Potterton Envoy Flowsure Installation and maintenance instructions

1
Boiler Module - G.C. No. 41 607 89
20 Litre Tank Module - G.C. No. 114 792
50 Litre Tank Module - G.C. No. 114 793
Installation & Service Instructions
Envoy Flowsure & Envoy Flowsure+
Wall Mounted Fan Powered Balanced Flue Gas Condensing
Combination Boiler and Storage Combination Boiler
EN0025A
THE GAS SAFETY (INSTALLATION AND USE) REGULATIONS 1994.
‘‘ 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.

Contents
Publication No. 559779
2
Contents – Page 2
Technical Data........................................................... 3
1Installation Requirements........................................ 5
2Installation............................................................... 12
3Commissioning....................................................... 16
4Boiler Display & Controls....................................... 19
5Servicing & Replacement of Parts ........................ 22
Servicing:
Preparation of the Boiler........................................... 22
Removing Fan........................................................... 23
Removing Combustion Chamber & Flue Hood......... 23
Examination of Flueways & Cleaning ....................... 24
Re-assembly of Boiler............................................... 24
Replacement of Parts
1Fan..................................................................... 25
2Hot Surface Igniter............................................. 25
3Flame Sensor..................................................... 25
4Insulation............................................................25
5Burner.................................................................26
6Syphon...............................................................26
7Flue Hood/Combustion Chamber Seals.............26
8Injector................................................................26
9Gas Valve Assembly..........................................26
10 Sight Glass.........................................................27
11 Water Temperature Sensor................................27
12 Diverter Valve Head...........................................27
13 Case Temperature Sensor.................................27
14 Boiler Control Board...........................................28
15 Boiler Control Board Fuses................................28
16 Water Components ............................................29
Pump..................................................................29
Diverter Valve.....................................................29
Water Pressure Switch.......................................29
Water Pressure Gauge.......................................29
6Fault Finding............................................................30
7Boiler Internal Wiring..............................................35
8Boiler Wiring Layout............................................... 36
9Short List of Spares................................................37
Introduction - Page 2
The Potterton Envoy Flowsure (20l) and Flowsure+ (50l) are
high efficiency, lightweight, automatically controlled wall
hung gas fired condensing combination boilers with Storage
Tanks. The flue system is room sealed and fan powered.
The combination boilers which are designed to provide
domestic hot water and/or central heating must be used on
FULLY PUMPED sealed systems only.
The combination boiler will adjust automatically to provide
central heating outputs between 23.45 kW and 14.8 kW to
suit the system requirements.
Domestic hot water has priority over the central heating
system and is generated within the integral indirect storage
tank.
The combination boilers can be supplied with either of the
following flue systems:-
Horizontal
1 metre, 1.5 metre, 2 metre, 2.5 metre or 3 metre
Vertical
1 metre, 1.5 metre, 2 metre, 2.5 metre or 3 metre
Accessories
The following Potterton Myson controls are
recommended for use with your boiler:-
Electronic Timer
Room Thermostat PRT2 or PRT100
Frost Thermostat PRT100FR
Thermostatic Radiator Valve
Data sheets describing these products are available on
request.
Optional Extras
Part No. 236349 Terminal Wall Plate - where
necessary can be fitted to the
outside face to improve the
appearance, after making good
around the terminal.
Part No. 236591 Terminal Guard.
Part No. 430080 Flat Roof Flashing Kit - for use
with Vertical Flue.
Part No. 430081 Pitched Roof Flashing Kit - for
use with Vertical Flue.
Part No. 236893 Outdoor Weather Compensator

Publication No. 559779
Technical Data
3
Technical Data – Page 3
Boiler Details Boiler Details Cont...
Flue Size 100mm Concentric
Heat Input kW 26.86 Water Capacity 3.4 litre
Btu/hr 91,600 ___________________________________________
Heat Output,
NON-CONDENSING kW 23.45 Storage Tank Details - 20 Litre
Btu/hr 80,000
Heat Output, Packed Weight 20kg
CONDENSING kW 25.0 Full Weight 39kg
Btu/hr 85,400
Gas Rate M3/h 2.56 Max. Cold Water
ft3/hr 90.4 Supply Pressure 10 bar
Burner Pressure mb 12.2 Normal Secondary
in/wg 4.9 Operating Pressure Mains Pressure
Injector Size mm 4.2 Water Capacity 17.0 litres primary
Classification I2H. C1. C3. IP20 1.7 litres secondary
Burner Furigas Pre-Mix ____________________________________________
Igniter Norton 401S Hot Surface
Flame Detector Morgon Matroc Storage Tank Details - 50 Litre
Gas Control Valve SIT Nova Mix 1 - 8 Air Gas
Ratio Packed Weight 20kg
Electrical Supply 230V ~ 50Hz Full Weight 65kg
Fuse Rating - External 3A
Packed Weight - Boiler 52kg Max. Cold Water
Gas Supply Connections 15mm Compression Supply Pressure 10 bar
Flow Connections 22mm Compression Normal Secondary
Return Connections 22mm Compression Operating Pressure 3.5 bar
Condense Discharge Secondary Expansion
Connection 21.5mm (¾"Plastic
Compression) Vessel Charge Pressure 3.5 bar
Maximum Flow Water Capacity 2.9 litres primary
Temperature 85°C 41.8 litres secondary
Expansion Vessel 13.5 litre T & P Valve 90°C / 7 bar
(charge pressure 1.0 bar) Pressure Relief Valve 6 bar
Pressure Relief Valve 3 bar
EN0016A
930
815
110
225
450
740 Flowsure
830 Flowsure +
150 177
370 Main Casing
384 Including Door
Boiler Dimensions

Technical Data
Publication No. 559779
4
Technical Data – Page 4
Fig. 2

Publication No. 559779 Installation Requirements
5
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 Flowsure and Envoy Flowsure+
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.
The appliance has been tested and approved by the
WRc as meeting the requirements of G3 and L of the
Building Regulations.
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.
If the area of installation is recognised as a hard water
area (above 200 p.p.m.), it is recommended that a
suitable water treatment device of an electronic,
magnetic or galvanic type be installed in the mains water
supply.
Codes of Practice
The boiler and tank must be installed in accordance with
the Gas Safety (Installation & Use) Regulations 1994,
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.

Installation Requirements
Publication No. 559779
6
Installation Requirements – Page 6
Condensate Drain
The condensate outlet on the boiler is designed to
accept 21.5mm 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’.
Location of Boiler and Tank
These boilers and tanks are not suitable for external
installation and should not be fitted directly above a
cooking appliance. The boiler and tank 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 and tank 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: 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 2920mm. 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 One
Metre Flue Extension kits 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 Flowsure and Flowsure+ boilers.
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.

Publication No. 559779 Installation Requirements
7
Installation Requirements – Page 7
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.
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 form 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 Recommended
S – From facing terminal 2000

Installation Requirements
Publication No. 559779
8
Installation Requirements – Page 8
EN0033A
Filling
Point
Boiler
Cold
DHW
By - Pass
Balancing Valve
The System
The Envoy Flowsure and Flowsure+ have an aluminium
alloy heat exchanger, therefore all systems need to 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.
To ensure sufficient pump head is available to overcome
system resistance, a system differential of 14° should be
allowed for.
Where all radiators may be controlled by thermostatic
radiator valves a by-pass should be fitted as far away
from the boiler as possible.
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 boiler 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.
c) Pressure Relief valve with a non-adjustable pre-
set 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).
The domestic hot water system must be in
accordance

Publication No. 559779 Installation Requirements
9
Installation Requirements – Page 9
with the relevant recommendations of BS 5546. Copper
tubing to BS 2871:1 is recommended for water carrying
pipework and MUST be used for pipework carrying
potable water. All capillary joints in the D.H.W pipework
must be joined with a lead free solder.
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.
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.
Central Heating Range Rate
Double
Check
Valve
Temporary
Connecting
Pipe
Stop
Valve
Pressure
Reducing
Valve
Service
Pipe
Fig. 5
For most installations the boiler will automatically adjust
the central heating output to match your heating system
requirement.
Pump
When set on maximum the 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.
(2) Booster Pump Method
The system may be filled through a self contained unit

Installation Requirements
Publication No. 559779
10
Installation Requirements – Page 10
0
0
0.10.20.30.40.5
1.0
2.0
3.0
4.0
5.0
CP63
Litres / Sec
M / Head
80,000
DIFFFLOW
RATE
10°c0.56
14°c0.40
16°c0.35
18°c0.31
20°c0.28
EN0017A
To ensure sufficient pump head is available to overcome system resistance,
a system differential of 14° should be allowed for.
Domestic Hot Water - 20 Litre Tank
The 20 litre tank is a primary store which is designed to
be kept heated to meet instantaneous hot water
demands. It is a compact unit designed to supply instant
hot water at a flow rate of approximately 6.5 litres/min at
a 50°C rise.
Domestic hot water always takes priority over central
heating.
If domestic hot water is drawn off while the central
heating is operating the boiler will automatically transfer
the boiler output to the domestic hot water supply.
The tank is provided with all the necessary equipment to
ensure correct operation, except when a water meter
and/or water softener have been fitted in the system. In
such cases, an external secondary mini expansion
vessel (Part No. 430029) will need to be fitted on the
mains inlet to the tank.
Domestic Hot Water - 50 Litre Tank
The 50 litre tank is a secondary store which is designed
to be kept heated to meet instantaneous hot water
demands that require intermittently higher flow rates.
At a flow rate of approximately 12 litres/min, hot water
will be delivered for around 4 minutes at a 50°C rise
reducing thereafter. The tank will fully recover after a
few minutes to again deliver 12 litres/min at a 50°C rise.
Domestic hot water always takes priority over central
heating.
If domestic hot water is drawn off while the central
heating is operating the boiler will automatically transfer
the boiler output to the domestic hot water supply.
A secondary water expansion vessel is supplied with the
tank and must be connected to the appropriate tapping
on the controls assembly.
Important
No valves should be fitted between the expansion vessel and the storage cylinder.
DHW Store Temperature both tanks
Water is stored in the tank at approximately 73C. To ensure a safe delivery temperature a thermostatic mixing valve is fitted
in the hot water outlet and should be adjusted to produce a hot water delivery temperature of 60C.

Publication No. 559779 Installation Requirements
11
Installation Requirements – Page 11
Temperature
Sensor
Boiler Water
Return
Flow Rate
LimiterDomestic Cold
Water Entry
Boiler Water Flow
Mixed Domestic
Hot Water
6.5 1/min
Mixing
Valve
Air Vent
EN0008A
Boiler Water
Return
Boiler Water
FlowFlow Rate
Limiter
Domestic Cold
Water Entry
Mixed Domestic
Hot Water
12.0 l / min
Temperature /
Pressure relief valve
P.R.Valve
Check Valve
Exp.
Vessel
Press.
Red. Valve
Temperature
Sensor
Mixing
Valve
20 l
50 l

Installation
Publication No. 559779
12
2. Installation – Page 12
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 4 cartons. The contents will be as follows:-
Carton 1:- Boiler Pack
Boiler
Outer Casing Assembly
Accessory Pack
Carton 2:- Tank Pack
Tank
Tank Frame
Controls Assembly
(50 litre Only)
Tundish (50 litre Only)
Secondary Expansion
Vessel & Support Brackets
(50 litre Only)
Carton 3:- Flue Pack
Flue System
Flue Installation Instructions
Carton 4:- Frame
Boiler Mounting Frame
Template
Boiler Connections Kit
Screw Pack
Tank Piping Jig
Literature Pack
Fig.8
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.
Hole Diameter Maximum Wall
Thickness
125mm 230mm
150mm 720mm
175mm 1000mm
Remove the template and drill the holes
using a 7mm drill. Carefully cut the flue
outlet hole through the wall or ceiling
allowing for any horizontal flue to rise at an
angle of 3° throughout its length.
The boiler mounting frame pack includes a
tank piping jig for both 20 and 50 litre
vessels. Discard as appropriate.

Publication No. 55977
Installation
13
Installation – Page 13

Installation
Publication No. 559779
14
Installation – Page 14
Safety device
(eg. temperature
relief valve)
Metal discharge pipe (D1) from
temperature relief valve to tundish
Tundish
Metal discharge pipe
(D2) from tundish,
with continuous fall
Discharge below
fixed grating
Trapped gulley
Fixed
grating
500mm
maximum
300mm
minimum
T & P Valve
Tundish
EN0038A
Assemble the tank piping jig to the boiler mounting frame as
illustrated.
Using 10 off wall plugs and screws from accessory pack
attach the boiler mounting frame and tank piping jig to the
wall ensuring that they are level.
Attach the tank mounting frame assembly to the wall and
boiler mounting frame as shown.
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. Drop the expansion
vessel forward and using the sealing washers provided
connect the flexible tank hoses to the boiler as shown (See
Fig. 2), it may be necessary to remove the vessel.
Connect the plastic condensate drain pipe to the mounting
frame.
Connect system pipework to the base of the mounting
frame as shown. Use a compression fitting for the pressure
relief pipe from the boiler.
Connect the gas supply to the base of the mounting frame
as shown.
Important
Ensure the flow limiter is fitted as shown in the outlet
connection of the cold water inlet valve - See Fig. 9.
50 litre vessel Only: Connect the controls assembly to the
base of the tank.
50 litre vessel Only: Connect the remote secondary
expansion vessel to the connection on the controls
assembly. Support brackets are supplied.
Tundish and T & P Valve:The tundish must be left visible
to the consumer once installed and must not come into
contact with any electrical components. Connect the
temperature and pressure relief valve to the tundish using
the pipe supplied. Attach a ¾ to 22mm compression fitting
to the tundish and run a relief pipe down the back of the
mounting frame as shown.
Sizing of Copper Discharge Pipe
Min size of
discharge
pipe (D1)
15mm
Min size of
discharge
pipe (D2)
from tundish
22mm
28mm
35mm
Max. resistance
allowed, expressed
as a length of
straight pipe no
elbows orbends
up to 9m
up to 18m
up to 27m
Resistance
created by
each elbow
or bend
0.8m
1.0m
1.4m

Publication No. 55977
Installation
15
Installation – Page 15
Pressure Relief Valve: The Flowsure has one P.R.V. fitted
within the boiler pre-set at 3 bar. The Flowsure+ has two
P.R.V's fitted, one within the boiler pre-set at 3 bar and one
within the tank controls pre-set at 6 bar.
Install a pressure relief valve discharge pipe to the boiler and
tank valves, 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. (see Fig. 9C) 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.
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.
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.
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.
Plug tank sensor cable into the mating connector on the
short cable coming from the bottom of the control box.

Commissioning
Publication No. 559779
16
3. Commissioning – Page 16
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 9 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 30.
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 CH & DHW control switches are in the 'Off'
position.
Turn on the gas service cock.
Ensure that the boiler and radiator isolating valves are
open.
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 or 10°C in the tank the
boiler will fire until the return temperature reaches 40°C
or the tank temperature reaches 15°C.
Ensure the electronic timer if fitted, is in an 'ON' period
(refer to the time control literature).
Ensure that the room thermostat if fitted is set to a high
temperature.
Switch both the CH & DHW switches to the On position.
The symbol in the Status/Function display will change
from to or .
The fan switches on and sets to maximum RPM to give
a pre-purge.
The hot surface igniter turns on and reaches a preset
temperature.
The gas valve is opened.
If the control fails to detect flame in the first 3 seconds,
the boiler will stop and a new ignition cycle started.
After 3 ignition attempts the control will go to lockout.
The Status/Function display will show an
and the Flow Temperature & settings display will show
. Refer to fault finding section on Page 30.
If ignition is successful the flow temperature is
measured by the control for the first twenty seconds to
ensure that there is a greater than 3°C rise in the flow
temperature. (If unsuccessful, the boiler will go to
lockout - see fault finding).
When the temperature rise has been detected, the
controls will adjust the boiler output depending on
whether the call for heat is from the domestic hot water
or central heating. When the set temperature is reached
the controls will close the gas valve, allow the fan to run
for a short time then set the pump overrun (if required).
It should be noted that the boiler control continuously
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 characters being displayed in
the Flow Temperature & Settings display and the
character
shown in the Status/Function. 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.

Publication No. 55977
Commissioning
17
Commissioning – Page 17
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.
Ensure the boiler is NOT modulating by operating in the
DHW mode with hot water taps fully open.
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 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 5 minutes
after burner shutdown to dissipate heat left within the
boiler. The times are adjustable and can be set via the
control panel.
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 Display & Controls
For full details of the boiler display and controls see
Page 19.
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.

Commissioning
Publication No. 559779
18
Commissioning – Page 18
Final Assembly
Remove the three M5 pozi head screws from the right hand
side of the boiler as shown, Secure the centre case support
bracket using the three screws previously removed. Attach
casing side panels onto the boiler as illustrated (Fig. 12)
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.

Publication No. 55977
Boiler Display & Controls
19
4. Boiler Display & Controls – Page 19
00
Status
Reset
34
H
bar
Central Heating
Switch
Domestic Hot Water
Switch
Plus Button
Minus Button
Flow Temperature
& Settings Display
Lockout Reset /
Function Button
Status / Function
Display
System Pressure
Gauge
EN0012
Boiler Controls
All boiler mounted user controls are situated in the front of
the boiler control box behind the hinged door.
Central Heating Switch: In the 'On' position the central
heating (CH) will be on unless connected to a timer when it
will operate on the timed settings.
Domestic Hot Water Switch: In the 'On' position, the
domestic hot water (DHW) will be available on demand.
Domestic hot water always takes priority over central
heating.
Flow Temperature & Settings Display: This shows the
boiler flow temperature under normal operation and error
condition numbers if a fault should occur.
Status Function Display: This shows the boiler operating
condition under normal operation and an error condition
letter if a fault should occur.
Under normal conditions of operation the following
characters appear:-
Display not illuminated. All power off.
Stand-by: This is displayed when the CH & DHW
switches are in the 'Off' position. Also shown when both
switches are in the 'On' position but there is no call for
heat.
The boiler flow temperature will be shown on the Flow
Temperature & Settings Display.
Central Heating: This is displayed with a flashing dot
when the CH switch is in the 'On' position (and there is a
call for heat from the time control, if fitted). When the
burner lights the dot will stop flashing.
The boiler flow temperature will be shown on the Flow
Temperature & Settings Display.
Temperature Adjustment: The boiler thermostat setting
can be adjusted as follows when in central heating
mode:-
1. Press the Lockout Reset/Function Button once and
the will flash. The Flow Temperature & Setting
Display will change to show the boiler thermostat
setting.
The setting can now be changed in 1°C steps
(between 50°C & 85°C) by pressing the Plus or
Minus buttons.
2. Press the Lockout Reset/Function Button once and
the flashing will change to a flashing this is the
installer adjustment mode entry point (and the
outdoor weather compensator slope adjustment
point if fitted).
3. Outdoor Weather Compensator Slope Adjustment:
(Optional Extra)
As well as the flashing a number between 10 and
30 (default is 20) will be shown on the Flow
Temperature & Settings Display. This feature is used
to optimize the boiler output (flow temperature) to the
heating demand (outside temperature) and takes into
consideration such factors as the standard of
insulation (heat loss) of the building, output of the
heating system and the level of comfort required.
Note: This feature only works when an outdoor weather
compensator is connected to the boiler, the display will
remain the same with or without sensor.
4. Press the Lockout Reset/Function Button once and
the flashing will change to an .

Boiler Display & Controls
Publication No. 559779
20
Boiler Display & Controls – Page 20
Note: If you hold the Lockout Reset/Function Button for
more than 5 seconds you will enter the installer
adjustment mode settings. If this happens, leave the
controls alone and they will reset after a few minutes.
Further information on installer adjustment is provided
below.
Pump Overrun: This is displayed on completion of a
heating period when the residual heat from the boiler is
being dissipated.
Hot Water: This is displayed when the storage tank
water is being heated.
Reset Button
Pressing the reset button will allow the control to be
reset and the boiler restarted should a lockout condition
have occurred. (The character is shown on the
status/function display and a number i.e. shown on
the temperature/settings display)
To Shut Off
Set both the CH & DHW switches to 'Off'.
____________________________________________
Installer Adjustment
The following functions allow you (the installer) to
configure the boiler to a particular site or to gain
information about the boiler and system including the
most recent faults that may have occurred. In most
cases the default settings will have been used to ensure
the most efficient operation and should not be changed
unless necessary. To enter the adjustment mode
proceed as follows:-
From Stand-by: Press the Lockout Reset/Function
Button twice and the display will change to a flashing.
From Central Heating: Press the Lockout
Reset/Function Button once and the flashing will
change to a flashing .
To enter the installer settings mode depress the
Lockout/Reset function button and hold down for around
5 seconds. The Status/Function display will change to
Important:
If a setting is changed when in this mode the Lockout
Reset/Function Button must be pressed through the
following sequence to store the change in memory.
Settings: Press the reset button after each selection to move
to the next function.
Storage Tank: The 50 litre is set at 50 and the 20 litre
tank is set at 20. The 20 litre may also use 00 in areas
where water hardness is a problem. Whilst in this mode
press the + or - buttons to select appropriate tank size as
indicated in the Flow Temperature & settings Display.
Minimum Flow Temp: See Outdoor Weather
Compensator.
Reference Temp: See Outdoor Weather Compensator -
if fitted.
Used only to change from the default setting of :
This allows the Setback Function to operate and means
that the boiler will run at times when the secondary
controls are satisfied due to the Outdoor Weather
Compensator controlling the boiler.
Return Water Temp: Actual reading (°C) shown in Flow
Temperature & Settings Display.
Pump Overrun: Settings available are 1, 5, 10, 15, 20,
25, 30, 35, 40, minutes and (continuous). Whilst in
this mode press the + or - buttons to select appropriate
timings as indicated in the Flow Temperature & settings
Display.
Flame Signal: When this is shown, the flame signal will
be shown as a percentage between & in the
Temperature & Settings Display.
Last Lockout: This is when a lockout has occurred and
the control has been reset. For more information see the
Fault Finding section.
Last Blocking Error: This is when a blocking error has
occurred and then cleared. For more information see the
Fault Finding section.
Maximum Fan Speed: This is normally set at 99 which
is equivalent to 4680 RPM. For more information see the
Fault Finding section.
Minimum Fan Speed: This is normally set at 40 which is
equivalent to 2920 RPM. For more information see the
Fault Finding section.
Fan Speed Offset: This allows for an offset in the fan
speed. For more information see the Fault Finding
section.
Control Status: From the information shown on the Flow
Temperature & Settings Display it is possible to
determine the function the control is performing at any
one time. For more information see the Fault Finding
section.
Display returns to User Mode at this point.