies on all mains fed
systems that are not fitted with flow balancing valves. If a
pressure equalising valve is fitted then the domestic hot water
temperature should be set to maximum.
Thermostatically controlled shower valves give extra comfort
and protection.
2.9 Safety
The appliance must not be operated with the inner casing cover removed.
The gas and electricity supplies must be turned off before
working on the appliance.
Temperature monitoring controls are fitted to prevent overheating.
Automatic frost protection is provided together with automatic
pump seizure protection.
The gas valve solenoids are automatically checked for gas soundness.
IMPORTANT: Where back-flow prevention devices, including
water meters, are fitted the expansion of hot water into cold
water main can be prevented. This can result in a pressure
build-up that may cause damage to the boiler and household
devices such as showers, washing machines etc.
In these cases we recommend that a mini-expansion vessel be
fitted adjacent to the boiler in the cold water pipe.
2.10 Operation
Central Heating
A demand for heat will ignite the burner. It will operate at
minimum pressure for 2 minutes before increasing to the maximum
8
12
7
6
1
1. CH Flow.
2. Domestic Hot Water
Supply.
3. Domestic Cold Supply.
4. CH Return.
5. Relief Valve Discharge.
6. Relief Valve.
2
3
4
5
7. Domestic Water Flow
Switch.
8. Pump.
9. Sealed System
Expansion Vessel.
10. Bi-thermal Gas to Water
Heat Exchanger.
11. Automatic Air Vent.
12. Fixed By-Pass.
pressure over a period of 1 minute and then automatically
match the system requirements. At the end of the demand the
burner will go out, the pump will continue to run for up to 4
minutes or the fan for 35 seconds. There is an anti-cycle time of 3
minutes.
Domestic Hot Water
A demand for hot water will ignite the burner. The burner
pressure will immediately rise to maximum.
At the end of the demand the fan will continue to run for 35
seconds if there is no heating demand.
The demand for hot water will override the CH function. In winter
it may be necessary to reduce the flow at the taps to maintain
the delivery temperature.
2.11 Conversion Instructions
The appliance can be converted from LPG to NG and vice versa
by replacing the burner and resetting the gas valve.
To replace the burner and transfer the electrodes refer to Section
15.4.2,3 and 4. The burner part numbers are:
NG (25Si and 28Si)
8 718 120 565 0
LPG (28Si)
8 718 120 566 0
LPG (25Si)
8 718 120 569 0
To reset the gas valve refer to Section 15.4.4, Section 12Commissioning and , for setting pressures, Table 1 in Section 3Technical Data.
Always check for gas soundness after replacing components in
the gas circuit.
3
3. Technical Data
Table 1.
The data plate is fixed to the inner casing cover.
25Si
Table 1.
NOMINAL BOILER RATINGS (10 Minutes After Lighting)
BOILER ADJUSTED FOR G20 (Natural Gas)
BURNER
OUTPUT
INPUT (Net)
GAS RATE
PRESSURE
kW
kW
m bar.
m3/h
8.5
10.5
0.7
1.12
25.0
27.8
11.5
2.98
8.5
25.0
28Si
NOMINAL BOILER RATINGS (10 Minutes After Lighting)
BOILER ADJUSTED FOR G20 (Natural Gas)
BURNER
OUTPUT
INPUT (Net)
GAS RATE
PRESSURE
kW
kW
m bar.
m3/h
8.5
10.5
0.7
1.12
28.0
31.1
14.1
3.38
BOILER ADJUSTED FOR G31 (Propane)
10.5
4.2
0.42
27.8
35.7
1.12
8.5
28.0
Natural Gas: Net Input = Gross Input x 0.901
BOILER ADJUSTED FOR G31 (Propane)
10.5
2.3
31.1
35.5
LPG (Propane): Net Input = Gross Input x 0.922
Table 2.
FLUE DETAILS
HORIZONTAL FLUE
mm
WALL HOLE DIAMETER
STANDARD FLUE
EXTENDED FLUE
EXTERNAL FIX
110
INTERNAL FIX
150
MINIMUM LENGTH
330/425 *
MAXIMUM LENGTH
725
MAXIMUM LENGTH
2975
FLUE ASSEMBLY DIAMETER
100
* NOTE : Flue lengths between 330 and 425mm require the flue to be cut
Table 3
MAXIMUM AVAILABLE PUMP HEAD
BOILER OUTPUT
kW
HEAD
Metres
MIN. FLOW RATE
L/min.
FLOW/RETURN
DIFFERENTIAL
°C
8.5
5.9
11.0
11
25
2.0
30.5
12
28
2.0
30.5
13
Table 4
MECHANICAL SPECIFICATIONS
CENTRAL HEATING FLOW - COMPRESSION
22mm
RETURN - COMPRESSION
22mm
COLD WATER INLET - COMPRESSION
15mm
DOMESTIC WATER FLOW - COMPRESSION
15mm
3
GAS INLET
Rp ⁄4
RELIEF VALVE DISCHARGE (PUSH FIT)
15mm
CASING HEIGHT
800mm
CASING WIDTH
440mm
CASING DEPTH
360mm
WEIGHT - LIFT
42.3kg
WEIGHT - UNPACKED
45.8kg
WEIGHT - PACKAGED
52kg
4
0.42
1.25
Table 5
PERFORMANCE SPECIFICATIONS
PRIMARY WATER CAPACITY
litres
25Si
2.0
28Si
2.0
MAXIMUM MAINS INLET PRESSURE
bar
10
10
MINIMUM MAINS INLET PRESSURE (WORKING) FOR MAXIMUM FLOW
bar
1.1
1.3
MINIMUM MAINS INLET PRESSURE (WORKING) FOR OPERATION
bar
0.5
0.5
DOMESTIC HOT WATER TEMPERATURE RANGE
°C
40 - 62
40 - 62
MAXIMUM CENTRAL HEATING FLOW TEMPERATURE
°C
82 (nom)
82 (nom)
MAXIMUM CENTRAL HEATING SYSTEM SET PRESSURE
bar
2.5
2.5
MINIMUM CENTRAL HEATING SYSTEM PRESSURE
bar
1
1
NATURAL GAS (G20)
8.5 - 25
8.5 - 28.0
LPG - PROPANE (G31)
8.5 - 25
8.5 - 28.0
NATURAL GAS (G20)
8.5 - 25
8.5 - 28.0
LPG - PROPANE (G31)
8.5 - 25
8.5 - 28.0
DOMESTIC HOT WATER SPECIFIC RATE -
30°C RISE l/min
12.0
13.4
MAXIMUM DOMESTIC HOT WATER FLOW RATE -
40°C RISE l/min
9.0
OUTPUT TO DOMESTIC HOT WATER
kw
OUTPUT TO CENTRAL HEATING
kw
10.0
NOx CLASSIFICATION FOR BOTH 25 & 28Si
Class 2
SEDBUK NUMBER
SEDBUK BAND
78.0
78.2
D
D
Table 6
DISCHARGE RATE l/min
TEMPERATURE RISE °C
TEMPERATURE RISE °C
DOMESTIC HOT WATER TEMPERATURE RISE
7
8
25Si
51
45
28Si
57
50
Table 7
GAS SUPPLY SYSTEM - BASED ON NG (G20)
TOTAL LENGTH OF GAS SUPPLY PIPE (COPPER) metres
3
6
9
12
GAS DISCHARGE RATE - PRESSURE DROP 1mbar. m3/h PIPE DIAMETER mm
8.7
5.8
4.6
3.9
22
18.0
12.0
9.4
8.0
28
Table 8
CLEARANCES
(mm)
INSTALLATION
ABOVE APPLIANCE AND/OR FLUE ELBOW
30
IN FRONT OF APPLIANCE
600
BENEATH APPLIANCE
200
RIGHT AND LEFT HAND SIDE
10
SERVICE
30
600
200
10
Refer to Section 6.
Table 9
INITIAL
PRESSURE bar
1.0
1.5
SYSTEM CAPACITY
TOTAL SYSTEM VOLUME litres
INITIAL CHARGE PRESSURE bar
0.5
1.0
1.5
57
75
N/A
31
42
52
5
9
40
45
10
36
40
4. Siting The Appliance
Fig. 3. Appliance casing dimensions and
required clearances (front view).
The appliance may be installed in any room but refer to the
requirements of the current IEE Regulations and, in Scotland, the
relevant electrical provisions of the Building Regulations with
respect to the installation of appliances in rooms containing
baths or showers.
Where a room sealed appliance is installed in a room containing
a bath or shower, any switch or appliance control using mains
electricity must NOT be able to be touched by a person using the
bath or shower.
The appliance is NOT suitable for external installation.
No special wall protection is required.
The wall must be able to support the weight of the appliance.
Refer to Table 4.
The specified clearances must be available for installation and
servicing. Refer to Table 8, Fig.3, 4 and Section 6. Air Supply.
The appliance can be installed in a cupboard/compartment to
be used for airing clothes providing that the requirements of
BS6798 and BS5440 Part 2 are followed. Refer to Section 2.4.
The airing space must be separated from the boiler space by a
perforated non-combustible partition. Expanded metal or rigid
wire mesh is acceptable provided that the major dimension is
less than 13mm.
The clearance between the front of the appliance and the
cupboard/compartment door should be not less than 75mm.
LPG Installation. Refer to Section 1.9.
30
170
440
10
10
200
All dimensions in mm
Fig.4. Appliance casing dimensions and
required clearances (side view).
200
106
Fig. 6. Pipework connections
Valves shown closed.
230
600
800
NOTE:
Casing is
3mm above
the top of the
wall mounting
frame. Refer to
Fig.15.
360
A
B
C
D
E
F
View on underside of appliance showing
connections
200
All dimensions in mm
Fig. 5. Side flue opening
20
106
A
B
190
C
230
D
E
(A, B, C, D,)
F
A
B
C
D
E
F
CH Flow
DHW Flow
Gas
Cold Water Inlet
CH Return
Relief Valve Discharge
=
=
=
=
=
=
55
120
185
250
315
375
All dimensions in mm
All dimensions in mm
6
5. Flue terminal positions
6. Air Supply
The flue system must be installed following the requirements of
BS5440: 1.
Standard flue kit length is 330 - 725mm (as measured from the
centre of the flue turret) with extension kits for flues up to
2975mm measured from the centre line of the flue turret.
The terminal must not cause an obstruction or the combustion
products a nuisance.
Under some conditions the terminal might steam and positions
where this might be a nuisance should be avoided. Refer to Fig 7
If the terminal is less than 2m above a surface to which people
have access then a guard must be fitted. The guard must be
evenly spaced about the terminal and fixed with plated screws.
A Type K2 guard is available from Tower Flue Components, Vale
Rise, Tonbridge, TN9 1TB.
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).
NG
LPG
Above the Turret
30mm
30mm
In front
75mm
250mm
Below
200mm
200mm
Right-hand side
10mm
75mm
Left-hand side
10mm
75mm
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:
Fig. 7. Siting of the flue terminal.
TERMINAL POSITION
MIN. DISTANCE
A– Directly below an openable window or
other opening e.g. air brick.
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.
I– From a terminal facing a terminal
J– From an opening in a car port (e.g. door
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).
300 mm
75 mm
200 mm
200 mm
75 mm
300 mm
300 mm
600 mm
1200 mm
POSITION OF
AIR VENTS
AIR FROM
THE ROOM
HIGH LEVEL
315cm
LOW LEVEL
315cm
AIR DIRECT
FROM OUTSIDE
2
2
158cm
2
2
158cm
1200 mm
1500 mm
300 mm
300 mm
A
L
G
B,C
K
L
D
K
F
F
HI
A
F
J
E
G
M
7
The system and the appliance must be properly vented.
Repeated venting loses water from the system, which must be
replaced. The make-up connection must be close to the
appliance in the heating return pipe through an approved nonreturn valve. Refer to Fig 10.
The connection to the mains water supply must have the
approval of the local Water Company.
The integral by-pass is not adjustable.
The pump is set at maximum and should not be adjusted.
All connections in the system must withstand a pressure of up to
3 bar.
The radiator valves must confirm to BS 2767:10 and other valves
to BS1010.
7. Sealed System
The system must comply with requirements of BS6798 and
BS5449 and must not be operated without being full of water
and correctly pressurised. Refer to Fig 8.
The pressure relief valve will operate at 3 bar. The discharge pipe
must be directed away from any electrics or from where it might
be a hazard.
The expansion vessel, to BS4814, has a capacity of 8 litres
charged to 0.5 bar, which is suitable for a static head of 5 metres.
A schraider type valve allows the pressure to be increased if the
static head is greater than 5 metres.
If the expansion vessel fails then it must be replaced with the
designated spare part.
Refer to BS 7074:1, BS5449 and Table 9 for a guide to the
available system capacity.
The maximum system design pressure is 1.5 bar. If the pressure
is above 2.65 bar when the appliance is at maximum
temperature then another expansion vessel must be fitted as
near to the appliance as possible in the return pipe. The pressure
gauge shows the system pressure.
Fill and pressurise the system through a WRc approved filling kit.
Refer to Fig 9.
Open Vent System
This appliance is NOT suitable for connection to an open vent
system.
Fig. 8. Sealed primary water system.
APPLIANCE
Mains cold
water
Refer to
'Water Flow
Diagram'
Fig.2.
Radiator
valve
Lockshield
valve
Hot water out
Heating
return
British Standard
stop valve.
Fixed spindle type
Heating
flow
NOTE: A drain cock should be installed at the
lowest point of the heating circuit and beneath the
appliance.
Water main
Fig 9 - System Fill
Fig 10 - System make up
4
2
1
300mm Above
the highest point
of the system
3
5
6
1.Central Heating Return
2.Auto Air vent
3.Non-return Valve
4.Make-up Vessel
5.Stop Cock
6.Fill Point
8
8. Domestic Hot Water
9. Gas Supply
It may be necessary to contact the local Water Company before
connecting the appliance.
Devices, which would prevent the flow of expansion water, must
not be fitted unless separate arrangements have been made. A
mini-expansion vessel kit is available as an optional extra.
The last 600mm of mains water pipe before the appliance must
be in copper.
The domestic hot water circuit of the appliance is suitable for a
mains pressure of up to 10 bar. A pressure reducing valve must
be fitted if necessary.
A mains water supply isolating valve is fitted.
The maximum hot water flow rate is set at the factory to 10
l/min [28Si] or 9 l/min [25Si] giving a nominal temperature rise
of 40°C with the temperature control at maximum. Refer to Table
6. The temperature rise, up to the maximum set by the user is
automatically maintained by the modulation of the heat input.
In winter it may be necessary to reduce the water flow at the tap
or shower to maintain the required delivery temperature.
It is recommended that long pipe runs to taps or showers are
insulated to prevent the rapid cooling of the water.
Hot and cold taps and mixing valves must be suitable for the
available mains pressure. If necessary, a pressure reducing valve
should be fitted.
No anti-syphonage arrangements are necessary for fixed head
showers.
The hose of a loose-head shower must be fixed so that the
shower head cannot get closer than 25mm to the top edge of the
bath to prevent its immersion in the water. Alternatively the
shower can be fitted with an anti-syphonage device at the
flexible hose connection.
Thermostatically controlled or pressure balancing shower valves
should be used where possible to give extra comfort and guard
against extreme temperature.
Hot and cold mains water direct to a bidet is, subject to the
approval of the local water company, permissible provided that
the bidet is of the overrim flushing type. The outlets must be
shrouded and unable to be fitted with a hand-held spray. No antisyphon arrangements are needed.
LIME SCALE: In areas of temporary hardness [ greater than
200ppm of calcium bicarbonate] it is suggested that a
proprietary scale reducer is fitted in the mains cold water
connection to the appliance. 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.
The appliance requires a maximum of 3.38 m3/h of natural gas
(G20) or 1.2 m3/h of propane (G31) [28Si] or 2.98 m3/h of natural
gas (G20) or 1.25 m3/h of propane (G31) [25Si]. Refer to Table 7.
A natural gas appliance must be connected to a governed meter.
The installation and connection of the gas supply to the
appliance must be in accordance with BS6891.
The meter (NG) and the pipework to the appliance must be
checked, preferably by the gas supplier, to ensure that a
dynamic pressure of 20mbar for natural gas and 37mbar for
propane is available at the appliance [equivalent to about
18mbar or 35mbar at the gas valve inlet pressure connection]
and that the gas flow is adequate for all the installed gas
appliances operating together.
10. Electrical
Mains supply: 230V ~ 50 Hz 180watts. External fuse 3A.
Internal fuses F1-2A, F2-1.6A (20mm). Spare internal fuses are
supplied with the appliance. Refer to Fig 13.
The appliance must be earthed and it must be possible to
completely isolate the appliance.
The mains cable must be 0.75mm2 (24x0.20 mm) to BS6500 Table 15 or 16.
The mains cable must be connected to the terminal ST12
marked L (red or brown lead), N (black or blue lead) and the
Earth stud (green or green/yellow lead) and secured with the
cable clamp. The Earth lead must be still be slack when the other
leads are taut. Refer to Fig 14.
The connection to the mains must be either : A 3A fused threepin plug and unswitched socket outlet (both complying with
BS1363) or a double pole isolator with a contact separation of
3mm in all poles and supplying the appliance and controls only.
A room thermostat or an externally mounted programmer must
be suitable for mains voltage operation, the leads must be
securely fixed in the cable clamps. Only double insulated mains
voltage controls not requiring an earth lead may be used. The
control board is accessed by removing the controls connections
cover. Refer to Fig 29.
A programmer or clock is available to fit into the facia. Full
instructions are sent with the control.
On very rare occasions an external frost thermostat might be
considered where parts of the system are remote from the
appliance. Refer to WHS Technical Department for more
information, Tel: 08705 266241.
Safety Check: If there is an electrical fault after installation check
for fuse failure, short circuits, incorrect polarity of connections,
earth continuity or resistance to earth.
9
Fig. 11. Wiring diagram.
Fan
Overheat cut-off
device
CH sensor
(front of heat
exchanger)
Flame sense
electrode
Spark
electrode
Air
pressure switch
Gas valve
Reg
Flow
switch
Pump
Main
Main
Spark
transformer
DHW sensor
Link
ST16
ST15
ST1
yellow
brown
ST8
blue
brown
blue
brown
Control Board
ST12
Mains in
2
pink
2 yellow
2 green
2 red
2 orange
10
2 blue
2 brown
2 violet
white
LIVE
IN
ST12 Pin N
ST12 Pin L
Fuse F1
(2A Slow)
On/Off
switch
11
ST1
Centre
Pin
ST15
Pin L
ST8
(LR)
Spark
Red
Indicators
Red
Settings
Electronics/
microprocessor
(Safety Low Voltage)
REL 3
Optional link
Room
thermostat
ST8
(NS)
Transformer
Fuse F2 (1.6A
Slow)
Spark
electrodes
DHW
demand
indicator
Red
Flame
detect
indicator
Outputs
REL 1
ST8
(LS)
Electronics
green
Mains
indicator
CH
demand
indicator
N
N
24V programmer
Overheat cut-off
Flame sense
Air pressure switch
DHW sensor
CH sensor
Flow switch
Main valve
Main valve
Regulator valve
Fig. 12. Functional flow diagram.
Inputs
DHW control knob
CH Control knob
CH pressure adjust pot
Gas valve mode switch
Reset button
Convert AC to low
voltage electronics
Electronics
Fan
Pump
Electronics
Fig 13 - Replacement internal fuses
Fig.14 . Mains electricity connections.
NOTE: Check the size of the fuse before fitting
1
Bottom Left Hand Side - Facia
ST12
230V
Live
Brown
N LS LR
2
L N
E
Blue
Neutral
Blue
Mains lead
Strain relief clamp
5. Clip on Facia cover
Note: When the mains ON/OFF switch on the facia is turned
OFF the 2amp fuse is still live. Refer to Fig.12.
appliance then they must be arranged to pass behind the
expansion vessel. Refer to Fig 3. Pipework must not run
horizontally within the limits of the casing.
Support the valves when tightening the connections to prevent
distortion of the manifold assembly
It is important that the pipes are not fixed near the appliance
using clips that put a strain on the connections.
Before the appliance is fitted to the wall thoroughly
flush the system and mains water supply.
11. Installing The Appliance
Note: READ THIS SECTION FULLY BEFORE COMMENCING THE
INSTALLATION
11.1 General
The appliance is only suitable for fitting to a sealed system.
The flue must be installed as specified in BS5440:1.
11.2 Unpacking
Remove the appliance from its packaging and check the contents
against the packing list.
Lie the appliance on its back and undo the union connections on
the manifold assembly. Refer to Fig 16. Slide the appliance off the
wall mounting assembly.
11.3 Site Preparation
Check that the correct position for the appliance has been
chosen. Refer to Section 4 and Table 8.
Check that the wall is flat and will support the weight of the
appliance. Refer to Table 4.
11.4 Fixing Holes and Flue Opening
Hold the wall mounting assembly against the wall. Check that
the assembly is level. The diamond cut-out on the assembly
indicates the centre-line of the appliance.
Mark the position of the fixing holes and the flue opening. Refer
to Fig. 5 and 15.
Mark the centrelines of the pipe connections to aid the preplumbing of the system pipework.
Check the position of the fixing points and flue opening before
drilling the fixing holes 60mm deep for the No. 12 size plugs and
cutting the flue duct hole at 110mm diameter [150mm diameter
for internally fitted flues].
11.5 Wall Mounting Plate and Manifold
Fit the plugs and insert the bottom screws. Offer the assembly to
the wall utilising the keyhole slots on the manifold assembly and
fix to the wall. Refer to Fig 15 and 16.
Check that the assembly is properly aligned before tightening
the screws.
11.6 Gas and Water Pipes
Remove the gas cock and fix the appropriate fitting to connect
the inlet pipe and refit. Refer Fig 16.
Pre-plumbing is not recommended if no movement in the pipes
is available.
If it is necessary for any of the pipes to run up the back of the
Fig.15 . Wall mounting assembly
338
65
60
60
367
540
797
Cabinet Height
800
75
218
20
12
1. Fuse -F1 T2A
2. Fuse -F2 T1.6A
3. Connections Cover
4. Connections Cover Fixing
Screw
3
External control
4
5
Earth
Green/Yellow
All dimensions in mm
Fig.18. Inner case and facia fixing
Fig.16 . Manifold assembly
Fixing screws
(4)
Position of
the cabinet
fixing screw
Wall
Frame
Wall
Frame
Fibre
Washer
Inner
case
cover
65
65
65
65
Facia panel
fixing screws
(2)
CH
Flow
DHW
Flow
Gas
DHW
Cold
Inlet
0
I
CH
Return
Facia
All dimensions in mm
11.7 Install the Boiler
Remove the cabinet by unscrewing the screw at the top front
and releasing the sides. Lift from the top location. Refer to Fig.
18.
Check that the gas and water valves are closed. Refer to Fig.16.
Fit the new seals, in the hardware pack, to the service valves on
the manifold.
Lift the appliance to the wall, engage in the top support and
lower onto the manifold assembly. Tighten the gas and water
connections.
Fit a discharge pipe to the relief valve leading it away from any
electrics or where it might be a hazard. Lower the facia to gain
access. The pipe must not be less than 15mm in diameter and
must run continuously downward outside the appliance. Refer to
Fig 17.
11.8 Air and Flue Duct Preparation
The method of installation of the flue system may be varied to
suit the actual site conditions. The instructions for connecting
and fixing the ducts must, however, be strictly followed.
Remove all packing material from the flue components.
Fit the flue restrictor ring by unscrewing and removing the flue
spigot from the boiler. Refer to Fig.19.
Restrictor Size 79mm to all Horizontal and Vertical flues
upto 725mm long.
The standard telescopic flue assembly is suitable (without
cutting) for flues from 425mm up to 725mm measured from the
centre-line of the boiler flue outlet to the outer face of the wall.
Refer to Fig.20.
The minimum length of the standard flue, after cutting is
330mm.
Fig.17 . Relief valve drain connection
Relief Valve
Drain
Connection
(push fit)
Pump
Fig.19. Flue spigot and restrictor
1
2
Boiler
Drain
3
4
1.
2.
3.
4.
Pressure
Gauge
Capillary
Relief
Valve
13
Flue spigot fixing screws
Flue spigot
Restrictor ring
Flue spigot fixing holes
11.9 Measure and Cut the Ducts.
General: Cut the ducts as necessary, ensuring that the ducts are
square and free from burrs. Always check the dimensions before
cutting.
Measure the distance L. Refer to Fig. 22 and 23.
Fig.20. Standard flue assembly
Flue
turret
assembly
The standard flue can be telescopically adjusted to any length
between 425mm and 725mm measured from the centre of the
turret.
Fix the flue assembly together using the self-tapping screws
provided. Refer to Fig. 20.
Terminal
assembly
L
Fixing screw
It will only be necessary to cut the standard assembly if L is less
than 425mm. Cut the flue turret assembly and the terminal
assembly by the same amount i.e L=350 - remove 75mm from
each assembly.
Telescopic adjustment
Appliance
casing
Minimum side flue length = 330mm
(accommodating a
10mm Service clearance and a 100mm wall)
Minimum rear flue length = 330mm
100mm wall)
If L is greater than 725mm then extension duct kit/s will be
required - each kit extends the flue by 750mm up to a maximum
of 2975mm. See table below.
EXTENSION
1
2
3
If L is between
MAXIMUM FLUE LENGTH mm
1475
2225
2975
(accommodating a
1175 - 1475mm
1925 - 2225mm
2675 - 2975mm
it is not necessary to cut the ducts.
(1 extension)
(2 extension)
(3 extension)
If L is between
(1 extension)
(2 extension)
(3 extension)
725 - 1175mm
1475 - 1925mm
2225 - 2675mm
It is necessary to shorten the assembly by cutting the first
extension duct assembly i.e. L = 1000mm - remove 175mm
from the air and flue ducts.
Fig.21. Extension duct
Terminal
assembly
L
Flue
turret
assembly
Appliance
Fixing screw
Fixing screw
casing
Ducts of equal length
Fig.22. Flue duct length - side
Flue
turret
assembly
Terminal
assembly
L
14
Fig.24 . Flue Turret Fixing
Fig.23. Flue duct length - rear
Flue
turret
assembly
L
Terminal
assembly
1
2
3
1.
2.
3.
4.
NOTE: Extension duct measurements do not include the
socketed end. Unless specifically instructed the socketed end
must not be removed.
Flue turret assembly
Clamp
Appliance
Fixing Screw
4
Fig.25 . Terminal assembly for internal
fitting of the flue.
Fix the flue ducts together before fixing the surrounding air duct,
the cut ducts fit into the flue assembly.
Fixing clamp
Flue centering ring
11.10 Fitting the Flue Assembly with Access to the Terminal.
Prepare the flue duct assembly as described in Section 11.8.
Apply the plastic tape to the air duct in contact with the external
brickwork.
From inside push the assembly through the wall. Align the flue
turret and push fully onto the spigot on the appliance. Tighten
the clamping ring and fix with the screw provided. Refer to
Fig.24.
Air duct
Flue Terminal
Rubber sealing gasket
Flue duct
Make good the internal wall face and the external brickwork or
rendering.
11.11 Fitting of the Flue Assembly without access to the Terminal.
A rubber gasket kit is available from Worcester Heat Systems.
NOTE: A larger diameter opening in the wall is required. Refer to
Table 2.
Rubber sealing
gasket
Prepare the flue assembly as described in Section 11.8.
Flue terminal
Fit the rubber sealing gasket centrally onto the terminal
assembly and tighten the clamp. Refer to Fig. 25.
Apply the plastic tape to the air duct in contact with the external
brickwork.
Clamping ring
From inside push the assembly through the wall so that the
gasket flange is against the outer face. Refer to Fig. 25.
It may be necessary to adjust the legs of the flue centering ring.
Align the flue turret and push fully onto the socket on the
appliance. Tighten the clamping ring and fix with the screw
provided. Refer to Fig. 24.
Seal the gap around the duct at the inner wall face with the
flexible seal provided and make good.
NOTE: The flue system ducts between the elbows, dimension Y,
requires the socketed ends (of the first extension if two or more
are used) to be removed and the air and flue tubes to be cut to
the same length.
Cut the ducts to a length Y - 162mm. Refer to Fig.26.
The final section, dimension Z, of the flue system must include a
section of plain duct assembly i.e . an extension assembly with
the sockets removed. Reduce the final section, including the
terminal assembly, by the appropriate amount i.e. Air duct Z 81mm and the flue duct Z - 51mm. Refer to Fig.26.
11.12 Flue Bends.
90° and 45° bends are available. A maximum of two bends may
be used in addition to the first bend on the flue turret.
A 90° bend is equivalent to 1m of straight duct.
A 45° bend is equivalent to 0.5m of straight duct.
If Z is less than 425mm it will be necessary to cut the air and flue
ducts of the extension to a plain length of 100mm and reduce
the length of the terminal assembly i.e Z=350mm - remove
75mm from the terminal assembly.
A maximum flue assembly of 2m is possible with 1 X 90° bend
and 1m with 2 X 90° bends.
Measure the lengths X,Y and Z. Refer to Fig.26.
The maximum value of X using the turret assembly only is
506mm. Reduce the ducts to the appropriate length i.e. X =
406mm, cut 100mm from the air duct and 120mm (to cover the
entry into the 45° or 90° elbow) from the flue duct. Refer to
Fig.27.
If Z is 425 - 725mm it is not necessary to cut the terminal
assembly or use a second extension duct as the length can be
set telescopically.
If Z is greater than 725mm then two extension duct assemblies
will be required, the first assembly being cut to length as plain
tubes.
15
Z
Fig.26. Flue bends
Y-162
Plain tube
Y
X
If more than two extension ducts are needed in any section to
achieve the required length then the final section of the
assembly must not be less than 325mm without cutting the
terminal assembly.
NOTE: The flue duct of the final extension must be 30mm longer
than the air duct.
Fig.27 - Elbow to Flue Turret
Assembly.
Each section must be connected to the previous section of the
flue bend by fixing the flue ducts together and then similarly
fixing the air ducts which engage the elbows.
120mm
100mm
Flue Turret
Fit the assembly as described in Section 11.9, 11.10 as
appropriate.
Make good the internal and external brickwork or rendering.
11.13 Vertical Adapter for Horizontal Flues.
An adapter is available for an initial short section of vertical flue.
Refer to Fig. 28.
Measure and cut the flue as described in Section 11.11.
The first, vertical, section (equivalent to dimension X) is
measured from the top of the boiler casing. Cut the vertical
section of the extension duct to 167mm less than the measured
distance. Do not remove the socketed ends.
The minimum measured distance is 167mm.
Seal the air duct to the spigot using silicone sealant.
Fix the adaptor with the clamp and screw provided.
Bend
Fig.28 Vertical Adapter.
Flue Duct
11.14 Completion of the Installation.
Check that all the connections on the manifold have been
tightened. Refer to Fig.6.
Air Duct
Remove the facia bottom panel. Refer to Fig.29.
Connect the mains electricity supply lead to the appliance and
secure the cable clamp. Refer to Fig.14.
Check there is sufficient loose lead to allow the release of the
facia panel assembly and that the earth lead of the mains supply
cable is longer than the live and neutral leads.
Adapter
Fit the facia mounted programmer if applicable. Refer to Fig.31.
Clamp
Connect any external controls ensuring that the leads pass
through the appropriate clamps. refer to Fig.32.
Flue Spigot
Test for gas soundness as described in BS6891.
If the appliance is not commissioned immediately, replace the
cabinet and facia bottom panel. Check that the gas and
electricity services have been turned off.
16
Fig.29. Facia connections cover
Cover panel
Fig.30. Programmer cover
Facia
Controls
connections
cover
Programmer
connections
Facia
Fixing screw
Facia bottom panel
(clip-on)
Fig 32 - Mains Voltage External Controls Connections
NOTE: Only double insulated controls not requiring an earth can be used
Ns Ls LR
Ns Ls LR
Control
board
ST8
Programmer
connector
Live
Switched Live
Remove Link
Neutral
Neutral
Facia
Switched Live
ST8
Live
Fig.31. Programmer connection
Remove Link
Motor
230 V Room Thermostat Connections
230 V Programmer Connections
230 V room thermostat and
Programmer Connections
Ns Ls LR
ST8
Fig.33. Facia connections
1
2
11
3
4
5
10
7
6
9
8
6. Controls 24V - ST13
7. Mains harness ST16
8. Fan ST1
9. Pump ST5
10. Earth tag
11. Cable clamps (threaded)
1. Earth screw
2. Mains connection (L N)
3. Fuse F1
4. Mains voltage room thermostat/external control-mains
voltage ST8
5. Fuse F2
17
Live
Series
connection
to be made
safe
Live
Motor
Ne
ut
ral
e
Liv
Pressure gauge
d
he
itc
Sw
Programmer
Neutral
Clip
Swit
che
d Liv
e
Programmer
connections
Fig. 35. Pump venting.
12. Commissioning The Appliance
Pump
Benchmark Water Treatment: For optimum performance after
installation, this boiler and its associated central heating
system should be flushed in accordance with the guidelines
given in BS7593:1992 - Treatment of water in domestic hot
water systems. Full instructions are supplied with proprietary
cleansers sold for this purpose. If an inhibitor is to be used
after flushing, it should be used in accordance with the
inhibitor manufacturers instructions.
Suitable flushing agents and inhibitors are available from Betz
Dearborn Tel: 0151 4209563 and Fernox Tel: 01799 550811.
Instructions for use are supplied with these products.
Pump cap
Electrical
connections
cover
Fig.34. Automatic air vent and combustion
test point
12.3 Set the System Pressure
Fill the system until the pressure gauge is at 2.5bar and check for
leaks.
Release water from the system using the relief valve test knob
until the required system pressure is obtained, upto a maximum
of 1.5bar.
Set the pointer on the pressure gauge to record the set system
pressure.
If the pressure indicated on the gauge is greater than 2.65bar
when operating at the maximum central heating temperature,
an extra expansion vessel must be fitted to the system as close
as possible to the appliance central heating return connection.
The appliance [as despatched] can accommodate a system
volume of 100 litres with a system pressure of 0.5bar. Refer to
BS7074 Part 1, BS5449 and Table 8. If the system volume is
greater then an extra vessel must be fitted as close as possible to
the appliance central heating return connection and pressurised
to the same figure as the integral vessel.
12.4 Clock/Programmer: The controls fitted to the appliance
should be set up at this stage.
12.5 Check that the gas and electricity supplies are turned off.
Connect a pressure gauge to the gas valve burner pressure test
point. Refer to Fig 36.
Flue connections
Automatic air vent
Expansion vessel charging point
Expansion vessel
Combustion products
test point (front cap)
Wall mounting frame
12.1 Remove the appliance cabinet by removing the screw at
the top centre of the cabinet.
Check that the electrical supply and the gas supply to the
appliance are turned off and that all the water connections
throughout the system are tight.
Open the system valves at the appliance. Refer to Fig.6.
Open all the radiator valves. Remove the automatic air vent cap.
Refer to Fig. 34.
Fill the system through the external filling loop. Refer to Section
7, Sealed System.
Vent each radiator in turn. The automatic air vent will vent the
appliance. Refer to Fig 34.
Remove the cap from the pump and turn the shaft about half a
turn. Replace the cap. Refer to Fig 35.
Check that the pressure relief valve operates by turning the knob
anti-clockwise until it releases. Lower the facia to gain access to
the relief valve. Refer to Fig 17. Water should be expelled from
the discharge pipe.
12.2 Set the Expansion Vessel Pressure
The charge pressure of the expansion vessel as dispatched is
0.5bar, which is equivalent to a static head of 5m [17ft]. The
charge pressure must not be less than the static head at the
point of connection. A Schraeder type valve is fitted to the
expansion vessel to allow the charge pressure to be increased if
necessary. Refer to Fig 34. The expansion vessel must be charged
to 0.35bar less than the initial system design pressure.
Note: 1bar = 10.2m = 33.5ft of water.
Fig. 36. Gas valve.
Modulating
solenoid
valve
Burner connection
Burner pressure test
point
Minimum
pressure
adjustment
screw
Maximum
pressure
adjustment
screw
Safety solenoid valves
Inlet pressure
test point
Gas
18
Remove the clip-on facia bottom cover and controls connections
cover. Refer to Fig 29.
Slide down the access panel to display the mode switch and the
adjusting tool. Refer to Fig 37.
12.6 Checking the Burner Pressure
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.
Set the temperature control knobs to maximum and the
clock/programmer to operate continuously.
Turn on the gas and electricity supplies.
Set the mode switch to MAX using the mode adjuster tool. Refer
to Fig 37 and 38. NOTE: Two red lights will flash rapidly on the
facia.
necessary for the central heating potentiometer to be adjusted to
change the burner pressure. If adjustment is required then the
adjusting tool is used to alter the setting of the potentiometer.
Refer to Fig 38.
Set the mode switch to MIN. NOTE: Two red lights will flash
rapidly on the facia.
The burner pressure will drop to the minimum pressure
appropriate to the appliance and the gas for both the central
heating and domestic hot water modes. Refer to Table 1. It
should not be necessary for the central heating potentiometer to
be adjusted.
Test for gas soundness at the joint between the burner and the
gas valve with leak detection fluid.
Set the mode switch back to Normal.
Turn the electricity supply off and then back on to reset the controls.
Replace the facia cover panels.
12.7 Domestic Hot Water
Turn the central heating temperature control knob fully anticlockwise. Refer to Fig. 39.
Open a hot tap near the appliance. The burner will light and go
to the maximum burner pressure appropriate to the appliance
and the gas . Refer to Table 1.
Gradually close the tap and check that the burner pressure falls.
Fully open the tap and check that the pressure rises.
Close the tap and check that the burner goes out.
The fan may continue running until the appliance has cooled to a
pre-set temperature.
12.8 Central Heating
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.
Check that the clock/programmer is set to operate continuously.
Set the room thermostat and the central heating temperature
control to maximum.
The burner will light and the appliance will modulate its output
from minimum to maximum over a period of about two minutes.
Check that all the radiators are heating up evenly.
Shut down all but one of the radiators and observe the burner
pressure fall. Open all the radiators and check that the burner
pressure rises.
12.9 Balance the system to give a temperature differential of
11°C. A non-adjustable by-pass is fitted to the appliance.
12.10 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 and follow the normal operating
procedure.
Turn off the gas service cock. The burner will go out but sparking
from the electrode will continue for 10 seconds when the
appliance will ‘lock-out’. After 60 seconds carefully open the gas
service cock, press the reset button and observe the burner relight and follow the normal sequence of operation. Refer to Fig 6 and 39.
Turn off the gas service cock and the electricity supply to the
appliance.
Drain the system while the appliance is hot.
Refill, vent and re-pressurise the system as described in Section
12.1 preceding, adding, if necessary, a suitable proprietary
inhibitor. Further information is available from Betz Dearborn
0151 420 9563 or Fernox 01799 550811.
12.11 Domestic Hot Water and Central Heating
Set all controls to maximum.
Turn on the electricity supply to the appliance and open the gas
service cock at the appliance.
The burner will light and heat will pass into the system. Turn on
a hot tap and check that hot water is soon discharged from the
tap. Close the tap.
The appliance will then return to the central heating mode and
automatically balance with the system requirements.
Turn off the appliance.
12.12 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.
Refit the cabinet.
Fig.37. Mode control cover
Mode adjuster
Facia
Mode adjustment cover
Fig.38. Mode adjustment
Central heating limit
potentiometer
Max/Min switch
Not operational
A continuous spark will occur until the burner is alight and
sensed by the control circuit. The burner will remain at its
maximum domestic hot water pressure for one minute. Refer to
Table 1.
It should not be necessary for the gas valve to be adjusted.
Note: The burner pressure is factory set and if, after checking
that the dynamic (working) supply pressure is sufficient i.e.
18.0mb (NG) approx, or 36mb (LPG) at the gas valve inlet
pressure test point, the correct pressure cannot be obtained then
Worcester Heat Systems Service Department should be
contacted.
If the appliance does not light then check that it is not in the
‘lock-out’ state by pressing the reset button. Refer to Fig 39.
Set the mode switch to Normal.
The burner pressure will drop to the minimum setting and will
ramp up to the maximum central heating pressure appropriate
to the appliance and the gas. Refer to Table 1. It should not be
19
If the appliance is to be passed over to the user immediately
then set the controls to the users requirements.
If the appliance is to be left inoperative in frosty conditions then
set the programmer, if fitted, to off. Do not turn the electricity or
gas supplies off. The appliance will operate under the control of
the integral frost protection facility.
If there is any possibility of the appliance being left totally
unused in freezing conditions then switch off the gas and
electricity and drain the appliance and the system.
starting any service procedures.
Always test for gas soundness after the service has been
completed.
14.3 Component Access
To service the appliance it may be necessary to remove some or
all of the following parts to gain access to components which
may need to be checked or replaced.
Cabinet
Unscrew the screw at the top of the cabinet, release
the sides. Lift up and away from the top locating
pegs.
Facia Panel Unscrew the two screws and lower. Refer to Fig 40.
Inner Case Cover Unscrew the four fixing screws and remove
the cover. Refer to Fig 40.
13. Handover
Fig. 39. Facia controls
Central Heating Reset
Indicator
Button
Light
Power ON
Indicator
Domestic Hot
Burner
Water Indicator
Operation Light
Light
Fig.40. Inner case and facia fixing
Fixing screws
(4)
!
0
I
Inner
case
cover
Mains
ON/OFF
Switch
Central Heating
Operation and
Temperature
Control Knob
Domestic
Hot Water
Temperature Control
Knob
System
Pressure
Gauge
Facia panel
fixing screws
(2)
13.1 Hand over the User Booklet.
13.2 Explain how to operate the appliance safely and efficiently.
13.3 Tell the user what to do if the appliance is not to be used in
very cold conditions.
13.4 Tell the user what to do if the system pressure falls.
13.5 Explain that regular servicing will maintain the safe and
efficient operation and extend the life of the appliance. WHS can
offer a comprehensive maintenance contract.
13.6 Tell the user that any work on the appliance must only be
carried out by a competent, CORGI registered, person.
13.7 Complete and hand over to the user the Benchmark
Log-Book.
0
I
Facia
Combustion Chamber Unscrew the two screws at the top and
the two wing nut extended screws at the sides, pull
forward and remove. Refer to Fig 41.
Fan
Carefully pull off the electrical connections and the
tubes from the airflow-sensing device. Unscrew the
four screws and remove the fan assembly. Refer to
Fig 42.
Flue Hood Remove the fan. Unscrew the four screws and
remove the hood. Refer to Fig 43.
Burner
Remove the combustion chamber. Carefully pull off
the connections to the spark and flame sensing
electrodes. Release the union nut beneath the
burner and remove. Refer to Fig 44.
14.4 Component Cleaning
Only use a non-metallic brush to clean components.
Clean the fan taking care not to block air flow detector.
Clean the burner to ensure that the blades and injectors are clear.
Do not us a metal probe to clean the injectors.
Clean the electrodes, replace if there is any sign of deterioration.
Clean the heat exchanger. Cover the gas inlet tube and remove
any deposits from the heat exchanger from the top and bottom.
Carefully straighten any distorted fins on the heat exchanger.
Check the combustion chamber insulation and replace if there is
any sign of damage or deterioration. Refer to Section 15.4.5.
Clean the controls in situ using a non-metallic brush.
Carefully refit any components removed in the reverse order.
Check that all screws are tight and the connections properly
remade with the appropriate gaskets/O-rings.
Re-commission, as necessary, for correct operation to the users
requirements. Refer to Section 12 Commissioning.
14. Inspection And Service
14.1 The extent of the service is determined by the operating
condition of the appliance when tested by a competent person.
It is the law that any service work is carried out by a competent
CORGI registered person.
14.2 Inspection
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. Refer to Table 8.
Check all the joints and connections in the system and remake
any that show signs of leakage. Refill and re-pressurise as
described in Section 12-Commissioning.
Operate the appliance and take note of any irregularities. Refer to
Section 18-Fault Finding for rectification procedures.
Check the combustion performance
Remove the cap from the sample point on the top of the
appliance. Refer to Fig 34.
Connect the sampling meter.
With the appliance at maximum rate and stable in the DHW
mode expect readings of NG 5.5 - 8.5% CO2, 0.002 - 0.015% CO.
These figures cover all flue conditions.
Refit the cap after the test.
Disconnect the electrical supply at the mains and turn off the
gas supply at the gas service cock on the appliance before
20
Fig.41. Inner case components
Flue spigot
Inner casing
Combustion
products test
point
(front cap)
Fan assembly
Flue hood
Overheat
thermostat
(at rear)
Combustion
chamber/flue
hood fixing
screws
Primary sensor
Heat
exchanger
Combustion
chamber fixing
screw
Combustion
chamber fixing
screw
Combustion
chamber
Burner
Burner
connection
21
Fig.43. Flue hood
Fig.42. Fan assembly
Fan assembly
Flue hood fixing screws
Fan assembly fixing
screws
Air flow sensing
tube
Flue hood
Air flow sensing
tube (red)
Flue hood
Flue hood/Heat exchanger guide
Fig.44. Burner assembly
Burner blade
assembly
Spark electrode assembly
Flame sense
electrode
Burner manifold
Fixing screw
Fixing screw
NOTE: Front and rear crosslighting strips are not shown
Spark electrode leads
Burner connection
union
Flame sense
electrode lead
Important: A small quantity of water will remain in some
components even after the appliance has been drained.
Protect any electrical components when removing items from
the water circuits.
15.4 Component Replacement
Refer to Fig 41 and 45 for an indication of the location of the
various components.
Replace any components removed from the appliance in the
reverse order using new gaskets/O-rings/sealant/heat transfer
paste where necessary. Always check that any electrical
connections are correctly made and that all screws are tight.
Remove casing and cover panels and lower the facia, as
necessary, to gain access to the components. Refer to Section 14,
Inspection and Servicing.
15.4.1 Gas Valve
Do not remove the inner casing.
Unscrew the union connections above and below the gas valve
and remove the assembly. Disconnect/unplug the electrical
connections from the valve. Use new gaskets when replacing the
valve. Refer to Fig 45.
Set the Gas Valve:
Connect a pressure gauge to the burner pressure test point on
the valve. Refer to Fig 36.
15. Replacement Of Parts
Important: Turn off the gas and electricity supplies before
replacing any components.
15.1 After the replacement of any components always check for
gas soundness where relevant and carryout functional checks as
described in Section 12-Commissioning.
Any O-ring or gasket that appears damaged must be replaced.
Complete gasket and O-ring packs are available for gas and
water connections on the appliance.
15.2 Component Access
Refer to Section 14, Inspection and Servicing for access to
components.
15.3 Draining the Appliance
Primary System: Turn off the heating flow and return valves at
the appliance. Refer to Fig 16.
Open the drain tap. Refer to Fig 17. Close the drain tap when the
flow from the appliance has stopped.
DHW Circuit: Turn off the mains cold water supply at the
appliance. Refer to Fig 16.
Open a hot tap below the level of the appliance to drain the
domestic hot water from the appliance.
22
Fig.45 . Lower casing - gas and water
controls.
Gas Valve
Pump connection
Air flow switch
Expansion vessel connection
Water flow
switch
Pump
Red tube
(+ve)
Pump connection
Clear tube
(-ve)
Pressure gauge
Relief valve
Earth
connection
Boiler drain
connection
1
Transformer
Facia assembly
Spark electrode lead
Switch on the gas and electricity supplies. Check for gas
tightness at the gas valve inlet.
Refer to Section12-Commissioning for the method of checking
the pressures.
Check for gas soundness at the gas valve outlet.
Adjust the maximum and start pressure [minimum], as
necessary, to obtain the required pressures.
Switch off the appliance and disconnect the pressure gauge.
15.4.2 Spark Electrode
Remove the inner casing and the combustion chamber.
Carefully pull off the leads from the electrodes. Loosen the screw
and remove the spark electrode assembly. Refer to Fig 46.
Fig.47. Flame sense electrode
Notched to aid
location in the fixing bracket
Flame sense
electrode
Burner blade
assembly
NOTE: Cross- lighting
strips are not
shown
Fixing bracket
Fig.46. Spark electrode assembly
Fixing screw
Notched to aid
location in the fixing bracket
Flame sense
electrode assembly
Spark
electrode
Burner blade
assembly
and remove the flame sensing electrode assembly. Refer to Fig
47. Ensure that the electrode is at the correct height above the
burner blade.
15.4.4 Burner
Remove the inner casing and the combustion chamber.
Remove the electrode connections.
Release the union connection beneath the burner and remove
the burner from the appliance. Refer to Fig 44.
Do not omit the gasket when fitting the new burner.
15.4.5 Combustion Chamber Insulation
Remove the burner as described in 15.3.4 preceding.
Remove the primary heat exchanger as described in 15.4.21
following.
Replace the side and front pads in the combustion chamber
assembly. Refer to Fig 48.
Replace the rear insulation pad.
NOTE: Cross- lighting
strips are not
shown
Fixing bracket
Fixing screw
Spark electrode
assembly
15.4.3 Flame Sense Electrode
Remove the inner casing and the combustion chamber.
Carefully pull off the lead from the electrode. Loosen the screw
23
Fig.48. Combustion Chamber Insulation.
Fig.50. Pressure Gauge capillary fixing
Pressure gauge
capillary fixing clip
Insulation
panel-front
Boiler drain
ON/OFF
Combustion
chamber
assembly
Boiler drain
tube
connection
(tube attached)
Fixing
screws
Relief valve
Pressure gauge
capillary
Insulation
panel-side
Relief valve
fixing clip
Do not omit the O-ring from the pressure capillary when fitting
the replacement gauge.
15.4.7 Relief Valve
Remove the cabinet and lower the facia.
Check that the appliance has been fully drained.
Disconnect the relief valve drainpipe. Unclip and pull-out the
valve.
Refer to Fig 51.
15.4.6 Pressure Gauge
Remove the cabinet and lower the facia panel. Refer to Fig 40.
Check that the appliance has been fully drained.
Withdraw the clip and remove the pressure-sensing head. Refer
to Fig 50.
Unclip the gauge head from its mounting bracket and
remove.Refer to Fig 49
Fig.51 . Relief valve drain connection
Relief Valve
Drain
Connection
(push fit)
Pump
Fig.49. Pressure Gauge head
Pump
Boiler
Drain
Casing side panel
Pressure
gauge
capillary
Mounting bracket
Pressure
Gauge
Capillary
Pressure gauge head
Facia panel
24
Relief
Valve
15.4.8 Flow Switch
Drain the DHW circuit as described in 15.3 preceding.
Remove the cabinet and lower the facia panel.
Carefully pull off the connections from the micro-switch. Undo
the two union connections on the valve and remove the valve.
Refer to Fig 52. Do not omit the gaskets when fitting the
replacement switch.
The new flow-switch must be set to deliver the correct flow rate
to give a temperature rise of 40°C ie 10 l/min (28Si) or 9 l/min
(25Si).
The adjustment is made by turning the red adjuster clockwise to
reduce the flow rate and anti-clockwise to increase the flow rate.
Make the adustment with the gas turned off.
15.4.10 Control Board
Remove the facia bottom panel and carefully disconnect all the
electrical connections. Refer to Fig 33.
Remove the cabinet and lower the facia panel as described in
Section 14.3, Inspection and Servicing.
Disconnect the earth connection at the appliance. Refer to Fig
45.
Unscrew the four screws and remove the metal cover. Refer to Fig
54.
Lift out the control board. Refer to Fig 55
Pull out and transfer the transformer to the new board together
with the plastic locating frame.
Re-commission the appliance to check and set the burner
pressures. Refer to Section 12, Commissioning.
Fig. 52. Water Flow switch.
Micro Switch
Fig.54. Control board cover
Seal
Flow Switch
RED KNOB NOT
SHOWN
Main earth
connection
Outlet Union
Cover panel
Control board
fixing screws
Facia assembly
pivot point
Inlet Union
(with seal)
Control
board
Cold Water
Inlet
Transformer
Facia assembly
15.4.9 Inlet Water Filter
Remove the flow switch as described in 15.4.8 preceding.
Unscrew the two screws and remove the securing plate. Firmly
withdraw the union connection assembly and pull out the filter.
Refer to Fig 53. Carefully clean or replace the filter.
Fig.55. Control board
Fig. 53. Inlet water filter
Control board
locating frame
Flow Switch
Filter
O-Ring
Securing
Plate and
Screws
Control
board
Seal
Inlet Union
Facia assembly
25
15.4.11 Transformer
Remove the cabinet and lower the facia panel as described in
Section 14, Inspection and Servicing.
Unscrew the four screws and remove the metal cover. Refer to Fig
54.
Pull out the transformer. Refer to Fig 56.
Do not omit the heat transfer paste when fitting the replacement
sensor.
15.4.16 Overheat Thermostat
Remove the cabinet and the inner casing.
Carefully pull-off the connections. Unscrew the two screws and
remove the sensor. Refer to Fig 58.
Fig.56. Transformer
Fig.58. Primary sensor and overheat
thermostat
Control board
Primary
sensor leads
(red)
Flue hood
Mounting
plate
Overheat
thermostat
leads
(orange)
Primary
sensor
Fixing screws
Overheat
thermostat
Transformer
Fixing clip
Mounting
plate
Facia
15.4.12 Clock/Programmer
Remove the clock/programmer assembly by carefully pulling it
from the facia to release the clips. Unplug the connector at the
control board. Comprehensive instructions are sent with the new
control. Refer to Fig 57.
Fig.57. Programmer connection
Apply a small quantity of heat transfer paste to the face of the
replacement sensor.
Carefully reposition the sensor so that the connections are away
from the flue hood. Reconnect the sensor.
15.4.17 DHW Sensor
Remove the cabinet and lower the facia.
Carefully pull off the connections. Unscrew the clip and remove
the sensor.
Apply a small quantity of heat transfer paste to the face of the
replacement sensor.
Refer to Fig 59.
Control
board
Facia
Programmer
connector
Programmer
connections
Fig.59. Domestic hot water sensor
Clip
Programmer
Cenral heating
flow pipe
Pressure gauge
Domestic hot
water
flow
pipe
Domestic hot
water
temperature
sensor
15.4.13 Fan
Remove the inner casing.
Remove the fan as described in Section 14.3, Inspection and
Servicing. Ensure that all the connections are correctly made to
the new fan.
15.4.14 Air Flow Detector
Remove the fan as described in 15.3.13 preceding.
Unscrew and , through the fan outlet, withdraw the airflow
detector. Refer to Fig 42.
15.4.15 Primary [CH] Sensor
Remove the cabinet and inner casing.
Carefully pull-off the connections.
Withdraw the clip and lift off the sensor. Refer to Fig 58.
Fixing clip
Air flow
switch
Sensor leads
(yellow)
Fixing
screws
26
15.4.18 Pump
Check that the primary circuit has been fully drained as
described in 15.3 preceding.
Release the water connections and remove the pump. Refer to
Fig 45.
Disconnect and transfer the electrical connections to the new
pump. Set the pump speed to maximum. Do not forget the
gaskets at the connections.
Alternatively the pump head only [Grundfos 15-60] may be
replaced by unscrewing the four securing screws. Take care not
to scratch the mating surfaces .
15.4.19 Expansion Vessel
The specified replacement can be fitted into the system return as
close to the appliance as possible. Re-fill and pressurise the
system as described in Section 12 Commissioning.
15.4.20 Auto Air Vent
Drain the primary circuit as described in 15.3 preceding.
Unscrew and remove the auto air vent.
Do not omit the sealant (Loctite 575) when fitting the
replacement air vent.
Remove the cap. Refer to Fig 34.
15.4.21 Primary Heat Exchanger
Check that the appliance has been fully drained as described in
15.3 preceding.
Remove the combustion chamber as described in Section 14.3,
Inspection and Servicing.
Remove the temperature sensors as described in 15.4. 15, 16
and 17 preceding.
Undo the four union connections and remove the heat
exchanger.
Do not omit the sealing washers when fitting the replacement
heat exchanger. Refer to Fig 60.
15.4.22 Air Flow Switch
Carefully pull-off the connections from the switch. Unclip and
remove the switch. Refer to Fig 61.
Ensure that the connections are correctly made on the
replacement switch.
Fig.60. Primary heat exchanger
Heat Exchanger
Central heating flow
Central heating return
Domestic water
inlet
Domestic hot water
flow
Fibre washer
Union connections
Union connections
Fibre washer
Fig.61. Air flow switch
Air flow switch
Air flow switch leads
(green)
Red tube
Clear tube
27
16. Short Parts List
Key
No.
G.C. No.
10
15
17
18
25
26
28
30
34
34
34
35
39
49
52
55
57
59
63
63
66
69
70
77
84
85
96
E27-572
E27-578
E27-580
E27-582
E27-586
E27-587
E01-601
E27-592
E27-596
E27-597
E27-598
E27-600
E27-605
E27-616
299-363
E27-618
E27-620
E27-623
375-696
375-696
299-495
E25-322
E25-323
E27-636
E27-643
E27-644
E27-648
Part
Flow Switch
Water Filter
Pressure Relief Valve
Pump
Pressure Gauge
Expansion Vessel
Automatic Air Vent
Gas Valve
Burner (NG)
Burner (LPG) 28Si
Burner (LPG) 25Si
Primary Heat Exchanger
Combustion Chamber Insulation
Fan Assembly
Air Flow Detector
Inner Case Seal
Air Flow Switch
Control Board
Primary (CH) Sensor
DHW Sensor
Overheat Thermostat
Spark Electrode Assembly
Flame Sense Electrode
Transformer
Fibre Washer Pack
O-Ring Pack
Digital Timer
Fuse Pack
Manufacturer
Prettl
Prettl
Altechnic
Grundfos 59896603
Inter Albion x 32556
Winkleman & Panhof 15KCaleffi 502632CST
Junkers
Vulcano
Vulcano
Vulcano
ELM
Avon
WHS
WHS
Huba 605. 99486
Junkers Heatronic
Elmwood
Elmwood
Elmwood
Vulcano
Vulcano
Junkers
Qty
WHS
Part No.
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
8 717 002 122 0
8 716 148 410 0
8 716 156 764 0
8 716 143 114 0
8 716 142 388 0
8 715 407 154 0
8 716 140 504 0
8 747 003 381 0
8 718 120 565 0
8 718 120 566 0
8 718 120 569 0
8 716 759 081 0
8 716 121 601 0
8 716 121 546 0
8 716 141 000 0
8 716 121 602 0
8 716 142 387 0
8 748 300 336 0
8 716 142 302 0
8 716 142 302 0
8 716 142 389 0
8 708 107 008 0
8 708 107 009 0
8 747 201 274 0
8 716 121 603 0
8 716 121 604 0
7 716 192 019
8 716 156 013 0
FLUE OPTIONS
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
Flue Elbow Kit
425 - 725mm
750mm
Telescopic Flue
90 deg.
45 deg.
28
7 716 191 068
7 716 191 006
7 716 191 069
7 716 191 016
7 716 191 019
7 716 191 013
7 716 191 014
29
17. Operational Flow Diagrams
Room
thermostat
and/or mains
programmer
(or link) On
AND
AND
Electronic
facia
programmer
(if fitted) On
AND
ST13 link in
AND
CH control
knob On
CENTRAL HEATING FUNCTION
MAIN SWITCH
ON
CENTRAL
HEATING
DEMAND
CH light On.
Pump On.
Fan ON/
ignition
Sequence.
Burner Light
On.
Three minute
wait
Green Light
On
Two minute
minimum
burner
pressure then
ramp up
pressure over
next one
minute
Modulate gas
to maintain
flow
temperature
set by control
knob
DEMAND
END
Overrun
function
(see overleaf)
Over temperature shutdown if flow
temperature
5°C above set
value
Gas valve Off.
(CH light still
on. Pump still
On)
DOMESTIC HOT WATER FUNCTION
MAIN SWITCH
ON
DOMESTIC
HOT WATER
DEMAND
(Priority over
CH demand)
YES
Is CH
interrupted?
NO
Flow switch
On
(Tap open)
Green Light
On
Pump continue
4 seconds if
primary temp
above DHW
setting. Burner
to MAX for 4
seconds
Modulate gas
to maintain
delivered
water
temperature
set by control
knob
Ignition
sequence and
burner to MAX
for 4 seconds
DHW temp
drops to user
set point
Primary
75°
Over
temperature
shut-down if
water
temperature
above 85°C
Gas valve off.
Fan on 35
seconds.
Pump on until
temp drops to
60°C
Primary
temperature
115°C
Gas valve off.
Fan on.
Pump on
30
DEMAND
END
Overrun
function
(see overleaf)
OVERRUN FUNCTION
END DHW
DEMAND
If primary temp
above 80° fan
runs until temp
below 80°C
(35 seconds
minimum)
Fan overrun
function active
for 3 minutes
If primary temp
below 80° run
fan for 35
seconds
If primary temp
over 85° pump
cycles for 2
seconds every 10
seconds until
temp below
85°
END CH
DEMAND
If primary rises
above 85° fan
runs until temp
falls below 80°
After 3 minutes the pump runs if:
primary temp over 95° until below 77°
hot water temp over 98° until below 63°
Pump runs
for
3 minutes
AUTOFROSTAT FUNCTION
No demand
and primary
temperature
below 8°C
Internal
“Autofrostat”
demand
Wait in normal
off state for
30 minutes
Run
Runpump
pumpfor
four minutes
Monitor
central
heating
sensor
Below
5°C
5°C
to
9°C
Above
9°C
Commence normal
central heating mode
until temperature
reaches 20°C
30°C
31
Return to
normal off
state
18. Fault Finding
Note: This fault-finding information is for guidance only. Worcester Heat Systems cannot be held responsible for costs incurred by
persons not deemed to be competent.
The electronic control system for this boiler incorporates four lights on the facia. These are used to show normal operating status. But as
a secondary function, by flashing, they can also be used to help provide fault diagnostics. Therefore, with individual or groups of lights
being permanently off, on or flashing, every normal fault can be identified.
To use the fault finding system, select a box below which represents the light situation during your fault. Then refer to the appropriate
following section. This fault-finding system assumes that the appliance has been operating correctly until the time of failure.
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.
2 lights flashing fast
FAIL POINT K
L
Note:
Slow flash is once per second, fast flash is five times per second.
Slow flash can only be cleared by using the facia reset button (press for at least one second).
Fast flash is cleared by removing fault and/or main switch off/on.
32
Is the facia on/off
switch turned on?
`(Clockwise)
No
Turn switch on.
FAIL POINT A
Yes
Is there a 230V AC live
supply across
Terminal ST12 pins L
and N
No
Check electrical
supply to boiler.
Yes
Has fuse F1 blown?
No
Replace control board
(Section 15.4.10)
Yes
Replace fuse and investigate cause. Suggestions: Cable
damage, connections to (or faults within) pump, fan,
external 230V controls, transformer or board.
FAIL POINT B
Has fuse F2 blown?
No
Yes
Replace fuse.
This will be caused by
fuse fatigue or by the
board.
Remove control board from facia
(See Section 15.4.10) and separate transformer from board.
Measure resistance across the
two pairs of adjacent pins on the
transformer. Are any pair above
100 ohms?
Yes
FAIL POINT C
Replace transformer.
Green diode is damaged.
Replace control board.
(Section 15.4.10)
33
No
Replace
control
board
(Section
15.4.10).
With CH control knob
fully clockwise, does
the boiler ignite and
appear to run
normally in central
heating mode?
No
Is there 230V AC
across terminal ST8
pins LR and N?
No
There is no heat
demand. Check room
thermostat or mains
programmer (or link).
Yes
Yes
Red diode is
damaged. Replace
control board.
(Section 15.4.10)
FAIL POINT D
Is there a link at
terminal ST13 pins 1
and 2?
No
Insert a link
Yes
Is there an electronic
programmer at
position ST5 at righthand end of board?
No
Replace control board.
(Section 15.4.10).
Yes
Remove programmer
connector from board
edge. Does CH lamp
now light?
No
Yes
FAIL POINT E
Correctly set or
replace electronic
programmer.
With a hot water tap
fully open, does the
boiler ignite and
appear to run
normally in hot water
mode?
Yes
Red diode is
damaged. Replace
control board.
(Section 15.4.10)
No
Remove multiway
connector from board
position ST16. With
tap still open is there
continuity across
contacts 19 and 20
(2 pink wires)?
No
Locate and observe the
flowswitch assembly
(behind the air pressure
switch). Does the lever
above the microswitch
move up and down with
the demands, thus
activating and
de-activating the
microswitch?
Yes
Yes
Replace control board.
(Section 15.4.10).
Check or replace
wiring or microswitch
34
No
Replace flowswitch
assembly
FAIL POINT F
Is the boiler in a very
cold environment (less
than 5°C)?
No
Replace control board.
(Section 15.4.10).
Note: A damp board
could cause this fault.
Yes
Boiler is running in
“Autofrost stat” mode.
See Section 17.
Is the boiler fully
water pressurised and
is all air vented?
No
Rectify fault.
FAIL POINT G “Primary Overheat”
Yes
Reset the controls and
restart the boiler.
Does the pump run?
No
Repair or replace
pump.
(Section 15.4.18).
Yes
Remove inner casing
cover and inspect the
primary sensor (left of
heat exchanger).
Is it correctly fixed to
pipe?
No
Re-fix sensor to pipe.
Yes
Remove the multiway
connector from board
position ST16.
Is there a short circuit
across contacts 5 & 6?
No
Replace overheat
thermostat or check
wiring to it
Yes
Fault caused by control
board or heat
exchanger
35
Is the gas supply
connected and at the
correct pressure?
No
Rectify gas supply
problem.
Yes
Remove front panel.
Reset and restart the
boiler. Can a flame be
seen through the spy
glass?
No
Remove inner cover.
Reset and restart the
boiler. Does a spark
occur across the
electrodes?
No
Are the electrodes and
gap and connections
in good order?
No
Repair or replace
spark electrode
(Section 15.4.2)
or HT leads
Yes
Replace control board.
(Section 15.4.10).
Yes
Turn off boiler. Remove
the multiway
connector from board
position ST16. Test
resistance across
contacts 7 and 8
(brown wires) and 9
and 10 (violet wires).
Are both reading
below 200 ohms?
FAIL POINT H “Burner Lockout”
Yes
No
Yes
Turn off boiler. Remove
inner cover and
combustion chamber
cover. Are the sense
electrode and lead in
good condition and is
gap correct?
Yes
Replace gas valve.
(Section 15.4.1).
Replace control board.
(Section 15.4.10).
If problem not solved
replace gas valve.
(Section 15.4.1)
No
Repair or replace flame
sensor
(Section 15.4.3)
or wiring.
Yes
Remove multiway
connector from board
position ST16.
Is there continuity
from contact 11 (white
wire) to flame sensor?
No
Yes
Does the flashing fault
signal occur at the
start of a demand?
No
Remove both brown
connectors from gas
valve.
Is there continuity
from brown and violet
wires to multiway
connector?
Flashing occurs at end
of demand. Replace
gas valve.
(Section 15.4.1).
Yes
Replace control board (Section 15.4.10).
Note: It is not possible to reliably check
the cross-light performance of the burner.
In the unlikely event of such a fault,
investigate flue problems or replace
burner or injector. (Section 15.4.4).
36
No
Repair or replace
harness.
Is the multiway
connector at board
position ST16 pushed
fully home on to the
board?
No
Push fully home
Yes
Check the DHW
sensor. Is it correctly
fitted onto the pipe
with heat conductive
paste between the
pipe and sensor?
No
Re-fix sensor onto pipe
Yes
FAIL POINT I “Sensor Fault”
Remove multiway
connector from board
position ST16. Test
resistance across
contacts 17 and 18
(yellow wires). Is it
between 1 kohm and
30 kohm?
No
No
Repair or replace
harness.
Yes
Check or replace
DHW sensor.
(Section 15.4.17).
Yes
Test resistance across
contacts 12 and 13
(red wires). Is it
between 1 kohm and
30 kohm?
Is there continuity
from contacts 17 and
18 to DHW sensor?
No
Is there continuity
from contacts 12 and
13 to CH sensor?
No
Repair or replace
harness.
Yes
Check or replace CH
sensor.
(Section 15.4.15).
Yes
Test resistance across
contacts 7 and 8
(brown wires) and 9
and 10 (violet wires).
Are both readings
below 200 ohms?
Yes
Replace control board.
(Section 15.4.10).
No
Remove both brown
connectors from
gas valve.
Is there continuity
from brown and violet
wires to the multiway
connector?
No
Yes
Replace gas valve.
(Section 15.4.1).
37
Repair or replace
harness.
Does the fan run
before the fault
occurs?
No
Turn off boiler. Is there
continuity across the
C and NO terminals of
the air pressure switch
(where green wires are
fitted)?
No
Remove the fan
connector from board
position ST1 and
restart the boiler. Is
there mains 230V
across the centre (L)
and left (N) tracks at
ST1? Note: Take care
not to short L to N.
No
Replace control board.
(Section 15.4.10).
Yes
Yes
Yes
Air pressure switch
is shorting.
Replace switch.
(Section 15.4.22)
FAIL POINT J “Air Pressure Fault”
Does the burner ignite
(burner light on)
before fault occurs?
No
Remove electrical
connectors from
pressure switch and
restart boiler. Is there
continuity between C
and NO terminal
(where green wires
were fitted) when the
fan runs?
Repair or replace fan
(Section 15.4.13) or
cable.
No
Pressure switch has
not closed. Are the
silicon tubes in good
condition and free of
condensation.
Replace tubes. If
condensation has
occurred, also replace
pressure switch and
check condition of
Venturi in the fan.
Yes
Inspect the flue. Is it
free of any
restrictions?
Yes
Replace air pressure
switch (Section
15.4.22). Note: In the
unlikely event of this
not solving the
problem inspect the
pressure pick-up
(Venturi) in the fan.
Yes
Yes
Remove multiway
connector from board
position ST16. Is there
continuity of the
green wires?
No
No
Yes
Replace control board.
(Section (15.4.10).
Pressure switch has
opened during
operation.
Check flue for
blockage.
Also investigate sense
tubes and pressure
switch.
38
Repair wires or replace
harness.
No
Rectify flue problem.
FAIL POINT K
The gas valve mode
switch (concealed by
the facia side panel)
is not set correctly
FAIL POINT L
Light indication
during fault not
covered by above
details.
Turn to 'NORM'
position
Control board is likely
to be wet or damaged
or malfunctioning.
Check for wet board or
connections. Dry and
re-use or replace
control board. (Section
15.4.10).
Hot water
temperature always
too hot during a
demand (not
regulating).
Hot water sensor
could be off or poorly
fixed to pipe.
Repair or replace
sensor.
(Section 15.4.15).
Water temperature
very low/low gas
pressure (with all
knobs set to
maximum)?
Is the gas set to correct
pressure?
No
Set pressure.
Yes
Remove multiway
connector from board
position ST16. Is the
resistance across
contacts 1 and 2
(blue wires) below
60 ohms.
No
Yes
Remove blue (top)
connector from gas
valve.
Is there continuity
along blue wires to
multiway connector?
Yes
Replace control board.
(Section 15.4.10).
Replace gas valve.
(Section 15.4.1).
39
No
Repair wires or replace
harness.
This manual is to be used in conjunction
with the variant part number of the bar
code below:
Bosch Group
Worcester Heat Systems Limited (Bosch Group), Cotswold Way, Warndon, Worcester WR4 9SW.
Telephone: (01905) 754624. Fax: (01905) 754619.
Technical Helpline (08705) 266241.
www.worcester-bosch.co.uk
This 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 8 716 115 067a (05/08)