Alpha Alpha CD50S User guide

Installation and Servicing
Instructions
Alpha CD50S and 70S
Wall Mounted, Fan Assisted, Gas Fired, High Efficiency
Condensing System Boilers
For use with Natural Gas or Propane Gas (LPG)
Leave these instructions with the User
Nepicar House, London Road,
Wrotham Heath, Sevenoaks,
Kent TN15 7RS
For Technical help or for Service call ...
ALPHAHELPLINE
Tel: [phone]
0051

2Alpha CD50S/70S - Contents/Introduction
CONTENTS
1 Introduction ....................................... 2
2 Technical data................................... 3
3 General boiler information.................. 8
4 Installation......................................... 15
5 Commissioning ................................. 19
6 Routineservicing............................... 24
7 Wiring diagram.................................. 29
8 Fault finding ...................................... 30
9 Short parts list ................................... 31
10 Benchmark Checklist ........................ 32
11 Service record ................................... 33
The Alpha CD50S and 70S are wall mounted high efficiency condensing, fan assisted 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. However, they may be used with an
open central heating system if required - refer to Section 3.8.
The boilers are supplied with type B23 flue configuration (open chamber and forced draught) but can be changed to type C
(room sealed) by using a kit.
The boilers are fitted with a pump, 4 bar pressure relief valve and pressure gauge fully assembled and tested. They are
designed for use with a fully pumped, sealed and pressurised central heating system. If used with an open system refer
to Section 3.8.
The CD50S boiler is suitable for central heating loads of between 10 and 53.8 kW (34 121 and 183 700 Btu/h).
The CD70S boiler is suitable for central heating loads of between 18.1 and 72.8 kw (61 800 and 248 600 Btu/h).
The boilers can be supplied for use with Natural gas or Propane Gas (LPG).
Note: There are a number of additional controls and accessories available for use with the boilers to enable cascade and
zone installations to be used. Further information is available from Alpha Therm Ltd.
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
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 5440:1:2000 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 IPX5D, 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 CORGI Gas Work Notification
Scheme.
3. The boiler must only be used with the flue components supplied with the boiler.
Propane Gas (LPG) - In addition to the regulations and requirements stated, the boiler must be installed in accordance
with BS 5482:1 - The Installation of Propane Burning Appliances in Permanent Dwellings.
1 INTRODUCTION

3
2.1 PERFORMANCE
NATURAL GAS (CAT: I2H 2H - G20 - 20 mbar)
2 TECHNICALDATA
Alpha CD50S/70S - Technical Data
Alpha CD50S
MAX.
56.4
192 400
50.8
173 300
53.8
183 700
50.0
170 600
5 180
5.37
189.6
MIN.
11.5
39 250
10.4
35 500
11.1
37 800
10.0
34 120
1 280
1.10
38.8
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
Fan Speed rpm
Gas Rate m³/h
ft³/h
Alpha CD70S
Note: The above appliances are fully modulating and are not range rated.
MAX.
77.5
264 300
69.8
238 200
72.8
248 600
67.9
231 700
5 240
7.4
261.2
MIN.
20.5
70 060
18.5
63 120
19.7
67 100
18.1
61 800
1 400
1.96
69.2
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
Fan Speed rpm
Gas Rate m³/h
ft³/h
Central Heating (Sealed System)
Max. Working System Pressure
Min. System Pressure
Max. System temperature
Pressure Relief Valve Setting
Flow Connection
Return Connection
Relief Valve Connection
Recommended System Pressure (cold)
CH Water Temp. (Approx. max.)
3.5 bar
0.5 bar
82°C
4 bar (58.8 PSI)
1½" BSP
1½" BSP
¾" BSP
1.0 bar
82°C (180°F)
2.2 SYSTEM
PROPANE GAS (CAT I3P 3P - G31 - 37 mbar)
Alpha CD50S
MAX.
56.4
192 400
50.8
173 300
53.8
183 700
50.0
170 600
5 200
2.15
75.9
MIN.
11.5
39 250
10.4
35 500
11.1
37 800
10.0
34 120
1 250
0.44
15.5
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
Fan Speed rpm
Gas Rate m³/h
ft³/h
Alpha CD70S
MAX.
77.5
264 300
69.8
238 200
72.8
248 600
67.9
231 700
5 240
2.96
104.5
MIN.
20.5
70 060
18.5
63 120
19.7
67 100
18.1
61 800
1 450
0.78
27.7
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
Fan Speed rpm
Gas Rate m³/h
ft³/h

4
CH Max
9.30
9.25
950 mm
600 mm
525 mm
28 mm
3.7 L
4.0 L
Case Dimensions Height
Width
Depth
Gas Connection
Water Content CD50S
CD70S
2.6 GENERAL
Min. Clearances for Servicing Top
(from casing) Bottom
Sides
Front
Flue Diameter Open Flue
Concentric Flue
Flue Protruding Outside Open Flue
Concentric Flue
Hole For Flue Assy. Open Flue
Concentric Flue
Lift Weight CD50S
CD70S
2.5 INSTALLATION
Burner
Main Heat Exchanger
Main Burner Injector CD50S NG
CD70S NG
CD50S LPG
CD70S LPG
Concentric Flue Outer Duct
Concentric Flue Inner Duct
Open Flue Single Flue Pipe
Stainless steel
Stainless steel
7.85 mm
13.0 mm
5.7 mm
7.8 mm
125 mm dia.
80 mm dia.
80 mm dia.
2.3 COMPONENTS 2.4 ELECTRICAL
Supply
External Fuse
Power Consumption
Internal Fuse - Main Terminal
PCB Fuse F1
PCB Fuse F3
Electrode Spark Gap
ElectricalEnclosureDegreeofMoistureProtection
230/240 V ~ 50 Hz
3 A
180 W
F2A
T2A
T4A
3 to 4 mm
IPX5D
Alpha CD50S/70S - Technical Data
2.7 PERFORMANCE DATA
%CO2content (± 0.2%) Sedbuk rating
Natural Gas Efficiency
band
A
A
Min
9.25
9.00
NOx class
5
5
Boiler model
CD50S
CD70S
350 mm
250 mm
10 mm
450 mm
80 mm
125 mm
80 mm
180 mm
100 mm dia.
127 mm dia.
63 kg
68 kg
CH Max
10.6
10.5
(LPG) Propane Gas
Min
10.1
9.7

5
2.9 AVAILABLE PUMP HEAD FOR CENTRAL HEATING
Alpha CD50S/70S - Technical Data
Fig. 1
2.10 ELECTRICAL CONNECTIONS
Note: This Appliance Must Be Earthed
Fig. 2
2.8 FLUE LENGTHS - See also Section 3.4
Open flue - Maximum horizontal or vertical flue with single 80 mm dia. open flue is 30 metre
90° bend is equivalent to 2.1 m of flue length
45° bend is equivalent to 1.3 m of flue length
Vertical terminal is equivalent to 3 m of flue length
Concentric flue - Maximum horizontal flue is 14 metre, maximum vertical flue is 18 metre
90° bend is equivalent to 1.9 m of flue length
45° bend is equivalent to 1.4 m of flue length
Vertical terminal is equivalent to 3.4 m of flue length
Notes: 1. Ensure all flues slope downwards towards the boiler by a minimum of 25 to 30 mm per metre of flue.
2. It is recommended that horizontal and vertical flue assemblies should be supported approximately every 1.5 m
with access provided to the joints.
0
1
2
3
4
5
6
7
8
9
TOTAL HEAD
(M water)
FLOW RATE (litre/h)
200 400 600 800 10001200 14001600 1800 20002200 2400 2600 2800 3000 32000
C
D
A
B
A = CD50S - Available head with pump at maximum speed
B = CD50S - Available head with pump at speed two
C = CD70S - Available head with pump at maximum speed
D = CD70S - Available head with pump at speed two
GJ MORHF E TS KVUY Z
X86
X85
LNNL
Fuse F2A
230V ~ 50Hz
Fused at 3A
External Pump
Max 1A
(Optional)
External sensor
(Optional)
Zone
manager
(Optional)
37
A
38
B
DHW
temp sensor
(Optional)
Diverter valve
motor
(Optional)
Summer switch
(Optional)
Analog
input
0 - 10 Volt
(Optional)
PQN
L
6
2
3
LINK
Room
thermostat
(Optional)
230/240 V ~ 50 Hz only Maximum 24 V connection only
Note: Do not connect 230/240 V ~ 50 Hz

6
2.11 BOILER SCHEMATIC - CD50S
Alpha CD50S/70S - Technical Data
1 Tundish
2 Pressure relief valve (4 bar)
3 Drain point
4 Primary pressure switch
5 Flow manifold
6 Condensate trap
7 Gas valve
8 Air inlet pipe
9 Fan
10 Injector
11 Flame sensing electrode
12 Combustion chamber cover
13 Heat exchanger
14 Flue overheat thermostat
Fig. 3 - CD50S
15 Flue hood
16 Air inlet sampling point
17 Flue sampling point
18 Primary flow temperature sensor
19 Air vent - manual
20 Primary return temperature sensor
21 Overheat thermostat
22 Ignition electrodes
23 Burner
24 Venturi positive point (P1)
25 Venturi
26 Automatic air vent
27 Pump
ReturnGasFlow Condensate
discharge
1
2
3
4
5
6
7
8
9
10
11
12
13
14
16 17 18
19
20
21
22
23
24
25
26
27
15

7
1 Tundish
2 Pressure relief valve (4 bar)
3 Drain point
4 Primary pressure switch
5 Flow manifold
6 Gas valve
7 Fan
8 Injector
9 Air inlet pipe
10 Ignition electrodes
11 Combustion chamber cover
12 Hear exchanger
13 Flue overheat thermostat
Fig. 4 - CD70S
14 Flue hood
15 Air inlet sampling point
16 Flue sampling point
17 Automatic air vent
18 Primary flow temperature sensor
19 Primary return temperature sensor
20 Overheat thermostat
21 Burner
22 Flame sensing electrode
23 Venturi
24 Venturi positive point (P1)
25 Pump
26 Condensate trap
Alpha CD50S/70S - Technical Data
ReturnGasFlow Condensate
discharge
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15 16
17
18
19
20
21
22
23
24
25
26
2.12 BOILER SCHEMATIC - CD70S

8
Table 1
Boiler model
Vents to outside air
Vents into a room
High level
Low level
High level
Low level
CD50S
255 cm²
510 cm²
510 cm²
1020 cm²
CD70S
350 cm²
700 cm²
700 cm²
1400 cm²
Alpha CD50S/70S - General Boiler Information
3.1 GAS SUPPLY
Natural Gas:
The Alpha CD50S boiler requires a gas rate of 5.37 m³/h (189.6 ft³/h).
The Alpha CD70S boiler requires a gas rate of 7.4 m³/h (261.2 ft³/h).
Propane Gas (LPG):
The Alpha CD50S boiler requires a gas rate of 3.94 kg/h (8.4 lb/h) or 7.6 litres/h of liquid gas.
The Alpha CD70S boiler requires a gas rate of 5.42 kg/h (11.6 lb/h) or 10.4 litres/h of liquid gas.
The local Propane Gas supplier should be consulted, at the installation planning stage, in order to establish the
availability of an adequate supply of gas.
The meter and supply pipes must be capable of delivering this quantity of gas in addition to the demand from any other
appliances. The boiler requires at least a 28 mm gas supply pipe and ensure the inlet supply pressure is at least 20 mbar
for Natural Gas or 37 mbar for Propane Gas (LPG).
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
Note: 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).
3.3 AIR SUPPLY
Open flued (Type B23 flue)
Alpha CD50S and CD70S boilers leave the factory with 'B23' type configuration (open chamber and forced draught -
single flue pipe) and receive the air for combustion from openings in the rear of the boiler, therefore air supply for
combustion and ventilation must be provided in accordance with BS5440:2.
1. If the boiler is installed in a room - The room must have a permanent air vent either direct to the outside air or to an
adjacent room which itself has a permanent air vent to the outside air. The minimum effective air vent(s) required is:
Alpha CD50S: 220 cm² Alpha CD70S 315 cm²
2. If the boiler is installed in a cupboard or compartment - Permanent air vents are required in the cupboard or
compartment, one at high level and one at low level, either direct to the outside air or to a room. Both the high and
low level air vents must communicate with the same room or must be on the same wall to outside air. The minimum
effective areas required are given in Table 1.
Where the cupboard or compartment is ventilated to a room, the room itself must have an effective air vent direct to
outside air of minimum effective area as given above in paragraph 1.
3 GENERAL BOILER INFORMATION
Room sealed (Type C flue)
If the boilers are converted to a 'C' type configuration (sealed chamber and forced draught - concentric flue pipe) as
described in Section 3.4 only air for ventilation is required.
1. If the boiler is installed in a room - No air vents are required in the room in which the boiler is installed.
2. If the boiler is installed in a cupboard or compartment - Permanent air vents for ventilation are required in the
cupboard or compartment, one at high level and one at low level, either direct to the outside air or to a room. Both
the high and low level air vents must communicate with the same room or must be on the same wall to outside air.
Both the high and low level vent must each have a free area as follows. The free area of each vent may be halved if
the ventilation is provided directly from outside.
Alpha CD50S: 510 cm² Alpha CD70S 700 cm²
The minimum clearances for servicing must always be maintained.

9
3.4 FLUE SYSTEM
The flue system must be installed in accordance with BS 5440:1.
For horizontal flues ensure the flue assembly slopes downwards towards the boiler by a minimum of 25 - 30 mm per
metre of flue.
It is recommended that horizontal and vertical flue assemblies should be supported approximately every 1.5 m with access
provided to the joints.
Alpha CD50S and CD70S boilers leave the factory with 'B23' type flue configuration (open chamber and forced draught -
single flue pipe). To change the configuration to 'C' type (sealed chamber and forced draught - concentric flue pipe),
remove the 80 mm dia. adapter, the bracket and gasket from the top of the boiler and fit the concentric flue adaptor, see
Section 4.5.
Note: 1. Under no circumstances must the flue length (including allowances for extra bends) exceed the maximum flue
lengths stated for each type of flue.
2. Failure to use the correct Alpha flue components with the boiler will invalidate the boilers CE approval, guarantee
and may be unsafe.
Seals for flue elements - If lubrication of components (already performed by the manufacturer) is not sufficient, remove
the residual lubricant using a dry cloth, then to ease fitting apply a small amount of common or industrial talc to the seal.
Ensure that the seals are correctly located in the elbows and extensions as shown in Fig. 5.
Alpha CD50S/70S - General Boiler Information
Fig. 5
Seal Seal
Flue components are available as follows:-
Open flue - 80 mm dia. single pipe
Horizontal terminal kit 80 mm dia. (includes 1 m straight with terminal, one 90° bend and two collars)
Vertical terminal kit 80 mm dia.
Extension pipe 1 m x 80 mm dia.
90° bend 80 mm dia.
45° bend 80 mm dia.
Concentric flue - 80/125 mm dia.
Horizontal terminal kit 80/125 mm dia. (includes 1 m straight with terminal, one 90° bend, two collars and adaptor)
Vertical terminal kit 80/125 mm dia. (includes adaptor)
Extension kit 1 m x 80/125 mm dia.
90° bend 80/125 mm dia.
45° bend 80/125 mm dia.

10
3.4.1 Horizontal Flue Options
Alpha CD50S/70S - General Boiler Information
3.4.2 Vertical Flue Options
L max
L max
L max
L max
Not less than
300 mm
Not less than
300 mm
H
Not less than
300 mm
Not less than
300 mm
H
Open flue: 80 mm dia. single pipe Hmax = 30 m
Concentric flue: 80/125 mm dia. Hmax = 18 m Open flue: 80 mm dia. single pipe Hmax = 27.4 m Concentric flue: 80/125 mm dia. Hmax = 15.2 m
Open flue: 80 mm dia. single pipe Lmax = 30 m
90° bend is equivalent to 2.1 m of flue length
45° bend is equivalent to 1.3 m of flue length
Concentric flue: 80/125 mm dia. Lmax = 14 m
90° bend is equivalent to 1.9 m of flue length
45° bend is equivalent to 1.4 m of flue length
Open flue: 80 mm dia. single pipe Lmax = 27.9 m
Concentric flue: 80/125 mm dia. Lmax = 12.1 m Open flue: 80 mm dia. single pipe Lmax = 27.4 m
Concentric flue: 80/125 mm dia. Lmax = 11.2 m
Fig. 6 - Horizontal flues
Fig. 7 - Vertical flues

11
Alpha CD50S/70S - General Boiler Information
3.5 FLUE TERMINAL LOCATION - Fig. 8
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.
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.
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
withouteffectingtheperformanceoftheboiler.
However, to ensure the condensate plume
does not affect adjacent surfaces the terminal
canbeextendedbeyondgutters,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 shouild not be
less than 2500 mm from car parking spaces,
building boundary walls, fences etc.
Note: A terminal must not be sited under a car port roof
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
HI
Q
Boundary
OP
N
Fig. 8
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.

12 Alpha CD50S/70S - General Boiler Information
Propane Gas (LPG): Installation pipes, cylinders and pressure regulators should be fitted in accordance with BS 5482:1.
Bulk tank installation must comply with the requirements of the Home Office code of practice for the storage of liquefied
petroleum gas at fixed installations. The boiler must not be installed in a room or internal space below ground level, e.g.
in a basement or cellar, except where at least one side is open to ground level.
3.7 FROST PROTECTION
The boiler is fitted with a frost thermostat that activates the pump and burner when the system water temperature in the
boiler falls below 3°C.
The electrical supply to the boiler must be left on for the thermostat to operate and the selector switch must be set to ON .
3.8 CENTRAL HEATING SYSTEM - Fig. 9
TheboilerisdesignedforuseinasealedcentralheatingsysteminaccordancewiththerequirementsofBS5449andBS6798.
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 graph
for guidelines (see Fig. 1).
However, if the boiler is to be used with an open central heating system refer to Fig. 9 and use a barrier heat exchanger (i.e.
separates the boiler primary circuit from the open heating circuit). This will also ensure the boiler heat exchanger is protected
from an old/dirty system.
Sealed system volume - An expansion vessel is not incorporated into the boiler. An expansion vessel must be fitted in
the position shown in Fig. 9. To check correct operation of the expansion vessel the system pressure should not be more
than 3.5 bar when the system is at maximum operating temperature (for further guidance refer to BS 7074:1), For
example an 8 litre expansion vessel is suitable for a sealed system of 80 litres.
The boiler is supplied with the following components built in:-
Pressure relief valve - complying with BS 6759 and set to operate at 4 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.
By-pass - The boiler has no built-in by-pass, therefore an automatic by-pass is required for the system.
Fig. 9
Installation on a low temperature heating system.
The boiler can directly feed a low temperature system, varying the maximum delivery temperature of the boiler and
setting a value of between 20 and 85°C. To vary the boiler maximum delivery temperature, modify the boiler maximum
delivery temperature of parameter No. 4 as described in Section 5.8 and Table 6.
In this mode it is advisable to include a safety limit thermostat set at 55°C in series with the boiler circulating pump. The
thermostat must be positioned in the system flow pipe at more than 2 metres from the boiler.
Make up vessel
(sealed system only)
Automatic
air vent
Expansion vessel
(sealed system only)
Double check valve assy.
(sealed system only)
Filling point
(sealed system only)
Static head of system
Heating return
System
drain tap
Heating flow
Note: A drain tap should be installed at the lowest
point of the heating circuit and beneath the appliance.
Boiler
Heating return
Fit pump if Barrier
heat exchanger used
Heating flow
Barrier heat exchanger used on
open or old/dirty systems
Return
Flow
Flow
Return
Drain
tap

13
Alpha CD50S/70S - General Boiler Information
3.9 FILLING THE SEALED CENTRAL HEATING SYSTEM - Figs. 10, 11
The system design pressure (cold) should be set to 1.0 bar. This pressure is equivalent to a static head (see Fig. 9) 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. 10 and 11. The position for connecting an automatic make-up vessel is indicated in Fig. 9. A double check valve
assembly must be used, as shown in Fig. 11.
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. 10. 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 4 bar.
Drain taps (to BS 2879) must be used to allow the system to be completely drained.
3.10 FLUSHING THE HEATING SYSTEM
It is essential that the central heating system is thoroughly cleaned and flushed when fitting an Alpha CD50S or CD70S
boiler. Failure to do so will invalidate the warranty. If this is difficult because the system is old/dirty refer to Section 3.8,
Fig. 9 gives consideration to using a barrier heat exchanger.
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 CD50S or CD70S boilers. Further information
can be obtained from Fernox (Tel: [phone]) or Sentinel (Tel: [phone]).
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.
Fig. 10 Fig. 11
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

14 Alpha CD50S/70S - General Boiler Information
3.11 DISPOSAL OF CONDENSATE
Provision must be made for the safe disposal of condensate produced by the flue gases of the Alpha CD50S or CD70S
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. 12 and 13.
Note: All pipework must have a continuous fall (see Figs. 12 and 13) 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.
Fig. 13 - 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. 12 - 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°

15
Alpha CD50S/70S - Installation
4.1 UNPACKING
1. The basic boiler is supplied in a single box, containing the following:-
Cased boiler supplied with water connections and washers
Mounting hooks and wall plugs
Tundish for pressure relief valve outlet
Condensate discharge pipe
Gas service cock and 28 mm connection tail
Literature pack and Wall template
Other parts of the flue system are supplied in seperate packs as ordered.
2. Unpack boiler and remove the loose items.
4.2 DIMENSIONS and CONNECTIONS- Fig. 14
4 INSTALLATION
Fig. 14
4.3 PREPARE THE WALL - Fig. 15
1. Decide upon the position of the boiler taking into account the clearances
requiredforservicing(refertoSection2.5)andtheflueterminalposition.
2. Tape the template to the wall (ensure it is level and the right way up)
and mark the position of the two holes for the boiler mounting hooks.
3. Drill the fixing holes (12 mm dia.) to accept the No.12 plugs supplied.
Screw the boiler mounting hooks fully into the plugs.
4. Cut suitable holes in the wall/roof 100 mm dia for open flue 80 mm dia.
pipe or 127 mm dia. for concentric flue. Use the centre line positions
given on the flue template.
5. Lift the boiler and locate it on the mounting hooks.
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.
Always grip the boiler firmly, and before lifting feel where the weight is
concentrated to establish the centre of gravity, repositioning yourself as
necessary.
Centre line for
vertical flues
Centre line
for horizontal
concentric flue
Centre line
for horizontal
open flue
Alpha
HEATING
FLOW
(11/2" BSP)
BOTTOM OF CASING
MINIMUM SIDE
CLEARANCE 10 mm
TOP OF CASING
WITH COVER
BOILER MOUNTING
HOOK FIXING HOLE
MINIMUM TOP CLEARANCE 350 mm
BOILER MOUNTING
HOOK FIXING HOLE
MINIMUM SIDE
CLEARANCE 10 mm
SAFETY
VALVE
(3/4" BSP)
GAS
(28 mm)
HEATING
RETURN
(11/2" BSP)
MINIMUM BOTTOM CLEARANCE 250 mm
WITHOUT HYDRAULIC OPTIONAL KIT
FOR USE WITH ALPHA CD50 - 70S
200 mm
170 mm
Fig. 15
300 300
23280 Dia.
1010
170
105
300
600
495
220
285
525
Heating flow B
Heating return B
Gas A
950
905
Alpha CD70S
Pressure relief valve discharge C
25
70
A
B
C

16 Alpha CD50S/70S - Installation
4.4 CONNECT THE PIPEWORK - Fig. 14
1. Thoroughly flush out all the water pipework. Refer to Section 3.10.
2. Connect the system flow and return pipework to the boiler using suitable
isolating valves.
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.
3. 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 3.11.
Pour at least 0.5 litre of water into the flue duct, as shown in Fig. 16, and
check the condensate discharge pipe for soundness
4. Ensure that all the valves are closed and do not turn on the water or gas supplies at
this stage.
4.5 'B23' TYPE SINGLE PIPE 80 mm FLUE KITS
Vertical kit - see Fig. 17 and 18, and refer to Section 3.4.
Fig. 17 shows the vertical flue kit parts.
To assemble the kit to the boiler - Slide the flue pipe down through the roof seal and place the seal over the flue duct. Push
the flue duct into the flue socket on top of the boiler up to the stop. Ensure the seal is pushed in position against the ceiling.
The maximum vertical length (without bends) for flue pipe is 30 metres (see Fig. 17 and 18)
To install extensions or other flue components, proceed as follows: fit the male end of the pipe or elbow up to the stop on
the female socket (with lip seals) of the previously installed component, this will ensure a secure fit and seal of the joints.
Ensure all joints have the seal located correctly and the tape supplied is applied around each joint to ensure the flue
ducts cannot be pulled apart.
It is recommended that the flue should be supported approximately every 1.5 m with access provided to the joints.
Fig. 17 Fig. 18
Horizontal through the wall kit - see Fig. 19 and 20, and refer to Section 3.4.
Fig. 19 shows the horizontal through the wall kit parts.
To assemble the kit to the boiler - Fit the male end of the flue elbow into central flue outlet on the top of the boiler to the
stop. Place the outer seal over the flue duct and slide it throught the wall from the outside. Place the inner seal over the
flue duct then insert the duct into the elbow up to the stop. Slide the seals along the duct to seal it to the inside and
outside of the wall.
To install extensions or other flue components, proceed as follows: fit the male end (smooth) of the pipe or elbow up to
the stop on the female socket (with lip seals) of the previously installed component, this will ensure a secure fit and seal
of the joints.
Extensions for flue kit - The maximum vertical/horizontal straight length (without flue bend) is 30 metres (refer to Section 3.4).
Note: To prevent condensate lying in the flue pipe, slope the pipe towards the boilers with a minimum slope of 2.5° - 3°
(25 - 30 mm per metre). When installing the extensions, a wall/ceiling mounted clamp must be installed every 1.5 metres.
Fig. 16
Flue pipe
Seal
Vertical terminal
Maximum
length 30 m
430 mm
minimum
Seal

17
Alpha CD50S/70S - Installation
4.6 'C' TYPE CONCENTRIC FLUE KITS
Convert the boiler from the factory supplied 'B23' type configuration to 'C' type, i.e. room sealed concentric flue by
removing the 80 mm dia. adaptor and four screws securing the fixing plate and gasket from the top of the boiler.
Horizontal through the wall concentric flue kit - see Fig. 21 and 22.
Fig. 21 shows the flue kit parts that need to be fitted to the boiler to ensure the room sealed concentric flue can be used.
To assemble the kit to the boiler - Fit the adapter into the central flue outlet on the top of the boiler up to the stop. Slide
the square gasket over the adapter up to the groove, then fix it to the cover by means of the previously removed fixing
plate and four screws. Fit the male end of the flue elbow up to the stop on the adapter. Place the outer seal over the
concentric flue pipe and slide it throught the wall from the outside. Place the inner seal over the concentric flue pipe then
insert the pipe into the elbow up to the stop. Slide the seals along the duct to seal it to the inside and outside of the wall.
To install extensions or other flue components, proceed as follows: fit the male end (smooth) of the concentric pipe or
concentric elbow up to the stop on the female socket (with lip seals) of the previously installed component, this will ensure
a secure fit and seal of the joints.
Extensions for horizontal kit - The horizontal kit can be extended up to a maximum horizontal distance of 14 metres
(Fig. 22), including the flue terminal and excluding the flue bend on the boiler (refer to Section 3.4).
Note: To prevent condensate lying in the flue pipe, slope the pipe towards the boilers with a minimum slope of 3° (25 - 30
mm per metre). When installing the extensions, a wall/ceiling mounted clamp must be installed every 1.5 metres.
Fig. 22
Outer seal
Inner seal
Flue elbow
Fixing plate
Square gasket
Adapter
Concentric flue pipe
Fig. 21
Flue elbow
Flue pipe Inner seal
Outer seal
Fig. 19 Fig. 20
200 mm
136 mm 13820 mm
Maximum 14000 mm
180 mm
Inner seal
Outer seal
Note: Ensure the flue slopes downwards towards
the boiler by a minimum of 25 to 30 mm per metre (2.5° - 3°)
80 mm
100 mm
170 mm
Note: Ensure the flue slopes downwards towards
the boiler by a minimum of 25 to 30 mm per metre (2.5° - 3°)

18 Alpha CD50S/70S - Installation
4.7 CONNECT THE MAINS SUPPLY - Fig. 2
1. Remove the four screws securing the plastic top cover so that it can be lifted slightly at the front edge.
2. Removethetwofixingscrews(oneeachsideatthebottom)securingthecasefrontpanel(refertoFig.25).Pullthebottom
of the panel outwards while pushing up at the same time and remove the panel then remove the two screws securing the
control panel and lower the panel to gain access to the terminal block. Refer to Technical Data, Section 2.10 for
connection details.
3. 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:-
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.
Do not switch on the electrical supply at this stage.
4. If any external control, i.e. room thermostat etc. is to be fitted, refer to Fig. 2.
Note: All external control connections are less than 24 volts.
Do not connect 230/240 volts to any of the terminals G to Z on the X86 terminal block or to the X84 terminal block.
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.

19
Alpha CD50S/70S - 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 as shown in Fig. 3, ensure that the vent is always open. The
CD50S also has a manual air vent (see Fig. 3)
2. Open the central heating flow and return valves.
3. Open the fill point valve on the filling loop until water is heard to flow.
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. 3 or 4) 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. If the system has been
over pressurised water may be released from the system by manually operating the drain point (see Fig. 3 or 4) until the
system design pressure is obtained. The system design pressure (cold) should be between 0.75 and 1.25 bar.
Refer to Sections 3.9 and 3.10. Filling and Flushing the system.
5.2 TEST FOR GAS TIGHTNESS AND PURGE THE SUPPLY
1. With the boiler gas service cock closed.
Pressure test the gas supply and inlet pipework
connection to the boiler gas service cock for
tightness in accordance with BS 6891.
2. Loosen the gas inlet pressure test point screw
on the gas valve (see Fig. 23). 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
tightness. Close the boiler gas service cock.
5 COMMISSIONING
Fig. 24
On/Off switch Pressure gaugeDisplay panel
ON
MODE STEP STORE
+
-
RESET
Alpha
5.3 BOILER CONTROLS - Fig. 24
Inlet gas
pressure
test point
Outlet gas
pressure
test point
Outlet flow
regulator
Off-set
adjusment
screw
P1
P3
Fig. 23
5.4 INITIAL LIGHTING - Refer to Fig. 24
1. Ensure that the gas and electrical supplies to the boiler are off and that the heating flow and return valves are open.
2. Turn on the gas and electrical supplies to the boiler.
3. Ensure any external controls are calling for heat.
4. Set the On/Off 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.

20 Alpha CD50S/70S - Commissioning
5.5 BOILER DISPLAY PANEL AND FUNCTION MODES
The boiler display panel (see Fig. 24, is composed of a 4-character display and 6 keys. By using these keys it is possible
to adjust the boiler as it would be by using traditional selector switches and knobs.
Table 2 gives the function of each key.
When the boiler is operating, the 4-figure display indicates the mode code (by means of the first 2 figures on the left) and
the boiler flow temperature (by means of the other two figures on the right).
For example if these values are shown on the display it means that the boiler is operating in
heating mode with a flow temperature of 60°C.
The boiler function modes are given in Table 3:
Table 2
RESET
MODE
STEP
STORE
+
-
Manual reset for possible boiler block
Display menu selection key
Selection of parameter to be displayed or edited
Data and storage confirmation key
Increase set value
Decrease set value
03 60
Table 3
Mode code
0
1
2
3
4
5
6
7
8
9 (flashing)
A
Mode description
Stand - by, no operation demand
Pre-ventilation
Burner ignition
Burner lit (system heating)
Burner lit (domestic hot water)
Fan check
Burner off, requested temperature reached
Pump over-run in system heating mode
Pump over-run in domestic hot water mode
Burner off for one of the reasons given in Table 8
3 - way valve check
5.6 BOILER FUNCTIONING PARAMETERS - Refer to Fig. 22
PARAMETER Mode - Press the MODE key once to enter Parameter mode. In this mode the preset operational values
can be changed. The first two figures indicate the parameter number, the last two give the setting value. To change the
boiler settings proceed as follows:
1. Press the MODE key once to enter parameter mode, using the STEP key select the parameter to be changed.
2. Change the value using the + or - keys, press the STORE key to store the new value.
3. Press MODE to make the new value effective.
Parameters that can be modified are given in Table 4
Table 4
0
1
85°C
20°C
20°C
1
2
3
4
Description
Domestic hot water setting value *
Domestic hot water functioning mode
Heating function mode
Max. heating flow temperature
Lower limit value Upper limit value New value
20°C
0 = disabled
1 = enabled
2 = disabled + continuous pump
3 = enabled + continuous pump
0 = disabled
1 = enabled
2 = disabled + continuous pump
3 = enabled + continuous pump
70°C
85°C
Parameter Factory set
*Only active with hot water function enabled when external accessories are fitted.