Alpha C23, C27 Installation and Servicing
Installation and Servicing
Instructions
Alpha C23/27
Range of Wall Mounted, Fan Assisted, Room Sealed,
Gas Fired Combination Boilers
For Technical help or for Service call ...
ALPHA HELPLINE
Tel: 0870 3001964
Nepicar House, London Road,
Wrotham Heath, Sevenoaks,
Kent TN15 7RS
Service Listed
Alpha C23 G.C. No. 47 532 22
Alpha C27 G.C. No. 47 532 23
For use with Natural Gas only
Leave these instructions with the User
CONTENTS
1 Introduction ....................................... 2
2 Technical data...................................3
3 General boiler information..................6
4 Installation......................................... 10
5 Commissioning ................................. 15
6 Boiler operation ................................. 17
7 Routine servicing...............................18
8 Component replacement ................... 20
9 Wiring diagrams ................................ 27
10 Fault finding ...................................... 29
11 Short parts list ................................... 33
12 Service history .................................. 34
1 INTRODUCTION
The Alpha C range of boilers are wall mounted, fan assisted room-sealed combination boilers. The burner is lit electronically
and the heat output is controlled by a modulating gas valve.
The boilers, providing both central heating and domestic hot water at mains pressure, are designed for use with a fully
pumped, sealed and pressurised heating system using only Natural Gas.
The boilers are supplied with a pump, flow switch, pressure relief valve, expansion vessel and pressure gauge fully assembled
and tested.
As supplied, the Alpha C23 boiler will automatically modulate to provide central heating outputs between 9.3 and 23.3 kW
(31 700 and 79 500 Btu/h). The Alpha C27 boiler will provide central heating outputs between 11.0 and 27.0 kW (37 500
and 92 200 Btu/h).
The maximum output available for domestic hot water is 23.3 kW (79 500 Btu/h), capable of providing 9.5 litres/min with a
temperature rise of 35°C for the Alpha C23 boiler, and 27.0 kW (92 200 Btu/h), capable of providing 11.0 litres/min with a
temperature rise of 35°C for the Alpha C27 boiler.
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
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.
Note: Ensure that the Benchmark Log Book has been completed after the boiler has been installed and commissioned.
Alpha C23/27 - Contents/Introduction
2
2 TECHNICAL DATA
2.1 PERFORMANCE - NATURAL GAS
Alpha C23 Alpha C27
Central Heating
Heat Input kW
(Gross) Btu/h
Heat Output (modulating) kW
Btu/h
Burner Pressure mbar
Settings in wg
Room sealed chamber
panel fitted
Gas Rate m³/h
ft³/h
MAX.
28.5
97 200
23.3
79 500
10.9
4.36
2.71
95.70
Alpha C23 Alpha C27
Domestic Hot Water
Heat Input kW
(Gross) Btu/h
Output to Water (modulating) kW
Btu/h
Burner Pressure mbar
Settings in wg
Room sealed chamber
panel fitted
Gas Rate m³/h
ft³/h
Flow Rate at 35°C Rise L/min
G.P.M.
MAX.
28.5
97 200
23.3
79 500
10.9
4.36
2.71
95.70
9.5
2.1
MIN.
12.3
42 000
9.3
31 700
2.3
0.9
1.16
40.96
MIN.
12.3
42 000
9.3
31 700
2.3
0.9
1.16
40.96
Central Heating
Heat Input kW
(Gross) Btu/h
Heat Output (modulating) kW
Burner Pressure mbar
Settings in wg
Gas Rate m³/h
Domestic Hot Water
Heat Input kW
(Gross) Btu/h
Output to Water (modulating) kW
Burner Pressure mbar
Settings in wg
Gas Rate m³/h
Flow Rate at 35°C Rise L/min
Room sealed chamber
panel fitted
Room sealed chamber
panel fitted
Btu/h
ft³/h
Btu/h
ft³/h
G.P.M.
MAX.
33.0
112 600
27.0
92 100
11.3
4.52
3.14
110.9
MAX.
33.0
112 600
27.0
92 100
11.3
4.52
3.14
110.9
11.0
2.42
MIN.
14.3
48 800
11.0
37 500
2.15
0.9
1.37
48.38
MIN.
14.3
48 800
8.1
27 600
1.21
0.48
1.03
36.4
2.2 SYSTEM
Central Heating (Sealed System)
Max. Working System Pressure
Min. System Pressure
Max. System temperature
Pressure Relief Valve Setting
Expansion Vessel Size (pre-charge press.)
Flow Connection
Return Connection
Relief Valve Connection
Recommended System Pressure (cold)
CH Water Temp. (Approx. max.)
2.3 COMPONENTS
Burner
Main CH/DHW Heat Exchanger
Main Burner Injectors C23
C27
Flue - Outer Duct
Flue - Inner Duct
Stainless steel
1.30 mm (x12)
1.30 mm (x14)
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)
Copper
White
Aluminium
Domestic Hot Water
Max. Mains Inlet Water Pressure
Min. Mains Water Pressure
Min. DHW Flow Rate
Mains Inlet Connection
DHW Outlet Connection
DHW Water Content C23
C27
Outlet Water Temp. (Approx. max.)
2.4 INSTALLATION
Min. Clearances for Servicing Top
(from casing) Bottom
Flue Terminal Size
Flue Terminal Protruding
Hole Size Required For Flue Assy.
Lift Weight C23
62°C (144°F)
Sides
Front
C27
8 bar
0.2 bar
2.5 l/min
15 mm
15 mm
0.2 L
0.24 L
220 mm
250 mm
5 mm
450 mm
100 mm Dia.
145 mm
110 mm Dia.
36 kg
37 kg
Alpha C23/27 - Technical Data
3
2.5 GENERAL 2.6 ELECTRICAL
Case Dimensions Height
(without bottom tray) Width
Depth
Gas Connection
Primary Water Content C23
C27
Air Duct Diameter
Flue Duct Diameter
720 mm
450 mm
330 mm
22 mm
1.6 L
1.8 L
100 mm
60 mm
Supply
External Fuse
Power Consumption
Internal Fuse
Ignition Electrode Spark Gap
Flame Sensing Electrode Gap
230/240 V ~ 50 Hz
2.7 FLUE LENGTHS
Flue length = 0.75 m (not including the terminal, which is supplied with the boiler)
Note: Additional flues (of the same length) are available.
Length of Flue Required:-
Rear Flue = wall thickness + 175mm
Side Flue = wall thickness + distance between wall and side of boiler + 185 mm
Vertical Flue = distance from top of boiler side panel to required roof position minus 1 m for vertical terminal assembly
Maximum flue length = 3 m Horizontal, 4 m Vertical
Each additional 90° Bend is equivalent to 1 m of flue length
Each 45° Bend is equivalent to 0.5 m of flue length
The Vertical Flue terminal assembly is equivalent to 1 m of flue length
3 A
170 W
F2 A
3 mm
6 mm
2.8 AVAILABLE PUMP HEAD FOR CENTRAL HEATING
Output Available pump head
kW
23.3
17.58
14.65
11.63
9.3
Btu/h
79 500
60 000
50 000
40 000
31 700
17°C 20°C
metres
1.4
2.8
3.5
4.1
4.95
feet
4.6
9.2
11.5
13.5
14.6
metres
2.2
3.4
3.8
4.35
4.65
feet
7.2
11.2
12.5
14.3
15.26
litre/min
19.6
14.8
12.3
9.8
7.8
This information is based on 17°C and 20°C system design temperature difference.
Note: For outputs upto 28 kW refer to section 3.7.
Flow rate
17°C 20°C 17°C 20°C
4.3
3.3
2.7
2.2
1.7
litre/min
16.7
12.6
10.5
8.3
6.7
gal/min
2.9 ELECTRICAL CONNECTIONS
Note: This Appliance Must Be Earthed
An optional integral Clock kit is available if required.
Blue
Red
Wire
Brown
Wire
Wire
12345
Red
Not
Wire
Used
Internal Clock Terminals
WARNING
1. Ensure wires are connected
correctly
2. Only fit the Alpha recommended
clock. Other clocks could cause
damage.
gal/min
3.7
2.8
2.3
1.8
1.5
Pressure loss across boiler
metres
metres
2.5
1.9
1.25
0.8
0.5
feet
8.2
6.2
4.1
2.6
1.6
2.3
1.3
0.95
0.65
0.4
feet
7.5
4.3
3.1
2.1
1.3
Clock connections
Alpha C23/27 - Technical Data
4
Boiler terminal block
Fig. 1
2.10 BOILER SCHEMATIC
1 - Flow regulator
2 - DHW flow switch
4 - Gas valve
5 - Primary temperature sensor
7 - Main burner
8 - Bi-thermal heat exchanger
9 - Room sealed chamber
10 - Fan
11 - Air pressure switch
12 - Flue hood
13 - Overheat thermostat
14 - Expansion vessel
15 - Automatic air vent
Fig. 2
16 - Pump
17 - Drain point
18 - Pressure relief valve
19 - Primary pressure switch
20 - Ignition electrode (front)
21 - Flame sensing electrode (rear)
22 - DHW temperature sensor
23 - Flue sampling point
24 - Gas service cock
25 - Mains inlet on/off valve
26 - On/off valve (2 off)
27 - Automatic by-pass
Alpha C23/27 - Technical Data
5
3 GENERAL BOILER INFORMATION
3.1 GAS SUPPLY
The Alpha C23 boiler requires a gas rate of 2.71 m³/h (95.7 ft³/h) and the Alpha C27 a gas rate of 3.14 m³/h (110.9 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 there is a slight downward slope towards the terminal.
Flue components are available as follows:Top easy-flue 500 mm (includes 90° bend), refer to separate instructions
0.75 m flue
90° bend
45° bend
Vertical flue terminal assembly. Refer to the separate installation instructions supplied with the assembly.
A Twin Pipe Flue system is available for use with all the boilers in the range. Refer to the separate instructions for details.
The following methods determine the correct length of flue required.
For rear exit flue L = B + 175 mm
For side exit flue L = B + C + 185 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 m. Each 45° bend used reduces the maximum
flue length by 500 mm.
2. Under no circumstances must the flue length (including allowances for extra bends) exceed 3 metres horizontal and 4
metres vertical.
3. Failure to use Alpha flue components with the boiler will invalidate the boilers CE approval, guarantee and may be unsafe.
Alpha C23/27 - General Boiler Information
6
HORIZONTAL FLUE OPTIONS - Lmax = 3 metres
L = B + C + 185 mm
C
E
L = B + E + F + 185 mm + (90° bend = 1 metre)
B
B
F
L = B + C + E + 185 mm
C
E
C
B
B
VERTICAL FLUE OPTIONS
L = B + C + 185 mm + (2 x 45° bends = 1 metre)
Fig. 3
Alpha C23/27 - General Boiler Information
7
3.5 FLUE TERMINAL LOCATION - Fig. 4
Fig. 4
Terminal position
A Directly below an opening, air brick, windows, etc.
B Below gutters, soil pipes or drain pipes
C Below eaves
D Below balconies or car port roof
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 From an opening in the car port (e.g. door, window) into dwelling
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
300 mm
75 mm
25 mm
25 mm
25 mm
25 mm
300 mm
600 mm
1200 mm
1200 mm
1500 mm
300 mm
300 mm
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.
In certain weather conditions the terminal may emit a plume of steam. Avoid positioning the terminal where this may cause a nuisance.
If the terminal is fitted within 850 mm of a plastic or painted gutter or 450 mm of painted eaves or 300 mm of a plastic car port
roof, an aluminium shield at least 1 m long should be fitted to the underside of the gutter or painted surface. If the terminal is
fitted less than 2 m above a surface to which people have access, the terminal must be protected by a terminal guard.
A suitable guard is available from:
Tower Flue Components Ltd., Vale Rise, Tonbridge, Kent TN9 1TB
3.6 BOILER LOCATION
The boiler is not suitable for external installation.
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 British Gas publication 'Guide for
Gas Installations in Timber Frame Housing', reference DM2.
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 C23/27 - General Boiler Information
8
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). For guidance on water contents contact Alpha Therm Ltd. for Technical Data Sheet 15.
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 to a drain, 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 that a system by-pass, preferably automatic, is fitted.
Make up vessel
Static head of system
Boiler
casing
Automatic
air vent
Additional expansion
vessel (if required)
Double check valve assy.
Heating
by-pass
(If required)
Note: If required, an automatic by-pass is
preferred.
Heating flow
Filling point
DHW outlet
Mains water inlet
Note: If the mains is fitted with water
meter, check valves or loose jumper stop
cock, then a DHW expansion device must
be fitted.
Note: A drain tap should be installed at the lowest
point of the heating circuit and beneath the appliance.
Heating return
System
drain tap
Fig. 5
3.8 FILLING THE CENTRAL HEATING SYSTEM - Figs. 6, 7
The system design pressure (cold) should be set to 1.0 bar. This pressure is equivalent to a static head (see Fig. 5) of 10.2 metres of water.
Provision should be made to replace water lost from the system. This can be by manual or automatic means, as shown in Figs.
6 and 7. The position for connecting an automatic make-up vessel is indicated in Fig. 5. A double check valve assembly must
be used, as shown in Fig. 7.
Filling of the system must be carried out in a manner approved by the local Water Undertaking. Where allowed, the system may
be filled via a temporary connection as shown in Fig. 6. After filling, always disconnect the flexible hose of the filling loop.
All fittings used in the system must be able to withstand pressures up to 3 bar.
Drain taps (to BS 2879) must be used to allow the system to be completely drained.
The heating system should be thoroughly flushed before the boiler is connected and again after the first heating.
If it is required to add inhibitor to the system, refer to Alpha Therm Ltd. for guidance.
Refer to BS 5449 and BS 6798 for further information.
Mains
water
supply
Feed cistern to be
located above highest
point in the system
Heating circuit
return
Stop
valve
temporarily connected
Hose
unions
Filling loop
Double check
valve assembly
Test cock
Stop
valve
Mains
water
supply
Heating circuit
return
Double check
valve assembly
Test cock
Overflow
Stop
valve
Fig. 6 Fig. 7
Alpha C23/27 - General Boiler Information
9
3.9 DOMESTIC HOT WATER SYSTEM
The minimum flow rate needed for the flow switch and burner to operate is 2.0 litres/min.
The incoming mains water pressure should be between 0.2 and 8 bar to ensure efficient operation. If the pressure is above 7 bar
a pressure reducing valve must be fitted.
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.
All taps and mixing valves used with the hot water system must be suitable for operating at a mains pressure of up to 8 bar.
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 overrim 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.
The mains water supply connection to the boiler must be the first connection from the mains supply.
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, union bends and washers
Mounting bracket plus screws and wall plugs
Flue terminal and flue sealing collar plus 2 screws
Literature pack and Wall template
Box 2 90° flue bend (not required for vertical flue)
Box 3 0.75 m flue (for side and rear flue) with two clamps and inner duct support
Note: If an Easy flue 500 mm is ordered, this will be supplied instead of boxes 2 and 3.
2. Unpack boiler and remove the loose items packs, i.e. mounting bracket, flue terminal and collar.
Note: The boiler can be stood in an upright position supported by the bottom tray, (to allow this, the union bends have been
turned upwards so that they do not protrude beneath the bottom tray - check this before standing the boiler on the bottom tray).
4.2 CLEARANCES REQUIRED - Fig. 8
Fig. 8
Alpha C23/27 - General Boiler Information/Installation
10
4.3 PREPARE THE WALL - Figs. 9, 10
1. Decide upon the position of the boiler taking into
account the clearances required for servicing and
the flue terminal position.
2. Tape the template to the wall (ensure it is level and
the right way up) and mark the position of the holes
for the boiler mounting bracket and bottom fixings. If
rear exit flue is used, mark the position of the hole
for the flue.
3. Side exit flue - Continue the horizontal centre line of
the flue across the wall to the side wall, then along the
side wall 215 mm (ensure the lines are horizontal). This
will give the position of the centre of the hole for the flue.
4. Cut the 110 mm diameter hole (or use a 107 mm
core drill) in the wall for the flue.
Note: For internal fitting of the flue, using the flue
sealing collar supplied, cut a 127 mm dia. flue hole
using a 127 mm core drill.
5. Drill the fixing holes (10 mm dia.) to accept the No.10
plugs supplied. Using the screws supplied, fit the
mounting bracket.
Fig. 9
Fig. 10
4.4 FIT THE BOILER - Refer to Fig. 10
1. Lift the boiler and locate it on the mounting bracket.
2. Fit the bottom screws to secure the boiler in position.
4.5 CONNECT THE PIPEWORK - Fig. 11
1. Thoroughly flush out all the water pipework.
2. The valves/fittings have been factory fitted, however, check that all the connections underneath the boiler have been
tightened, especially the union bends.
To gain access to all the connections, remove the bottom tray by removing the four fixing screws. When all the
connections have been checked for soundness replace the tray and secure with the four screws previously removed.
Note: When soldering to the boiler union bends, ensure the bends are not connected to the valves, otherwise the internal
seals may be damaged.
3. Connect the system pipework to the boiler.
Note: Do not forget that the pressure relief valve discharge pipe must be routed clear of the boiler to a drain in such a
manner that it may be seen, but cannot cause injury to persons or property.
4. Ensure that all the valves are closed (spindle flats at right angles to valve) and do not turn on the water or gas supplies at this stage.
Alpha C23/27 - Installation
11
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