Alpha CD12S User guide

Installation and Servicing
Instructions
Alpha CD12S/20S/28S
Range of Wall Mounted, Fan Assisted, Room Sealed,
Gas Fired, High Efficiency Condensing System Boilers
Alpha CD12S G.C. No. 41 532 16
Alpha CD20S G.C. No. 41 532 18
Alpha CD28S G.C. No. 41 532 20
British Gas
Service Listed
For use with Natural Gas only
Leave these instructions with the User
0051
Nepicar House, London Road,
Wrotham Heath, Sevenoaks,
Kent TN15 7RS
For Technical help or for Service call ...
ALPHA HELPLINE Tel: [phone]
website: www.alpha-innovation.co.uk

2Alpha CD12S/20S/28S - Contents/Introduction
CONTENTS
1 Introduction........................................2
2 Technical data ...................................3
3 General boiler information .................7
4 Installation .........................................14
5 Commissioning..................................22
6 Boiler operation .................................25
7 Routine servicing...............................26
8 Component replacement ...................29
9 Wiring diagrams ................................35
10 Fault finding .......................................37
11 Short parts list ...................................40
12 Benchmark Checklist.........................41
13 Service record ...................................42
The Alpha CD range of high efficiency condensing boilers are 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 boilers are supplied with a pump, pressure relief valve, expansion vessel and pressure gauge fully assembled and
tested. They are designed for use with a fully pumped, sealed and pressurised central heating system using only Natural gas.
The CD12S boiler is suitable for central heating loads of between 2.4 and 12.8 kW (8 200 and 43 650 Btu/h).
The CD20S boiler is suitable for central heating loads of between 3.3 and 19.5 kw (11 260 and 66 500 Btu/h).
The CD28S boiler is suitable for central heating loads of between 5.4 and 30.1 kw (18 420 and 102 700 Btu/h).
IMPORTANT
It is the law that all gas appliances are installed by a competent person, ie Gas Safe 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
UK Water Regulations/Byelaws (Scotland)
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 Flues
BS 5449: Forced circulation hot water systems
BS 5546: Installation of hot water supplies for domestic purposes
BS 6700: Design, installation, testing and maintenance of services supplying water
BS 6798: Installation of gas fired hot water boilers
BS 6891: Gas installation
BS 7593: Code of Practice for treatment of water in heating systems
BS 7671: 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.
This appliance contains no asbestos and no substances have been used in the construction process that contravene the
COSHH Regulations (Control of Substances Hazardous to Health).
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. It is the law that all boiler installations are registered by the installer through the Gas Safe Gas Work Notification
Scheme.
3. The boiler must only be used with Alpha CD condensing flue components.
1 INTRODUCTION

3
2.1 PERFORMANCE - NATURAL GAS (CAT: I2H 2H - G20 - 20 mbar)
2 TECHNICAL DATA
Alpha CD12S/20S/28S - Technical Data
Alpha CD12S
MAX.
13.6
46 400
12.3
41 960
12.8
43 650
12.0
40 950
6.6
2.64
1.30
45.9
MIN.
2.9
9 890
2.6
8 870
2.5
8 530
2.4
8 200
0.2
0.08
0.28
9.9
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.
20.4
69 600
18.4
62 780
19.5
66 500
18.0
61 420
6.65
2.66
1.96
69.2
MIN.
3.8
12 960
3.5
11 950
3.5
11 950
3.3
11 260
0.33
0.13
0.37
13.0
Room sealed
chamber panel
fitted
Central Heating
Heat Input (Hs) kW
(Gross) Btu/h
Heat Input (Hi) kW
(Net) Btu/h
Heat Output (Hs condensing) kW
(50°C/30°C) Btu/h
Heat Output (Hi non-condensing)kW
(80°C/60°C) Btu/h
Differential Burner mbar
Pressure in wg
Gas Rate m³/h
ft³/h
Alpha CD20S
MAX.
31.8
108 500
28.7
97 920
30.1
102 700
28.0
95 540
6.3
2.52
3.04
107.3
MIN.
6.3
21 500
5.7
19 450
5.7
19 450
5.4
18 420
0.25
0.10
0.6
21.2
Room sealed
chamber panel
fitted
Central Heating
Heat Input (Hs) kW
(Gross) Btu/h
Heat Input (Hi) kW
(Net) Btu/h
Heat Output (Hs condensing) kW
(50°C/30°C) Btu/h
Heat Output (Hi non-condensing)kW
(80°C/60°C) Btu/h
Differential Burner mbar
Pressure in wg
Gas Rate m³/h
ft³/h
Alpha CD28S
Note: The above appliances are fully modulating and are not range rated.

4
CH Max
9.4
9.4
9.4
720 mm
440 mm
300 mm
345 mm
15 mm
22 mm
1.5 L
1.8 L
2.5 L
100 mm
60 mm
Case Dimensions Height
Width
Depth
Depth (with Jig)
Gas Connection CD12S/CD20S
CD28S
Primary Water Content CD12S
CD20S
CD28S
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 CD12S
CD20S
CD28S
2.5 INSTALLATION
235 mm
250 mm
5 mm
450 mm
100 mm Dia.
90 mm
110 mm Dia.
37 kg
38 kg
40 kg
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)
2.2 SYSTEM
Burner
Main Heat exchanger
DHW Heat Exchanger
Main Burner Injector CD12S
CD20S
CD28S
Flue - Outer Duct
Flue - Inner Duct
Stainless steel
Stainless steel
Stainless Steel
3.5 mm
4.2 mm
5.4 mm
White
Plastic
2.3 COMPONENTS 2.4 ELECTRICAL
Supply
External Fuse
Power Consumption
Internal Fuse - Main Terminal
PCB Fuse F1
PCB Fuse F2 and F3
Electrode Spark Gap
Electrical Enclosure Degree of Moisture Protection
230/240 V ~ 50 Hz
3 A
120 W
F2 A
315 mAT
2.5 AF
3 - 4 mm
IPX4D
Alpha CD12S/20S/28S - Technical Data
2.7 PERFORMANCE DATA
%CO2content (± 0.2%) Sedbuk rating
Natural Gas Efficiency
band
A
A
A
SAP efficiency
(%)
90.1
90.1
90.1
Min
8.9
8.9
9.1
NOx class
5
5
5
Boiler model
CD12S
CD20S
CD28S
Note: The differential burner pressure and the combustion performance value of %CO2content have been factory preset and
do not require adjusting.

5
Alpha CD12S/20S/28S - Technical Data
2.8 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 1000 mm flue extensions are available.
Length of Flue Required:-
Rear Flue = wall thickness + 160 mm (includes terminal). This is without back frame, add 45 mm if the wall jig is used.
Side Flue = wall thickness + distance between wall and side of boiler + 245 mm (includes terminal)
Vertical Flue = distance from top of boiler side panel to required roof position minus 1000 mm 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.
2.9 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 28 kW refer to Section 3.7.
2.10 ELECTRICAL CONNECTIONS
Note: This Appliance Must Be Earthed
An optional integral two channel Clock kit is available if required.
Note: Only use an Alpha two channel clock. Do not fit any single channel clocks.
L
N
1
2F2A
3
4
Fig. 1
Boiler terminal block
Clock connections
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 t 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
tted

6
2.11 BOILER SCHEMATIC
Fig. 2
Alpha CD12S/20S/28S - Technical Data
1 - Flue sampling point
2 - Flue temperature sensor
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
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 (if applicable)
28 - Condensate trap
29 - Heat exchanger thermal fuse
Gas
Condensate
discharge
Primary
Heating
return Primary
Heating
flow
24
4
1
-
-
+
+
9
10
28
11
2
13
5
20
14
22
23
15
19
16
17
18
26
27
25
12
8
721
6
3
29

7
3.1 GAS SUPPLY
The Alpha CD12S boiler requires a gas rate of 1.3 m³/h (45.9 ft³/h).
The Alpha CD20S boiler requires a gas rate of 1.96 m³/h (69.2 ft³/h).
The Alpha CD28S boiler requires a gas rate of 3.04 m³/h (107.3 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 boiler requires at least a 22 mm gas supply pipe.
The complete installation, including the meter, must be tested for gas tightness 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 that the Easy-Flue outer duct is installed horizontally (please note that the Easy-Flue inner duct
already has a pre-determined slope towards the boiler for condensate to run back towards the boiler).
When additional flue extensions are used, ensure the flue slopes downwards towards the boiler by a minimum of 25 - 30 mm
per metre of flue.
It is recommended that horizontal flue assemblies should be supported approximately every 1.5 m with access provided to
the joints.
Flue components are available as follows:-
CD Easy-Flue 500 mm (includes 90° bend and terminal) - Part No. 6.2000510.
CD Easy-Flue 1000 mm (includes 90° bend and terminal) - Part No. 6.2001010.
CD 750 mm flue extension - Part No. 6.2000750.
CD 1000 mm flue extension - Part No. 6.2001050.
CD 100 mm flue support brackets (pack of 5) - Part No. 6.1000355.
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.
CD Ridge flue terminal assembly. Refer to separate installation instructions supplied with assembly.
The following methods determine the correct length of flue required.
For rear exit flue (including terminal) L = B + 160 mm (205 mm if wall jig is used)
For side exit flue (including terminal) L = B + C + 245 mm (min. side clearance required is 5 mm)
For vertical flue L = H - 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 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.
4. Further plume management flue accessories are available - refer to the Easy-Flue installation instructions.
3 GENERAL BOILER INFORMATION
Alpha CD12S/20S/28S - General Boiler Information

8
L = B + C + E + 245 mm
Alpha CD12S/20S/28S - General Boiler Information
L = B + C + 245 mm
CB
E
CB
E
B
F
B
C
L = B + E + F + 245 mm + (90° bend = 1.3 metre)
(add 40 mm to 'F' if a jig is used)
L = B + C + 245 mm + (2 x 45° bends = 1.8 metre)
Fig. 3
VERTICAL FLUE OPTIONS
Not less than
300 mm
Not less than
300 mm
H
Hmax = 15 m
Not less than
300 mm
Not less than
300 mm
H
Hmax = 13.2 m
HORIZONTAL FLUE OPTIONS - Lmax = 12 metres
(245 mm length includes terminal)

9
3.5 FLUE TERMINAL LOCATION - Figs. 4 and 5
Alpha CD12S/20S/28S - 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 or boundary 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.
N Minimum protrusion through a roof
O From a vertical obstruction
P From an openable window
Q From an adjacent vertical terminal
Min. distance (mm)Terminal position
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)
300 mm
300 mm
600 mm
600 mm
J
D
G
H I
Q
Boundary
OP
N
Fig. 4
Notes:
1. In addition, the terminal should not be nearer than 150 mm to the framework of an opening into the building, 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 can be extended beyond gutters, pipes, eaves,
balconies etc. by upto 500 mm. If the flue is extended more than 500 mm outside, it should be boxed and insulated.
4. To reduce the possibility of nuisance to neighbouring buildings etc. it is recommended the terminal should not be less
than 2500 mm from car parking spaces, building boundary walls, fences etc.
5. A terminal must not be sited under a car port roof.
6. 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.
7. 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.
8. A terminal must not be sited below 2 m where people have access to, such as public footpaths, access routes, patios
etc. However, If the terminal is fitted less than 2 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.

10
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 (BS 7671) 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 CD12S/20S/28S - General Boiler Information
Fig. 5
600 mm
2000 mm
600 mm
300 mm
300 mm
Terminal facing the boundary
Terminal facing an opening
in adjacent building
Terminal at an angle to the boundary
Terminal parallel to the boundary
Boundary
Boundary
Boundary
Boundary
Terminal
Terminal
Terminal
Terminal
Building Building
Building
Building
Adjacent building Window
Proximity of flue duct outlets to boundaries
The flue duct shall be sited so that it is at least 600 mm (see Fig. 5) from the boundary line when facing it and at least 300 mm
from the boundary line when running parallel to it.

11
3.7 CENTRAL HEATING SYSTEM - Fig. 6
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. 6. 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 an automatic by-pass, therefore an automatic by-pass is not required for the system.
Cyclone (if applicable) - This is a device fitted in the heating return within the optional Premier Pack wall jig to remove any
foreign or solid matter etc. from the system.
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.
Fig. 6
Fig. 7 Fig. 8
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
3.8 FILLING THE CENTRAL HEATING SYSTEM - Figs. 7, 8
The system design pressure (cold) should be set to 1.0 bar. This pressure is equivalent to a static head (see Fig. 6) 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. 7 and 8. The position for connecting an automatic make-up vessel is indicated in Fig. 6. 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. 7. 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.
Alpha CD12S/20S/28S - General Boiler Information

12 Alpha CD12S/20S/28S - 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]).
If applicable - Although the Cyclone is fitted in the heating return within the Premier Pack wall jig, the heating system should
still be thoroughly flushed as detailed below. The Cyclone collection point should be emptied via the drain point (see Fig. 14b)
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 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 protected from the risk of freezing with
waterproof insulation and the length should be kept to a maximum of 3 m. Alternatively the condensate pipework could be
increased to a minimum of 32 mm diameter without the requirement to insulate the pipework. Termination should be into an
external gulley or soakaway as shown in Figs. 9 and 10.
Note: All pipework must have a continuous fall (see Figs. 9 and 10) 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.

13
Alpha CD12S/20S/28S - General Boiler Information
Fig. 10 - External soakaway
Ground level (either/or)
22mm termination
from boiler
2½ fall
O
25mm
300mm
Two rows of 3 x 12mm
holes at 25mm centres,
50mm from the bottom
of the tube. Holes to face
away from house.
Cement mortar
sealing
100mm plastic tube
Bottom of tube sealed
Soakaway depth 400mm
filled with limestone chippings
500 mm min.
Fig. 9 - External gully
Open end of pipe
diverted into gully
below grid but above
water level
Use waterproof
pipework insulation
in very exposed
positions
Ensure pipe is
adequately supported
Plastic pipe
Minimum gradient 2½°

14
4.3 PREPARE THE WALL - Fig. 12
If the optional wall jig is used refer to the
instructions supplied with the kit.
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 or, if applicable the wall jig fixings. If
rear exit flue is used, mark the position of the
hole for the flue.
The wall jig is supplied with a pressure relief
valve discharge pipe for use when the boiler
is mounted on an external wall where the
outside is inaccessible, if you wish to use this
pipe - mark it's position.
3. Side exit flue - Continue the horizontal centre
line of the flue across the wall to the side wall,
then along the side wall 140 mm, 185 mm if the
wall jig is used (ensure the lines are horizontal).
This will give the position of the centre of the
hole for the flue.
Alpha CD12S/20S/28S - Installation
4 INSTALLATION
Fig. 11
Fig. 12
Template
Outline of
boiler
Wall
mounting
bracket
fixing holes
Wall jig
fixing holes
140 mm
(185 mm if wall jig used)
Ensure line is level
Rear exit hole
110 mm dia.
Position of
110 mm hole
to be cut for
side exit flue
145 mm
==
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, union bends and washers
Mounting bracket plus screws and wall plugs
Condensate discharge pipe
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.
Box 3 (if applicable) ....... Premier Pack includes: wall mounting jig with template, cyclone, bottom tray,earth bonding plate,
spacers, pressure relief pipe terminal, split flow and return union bends, screw pack and fitting
instructions.
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. 11
720 mm
300 mm
Minimum
clearance
of 450 mm
from front
of boiler
440 mm
235 mm
250 mm
5 mm 5 mm
Boiler
Minimum
clearances
(345 mm if
wall jig
fitted)

15
4. Cut the 110 mm diameter hole (or use a 107 mm core drill) in the wall for the flue.
Notes: 1. Ensure the hole is horizontal.
2. 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 plugs supplied. Using the screws supplied, fit the mounting bracket
or wall jig if used. If applicable drill a 22 mm dia. hole for the pressure relief valve discharge pipe terminal supplied with
the jig.
IMPORTANT: If the wall jig is used, follow the instructions supplied with the Premier Pack to fit the jig,
mount the boiler and connect the pipework.
4.4 FIT THE BOILER - Refer to Figs. 12,13
Lift the boiler and locate it on the mounting bracket.
Note: When handling or lifting always use safe techniques - keep your
back straight, bend your knees, don't twist - move your feet, avoid bending
forwards and sideways and keep the load as close to your body as possible.
Where possible transport the boiler using a sack truck or other suitable
trolley.
Alwaysgrip theboiler firmly, andbeforeliftingfeel wherethe weightisconcentrated
to establish the centre of gravity, repositioning yourself as necessary.
4.5 CONNECT THE PIPEWORK - Fig. 14
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.
Note: If applicable the heating union bends supplied with the wall jig
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. One metre of copper pipe must be fitted to the boiler before connecting to
any plastic pipework.
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 using the clip supplied.
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.13, 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.
Alpha CD12S/20S/28S - Installation
Fig. 13 - rear of boiler
Location for
wall mounting
bracket on
rear of boiler
Pour water into flue duct
Fig. 14a - Without wall jig
A- Heating flow (22 mm)
B- Gas inlet (22 mm)
C- Heating return (22 mm)
D- Pressure relief valve (15 mm)
23
Heating drain
point
Condensate
trap
Heating return
valve
Heating flow
valve
B D CA
65 457058202
Condensate
discharge pipe
Note: Disconnect the filling loop after
filling the central heating system.

16
23
20
Heating drain
point
Cyclone drain
point
Wall jig
Condensate
trap
Heating return
valves
Heating flow
valve
B D CA
65 457058202
Condensate
discharge pipe
4.6 FIT THE FLUE - Figs. 15, 16
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.
2. Determine the overall length (L) of flue required, (see Fig. 17) as follows:-
Rear flue L = wall thickness (B) + 60 mm (105 mm if the wall jig is used)
Side flueL = wall thickness (B) + distance between boiler and wall (C) + 145 mm
Alpha CD12S/20S/28S - Installation
Fig. 14b - With wall jig
A- Heating flow (22 mm)
B- Gas inlet (22 mm)
C- Heating return (22 mm)
D- Pressure relief valve (15 mm)
Note: Disconnect the filling loop after
filling the central heating system.
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.
Note: Always ensure that the two sections overlap by at least 25 mm when extending to the maximum length.
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.
Fig. 15 Fig. 16
CD Easy-Flue
500 mm
1000 mm
B (mm)
Max
525
970
Min
300
760
CD Easy-Flue
500 mm
1000 mm
Max
440
885
Min
215
675
B + C (mm)
Note: Add 45 mm to
dimension B if the wall jig is
used.
(B)
Rear Flue
(B + C)
Side Flue
Fig. 17
Seal Joint with Tape
L

17
4.7 REDUCING THE FLUE - Fig. 20
When the flue length required is less than the minimum stated in Section 4.6, paragraph 1, refer to Fig. 20.
Discard the first telescopic section (not the section with the terminal) of the Easy-Flue 1000 mm or 500 mm and cut to the
required length.
Note: Ensure that all cuts are square and free from burrs.
Once assembled with the components pushed home, the flue is fully sealed.
Alpha CD12S/20S/28S - Installation
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 90 mm out of the wall and the inner duct of the terminal is positioned correctly
(see Fig. 19).
8. Make good the inside wall by pushing the inside flue sealing collar upto the wall.
Fig. 18 - Fitting the flue from inside
Check collar is sealing
the wall and it is not
restricting any openings
of the flue terminal
130 mm
120
Inner duct
Elbow seal joint
90° bend
Easy-Flue
40 mm clamp
and seal
Easy-Flue 45 mm clamp
Terminal
Flue sealing collar
Note: Ensure the outer flue duct is horizontal
Side of boiler
CD Easy-Flue
Ensure the inner duct within
the terminal is at the top.
The inner duct must
be positioned to slope towards
the boiler
Note:
20
65
Inner duct seal
40 (80 if wall jig used)
140 (185 if wall jig used)
Fig. 19 - Rear flue
Allow 20 mm 30 mm
Do not cut past this point
Fig. 20

18 Alpha CD12S/20S/28S - Installation
4.8 EXTENDING THE FLUE - Fig. 21
Note: The flue assembly length must not exceed the maximum length stated, including the equivalent lengths of any
extensions, bends etc, used for plume management components. CD boilers must not exceed the maximum of an
equivalent horizontal flue length of 12 m.
1. When the flue length required is more than the maximum stated in Section 4.6, paragraph 1, refer to the table below
and Figs 15 and 16.
Rear Flue length (B)
Up to maximum:-
11.885 m
(Subtract 45 mm if the
wall jig is used)
Side Flue length (B + C)
Up to maximum:-
11.805 m
Comments
Alpha CD 750 mm flue extension (Part No. 6.2000750) or 1000 mm extension
(Part No. 6.2001050) is required to extend the range of telescopic flue.
Refer to Section 4.8 for instructions on how to extend the flue.
Note: A 130 mm flue hole (127 mm core drill) may be required in the wall.
This is when the extended flue is passed through the wall.
Additional support brackets are required when extending the flue. These are available from Alpha, Part No. 6.1000355.
2. Use the template (supplied with the boiler) to mark the required flue position, ensure the slope towards the boiler is correct.
3. Determine the overall flue length as described in Section 4.6, paragraph 2 to determine the number of Alpha CD 750 or
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 extension 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 20 mm longer than the outer duct.
Ensure that all cuts are square and free from burrs.
Once assembled with the components pushed home, the flue is fully sealed.
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.
8. Position the smaller Easy-Flue 40 mm clamp (with seal) supplied, over the bend. Fit the bend to the boiler and rotate to
the correct position and secure in position. Ensure the seal is located centrally over both the bend and boiler adaptor. If
the inside sealing collar (white) is being used to make good the inside wall, then it will need to be fitted before assembling
the flue.
9. Slide the larger Easy-Flue 45 mm clamp (two screws) over the outer duct and pull the flue assembly towards the bend,
locating the inner duct into the seal joint on the bend.
Easy-Flue 45 mm clamp
Easy-Flue
40 mm clamp
and seal
45
Front of boiler
Extension clamp
Inner seal joint
Inner seal joint
Flue length (L)
90° bend
Seal joint
CD Easy-Flue
Ensure outer flue duct of Easy-Flue is horizontal
Ensure the flue extension slopes
downwards towards the boiler by a
minimum of 25 - 30 mm per metre
CD Flue extension
Flue sealing
collar
Ensure the inner duct within the terminal is at the top.
The inner duct must be positioned to slope towards the boilerNote:
120
Terminal
20
125
220
Fig. 21 - Side flue

19
Alpha CD12S/20S/28S - Installation
10. Secure the flue assembly to the bend with the clamp 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 120 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. 21.
11. Make good the outside wall by fitting the outside sealing collar (black) onto the location provided immediately behind the
flue terminal grille. Make good the inside wall using the inside sealing collar (white) if required.
4.9. FIT PLUME MANAGEMENT COMPONENTS - (OPTIONAL)
The following procedures detail the options for management of the exhaust flue gas/plume emitted from the terminal.
a. The terminal supplied with the Easy-Flue can be altered to divert exhaust flue gas/plume at an angle.
This can be achieved by simply turning the end section of the terminal to the desired angle.
b. The CD Easy-Flue can be converted to allow the inner flue duct to be extended so as to position the terminal in an area
where the exhaust flue gas/plume will not cause a nuisance. This can be done before or after installation of the flue,
providing there is access to the terminal from outside.
i. Remove the screws (1 in Fig. 22) securing the terminal and remove the terminal by pulling it from the flue assembly.
Remove the screw (2 in Fig. 22) securing the terminal end section and remove the end section from the terminal.
ii. Locate a 93° Plume Management bend into the flue assembly and rotate it to the direction required.
iii. Connect to the 93° bend the required Plume Management components as detailed and refer to Fig. 22.
Notes:
1. The wall support brackets must be used to secure the Plume Management pipework to the wall and
prevent disconnection of the 93° bend from the flue assembly or any other component.
2. Each joint must be secured with one of the screws provided to prevent accidental disconnection.
3. Ensure there is always a slight slope towards the flue assembly fitted in the wall and there is no part
of the plume management pipework where condensate/rain will collect and cause a blockage or any
restriction.
iv. Terminate the Plume Management pipework by fitting the terminal end section (push-fit) previously removed. Refer
to Fig. 23.
v. The Plume Management components available for extending the inner flue duct are as follows:-
Plume Management 93° bend 60 mm dia. (each 93° bend equivalent to 1.3 m flue length)
Plume Management 45° bend 60 mm dia. (each 45° bend equivalent to 0.9 m flue length)
Plume Management 1000 mm extension 60 mm dia. (equivalent to 1 m flue length)
60 mm dia. wall bracket
Fig. 22
1
1
2

20 Alpha CD12S/20S/28S - Installation
PM length = C + (1 x 93° bend = 1.3 m) + (2 x 45° bends = 1.8 m)
C
Min.
400 mm
CD Easy-Flue
Flue sealing collar
Terminal end section
from CD Easy-Flue
PM length = C + (2 x 93° bend = 2.6 m) + (2 x 45° bends = 1.8 m)
C
Terminal end section
from CD Easy-Flue
PM length = C + (4 x 93° bend = 5.2 m)
C
Terminal end section
from CD Easy-Flue
Ensure there is a slope of approximately
3° back towards the Easy-Flue
Fig. 23
Note: The equivalent horizontal flue assembly length + the equivalent plume management length (PM length) must not
exceed the maximum flue length stated for each boiler, i.e.
Alpha CD boiler maximum equivalent flue length must not exceed 12 metres.