Alpha Boilers Alpha 500E User guide

Installation and Servicing
Instructions
For use with Natural Gas only
Leave these instructions with the User
Alpha 500E
Wall Mounted, Fan Assisted, Room Sealed, Gas Fired
Combination Boiler with Unvented Hot Water Storage
Alpha 500E G.C. No. 47 532 07
*HEJEID/=I
Service Listed
0051
Goldsel Road,
Swanley, Kent BR8 8EX
Fax:[phone]
ForTechnical help or for Service call ...
ALPHA HELPLINE
Tel: [phone]
Building Regulations
Certificate No. ETC 00795

2Alpha 500E - Contents/Introduction
CONTENTS
1 Introduction ....................................... 2
2 Technical data................................... 3
3 Generalboilerinformation.................. 6
4 Installation......................................... 12
5 Commissioning ................................. 17
6 Boileroperation ................................. 19
7 Routine servicing............................... 20
8 Componentreplacement ................... 22
9 Wiringdiagrams ................................ 29
10 Faultfinding ...................................... 31
11 Short parts list ................................... 35
12 Service history .................................. 36
The Alpha 500E boiler is a wall mounted, fan assisted room-sealed combination boiler, incorporating a 54 litre unvented hot
water storage cylinder. Heat output is controlled by a modulating gas valve, with fully automatic direct burner ignition.
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 10.4 and 28.0 kW (35 500 and
95 550 Btu/h).
The maximum output available for domestic hot water is 28.0 kW (95 550 Btu/h) and provides hot water at temperatures of up
to 65°C and flow rates of up to 20 litres/min (4.4 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:-
Gas Safety (Installation and Use) Regulations 1984 (as amended)
All relevant Building Regulations issued by the Department of the Environment
Building Standards (Scotland) (Consolidation) Regulations issued by the Scottish Development Department
Local Water Bye Laws
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 5440:1:1990 Flues
BS 5440:2:1989 Air supply
BS 5449:1990 Forced circulation hot water systems
BS 5546:1990 Installation of hot water supplies for domestic purposes
BS 6700:1987 Design, installation, testing and maintenance of services supplying water
BS 6798:1987 Installation of gas fired hot water boilers
BS 6891:1989 Gas installation
BS 7593:1992 Code of Practice for treatment of water in heating systems
BS 7671:1992 Requirements for electrical installations, IEE Wiring Regulations
If installation is in a timber framed building, refer to the British Gas publication 'Guide for Gas Installations in Timber Frame
Housing' reference DM2.
This appliance meets the requirements of IP20, 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.
Notes: 1. Prior to installation ensure the appliance is stored upright in dry conditions and is transported in an upright position.
2. Ensure the appliance has been supplied with the unvented package and flue system.
1 INTRODUCTION

3
2 TECHNICAL DATA
Alpha 500E - Technical Data
950 mm
600 mm
450 mm
22 mm
3.2 L
100 mm
60 mm
Dimensions Height
Width
Depth
Gas Connection
Primary Water Content
Air Duct Diameter
Flue Duct Diameter
MAX.
34.5
117 700
28.0
95 550
10.8
4.32
11.5
4.6
3.25
114.8
82
180
MIN.
13.2
45 000
10.4
35 500
1.9
0.76
2.6
1.04
1.24
43.9
30
86
Room sealed chamber
panel fitted
Room sealed chamber
panel removed
Central Heating
Heat Input kW
(Gross) Btu/h
Heat Output (modulating) kW
Btu/h
Burner Pressure mbar
Settings in wg
mbar
in wg
Gas Rate m³/h
ft³/h
CH Water Temp. (Approx.) °C
°F
2.1 PERFORMANCE - NATURAL GAS (Cat I2H )
8 bar
16 bar
0.1 bar
15 mm
15 mm
54 L
5L at 3.5 bar
3.5 bar
90°C/7 bar
6 bar
Domestic Hot Water
Max. Hot Water 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
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)
2.5 bar
0.5 bar
82°C
3 bar (44 PSI)
7.5 L at 0.8 bar
22 mm
22 mm
15 mm
1.0 bar
2.2 SYSTEM
Burner (18 blade)
Main Heat exchanger
DHW Storage Cylinder
Main Burner Injectors
Flue - Outer Duct
Flue - Inner Duct
Stainless steel
Copper
Stainless Steel
1.18 mm
Epoxy coated
Aluminium
2.3 COMPONENTS
2.5 GENERAL
MAX.
34.5
117 700
28.0
95 550
10.8
4.32
11.5
4.6
3.25
114.8
20.0
4.4
65
149
MIN.
13.2
45 000
10.4
35 500
1.9
0.76
2.6
1.04
1.24
43.9
1.0
0.22
5
41
Domestic Hot Water
Heat Input kW
(Gross) Btu/h
Output to Water (modulating) kW
Btu/h
Burner Pressure mbar
Settings in wg
mbar
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 storage 50°C
Reheat time for 70% of storage
Room sealed chamber
panel fitted
Room sealed chamber
panel removed
12.0 minutes
5.0 minutes
Minimum Clearances for Servicing
Top
Bottom
Side (L/H)
Side (R/H)
Front
Flue Terminal Size
Flue Terminal Protruding
Hole Size Required For Flue Assy.
Lift Weight
Weight Full and Operational
200 mm
250 mm
20 mm
5 mm
450 mm
100 mm Dia.
115 mm
110 mm Dia.
70 kg
130 kg
2.4 INSTALLATION
Supply
External Fuse
Power Consumption
Internal Fuse
Electrode Spark Gap
230/240 V ~ 50 Hz
3 A
190 W
F2 A
2.0 to 3.5 mm
2.6 ELECTRICAL

4
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 +115 mm
Side Flue = wall thickness + distance between wall and side of boiler + X mm (L/H side X = 380, R/H side X = 130)
Vertical Flue = distance from top of boiler side panel to required roof position minus 1 m for vertical terminal assembly
Maximum flue length = 4 m horizontal or 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.
Alpha 500E - Technical Data
2.8 AVAILABLE PUMP HEAD FOR CENTRAL HEATING
gal/min
4.1
3.4
2.78
2.32
1.86
1.65
Btu/h
95563
80 000
60 000
50 000
40 000
35 495
metres
1.0
2.2
3.6
4.2
4.8
5.0
feet
3.28
7.22
11.8
13.7
15.7
16.4
Output Available pump head
metres
2.1
3.4
4.2
4.6
5.1
5.3
feet
6.9
11.1
13.7
15.1
16.7
17.3
metres
3.5
2.6
1.6
1.2
0.9
0.8
feet
11.5
8.5
5.2
3.9
2.9
2.6
metres
2.7
1.8
1.2
1.0
0.7
0.6
feet
8.9
5.9
3.9
3.3
2.3
2.0
Pressure loss across boiler
gal/min
4.8
4.0
3.27
2.73
2.18
1.94
litre/min
18.4
15.2
12.60
10.50
8.40
7.45
17°C 20°C litre/min
21.7
18.3
14.82
12.35
9.88
8.77
17°C 20°C 17°C 20°C
Flow rate
kW
28.00
23.44
17.58
14.65
11.72
10.40
1. Ensure wires are connected
correctly
2. Only fit the Alpha recommended
clock. Other clocks could cause
damage.
WARNING
Blue
Wire
Brown
Wire
Black
Wire
12345Internal Clock Terminals
Black
Wire
Not
Used
Clock connections
2.9 ELECTRICAL CONNECTIONS
Note: This Appliance Must Be Earthed
An optional integral Clock kit is available if required.
Boiler terminal block
Fig. 1
This information is based on 17°C and 20°C system design temperature difference.

5
2.10 BOILER SCHEMATIC
Fig. 2
Alpha 500E - Technical Data
1. Gas Service Cock
2. Heating On/Off Valve
3. Gas Valve
4. Pressure Gauge
5. Pump and Air Separator
6. Primary Return Temperature Sensor
7. Differential Water Flow Switch
8. Adjustable By-Pass
9. Flow restrictor
10. 3-Port Diverter Valve
11. Primary Flow temperature Sensor
12. Overheat Thermostat
13. C.H. Pressure Relief Valve
14. Auto Air Vent
15. Main Burner
16. Main Heat Exchanger
17. Fan
18. Air pressure Switch
19. Unvented Kit
20. C.H. Expansion Vessel
21. Storage Cylinder
22. Temperature/Pressure Relief Valve
23. Hot Water Storage Temperature Sensor
24. Secondary Heat Exchanger
25. DHW Expansion Vessel
26. Check Valve
27. Pressure Reducing Valve with Filter
28. Tundish
29. Ignition Electrodes
30. Flame Sensing Electrodes
31. Positive Pressure Point
32. Negative Pressure point
33. Flue Adaptor
34. Flue Sample Point
35. Room Sealed Chamber
36. Expansion Relief Valve

6
3.1 GAS SUPPLY
The boiler requires a gas rate of 3.25 m³/h (114.8 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.
Using 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 240 V switching
3.3 AIR SUPPLY
The boiler does not require any air vents in the room in which it is installed. If the boiler is installed in a cupboard or
compartment, permanent air vents are required in the cupboard or compartment at high and low levels. The vents must
communicate with the same room or be direct to outside air on the same wall.
If the boiler is installed in a cupboard or compartment with a door, allow at least 75 mm clearance between the front of the
boiler and the door for air movement.
3.4 FLUE SYSTEM - Fig. 3
The flue system must be installed in accordance with BS 5440:1.
The flue assembly supplied for the boiler is 0.75 m in length.
For horizontal flues ensure there is a slight downward slope towards the terminal.
Additional flue components are available as follows:-
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 and an Easy Flue system are available for use with the boiler. Refer to the separate instructions for
details.
The following methods determine the correct length of flue required.
For rear exit flue L = B + 115 mm
For side exit flue L = B + C + X mm (L/H side X = 380, R/H side X = 130).
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
Notes: 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. Minimum side clearance required is L/H side 20 mm, R/H side 5 mm.
3. Under no circumstances must the flue length (including allowances for extra bends) exceed the maximum
recommended length.
4. Failure to use Alpha flue components with the boiler will invalidate the boilers CE approval, warranty and may be
unsafe.
3 GENERAL BOILER INFORMATION
Position of vent
High
Low
Air from room/internal space
310 cm² (48 in²)
310 cm² (48 in²)
Air direct from outside
155 cm² (24 in²)
155 cm² (24 in²)
Alpha 500E - General Boiler Information

7
Fig. 3
Alpha 500E - General Boiler Information
HORIZONTAL FLUE OPTIONS
Lmax = 4 metres, For L/H side flue X = 380, for R/H side flue X = 130
VERTICAL FLUE OPTIONS
Hmax = 4 metres
L = B + E + F + X mm + (90° bend = 1 metre)
L = B + C + X mm + (2 x 45° bends = 1 metre)
L = B + C + E + X mmL = B + C + X mm
Front
Front
RHS
LHS CB
E
CB
E
B
F
B
C
Not less than
300 mm
Not less than
450 mm
HH
Not less than
450 mm
Not less than
300 mm

8Alpha 500E - General Boiler Information
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, 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 (type K3 - G.C. No. 393 554) is available from:
Alpha Therm Ltd., Goldsel Road, Swanley, Kent BR8 8EX, or 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, i.e. 130 kg.
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.
Theboilermaybeinstalledinanyroomorinternalspace,althoughparticularattentionisdrawntotherequirementsofthecurrentIEEWiring
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,itmustnotbepossibleforapersonusingthebathorshowertotouchanyelectricalswitchorboilercontrolutilisingmainselectricity.
The boiler may be installed in a cupboard or compartment, provided it is correctly designed and sufficiently ventilated for that
purpose and that the requirements of BS 6798 and BS 5440:2 are complied with.
3.5 FLUE TERMINAL LOCATION - Fig. 4
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
300 mm
75 mm
25 mm
25 mm
25 mm
25 mm
300 mm
600 mm
1200 mm
1200 mm
1500 mm
300 mm
Min. distance
Terminal position
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). 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:-
CH 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 7.5 litres and pre-charged to a pressure of 0.5 bar.
By-pass - The boiler incorporates an adjustable by-pass. However, where all radiators are fitted with thermostatic radiator
valves, an external by-pass may be required.
Alpha 500E - General Boiler Information
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 the maximum 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 necessary to add inhibitor to the central heating system, contact Alpha Therm Ltd. for guidance.
Refer to BS 5449 and BS 6798 for further information.
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
Heating circuit
return Mains
water
supply
Double check
valve assembly
Stop
valve Test cock
Air inlet
valve
Filling loop
temporarily connected
Hose
unions
Fig. 6 Fig. 7
Note: A drain tap should be installed at the lowest
point of the heating circuit and beneath the appliance.
System
drain tap
Static head of system
Make up vessel
DHW outlet
Mains water
inlet
Additional expansion
vessel (if required)
Automatic
air vent
Boiler
Heating flow
Heatingreturn
Filling point
By-pass could be a 15 mm pipe controlled
by a valve or an uncontrolled radiator.
Heating
by-pass
(If required)
Temperature/pressure
relief valve
Radiator
valve
Lockshield
valve

10 Alpha 500E - General Boiler Information
3.9 DOMESTIC HOT WATER SYSTEM
The mains water supply must be first connected to the components detailed in section 3.10 before the boiler. No valves must
be fitted between these components and the boiler. The incoming mains water pressure to the boiler is regulated to 3.5 bar by
the pressure reducing valve supplied in the unvented package. However, all taps and mixing valves used with the hot water
system must be suitable for operating at a pressure of up to 8 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.
3.10 UNVENTED HOT WATER STORAGE SYSTEM
TocomplywiththeBuildingRegulationsforunventedhotwaterstorage,itisrequiredthatthecomponentsdetailedinFig.8arefitted
before the mains cold water inlet to the boiler. No isolating valves must be fitted between these components and the boiler.
All these components are supplied with the boiler in a separate package and must be fitted by a competent person in
accordance with the instructions.
The installation is subject to Building Regulations approval and the Local Authority must be notified of the intention to install.
Primary return
Boiler
Storage cylinder
Heating Primary
flow
Hot
water
Discharge
pipe
Pump
Tundish
Expansion
relief valve
Temperature/pressure
relief valve
DHW expansion vessel
Pressure
reducing
valve
Filter
Stop valve
Mains
water
supply
Cold water supply
These components are supplied
in separate box with boiler
Diverter
valve
Check
valve
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. 9
Fig. 8
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.
Tundish - The tundish must be positioned within 500 mm horizontally of the temperature/pressure relief valve, 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.

11
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. onto the surface of an external wall or 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.
Refer to Fig. 9 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.
Alpha 500E - General Boiler Information
Fig. 9
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 Tundish
D1
D2
300 mm
minimum
D1
D2
300 mm
minimum
Tundish
Type 'A' air gap
End of pipe to be
clearlyvisible
300 mm
minimum
Tundish
500 mm max.
from temp/press
relief valve
Metal discharge pipe (D2) from
tundishwithcontinuousfall
Metal discharge pipe (D1)
from relief valve to tundish
Temperature/pressure
relief valve
300 mm
minimum
100 mm max.
70 mm min.
Gulley if
available
Pipe close to wall to
allow water to fan out
safely
Groundlevel
D2
D1
LOW LEVEL TERMINATION
Toexpansion
relief valve

12
4.1 UNPACKING
1. The boxes required when the boiler is installed with a horizontal flue are as follows:-
Box 1 Cased boiler
Water and gas valves plus washers
Water fittings
Mounting bracket plus screws and wall plugs
Flue terminal and wall sealing plate plus 2 screws and mastic
Literature pack and Wall template
Box 2 90° flue bend with clamp (not required for vertical flue)
Box 3 0.75 m flue (for side and rear flue) with two clamps and inner duct support
Box 4 Pressure reducing valve
5 litre expansion vessel, mounting bracket plus screws and wall plugs
Tundish
Expansion relief valve/check valve
2. Unpack boiler and remove loose items packs.
3. Remove the two screws at the top of the front casing. Slide it up and lift it off.
4.2 CLEARANCES REQUIRED - Fig. 10
Alpha 500E - Installation
4 INSTALLATION
4.3 PREPARE THE WALL - Fig. 11
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. If side exit flue is to be used, continue the horizontal
centrelineoftheflueacrossthewalltothesidewall,
then along the side wall 160 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 in the wall for the
flue.
5. Drill the fixing holes (8 mm dia.) to accept the plugs
supplied.Usingthewasherssuppliedwiththescrews,
fit the mounting bracket.
Fig. 10
Fig. 11
200 mm
20 mm 5 mm
600 mm
250 mm
450 mm
950 mm
Minimum
clearance
of 450 mm
from front
of boiler
175 mm
425 mm
Rear exit hole
110 mm dia.
Positionof
110 mm hole
to be cut for
side exit
flue
Bottom
fixingholes
Ensure line is level
Wall
mounting
bracket
Side
wall
160 mm
Boiler
outline
Template
Fixing
holes
120 mm

13
Alpha 500E - Installation
4.4 FIT THE BOILER - Refer to Fig. 11
1. Lift the boiler and locate it on the mounting bracket.
2. Adjust the position of the boiler, as necessary. Fit the bottom screws to secure the boiler in position.
4.5 FIT THE UNVENTED KIT (BOX 4) - Fig 12
1. Unpack Box 4 and check the contents.
2. Locate the expansion vessel mounting bracket in a suitable position as close to the boiler as possible and secure in
position with the screws and wall plugs provided.
3. Secure the expansion vessel to the mounting bracket using the metal band, nut, washers and bolt.
4. Connect the expansion relief valve to the expansion vessel as shown in Fig. 12.
Notes: 1. The plug must be removed from the capped connection on the expansion vessel relief valve to enable
connection to the expansion vessel.
2. Mount the valve in either the horizontal or vertical orientation. An inverted orientation may allow debris deposits
onto the valve seating and cause the valve to malfunction.
3. Ensure the valve is mounted correctly, i.e. the arrow marking on the valve body is pointing in the direction of flow.
5. Connect the mains water supply to the pressure reducing valve and thoroughly flush out the water pipework.
Refer to Domestic Hot Water System, section 3.9.
4.6 CONNECT THE PIPEWORK - Fig. 13
1. Thoroughly flush out all the water pipework.
Ensure that all the plastic caps are removed from the boiler connections.
2. Secure all the valves/fittings to the boiler- use the washers supplied, ensuring they are facing the rear wall. Fit the union
bends to the valves.
Note: If soldering to the boiler union bends, ensure that the bends are not connected to the valves, otherwise the internal
seals may be damaged.
3. Connect the pipework from the boiler to the unvented kit.
Note: No valves must be fitted between the boiler and the unvented kit.
4. Connect the system pipework to the boiler and the discharge pipe to the heating system pressure relief valve.
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 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 3.10.
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.
DHWexpansion vessel
Pressure reducing valve
(incorporatingfilter)
Mountingbracket
Expansionrelief valve
(incorporatingcheckvalve)
Dischargepipe To boiler
Mainswater
supply
Cold water
supply
Fig. 12

14 Alpha 500E - Installation
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 return filter and drain point
H- Adjustable heating by-pass
I- Drain point for DHW storage
J- Flow restrictor housing
4.7 FIT THE FLUE - Figs. 14, 15
1. The following procedure applies to both rear or side exit flue. The only difference being the lengths to which the ducts are cut.
Rear flue Outer air duct length = finished wall thickness + 35 mm.
Inner flue duct length = finished wall thickness + 112 mm.
Side flue Outer air duct length = finished wall thickness + the distance from the inside wall to the side of the boiler + a mm.
Inner flue duct length = finished wall thickness + the distance from the inside wall to the side of the boiler + b mm.
Note: L/H side a = 300, b = 377. R/H side a = 50, b = 127.
2. Iftheoveralllengthoftheinnerductisgreaterthan750mm,aflueextensionisrequired.Tofitanextensionrefertothefollowingsection.
3. Withdraw the inner flue duct from the outer air duct.
4. Mark the outer air duct to match the length given above, measure from the end of the tube as shown in Figs. 14 and 15.
5. Mark the inner flue duct to match the length given above.
6. Cut both the inner and outer ducts to length.
Note: Do not cut the outer duct end with the two holes, these are for securing the terminal.
Ensure that all cuts are square and burr free.
7. Fittheflueterminaltotheouterductbyinsertingitintotheendwithtwoholes.Aligntheholesandsecurewiththetwoscrewsprovided.
8. Place the inner flue duct back into the outer duct.
9. 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 and secure the flue sealing collar onto
the outer duct of the flue immediately before the terminal. Push the flue assembly through the 127 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.
10. Position the seal and clamp (two screws), supplied with the bend, over the boiler flue adaptor. Fit the bend and rotate to
the correct position, then secure in position. See Fig 14.
Note: Ensure that the seal is located over both the bend and the flue adaptor.
11. Placetheinner(noseal)ductclampinpositionoverthebendoutletasshowninFigs.14,15.Positiontheouterductsealoverthebend.
12. Push the outer duct into the wall slightly at the same time as pulling the inner duct towards the bend, inserting it fully into
the clamp on the bend. Tighten the clamp to secure the inner duct.
13. Pull the outer duct towards the bend, to within 40 mm of the bend. Check that the flue terminal protrudes 115 mm out of
the wall, then position the seal equally over the gap. Dismantle the clamp, position it over the seal and secure in position.
14. Make good the inside and outside walls. The flue sealing collar could be used for making good either the outside or inside
by locating it over the outer duct of the flue and pushing it tight against the wall. If fitting the collar externally, ensure it does
not restrict any of the openings of the flue terminal.
Fig. 13
20
J
H
G
I
23
118 100 110 100 55 55 62
AEFDCB

15
Alpha 500E - Installation
Fig. 14 - Rear flue
Fig. 15 - Side flue
4.8 FIT A FLUE EXTENSION - Figs. 14, 15
Note: The maximum flue assembly length must not exceed a length of 4 metres.
1. Withdraw the inner flue duct from the outer air duct supplied with the boiler.
2. Withdraw the inner flue duct from the extension. Secure the two ducts together using the clamp supplied with the
extension, ensure that the ducts are butted together and the clamp is central over the joint.
3. Secure the outer ducts together using the silicone seal and clamp supplied with the extension. Lubricating the silicone
seal with a soap solution will aid assembly.
4. With all the ducts assembled together, cut to the following lengths:-
Rear flue Outer air duct length = finished wall thickness + 35 mm.
Inner flue duct length = finished wall thickness + 112 mm.
Side flue Outer air duct length = finished wall thickness + the distance from the inside wall to the side of the boiler + a mm.
Inner flue duct length = finished wall thickness + the distance from the inside wall to the side of the boiler + b mm.
Note: L/H side a = 300, b = 377. R/H side a = 50, b = 127.
5. When measuring the outer duct, measure from the end of the tube as shown in Figs. 14 and 15.
6. Cut both the inner and outer ducts to length.
Note: Do not cut the outer duct end with the two holes, these are for securing the terminal.
Ensure that all cuts are square and burr free.
7. Fit the flue terminal to the outer duct by inserting it into the end with two holes. Align the holes and secure with the two
screws provided.
Outer air duct length
Inner flue duct length
Outer duct clamp and seal
90° bend
BOILER SIDE
Terminal
Sealing plate
(optional)
20
15
72
60
160
20
20 20
325
175
(RHS)
425
(LHS)
15
72
115 Outer duct clamp
and seal
Inner duct clamp
Seal
BOILER
FRONT
Outer air duct length
Inner flue duct length
Bend clamp
and seal
Note: For horizontal flue ensure there
is a slight downward slope
towardsterminal.
115
Inner duct clamp
120
40
Note: 40 mm gap between
boiler 90° bend and
outer air duct
20
40

16
8. Place the inner flue duct back into the outer duct. Use the inner duct supports to centralise the duct in the outer duct.
9. Fit the flue assembly as described in the previous section. Due to the size of the flue clamps the flue must be fitted from
inside the building.
10. It may be necessary to support the flue with suitable brackets (every metre) when flue lengths approaching the maximum
are used.
4.9 CONNECT THE MAINS SUPPLY - Fig. 16
1. Gain access to the boiler terminal block by removing the
two fixing screws (one each side) securing the control
panel. Lower the control panel forwards on its hinge. Refer
to Technical Data, section 2.9 for connection details.
2. Remove the screw securing the terminal block cover from the
back of the control box (see Fig. 16). Pass the mains supply
cable through the cable clamp, terminal block grommet 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, through the grommet (cut as necessary) and connect it to terminals 1 and 2. (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.
4.10 FIT THE CLOCK KIT - Fig. 17
Ensure the electrical supply to the boiler is isolated.
1. Remove and discard the clock blanking panel.
2. Insert the clock into the opening and secure in place with the screws supplied.
3. Disconnect the clock wiring from the terminal block and connect it to the clock as follows:-
Blackwires toterminals 3and 4,Brown to terminal2 andBlue toterminal 1,(or asper the instructionssupplied withthe clock).
Ensure wiring is correct.
4. Leave the control panel open until commissioning procedures have been completed.
Alpha 500E - Installation
Cable clamps
Terminal block
cover
Fuse F2A
Remove link to
connect external
control
Fig. 16
Fig. 17
Clock
Controlpanel
Terminalwithout clock fitted

17
When commissioning the boiler, ensure the Benchmark Log Book 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 fitted with a non-sealing cap.
2. Open the central heating flow and return valves (spindle flats in-line with valve) (see Fig. 13).
3. Open the fill point valve on the filling loop until water is heard to flow.
4. To remove the air - Vent each radiator in turn, starting with the lowest in the system.
5. It is important that the pump is properly vented to avoid it running dry and damaging its bearings. Unscrew and remove the
cap from the centre of the pump. Using a suitable screwdriver rotate the exposed spindle about half a turn, then replace
the cap.
6. Check the operation of the heating 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 venting a radiator 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 and Filling the system.
8. Open the mains water supply valve and allow the storage cylinder in the boiler to fill. Turn on all hot water taps and allow
water to flow until no air is present. Turn off taps.
5.2 BOILER CONTROLS - Fig. 18
Alpha 500E - Commissioning
5 COMMISSIONING
5.3 TEST FOR GAS SOUNDNESS AND PURGE THE SUPPLY
1. With the boiler gas service cock closed (spindle flats 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. 19). 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.
Fig. 18
Clock
(if fitted)
System
Pressure
Gauge
Central
Heating
Thermostat
Domestic
Hot Water
Thermostat
Selector
Switch
Burner
Viewing
Window
0THERMOSTAT 0THERMOSTAT 0SELECTOR
bar
04
3
2
1
Indicator
Neons
Red
Reset
Button
White
Reset
Button
RESET
RESET

18 Alpha 500E - Commissioning
5.4 INITIAL LIGHTING - Refer to Fig. 18
Note: Remove the protective plastic coating from the boiler painted panels before lighting.
1. Ensure that the gas and electrical supplies to the boiler are off, the selector switch is set to '0' and the central heating flow
and return valves are open.
2. Turn on the gas and electrical supplies to the boiler.
3. Ensure all external controls are calling for heat. If the optional Clock is fitted, refer to the User's instructions, set the time
and ensure the Clock is in an 'on' mode.
4. Set the hot water and central heating temperature selectors to maximum.
5.5 CHECK THE BURNER PRESSURES - Fig. 19
Ensure the selector switch is set to 0, to turn off the boiler. Loosen the burner pressure test point screw on the gas valve and
connect a pressure gauge.
Hot water mode
1. Set the selector switch to (DHW only) and the DHW
thermostat to maximum, the electrical supply neon will
illuminate.
2. The burner will light and the burner pressure will increase to
maximum.
3. The burner will stay at maximum output for approximately 3
minutes and then the burner pressure will decrease slowly
to its minimum, until the hot water store obtains a
temperature of 65°C.
4. Check the burner pressures and that the burner goes out
when the store is satisfied.
The burner pressure settings have been factory set and do
not require adjusting. If incorrect, check that the inlet gas
pressure is 20 mbar. If the inlet gas pressure is not 20 mbar,
either the pipework is too small or the gas supply to the
house is insufficient, in which case contact British Gas.
Central heating mode
1. Set the selector switch to (DHW and CH) and turn the CH thermostat to maximum.
2. The burner will light at the factory pre-set maximum output.
3. Set the selector switch to 0 to turn off the boiler. Disconnect the pressure gauge and tighten the test point screw.
Test for gas soundness using suitable leak detection fluid.
Note: Refer to Technical Data, section 2.1 for burner pressure settings.
5.6 FINAL COMMISSIONING
1. Allow the heating system to heat up, then balance the system to achieve the necessary temperature difference across the
heating flow and return pipes at the boiler and check the system volume and pressure. (Refer to Technical Data, section
2.8).
2. Set the selector switch to 0 to turn off the boiler.
3. Thoroughly flush out the water pipework and clean the filters in the heating return and pressure reducing valve on the
unvented kit.
4. Re-pressurise the system as described in section 5.1.
5.7 FINAL ASSEMBLY
1. Raise the control panel and secure in position with the screws previously removed.
2. Place the front casing in position over the boiler ensuring the bottom is located behind the control panel and secure in
position at the top using the screws previously removed.
3. If the boiler is to be left in service with the User, set the controls, clock (if fitted, see User's Operating manual) and room
thermostat (if fitted) to the User's requirements.
4. If the boiler is not to be handed over immediately, close the boiler gas service cock and switch off the electrical supply.
5. If there is any possibility of the boiler being left during frost conditions, then the boiler and system should be drained.
(Refer to Component Replacement, section 8.2).
It is recommended that a label is attached to the boiler drawing attention to the fact that the system has been drained.
6. Complete the details of the installation on the back page of this manual.
Fig. 19
Burner pressure
test point
Inlet gas pressure
test point

19
Alpha 500E - Commissioning/Boiler Operation
5.8 USER INFORMATION
The User must be advised (and demonstrated if necessary) of the following important points:-
1. How to light and turn off the boiler and how to operate the system controls.
2. The importance of annual servicing of the boiler to ensure safe and efficient operation.
3. That any servicing or replacement of parts must only be carried out by CORGI registered personnel.
4. Ensure that the boiler controls and room thermostat (if fitted) are set to the User's requirements.
5. Tell the User about the sealed system pressure.
6. Tell the User that if the electrical supply neon is illuminated and the boiler has not operated for 24 hours for heating or
hot water, the pump will automatically operate for 5 minutes.
7. Explain to the User that an internal frost thermostat is fitted in the boiler, and that electrical supply to the boiler must be left
on (electrical supply neon illuminated) for the thermostat to operate.
8. Show the User the position of the pressure relief valve discharge pipes and tundish for the heating and DHW systems.
9. Hand the User's instructions and the Benchmark Log Book to the User.
10. Leave these Installation and Servicing instructions with the User for use on future calls.
6 BOILER OPERATION
The boiler operating mode is controlled by the selector switch on the facia panel. When set to , the boiler will only operate in
the Domestic Hot Water mode. When set to , it will operate in the Domestic Hot Water and Central Heating mode.
Note: The clock (if fitted) only controls the operating times of the central heating, not domestic hot water - DHW is available
continuously.
Domestic hot water supply always takes priority over central heating. If a demand for hot water is required during a central
heating period, the boiler will automatically switch to the hot water mode until the demand is satisfied i.e. storage water is to the
required temperature. This interruption in the central heating is only when the demand for hot water is present and should not
be noticed by the User.
6.1 CENTRAL HEATING MODE
If there is a call for central heating the diverter valve is operated, the pump will start to circulate the primary heating water,
operating the flow switch. The fan will run at full speed; once the air pressure switch is proved the burner will light. The burner
output then automatically adjusts to suit the system demand; as the temperature of the heating water in the boiler approaches
that set by the adjustable central heating thermostat the burner output is reduced. When this set temperature is reached, the
burner is turned off and the fan stops. The pump continues to run for 3 minutes to remove residual heat build up in the boiler.
The burner will not relight for 3 minutes; unless there is a demand for domestic hot water during this delay.
In this instance, the boiler will operate to satisfy the domestic hot water demand and the boiler will then immediately revert to
provide central heating, if there is a demand.
6.2 DOMESTIC HOT WATER MODE
When there is a demand for hot water (temperature of stored hot water is below that set by the thermostat), the pump will start
to circulate the primary heating water, operating the flow switch. The fan will run at full speed; once the air pressure switch is
proved the burner will light. The burner output then automatically adjusts to suit the demand required to raise the temperature
of the domestic hot water within the store to the temperature set by the adjustable domestic hot water thermostat. When this set
temperature is reached the burner is turned off and the fan stops. The pump continues to run for 3 minutes to remove residual
heat build up in the boiler.
When the hot water demand has been satisfied, the 3-way diverter valve operates to divert the primary heating water to the
central heating, if there is a demand.
6.3 FROST THERMOSTAT
The boiler incorporates a built in frost thermostat which automatically turns on the boiler and pump if the water in the boiler falls
below 5°C, providing the electrical supply neon is illuminated. The boiler will operate until the water temperature in the
system reaches approximately 30°C.
6.4 PUMP
If the electrical supply neon is illuminated and the boiler has not operated for 24 hours for heating or hot water, the pump will
operate automatically for five minutes every 24 hours.

20
6.5 INDICATOR NEONS
When illuminated, the following conditions apply:-
Warning light (continuously on) - blocked flue or fan fault, contact your Service Engineer.
Overheat thermostat has operated - press white reset button (see Fig. 18) to reset.
Electrical supply to the boiler is on.
Boiler is supplying hot water.
Boiler is supplying central heating.
When the red reset button ( ) is illuminated it indicates that the burner has failed to light - Press the red reset button
(see Fig. 18) and the ignition sequence will restart.
Alpha 500E - Boiler Operation/Routine Servicing
7 ROUTINE SERVICING
To ensure efficient operation of the boiler it is recommended that it is checked and serviced as necessary at regular intervals.
The frequency of servicing will depend upon the particular installation conditions and usage, but in general once per year
should be adequate.
It is the law that any service work must be carried out by a competent person, i.e. CORGI registered personnel.
7.1 IMPORTANT NOTES PRIOR TO SERVICING
1. Check the flue terminal outside and ensure it is not blocked.
2. Run the boiler and check the operation of its controls.
3. Refer to Fig. 2 for location of flue sampling point.
4. Ensure that all system connections and fittings are sound. Remake any joints and check the tightness of any fittings that
may be leaking.
5. It is recommended that the operation of the heating pressure relief valve is checked 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.
6. Refill, vent and re-pressurise the system as necessary. (Refer to Commissioning, section 5.1).
7. If the boiler is in a cupboard or compartment, ensure that the ventilation openings are adequate and are clear. (Refer to
General Boiler Information, section 3.3).
8. Record details of the service in the Service History section on page 37 of this manual.
9. Inspect and clean, if required, the filter and cartridge in the pressure reducing valve and cartridge in the expansion relief
valve fitted to the unvented kit.
10. Check the charge in the central heating and domestic hot water expansion vessels and re-pressurise, if necessary.
Warning: Before servicing the boiler, set the selector switch to 0, isolate the electrical supply and close the boiler gas service
cock. Allow the boiler to cool.
The data label is positioned on the left hand case side panel and is visible after removing the front casing.
Always test for gas soundness after servicing any gas carrying components.
7.2 PREPARE FOR SERVICING - Fig. 20
1. Ensure the electrical supply is isolated and the gas supply is off.
2. Remove the two screws securing the top of the front casing. Lift the cover up slightly and remove.
3. Remove the four screws securing the room sealed chamber panel and remove the panel, taking care not to damage the seal.
4. Remove the two fixing screws (one each side) securing the control panel and hinge it forward.
5. Disconnect the electrode leads from the ignition electrodes.
6. Remove the four screws securing the combustion chamber front cover and remove the cover.
7. Disconnect the main burner's union and withdraw the burner out of the boiler. During removal of the burner, disconnect the
flame sensing electrode lead and take care not to damage the side insulation panels.