Glowworm SwiftFlow 120 User guide

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221045A.05.97
Servicing Instructions
120
G.C. No. 47 313 13
One Contact Total Service
Hepworth Heating Ltd.,
Nottingham Road, Belper, Derbyshire. DE56 1JT
General/Sales enquiries:
Tel: [phone] Fax: [phone]
Fanned Flue Combination Boiler
This is a Cat I 2H appliance
Customer Services:
Tel: [phone]
Fax: [phone]
Tobeleftwiththeuser
4559

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An Aid to Servicing
To obtain a products of combustion reading, make sure
that the main burner is alight. Remove the plastic cap,
see diagram 1.4 and connect the analyser probe to the
tube, replace cap after use.
1.2 Data Label
The data label is positioned on the front of the inner case
cover, see diagram 1.3.
1 G e n e r a l
Diagram 1.1
Diagram 1.2
The instructions consist of three parts, Installation,
Servicing and Instructions for Use which includes the
Guarantee Registration Card. The instructions are an
integral part of the appliance and must, to comply with
the current issue of the Gas Safety (Installation and Use)
Regulations, be handed to the user on completion of the
installation.
CE Mark
This boiler meets the requirements of Statutory
Instrument, No. 3083 The Boiler (Efficiency)
Regulations, and therefore is deemed to meet the
requirements of Directive 92/42/EEC on the efficiency
requirements for new hot water boilers fired with liquid
or gaseous fuels.
Type test for purposes of Regulation 5 certified by:-
Notified body 0087.
Product/production certified:- Notified body 0087.
The CE mark on this appliance shows compliance with:-
1. Directive 90/396/EEC on the approximation of the
Laws of the Member States relating to appliances
burning gaseous fuels.
2. Directive 73/23/EEC on the harmonization of the
Laws of the Member States relating to electrical
equipment designed for use within certain voltage limits.
3. Directive 89/336/EEC on the approximation of the
Laws of the Member States relating to electromagnetic
compatibility.
1.1 Servicing or Replacing Parts
To ensure the continued efficient and safe operation of
the boiler it is recommended that it is checked and
serviced as necessary at regular intervals. The frequency
of servicing will depend upon the particular installation
conditions and usage, but in general once a year should
be enough.
The servicing of this boiler must be carried out by a
competent person in accordance with the rules in force in
the countries of destination.
Unless stated otherwise, parts removed or renewed
during servicing should be fitted in the reverse order
to removal.
After completing any servicing, or renewing of gas
carrying components, ALWAYS test for gas soundness
and carry out functional checks of controls.
Discard all used sealing washers, gaskets and “O” rings
when renewing components.
Use the new ones supplied with the replacement.
SLOT (CLOSED) DRAIN
POINT
HEATING
FLOW
SAFETY
VALVE
DISCHARGE SLOT (CLOSED)
COLD WATER
SUPPLY IN GAS SERVICE COCK HOT WATER OUT
HEATING
RETURN
2793
DOOR
PLASTIC PLUGS (2)
COVER PLATE
OUTER CASE
OUTER CASE SECURING
SCREW (2)
SELECTOR SWITCH
4578

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1 G e n e r a l
Diagram 1.3
Diagram 1.4
PLASTIC
CAP
DATA
LABEL
PILOT WINDOW
SCREW (2)
INNER
CASE
COVER
SECURING
SCREW (4)
4579
4580
1.3 Isolation of Boiler
Before commencing any servicing or the replacement of
parts, isolate the boiler from the electrical supply at the
external isolator and close the gas service cock, see
diagram 1.1.
BEFORE DRAINING THE BOILER, REFER TO
SECTION 1.6.
1.4 Outer Case Removal
The door opens to the left or right hand side. The door
catch is spring loaded, to open, push the side opposite to
the hinge then pull.
Remove the two screws securing the outer case then
unhook the case at the top and pull it forward and off,
see diagram 1.2.
1.5 Cover - Inner Case
Remove the cover of the inner case, secured by four
screws, see diagram 1.3.
1.6 System Pressures and Draining
WARNING. All parts containing water of the central
heating circuit within the boiler, are under the system
pressure. Before any parts of this circuit are
disconnected, reduce the system pressure at the external
draining tap. Turn the central heating isolating valves
off and drain at the drain points on the appropriate
valves, see diagram 1.1.
All water containing parts of the domestic hot water
circuit of the boiler will be under the supply water
pressure. Before any parts of this circuit are
disconnected, turn the domestic cold water isolating
valve off, open the hot water taps to reduce the water
pressure in the boiler, close the hot water isolating valve
and drain the boiler at the valves, see diagram 1.1.
After replacing any water containing part of the central
heating circuit, make up the water loss, vent all air and
pressurise the system. Refer to “Commissioning” in the
Installation Instructions.
Check for water soundness.

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2 S e r v i c i n g
Diagram 2.2
SPARK GAP
4.5mm to 5.5mm
Diagram 2.1
FAN OUTLET
SEAL PLUG
STEP 1
Slacken do
not remove
2.1 Pilot Check
Check that the pilot flame is burning correctly and of the
correct size, see diagram 2.1. If the pilot flame is not
correct, the pilot injector will require removing, as
detailed later.
2.2 Isolation and Access
Before starting, refer to Section 1.1.
Isolate the boiler from the electrical supply and close the
gas service cock, refer to Section 1.3.
Remove the outer case and the inner case cover, refer to
Sections 1.4 and 1.5.
Disconnect the electrical plug connector and air pressure
tube from the fan, see diagram 2.2.
Follow steps 1 to 4 on diagram 2.2 to remove the
hooks bolts.
Step 1 - Slacken the two thumb screws securing the
collector but do not remove.
Step 2 - Unhook the hook bolts.
Step 3 - Turn the hook bolts.
Step 4 - Remove the hook bolts.
Remove the fan securing screws.
Pull the fan forwards, at the bottom and rotate to
disengage the fan outlet to flue elbow and rear bracket.
Take care not to damage the seal.
Tilt the fan and withdraw.
Remove the flue collector, note, this may be a tight fit.
Remove the combustion chamber front panel, secured
with four screws, see diagram 2.3.
Slacken, but do not remove the gland seal
securing screw.
Should the pilot burner assembly require servicing, it
will be necessary to disconnect the pilot and
thermocouple nut as this stage, see diagram 2.4.
Remove the pilot burner assembly securing screws
and washers.
When removing the pilot burner assembly, note the pilot
injector is loose and that the electrode and lead are
connected and must not be used to hang the assembly by,
see diagram 2.4.
Remove the main burner from the main injector at the
rear. Raise the burner up and forward, easing the pilot
assembly forward and clear, taking care not to damage
the combustion chamber insulation or pilot burner
assembly, see diagram 2.5.
FLAME
LENGTH
25mm
THUMB
SCREW (2)
FAN
SECURING
SCREWS
AIR
PRESSURE
TUBE
STEP 3
STEP 2
STEP 4
FLUE
COLLECTOR
4574
4581

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2 S e r v i c i n g
Diagram 2.4
Diagram 2.3
SECURING
SCREW (4)
COMBUSTION
CHAMBER FRONT PANEL
SPARK
ELECTRODE
SEALING GLAND
SECURING SCREW
IGNITION
LEAD
PILOT INJECTOR
SPARK
ELECTRODE
RETAINING CLIP
THERMO-
COUPLE
NUT
PILOT TUBE
NUT
WING NUT
SECURING
SCREW AND
WASHER (2)
2.3 Heat Exchanger
Place a sheet of paper or similar in the combustion
chamber, to act as a collector for deposits removed.
Brush the heat exchanger with a suitable brush, remove
paper together with any debris.
2.4 Main Injector
Inspect the injector and clean as necessary.
Do not use wire or a sharp instrument on the hole.
2.5 Main Burner
Use a vacuum cleaner or suitable brush to clean the
burner thoroughly, making sure that all burner ports are
clear and free from obstructions.
Do not use a brush with metallic bristles.
2.6 Service Checks
Before replacing any parts removed during servicing,
inspect the condition of all seals and joints, renewing
them as necessary.
Check the condition of the combustion
chamber insulation.
Check that the spark gap is as shown in diagram 2.1.
2.7 Note. Reassembly
Make sure that the main burner baffle has located in the
side guides and that the burner is located on the
main injector.
Refit the hook bolts.
The combustion chamber front panel should be fitted
loosely, then the flue collector also fitted loosely, make
sure that it is seated onto the heat exchanger and over the
top edge of the front panel.
To fit the fan, locate it into the rear bracket and ease the
flue elbow onto the fan outlet, making sure that the fan
outlet seal is correctly positioned. Secure with the two
screws, see diagram 2.2.
Refit electrical connector making sure that the red spots
are aligned.
Secure the flue collector and combustion chamber front
panel by tightening the thumb screws and securing
screws, see diagram 2.2 and 2.3.
2.8 Operational Checks
Light the boiler, carry out operational checks and any
necessary adjustments as described in “Commissioning”
in the Installation Instructions.
HEAT
EXCHANGER
4582
4583

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2 S e r v i c i n g
Diagram 2.5
STEP 1 STEP 3
STEP 2 STEP 4
SECURING
SCREW
WING NUT
BURNER
BRACKET
WING NUT
BURNER
BRACKET
BURNER
GUIDE
BURNER
SIDE
GUIDES MAIN INJECTOR
BURNER
4586
45844585
4587

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3 F a u l t F i n d i n g
Diagram 3.1
3.1 Initial Checks
If the boiler fails to operate, first check the following:
1. That the electrical supply is available at the boiler and
the fuses are in order.
NOTE: THE BOILER CONTROL BOARDS CAN BE
DAMAGED BY INCORRECT TESTING WITH THE
POWER ON.
2. Make sure that the system pressure gauge registers
0.7bar, minimum and that the automatic air vent works.
Refer to Installation Instructions, Section 11.2.
3. That the gas supply is available at the boiler and
purged of air.
4. Is the pilot burner lit? - If the pilot burner will not
light refer to Section 3.2. If the pilot burner fails to
remain alight, refer to Section 3.3
5. That the boiler is set for the required service.
6. With the boiler central heating selector switched
“Off”, see diagram 3.2 check that the domestic water
supply is available and water flows freely from the hot
taps. Close the taps.
7. With the boiler central heating selector switched
“ON”, see diagram 3.2, check that all heating system
controls, if fitted, are working correctly and calling for
heat. If not isolate the boiler from the electrical supply.
Disconnect the rear multi-pole connector at the base of
the boiler and release the cable from the clamp.
Remove the connector cover and dependent on the type
of control fitted test for continuity, mains or low voltage
at terminals 1 and 2, see diagram 3.1.
If this is satisfactory continue with the detailed
fault finding.
Diagram 3.2
Orange Light
‘MAINS’
Green Light
‘RUNNING’
SWITCH
(OFF)
C.Htg.
SELECTOR
SWITCH
Red Light
LOW C.Htg.
WATER
PRESSURE
SWITCH
(ON)
GAS CONTROL KNOB
PIEZO BUTTON
PRESSURE
GAUGE
CABLE
CLAMP/COVER
SCREW (2)
MAINS
CABLE
LNE2
3
1CABLE
CLAMP
2883
CABLE TO
REMOTE
HEATING
CONTROLS
CLOCK/TIMER
(IF FITTED)

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3 F a u l t F i n d i n g
Check gas line - open all cocks,
rectify any blockages, purge out
any air. Does pilot light?
Apply match to pilot burner instead
of pressing piezo unit button.
Does pilot light?
Undo tubing nut at pilot burner.
Press multifunctional control knob.
Does gas flow freely?
Does pilot stay alight when
multi-functional control knob
is released?
Does pilot flame
envelope thermocouple?
Check aeration. If necessary -
clean pilot, rectify blockage in pilot
injector, or replace.
Check thermocouple circuit using
thermocouple and boiler overheat
cut-off fault finding.
On pressing piezo unit button is
there a spark across electrode gap?
Undo tubing nut at pilot outlet of
mulitfunctional control.
Press multifunctional control knob.
Does gas flow freely?
Rectify blockage in pilot injector,
or renew pilot injector.
Change blocked pilot tube.
Change multifunctional control.
Check electrode gap. Reposition,
or replace electrode as necessary.
Change
piezo unit.
PILOT SATISFACTORY
PILOT WILL NOT LIGHT
START HERE
NO
NO
NO
NO
NO
NO
YES
YES
YES
YES
NO YES
NO
NO
NO
NO
YES
YES
YES
YES
Diagram 3.3
Remove electrode from pilot bracket.
Hold tip close to pilot burner and
operate piezo unit.
Is there a spark across gap?
Pull ignition lead off piezo unit.
Using blade of an insulated screw-
driver, touch unit chassis and leave
approx. 4mm gap from connection
tag on piezo unit. Operate piezo.
Is there a spark across gap?
Change electrode
assembly.

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3 F a u l t F i n d i n g
Diagram 3.5
CONNECTION
'D'
MULTIFUNCTIONAL
CONTROL
BOILER
OVERHEAT CUTOFF
CONNECTION 'E'
CONNECTION
'C'
CONNECTION
'B'
CONNECTION
'A'
With the boiler cold, check connections of the thermocouple, boiler overheat cut-off and multifunctional
control. Disconnect overheat cutoff connectors at points A and B at the multifunctional control,
see diagram 3.5. Test continuity of the overheat cutoff. Is there continuity?
Re-connect boiler overheat cutoff to points
A and B. Disconnect thermocouple at point
D of the mulitfunctional control. Test continuity
between point C and the body of the multi-
functional control. Is there continuity?
Test continuity of thermocouple between inner
connection point D and point E.
Is there continuity?
Thermocouple and boiler overheat
circuit satisfactory.
Faulty cutoff connectors into
multifunctional control, either at A or
C. Renew where faulty.
Faulty boiler overheat cutoff, renew.
Faulty thermocouple, renew.
YES
YES
NO
NO
NO
YES
Diagram 3.4
3.2 Pilot Burner and Ignition System
Symptom: The pilot burner will not light or stay alight.
Test the pilot burner and ignition system as shown in
diagram 3.3.
3.3 Thermocouple and Overheat Cutoff
Symptom: The pilot burner fails to stay alight.
On completion of initial checks, as Section 3.1.
Test the thermocouple, overheat cutoff and thermocouple
connectors, as described in Fault Finding diagram 3.4
and shown in diagram 3.5.
Check the millivoltage of the thermocouple closed
circuit at points “A” and “E”, this should be within the
range of 6 to 11mV, see diagram 3.5.
4588

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(N)
br
b
LN
(L)
PERMANENT
LIVE
240V~50Hz
OPTIONAL
SWITCHED LIVE
FROM ROOM
STAT. 240V~50Hz
b
br
PUMP
TRANSFORMER
b
br
240V~
LOW
VOLT.
26V~
CONTROL BOARD
2A
FUSE 1
3 3
2
2
2
2
M
COMMON
ON
(N)
(L)
CLOCK/TIMER
br
b
p
br
p
4
3 F a u l t F i n d i n g
Diagram 3.6
CONTROL BOARD
TERMINALS, CN 3
CONTROL BOARD
TERMINALS, CN 4
CONTROL BOARD
TERMINALS, CN 2
3
2
KEY
br........................BROWN
b.........................BLUE
p.........................PURPLE
4
3.4 Clock/Timer - if fitted
If the clock has failed it can be bypassed by
disconnecting the plug at the wall frame.
Disconnect the plug at the control box and connect this
plug to the connection at the wall frame.
This is a temporary measure and the clock should be
repaired or replaced as soon as possible.
3.5 Electrical
Preliminary electrical system checks, as outlined in a
Multimeter Instruction book, are the first checks to be
carried out during a fault finding procedure.
Isolate the boiler from the electrical supply, refer to
Section 1.3.
Gain access to the boiler controls by removing the outer
case, refer to Section 1.4. Check that all cables and
connectors are secure.
Gain access to the control board, refer to Section 4.13.
Check all cables at the multi-pin connectors on
the board.
Test the two fuses on the main control board and renew
as necessary, the fuse are, type 2AT and type 3.15AT.
If a fuse fails repeatedly or the initial fault finding
checks described in Section 3.1 indicate a boiler fault,
check the boiler electrical circuits and follow the fault
finding procedures, see diagram 3.5, 3.6, 3.7 and 3.8
and for clock/timer fault diagram 3.9.
On completion of a fault finding task that has required
the disconnection and making of electrical connections
then checks, for earth continuity, polarity and resistance
to earth must be carried out.
0192M

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3 F a u l t F i n d i n g
0195M
or
or
br
br
w
w
r
r
r
bk
LN
r
p
p
bk
p
p
y
gry
p
y
or
v
r
gry
6
2 2 2 2 2 2 2 2 1
1
1
1
1
2
5
4
1
p
p
gry
p
or
y
p g y b gry w r Screen
6
6
6
5
4
4
4
4
4
4
4
4
4
4
7
7
7
7
7
1
1
1
1
1
1
5
5
5
MAIN MULTIFUNCTIONAL CONTROL SOLENOID
DHW CUT OFF
CONTROL
WATER PRESSURE
SWITCH
(SHOWN IN
PRESSURISED
STATE)
240V~
26V~
TRANS-
FORMER
TO REMOTE
HEATING
CONTROL 5 WAY PLUG/SOCKET
DHW
FLOW
SWITCH SELECTOR
SWITCH
CH
THERMISTOR
DHW
THERMISTOR
USER
CONTROL
BOARD
AIR PRESSURE
SWITCH
FAN DRIVER
P.C.B.
D.C.
FAN
N/C
N/O
C
N/CN/O
C
KEY
br
bk
b
g
gry
or
p
r
v
w
y
- Brown
- Black
- Blue
- Green
- Grey
- Orange
- Purple
- Red
- Violet
- White
- Yellow
CN 1
CN 4
CN 1
CN 2
CN 5
CN 6
CN 7
CONTROL
BOARD
MAIN PCB FAN DRIVER PCB
Diagram 3.7

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3 F a u l t F i n d i n g
Diagram 3.8
Remove the outer case, control housing and it's cover.
Check all connections on the control board and the boiler components, rectify or renew as necessary.
Two dummy two way connectors are provided for ease of testing continuity.
Remove fuses and test for continuity, if faulty, check cables and connections for shorting to E or N, rectify if
necessary and replace fuse, with spare provided.
Check central heating water pressure, repressurize if necessary.
Make sure boiler is cold. Check all pipes and connections between the Air Pressure Switch (APS) fan and
combustion sample point, also between fan and gas/air ratio unit. Make sure sample point cap is fitted correctly.
Make sure the pilot is alight. Make sure venturi is not blocked.
Carry out the initial fault finding checks described in Section 3.1.
Check that gas, water and electricity are available at the boiler.
Before commencing tests isolate the boiler, make sure that the remote controls are not calling for duty and there
is no domestic hot water demand.
Replace CN6.
With no demand to the boiler.
Restore power.
Does the mains Orange LED
come on?
Does the boiler light? Isolate supply, is there
continuity at flow switch?
YES
YES
Is there 240V ac at
Blue and Brown on CN3.
NO
Check electricity
supply.
Faulty LED.
Does not effect
boiler operation.
YES
NO
Isolate supply
remove CN6 is
there continuity
between
Red and Violet?
Faulty APS.
Replace.
NO
YES Does fan run at full
speed for approx
30 seconds?
YES
Isolate supply. Is the
resistance at CN2 on the
fan driver pcb between
White and Grey, Grey
and Purple, Purple and
White approx 2.5Ω?
YES
Faulty fan.
Replace.
YES
Faulty fan driver
pcb. Replace.
NO
continued
(a)
Is there continuity at CN2
on the fan driver pcb
between White and the
fan motor laminations?
(repeat with Grey and
Purple)
Faulty fan.
Replace.
NO
Faulty main PCB.
Replace.
NO
Faulty transformer.
Replace.
NO
Faulty main PCB.
Replace.
NO
NO
Faulty flow switch.
Replace.
YES
YES
Is there 26V ac on
Orange and Yellow at
CN7 and greater than 3V
dc on Grey and Purple?
Isolate supply.
Restore supply.
During the 30 second is
there approx 26V ac on
Black and Red from the
transformer at CN1?
YES
NO

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3 F a u l t F i n d i n g
Diagram 3.8 cont.
After about 30 seconds from
“switch on” does fan go to low
speed?
Isolate supply disconnect central heating thermistor,
is resistance of thermistor between 8KΩand 11KΩ?
YES
NO
continued
(a) continued (b)
(a)
YES NO YES
Isolate supply. Restore
supply with no demand.
Is there 24Vac between
grey wire on CN6 and Pin 2
on CN1 for about 30
seconds.
Faulty APS.
Replace.
NO
YES
Isolate supply.
Reconnect CN6,
restore power supply.
YES
Faulty main PCB.
Replace.
NO
YES
YES
NO
Open DHW tap at full
rate. Does burner
pressure go to 13.1mb?
YES
Is the burner
pressure between
0.1 and 13.1 mb ?
Faulty main PCB.
Replace.
Faulty thermistor.
Replace.
During the 30
second period is
there 240V at pump.
NO
Faulty pump.
Replace.
YES
Faulty main PCB.
Replace.
Check venturi air
signal at test point
Is this approx 2.5mb
YES
NO
NO
Faulty gas/air ratio
unit. Replace.
Faulty fan.
Replace.
continued
(c)
Does green
demand light
come on?
NO
YES NO
YES
Does pump run for
about 30 seconds?
After about 30 seconds
does pump go off?

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3 F a u l t F i n d i n g
Diagram 3.8 cont.
Isolate supply disconnect Red in line connectors to
flow switch, is there continuity across flow switch?
Faulty LED.
Does not
effect boiler
operation.
Faulty DHW thermistor.
Replace.
Reconnect flow switch,
disconnect Purple in line
connectors to DHW thermistor.
Is the resistance between
8KΩand 11KΩ?
Faulty flow switch.
Replace.
NOYES
Turn the DHW flow off.
Turn on the CH.
Does pump run?
Faulty main PCB.
Replace.
YES
Faulty DHW O/H stat.
Replace.
Is there continuity across
C and N/O at low water
pressure switch?
Faulty main PCB.
Replace. Faulty water pressure switch.
Replace.
Isolate supply, remove
CN1. Is there continuity
across DHW O/H stat?
(a) (b) (c)
YES
YES
YES
YES
YES
NO
NO
YES NO
NO
NO
NO
YES
SYSTEM O.K.
YES
NO
Faulty
multifunctional
control.
Restore supply.
Is there about 24V
ac multifunctional
control?
Is burner pressure
about 5.6mb?

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15 221045A
3 F a u l t F i n d i n g
If a mains potential room thermostat is connected, ensure that the switch live is connected to PIN 1 in the
5 pole connector.
Check continuity of clock/timer harness, ensure an electrical supply is available, ensure that remote
controls are calling for heat.
Disconnect and insulate the purple cables
from heating common and heating on.
Switch on electrical supply, is there a display
on clock/timer?
Advance clock/timer until a demand is indicated
Is there now continuity between heating
common and heating on?
Faulty clock/timer.
Replace.
Faulty clock/timer.
Replace.
NO
NO
YES
YES
Clock/timer in order if no central heating,
refer to main fault finding.
YES
Isolate the boiler from electrical supply, remove outer case.
YES
Diagram 3.9
DIGITAL CLOCK/TIMER STYLE 1 and 2 FAULT FINDING
ELECTRO/MECHANICAL CLOCK/TIMER FAULT FINDING Diagram 3.9
5667
Does clock keep time
Set clock to off period. Is there continuity
across common and heating on
Clock in order if no
central heating refer to
main fault finding
Isolate electrical supply set clock to on period
Is there continuity across
common and heating on
Faulty clock
replace
No
No
No
Yes
Yes Yes
CLOCK FAULT FINDING
If a mains potential room thermostat is connected, make sure that the switch line is connected to pin 1 in
the 5 pole connector.
Check continuity of clock harness, make sure an electrical supply is available make sure that remote
controls are calling for heat.
Make sure the override switch if fitted is in the " " position

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4 R e p l a c e m e n t o f P a r t s
Diagram 4.1
Before replacing any part please read points below:-
Replacement of parts must only be carried out by a
competent person.
Unless stated otherwise all parts are refitted in the
reverse order to removal.
1. Refer to Section 1.1.
2. Always isolate the boiler from the electrical and as
required the gas supply as Section 1.3.
3. Unless stated otherwise, gain access as appropriate
parts of Sections 1.4 and 1.5.
4. On completion, make good any water loss and
pressurise the system to initial design pressure, refer to
“Commissioning” in the Installation Instructions.
If the red light “flashes”, momentarily interrupt the
electrical supply.
4.1 Fan
Refer to the appropriate parts of Section 2.2.
After fan has been fitted, check the burner pressure and
if necessary adjust.
4.2 Main Burner
Refer to the appropriate parts of Section 2.2.
Note. There is no need to remove the fan or flue
collector assemblies.
4.3 Main Injector
Refer to the appropriate parts of Section 2.2.
Note. There is no need to remove the fan or the flue
collector assemblies.
4.4 Pilot Burner/Injector
Refer to the appropriate parts of Section 2.2
Note. There is no need to remove the fan or flue
collector assemblies.
4.5 Spark Electrode/Ignition Lead
Refer to the appropriate parts of Section 2.2.
Note. There is no need to remove the fan or flue
collector assemblies.
Remove the controls housing assembly and support, see
diagram 4.1.
If this is not possible place on a surface, making sure that
the control knob is protected.
Remove the spark electrode/ignition lead from the pilot
burner assembly, see diagram 2.4.
Disconnect the ignition lead from the piezo unit, refer to
Section 4.11.
CONTROL
HOUSING
SECURING
SCREW (2)
SUPPORT
BRACKET
CLOCK/TIMER
(if fitted)
FAN DRIVER
CONTROL
HOUSING)
BOTTOM CONTROL
HOUSING COVER
TOP CONTROL
HOUSING COVER
CLOCK/TIMER
(if fitted)
SCREW(2)
4589

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Diagram 4.3
Diagram 4.4
Diagram 4.2
SECURING
SCREW (2)
THERMOCOUPLE NUT
4.6 Thermocouple
Remove the sealing gland, secured with a single screw,
see diagram 2.4.
Remove the spark electrode/lead, see diagram 2.4.
Disconnect the thermocouple at both ends, see diagram
2.4 and 4.2.
Remove the thermocouple.
Do not tighten the thermocouple nut more than a quarter
turn beyond finger tight or make any sharp bends in the
capillary.
4.7 Boiler Overheat Cutoff
Remove the control housing as the appropriate part of
Section 4.1.
Remove piezo unit bracket, disconnect lead, see
diagram 4.3.
Disconnect the boiler overheat cutoff electrical
connectors from the multifunctional control, see
diagram 4.2.
Remove the boiler overheat cutoff, secured with two
screws, see diagram 4.2.
Use the heat sink compound supplied, between the
mounting plate and the cutoff, when fitting it.
4.8 Water Pressure Switch
Release the water pressure and drain the central heating
circuit of the boiler, refer to Section 1.3 and 1.6.
Disconnect the electrical connectors at the water pressure
microswitch, see diagram 4.4.
Remove pressure switch.
Replace the “O” ring seal with the new seal provided.
Make sure that the switch terminals are facing diagonally
forwards to give access, as shown in diagram 4.4.
Reconnect the electrical connections, refer to
diagram 4.11.
PIEZO
UNIT
SELECTOR SWITCH
SECURING
SCREW (2)
IGNITION
LEAD
PIEZO UNIT
BRACKET
WATER
PRESSURE
SWITCH
4 R e p l a c e m e n t o f P a r t s
ELECTRICAL
CONNECTORS
OVERHEAT
CUTOFF
CONNECTORS
4591
2848
4592

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18221045A
4 R e p l a c e m e n t o f P a r t s
Diagram 4.5
Diagram 4.6
4.9 Pump
Release the water pressure and drain the central heating
circuit of the boiler, refer to Section 1.3 and 1.6.
Disconnect the electrical connectors at the water pressure
microswitch. Remove the water pressure switch, refer to
Section 4.8.
Remove the terminal cover from the pump and
disconnect the cable, see diagram 4.5.
Disconnect the pump at the unions.
Discard the sealing washers.
Make sure that the flow direction arrow is pointing
upward when fitting and use the new sealing washers.
Refit water pressure switch, refer to Section 4.8.
The flow adjuster on the new pump should be set to that
of the original, refer also to Section 4.6 in the
Installation Instructions.
The flow rate should be controlled by means of a valve
in the heating flow, refer to Section 11.10 in the
Installation Instructions.
Note: Should the pump fail to operate, refer to diagram
3.8. If all is in order, but the pump still does not operate,
remove the end screw, see diagram 4.5, then turn the
pump spindle to release any temporary seizure.
DO NOT HIT THE SPINDLE.
4.10 Domestic Hot Water High Limit Control
Remove the pump, see Section 4.9.
Disconnect the electrical connectors at the domestic hot
water high limit control, see diagram 4.6.
Remove the high limit control from the flow pipe,
secured with two screws.
Use the heat sink compound supplied, between the
mounting plate and the control.
When refitting the electrical connections to the high limit
control the polarity is not important, see diagram 4.11.
4.11 Piezo Unit
Remove the piezo unit bracket, see diagram 4.3.
Disconnect the ignition lead at the piezo unit.
Remove the piezo unit from the bracket.
LOWER
PUMP
UNION
END
SCREW
PUMP
SPINDLE
PUMP
ADJUSTER
TERMINAL COVER
SCREW
UPPER
PUMP
UNION
FLOW DIRECTION
ARROW
D.H.W. HIGH LIMIT CONTROL
ELECTRICAL
CONNECTORS
D.H.W.
HIGH
LIMIT
CONTROL
SECURING
SCREW (2)
4593
4594

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4 R e p l a c e m e n t o f P a r t s
Diagram 4.7
Diagram 4.8
4.12 Pressure Gauge
Remove the control housing assembly, see diagram 4.1.
Release the water pressure and drain the central heating
circuit of the boiler, refer to Section 1.3 and 1.6.
Remove the pressure gauge bracket.
Disconnect the pressure gauge connection from the
safety valve, discard the washer, see diagram 4.7.
Remove the pressure gauge secured with the
retaining tabs.
Locate the supplied new washer under the pressure
gauge connection when refitting the safety valve.
4.13 Control Boards
CAUTION. Great care must be taken when handling
any control board.
THE MAIN CONTROL BOARD MUST BE KEPT IN
THE ANTI STATIC HOLDER UNTIL NEEDED.
Note. Timer/clock may be removed to improve access,
see Section 4.32 or the control housing bottom half can
be removed.
Main Control Board
Remove control housing cover securing screw, see
diagram 4.8.
Remove the control housing assembly as shown in
diagram 4.1.
Lift the control housing cover to gain access to
the board.
Disconnect all multipin connectors, see diagram 4.8.
Remove the control board from the support posts.
To reconnect the multipin connectors correctly, see
diagram 4.11.
When replacing the main control board check and if
necessary adjust the main burner gas pressure in both the
domestic hot water and central heating modes. Refer to
“Commissioning” in the Installation Instructions.
Fan Driver Board
Remove the fan driver control housing assembly
securing screws.
Remove the multipin connectors, see diagram 4.9.
Release the board from its support posts then remove the
nut and screw securing the board to the cover, see
diagram 4.9.
User Control Board
Remove the fascia, see diagram 4.8.
Remove the multipin connector.
Remove the control board from the supports posts.
PRESSURE
GAUGE
CONNECTION
SAFETY
VALVE
SEALING
WASHER
SECURING
SCREW (2)
PRESSURE GAUGE
PRESSURE
GAUGE
BRACKET
FASCIA
HINGE PIN
CONTROL
HOUSING
COVER
SUPPORT POSTS
MULTI-PIN
CONNECTORS
USER CONTROL
BOARD
FASCIA
SECURING
SCREW (3)
TEMPERATURE
CONTROL KNOB
CONTROL
HOUSING
COVER
SECURING
SCREW
CONTROL
HOUSING
SECURING
SCREW (2)
TRANSFORMER
2831
4595

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p
4 R e p l a c e m e n t o f P a r t s
Diagram 4.9
Diagram 4.10
4.14 Transformer
Note. Timer/clock may be removed to improve access,
see Section 4.32 or the control housing bottom half can
be removed.
Remove the control housing cover screw, see
diagram 4.8.
Remove control housing assembly, see diagram 4.1.
Remove the control housing cover and disconnect the
electrical connectors from the transformer, see
diagram 4.8.
Remove the transformer securing screws (2 off) from
beneath the control housing, remove the transformer and
insulation.
To connect the transformer cables correctly, refer to
diagram 4.11.
FAN DRIVER
BOARD FAN DRIVER CONTROL
HOUSING
SECURING
SCREW NUT
SUPPORT
POSTS MULTI-PIN
CONNECTORS
4596
CLOCK/
TIMER
HEATING ON
240V~50Hz PERMANENT
MAINS SUPPLIED
FUSED AT 3A
b
br
p
r
g/y
b
br
p
b
br
pb
(N)
(L)
COMMON
KEY
PURPLE
RED
BLUE
BROWN
GREEN/YELLOW
p
r
b
br
g/y
br
g/y
r
4774