Potterton Puma Flowsure+ Installation and maintenance instructions

Part No. 27/20334 - 01
Puma Flowsure+ - G.C. No. 47 590 18
Installation & Service Instructions
Puma Flowsure+
Wall Mounted, Fanned, Room Sealed,
Storage Combination Boiler
THE GAS SAFETY (INSTALLATION AND USE) REGULATIONS 1994.
‘‘ 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.’’
The polythene bags used for packaging are a potential hazard to babies and young children
and MUST BE DISPOSED OF IMMEDIATELY.
LEAVE THESE INSTRUCTIONS WITH THE USER FOR USE ON FUTURE CALLS
For Use With Natural Gas
(G20) Only At 20mbar
For Use in GB & IE
IMPORTANT
PLEASE READ THIS BOOK
BEFORE INSTALLING,
OPERATING OR SERVICING
THIS APPLIANCE.

2Contents Part No. 27/20334
Contents - Page 2
Technical Data........................................................3
Introduction ............................................................4
1. Installation Requirements.....................................6
1.1 General Information.......................................6
1.2 Location of Boiler...........................................7
1.3 Flue Terminal and Ducting ............................8
1.4 Air Supply......................................................9
1.5 Guide to System Requirements.....................9
1.6 Mains Water Feed C.H..................................10
1.7 Installation to an Existing System..................10
1.8 Hard Water Areas..........................................10
1.9 Pump Performance Curve.............................10
1.10 Domestic Hot Water - 50 Litre Tank..............11
1.11 Electrical Supply............................................13
1.12 Clearance Around the Appliance...................14
2. Installation..............................................................15
2.1 Unpacking......................................................16
2.2 Installation - Boiler.........................................16
2.3 Installation - Storage Tank.............................17
2.4 Gas Connection.............................................18
2.5 D.H.W Supply................................................18
2.6 C.H. Supply ...................................................18
2.7 Pressure Relief Valve....................................19
2.8 Wiring the Appliance......................................19
3. Commissioning......................................................20
3.1 Electrical Installation......................................20
3.2 Gas Installation..............................................20
3.3 Initial Lighting.................................................21
3.4 Gas Pressure Adjustment..............................22
3.5 Products of Combustion Measurement.........23
3.6 D.H.W Flow Rate...........................................24
3.7 Central Heating..............................................24
3.8 Temperature Controls....................................24
3.9 Appliance Protection Devices........................24
3.10 Re-fit Outer Case...........................................25
3.11 Handing Over to the User..............................25
4. Servicing.................................................................26
5. Routine Maintenance.............................................27
5.1 Remove the White Front Case......................27
5.2 Remove Base Panel......................................27
5.3 Remove the Air Box Covers..........................27
5.4 Remove the Fan Assembly........................27
5.5 Remove the Flue Hood..............................27
5.6 Remove the Combust. Cham.
Front Panel................................................27
5.7 To Inspect and Clean the Boiler ................27
5.8 To Remove the Burner ..............................29
5.9 Gas Pressure Adjustment..........................29
5.10 The Central Heating Sealed System.........29
5.11 Other Components ....................................29
6. Component Replacement..................................31
6.1 Central Heating Overheat Thermostat.......32
6.2 Sensor and Ignition Electrode....................32
6.3 Sensor and Ignition Leads.........................32
6.4 Burner........................................................32
6.5 Injectors.....................................................32
6.6 Gas Valve..................................................32
6.7 Modulating Valve.......................................33
6.8 First Solenoid Valve...................................33
6.9 Second Solenoid Valve..............................33
6.10 Case Seal..................................................33
6.11 Central Heating and Boiler Switch.............33
6.12 Electronic Control Boards..........................35
6.13 Air Pressure Switch ...................................36
6.14 Fan.............................................................36
6.15 Fan Seals...................................................36
6.16 Flow Temperature Sensor.........................36
6.17 Pressure Gauge.........................................36
6.18 Pump.........................................................37
6.19 Expansion Vessel C.H...............................37
6.20 Heat Exchanger.........................................38
6.21 Automatic Air Vent.....................................39
6.22 Pressure Relief Valve................................39
6.23 Transformer Assembly...............................40
7. Fault Finding .......................................................41
8. Control Flow Sequence...................................... 42
9. Functional Flow...................................................43
10. Schematic Wiring Diagram................................44
11. Electrical Diagrams ............................................ 45
12. Short List of Spares............................................ 46

Part No. 27/20334 Technical Data 3
Technical Data - Page 3
Boiler Details
Heat Input: kW 30.00 - Max.
Btu/hr 102,350
kW 22.5 - Range Rate
Btu/hr 76,760
kW 14.4 - Min
Btu/hr 49,130
Heat Output: kW 24.00 - Max.
Btu/hr 81,880
kW 17.2 - Range Rate
Btu/hr 58,680
kW 10.4 - Min
Btu/hr 35,480
Gas Rate m³/hr 2.86
ft³/hr 101
Inlet Pressure mbar 20 (18 - 25mbar)
Burner Pressure mbar 15.0 - Max
in/wg 6.0
mbar 8.3 - Range Rate
in/wg 3.3
mbar 3.5 - Min
in/wg 1.4
Classifications I2H, C12 & C32 IP20
Pilot Burner Bray AB 1920
Main Burner Bray AB 24081M
Gas Control Valve: SIT Controls Nova 827 (0.827.127)
Inc. 1st Solenoid Valve (0.007.424)
Inc. 2nd Solenoid Valve (0.007.406)
Inc. Modulator - 28V. DC. (0.007.413)
Burner Injector 3 off
Electrical Supply 230V ~ 50Hz
Fuse Rating External 3A
Packed Weight 58.5kg (129lbs)
Water Content 1.85 litres - C.H.
Connections - Gas
Gas ½" B.S.P.F. Gas Cock
Connections - Water
Inlet DHW 15mm Compression Isolating Valve
Outlet DHW 15mm Copper Pipe
Flow CH 22mm Compression Isolating Valve
Return CH 22mm Compression Isolating Valve
Safety Discharge 15mm Copper Pipe
C.H. Sealed System
Operating Pressure 2.5bar (36.3lb/in²) Max
Operating Pressure 0.5bar (7.25lb/in²) Min
Expansion Vessel 10 litre
(Pre-charge Pressure 1.0bar)
Temperature Rise across
the Boiler 30°C - Max
Central Heating Flow
Temperature 85°C - Max. Load
90°C - Min. Load
Central Heating Return
Temperature 74°C (Nominal)
Storage Tank Details - 50 Litre
Packed Weight 20kg
Full Weight 65kg
Max. Cold Water
Supply Pressure 10 bar
Normal Secondary
Operating Pressure 3.5 bar
Secondary Expansion
Vessel Charge Pressure 3.5 bar
Water Capacity 2.9 litres primary
41.8 litres secondary
T & P Valve 90°C / 7 bar
Pressure Relief Valve 6 bar

4Introduction Part No. 27/20334
Introduction - Page 4
GAS SAFETY (INSTALLATION AND USE)
REGULATIONS 1994.
The appliance must be installed and serviced by a
competent person, in accordance with the above
Regulations.
In the UK 'Corgi' Registered Installers (including the
Regions of British Gas) undertake the work to a safe and
satisfactory standard.
Failure to install appliances correctly could lead to
prosecution.
It is in your own interest, and that of safety, to ensure that
the Regulations are complied with.
Samples of the Puma Flowsure+ gas boilers have been
examined by Gastec, a Netherlands Notified Body. The
range is certified to comply with the essential requirements
of 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.
The Puma Flowsure+ boilers are fully automatic, wall
mounted, fan assisted, room sealed storage combination
boilers, designed to operate on Natural Gas only.
The Puma Flowsure+ 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.
Domestic hot water has priority over the central heating
system and is generated within the tank.
The range of horizontal and vertical flue systems with small
terminals simplify siting and installation.
The combination boilers are designed for use with fully
pumped sealed system only.
They are supplied fully tested and assembled with a
circulating pump, diverter valve, pressure gauge, pressure
relief valve, and expansion vessels.
Fig. 1 shows the main components of the boiler assembly.
A central heating switch controls the choice of service
between central heating/hot water and hot water only.
The boiler water flow system is shown in Fig. 2.
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 and occasionally to maintain the
temperature of the stored hot water.
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 temperature of the central heating can be changed by
adjusting the knob on the front of the appliance.
The domestic hot water is supplied at a pre-set
temperature determined by the d.h.w mixing valve 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.
At the minimum hot water draw-off rate the maximum
temperature is limited to 60°C by the mixing valve in the
tank. This temperature can be changed by adjusting the
mixing valve knob.
The combination boiler has a white front case which can be
removed for servicing.
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.
A data badge is also located on the tank.

Part No. 27/20334 Introduction 5
Introduction - Page 5

6Installation Requirements Part No. 27/20334
1. Installation Requirements - Page 6
1.1 General Information
Prior to installation the boiler should be stored as directed
on the carton and in a dry place. 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. If
you need advice on any points, Potterton's Service
Operations will be pleased to help (see back page). It is
recommended that tools suitable for brass fittings are used,
and have a capability to accommodate hexagon sizes up to
50mm.
Codes Of Practice
I.E.E Regulations
Model Water Bye Laws
Building Regulations/Building Standards for Scotland.
Health and Safety Document No.635. (The Electricity at
Work Regulations 1989)
BS. 6891 Installation of low pressure pipes.
BS. 6798 Installation of gas boilers of rated input not
exceeding 60kW.
BS. 5449 Forced circulation hot water C.H. systems.
Including smallbore and microbore domestic
central heating systems.
BS. 5546 Installation of gas hot water supplies for
domestic purposes.
BS. 5440:1 Flues (for gas appliances of rated input not
exceeding 60 kW).
BS. 5440:2 Air supply (for gas appliances of rated input
not exceeding 60 kW).
BG. DM2 Guide for gas installation in timber framed
buildings.
It is important that no external control devices e.g. flue
dampers, economisers etc., be directly connected to this
appliance unless covered by these Installation and Service
instructions or otherwise recommended by Potterton in
writing. If in doubt please enquire.
Any direct connection of a control device not recommended
by Potterton could invalidate the certificate and the normal
appliance warranty and could also infringe the Gas Safety
Regulations.
Manufacturers instructions must not be taken in any way as
over-riding statutory obligations.
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.
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 - Ceramic Fibre. Alumino - Silicone 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. Irritation to respiratory tract.
Precautions - 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
discomfort, follow good hygiene practices, wash hands
before 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.

Part No. 27/20334 Installation Requirements 7
Installation Requirements Page 7
Fig 2
1.2 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 of British Gas.
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.

8Installation Requirements Part No. 27/20334
Installation Requirements - Page 8
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 300
GABOVE ADJACENT GROUND OR BALCONY
LEVEL 300
HFROM A SURFACE FACING THE TERMINAL 600
IFACING TERMINALS 1,200
JFROM OPENING (DOOR/WINDOW) IN
CARPORT INTO DWELLING 1,200
KVERTICALLY FROM A TERMINAL ON THE
SAME WALL 1,500
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 1,200
1.3 Flue Terminal and Ducting (Fig: 3 - a, b & c)
The standard horizontal flue system (Potterton Part
No.31-19619) is suitable for installations up to 1092mm,
measured from the centre line of the boiler outlet to the
outside face of the wall. The wall liner enclosed will
accommodate thicknesses of 400mm and can be cut to a
minimum length of 76mm.
One metre flue extension kits (Part No. B4286 or 31-19033)
are available to extend horizontal flues to a maximum length of
3078mm.
90° In-line elbow kits (Part No. 31-19034) and 135° In-line
Bend kits (Part No. 31-19035) 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. The siting positions for horizontal
flue terminals are shown in Figs. 3. - a) & b).
A Concentric Vertical flue system is available (Part No.31-
19036) which when used in conjunction with One metre flue
extension kits (Part No. 31-19033) 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 (Part No. 31-19037) when used in
conjunction with one metre twin tube extension kits (Part
No. 31-19038).
A Pitched Roof Flashing kit (Part No. 31/19041) and Flat
Roof Flashing kit (Part No. 31/19040) are available for use
with the vertical flue systems.
135° Off-set kits are available for both types (Part No.31-
19035 concentric) and (Part No.31-19039 twin tube). The
siting of the flue terminal through a roof is shown in Fig 3. - c).
Only the above flue systems should be used with Puma
Flowsure+ storage combination boilers.
If a horizontal flue is sited less than 2m 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. A terminal guard is
available (Part No. 929729).
Note: Where a flue terminal is installed less than 1 metre from
a plastic, or painted gutter, or 500mm 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.
1.4 Air Supply (See Table 2)
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.

Part No. 27/20334 Installation Requirements 9
Installation Requirements - Page 9
Position of
Air Vent Air from Room/ Internal Space Air Direct from Outside
High
Level 264 cm2 40 in2132 cm2 20 in2
Low
Level 264 cm2 40 in2132 cm2 20 in2
Table 2. Air Supply
1.5 Guide to System Requirements (Figs. 4 & 6)
These combination boilers are 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 boiler.
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).
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.
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 (Fig.
4). Guidance on vessel sizing is given in Table 3.
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.
Safety Valve Setting (bar) 3.0
Initial System Pressure (bar) 1.0 1.5
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 3. Expansion Vessel Requirements
Deduct from the value given in the table the 10 litre expansion vessel supplied.
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
Part No. 31-19053 - Electro-mechanical)
Part No. 31-19054 - Electronic).
b) Room thermostat
c) Thermostatic radiator valves (TRV's)
d) 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.

10 Installation Requirements Part No. 27/20334
Installation Requirements - Page 10
Frost Protection
The tank of hot water will provide frost protection. This is
purely for the protection of the appliance. If any other part of
the central heating system requires frost protection, an
external frost thermostat must be fitted in the usual manner,
refer to Fig. 9 for wiring.
1.6 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
Note: The Puma combination boiler range is fitted with a
diverter valve design which has a manual operation lever to
aid filling. To ease filling of the pump manifold an air bleed
valve is fitted to the diverter and must be opened during filling
until water flows out. The valve should then be closed.
See Fig.13.
(1) DIRECT METHOD (Fig. 5)
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. See section on
Permissible Methods of Filling.
Reference should be made to British Gas Publications
"Material and Installation Specifications for Domestic Central
Heating and Hot Water".
1.7 Installation to an Existing Central
Heating System
The boilers are 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.
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.
1.8 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.
To assess water hardness, immerse the test strip supplied, for
about one second in a water sample (NOT IN RUNNING
WATER) so as to moisten all the zones.
Inspect the strip after 1-2 minutes, check the zones, if two or
more zones have changed colour the hardness of the water is
above 200 p.p.m. and a water treatment device will be
required.
1.9 Pump Performance Curve
The circulating pump fitted within the appliance should be
capable of satisfying most system requirements. Fig. 6
indicates the amount of pump head available for the system.
The boiler resistance is already taken into account in this
curve.