Potterton Combi 80 Installation and maintenance instructions

Combi 80 Installation & Service Instructions
About the Boiler See inside cover for models covered by these instructions.
This is a wall mounted, fanned, room sealed combination boiler.
This boiler is for use with Natural Gas (G20) Only at 20 mbar and for use in GB & IE.
About Safety The Gas Safety (Installation and Use) Regulations 1998.
‘‘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.

Contents - Page 2
Introduction................................................................. 3
1. Installation Requirements.......................................... 5
General Information.............................................. 5
1.1 Gas Supply........................................................... 5
1.2 Electrical Supply................................................... 5
1.3 Location of Boiler.................................................. 7
1.4 Air Supply............................................................. 7
1.5 Flue Systems & Termibal Location....................... 7
1.6 Installation to an Existing System......................... 9
1.7 Hard Water Areas................................................. 9
1.8 System Requirements.......................................... 9
2. Boiler Installation.......................................................13
2.1 Unpacking ...........................................................13
2.2 Gas Connection...................................................13
2.3 D.H.W Supply......................................................13
2.4 C.H. Supply.........................................................14
2.5 Pressure Relief Valve..........................................14
2.6 Wiring the Appliance ...........................................15
3. Commissioning..........................................................16
3.1 Electrical Installation............................................16
3.2 Gas Installation....................................................16
3.3 Initial Lighting ......................................................17
3.4 Gas Pressure Adjustment ...................................18
3.5 Products of Combustion Measurement...............18
3.6 D.H.W Flow Rate ................................................19
3.7 Central Heating ...................................................19
3.8 Appliance Protection Devices..............................19
3.9 Complete the Installation.....................................20
4. Servicing & Routine Maintenance............................21
4.1 Remove the White Front Case............................22
4.2 Remove Base Panel............................................22
4.3 Remove the Air Box Covers................................22
4.4 Remove the Fan Assembly.................................22
4.5 Remove the Flue Hood .......................................22
4.6 Remove the Combust. Cham. Front Panel .........22
4.7 To Inspect and Clean the Boiler..........................22
4.8 To Remove the Burner........................................24
4.9 Gas Pressure Adjustment ...................................24
4.10 The Central Heating Sealed System...................24
4.11 Other Components..............................................24
5. Replacement of Parts...............................................26
5.1 Central Heating Overheat Thermostat...............27
5.2 Dom. H/Water Limit & Frost Thermostat............27
5.3 Sensor and Ignition Electrode............................27
5.4 Sensor and Ignition Leads .................................27
5.5 Burner ................................................................27
5.6 Injectors..............................................................27
5.7 Gas Valve...........................................................28
5.8 Modulating Valve................................................28
5.9 First Solenoid Valve...........................................28
5.1 Second Solenoid Valve......................................28
5.11 Case Seals.........................................................28
5.12 Central Heating and Boiler Switch .....................30
5.13 Electronic Control Boards ..................................30
5.14 Air Pressure Switch............................................31
5.15 Fan.....................................................................31
5.16 Fan Seals...........................................................31
5.17 Temperature Sensor D.H.W and C.H................31
5.18 Pressure Gauge.................................................31
5.19 Water Flow Switch D.H.W..................................32
5.20 Microswitch (D.H.W Flow Switch)......................32
5.21 Pump..................................................................32
5.22 Diverter Valve.....................................................33
5.23 Expansion Vessel C.H.......................................34
5.24 Expansion Vessel D.H.W...................................35
5.25 Heat Exchanger .................................................35
5.26 Automatic Air Vent .............................................36
5.27 Pressure Relief Valve.........................................36
5.28 Transformer Assembly.......................................37
5.29 Sight Glass with Securing Frame.......................37
6. Fault Finding.............................................................38
7. Electrical Layouts.....................................................39
Control Flow Sequence..............................................40
Functional Flow ..........................................................40
Electrical Diagram ......................................................41
8. Product Specification...............................................42
9. Optional Extras.........................................................43
10. Short List of Spares .................................................46
The model covered by these instructions is:-
Combi 80 G.C. No. 47-393-03

Introduction Page 3
SAFETY, PERFORMANCE & QUALITY
This appliance has been assessed by a Government
appointed Notified Body and shown to meet the '‘ssential
Requirements’ of the European Gas Appliance Directive
The Directive lays down requirements for the safety and
efficiency of the appliance, together with its design,
construction, and use of materials.
It also requires the production process to be covered by an
approved and monitored system of quality assurance.
About the Boiler
•The Combi 80 adjusts automatically to provide central
heating outputs between 24 kW (81,880 Btu/h) and 10.4
kW (35,480 Btu/h) to suit the system requirements.
•The boiler is designed for use with fully pumped sealed
system only.
•It is supplied fully tested and assembled with a
circulating pump, diverter valve, pressure gauge,
pressure relief valve, and expansion vessels.
IMPORTANT
This appliance has been certified for safety. It is therefore
important that no external control device (e.g. flue dampers,
economisers, etc.) be directly connected to the appliance
unless covered by these Installation & Service Instructions or
otherwise recommended in writing.
Any direct conenction of a control device not approved by
Potterton Limited, could invalidate the CE Certification and
normal appliance warranty.
•The appliance has two completely separate heating
systems embedded into a copper heat exchanger. Both
systems are completely independent.
Central Heating:A central heating switch controls the
choice of service between central heating and hot water
only. The boiler water flow system is shown in Fig. 1.
With the central heating switch set to 'Off' and the boiler
switch set to 'On', the combination boiler fires only when
hot water is drawn off.
Codes of Practice
•The boiler must be installed in accordance with: The
Gas Safety (Installation & Use) Regulations 1998 and
the current issue of:-
The Building Regulations, Building Standards (Scotland)
Regulations, Local Building Regulations, Model & Local
Water Undertaking Bye Laws. I.E.E Regulations, Health
and Safety Document No.635. (The Electricity at Work
Regulations 1989), BS. 6891, BS. 6798, BS. 5449, BS.
5546, BS. 5440:1, BS. 5440:2, BS 7593 & BG. DM2.
•Samples of the Combi 80 combination boiler have been
examined by Gastec, a Netherlands Notified Body. The
range is certified to comply with the essential
requirements of the Efficiency Directive 92/42/EEC, the
Gas Appliance Directive 90/396/EEC, the Low Voltage
Directive 72/23/EEC and shows compliance with the
Electro Magnetic Compatibility Directive 89/336/EEC
and are therefore permitted to carry the CE Mark.
•The appliance has been tested and approved by the
WRc as meeting the requirements of G3 and L of the
Building regulations and water Bylaws Scheme -
Approved Products.
With the central heating switch set to 'Timed' the boiler
will operate the central heating for the time periods set
on the optional internal or externally mounted
timeclocks. If 'Constant' is selected the boiler will
operate continuously.
The central heating is supplied at a pre-set temperature
determined by the central heating thermostat setting.
If domestic hot water is drawn off while the central
heating is running the combination boiler will
automatically transfer the boiler heat output to the
domestic hot water supply.
Domestic Hot Water:Domestic hot water has priority
over the central heating system and is generated
instantaneously within the appliance.
At the minimum hot water draw-off rate the maximum
temperature is limited to 70 °C by the modulating gas
control.
•Data plates are positioned on the front of the air box
door and a boiler serial badge is on the underside of the
air box. A duplicate serial badge is positioned on the
underside of the case base for customer reference.

Introduction - Page 4
Delivery
•The boiler is delivered in two packages (1) the boiler and
(2) the flue assembly.
Health and Safety Information for the Installer and
Service Engineer
•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.
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 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
appliance.
Central Heating Waterways
Material - Water corrosion inhibitor
Description - Low concentration of inhibitor in residual water.
Known Hazards - Irritant to eyes.
Precautions - Avoid contact with eyes.
First Aid - Eye contact, flush with plenty of running water
immediately. Seek medical attention.

1. Installation Requirements - Page 5
General Information
•Both the user and the manufacturer rely heavily on the
installer, whose job it is to install the combination boiler,
and connect it to a correctly designed heating system.
Acquaint yourself with the British Standards concerning
installation requirements.
It is recommended that tools suitable for brass fittings
are used, and have a capability to accommodate
hexagon sizes up to 50 mm.
Please read the information on Inhibitors - Page 12.
Manufacturers instructions must not be taken in any way
as over-riding statutory obligations.
1.1 Gas Supply
•The local Gas Region should be consulted, at the
installation planning stage, in order to establish the
availability of an adequate supply of gas.
•An existing service pipe must NOT be used without prior
consultation with the Local Gas Region.
•A gas meter can only be connected by the Local Gas
Region, or by a Local Gas Region Contractor.
•An existing meter should be checked, preferably by the
Gas Region, to ensure the meter is adequate to deal
with the rate of gas supply required.
•Installation pipes should be fitted in accordance with BS
6891.
•Pipework from the meter to the combination boiler must
be of an adequate size.
•Do NOT use pipes of a smaller size than the
combination boiler inlet gas connection (15mm).
•The complete installation must be tested for gas
soundness and purged as described in BS 6891.
1.2 Electrical Supply
•Wiring external to the appliance MUST be in accordance
with the current I.E.E. Regulations for Electrical
Installations, and any Local Regulations which apply.
The combination boiler is supplied for 230 Volts ~ 50 Hz,
Single Phase. To protect the appliance it is essential
that the electrical supply is fused at 3 A rating.
•THIS APPLIANCE MUST BE EARTHED.
•The method of connection to the mains electricity supply
must provide means of completely isolating the electrical
supply to the combination boiler and its ancillary
controls.
•The appliance is designed to be the wiring centre for the
installation, therefore no additional live supplies are
required from either timers or room thermostats.
•Isolation is preferably by the use of a fused three-pin
plug and unswitched shuttered socket-outlet, both
complying with the requirements of BS 1363. OR a 3 A
fused double-pole switch, having a 3mm contact
separation on both poles can be used. It is important
that the point of connection to the mains should be
readily accessible and adjacent to the combination
boiler.

Installation Requirements - Page 6
Fig 3

Installation Requirements - Page 7
1.3 Location Of Boiler
•In siting the combination boiler, the following limitations,
MUST be observed:
a) The position selected for installation should be
within the building, unless otherwise protected by a
suitable enclosure. It must allow adequate space for
installation, servicing and air circulation around the
appliance.
b) This position MUST also allow the chosen flue
termination to be made correctly. The boiler must be
installed on a flat vertical wall which is capable of
supporting the weight of the appliance and any
ancillary equipment.
•The appliance may be installed on a combustible wall,
subject to the requirements of the Local Authorities and
Building Regulations.
•IMPORTANT NOTICE: If the combination boiler is to
be fitted in a timber framed building it should be fitted in
accordance with the British Gas publication 'Guide for
Gas Installations in Timber Frame Housing'. (Reference
DM2). If in doubt advice must be sought from the Local
Gas Region.
•The combination boiler 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 electrical provisions of
the Building Regulations applicable in Scotland, with
respect to the installation of the combination boiler in a
room or internal space containing a bath or shower.
•Where a room-sealed appliance is installed in a room
containing a bath or shower, any electrical switch or
appliance control, utilising mains electricity should be so
situated that it cannot be touched by a person using the
bath or shower.
•A compartment used to enclose the combination boiler
MUST be designed and constructed specifically for this
purpose. An existing cupboard, or compartment, may
be used provided it is modified accordingly. See Section
1.4 'Air Supply'.
•Where installation will be in an unusual location, special
procedures may be necessary. BS 6798 gives detailed
guidance on this aspect.
•Clearances around the Appliance - Fig. 4.
Side Clearance: For operation and servicing, 25 mm
each side.
Top Clearance: A minimum of 160 mm, but 300 mm is
preferred to allow removal of the central heating
expansion vessel, without removing the appliance from
the wall, if replacement is required.
Bottom Clearance: A bottom clearance of 220 mm is
required between the appliance and any surface.
Frontal Clearance: A minimum of 500 mm is required in
front of the appliance for access during servicing, the
front clearance can be reduced providing the door/cover
can be removed to expose the entire case front.
1.4 Air Supply
•Detailed recommendations for air supply are given in BS
5440:2. The following notes are intended for general
guidance: It is not necessary to have a purpose provided
air vent in the room or internal space in which the
combination boiler is installed. If the combination boiler is
to be installed in a cupboard or compartment, permanent
air vents are required (for cooling purposes) in the
cupboard/compartment, at both high and low levels. The
air vents must either communicate with a room/or be
direct to outside air.
Table 1. Air Supply
1.5 Flue Systems & Terminal Location
•The standard horizontal flue system is suitable for
installations up to 1092 mm, measured from the centre
line of the boiler outlet to the outside face of the wall. The
wall liner enclosed will accommodate thicknesses of 400
mm and can be cut to a minimum length of 76 mm.
•One metre flue extension kits are available to extend
horizontal flues to a maximum length of 3078 mm.
•90° In-line elbow kits and 135° In-line Bend kits are also
available for more flexible siting. Horizontal flues can be
set at 45° angles to the combination boiler, through 360°,
to the miniature terminal on the outside of the building.
•A Concentric Vertical flue system is available which
when used in conjunction with One metre flue
extension kits is suitable flue heights up to 3 metres to
terminate through a roof.
•A Twin tube Vertical flue system is also available for
flue heights up to 8025 mm when used in conjunction
with one metre twin tube extension kits.

Installation Requirements - Page 8
•135° Off-set kits are available for both concentric and
twin tube.
•A Pitched Roof Flashing kit and Flat Roof Flashing kit
are available for use with the vertical flue systems.
•If a horizontal flue is sited less than 2 metres above a
balcony, above ground, or above a flat roof to which
people have access, a suitable terminal guard must be
fitted. This serves two purposes, to protect the terminal
against damage or interference and to protect passers-
by.
Note: Where a flue terminal is installed less than 1
metre from a plastic, or painted gutter, or 500 mm from
painted eaves, an aluminium shield 1 metre long, should
be fitted to the underside of the gutter or painted
surface. A suitable wall plate should be fitted to the
painted wall surface of a mobile home.
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.
POSITION MIN. DISTANCE mm
ADIRECTLY BELOW AN OPENABLE
WINDOW, AIR VENT, OR ANY OTHER
VENTILATION OPENING 300
BBELOW GUTTER, DRAIN/SOIL PIPE 75
CBELOW EAVES 200
DBELOW A BALCONY/CARPORT ROOF 200
EFROM VERTICAL DRAIN PIPES AND
SOIL PIPES 75
FFROM INTERNAL OR EXTERNAL CORNERS 25
GABOVE ADJACENT GROUND OR BALCONY
LEVEL 300
HFROM A SURFACE FACING THE TERMINAL 600
IFACING TERMINALS 1200
JFROM OPENING (DOOR/WINDOW) IN
CARPORT INTO DWELLING 1200
KVERTICALLY FROM A TERMINAL ON THE
SAME WALL 1500
LHORIZONTALLY FROM A TERMINAL ON
THE SAME WALL 300
MADJACENT TO OPENING 300
NABOVE ROOF LEVEL (TO BASE OF TERMINAL) 300
PFROM ADJACENT WALL TO FLUE 210
QFROM INTERNAL CORNER TO FLUE 230
RBELOW EAVES OR BALCONY 600
SFROM FACING TERMINAL 1200

Installation Requirements - Page 9
1.6 Installation to an Existing Central Heating
System
•The appliance is designed to operate on a sealed
system only, therefore if the existing system is of the
open type it will have to be modified to comply with BS
6798.
•Before installing a new combination boiler to an existing
system flush out the old system with a recommended
descaling/flushing agent at least twice, see Inhibitors on
Page 12.
•Also check pipework and renew any corroded pipework
or fittings. Valve glands must be re-packed or replaced
wherever necessary and any defective controls
replaced.
1.7 Hard Water Areas
•If the area of installation is recognised as a hard water
area, (above 200 p.p.m.) it is essential that a suitable
water treatment device of an electronic, magnetic or
galvanic type be installed in the mains water supply.
Consult with the Local Water Company.
1.8 System Requirements
Before installing the boiler onto the system read the
section on Page 12 about Inhibitors.
Domestic Hot Water
•The domestic hot water system must be in accordance
with the relevant recommendations of BS 5546. Copper
tubing to BS 2871:1 is recommended for water carrying
pipework and MUST be used for pipework carrying
potable water. All capillary joints in the D.H.W pipework
must be joined with a lead free solder.
Central Heating
•This appliance has been specifically designed for
sealed systems only. Therefore the central heating
system should be in accordance with the relevant
recommendations given in BS 6798 and also, smallbore
and microbore systems BS 5449 Part 1.
•For correct operation the boilers require a by-pass.
A valved by-pass should be fitted and the flow reduced
to balance the system correctly. The length of the by-
pass pipework is not important.
Note: If the by-pass flow is reduced too much this will
cause the appliances to overheat and go to lockout.
•The installation should be designed to work with flow
temperatures of up to 90 °C. All components of the
system must be suitable for a maximum pressure of 3
bar (45 psi) and a temperature of 110 °C.
•The following components are incorporated within the
appliance.
a. Circulating pump.
b. Diverter valve.
c. Pressure Relief valve with a non-adjustable pre-set
lift pressure of 3 bar (45 psi).
d. Pressure gauge covering the range 0-4 bar (0-60
psi).
e. 10 litre expansion vessel with initial charge pressure
of 1.0 bar (14 psi).
f. Domestic Hot Water flow switch.
•The central heating output from the boiler can easily be
downrated if a lower temperature drop across the
system is prefered.
•Ancillary pipework, not forming part of the useful heating
surface, should be lagged to prevent heat loss and any
possible freezing, particularly where pipes run through
roof spaces and ventilated under-floor spaces.
•If the capacity of the central heating system should
exceed 100 litres, an additional vessel should be
installed on the return to the combination boiler from the
heating system. Guidance on vessel sizing is given in
Table 2 - Page 10.
•To allow the maximum central heating expansion
capacity in the boiler the pre-charge pressure in the
central heating expansion vessel must be marginally
greater than the initial (cold) system pressure at the
appliance (as shown on the appliance pressure gauge).
•Draining taps should be at least 1/2 in BSP nominal size
and be in accordance with BS 2879.
•External Controls
To obtain economical use of the appliance it is advisable
to fit external controls. The controls can take the form
of:-
a. Time clock (two internal options are available)
b. Room thermostat
c. Thermostatic radiator valves (TRV’s)
c. Zone valves
A combination of these controls will produce economical
and effective use of the heat generated by the boiler. It
is advisable to control the temperature of the main living
area with a room thermostat and other areas by TRV’s.

Installation Requirements - Page 10
Safety Valve Setting (bar) 3.0
Initial System Pressure (bar) 1.0 1.5
Fig 6 Total Water Content of System VESSEL VOLUME (L)
litres
25
50
75
100
125
150
175
200
225
250
275
300
325
350
375
400
425
450
475
500
litres
2.7
5.4
8.2
10.9
13.6
16.3
19.1
21.8
24.5
27.2
30.0
32.7
35.7
38.1
40.9
43.6
46.3
49.0
51.8
54.5
litres
3.9
7.8
11.7
15.6
19.5
23.4
27.3
31.2
35.1
39.0
42.9
46.8
50.7
54.6
58.5
62.4
66.3
70.2
74.1
78.0
For system volumes other than
those given above, multiply the
system volume by the factor across 0.109 0.156
Table 2. Expansion Vessel Requirements
Deduct from the value given in the table
the10 litre expansion vessel supplied.

Installation Requirements - Page 11
•Frost Protection
The appliance is fitted with an internal frost thermostat,
however this device is purely for the protection of the
appliance. If any other part of the central heating system
requires frost protection, an external frost thermostat
should be fitted.
•Mains Water Feed: Central Heating
A connection must be incorporated into the central
heating system to facilitate filling. There must be no
direct connection to the mains water supply, even
through a non-return valve, without the approval of the
Local Water Authority.
Permissible methods of filling
(1) Direct Method - Fig. 6
A detachable flexible hose is connected to a stop valve
fitted to an outlet on the service main. The other end of
the hose is connected to a second stop valve and a
double check valve. The double check valve is fitted to
an inlet connection on the central heating return pipe
under the appliance. The hose should be disconnected
after filling. Where the mains pressure is excessive a
pressure reducing valve shall be used to make filling
easier. The following fittings shall form a permanent part
of the system and shall be fitted in the order stated.
a. A stop valve complying with the requirements of BS
1010 Part 2, (the temporary hose from the draw off
tap shall be connected to this fitting).
b. Double check valve of an accepted type.
(2) Booster Pump Method
The system may be filled through a self contained unit
comprising a cistern, pressure booster pump and if
necessary, an automatic pressure-reducing valve or flow
restrictor.
The pressure booster pump must be capable of
pressurising the system to a minimum of 1.0 bar (14
p.s.i.) measured at the appliance.
The cistern should be supplied through a temporary
connection from a service pipe or cold water distributing
pipe. The unit may remain permanently connected to the
heating system to provide limited water make-up.
Provisions for make up water
Provision should be made for replacing water loss from
the system by re-pressurisation of the system.
Reference should be made to British Gas Publications
"Material and Installation Specifications for Domestic
Central Heating and Hot Water".
•Pump Performance Curve
The circulating pump fitted within the appliance should
be capable of satisfying most system requirements. For
central heating systems greater than 15 kW it may be
necessary to use a higher "design temperature drop
across system" to meet the system pump head
requirement. The design temperature drop should not
exceed 20 °C (36 °F). Fig. 7 indicates the amount of
pump head available for the system. The boiler
resistance is already taken into account in this curve.
How to Use Fig. 7.
Starting with the required SYSTEM HEATING LOAD,
draw a vertical line downwards so that it intersects the
chosen SYSTEM DESIGN TEMPERATURE DROP line,
normally this would be 11 °C (20 °F) although up to 17
°C (30 °F) can be used without increasing radiator sizes.
From this intersection point draw a horizontal line so that
it intersects the PUMP CURVE. From this intersection
draw a vertical line upwards.
The AVAILABLE PUMP HEAD can now be read from
the horizontal scale, and the corresponding FLOW
RATE from the vertical scale in the centre of the chart.
The system must be designed so that its hydraulic
resistance does not exceed the available head unless
an additional circulating pump is fitted.
If the designed flow rate through the boiler is less than
11.5 l/min, the boiler could be noisy and ultimately
overheat. See note on system by-pass in Section 1.8.
•Central Heating Range Rate
For most installations the boiler will automatically adjust
the central heating output to match your heating system
requirement.
Systems which have very low water content and a low
heating requirement may benefit by reducing the
maximum boiler output. This is achieved by rotation of
the adjustment knob, located on the electronic
modulation control board. (Fig. 19, Page 30).
The boiler central heating output can be adjusted
between the maximum and minimum values stated on
the data badge. Operation of this adjuster will not affect
the maximum boiler output when domestic hot water is
being drawn off.

Installation Requirements - Page 12
•Inhibitors
When the heating system has been completed, it should
be cleaned thoroughly in accordance with BS 7593
(code of practice for Treatment of Water in Domestic Hot
Water Central Heating Systems) to prevent foreign
matter from entering the boiler.
Ideally, it should be flushed before the boiler is
connected, and again after the system has been heated
and is still warm. BetzDearborn Sentinel X300 or Fernox
Superfloc are our recommended cleansers for new
systems.
Where a boiler is being fitted as a replacement to an
existing system, it is best practice to clean the system
prior to fitting the new boiler. In this case BetzDearborn
Sentinel X400 or Fernox Superfloc should be used.
In order to minimise corrosion in the system, inhibit scale
formation and microbiological growth, we recommend
that an inhibitor is added to the system when it is refilled
following the final (hot) flushing. BetzDearborn Sentinel
X100 or Fernox MB-1 are suitable products.
For more information regarding cleansers and inhibitors,
contact:
BetzDearborn Ltd.
Widnes, Cheshire.
WA8 8UD.
Telephone [phone].
Fernox Alpha Fry Ltd.
Tandem House, Marlowe Way,
Beddington Farm Road,
Croydon. CR0 4XS.
Telephone [phone].

2. Installation - Page 13
•It is MOST IMPORTANT that the appliance is installed
in a VERTICAL POSITION, with the flue system passing
through the wall or ceiling in a Horizontal or Vertical
plane. A minor deviation from the horizontal is
acceptable, provided that this results in a downward
slope of the flue system away from the combination
boiler.
2.1 Unpacking
1. Unpack the cartons and check the contents.
2. Remove the white front case as follows; undo the two
securing screws at the base of the panel, pull the base
of the panel forward approx. 50 mm and lift off the
supporting top hooks. (Fig. 8)
3. Remove the base cover by removing the two fixing
screws and push the cover towards the rear to release
4. Each side panel can now be individually removed by
removing the two front fixing screws, loosening the lower
rear fixing screw and sliding the panel upwards to
unhook from the upper rear fixing. Place each panel
safely to one side.
5. Position the appliance onto its side and remove the four
screws retaining the lowest rear cross brace. This brace
is for transit purposes only and should be discarded.
Remove all plastic plugs from the pipes, a small quantity
of water may be present.
6. At this point follow the Installation Instructions supplied
with the Flue System, then proceed as follows:-
7. Boiler Connections: All connections to the appliance are
supplied unassembled in the boiler carton on a vacuum
formed card. Remove all fittings and assemble to the
appliance.
Note: When fitted, the Red levered central heating tail
(C.H.flow) should be to the left of the Blue.
2.2 Gas Connection
A minimum gas pressure of 20 mbar (8" w.g.) must be
available at the combination boiler inlet at full flow rate.
Install a gas supply pipe not less than 15mm diameter
copper to the combination boiler and connect to the gas
service cock. 15 mm diameter pipe will be adequate if
the length of pipe from the boiler to the gas meter is less
than 3 m, longer lengths will require 22 mm pipe.
2.3 D.H.W. Supply
1. The domestic hot water circuit does not need a pressure
relief valve, but it is essential to ensure that the pressure
of the cold water supply does not exceed 10 bar (145
lb/in), if in doubt it is advisable to install a pressure
reducing valve. The minimum pressure needed to
operate the domestic hot water system is 1 bar with a
flow of approximately 2.5 litres per minute.
2. Flush out all foreign matter from the supply pipe before
connecting to the appliance.
Fig 8

Installation - Page 14
3. Connect the cold water supply to the 15 mm isolating
cock.
4. Connect the hot water outlet pipe using a 15 mm
compression fitting.
Note: The cold water supply isolating cock incorporates
a water strainer. There is an automatic flow limiting
device in the inlet fitting - see Fig. 13.
Showers
If a shower control is to be supplied from the
Combination unit it should be of the type which
incorporates a pressure balancing valve (i.e. MIRA 415
EQUAMATIC).
If the shower control is existing and is of a mechanical
type, it may be necessary to fit a drop tight pressure
reducing valve to the mains supply. Refer to the Shower
Manufacturers instructions.
Note: Showers with a loose flexible hose may require
the fitting of a double check valve, to comply with water
Bye-law 17. This should be fitted down stream of the
appliance.
2.4 C.H. Water Connections
1. Before any central heating connections are made to the
combination boiler, all system valves should be opened
and the system thoroughly flushed out with cold water.
2. Connect the central heating return pipe to the isolating
cock identified by a Blue lever. (right hand of the two
pipes)
3. Connect the central heating flow pipe to the isolating
cock identified by a Red lever. (left hand of the two
pipes)
2.5 Pressure Relief Valve
The pressure relief valve is pre-set at 3 bar.
Install a pressure relief valve discharge pipe, not less
than 15 mm diameter and connect to the pressure relief
outlet.
The position of the discharge pipe should be such that
any discharge of water or steam cannot create a hazard
to persons in or about the premises, or damage to
electrical components or wiring, and the point of
discharge should be clearly visible.
It is recommended that the discharge point be over an
outside drain.

Installation - Page 15
2.6 Wiring the Appliance
The wiring diagram is located on the inside of the front
casing panel.
1. Undo the single retaining screw on the top of the
controls panel and allow the panel to swing down.
2. Using PVC insulated cable of not less than 0.75 mm².
(24/0.2 mm to BS 6500 Table 16), wire up the panel
referring to the termination label. (Fig. 10).
3. Check all wiring and reposition the control panel.
4. Secure with screw provided.
Note: The electrical mains supply must be fused at 3 A,
and the connection must be made to the wiring panel in
such a way that should the lead disengage from the
cable clamp, the current carrying conductors become
taut before the earth conductor.
Note: Ensure cables pass through the bushes and are
securely fixed by the cable clamps.
If a room thermostat is to be fitted, remove the Red link
wire between terminals 3 and 4 and discard prior to
wiring in the thermostat. If no room thermostat is to be
fitted retain link wire.
If a programmable room thermostat is to be used it must
be fitted in place of the external timer and the link
between 3 & 4 retained.
If the installation does not have an internal or external
timer the central heating switch on the front of the
appliance must be set to Constant during periods when
central heating is required.
If using an internal timer connect the timers lead to PL11
on the modulation control board - See
Electrical Diagram, Page 41.
If an external frost thermostat is required it should be
connected to terminals 3 and 8 on the boiler terminal
block. For the frost thermostat to function the boiler
switch must be set to 'On'.
Fig 10
Notes:
1. If a Room Thermostat is to be fitted the link wire
between 3 & 4 on the wiring panel must be
removed.
2. If an External timer is not required, two internal
timers are available.
3. If using an internal timer, connect it to plug 11 on
the PCB. If a timer is not being installed, the central
heating switch on the front of the appliance must be
set to ‘Constant’ for the heating to operate.

3. Commissioning - Page 16
3.1 Electrical Installation
Conduct a preliminary electrical test by checking: for short
circuits, fuse failure, incorrect polarity, earth continuity and
resistance to earth.
3.2 Gas Installation
The whole of the gas installation including the meter, should
be inspected and tested for soundness and purged in
accordance with the recommendations of BS 6891. Purging
air from the gas line may be carried out by loosening the
union on the gas service cock and purging. Re-tighten the
union when completed and check for gas soundness.
N.B. Open all doors and windows, extinguish naked lights
and DO NOT SMOKE when carrying out the gas soundness
tests and purging.

Commissioning - Page 17
3.3 Initial Lighting
WARNING:
Before operating the appliance, check that the air box
covers are correctly fitted. The outer white front case should
be left off for the time being.
WARNING:
When the appliance is operating, wiring in the area around
the gas valve and printed circuit boards will be live. When it
is necessary in the following sections to work in this area
temporarily isolate the electrical supply. However this can
not be done when adjusting the gas pressure therefore extra
care must taken during this operation. Where it is necessary
to disconnect a modulator coil wire disconnection should be
made with the use of electrically insulated pliers and the
connection should be taped.
IMPORTANT
The pressure relief valve is factory tested and does not need
testing during the commissioning of the boiler.
It must not be used to reduce system pressure as it may
cause debris in the system to foul the valve
Carry out the following procedure in the order listed.
1. Thoroughly flush out the whole of the heating system
with cold water.
2. Fill and vent the system until the pressure gauge
registers 1.5 bar (21.5 psi), examine for leaks and
rectify. Do not overtighten joints. During filling ensure
that the plastic screw on top of the automatic air vent is
not tight and air can escape. Do not tighten the air
vent screw after filling.
3. Release water from the system using an external drain
tap until the minimum system design pressure is
reached. (Generally 1.0 bar). To allow maximum central
heating expansion capacity the pre-charge pressure in
the central heating expansion vessel must be marginally
greater than the initial (cold) system pressure at the
appliance. If the position of the appliance in the system
will cause the pressure at the appliance to be greater
than 1 bar (14.5 lb/in) increase the pre-charge pressure
in the central heating expansion vessel to a marginally
greater value prior to filling the system.
Set the red pressure gauge indicator to coincide with
this pressure, grip and turn the outer casing of the
gauge clockwise.
Check the pump spindle is free to rotate by unscrewing
the black octagonal nut, withdraw to engage the motor
spindle. The knob should rotate freely. The pump will
normally self vent the air from the rotor chamber within
a short while of switching on, however should manual
venting of the bearings be required, sideways pressure
should be applied and maintained to the knob until a
small amount of water becomes visible. The manual
restart knob should now be screwed back to its original
position, finger tight.
4. Check that the boiler switch is set to Stand-by and the
central heating switch is set to the Off position. (Mid
position)
5. Check the Gas service cock is On.
6. Check that the boiler isolating valves and radiator
valves are open.
7. Check that any time controls are in an On condition,
and any room thermostats are calling for heat.
8. Switch On the main electricity supply to the combination
boiler at the wall isolating switch. The Mains light will
now illuminate.
9. Loosen or remove the outlet (burner) pressure test point
screw in the gas valve body (Fig. 18), and connect via a
flexible tube to the + or Hi side of pressure gauge. Then
connect the - or Lo side of pressure gauge via another
flexible tube to the pressure test point in the base of the
inner casing. (Fig. 11)
10. Switch the Boiler switch to On.
IMPORTANT
Commission the boiler in Central Heating Mode before
Domestic Hot Water Mode but do not isolate the D.H.W.
11. Adjusting the Central Heating Range Rate Pressure.
This pressure can only be measured in the central
heating mode.
i. Ensure all D.H.W outlets are turned off.
ii. Ensure all radiator control valves are fully open
and any room thermostats are calling for heat.
iii. Set central heating switch to Constant. The burner
will light but remain at low burner pressure for
around 2 minutes, after which it will go to maximum
pressure. Allow the central heating to run for 5 or
10 minutes.
iv. Using the range rate adjustment knob on the
electronic control board adjust to the values for
Range Rate in Table 3.
12. Fully open a hot water tap. (After a short delay the main
burner will light and the flame light will illuminate).
13. Turn off the hot tap.
WARNING: The pipes under the appliance could be hot,
avoid contact with bare skin.

Commissioning - Page 18
14. Fully open all domestic hot water outlets, vent flexible
hose connections to the washing machine and
dishwasher. Remove air from the domestic hot water
distribution system. If this is not done the internal water
flow switch will not function properly. Test for gas
soundness around the gas components using leak
detector fluid.
15. Check the minimum burner pressure (Table 3) by
disconnecting one of the Modulating Coil electrical
connections (wire colours Red or Black).
Note: The modulating coil connections are 24V only.
Fig. 18.
16. Reconnect and check maximum burner pressure
against Table 3. If any adjustment is necessary see
Section 3.4, 'Gas Pressure Adjustment'.
Note: The boiler is so designed that if required the
central heating output can be down rated to the lowest
setting stated on the data plate without affecting the
D.H.W output. If adjustment is required see Section 3.4
'Gas Pressure Adjustment'.
3.4 Gas Pressure Adjustment
Note: The gas pressures are set at the factory (with
central heating output set at maximum) and should not
require further adjustment. If gas pressure readings are
being obtained which differ from that stated in Table 3,
check the inlet pressure using the inlet pressure test
point on the gas valve (Fig. 18). The inlet pressure
should be checked with the appliance at full gas rate, to
ensure this occurs put a high water flow through the
domestic hot water side of the system.
Note: Full rate will be achieved with cold water supply
temperatures below 15 °C.
Note: When checking gas inlet pressure only connect
one tube from the measuring manometer's +ve side
(positive). Do not connect the -ve (negative) tube as
with minimum and maximum pressure readings.
Adjustment of the Modulating Valve
Pressures are measured by connecting the +ve
connection to the gas outlet and -ve connection to the
base of the inner casing as described in Section 3.3 .
Set the pressures to the values in Table 3 by adjusting
the gas valve in the following manner.
Note: It is important to note the order in which the
maximum and minimum pressures are set.
The maximum pressure must always be set before
adjustment of the minimum pressure.
Adjusting the Maximum Pressure - Fig. 12.
i. Cut off cable tie retaining modulator Cover.
ii. Remove Cover (C) by twisting it anticlockwise 90°
and levering off with a small screwdriver.
iii. With a 10 mm spanner turn nut (B), (Clockwise to
increase pressure). Adjust to the value for
maximum pressure stated in Table 3.
Adjusting the Minimum Pressure - Fig. 12.
This adjustment is only to be made after the maximum
setting has been completed.
i. Disconnect one of the electrical connections of the
modulating coil and tape. (24V only)
ii. Using a 10 mm spanner hold nut (B) and adjust
screw (A) with a screwdriver (clockwise rotation will
increase the pressure). Set to the value for
minimum pressure stated in Table 3.
iii. Reconnect the electrical connection to the
modulator.
iv. Check maximum and minimum settings. Repeat
adjustment if required.
v. Refit cover (C), snap into place and turn.
After the setting operation remove the pressure gauge
tubes from the gas valve body and inner casing. Refit
the pressure test point screws.
3.5 Products Of Combustion Measurement
The combustion performance can be assessed by
placing a suitable sampling probe through the access
hole in the inner casing door whilst the appliance is
running. Typical figures based on a 500 mm flue length
with the boiler operating at maximum output are:-
CO. 0.002 - 0.005%
CO24.5 - 5.0%
Re-fit the screw in access hole after test.
Setting
Pressure Tolerance Gas Rate
Maximum
Pressure 15.0 mbar 15.2 mbar 14.8 mbar 2.79 m³/hr 98.1 ft³/hr
Range Rate 8.3 mbar 8.4 mbar
8.2 mbar 2.10 m³/hr 73.7 ft³/hr
Inlet Pressure 20 mbar (8” w.g.)
Minimum
(Ignition)
Pressure 3.5 mbar 3.6 mbar
3.4 mbar 1.34 m³/hr 47.1ft³/hr
Table 3. Gas Pressures

Commissioning - Page 19
3.6 D.H.W Flow Rate
The appliance contains an automatic flow regulator
supplying a nominal flow rate of 7.6 litres/minute. This
flow rate will give a nominal temperature rise of 45°C.
3.7 Central Heating
1. Ensure that all external controls such as a timers
are switched On and that room thermostat/s are
calling for heat.
2. Set the Central Heating switch to Timed (if system
fitted with Timer) or Constant. The appliance will
control the flow temperature between 79 °C & 87 °C
dependent on system load.
3.8 Appliance Protection Devices
•Loss of gas supply, flame failure, or over-heating of the
central heating water will cause the appliance to shut
down or Lockout. This will be indicated by the lockout
light being illuminated. To Reset the appliance press the
RESET button on the front panel and hold in that
position for 10 seconds and release. The appliance
should now operate normally.
If this is not the case refer to the Fault Finding guide
either on the rear of the white front case or in these
instructions.
•If the central heating system loses pressure for any
reason the system and the appliance should be checked
for leaks (including discharge from the pressure relief
pipe). Correct any faults and re-pressurise the system
with reference to Section 1.6. Mains Water Feed Central
Heating.

Commissioning - Page 20
•A Frost thermostat is fitted which will bring the appliance
on when the local temperature around the appliance
falls below 5 °C The appliance will shut down when the
temperature of the system water has been raised by
approximately 10 °C
•The appliance is protected provided the mains light is
illuminated and the boiler switch is set to On,
irrespective of the settings of any external controls.
Note: the Frost thermostat will operate with the central
heating switch in any position therefore when leaving the
property in cold weather for extended periods, the boiler
will be protected even when the switch is set to Off (Mid
position).
Note: While the appliance is being used to provide hot
water at any draw off point, the central heating will not
operate. When hot water is no longer required the
appliance will automatically revert to central heating.
3.9 Complete the Installation
•After completion of installation and commissioning of the
system re-fit the white front case.
•The installer should hand over to the User by the
following actions:
1. Explain to the Householder where to find the User's
Guide and his/her responsibilities under the 'Gas Safety
(Installation and Use) Regulations 1994. (As Amended)'.
2. Explain and demonstrate the lighting and shutting down
procedures.
3. Demonstrate the operation of the boiler including the
use and adjustment of all system controls. This then
ensures the greatest possible fuel economy consistent
with household requirements of both heating and hot
water consumption. Advise the User of the precautions
necessary to prevent damage to the system, and to the
building, in the event of the system remaining
inoperative during frost conditions.
4. Explain the function and the use of the boiler switch,
central heating switch and Reset button.
5. Explain and demonstrate the function of time and
temperature controls, external frost thermostat (if fitted)
and radiator valves, etc. for the economic use of the
system.
6. If a Time Control is fitted (internal or external), then draw
attention to the timer 'User Instructions' and hand them
to the householder.
7. Stress the importance of regular servicing by a qualified
Heating Engineer and that a comprehensive service
should be carried out AT LEAST ONCE A YEAR.
8. An internal frost thermostat is fitted to the appliance, it
must be explained that the Boiler switch must be in the
On position (with the mains light illuminated) to provide
protection of the appliance, if it is not to be used during
winter periods.
Note: the Frost thermostat will operate with the central
heating switch in any position therefore when leaving the
property in cold weather for extended periods, the boiler will
be protected even when the switch is set to Off (Mid
position).