Potterton envoy 30 Installation and maintenance instructions

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Envoy System 30, 40, 50, 60 & 80
Installation & Service Instructions
Envoy System
Wall Mounted, Fan Powered, Balanced Flue,
Gas Condensing System Boiler
EN0040A
THE GAS SAFETY (INSTALLATION AND USE) REGULATIONS 1994 (as amended).
‘‘ In your own interest, and that of safety, it is law that all gas appliances are installed by competent persons,
in accordance with the above regulations. Failure to install appliances correctly could lead to prosecution.’’
The polythene bags used for packaging are a potential hazard to babies and young children and
MUST BE DISPOSED OF IMMEDIATELY.
Installation must be in accordance with the Installation & Service Instructions and the rules in force.
LEAVE THESE INSTRUCTIONS WITH THE USER FOR USE ON FUTURE CALLS
For Use With Natural Gas
(G20) Only At 20mbar
For Use in GB & IE
IMPORTANT
PLEASE READ THIS BOOK
BEFORE INSTALLING,
OPERATING OR SERVICING
THIS BOILER.

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2Contents Publication No. 559787
Contents - Page 2
Technical Data........................................................... 3
1Installation Requirements........................................ 5
2Installation................................................................. 10
3Commissioning......................................................... 14
4Servicing & Replacement of Parts .......................... 17
Servicing:
Preparation of the Boiler............................................. 17
Removing Fan............................................................. 18
Removing Combustion Chamber & Flue Hood........... 18
Examination of Flueways & Cleaning ......................... 19
Re-assembly of Boiler................................................. 19
Replacement of Parts
1Fan.............................................................................. 20
2Hot Surface Igniter...................................................... 20
3Flame Sensor.............................................................. 20
4Insulation..................................................................... 20
5Burner......................................................................... 21
6Syphon.......................................................................21
7Flue Hood/Combustion Chamber Seals....................21
8Injector.......................................................................21
9Gas Valve Assembly..................................................21
10 Sight Glass ................................................................22
11 Water Temperature Sensor.......................................22
12 Dry Fire Temperature Sensor....................................22
13 Case Temperature Sensor ........................................22
14 Diverter Valve Head...................................................23
15 Boiler Control Board ..................................................23
16 Boiler Control Board Fuses........................................23
17 Water Components....................................................24
Pump........................................................................ 24
Diverter Valve...........................................................24
Water Pressure Gauge.............................................24
5Fault Finding ............................................................25
6Boiler Internal Wiring ..............................................28
7Boiler Wiring Layout................................................29
8Short List of Spares.................................................30
Introduction - Page 2
The Potterton Envoy System is a high efficiency lightweight,
automatically controlled wall hung gas fired condensing
boiler. The flue system is room sealed and fan powered.
There are five models available with outputs of 8.8kW
(30,000 Btu/hr), 11.7kW (40,000 Btu/hr), 14.6kW (50,000
Btu/hr), 17.6kW (60,000 Btu/hr) and 23.4kW (80,000 Btu/hr).
These boilers are designed to provide domestic hot water
and/or central heating and must be used on FULLY
PUMPED sealed systems only.
Concentric horizontal and vertical flues are available from 1
metre to 3 metres in steps of 0.5 metre using the following
options:-
Sales Code. Description.
EFLUEXT 500 - 0.5 metre Flue Extension
EFLUEXT - 1.0 metre Flue Extension
1EFLUEH - Std 1 metre Horizontal Flue
1EFLUEV - Std 1 metre Vertical Flue
Accessories
The following Potterton Myson controls are
recommended for use with your boiler:-
Electronic Programmer EP2002, EP3002 or EP6002
Cylinder Thermostat PTT2 or PTT100
Room Thermostat PRT2 or PRT100
Frost Thermostat PRT100FR
Motorised Zone Valve MSV222 or MSV228
Motorised Diverter Valve MSV322
Thermostatic Radiator Valve
Data sheets describing these products are available on
request.
Optional Extras
Sales Code. Description.
EWPLATE Terminal Wall Plate - where necessary
can be fitted to the outside face to
improve the appearance, after making
good around the terminal.
EGUARD Terminal Guard.
EFRFKIT Flat Roof Flashing Kit - for use with
Vertical Flue.
EPRFKIT Pitched Roof Flashing Kit - for use with
Vertical Flue.
ENVOYDIV Mid Position Diverter Valve Kit

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Publication No. 559787 Technical Data 3
Technical Data - Page 3
Boiler Details 30 40 50 60 80
Heat Input KW 10.1 13.43 16.87 20.2 26.86
Btu/hr 34,500 45,800 57,600 68,900 91,600
Heat Output,
NON-CONDENSING KW 8.79 11.72 14.65 17.58 23.45
Btu/hr 30,000 40,000 50,000 60,000 80,000
Heat Output,
CONDENSING KW 9.7 12.8 16.1 19.0 25.0
Btu/hr 33,100 43,700 55,000 64,800 85,400
Gas Rate M3/h 0.96 1.28 1.6 1.92 2.56
ft3/hr 34.0 45.2 56.7 68.0 90.4
Burner Pressure Mb 11.4 11.8 11.8 10.6 12.2
in/wg 4.6 4.7 4.7 4.24 4.9
Injector Size Mm 2.5 2.9 3.2 3.7 4.2
Classification I2H. C1. C3. IP20 Water Capacity 3.4 litre
Burner Furigas Pre-Mix Condense Discharge
Igniter Norton 401S Hot Surface Connection 21.5mm (¾"Plastic Compression)
Flame Detector Morgon Matroc Maximum Flow
Gas Control Valve SIT Nova Mix 1 - 8 Air Gas Ratio Temperature 82°C
Electrical Supply 230V ~ 50Hz Expansion Vessel 13.5 litre
Fuse Rating - External 3A (charge pressure 1.0 bar)
Packed Weight - Boiler 52kg Pressure Relief Valve 3 bar
Gas Supply Connections 15mm Compression Pump 30 - 60 Models CP53
Flow Connection 22mm Compression Pump 80 Model CP63
Return Connection 22mm Compression Flue Size 100mm Concentric
EN0030A
930
815
110
450
150
370 Main Casing
384 Including Door
Boiler Dimensions
Fig.1

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4Technical Data Publication No. 559787
Technical Data - Page 4
Fig.2

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1. Installation Requirements - Page 5
General Information
Prior to installation the boiler should be stored as
directed on the carton and in a dry place. Both the user
and manufacturer rely heavily on the installer, whose job
it is to install the boiler and connect it to a correctly
designed heating system. Acquaint yourself with the
British Standards concerning installation requirements. If
you need advice on any points, Potterton Myson’s
Service Operations will be pleased to help
(see back page).
Samples of the Envoy System Boilers have been
examined by Gastec, a Netherlands Notified Body. The
range is certified to comply with the essential
requirements of the Gas Appliance Directive
90/396/EEC, the Low Voltage Directive 72/23/EEC and
shows compliance with the Electro Magnetic
Compatibility Directive 89/336/EEC and are therefore
permitted to carry the CE mark.
It is important that no external devices e.g. flue
dampers, economisers etc, be directly connected to this
appliance unless covered by these Installation and
Service Instructions or otherwise recommended by
Potterton Myson Ltd. in writing. If in doubt please
enquire.
Any direct connection of a control device not
recommended by Potterton Myson could invalidate the
certificate and normal appliance warranty and could also
infringe the Gas Safety Regulations. Manufacturers
instructions must not be taken in any way as over-riding
statutory obligations.
Codes of Practice
The boiler must be installed in accordance with the Gas
Safety (Installation & Use) Regulations 1994 (as
amended), and the current issue of:-
I.E.E. Regulations.
Model Water Bye Laws.
Building Regulations.
Building Standards for Scotland.
Health and Safety Document No. 635. (The
Electricity at Work Regulations 1989).
Health and Safety Information for the
Installer and Service Engineer
Under the Consumer Protection Act 1987 and Section 6
of the Health and Safety at Work Act 1974, we are
required to provide information on substances
hazardous to health. Small quantities of adhesives and
sealants used in the product are cured and present no
known hazards. The following substances are also
present.
Insulation and Seals
Material - Ceramic Fibre. Alumino - Silicone Fibre.
Description - Boards, Ropes, Gaskets.
Known Hazards - Some people can suffer reddening
and itching of the skin. Fibre entry into the eye will cause
foreign body irritation. Irritation to respiratory tract.
Precautions - People with a history of skin complaints
may be particularly susceptible to irritation. High dust
levels are only likely to arise following harsh abrasion.
In general, normal handling and use will not present
discomfort, follow good hygiene practices, wash hands
before consuming food, drinking or using the toilet.
First Aid - Medical attention must be sought following
eye contact or prolonged reddening of the skin.
Electricity Supply
A 230 volts ~ 50Hz, single phase electricity supply fused
to 3A, must be provided in accordance with the latest
edition of the IEE Wiring Regulations and any other local
regulations that apply. The current rating of the wiring to
the boiler must exceed 3 A and have a cross sectional
area of at least 0.75mm in accordance with BS 6500,
Table 16.
The supply to the boiler and its associated equipment
should be controlled by an exclusive 3A fused double
pole switch (having at least 3mm contact separation in
both poles) so that complete isolation from the supply
can be achieved to enable servicing work to be carried
out in safety.
Gas Supply
A gas supply pressure of 20mbar is required at the inlet
of the appliance. Performance data is based on use of
reference gas G20. 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 and
must be governed at the meter.
Condensate Drain
The condensate outlet on the boiler is designed to
accept 21.5mm (¾") plastic overflow pipe, which if
possible should discharge into the household drainage
system and have an internal termination. If this is not
practical, discharge into an outside gully or soak away is
acceptable. To avoid blockage of this pipe due to
freezing it should be routed internally where possible
and have sufficient fall over its entire length to dispose
of condensate quickly. See British Gas ‘Guidance Notes
for the Installation of Domestic Gas Condensing Boilers’.

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Installation Requirements - Page 6
Location of Boiler
These boilers are not suitable for external installation and
should not be fitted directly above a cooking appliance. The
boiler may be installed in any room, although particular
attention is drawn to the requirements of the current IEE Wiring
Regulations and in Scotland, the electrical provisions of the
Building Standards applicable in Scotland with the respect to
the installation of the appliance in a room containing a bath or
shower.
Where a room-sealed appliance is installed in a room
containing a bath or shower, any electrical switch or appliance
control, utilising mains electricity should be so situated that it
cannot be touched by a person using the bath or shower.
Where the installation of the boiler will be in an unusual
position, special procedures may be necessary and BS6798
and BS5546 give detailed guidance on this aspect.
It should be noted that due to the high efficiency of this boiler a
white plume of condensate will be emitted from the flue
terminal, therefore care should be taken when selecting the
terminal position.
Boiler Mounting Surface
The boiler must be mounted on a flat wall, which may be of
combustible material and must be sufficiently robust to take the
weight of the boiler. The requirements of the Local Authorities
and the Building Regulations must be adhered to.
Timber Framed Houses
If the boiler is to be installed in a timber framed building it
should be fitted in accordance with the British Gas publication-
Part 19 - Building and Kitchen Work. If in doubt advice must be
sought from the local region of British Gas or from Potterton
Myson.
Clearances around the Boiler and Tank
The following minimum clearances must be maintained after
installation for correct operation and servicing of the boiler and
tank.
Front: 15mm (610mm for servicing)
Sides: 5mm each side
Top: 140mm (from top of boiler case)
Bottom: 120mm
Ventilation
The room in which the boiler is installed does not require a
purpose provided air vent.
If the boiler is installed in a cupboard or compartment,
permanent air vents are required in the cupboard or
compartment, one at high level and one at low level, either
direct to the outside air or to a room. Both high level and low
level air vents must communicate with the same room or must
be on the same wall to outside air. Both the high level and low
level vent must each have a free area as stated below. The
free area of each vent may be halved if the ventilation is
provided directly from outside.
High and Low air vent areas:
Envoy System 30 103 cm²
Envoy System 40 135 cm²
Envoy System 50 170 cm²
Envoy System 60 206 cm²
Envoy System 80 277 cm²
If the boiler is installed in a cupboard or compartment with a
door, allow at least 15 mm clearance between the front of the
boiler and the door for air movement.
Flue Terminal and Ducting
The Standard Horizontal Flue system (Part No. 236346) is
suitable for installations up to 1030mm, measured from the
centre line of the boiler outlet to the outside face of the wall.
0.5 & 1 Metre Flue Extension kits (0.5m - Part No. 430092,
1m - Part No. 430085) are available to extend horizontal flues
to a maximum length of 2920 mm and vertical flues to a
maximum length of 3 metres. The siting positions for horizontal
flue terminals are shown in Fig. 3.
A Concentric Vertical Flue system is available (Part No.
236348) when used in conjunction with the 0.5 & 1 Metre Flue
Extension kits and is suitable for flue heights up to 3 metres to
terminate through a roof.
The siting of the flue terminal through a roof is shown in Fig. 3.
Only the flue systems shown here can be fitted to the Envoy
System boilers.
As with all condensing boilers, the flue will produce a plume of
visible condensation for much of the time that the boiler is
running.
Care must therefore be taken in the siting of the terminal so as
not to be a nuisance to adjacent property.
In particular, prolonged wetting of a facing wall should be
avoided, if necessary by use of an appropriate deflector.
If the terminal is fitted less than 2m (6.6 ft) above a balcony,
above ground or above a flat roof to which people have access
then a suitable terminal guard must be provided and fitted.
A protective guard is available from the Potterton Myson Sales
Office whose address and telephone number are shown on the
rear cover. The guard (Part No 236591) must be securely fitted
to the wall and centrally located over the flue terminal.
Where a flue terminal is installed less than one metre from a
plastic, or painted gutter, or 500mm from painted eaves, an
aluminium shield one metre long, should be fitted to the
underside of the gutter or painted surface. A suitable wall plate
should be fitted to the painted wall surface of a mobile home.

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Installation Requirements - Page 7
It is absolutely ESSENTIAL to ensure that products of
combustion discharging from the terminal cannot re-enter
the building, or any other adjacent building, through
ventilators, windows, doors, natural air infiltration, or forced
ventilation/air conditioning. If products of combustion are
found to be re-entering any building, the appliance MUST be
turned OFF IMMEDIATELY.
G
A
A
B,C
B,C
C
E
FGGG
G
K
LL
K
K
F F
EN0006A
Horizontal Flues
Vertical Flues
Flue Terminals
Facing Terminal
or Wall
A
P
R
Q
Q
S
N
N
N
H,I
Fig.3
Terminal position Minimum spacing
A - Directly below an openable window, air vent or any other ventilation opening 300 mm
B - Below gutters, soil pipes or drain pipes 75 mm
C - Below eaves (Horizontal Flue Only) 200 mm
* - Below balconies/Carport Roof Not Recommended
E - From vertical soil pipes or drain pipes 75 mm
F - From an internal or external corner 300 mm
G - Above adjacent ground or balcony level 300 mm
H - From a surface facing the terminal 2000 mm
I - From a terminal facing the terminal 2000 mm
* - From opening (Door/Window) in carport into dwelling Not Recommended
K - Vertically from a terminal on the same wall 1500 mm
L - Horizontally from a terminal on the same wall 300 mm
M - Adjacent to opening 300 mm
N - Above roof level (to base of terminal) 300 mm
P - From adjacent wall to flue 300 mm
Q - From internal corner to flue 400 mm
* - Below eaves or balcony (Vertical flue) Not Recommend
S - From facing terminal 2000

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Installation Requirements - Page 8
EN0004A
Filling
Point
By-pass
Balancing
Valve
Optional
Zone
Valves
Optional
3 Port
Valve
VentCylinderMake Up
Vessel
Fully Pumped
Sealed System
Alternative By-pass
Arrangement Using
The Bathroom
Radiator Fitted With
Two Lockshield Valves
Flow
(22mm)
Return
(22mm)
Boiler
Fig.4
The System
The Envoy System boiler has an aluminium alloy heat
exchanger, therefore all systems must be thoroughly
cleansed and the correct treatment added to the system
water.
The only system additives recommended by Potterton
Myson Ltd. are FERNOX-COPAL or GRACE
DEARBORN - SENTINEL X 100 and should be used in
accordance with the manufacturers instructions. This will
include use of the appropriate system cleanser.
The boiler must only be used on INDIRECT FULLY
PUMPED SEALED Systems.
To ensure sufficient pump head is available on the 80
model to overcome system resistance, a system
differential of 14°C should be allowed for when sizing
radiators.
Where the the D.H.W & C.H circuits are controlled by
two 2 port zone valves as illustrated or where all
radiators may be controlled by thermostatic radiator
valves a by-pass must be fitted.
Drain off taps should be fitted in the pipework close to
the boiler and at all low points of the system.
Note: Although the system can be emptied using the
drain off taps installed in the pipework around the
system, to empty the heat exchanger it is necessary to
remove the drain off cap positioned within the boiler
case.
Installation
The installation must comply with the requirements of
BS 6798: 1987 and BS 5449: Pt 1.
The British Gas publication "British Gas Specification for
Domestic Wet Central Heating Systems" should also be
consulted.
The following components are incorporated within the
appliance.
a) Circulating pump.
b) Diverter valve (Optional Extra).
c) Pressure Relief valve with a non-adjustable pre-set

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Installation Requirements - Page 9
lift pressure of 3 bar (45 psi).
d) Pressure gauge covering the range 0-4 bar (0-60
psi).
e) 13.5 litre expansion vessel with initial charge
pressure of 1.0 bar (14 psi).
Ancillary pipework, not forming part of the useful heating
surface, should be lagged to prevent heat loss and any
possible freezing, particularly where pipes run through
roof spaces and ventilated under-floor spaces.
The expansion vessel on this appliance is suitable for
central heating systems up to 135 litres. For systems
greater than this, an additional expansion vessel will be
required.
Mains Water Feed: Central Heating
A connection must be incorporated into the central
heating system to facilitate filling. There must be no
direct connection to the mains water supply, even
through a non-return valve, without the approval of the
Local Water Authority.
Permissible Methods of Filling
(1) Direct Method (Fig. 5)
A detachable flexible hose is connected to a stop valve
fitted to an outlet on the service main. The other end of
the hose is connected to a second stop valve and a
double check valve. The double check valve is fitted to
an inlet connection on the central heating return pipe
under the appliance. The hose should be disconnected
after filling. Where the mains pressure is excessive a
pressure reducing valve could be used to make filling
easier. The following fittings shall form a permanent part
of the system and shall be fitted in the order stated.
a) A stop valve complying with the requirements of
BS 1010 Part 2, (the temporary hose from the
draw off tap shall be connected to this fitting).
b) Double check valve of an accepted type.
(2) Booster Pump Method
The system may be filled through a self contained unit
comprising a cistern, pressure booster pump and if
necessary, an automatic pressure-reducing valve or flow
restrictor.
The pressure booster pump must be capable of
pressurising the system to a minimum of 1.0 bar (14
p.s.i.) measured at the appliance.
The cistern should be supplied through a temporary
connection from a service pipe or cold water distributing
pipe. The unit may remain permanently connected to the
heating system to provide limited water make-up.
Provisions for make up water
Provision should be made for replacing water loss from
the system by re-pressurisation of the system. See
section on Methods of Filling.
Reference should be made to British Gas Publications
"Material and Installation Specifications for Domestic
Central Heating and Hot Water".
Note: The pre-charge pressure of the expansion vessel
is set at 1 bar, therefore, the cold fill pressure should be
1 bar.
Installation to an Existing Central Heating
System
The boilers are designed to operate on a sealed system
only, therefore if the existing system is of the open type
it will have to be modified to comply with BS 6798.
Before installing a new boiler to an existing system flush
out the old system with a recommended
descaling/flushing agent at least twice.
Also check pipework and renew any corroded pipework
or fittings. Valve glands must be re-packed or replaced
wherever necessary and any defective controls
replaced.
Pump
The variable speed circulating pump fitted within the
appliance should be capable of satisfying most system
requirements. Fig. 6 indicates the amount of pump head
available for the system. The boiler resistance is already
taken into account in this curve.

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Installation Requirements - Page 10
0
0
0.10.20.30.40.5
1.0
2.0
3.0
4.0
5.0
CP63
CP53
Litres / Sec
M / Head
EN0042A
To ensure sufficient pump head is available on 80 model to overcome system
resistance, a system differential of 14° should be allowed for.
Boiler Size Water Flow Rate System
Litres/sec gal. min Differential
30 0.19 2.50 10ºC
40 9.25 3.34 10ºC
50 0.32 4.17 10ºC
60 0.38 5.00 10ºC
80 0.40 5.27 14ºC
2. Installation
It is the law that gas appliances are installed and serviced by a competent person as stated in the Gas Safety (Installation &
Use) Regulations 1994.
Electrical test work should be carried out by a competent person in accordance with IEE wiring regulations.
The boiler and its associated equipment will arrive on site in 3 cartons. The contents will be as follows:-
Carton 1:- Boiler Pack Carton 2:- Flue Pack Carton 3:- Frame
Boiler Flue System Boiler Mounting Frame
Outer Casing Assembly Flue Installation Instructions Template
Accessory Pack Screw Pack
Literature Pack

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Publication No. 559787 Installation 11
Installation - Page 11
Installation
Taking due account of the terminal position and making
allowance for all horizontal flues to rise at an angle of 3°
(52mm per metre) from the boiler, place the template in
proposed boiler position. Ensure the template is level and
mark the ten fixing hole positions. If rear fluing mark flue
outlet hole through template.
When side or vertical fluing extend flue outlet centre line on
the template horizontally or vertically as appropriate and
mark flue outlet hole on adjacent surface as illustrated.
Vertical flues require a 105mm diameter hole unless
extension kits are used when the hole size will need to be
increased to 125mm to allow joining clamps to pass through.
Horizontal flues require a hole diameter of 125mm for all wall
thicknesses providing the hole rises through the wall at an
angle of 3°.
Where a horizontal hole is produced using a core drill the
hole diameter will need to be increased for thicker walls as
shown in the following table.
177mm
177mm
3°
Hole Diameter Maximum Wall Thickness
125mm 230mm
150mm 720mm
175mm 1000mm
Remove template and drill holes using a 7mm drill. Carefully
cut flue outlet hole through wall or ceiling allowing for any
horizontal flue to rise at an angle of 3° throughout its length.
Using wall plugs and screws from accessory pack attach
boiler mounting frame to wall ensuring that it is level.
EN0049A
Fig.8

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12 Installation Publication No. 559787
Installation - Page 12
EN0050A
Remove functional case door by undoing the two lower
securing screws and lift door off the two upper hinge
brackets.
From the accessory pack, connect the fittings to the base of
the mounting frames as shown - see Fig. 2 for guidance.
Slide the nuts and olives from the fittings onto the boiler
pipes and temporarily tape them clear of the pipe ends.
Lift and hang the boiler onto the mounting frame ensuring
the pipework at the base of the boiler locates into the fittings
in the base of the mounting frame.
Connect the plastic condensate drain pipe to the mounting
frame.
Connect system pipework to the base of the mounting frame
as shown.
Connect the gas supply to the base of the mounting frame
as shown.
Fig.9
Pressure Relief Valve: The pressure relief valves is pre-set
at 3 bar.
Install a pressure relief valve discharge pipe to the boiler
valve, not less than 15 mm diameter and connect to the
pressure relief outlet connection using a 15mm Compression
fitting. The pipe run should be as short as possible, run
continuously downwards and discharge to the outside of the
building, where possible over a drain. The pipe end should
be directed towards the wall. The discharge point must be
such that it will not be hazardous to occupants or cause
damage to external electrical components or wiring.
IT MUST NOT DISCHARGE ABOVE AN ENTRANCE, OR
WINDOW, OR ANY TYPE OF PUBLIC ACCESS. THE
INSTALLER MUST CONSIDER THAT THE OVERFLOW
COULD DISCHARGE BOILING WATER.

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Publication No. 559787 Installation 13
Installation - Page 13
Flue System
Assemble and attach the flue system to the boiler by
following the instructions supplied with the flue kit.
EN0052A
Fig.11
Electrical Connections
The boiler and all external control circuit wiring must be
supplied from the same isolating switch or plug and socket.
The boiler terminal block which is situated in the control box
is not designed to accept wiring from all the on-site controls
therefore the installer will need to incorporate an external
junction box.
Remove the securing screw and lower the expansion vessel.
Open the control box by removing the two M4 securing
screws and lowering the access door as illustrated.
Electrical Wiring
Route a four core cable from the external junction box
through the cable clamp in the underside rear of the control
box and connect to boiler terminal block as follows.
EN0044A
Fig.12
Permanent live to terminal marked L
Neutral to terminal marked N
Earth to terminal marked
Switched live from external controls to terminal marked SwL
If there are no external controls fitted connect SwL terminal to permanent live in the junction box.
Note: The electrical mains supply must be fused at 3A and the connection must be made to the boiler terminals in such a
way that should the lead disengage from the cable clamp, the current carrying conductors become taut before the earth
conductor.
Close the control box and replace the two M4 securing screws.

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14 Commissioning Publication No. 559787
3. Commissioning - Page 14
All Systems
Note: The system can be filled using a sealed system
filler pump with a break tank or by any other method
approved by the Local Water Authority. Refer to
'THE SYSTEM' section Page 8 in these instructions,
also BS.6798 1987.
Flush out the system thoroughly with cold water. Fill and
vent the system until the pressure gauge registers 1.5
bar (21.5 lbf/in²). Examine for leaks. Raise the pressure
until the safety valve lifts. This should occur within ± 0.3
bar of the preset lift pressure of 3 bar. Release water to
attain the correct cold fill pressure.
The whole of the gas installation including the meter
should be inspected and tested for soundness and
purged in accordance with the recommendations of
BS.6891.
Electrical testwork should be carried out by a competent
person in accordance with the IEE Wiring Regulations.
Conduct a preliminary electrical test by checking: for
short circuits, fuse failure, incorrect polarity, earth
continuity and resistance to earth. If a fault has occurred
on the appliance, the fault finding procedure should be
followed. See Page 25.
Fit the functional case door into position by lifting it onto
the top hinge brackets and secure it with the lower two
fixing screws.
First Lighting
WARNING: Before lighting the boiler ensure that the
functional case door HAS BEEN CORRECTLY FITTED
and that the sealing strip fitted to the door is forming a
tight seal with the main boiler casing.
Before proceeding to light the boiler, check that the
external electricity supply to the boiler is switched off
and that the boiler control switch is in the mid i.e
position.
Turn on the gas service cock.
Ensure that the boiler and radiator isolating valves are
open.
Ensure the electronic timer if fitted, is in an 'ON' period
(refer to the time control literature).
Ensure that the room and/or cylinder thermostats where
fitted are set to a high temperature.
Switch ON the main electricity supply (character will
be displayed).
Note: The boiler is protected by an automatic frost
Protection device, therefore if the water temperature
within the boiler is below 5°C the character will be
displayed and the boiler will fire until a return
temperature of 10°C is reached. The boiler will then shut
down and the character will be displayed.
Switch the boiler control switch to the “H” position and
the character will be displayed. After approximately
10 seconds the boiler should light. Due to the presence
of air in the gas supply it is possible that the boiler will
not light at the first attempt but will automatically cycle
and make two further attempts. If the boiler still fails to
light it will go to lockout indicated by the character
shown flashing on the display. If this should occur wait
10 seconds then press the lockout reset button and the
boiler will go through another start sequence.
If the boiler fails to start after 1 or 2 attempts refer to
fault finding section.
It should be noted that the boiler control continually
monitors the temperature rise across the heat
exchanger. Therefore if the system is not correctly
vented, air passing through the pump may lead to boiler
shut down with the character being displayed. If this
occurs, thoroughly vent the system and press the reset
button.
Burner Pressure
This appliance is fitted with a Gas/Air ratio control valve.
This gas valve ensures that the correct amount of gas is
delivered to the burner to match the available air supply
under all operating conditions.
THE BURNER PRESSURE AND GAS RATE HAVE
BEEN PRECISELY SET AND CHECKED DURING
MANUFACTURE AND NO ATTEMPT SHOULD BE
MADE TO ADJUST IT.
To check the correct operation of the gas valve follow
the instructions below carefully.
a. A good indication of correct operation of the boiler
will be obtained by measuring the gas rate at the
gas meter.
1. Run the appliance for at least 10 minutes.
2. With all other gas appliances turned off
measure the gas rate at the meter for a period
of at least 5 minutes. Check that the measured
rate is within ±5% of the rate stated on the data
plate.
b. To measure the burner pressure.
1. Turn off the gas service cock. Fit a pressure
gauge to the gas inlet pressure test point on the

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Publication No. 559787 Commissioning 15
Commissioning - Page 15
gas control valve. Connect a differential pressure
gauge or 'U' tube manometer between the burner
pressure gauge test point (high pressure side) and
the reference pressure test point (low pressure side)
on the gas valve (see Fig. 11).
2. Turn on the gas service cock and run the appliance
for at least 10 minutes. Check that the gas inlet
pressure is between 19-20 mbar.
3. Check that the differential burner pressure is within
±1.0 mbar of that stated on the data plate.
4. Turn off the gas service cock and remove the
pressure gauge and replace the pressure test point
sealing screws on the gas valve.
Should the gas rate or differential burner pressure fall
outside the specified range run the boiler for a further 10
mins and carry out a re-check, if after re-checking either the
gas rate or the burner pressure falls outside the tolerance
specified, Potterton Myson Service Department should be
called as specialist equipment is required to enable
adjustment to be made.
Relight the boiler and reheat the system to maximum. Check
for water leaks, turn the boiler off, drain the system whilst
hot.
Remove functional case door and ensure there are no
condensate leaks from around the boiler or the condensate
drainage system.
Refit functional case door ensuring a good seal.
Refill the system and add the correct concentration of
FERNOX COPAL or GRACE DEARBORN SENTINEL X100
water treatment.
Adjust to the correct cold fill pressure (1 bar).
If a by-pass circuit is fitted the by-pass valve should be
adjusted with the boiler operating under minimum load
conditions to maintain sufficient water flow through the
boiler to ensure that the overheat device does not
operate under normal operating conditions.
Pump Overrun Timer
Will keep the pump running for approximately 3 minutes
after burner shutdown to dissipate heat left within the
boiler. The times are pre-set and no adjustment is
possible.
Overheat Protection Device
The overheat protection device is pre-set and no
adjustment is possible. Manual resetting is required if an
overheat condition occurs. The reset button is situated in
the front of the boiler control box.
Boiler Control Switch
In the mid i.e. “ ” position holds the boiler in a standby
condition. In the “ ” position allows the boiler to operate
automatically but controlled at a maximum flow
temperature of 60°C. In the “ ” position the boiler will
operate automatically at a maximum flow temperature of
82°C.
Boiler Display
Under normal conditions of operation the following
characters appear:-
Display not illuminated. All power off.
.Power on, boiler at standby.
.Heat demand, boiler operating at higher flow
temperature.
Heat demand, boiler operating at lower flow
temperature.
Boiler operating but up to temperature.
Boiler re-start delayed to prevent rapid cycling. (Max.
delay time is 5 minutes)
Main burner off, pump running to transfer remaining
heat from boiler into the system.
Flashing - boiler at Lock-Out
Other characters will be displayed if a fault condition
should occur. Their purpose is to assist the service
engineer and more information is provided in the
SERVICING section of these instructions.
Other Boiler Controls
All boiler mounted controls are designed so that if any
fault should occur they will fail safe. No further setting or
checking is necessary.

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16 Commissioning Publication No. 559787
Commissioning - Page 16
Final Assembly
Attach casing side panels onto the boiler as illustrated
(Fig. 14) ensuring that the three lugs on each panel are
correctly located. Slide in the bottom panel and push
fully home. Engage hooks on the top rear of the front
panel into the slot in the top front corner of each side
panel. Lower the front panel to engage brass studs into
the retaining clips, press fully home to lock panel into
position.
External Controls
Check that any other external control connected in the
system, such as timers and thermostats, control the
boiler as required.
User's Instructions
A User's Guide is provided with this boiler but the
householder must have the operation of the boiler and
system explained by the installer. The householder must
also be advised of the importance of annual servicing
and of the precautions necessary to prevent damage to
the system and building, in the event of the system
remaining out of commission in frost conditions.
Information must also be passed to the customer on the
type of corrosion inhibitor that has been added to
the system and of the need to maintain the correct
concentration levels as recommended by the
manufacturer.

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Publication No. 559787 Servicing & Replacement of Parts 17
4. Servicing & Replacement of Parts - Page 17
It is the law that all gas appliances are installed and serviced
by a competent person as stated in Gas Safety (Installation
and Use) Regulations 1994.
For Health and Safety Information see Page 5.
Electrical test work and servicing should be carried out by a
competent person in accordance with the I.E.E. Wiring
Regulations.
Regular skilled servicing and cleaning of the appliance is
essential to ensure continued safe and efficient operation.
The frequency of cleaning will depend upon the particular
installation conditions, and the use to which the appliance is
put, but in general, once a year should be adequate.
The boiler DATA PLATE and WIRING DIAGRAM are located
on the front of the boiler functional casing.
The boiler code number which is on the code badge located
on the boiler top panel see Fig.2 should always be quoted
when ordering spares or requesting information.
Before commencing the servicing of the boiler it is
advisable to carry out a pre-check on the boiler to
establish that it is functioning correctly.
a) Set boiler control switch to the mid i.e. “ ” and the
display should read “ ”.
b) Set boiler control switch to “ ”, the display should
read “ ” and the boiler should light.
Note: If the boiler fails to start or does not follow the
sequence above then refer to
fault finding section on Page 25.
WARNING
Before the start of any servicing or replacement of parts
ensure that you have:
a) Switched off at the external electrical supply by
removing the plug from the wall socket or by
switching off the appliance at the external isolating
switch.
b) Isolated the gas supply at the boiler service cock.
Preparation of the Boiler
Preparation for servicing should be carried out in the
following manner.
1) Remove decorative outer casing doors by pulling the
bottom of the door from its fixing clips and pushing
upwards until it is clear of its top fixing.
2) Remove bottom decorative panel.
3) Remove functional case door by undoing the two lower
securing screws and lift door off the two upper hinge
brackets. Fig. 15.

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18 Servicing & Replacement of Parts Publication No. 559787
Servicing & Replacement of Parts - Page 18
Removing Fan
1) Disconnect electrical connection from fan motor. Fig. 16.
2) Disconnect flexible sensing tube from the fan inlet housing.
3) Remove fan by slackening two wing screws on left hand side and removing the M5 wing screw on the right hand side
of the fan.
4) Slide fan to the right then forward and remove from boiler.
Removing Combustion Chamber & Flue Hood
5) Disconnect flexible condensate pipe from the rear of the combustion chamber/sump casting.
6) Disconnect inline connectors for the hot surface igniter and the flame sensor on the right hand side of the combustion
chamber. Fig. 17.
Note the hot surface igniter is a fragile component and requires extreme care when handling.
7) Remove two M6 screws retaining clamps around flue hood and combustion chamber.
8) Remove the top clamps from their anchor points at the rear of the casing.

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Publication No. 559787 Servicing & Replacement of Parts 19
Servicing & Replacement of Parts - Page 19
Removing Combustion Chamber and Flue Hood - Continued.
9) Disconnect electrical connections from dry fire sensor. Fig. 17.
10) Fold back flue sealing gaiter between the flue hood and flue elbow. Fig.18.
11) Carefully remove flue hood by moving the right hand side of the flue hood forward and gently guide the hood around
the flow tapping on the heat exchanger.
12) Pull combustion chamber forward until it is clear of the boiler casing.
Fig.18
Examination of Flue Ways and Cleaning
1) Place a sheet of clean paper over the inlet of the
condense syphon and the gas assembly. It is particularly
important that debris is prevented from entering the
short upward facing tube from the gas control valve.
2) Cleaning of the heat exchanger must be carried out
using a Potterton scraper Part No. 907736.
3) Working from below and above the heat exchanger
remove all deposits from between the fins.
4) Examine top and bottom sealing face of the heat
exchanger for deep scratches and remove any debris
with a soft brush to provide a smooth flat sealing face.
5) Examine Syphon for evidence of leakage or build up of
debris.
Note: Place a catch tray beneath the syphon cleaning eye
plug and remove plug this should remove any debris which
has collected in the pipe section. If necessary the syphon
should be removed and flushed with tap water. See
replacement of parts for further information.
Re-assembly of Boiler
6) Before reassembling combustion chamber and flue hood
to the boiler examine for the following:-
-The 'O' ring seals for damage
-The insulation in the combustion chamber. Note if there
is any visible deterioration of this material it MUST be
replaced
-Damage to the hot surface igniter
-Damage to the surface of the burner
-Damage to sight glass
-Build up of debris in the condensate sump (This may be
removed with a soft brush)
If any of the above components require changing see
section 'Replacement of Parts' for further information.

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20 Servicing & Replacement of Parts Publication No. 559787
Servicing & Replacement of Parts - Page 20
7) Replacement of components is the reverse of removal.
Note: great care should be taken not to damage the flue
hood and combustion chamber seals during
replacement of these assemblies.
8) When refitting retaining clamps ensure that they are
located correctly in the guides on both the flue hood and
combustion chamber.
9) Ensure that the combustion chamber seats correctly
onto the heat exchanger, that the screws are fully
tightened and that the clamps fix the combustion
chamber and flue hood securely.
10) Ensure connection from sump to syphon is made
before refitting fan.
11) Ensure that the flue sealing gaiter between the flue
hood and elbow is correctly positioned untwisted and
forms a good seal to both components.
12) Relight the boiler as described by following the lighting
procedure in the commissioning section of these
instructions.
Replacement of Parts
Before replacing any component carry out pre-check
detailed at the beginning of the Service section and then
refer to fault finding section of these instructions.
WARNING
Before the start of any servicing or replacement of parts
ensure that you have:
a) Switched off at the external electrical supply by
removing the plug from the wall socket or by switching
off the appliance at the external isolating switch.
b) Isolated the gas supply at the boiler service cock.
If the combustion chamber has been removed follow
procedure in Service section ‘Re-assembly of boiler’
1) Fan
a) Follow procedure in ‘Preparation for servicing’ at the
beginning of the servicing section.
b) Replacement of fan is the reverse of removal.
2) Hot Surface Igniter
WARNING This component is fragile and requires
careful handling.
a) Remove combustion chamber as described in
‘Servicing Boiler’.
b) The igniter assembly is retained by two M5 pozi drive
screws. Remove screws and carefully remove old
igniter, if the igniter has become damaged, invert the
combustion chamber and shake gently to allow
damaged segments to be removed from the chamber.
See Fig. 19.
c) Replacement of the igniter is the reverse of removal
ensure that a new sealing gasket is always fitted and
that a good seal is made between the igniter and
combustion chamber.
3) Flame Sensor
a) Remove combustion chamber as described in
‘Servicing Boiler’.
b) Remove screw retaining sensor and withdraw from the
combustion chamber. See Fig. 19.
c) Replacement of the sensor is the reverse of removal,
ensure new gasket is always fitted.
4) Insulation
Note: all four insulation pads must be replaced.
a) Remove combustion chamber as described in
'Servicing Boiler'. See Fig. 17.
b) Remove hot surface igniter, flame sensor. Fig. 19 and
burner Fig. 20.
c) Remove old insulation.
d) Replace front pad first ensuring that bevelled edge is
uppermost and fits into the chamber correctly.
e) Fit rear pad and use end insulation to retain rear pad.