Main Mersey Super User guide

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About the Heater See inside cover for models covered by these instructions.
This is a non spouted, gas fired, multipoint water heater.
For use with Natural Gas (G20) Only at 20 mbar and for use in GB/IE Only.
About Safety The Gas Safety (Installation and Use) Regulations.
‘‘ In your own interest, and that of safety, it is law that all gas appliances are installed by
competent persons, in accordance with the above regulations. Failure to install appliances
correctly could lead to prosecution.’’
Installation must be in accordance with the User, Installation & Servicing Instructions and the
rules in force.
Polythene bags used for packaging are a potential hazard to babies and young children and
MUST BE CAREFULLY DISPOSED OF IMMEDIATELY.
Leave these instructions with the user for use on future calls.
User, Installation & Service
Instructions Multipoint
Water Heater

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2Part No. 5000893
Contents
Contents
User Instructions - For the User & Installer
User Information...................................................3
To Light the Pilot...................................................4
To Obtain Hot Water..............................................4
To Shut Down the PIlot.........................................4
To Alter the Settings.............................................5
Care ofYour Appliance.........................................6
Installation Instructions - For the Installer
1. Dimensions, Clearances &
Product Specificatin.............................................7
2. Installation Requirements....................................9
Codes of Practice...............................................9
Health & Safety Information...............................9
Energy Cut-Off Device.......................................9
Under Draining Board Installation......................9
Ventilation..........................................................9
Installation Conditions........................................9
Siting the Flue Terminal...................................10
3. Installation...........................................................11
3.1 Location.............................................11
3.2 Gas Connection.................................12
3.3 Water Connections.............................13
3.4 Lint Filter............................................13
4. Commissioning...................................................14
Servicing Instructions - For the Installer
5. Servicing.............................................................16
6. Replacement of Parts.........................................17
6.1 Piezo Unit...........................................18
6.2 General Access/Main Burner.............18
6.3 Thermocouple & Spark Electrode......19
6.4 Pilot Injector.......................................19
6.5 Flame Safety Device..........................19
6.6 Pilot Viewing Glass & Seal.................20
6.7 Energy Cut-Off Device.......................20
6.8 To Drain the Appliance.......................21
6.9 Pressure Relief Valve.........................21
6.10 Water Governor..................................21
6.11 Automatic Valve..................................23
6.12 Water Governor Venturi......................23
6.13 Thermostat Assembly -Thames.........24
6.14 Throttle Assembly -Thames...............24
6.15 Heating Unit -Thames........................25
6.16 Heating Unit - Mersey/Medway...........26
6.17 Descaling the Heating Unit.................26
7. Fault Finding.......................................................27
8. Short List of Spares............................................31
Washing Machine Information..................................33
Shower Information...................................................34
Models covered by these Instructions.
Mersey Super - G.C. No. 52 476 38
Medway Super - G.C. No. 52 476 39
Thames - G.C. No. 52 476 40
Important - Installation, Commissioning, Service &
Repair
This appliance must be installed in accordance with the
manufacturer’s instructions and the regulations in
force. Read the instructions fully before installing or
using the appliance.
In GB this must be carried out by a competent person
as stated in the Gas Safety (Installation & Use)
Regulations.
Definition of competence: A person who works for a
CORGI registered company and holding current
certificates in the relevant ACS modules, or valid ACoP
equivalents, is deemed competent.
In IE this must be carried out by a competent person as
stated in I.S. 813. "Domestic Gas Installations".
Important –Failure to install and commission this
appliance to manufacturer’s instructions may invalidate
the warranty. This note does not affect your statutory
rights.
Warning - The addition of anything that may interfere
with the normal operation of the appliance without
express written permission from the manufacturer or
his agent could invalidate the appliance warranty.In GB
this could also infringe the GAS SAFETY (Installation
and Use) REGULATIONS.
CORGI
All CORGI registered installers carry a CORGI
identification card and have a registration number.Both
should be recorded in your boiler Log Book.
You can check your installer is registered by
telephoning [phone] or writing to:-
CORGI. 1 Elmwood, Chineham Business Park,
Crockford Lane, Basingstoke, RG24 8WG.

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3
Part No. 5000893 Introduction & User Information
Introduction and User Information
•Samples of the Main multipoint water heaters have
been examined by Advantica Technologies Limited, a
United Kingdom Notified Body.The range is certified
to comply with the essential requirements of the Gas
Appliance Directive 90/396/EEC and are therefore
permitted to carry the CE Mark.
•This appliance is not suitable for use with a swivel
spout.
•This appliance is room sealed instantaneous water
heater designed to supply hot water to several taps
which may be situated in different rooms, but not
necessarily at the same time.
•The pilot is lit by a piezo spark igniter; batteries or
electricity are not required.
•The main burners will automatically light when a
domestic hot water tap is turned on and go out when
the tap is turned off.
• Ensure that the clearances shown in (Page 7,
Installers section) are maintained at all times.
• Please take time to read through these
instructions to familiarise yourself with the water
heater.
•This appliance contains an energy cut-off device that
will shut down the gas supply to the appliance if the
water in the heat exchanger exceeds the anticipated
temperature limit.Although intended to guard against
an internal fault, it may be triggered inadvertently by
other causes, especially during the summer months
when the inlet water temperature is unusually high.
Allow the appliance to cool before re-lighting.
WARNING:
If the energy cut-off device is reacting to an
internal fault, the shut down may be accompanied
by noises from the heat exchanger and pipework,
and it is possible that STEAM will come out of the
hot tap when turned on. If this occurs, arrange for
the appliance to be serviced.
Your installer/engineer will recommend
replacement of the Pressure Relief Valve
Assembly to ensure continued safety.
•Running Costs.To work out the approximate running
costs per hour for this fire, perform the following
calculation:-
Heat Input in kW x Cost Per kWh
= Running Cost Per Hour
Heat inputs for the various settings are shown in the
Technical Data & Costs per kWh are shown on your
gas bill.
•Washing Machines
Information regarding the use of washing machines
with this appliance is shown at the rear of these
instructions.
•Shower Systems
Information regarding the use of shower systems
with this appliance is shown at the rear of these
instructions. In hard water areas, shower roses may
require regular cleaning as scale my form and restrict
the flow of water.
The Mersey Super is Not suitable for use
with a shower system.
•WARNING:
The Outer Case of this Appliance MUST BE
CORRECTLY positioned and secured in
place before any attempt is made to light the
burners. If in doubt, call your Installer.
•IMPORTANT:
If it is known or suspected that a fault exists
on the appliance, it must not be used until
the fault has been corrected by a competent
person.
•REPLACEMENT PARTS:
WARNING:The use of replacement parts on
this appliance which are not recommended
by Potterton may affect the product safety,
performance and warranty.
We recommend that replacement parts be
obtained only from Curzon branches or
other recognised Potterton spares outlets.

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4Part No. 5000893
Read Through Before Lighting or Operating
Light the Pilot
Fig. 2
To Light The Pilot
Fig. 1
CAUTION: Should the pilot flame ever be
found to have gone out, press the OFF button
and wait at least 5 minutes for any
residual gas to dissipate before relighting the
pilot.
1.Ensure that the gas and water supplies are
turned ON, that all domestic hot water taps
are turned OFF.
2. Fully depress and hold the ON button
and repeatedly press and release the IGN
button until the pilot is lit.The pilot flame
can be observed through the pilot viewing
window.
3. Hold the ON button in for a further 10
seconds after the pilot is lit, then release.If
the pilot goes out, repeat the lighting
operation keeping the ON button
depressed a little longer.
•Once the pilot is lit and the appliance is in
the working position, hot water will be
obtained by turning on any of the hot taps.
Obtain Hot Water
•If the heater is in regular use the pilot may
be left alight.
•If the heater is not going to be used for
long periods press the OFF button .
The gas supply to both the pilot and main
burner will now be shut off.
•Check through the pilot viewing window
that the pilot flame is extinguished.
Shut Down the Pilot
Fig. 3

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5
Part No. 5000893
To Alter the Settings
Fig. 4
Fig. 5
To Alter The Settings
Medway Super
The temperature selector fitted to this appliance gives
access to a wide range of outlet temperatures.
Because the temperature of the water in the mains
supply varies with the seasons, the selector can be
used to compensate for this and the effect it has upon
the temperature of the water delivered to the hot taps.
In hard water areas, temperatures above 60 °C
encourage rapid scale formation and the selector
should be used to keep the water below this
temperature.
By turning the selector between '+' and '-', you can
draw water from the hot taps that ranges from very hot
to hand warm, however, when using a shower supplied
with water from this appliance, the selector should be
set in a high position and the shower mixer itself be
used to achieve a comfortable temperature.This
ensures that the control of the shower temperature is
at the point of use, and that the selector could not
accidentally be turned up, causing discomfort to the
shower user.
Thames
This appliance has a temperature selector with the
widest adjustment range of any Main Instantaneous
Water Heater.The actual temperature selected in the
lower part of the range will be subjected to the effect of
seasonal temperature variations in the mains supply.
This means that the lowest setting will give an
obviously lower temperature in winter than in the
summer.
The appliance has an integral thermostat which
automatically comes into operation to guard against
the selection of excessively high temperatures.There
are two benefits here, the first being safety, the second
is hard water scale. In hard water areas, temperatures
above 60 °C encourage rapid scale formation and the
thermostat helps to avoid this.
By turning the selector between ' 5 ' and ' 1 ' , you can
draw water from the hot taps that ranges from very hot
to hand warm, however when using a shower supplied
with water from this appliance, the selector should be
set in a high position and the shower mixer itself be
used to achieve a comfortable temperature.This
ensures that the control of the shower temperature is
at the point of use, and that the selector could not
accidentally be turned up, causing discomfort to the
shower user.

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6Part No. 5000893
Care of your Appliance
This is the end of the User Instructions,
Page 7 onwards are for the Installers use only.
Care of Your Appliance
Servicing
As with all gas appliances, to ensure long life and safe, trouble free operation, your appliance must be inspected and
serviced at regular intervals by a competent person.
This should include a check to ensure continued clearance of combustion products and that there is no excessive
build up of scale on the heat exchanger in hard water areas.
The frequency of servicing will depend upon the particular installation conditions and usage but in general, once per
year should be adequate.
If service or spare parts are required, always quote the Appliance Identification Number and G.C.Number shown on
the Identification Badge.
The Identification Badge is brightly coloured and located underneath the controls tray at the front of the appliance
and will be visible after removal of the bottom cover.
Cleaning
The outer casing is stoved enamel and should be cleaned with warm, soapy water. DO NOT USE ABRASIVE
POWDERS SINCE THEY WILL SCRATCH THE ENAMEL SURFACE.
Frost Precaution
In frosty weather the pilot should be left alight. If the house is to be unoccupied for several days the heater should
be drained. Place a suitable receptacle below the appliance.
IMPORTANT
Check that the water service cock is fitted
correctly.The arrow on the service cock must
point towards the appliance.
If it points the other way DO NOT attempt to
drain the appliance and contact your Installer.
1. Turn OFF the gas at the gas service cock - A.
2. Turn OFF the water at the water service cock
- B.
3. Turn ON a domestic hot water tap to release
the pressure - C.
4. Remove the drain screw in the water service
cock , drain the appliance and refit the drain
screw - D.
5. Turn OFF the domestic hot water tap - E.
Fig. 6

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7
Part No. 5000893
1. Dimensions, Clearances & Product Specification
Dimensions, Clearances & Product Specification
Minimum Clearances
For ease of servicing, allow as much clearance as possible below the appliance.
If the appliance is to be installed in a cupboard, DO NOT USE THE CUPBOARD FOR STORAGE.
Mersey Super
Medway Super
Thames
Fig. 7
Note: All models - the data
badge will be visible after
removing the outer case.The
identification badge will be
visible after removing the
bottom cover.
Clearance for All Appliances:
Above: 60mm (from case)
Below: 75mm
Sides: 5mm (each)
Front: A clearance of 220mm is
required in front of the appliance
for access during servicing.The
front clearance can be reduced
to 10mm providing the
door/cover installed can be
removed to expose the entire
case front.

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8Part No. 5000893Dimensions, Clearances & Product Specification
Models
Mersey Super Medway Super Thames
Output kW 22.7 23.3 23.3
Input kW 30.3 30.3 30.3
Gas rate m∆/h 2.91 2.91 2.91
Burner Pressure** mbar 12.5 12.5 12.5
Burner Injector Size mm 1.2 1.2 1.2
Pilot Injector Size mm 0.27 0.27 0.27
Appliance Weight
Installed with Water kg 18.6 18.6 18.5
Water Capacity litre 0.75 0.75 0.75
Flow Rate l/min 6.5 (at 50 °C rise)
Maximum Pressure Head bar 13
Minimum Pressure
Head Requirement at
Water Heater bar 1 (Under Flow Conditions)
Connections - Gas mm 15 (Copper Tail)
- Water mm 15 (Compression)
Telescopic Flue Kits mm (in) 100 - 150 (4 - 6) Sales Code 31/10321
150 - 230 (6 - 9) Sales Code 31/10322
230 - 380 (9 - 15) Sales Code 31/10323
380 - 610 (15 - 24) Sales Code 31/10324
SeDuct Flue Kit Sales Code 31/12968
Finish White stoved paint with contrasting chassis
Classifications CAT 1 2H
C11, C21,
CE Pin No. 87AP121 87AP125 87AP124
Notes:
* Additional external pipework and fittings may affect the resistance and must be taken into account on
installation.
** The nominal burner pressure should be 12.5 mbar and will only be obtained if the appliance inlet pressure
is correct at 20 mbar even when the appliance is running at full heat input.The meter should be capable of
passing 3 m∆/h of natural gas plus the requirements of any other gas appliances.See also Section 3.2, page
12.
Conversions: kW to Btu/h = kW x 3412.14, m∆/h to ft∆/h = m∆/h x 35.31, mbar to in wg = mbar x 0.4
Product Specification
Heat Input figures are
quoted as gross.

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9
Part No. 5000893
2. Installation Requirements
•Codes of Practice
The appliance is suitable only for installation in GB and
IE and should be installed in accordance with the rules
in force. In GB, the installation must be carried out by
a CORGI Registered Installer. It must be carried out in
accordance with the relevant requirements of the:
•Gas Safety (Installation & Use) Regulations.
•The appropriate Building Regulations either The
Building Regulations, The Building Regulations
(Scotland), Building Regulations (Northern Ireland).
•The Water Fittings Regulations or Water byelaws in
Scotland.
Where no specific instructions are given, reference
should be made to the relevant British Standard Codes
of Practice.
In IE, the installation must be carried out by a Competent
Person and installed in accordance with the current
edition of I.S. 813 "Domestic Gas Installations" and the
current Building Regulations.
•Health and Safety Information
Under the Consumer Protection Act 1987 and Section
6 of the Health and Safety at Work Act 1974, we are
required to provide information on substances
hazardous to health. Small quantities of adhesives and
sealants used in the product are cured and present no
known hazards.The following substances are also
present.
Important: Later products are fitted with heat exchangers
that have a painted coating (in place of lead/tin) and
present no known hazards.
Insulation and Seals
Material - Man Made Mineral Fibre.
Description - Boards, Ropes, Gaskets.
Known Hazards - Some people can suffer reddening and
itching of the skin.Fibre entry into the eye will cause foreign
body irritation which can cause severe irritation to people
wearing contact lenses. Irritation to respiratory tract.
Precautions - Dust goggles will protect eyes.People with a
history of skin complaints may be particularly susceptible to
irritation. High dust levels are only likely to arise following
harsh abrasion. In general, normal handling and use will
not present high risk, follow good hygiene practices, wash
hands before, touching eyes, consuming food, drinking or
using the toilet.
First Aid - Medical attention must be sought following eye
contact or prolonged reddening of the skin.
Heat Exchanger
Material - Copper with lead/tin coating.
Description - Finned copper tube.
Known Hazards - Inhalation or ingestion of lead dust or
fumes may cause headache and nausea.
Precautions - Unused heat exchangers present minimal
Installation Requirements
risk to health other than normal hygiene practices would
demand regarding washing before eating etc. Deposits
found on or below a heat exchanger that has been in use
could contain lead oxide. Avoid inhalation by using a
vacuum cleaner in conjunction with other cleaning tools
when servicing the boiler.
•Energy Cut-Off Device
This appliance contains an Energy Cut-Off Device that
will shut down the gas supply to the appliance if the water
in the heat exchanger exceeds the anticipated
temperature.
•Under Draining Board Installations
This appliance can be installed under a draining board,
a kit (Sales Code 22/18276) is available that contains
connection bends and a sheet showing recommended
pipework layouts.
•Ventilation
It is not necessary to have a purpose provided air vent in
the room or internal space in which the Water Heater is
installed. If the Water Heater is to be installed in a
cupboard or compartment, permanent air vents are not
required. Detail recommendations for air supply are given
in BS 5440:2.
•Installation
IMPORTANT: The area of wall covered by the appliance
must be flat.
The clearances required around the Flue Terminal are
shown on the Flue Template supplied with the Terminal
Pack.
The appliance must be fitted on an external wall to allow
the Flue Terminal to pass directly through the wall to the
outside air.
The Water Heater is suitable for installation against a
combustible wall e.g. wood cladding, provided the flue
duct is not closer than 25mm to combustible material. A
non-combustible sleeve should be installed to surround
the flue duct to provide a 25mm annular space. Further
guidence is given in BS5440:1
If the water heater is to be fitted into a building of
timber frame construction then reference must be
made to the current edition of Institution of Gas Engineers
Publication IGE/UP/7/ (Gas Installation in Timber Framed
Housing).
If the appliance is to be installed into a ‘‘SEDUCT’’ the
minimum duct required is 228 mm (9 in.) deep, 349 mm
(15fiin.) wide.
This appliance may take the place of an existing
appliance and will mount onto the original flue terminal
of any of the following: AVON, BRISTOL, MEDINA,
MEDINA D/L, MEDWAY, MERSEY, SEVERN 3,
SEVERN 4, SEVERN 5 and TRENT.

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10 Part No. 5000893Installation Requirements
Fig. 8
•Siting the Flue Terminal
The following guidelines indicate the general
requirements for siting balanced flue terminals.
For GB recommendations are given in BS 5440 Pt. 1.
For IE recommendations are given in the current
edition of I.S. 813 "Domestic Gas Installations".
The terminal must be positioned such that the
combustion products can disperse freely at all times.
In certain weather conditions a terminal may steam and
positions where this could cause a nuisance should be
avoided.
If a terminal is less than 2m above a balcony, above
ground, or above a flat roof to which people have
access, then a suitable terminal guard must be fitted.A
terminal guard is available (Part No. 205792), this
should be fitted centrally about the terminal.
If the terminal discharges onto a pathway or
passageway, check that the combustion products will
not cause a nuisance and that the terminal will not
obstruct the passageway.
If the flue terminal is fitted within 1 metre of a plastic
gutter, within 500 mm of a painted eave or a painted
gutter, an aluminium shield of at least 1 metre long,
should be fitted to the underside of the gutter or painted
surface. An air space of 5 mm should be left between
shield and gutter.
IMPORTANT: It is absolutely ESSENTIAL, to ensure
that products of combustion discharging from the
terminal cannot re-enter the building, or any other
adjacent building, through ventilators, windows, doors,
natural air infiltration, or forced ventilation/air
conditioning. If products of combustion are found to be
re-entering any building, the appliance MUST be
turned OFF IMMEDIATELY.
The distance from a natural draught appliance terminal installed parallel to
a boundary may not be less than 600 mm in accordance with the diagram
below.
Terminal
Assembly
Property Boundary Line
Natural Draught
600 min.
Top View
FLU0006A
N
I
I
G
L
F
M
I
AAF
H
J,K
D,E
H
Likely flue positions requiring
a flue terminal guard
B
C
FLU0001A
Natural Draught Balanced Flue
AaDirectly below an opening, air brick,
opening windows, etc.
BaAbove an opening, air brick, opening window, etc.
CaHorizontally to an opening, air brick,
opening window, etc.
DBelow gutters, soil pipes or drain pipes.
EBelow eaves.
FBelow balconies or car port roof.
GFrom a vertical drain pipe or soil pipe.
HFrom an internal or external corner.
IAbove ground, roof or balcony level.
JFrom a surface facing a terminal.
KFrom a terminal facing the terminal.
LFrom an opening in a carport (e.g. door, window)
into the dwelling.
MVertically from a terminal on the same wall.
NHorizontally from a terminal on the same wall.
Terminal Position with Minimum Distance (mm)
For IE, refer to I.S. 813 "Domestic Gas Installation".
1500
300
600
300
300
600
300
600
300
600
600
1200
1500
300
aIn addition, the terminal should not be nearer than 300 mm to an opening
in the building fabric formed for the purpose of accommodating a built-in
element such as a window frame. See BS 5440 Pt. 1.

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11
Part No. 5000893 Installation
Fig. 11
3. Installation
3.1 Location
1. If the appliance is to be fixed to a suitable
existing terminal first isolate and remove
the old appliance.Leave the flue terminal
in place. Retain the fixing nuts and
washers. Make good any damage to the
brickwork or plaster around the terminal.
Cut off the existing pipework at a
convenient point below the appliance.
Important: Refer to the template
supplied with the flue for the positions of
the new water inlet, water outlet and gas
pipes.
2. If installing a new flue terminal, guidance
is given on the template sheet supplied
with the terminal pack.
Note: Where the appliance is to be
installed into a SEDUCT the minimum
duct required is 228mm (9in) deep,
349mm (15fiin) wide.
3. Where the building regulations require it,
a flue terminal guard should be fitted
symmetrically around the outer part of
the flue terminal.
4. Unpack the water heater. Find the bags
of accessories before discarding the
packaging.
5. Slide off the bottom cover then remove
the three screws securing the outer case
and carefully lift it off.
6. Use the self adhesive discs supplied to
cover the unwanted fixing holes in the
back of the new appliance as shown.
Fig. 9
Fig. 10

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MY99004A
Securing Nuts &
Washers
Flue
Terminal
Sealing
Strip
Rear View
Of Water
Heater
Sealing
Strip
12 Part No. 5000893Installation
Fig. 13
7. Fit the flue terminal sealing strip (packed
separately in the carton) into the recess
around the flue aperture in the back of
the appliance.
8. Lift the appliance into position, locating
the flue outlet into the circular duct on the
flue terminal.
9. Secure with the appropriate nuts and
washers.
3.2 Gas Connection
The meter and supply pipes must be capable
of delivering this quantity of gas in addition to
the demand from any other appliances in the
house and must be governed at the meter.
The pipe diameter required will depend on
the distance from the gas meter and the
number of bends used.
The gas installation should be in accordance
with the relevant standards. In GB this is BS
6891. In IE this is the current edition of I.S.
813 "Domestic Gas Installations".
1. Assemble the filter, ‘O’ring and inlet tail
to the gas inlet.
2. Depending on whether the main supply
pipe is to be routed vertically or
horizontally to the appliance, connect the
gas service cock (stamped 'GAS') either
directly to the gas inlet tail or within the
supply pipe.
Note: The service cock should be as
close to the appliance as possible and
the ON/OFF screw in an accessible
position.
3. Ensure that the gas supply is isolated.
4. Connect to the gas supply.
5. Turn the gas supply on and purge
according to;in GB BS 6891 and in IE the
current edition of I.S.813 “Domestic Gas
Installations”.
IMPORTANT: DO NOT TRY TO LIGHT
THE APPLIANCE AT THIS STAGE. TO
ALLOW THE MAIN BURNER TO
IGNITE WITHOUT THE OUTER CASE
SECURED IN POSITION IS A HAZARD.
Fig. 12

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13
Part No. 5000893 Installation
Fig. 14
Fig. 15
3.3 Water Connections
IMPORTANT: Flush out all foreign matter
from the supply pipe before connecting to the
service cock.
1. Assemble the filter, olive and inlet tail to
the water inlet. Note: The inlet tail need
not be used as a vertical supply can be
routed directly onto the water inlet.
2. Depending on whether the main supply
pipe is to be routed vertically or
horizontally to the appliance, connect the
water service cock either directly to the
water inlet tail or within the supply pipe.
Note: The service cock should be as
close to the appliance as possible and
the ON/OFF screw in an accessible
position.
3. Ensure that the mains water supply is
turned OFF.
IMPORTANT: When routing the supply pipe
to the appliance, ensure that it can be
lowered by approx. 25 mm to allow for
disconnection when servicing.
4. Connect the hot water supply pipes to the
water outlet - 15 mm compression.
5. Turn ON the mains water supply, turn ON
the water service cock and open all the
hot water outlets to allow water to flow.
Purge the air from the system by closing
the hot water outlets starting with the
lowest level and ending with the outlet at
the highest level.
6. Check for water leaks and remedy if
found.
IMPORTANT: DO NOT TRY TO
LIGHT THE APPLIANCE AT THIS
STAGE.
3.4 Lint Filter
This appliance has a lint filter fitted around
the base of the pilot tube.
Ensure that the filter gauze is located inside
both end caps and that the complete
assembly is correctly seated over the union
nut at the base of the pilot tube.

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14 Part No. 5000893
4. Commissioning
Complete the Installation
Fig. 16
WARNING:
The outer case of this appliance is not
merely a cosmetic device. It is a
functioning component in the air supply
to the burner and MUST BE replaced
with great care NOW, before any
attempt is made to light the burners.
TO ALLOW THE MAIN BURNER TO
IGNITE WITHOUT THE CASE IN
POSITION IS A HAZARD.
1. Refit the outer case ensuring it is
correctly seated then secure (3 screws).
Ensure that the temperature selector
control rod (if fitted) is set at its maximum
setting.
2. Ensure that the gas and water supplies
are turned ON.
3. Ensure that all hot water outlets are
closed.
4. Remove the screw and sealing ring from
the burner pressure test point and attach
a pressure gauge.
5. Fully depress and hold the ON button
and repeatedly press and release the
IGN button until the pilot is lit.The pilot
flame can be observed through the pilot
viewing window.
6. Hold the ON button in for a further
10 seconds after the pilot is lit, then
release. If the pilot goes out, repeat the
lighting operation keeping the ON button
depressed a little longer.
7. Test for gas soundness using a suitable
leak detection fluid on all external gas
joints.
8. Open a hot water outlet and the burner
will ignite.Allow the water to run for a few
minutes then check the burner pressure -
it should be 12.5 mbar (5 in w.g.), if the
pressure is not correct see the FAULT
FINDING section.
Fig. 17
Fig. 18

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15
Part No. 5000893 Commissioning
Fig. 20
Note: Check the gas rate check, the gas
consumption after 3 minutes running should
be approximately 2.91 m3/hr (102.8 ft3/hr).
9. Turn the temperature selector spindle (if
fitted) from right to left , there will be a
noticeable change in the outlet
temperature.Turn the rod back to the
right (maximum).
10. Turn OFF the hot water outlet and press
the OFF button on the appliance.
Remove the pressure gauge and replace
the screw and sealing ring.
11. Relight the pilot.Turn ON a hot water
outlet and check for gas soundness at
the pressure test point.
12. Turn OFF the hot water outlet. Slide the
bottom cover onto the appliance. Ensure
that the temperature selector spindle is
aligned with the selector knob, push the
bottom cover and with slight adjustment
the selector will positively locate on the
spindle.
•Explain to the user how to operate the
appliance.
•Show the user the position of the
Identification Badge.
•Advise the User that to ensure long life
and safe, trouble free operation, the
appliance must be inspected and
serviced at regular intervals by a
competent person.
•Leave these Instructions with the User
future use.
Fig. 19

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16 Part No. 5000893Servicing
5. Servicing
Note: In hard water areas, scale may build
up on the push rod, seals and on the
underside of the diaphragm housing. They
may require regular descaling and
regreasing.
Operate the appliance noting any faults in the
component units.
Carry out the servicing procedure then
correct any other faults by reference to
'Replacement of Parts', in which section you
will find details of how to dismantle and
reassemble the following detailed
components.
Check that the burner ignition is smooth and
quiet when a hot tap is opened. The burner
ignition has been factory set and should not
need adjustment. However, if adjustment is
required a slow ignition screw is fitted to the
appliance and is situated above the cap
screw in the water governor body (Fig.23).
The screw is factory set 2 full turns out (anti-
clockwise) from the fully in position. Turning
the screw clockwise delays the ignition, anti-
clockwise advances the ignition.
WARNING:
NEVER OPERATE THIS APPLIANCE
WITH THE OUTER CASE REMOVED.
1. Check the piezo unit, flame safety device
and thermocouple, clean or replace if
necessary.
2. Remove the burner assembly and clean
using a soft brush or vacuum cleaner.
3. Check the pilot injector and clean or
replace if necessary. Also clean the lint
filter.
4. Remove the water governor assembly
complete with push rod. Replace the
seals if necessary. Descale and regrease
the push rod, washers and diaphragm
housing using Dow Corning 111 silicone
grease.
5. Check for water and gas soundness.
Replace 'O' rings, sealing washers and
gaskets where required.
6. Clean any deposits off the heating unit by
washing or brushing.Descale the heating
unit if required.
Fig. 21
Fig. 22
Fig. 23

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17
Part No. 5000893 Replacement Of Parts
6. Replacement of Parts
1. When refilling, if water has been
drained from the system, turn on
all hot taps to purge air from the
system.Turn them off in
sequence starting with the tap
at the lowest level.
2. When replacing parts, re-
assemble in reverse order
unless otherwise stated.
This chart shows the steps to be
taken in order access a specific part
or perform a particular function. Use
this chart in conjunction with the
detailed procedures on the following
pages.
Start
Descale Heating Unit - 6.17
Remove Piezo Unit - 6.1
General Access/Main Burner -
6.2
Thermocouple & Electrode - 6.3
Pilot Injector - 6.4
Flame Failure Device - 6.5
Pilot Viewing Glass
& Seal - 6.6
Energy Cut-Off Device - 6.7
Pressure Relief Valve - 6.9
Remove Heating Unit - 6.15/6.16
Water Governor Venturi - 6.12
Descale & Regrease
Water Governor &
Push Rod - 6.10 Automatic Valve & Burner
Manifold Complete - 6.11
Thermostat Assembly - 6.13 Throttle Assembly - 6.14
Descale & Regrease
Mersey/Medway
Thames
IMPORTANT:THE FOLLOWING WORK SHOULD ONLY BE CARRIED OUT BY A COMPETENT PERSON.
Drain the Appliance - 6.8

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18 Part No. 5000893
6.1 Piezo Unit
It will NOT be necessary to remove the outer
case.
a. Slide out the bottom cover.
b. Disengage the electrode lead from the
piezo unit.
c. Remove or loosen and pull aside the
spark button retainer, taking care not to
lose the shakeproof washer.
d. Pull off the button and unscrew (anti-
clockwise) the piezo from its housing.
Note: When refitting the bottom cover,
ensure the temperature selector spindle (if
fitted) is aligned with the selector. Push the
bottom cover and with slight adjustment, the
selector will positively locate on the spindle.
6.2 General Access/Main Burner
a. Turn OFF the gas and water supplies at
the service cocks.
b. Slide out the bottom cover.
c. Remove the 3 fixing screws and pull off
the outer case.
d. Remove 4 fixing screws from the burner
assembly (2 each side).
e. Remove 2 screws securing the front to
the heating unit.
f. Pull the burner assembly slightly
forwards to clear the injectors, then pull
apart and withdraw taking care not to
snag the pilot assembly.
Note: If required, the burner assembly can
be dismantled and the burner bars replaced
individually. On re-assembly ensure that the
burner inlets locate in the 14 holes.
Note: On re-assembly of the burner
assembly take care not to snag the pilot
assembly. Ensure the front face of the
assembly has located on the two studs on
the heating unit. Re-fit the bottom cover as
outlined in Section 6.1.
Fig. 24
Fig. 25
Fig. 26
Replacement Of Parts

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19
Part No. 5000893
6.3 Thermocouple & Spark
Electrode
a. Gain general access - See 6.2.
b. Disconnect the nut securing the
thermocouple to the interrupter at the
chassis base.
c. Disconnect the electrode lead from the
back of the piezo unit, pull the lead up
through the grommet and remove.
d. Remove the fixing screw and bracket
then lower the spark electrode.
e. On re-assembly, ensure that the pilot
tube bends towards the rear of the
appliance. (The thermocouple will be
vertical and nearest the burner manifold).
The thermocouple connection need only
be finger tight and a ⁄turn.
6.4 Pilot Injector
a. Gain general access - See 6.2.
b. Lift up the lint filter, disconnect the union
nut and carefully lift up the pilot tube
taking care not to lose the pilot injector.
c. On re-assembly ensure the pilot injector
is correctly seated (taper side down) and
that the lint filter is correctly assembled
and located on the union nut.
Note: The lint filter can be cleaned if
required.
6.5 Flame Safety Device
a. Gain general access - See 6.2.
b. Disengage the electrode lead from the
piezo unit.
c. Release the thermocouple from the back
of the flame safety device.
d. Release the union nuts above and below
the flame safety device.
e. Release the union nut securing the pilot
transfer tube to the flame safety device.
f. Remove the 3 screws securing the flame
safety device to the chassis base and
carefully withdraw the unit.
g. Re-assemble in reverse order.The
thermocouple connection need only be
finger tight and a ⁄turn.
Fig. 27
Fig. 28
Fig. 29
Replacement Of Parts

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20 Part No. 5000893
h. Test for gas soundness as follows:-
- Ensure the water service cock is in the
OFF position.This will ensure water
cannot flow and open the automatic
valve.
- Turn ON the gas, purge and light the
pilot, this will pressurise the burner
supply pipe.
- Test the gas supply to flame safety
device and burner supply pipe above the
flame safety device for gas soundness
using leak detection fluid.
j. Re-assemble remaining parts and
ensure the water service cock is in the
ON position.
6.6 Pilot Viewing Glass & Seal
a. Complete steps a., b. and c. of Section
6.2.
b. The viewing glass and seal are fixed to
the inside of the outer case by 2 metal
tabs. Bend back the tabs and remove
the glass and seal. Secure the new
glass and seal to the outer case by
bending over the 2 spare straight tabs.
6.7 Energy Cut-Off Device
a. Gain general access - See 6.2.
b. Disconnect the energy cut-off leads
from the interrupter located on the
underside of the chassis.
c. Remove the 2 screws securing the
energy cut-off device to the heating unit
(located top front left).
d. Pull the leads complete with grommets
up through the chassis base.
e. Fit the new energy cut-off device which
comes complete with grommets.
Replacement Of Parts
Fig. 30
Fig. 31
Fig. 32