Ideal Boilers British Gas RD2 User guide

INSTALLATION
MANUAL
British/Scottish
Gas RD2
the floor standing boiler
Floor standing, gas
fired fanned flue boiler
40 - 80 RD2
Installers guide to central heating boilers
& SERVICING

2British Gas 40 - 80 RD2 - Installation & Servicing
British Gas:
(Any internal reference to British Gas applies equally to Scottish Gas)
The British Gas RD2 is a range of cast iron floor standing gas central heating boilers.
A complete range of natural gas models is available.
The ideal replacement boiler...
Easy to install, easy to operate and easy to service. The British Gas RD2 really is the
ultimate replacement floor standing range - you can depend on it.
Proven reliability...
Proven cast iron heat exchanger engineered and refined to be the most dependable
floor standing boiler ensuring totally calm operation and quiet running, whatever the
system demands.
Complete range...
There are 7 models in the range. All models include an overheat thermostat and a Flue
Directional kit for side and top outlet installations.
Full system suitability...
All models are suitable for connection to pumped open vent central heating systems,
pumped central heating combined with pumped or gravity indirect domestic hot water
supply systems. They can also be used on sealed water systems.
Free Three Star Service Cover:
In addition to the guarantee, we will provide absolutely free a British Gas Services
Three Star Service Cover agreement to cover your complete new system during the
first year. The benefits of this cover include priority attention and a 24 hours a day 365
days a year helpline. Full details of the terms and conditions for Three Star Cover
schemes are available separately on request.

3
British Gas 40 - 80 RD2 - Installation & Servicing
GENERAL
CAUTION. To avoid the possibility of injury during the installation, servicing or cleaning of
this appliance, care should be taken when handling edges of sheet steel components.
Boiler Size 40 50 60 70 80
Gas Supply Connection in. BSP Rc 1/2 (1/2)
Number of Boiler Sections 2 3 3 3 3
Flow and Return Connections Rc 1 (1" BSP)
MAXIMUM Static Water Head m (ft.) 30.5 (100) (3 bar)
MINIMUM Static Water Head m (ft.) 1.0 (3.3)
Electrical Supply (Power Consumption) 230 V ~50 Hz (150 W)
Fuse Rating External: 3 A Internal: 2A to BS4265
Water Content litre (gal.) 5.0 (1.1) 7.4 (1.6)
Dry Weight kg. (lb.) 68 (150) 90 (198)
Boiler Size Height mm (in.) 850 (33.5)
Width mm (in.) 440 (17.4)
Depth mm (in.) 533 (21.0)
Gas Type Natural 2 H
Gas Supply Pressure 20 mb
Flue duct diameter mm (in.) 100 (4.0)
Flue duct length (max) m (ft) 3 (9.8)
Table 1 - General Data
Table 2 - Performance Data
Boiler Size 40 50 60 70 80
Boiler Input Nett CV kW (Btu/h) 13.2 (45 000) 16.5 (56 300) 19.8 (67 600) 23.1 (78 800) 26.4 (90 100)
Gross CV kW (Btu/h) 14.7 (50 000) 18.3 (62 500) 22.0 (75 000) 25.6 (87 500) 29.3 (100 000)
Gas Consumption l/s (ft.3/h) 0.38 (48.2) 0.47 (60.2) 0.57 (72.3) 0.66 (84.3) 0.76 (96.3)
Boiler Output to Water kW (Btu/h) 11.7 (40 000) 14.7 (50 000) 17.6 (60 000) 20.5 (70 000) 23.4 (80 000)
Burner Setting Pressure (hot) mbar (in w.g.) 10.4 (4.2) 11.6 (4.7) 12.6 (5.1) 10.9 (4.4) 14.0 (5.6)
Seasonal Efficiency (SEDBUK)* Band[ ]% E[76.7]% E[76.7]% E[77.1]% E[77.6]% D[79.7]%
Key to symbols
GB = United Kingdom (Countries of destination)
PMS = Maximum operating pressure of water
C12 = A room sealed appliance designed for connection via ducts
to a horizontal terminal, which admits fresh air to the burner
and discharges the products of combustion to the outside
through orifices which, in this case, are concentric. The
fan is down stream of the combustion chamber.
I2H = An appliance designed for use on 2nd Family gas,
Group H only.
Note.
Gas consumption is calculated using a calorific value of 38.7
MJ/m3(1038 Btu/ft3) gross or 34.9 MJ/m3 (935 Btu/ft3) nett. To
obtain the gas consumption at a different calorific value:-
a. For l/s - divide the gross heat input (kW) by the gross C.V.
of the gas (MJ/m3)
b. For ft3/h - divide the gross heat input (Btu/h) by the gross
C.V. of the gas (Btu/ft3)
c. The appliance is preset at the factory to the nominal rating.
*The value is used in the UK Government's Standard Assessment Procedure (SAP) for energy rating of dwellings.
The test data from which it has been calculated have been certified by BG plc 0087.

4British Gas 40 - 80 RD2 - Installation & Servicing
GENERAL
INTRODUCTION
British Gas RD2 above range is of floor standing, fanned
flue gas boilers. They are rated to provide central heating
outputs of 11.7 kW (40,000 Btu/h) to 23.4 kW (80,000 Btu/h).
The boiler has a cast iron heat exchanger and is supplied
fully assembled, complete with a white enamelled mild
steel casing.
A door at the top of the casing front panel hinges down,
revealing the boiler thermostat control.
The boilers are supplied with kits for rear, side and top flue
outlets.
The boilers are suitable for connection to open-vented
systems and sealed water systems.
The systems may be:
zpumped or gravity circulating indirect DHW only
zpumped central heating only
zpumped central heating combined with either a pumped
or gravity circulating indirect DHW circuit.
The diagnostic controls within the boiler are capable of
communicating key operational data to a central computer data
processing system via the house ring main and public telephone
system known as Remote Appliance Diagnostic System (or
RADS).
RADS can identify actual failure, or predict imminent failure of
components and specify the corrective procedures to the British
Gas Service Engineer.
To enable the system to operate, a remote mounted interface
(Gateway) is required to receive and transmit data from the
boiler.
Without this facility, the boiler operates as standard fanned flued
boiler.
OPTIONAL EXTRA KITS
Extension Duct kit To extend standard flue.
90oFlue Elbow Kit
CONTENTS
Air Supply. ..................................................................... 7
Boiler Assembly - Exploded view ............................. 12
Boiler Clearances ......................................................... 6
Electrical Connections ............................................... 23
Electrical Diagrams ........................................... 23 & 24
Electrical Supply ........................................................... 8
Extension Ducts - Fitting ........................................... 21
Fault Finding ............................................................... 38
Flue Fitting ............................................................. 15-21
Flue Installation ............................................................ 7
Gas Safety Regulations ............................................... 5
Gas Supply .................................................................... 7
Initial Lighting ............................................................. 27
Installation ................................................................... 13
Mandatory Requirements ......................................... 5-7
Pump .............................................................................. 9
System Diagrams (Electrical) ........................... 25 & 26
Terminal Guards. .......................................................... 7
Water Connections ......................................... 5,15 & 22
Water Circulation .......................................................... 8
Water Systems ......................................................... 9-11
British Gas RD2
40 RD2 G.C. No. 41 387 53
50 RD2 G.C. No. 41 387 54
60 RD2 G.C. No. 41 387 55
70 RD2 G.C. No. 41 387 56
80 RD2 G.C. No. 41 387 57
Natural Gas only Appliance type: C12
Certified - P.I. No. 87 BL 30 Destination Countries: GB
NOTE TO THE INSTALLER: LEAVE THESE
INSTRUCTIONS ADJACENT TO THE GAS METER.
ALSO COMPLETE THE BENCHMARK LOG BOOK
AND GIVE THIS TO THE CUSTOMER.
BENCHMARK LOG BOOK DETAILS
Boiler Page
Make and model ........................................................ 4
Appliance Serial No. on Data Badge ........................ 9
Controls ............................................... as applicable
Forall boilers
Flushing to BS.7593 .................................................. 8
Inhibitor ...................................................................... 8
Gas inlet working pressure ....................................... 7
Burner operating pressure ........................................ 3
Heat input .......................................... to be calculated
Temperature differential ............. measure and record
For combination boilers only ................. Not applicable
For domestic hot water mode ................ Not applicable
For condensing boilers ........................... Not applicable
For all boilers: complete, sign & hand over to customer
For assistance see Technical Helpline on the back page

5
British Gas 40 - 80 RD2 - Installation & Servicing
GENERAL
GAS SAFETY
Current Gas Safety (Installation and Use) Regulations,
or the rules in force.
It is law that all gas appliances are installed by a CORGI
registered installer in accordance with the above regulations.
Failure to install appliances correctly could lead to prosecution.
It is in your own interest, and that of safety, to ensure the law is
complied with.
The installation of the boiler MUST also be in accordance with
the latest I.E.E (BS 7671) Wiring Regulations, local building
regulations, bylaws of the local water authority, the Building
Regulations and Building Standards (Scotland) and any relevant
requirements of the local authority.
Detailed recommendations are contained in the following British
Standard Codes of Practice:
BS. 6891 Low pressure installation pipes.
BS. 6798 Installation of gas fired hot water boilers of rated
input not exceeding 60 kW.
BS. 5449:1 Forced circulation hot water systems (small bore
and microbore domestic central heating systems).
BS. 5546 Installation of gas hot water supplies for domestic
purposes (2nd Family Gases).
BS. 5440: 1 Flues for gas appliances of rated input not
exceeding 70 kW.
BS. 5440: 2 Ventilation for gas appliances of rated input not
exceeding 70 kW.
BS 7593 Treatment of water in Domestic Hot Water Central
Heating Systems.
Health and Safety Document No. 635.
The Electricity at Work Regulations, 1989.
Manufacturer’s notes must NOT be taken in any way as
overriding statutory obligations.
IMPORTANT. These appliances are certificated by the BG
Technology Certification Services for safety and performance. It
is important, therefore, that no external control devices, e.g. flue
dampers, economisers etc., are directly connected to these
appliances unless covered by these Installation and Servicing
Instructions or otherwise recommended by British Gas
Services in writing. If in doubt please enquire.
Any direct connection of a control device not approved by
British Gas Services could invalidate the certification and the
normal appliance warranty. It could also infringe the Gas Safety
Regulations and the above regulations or other statutory
requirements.
SAFE HANDLING OF SUBSTANCES
Care should be taken when handling the boiler insulation
panels, which can cause irritation to the skin. No asbestos,
mercury or CFC's are included in any part of this boiler.
LOCATION OF BOILER
The boiler must be installed on a flat and level floor, capable of
adequately supporting the weight of the boiler and any ancillary
equipment.
The boiler may be fitted on a combustible floor.
Insulation is not necessary, unless required by the local
authority.
The boiler must not be fitted outside.
Timber Framed Buildings
If the boiler is to be fitted in a timber framed building it should be
fitted in accordance with the Institute of Gas Engineers
document IGE/UP/7 : 1998.
1. This appliance is NOT suitable for use in a
direct hot water system.
2. The boiler is suitable to be used on a sealed
system. Overheat Thermostat is fitted as
standard.
Boiler Dimension A
40 152mm (6")
50 / 60 226mm (8 7/8")
70 / 80 226mm (8 7/8")
1 BOILER WATER CONNECTIONS

6British Gas 40 - 80 RD2 - Installation & Servicing
GENERAL
Bathrooms
The boiler may be installed in any room or internal space,
although particular attention is drawn to the requirements of the
current I.E.E. (BS 7671) Wiring Regulations and, in Scotland,
the electrical provisions of the building regulations applicable in
Scotland with respect to the installation of the 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 then the appliance and 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.
Where installation will be in an unusual location, special
procedures may be necessary and BS.6798 gives detailed
guidance on this aspect.
Compartment Installations
A compartment used to enclose the boiler MUST be designed
and constructed specially for this purpose.
An existing cupboard or compartment may be used, providing it
is modified for the purpose.
2 FLOOR MOUNTING AND BOILER CLEARANCES
Flammable materials must not be placed in close proximity to
the appliance. Materials giving off flammable vapours must
not be stored in the same room as the appliance.
Floor mounting
1. The floor must be flat, level and of suitable load bearing
capacity.
2. The back of the boiler may be fitted up to the wall.
Boiler clearances
The minimum overall dimensions of the space in which the
boiler is to operate and to facilitate servicing are as shown in
the Table.
Additional space will be required for installation, depending
upon site conditions.
IMPORTANT.
In order to facilitate gas connection, a clearance of at least
100 mm (4") must be available at either the left hand side or
the right hand side DURING installation. Refer to Frame 31.
In addition a MINIMUM clearance of 533 mm (21") MUST
be available at the front of the boiler, for servicing.
In both cases details of essential features of cupboards/
compartment design, including airing cupboard installation, are
to conform to the following:
zz
zz
zBS. 6798.
zz
zz
zThe position selected for installation MUST allow
adequate space for servicing in front of the boiler
and for air circulation around the boiler.
Side clearance is only necessary for installation. The amount
of side clearance will depend upon the type of connection
used.
zThis position MUST also permit the provision of a
satisfactory flue termination.
zFor the minimum clearances required for safety, and
subsequent service, see Frame 2.
Boiler Flue Overall Space dimension Minimum Side Clearance 'A'
Model Length Depth Height Width Width Rear Flue Side/Top Flue
Rear Flue Side/Top
40, 50, 114 to 533 mm 870 mm 460 mm 510 mm 10 mm 35 mm
60, 70 600 mm (21") (34 1/4") (18 1/8") (20 1/8")(3/8") (1 3/8")
80 (41/2"-23 5/8")
40, 50, 600 to 533 mm 870 mm 510 mm 510 mm 35 mm 35 mm
60, 70 3000mm (21") (34 1/4") (20 1/8") (20 1/8") (1 3/8") (1 3/8")
80 (23 5/8"-118")

7
British Gas 40 - 80 RD2 - Installation & Servicing
GENERAL
Table 3 - Balanced flue terminal position
Terminal Position
Minimum Spacing
1. Directly below or alongside an
opening window, air vent or other
ventilation opening 300 mm (12")
2. Below guttering, drain pipes or soil
pipes 75 mm ( 3")
3. Below eaves 200 mm ( 8")
4. Below balconies or a car port roof 200 mm ( 8")
5. From vertical drain pipes or soil pipes 75 mm ( 3")
6. From internal or external corners 300 mm ( 12")
7. Above adjacent ground, roof or
balcony level 300 mm (12")
8. From a surface facing the terminal 600 mm (24")
9. From a terminal facing a terminal 1200 mm (48")
10. From an opening in a car port
(e.g. door or window) into dwelling 1200 mm (48")
11. Vertically from a terminal on the
same wall 1500 mm (60")
12. Horizontally from a terminal on the wall 300 mm (12")
Terminals guards are available from boiler suppliers - ask for
Tower Flue Guard, Model K1. In case of difficulty seek advice
from:
Tower Flue Components Ltd.,
Vale Rise, Tonbridge, Kent TN9 1TB (Model K1)
Telephone No. 01732 351 555
Ensure that the guard is fitted centrally.
5. Where the terminal is fitted within 1000mm (39 1/2") of a
plastic or painted gutter or 500mm (19 1/2") of painted eaves
then an aluminium shield at least 1000mm (39 1/2") long
should be fitted to the underside of the gutter or painted
surface.
6. The air inlet/products outlet duct and the terminal of the
boiler MUST NOT be closer than 25mm (1") to combustible
material. Detailed recommendations on the protection of
combustible material are given in BS.5440: 1990.
IMPORTANT.
It is absolutely ESSENTIAL to ensure, in practice, that products
of combustion discharging from the terminal cannot re-enter the
building or any other adjacent building through ventilators,
windows, doors, other sources of natural air infiltration or forced
ventilation/air conditioning. If this should occur, the appliance
MUST be turned OFF, labelled 'unsafe' and corrective action
taken.
TERMINAL
WARNING.
For top outlet installations the flue terminal MUST always be in
the horizontal position.
The terminal assembly can be adapted to accommodate various
wall thicknesses. Refer to Frames 11 and 28.
AIR SUPPLY
Detailed recommendations for air supply are given in BS.5440:2.
The following notes are for general guidance:
1. It is NOT necessary to have a purpose provided air vent in
the room or internal space in which the boiler is installed.
2. If the 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 room/internal space,
or be direct to outside air. The minimum effective areas of
the permanent air vents, required in the cupboard/
compartment, are specified as follows and are related to
maximum rated heat input.
3. Both air vents MUST communicate with the same room or
internal space or MUST be on the same wall to outside air.
4. In siting the air vents care must be taken to avoid the
freezing of pipework.
Table 4 - High and low vent areas
Boiler Air from room/internal Air direct from
space cm2(in.2) outside cm2(in.2)
High level Low level High level Low level
40 143 (23) 143 (23) 72 (12) 72 (12)
50 173 (27) 173 (27) 87 (14) 87 (14)
60 208 (33) 208 (33) 104 (17) 104 (17)
70 245 (38) 245 (38) 123 (19) 123 (19)
80 282 (44) 282 (44) 141 (22) 141 (22)
GAS SUPPLY
The local gas supplier 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 supplier.
The boiler is to be installed only on a gas supply with a
governed meter.
A gas meter can only be connected by the local gas supplier or
by a local regional contractor.
Check that the appliance is suitable for the proposed gas
supply. An existing meter should be checked, preferably by the
gas supplier, to ensure that the meter is adequate to deal with
the rate of gas supply required. A minimum gas pressure of
20 mbar MUST be available at the boiler inlet, with the boiler
operating.
Installation pipes MUST be fitted in accordance with BS. 6891.
Pipework from the meter to the boiler MUST be of an adequate
size.
The complete installation MUST be tested for gas soundness
and purged as described in the above code.
FLUE INSTALLATION
Some pluming may occur at the termination so terminal
positions where this could cause a nuisance should be avoided.
The flue must be installed in accordance with the
recommendations of BS. 5440:1.
The following notes are intended for general guidance:-
1. The boiler MUST be installed so that the terminal is exposed
to external air.
2. It is important that the position of the terminal allows the free
passage of air across it at all times.
3. Minimum acceptable spacing from the terminal to
obstructions and ventilation openings are specified in
Table 3.
4. Where the lowest part of the terminal is fitted less than 2m
(6'6") above a balcony, above ground or above a flat roof to
which people have access then the terminal MUST be
protected by a purpose designed guard.

8British Gas 40 - 80 RD2 - Installation & Servicing
GENERAL
Water Flow Rate and Pressure Loss
WATER TREATMENT
The boiler incorporates a cast iron heat exchanger. As part of
the installation the central heating system should be thoroughly
flushed with appropriate water treatment in order to comply with
BS7593:1992
British Gas Services recommend the use of Fernox or Betz
Dearborn water treatment products which must be used in
accordance with the manufacturers instructions. For further
information contact :-
Fernox Manufacturing. Co. Ltd., Tandem House, Marlowe
Way, Croydon, Surrey CRO 4XS, tel [phone]
or
Betz Dearborn Ltd., Widnes, Cheshire, tel. [phone]
IMPORTANT.
ANY OTHER TREATMENT FOR THIS PRODUCT MAY
RENDER THE GUARANTEE OF BRITISH GAS SERVICES
INVALID.
Notes.
1. If an inhibitor is used, and in hard water areas where
treatment to prevent lime deposits is necessary, it is most
important that the water treatment MUST be maintained at
the correct concentrations recommended by the treatment
manufacturer.
2. Artificially softened water must not be used in the system,
under any circumstances.
THERMOSTATIC RADIATOR VALVES
British Gas Services recommend that heating systems utilising
full thermostatic radiator valve control of temperature in
individual rooms should also be fitted with a room thermostat
controlling the temperature in a space served by radiators not
fitted with such a valve, as stated in BS. 5449.
When thermostatic radiator valves are used, the space heating
temperature control over a living / dining area or hallway having
a heating requirement of at least 10% of the boiler heat output
should be achieved using a room thermostat, whilst other rooms
are individually controlled by thermostatic radiator valves.
However, if the system employs thermostatic radiator valves on
all radiators or two port valves without end switches then a
bypass must be fitted in order to ensure a flow of water should
all the valves be in the closed position.
ELECTRICAL SUPPLY
WARNING. The appliance MUST be efficiently earthed.
Wiring external to the appliance MUST be in accordance with
the current I.E.E. (BS 7671) Wiring Regulations and any local
regulations which apply.
The boiler is supplied for 230 V ~ 50 Hz single phase. The fuse
rating is 3A.
Connection must be made in a way that allows complete
isolation of the electrical supply - such as a double pole switch,
having a 3mm (1/8") contact separation in both poles, or a plug
and socket serving only the boiler and system controls.
The means of isolation must be accessible to the user after
installation.
For bathroom installations the point of connection to the mains
must be situated outside the bathroom.
FLOW RATE (gals/hr)
PRESSURE LOSS (mbar)
FLOW RATE (l/min)
PRESSURE LOSS (ft.water)
140
100
60
20
10 20 30 40 50
MEX 707-5
1.0
2.
3.0
4.0
5.0
200 400 600
70 & 80
40
60
70
80
50&60
40
50
Dotted lines indicate flow rates equivalent to a
temperature rise of 11 OC (20 OF)
WATER CIRCULATION SYSTEM
The boiler must NOT be used for direct hot water supply or for
sealed systems. The boiler is suitable for connection to pumped
open vent central heating systems, pumped central heating
combined with pumped or gravity indirect domestic hot water
supply systems.
The boiler is NOT suitable for gravity heating systems. The
hydraulic resistances of the boilers at maximum output with 11OC
(20 OF) temperature differentials are shown in the graph below.
Maximum boiler operating temperature should be 82OC (180OF).
The central heating system should be in accordance with
BS. 6798 and, in addition, for smallbore and microbore
systems, BS. 5449:1.
The domestic hot water system, if applicable, should be in
accordance with the relevant recommendations of BS. 5546.
Copper tubing to BS. 2871:1 is recommended for water carrying
pipework.
The hot water storage cylinder MUST be of the indirect type and
should preferably be manufactured of copper.
Single feed, indirect cylinders are not recommended and MUST
NOT be used on sealed systems.
The hot water cylinder and 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 underfloor spaces.
IMPORTANT.
The boiler must be vented. If venting cannot be done via a flow
connection a separate vent MUST be fitted by the installer.
Draining taps MUST be located in accessible positions, which
permit the draining of the whole system - including the boiler and
hot water storage vessel. They should be at least 1/2" BSP
nominal size and be in accordance with BS. 2879.
If required, a drain tap (not supplied) may be fitted to an unused
bottom (1" BSP) tapping on the front of the boiler.

9
British Gas 40 - 80 RD2 - Installation & Servicing
GENERAL
Notes.
a. Flow and return pipes should rise vertically on leaving the
boiler.
b. Horizontal pipes should be ABOVE ceiling level and as short
as possible.
c. A MINIMUM inclination of 25 mm per 3 m run (1" per 10') is
required to avoid air locks.
If the above conditions cannot be met pumped primaries should
be used.
1. Separate flow and return connections are used for each
service. All possible configurations are given in Frame 12
and ONLY those shown should be used.
2. The schematic pipework graph is based on the assumption
that NO MORE than 8 elbows are used in the gravity loop,
including entry to the boiler.
3. For each extra elbow in excess of 8 (R) MUST be reduced by
300 mm (12") or (H) increased by 100 mm (4")
4. Whatever value is selected for (R), the value of (H) MUST be
at least that indicated by the graph.
(R) = the horizontal distance between the centre line of the
cylinder and the boiler tappings used - measured along
the pipe run.
(H) = the vertical distance between the top of the boiler and
the base of the cylinder.
3 MINIMUM REQUIREMENTS Fully pumped systems
1. Open vent and cold feed connections must be made to the
boiler flow and return tappings according to the options
shown in Frame 12.
2. The boiler is assumed to be the highest point of the
circulating system.
3. The circulating pump is positioned on the FLOW and the
vertical distance, between the pump and feed/ expansion
tank, must comply with the pump manufacturer's minimum
requirements, to avoid cavitation. Should these conditions
not apply, either lower the pump position or raise the feed/
expansion tank above the minimum requirements of
British Gas Services.
4. The water velocity through the boiler flow / return pipes is
assumed to be below 1.5 m/s (5 ft./s), whilst the pump flow
rate is set to provide a temperature difference of
11 oC (20 oF) across the boiler flow / return, at design input.
5. This information is intended as a GUlDE ONLY and cannot
take into account instantaneous changes in head caused
by the operation of motorised valves, pumps etc.
Due allowance MUST be made if surging is liable to occur.
If in any doubt, contact British Gas Services.
4 GRAVITY HOT WATER & PUMPED CENTRAL HEATING

10 British Gas 40 - 80 RD2 - Installation & Servicing
GENERAL
5 SEALED SYSTEM REQUIREMENTS
Make-up vessel
(max. capacity
3 litres )
Hose
union
bib
tap
Non-return
valve
Air vent
Water
supply
Pressure gauge Automatic
air vent
Safety valve
Drain cock
BOILER Expansion
vessel
Pump
Hose
connector
HEATING
CIRCUIT Hosepipe
(disconnect
after filling)
BS.1010:2
stop tap
Test cock
Double check valve
Mex 903
Note. The method of filling, refilling, topping up or flushing
sealed primary hot water circuits from the mains via a
temporary hose connection is only allowed if acceptable to the
local water authority.
1. General
a. The installation must comply with the requirements of
BS.6798 and BS.5449.
b. The installation should be designed to work with flow
temperatures of up to 82oC.
c. All components of the system, including the heat exchanger
of the indirect cylinder, must be suitable for a working
pressure of 3 bar (45 lb/in2) and temperature of 110oC. Care
should be taken in making all connections so that the risk
of leakage is minimised.
2. Safety Valve
A spring loaded safety valve complying with the relevant
requirements of BS.6759 must be fitted in the flow pipe, as
close to the boiler as possible and with no intervening valve
or restriction. The valve should have the following features:
a. A non-adjustable pre-set lift pressure not exceeding 3 bar
(45 lb./in2)
b. A manual testing device.
c. Provision for connection of a discharge pipe. The valve or
discharge pipe should be positioned so that the discharge
of water or steam cannot create a hazard to the occupants
of the premises or cause damage to electrical components
and wiring.
3. Pressure Gauge
A pressure gauge covering at least the range 0-4 bar (0-60
lb./in2) must be fitted to the system. The gauge should be
easily seen from the filling point and should preferably be
connected at the same point as the expansion vessel.
4. Expansion Vessel
a. A diaphragm type expansion vessel must be connected at
a point close to the inlet side of the pump, the connecting
pipe being not less than 15mm (1/2" nominal) size and not
incorporating valves of any sort.
b. The vessel capacity must be adequate to accept the
expansion of the system water when heated to 110oC
(230oF)
c. The charge pressure must not be less than the static water
head above the vessel The pressure attained in the system
when heated to 110oC (230oF) should be at least 0.35 bar
(5lb/in2) less than the lift pressure of the safety valve.
For guidance on vessel sizing refer to the table in Frame 6.
For further details refer to BS.5449 and the British Gas
Corporation publication : Material and Installation
Specifications for Domestic Central Heating & Hot Water.
5. Cylinder
The cylinder must be either of the indirect coil type or a direct
cylinder fitted with an immersion calorifier which is suitable
for operating on a gauge pressure of 0.35 bar (5lb./in2) in
excess of the safety valve setting. Single feed indirect
cylinders are not suitable for sealed systems.
6. Make-up Water
Provision must be made for replacing water loss from the
system, either:
a. From a manually fitted make-up vessel with a readily visible
water level. The vessel should be mounted at least 150mm
(6") above the highest point of the system and be
connected through a non-return valve to the system, fitted
at least 300mm (12") below the make-up vessel on the
return side of the domestic hot water cylinder or radiators.
b. Where access to a make-up vessel would be difficult by
pre-pressurisation of the system. Refer to 'Filling.'

11
British Gas 40 - 80 RD2 - Installation & Servicing
GENERAL
6 SEALED SYSTEM REQUIREMENTS - continued
c. Through a temporary hose connection from a draw-off tap
supplied from a service pipe under mains pressure. Where
the mains pressure is excessive a pressure-reducing valve
shall be used to facilitate filling.
The following fittings shall form a permanent part of the
system and shall be fitted in the order stated:
A stop valve complying with the requirements of
BS. 1010, Part 2 (the hose from the draw-off tap shall be
connected to this fitting).
A test cock.
A double check valve of an approved type.
• Thoroughly flush out the whole of the system with cold
water, without the pump in position.
• With the pump fitted, fill and vent the system until the
pressure gauge registers 1.5 bar (21.5lb/in2).
Examine for leaks.
• Check the operation of the safety valve by manually
raising the water pressure until the valve lifts. This
should occur within ± 0.3 bar (± 4.3lb/in2.) of the pre-set
lift pressure.
• Release water from the system until the initial system
design pressure is reached.
• Light the boiler and heat the system to the maximum
working temperature. Examine for leaks.
• Turn off the boiler and drain the system while still hot.
• Refill and vent the system.
• Adjust the initial pressure to the required value.
7. Mains Connection
There must be no direct connection to the mains water supply
or to the water storage tank supplying domestic water, even
through a non-return valve, without the approval of the local
water authority.
8. Filling
The system may be filled by one of the following methods:
a. Through a cistern, used for no other purposes, via a ball
valve permanently connected directly to a service pipe and
/ or a cold water distributing pipe.
The static head available from the cistern should be
adequate to provide the desired initial system design
pressure. The cold feed pipe from the cistern should include
a non-return valve and a stop valve with an automatic air
vent connected between them, the stop valve being located
between the system and the automatic air vent. The stop
valve may remain open during normal operation of the
system if automatic water make-up is required.
b. Through a self-contained unit comprising a cistern,
pressure booster pump (if required) and, if necessary, an
automatic pressure reducing valve and flow restrictor. The
cistern should be supplied through a temporary connection
from a service pipe or cold water distributing pipe.
This unit may remain permanently connected to the heating
system to provide limited automatic water make-up. Where
the temporary connection is supplied from a service pipe
or distributing pipe which also supplies other draw-off points
at a lower level then a double check valve shall be installed
upstream of the draw-off point.
Sizing procedure for expansion vessels: The volume of the expansion vessel (litres) fitted to a sealed system shall not be
less than that given by the table below, multiplied by a factor of 0.8 (for flow temperatures of less than 88 oC).
Safety valve setting 3.0 bar 2.5 bar 2.0 bar
Vessel charge and initial 0.5 1.0 1.5 0.5 1.0 1.5 0.5 1.0
system pressure bar bar bar bar bar bar bar bar
Total water content of system Expansion vessel volume
(litres) (litres)
25 2.1 2.7 3.9 2.3 3.3 5.9 2.8 5.0
50 4.2 5.4 7.8 4.7 6.7 11.8 5.6 10.0
75 6.3 8.2 11.7 7.0 10.0 17.7 8.4 15.0
100 8.3 10.9 15.6 9.4 13.4 23.7 11.3 20.0
125 10.4 13.6 19.5 11.7 16.7 29.6 14.1 25.0
150 12.5 16.3 23.4 14.1 20.1 35.5 16.9 30.0
175 14.6 19.1 27.3 16.4 23.4 41.4 19.7 35.0
200 16.7 21.8 31.2 18.8 26.8 47.4 22.6 40.0
225 18.7 24.5 35.1 21.1 30.1 53.3 25.4 45.0
250 20.8 27.2 39.0 23.5 33.5 59.2 28.2 50.0
275 22.9 30.0 42.9 25.8 36.8 65.1 31.0 55.0
300 25.0 32.7 46.8 28.2 40.2 71.1 33.9 60.0
Multiplying factors for
other system volumes 0.0833 0.109 0.156 0.094 0.134 0.237 0.113 0.20

12 British Gas 40 - 80 RD2 - Installation & Servicing
INSTALLATION
7 BOILER ASSEMBLY - Exploded View With casing removed.
42 Fan sensor
38
12
14
49
41
5
1
7
Tie rod
8
46
Mex 1304
Data badge
65
28 16
18
Return sensor
Overheat sensor
Flow
sensor
92
6A
6B
6
2
4
3
14. Fan assembly.
16. Front plate assy.
18. Burner manifold.
28. Gas cock.
38. Pressure switch.
41. Air inlet duct.
42. Turret access cover assy.
46. Boiler base plate.
49. Flue baffle.
65. Control box.
92. Thermostat bush.
LEGEND
1. Heat exchanger assembly.
2. Front section.
3. Centre section.
4. Section alignment rings and 'O' rings.
5. Back section.
6. Flow thermistor sensor pocket.
6A.Return thermistor sensor pocket.
6B.O/heat thermostat sensor pocket.
7. Distributor tube.
8. Combustion chamber.
12. Collector hood.
INSTALLATION

13
British Gas 40 - 80 RD2 - Installation & Servicing
INSTALLATION
9 BOILER CASING REMOVAL
The boiler is supplied fully assembled in
Pack A, together with a standard flue
assembly for lengths up to 600mm
(23 1/2") rear or side flue outlet in Pack B.
Unpack and check the contents.
8 UNPACKING
Complete boiler
assembly
PACK 'A' CONTENTS
zComplete boiler assembly
zThe Boiler Hardware Pack (listed
separately)
zThe Flue Hardware Pack (listed
separately)
zThese Installation Instructions
zUser's/Servicing Instructions.
zTemplate
BOILER HARDWARE PACK
z1" BSP plugs - 3 off.
zDistributor tube - 1 off.
z28mm x 1"BSP male straight
adapter compression fitting - 3
off.For connection to the boiler
PUMPED & GRAVITY flow /return
tappings.
zFlow sensor pocket -1 off.
zReturn sensor pocket kit
comprising:
Hexagon bush - 1 off.
Sensor pocket - 1 off.
'O' ring - 1 off.
Heyco bush - 1 off.
M5 x 10mm Pozi screw - 3 off.
Washers - 3 off.
zO/heat thermostat pocket - 1off
z1/2" square bar - 1 off.
zCable tie - 4 off.
zControl thermostat knob - 1 off.
zM3 x 6mm Pozi pan screw- 1 off.
zSelf tapping screw - 2 off.
zBritish Gas Logo- 1 off.
zScottish Gas Logo - 1 off.
To install the boiler the casing MUST be removed.
1. Undo the 2 screws and lift off the lower front panel.
2. Remove the 2 screws and lift off the grille assembly.
3. Release the 'Burner On' neon from the rear of the
control panel.
4. Release the wiring harness leads from the edge clips
on the RH side panel.
5. Remove the 2 screws securing the control panel and
pull down to release the tabs from under the top
panel.
Mex 1841
Grille
assy.
Control
panel
FLUE PACK. Pack B Contents
zDuct cutting support - 2 off (cardboard )
zTerminal wall plate - 1 off.
zTerminal grille assy. - 1 off.
zPolyurethane foam seal 400 lg. - 1 off.
zNo. 8 x 8 lg. Pozi pan hd. screws - 3 off.
FLUE HARDWARE PACK
Side outlet plate
zFlue extension tube (rear).
zFlue extension tube (side).
zFlue extension tube (top).
zElbow .
zSealing ring.
zM5 wing nuts - 3 off.
zSide outlet plate.
zNo. 10 x 2" lg. Rd Hd.wood
screws - 4 off.
zWall plugs - 4 off.
Flue terminal Terminal wall plate
INSTALLATION

14 British Gas 40 - 80 RD2 - Installation & Servicing
INSTALLATION
FLUE KITS
Pack B: supplied as standard.
Pack D: optional extension kit for side
flue, top or rear flue outlet. Refer to 'Flue
Extension Ducts'
1. A maximum of 3 extension ducts (plus
the standard flue duct) may be used
together.
2. Flue extensions of greater than 1m
(39") should be supported with the
bracket provided.
It is MOST IMPORTANT that the boiler is installed in a vertical position.
11 DETERMINING THE FLUE LENGTH
10 BOILER CASING REMOVAL - continued
6. Release the screw securing the control box to the
baseplate and slide to the left to release the box.
7. Remove the 2 screws securing the top panel to the
sides.
8. Draw the top panel forward and lift it off the boiler.
9. Remove the 2 screws securing the LH side panel to
the turret front panel and baseplate.
10. Pull the panel forward, disengaging from the
collector hood tab, lift it clear of the locating peg
and remove.
11. Repeat steps 9 and 10 to remove the RH panel.
12. The boiler is held to the packaging base by 4 M6
hex head screws. Remove the front screws,
slacken the rear screws and remove the boiler from
the packaging base.
WARNING.
For top outlet installation the flue
terminal MUST always be in the
horizontal position.
Top outlet flue length
= A + B + Elbow allowance
90oElbow = 1m
45oElbow = 0.7m
Flue length mm Pack Requirement Product No.
Up to 600 B, 1 off 150 308
600 to 1550 B, 1 off + D, 1 off 150 308+152132
1550 to 2500 B, 1 off + D, 2 off 150 308+
152132, 2 off
2500 to 3000 B, 1 off + D, 3 off 150 308+
152132, 3 off
INSTALLATION

15
British Gas 40 - 80 RD2 - Installation & Servicing
INSTALLATION
FLUE OUTLET
12 PREPARING THE BOILER
Notes.
zBefore placing the boiler in the selected position any gas
and water connections at the rear of the boiler should be
prepared, due to the possible lack of access.
zThe pump may be fitted to the FLOW or the RETURN.
1. Screw the distributor tube (supplied with a 1" BSP x 28mm
copper adaptor) into the selected heating return tapping,
using an appropriate jointing material.
IMPORTANT.
It is IMPERATIVE that the index mark on the distributor tube
bush is in alignment with the mark on the section boss, as
shown in Frame 3.
DO NOT disturb it when connecting subsequent pipework.
Fully pumped systems using more than 1 pump, serving
separate zones, must have a common return connection to the
distributor tube.
2. Select the desired pumped flow tapping and fit a 28mm x
1"BSP adapter.
3. Fit the boiler return sensor pocket into the appropriate front
section tapping as follows:
a. Screws the hexagon bush into the tapping using
approved jointing material. Refer to Tables 7 and 8.
b. Fit the 'O' ring into the bush.
c. Insert the sensor pocket, ensuring that it enters the hole
in the end of the distributor tube.
d. Secure the pocket with the 3 screws and washers
provided.
4. Screw the supplied overheat thermostat sensor pocket into
the appropriate front section tapping using approved
jointing material. Refer to Tables 7 and 8.
5. Screw the supplied boiler flow sensor pocket into the
appropriate front section tapping, using an approved
jointing material. Refer to Tables 7 and 8.
6. Fit 28mm x 1"BSP adapter pipe fittings to the appropriate
rear tappings for DHW if required and plug any unused
tappings.
Connections Sensor Position
(as viewed at front)
Back Section Front Section
CH DHW Flow Return O/heat
Flow Return Flow Return Top Bottom Bottom
LH LH RH RH LH LH RH
LH RH RH LH LH RH LH
RH RH LH LH RH RH LH
RH LH LH RH RH LH RH
Table 8
- Gravity Dom. Hot Water & Pumped Central Heating
Table 7 - Fully Pumped Systems
Connections Sensor Position
(as viewed at front)
Back Section Front Section
Flow Return Flow Return O/heat
Top Bottom Top Bottom Bottom
LH LH LH LH RH
LH RH LH RH LH
RH RH RH RH LH
RH LH RH LH RH
13 REAR FLUE ASSEMBLY - Exploded view
56 7
8
1
2
34
Mex 1842
LEGEND
1. Terminal.
2. Weather seal.
3. Flue assembly.
4. Boiler sealing ring.
5. Flue extension tube.
6. Sealing plate.
7. Flue connector.
8. Turret access cover.
1. The boiler turret assembly is factory built for rear flue installation.
2. Remove the turret access cover.
3. Fit the flue extension tube (supplied with the boiler) to the flue
connector, rotate in the bayonet slot and secure with the M4 screws.
For wall thickness 114mm to 600mm

16 British Gas 40 - 80 RD2 - Installation & Servicing
INSTALLATION
FLUE OUTLET
Note. For lengths greater than 600mm see Frame 11.
1. The boiler turret assembly is factory built for rear flue
installation.
2. Remove the turret access cover.
3. Remove the sealing plate from the appropriate side to be
used and refit in the rear outlet.
14 SIDE FLUE ASSEMBLY - Exploded view - For wall thickness 114mm to 600mm
3. Flue assembly.
4. Boiler sealing ring.
5. Flue extension tube ( with ring).
LEGEND
1. Terminal.
2. Weather seal.
4. Fit the outlet elbow pointing in the desired direction. Rotate
in the bayonet slot and secure with the M4 screw.
5. Fit the kit extension tube (with ring) to the flue elbow, rotate
in the bayonet slot and secure with the M4 screw.
6. When cutting the ducts always use the cardboard support
provided.
4
5
32
1
Mex 1843
610 987
15 TOP FLUE OUTLET ASSEMBLY - Exploded view
Note. For lengths greater than 600mm see Frame 11.
1. The boiler turret assembly is factory built for rear flue
installation.
5
Mex 1844
1
6
3
24
7
LEGEND
1. Terminal.
2. Weather seal.
3. Flue assembly.
4. Boiler sealing ring.
5. Flue extension tube.
6. Elbow.
7. Flue connector.
8. Turret access cover.
2. Remove the turret access cover.
3. Remove the sealing plate from the turret access cover and
refit in the rear outlet.
4. Fit the outlet flue elbow pointing upwards, rotate in the
bayonet slot and secure with the M4 screw.
5. Fit the kit extension tube (with no ring) to the flue elbow,
rotate in the bayonet slot and secure with the M4 screw.
6. When cutting the ducts always use the cardboard support
provided.
6. Elbow.
7. Side outlet plate.
8. Flue connector.
9. Sealing plate.
10. Turret access cover.

17
British Gas 40 - 80 RD2 - Installation & Servicing
INSTALLATION
FLUE OUTLET
17 CUTTING THE FLUE - wall thicknesses of 114 to 600mm
1. Measure and note the wall thickness X.
2. Mark the wall thickness onto the flue.
3. To ensure the tube is cut square, mark the flue all
the way round.
4. Cut to length X, using the cardboard ring for
support.
5. Remove cardboard ring and remove any burrs.
16 PREPARING THE WALL
1. Tape the template into the selected position.
2. Mark onto the wall the position of the flue
duct hole.
IMPORTANT. Ensure that, during the cutting
operation, masonry falling outside of the building
does not cause damage or personal injury.
3. Cut the flue hole, preferably with a 125mm
(5") core boring tool, ensuring that the hole is
square to the wall. If the hole has been quite
accurately cut with a drill then making good
the wall faces is not essential as seals are
provided at both ends of the flue. However,
both wall faces immediately around the cut
hole should be flat; make good if necessary.
For less accurate holes make good to
approximately 125mm (5") diameter at the 2
wall faces.
4. Remove the template from the wall.
Note.
If the terminal is to be
sited within 25-40mm
of a corner or vertical
pipe (refer to Table 3)
then the hole MUST
be accurately cut and
the rubber weather
seal trimmed around
the groove provided.
The terminal wall plate
need not be fitted.
18 FITTING THE BOILER SEALING RING TO THE FLUE - Rear and Side
1. Fit the boiler sealing ring inside the outer flue duct. Ensure
the boiler sealing ring is fully engaged.
Ensure the notch aligns with the groove on the outer flue
duct. This ensures correct alignment of the flue terminal.
2. Drill 3 holes 3.2mm (1/8") dia. through the outer flue duct
and boiler sealing ring. Do NOT drill the inner flue
duct.
3. Insert the self-tapping screws, provided, in order to fix the
boiler sealing ring in position.
4. If the boiler is located with the rear against the wall, stick
the self adhesive foam strip, provided, onto the flue
immediately behind the boiler sealing ring. Otherwise refer
to Frame 20.

18 British Gas 40 - 80 RD2 - Installation & Servicing
INSTALLATION
FLUE OUTLET
19 FITTING BOILER SEALING RING TO THE FLUE - Top
1. Fit the boiler sealing ring inside the appropriate
length (A) of outer flue duct (refer to Frame 11).
Ensure the boiler sealing ring is fully engaged.
2. Drill 3 holes 3.2mm (1/8") dia. through the outer flue
duct and boiler sealing ring. Do not drill the inner
flue duct.
3. Insert the self tapping screws, provided, in order to
fix the boiler sealing ring in position.
4. Fit the turret access cover to the sealing ring.
1. To determine the position for the foam seal
measure the wall thickness and mark it onto
the flue, measuring from the groove near the
terminal.
2. Wrap the self-adhesive foam strip round the
flue, ensuring that the foam is on the terminal
side of the line. This seals the gap between
the flue and the wall.
20 FITTING THE FOAM SEAL
21 FITTING THE FLUE ASSEMBLY
A. Inside fitting.
If the flue assembly cannot be fitted from the outside,
proceed as follows:
1. Insert the flue assembly through the hole far
enough to allow the rubber seal to unfold
completely and form an adequate seal on the
outside wall.
2. Ensure the notch is at the top. This will aid the
location of the studs into the boiler back panel.
3. Proceed to Frame 22, item B.
B. Outside fitting.
Proceed to Frame 22, item A.

19
British Gas 40 - 80 RD2 - Installation & Servicing
INSTALLATION
FLUE OUTLET
23 CONNECTING THE FLUE TO THE BOILER - Rear
1. Secure the flue to the boiler
using the three M5 wing nuts
provided.
Note.
The sealing ring studs will locate in
the back panel one way only. This
will ensure that the terminal is
correctly aligned.
1. Secure the flue to the boiler, using the
three M5 wing nuts provided.
2. Fit the kit extension tube (with ring) to the
flue elbow, rotate in the bayonet slot and
secure with the M4 screw.
3. Engage the extension tube into the flue
outlet, connect the elbow to the fan outlet
and secure with the M4 screw.
Note.
The sealing ring studs will locate in the back
panel one way only. This will ensure that the
terminal is correctly aligned.
24 CONNECTING THE FLUE TO THE BOILER - Side
22 LOCATING THE BOILER
Rear and Side flue
A. If the flue assembly can be fitted from the outside,
proceed as follows:
1. Move the boiler into position ensuring that the flue
outlet is in line with the wall opening.
2. Insert the flue assembly ensuring that the flue slides
into the flue extension and the 3 sealing ring studs
locate into the boiler.
B. If the flue assembly has been fitted from the inside
proceed as follows:
1. Move the boiler into position ensuring that the flue
slides into the flue extension tube and the 3
sealing ring studs locate into the boiler back
panel.
Top flue
Position the boiler beneath the flue assembly.
6A.Return thermistor sensor pocket.

20 British Gas 40 - 80 RD2 - Installation & Servicing
INSTALLATION
FLUE OUTLET
26 FITTING THE SIDE OUTLET PLATES
Note. If the boiler is fitted closer than 25mm to the side wall
the side outlet plate must be fitted now.
1. Split the side outlet plate into 2 down the split line.
2. Fit the 2 halves of the side outlet plate to the wall,
ensuring they are behind the boiler sealing ring.
1. Connect the flue terminal to the boiler,
using the length (A) of flue duct
previously cut and ensuring that the
inner flue locates into the kit extension
tube (without ring).
2. Secure the flue to the boiler using the 2
M4 x 16mm screws previously
removed.
25 CONNECTING THE FLUE TO THE BOILER - Top
(Supplied in the Flue Directional Kit)