Alpha Alpha CD50 User guide

Installation and Servicing
Instructions
Alpha CD50
Wall Mounted, Fan Assisted, Room Sealed, Gas Fired,
High Efficiency, Condensing Combination Boiler with
Unvented Hot Water Storage
Alpha CD50 G.C. No. 47 532 24
British Gas
Service Listed
For use with Natural Gas only
Leave these instructions with the User
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 CD50 - Contents/Introduction
CONTENTS
1 Introduction ....................................... 2
2 Technical data................................... 3
3 General boiler information.................. 7
4 Installation......................................... 14
5 Commissioning ................................. 20
6 Boileroperation ................................. 23
7 Routineservicing............................... 24
8 Component replacement ................... 26
9 Wiring diagrams ................................ 33
10 FaultFinding ..................................... 35
11 Short parts list ................................... 39
12 Benchmark Checklist ........................ 40
13 Service record ................................... 41
The Alpha CD50 is a wall mounted, high efficiency, fan assisted, room-sealed, condensing combination boiler - incorporating a
52 litre unvented hot water storage cylinder. The burner is lit electronically and the heat output is controlled by a modulating
fan and gas valve.
The boiler, providing both central heating and domestic hot water at mains pressure, is designed for use with a fully pumped,
sealed and pressurised heating system using only Natural Gas.
The boiler is supplied with a pump, diverter valve, pressure relief valve, expansion vessel and pressure gauge fully assembled
and tested.
As supplied, the boiler will automatically modulate to provide central heating outputs between 6.3 and 29.7 kW (21 500 and
101 430 Btu/h).
The maximum output available for domestic hot water is 32.0 kW (109 200 Btu/h) and provides hot water at temperatures of up
to 65°C and flow rates of up to 18 litres/min (4 gal/min).
IMPORTANT
This boiler has been approved to the Building Regulations for unvented hot water storage systems and the Local Authority
must be notified of the intention to install. Therefore the installation must be carried out by a person competent to install
unvented hot water systems.
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 5440:1:2008 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 7593:2006 Code of Practice for treatment of water in heating systems
BS 7671:2001 Requirements for electrical installations, IEE Wiring Regulations
Reference should be made to DEFRA document 'Guide to condensing boiler installation assessment procedures for dwellings'.
If installation is in a timber framed building, refer to the Institute of Gas Engineers document IGE/UP/7.
This appliance meets the requirements of IPX4D, ie degree of protection against moisture.
Failure to install this appliance correctly could lead to prosecution. It is in your own interest and that of safety to ensure that the
law is complied with.
Manufacturer's instructions must NOT be taken in anyway as over-riding statutory obligations.
Notes: 1. Ensure that the Benchmark Checklist has been completed after the boiler has been installed and commissioned.
2. The boiler must only be used with Alpha CD condensing flue components.
1 INTRODUCTION

3
7 minutes
3 minutes
5 minutes
2.1 PERFORMANCE - NATURAL GAS (CAT: 2H-G20-20 mbar)
2 TECHNICALDATA
Alpha CD50 - Technical Data
MAX.
31.0
105 770
28.0
95 230
29.7
101 430
27.6
94 130
2.91
1.16
2.95
104.1
MIN.
7.4
25 360
6.6
22 830
7.0
23 980
6.5
21 500
0.27
0.11
0.71
25.1
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
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 Storage Cylinder
Main Burner Injector
Flue - Outer Duct
Flue - Inner Duct
Stainless steel
Stainless steel
Stainless Steel
6.6 mm
White
Plastic
2.3 COMPONENTS 2.4 ELECTRICAL
Supply
External Fuse
Power Consumption
Internal Fuse
Electrode Spark Gap
230/240 V ~ 50 Hz
3 A
140 W
F2 A
3 - 4 mm
MIN.
7.4
25 360
6.6
22 830
6.3
21 500
0.27
0.11
0.71
25.1
1.0
0.22
5
41
Domestic Hot Water
Heat Input (Hs)kW
(Gross) Btu/h
Heat Input (Hi)kW
(Net) Btu/h
Output to Water (Hs)kW
(modulating) Btu/h
Differential Burner mbar
Pressure in wg
Gas Rate m³/h
ft³/h
Flow Rate L/min
G.P.M.
Outlet Water Temp. (Approx.) °C
°F
Time to raise water store by 50°C
Reheat time for 70% of store (boiler ON)
(boiler OFF)
5.5 bar
12 bar
0.1 bar
15 mm
15 mm
52 L
4 L at 2.5 bar
2.5 bar
90°C/7 bar
6 bar
Domestic Hot Water
Max. Hot Water Working Pressure
Max. Mains Inlet Pressure (inlet of pressure reducing valve)
Min. Mains Water Pressure
Mains Inlet Connection
DHW Outlet Connection
DHW Water Storage
Expansion Vessel Size (pre-charge press.)
Pressure Reducing Valve Setting
Temperature and Pressure Relief Valve
Expansion Relief Valve Setting
900 mm
600 mm
450 mm
22 mm
3.2 L
100 mm
60 mm
Case Dimensions Height
Width
Depth
Gas Connection
Primary Water Content
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
Weight Full and Operational
2.5 INSTALLATION
220 mm
250 mm
10 mm
450 mm
100 mm Dia.
100 mm
110 mm Dia.
70 kg
130 kg
Room sealed
chamber panel
fitted
MAX.
36.1
123 190
32.6
110 910
32.0
109 200
3.70
1.48
3.44
121.4
18.0
4.0
65
149

4Alpha CD50 - Technical Data
2.7 FLUE LENGTHS
CD Easy-Flue 500 mm with terminal and 90° bend. A CD Easy-Flue 1000 mm with terminal and 90° bend is also available.
CD 750 mm and 1000 mm flue extensions are available.
Length of Flue Required:-
Rear Flue = wall thickness + 170 mm (includes terminal)
Side Flue = wall thickness + distance between wall and side of boiler + 230 mm (includes terminal)
Vertical Flue = distance from top of boiler side panel to required roof position minus 1 m for vertical terminal assembly
Maximum horizontal flue length = 12 m.
Maximum vertical flue length including terminal is 15 m.
Each additional CD 90° Bend is equivalent to 1.3 m of flue length.
Each CD 45° Bend is equivalent to 0.9 m of flue length.
The CD Vertical Flue terminal assembly is equivalent to 1 m of flue length.
2.8 AVAILABLE PUMP HEAD FOR CENTRAL HEATING
gal/min
3.7
2.8
2.3
1.8
0.7
Btu/h
86 700
64 000
53 000
42 200
18 100
kW
25.40
18.70
15.60
12.35
5.30
Output (50/30°C) Available pump head
metres
2.3
3.5
3.8
4.0
4.6
feet
7.6
11.6
12.6
13.2
15.2
litre/min
16.6
12.6
10.5
8.3
3.2
20°C 20°C
Flow rate
This information is based on 20°C system design temperature difference.
Note: For outputs upto 28 kW refer to Section 3.7.
Fig. 1
2.9 ELECTRICAL CONNECTIONS
Note: This Appliance Must Be Earthed
An optional integral single channel Clock kit is available if required.
Note: Only use the Alpha single channel clock. Do not fit any two channel clocks.
Boiler terminal block
Clock connections
1. Ensure wires are connected
correctly
2. Only fit the Alpha recommended
single channel clock. Other
clocks could cause damage.
WARNING
Blue
Wire
Brown
Wire
Red
Wire
12345Internal Clock Terminals
Red
Wire
Not
Used

5
2.10 BOILER SCHEMATIC
Alpha CD50 - Technical Data
Fig. 2
1 Flue sampling point
2 Flue thermostat
3 Injector
4 Gas valve
5 Primary temperature sensor
6 Venturi
7 Main burner
8 Primary/condensing heat exchanger
9 Room sealed chamber
10 Fan
11 Pressure differential test points
12 Flue hood
13 Overheat thermostat
14 CH Expansion vessel
15 Automatic air vent
16 Pump
17 Drain point
18 Pressure gauge
19 Primary pressure switch
20 Ignition electrodes
21 Flame sensing electrode
22 Venturi negative point
23 Venturi positive point
24 Gas service cock
25 On/off valve (2 off)
26 Automatic by-pass
27 Cyclone separator
28 Condensate trap
29 CH Pressure Relief Valve
30 DHW Expansion Vessel
31 DHW Storage Temperature Sensor
32 DHW Temperature/Pressure Relief Valve
33 Storage Cylinder
34 Secondary Heat Exchanger
35 DHW Drain Point
36 DHW Expansion Relief Valve
37 Mains Inlet Filter
38 Check Valve
39 Mains Inlet Valve
40 Pressure Reducing Valve with Filter
41 Automatic Flow Regulator
42 Tundish
43 Diverter Valve

6
3.1 GAS SUPPLY
The Alpha CD50 boiler requires a gas rate of 3.44 m³/h (121.4 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 soundness and purged as described in BS 6891.
3.2 ELECTRICAL SUPPLY
The boiler requires a 230/240 V ~ 50 Hz mains supply, fused at 3 A
The boiler must be earthed.
There must only be one common isolator, providing complete electrical isolation, for the boiler and any external controls.
This boiler has been fitted with a supply cable, however, if it is necessary to fit a cable use PVC insulated cable not less than
0.75 mm² (24 x 0.2 mm) to BS 6500 Table 16. The boiler should be connected to a fused three pin plug and unswitched
shuttered socket outlet (both complying with BS 1363), or a fused double pole switch with a contact separation of at least 3 mm
in both poles.
Wiring external to the boiler must be in accordance with the current IEE Wiring Regulations (BS 7671).
Note: If a room thermostat is fitted, it must be suitable for 230/240 V switching.
3.3 AIR SUPPLY
The boiler does not require any air vents for cooling in the room in which it is installed or when installed in a cupboard or
compartment. The minimum clearances for servicing must always be maintained.
Note: A cupboard or compartment used to enclose the boiler must be designed and constructed specifically for the purpose,
i.e. comply with the Building Regulations.
3.4 FLUE SYSTEM - Fig. 3
The flue system must be installed in accordance with BS 5440:1.
For horizontal flues ensure the flue assembly is horizontal and the inner duct is sloping downwards towards the boiler.
Flue components are available as follows:-
CD Easy-Flue 500 mm (includes 90° bend and terminal) - Part No. 6.2000510.
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 90° bend - Part No. 6.2000590.
CD 45° bend - Part No. 6.2000545.
CD Vertical flue terminal assembly. Refer to the separate installation instructions supplied with the assembly.
The following methods determine the correct length of flue required.
For rear exit flue (including terminal) L = B + 140 mm
For side exit flue (including terminal) L = B + C + 225 mm (min. side clearance required is 5 mm)
For vertical flue L = H minus 1000 mm for vertical terminal assembly
Where L = Required flue length
B = Finished wall thickness
C = Distance from the inside wall to the side of the boiler
H = Distance from top of boiler side panel to roof position
Note: 1. If an extra 90° bend is used, this reduces the maximum flue length by 1.3 m. Each 45° bend used reduces the maximum
flue length by 0.9 m.
2. Under no circumstances must the flue length (including allowances for extra bends) exceed 12 metres horizontally and
only 15 metres vertically.
3. Failure to use Alpha CD flue components with the boiler will invalidate the boilers CE approval, guarantee and may be
unsafe.
4. Further Plume management flue accessories are available - Refer to the Easy-Flue installation instructions.
3 GENERAL BOILER INFORMATION
Alpha CD50 - General Boiler Information

7
HORIZONTAL FLUE OPTIONS
Lmax = 12 metres (L/H side X = 185 mm, R/H side X = 425 mm)
L = B + C + E + X
Alpha CD50 - General Boiler Information
L = B + C + X
L = B + E + F + X + (90° bend = 1.3 metre)
L = B + C + X + (2 x 45° bends = 1.8 metre)
Fig. 3
E
CB
B
C
CB
E
B
F
VERTICAL FLUE OPTIONS
Hmax = 15 metres Hmax = 13.2 metres
Not less than
300 mm
H
Not less than
300 mm
Not less than
300 mm
H
Not less than
300 mm

8
3.5 FLUE TERMINAL LOCATION - Fig. 4
Note: Incertainweather conditions the terminal will emit a plume of steam. If possible avoid positioning the terminal where this maycause
a nuisance, i.e. positions A, D, G, H, J or M.
The flue terminal must be exposed to the external air and the position must allow the free passage of air across it at all times.
If the terminal is fitted within 850 mm of a plastic or painted gutter or 450 mm of painted eaves, an aluminium shield at least 1 m
long should be fitted to the underside of the gutter or painted surface. A terminal must not be sited below 2 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.
For further information refer to BS 5440 Pt1:2008.
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, i.e. 130 kg. The boiler can
be fitted to or adjacent to a wall comprising of a combustible material without the need for a special thermal insulation barrier.
If the boiler is to be fitted in a timber framed building, it should be fitted in accordance with the Institute of Gas Engineers 'Guide
for Gas Installations in Timber Frame Housing', reference IGE/UP/7.
The boiler may be installed in any room or internal space, although particular attention is drawn to the requirements of the
current IEE Wiring (BS7671) Regulations, and in Scotland, the electrical provisions of the Building Regulations applicable in
Scotland, with respect to the installation of the boiler in a room or internal space containing a bath or shower. Where a room-
sealed boiler is installed in a room containing a bath or shower, it must not be possible for a person using the bath or shower
to touch any electrical switch or boiler control utilising mains electricity.
The boiler may be installed in a cupboard or compartment, provided it is correctly designed for that purpose, i.e. complies with
the Building Regulations and the requirements of BS 6798.
Alpha CD50 - General Boiler Information
Note: A terminal must not be sited under a car port roof
Notes:1.In addition, the terminal should not be nearer
than 150 mm to the framework of an
opening into the buiding, i.e. a window
surround or door surround.
2.This clearance may be reduced to 25 mm
without effecting the performance of the
boiler. However, to ensure the condensate
plume does not affect adjacent surfaces a
clearance of 300 mm is preferable.
3.These clearances may be reduced to 25 mm
without effecting the performance of the
boiler. However, to ensure the condensate
plume does not affect adjacent surfaces the
terminal should be extended beyond gutters,
pipes, eaves, balconies etc.
4.It is recommended the terminal should not
be less than 2000 mm from boundary walls,
fences etc. if the plume is likely to cause a
nuisance.
5.This distance may be reduced to 300 mm if
terminal is not facing the 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 facing the terminal
I From a terminal facing the terminal
J Above an opening, air brick, window etc.
K Vertically from a terminal on the same wall
L Horizontally from a terminal on the same wall
M Horizontally from an opening, air brick, window etc.
Min. distance (mm)Terminal position 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 & 5)
1200 mm
300 (See Note 1)
1500 mm
300 mm
300 mm (See Note 1)
Fig. 4

9
3.7 CENTRAL HEATING SYSTEM - Fig. 5
The boiler is designed for use in a sealed central heating system in accordance with the requirements of BS 5449 and BS 6798.
The system should be designed to operate with flow temperatures of up to 82°C. When designing the system, the pump head, expansion
vessel size, mean radiator temperature, etc. must all be taken into account. Refer to the pump performance table for guidelines.
System volume - The expansion vessel incorporated into the boiler is suitable for a sealed heating system with a maximum
water content of 80 litres (18 gal). Above 80 litres, consideration should be given to fitting an additional expansion vessel fitted
in the position shown in Fig. 5. To check correct operation of the expansion vessel(s) the system pressure should not be more
than 2.5 bar when the system is at maximum operating temperature (for further guidance refer to BS 7074:1).
The boiler is supplied with the following components built in:-
Pressure relief valve - complying with BS 6759 and set to operate at 3 bar. The discharge pipe must be routed clear of the
boiler and terminated in such a manner that it can be seen, but cannot cause injury to persons or property.
Pressure gauge - To indicate the system pressure to be maintained.
Expansion vessel - Conforming to BS 4814 with a capacity of 8 litres and pre-charged to a pressure of 0.8 bar.
By-pass - The boiler incorporates a by-pass, however where all radiators are fitted with thermostatic radiator valves it is
recommended a system by-pass, preferably automatic is fitted.
Cyclone - This is a device fitted in the heating return within the boiler to remove any foreign or solid matter etc. from the system.
Alpha CD50 - General Boiler Information
3.8 FILLING THE CENTRAL HEATING SYSTEM - Figs. 6, 7
Thesystem designpressure (cold)should beset to1.0bar.Thispressure isequivalent toa statichead(seeFig.5)of10.2 metresof water.
Provision should be made to replace water lost from the system. This can be by manual or automatic means, as shown in Figs.
6 and 7. The position for connecting an automatic make-up vessel is indicated in Fig. 5. A double check valve assembly must
be used, as shown in Fig. 7.
Filling of the system must be carried out in a manner approved by the local Water Undertaking. Where allowed, the system
may be filled via a temporary connection as shown in Fig. 6. After filling, always disconnect the flexible hose of the filling loop.
All fittings used in the system must be able to withstand pressures up to 3 bar.
Drain taps (to BS 2879) must be used to allow the system to be completely drained.
Fig. 5
Fig. 6 Fig. 7
Filling loop
temporarily connected
Heating circuit
return Mains
water
supply
Stop
valve
Hose
unions
Stop
valve
Double check
valve assembly
Test cock
Feed cistern to be
located above highest
point in the system
Mains
water
supply
Stop
valve
Test cock
Double check
valve assembly
Overflow
Heating circuit
return

10 Alpha CD50 - General Boiler Information
3.9 FLUSHING THE HEATING SYSTEM
It is essential that the central heating system is thoroughly cleaned and flushed when fitting an Alpha CD boiler. Failure to do so
will invalidate the warranty.
The primary condensing heat exchanger is constructed in stainless steel and therefore is compatible with most materials used
in a heating system.
If a cleaning agent and inhibitor are used, they must be applied in accordance with their manufacturers instructions. Only
products from Fernox and Sentinel are acceptable for use with the Alpha CD boilers. Further information can be obtained from
Fernox (Tel: [phone]) or Sentinel (Tel: [phone]).
Although the Cyclone is fitted in the heating return on the boiler, the heating system should still be thoroughly flushed as
detailed below. The Cyclone collection point should be emptied via the drain point (see Fig. 11) after flushing has been
completed.
The system should be flushed in accordance with BS 7593 and BS 5449. The following procedures are recommended:
1. Installing onto a new system:-
a.Fill the system, vent at high points, at pump and radiators.
b.Check for leaks.
c.Rapidly drain the system.
d.If required, chemically clean the system as instructed by the recommended cleaner manufacturer.
Note: Ensure that the system is flushed to remove any remains of the cleaner.
e.If chemical cleaner is not used to clean the system:-
i) Refill the system.
ii) Switch on the boiler and allow the system to heat up to the normal operating temperature.
iii) Rapidly drain the system while the water is still hot.
iv) Refill the system.
f. As required, add the recommended inhibitor to the system as instructed by the inhibitor manufacturer.
g.Recheck for leaks.
2. Installing onto an existing system, clean the system before fitting the new boiler:-
a.If the old boiler is still working:-
i) Switch on the boiler and allow the system to heat up to the normal operating temperature.
ii) Rapidly drain the system while the water is still hot.
iii) Refill and chemically clean the system as instructed by the recommended cleaner manufacturer.
iv) Ensure the system is flushed to remove any remains of the cleaner.
v) Fit the new boiler.
b.If the old boiler is not working:-
i) Rapidly drain the system.
ii) Remove the old boiler.
iii) Flush the system through.
iv) Fit the new boiler.
v) Refill and chemically clean the system as instructed by the recommended cleaner manufacturer.
vi) Ensure the system is flushed to remove any remains of the cleaner.
c.As required, add the recommended inhibitor to the system as instructed by the inhibitor manufacturer.
d.Check for leaks.
3.10 DISPOSAL OF CONDENSATE
Provision must be made for the safe disposal of condensate produced by the flue gases of the Alpha CD boilers and reference
should be made to BS 6798: 2000 for the requirements on the disposal of condensate.
The boilers incorporate a condensate trap which has a seal of 75 mm, therefore no additional trap is required.
The condensate should ideally be discharged internally into an internal waste pipe (washing machine/sink waste) or soil pipe to
avoid the possible risk of freezing. The pipework must be in 22 mm pipe.
External pipe runs should be avoided, but if it is necessary, the pipework should be 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. 8 and 9.
Note: All pipework must have a continuous fall (see Figs. 8 and 9) from the boiler and must be of an acid resistant material
such as plastic waste pipe. (copper or steel is not suitable).
It should be noted that the connection of a condensate pipe to a drain may be subject to local building control requirements.

11
Alpha CD50 - General Boiler Information
Fig. 9 - External soakaway
3.11 DOMESTIC HOT WATER SYSTEM
The mains water supply must be first connected to the pressure reducing valve (supplied with the boiler) which will regulate the
water supply to 2.5 bar. However, all taps and mixing valves used with the hot water system must be suitable for operating at a
pressure of up to 5.5 bar.
To ensure economic use, the pipe runs between the boiler and taps should be in 15 mm copper pipe and be as short as
possible. Where possible the pipework should be insulated to reduce heat loss.
Showers - A shower may be used with the boiler if required.
If a loose or flexible head type shower is used it may require the fitting of a double check valve, to comply with Water Bye Law 17.
Bidets - No anti-syphonage arrangements are necessary, provided the outlets are shrouded and it is not possible to attach a temporary
hand held spray. A supply of direct mains fed hot and cold water is permitted provided the appliance is of the over-rim flushing type.
Before the mains water supply pipe is connected to the boiler, it should be thoroughly flushed out to avoid the danger of dirt or
foreign matter entering the boiler and the filter incorporated within the pressure reducing valve cleaned.
The stored water temperature is adjustable to a maximum of 65°C. In hard water areas this should avoid possible scale build-up,
although it is still advisable to reduce the DHW thermostat setting in such areas. However, if descaling is necessary contact Alpha
Therm Ltd. for guidance.
Fig. 8 - External gully
Open endof pipe
divertedinto gully
below grid butabove
waterlevel
Use waterproof
pipework insulation
invery exposed
positions
Ensurepipeis
adequately supported
Plastic pipe
Minimumgradient 2½°

12
3.12 UNVENTED HOT WATER STORAGE SYSTEM
The installation is subject to Building Regulations approval and the Local Authority must be notified of the intention to install.
The CD50 boiler is supplied with all the components required for an unvented hot water system, i.e. temperature/pressure and
expansion relief valves, expansion vessel, check valve and tundish. All these components are factory fitted, except for the
tundish which must be installed as follows:-
Discharge pipe - The discharge pipes from the temperature/pressure and expansion relief valves must be routed to the
tundish supplied and in 15 mm pipe. The discharge pipework from both relief valves may be joined together in the same sized
pipe, providing at least 22 mm pipework is connected downstream of the tundish.
Alpha CD50 - General Boiler Information
Tundish - The tundish must be positioned within 500 mm of the appliance, so that it is visible to the User and away from electrical
devices. The minimum size of the discharge pipe downstream of the tundish is given in the following table.
Primary return
Boiler
Storage cylinder
Heating Primary
flow
Hot
water
22 mm discharge
pipe
Pump
Tundish
6 bar expansion
relief valve
Temperature/pressure
relief valve
4L DHW expansion vessel
2.5 bar pressure
reducing valve
(supplied)
Filter
Stop valve
Mains
water
supply
Cold water supply
Diverter
valve
Check
valve
Fig. 10
Resistance created
by each elbow
or bend
0.8 m
1.0 m
1.4 m
Maximum resistance allowed,
expressed as a length of straight
pipe (i.e. no elbows or bends)
up to 9 m
up to 18 m
up to 27 m
Minimum size of discharge
pipe 'D2' from tundish
22 mm
28 mm
35 mm
Minimum size of discharge
pipe 'D1' to tundish
15 mm
Valve
outlet size
G½
Sizing of copper discharge pipe 'D2' - refer also to Fig. 11Table 1
The discharge pipework from the tundish:-
1. Shall fall continuously through its length.
2. Shall be of a heat resistant material, e.g. metal.
3. Shall not be fitted with any valves or taps.
4. Shall discharge to a safe visible position, e.g. into a gulley.
5. Shall have a minimum of 300 mm straight pipework directly from the tundish.
Note: Where children may play or otherwise come into contact with discharges, a wire cage or similar guard must be
positioned to prevent contact whilst maintaining visibility.

13
Alpha CD50 - General Boiler Information
Fig. 11
TERMINATION INTO A HOPPER
At high level, discharge onto a roof is acceptable providing the roof is capable of withstanding high temperatures and there is a
distance of 3 m from any plastic guttering systems that would collect such discharge.
Note: The discharge will consist of scalding water and steam. Asphalt, roofing felt and non-metallic rainwater goods may be
damaged by such discharges.
HIGH LEVEL TERMINATION
D1
D2
300 mm
minimum
Tundish
Type 'A'
air gap
End of pipe to be
clearlyvisible
300 mm
minimum
Tundish
500 mm max.
Metal discharge pipe (D2) from
tundishwith continuous fall
Metal discharge pipe (D1)
from relief valve to tundish
Temperature/pressure
reliefvalve
300 mm
minimum
100 mm max.
70 mm min.
Gulleyif
available
Pipe close to wall to
allow water to fan out
safely
Groundlevel
D2
D1
LOW LEVEL TERMINATION
Toexpansion
reliefvalve
Worked example:-
The example below is for a G½ temperature relief valve with a discharge pipe (D2)
having four elbows and a length of 7 m from the tundish to the point of discharge.
From Table 1 (page 10):-
Maximum resistance allowed for a straight length of 22 mm copper discharge pipe
(D2) from a G½ temperature relief valve is 9 m.
Subtract the resistance for four 22 mm elbows of 0.8 m each = 3.2 m.
Therefore the maximum permitted length equates to 9 - 3.2 = 5.8 m
5.8 m is less than the actual length of 7 m therefore calculate the next largest size.
Maximum resistance allowed for a straight length of 28 mm pipe (D2) from a G½
temperature relief valve equates to 18 m.
Subtract the resistance for four 28 mm elbows at 1.0 m each = 4 m.
Therefore the maximum permitted length equates to 18 - 4 = 14 m
As the actual length is 7 m, a 28 mm (D2) copper pipe will be satisfactory.
Refer to Fig. 11 for suggested methods of terminating the discharge pipe safely.
Where a single pipe serves a number of discharges, such as in blocks of flats, the number served should be limited to not more
than 6 systems so that any installation can be traced reasonably easily. The single common discharge pipe should be at least
one pipe size larger than the largest individual discharge pipe to be connected.
If the system is installed where discharges from safety devices may not be apparent, i.e. in dwellings occupied by blind, infirm or disabled
people, consideration should be given to the installation of an electronically operated device to warn when discharge takes place.

14 Alpha CD50 - Installation
4 INSTALLATION
4.1 UNPACKING
1. The boxes required when the boiler is installed with a horizontal flue are as follows:-
Box 1 Cased boiler fitted with water and gas valves, filling loop, union bends and washers
Mounting bracket plus screws and wall plugs
Pressure reducing valve and Tundish
Literature pack and Wall template
Box 2 CD Easy-Flue 500 mm or CD Easy-Flue 1000 mm. Both include 90° bend and horizontal flue terminal
Note: NOT required for vertical flue
Notes: a. All flues must be suitable for CD condensing boilers.
b. CD 750 mm and 1000 mm flue extensions are available, if required.
2. Unpack boiler and remove the loose items packs and mounting bracket.
Note: The boiler can be stood in an upright position, (to allow this, the union bends have been turned upwards so that they
do not protrude beneath the bottom - check this before standing the boiler upright).
4.2 CLEARANCES REQUIRED - Fig. 12
Fig. 12
4.3 PREPARE THE WALL - Figs. 12, 13
1. Decide upon the position of the boiler taking into
account the clearances required for servicing and the
flue terminal position.
2. Tape the template to the wall (ensure it is level and the
right way up) and mark the position of the holes for the
boiler mounting bracket and bottom fixings. If rear exit
flue is used, mark the position of the hole for the flue.
3. Side exit flue - Continue the horizontal centre line of the
flueacrossthewalltothesidewall,thenalongthesidewall
235mm(ensurethelinesarehorizontal).Thiswillgivethe
position of the centre of the hole for the flue.
4. Cut the 110 mm diameter hole (or use a 107 mm core
drill) in the wall for the flue.
Notes: a. Ensure the hole is horizontal.
b. For internal fitting of the flue, using the flue
sealing collar supplied, cut a 130 mm dia. flue
hole using a 127 mm core drill.
5. Drillthefixingholes(10mmdia.)toaccepttheNo.10plugs
supplied. Using the screws supplied, fit the mounting
bracket.
4.4 FIT THE BOILER - Refer to Fig. 13
1. Lift the boiler and locate it on the mounting bracket.
Fig. 13
420 mm
180 mm
Rear exit hole
110 mm dia.
Positionof
110 mm hole
to be cut for
side exit
flue
Ensure line is level
Wall
mounting
bracket
Side
wall
235 mm
Boiler
outline
Template
Fixing
holes
140 mm
220 mm
10 mm 10 mm
600 mm
250 mm
450 mm
900 mm
Minimum
clearance
of 450 mm
from front
of boiler

15
Alpha CD50 - Installation
Fig. 14
4.5 CONNECT THE PIPEWORK - Fig. 15
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: 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 cold water supply pipework to the pressure reducing valve (supplied) and then to the boiler.
Refer to Domestic Hot Water System, Section 3.11.
Note:Ensure thatthepressure reducingvalveis connectedcorrectly,i.e. flowisin thedirection of thearrow on thevalve body.
4. Connect the system pipework to the boiler.
Note: Do not forget that the pressure relief valve discharge pipe must be routed clear of the boiler to a drain in such a
manner that it may be seen, but cannot cause injury to persons or property.
5. Connect the 22 mm condensate trap drain pipe to the condensate discharge pipe.
Ensure that the condensate discharge pipe is as required in Section 3.12.
Pour at least 0.5 litre of water into the flue duct, as shown in Fig. 14, and check the condensate discharge pipe for soundness.
6. 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.
7. Connect the discharge pipework to the temperature/pressure relief and expansion relief valves via the tundish supplied.
This pipework must be installed as recommended in Unvented Hot Water Storage System, Section 3.12.
A- Hot water outlet (15 mm)
B- Cold water inlet (15 mm)
C- Heating return (22 mm)
D- Heating flow (22 mm)
E- Gas inlet (22 mm)
F- Heating pressure relief valve (15 mm)
G- Heating drain point
H- DHW expansion relief valve (15 mm)
I- Drain point for DHW store
J- Cold water inlet filter
K- Check valve
L- Automatic flow regulator valve
M- Temperature/pressure relief valve discharge pipe
N - Condensate discharge pipe
O- Condensate trap
P- Cyclone Fig. 15
Pour water into flue duct

16
3. Adjust the telescopic section of the flue to the distance 'L', ensuring that the two labels marked 'TOP' are aligned, then seal
and secure the joint between the ducts with the sealing tape supplied.
4. Pass the flue assembly through the wall (from inside or outside).
Note: Internal fitting - If there is no access to make good the outside wall, locate the flue sealing collar onto the outer duct
of the flue immediately before the terminal grille onto the location provided. Push the flue assembly through the 130 mm flue
hole, so that the collar completely passes through the wall. Then pull the flue assembly back into the correct position. Visually
check that the collar is sealing the outside wall and that it is not restricting any of the openings of the flue terminal.
Fig. 18
Fig. 19 - Fitting the flue from inside
4.6 FIT THE FLUE - Figs. 16, 17
The following procedure applies to fitting an Alpha CD Easy-Flue to both rear or side exit flue - horizontally only.
1. The CD Easy-Flues are suitable for use in the flue length ranges shown in the tables below.
Note: Where the length is less than the minimum or more than the maximum, refer to Section 4.7.
Alpha CD50 - Installation
Fig. 16 Fig. 17
CD Easy-Flue
500 mm
1000 mm
B (mm)
Max
440
885
Min
250
675
2. Determine the overall length (L) of flue required, (see Fig. 18) as follows:-
Rear flue L = wall thickness (B) + 160 mm
Side flue L = wall thickness (B) + distance between boiler and wall (C) + X
(L/H side X = 105 mm, R/H side X = 345 mm)
CD Easy-Flue
500 mm L/H flue
500 mm R/H flue
1000 mm L/H flue
1000 mm R/H flue
Max
490
250
935
695
Min
300
60
725
485
B + C (mm)
Rear Flue
(B)
SideFlue
(B+C)
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.
f. 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. 20).
g. Make good the inside wall by pushing the inside flue sealing collar up to the wall.

17
Alpha CD50 - Installation
Fig. 20 - Rear flue
4.7 EXTENDING THE FLUE - Fig. 21
Note: The maximum horizontal flue assembly length must not exceed a length of 12 metres.
1. When the flue length required is more than the maximum or less than the minimum stated in Section 4.6, paragraph 1,
refer to the table below.
2. Use the template (supplied with the boiler) to mark the required flue position and cut a 130 mm diameter hole for the flue
(use a 127 mm core drill). The size of the hole provides sufficient clearance for the clamps on the flue extension to pass
through the hole.
3. Determinethe overall fluelength as describedinSection 4.6,paragraph2 todeterminethe numberofAlpha CD750/1000mm
flue extensions required.
90
Outerduct clamp
Innerduct seal joint
Innerduct seal joint
90° bend
Terminal
Flue sealingcollar
Note: Ensure the outerflue duct is horizontal
Boilerside
CD Easy-Flue
Ensure the innerduct within
the terminal is at the top.
The innerduct must
be positionedto slope towards
the boiler
Note:
140 mm
235 mm
Flue Length
Up to maximum:-
Between:-
Between:-
Between:-
Between:-
Less than above
Rear Flue (B)
11.86 m
665 - 870 mm
20 - 610 mm
225 - 430 mm
20 - 170 mm
Left hand
11.91 m
715 - 920 mm
70 - 660 mm
275 - 480 mm
70 - 220 mm
Comments
Alpha CD 750 mm or 1000 mm flue extension
(Part No. 6.2000750 or 6.2001050) is required to
extend the range of telescopic flue.
Refer to Section 4.7 for instructions on how to extend
the flue.
Note: A 130 mm flue hole (127 mm core drill) is
required in the wall.
Within the standard Easy-Flue 1000 mm
(Part No. 6.2001010) telescopic range.
Discard the first telescopic section of the Easy-Flue
1000 mm (i.e. not with terminal) and cut to the required
length.
Within standard Easy-Flue 500 mm
(Part No. 6.2000510) telescopic range.
Discard the first telescopic section of the Easy-Flue 500
mm (i.e. not with terminal) and cut to the required
length.
Terminal may protrude somewhat from the outside wall.
Side Flue (B + C)
Right hand
11.67 m
475 - 680 mm
20 - 420 mm
35 - 240 mm
N/A

18
Fig. 21 - Side flue
4. Assemble the flue extensions together by locating the inner duct into the seal joint and secure each extension together
with the clamps supplied (three screws). Ensure that the clamps are positioned centrally over the joints.
Note: If it is required to cut an extension, DO NOT cut the end of the inner duct that incorporates the seal joint. Ensure the
inner duct end without the seal joint is cut so that it is 15 mm longer than the outer duct.
5. Adjust the telescopic section of the Easy-Flue to the required length and secure the Easy-Flue with the sealing tape
supplied. Fit the Easy-Flue to the extensions by locating the inner duct into the seal joint and secure with the clamp (three
screws), ensuring it is located centrally over the joint.
6. Mark the end of the flue assembly 'TOP' where it is connected to the boiler, so that the 'TOP' of the flue terminal is aligned
with the 'TOP' at the boiler end of the flue assembly.
7. Pass the complete flue assembly through the wall.
8. Position the seal and clamp (two screws) supplied, over the bend. Fit the bend to the boiler and rotate to the correct
position and secure in position using the seal and clamp, ensuring that the seal is positioned centrally over both the bend
and adaptor.
9. Slide the clamp (three screws) over the outer duct and pull the flue assembly towards the bend, locating the inner duct into
the seal joint on the bend.
10. Secure the flue assembly to the bend with the clamp (three screws) ensuring it is positioned centrally over the joint,
ensuring the 'TOP' marked on the outer duct is positioned at the top.
Note: Check the flue terminal protrudes 100 mm out of the wall and that the inner duct of the terminal is positioned
correctly, i.e. the inner duct within the terminal is at the top. See Fig. 21.
11. Make good the outside wall by fitting a flue sealing collar onto the location provided immediately behind the flue terminal
grille. Make good the inside wall as required.
Note: If flue sealing collars are being used to make good the inside wall, then they will need to be fitted before assembling
the flue.
Alpha CD50 - Installation
LHS
RHS
180 mm
420 mm
LHS
RHS
85 mm
325 mm
90
25
Note: Ensure the flue extension slopes
downwards towards the boilerby a
minimum of25 - 30 mm permetre
Boilerfront
Outerduct clamp
Innerseal joint
Innerseal joint
Flue length (L)
Clamp
andseal
90°bend
Seal joint
CD Easy-Flue
CD Flue extension
Flue sealing
collar
Flue
terminal
Ensure the innerduct within
the terminal is at the top.
The innerduct must
be positionedto slope towards
the boiler
Note:

19
Alpha CD50 - Installation
4.8 CONNECT THE MAINS SUPPLY - Fig. 22
1. Gainaccesstotheboilerterminalblockbyreleasingthe
two fixing screws (one each side) securing the control
panel and lowering the panel. Refer to Technical Data,
Section 2.9 for connection details.
2. Note: This boiler has been fitted with a mains supply
cable. However, if it is necessary to fit an alternative
supply cable, ensure the cable clamp that has been
fitted is removed and connect as follows:-
Remove the two screws securing the terminal block
cover from the back of the control box (see Fig. 22).
Pass the mains supply cable through the cable clamp
and connect as follows:- Brown to L, Blue to N and
Green/Yellow to . Ensure correct polarity.
Note: Ensure that the length of the earth wire is such
that if the supply cable is pulled out of its clamp the
live and neutral wires become taut before the earth
wire.
The main terminal block can be removed by pulling it
off the pins to give easy access to the terminals.
Do not switch on the electrical supply at this stage.
3. If an external control, i.e. room thermostat or external clock is to be fitted, remove the terminal block cover and remove the
link between terminals 1 and 2. Pass the cable through the cable clamp and connect it to terminals 1 and 2. Replace the
terminal block cover. (Refer to Section 2.9).
4. Replace the terminal block, ensuring it is located correctly on the plastic pins and replace the cover.
5. Ensurethatthereissufficientfreecabletoallowthecontrolpaneltoberaisedandloweredthentightenthecableclampscrews.
6. Leave the control panel open until commissioning procedures have been completed.
7. Carry out electrical system checks - Short circuit, Polarity, Earth continuity and Resistance to earth with a suitable multimeter.
4.9 FIT THE CLOCK KIT - Fig. 23
Ensure the electrical supply to the boiler is isolated.
Important: Only use an Alpha single channel clock. Do not fit a two channel clock.
1. Remove the two screws securing the clock cover at the rear of the control panel.
2. Remove and discard the clock blanking panel.
3. Insert the clock into the opening and secure in place with the screws supplied.
4. Disconnect the clock wiring from the terminal block and connect it to the clock as follows:-
Blue wire to terminal 1, Brown wire to terminal 2 and Red wires to terminals 3 and 4, (or as per the instructions supplied with
the clock). Ensure wiring is correct.
5. Replace the clock cover. Do not overtighten the fixing screws.
6. Leave the control panel open until commissioning procedures have been completed.
Fig. 22
Fig. 23

20 Alpha CD50 - Commissioning
5 COMMISSIONING
When commissioning the boiler, ensure the Benchmark Checklist is completed.
5.1 FILL THE SYSTEM
1. The boiler is fitted with an automatic air vent positioned on the pump (see Fig. 2). The vent is always open and has no
sealing cap.
2. Open the central heating flow and return valves (slot in-line with valve) (see Fig. 15).
3. Open the fill point valve on the filling loop until water is heard to flow. To aid venting, the boiler drain point (see Fig. 2) may
be opened until water flows out. Close the drain point as soon as water appears.
4. To remove the air - Vent each radiator in turn, starting with the lowest in the system.
5. Itisimportant that the pumpisproperly vented to avoiditrunning dry anddamagingitsbearings. Unscrew andremovethe cap
from the centre of the pump. Using a suitable screwdriver rotate the exposed spindle about half a turn, then replace the cap.
6. Check the operation of the pressure relief valve (see Fig. 2) by turning the head anti-clockwise until it clicks. The click is
the valve lifting off its seat allowing water to escape from the system - check that this is actually happening.
7. Continue to fill the system until the pressure gauge indicates 1.0 bar. Close the fill point valve and check the system for
water soundness, rectifying where necessary. Disconnect the filling loop from the mains supply.
Water may be released from the system by manually operating the drain point (see Fig. 2) until the system design
pressure is obtained. The system design pressure (cold) should be between 0.75 and 1.25 bar.
Refer to Sections 3.7 and 3.8. System volume, Flushing and Filling the system.
8. Open the mains water inlet valve (see Fig. 15). Thoroughly flush out the hot water system by turning on all hot water taps
and allow water to flow until no air is present, this will automatically vent the store of air. Turn off taps and close the mains.
9. Ensure that the condensate trap has been filled with water. Refer to Section 4.5, paragraph 5.
10. Drain the store, using the drain point (I in Fig. 15), to flush any debris that may have collected in the store. Refill and vent
the system as described above.
Note: When draining the system ensure all electrical components are protected from water.
5.2 BOILER CONTROLS - Fig. 24
Fig. 24
5.3 TEST FOR GAS SOUNDNESS AND PURGE THE SUPPLY
1. With the boiler gas service cock closed (slot at right angles to valve). Pressure test the gas supply and inlet pipework
connection to the boiler gas service cock for soundness in accordance with BS 6891.
2. Loosen the gas inlet pressure test point screw on the gas valve (see Fig. 26). Ensure the gas supply is on and open the
boiler service cock to purge in accordance with BS 6891.
3. Retighten the test point screw and test for gas soundness. Close the boiler gas service cock.
System
Pressure Gauge
Central
HeatingThermostat
Domestic
Hot WaterThermostat
SelectorSwitch
Clock (if fitted)
0
Indicator
Neons
1
2
3
1
2
3
4
5
6
7
8
9
1
2
3
4
5
6
7
8
9
bar
04
3
2
1
RESET
A
D
B
C
SELECTOR THERMOSTAT TH ERMOSTAT
OFF
CD50