VOKERA Option User guide

1
INTRODUCTION
Fig.1 General Layout
1 Flue Analysis Test Point
2 Pressure Tube Negative
3 Fan Assembly
4 Heat Exchanger
5 econdary thermistor
6 Combustion chamber
7 Burner
8 Expansion vessel
9 Water pressure switch
10 Domestic Hot Water Flow witch
11 Gas Valve
12 Mode selector switch
13 Fault indicator led
14 Timeclock
15 Low pressure indicator led
16 Pressure gauge
17 afety valve
18 Pump
19 Auto air vent
20 Electrode
21 High limit thermistor
22 Primary thermistor
23 Air chamber (with cover removed)
24 Air pressure switch
25 Auto by pass (fig. 2)
26 Water flow restrictor (fig. 2)
The Vokèra Option is a combined central heating and
domestic hot water appliance. By design, it incorpo-
rates full sequence electronic ignition, circulating pump,
expansion vessel, safety valve, pressure gauge, and
mechanical timeclock.
The appliance is produced as a room sealed boiler,
suitable for wall mounted applications only. It is pro-
vided with a fan powered flue outlet with an annular co-
axial combustion air intake located on the top rear of the
appliance.
The appliance has been designed for use with a sealed
heating system, consequently it is not intended for use
with an open vented system.
The appliance can be used in conjunction with an ‘Y’ or
‘S’ Plan system when stored hot water via an in-direct
cylinder is required.
An automatic range-rating facility is incorporated in the
boiler,whichautomaticallyadjustsboileroutputtomatch
the current demand.
Domestic hot water is provided directly, via the bi-
thermic heat exchanger
Fig. 1
12
1314
15
2
3
4
5
6
7
8
9
1
10
11
16
17
18
19
20
21
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2
SECTION 1 DESIGN PRINCIPLES AND OPERATING SEQUENCE
Fig. 2
1.1 PRINCIPLE COMPONENTS
●A fully integrated, electronic control board
featuringmodeselectionswitch,fullsequence-
electronic ignition, temperature control sys-
tem, and appliance status indicator.
●A BI-thermal gas to water heat exchanger.
●A multi-functional gas valve.
●Two-stage, primary water pressure switch.
Integral pump, expansion vessel, pressure
relief valve, pressure gauge, domestic water
flowswitch,fan,differentialairpressureswitch,
and time clock.
MODES OF OPERATION
1.2 CENTRAL HEATING MODE
When there is a request for central heating via
the time-clock and/or any external controls, the
pump and fan are started, the fan proves the
differential air pressure switch which in-turn,
allows an ignition sequence to begin.
Ignition is sensed by the electronic circuitry to
ensure flame stability at the burner. Once suc-
cessful ignition has been achieved the appli-
ance operates al 75% of maximum for a fifteen-
minute period, and thereafter the appliance
operates on maximum output until the desired
temperature setting is reached.
Once the desired temperature is reached, the
burner will modulate to maintain that tempera-
ture, however should the temperature within the
appliance continue to rise, the burner will shut
down and the boiler will perform a three-minute
anti-cycle (timer delay).
1.3 HOT WATER MODE
When there is a demand for domestic hot water
the domestic hot water flow switch is proved by
the flow of water through the appliance, this
allows the fan to run, the fan proves the differen-
tial air pressure switch which in-turn, allows an
ignition sequence to begin.
Ignition is sensed by the electronic circuitry to
ensure flame stability at the burner. Once
successfulignition has been achieved the appli-
ancewillmodulateburner gas pressure to main-
tain the desired water temperature, should the
temperature of the domestic hot water exceed
the temperature setting by 5ºC the burner will
shut down until the water temperature drops
below the required setting.
1.4 SAFETY DEVICES
In both central heating and domestic hot water
modes, safe operation is ensured by.
●A water pressure switch that monitors the
system pressure and will deactivate the pump
and prevent burner ignition should the pres-
sure or primary flow rate fall below the rated
tolerance.
●Differential air pressure switch that checks
thecorrectoperationofthefan andfluethereby
preventing or interrupting burner operation.
●A high limit thermostat that overrides the
control circuit to prevent or interrupt burner
ignition.
●A safety valve which releases excess pres-
sure from the primary circuit.
1.5 FROST PROTECTION
The appliance has built-in frost protection that
allows the pump to operate if the appliance
temperature drops to 7ºC, should the tempera-
turecontinue to drop theburner will lightuntil the
primary circuit temperature exceeds 30ºC
Fig. 2
return flow hw
outlet cold inlet
26
5
9
10
25
18
8
22
4
19
17

3
SECTION 2 TECHNICAL DATA
Ref. Condition 15 °C , 1013,25 mbar, dry gas
NOTE: L.P.G. data refer to section 10
2.1 Central heating
Heat input 28.86 kW 98,464 BTU
Heat output (max) 23.65 80,006 BTU
Heat output (min) 9,3 kW 31,700 BTU
Maximum working pressure 3.0 bar
Minimum flow rate 350 l/h
Max temperature 90 °C
Minimum working pressure 0,5 bar
2.2 Domestic hot water
Heat input 28.86 kW 98,464 BTU
Heat output (max) 23.65 80,006 BTU
Heat output (min) 8.1 kW 27,600 BTU
Flow rate (35°C) rise) 9.7 l/min
Maximum inlet pressure 6.0 bar
Minimum inlet pressure to operate 0.15 bar
Minimum flow rate to operate 2 l/min.
2.3 Gas pressure Maximum
Inlet pressure (G20) 20.0 mbar
Max burner pressure 9.8 mbar
Gross rate 2.75 m3/h
Injectors 1.35 mm x 12
2.4 Expansion vessel
Capacity 8 litres
Max system volume 76 litres
Pre-charge pressure 0.8 bar
2.5 Dimensions
Height 750mm
Width 400mm
Depth 328mm
Dry weight 33 kg
2.6 Clearances Rear flue outlet Top flue outlet
Left hand side 50 mm 50 mm
Right hand side 12 mm 12 mm
Top 150 mm 180 mm
Bottom 150 mm 150 mm
Front 600 mm 600 mm
2.7 Connections
Flow & return 22 mm compression
Hot & cold water 15 mm compression
Gas 15 mm compression
Safety valve 15 mm compression
2.8 Electrical
Voltage 230V/~ 50hz
Power consumption 125 W
Internal fuse 2 A
External fuse 3 A
Appliance type C12
Maximum flue length 1 m
Category II2H3P
NOx class 3

4
2.10 PUMP DUTY
Fig. 3 shows the flow rate available – after
allowing for pressure loss through the appliance
– against system pressure loss. When using this
graph apply only the pressure loss of the sys-
tem. The graph is based on a 20ºC temperature
differential.
Fig. 3
Fig. 4
Water pressure (mbar)
Litres Per Hour (x100)
0
100
200
300
400
500
600
12345678910111213
Terminal osition for fan assisted boiler
(minimum distance) mm
A - Directly below an open window or other 300
opening (e.g. air brick)
B - Below gutters, soil pipes or drain pipes 25
C - Below eaves 25
D - Below balconies or car port roof 25
E - From vertical drain pipes and soil pipes 75
F - From internal or external corners 25
G - Above ground or below balcony level 300
H - From a surface facing a terminal 600
I - From a terminal facing a terminal 1200
J - From an opening in the car port (e.g. door
window) into dwelling. 1200
K - Vertically from a terminal on the same wall 1500
L - Horizontally from a terminal on the same wall 300
M - Horizontally from a vertical terminal to a wall 300
N – Horizontally from an o ening, airbrick, o enable
window, etc. 300
NOTE: The flue must be terminated in a place not likely
to cause a nuisance.

5
SECTION 3 GENERAL REQUIREMENTS
BS 5440 PART 1 FLUES
BS 5440 PART 2 FLUES AND VENTILATION
BS 5449 PART 1 FORCED CIRCULATION HOT WATER SYSTEMS
BS5546 INSTALLATION OF GAS HOT WATER SUPPLIES FOR DOMESTIC
PURPOSES (2ND FAMILY GASES)
BS 6798 BOILERS OF RATED INPUT NOT EXCEEDING 60kW
BS 6891 LOW PRESSURE INSTALLATION PIPES
BS 7074 PART 1 APPLICATION, SELECTION, AND INSTALLATION OF EXPANSION
VESSELS AND ANCILLARY EQUIPMENT FOR SEALED WATER SYSTEMS
This appliance must be installed by a competent
person in accordance with the Gas Safety (Installa-
tion And Use) Regulations.
3.1 RELATED DOCUMENTS
The installation of this boiler must be in accord-
ance with the relevant requirements of the Gas
Safety (Installation and Use) Regulations, the
Local Building Regulations, the current I.E.E.
wiring regulations, the bylaws of the local water
undertaking, the Building Standards (Scotland)
Regulation and building standards (Ireland)
regulations.
It should be in accordance also with any rel-
evant requirements of the local authority and
the relevant recommendations of the following
British Standard Codes of Practice.
3.2 LOCATION OF APPLIANCE
The appliance may be installed in any room or
internal space, although particular attention is
drawn to the requirements of the current I.E.E.
wiring regulations, and in Scotland, the electri-
cal provisions of the Building Regulations, with
respect to the installation of the appliance in a
room or internal space containing a bath or
shower.
When an appliance is installed in a room or
internal space containing a bath or shower, the
appliance or any control pertaining to it must not
be within reach of a person using the bath or
shower.
The location chosen for the appliance must
permit the provision of a safe and satisfactory
flue and termination. The location must also
permit an adequate air supply for combustion
purposes and an adequate space for servicing
and air circulation around the appliance.
Where the installation of the appliance will be in
an unusual location special procedures may be
necessary, BS 6798 gives detailed guidance on
this aspect.
A compartment used to enclose the appliance
must be designed and constructed specifically
for this purpose.
An existing compartment/cupboard may be uti-
lised provided that it is modified to suit.
Details of essential features of compartment/
cupboard design including airing cupboard in-
stallations,are given in BS 6798. Thisappliance
is not suitable for external installation.
3.3 GAS SUPPLY
The gas meter – as supplied by the gas
supplier – must be checked to ensure that it is
of adequate size to deal with the maximum
rated input of all the appliances that it serves.
Installation pipes must be fitted in accord-
ance with BS 6891.
Pipe-work from the meter to the appliance
must be of adequate size. Pipes of a smaller
size than the appliance gas inlet connection
must not be used.
The installation must be tested for soundness
in accordance with BS 6891.
If the gas supply serves more than one appli-
ance, it must be ensured that an adequate
supply is maintained to each appliance when
they are in use at the same time.
3.4 FLUE SYSTEM
The terminal should be located where the disper-
sal of combustion products is not impeded and
with due regard for the damage and discoloration
thatmayoccurtobuildingproductslocatednearby.
The terminal must not be located in a place
where it is likely to cause a nuisance (see fig. 4).
In cold and/or humid weather, water vapour may
condense on leaving the flue terminal, the effect
of such pluming must be considered.

6
Fig. 5
3.6.3 DRAIN COCKS
These must be located in accessible positions to
facilitate draining of the appliance and all water
pipes connected to the appliance. The drain cocks
must be manufactured in accordance with BS
2879.
3.6.4 AIR RELEASE POINTS
These must be positioned at the highest points in
the system where air is likely to be trapped. They
should be used to expel trapped air and allow
complete filling of the system.
3.6.5 EXPANSION VESSEL
The appliance has an integral expansion vessel to
accommodatetheincreasedvolumeofwaterwhen
the system is heated. It can accept up to 8 litres of
expansion from within the system, generally for a
modern system this is sufficient, however if the
systemhasanunusuallyhighwatercontent,itmaybe
necessary to add additional expansion capacity (see
6.21).
3.6.6 FILLING POINT
A method for initial filling of the system and replac-
ing water lost during servicing etc. must be pro-
vided. This method of filling must comply with local
water authority regulations. Figure 5 shows a
widely accepted method.
Above a pavement or platform to which people
have access (including balconies or flat roofs) the
terminal must be protected by a guard of durable
material.(AsuitableguardisavailablefromVokera
Ltd. Part no. 018). The guard must be fitted
centrally over the terminal. Refer to BS5440 part
1, where the terminal is less than 1.0 metres
below plastic guttering or 1 metre below painted
eaves.
3.5 AIR SUPPLY
The following notes are intended for general
guidance only.
This appliance is a room sealed, fan-flued boiler,
consequently it does not require a permanent air
vent for combustion air supply.
When installed in a cupboard or compartment,
ventilation for cooling purposes is also not re-
quired.
3.6 WATER CIRCULATION
Detailed recommendations are given in BS 5449
part 1 and BS 6798 . The following notes are for
general guidance only.
3.6.1 PIPEWORK
It is recommended that copper tubing to BS2871
part 1 used in conjunction with soldered capillary
joints is used.
Where possible pipes should have a gradient to
ensure air is carried naturally to air release points
and that water flows naturally to drain cocks.
Except where providing useful heat, pipes should
be insulated to avoid heat loss and in particular to
avoid the possibility of freezing. Particular atten-
tion should be paid to pipes passing through
ventilated areas such as under floors, loft-space,
and void areas.
3.6.2 AUTOMATIC BY-PASS
The appliance has a built-in automatic by-pass,
consequentlythere is no requirement foranexter-
nal by-pass, however the design of the system
should be such that it prevents boiler ‘cycling’.
Fig. 5 A

7
Fig. 6
3.6.7 LOW PRESSURE SEALED SYSTEM
An alternative method of filling the system
would be from an independent make up vessel
or tank mounted in a position at least 1 metre
above the highest point in the system and at
least 5 metres above the boiler. (see fig.5a)
The cold feed from the make-up vessel or tank
must be fitted with an approved non-return
valve and stopcock for isolation purposes. The
feed pipe should be connected to the central
heating return pipe as close to the boiler as
possible.
3.6.8 FREQUENT FILLING
Frequent filling or venting of the system may be
indicative of a leak. Care should be taken
during the installation of the appliance to en-
sure all aspects of the system are capable of
withstanding pressures up to at least 3 bar.
3.7 ELECTRICAL SUPPLY
The appliance is supplied for operation on
230V @ 50Hz electrical supply, it must be
protected with a 3-amp fuse. The method of
connection to the mains electricity supply must
allow for complete isolation from the supply.
The preferred method is by using a fused,
double pole switch with a contact separation of
at least 3mm. The switch must only supply the
appliance and its corresponding controls, i.e.
time clock, room thermostat, etc. Alternatively
an un-switched shuttered socket outlet with a
fused 3-pin plug both complying with BS 1363
is acceptable.
3.8 SHOWERS
If the appliance is intended for use with a
shower, the shower must be thermostatically
controlled and be suitable for use with a com-
bination boiler.
3.9 MOUNTING ONACOMBUSTIBLE SURFACE
If the appliance is to be fitted on a wall of
combustible material, a sheet of fireproof ma-
terial must protect the wall.
3.10 TIMBER FRAMED BUILDING
If the appliance is to be fitted in a timber framed
building, it should be fitted in accordance with
the Institute of Gas Engineers publication (IGE/
UP/7) “Guide for Gas Installations in Timber
Frame Buildings” .
3.11 SCALE REDUCER
Although the appliance has been designed to
reduce the possibility of scaling, it is recom-
mended that in hard water areas (above 18
Clarke degrees), a scale reducer be fitted on
the main supply to the appliance.

8
SECTION 4 INSTALLATION
Fig. 7
4.1 DELIVERY
The appliance is delivered in a heavy-duty card-
board carton. Lay the carton on the floor with the
writing the correct way up.
4.2 CONTENTS
Contained within the carton is.
●The boiler.
●The wall mounting bracket.
●Anaccessories pack containing. servicevalves,
and sealing washers.
●The instructions pack containing. installation &
servicing instructions, appliance logbook, user
instructions,guaranteeregistrationcard, 3amp
fuse and flue restrictor ring.
4.3 UNPACKING
At the top of the carton pull both sides open – do
not use a knife – unfold the rest of the carton from
around the appliance, carefully remove all pro-
tective packaging from the appliance, and lay the
accessories etc. to one side.
4.4 PREPARATION FOR MOUNTING THE
APPLIANCE
The appliance should be mounted on a smooth,
non-combustible, vertical surface, which must be
capable of supporting the full weight of the
appliance. Care should be exercised when
determining the position of the appliance with
respect to hidden obstructions such as pipes,
cables, etc.
When the position of the appliance has been
decided – using the template supplied – carefully
mark the position of the wall bracket (see fig. 7)
and flue-hole (if applicable).
4.4.1 IMPORTANT
There are two holes on the tem late. The
lower hole should be used with the telesco ic
flue kit ( art no. 0225705 & 0225710). The
u er hole is for use with all other horizontal
flue kits.
4.4.2 MAXIMUM FLUE LENGTHS
4.5 FITTING THE FLUE
The top flue outlet permits both horizontal and
vertical flue applications to be considered,
alternatively, the Vokera twin flue system can be
utilised if longer flue runs are required.
4.5.1 CONCENTRIC HORIZONTAL FLUE
(For concentric vertical flue, see 4.5.2)
(For twin flue applications, see 4.5.3)
The appliance flue outlet elbow can be rotated
through 360º on its vertical axis. In addition the
flue may be extended from the outlet elbow in the
horizontal plane (see 4.4.2), however if the flue is
to be extended or additional bends are to be
fitted, the standard horizontal flue kit (part no.
2359029) must be used. A reduction must also
be made to the maximum length (see table)
when additional bends are used.
Bend Reduction in maximum flue
length for each bend
45º bend 0.5 Metre
90º bend 1.0 Metre
Using the template provided (see 4.4.1), mark
and drill a 125mm hole for the passage of the
flue pipe. The hole should have a 1º drop from
the boiler to outside, to eliminate the possibility
of rainwater entering the appliance via the flue.
The fixing holes for the wall-mounting bracket
should now be drilled and plugged, an appropriate
type and quantity of fixing should be used to
ensure that the bracket is mounted securely.
Once the bracket has been secured to the wall,
mount the appliance onto the bracket.
Horizontal flue terminals and accessories
Part No. Description Min-Max Length
0225705 tandard telescopic flue 380mm – 600mm
(Dimension ‘X’)
0225710 Extended telescopic flue 600mm – 920mm
(Dimension ‘X’)
2359029 Horizontal flue kit
For use with add. Bends 833mm
& extensions (dimension ‘X’)
2359069 750mm extension 750mm
2359079 1500mm extension 1500mm
2359049 45º bend (pair) N/A
2359059 90º bend N/A
0225760 Wall bracket (5) N/A
Flue system O tion 24
Concentric Horizontal 4.5m
Concentric Vertical 5.25m
Twin flue 14m/14m
+ terminal
type 1 = centre of rear flue
hole using only
0225705 or
0225710 flue
type 2 = centre of rear flue
hole for all other
flues

9
FITTING THE TELESCOPIC FLUE KIT (0225705
& 0225710)
Carefully measure the distance from the centre of
the appliance flue outlet to the face of the outside
wall (dimension ‘X’ see fig. 8). Add 50mm to
dimension ‘X’ to give the overall flue length
(dimension ‘Y’). Using the complete telescopic
flue assembly adjust the length to suit dimension
‘Y’. Once the telescopic flue terminal has been
adjusted to the correct length, secure the flue
assembly with the screw supplied.
Insert the flue restrictor ring (supplied in the
instruction pack) into the appliance flue gas outlet.
lide the flue assembly into the previously drilled
flue hole and locate the flue bend over the appliance
flue outlet. Push the flue bend down over the
appliance flue outlet and ensure the correct seal is
made. Pull the flue assembly towards and over
the flue bend – using a twisting action – ensuring
the correct seal is made. Check that the terminal
protrudes past the finished outside wall by the
correct length (115mm).
NOTE
You must ensure that the entire flue system is
properly supported and connected.
eal the flue assembly to the wall using cement or
a suitable alternative that will provide satisfactory
weatherproofing. The interior and exterior trim
can now be fitted.
FITTING THE STANDARD (2359029)
HORIZONTAL FLUE KIT (see 4.4.1)
Carefully measure the distance from the centre
of the appliance flue outlet to the face of the
outside wall (dimension ‘X’ see fig. 8A). Ensure
the inner (60mm) pipe is fully inserted into the
outer (100mm) pipe (when the inner pipe is fully
inserted, it stands proud of the outer pipe by
7.5mm). Add 32mm to dimension ‘X’ to give the
overall flue length (dimension ‘Y’). The standard
horizontal flue kit (part no. 2359029) is suitable
for a distance (dimension ‘Y’) of up to 865mm.
NOTE
Dimension ‘Y’ is measured from the end of the
terminal to the end of the outer (100mm) pipe.
Fig. 8
Fig. 8 a
Fig. 8 b
The internal trim should be fitted to the flue pipe
before connection of the 90º bend.
Insert the flue restrictor ring (supplied with
instruction pack) into the appliance flue gas outlet
if the total flue length is less than 1.0 metre.
If the horizontal flue kit (2359029) requires to be
cut to the correct size (dimension ‘Y’), you must
ensure that the inner (60mm) pipe stands proud of
the outer (100mm) pipe by 7.5mm (see fig. 8B).
Ensure any burrs are filed or removed and that
any seals are located properly before assembly.
Connect the inner (60mm) pipe of the terminal
assembly to the push-fit end of the 90º bend
(supplied) using a twisting action. Insert the
assembled flue into the previously drilled hole.
Using the clips & screws supplied, connect the
flue assembly to the boiler, ensuring that the
terminal protrudes past the finished outside wall
by the correct length (135mm).
You must ensure that the entire flue system is
properly supported and connected.
eal the flue assembly to the wall using cement or
a suitable alternative that will provide satisfactory
weatherproofing. The exterior trim can now be
fitted.
EXTENDING THE HORIZONTAL FLUE
If the horizontal flue requires extension/s or additional
bend/s, the standard horizontal flue terminal
(2359029) must be used. Connect the bend –
supplied with the terminal kit – to the top of the boiler
using the clips, screws, & gaskets supplied. The
additional bends & extensions have an internal
push-fit connection, care should be taken to ensure
that the correct seal is made when assembling the
flue system. Connect the required number of flue
extensions or bends (up to the maximum equivalent
flue length) to the flue terminal using the clips,
screws, & gaskets supplied (see fig. 8A & 8B).

10
Fig. 9
NOTE
When cutting the horizontal flue terminal or an
extension to the required length, you must ensure
that the excess is cut from the plain end of the
terminal or extension, and that the inner (60mm)
pipe is 7.5mm longer than outer (100mm) pipe
(see fig. 8A & 8B). Remove any burrs, and check
that any seals are located properly.
You must ensure that the entire flue system is
properly supported and connected.
eal the flue assembly to the wall using cement or
a suitable alternative that will
provide satisfactory weatherproofing. The interior
and exterior trim can now be fitted.
4.5.2 CONCENTRIC VERTICAL FLUE
The vertical flue terminal can be connected directly
to the appliance flue outlet. Alternatively, an
extension or bend can be connected to the
appliance flue outlet if desired (see 4.4.2), however
if additional bends are fitted, a reduction must be
made to the maximum flue length (see table
below).
Reduction for bends
Using the dimensions given in fig. 9 as a reference,
mark and cut a 105mm hole in the ceiling and/or roof.
Fit the appropriate flashing plate to the roof and
insert the vertical flue terminal through the flashing
plate from the outside, ensuring that the collar on
the flue terminal fits over the flashing.
The fixing holes for the wall-mounting bracket
should now be drilled and plugged, an appropriate
type and quantity of fixing should be used to
ensure that the bracket is mounted securely.
Once the bracket has been secured to the wall,
mount the appliance onto the bracket.
IMPORTANT
The vertical flue terminal is 1.0 metre in length
and cannot be cut; therefore it may be necessary
to adjust the height of the appliance to suit or use
a suitable extension.
Insert the flue restrictor ring into the appliance
flue outlet (see fig. 1), if the total flue length –
including the allowance for any additional bends
– does not exceed 1.0 metre.
Connect the vertical flue assembly to the boiler
flue spigot using the 60mm & 100mm clips,
gaskets, & screws (supplied), ensuring the correct
seal is made. The flue support bracket (supplied
with the vertical flue kit) can now be fitted.
If the vertical flue requires extension/s or additional
bend/s, connect the required number of flue
extensions or bends (up to the maximum
equivalent flue length) between the boiler and
vertical flue assembly (see fig. 8B).
NOTE
When cutting an extension to the required length,
you must ensure that the excess is cut from the
plain end of the extension and that the inner
(60mm) pipe is 7.5mm longer than outer (100mm)
pipe (see fig. 8B). Remove any burrs, and check
that any seals are located properly.
You must ensure that the entire flue system is
properly supported and connected.
Bend Reduction in maximum flue length for
each bend
45º bend 0.5 metre
90º bend 1.0 metre
Vertical flue terminal and accessories
Part No. Description Length
2359039 Vertical flue terminal 1.0 metre
0225770 Pitched roof flashing
plate N/A
0225765 Flat roof flashing plate N/A
2359069 750mm extension 750mm
2359079 1500mm extension 1500mm
2359049 45º bend (pair) N/A
2359059 90º bend N/A
0225760 Wall bracket (5) N/A

11
4.5.3 TWIN FLUE SYSTEM
The Vokera twin flue system enables greater flue
distances to be achieved (see 2.8) than that of
the standard concentric flue system. It can be
used for horizontal or vertical applications,
however the twin flue system must be converted
to the dedicated concentric flue kit for termination.
It is essential that the installation of the twin flue
system be carried out in strict accordance with
these instructions.
GUIDANCE NOTES ON TWIN FLUE
INSTALLATION
●The flue must have a fall back of 1º back to the
appliance to allow any condensate that may
form in the flue system to drain via the
condensate drain. Consideration must also be
given to the fact that there is the possibility of a
small amount of condensate dripping from the
terminal.
●Ensure that the entire flue system is adequately
supported, use at least one bracket for each
extension.
●The entire flue system must be adequately
insulated to maintain heat within the flue system
thereby reducing the possibility of condensate
production.
●As the exhaust outlet pipe can reach very high
temperatures it must be protected to prevent
persons touching the hot surface.
Bend Reduction in maximum flue length for
each bend
45º bend 1.0 metre
90º bend 1.0 metre
Twin flue accessories
Part No. Description Length
0225805 Horizontal flue terminal 1.0 metre
0225810 Vertical flue terminal 1.0 metre
300 Twin adapter kit N/A
0225770 Pitched roof flashing plate N/A
0225765 Flat roof flashing plate N/A
0225815 Condensate drain kit N/A
0225820 0.25m extension (pair) 250mm
0225825 0.5m extension (pair) 500mm
0225830 1.0m extension (pair) 1000mm
0225835 2.0m extension (pair) 2000mm
0225840 45º bend (pair) N/A
0225845 90º bend (pair) N/A
0225850 Twin bracket (5) N/A
0225855 Single bracket (5) N/A
MOUNTING THE BOILER
The fixing holes for the wall-mounting bracket
should now be drilled and plugged, an
appropriate type and quantity of fixing should be
used to ensure that the bracket is mounted
securely. Once the bracket has been secured to
the wall, mount the appliance onto the bracket.
4.5.3.1 INSTALLATION OF TWIN ADAPTOR KIT (fig. 10)
●Insert the restrictor ring (supplied with the
instruction pack) if the total flue length –
including the allowance for any bends – is less
than 7.5 m (20e) and 5 m (14e & 10e).
●Insert the exhaust connection manifold onto the
appliance flue outlet.
●Place the silicone seal (supplied with twin
adapter kit) over the rim of the exhaust
connection manifold.
●Remove the blanking plate (located to the left
of the appliance flue outlet) and – using the
same screws – install the air baffle.
Fig. 10
4.5.3.2 INSTALLATION OF CONDENSATE DRAIN KIT
(fig. 10a)
The condensate drain kit must be fitted within 1
metre of the appliance flue outlet. It is
recommended that the condensate drain kit
should be fitted in the vertical plane, however it
can be fitted horizontally with care.
●Fit the first bend to the condensate drain kit or
exhaust connection manifold by firmly pushing
in to position.
●Using the two holes in the exhaust connection
manifold as a guide, drill a 3mm hole in each
and secure using the screws provided.
●Connect the air inlet pipe to the air baffle as
above.
●The twin flue pipes extensions and accessories
can now be installed by pushing together (the
plain end of each extension or bend should be
pushed approximately 50mm into the female
socket of the previous piece).
The condensate drain trap must be connected to
the drain in accordance with building Regulations
or other rules in force.
Fig. 10a
restrictor ring
flue outlet
air inlet

12
4.5.3.3 HORIZONTAL TERMINATION
(See fig. 10b)
The twin flue system must be converted to the
dedicated concentric flue kit for termination.
●The horizontal terminal is supplied with a built-
in converter box and cannot be shortened.
●A 130mm hole is required for the passage of
the concentric terminal through the wall.
Depending on site conditions it may be preferable
to install the terminal assembly prior to fitting the
twin flue pipes.
Mark and drill a 130mm hole for the passage of
the horizontal flue terminal, ensuring that there
is a 1º fall back to the boiler (17mm per 1000mm).
Insert the terminal assembly into the flue hole.
Push-fit the twin flue pipes onto the concentric to
twin converter box ensuring that the exhaust pipe
connects to the exhaust connection on the
concentric to twin converter.
If necessary cut the plain ends (male) of the twin
flue pipes to allow connection to the concentric
to twin converter.
NOTE
Before cutting twin flue pipes ensure allowances
have been made for connection onto the previous
piece and onto the concentric to twin converter.
The last twin flue pipes must be pushed 50mm
onto the male sockets of the concentric to twin
converter.
NOTE
You must ensure that the entire flue system is
properly supported and connected.
When cutting an extension to the required length,
you should ensure that the excess is cut from
the plain end of the extension. Remove any
burrs, and check that both seals are located
properly.
eal the flue terminal assembly to the wall using
cement or a suitable alternative that will provide
satisfactory weatherproofing. The interior and
exterior trim can now be fitted.
4.5.3.4 VERTICAL TERMINATION
(See fig. 10c)
The twin flue system must be converted to the
dedicated concentric flue kit for termination.
●The vertical terminal is supplied with a built-in
converter box and cannot be shortened.
●A 130mm hole is required for the passage of
the concentric terminal through the ceiling and/
or roof.
Depending on site conditions it may be preferable
to install the terminal assembly prior to fitting the
twin flue pipes.
Fit the appropriate flashing plate to the roof and
insert the vertical flue terminal through the
flashing plate from the outside, ensuring that the
collar on the flue terminal fits over the flashing.
Push-fit the twin flue pipes onto the concentric to
twin converter ensuring that the exhaust pipe
connects to the exhaust connection on the
concentric to twin converter.
If necessary cut the plain ends (male) of the twin
flue pipes to allow connection to the concentric
to twin converter.
NOTE
•Before cutting twin flue pipes ensure
allowances have been made for connection
onto the previous piece and onto the concentric
to twin converter. The last twin flue pipes must
be pushed 50mm onto the male spigots of the
concentric to twin converter.
•You must ensure that the entire flue system is
properly supported and connected.
•Ensure that any horizontal sections of pipe
have a 1º fall towards the appliance (17mm per
1000mm).
•The convertor box on the vertical terminal will
have to be temporarily removed when inserting
the terminal through the flashing.
•The condensate trap must be primed with water
prior to commissioning the boiler.
Fig. 10b
Fig. 10c

13
Appliance terminal strip cover and screws
Fig.12
4.6 CONNECTING THE GAS AND WATER (fig. 6)
The appliance is supplied with an accessories
pack that contains large and small sealing wash-
ers, service valves, and pipe connections.
The service valves are of the compression type,
the pipe connections have plain copper ends.
When connecting pipework to the valves or con-
nections, tighten the compression end first, then
insert the sealing washers before tightening the
valve or connection to the appliance. It will be
necessary to hold the valve or connection with
one spanner whilst tightening with another.
4.6.1 GAS (fig. 6)
The appliance is supplied with a 15mm service
valve, connect a 15mm pipe to the inlet of the
valve, and tighten both nuts.
Note; It will be necessary to calculate the diam-
eter of the gas pipe to ensure the appliance has
an adequate supply of gas.
4.6.2 HEATING (FLOW & RETURN) fig. 6
The appliance is supplied with 22mm service
valves for the heating connections, connect 22mm
pipe to the inlet of each valve and tighten both
nuts.
4.6.3 HOT WATER OUTLET fig. 6
The appliance is supplied with a 15mm compres-
sion coupling. Connect a 15mm pipe to the cou-
pling and tighten. It may be necessary to fit a non-
return valve if the installation is subject to mains
knock, in order to eliminate false activation of the
domestic hot water flow switch.
4.6.4 COLD WATER INLET (fig. 6)
The appliance is supplied with a 15mm stopcock,
connect a 15mm service pipe to the inlet of the
service valve and tighten both nuts. It may be
necessary to fit a pressure reducing valve if the
installation is subject high-pressure fluctuations
or high pressure surges.
4.6.5 SAFETY VALVE DISCHARGE PIPE (fig. 6)
The appliance is supplied with a 15mm copper
tail, connect a 15mm pipe and suitable coupling
to the tail and tighten. The discharge pipe must
have a continuos fall away from the boiler to
outside and allow any water to drain away thereby
eliminating the possibility of freezing. The dis-
charge pipe must terminate in a position where
any water – possibly boiling – discharges safely
without causing damage or injury, but is still
visible.
4.7 ELECTRICAL CONNECTIONS figs. (12, 13, 14.)
The appliance is supplied with a factory fitted
timeclock. hould additional controls be re-
quired, please refer to the detailed wiring dia-
grams in section 8 for detailed instructions.
A qualified electrician should connect the electri-
cal supply to the appliance. A competent person
must undertake the design of any external elec-
trical circuits. ANY EXTERNAL CONTROL OR
WIRING MU T BE ERVED FROM THE AME
I OLATOR A THAT OF THE APLIANCE. The
supply cable from the isolator to the appliance
must be 3-core flexible sized 0.75mm to B 6500.
Wiring to the appliance must be rated for opera-
tion in contact with surfaces up to 90ºC.
To gain access to the appliance electrical con-
nections you must first remove the casing, pro-
ceed as follows.
●Unscrew the two brass slot head screws lo-
cated left and right, beneath the grey control
panel – please note these screws are captive
and will only drop down approximately 10mm –
●Gently lower the control panel ensuring the
ensuring the electrode lead does not snag
on the a liance casing.
●Unscrew the two-crosshead screws located
left and right at the base of the white casing.
●Gently ease the casing towards you and then
lift upward to disengage the casing from the top
hooks.
●Ensure the casing and screws are stored in a
safe place until required.
Control panel screws and casing screws
Fig. 11
Locate the appliance terminal cover (fig.12) and
remove both screws, lift off cover and place to
one side, locate the cable entry on the appliance
(fig.13) and pass the cable through. On the
applianceterminalstripthereare five connectors,
from left to right they are.
● Earth (green & yellow),
● Live (brown),
● Neutral (blue),
● Room thermostat terminals (black).

14
cable entry
Fig.13 Fig.14
E L NLINK
Heating & hot
water position
Off position
Hot water only
position
Mode selector shaft
Hot water
potentiometer
Heating
potentiometer
co. position
Fig. 15
Fig. 16
Modulating coil plug
Protective cap
Inlet test nipple
Outlet test nipple
upply plug
Connect the supply cable wires (earth,
live, & neutral) to their corresponding
terminals on the appliance terminal
strip, ensuring the Earth wire is slightly
longer than the Live and Neutral, this
preventsstrain on the earth wireshould
the cable become taut. Do not remove
the link wire that connects the room
thermostat terminals unless you are
intendingto fitaroom thermostat. Once
all connections have been made, re-fit
the appliance terminal cover.
At this point it is essential that the
securing screw on the cable entry is
now tightened, this must be done be-
fore the control panel is re-fitted in its
upright position. Re-fit appliance cas-
ing and screws.

15
5.1 GAS SUPPLY INSTALLATION
Inspect the entire installation including the gas
meter, test for soundness and purge. Refer to BS
6891 for specific instruction.
5.2 THE HEATING SYSTEM
The appliance contains components that may
become damaged or rendered inoperable by oils
and/or debris that are residual from the installa-
tion of the system, consequently it is essential
that the appliance is flushed in accordance with
the following instructions.
5.3 INITIAL FILLING OF THE SYSTEM
Ensure both flow and return service valves are
open, remove appliance casing as described in
4.7.1, identify the automatic air release valve,
and loosen the dust cap by turning cap anti-
clockwise one full turn. IMPORTANT, THERE
ARE NO MANUAL AIR RELEASE VALVES
LOCATED ON THE APPLIANCE. Ensure all
manual air release valves located on the heating
system are closed. Using the method of filling as
described in fig. 5, slowly proceed to fill the
system, as water enters the system the pressure
gauge will begin to rise, once the gauge has
reached 1BAR close the filling valve and begin
venting all manual air release valves, starting at
the lowest first. It may be necessary to go back
and top-up the pressure until the entire system
has been filled. Inspect the system for water
soundness, rectifying any leaks.
5.4 INITIAL FLUSHING
The whole of the heating system must be flushed
both cold and hot as detailed in 5.9. open all
radiator or heating valves and the appliance
central heating valves. Drain the boiler and
system from the lowest points. Open the drain
valve full bore to remove any installation debris
from the boiler prior to lighting. Refill the boiler
and heating system as described in 5.3.
5.5 FILLING THE HOT WATER SYSTEM
Close all hot water outlets, turn appliance stop-
cock on (anti-clockwise), slowly open each outlet
until all air has been expelled and clear water is
discharged. Checkpipe-work etc. for water sound-
ness.
SECTION 5 COMMISSIONING
5.6 PRE-OPERATION CHECKS
Before attempting to initial lighting of the appli-
ance, the following checks must be carried out.
●Ensure all gas service valves from the meter to
the appliance are open and the supply pipe has
been properly purged.
●Ensure the proper electrical checks have been
carried out, (7.11) particularly. continuity, po-
larity, and resistance to earth.
●Ensure the 3amp fuse – supplied with the
appliance – has been fitted.
●Ensure the system has been filled, aired, and
the pressure set to 1bar.
●Ensure the flue has been fitted properly and in
accordance with the instructions.
●Ensure all appliance service valves are open.
5.7 INITIAL LIGHTING
Ensure electrical supply to the appliance is
switched off, remove mode selector switch and
gently rotate the heating and hot water
potentiometers to their lowest positions (anti-
clockwise)(see fig. 16), refitmodeselectorswitch.
Turn on electrical supply to the appliance, switch
time-clock to an ‘on’ position, ensure any external
controls (if fitted) are calling for heat, turn mode
selector switch to the heating and hot water
position.
The appliance will now go through an ignition
sequence as described in 1.2. Should the appli-
ance fail to ignite, refer to pre-operation checks.
Once the appliance has ignited it will remain on
minimum output for two minutes. At this point a
hot water outlet should be opened to check
appliance operation in hot water mode should the
appliance fail to ignite, refer to pre-operation
checks.
5.8 CHECKING BURNER PRESSURES
MAXIMUM (10.1mbar)
Although burner pressure settings are factory
set, it is necessary to check them during
commissioning. Isolate boiler from the electrical
supply, turn the mode selector switch to the hot
water only position, remove the mode selector
switch and adjust the hot water potentiometer to
maximum (clockwise), attach a suitable manom-
eter to the gas valve outlet test nipple. (see fig.
Fig. 17
Gas pressure adjustment
protective cover
Maximum pressure
adjustment screw (a) Minimum pressure ad-
justment screw (b)

16
15,17) Restore the electrical supply to the appli-
ance and open a hot water outlet – preferably the
bath-tap – ensuring a high flow rate. The appli-
ance will now fire and go to maximum gas rate
(10.1mbar), if the pressure is wrong it should be
adjusted as instructed in 7.6 Once the check has
been concluded, close hot water outlet, isolate
appliance from electrical supply, remove ma-
nometer and tighten test nipple screw.
MINIMUM (1.5mbar)
Although burner pressure settings are factory
set, it is necessary to check them during commis-
sioning. Isolate boiler from the electrical supply,
attach a suitable manometer to the gas valve
outlet test nipple, (see fig. 15,17) and remove the
black plug connected to the modulating coil on
the gas valve. Restore the electrical supply to the
appliance and open a hot water outlet. The
appliance will now fire and go to minimum gas
rate (1.5mbar), if the pressure is wrong it should
be adjusted as instructed in 7.6. Once the check
has been concluded, close hot water outlet, iso-
late appliance from electrical supply, refit plug to
modulating coil, remove manometer and tighten
test nipple screw.
HEATING MINIMUM (1.9mbar)
Although burner pressure settings are factory set,
it is necessary to check them during
commissioning. Isolate boiler from the electrical
supply, attach a suitable manometer to the gas
valve outlet test nipple (see fig. 15 & 17). Restore
the electrical supply to the appliance and ensure
all controls are calling for heat, turn the appliance
mode selector switch to heating and hot water,
the appliance will now fire. Once the burner has
lit, open – for a few seconds only – a hot water
outlet, the burner will now remain on minimum
output (1.9mbar) for 30 seconds. If the pressure
is wrong it should be adjusted as instructed in
7.6. Once the check has been concluded, isolate
appliance from electrical supply, remove
manometer and tighten test nipple screw.
HEATING MAXIMUM
There is no range rating facility on the appliance.
The appliance automatically adjusts its output
tooptimise efficiency.
After adjustment to the gas valve, the protective
cap should be re-sealed.
5.9 FINAL FLUSHING OF THE HEATING SYSTEM
The system should be flushed in accordance with
BS7593. Turn on the boiler for central heating
and allow the boiler and system to reach tem-
perature. Turn off the boiler and drain the system
whilst still hot.
Refill the boiler and heating system as described
in 5.3.
Although not necessary for correct operation of
the boiler, an inhibitor may be added at this point.
Contact the inhibitor manufacturer for further in-
formation concerning application and dosage.
5.10 SETTING THE BOILER OPERATING TEM-
PERATURE
The flow outlet temperature can be adjusted from
40ºC. - 80ºC. via the potentiometer located be-
hind the mode selector switch, the potentiometer
has three temperatures sectors.
●Sector 1. 40ºC - 55ºC
●Sector 2. 55ºC - 65ºC
●Sector 3. 65ºC - 80ºC
When the potentiometer is set within sector 2 the
appliance will automatically raise the outlet tem-
perature to maintain comfort levels during cold
weather conditions. To adjust the heating
potentiometer proceed as follows.
SECTOR 1
Ensure the appliance has been set to hot water
and heating mode, remove the mode selector
switch, and gently rotate the potentiometer clock-
wise, until the green LED on the appliance fascia
flashes, now rotate the potentiometer anti-clock-
wise by a few degrees, the potentiometer is now
in sector 1. Replace mode selector switch.
SECTOR 2
Ensure the appliance has been set to hot water
and heating mode, remove the mode selector
switch, and gently rotate the potentiometer clock-
wise, until the green LED on the appliance fascia
flashes, the potentiometer is now in sector 2.
Replace mode selector switch.
SECTOR 3
Ensure the appliance has been set to hot water
and heating mode, remove the mode selector
switch, and gently rotate the potentiometer fully
clockwise until the stop is reached, the
potentiometer is now in sector 3. Replace mode
selector switch.
NOTE
When the potentiometer moves from sector 1 to
sector 2, the green LED will flash for 4 seconds.
When the potentiometer moves from sector 3 to
sector 2, the green LED will flash for 4 seconds.
5.11 SETTING THE SYSTEM DESIGN PRESSURE
The design pressure should be I minimum of 1
bar and a maximum of 1.5 bar.
The actual reading should ideally be 1 bar plus
the equivalent height in metres to the highest
point in the system above the base of the appli-
ance. (Up to the maximum of 1.5 bar total).
N.B. The safety valve is set to lift at 3 bar/ 30m/
45psig.
To lower the system pressure to the required
value, pull lever on head of safety valve to re-
lease water until the required figure registers
on the pressure gauge (see fig.1).

17
5.12 REGULATING THE CENTRAL HEATING SYS-
TEM
Fully open all radiator and circuit valves and run
the appliance in the central heating mode until
heated water is circulating. If conditions are warm
remove any thermostatic valve heads.
Adjust radiator return valves and any branch
circuit return valves until the individual return
temperatures are correct and are approximately
equal.
5.13 REGULATING THE DOMESTIC HOT WATER
The appliance will ignite in hot water mode when
the domestic hot water flow switch senses a flow
rate through the appliance of 2 litres or more, the
appliance has a built-in flow restrictor, which
limits the maximum flow rate to 10 litres.
If the mains supply suffers from an unusually high
or low pressure, adjustment of the hot water
output may be necessary.
Once the pre-operation checks – as described in
5.6 – have been carried out, the domestic hot
water can be regulated if required.
Ensure the appliance is switched to hot water
only, remove the mode selector switch, rotate the
hot water potentiometer to its maximum position,
and turn on the bath tap fully.
The appliance will now fire in domestic hot water
mode. Allow the temperature to stabilise.
The hot water can now be regulated to set the
temperature.
To reduce the hot water temperature, slowly
rotate the hot water potentiometer anti-clockwise
untilasatisfactorytemperatureisobtained. Please
note that it is prudent to set the hot water tem-
perature at the lowest acceptable temperature as
higher temperatures can be realised by reducing
the flow-rate at the hot water outlet. Re-fit mode
selector switch.
To increase the hot water temperature, slowly
turn the adjustable stopcock clockwise until a
satisfactorytemperatureisobtained. Please note
that it is prudent to set the hot water temperature
at the lowest acceptable temperature as higher
temperatures can be realised by reducing the
flow-rate at the hot water outlet. Re-fit mode
selector switch.
5.14 FINAL CHECKS
●ENSURE OUTLET TEST NIPPLES ON THE
APPLIANCEGAS VALVE HAVEBEENTIGHT-
ENED AND CHECKED FOR SOUNDNESS.
●ENSURE THE APPLIANCE FLUE SYSTEM IS
FITTED CORRECTLY AND IS SECURED.
●ENSURE ALL PIPE-WORK IS RE-CHECKED
FOR SOUNDNESS.
●REFIT APPLIANCE CASING.
●COMPLETE APPLIANCE LOGBOOK.
Complete details of the boiler, controls, installa-
tion and commissioning in the log book supplied
with the boiler. This is an important document
which must be correctly completed and handed
to the user. Failure to install and commission the
appliance to the manufacturers instructions may
invalidate the warranty.
Hand over all documentation supplied with this appliance
– including these instructions – and explain the impor-
tance of keeping them in a safe place.
Explain to the user how to isolate the appliance from the
gas, water, and electricity supplies, and the locations of
all drain points.
Show the user how to operate the appliance and its
associated controls correctly.
Show the user the position of the filling valve and how to
top-up the system pressure correctly, and show the
location of all manual air release points.
Explain to the user how to turn off the appliance for both
long and short periods, and advise on the necessary
precautions to prevent frost damage.
Explain to the user that for continued safe and efficient
operation, the appliance must be serviced annually by a
competent person.
INSTRUCTING THE USER

18
SECTION 6 SERVICING INSTRUCTIONS
6.1 GENERAL
To ensure the continued safe and efficient opera-
tion of the appliance, it is recommended that it is
checked and serviced at regular intervals.
The frequency of servicing will depend upon the
particular installation conditions, but in general,
once per year should be adequate.
It is the law that any servicing work is carried out
by a competent person such as a Vokera service
engineer, approved service agent, British Gas, or
other CORGI registered personnel.
The following instructions apply to the boiler and
its controls, but it should be remembered that
the central heating and the domestic hot water
systems will also require attention from time to
time.
6.2 ROUTINE ANNUAL SERVICING
Check the operation of the appliance in both ‘hot
water only’ and ‘heating and hot water’ modes.
Ensure the appliance functions as described in
section 7. Compare the performance of the appli-
ance with its design specification. The cause of
any noticeable deterioration should be identified
and rectified without delay.
Thoroughly inspect the appliance for signs of
damage or deterioration especially the flue sys-
tem and the electrical apparatus.
Check and adjust – if necessary – all burner
pressure settings. (see 7.6)
Check and adjust – if necessary – the system
design pressure. (see 5.11)
Carry out an analysis of the flue gases (see
section 7.7), and visually check the condition of
the entire flue assembly. Compare the results
with the appliance design specification. Any
deterioration in performance must be identified
and rectified without delay.
Ensure both flue venturis are clean and free from
any debris or obstruction.
Ensure both the burner and heat exchanger are
clean and free from any debris or obstruction.
Inspect all joints for signs of leakage and repair if
necessary.
Refer to the commissioning section and/or re-
placement of parts section for detailed instruction
if required.
6.3 REPLACEMENT OF COMPONENTS
Although it is anticipated that this appliance will
give years of reliable, trouble free service, the life
span of components will be determined by fac-
tors such as operating conditions and usage.
Should the appliance develop a fault, the fault
finding section will assist in determining which
component is malfunctioning.
6.4 MAIN HEAT EXCHANGER (de-scaling)
The main heat exchanger may – when operating
under certain conditions – become affected by
scaling. Evidence of this will be a deterioration of
the hot water performance. The heat exchanger
can be de-scaled using a proprietary de-scalant
without having to remove it from the appliance.
However the appliance must be disconnected
from the hot and cold service pipes, the de-
scalant should be administered with strict adher-
ence to the manufacturers instructions. Re-
connect the hot and cold services only after
thorough flushing with clean water has taken
place.
6.5 COMPONENT REMOVAL PROCEDURE
To remove a component, access to the interior of
the appliance is essential. Isolate the appliance
from the electrical supply and remove the fuse.
And when necessary, close all service valves on
the appliance, remove the appliance casing as
described in section 4.7.1, drain the primary
water content from the appliance via the safety
valve, and drain off secondary water content
from the appliance via a hot water outlet. Ensure
some water absorbent cloths are available to
catch any residual water that may drip from the
appliance or removed component. Undertake a
complete commissioning check as detailed in
section 5, after replacing any component. AL-
WAYS TEST FOR GAS SOUNDNESS IF ANY
GAS CARRYING COMPONENTS HAVE BEEN
REMOVED OR DISTURBED.
6.6 PUMP HEAD fig. 18
Carry out component removal procedure as de-
scribed in 6.5.
Using a 4mm Allen key or ‘T’ bar, unscrew and
remove the four Allen screws that hold the pump
in position, pull firmly on the pump head to
release it from the base. Disconnect the electri-
cal leads. Replace in the reverse order.
Fig. 18
Pump
Safety valve

19
6.10 DOMESTIC WATER FLOW SWITCH fig. 21
Carry out component removal procedure as de-
scribed in 6.5.
Remove black electrical plug from the domestic
water flow switch, disconnect and remove inlet
pipe between the domestic water flow switch and
the heat exchanger, remove locking pin from the
domestic water flow switch, the switch can now
be removed from the appliance. Replace in the
reverse order.
6.11 PRESSURE GAUGE fig. 1
Carry out component removal procedure as de-
scribed in 6.5.
Remove pressure gauge locking pin, located on
pump base, and withdraw the pressure gauge
pipe, locate the spring tabs on the pressure
gauge body, push and hold tabs in, to enable
extraction of the gauge from its location. Replace
in the reverse order.
6.12 PRIMARY AND SECONDARY THERMISTORS
fig. 22-23
Carry out component removal procedure as de-
scribed in 6.5.
Pull back protective rubber cover from the ther-
mistor, disconnect thermistor electrical plug, us-
ing a 13mm spanner slacken and remove the
thermistor and sealing washer. Replace in the
reverse order.
6.7 SAFETY VALVE fig. 18
Carry out component removal procedure as de-
scribed in 6.5.
Disconnect the outlet pipe from the safety valve,
unscrew and remove the hex bush from the
safety valve outlet, remove safety valve locking
pin from appliance manifold. Replace in the
reverse order
6.8 AUTOMATIC AIR RELEASE VALVE (AAV) fig.
19
Carry out component removal procedure as de-
scribed in 6.5.
Remove the locking pins at the pump outlet, and
the flow & return connection of the heat ex-
changer, disconnect both pipes from the heat
exchanger, and remove the return pipe from the
pump outlet. Remove the locking pin and expan-
sion pipe from the pump base. Using a suitable
pair of pliers, unscrew the AAV from the pump
base. Replace in the reverse order.
6.9 WATER PRESSURE SWITCH fig. 20
Carry out component removal procedure as de-
scribed in 6.5.
Remove locking pin from heating flow pipe at the
heating manifold and withdraw the pipe from the
manifold. Remove locking pin and the water
pressure switch from the heating manifold, pull
back protective cover – and after taking note of
the electrical connections – disconnect the wir-
ing. Replace in the reverse order.
Fig. 19
Fig. 20
Fig. 21
Fig. 22
AAV
primary thermistor
high limit thermostat
WATER PRESSURE
SWITCH

20
Fig. 23
6.13 HIGH LIMIT THERMOSTAT fig. 22
Carry out component removal procedure as de-
scribed in 6.5.
Pull off electrical plug from the high limit thermo-
stat, slacken and remove retaining screws. Re-
place in reverse order.
6.14 PRINTED CIRCUIT BOARD (PCB) fig. 12
Carry out component removal procedure as de-
scribed in 6.5.
Remove mode selector switch, locate and re-
move the five screws which secure the PCB
cover, then remove cover, after carefully taking
note off all wiring connections, disconnect all
wiring from the PCB, locate and remove the PCB
securing screws, remove PCB. Replace in the
reverse order.
6.15 GAS VALVE fig. 15
Carry out component removal procedure as de-
scribed in 6.5.
The gas valve must be changed as complete unit.
Disconnect both electrical plugs from the gas
valve, disconnect silicone tube from gas valve
regulator, slacken and unscrew gas valve inlet
and outlet connections, please note, the sealing
washers must be discarded and replaced with
new sealing washers, locate and remove gas
valve retaining screws on the underside of the
boiler, the gas valve can now be removed. Re-
place in the reverse order. Check and adjust
burner pressure settings. WARNING, A GAS
SOUNDNESS CHECK MUST BE CARRIED
OUT.
6.16 INTEGRAL TIME SWITCH fig. 12
Carry out component removal procedure as de-
scribed in 6.5.
Locate and remove the five screws which secure
the PCB cover, then remove cover, locate and
remove the time clock retaining screws, remove
time clock after carefully taking note off all wiring
connections. Replace in the reverse order.
6.17 BURNER, INJECTORS, AND SPARK/SENSE
ELECTRODE fig. 24 & 25
Carry out component removal procedure as de-
scribed in 6.5.
Fig. 24
secondary thermistor
Remove outer combustion cover by un-clipping
the two retaining clips located at the base of the
combustion cover, gently pull the cover towards
you before lifting and disengaging it from the top
retaininglugs. Locate and remove the two screws
at the base of the inner combustion cover, pull the
cover towards you before lifting and disengaging
it from the top retaining lugs.
Disconnect both the electrode lead from its con-
nector at the top of the control fascia, and the
electrode earth lead from the spade connector on
the appliance frame. Locate and remove the four
screws which secure the burner in position, gen-
tly ease the burner out of its location whilst also
easing the electrode sealing grommet from its
location.
Once the burner has been removed, locate the
burner injectors – located to the rear of the
combustion chamber – and remove. Replace in
the reverse order. Please note, the injector
sealing washers must be replaced if the injectors
have been removed, ensure all seals are in good
condition, taking care to ensure they are replaced
correctly.
Fig. 25