Alpha CD50S, CD70S Installation and Servicing Instructions
Installation and Servicing
Instructions
Alpha CD50S and 70S
W all Mounted, Fan Assisted, Gas Fired, High Efficiency
Condensing System Boilers
For Technical help or for Service call ...
ALPHA HELPLINE
Tel: 0870 3001964
Nepicar House, London Road,
Wrotham Heath, Sevenoaks,
Kent TN15 7RS
0051
For use with Natural Gas or Propane Gas (LPG)
Leave these instructions with the User
CONTENTS
1 Introduction ....................................... 2
2 Technical data................................... 3
3 General boiler information..................8
4 Installation......................................... 15
5 Commissioning ................................. 19
7 Wiring diagram.................................. 29
8 Fault finding ...................................... 30
9 Short parts list ................................... 31
10 Benchmark Checklist ........................ 32
11 Service record ................................... 33
6 Routine servicing............................... 24
1 INTRODUCTION
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.
Alpha CD50S/70S - Contents/Introduction
2
2 TECHNICAL DA T A
2.1 PERFORMANCE
NATURAL GAS (CAT: I2H 2H - G20 - 20 mbar)
Alpha CD50S
Central Heating
Heat Input (H
)kW
s
(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
Fan Speed rpm
Gas Rate m³/h
ft³/h
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
PROPANE GAS (CAT I3P 3P - G31 - 37 mbar)
Alpha CD50S
Central Heating
Heat Input (H
)kW
s
(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
Fan Speed rpm
Gas Rate m³/h
ft³/h
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
Alpha CD70S
Central Heating
Heat Input (H
)kW
s
(Gross) Btu/h
Heat Input (Hi)kW
(Net) Btu/h
Heat Output (Hs condensing) k W
(50°C/30°C) Btu/h
Heat Output (Hi non-condensing) kW
(80°C/60°C) Btu/h
Fan Speed rpm
Gas Rate m³/h
ft³/h
MAX.
77.5
264 300
69.8
238 200
72.8
248 600
67.9
231 700
5 240
7.4
261.2
70 060
63 120
67 100
61 800
Alpha CD70S
Central Heating
Heat Input (H
)kW
s
(Gross) Btu/h
Heat Input (Hi)kW
(Net) Btu/h
Heat Output (Hs condensing) k W
(50°C/30°C) Btu/h
Heat Output (Hi non-condensing) kW
(80°C/60°C) Btu/h
Fan Speed rpm
Gas Rate m³/h
ft³/h
MAX.
77.5
264 300
69.8
238 200
72.8
248 600
67.9
231 700
5 240
2.96
104.5
70 060
63 120
67 100
61 800
MIN.
20.5
18.5
19.7
18.1
1 400
1.96
69.2
MIN.
20.5
18.5
19.7
18.1
1 450
0.78
27.7
Note: The above appliances are fully modulating and are not range rated.
2.2 SYSTEM
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)
Alpha CD50S/70S - Technical Data
3
2.3 COMPONENTS 2.4 ELECTRICAL
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
2.5 INSTALLATION
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
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.
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
Supply
External Fuse
Power Consumption
Internal Fuse - Main Terminal
PCB Fuse F1
PCB Fuse F3
Electrode Spark Gap
Electrical Enclosure Degree of Moisture Protection
2.6 GENERAL
Case Dimensions Height
Width
Depth
Gas Connection
Water Content CD50S
CD70S
230/240 V ~ 50 Hz
3 A
180 W
F2A
T2A
T4A
3 to 4 mm
IPX5D
950 mm
600 mm
525 mm
28 mm
3.7 L
4.0 L
2.7 PERFORMANCE DATA
Boiler model
CD50S
CD70S
Natural Gas Efficiency
Min
9.25
9.00
%CO2 content (± 0.2%) Sedbuk rating
(LPG) Propane Gas
CH Max
9.30
9.25
Min
10.1
9.7
CH Max
10.6
10.5
band
A
A
NOx class
5
5
Alpha CD50S/70S - Technical Data
4
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.
2.9 AVAILABLE PUMP HEAD FOR CENTRAL HEATING
9
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
D
C
TOTAL HEAD
(M water)
8
7
6
5
4
3
2
1
0
200 400 600 800 10001200 14001600 1800 20002200 2400 2600 2800 3000 32000
2.10 ELECTRICAL CONNECTIONS
Note: This Appliance Must Be Earthed
External Pump
Max 1A
(Optional)
N
N
Fuse F2A
230V ~ 50Hz
Fused at 3A
L
L
L
PQN
B
A
FLOW RATE (litre/h)
Fig. 1
External sensor
(Optional)
Zone
manager
(Optional)
37A38
temp sensor
(Optional)
B
DHW
thermostat
Room
(Optional)
LINK
Diverter valve
motor
(Optional)
3
6
Summer switch
2
(Optional)
X85
GJ MOR HF E TS KVUY Z
Analog
input
0 - 10 Volt
(Optional)
X86
230/240 V ~ 50 Hz only Maximum 24 V connection only
Note: Do not connect 230/240 V ~ 50 Hz
Fig. 2
Alpha CD50S/70S - Technical Data
5
2.11 BOILER SCHEMATIC - CD50S
15
14
13
12
11
10
16 17
9
8
7
6
5
18
19
20
21
22
23
24
25
4
3
2
1
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
26
27
ReturnGasFlow Condensate
discharge
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
Alpha CD50S/70S - Technical Data
6
Fig. 3 - CD50S
2.12 BOILER SCHEMATIC - CD70S
15 16
14
13
12
11
10
17
18
19
20
21
9
8
7
6
5
4
22
23
24
3
2
1
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
25
26
ReturnGasFlow Condensate
discharge
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
Fig. 4 - CD70S
Alpha CD50S/70S - Technical Data
7
3 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.
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
Table 1
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.
Alpha CD50S/70S - General Boiler Information
8
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.
Seal Seal
Fig. 5
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.
Alpha CD50S/70S - General Boiler Information
9
3.4.1 Horizontal Flue Options
L max
L max
L max
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
3.4.2 Vertical Flue Options
Not less than
300 mm
Not less than
300 mm
H
L max
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
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
Alpha CD50S/70S - General Boiler Information
10
Open flue: 80 mm dia. single pipe Hmax = 27.4 m
Concentric flue: 80/125 mm dia. Hmax = 15.2 m
Fig. 7 - Vertical flues
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.
Q
P
O
G
N
D
J
Boundary
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
HI
Min. distance (mm)Terminal position
300 mm (See Note 1)
Note: A terminal must not be sited under a car port roof
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
300 mm
600 mm
600 mm
Fig. 8
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
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 shouild not be
less than 2500 mm from car parking spaces,
building boundary walls, fences etc.
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 roomsealed 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 CD50S/70S - General Boiler Information
11
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