Benchmark Alpha CD18S User guide

Installation and Servicing
Instructions
Alpha CD18S/24S/30S
Wall Mounted, Fan Assisted, Room Sealed, Gas Fired,
High Efficiency Condensing System Boiler Range
Nepicar House, London Road,
Wrotham Heath, Sevenoaks,
Kent TN15 7RS
For Technical help or for Service call ...
ALPHA HELPLINE
Tel: [phone]
Alpha CD18S G.C. No. 41 532 06
Alpha CD24S G.C. No. 41 532 02
Alpha CD30S G.C. No. 41 532 08
!"#$#%&'()%
Service Listed
For use with Natural Gas only
Leave these instructions with the User

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2Alpha CD18S/24S/30S - Contents/Introduction
CONTENTS
1 Introduction ....................................... 2
2 Technical data ................................... 3
3 General boiler information .................. 6
4 Installation ......................................... 12
5 Commissioning ................................. 18
6 Boiler operation ................................. 21
7 Routine servicing ............................... 22
8 Component replacement ................... 24
9 Wiring diagrams ................................ 29
10 Fault finding ...................................... 31
11 Short parts list ................................... 34
12 Benchmark Checklist ......................... 35
13 Service record ................................... 36
The Alpha CD18S, 24S and 30S are high efficiency condensing, wall mounted, fan assisted, room-sealed system boilers. The
burner is lit electronically and the heat output is controlled by a modulating fan and gas valve.
These are system boilers providing heating only for sealed central heating systems.
The boiler is supplied with a pump, pressure relief valve, expansion vessel and pressure gauge fully assembled and tested.
The boiler provides central heating, and is designed for use with a fully pumped, sealed and pressurised central heating
system using only Natural gas.
The CD18S boiler is suitable for central heating loads of between 4.7 and 19.5 kW (16 050 and 66 500 Btu/h).
The CD24S boiler is suitable for central heating loads of between 4.7 and 25.4 kW (16 050 and 86 700 Btu/h).
The CD30S boiler is suitable for central heating loads of between 6.5 and 29.8 kW (22 200 and 101 700 Btu/h).
IMPORTANT
It is the law that all gas appliances are installed by a competent person, ie CORGI registered personnel, in accordance with
the following recommendations:-
Current Gas Safety (Installation and Use) Regulations
All current Building Regulations issued by the Department of the Environment, i.e. Approved Document L1.
Building Standards (Scotland) (Consolidation) Regulations issued by the Scottish Development Department
Health & Safety Document No. 635 (The Electricity At Work Regulations 1989)
The installation should also be in accordance with the following British Standard Codes of Practice:-
BS 5440:1:2000 Flues
BS 5449:1990 Forced circulation hot water systems
BS 5546:2000 Installation of hot water supplies for domestic purposes
BS 6700:1997 Design, installation, testing and maintenance of services supplying water
BS 6798:2000 Installation of gas fired hot water boilers
BS 6891:1998 Gas installation
BS 7593:1992 Code of Practice for treatment of water in heating systems
BS 7671:2001 Requirements for electrical installations, IEE Wiring Regulations
Reference should be made to DEFRA document 'Guide to condensing boiler installation assessment procedures for
dwellings'.
If installation is in a timber framed building, refer to the Institute of Gas Engineers document IGE/UP/7.
This appliance meets the requirements of IPX4D, ie degree of protection against moisture.
Failure to install this appliance correctly could lead to prosecution. It is in your own interest and that of safety to ensure that the
law is complied with.
Manufacturer's instructions must NOT be taken in anyway as over-riding statutory obligations.
Notes: 1. Ensure that the Benchmark Checklist has been completed after the boiler has been installed and commissioned.
2. The boiler must only be used with Alpha CD condensing flue components.
1 INTRODUCTION

3
2.1 PERFORMANCE - NATURAL GAS !"#$%&'()&()&*&+(,&*&(,&-./01
2 TECHNICAL DATA
Alpha CD18S/24S/30S - Technical Data
Alpha CD18S
MAX.
20.3
69 200
18.3
62 400
19.5
66 500
18.1
61 800
3.5
1.4
1.93
68.2
MIN.
5.5
18 800
5.0
17 000
5.3
18 100
4.7
16 050
0.3
0.12
0.52
18.36
Room sealed
chamber panel
fitted
Central Heating
Heat Input (Hs) kW
(Gross) Btu/h
Heat Input (Hi) kW
(Net) Btu/h
Heat Output (Hscondensing) kW
(50°C/30°C) Btu/h
Heat Output (Hinon-condensing) kW
(80°C/60°C) Btu/h
Differential Burner mbar
Pressure in wg
Gas Rate m³/h
ft³/h
2.4 ELECTRICAL
Supply
External Fuse
Power Consumption CD18/24
CD30
Internal Fuse
Electrode Spark Gap
230/240 V ~ 50 Hz
3 A
130 W
140 W
F2 A
3 - 4 mm
Burner
Main Heat exchanger
Main Burner Injector CD18/24
CD30
Flue - Outer Duct
Flue - Inner Duct
Stainless steel
Stainless steel
5.0 mm
6.6 mm
White
Plastic
2.3 COMPONENTS2.2 SYSTEM
Central Heating (Sealed System)
Max. Working System Pressure
Min. System Pressure
Max. System temperature
Pressure Relief Valve Setting
Expansion Vessel Size (pre-charge press.)
Flow Connection
Return Connection
Relief Valve Connection
Recommended System Pressure (cold)
CH Water Temp. (Approx. max.)
2.5 bar
0.5 bar
82°C
3 bar (44 PSI)
8 L at 0.8 bar
22 mm
22 mm
15 mm
1.0 bar
82°C (180°F)
Alpha CDS models
Alpha CD24S
Alpha CD30S
MAX.
26.4
90 100
24.0
82 000
25.4
86 700
23.5
81 135
5.78
2.30
2.54
89.7
MIN.
5.5
18 800
5.0
17 100
5.3
18 100
4.7
16 050
0.35
0.14
0.53
18.7
Room sealed
chamber panel
fitted
Central Heating
Heat Input (Hs) kW
(Gross) Btu/h
Heat Input (Hi) kW
(Net) Btu/h
Heat Output (Hscondensing) kW
(50°C/30°C) Btu/h
Heat Output (Hinon-condensing) kW
(80°C/60°C) Btu/h
Differential Burner mbar
Pressure in wg
Gas Rate m³/h
ft³/h
MAX.
31.1
106 100
28.0
95 550
29.8
101 700
28.0
95 500
3.33
1.33
2.98
105.2
MIN.
7.3
24 900
6.6
22 500
7.0
23 900
6.5
22 200
0.39
0.16
0.69
24.4
Room sealed
chamber panel
fitted
Central Heating
Heat Input (Hs) kW
(Gross) Btu/h
Heat Input (Hi) kW
(Net) Btu/h
Heat Output (Hscondensing) kW
(50°C/30°C) Btu/h
Heat Output (Hinon-condensing) kW
(80°C/60°C) Btu/h
Differential Burner mbar
Pressure in wg
Gas Rate m³/h
ft³/h

4
2.7 FLUE LENGTHS
CD Easy-Flue 500 mm with terminal and 90° bend. A CD Easy-Flue 1000 mm with terminal and 90° bend is also available.
CD 750 mm and CD 1000 mm flue extensions are available.
Length of Flue Required:-
Rear Flue = wall thickness + 170 mm (includes terminal)
Side Flue = wall thickness + distance between wall and side of boiler + 230 mm (includes terminal)
Vertical Flue = distance from top of boiler side panel to required roof position minus 1 m for vertical terminal assembly
Maximum horizontal flue length = 12 m.
Maximum vertical flue length including terminal is 15 m.
Each additional CD 90° Bend is equivalent to 1.3 m of flue length.
Each CD 45° Bend is equivalent to 0.9 m of flue length.
The CD Vertical Flue terminal assembly is equivalent to 1 m of flue length.
2.8 AVAILABLE PUMP HEAD FOR CENTRAL HEATING
gal/min
3.7
2.8
2.3
1.8
0.7
Btu/h
86 700
64 000
53 000
42 200
18 100
kW
25.40
18.70
15.60
12.35
5.30
Output (50/30°C) Available pump head
metres
2.3
3.5
3.8
4.0
4.6
feet
7.6
11.6
12.6
13.2
15.2
litre/min
16.6
12.6
10.5
8.3
3.2
20°C 20°C
Flow rate
This information is based on 20°C system design temperature difference. Note: For outputs upto 30 kW refer to Section 3.7.
Alpha CD18S/24S/30S - Technical Data
L
N
1
2F2A
3
4
Fig. 1
Boiler terminal block
Clock connections
2.9 ELECTRICAL CONNECTIONS
Note: This Appliance Must Be Earthed
An optional integral two channel Clock kit (Part No. 6.1000220) is available if required.
Note: Only use the Alpha two channel clock. Do not fit any single channel clocks.
1. Ensure wires are connected
correctly
2. Only fit the Alpha recommended
2 channel clock. Other clocks
could cause damage.
WARNING
12345
Internal 2 Channel Clock Terminals
White
wire
Grey
wire
Black
wire
Blue
wire
Brown
wire
Fuse - Always fit fast blow 2 A
230/240 V ~ 50 Hz
Fuse supply 3 A
Note: To connect external
control, remove link from
terminals 1 and 2 and
connect a 230/240 V
switched live to terminal 1
Live (Brown wire)
Neutral (Blue wire)
Earth (Green/Yellow wire)
Switched Live
230/240 V (Ch1 ON)
Ch1 OFF
Ch2 ON
Use only when internal
two channel clock is
fitted
850 mm
450 mm
345 mm
380 mm
15 mm
22 mm
2.5 L
3.0 L
100 mm
60 mm
Case Dimensions Height
Width
Depth CD18/24
Depth CD30
Gas Connection CD18
CD24/30
Primary Water Content CD18/24
CD30
Air Duct Diameter
Flue Duct Diameter
2.6 GENERAL
Min. Clearances for Servicing Top
(from casing) Bottom
Sides
Front
Flue Terminal Size
Flue Terminal Protruding
Hole Size Required For Flue Assy.
Lift Weight CD18/24
CD30
2.5 INSTALLATION
220 mm
250 mm
5 mm
450 mm
100 mm Dia.
100 mm
110 mm Dia.
46 kg
48 kg

5
2.10 BOILER SCHEMATIC
Alpha CD18S/24S/30S - Technical Data
1 - Flue sampling point
2 - Flue thermostat
3 - Injector
4 - Gas valve
5 - Primary temperature sensor
6 - Venturi
7 - Main burner
8 - Primary/condensing heat exchanger
9 - Room sealed chamber
10 - Fan
11 - Pressure differential test points
Fig. 2
12 - Flue hood
13 - Overheat thermostat
14 - Expansion vessel
15 - Automatic air vent
16 - Pump
17 - Drain point
18 - Pressure relief valve
19 - Primary pressure switch
20 - Ignition electrodes
21 - Flame sensing electrode
22 - Venturi negative point
23 - Venturi positive point
24 - Gas service cock
25 - On/off valve (2 off)
26 - Automatic by-pass
27 - Cyclone separator
28 - Condensate trap

6
3.1 GAS SUPPLY
The Alpha CD18S boiler requires a gas rate of 1.93 m³/h (68.2 ft³/h).
The Alpha CD24S boiler requires a gas rate of 2.54 m³/h (89.7 ft³/h).
The Alpha CD30S boiler requires a gas rate of 3.45 m³/h (121.8 ft³/h).
The meter and supply pipes must be capable of delivering this quantity of gas in addition to the demand from any other
appliances in the house. The CD18S boiler requires at least a 15 mm gas supply pipe and the CD24/30S boilers require a 22
mm gas supply.
The complete installation, including the meter, must be tested for gas soundness and purged as described in BS 6891.
3.2 ELECTRICAL SUPPLY
The boiler requires a 230/240 V ~ 50 Hz mains supply, fused at 3 A
The boiler must be earthed.
There must only be one common isolator, providing complete electrical isolation, for the boiler and any external controls.
This boiler has been fitted with a supply cable, however, if it is necessary to fit a cable use PVC insulated cable not less than
0.75 mm² (24 x 0.2 mm) to BS 6500 Table 16. The boiler should be connected to a fused three pin plug and unswitched
shuttered socket outlet (both complying with BS 1363), or a fused double pole switch with a contact separation of at least 3 mm
in both poles.
Wiring external to the boiler must be in accordance with the current IEE Wiring Regulations (BS 7671).
Note: If a room thermostat is fitted, it must be suitable for 230/240 V switching.
3.3 AIR SUPPLY
The boiler does not require any air vents for cooling in the room in which it is installed or when installed in a cupboard or
compartment. The minimum clearances for servicing must always be maintained.
Note: A cupboard or compartment used to enclose the boiler must be designed and constructed specifically for the purpose,
i.e. comply with the Building Regulations.
3.4 FLUE SYSTEM - Fig. 3
The flue system must be installed in accordance with BS 5440:1.
For horizontal flues ensure the flue assembly is horizontal and the inner duct is sloping downwards towards the boiler.
Flue components are available as follows:-
CD Easy-Flue 500 mm (includes 90° bend and terminal) - Part No. 6.2000500.
CD Easy-Flue 1000 mm (includes 90° bend and terminal) - Part No. 6.20001000.
CD 0.75 m flue extension - Part No. 6.2000750.
CD 90° bend - Part No. 6.2000590.
CD 45° bend - Part No. 6.2000545.
CD Vertical flue terminal assembly. Refer to the separate installation instructions supplied with the assembly.
The following methods determine the correct length of flue required.
For rear exit flue (including terminal) L = B + 170 mm
For side exit flue (including terminal) L = B + C + 230 mm (min. side clearance required is 5 mm)
For vertical flue L = H minus 1000 mm for vertical terminal assembly
Where L = Required flue length
B = Finished wall thickness
C = Distance from the inside wall to the side of the boiler
H = Distance from top of boiler side panel to roof position
Note: 1. If an extra 90° bend is used, this reduces the maximum flue length by 1.3 m. Each 45° bend used reduces the maximum
flue length by 0.9 m.
2. Under no circumstances must the flue length (including allowances for extra bends) exceed 12 metres horizontally and
only 15 metres vertically.
3. Failure to use Alpha CD flue components with the boiler will invalidate the boilers CE approval, guarantee and may be
unsafe.
3 GENERAL BOILER INFORMATION
Alpha CD18S/24S/30S - General Boiler Information

7
HORIZONTAL FLUE OPTIONS - Lmax = 12 metres
L = B + C + E + 230 mm
Alpha CD18S/24S/30S - General Boiler Information
L = B + C + 230 mm
CB
E
CB
E
B
F
B
C
L = B + E + F + 230 mm + (90° bend = 1.3 metre)
L = B + C + 230 mm + (2 x 45° bends = 1.8 metre)
Fig. 3
VERTICAL FLUE OPTIONS

8
3.5 FLUE TERMINAL LOCATION - Fig. 4
Note: In certain weather conditions the terminal will emit a plume of steam. If possible avoid positioning the terminal where this may cause
a nuisance, i.e. positions A, D, G, H, J or M.
The flue terminal must be exposed to the external air and the position must allow the free passage of air across it at all times.
If the terminal is fitted within 850 mm of a plastic or painted gutter or 450 mm of painted eaves, an aluminium shield at least 1 m
long should be fitted to the underside of the gutter or painted surface. A terminal must not be sited below 2.1 m where people
have access to, such as public footpaths, access routes, patios etc. However, If the terminal is fitted less than 2.1 m above a
surface where there is no public access, the terminal must be protected by a terminal guard.
A suitable guard is available from Alpha Therm Ltd.
3.6 BOILER LOCATION
The boiler is not suitable for external installation unless it is installed within a purpose designed weatherproof building.
The boiler must be installed on a flat vertical wall which is capable of supporting the weight of the boiler. The boiler can be fitted
to or adjacent to a wall comprising of a combustible material without the need for a special thermal insulation barrier.
If the boiler is to be fitted in a timber framed building, it should be fitted in accordance with the Institute of Gas Engineers 'Guide
for Gas Installations in Timber Frame Housing', reference IGE/UP/7.
The boiler may be installed in any room or internal space, although particular attention is drawn to the requirements of the
current IEE Wiring (BS7671) 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 boiler is installed in a room containing a bath or shower, it must not be possible for a person using the bath or shower
to touch any electrical switch or boiler control utilising mains electricity.
The boiler may be installed in a cupboard or compartment, provided it is correctly designed for that purpose, i.e. complies with
the Building Regulations and the requirements of BS 6798.
Alpha CD18S/24S/30S - General Boiler Information
A Directly below an opening, air brick, windows, etc.
B Below gutters, soil pipes or drain pipes
C Below eaves
D Below balconies
E From a vertical drain pipe or soil pipe
F From an internal or external corner
G Above ground, roof or balcony level
H From a surface facing the terminal
I From a terminal facing the terminal
J Above an opening, air brick, window etc.
K Vertically from a terminal on the same wall
L Horizontally from a terminal on the same wall
M Horizontally from an opening, air brick, window etc.
Min. distance (mm)Terminal position
Fig. 4
300 (See Note 1)
75 (See Note 3)
200 (See Note 3)
200 (See Note 3)
150 (See Note 3)
300 (See Note 2)
300
600 (See Note 4)
1200 mm
300 (See Note 1)
1500 mm
300 mm
300 mm (See Note 1)
Note: A terminal must not be sited under a car port roof
Notes: 1. In addition, the terminal should not be nearer
than 150 mm to the framework of an
opening into the buiding, i.e. a window
surround or door surround.
2. This clearance may be reduced to 25 mm
without effecting the performance of the
boiler. However, to ensure the condensate
plume does not affect adjacent surfaces a
clearance of 300 mm is preferable.
3. These clearances may be reduced to 25 mm
without effecting the performance of the
boiler. However, to ensure the condensate
plume does not affect adjacent surfaces the
terminal should be extended beyond gutters,
pipes, eaves, balconies etc.
4. To reduce the possibility of nuisance to
neighbouring buildings etc. it is
recommended the terminal shouild not be
less than 2500 mm from car parking spaces,
building boundary walls, fences etc.

9
3.7 CENTRAL HEATING SYSTEM - Fig. 5
The boiler is designed for use in a sealed central heating system in accordance with the requirements of BS 5449 and BS 6798.
The system should be designed to operate with flow temperatures of up to 82°C. When designing the system, the pump head, expansion
vessel size, mean radiator temperature, etc. must all be taken into account. Refer to the pump performance table for guidelines.
System volume - The expansion vessel incorporated into the boiler is suitable for a sealed heating system with a maximum
water content of 80 litres (18 gal). Above 80 litres, consideration should be given to fitting an additional expansion vessel fitted
in the position shown in Fig. 5. To check correct operation of the expansion vessel(s) the system pressure should not be more
than 2.5 bar when the system is at maximum operating temperature (for further guidance refer to BS 7074:1).
The boiler is supplied with the following components built in:-
Pressure relief valve - complying with BS 6759 and set to operate at 3 bar. The discharge pipe must be routed clear of the
boiler and terminated in such a manner that it can be seen, but cannot cause injury to persons or property.
Pressure gauge - To indicate the system pressure to be maintained.
Expansion vessel - Conforming to BS 4814 with a capacity of 8 litres and pre-charged to a pressure of 0.8 bar.
By-pass - The boiler incorporates a by-pass, however where all radiators are fitted with thermostatic radiator valves it is
recommended a system by-pass, preferably automatic is fitted.
Cyclone - This is a device fitted in the heating return within the boiler to remove any foreign or solid matter etc. from the
system.
Alpha CD18S/24S/30S - General Boiler Information
3.8 FILLING THE CENTRAL HEATING SYSTEM - Figs. 6, 7
The system design pressure (cold) should be set to 1.0 bar. This pressure is equivalent to a static head (see Fig. 5) of 10.2 metres of water.
Provision should be made to replace water lost from the system. This can be by manual or automatic means, as shown in Figs.
6 and 7. The position for connecting an automatic make-up vessel is indicated in Fig. 5. A double check valve assembly must
be used, as shown in Fig. 7.
Filling of the system must be carried out in a manner approved by the local Water Undertaking. Where allowed, the system may
be filled via a temporary connection as shown in Fig. 6. After filling, always disconnect the flexible hose of the filling loop.
All fittings used in the system must be able to withstand pressures up to 3 bar.
Drain taps (to BS 2879) must be used to allow the system to be completely drained.
Note: A drain tap should be installed at the lowest
point of the heating circuit and beneath the appliance.
System
drain tap
Static head of system
Make up vessel
Additional expansion
vessel (if required)
Automatic
air vent
Boiler
casing
Heating flow
Heating return
Filling point
Double check valve assy.
Note: if required, an automatic by-pass is
preferred.
Heating
by-pass
(If required)
Fig. 5
Fig. 6 Fig. 7
Filling loop
temporarily connected
Heating circuit
return Mains
water
supply
Stop
valve
Hose
unions
Stop
valve
Double check
valve assembly
Test cock
Feed cistern to be
located above highest
point in the system
Mains
water
supply
Stop
valve
Test cock
Double check
valve assembly
Overflow
Heating circuit
return

10 Alpha CD18S/24S/30S - General Boiler Information
3.9 FLUSHING THE HEATING SYSTEM
It is essential that the central heating system is thoroughly cleaned and flushed when fitting an Alpha CD boiler. Failure to do so
will invalidate the warranty.
The primary condensing heat exchanger is constructed in stainless steel and therefore is compatible with most materials used
in a heating system.
If a cleaning agent and inhibitor are used, they must be applied in accordance with their manufacturers instructions. Only
products from Fernox and Sentinel are acceptable for use with the Alpha CD boilers. Further information can be obtained from
Fernox (Tel: [phone]) or Sentinel (Tel: [phone]).
Although the Cyclone is fitted in the heating return on the boiler, the heating system should still be thoroughly flushed as
detailed below. The Cyclone collection point should be emptied via the drain point (see Fig. 11) after flushing has been
completed.
The system should be flushed in accordance with BS 7593 and BS 5449. The following procedures are recommended:
1. Installing onto a new system:-
a.Fill the system, vent at high points, at pump and radiators.
b. Check for leaks.
c. Rapidly drain the system.
d.If required, chemically clean the system as instructed by the recommended cleaner manufacturer.
Note: Ensure that the system is flushed to remove any remains of the cleaner.
e.If chemical cleaner is not used to clean the system:-
i) Refill the system.
ii) Switch on the boiler and allow the system to heat up to the normal operating temperature.
iii) Rapidly drain the system while the water is still hot.
iv) Refill the system.
f. As required, add the recommended inhibitor to the system as instructed by the inhibitor manufacturer.
g. Recheck for leaks.
2. Installing onto an existing system, clean the system before fitting the new boiler:-
a. If the old boiler is still working:-
i) Switch on the boiler and allow the system to heat up to the normal operating temperature.
ii) Rapidly drain the system while the water is still hot.
iii) Refill and chemically clean the system as instructed by the recommended cleaner manufacturer.
iv) Ensure the system is flushed to remove any remains of the cleaner.
v) Fit the new boiler.
b.If the old boiler is not working:-
i) Rapidly drain the system.
ii) Remove the old boiler.
iii) Flush the system through.
iv) Fit the new boiler.
v) Refill and chemically clean the system as instructed by the recommended cleaner manufacturer.
vi) Ensure the system is flushed to remove any remains of the cleaner.
c. As required, add the recommended inhibitor to the system as instructed by the inhibitor manufacturer.
d. Check for leaks.
3.10 DISPOSAL OF CONDENSATE
Provision must be made for the safe disposal of condensate produced by the flue gases of the Alpha CD boilers and reference
should be made to BS 6798: 2000 for the requirements on the disposal of condensate.
The boilers incorporate a condensate trap which has a seal of 75 mm, therefore no additional trap is required.
The condensate should ideally be discharged internally into an internal waste pipe (washing machine/sink waste) or soil pipe to
avoid the possible risk of freezing. The pipework must be in 22 mm pipe.
External pipe runs should be avoided, but if it is necessary, the pipework should be at least 32 mm and protected from the risk
of freezing with a waterproof insulation and the length should be kept to a maximum of 3 m. Termination should be into an
external gulley or soakaway as shown in Figs. 8 and 9.
Note: All pipework must have a continuous fall (see Figs. 8 and 9) from the boiler and must be of an acid resistant material
such as plastic waste pipe. (copper or steel is not suitable).
It should be noted that the connection of a condensate pipe to a drain may be subject to local building control requirements.

11
Alpha CD18S/24S/30S - General Boiler Information
Fig. 9 - External soakaway
Fig. 8 - External gully

12 Alpha CD18S/24S/30S - Installation
4 INSTALLATION
4.1 UNPACKING
1. The boxes required when the boiler is installed with a horizontal flue are as follows:-
Box 1 Cased boiler fitted with water and gas valves, filling loop, union bends and washers
Mounting bracket plus screws and wall plugs
Literature pack and Wall template
Box 2 CD Easy-Flue 500 mm or CD Easy-Flue 1000 mm. Both include 90° bend and horizontal flue terminal
Note: NOT required for vertical flue
Notes: a. All flues must be suitable for CD condensing boilers.
b. CD 750 mm and 1000 mm flue extensions are available, if required.
2. Unpack boiler and remove the loose items packs and mounting bracket.
Note: The boiler can be stood in an upright position, (to allow this, the union bends have been turned upwards so that
they do not protrude beneath the bottom - check this before standing the boiler upright).
4.2 CLEARANCES REQUIRED - Fig. 10
Fig. 10
4.3 PREPARE THE WALL - Figs. 11, 12
1. Decide upon the position of the boiler taking into
account the clearances required for servicing and the
flue terminal position.
2. Tape the template to the wall (ensure it is level and the
right way up) and mark the position of the holes for the
boiler mounting bracket and bottom fixings. If rear exit
flue is used, mark the position of the hole for the flue.
3. Side exit flue - Continue the horizontal centre line of the
flue across the wall to the side wall, then along the side
wall 165 mm (ensure the lines are horizontal). This will
give the position of the centre of the hole for the flue.
4. Cut the 110 mm diameter hole (or use a 107 mm core
drill) in the wall for the flue.
Notes: a. Ensure the hole is horizontal.
b. For internal fitting of the flue, using the flue
sealing collar supplied, cut a 130 mm dia. flue
hole using a 127 mm core drill.
5. Drill the fixing holes (10 mm dia.) to accept the No.10
plugssupplied.Using thescrews supplied, fitthe mounting
bracket.
6. Top pipe connections - Preform the pipework at the back of the boiler before hanging the boiler, see Fig. 12, and secure in
the clips provided.
Fig. 11

13
4.4 FIT THE BOILER - Refer to Fig. 11
1. Lift the boiler and locate it on the mounting bracket. Fit the bottom screws to secure the boiler in position.
Alpha CD18S/24S/30S - Installation
Fig. 12
4.5 CONNECT THE PIPEWORK - Fig. 13
1. Thoroughly flush out all the water pipework. Refer to Section 3.9.
2. The valves/fittings have been factory fitted, however, check that all the connections underneath the boiler have been
tightened, especially the union bends.
The heating union bends have been designed to enable the heating pipes to be routed from above and/or below using the
same fitting.
Note: When soldering to the boiler union bends, ensure the bends are not connected to the valves, otherwise the internal
seals may be damaged.
3. Connect the system pipework to the boiler.
Note: Do not forget that the pressure relief valve discharge pipe must be routed clear of the boiler to a drain in such a
manner that it may be seen, but cannot cause injury to persons or property.
4. Connect the 22 mm condensate trap drain pipe to the condensate discharge pipe.
Ensure that the condensate discharge pipe is as required in Section 3.10.
Pour at least 0.5 litre of water into the flue duct, as shown in Fig. 12, and check the condensate discharge pipe for soundness.
5. Ensure that all the valves are closed (spindle flats at right angles to valve) and do not turn on the water or gas supplies at this stage.
Cyclone
G
E
F
Condensate
trap
23
70 212.5 70 50
47.5
B D C A
Heating return
valve
Fig. 13
A- Heating flow (22 mm)
B- Gas inlet (22 mm)
C- Heating return (22 mm)
D- Pressure relief valve (15 mm)
E- Heating drain point
F - Condensate discharge pipe
G - Cyclone drain point

14
2. Determine the overall length (L) of flue required, (see Fig. 16) as follows:-
Rear flue L = wall thickness (B) + 170 mm
Side flue L = wall thickness (B) + distance between boiler and wall (C) + 230 mm
Fig. 16
3. Adjust the telescopic section of the flue to the distance 'L', ensuring that the two labels marked 'TOP' are aligned, then seal
and secure the joint between the ducts with the sealing tape supplied.
4. Pass the flue assembly through the wall (from inside or outside).
Note: Internal fitting - If there is no access to make good the outside wall, locate the flue sealing collar onto the outer duct
of the flue immediately before the terminal grille onto the location provided. Push the flue assembly through the 130 mm flue
hole, so that the collar completely passes through the wall. Then pull the flue assembly back into the correct position. Visually
check that the collar is sealing the outside wall and that it is not restricting any of the openings of the flue terminal.
5. Position the seal and clamp (two screws) supplied, over the bend. Fit the bend to the boiler and rotate to the correct position.
Secure in position using the seal and clamp, ensuring the seal is located centrally over both the bend and boiler adaptor.
6. Fit the inside flue sealing collar over the Easy-Flue. Fit the outside flue sealing collar onto the flue immediately before the
terminal grille onto the location provided.
7. Slide the clamp (three screws) over the outer duct and pull the flue assembly towards the bend, locating the inner duct into
the seal joint on the bend. Ensure the labels marked 'TOP' are positioned at the top before securing the flue assembly to
the bend with the clamp (three screws) located centrally over the joint.
Note: Check the flue terminal protrudes 100 mm out of the wall and the inner duct of the terminal is positioned correctly
(see Fig. 18).
8. Make good the inside wall by pushing the inside flue sealing collar upto the wall.
Fig. 17 - Fitting the flue from inside
4.6 FIT THE FLUE - Figs. 14, 15
The following procedure applies to fitting an Alpha CD Easy-Flue to both rear or side exit flue - horizontally only.
1. The CD Easy-Flues are suitable for use in the flue length ranges shown in the tables below.
Note: Where the length is less than the minimum or more than the maximum, refer to Section 4.7.
Alpha CD18S/24S/30S - Installation
Fig. 14 Fig. 15
CD Easy-Flue
500 mm
1000 mm
B (mm)
Max
520
915
Min
280
675
CD Easy-Flue
500 mm
1000 mm
Max
460
855
Min
220
615
B + C (mm)

15
4.7 EXTENDING THE FLUE - Fig. 19
Note: The maximum horizontal flue assembly length must not exceed a length of 12 metres.
1. When the flue length required is more than the maximum or less than the minimum stated in Section 4.6, paragraph 1,
refer to the table below.
Alpha CD18S/24S/30S - Installation
Fig. 18 - Rear flue
2. Use the template (supplied with the boiler) to mark the required flue position and cut a 130 mm diameter hole for the flue
(use a 127 mm core drill). The size of the hole provides sufficient clearance for the clamps on the flue extension to pass
through the hole.
3. Determine the overall flue length as described in Section 4.6, paragraph 2 to determine the number of Alpha CD 750/1000 mm
flue extensions required.
4. Assemble the flue extensions together by locating the inner duct into the seal joint and secure each extension together
with the clamps supplied (three screws). Ensure that the clamps are positioned centrally over the joints.
Note: If it is required to cut an extension, DO NOT cut the end of the inner duct that incorporates the seal joint. Ensure the
inner duct end without the seal joint is cut so that it is 15 mm longer than the outer duct.
5. Adjust the telescopic section of the Easy-Flue to the required length and secure the Easy-Flue with the sealing tape
supplied. Fit the Easy-Flue to the extensions by locating the inner duct into the seal joint and secure with the clamp (three
screws), ensuring it is located centrally over the joint.
6. Mark the end of the flue assembly 'TOP' where it is connected to the boiler,so that the 'TOP' of the flue terminal is aligned
with the 'TOP' at the boiler end of the flue assembly.
7. Pass the complete flue assembly through the wall.
Flue Length
Up to maximum:-
Between:-
Between:-
Between:-
Less than:-
Rear Flue (B)
11.83 m
675 mm and 915 mm
520 mm and 675 mm
280 mm and 520 mm
280 mm
Side Flue (B + C)
11.77 m
615 mm and 855 mm
460 mm and 615 mm
220 mm and 460 mm
220 mm
Comments
Alpha CD 750 mm or 1000 mm flue extension
(Part No. 6.2000750 or 6.2001050) is required to
extend the range of telescopic flue.
Refer to Section 4.7 paragraph 2 for instructions
on how to extend the flue.
Note: A 130 mm flue hole (127 mm core drill) is
required in the wall.
Within the standard Easy-Flue 1000 mm
(Part No. 6.20001000) telescopic range.
Use an Easy-Flue 1000 mm (Part No. 6.20001000)
and the terminal may protrude somewhat from the
outside wall.
Within standard Easy-Flue 500 mm
(Part No. 6.2000500) telescopic range.
Terminal may protrude somewhat from the outside
wall.

16 Alpha CD18S/24S/30S - Installation
8. Position the seal and clamp (two screws) supplied, over the bend. Fit the bend to the boiler and rotate to the correct
position and secure in position using the seal and clamp, ensuring that the seal is positioned centrally over both the bend
and adaptor.
9. Slide the clamp (three screws) over the outer duct and pull the flue assembly towards the bend, locating the inner duct into
the seal joint on the bend.
10. Secure the flue assembly to the bend with the clamp (three screws) ensuring it is positioned centrally over the joint,
ensuring the 'TOP' marked on the outer duct is positioned at the top.
Note: Check the flue terminal protrudes 100 mm out of the wall and that the inner duct of the terminal is positioned
correctly, i.e. the inner duct within the terminal is at the top. See Fig. 19.
11. Make good the outside wall by fitting a flue sealing collar onto the location provided immediately behind the flue terminal
grille. Make good the inside wall as required.
Note: If flue sealing collars are being used to make good the inside wall, then they will need to be fitted before assembling
the flue.
4.8 CONNECT THE MAINS SUPPLY - Fig. 20
1. Gain access to the boiler terminal block by releasing the two
fixing screws (one each side) securing the control panel and
lowering the panel. Refer to Technical Data, Section 2.9 for
connection details.
2. Note: This boiler has been fitted with a mains supply cable.
However, if it is necessary to fit an alternative supply cable,
ensure the cable clamp that has been fitted is removed and
connect as follows:-
Remove the two screws securing the terminal block cover
from the back of the control box (see Fig. 20). Pass the mains
supply cable through the cable clamp and connect as follows:-
Brown to L, Blue to N and Green/Yellow to . Ensure correct
polarity.
Note: Ensure that the length of the earth wire is such that if
the supply cable is pulled out of its clamp the live and
neutral wires become taut before the earth wire.
The main terminal block can be removed by pulling it off the
pins to give easy access to the terminals.
Do not switch on the electrical supply at this stage.
Fig. 19 - Side flue
Fig. 20
Terminal block cover
Cable clamps
Fuse
Remove link
to connect
external
controls
Main terminals 3 and 4
(refer to Fig. 1b)

17
Fig. 21
Alpha CD18S/24S/30S - Installation
3. If an external control, i.e. room thermostat or external clock is to be fitted, remove the terminal block cover and
remove the link between terminals 1 and 2. Pass the cable through the cable clamp and connect it to terminals 1 and 2.
Replace the terminal block cover. (Refer to Section 2.9).
Note: If an internal clock is being fitted, refer to Section 2.9, Fig. 1 for connecting to terminals 3 and 4.
4. Replace the terminal block, ensuring it is located correctly on the plastic pins and replace the cover.
5. Ensure that there is sufficient free cable to allow the control panel to be raised and lowered then tighten the cable clamp screws.
6. Leave the control panel open until commissioning procedures have been completed.
7. Carry out electrical system checks - Short circuit, Polarity, Earth continuity and Resistance to earth with a suitable multimeter.
4.9 FITTING AN INTERNAL CLOCK KIT (Optional) - Fig. 21
Ensure the electrical supply to the boiler is isolated.
IMPORTANT - Only use an Alpha two channel clock. Do not fit a single channel clock.
1. Remove the two screws securing the clock cover at the rear of the control panel.
2. Remove and discard the clock blanking panel.
3. Insert the clock into the opening and secure in place with the screws supplied - do not overtighten the screws.
4. i). Disconnect the clock wiring from the in-line connector and connect the wires to the clock as follows:-
Brown wire to terminal 1, Blue wire to terminal 2, Black wire to terminal 3, Grey wire to terminal 4 and White wire to
terminal 5, (or, as per the instructions supplied with the clock). Ensure wiring is correct.
ii). Replace the clock cover. Do not overtighten the fixing screws.
iii). Leave the control panel open until commissioning procedures have been completed.

18 Alpha CD18S/24S/30S - Commissioning
5 COMMISSIONING
When commissioning the boiler, ensure the Benchmark Checklist is completed.
5.1 FILL THE SYSTEM
1. The boiler is fitted with an automatic air vent positioned on the pump (see Fig. 2). The vent is always open and has no
sealing cap.
2. Open the central heating flow and return valves (slot in-line with valve) (see Fig. 13).
3. Open the fill point valve on the filling loop until water is heard to flow. To aid venting, the boiler drain point (see Fig. 2) may
be opened until water flows out. Close the drain point as soon as water appears.
4. To remove the air - Vent each radiator in turn, starting with the lowest in the system.
5. It is important that the pump is properly vented to avoid it running dry and damaging its bearings. Unscrew and remove the cap
from the centre of the pump. Using a suitable screwdriver rotate the exposed spindle about half a turn, then replace the cap.
6. Check the operation of the pressure relief valve (see Fig. 2) by turning the head anti-clockwise until it clicks. The click is
the valve lifting off its seat allowing water to escape from the system - check that this is actually happening.
7. Continue to fill the system until the pressure gauge indicates 1.0 bar. Close the fill point valve and check the system for
water soundness, rectifying where necessary. Disconnect the filling loop from the mains supply.
Water may be released from the system by manually operating the drain point (see Fig. 2) until the system design
pressure is obtained. The system design pressure (cold) should be between 0.75 and 1.25 bar.
Refer to Sections 3.7 and 3.8. System volume, Flushing and Filling the system.
8. Open the mains water inlet valve (see Fig. 13). Turn on all hot water taps and allow water to flow until no air is present.
Turn off taps.
9. Ensure that the condensate trap has been filled with water. Refer to Section 4.5, paragraph 4.
5.2 BOILER CONTROLS - Fig. 22
Fig. 22
5.3 TEST FOR GAS SOUNDNESS AND PURGE THE SUPPLY
1. With the boiler gas service cock closed (slot at right angles to valve). Pressure test the gas supply and inlet pipework
connection to the boiler gas service cock for soundness in accordance with BS 6891.
2. Loosen the gas inlet pressure test point screw on the gas valve (see Fig. 24). Ensure the gas supply is on and open the
boiler service cock to purge in accordance with BS 6891.
3. Retighten the test point screw and test for gas soundness. Close the boiler gas service cock.
5.4 INITIAL LIGHTING - Refer to Fig. 22
1. Ensure that the gas and electrical supplies to the boiler are off and that the mains water inlet valve and the central heating
flow and return valves are open.
2. Turn on the gas and electrical supplies to the boiler.
3. Ensure all external controls are calling for heat.
If the optional clock is fitted, refer to the clock's User instructions, set the time and ensure the clock is in an 'on' mode.
4. Set the central heating thermostat to maximum.
5. Set the boiler selector switch to 'ON'. The boiler will now run in the central heating mode. The pump will start, the fan will
start and the main gas valve solenoid will open allowing the main burner to light.

19
5.5 CHECK THE BURNER PRESSURES - Figs. 23, 24
Turn the boiler off. Remove the two pressure test point screws at the top of the boiler and connect a differential pressure gauge
to P1 and P2 as shown in Fig 24. Allow the boiler to run for 10 minutes and check the differential burner pressures.
1. Set the boiler selector switch to 'ON'.
2. The burner will light at the ignition rate and will increase to the factory pre-set maximum output after 1 minute.
Note: The burner pressure settings have been factory set and do not require adjusting. If incorrect, check that the inlet gas
pressure is 20 mbar.
If the inlet gas pressure is not 20 mbar, either the pipework is too small or the gas supply to the house is insufficient, in which
case contact your gas supplier.
3. Turn off the boiler. Disconnect the pressure gauge and tighten the test point screws.
Test for gas soundness using suitable leak detection fluid.
Note: Refer to Technical Data, Section 2.1 for the required differential burner pressures.
Alpha CD18S/24S/30S - Commissioning
Fig. 24
Fig. 23
Differential
Burner
pressure
5.6 FINAL COMMISSIONING
1. Allow the heating system to heat up, then balance the system to achieve the necessary temperature difference across the
heating flow and return pipes at the boiler and check the system volume and pressure. (Refer to Technical Data, Sections
2.2 and 2.8).
2. Turn off the boiler.
3. Thoroughly flush out the water pipework (refer to Section 3.9) and with no pressure in the boiler heating circuit, empty the
cyclone at it's drain point (see Fig. 13) of any debris.
4. Re-pressurise the system as described in Section 5.1.
5.7 FINAL ASSEMBLY
1. Raise the control panel and secure in position with the screws provided.
2. If the boiler is to be left in service with the User, set the controls, clock (if fitted, see User's Operating manual) and room
thermostat (if fitted) to the User's requirements.
3. If the boiler is not to be handed over immediately, close the boiler gas service cock and switch off the electrical supply.
4. If there is any possibility of the boiler being left during frost conditions, then the boiler and system should be drained (refer to Section
8.2). It is recommended that a label is attached to the boiler drawing attention to the fact that the system has been drained.
5. Complete the details of the installation in the Benchmark Checklist on page 35.