Worcester Gas boiler User manual

UK/IE
INSTALLATION INSTRUCTIONS
WALL HUNG RSF GAS FIRED CONDENSING BOILER
GREENSTAR i SYSTEM OPTIONAL
INTEGRAL DIVERTER VALVE
6720645222-00.2Wo
FOR CENTRAL HEATING SYSTEMS AND INDIRECT FED DOMESTIC HOT WATER
6 720 645 222a (2012/05)
Diverter valve kits contain:
1 Copper return pipe
1 Brass service valve
1 15mm Compression nut
1 15mm Olive
1 Diverter valve motor
1 Diverter valve harness
2Screws
2Codeplugs
1Codeplugtie
Diverter valve kit numbers
12kW 7 716 192 566
15kW 7 716 192 567
18kW 7 716 192 568
24kW 7 716 192 409
Code plug numbers
12i System Natural gas 1118
L.P.G. 1119
15i System Natural gas 1122
L.P.G. 1123
18i System Natural gas 1126
L.P.G. 1127
24i System Natural gas 1114
L.P.G. 1115

CONTENTS
6 720 645 222a (2012/05)
2
CONTENTS
1 KEY TO SYMBOL AND SAFETY PRECAUTIONS . 3
1.1 Explanation of symbols . . . . . . . . . . . . . . . 3
1.2 Safety precautions . . . . . . . . . . . . . . . . . . 4
2 PLUMBING MANIFOLD . . . . . . . . . . . . . . . . . . . . 6
3 BOILER CONNECTIONS . . . . . . . . . . . . . . . . . . . 7
3.1 Assembly of the internal cylinder return
pipe to the boiler . . . . . . . . . . . . . . . . . . . . 7
3.2 Gas and water connections . . . . . . . . . . . . 8
4 fITTING THE DIVERTER VALVE & CODE PLUG 10
4.1 Fitting the diverter valve motor: . . . . . . . 10
4.2 Access to the code plug . . . . . . . . . . . . . 10
4.3 Fitting the code plug . . . . . . . . . . . . . . . . 11
4.4 Fitting the cylinder temperature sensor . 11
4.5 Diverter valve and sensor connections . . 11
5 ELECTRICAL . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5.1 Internal diverter valve with a
vented cylinder . . . . . . . . . . . . . . . . . . . . . 12
5.2 Internal diverter valve with an unvented
cylinder . . . . . . . . . . . . . . . . . . . . . . . . . . 13
5.3 Position of wired components . . . . . . . . 14
6 PRE-COMMISSIONING CHECKS . . . . . . . . . . . 15
7 BOILER FUNCTION . . . . . . . . . . . . . . . . . . . . . . 16
7.1 Fault finding . . . . . . . . . . . . . . . . . . . . . . 16
7.2 Boiler function . . . . . . . . . . . . . . . . . . . . . 17
7.3 Protection function . . . . . . . . . . . . . . . . . 18

KEY TO SYMBOLS AND SAFETY PRECAUTIONS
6 720 645 222a (2012/05) 3
1 KEY TO SYMBOLS AND SAFETY PRECAUTIONS
1.1 EXPLANATION OF SYMBOLS
WARNING SYMBOLS
Signal words indicate the seriousness of the hazard in
terms of the consequences of not following the safety
instructions.
•NOTICE indicates possible damage to property or
equipment, but where there is no risk of injury.
•CAUTION indicates possible injury.
•WARNING indicates possible severe injury.
•DANGER indicates possible risk to life.
IMPORTANT INFORMATION
ADDITIONAL SYMBOLS
SYMBOLS USED IN THIS MANUAL
PLEASE READ THESE INSTRUCTIONS CAREFULLY
BEFORE STARTING INSTALLATION.
THESE INSTRUCTIONS ARE APPLICABLE TO THE
WORCESTER APPLIANCE MODEL(S) STATED ON THE
FRONT COVER OF THIS MANUAL ONLY AND MUST NOT
BE USED WITH ANY OTHER MAKE OR MODEL OF
APPLIANCE.
THE INSTRUCTIONS APPLY IN THE UK ONLY AND MUST
BE FOLLOWED EXCEPT FOR ANY STATUTORY
OBLIGATION.
THIS APPLIANCE MUST BE INSTALLED BY A GAS SAFE
REGISTERED, COMPETENT PERSON. FAILURE TO
INSTALL CORRECTLY COULD LEAD TO PROSECUTION.
IF YOU ARE IN ANY DOUBT CONTACT THE WORCESTER
TECHNICAL HELPLINE.
DISTANCE LEARNING AND TRAINING COURSES ARE
AVAILABLE FROM WORCESTER.
PLEASE LEAVE THESE INSTRUCTIONS WITH THE
COMPLETED BENCHMARK CHECKLIST, (OR A
CERTIFICATE CONFIRMING COMPLIANCE WITH IS 813,
EIRE ONLY) AND THE USER MANUAL WITH THE OWNER
OR AT THE GAS METER AFTER INSTALLATION OR
SERVICING.
THE BENCHMARK CHECKLIST CAN BE FOUND IN THE
BACK PAGES OF THE INSTALLATION MANUAL.
ABBREVIATIONS USED IN THIS MANUAL:
Safety instructions in this document are
framed and identified by a warning triangle
which is printed on a grey background.
Electrical hazards are identified by a
lightning symbol surrounded by a warning
triangle.
Notes contain important information in
cases where there is no risk of personal
injury or material losses and are identified
by the symbol shown on the left. They are
bordered by horizontal lines above and
below the text.
Symbol Meaning
Ba step in an action sequence
Æa reference to a related part in the
document or to other related documents
•a list entry
–a list entry (second level)
Tab. 1 Symbols
Domestic Hot Water
Central Heating
Hot Water Storage Cylinder
Domestic Cold Water Supply
Electrical Supply
Gas Supply
Tab. 2 Commonly used symbols
ØDiameter
NG Natural Gas
LPG Liquid Petroleum Gas
CH Central Heating
DHW Domestic Hot Water
PRV Pressure Relief Valve
NTC Negative Temperature Coefficient (sensor)
IP Ingress Protection
RCD Residual Current Device
TRV Thermostatic Radiator Valve
WRAS Water Regulations Advisory Scheme
SEDBUK Seasonal Efficiency of Domestic Boilers in
the United Kingdom
Tab. 3 Abbreviations

KEY TO SYMBOLS AND SAFETY PRECAUTIONS
6 720 645 222a (2012/05)
4
1.2 SAFETY PRECAUTIONS
IF YOU SMELL GAS:
BCALL NATIONAL GAS EMERGENCY SERVICE ON
0800 111 999
BLPG BOILERS CALL THE SUPPLIER‘S NUMBER ON
THE SIDE OF THE LPG TANK
BTURN OFF THE ECV (EMERGENCY CONTROL VALVE)
AT THE METER
BDO NOT TURN ELECTRICAL SWITCHES ON OR OFF
BDO NOT STRIKE MATCHES OR SMOKE
BPUT OUT NAKED FLAMES
BOPEN DOORS AND WINDOWS
BKEEP PEOPLE AWAY FROM THE AFFECTED AREA
BOILER OPERATION:
This boiler must only be operated by a responsible
adult who has been instructed in, understands, and is
aware of the boiler‘s operating conditions and effects.
Benchmark places responsibilities on both
manufacturers and installers. The purpose is to ensure
that customers are provided with the correct equipment
for their needs, that it is installed, commissioned and
serviced in accordance with the manufacturer's
instructions by competent persons and that it meets the
requirements of the appropriate Building Regulations.
The Benchmark Checklist can be used to demonstrate
compliance with Building Regulations and should be
provided to the customer for future reference.
Installers are required to carry out installation,
commissioning and servicing work in accordance with
the Benchmark Code of Practice which is available from
the Heating and Hotwater Industry Council who manage
and promote the scheme.
Visit centralheating.co.uk for more information.
HEALTH AND SAFETY
The appliance contains no asbestos and no substances
have been used in the construction process that
contravene the COSHH Regulations (Control of
Substances Hazardous to Health Regulations 1988).
COMBUSTION AND CORROSIVE MATERIALS
Do not store or use any combustible materials (paper,
thinners, paints etc.) inside or within the vicinity of the
appliance.
Chemically aggressive substances can corrode the
appliance and invalidate any warranty.
FITTING AND MODIFICATIONS
Fitting the appliance and any controls to the appliance
may only be carried out by a competent engineer in
accordance with the current Gas Safety (Installation and
Use) Regulations.
Flue systems must not be modified in any way other than
as described in the fitting instructions. Any misuse or
unauthorised modifications to the appliance, flue or
associated components and systems could invalidate
the warranty. The manufacturer accepts no liability
arising from any such actions, excluding statutory rights.
SERVICING
Advise the user to have the system serviced annually by
a competent, qualified Gas Safe registered engineer.
Approved spares must be used to help maintain the
economy, safety and reliability of the appliance.
IMPORTANT
The service engineer must complete the Service Record
on the Benchmark Checklist after each service.
INSTALLATION REGULATIONS
Current Gas Safety (Installation & Use) Regulations:
All gas appliances must be installed by a competent
person in accordance with the above regulations.
Failure to install appliances correctly could lead to
prosecution.
The appliance must be installed in accordance with, and
comply to, the current: Gas Safety Regulations, IEE
Regulations, Building Regulations, Building Standards
(Scotland) (Consolidation), Building Regulations
(Northern Ireland), local water by-laws, Health & Safety
Document 635 (The Electricity at Work Regulations
1989) and any other local requirements.

KEY TO SYMBOLS AND SAFETY PRECAUTIONS
6 720 645 222a (2012/05) 5
British Standards:
Where no specific instruction is given, reference should
be made to the relevant British Standard codes of
Practice.
BS7074:1 Code of practice for domestic and hot water
supply
BS6891 Installation of low pressure gas pipe work up
to 28mm (R1)
BS5546 Installation of gas hot water supplies for
domestic purposes
EN12828 Central heating for domestic premises
BS5440:1 Flues and ventilation for gas appliances of
rated heating not exceeding 70kW (net) :
Flues
BS5440:2 Flues and ventilation for gas appliances of
rated heating not exceeding 70kW (net) : Air
Supply
BS7593 Treatment of water in domestic hot water
central heating systems
BS6798 Installation of gas fired boilers of rated input
up to 70kW (net)
Irish Standards
The relevant Irish standards should be followed,
including:
•ECTI National rules for electrical installations
•IS 813:2002 for Domestic Gas Installations.
LPG Installations
An appliance using L.P.G. must not be installed in a room
or internal space below ground level unless one side of
the building is open to the ground.
Timber framed building:
Where the boiler is to be fitted to a timber framed
building the guidelines laid down in BS5440: Part 1 and
IGE "Gas Installations in Timber Frame Buildings” should
be adhered to.
Potable water:
All seals, joints and compounds (including flux and
solder) and components used as part of the secondary
domestic water system must be approved by WRAS.
CH Water:
Artificially softened water must not be used to fill the
central heating system.

PLUMBING MANIFOLD
6 720 645 222a (2012/05)
6
2 PLUMBING MANIFOLD
CONNECTIONS:
•Heating System: 22mm compression fittings
•Gas: 22mm compression fitting
•Cylinder Return 15mm compression fitting
•Use the fittings supplied in the Hardware literature
pack and the Optional Diverter Valve Kit.
If the boiler pipes are to be run behind the appliance
ensure that the pipes pass through the slot in the
guide (9). This is fitted to the boiler frame.
Fig. 1 Pipe dimensions
Fig. 2 Plumbing manifold with wall frame
NOTICE: Fitting the service valve
BRefer to figure 2
BThe service valve (7) from the Optional
Diverter Valve Kit must be fitted and
secured to the wall mounting frame with
two screws (8) supplied, before the wall
mounting frame is fitted to the wall.
Further guidance on pipe routing can be
found printed on the boiler template
(supplied with the boiler).
123 456
6720645222-12.1Wo
#Function
From left
case edge
Diameter
of pipe
1 CH and cylinder flow 70 mm 22 mm
2Gas 200 mm 22 mm
3CHReturn 330 mm 22 mm
4Condensate 35 mm 22 mm
5 Pressure Relief Valve 367 mm 15 mm
6 Cylinder return 267 mm 15mm
Tab. 4 Key to figures 1 & 2
12
3
6
1
6
23
4
5
6720644222-01.1Wo
9
7
8

BOILER CONNECTIONS
6 720 645 222a (2012/05) 7
3 BOILER CONNECTIONS
3.1 ASSEMBLY OF THE INTERNAL CYLINDER RETURN PIPE TO THE BOILER
Use the packaging as protection, turn the boiler on its left hand side to enable fitting of the hot water return pipe.
BMove the control panel into the service position by removing the screw from the retaining bracket.
1. Loosen the two retaining screws to free the back clamping plate on the hydraulic block as shown in figure 3.
2. Remove the brass bung assembly from the hydraulic block by removing the screw and sliding it free from the flange
on the clamping plate. Make sure that the other brass bung assembly is retained in place.
3. Remove the copper pipe from the Optional Integral Diverter Valve Kit and feed the flat end of the pipe through the
rear of the boiler as shown.
4. Before fitting the pipe, check that the seal is in position on the plastic moulding. Slide the flat end of the pipe under
the flange on the hydraulic block clamping plate ensuring that pipe is located correctly.
5. Secure the clamping plate by re-tightening the two screws (1) loosened in step 1.
Fig. 3 Hot water return pipe fitting
CAUTION: CYLINDER RETURN PIPE
BThe following must be completed before the boiler is mounted onto the wall mounting frame
4.
3.
2. 5.
1.
1.
6720645222-02.1Wo

BOILER CONNECTIONS
6 720 645 222a (2012/05)
8
3.2 GAS AND WATER CONNECTIONS
BRemove template and secure the wall mounting frame
to the wall with the fittings supplied.
BSystem pipes may be run vertically upwards behind
the boiler or below it.
See Plumbing Manifold Section on page 6.
1. CH and cylinder flow (22mm),
2. Gas inlet (22mm),
3. Cylinder return(15mm),
4. CH return (22mm)
If using the optional filling loop: 7 716 192 281 (not
supplied with the boiler) fit it before hanging the boiler
on the wall frame.
BFit sealing washers to service valves before hanging
boiler.
Fig. 4 Sealing washers
1. Pull the extended tab/lever forward and down until
there is no further travel.
Fig. 5 PRV connection in the down position
BHang the boiler on to the wall mounting frame by the
two brackets positioned left and right at the top rear
of the appliance.
Do not lift the appliance by the air gas manifold. There
are two handling holes incorporated into the inner
casing left and right in the lower section of the
appliance.
Fig. 6 Hanging the boiler
CAUTION:
BISOLATE THE MAINS GAS SUPPLY
BEFORE STARTING ANY WORK AND
OBSERVE ALL RELEVANT SAFETY
PRECAUTIONS.
The bonded washer supplied is for the Gas
connection only.
NOTICE: Before hanging the boiler onto the
wall mounting frame ensure that the
pressure relief valve connection is in the
DOWN position.
This is located on the right hand side of the
wall frame at the rear.
1. 2. 3. 4.
6720645222-04.1Wo
CAUTION: Caps or plastic strip fitted to
pipes must be removed before hanging the
boiler.
NOTICE: The pressure relief connector
must be repositioned after the boiler has
been correctly mounted to the wall
mounting frame.
6720643895-116.1Wo
1.
6720643895-22.1Wo

BOILER CONNECTIONS
6 720 645 222a (2012/05) 9
1. Push the lever on the pressure relief connector UP
until the stop on the inside of the handle is over the
shoulder of the metal bracket to secure in place.
Fig. 7 PRV in the up position
BRemove the screw from the control panel retaining
bracket and lower the control panel into the service
position.
BMake connections to the heating system and cylinder.
Connect the gas supply to the boiler gas cock 22mm
compression.
To connect the expansion vessel flexible pipe to the
hydraulic manifold situated to the left of the pump:
BRemove and discard the plastic cap from the
expansion vessel flexible pipe.
1. Refer to figure 8, release the retaining clip.
2. Remove and discard the orange plastic blanking plug
(2) from the pressure vessel connection at the
hydraulic manifold.
Fig. 8 Blanking plug removal
1. Refer to figure 9 and insert the expansion vessel
flexible pipe it to the fitting on the pump.
2. Secure in place with the wire retaining clip.
Fig. 9 Expansion vessel connection
BConnect the pressure relief drain pipe to 15mm
compression joint using the compression nut and
olive supplied in the literature/hardware pack.
6720644743-17.1Wo
1.
6720645222-05.1Wo
1.
2.
6720645222-06.1Wo
1.
2.

FITTING THE DIVERTER VALVE AND CODE PLUG
6 720 645 222a (2012/05)
10
4 FITTING THE DIVERTER VALVE AND CODE PLUG
4.1 FITTING THE DIVERTER VALVE
MOTOR:
1. Remove the diverter blanking plate by pulling it
forwards to free it from its location.
Fig. 10 Removing Diverter valve blanking plate
1. To fit the diverter valve motor, push the motor into the
housing until the motor “clicks” securely into place,
ensuring that the actuator arm locates into the middle
of the “H” receptor on the motor.
2. Connect the plug of the diverter valve motor harness
into the socket on the diverter valve motor.
3. Slide the protective cover over the diverter valve
motor.
Fig. 11 Fitting Diverter motor and cover
4.2 ACCESS TO THE CODE PLUG
1. Referring to figure 12, unscrew the three screws in
the control panel.
2. Pull off the connections cover.
Fig. 12 Removing the connection cover
BIdentify ST18, the code plug and connector.
Fig. 13 Connector locations
1.
6720645222-07.1Wo
3. 2.
1.
6720645222-08.1Wo
NOTICE: RESET THE CONTROL BOARD
Following changes to the wiring of ST15 and
ST8 the control board will need to be reset
to recognise the new connection.
To reset the control board:
BHold the Service mode “Spanner” and the
Eco buttons down for at least five
seconds.
1. 1.
1.
2.
6720643895-40.1Wo
6720645222-09.1Wo
ST15
ST17
ST10 ST8
ST6
ST18

FITTING THE DIVERTER VALVE AND CODE PLUG
6 720 645 222a (2012/05) 11
4.3 FITTING THE CODE PLUG
1. Refer to figure 14. Remove the code plug from the
controller, cut the tie securing the plug to the boiler
chassis and discard the plug and tie.
2. Fit the code plug from the kit making sure that code
plug is secured to the boiler chassis with the new tie.
BConfirm that the number on the code plug
corresponds to the boiler type in the table above.
Fig. 14 Fitting new code plug
4.4 FITTING THE CYLINDER
TEMPERATURE SENSOR
Refer to the cylinder installation instructions for the
position of the sensor, there may already be a “sensor
pocket” available. If no “pocket” is available, for foam
insulated cylinders only with no metal jacket, follow the
steps below.
1. Mark a rectangular hole of approximately 50 by
100mm approximately one third of the cylinder length
from the bottom of the cylinder.
1. Using a sharp knife, cut through the insulation,
remove and retain the piece of insulation.
2. Apply heat conductive paste to the sensor and place
the sensor on the cylinder body in the middle of the
cut-out.
3. Hold the sensor in position with a piece of aluminium
tape.
4. Replace the insulation material.
5. Secure the insulation in place with suitable cloth
tape.
Fig. 15 Sensor connection to cylinder
4.5 DIVERTER VALVE AND SENSOR
CONNECTIONS
1. Connect the Diverter valve motor harness to the edge
connector ST17.
2. Connect the cylinder temperature sensor (1) to the
edge connector ST15.
Fig. 16 Diverter motor and sensor connections
BReplace the control panel cover.
BMove the control panel to the up position and secure.
Boiler size Gas Code plug no.
12kW i System kit NG 1118
LPG 1119
15kW i System kit NG 1122
LPG 1123
18kW i System kit NG 1126
LPG 1127
24kW i System kit NG 1114
LPG 1115
CAUTION: Cut carefully!
BDo not to pierce the wall of cylinder.
BDo not cut any metal insulation jacket.
6720645222-10.1Wo
1.
2.
ST18
NOTICE: Figure 15 applies only to foam
covered open vent cylinders.
NOTICE: Do not route low voltage cables
alongside mains voltage cables.
This can cause interference on the low
voltage cables.
If the ST15 connector and sensor is being
used do not connect ST8 as well.
The link is not required.
6720645222-24.1Wo
6. 3.
4.
5.
2.
1.
1
6720645222
-
11.1Wo
1.
2.
ST15
ST17

ELECTRICAL
6 720 645 222a (2012/05)
12
5 ELECTRICAL
5.1 INTERNAL DIVERTER VALVE WITH A VENTED CYLINDER
ACCESS TO ELECTRICAL CONNECTIONS:
Remove boiler casing to access control panel.
1. Unscrew the single screw and lower the control box
into the horizontal position.
2. Unscrew the three screws in the control panel and
pull off the connections cover.
3. 230V room thermostat with timer 7 716 192 038
(ST10):
BRemove link - LS/LR
BConnect room stat LIVE supply to terminal (LS)
BConnect room stat LIVE return to terminal (LR)
BConnect room stat NEUTRAL to terminal (NS)
4. Hot water channel
5. Optional external frost stat connection (ST6):
BConnect frost stat wires to terminal (FS) and (FR)
6. Diverter valve motor (ST17):
BConnect electrical harness from diverter valve motor
to ST17 (see following page).
Fig. 17
NOTICE:
BMains supply to the boiler must be through a fused double pole isolator situated adjacent to the
appliance. The isolator must have a contact separation of 3mm minimum in both poles. External fuse
rating 3A.
BWhen stripping wires always ensure copper strands do not fall into the control box.
BThere should be no external wiring centre.
BA fascia mounted twin channel programmer must be used.
Timers available:
DT20 Twin Channel Programmer (7 716 192 038),
DT10RF Digistat (7 716 192 052),
DT20RF Digistat (7 716 192 054).
NOTICE:
BIf the timer 7 716 192 052 or 7 716 192
054 is used, the room thermostat is
incorporated in the transmitter.
Therefore keep link fitted across LS/LR.
L
NSN
LSLR
N
blue
brown
green/yellow
live
switched live
neutral
E
ST10
230V
MAINS
SUPPLY
L
Room Thermostat
DT20 Twin Channel
Programmer
Cylinder
temperature
sensor
6720645222-17.1Wo

ELECTRICAL
6 720 645 222a (2012/05) 13
5.2 INTERNAL DIVERTER VALVE WITH AN UNVENTED CYLINDER
OPTIONAL EXTERNAL FROST STAT CONNECTION ST6
Fig. 18 Frost Thermostat
BConnect frost thermostat cables to terminals FS& FR.
BThese are not polarity sensitive.
CONNECTOR LOCATIONS
Fig. 19 Electrical connector information
6720645222-20.1Wo
L
NSN
LSLR
Nblue
brown
green/yellow
live
switched live
neutral
E
230V
MAINS
SUPPLY
L
Cylinder
temperature
sensor
Twin Channel
Programmer
Room Thermostat
HIGH LIMIT
THERMAL CUT-OUT
HOT WATER CONTROL
THERMOSTAT
DUAL THERMOSTAT
*
Frost Thermostat
FSFR NP LP
ST6
6720643895-43.1Wo
6720645222-09.1Wo
ST15
ST17
ST10 ST8
ST6
ST18

ELECTRICAL
6 720 645 222a (2012/05)
14
5.3 POSITION OF WIRED COMPONENTS
Fig. 20 Wired components
FAN
FSFR NP LP
L
NSN
LSLR
ST8
ST9
ST17
ST18
ST5 ST4
ST10
Earth
MAINS
SUPPLY
PUMP
SUPPLY
SPARK
TRANSFORMER
DIVERTER
VALVE
ST1 DIAGNOSTIC
INTERFACE
CODE PLUG
Fuse F1, slow
2.5 A, AC 230 V
Fuse F3, slow T 0.5 A
Fuse F2, slow T1.6 A
ST6
CH TEMPERATURE
CONTROL
Red
Neutral Supply
230V
EXTERNAL
ROOM STAT
WHEN USED
WITH DT20
WORCESTER 24V CONTROLS, PLUG IN POINT
OPTIONS: DT20 OR DT20 RF OR DT10 RF
(under blanking cover on fascia)
Live Supply
Live Return
Neutral
Live
Orange
Blue
Yellow
Green
Black
Colour sequence †
Purple
Purple
Red
Red
Orange
Orange
Colour sequence †
230V/AC
9V 25V
*
PRE WIRED LINK
*
EMS BUS contacts
(for FX controls)
Outside sensor
(FW 100)
B
B
4
2
1
A
F
Wall plate contacts
(for FX controls)
BB
EXTERNAL
FROST STAT
(OPTIONAL)
ST15
Cylinder
temperature
sensor
FLAME SENSE
ELECTRODE
SPARK
ELECTRODES
OVERHEAT
STAT
FLUE
OVERHEAT
STAT
PUMP
Green
DHW TEMPERATURE
CONTROL (CYLINDER)
GAS
VALVE
SAFETY
SOLENOID
SAFETY
SOLENOID
6720645222-22.1Wo
† Fan wiring:
Live = purple
Neutral = brown FLOW TEMP.
SENSOR (NTC)
SI1
SI2
SI3
Blue
Blue

PRE-COMMISSIONING CHECKS
6 720 645 222a (2012/05) 15
6 PRE-COMMISSIONING CHECKS
1. Check that the service and water pipes are connected
to the correct position on the manifold.
–A - Flow (22mm)
–B - CH Return (22mm)
–C - Gas inlet (22mm)
–D - Cylinder Return (15mm)
2. Check the gas type specified on the identification
plate matches that of the gas supply. Turn on the main
gas supply, check the gas pipework, connections and
rectify any leaks.
3. Check that the condensate pipe has been connected
to the syphon.
4. Check pressure relief drain pipe is correctly fitted and
securely tightened.
NOTICE: If the boiler is not to be
commissioned immediately then:
Bafter successfully completing all of the
checks and any rectification work, close
the gas and water valves, shut off the gas
supply, electrically isolate the boiler and
label appropriately.
NOTICE:
BNOW RETURN TO THE I SYSTEM
INSTRUCTION MANUAL (FILLING THE
SYSTEM) TO CONTINUE INSTALLATION.

BOILER FUNCTION
6 720 645 222a (2012/05)
16
7 BOILER FUNCTION
7.1 FAULT FINDING
If in the unlikely event the boiler does not give complete
satisfaction, before calling for a service engineer, the
installer should check the following:-
FOR BOILERS WITH INTEGRAL DIVERTER VALVE AND
CONTROLS
NO CENTRAL HEATING, BUT HOT WATER OK
Remove the room stat wiring from Ls, LR and N from
terminal block ST10. Fit a link between Ls and LR, if the
CH now works there is likely to be a problem with the
room stat or wiring to it.
NO HOT WATER, BUT CENTRAL HEATING OK
If a cylinder stat is used, remove the cylinder stat wiring
from 7 and 9 on the terminal block ST8. Fit link across 7
and 9.
If the HW now functions, there is likely to be a problem
with the cylinder stat or wiring to the stat.
FOR ALL BOILERS WITH INTERNAL OR EXTERNAL
CONTROLS
Burner lights then goes out in DHW or CH mode
Does the boiler run normally with the front cover off and
then fail when the cover is put back on?
If yes there is likely to be a flue problem - either the air
inlet is blocked or the inner flue is leaking flue gases into
the air inlet.
BOILER NOISY OR GOING TO OVERHEAT
1. Was the system flushed?
2. Has the pump been bled and the dust cap released.
GENERAL CHECKS
1. Is all the air bled from the gas supply?
2. Is all the air bled from the primary water system?
3. Is there 230v ac across the boiler live and neutral
terminals?
(L & N on ST10)
4. Is the polarity correct?
5. Is the incoming gas pressure at least 18mbar with the
boiler at maximum output?

BOILER FUNCTION
6 720 645 222a (2012/05) 17
7.2 BOILER FUNCTION
Fig. 21 Boiler function
NO
YES
MAINS
POWER
SUPPLY
ON
BOILER
DEMAND
Fan to
start
speed.
Pump ON.
IGNITION
SEQUENCE
(see detail)
BLUE
LIGHT
ON
BURNER
LIT?
GREEN
FLAME
LIGHT
ON
Stop spark
and gas.
Wait
10 seconds
5th
attempt?
LOCKOUT
10 second
stabilisation
period.
Fan
modulation
to achieve
set
temperature
(40-82°C)
END OF
BOILER
DEMAND
Gas valve
OFF
Pump run 3
minutes
Fan run 30
seconds
Over temperature shut-
down if water tempera-
ture is 5°C above set
value.
Gas valve OFF.
Fan overrun
30 seconds
3 minute pump
over run
Spark
ignition and gas
4 seconds
NO
YES
Room
thermostat and/or
mains
programmer ON
(or link fitted at
ST10)
AND
Facia mounted
programmer (if
fitted) ON
AND
CH control knob
ON
IGNITION SEQUENCE
6720645222-25.1Wo
Diverter valve
CH position down
Cylinder position up

BOILER FUNCTION
6 720 645 222a (2012/05)
18
7.3 PROTECTION FUNCTION
Fig. 22 Protection function
Internal boiler
temperature
between
8°C & 5°C
Boiler automatic
frost function
(monitors internal boiler
primary temperature)
Internal boiler
temperature
below 5°C
Internal boiler
temperature
rises above 9°C
Pump runs
Pump switches off
after a 3 minute
overrun period
Internal boiler
temperature
rises above 12°C
Central heating
demand switches
off
Pump switches off
after a 3 minute
overrun period
Central heating
demand is activated
Pump runs for 3 minutes
to dissipate heat from
the boiler into the system
End of boiler demand
(central heating or
domestic hot water)
AUTOMATIC INTERNAL FROST FUNCTION
PUMP OVERRUN FUNCTION
A central heating demand
activated, pump runs
normally
Pump runs 5 seconds
every 24hrs from
last time pump ran
No central heating
demand after
a 24hr period
PUMP ANTISEIZE FUNCTION
6720643895-111.1Wo

BOILER FUNCTION
6 720 645 222a (2012/05) 19
NOTES

Worcester, Bosch Group
Cotswold Way, Warndon, Worcester WR4 9SW.
Tel. [phone]
Worcester, Bosch Group is a brand name of Bosch Thermotechnology Ltd.
worcester-bosch.co.uk
6 720 645 222a (2012/05)
WORCESTER, BOSCH GROUP:
TECHNICAL SUPPORT: 0844 892 3366
APPOINTMENTS: 0844 892 3000
SPARES: 01905 752571
LITERATURE: 0844 892 9800
TRAINING: 01905 752526
SALES: 01905 752640