Alpha Alpha CD25C User guide

Installation and Servicing
Instructions
Alpha CD25C/28C/35C
Range of Wall Mounted, Fan Assisted, Room Sealed,
Gas Fired, High Efficiency Condensing Combination Boilers
Alpha CD25C G.C. No. 47 532 31
Alpha CD28C G.C. No. 47 532 33
Alpha CD35C G.C. No. 47 532 35
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 ...
ALPHAHELPLINE
Tel: [phone]
0051

2Alpha CD25C/28C/35C - Contents/Introduction
CONTENTS
1 Introduction ....................................... 2
2 Technical data................................... 3
3 General boiler information.................. 7
4 Installation......................................... 13
5 Commissioning ................................. 19
6 Boileroperation ................................. 22
7 Routineservicing............................... 23
8 Component replacement ................... 25
9 Wiring diagrams ................................ 31
10 Fault finding ...................................... 33
11 Short parts list ................................... 37
12 Benchmark Checklist ........................ 38
13 Service record ................................... 39
The Alpha CD range of high efficiency condensing boilers are wall mounted, fan assisted room-sealed combination boilers.
The burner is lit electronically and the heat output is controlled by a modulating fan and gas valve.
The CD25C, CD28C and CD35C are combination boilers providing both central heating and domestic hot water at mains
pressure.
The boilers are supplied with a pump, pressure relief valve, expansion vessel and pressure gauge fully assembled and tested.
They are designed for use with a fully pumped, sealed and pressurised central heating system using only Natural gas.
The CD25C boiler is suitable for central heating loads of between 5.5 and 19.5 kW (18 766 and 66 550 Btu/h).
The CD28C boiler is suitable for central heating loads of between 6.3 and 25.9 kw (21 496 and 88 400 Btu/h).
The CD35C boiler is suitable for central heating loads of between 7.8 and 30.3 kw (26 614 and 103 400 Btu/h).
The maximum output available for domestic hot water is 24.3 kW (84 800 Btu/h), capable of providing 9.6 litres/min for the Alpha
CD25Cboiler,28.7kW(97900Btu/h),providing11.4litres/min fortheAlphaCD28C boiler and34.6kW(118100Btu/h),providing
14.2 litres/min for the Alpha CD35C boiler, all with a temperature rise of 35°C.
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 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. 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 Alpha CD condensing flue components.
1 INTRODUCTION

3
2.1 PERFORMANCE - NATURAL GAS (CAT: I2H 2H - G20 - 20 mbar)
2 TECHNICALDATA
Alpha CD25C/28C/35C - Technical Data
Alpha CD25C
MAX.
20.4
69 600
18.4
62 780
19.5
66 550
18.0
61 420
2.82
1.13
1.94
68.5
MIN.
6.4
21 960
5.8
19 780
6.1
20 820
5.5
18 780
0.40
0.16
0.61
21.5
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 9.6
2.2
11.2
2.5
MAX.
26.7
91 100
24.1
82 200
24.3
84 800
5.49
2.20
2.55
90.0
MIN.
6.4
21 960
5.8
19 780
5.5
18 780
0.40
0.16
0.61
21.5
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 at 35°C Rise L/min
gal/min
Specific Flow Rate (D) at 30°C Rise L/min
(Flow rate @ 30K to EN625) gal/min
Room sealed
chamber panel
fitted
Alpha CD25C
MAX.
27.1
92 400
24.4
83 250
25.9
88 400
24.0
81 900
5.73
2.29
2.59
91.4
MIN.
7.3
24 900
6.6
21 500
6.9
23 500
6.3
21 500
0.52
0.21
0.70
24.7
Room sealed
chamber panel
fitted
Central Heating
Heat Input (Hs)kW
(Gross) Btu/h
Heat Input (Hi)kW
(Net) Btu/h
Heat Output (Hs condensing) kW
(50°C/30°C) Btu/h
Heat Output (Hi non-condensing) kW
(80°C/60°C) Btu/h
Differential Burner mbar
Pressure in wg
Gas Rate m³/h
ft³/h
Alpha CD28C
11.4
2.5
13.3
2.9
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 at 35°C Rise L/min
gal/min
Specific Flow Rate (D) at 30°C Rise L/min
(Flow rate @ 30K to EN625) gal/min
Room sealed
chamber panel
fitted
Alpha CD28C
MIN.
7.3
24 900
6.6
22 500
6.3
21 500
0.52
0.21
0.70
24.7
MAX.
31.6
107 900
28.5
97 200
28.7
97 900
7.47
2.98
3.02
106.6
MAX.
31.6
107 800
28.5
97 200
30.3
103 400
28.0
95 550
2.01
0.80
3.02
106.6
MIN.
8.9
30 600
8.1
27 600
8.5
29 000
7.8
26 600
0.25
0.10
0.86
30.4
Room sealed
chamber panel
fitted
Central Heating
Heat Input (Hs)kW
(Gross) Btu/h
Heat Input (Hi)kW
(Net) Btu/h
Heat Output (Hs condensing) kW
(50°C/30°C) Btu/h
Heat Output (Hi non-condensing) kW
(80°C/60°C) Btu/h
Differential Burner mbar
Pressure in wg
Gas Rate m³/h
ft³/h
Alpha CD35C
14.2
3.13
15.6
3.44
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 at 35°C Rise L/min
gal/min
Specific Flow Rate (D) at 30°C Rise L/min
(Flow rate @ 30K to EN625) gal/min
Room sealed
chamber panel
fitted
Alpha CD35C
MIN.
8.9
30 600
8.1
27 600
8.0
27 300
0.25
0.10
0.86
30.4
MAX.
38.0
129 600
34.3
117 000
34.6
118 100
3.07
1.23
3.64
128.5
Note: The above appliances are fully modulating and are not range rated.

4
720 mm
440 mm
300 mm
340 mm
22 mm
2.5 L
2.8 L
3.2 L
100 mm
60 mm
Case Dimensions Height
Width
Depth
Depth (with Jig)
Gas Connection
Primary Water Content CD25C
CD28C
CD35C
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 CD25C
CD28C
CD35C
2.5 INSTALLATION
235 mm
250 mm
5 mm
450 mm
100 mm Dia.
100 mm
110 mm Dia.
43 kg
44 kg
45 kg
Central Heating (Sealed System)
Max. Working System Pressure
Min. System Pressure
Max. System temperature
Pressure Relief Valve Setting
Expansion Vessel Size (pre-charge press.)
Flow Connection
Return Connection
Relief Valve Connection
Recommended System Pressure (cold)
CH Water Temp. (Approx. max.)
2.5 bar
0.5 bar
82°C
3 bar (44 PSI)
8 L at 0.8 bar
22 mm
22 mm
15 mm
1.0 bar
82°C (180°F)
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 CD25C
CD28C
CD35C
Outlet Water Temp. (Approx. max.)
8 bar
0.2 bar
2.5 l/min
15 mm
15 mm
0.2 L
0.26 L
0.32 L
62°C (144°F)
2.2 SYSTEM
Burner
Main Heat exchanger
DHW Heat Exchanger
Main Burner Injector CD25C
CD28C
CD35C
Flue - Outer Duct
Flue - Inner Duct
Stainless steel
Stainless steel
Stainless Steel
5.2 mm
5.4 mm
8.5 mm
White
Plastic
2.3 COMPONENTS 2.4 ELECTRICAL
Supply
External Fuse
Power Consumption
Internal Fuse
Electrode Spark Gap
ElectricalEnclosureDegreeofMoistureProtection
230/240 V ~ 50 Hz
3 A
130 W
F2 A
3 - 4 mm
IPX4D
Alpha CD25C/28C/35C - Technical Data
2.7 PERFORMANCE
Band 'A'
5
SEDBUK Rating
NOx Classification
Boiler Model
CD25C
CD28C
CD35C
%CO2content (± 0.2%)
Natural Gas
Min.
9.0
9.1
9.0
CH Max.
9.4
9.3
9.3
DHW Max.
9.4
9.3
9.3

5
Alpha CD25C/28C/35C - Technical Data
Fig. 1
2.8 FLUE LENGTHS
CD Easy-Flue 500 mm with terminal and 90° bend. A CD Easy-Flue 1000 mm with terminal and 90° bend is also available.
CD 750 mm and 1000 mm flue extensions are available.
Length of Flue Required:-
Rear Flue = wall thickness + 140 mm (includes terminal). This is without back frame, add 40 mm if the wall jig is used.
Side Flue = wall thickness + distance between wall and side of boiler + 225 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.
2.9 AVAILABLE PUMP HEAD FOR CENTRAL HEATING
gal/min
3.7
2.8
2.3
1.8
0.7
Btu/h
86 700
64 000
53 000
42 200
18 100
kW
25.40
18.70
15.60
12.35
5.30
Output (50/30°C) Available pump head
metres
2.3
3.5
3.8
4.0
4.6
feet
7.6
11.6
12.6
13.2
15.2
litre/min
16.6
12.6
10.5
8.3
3.2
20°C 20°C
Flow rate
This information is based on 20°C system design temperature difference.
Note: For outputs upto 28 kW refer to Section 3.7.
2.10 ELECTRICAL CONNECTIONS
Note: This Appliance Must Be Earthed
An optional integral 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

6
2.11 BOILER SCHEMATIC
1 - Seasonality valve
2 - DHW flow switch and filter
3 - Diverter valve
4 - Gas valve
5 - Primary temperature sensor
6 - DHW heat exchanger
7 - Main burner
8 - Primary/condensing heat exchanger
9 - Room sealed chamber
10 - Fan
11 - Pressure differential test points
12 - Flue hood
Fig. 2
13 - Overheat thermostat
14 - Expansion vessel
15 - Automatic air vent
16 - Pump
17 - Drain point
18 - Pressure relief valve
19 - Primary pressure switch
20 - Ignition electrodes
21 - Flame sensing electrode
22 - 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
28 - Cyclone separator (if applicable)
29 - Condensate trap
30 - Injector
31 - Venturi
32 - Venturi negative point
33 - Venturi positive point
34 - Flue thermostat
35 - Diverter valve motor
Alpha CD25C/28C/35C - Technical Data
Gas
Condensate
discharge
Primary
Heating
return Primary
Heating
flow
24
4
23
-
-
+
+
9
10
29
35
11
34
5
13
20
14
32
33
15
16
17
18
27
28
26
Domestic
hot water
outlet
Cold mains
water inlet
1
2
3
6
19
22
25
12
8
721
31
30

7
3.1 GAS SUPPLY
The Alpha CD25C boiler requires a gas rate of 2.55 m³/h (90.1 ft³/h).
The Alpha CD28C boiler requires a gas rate of 3.02 m³/h (106.7 ft³/h).
The Alpha CD35C boiler requires a gas rate of 3.64 m³/h (128.5 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 Easy Flue assembly is horizontal and the inner duct is sloping downwards towards the boiler.
When additional flue extensions are used, ensure the flue slopes downwards towards the boiler by a minimum of 25 - 30 mm
per metre of flue.
Flue components are available as follows:-
CD Easy-Flue 500 mm (includes 90° bend and terminal) - Part No. 6.2000500.
CD Easy-Flue 1000 mm (includes 90° bend and terminal) - Part No. 6.2001000.
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 (180 mm if wall jig is used)
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.
3 GENERAL BOILER INFORMATION
Alpha CD25C/28C/35C - General Boiler Information

8
HORIZONTAL FLUE OPTIONS - Lmax = 12 metres
L = B + C + E + 225 mm
Alpha CD25C/28C/35C - General Boiler Information
L = B + C + 225 mm
CB
E
CB
E
B
F
B
C
L = B + E + F + 225 mm + (90° bend = 1.3 metre)
(add 40 mm to 'F' if a jig is used)
L = B + C + 225 mm + (2 x 45° bends = 1.8 metre)
Fig. 3
VERTICAL FLUE OPTIONS
Not less than
300 mm
Not less than
300 mm
H
Hmax=15m
Not less than
300 mm
Not less than
300 mm
H
Hmax = 13.2 m

9
3.5 FLUE TERMINAL LOCATION - Fig. 4
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.
3.6 BOILER LOCATION
The boiler is not suitable for external installation unless it is installed within a purpose designed weatherproof building.
The boiler must be installed on a flat vertical wall which is capable of supporting the weight of the boiler. The boiler can be fitted
to or adjacent to a wall comprising of a combustible material without the need for a special thermal insulation barrier.
If the boiler is to be fitted in a timber framed building, it should be fitted in accordance with the Institute of Gas Engineers 'Guide
for Gas Installations in Timber Frame Housing', reference IGE/UP/7.
The boiler may be installed in any room or internal space, although particular attention is drawn to the requirements of the
current IEE Wiring (BS7671) Regulations, and in Scotland, the electrical provisions of the Building Regulations applicable in
Scotland, with respect to the installation of the boiler in a room or internal space containing a bath or shower. Where a room-
sealed boiler is installed in a room containing a bath or shower, it must not be possible for a person using the bath or shower
to touch any electrical switch or boiler control utilising mains electricity.
The boiler may be installed in a cupboard or compartment, provided it is correctly designed for that purpose, i.e. complies with
the Building Regulations and the requirements of BS 6798.
Alpha CD25C/28C/35C - General Boiler Information
Notes: 1.In addition, the terminal should not be nearer
than 150 mm to the framework of an
opening into the buiding, i.e. a window
surround or door surround.
2.This clearance may be reduced to 25 mm
without effecting the performance of the
boiler. However, to ensure the condensate
plume does not affect adjacent surfaces a
clearance of 300 mm is preferable.
3.These clearances may be reduced to 25 mm
withouteffectingtheperformanceoftheboiler.
However, to ensure the condensate plume
does not affect adjacent surfaces the terminal
canbeextendedbeyondgutters,pipes,eaves,
balconies etc. by upto 500 mm. If the flue is
extended more than 500 mm outside, it should
be boxed and insulated.
4.To reduce the possibility of nuisance to
neighbouring buildings etc. it is
recommended the terminal shouild not be
less than 2500 mm from car parking spaces,
building boundary walls, fences etc.
Note: A terminal must not be sited under a car port roof
A Directly below an opening, air brick, windows, etc.
B Below gutters, soil pipes or drain pipes
C Below eaves
D Below balconies
E From a vertical drain pipe or soil pipe
F From an internal or external corner
G Above ground, roof or balcony level
H From a surface or boundary facing the terminal
I From a terminal facing the terminal
J Above an opening, air brick, window etc.
K Vertically from a terminal on the same wall
L Horizontally from a terminal on the same wall
M Horizontally from an opening, air brick, window etc.
N Minimum protrusion through a roof
O From a vertical obstruction
P From an openable window
Q From an adjacent vertical terminal
Min. distance (mm)Terminal position 300 (See Note 1)
75 (See Note 3)
200 (See Note 3)
200 (See Note 3)
150 (See Note 3)
300 (See Note 2)
300
600 (See Note 4)
1200 mm
300 (See Note 1)
1500 mm
300 mm
300 mm (See Note 1)
300 mm
300 mm
600 mm
600 mm
J
D
G
HI
Q
Boundary
OP
N
Fig. 4

10
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 an automatic by-pass, therefore an automatic by-pass is not required for the system.
Cyclone - This is a device fitted in the heating return within the optional wall jig to remove any foreign or solid matter etc. from
the system.
Alpha CD25C/28C/35C - General Boiler Information
3.8 FILLING THE CENTRAL HEATING SYSTEM - Figs. 6, 7
Thesystem designpressure(cold)shouldbesetto1.0bar.This pressureisequivalent toastatic head(seeFig. 5)of10.2 metresofwater.
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.
Note: A drain tap should be installed at the lowest
point of the heating circuit and beneath the appliance.
System
drain tap
Note: If the mains is fitted with water
meter, check valves or loose jumper stop
cock, then a DHW expansion device must
be fitted.
Static head of system
Make up vessel
DHW outlet
Mains water inlet
Additional expansion
vessel (if required)
Automatic
air vent
Boiler
casing
Heatingflow
Heatingreturn
Filling point
Double check valve assy.
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